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ASME Conference Presenter Attendance Policy and Archival Proceedings

2017;():V001T00A001. doi:10.1115/ICNMM2017-NS.
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This online compilation of papers from the ASME 2017 15th International Conference on Nanochannels, Microchannels, and Minichannels (ICNMM2017) 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presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.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

Two-Phase Flows

2017;():V001T03A001. doi:10.1115/ICNMM2017-5540.

Gas-liquid flow in microchannels has drawn much attention in the last years in research fields of analytics and applications such as oxidations or hydrogenations. High interfacial area leads to increased mass transfer and intensified reactions. Since surface forces are increasingly important on small scale, bubble coalescence is detrimental and leads to Taylor bubble flow in microchannels. To overcome this limitation, we have investigated the gas-liquid flow through nozzles and particularly the bubble breakup behind the nozzle. Two different regimes of bubble breakup were identified, laminar and turbulent with different mechanisms. Although turbulent breakup is not common in microchannels, its mechanisms were studied for the first time and can give new insight for two-phase flow mechanisms.

Commentary by Dr. Valentin Fuster
2017;():V001T03A002. doi:10.1115/ICNMM2017-5541.

The present study investigates the effects of tube roughness and wettability on oil-water flow regimes in mini channels. The tube material examined included borosilicate glass (i.e., e = 0.1 μm) and stainless steel (i.e., e = 5 μm). Flow patterns and pressure drop were measured and presented for different combinations of oil and water superficial velocities, 0.28–3.36 m/s and 0.07–5 m/s, respectively. Stratified, annular, intermittent, and dispersed flow regimes were observed in all tubes and between tubes, many similarities in flow regime emerged. Tube wettability affected flow regime and flow transition from stratified to annular and intermittent flows. Surface roughness had an observable effect overall flow regime and particularly on pressure drop measurements as stainless steel recorded higher pressure drops.

Commentary by Dr. Valentin Fuster
2017;():V001T03A003. doi:10.1115/ICNMM2017-5552.

In this paper a new microfluidic technique is proposed for ultra-high-throughput generation of micron-sized water droplets using a high-speed air. We use a 3D flow-focusing microchannel fabricated in PDMS by multilayer lithography process. The interaction of liquid and gas created three main flow conditions which are: Flooded, Dripping, and Jetting. We characterize the Jetting regime where a capillary jet surrounded by the air breaks up into uniform array of droplets. Frequency of generation and droplet size are reported for the jetting regime under different liquid and gas flows. It was possible to obtain 25μm diameter droplets and much higher frequencies (f≈120 kHz) compared to the state-of-the-art microfluidic systems. We believe the advantages of this platform enables many novel applications such as high-throughput screening of airborne targets and large-scale production of oil-free particles. The 3D structure of this device also eliminates the limitation of the conventional droplet-based microfluidic systems, namely clogging issues due to particle aggregation.

Commentary by Dr. Valentin Fuster

Evaporation, Boiling and Condensation

2017;():V001T04A001. doi:10.1115/ICNMM2017-5530.

As the need for efficient thermal management grows, pool boiling’s ability to dissipate high heat fluxes has gained significant interest. The objective of this work was to study the performance of pool boiling at atmospheric pressure using a dielectric fluid, HFE7000. Both plain and enhanced copper surfaces were tested, and these results were then compared to similar testing performed with water and FC-87. The enhanced surfaces utilized microchannels with porous coatings selectively located on different regions of the heat transfer surface. A maximum critical heat flux (CHF) of 41.7 W/cm2 was achieved here, which translated to a 29% CHF increase in comparison to a plain chip. A maximum heat transfer coefficient (HTC) of 104.0 kW/m2°C was also achieved, which translated to a 6-fold increase in HTC when compared to a plain copper chip. More notably, this HTC was achieved at a wall temperature of 38.4 °C. This HTC enhancement was greater than that of water and FC-87 when using the same enhanced surface. The effect of sintering location was found to have a similar effect on CHF with HFE7000 in comparison with water. The effect of microchannel size was shown to have similar effects on CHF when compared with FC-87 and water. From the results found here, it is concluded that the employment of selectively sintered open microchannels with HFE7000 has significant potential for enhanced heat dissipation in electronics cooling applications.

