Technical, economic and environmental investigation on heating performance of quasi-two stage compression air source heat pump in severe cold region

Abstract

The quasi-two stage compression air source heat pump (QTASHP) is still restricted in use in severe cold region due to the excessive discharge temperature caused by ultra-low ambient temperature. To promote the application of QTASHP in severe cold region, a novel control strategy was proposed, and it was used in a test rig in Harbin. The test rig adopted a scroll compressor with vapor injection, and its technical feasibility was investigated through supplying heating for a lab in the whole heating season. Then based on experimental results, its economic and environmental benefits were analyzed. Results showed that QTASHP could run smoothly in the whole heating season, and its highest discharge temperature was 118.82 °C at the highest compression ratio of 12.13. This indicated the proposed control strategy could solve the excessive discharge temperature problem effectively. Apart from ultra-low temperature, low temperature frosting was also a main challenge for QTASHP in severe cold region. Besides, comparing with central heating and electric boiler, its primary energy efficiency increased by 18.67% and 140.54%, while pollutants/CO2 emission decreased by 15.41% and 58.27%. However, its economic benefit was worse than central heating due to high initial investment, while far better than electric boiler.