Effects of injection-port angle and internal heat exchanger length in vapor injection heat pumps for electric vehicles

Abstract Vapor injection heat pumps have been proposed for cabin heating in electric vehicles (EVs) to improve the performance and reliability under severe weather conditions. However, the geometric optimizations of the injection-port and internal heat exchanger (IHX) in vapor injection heat pumps designed for EVs have rarely been investigated. The objective of this study is to investigate the effects of the injection-port angle and IHX length in a vapor injection heat pump for use in EVs at various startup conditions. The heating performance of a vapor injection heat pump with R134a is measured by varying the IHX length from 100 to 400 mm and injection-port angle from 320° to 440° at various cabin temperatures. The effects of the IHX length and injection-port angle are analyzed in terms of coefficient of performance (COP) and heating capacity. The optimum IHX length and injection-port angle for the maximum COP are determined to be 300 mm and 400°, respectively.