Effects of intermediate pressure on the heating performance of a heat pump system using R410A vapor-injection technique

Recent heat pumps are actively equipped with a refrigerant vapor-injection technique to acquire better performance in severe operating conditions. In this study, the target system which has an additional expansion valve at the outlet of condenser was presented. The concept of intermediate pressure was generated in the target system. Effects of the intermediate pressure on the heating performance with various injection ratios were measured and analyzed according to the compressor frequencies ranging from 60 to 100 Hz. Unlike conventional vapor-injection cycle, the maximum injection ratio was highly affected by the intermediate pressure. The high intermediate pressure provided high initial heating capacity and COP; but it restricted the available range of vapor-injection within narrow limits. The result indicates that a proper operating strategy is needed for the vapor-injection cycle.

► We report the vapor-injection cycle with an additional expansion valve.
► By installing additional expansion valve, an intermediate pressure is investigated.
► Low intermediate pressure increases initial heating capacity and COP.
► Maximum injection ratio is affected by the intermediate pressure.