Abstract: China government carried out and implements the rural “coal to electricity heating” policy, air-source heat pump has been applied universally with the advantage of low-temperature heating performance. By adopting the enhanced vapor injection technology, which can effectively improve the heating capacity and the compressor operation stability in low-temperature environment, it can fully meet the needs of low-temperature heating in cold regions. But the design should also consider the coupling control of enhanced vapor injection and electronic expansion valves, so that the system fluctuation is reduced after frosting, to realize the stability in low-temperature heating and improve the heating capacity. Based on the theoretical study and experimental verification on enhanced vapor injection technique, a series of progresses have been obtained in the performance improvement and control stability of the low-temperature heating, it achieves a set of application of enhanced vapor injection technique in air-source heat pump.

Key words: Low-temperature heating, Enhanced vapor injection, Performance improvement, Control stability