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A review of the effects and mitigation of frost with focus on air-source heat pump applications.

Number: 2123

Author(s) : MASHHADIAN A., ISMAIL T., BACH C. K., ALEXANDER A.

Summary

Air source heat pumps (ASHPs) are commonly used to provide thermal comfort for both residential and commercial purposes and are seen as a key technology for the decarbonization of the built environment. However, frost forms on the outdoor coil (evaporator) under low temperature conditions. Frost reduces the heat transfer rate and efficiency of the ASHP, requiring energy costly defrosting processes. The frequency and impact of these defrosting processes can be reduced through frost retardation as well as the optimization of the defrost process and its initiation.
This review presents methods for retarding the onset of frosting, including changing the ambient conditions, modifying the system, adjusting the outdoor coil design, and exploiting external sources. As frost grows on the heat exchanger surface, heat exchanger capacity degrades, eventually requiring frost removal. Direct and indirect methods for evaluating frost severity were identified and classified into direct and indirect methods. Various defrosting techniques can be employed with reverse cycle defrosting (RCD) being most popular for commercial and residential ASHPs, followed by hot gas bypass defrosting (HGBD).
Defrosting is vital to maintaining ASHPs performance with robustness and simplicity of the controls being most critical for practical applications. Time-based defrosting control strategies are simple approach but cannot adapt well to changing ambient conditions. Advanced methods targeting optimal defrost initiation and process control are presented. Finally, we recommend areas for future research to increase ASHPs efficiency and climatic application range.

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Pages: 10 p.

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Details

  • Original title: A review of the effects and mitigation of frost with focus on air-source heat pump applications.
  • Record ID : 30030476
  • Languages: English
  • Subject: Technology
  • Source: 2022 Purdue Conferences. 19th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2022/07/10

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