Commentary by Dr. Valentin Fuster
2017;():V001T04A002. doi:10.1115/ICNMM2017-5531.

A typical pool boiling curve relating the heat flux and wall superheat is often used to quantify the efficacy of the engineered surfaces. Surface enhancements promoting nucleation activity, wicking, roughness and microlayer partitioning have shown remarkable enhancements in CHF and HTC. The boiling curve for these surfaces show an increase in wall superheat with an increase in heat flux. However, recently developed surfaces using the concept of separate liquid-vapor pathways and enhanced macroconvection have shown a reverse trend where an increase in heat flux is accompanied by decreasing wall superheats. This counter intuitive trend in the boiling curve characteristics is called as boiling inversion in this work. The macroconvection heat transfer is identified as the contributing mechanism to the boiling inversion trend. The vapor-stream induced flow transition and the impinging liquid jet characteristics is quantitatively explained through analytical models available in literature. Furthermore, two surfaces exploiting this mechanism is also demonstrated in this work which sheds light on the interplay mechanisms.

Topics: Vapors , Pool boiling
Commentary by Dr. Valentin Fuster
2017;():V001T04A003. doi:10.1115/ICNMM2017-5535.

Microstructures on boiling surfaces had been adopted to study heat transfer enhancement mechanism because of its controllability of precise geometries by MEMS techniques. In addition, several bubble-inducing surfaces such as porous or hydrophobic surfaces were verified to be combined with microstructures for further enhancement of cooling efficiency. In this research, microstructures with porous and dual-wettability (Janus) were fabricated by soft-lithography with replicating molds. In saturated pool boiling at atmospheric pressure, the porous and Janus microstructures increased the heat transfer coefficient by 50% over that of plain-cylindrical microstructures. The increase occurred because the porous and wettability-controlled structures favored vigorous bubble generation, and supported high contact line density, which is strongly related to effective cooling through the near-bubble region.

Commentary by Dr. Valentin Fuster
2017;():V001T04A004. doi:10.1115/ICNMM2017-5537.

In this study, a computational model for the evaporation from a sessile liquid droplet fed from the center to keep the diameter of the droplet constant is presented. The continuity, momentum and energy equations are solved with temperature dependent thermo-physical properties using COMSOL Multi-physics. At the surface of the droplet, convective heat and evaporative mass fluxes are assigned. Since the flow field is affected by evaporative flux, an iterative scheme is built and the computation is automated using COMSOL-MATLAB interface. Correlations are implemented to predict the convective heat transfer coefficients and evaporative flux. Three different wall temperatures are used in simulations. The results show that the flow inside the droplet is dominated by buoyancy when the effect of the thermo-capillarity is neglected. The resulting flow generates a circulation pattern emerging from the entrance to the apex, along the surface of the droplet to the bottom heated wall and back to the entrance.

Commentary by Dr. Valentin Fuster
2017;():V001T04A005. doi:10.1115/ICNMM2017-5555.

This paper investigates an approach to collect evaporated water from a moist air stream, a scenario found in many power plant cooling towers which utilize evaporation to cool, thereby resulting in evaporative water losses. For example, a 500 MW power plant may lose about 27m3/h (7133 gal/h) of water to evaporation during operation. When a cooled surface is placed in a warm humid environment, water condenses on the surface. The condensed liquid forms a thermal resistance, thereby reducing the condensation rate and water collected. The concept presented in this paper is to vibrate the cooled surface, thereby rapidly removing more droplets than gravity alone. With forced movement and through droplet coalescence, new droplets can nucleate in the space created by departing water droplets. Droplet nucleation, coalescence, and departure were investigated on vibrating and stationary Teflon films (contact angle 105°) in an environmental chamber at 30°C and 50% RH. Film vibrations of approximately 100 Hz were investigated. Droplet departure diameters were approximately 2–3 mm diameter on the vibrating surface and 6 mm on the stationary surface.

