泡沫金属对含油制冷剂管内流动沸腾换热特性的影响

实验研究了制冷剂-润滑油混合流体在内嵌泡沫金属圆管内流动沸腾的换热特性。泡沫金属为10ppi、90%孔隙率;制冷剂为R410A,润滑油为VG68,油浓度为0～5%。实验结果表明:纯制冷剂工况下,泡沫金属强化流动沸腾换热系数,换热系数提高30%～120%;含油工况下,泡沫金属只强化流动沸腾换热系数20%以下,在低质流密度或者高质流密度的高干度情况下出现恶化换热的情况。润滑油总是恶化制冷剂在内嵌泡沫金属圆管内流动沸腾的换热系数,换热系数最多恶化71%,且在低质流密度下对换热的恶化比在高质流密度工况下严重。

Effect of Metal Foam on Heat Transfer Characteristics of Refrigerant/Oil Mixture Flow Boiling Inside Tubes

Heat transfer characteristics of refrigerant/oil mixture flow boiling inside tubes filled with metal foam was investigated experimentally.Copper foam with 10 PPI and 90%porosity was selected in the present study.The refrigerant is R410A,and the lubricating oil is VG68 with oil concentrations from 0%～5%.The test results show that:for oil free conditions,metal foam always enhances the flow boiling heat transfer of refrigerant,and the heat transfer coefficient is 30%to 120%higher than that of smooth tube;for oil presence conditions,the enhancement effect of metal foam on flow boiling heat transfer is smaller than 20%,and there may be deterioration effect of metal foam on heat transfer under the conditions of low mass flux,or high vapor quality and high mass flux conditions.The presence of oil always deteriorates the heat transfer of refrigerant flow boiling inside tubes filled with metal foam by maximum of 71%.and the deterioration effect of oil on heat transfer under low mass flux condition is more evident than that under high mass flux condition.