水平管降膜蒸发器传热优化研究

基于分布参数方法,对大型制冷系统中的水平管外降膜蒸发进行了传热优化数值模拟计算.在计算中,分析了饱和的液态制冷剂R134a在水平的铜管束外流动蒸发的换热特性.模型考虑了不同的管子类型和2流程不同管程布置对蒸发器换热特性的影响,结果表明,蒸发器采用Turbo-EHP管的性能高于其它管;不同管程布置对蒸发器性能的影响比较大,其中,下进上出管程布置的换热性能优于其它管程布置.同时,本文考虑了传热管外"干斑"对换热的影响.本文结论对于大型制冷系统中的降膜蒸发器传热优化设计具有指导性意义.

HEAT TRANSFER OPTIMIZATION OF THE HORIZONTAL TUBE BUNDLES IN FALLING FILM EVAPORATORS

An analysis of optimizing horizontal heat transfer tube bundles in a falling film evaporator iS carried out with numerical simulation with distributed parameters in large refrigeration systems.In this simulation,the heat transfer performances of a saturated liquid refrigerant R134a flowing on horizontal copper tube bundles are considered.In this paper,the impacts of such factors as tube kind and two tube passes arrangement on the evaporator performance are analyzed.The results show that the Turbo-EHP tube presents better heat transfer performance than the other tubes and the bottom-to-top tube pass arrangement provides a higher external heat transfer coefficient than other tube pass arrangements.In addition,the impact of dry patch area on tube surface is considered.These results from this study can be used to guide the design of falling film evaporators in large refrigeration systems.