Topics: Condensation , Drops
Commentary by Dr. Valentin Fuster
2017;():V001T04A006. doi:10.1115/ICNMM2017-5574.

Copper pool boiling surfaces are tested for pool boiling enhancement due to femtosecond laser surface processing (FLSP). FLSP creates self-organized micro/nanostructures on metallic surfaces and creates highly wetting and wicking surfaces with permanent surface features. In this study two series of samples were created. The first series consists of three flat FLSP copper surfaces with varying microstructures and the second series is an open microchannel configuration with laser processing over the horizontal surfaces of the microchannels. These microchannels range in height from 125 microns to 380 microns. Each of these surfaces were tested for pool boiling performance. It was found that all the processed surfaces except one resulted in a decrease in critical heat flux and heat transfer coefficient compared to an unprocessed surface. It was found that the laser fluence parameter had a significant role in whether there was an increase in CHF or HTC. A cross sectioning technique was employed to study the different layers of the microstructure and to understand how FLSP could have a negative effect on the CHF and HTC. It was found that a thick oxide layer forms during the FLSP process of copper in an open-air atmosphere. The thickness and uniformity of the oxide layer is highly dependent on the laser fluence. A low fluence sample results in an inconsistent oxide layer of nonuniform thickness and subsequently an increase in CHF and HTC. A high laser fluence sample results in a uniformly thick oxide layer which increases the thermal resistance of the sample and allows for a premature CHF and decrease in HTC.

Topics: Copper , Lasers , Pool boiling
Commentary by Dr. Valentin Fuster

Electronics Cooling and Heat Pipes

2017;():V001T05A001. doi:10.1115/ICNMM2017-5523.

The present work represents a 2-D numerical investigation of forced convection heat transfer over three electronic blocks (silicon chip) in an inline arrangement with elliptical shaped vortex generators (VG-copper made) placed on top of the channel, for a range of Reynolds numbers. The block is prescribed with a 1,000 W/m2 heat flux due to heating of the electronic components installed in the CPU casing. The results show that, vortex generators could effectively enhance the heat transfer in the channel. Subsequently, the effects of Reynolds number (from 500 to 1050), the number of vortex generators (baseline, 1, 2 and 3), aspect ratio of heated block (0.125, 0.15, 0.22), and aspect ratio of vortex generators (0.3125, 0.4, 0.5) on the heat transfer and fluid flow characteristics are examined. The characteristics of the performance parameters are studied numerically with the aid of computational fluid dynamics (CFD). The 3 VG demonstrates nearly 28.35% enhancement of Nusselt number compared to the 1 VG case at Re = 479. The change in pressure drop is less at low Reynolds number compared to higher Reynolds number respective to other parameters. Increasing the aspect ratio of the block increases the convection coefficient while decreasing aspect ratio of VG increases heat transfer coefficient. This enhancement is less significant for the third block as the cooling effect is predominant close to the channel inlet. Increasing consecutive distance between the blocks, enhances the heat transfer coefficient with the penalty of additional pressure drop. However, parametric studies are conducted for the maximum heat transfer enhancement.

Commentary by Dr. Valentin Fuster
2017;():V001T05A002. doi:10.1115/ICNMM2017-5529.

