二氧化碳两相冷却系统的特性

Theoretical and Experimental Investigation on Characteristics of CO_2 Mechanically Pumped Two Phase Cooling System

将CO2作为新型机械泵驱动两相流冷却系统的循环工质研究其在两相区的工作特性.在对该系统的各个重要组成器件和工作原理进行阐述后,通过实验对系统在变热负荷变流量条件下的动态响应特性进行研究,并由实验数据对储液器与主回路之间的热质交换进行分析.结果表明:由于系统参数和边界条件的改变引起储液器内气液相界面的震动,使得系统的绝对压力有所变化,从而引起储液器内处于两相状态工质温度的变化,而储液器的温度决定了蒸发器的温度,所以在流量改变和热负荷变化的时候蒸发器内工质会产生温度的脉动;由于CO2具有稳定的化学性质和良好的热力学特性,特别是在饱和态下比其他制冷剂更小的液/气密度比,使其作为机械泵驱动环路式热管系统的循环工质不仅减小了系统的设计体积和质量,而且能够实现长距离复杂回路小温度梯度均匀的散热效果和稳定的工作状态.

The two-phase mechanical pumped cooling loop （MPCL）by using CO2 as the working fluid is a promising thermal control system which is just like a heat pipe to realize heat extraction from ener-lectrical equipment by phase change efficiently. A brief review of system design and work principle was presented and a proposed experimental system was described. In order to apply CO2 as a high quality work fluid, tests are performed to clearly comprehend its capability and to characterize the operation in different condi- tions. Special attention is paid to the system dynamic working characteristics under different conditions such as variation heat load and mass flow process. According to the experimental findings, the transient liquid transfer between the main loop and accumulator is analyzed to explain the temperature or pressure fluctuation in the accumulator and evaporator. It is concluded that the work fluid flowing into or out of the accumulator causes the absolute pressure and the temperature fluctuate in the accumulator, and the evaporator temperature would change as the following. At last, some characters were analyzed, it is demonstra-ted that a CO2 MPCL presents a good performance and has more stable and robust characteristics for the special operation than the system by using other work fluid.