超临界流体水平流动换热中浮升力效应分析与判据评价

Analysis of Buoyancy Effect in Heat Transfer to Supercritical Fluids in Horizontal Flow and Evaluation of the Criterion

为了准确判断浮升力对换热模型精度的影响,收集整理了多种超临界流体(水、CO_(2)和R125等)水平流动换热的实验数据,对不同浮升力影响判断准则进行了评价,并提出了对浮升力判别式展开修正应遵循的原则。结果表明:目前被广泛认为适应性最好的判别式Gr_(q)/Gr_(th)仍存在拟气区表现效果不佳、拟液区与拟气区数值无一致性、其峰值对应的主流焓值与壁温差峰值对应的主流焓值无相关性等局限性;壁温差峰值处流体焓值也是衡量管内浮升力影响程度的重要因素。

In order to accurately judge the influence of buoyancy on the accuracy of heat transfer models,experimental data of horizontal flow heat transfer of supercritical fluids(water,carbon dioxide,R125,etc.)were collected,different judgemengt criterion for the influence of buoyancy force were evaluated,and the principles that should be followed to develop corrections to the discriminant of buoyancy force were proposed.Results show that the best verified buoyancy criteria formula Gr_(q)/Gr_(th) still has its limits.Such as the performance in gas-like region is not ideal,no consistency in liquid-like region and gas-like region,the mainstream enthalpy value corresponding to its peak value and the peak position of wall temperature difference has no correlation.The enthalpy of the fluid at the peak of the wall temperature difference is an important factor in measuring the degree of influence of the buoyancy force in the tube.