The efficient cooling of servers in data center offers unique challenge to reduce the worldwide energy consumption and fluid inventory. The presented work addresses the great potential of a thermosiphon system using two-phase heat transfer process which improves the efficiency of the system by significantly improving the heat dissipation ability. The latent heat transfer is more effective than sensible heat. However, the system performance is limited by Critical Heat Flux (CHF) and Heat Transfer Coefficients (HTC). An increase in CHF offers wide temperature operating range while HTC defines the efficiency of the process. In the current design of the cooling solution, a manifold with a taper is employed over the heater surface to guide vapor away from the surface along the flow length. The incoming liquid flows over the heating surface unobstructed developing separate liquid-vapor pathways. A 6° taper manifold is analyzed with HFE7000 as the working fluid. The performance of thermosiphon loop is evaluated for three different liquid volumes resulting in three different liquid heads available in the thermosiphon loop. The respective heat flux and HTC are compared. The maximum heat dissipation was observed for 325ml liquid with a microchannel chip resulting in a CHF of 42.1W/cm2 at a wall superheat of 17.8°C. The observed performance data shows that thermosiphon loop is an eligible replacement for conventional single-phase cooling techniques used for CPU cooling in data centers.

Commentary by Dr. Valentin Fuster
2017;():V001T05A003. doi:10.1115/ICNMM2017-5550.

This paper describes extended experiments on a pulsating heat pipe (PHP) fabricated by using a 3-D printer and a graphene-laden PLA (PolyLactic Acid) filament. Water was used as a working fluid. To maintain airtightness, the 3-D printed PHP was electroplated by copper since the graphene in the filament allows electric currents to pass through. The PHP had ten square channels. A cross section and a length of the square channel were 1.5 mm × 1.5 mm and 80 mm, respectively. Ends of each channel were connected to form a single serpentine channel. A filling ratio of the working fluid was 50%. In experiments, an evaporator section of the PHP was heated by a heater and a condenser section was cooled using a water-cooling jacket. The heater power was increased stepwise from 2.0 W to 7.0 W while the cooling water temperature and its flow rate were maintained at 4.0 °C and 0.25 LPM, respectively. Transient temperature distributions of the PHP were measured by K-type thermocouples. From the experimental results, steady-state two-phase heat transport operation of the PHP was confirmed for the heater power between 3.0 W and 6.0 W. Moreover, the present experimental results were compared with the previous ones, where ethanol was used as the working fluid. It was also confirmed that the thermal resistance of the PHP with ethanol was slightly smaller than that with water.

Commentary by Dr. Valentin Fuster

Electrokinetic Flows

2017;():V001T06A001. doi:10.1115/ICNMM2017-5501.

Electro-kinetic manipulation Janus particles and droplets has attracted attention in recent years due to their potential application in microfluidics. Due to the presence of two different zone on the surface of particles with different charge distribution, the motion of the Janus particles are quite different than the that of regular particles. Therefore; the fundamental understanding of this motion is the key element for the further development of the microfluidic systems with Janus particles. In present study, electro-kinetic motion of Janus droplets inside a micro-channel is modeled using boundary element formulation. 2D formulation is verified against the reported experimental data in the literature. Results show that the 2D boundary element formulation is successful for the prediction of the electrophoretic velocity of the Janus droplets. The current formulation has a potential to model non-spherical particles and to study particle-particle and particle-wall interactions.

Commentary by Dr. Valentin Fuster

Energy Applications of Micro- and Nano-Scale Devices

2017;():V001T07A001. doi:10.1115/ICNMM2017-5524.

Microscale heat and fluid flow in macro geometries have been made practical in terms of cost and fabrication, by superimposing two macro geometries which are fabricated using readily-available CNC machining methods. Wavy-profile has been proposed to enhance heat transfer performance in the microchannel owing to the simplicity of geometry and feasibility to be fabricated using simple turning process. Experimental studies were conducted on single-phase, forced convective heat transfer using water as the working fluid for the Reynolds number range of 1300 to 4600, for a constant heat flux of 53.0 W/cm2. Three sinusoidal waves with different wavelength and same amplitude are studied to examine the effect of the total number of waves on the heat transfer and hydrodynamic performance within constant microchannel length. The maximum performance index, which evaluates heat transfer performance per unit pumping power, is 1.39, achieved by wavy profile with the shortest wavelength at Reynolds number of 2800. The performance index for all the enhanced microchannels peaks at the Reynolds number range of 2500 to 2800. Beyond that, the performance index is not a strong function of the wavelength. At lower Reynolds numbers, profile with the shortest wavelength achieves substantially higher performance indices, as the increment in pressure drop is accompanied by a comparable increment in heat transfer. Future work includes the introduction of correlations for the implementation of such geometries in industrial heat exchangers.

