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Experimental study of frost formation and various defrosting techniques on a microchannel evaporator in a real reversible air source heat pump system.

Number: 2125

Author(s) : GHADDAR D., CHETTIAR K., HAIDER S. A., LIU J., BOYINA K., MILJKOVIC N.

Summary

One of the primary concerns during the heating operation of air source heat pumps is the frosting phenomena on the evaporator's surface, which serves as the outdoor heat exchanger. In outdoor conditions characterized by low temperatures and high humidity, the water vapor in the air condenses and freezes on the external surface of the evaporator. Various factors, including air temperature, humidity, and surface temperature, influence frost formation on heat transfer surfaces. This frost formation increases heat resistance and air pressure drop, leading to the deterioration of the evaporator's performance and a reduction in the evaporation temperature of the refrigerant. Consequently, the specific volume increases, the mass flow rate decreases, and the overall heat capacity of the heat pump diminishes. Once the system performance reaches its minimum acceptable level, a defrost process is initiated to eliminate the frost layer and attempt to restore the performance at the start of the cycle. During the defrosting process, ice can be melted by reversing the cycle, using resistive heating methods, or through natural defrosting processes.
The current study offers an experimental comparison of frosting heat transfer rates, frosting cycle durations, and frost patterns on a microchannel evaporator within a vapor compression system using R134a refrigerant under different ambient conditions. Three distinct defrosting techniques are developed and implemented following the determination of full frosting on the evaporator, which was based on air side pressure drop data and microscopy analysis, aiming to evaluate the most effective defrosting technique.

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  • Original title: Experimental study of frost formation and various defrosting techniques on a microchannel evaporator in a real reversible air source heat pump system.
  • Record ID : 30032986
  • Languages: English
  • Source: 2024 Purdue Conferences. 20th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2024/07/17

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