Water Heating and Operational Mode Switching Effects on the Performance of a Multifunctional Heat Pump

Abstract

In this study, a multifunctional air and water source heat pump system was developed with a parallel refrigerant piping arrangement, which possessed six operational functions: space cooling (SC), space heating (SH), water heating (WH), water cooling (WC) and two composite operational modes. The two composite operational modes were the SC/WH mode and the SH/WH mode. The performance of the multifuctional heat pump system under different ambient conditions was investigated based on the testing standards of CNS 14464 and CNS 15466. In this study, the effect of the direct water heating (DWH) and circulating water heating (CWH) methods on the performance was investigated. It was found that the water heating performance of the system by the DWH method is better than that of the system by the CWH method. The water heating capacity and COPw,h of the DWH method can be improvement by 2.6% to 22.1% and 2.9% to 50.8%, respectively. Moreover, this study developed a refrigerant pressure balance method to achieve an effective steady state of the refrigerant pressure after operational mode switching. By the refrigerant pressure balance method, the required time to attain the steady state could be greatly reduced—by 50%. However, the deviation of the refrigerant mass flow rate between the refrigerant pressure balance method and the refrigerant pump down method after operational mode switching ranged from 0.15% to 7.6%.

Performance Analysis of High-temperature Two-stage Compression Heat Pump with Vapor Injection Dynamic Control

“…The heat pump has the advantages of little pollution, easy control, and high heating efficiency, and is considered to be a preferable heating method for space heating and sanitary water generation. (4) However, for the applications of the heat pump in industry, high-temperature water in the temperature range from 60 to 90 ℃ is sometimes necessary in dehumidification processes, food processing, and water preheating for a steam boiler. Because of the high compression ratio in the compression process of the high-temperature heat pump, a two-stage compression heat pump system with an economizer is sometimes employed to improve the operational efficiency of the system.…”

“…Vapor injection technology has been applied to the two-stage compression system to reduce the operational temperature of the compressor, increase the subcooling degree of the refrigeration cycle, and further enhance the performance of the system. (4) Regarding the development of vapor injection technology in the literature, Wang et al (5) investigated the effect of the vapor injection pressure on the performance of a multistage compression system. To reduce energy use, they suggested that the compression ratio of both compression stages should be the same for a two-stage compression system.…”

Performance Enhancement of a Sludge Continuous Feed Heat Pump Drying System by Air Deflectors and Auxiliary Cooling Subsystems

“…However, several disadvantages of using these combustion fuels have to be considered, including their low burning efficiency, high operational cost and carbon dioxide emissions. To address this problem, meet energy-saving goals and reduce carbon emissions, heat pump drying systems with high operating efficiency, low operational cost and low environmental impact have been gradually adopted [2][3][4][5].…”