Visualization Study on Oil Return Characteristics of Vapor Compression Heat Pump System

Chuhao Tang, Zhanfeng Huang and Tingxun Li ()
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Chuhao Tang: School of Intelligent Systems Engineering, Sun Yat-sen University, West Xingang Road 135, Guangzhou 510275, China
Zhanfeng Huang: School of Intelligent Systems Engineering, Sun Yat-sen University, West Xingang Road 135, Guangzhou 510275, China
Tingxun Li: School of Intelligent Systems Engineering, Sun Yat-sen University, West Xingang Road 135, Guangzhou 510275, China

Energies, 2024, vol. 17, issue 21, 1-16

Abstract: Vapor compression heat pump technology is a widely utilized method for energy conversion. Lubricating oil plays a crucial role in the heat pump system cycle by effectively reducing wear on the compressor’s moving parts and preventing refrigerant leakage. However, it can also create an oil film in the heat exchange equipment, which increases thermal resistance and diminishes heat transfer efficiency. This study utilizes a vapor compression heat pump system test bench to investigate factors influencing the system’s oil circulation rate, the two-phase flow patterns of refrigerant and lubricating oil, and the impact of oil circulation on system performance. The findings reveal that as the compressor speed increases, the oil circulation rate initially decreases before increasing again. Additionally, a decrease in the evaporator’s heat load leads to a reduction in oil circulation at high temperatures, while it increases at low temperatures. Furthermore, increasing the opening of the electronic expansion valve results in a gradual decrease in the oil circulation rate, whereas an increase in the refrigerant charge correlates with a rise in the oil circulation rate. The oil return flow pattern can primarily be categorized into three states: slow oil return, oil film flow, and high-speed oil return. These patterns are closely related to the degree of superheat, with lower superheat levels intensifying oil return.

Keywords: vapor compression heat pump; oil circulation rate; visualization (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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