ASME Conference Presenter Attendance Policy and Archival Proceedings

2013;():V08AT00A001. doi:10.1115/IMECE2013-NS8A.

This online compilation of papers from the ASME 2013 International Mechanical Engineering Congress and Exposition (IMECE2013) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Heat Transfer and Thermal Engineering: Biomass and Biofuels

2013;():V08AT09A001. doi:10.1115/IMECE2013-62798.

Bottom ash from Municipal Waste fired boilers have sufficient heat content and this can be used to pre-heat the boiler feed water or the combustion air. A study of the recent developments in this area is done with a focus on the air based cooling method. Modeling and simulation of the thermal performance of an air cooled ash cooling system is done with the help of Gambit/Fluent software. Among several methods of waste disposal, incineration of Municipal Waste is opted mainly due to its energy potential and specific advantages like high volume reduction ratio and convenience in plant location. However, the inherent fuel qualities that confront this method are its high moisture and ash content and the consequent low calorific values. The fuel bed temperature in stoker fired incineration systems can reach up to 1200K and a considerable part of this heat is wasted by way of ash sensible heat loss. The methods used for ash cooling include the water cooled ash screw system, the rolling cylinder ash cooler, fluidized bed ash cooler and the high strength steel belt ash cooler. In this study, the simulation of the performance of water based and air based ash cooling systems is done for a certain municipal waste fired boiler. The effect of the two methods on the overall boiler efficiency is studied. Comparison of results with that of a working system indicates that air cooling systems can be as efficient as the water cooled systems. With the help of this study, bottom ash heat recovery, especially for waste fired boilers, will be appreciated better and power plant designers will have a better insight into this area.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A002. doi:10.1115/IMECE2013-62882.

This parametric study shows that thermal radiation from particles, fly ash and char, can be highly relevant for estimating the radiative heat flux to surfaces in grate fired furnaces, especially to the hot bed. The large effects of particle radiative heat transfer come from cases with municipal solid waste (MSW) as fuel whereas biomass cases have moderate effect on the overall radiative heat transfer. The parameters investigated in the study were the fuel parameters, representing a variety of particle loads and size distributions, emissivities of walls and bed, and the size of furnace. The investigations were conducted in a 3-D rectangular environment with a fixed temperature field, and homogeneous distribution of gases and particles. The choice of boundary emissivity was found to be much more or equally important as the particle radiation effects, dependent if biomass or MSW, respectively, was used as the fuel. The effect of particle radiation increased with increasing furnace size, mostly evident in the change of the radiative source term and the heat flux to the bed. Compared to previous studies of particle radiation in grate fired combustion, this study used realistic particle mass size distributions for fly ash. Estimates of char mass size distributions inside the furnace were conducted and used.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A003. doi:10.1115/IMECE2013-63917.

The goal of this work was to carry out transesterification using computational fluid dynamics (CFD) method and obtain yield comparable to experimental values. First of all, the single–phase flow field was simulated and compared with experimental data obtained by means of particle image velocimetry (PIV) measurements. The velocities calculated from the RSM approach agreed quite well with those from PIV. The CFD simulations of biodiesel production were performed using the Reynolds stress model (RSM) coupled with the eddy dissipation model (EDM). CFD analysis of biodiesel yield compared fairly well with the experimental results available.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A004. doi:10.1115/IMECE2013-64302.

Injection timing variations have a strong effect on NOx emissions for direct injection diesel engines. Retarded injection is commonly used to control NOx emissions. Biodiesel is a non-toxic, biodegradable and renewable fuel with the potential to reduce engine exhaust emissions. The methyl ester of jatropha oil, known as biodiesel, is receiving increasing attention as an alternative fuel for diesel engines. In the present investigation neat jatropha oil methyl ester (JME) as well as the blends of varying proportions of jatropha oil methyl ester (JME) and diesel were used to run a CI engine with standard injection timing and retarded injection timing. Significant improvements in engine performance and emission characteristics were observed for JME fuel. The addition of JME to diesel fuel has significantly reduced HC, CO, and smoke emissions but it increases the NOx emission slightly with standard injection timing. The NOX emission was decreased with retarded injection timing with negligible effect on fuel consumption rate. Similar trend in brake thermal efficiency and exhaust gas temperature was observed with retarded injection timing while maximum cylinder gas pressure and ignition delay was decreased.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A005. doi:10.1115/IMECE2013-64618.

India does not have large reserves of crude petroleum and spends a huge amount of foreign exchange for importing crude petroleum. The environmental degradation caused by burning of petroleum derived fuels is also causing an ecological imbalance. Research is carried world over on renewable fuels which could either be used as an extender or substitute to petroleum origin fuels and in this context alcohols such as ethanol and butanol have an immense potential. The earlier work on use of alcohols as a blend with diesel in the compression ignition engine has suggested reduction in emissions, however, problems such as phase separation and increase in fuel consumption has also been encountered while utilizing ethanol in diesel engines. To alleviate this problem, isobutanol has the potential to be used along with ethanol to make a homogenous blend without any phase separation and simultaneous advantage of alcohol being an oxygenated fuel which shall improve the combustion and reduce emission. The present study was carried out to explore the potential utilization of ethanol-isobutanol-diesel blends (containing up to 20% ethanol-isobutanol mixture in equal proportions) in compression ignition engine. Three blends were prepared having 5%, 10%, 20% ethanol-isobutanol mixtures respectively and calorific value, kinematic viscosity; specific gravity and density of blends were found to decrease with increase in ethanol-isobutanol percentage. The engine trial was conducted on an unmodified diesel engine to evaluate the performance and emission characteristics on ethanol-isobutanol-diesel blends and results were compared with baseline data of diesel. The results obtained from the engine trial suggested that brake thermal efficiency (BTE) increased and brake specific energy consumption (BSEC) decreased for the blends and considerable reduction in carbon monoxide (CO) and carbon dioxide (CO2) was observed with blends with a small increase in unburnt hydrocarbon (UBHC). The nitrogen oxide (NOx) and smoke emissions were also found to reduce for the ethanol-isobutanol-diesel blends.

Topics: Diesel engines
Commentary by Dr. Valentin Fuster
2013;():V08AT09A006. doi:10.1115/IMECE2013-64777.

In a bubble column-based photobioreactor, sparger design and placement govern the bubble size distribution and gas hold-up. These factors in turn influence flow pattern, effective interfacial area, rates of mass and heat transfer, and mixing. Previous computational studies of the hydrodynamic and heat transfer effects within a column photobioreactor for one sparger row have found that bubble Nusselt number and heat transfer coefficient with respect to superficial velocity do not follow any particular pattern. This study evaluates the temperature distribution and heat transfer within a photobioreactor in an effort to explain the earlier study results. Experimental and computational studies will focus on the bubble flow pattern and heat transfer within a rectangular column photobioreactor (33.65 cm long × 30.48 cm wide × 33.97 cm tall) with a single row sparger located either lengthwise or widthwise at the center of the base (27.94 cm long × 1.27 cm wide). Temperature distribution and heat transfer for both sparger positions will be compared. Carbon dioxide, water, light photons, algal cells, and nutrients need to come together continuously for successful algal production, hence mixing of the nutrients, algal cells, and carbon dioxide is essential. Instead of a light source, a heat source is used in the system. Constant electric energy is supplied to the heating pad, which converts the electric energy to thermal energy. Thermocouples are placed inside the PBR to record temperature at 36 different spatial positions. The experimental results are compared with previously developed CFD simulations. The sparger not only effects the aeration inside the PBR, but also creates mixing in the PBR. Proper design and placement of the sparger ensures proper mixing in the PBR. The present study shows the effects bubble movement and flow pattern have on the temperature distribution and how well the simulation predicts the temperature distribution inside a PBR. The present research is a continuum of previous work aimed at pursuing the optimum design of a column PBR which is commercially viable and effective at producing algal biofuels and bioproducts.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A007. doi:10.1115/IMECE2013-64956.

The autoignition of three biodiesel surrogates (methyl decanoate, methyl 9-decenoate, and a mixture of methyl 5-decenoate and methyl 6-decenoate), representative of the organic structures found in fatty-acid methyl ester (FAME) biodiesels, has been studied using the reflected shock technique. Measurements of ignition delay times were carried out at 20 atm for temperatures ranging from 700 to 1300 K, spanning all three regimes of reactivity of interest to diesel engines. At high temperatures (> 900 K) the three surrogate components have indistinguishable ignition delay. While in the negative-temperature-coefficient (NTC) and low-temperature regimes (< 900 K) the deviation in ignition delay based on the location of the double bond with the methyl decenoate carbon chain is around a factor of two. The results show that location of double bonds within FAME biodiesel components will have an important role in governing the NTC and low-temperature reactivity for FAME biodiesels but is unimportant at high-temperatures, of significance for the development of biodiesel surrogates and modeling strategies for diesel engine simulations.