Commentary by Dr. Valentin Fuster
2017;():V001T07A002. doi:10.1115/ICNMM2017-5556.

Water management is a critical component of extracting optimum performance and efficiency from polymer electrolyte membrane (PEM) fuel cells. During fuel cell operation, a balance needs to be maintained between excess water blocking the reactant pathways through the gas diffusion layer, and the requirement for membrane hydration. The ionic conductivity through the membrane depends strongly on the hydration of the membrane.

The reactant gases in a PEM fuel cell are supplied through a humidification system to maintain appropriate levels of hydration in the membrane. The removal of the anode humidifier would significantly reduce the balance of plant costs and reduce the volume required for the fuel cell in an automotive setting. However, removing the anode humidification system could have adverse effects on membrane hydration and on fuel cell performance.

In this study, the anode humidification was varied and the cell performance and the membrane resistance were monitored. Synchrotron X-ray radiography was conducted simultaneously to visualize the water distribution in the membrane, the gas diffusion layer, and the associated interfaces. It was observed that the anode humidification had a strong impact on the performance of the fuel cell, with the dry condition leading to voltage instability at a current density below 1.0 A/cm2. The membrane water content was observed to decrease with increases in operating current density.

Commentary by Dr. Valentin Fuster

Thin Film, Interfacial Phenomena, and Surface Tension Driven Flows

2017;():V001T08A001. doi:10.1115/ICNMM2017-5512.

Controlling the wetting property of the surface present a major challenge but at the same time, it open the possibility of designing surfaces customized for particular applications. For example, allowing self-cleaning surfaces when the surface presents a hydrophobic state with high static contact angle and low contact angle hysteresis. In this work, the effect on the wetting property of patterned surfaces with Si microcones has been studied. It was observed that the height of the structure and center-to-center distance are controlling the wetting property of the surface. Three different wetting states (Cassie-Baxter state, the Wenzel state, and the sunny-side-up state) and the corresponding transition between the states were observed. A sharp Cassie-Wenzel transition was triggered with decreasing the area fraction of the surface.

Topics: Wetting , Silicon
Commentary by Dr. Valentin Fuster
2017;():V001T08A002. doi:10.1115/ICNMM2017-5545.

Bubble generation is a very dynamic process including surface forces with fluid flow and structure interaction on short time and length scales. This study describes interaction effects during bubble generation in combination with bubble flow through a nozzle for redispersion purpose. At certain flow velocities and phase ratios, liquid jets within gas bubbles have been observed in microchannels, which origin from the rear tip of the bubble cap and penetrate through the whole bubble. The penetration of the filament or thread leads to bubble surface corrugation and causes bubble breakup, when the opposite cap of the bubble is hit. In the case of micronozzles behind the contact element, jet formation within the bubble is also caused by another bubble leaving the micronozzle and probably leading to a pressure disturbance acting on the just generated bubble. First data indicate major influence parameters in jet formation; however, systematic investigations are following.

Commentary by Dr. Valentin Fuster
2017;():V001T08A003. doi:10.1115/ICNMM2017-5557.

In this paper, the effect of Si sub-micron tapered pillars on the Leidenfrost point of water droplets at different impact velocities is presented. In the Leidenfrost regime, the low thermal conductivity of the vapor layer deteriorates the heat transfer performance. Micro and nanostructured surfaces can significantly shift the Leidenfrost point towards higher temperatures. To determine this point, the droplet lifetime method was employed. The cooling performance was discussed in terms of the droplet evaporation time and the Weber number. It was observed that Si sub-micron tapered pillars can shift the Leidenfrost point for all the Weber numbers investigated (1–60). The displacement of the Leidenfrost point is enhanced by increasing the droplet impact velocity.

