小型CO2热泵系统用气体冷却器仿真研究

摘要

The structure and heat transfer performance of CO2 gas cooler have great impact on CO2 transcritical cycle performance.In order to design a gas cooler with high efficiency,it is necessary to conduct the performance study by numerical simulation and thus the optimization of CO2 gas cooler.Steady-state distributed parameter model of gas cooler in a small CO2 heat pump system was established using finite element method.The flow and heat transfer characteristics on both sides of water and CO2 were studied.The effect of CO2 inlet pressure on designed tube length and heat transfer coefficient of CO2 was analyzed.The results showed that when the CO2 inlet pressure increased from 8 to 12 MPa in 1 MPa increments,the maximum heat transfer coefficient of CO2 decreased by 57.14%,33.33%,25.00% and 9.83% in order.The designed tube length of gas cooler decreased by 55.60%,18.75%,11.33% and 9.09% in order.The reasonable inlet pressure of CO2 was achieved in the range of 8.5 to 10 MPa,taking the tube cost and heat transfer coefficient of CO2 into consideration.The model can provide a theoretical guidance for the design of gas cooler.%CO2气体冷却器的结构和换热效果对CO2跨临界循环影响较大.为设计出高效的气体冷却器,有必要对其性能进行模拟和优化.采用有限单元法建立了小型CO2热泵热水器中气体冷却器稳态分布参数模型,分别对其CO2侧和水侧的流动与换热进行了数值仿真,运用该模型分别针对CO2侧进口压力对气体冷却器设计管长和CO2换热性能的影响进行了分析.结果表明,CO2侧进口压力在8~12MPa时,从8MPa开始每递增1MPa,换热系数峰值比压力增加1MPa前的依次递减约57.14%、33.33%、25.00%、9.83%,设计管长比压力增加1MPa前的依次递减约55.60%、18.75%、11.33%、9.09%.综合考虑管道耗材与CO2换热能力,针对小型CO2热泵系统,气体冷却器CO2侧进口压力取8.5~10MPa较合理.研究可为气体冷却器设计提供理论指导.