Topics: Biodiesel
Commentary by Dr. Valentin Fuster
2013;():V08AT09A008. doi:10.1115/IMECE2013-65246.

The market for residential pellet burning equipments is well developed in some European countries like Germany, Austria and Italy and rapidly expanding in others. As a consequence the pellet production has also grown, although a large fraction is destined for industrial applications such as coal co-combustion. Due to the existence of chemical elements such as Na, K and Si, the pellet combustion can lead to agglomerated ashes on the grate of the burner causing problems for its proper operation.

The present work aimed to study the influence of temperature and air flows in the ash agglomeration at the grate. For this purpose, it was assembled an experimental setup that, in a brief, description consists of: i) boiler, whose burner allows the regulation of the primary and secondary air flow, ii) variable flow exhaust gases extraction system, iii) controllable feeding system, iv) heat dissipation system, v) data acquisition and control system, vi) exhaust gases analysis system.

The results indicate an increased formation of agglomerated ash with increasing of temperature. In addition, they also suggest the influence of excess air and primary air fraction in that formation, and the existence of an optimum working condition for high excess air and a primary air fraction of around 30%. The application of swirl in the secondary air improves both the flame stability and enables an efficient combustion into regions where the ash agglomeration is reduced. Moreover, they also show that there are other factors that influence the ash agglomeration, mostly related to the changing of the chemical elements ratio due to vaporization of the more volatile species.

Topics: Sintering , Biomass , Boilers
Commentary by Dr. Valentin Fuster
2013;():V08AT09A009. doi:10.1115/IMECE2013-65615.

Fuel combustion performance was quantified through measurement of the gravimetric response of the fuel as well as the energetic behavior. A Simultaneous Thermogravimetric Analyzer (STA) was used to measure the gravimetric, sensible energy, and latent heat energy (including heat of pyrolysis) for fuels. The heat release rate and heat of combustion of the fuels as a function of temperature released due to the combustion of the pyrolysis gases was measured using a Micro-Combustion Calorimeter (MCC). Fuels were tested at a heating rate of 20°C/min from room temperature to 800°C in inert (nitrogen) environment. Fuels considered in this study included US eastern coal, biomass (cornstover and switchgrass), polystyrene, glycerol and mixtures of some of these fuels. Biomass feedstocks were also evaluated for the effect of water leaching on fuel performance. A lumped model energy balance on a fuel particle revealed that fuel volatility can be ranked based on the net energy required to produce the volatile gas times the ratio of the heat of combustion to the heat of decomposition. This is different compared with previous research results in that it includes the temperature dependence of the fuel production in the volatility.

Commentary by Dr. Valentin Fuster

Heat Transfer and Thermal Engineering: Combustion and Fire — Experimental Techniques

2013;():V08AT09A010. doi:10.1115/IMECE2013-62148.

Earlier studies on burning a pool fire in a vertical shaft model indicated that appropriate sidewall ventilation provision is a key factor for the onset of an internal fire whirl. Experiments on burning a pool fire inside a real-scale shaft model of 9 m tall were performed to further investigate the swirling motion. The full-scale modeling burning tests were carried out at a remote site in China. Four different ventilation openings were arranged. Results of onsetting of internal fire whirls for the four tests will be reported.

Topics: Fire , Whirls
Commentary by Dr. Valentin Fuster
2013;():V08AT09A011. doi:10.1115/IMECE2013-62367.

Airplane as one of the important transport vehicles in our life, its safety problem related to in-flight fire has attracted a wide-spread attention. The combustion behavior of the cabin fire in flight shows some special characteristics because of the high-altitude environment with low-pressure and low oxygen concentration. A low-pressure chamber of size 2 m×3 m×2 m has been built to simulate high-altitude environments, where multiple static pressures for pool fire tests can be configured in the range between standard atmospheric pressure 101.3KPa and 30KPa. Two different sizes of pool fires were tested. Then corresponding modeling were conducted by a LES code FDS V5.5 to examine the mechanism of pressure effect on the n-Heptane pool fire behavior. The burning of liquid fuel was modeled by a Clausius-Clapeyron relation based liquid pyrolysis model. The modeling data was validated against the experimental measurements. The mass burning rate of free-burning pool fire decreases with the decreasing of pressure, which was observed from the modeling to be due to the reduction of flame heat feedback to the fuel surface. Under low pressure, the fire plume temperature increases for the same burning rate. The mechanism of pressure effect on fire behavior was analyzed based on the modeling data.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A012. doi:10.1115/IMECE2013-62738.

A new and simple expression for the calculation of the total gas emittance of H2O-CO2 mixtures for modeling radiation transfer in combustion furnaces is presented. Its accuracy is established by comparing the predictions with those based on the well established exponential wide band model. The computational time was found to be reduced by a factor of 10–30 in comparison to other methods for computing the total emittance of combustion gas mixtures.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A013. doi:10.1115/IMECE2013-62810.

With the emergence of large scale buildings, how to improve the efficiency of the fire prediction model has urgently been a problem in the field of fire emergency. Based on an existing fire zone model, CFAST, and some other assumptions, this paper puts forward a distributed fire model capable to make a fast and acceptable prediction. The whole building structure is divided into some small basic zones in which a group of control equations run independently relying on the local information. With a small scale of the local structure, the computational complexity will not increase significantly as the building scale enlarges. In this paper, a typical building structure with multiple rooms and a long corridor is discussed. Two kinds of models, namely fire zone model and corridor zone model are set up and run locally. At a prescribed time, based on the limited communication between those two kinds of models, the properties of the corridor can be updated. By repeating these steps, the global state can be predicted. One typical floor of a real building is used to test this distributed fire model with a 3 MW steady fire and the comparison against the conventional CFAST model is carried out. The results show that the proposed distributed fire model can perform well in a short term prediction (about 150s after fire breaks out), but for the long term prediction, the simulations are affected by the “far away” wall and HVAC condition, which resulting in a diverging solution from the conventional CFAST model.

Topics: Fire
Commentary by Dr. Valentin Fuster
2013;():V08AT09A014. doi:10.1115/IMECE2013-62901.

Although diffusion flame is free from many problems associated with premixed flame, soot formation is a major problem in diffusion flame. The techniques of dilution of fuel or air with inert gases such as nitrogen and argon are used to decrease soot level in the flame. In this work, a CFD code has been developed to predict the flame height, soot volume fraction and soot number density in an axisymmetric laminar confined methane-air diffusion flame after diluting the fuel with nitrogen. The temperatures of the air and fuel at inlet are taken as 300K. Mass flow rate of the fuel stream is considered as 3.71×10−6 kg/s and mass flow rate of the air is taken as 2.2104×10−6 kg/s. The total mass flow rate through the central jet (fuel jet) is, however, kept constant. The radiation effect is also included through an optically thin radiation model. An explicit finite difference technique has been adopted for the numerical solution of reacting flow and two equations soot model with variable thermodynamic and transport properties. The prediction shows that flame height decreases with the addition of nitrogen to the fuel. Temperature of the flame is considerably reduced in the given computational domain. Both soot volume fraction and soot number density decrease with dilution by adding nitrogen in the fuel jet. The soot formation at different nitrogen dilution level of 0%, 10%, 20%, 30%, 40% and 50% are plotted and the soot get considerably reduced as the concentration of nitrogen is increased in the fuel stream.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A015. doi:10.1115/IMECE2013-63196.

The objective of this work is to investigate the flame stabilization mechanism and the impact of the operating conditions on the characteristics of the steady, lean premixed flames. It’s well known that the flame base is very important to the existence of a flame, such as the flame after a V-gutter, which is typically used in ramjet and turbojet or turbofan afterburners and laboratory experiments. We performed two-dimensional simulations of turbulent premixed flames anchored downstream of the heat-conducting V-gutters in a confined passage for kerosene-air combustion. The flame bases are symmetrically located in the shear layers of the recirculation zone immediately after the V-gutter’s trailing edge. The effects of equivalence ratio of inlet mixture, inlet temperature, V-gutter’s thermal conductivity and inlet velocity on the flame base movements are investigated. When the equivalence ratio is raised, the flame base moves upstream slightly and the temperature gradient dT/dx near the flame base increases, so the flame base is strengthened. When the inlet temperature is raised, the flame base moves upstream very slightly, and near the flame base dT/dx increases and dT/dy decreases, so the flame base is strengthened. As the V-gutter’s thermal conductivity increases, the flame base moves downstream, and the temperature gradient dT/dx near the flame base decreases, so the flame base is weakened. When the inlet velocity is raised, the flame base moves upstream, and the convection heat loss with inlet mixture increases, so the flame base is weakened.

