OIL CIRCULATION RATE IN EJECTOR COOLING CYCLES

摘要

The use of two-phase ejectors to recover expansion work to improve COP of transcritical R744 systems hasrnbeen the subject of numerous investigations during the past decade. However, there is little understanding asrnto how oil in circulation in different parts of the system is affected when a two-phase ejector is used tornreplace the expansion valve. This paper presents detailed measurement results conducted on a transcriticalrnR744 ejector system using polyalkylene glycol (PAG) oil, demonstrating that at the same test condition, thernoil circulation rates (OCRs) in different parts of the system can easily vary by an order of magnitude. Thernhighest OCRs of approximately 10% by mass were measured close to the evaporator inlet. The influence ofrncompressor speed, ejector motive nozzle needle position and evaporator inlet metering valve opening on thernOCRs was investigated and it is explained why these condition changes will result in variation of oil inrncirculation.