Comparative feasibility study of two direct expansion solar water heater heat pump systems in Rasht climate

Document Type : Research Article

Authors

1 Faculty Member, Department of Mechanical Engineering, National University of Skills (NUS), Tehran, Iran.

2 Assistant Professor, Department of Electrical Engineering, Technical and Vocational University (TVU), Tehran, Iran

3 Associate Professor, Department of Mechanical Engineering, Technical and Vocational University (TVU), Tehran, Iran

Abstract

In this research, an experimental and numerical comparative study has been conducted on two systems: conventional heat pump (ASHP) and direct expansion solar water heater heat pump (DX-SAHP) for the potential of hot water production. The system (DX-SAHP) consists of a flat plate solar collector as an evaporator, a rotary hermetic compressor with R134a refrigerant, a capillary tube as an expansion valve, and a submerged finned spiral condenser and a 100-liter water storage tank. The simulation results were used to achieve optimal system design and determine the appropriate strategy for four operating conditions: sunny day, cloudy day, clear night, and cloudy night. The simulation results were used to achieve optimal system design and determine the appropriate strategy for four operating conditions: sunny day, cloudy day, clear night, and cloudy night. The effects of operating conditions have been analyzed and a comparison of performance under different operating conditions between the two systems has been made. The results show that under sunny day conditions, the coefficient of performance (COP) of the (DX-SAHP) system is significantly higher than that of (ASHP). Under cloudy day conditions, the coefficient of performance of both systems is almost the same, and under night conditions, especially under clear night conditions, (DX-SAHP) shows poor performance due to poor performance of convective heat exchange of solar collector-evaporator and radiant heat loss to the night sky.

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Amirkabir Journal of Mechanical Engineering
Volume 57, Issue 5
August 2025
Pages 589-610

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