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 performance of both systems has been investigated experimentally and numerically. The effects of operating conditions (air temperature, water temperature, solar radiation intensity, etc.) 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.

Keywords

Main Subjects

References

[1] E. Hervás-Blasco, E. Navarro-Peris, J.M. Corberán, Closing the residential energy loop: Grey-water heat recovery system for domestic hot water production based on heat pumps, Energy and Buildings, 216 (2020) 109962.
[2] J. Fernández-Seara, C. Piñeiro, J.A. Dopazo, F. Fernandes, P.X. Sousa, Experimental analysis of a direct expansion solar assisted heat pump with integral storage tank for domestic water heating under zero solar radiation conditions, Energy Conversion and Management, 59 (2012) 1-8.
[3] X. Kong, P. Sun, S. Dong, K. Jiang, Y. Li, Experimental performance analysis of a direct-expansion solar-assisted heat pump water heater with R134a in summer, International Journal of Refrigeration, 91 (2018) 12-19.
[4] W.M. Duarte, T.F. Paulino, S.G. Tavares, A.A. Maia, L. Machado, Feasibility of solar-geothermal hybrid source heat pump for producing domestic hot water in hot climates, International Journal of Refrigeration, 124 (2021) 184-196.
[5] X. Kong, Y. Yang, M. Zhang, Y. Li, J. Li, Experimental investigation on a direct-expansion solar-assisted heat pump water heater using R290 with micro-channel heat transfer technology during the winter period, International Journal of Refrigeration, 113 (2020) 38-48.
[6] W.M. Duarte, T.F. Paulino, J.J. Pabon, S. Sawalha, L. Machado, Refrigerants selection for a direct expansion solar assisted heat pump for domestic hot water, Solar Energy, 184 (2019) 527-538.
[7] M. Masiukiewicz, M. Tańczuk, S. Anweiler, G. Streckienė, S. Boldyryev, Long-term climate-based sizing and economic assessment of air-water heat pumps for residential heating, Applied thermal engineering, 258 (2025) 124627.
[8] J.Y. Lee, T. Yim, Energy and flow demand analysis of domestic hot water in an apartment complex using a smart meter, Energy, 229 (2021) 120678.
[9] F. Velasco, M. Haddouche, F. Illán-Gómez, J. García-Cascales, Experimental characterization of the coupling and heating performance of a CO2 water-to-water heat pump and a water storage tank for domestic hot water production system, Energy and Buildings, 265 (2022) 112085.
[10] W. Xu, C. Liu, A. Li, J. Li, B. Qiao, Feasibility and performance study on hybrid air source heat pump system for ultra-low energy building in severe cold region of China, Renewable Energy, 146 (2020) 2124-2133.
[11] S. Bhadra, A. Mwesigye, Influence of control strategy on the energetic performance of an air source heat pump coupled with a solar air collector for domestic hot water in a cold climate, Renewable Energy, 244 (2025) 122682.
[12] A. Anastas, A. Mwesigye, Investigation of a Photovoltaic Thermal-Direct Expansion Solar-Assisted Heat Pump (PVT-DXSAHP) Collector with Different Photovoltaic Characteristics in Cold Climates, American Journal of Undergraduate Research, 22(1) (2025).
[13] V. Rezaee, A. Taghizadeh, Evaluating the impact of environmental indicators on thermal comfort for different climates of Iran using the PMV model, Amirkabir Journal of Mechanical Engineering, 57(1) (2025) (in persian).
[14] A. Moreno-Rodríguez, A. González-Gil, M. Izquierdo, N. Garcia-Hernando, Theoretical model and experimental validation of a direct-expansion solar assisted heat pump for domestic hot water applications, Energy, 45(1) (2012) 704-715.
[15] X. Kong, D. Zhang, Y. Li, Q. Yang, Thermal performance analysis of a direct-expansion solar-assisted heat pump water heater, Energy, 36(12) (2011) 6830-6838.
[16] Y. Kuang, K. Sumathy, R. Wang, Study on a direct‐expansion solar‐assisted heat pump water heating system, International journal of energy research, 27(5) (2003) 531-548.
[17] H. Safarzarzadeh, S. Fathollahi, Simulation Study on the Thermal Performance of a direct-expansion solar-assisted heat pump for water heating in Kermanshah climate, Modares Mechanical Engineering, 15(12) (2016) 232-242. (in persian)
[18] X. Sun, Y. Dai, V. Novakovic, J. Wu, R. Wang, Performance comparison of direct expansion solar-assisted heat pump and conventional air source heat pump for domestic hot water, Energy Procedia, 70 (2015) 394-401.
Amirkabir Journal of Mechanical Engineering
Volume 57, Issue 5
August 2025
Pages 589-610

Files

Share

How to cite

Statistics