Topics: Gutters , Flames
Commentary by Dr. Valentin Fuster
2013;():V08AT09A016. doi:10.1115/IMECE2013-63219.

In industrial environments, boiler units are widely used to supply heat and electrical power. At an integrated steel mill, industrial boilers combust a variable mixture of metallurgical gases combined with additional fuels to generate high-pressure superheated steam. Most tangentially fired boilers have experienced water wall tube failures in the combustion zone, which are thought to be caused by some deficiency in the combustion process. The challenge faced in this present process is that there are very limited means to observe the boiler operation. In this study, a three-dimensional Computational Fluid Dynamics (CFD) modeling and simulation of an industrial tangentially fired boiler firing metallurgical gases was conducted. Simulation results obtained from the assembled CFD model were validated by industrial experiments. A quick comparison of the flame shape from the simulation to the actual flame in the boiler showed a good agreement. The flow field and temperature distribution inside the tangentially fired boiler were analyzed under the operation conditions, and a wall water tube overheating problem was observed and directly related to the flow characteristics.

Topics: Gases , Simulation , Boilers , Firing
Commentary by Dr. Valentin Fuster
2013;():V08AT09A017. doi:10.1115/IMECE2013-63244.

Investigating the impact of JP-8 and pure Karanja oil biodiesel fuel on diesel engine performance, emission and pump wear are very important for military track and wheeled vehicles due to their great potential as alternative fuels. In the present study, a military 780 hp CIDI engine was fuelled and tested with diesel, JP-8 and pure Karanja oil biodiesel respectively. The performances of fuels were evaluated in terms of brake horse power, specific fuel consumption, brake specific energy consumption, brake mean effective pressure, thermal efficiency and heat release rates. The emission of carbon monoxide (CO), unburnt hydrocarbon (UHC), and oxides of nitrogen NOx with the three fuels were also compared. Both Karanja oil, after transesterification and JP-8 exhibit the properties (density, viscosity and calorific value) within acceptable limits of ASTM standard. Performance of both JP-8 and pure Karanja oil biodiesel were slightly lower than diesel. Emissions of CO and UHC were found lower with both JP-8 and Karanja oil biodiesel as compared to diesel fuel. However, only JP-8 fuel had lower NOx emission whereas Karanja oil biodiesel had 10% higher NOx emission. The fuel pump wear was tested after a 100 hours run.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A018. doi:10.1115/IMECE2013-63968.

An experimental study has been conducted to investigate the effect of helical vane swirler geometry on heat transfer characteristics for compressed natural gas (CNG)/air swirling flame impinging on a flat surface. Effects of helical vane swirler geometric parameters like, length of helical insert (25 mm, 45 mm and 65 mm), depth of groove on the helical insert (2.5 mm, 3.5 mm and 4.5 mm) and number of helical vanes (8, 10 and 12), on heat transfer characteristics have been studied. All the inserts were having fixed helical vane angle of 45°. Also, the burner exit diameter was kept constant (d = 20 mm). Experiments were conducted at different dimensionless separation distances (6, 4, 3 and 2) for fixed values of Reynolds number (6000) and equivalence ratio (1.3). Significant variation in the heat flux profiles has been observed for different swirler inserts till the radial hump in heat flux. After the radial hump, almost in all cases, the heat flux lines merged together. These variations in the heat flux profiles were due to different level of swirling intensities produced by different swirlers at fixed value of the helical vane swirler angle. It was observed that the heating was comparatively more uniform at larger separation distances (H/d = 6). It has been concluded that defining swirl intensity only with the helical vane swirler angle would be incorrect for such type of swirlers. Other geometric parameters of the swirler like, number of vanes, length of the swirler and the depth of the groove should also be included in swirl intensity definition.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A019. doi:10.1115/IMECE2013-63981.

It is critical for the construction industry to ensure that new building designs and materials, including wall and floor assemblies (e.g., a studded wall with insulation and drywall) provide an acceptable level of fire safety. A key fire safety requirement that is specified in building codes is the minimum fire resistance rating, which is a measure of the ability of an assembly to limit fire spread within a building. A manufacturer of building materials (e.g., insulation or drywall) is required to perform full-scale fire resistance furnace tests to determine the fire resistance ratings of assemblies that use their products. Fire resistance test facilities are very limited and these tests are very expensive to perform. Therefore, it can be difficult to properly assess the impact of changes to individual components on the overall fire performance of an assembly during the design process.

As part of a project to develop methods of using small-scale fire test data to predict full-scale fire resistance test results, the heat transfer through scale models of common wall assembly designs was measured during cone calorimeter tests using an incident heat flux of 75 kW/m2. Wall assemblies consisting of single and double layers of 12.7 mm (1/2 in.) regular and lightweight gypsum board, and 15.9 mm (5/8 in.) type X gypsum board, along with mineral wool insulation and wood studs were tested. Temperature measurements made at various points within these assemblies are presented in this paper, and are discussed using results from thermal gravimetric analysis tests of the three types of gypsum board. Implications of this research to the development of heat transfer models and scaling relationships are also briefly discussed.

Topics: Heat transfer
Commentary by Dr. Valentin Fuster
2013;():V08AT09A020. doi:10.1115/IMECE2013-63987.

A wide band cumulative absorption coefficient distribution, g(k), model is adopted to predict radiative transport in combustion gas mixtures. Prior research has demonstrated similar accuracy of the model to the statistical narrow-band model and superiority to the exponential wideband model under isothermal and homogeneous conditions. This study aims to assess its usefulness in nonhomogeneous media. Sample calculations are performed in a 1D planar slab containing H2O/CO2 mixtures. The six-flux discrete ordinate method (S6-DOM) is employed to solve the radiative transfer equation (RTE), followed by an eight-point Gaussian quadrature of moments with zeroth-order fit. Predictions on the radiative source distribution along the slab and the net radiative flux at the walls are compared to the benchmark line-by-line calculation (LBL) and the statistical narrow-band correlated-k distribution model using the 7-point Gauss-Lobatto quadrature scheme (SNBCK-7). The differences between the g(k) model and LBL are below 5% for a large domain of the layer, with a CPU reduction by a factor of over 30 compared to SNBCK-7 and on the order of 104∼105 compared to LBL. The wide band g(k) model shows significant promise as an accurate and efficient tool to predict radiative transfer in nonhomogenerous media for combustion and fire simulations.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A021. doi:10.1115/IMECE2013-64178.

An experimental investigation has been carried out to determine the effect of swirl intensity on heat transfer characteristics of swirling flame impinging on a flat surface. The swirl intensity was varied by using helical vane swirlers having angles of 15°, 30° and 60° (low, medium and high swirl). Qualitative flame structures were studied by taking direct photographs of impinging flames. Experiments were conducted for different helical vane swirlers at different dimensionless separation distances (H/d = 1–6) for fixed value of Reynolds number (Re = 5000) and equivalence ratio (ϕ = 1.0). A dip in heat flux was observed at stagnation point for all levels of swirl. Peak heat flux was observed slightly away from the stagnation point due to centrifugal effect. A comparison of stagnation point heat flux has been done for different swirl intensities and for fixed operating conditions. Most uniform heat flux distribution was obtained corresponds to 30° helical vane swirler (medium swirl) at all separation distances.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A022. doi:10.1115/IMECE2013-64286.

An experimental study is carried out to investigate the combustion process in a Wärtsilä 34SG spark-ignited lean burn four-stroke large bore engine (bore 340 mm) by means of optical diagnostics when operating on natural gas. The main focus of this work is to gain knowledge about in-cylinder combustion phenomena when igniting a lean air/fuel mixture with pre-combustion chamber induced jets. Especially the origin of cyclic variability is of interest. The flame propagation process in a single cycle was captured using a high speed video camera. The analysis is based on apparent heat release rates in the pre-combustion chamber and main chamber, in order to find correlations with the imaged phenomena. The results show that the flame propagation inside the main chamber starts at the end of the pre-chamber combustion heat release and that variation in main chamber heat release does not correlate with variations in the pre-combustion chamber.

Topics: Heat , Combustion , Engines , Imaging
Commentary by Dr. Valentin Fuster
2013;():V08AT09A023. doi:10.1115/IMECE2013-64912.

Platinum has been recognized as a viable combustion catalyst. Its change in electrical resistance with temperature has been used to measure light-off temperatures and rates of heat generation for various fuel-oxygen mixtures at the University of Idaho. In an attempt to maximize the surface area for these reactions to occur, platinum-coated nanosprings have been manufactured. A reliable method of determining an effective temperature-dependent temperature coefficient of resistance (α(T)) for the nanosprings assembly has been developed and verified using pure platinum. Measured values of α(T) for platinum were matched against literature data at 373 and 1100 K. A linear fit was assumed for the gap between these temperatures; measurements made with platinum at intermediate temperatures were in good agreement. Using the same methodology, α(T) for the nanosprings assembly will be determined, which will allow for further research of the nanosprings in catalytic combustion.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A024. doi:10.1115/IMECE2013-65100.

