A critical research topic is the improvement of the system performance by efficiently cooling carbon dioxide in transcritical vapor compression cycles. In this study, a distributed compression cycle system (DCCS) is proposed. For the DCCS, the transcritical CO₂ from the gas cooler outlet is not further subcooled but boosted. It is then cooled by conventional heat sink conditions. The DCCS performance under different operating conditions with variations in the second boost ratio is calculated by a thermodynamical cycle model. It is shown that the DCCS can effectively improve the system performance compared with the baseline system, with the maximum refrigeration COP increase ranging from 8.2% to 10.76% at a constant gas cooler outlet temperature. The refrigeration capacity is increased up to approximately 26%. The maximum refrigeration COP increase ranges from 8.57% to 13.51% at a constant evaporating temperature. The ideal second boost ratio requirements in DCCS are not high, and the additional system power consumption for the second boost is not more than 20% compared with the baseline system. The DCCS still has advantages in terms of the system COP compared with current systems that only adopt a single subcooling technology. The proposed DCCS provides a new path for improving and refining the performance of the carbon dioxide transcritical vapor compression cycle systems.

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.