Commentary by Dr. Valentin Fuster

Surface Engineering for Phase Change Heat Transfer

2017;():V001T09A001. doi:10.1115/ICNMM2017-5533.

This paper focuses on experimental studies of boiling heat transfer on surfaces with reentrant tunnels and pores. Three structured surface which have same tunnel width and height but different pore diameter, have been developed for enhancement boiling heat transfer. The experimental studies were carried out for the structured surfaces using distilled water at atmospheric pressure. The narrow reentrant tunnels are parallel to each other and have 3 mm width, 4 mm height. A number of pores whose diameter 1.5 and 2.0 mm were machined on lateral surfaces of tunnels. The surfaces were termed according to their geometric specifications as 3.0W-30-30, 1.5D-3.0W-30-30, 2.0D-3.0W-30-30. D and W capitals represent pore diameter and tunnel width, respectively. 30-30 part of name shows the dimension of square surface. The tunnels were used to increase area of heat transfer and active nucleation sites of vapor bubbles. In addition, sufficient amount of liquid must be supplied and vapor bubbles should be released fast from the boiling surface before they merge on the surfaces under conditions especially with high heat fluxes. Therefore, it was considered that pore structures would help for fluid transition hence the bubble frequency will increase. Pool boiling experiments were held to determine the performance of surfaces in different range of heat fluxes. Besides, high-speed visualization studies were conducted with high speed camera to observe behavior of nucleation of vapor bubbles. Amongst different geometry sizes the surface which has 1.5 mm of pore diameter (1.5D-3.0W-30-30) demonstrated the best nucleate boiling performance at high heat fluxes. However, the pored ones without pores has higher augmentation than pored structures at low heat fluxes. Thus, it is concluded that pored structures caused active nucleation sites to decrease under low heat fluxes.

Commentary by Dr. Valentin Fuster
2017;():V001T09A002. doi:10.1115/ICNMM2017-5562.

Condensation phenomena are important for several engineering fields including HVAC, refrigeration, distillation/desalination of water, dehumidification, aerospace, and water harvesting applications. In this work, Microsphere Photolithography (MPL), a low-cost, bottom-up fabrication technique, was used for fabricating a silica nanopillar surface (0.7 μm to 1.2 μm pillar diameters in a 2 μm hexagonal close packed array) on silicon. Condensation experiments on the surface was studied under the influence of environmental factors (ambient temperature and relative humidity) and substrate characteristics (topology and temperature). Droplet growth dynamics and size distribution were explored for condensation on a plain silicon substrate and a fabricated hydrophilic nanopillar substrate at different relative humidities (40% and 60%) at a surface temperature of 5°C. It was revealed that the nanopillar surfaces have a profound impact on condensation behavior. Small coalescence dominated on the silicon substrate as opposed to the nanopillar substrate, where extensive pinning deters the merging of droplets until it touches neighboring droplets. The change in condensation dynamics creates favorable conditions for collection of water.

Commentary by Dr. Valentin Fuster

Modeling and Simulation

2017;():V001T11A001. doi:10.1115/ICNMM2017-5563.

Naonofluidics is increasingly attracting more attention for their wide range of potential applications such as water desalination and purification, biosensing, osmotic energy conversion, drug delivery and DNA analysis. It is critical to understand the behavior of the water fluid in nanochannels in order to better design nanofluidic-based systems for these applications. Most applications use Carbon Nanotubes (CNT), boron nitride nanotubes, graphene and graphene oxide. CNTs are good pore models for studying the transport of gases and liquids through nanoporous materials to design ultrafiltration devices and energy efficient water filters. It should be mentioned that fluids confined in nanoscale tubes exhibit significantly different behaviors compare to fluids in the macroscale and microscale. As experimental study in nanoscales is still a challenging task facing scientific society, different numerical technologies such as Molecular Dynamics (MD) method are becoming powerful tools for understanding the fluid behaviors at molecular level in nanofluidics. In the present study, MD simulation method, which is based on Newton’s second law, is employed to study the water flow through smooth CNT. The effect of CNT diameter on density and velocity profiles are investigated. Our results show that by increasing the diameter of CNT, the results are approaching to the continuum condition.