Swirl is used in a wide range of combustions systems such as engines, furnaces, gasifiers, and boilers, to enhance mixing, stabilize flames, and reduce pollutant emissions. Numerical modeling of swirling flows remains a challenging task, since there may exist complex recirculating flow patterns and flow instabilities associated with vortex breakdown, precessing vortex core, and jet precession. In swirling flames, the situation becomes more complex because the unsteady heat release can add other modes of instability. The origins and nature of these instabilities are still not well understood despite many experimental and numerical studies have been conducted in the area. The Sydney swirl burner flame series provide an excellent platform for validating numerical methods for turbulence-chemistry interactions and have been target flames for the TNF workshop series. The burner has well-defined boundary conditions and comprehensive experimental data sets have been documented for different fuel compositions and flow conditions. Compared with the piloted and bluff-body stabilized flames, swirl-stabilized flames pose an additional challenge to numerical modeling because of the complex flow patterns and inherent flow instabilities. In this study, a large eddy simulation (LES)-based multi-environment turbulent combustion model is used to model the Sydney swirl burner flame SMH1. The multi-environment filtered density function model (MEFDF) depicts the filtered density function (FDF) as a weighted summation of a small number of multi-dimensional Dirac delta functions in composition space. It is derived from the transport FDF equation using the direct quadrature method of moments (DQMOM). The MEFDF method with multiple reactive scalars retains the unique property of the joint FDF model of treating the chemical source term exactly. A 19-species mechanism reduced from GRI-Mech 2.11 is employed for chemical kinetics. The in situ adaptive tabulation algorithm (ISAT) is used to speed-up the evaluation of the chemical source term. The predicted radial profiles of the axial velocity, azimuthal velocity, mixture fraction, temperature, and species mass fractions of CO2, CO, and NO are in reasonable agreement with the experimental data. It has been found that, compared with the experimental data, the profiles of the temperature and species mass fractions shifted slightly outward in the radial direction at downstream locations and NO mass fraction is slightly over-predicted at most locations. Further work will be needed to find out possible reasons for these discrepancies.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A025. doi:10.1115/IMECE2013-66367.

When firefighters are overcome by the heat or smoke of a fire and become disoriented or trapped in a structure, it is crucial that there is a reliable means to alert other fireground personnel to their need for assistance. Personal Alert Safety System (PASS) devices are designed to signal for aid using audible signal technology. Normal operation is for the PASS devices to activate a 95-decibel multiple-frequency alarm signal if the device is stationary for a specific period of time or is manually activated. However, despite its widespread use throughout the fire service and on-going enhancements in recent years, certain problems still exist with audible PASS technology. Foremost among these problems is that nationally recognized standards currently do not specify a unique PASS alarm signal, and this has resulted in multiple different PASS alarms being used in the field. In this work, we present results that seek to establish a scientific basis for an optimum PASS alarm signal for use throughout the U.S fire service. We present typical sounds recorded from firefighter operations. We discuss how these sounds interfere with typical PASS signals both in compartments with and without fire. Using experimental and computational results for sound propagation within compartments with fire and thermal stratification, we show how acoustic signals are modified and affected in the gas phase by the fire evolution. Additionally, the effects of thermal degradation of typical building materials such as gypsum board is discussed in terms of the impacts on sound propagation.

Topics: Fire , Signals
Commentary by Dr. Valentin Fuster

Heat Transfer and Thermal Engineering: Computational Heat Transfer

2013;():V08AT09A026. doi:10.1115/IMECE2013-62063.

The vibration of a left vertical hot wall in a square cavity with thermally insulated vertical walls facing unsteady natural convection is investigated numerically. The cavity is filled with an ideal gas and the top wall is exposed to free stream conditions. Using the primitive variables of velocity and pressure, the staggered grid technique and the marker-and-cell (MAC) method is used to solve the governing equations using the Boussinesq approximation for natural convection. The numerical solution is obtained by using Matlab platform. Sample results are shown in the form of contour plots for pressure, velocity vectors, vorticity, and temperature fields for fixed values of Reynolds number. Detailed analyses of unsteady laminar flow and thermal fields are exhibited over broad ranges of Reynolds number and frequency of the oscillating wall. Systematically-organized computational results based on the MAC method with an explicit formulation indicate enhancement of heat transfer demonstrated by higher average Nusselt number values for selected values of the Reynolds number.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A027. doi:10.1115/IMECE2013-62182.

Continuous casting is a promising technique for massive production of multicrystalline silicon (mc-Si). A theoretically advanced study is performed here to investigate the growth of mc-Si with large grain size, which has much higher photoelectric efficiency than normal mc-Si. However, the casting technique results in high thermal stresses due to its inherent features, and limits the photovoltaic applications of mc-Si because of the stress-induced dislocations. For the analysis and optimization of dislocation formation, a computer-aided method has been applied to investigate thermal stress distribution in the growing ingot of continuous casting. The regions of dislocation multiplication are evaluated by comparing von Mises stress to the critical resolved shear stress. It is found that the stress levels are especially high in the regions close to the solid and liquid (S/L) interface, and that the mold wall has a significant effect on the von Mises stress distribution if the billet were attached on the wall. The triple point is better to keep below the mould bottom to avoid its effect during the growth by certain techniques during the industrial production. Parametric studies were further performed to discuss the effects of growth conditions, such as sheath height, environment temperature, and pulling rate on the distribution of the maximum von Mises stress in the billet. The results imply theoretically that multicrystalline silicon with low stress-induced dislocation could be produced by continuous casting with strictly controlled growth parameters.

Topics: Casting , Stress , Silicon
Commentary by Dr. Valentin Fuster
2013;():V08AT09A028. doi:10.1115/IMECE2013-62388.

Turbulent flow of air with variable properties in a set of regular polygonal ducts and circular tube have been numerically simulated. All the ducts have the same hydraulic diameter as their characteristic length dimension in the Reynolds number. The flow is modeled as three-dimensional and fully elliptic by using the finite volume method and the standard k-ε turbulence model is adopted. The performances of the flow and heat transfer have been thoroughly investigated. The results showed that comparatively strong secondary flow can be observed with variable properties fluid. For the regular polygonal duct, the local heat transfer coefficient along circumferential direction is not uniform and there is an appreciable reduction in the corner region. The use of hydraulic diameter for regular polygonal ducts to determine turbulent flow heat transfer from circular tube correlations leads to unacceptably large errors. Based on the simulation results, a correction factor Cϕ is proposed to ameliorate the previous correlations, and the error in the prediction of turbulent heat transfer with the new correlation is within 6%.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A029. doi:10.1115/IMECE2013-62389.

The Lattice Boltzmann method is used to simulate the flow patterns of natural convection in horizontal cylindrical annulus for aspect ratios in the range of 0.4≤A≤10 and for Prandtl numbers varying from 0.1 to 0.7. At Pr = 0.3 and A = 2, flow patterns on the whole range of Rayleigh number are mapped indicating the lower and upper critical values for transitions. At Pr = 0.7, the influence of aspect ratio on flow pattern is analyzed acquiring the result that the oscillation flow never happens at A≤3. At A = 2, several Prandtl numbers are calculated at certain Rayleigh number and the conclusion is that the steady upward flow keeps when 0.5≤Pr. The results are found in good agreement with existed studies.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A030. doi:10.1115/IMECE2013-62680.

Heat transfer in horizontal concentrically insulated cylinders exposed to free convection is of importance in industry. However, the NuD and the surface temperature are not constant around the cylinder, raising the point that the use of concentric insulation may not be the best way to arrange the insulating layer. Thus, if an eccentric layer is used, the surface temperature should have a larger variation, changing the flow around the cylinder and the heat dissipation. A numerical analysis of the heat dissipation in horizontal isothermal eccentrically insulated cylinders exposed to free convection (Pr ≅ 0.715) is presented. The conduction through the insulating layer was solved analytically (using the bicylindrical coordinate system) and integrated numerically, while the free convection was solved by the PHOENICS software. The parameters analyzed were the ratio between the outer and inner radius of the insulating layer, the ratio between the insulation and air thermal conductivities, the Rayleigh number and the eccentricity of the insulation. An equation is suggested to calculate the total heat of an eccentric arrangement in terms of the total heat of the corresponding concentric arrangement and the ratio between the convective and conductive thermal resistances, for a given ratio of radius and eccentricity.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A031. doi:10.1115/IMECE2013-62887.

