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Development of a More Efficient Defrost Control System for Heat Pumps

[+] Author Affiliations
Emin Yilmaz

University of Maryland Eastern Shore

Paper No. IMECE2006-15142, pp. 463-470; 8 pages
  • ASME 2006 International Mechanical Engineering Congress and Exposition
  • Innovations in Engineering Education: Mechanical Engineering Education, Mechanical Engineering Technology Department Heads
  • Chicago, Illinois, USA, November 5 – 10, 2006
  • Conference Sponsors: Mechanical Engineering Education, Mechanical Engineering Technology Department Heads
  • ISBN: 0-7918-4781-0 | eISBN: 0-7918-3790-4
  • Copyright © 2006 by ASME


The purpose of this research project was to design a more efficient defrost control system for residential heat pumps. Defrost systems are used to melt the accumulated ice on evaporator coils of outdoor units. The purpose of the new control system is to prevent the initiation of defrost cycle when there is no substantial ice accumulation on the outdoor unit. Two of the envisioned ice accumulation sensing methods were (a). Increase in pressure loss across the evaporator coil and (b). Resistance change across two electrodes when ice bridges the electrodes. A differential pressure sensor was used to sense an increase in pressure loss across outdoor coil for this research project. Results indicate that, although maximum time interval of 90 minutes was used, about 55% of defrost cycles initiated were not necessary since there was no ice to melt. An ASYST based data acquisition system was used to monitor, measure and store key parameters. It is expected that with the new control system one can improve efficiency by about 3%. A similar project has been undertaken on a heat pump recently installed on our HVAC experimental unit as an undergraduate research project. Installation of temperature and humidity controlled enclosure, and thermocouples have been completed. Some results were reported here. If any additional progress is made, results of this project will be reported at the meeting.

Copyright © 2006 by ASME



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