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ABSTRACT
An experimental study was conducted on the optimal charge of carbon dioxide in water–water heat pump systems (WWHPSs) with and without an internal heat exchanger (IHX). An appropriate carbon dioxide charge standard was obtained from the experimental results. All tests were conducted with the inlet and outlet water temperatures set to 12°C and 7°C in the evaporator, respectively and 20°C and 55°C in the gas cooler, respectively. During the tests, the evaporation temperature was 0°C. The coefficient of performance of cooling (COPc) and coefficient of performance of heating (COPh) increased by 8.3% and 0.7% in the WWHPS with an IHX compared with the WWHPS without an IHX. Under the test conditions, the optimal carbon dioxide charges with and without an IHX were found to be 2.0 kg and 2.25 kg, respectively. The test results show that the optimal carbon dioxide charge decreases by 11.1% when an IHX is included in the WWHPS.
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Notes on contributors
Zhili Sun
Dr Zhili Sun is a Lecturer at the Department of Refrigeration and Air-conditioning, Tianjin University of Commerce (TJCU). He obtained his B.Sc. degree in Building Environment and Energy Engineering from the Hebei Jianzhu University in 2007, and his M.Sc. degree in Refrigeration and Cryogenic Engineering from the TJCU in 2010, and his D.Sc. degree in Engineering Thermo-Physics from the Tianjin University in 2014. His research interests include energy saving and optimisation of refrigeration system, the scientific problems of equal mass flow distribution of two-phase fluid and heat transfer enhancement technology.
Shengchun Liu
Dr Shengchun Liu is an Associate Professor at the TJCU. He graduated from the Tianjin University in 2006, went to the West Virginia University in the United States, LMT Laboratory/ENSC in Paris and The University of Tokyo to be a Visiting Scholar. Now he is a member of heat and mass transfer young society in China. His research works focus on the heat and mass transfer, phase change mechanism, refrigeration system optimisation and energy saving, heat transfer and heat exchange study on refrigeration and air-conditioning systems and performance study of natural refrigerants.
Youcai Liang
Dr Youcai Liang is a Lecturer at the Department of Refrigeration and Air-conditioning, the TJCU. He graduated from the Tianjin University. His research interests include energy saving, optimisation of refrigeration system and organic rankine cycle (ORC).
Mengjie Song
Dr Mengjie Song is an Associate Professor at the Department of Energy Engineering, and “One Hundred Young Talents” of the Guangdong University of Technology (GDUT). He graduated from the Hunan University, Harbin Institute of Technology and The Hong Kong Polytechnic University, respectively. His research interests include frosting and defrosting for air source heat pump (ASHP) unit, indoor thermal comfort, thermal characteristic stability of phase change materials (PCMs), and fin surface treatment for heat transfer enhancement. On the topic of frosting and defrosting for ASHP unit, he had nearly eight years' research experience, and defined a series of phenomenon, such as uneven frosting, even frosting, frosting evenness value, uneven defrosting, and defrosting evenness value.
Jianghe Guo
Mr Jianghe Guo obtained his B.Sc. degree in Building Environment and Energy Engineering from the Hebei Jianzhu University in 2014, and his M.Sc. degree in Refrigeration and Cryogenic Engineering from the TJCU in 2016. Now, he is an Engineer of the Zhejiang King Co Ltd.