The thermal comfort in the cabin of construction equipment has been becoming one of the important issues of cabin design. In this study, a performance index related to thermal comfort is proposed as a way to evaluate the effect of location of air-conditioning vents. As the first step, cooling performance at the position of operator in the cabin is calculated by using CFD. For more reliable analysis, the results of the simulation are compared with experimental data. The evaluation of the thermal comfort is then carried out considering the change of the location of air-conditioning vent with the same boundary conditions. Cooling performance for initial 1 minute after turn on the air-conditioning is predicted from the results of thermal comfort. All of the results are used to optimize the location of air-conditioning vent in the cabin to improve the thermal conditions for the operator.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A032. doi:10.1115/IMECE2013-63167.

Macroscopic modeling of hydrodynamic behavior of nanofluid flow in a uniformly heated circular pipe is considered. Single-phase models with Brownian and dispersion viscosity models are evaluated by comparing predicted pressure drop and apparent friction factor with experimental and two-phase Eulerian-Eulerian model results from literature. Single-phase models are capable of predicting heat transfer of nanofluids better when dispersion models are used. However, they fail to accurately predict pressure drop when used with standard viscosity models. Two-phase models on the other hand, can accurately predict both thermodynamic and hydrodynamic field at the expense of computational time. A new viscosity model, which is based on dispersion viscosity, is proposed to increase accuracy of single-phase models in predicting hydrodynamic field of nanofluid flow. Results suggest that single-phase dispersion viscosity model is the most accurate single-phase model.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A033. doi:10.1115/IMECE2013-63301.

Numerous investigations have been conducted to extend adiabatic liquid-gas VOF flow solvers to include condensation phenomena by adding an energy equation and phase-change source terms. Some proposed phase-change models employ empirical rate parameters, or adapt heat transfer correlations, and thus must be tuned for specific applications. Generally applicable models have also been developed that rigorously resolve the phase-change process, but require interface reconstruction, significantly increasing computational cost and software complexity. In the present work, a simplified first-principles-based condensation model is developed, which forces interface-containing mesh cells to the equilibrium state. The operation on cells instead of complex interface surfaces enables the use of fast graph algorithms without reconstruction. The model is validated for horizontal film condensation, and converges to exact solutions with increasing mesh resolution. Agreement with established results is demonstrated for smooth and wavy falling-film condensation.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A034. doi:10.1115/IMECE2013-63668.

A numerical solution of heat transfer by combined natural convection and surface radiation in a square enclosure with thick adiabatic top and bottom walls and isothermal vertical walls is presented. The present model was used to obtain new results with the addition of thermal conduction at the thick top and bottom walls for a thermal conductivity ratio, K = ksolid/kfluid, that ranges from 0 to 10, emissivity of the adiabatic walls that ranges from 0 to 1, and the Rayleigh Number that ranges from 103 to 106. The model was validated by comparing the results to a benchmark solution and other solutions found in the literature. The results showed that with an increase in thermal conductivity ratio, the flow circulation decreases while the average Nusselt Number increases indicating increased heat transfer across the thick walls and the fluid in the corners. The results indicate that while past studies have shown negligible impact of the emissivity of the adiabatic walls on characteristics of the flow and heat transfer within the cavity, when a wall with moderate heat capacity and conductivity is considered, the resulting flow velocity and temperature distribution within the cavity are found to be significantly influenced by the thick wall emissivity. As the conductivity ratio increases this discrepancy between thin and thick walls becomes greater, there is further need for a more complex and accurate model including the thick walls. The results also showed that an increase in the emissivity of the adiabatic walls results in a slight decrease in the average Nusselt Number.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A035. doi:10.1115/IMECE2013-64092.

The present study numerically explores the melting process of a phase change materials in a rectangular geometry. More specifically, it investigates flow field, thermal phenomena, detailed phase and melting process by means of numerical simulation which is using as parameter; melting temperature, latent and specific heat capability, thermal conductivity and density in solid and liquid states, are based on paraffin wax. The study is performed for melting in rectangular container of without fin and 5 fins, when the wall temperature is uniform. Transient numerical simulations are performed using the ANSYS-Fluent 12.0 commercial software. The simulation results show that the transient phase change process depends on PCM properties, thermal condition and geometrical parameters of system. It includes the paraffin wax properties, thermal difference between hot and cold wall, and number of fins in the rectangular container. Results also indicate that the presence of fins embedded in the container significantly accelerates the melting process.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A036. doi:10.1115/IMECE2013-64179.

In order to reach a more efficient and compact heat exchanger, it is essential to optimize the design, having in mind the impact of different geometrical parameters. Many of the previously cited studies in the area of heat transfer enhancement using vortex generators were confined only to defined points in the possible design space. Thus, a multi-objective optimization study is particularly suitable in order to cover this space entirely. A CFD simulation along with Pareto method were used to simulate the air flow and heat transfer and optimize the design parameters. The angle of attack of a pair of delta-winglets mounted behind each tube is varied between β = −90° and β = +90°. Three elliptical tube rows with inline arrangements are investigated for Reynolds numbers from 500 to 1500 (based on the inlet properties). Use of delta-winglets as heat transfer enhancement elements increases the performance of elliptical-tubes heat exchanger. This enhancement is mainly due to the fact that delta-winglets increase the level of vorticity inside these devices and thus the mixing of the fluid is enhanced.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A037. doi:10.1115/IMECE2013-64341.

The real-time measurement of heat flux is an important challenge for several industrial applications including furnace control. For efficient operation of high-temperature process furnaces, accurate and stable temperature measurements are needed. Directional Flame Thermometers (DFTs) offer the ability to use both temperature and heat flux measurements for furnace control. Currently, analysis of dynamic temperature data from the DFTs to compute heat flux information must be performed off-line based on the gathered data by using a full-non-linear inverse heat conduction problem (IHCP) analysis. Availability of a near real-time algorithm for accurate reduction of the data will allow for continual monitoring of the furnace during operation. This will result in better furnace control and significant savings in energy and cost. The purpose of this paper is to provide a solution strategy based on filter concept for the inverse heat conduction problem associated with DFT. The filter based solution has the capability of heat flux estimation in a near real time manner. Two IHCPs are discussed and a coupled solution is proposed to estimate the unknown surface heat flux. The solution procedure is then validated using numerical test cases. Results are then computed using data from a physical experiment with DFT (see Reference [13]). The heat fluxes obtained are found in satisfactory agreement with those obtained from a full non-linear IHCP analysis.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A038. doi:10.1115/IMECE2013-64343.

This paper describes the results of the mathematical and computer modeling efforts of heat generation in the contact area of a moving object on an infinite plane with friction. The distribution of contact pressure with a linear approximation was obtained. The heat equations for a nonlinear volume heat source were solved. It is shown, that at the initial stages of the linear friction welding (LFW) process temperature distribution is non-elliptical with two hot spots appearing near the edges of the moving specimen. Then as the process progresses these two spots expand and move to the center of the specimen. The results of the mathematical and the numerical modeling in ANSYS APDL software are in good quantitative agreement.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A039. doi:10.1115/IMECE2013-64430.

This paper is focused on developing numerical modeling techniques aimed at automating and simplifying the process of generating detailed models for simulating building thermal physics. However, the methodology described can be applied in numerous application areas across the thermals sector. Automated approaches to developing energy models for buildings are of particular importance to alleviate current labor intensive practices of manual generation so that large real-estate portfolios can be analyzed within a reasonable time frame, hence providing a decision making tool that can lead to smarter renovation plans for implementation across the fleet. This process is achieved by developing custom built software code in MathWorks MATLAB® with all aspects discussed herein. The starting point in this analysis is a series of individual CAD drawings for each building in the fleet with spatial coordinates for all lines and nodes loaded into matrices within MATLAB®. A constrained Delaunay triangulation technique is then applied to automatically differentiate building fabric components such as walls, columns, windows, etc., their physical scale, and all interior zones within the building. Multiple floor plans are also automatically linked by layer information, and a series of logical steps are then followed to identify zone-to-zone interactions and exterior building fabrics. A number of generic thermal resistance/capacitance models capable of modeling the anticipated thermal responses of all building elements are defined. These are assigned to the appropriate elements of the building fabric and linked based on the aforementioned zone identification process. The overall result of this process is the automated generation of a thermal energy model for any specific building that is capable of accurately modeling its thermal physics. However, property information specifically relating to on-premise building elements is not automatically discernible from these CAD-based models. In order to address this deficit, typical material properties are assumed for each element of the building fabric in the first instance, and an inverse heat transfer approach is implemented based on a set of limited sensor data for the building in question. This process results in optimizing estimated parameters so that predicted thermal physics match that of measured sensor data. Overall, the paper describes the development of this automated procedure, presents indicative results of its application, and discusses some possible limitations as well as guidelines aimed at alleviating some of these limitations.

Topics: Heat transfer
Commentary by Dr. Valentin Fuster
2013;():V08AT09A040. doi:10.1115/IMECE2013-64519.

