Experimental investigation on the space heating performance of air source heat pump with vapor injection under frosting condition

Abstract

For air source heat pump with vapor injection (ASHPVI), the vapor injection can improve its heating performance of ASHPVI at non-frosting low temperature condition. However, its effect under the frosting condition is still unclear. To improve the heating performance of ASHPVI under frosting condition, a test rig for the frosting of ASHPVI was built in a psychrometer testing room. Then, a new control strategy for vapor injection was proposed to ensure its safety, and two groups of frosting experiments with and without vapor injection were conducted. Results showed that under frosting condition, vapor injection can still improve the heating capacity of ASHPVI by 11.31 %. It can also make the outdoor coil surface temperature decreased by 0.8–4.6 °C, and further result in a faster frosting speed. Compared with the frosting duration without vapor injection (64 min), the frosting duration with vapor injection is shortened by 14 min. Owing to the faster frosting speed, the average COP with vapor injection decreases by 0.17, with a decrease rate of 6.03 %. When the heating capacity of AHSPVI without vapor injection under frosting condition can meet the building heating load, the vapor injection should not be adopted.