When the temperature of the heat source is higher than the temperature of the heat sink, heat transfer can occur spontaneously. In a system where heat transfer can occur spontaneously, a working fluid phase change cycle heat transfer system can be constructed through heat pipes or heat pumps. This article uses the entransy theory to explain the role of external input work in the positive heat transfer scenario where the heat source temperature is higher than the heat sink temperature in the working fluid phase change cycle heat transfer system. The viewpoint of useless entransy is proposed, and the characteristics of the power heat pipe and heat pump system are analyzed using useless entransy. A judgment method for the energy utilization superiority of the working fluid phase change cycle system related to the system input work is obtained. In addition, the starting problem of an unpowered heat pipe is studied using an entransy flow diagram, and a mathematical expression for the minimum starting temperature difference of the heat pipe under ideal conditions is obtained. The results of this article can enrich the research of fire accumulation theory in cyclic heat transfer systems, and provide new ideas for the optimization design of cyclic heat transfer systems.