Thermal diffusivity is a thermophysical property that quantifies the ratio of the rate at which heat is conducted through a material to the amount of energy stored in a material. The pulsed laser diffusion (PLD) method is a widely used technique for measuring thermal diffusivities of materials. This technique is based on the fact that the diffusivity of a sample may be inferred from measurement of the time-dependent temperature profile at a point on the surface of a sample that has been exposed to a pulse of radiant energy from a laser or flash lamp. The standard approach to PLD is based on a simple model that produces an explicit relationship between the diffusivity and the time required for the temperature of the sample surface to reach a specified fraction of the peak temperature. However, the standard approach is based on idealizations that are difficult to achieve in practice, so models that represent a PLD measurement system with greater fidelity are desired.

Assessment of the impact of the approximations made in the development of the standard approach showed that neglect of the spatial and temporal variations of the input power leads to significant errors in measurement of the thermal diffusivity. The objective of this paper is to present the Distributed Source Finite Absorption model which represents the spatial and temporal variations in the pulse with greater fidelity.

The cost of the increased fidelity is an increase in the complexity of the algorithm used to determine values of the thermal diffusivity. A simple relationship between an easily determined characteristic of the measured temperature profile and the thermal diffusivity does not exist. Therefore, a new method of extracting values from measured time dependent-temperature profiles based on a genetic algorithm and on reduced order modeling has been developed. This paper also presents a numerical verification of this proposed new method for measuring the thermal diffusivity.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A041. doi:10.1115/IMECE2013-64554.

A meshless local Petrov-Galerkin (MLPG) method is proposed to obtain the numerical solution of nonlinear heat transfer problems. The moving least squares scheme is generalized, to construct the field variable and its derivative continuously over the entire domain. The essential boundary conditions are enforced by the direct scheme. The radiation heat transfer coefficient is defined, and the nonlinear boundary value problem is solved as a sequence of linear problems each time updating the radiation heat transfer coefficient. The matrix formulation is used to drive the equations for a 3 dimensional nonlinear coupled radiation heat transfer problem. By using the MPLG method, along with the linearization of the nonlinear radiation problem, a new numerical approach is proposed to find the solution of the coupled heat transfer problem. A numerical study of the dimensionless size parameters for the quadrature and support domains is conducted to find the most appropriate values to ensure convergence of the nodal temperatures to the correct values quickly. Numerical examples are presented to illustrate the applicability and effectiveness of the proposed methodology for the solution of heat transfer problems involving radiation with different types of boundary conditions. In each case, the results obtained using the MLPG method are compared with those given by the FEM method for validation of the results.

Topics: Heat transfer
Commentary by Dr. Valentin Fuster
2013;():V08AT09A042. doi:10.1115/IMECE2013-64558.

Natural convective heat transfer from a vertical isothermal cylinder mounted on a flat adiabatic base has been numerically studied. The cylinder has an exposed top surface. The cylinder is relatively very short, i.e., has a height that is equal to or less than the cylinder diameter. Both the cases where the cylinder is pointing upward and where it is pointing downward have been considered. The governing equations have been numerically solved using the commercial CFD solver ANSYS FLUENT©. Results have only been obtained for Prandtl number = 0.74. The mean heat transfer rates have been expressed in terms of a Nusselt number, consideration being given both to the heat transfer rate from the entire cylinder surface and to the heat transfer rates from the side and top surfaces of the cylinder. The effect of the dimensionless cylinder height–to–diameter ratio on the Nusselt number variation has been studied in detail.

Topics: Convection , Cylinders
Commentary by Dr. Valentin Fuster
2013;():V08AT09A043. doi:10.1115/IMECE2013-64772.

A laminar two-dimensional thermal-flow generated by multiple confined jets impinging on an isothermal plate is investigated numerically using the lattice Boltzmann method. The impinging plate is kept at a constant high temperature while a cold air is flowing through the jets. The effect of different parameters (Reynolds number (Re), and the ratio between the jets height (H) and jets width (W))on the hydrodynamics and thermal characteristics of the flow field is discussed. The Reynolds number is ranging from 50 to 400, and the (H/W) ratio is varying between 1 and 3W.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A044. doi:10.1115/IMECE2013-64786.

Local/State building codes mandate the supply of fresh air to classrooms. Most designs adhere to these requirements through mechanical HVAC systems. For buildings that depend upon natural ventilation in which fresh air is supplied through windows, care must be taken to account for ambient conditions, i.e., air temperature, humidity, and wind velocity and direction, that can strongly affect the amount of fresh air. For classroom with multiple windows the question is which windows to open at any given time. This paper describes the measurement of air flow in a simple classroom and the use of CFD simulation to predict the circulation of air with an aim of determining if such a simulation may be used to define optimal window opening schedules.

Topics: Air flow
Commentary by Dr. Valentin Fuster
2013;():V08AT09A045. doi:10.1115/IMECE2013-64973.

By minimizing the differences between measured and predicted transmissivity spectra, an inverse radiation model was developed to reconstruct temperature and species concentration from homogeneous gas media. The model was validated by retrieving temperatures and concentrations from experimental medium-resolution CO2 transmissivity data obtained by Bharadwaj and Modest [1, 2]. Optimal wavenumber ranges for CO2 transmissivity measured across a wide range of temperatures and concentrations were determined according to the performance of inverse calculations. Results indicate that the inverse radiation model works well and the inverse radiation technique is superior to thermocouples and flow meters for measurements of temperature and gas concentration.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A046. doi:10.1115/IMECE2013-65515.

The metal organic chemical vapor deposition (MOCVD) process is widely used to form a multi-layered structure with thin films for diverse semiconductor materials. The MOCVD process is the most promising method for manufacturing chips that are based on the compound semiconductor, but its technology is partly still insufficient. If a device, for example, lacks a non-uniformity related to the composition and thickness of the film, it decreases the reliability of the final product and affects the economics. To ensure that the equipment is competitive in the worldwide markets, a high reliability including the controllability of compositions is required for the equipment. In this study the CFD analysis was used to investigate the behavior of the process gas in a MOCVD reactor where the process gases including the component of the GaN films are injected as separated through a multi-module showerhead for eventually targeting multi-component films such as AlGaInN materials. After applying of Porous Media, a stabilization of process gas was confirmed from the results of pressure distribution.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A047. doi:10.1115/IMECE2013-65841.

A study was conducted to simulate the circulation patterns and heat transfer characteristics of flows in a square cavity during transition from laminar to turbulent mixed convection conditions using numerical techniques. The cavity under study is assumed to be filled with a compressible fluid. The bottom of the cavity is insulated and stationary where as the top of the cavity (the lid) is assumed to be stationary initially and then pulled at constant speed for times greater than zero. The vertical walls of the cavity are kept at constant but unequal temperatures. A two-dimensional, physics based mathematical model is adopted to predict the momentum and heat transfer inside this rectangular cavity. A standard two equation turbulence model is used to model the turbulent flow inside the enclosure and the compressibility of the working fluid is represented by an ideal gas relation. The numerical solution techniques adopted in this study is a hybrid one (implicit-explicit) where the conservation equations for the velocity, temperature, and pressure are solved using an implicit technique (Coupled Modified Strongly Implicit Procedure -CMSIP) whereas the equations for the standard K-ε turbulence model are solved using an explicit (MacCormack) technique. In both techniques, a second order accurate finite difference technique is used to discretize the governing equations. Then numerical experiments were carried out to simulate the unsteady flow and heat transfer characteristics of mixed convection flow inside a square cavity filled with air (Pr = 0.72) for different Richardson numbers in the range of 0.00868–0.03470; corresponding to Reynolds numbers ranging from 2000 to 4000, respectively, when the Rayleigh number was kept constant at 105. Vertical and horizontal temperature and velocity profiles were generated while the flow goes through transition from laminar to turbulent. Changes in wall heat flux were calculated and average Nusselt numbers were determined for each parametric study.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A048. doi:10.1115/IMECE2013-66029.