Commentary by Dr. Valentin Fuster

Mixing, Mass Transfer and Chemical Reactions

2017;():V001T13A001. doi:10.1115/ICNMM2017-5536.

The purpose of this study is presenting an active micro-mixer, which is based on AC electro-osmotic flow driven on 3D micro wires. In order to solve governing equations of AC electroosmosis, a commercial software COMSOL Multiphysics® is implemented. Different wire configurations with various imposed electric fields and flow rates are tested for evaluating mixing efficiencies. The analyses show that mixing performance is significantly improved by number of the wires as well as wire orientation. It is also revealed that the degree of mixing can also be controlled by the tuning of the applied voltage for a given flow rate.

Commentary by Dr. Valentin Fuster
2017;():V001T13A002. doi:10.1115/ICNMM2017-5538.

Gas-liquid reactions in microstructured devices have recently gained much attention in scientific research and industry. Enhanced heat and mass transfer can be employed to overcome mass transfer limitations in gas-liquid reactions. Helically coiled capillaries can further increase mass transfer due to Dean vortices, which narrow the residence time distribution, too. In this work, a colorimetric technique is implemented in order to visualize local mass transfer phenomena and concentration gradients of gas-liquid reactions in straight and helically coiled capillaries. The method enables on-line and non-invasive investigation of mass transfer and chemical selectivity in microchannels with high spatial resolution. Straight and helically coiled capillaries are fabricated from FEP tubes with inner diameter of 1.6 mm. Bubbles are generated by a hypodermic needle, which is placed in the center of the FEP tube generating a stable slug flow. Total volumetric flow rate is varied from 1.6 to 6.5 mL/min and volume ratios of gas/liquid flow from 0.17 to 6.0. Selectivity experiments are performed with the consecutive oxidation of leuco-indigo carmine.

Topics: Mass transfer
Commentary by Dr. Valentin Fuster
2017;():V001T13A003. doi:10.1115/ICNMM2017-5539.

Reaction calorimetry is one of the most important steps in designing chemical reactors. This contribution describes a continuously operated micro calorimeter using Seebeck elements for microreactors made of PVDF-foils. Seebeck elements allow for local and temporal resolution of heat flux profiles. Various calibration methods for the Seebeck effect based heat flux sensors are presented. Here, the direct correlation between measured thermoelectric voltage and heat flux is found to be the most promising one. Commissioning of the calorimeter and validation of its performance are done by means of heat transfer measurement of warm water and an acid base reaction. Obtained reaction enthalpy values of the neutralization reaction of acetic acid and sodium hydroxide agree very well with literature data. The progression of the reaction can be followed optically using phenolphthalein as color indicator and can be compared to measured data. Heat profiles over the course of the microreactor were shown and checked for consistency. Consequently, this approach helps to characterize reactors and aids reactor development.

Commentary by Dr. Valentin Fuster

Transport in Membranes and Nanofluids

2017;():V001T15A001. doi:10.1115/ICNMM2017-5567.

There has been a rapidly increasing attention to study nanofluidic devices due to their broad potential applications such as water desalination and purification, biosensing and energy saving. CNTs are often used to achieve the transport of gases and liquids in the ultrafiltration devices and energy efficient water filters. In this study, the water flow inside a CNT which is connected by two reservoirs at the two ends of nanotube is investigated. Two movable wall pistons of graphene are used to drive the water molecules through the CNT. Our results show that the velocity profile in the nanotube is similar to a plug flow instead of a fully developed flow and a large pressure difference is required between two reservoirs to drive the water flow in the system. Also, the local pressure distribution and mass flow rate in the CNT is analyzed in details.

Commentary by Dr. Valentin Fuster

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