Vapor compression heat pump has a good prospect of application in high temperature environments and high-power spacecraft thermal control system. Aerospace vapor compression heat pump operates in the microgravity environment. Microgravity vapor compression heat pump adaptability is the key to a vapor compression heat pump technology aerospace research and development. The evaporator is a key component of the vapor compression heat pump.By calculating vapor compression heat pump evaporator to explore its gravity-independent conditions and get gravity-independent critical velocity and critical diameter at different evaporation temperatures and under different flow rates. The results showed that the minimum critical velocity in the evaporator gravity-independent region in 1.45-1.5 m·s-1. The maximum critical diameter increases with cooling capacity

and cooling capacity from 50 W to 300 W

the critical diameter from 0.42 mm to 1.02 mm.