Research activities are ongoing for High performance light water reactor (HPLWR) with square double rows fuel assembly to develop nuclear power plants with the purpose to achieve a high thermal efficiency and to improve their economical competitiveness. However, there is still a big deficiency in understanding and prediction of heat transfer in supercritical fluids. This paper evaluates three-dimensional turbulent flow and convective heat transfer in a single-phase and steady-state sub-channel of HPLWR by using general computational fluid dynamics code, Ansys 14 Fluent. The major concern using supercritical water as work fluid is the heat transfer characteristics due to large variations of thermal properties of supercritical water near pseudo-critical line. In order to ensure the safety of operation in High performance light water reactor (HPLWR), heat transfer deterioration (HTD) must be avoided. Numerical results prove that the RNG k-e model with the enhanced near-wall treatment obtained the most satisfactory prediction and lead to satisfactory simulation results. The HPLWR Square fuel assembly has many square-shaped water rods, Out of four types of sub-channels; three sub-channels SC-1, SC-2 and SC-3 are investigated (adjacent to the side of the moderator flow channels (SC-1) (moderator tube and assembly gap), central sub-channels formed by four fuel rods (SC-2), adjacent to the corner of the moderator tube (SC-3). Since coolant flow distribution in the fuel assembly strongly depends on the gap width between the fuel rod and water rod, fuel rod pitch to diameter ratio 1.1–1.4 with 8mm diameter are considered for simulation. Sub-channel analysis clarifies that coolant flow distribution becomes uniform when the gap width is set to 1.0 mm. was less than 620°C. Effects of various parameters, such as boundary conditions and pitch-to-diameter ratios, on the mixing phenomenon in sub-channels and heat transfer are investigated. The effect of pitch-to-diameter ratio (P/D) on the distributions of surface temperature and heat transfer coefficient (HTC) in a sub-channel, it was found that HTC increases with P/D 1.1 first and then decreases with increasing P/D ratio. Apart from the basic geometry sub-channel, a square sub-channel with a wire-wrapped rod inside has been chosen to investigate the “wire effect”.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A049. doi:10.1115/IMECE2013-66060.

This study presents a more realistic approach to evaluate in-service performance of thin layers of materials such as thermal barrier coatings (TBCs) typically found in hot sections of air, land and sea based gas turbine engines. The results of this study can also be used to analyze thermal damage to biological tissues caused by lasers in the treatment of certain diseases. The governing differential equation for the DPL model, which is second order in time and space, is reduced to a system of first order equations by the introduction of an intermediate function. The system of equations is solved numerically using a new numerical scheme codenamed the Mean Value Finite Volume Method (MVFVM). The numerical method yields minimal numerical dissipation and dispersion errors and captures discontinuities in solution domains very well. The study further showed that for thin film structures subject to short time durations, the DPL model is a better model for heat transfer as it is suitable for both microscopic and macroscopic systems.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A050. doi:10.1115/IMECE2013-66155.

This paper presents the development of the three-dimensional flow architecture of conjugate cooling channels in forced convection with internal heat generation within the solid for an elliptical cooling channel configuration. The main objective was to optimise the configuration in such a way that the peak temperature was minimised subject to the constraint of the fixed global volume of solid material. The cooling fluid was driven through the channels by the pressure difference across the channel.

The structure had three degrees of freedom as design variables: elemental volume, channel hydraulic diameter and channel-to-channel spacing. The shape of the channel is allowed to morph to determine the best configuration that gave the lowest thermal resistance. A gradient-based optimisation algorithm was applied in order to search for the best optimal geometric configuration that improved thermal performance by minimising thermal resistance for a wide range of dimensionless pressure difference. The effect of porosities, applied pressure differences and heat generation rate on the optimal geometry was reported. There are unique optimal design variables for a given pressure difference. Results obtained show that the effects of dimensionless pressure drop on minimum thermal resistance were consistent with those obtained in the open literature.

Topics: Heat , Cooling , Optimization
Commentary by Dr. Valentin Fuster
2013;():V08AT09A051. doi:10.1115/IMECE2013-66264.

This research numerically investigates the heat transfer of water-Al2O3 nanofluids in a two dimensional sinusoidal wavy channel. Simulation studies are performed for fully developed flow conditions in a channel with eight waves. The temperature of the input fluid is taken to be less than that temperature of wavy walls. The governing continuity, momentum and energy equations are numerically solved using finite volume method based on SIMPLE technique. Numerical simulations were carried out for a Reynolds number ranging from 400 to 1600 and a nanofluid volume fraction, Ø where 0≤Ø≤8%. The effect of distance between channel walls are studied by varying Hmin/Hmax ratio from 0.3 to 0.5 for keeping wave length and wave amplitude values fixed. The effect of these parameters on local and average Nusselt numbers and heat transfer enhancement are presented and discussed. The results revealed that the addition of nano-particles can increase heat transfer significantly.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A052. doi:10.1115/IMECE2013-66265.

This paper presents heat transfer analysis of single horizontal bare tube and in-line arrangement of bare tube bundles in gas-solid (air-solid) fluidized bed and predictions are done by using Artificial Neural Network (ANN) based on the experimental data. Measurement of average heat transfer coefficient was made by local thermal simulation technique in a cold square bubbling air-fluidized bed of size 0.305m × 0.305m. Studies were conducted for single bare tube and bare tube bundles of in–line arrangement using beds of small (average particle diameter less than 1mm) silica sand particles and of large (average particle diameter greater than 1mm) particle (raagi and mustard). Within the range of experimental conditions influence of bed particle diameter (Dp), fluidizing velocity (U) were studied, which are significant parameters affecting heat transfer.

Artificial neural networks (ANNs) have been receiving an increasing attention for simulating engineering systems due to some interesting characteristics such as learning capability, fault tolerance, and non-linearity.

Here, feed-forward architecture and trained by back-propagation technique is adopted to predict heat transfer analysis found from experimental results. The ANN is designed to suit the present system which has 3 inputs and 2 outputs. The network predictions are found to be in very good agreement with the experimental observed values of bare tube heat transfer coefficient (hb) and Nusselt number of bare tube (Nub).

Commentary by Dr. Valentin Fuster

Heat Transfer and Thermal Engineering: Environmental Heat Transfer

2013;():V08AT09A053. doi:10.1115/IMECE2013-62233.

In this paper, orthogonal test design method and the CFD method were used to study the different building envelopes, and the outdoor environment of natural ventilation effect of single span of high temperature industrial workshop. Firstly, 18 ventilation models of workshop with heat source were constructed with orthogonal test design. Secondly, 18 ventilation models of workshop with heat source were simulated with CFD method. Finally, the order of the influencing factors on the ventilation of workshop was obtained through multiple index range analysis of the orthogonal experiment results according to the average temperature inside the workshop. Then the optimal combination of the best ventilation effect was selected. The research results can provide effectively theoretical basis for the future industrial plant ventilation design and optimization.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A054. doi:10.1115/IMECE2013-62774.

Personal ventilation (PV) strategy is increasing very rapidly in ventilating the indoor spaces. Compared to the traditional ventilation system, the use of PV system can provide several advantages such as: energy reduction, comfort and healthy environment. Previous study reported in earlier paper [Schiavon et al. 2010] indicated that the use of PV system may reduce the energy consumption substantially (up to 51%) compared to mixing ventilation. Additionally, healthy environment is assured in the PV system due to the direct supply of fresh “clean” air to the occupant face. In the current study, detailed assessment of PV system and displacement ventilation (DV) system in a cubicle workstation (office cubicle) is presented. This assessment is based on CFD simulations. Five ventilation cases have been studied on the office cubicle. One case is performing a DV system only; another is performing a PV system only; the remaining three cases are performing a combined of PV and DV system. These cases have been evaluated using the PMV and PPD comfort indices, developed by Fanger 1970 and 1982. The target was to achieve a ventilation case that satisfies the best comfort indices near the occupant in the office cubicle. The five cases conditions and the best case conditions are presented in this paper.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A055. doi:10.1115/IMECE2013-63304.

In this paper, the influence of various bench arrangements on the microclimate inside a two-span greenhouse is numerically investigated using three-dimensional Computational Fluid Dynamics (CFD) models. Longitudinal and peninsular arrangements are investigated for both leeward and windward opened roof ventilators. The velocity and temperature distributions at plant level (1m) were of particular interest. The research in this paper is an extension of two-dimensional work conducted previously [1]. Results indicate that bench layouts inside the greenhouse have a significant effect on the microclimate at plant level. It was found that vent opening direction (leeward or windward) influences the velocity and temperature distributions at plant level noticeably.

Results also indicated that in general, the leeward facing greenhouses containing either type of bench arrangement exhibit a lower velocity distribution at plant level compared to windward facing greenhouses. The latter type of greenhouses has regions with relatively high velocities at plant level which could cause some concern. The scalar plots indicate that more stagnant areas of low velocity appear for the leeward facing greenhouses. The windward facing greenhouses also display more heterogeneity at plant level as far as temperature is concerned.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A056. doi:10.1115/IMECE2013-63999.

Heat transfer characteristics of cool coating for building roofs in the tropical climate have been investigated by formulating a cool roof heat transfer (CRHT) model for transient heat flux through a cool-coated multi-layered roof (MLR). Furthermore, the impact of the cool coating on heat flux through roof was quantified by extending the CRHT model to estimate the equivalent thickness of uncoated roof required and the equivalent thermal insulation material thickness to be added over uncoated roof to achieve the same daily heat gain as for a cool-coated roof. It was observed that the impact of cool coating is much more significant for low R-value (5–15 cm2-K/W) roof materials, such as metal roofs, as compared to high R-value (>800 cm2-K/W) roof materials such as concrete, asphalt shingle, wood shingle, etc.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A057. doi:10.1115/IMECE2013-66347.

In the presented research, numerical modeling tools are applied to study relation between the moisture distribution and related stress and strain in a painted wooden desk. The research is motivated by a Case study analysis of the impact of indoor air relative humidity (RH) changes to the collection of mediaeval wooden panel paintings located in the Chapel of the Holy Cross at Karlstejn Castle. This problem is being investigated as one of the tasks of the European project Climate for Culture (http://www.climateforculture.eu/). In the analysis, CFD model of airflow movement and RH distribution in the chapel is linked with a Matlab script used to simulate moisture and stress/strain fluctuations related to RH changes in diurnal and annual cycles. The temperature and RH distribution in the room obtained by Fluent 3D CFD model of the chapel, which is generated in GAMBIT, are used as boundary conditions for the numerical computing of the moisture transfer and stress field implemented in the Matlab script.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A058. doi:10.1115/IMECE2013-66637.

The objective of this paper is to analysis the wind farm properties in suburban environment by Computational Fluid Dynamics (CFD) simulations. In order to do the simulation of a suburban environment, geometry model was built and mesh was generated by commercial software GAMBIT®. Simulation was conducted by FLUENT®. Parallel computing technique was applied in simulation. Simulation results showed different kinds of wind properties such as path lines, velocity distributions, turbulence intensity, etc., and it is also indicated that parallel computing is an appropriate way to conduct wind farm simulation [1].

Commentary by Dr. Valentin Fuster

Heat Transfer and Thermal Engineering: Heat and Mass Transfer in Biotechnology

2013;():V08AT09A059. doi:10.1115/IMECE2013-62436.

Kinetic (very rapid) vitrification (K-VF) is a promising approach for cryopreservation (CP) of cells but existing methods are not scalable due to the Liedenfrost effect (LFE), which substantially impedes the rate of cooling. Here, we compare 4 emerging approaches that discuss scalability and ultra-fast cooling, namely, cryogenic oscillating heat pipes (COHP), microstructured evaporation in thin films, K-VF in nanodroplets and thin film evaporation in microstructured with our methods of hyperfast cooling KrioBlastTM. We show that only KrioBlastTM can ensure hyper-fast rates of cooling by elimination of the LFE. The logistics and other aspects of practicality of 4 methods are also discussed.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A060. doi:10.1115/IMECE2013-63275.

Analytical study of bioheat transfer is of significant importance for a number of biomedical applications including cryopreservation of tissue and thermal therapy for cancer. A sound fundamental understanding of thermal behavior of tissue in response to an externally applied stimulus helps design effective therapies and protocols. This paper derives an analytical solution in a multi-layer two-dimensional structure with arbitrary, space-dependent heat generation occurring in each layer. This geometry effectively models multiple layers of skin, with heat generation due to cancerous cells in the basal layer. The Pennes bioheat transfer equation is solved for the multi-layer analytically, wherein the temperature in each layer is explicitly a function of space and the thermo-physical properties of the layer. The resulting analytical temperature profile agrees well with finite-element simulations and is also in good agreement with a previously published experimental study. Results derived in this work illustrate the effect of the presence of cancerous cells on the thermal profile of the skin. Further, the model helps to understand the effect of external cooling and heating stimuli.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A061. doi:10.1115/IMECE2013-65434.

The levitation (“hovering”) of a liquid droplet on the surface of the coolant such as liquid nitrogen (LN2) is a useful model for studying the Leidenfrost effecr (LFE), that is formation of a vapor film of boiling coolant around the surface of a relative,ly hotter sample, at cryogenic temperatures. Several models of the cryogenic droplet levitation (CDL) have been proposed but no experimental verifications had been proposed for this model in earlier papers. Utkan Demirci’s group has recently developed fast ice-free cooling (vitrification) of microdroplets formed by an ink-jet printer. The group proposed a combination of a theoretical model of film boiling on a hot sphere with the zone theory of non-isothermal kinetic ice propagation within an initially liquid levitating droplet, and they gave theoretical predictions and experimental evaluations of the CDL (Leidenfrost) time tLF of droplets hovering on the surface of LN2 [6]. Here, we report our own experiment results of verification of the data and predictions reported in [6] and describe a thermodynamical model that for elucidating the fate of the levitating droplets. This model adequately explains our experimental results on measuring tLF but almost predicts somewhat 4-fold departure from the numbers claimed by Demirci’s group. We also discuss possible flaws of the model and, especially, experimental claims presented in [6].

Commentary by Dr. Valentin Fuster
2013;():V08AT09A062. doi:10.1115/IMECE2013-66424.

Gold nanospheres (GNSs), biocompatible nanoparticles that can be designed to absorb visible and near-infrared light, have shown great potential in induced thermal treatment of cancer cells via Plasmonic Photothermal Therapy (PPTT) [3]. In this study, light induced heating of a water-based dispersion of 20 nm diameter GNSs was investigated at their plasmon resonance wavelength (λ = 520 nm). Temperature changes of the solution at the point of light irradiation were measured experimentally. A heat transfer model was used to verify the experimental data. The effect of two key parameters, light intensity and particle concentration, on the solution’s temperature was investigated. The experimental results showed a significant temperature rise of the GNS solution compared to de-ionized water. The temperature rise of GNS solution was linearly proportional to the concentration of GNS (from 0.25–1.0 C, C = 1×1013 particles per ml) and the light intensity (from 0.25 to 0.5 W cm−2). The experimental data matches the modeling results adequately. Overall, it can be concluded that the hyperthermic ablation of cancer cells via GNS can be achieved by controlled by the light intensity and GNS concentration. A novel component of this study is that a high power lamp source was used instead of a high power laser. This means that only low cost components were used in the current experimental set-up. Moreover, by using suitable filters and white light from the high power lamp source, it is possible to obtain light in many wavelength bands for the study of other nanoparticles with different plasmon wavelength ranges. The current results represtent just one example in this versatile experimental set-up developed. It should be noted, however, the plasmon resonance wavelength used in this study is not within the therapeutic window (750–1300 nm) [13]. Therefore, the GNSs used in this experiment are only applicable to the surface induced thermal treatment of cancer cells, for instance, in the skin.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A063. doi:10.1115/IMECE2013-66428.

The continued efforts in the biological community to optimize methodologies such as PCR and to characterize biological reactions and processes are motivating reductions in sample volume. There is a growing need for the detection of thermal phenomena in these small volumes, such as the heat released by recombination and the effective conductivities and capacities in extremely small fluidic regions. While past work has focused largely on heat transport in essentially bulk fluid volumes, there is a need to scale these techniques to the much smaller volumes of interest for biological and biomedical research.”

This work applies the 3ω measurement technique to μL volumes by using heaters with dimensions of 200–700μm in lengths and 2–5μm in widths. We investigate fluid samples of DI water, silicone oil, and a salt buffer solution to experimentally determine their temperature-dependent thermal properties from 25°C to 80°C. Validation is achieved through comparison of these values of thermal conductivity κ and volumetric heat capacity Cν to literature. The work also demonstrates the device capability to conduct temperature-dependent measurements down to pL droplet volumes by conducting a volume analysis given the dimensions of heaters used, independent of droplet boundary conditions. Sensitivity and uncertainty analyses based on these heater dimensions and surrounding material stack show the detection capabilities of these heaters, as they are optimally designed to maximize signal while accommodating the size restrictions of small volume droplets.

Commentary by Dr. Valentin Fuster
2013;():V08AT09A064. doi:10.1115/IMECE2013-66601.

Laptop computer has become increasingly popular over the past decade owing to its portable and high feature benefiting from the high integration chips densely packed inside. However, it also leads to intense heat generation, which will cause thermal discomfort even injury to human body. In fact, there are increasing cases reported regarding low temperature burning. This paper is aimed to demonstrate and evaluate the extreme thermal interaction between laptop computer and human body based on infrared (IR) imaging quantification. The whole surface temperatures of laptop were recorded and analyzed to detect the hot spot, which may cause potential thermal injury to the human skin. The maximum temperature of the exhaust air from the inner laptop was found to be up to 70.4°C for a double-cored laptop with full-loaded operation. This leads to a burning of hand skin even for short exposure time (5 minutes). Such injury would further be exacerbated by prolonged exposure time. In addition, a three dimensional simulation based on Pennes bioheat transfer model was used to investigate the temperature response of skin subject to thermal stimulation from desktop. The present study is expected to be valuable for a wide public concern regarding a better and safer laptop in the near future.

Commentary by Dr. Valentin Fuster

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