新型制冷剂R1234ze(E)(trans-1,3,3,3-tetrafluoropropene)因较低的GWP而被广泛关注,有望在热泵中作为R134a的替代品。本文对R1234ze(E)在内径为8 mm水平管内流动沸腾过程中摩擦压降特性进行实验研究,并在相同实验工况下与R134a进行对...新型制冷剂R1234ze(E)(trans-1,3,3,3-tetrafluoropropene)因较低的GWP而被广泛关注,有望在热泵中作为R134a的替代品。本文对R1234ze(E)在内径为8 mm水平管内流动沸腾过程中摩擦压降特性进行实验研究,并在相同实验工况下与R134a进行对比。实验研究的流动沸腾换热的饱和温度为10℃,热流密度为5.0 k W/m^2和10.0 k W/m^2,质流密度范围为300~500 kg/(m^2·s),并分析质流密度、热流密度对R1234ze(E)和R134a饱和流动沸腾过程中摩擦压降的影响。结果表明,在相同工况下R1234ze(E)的流动沸腾过程的摩擦压降略大于R134a,如质流密度为500 kg/(m^2·s)时,R1234ze(E)的平均摩擦压降值比R134a大8.4%左右。最后,将实验结果同四种摩擦压降经验关联式进行比较分析。展开更多
In this paper, the simulation approach and exergy analysis of multi-stage compression high tempera- ture heat pump （HTHP） systems with R1234ze（Z） working fluid are conducted. Both the single-stage and multi-stage ...In this paper, the simulation approach and exergy analysis of multi-stage compression high tempera- ture heat pump （HTHP） systems with R1234ze（Z） working fluid are conducted. Both the single-stage and multi-stage compression cycles are analyzed to compare the system performance with 120℃ pressurized hot water supply based upon waste heat recovery. The exergy destruction ratios of each component for different stage compression systems are compared. The results show that the exergy loss ratios of the compressor are bigger than that of the evaporator and the condenser for the single-stage compres- sion system. The multi-stage compression system has better energy and exergy etticiencies with the increase of compression stage number. Compared with the single- stage compression system, the coefficient of performance （COP） improvements of the two-stage and three-stage compression system are 9.1% and 14.6%, respectively. When the waste heat source temperature is 60℃, the exergy efficiencies increase about 6.9% and 11.8% for the two-stage and three-stage compression system respec- tively.展开更多
为了解新型环保工质R1234ze(E)微小通道内的冷凝换热及阻力特性,提出采用VOF(volume of fluid)模型对R1234ze(E)和R134a(Tsat=40℃)在水平微细圆管(Dh=1mm)内的冷凝过程进行数值模拟研究,探讨质量流量、干度以及物性对管内冷凝换热和阻...为了解新型环保工质R1234ze(E)微小通道内的冷凝换热及阻力特性,提出采用VOF(volume of fluid)模型对R1234ze(E)和R134a(Tsat=40℃)在水平微细圆管(Dh=1mm)内的冷凝过程进行数值模拟研究,探讨质量流量、干度以及物性对管内冷凝换热和阻力性能的影响。结果表明,R1234ze(E)和R134a的换热系数和压降都随质量流速和干度的增大而增大。相同情况下,R1234ze(E)换热系数小于R134a,但压降大于R134a。R1234ze(E)的液膜厚度平均要比R134a薄15.7%。当气液两相都为湍流,有效热导率对不同工质在水平圆管内的冷凝换热性能有重要影响。R1234ze(E)在管内的液膜分布特性整体上和R134a相似。现有的关联式对R1234ze(E)的压降都存在一定的低估,平均绝对误差都在30%左右。展开更多
文摘新型制冷剂R1234ze(E)(trans-1,3,3,3-tetrafluoropropene)因较低的GWP而被广泛关注,有望在热泵中作为R134a的替代品。本文对R1234ze(E)在内径为8 mm水平管内流动沸腾过程中摩擦压降特性进行实验研究,并在相同实验工况下与R134a进行对比。实验研究的流动沸腾换热的饱和温度为10℃,热流密度为5.0 k W/m^2和10.0 k W/m^2,质流密度范围为300~500 kg/(m^2·s),并分析质流密度、热流密度对R1234ze(E)和R134a饱和流动沸腾过程中摩擦压降的影响。结果表明,在相同工况下R1234ze(E)的流动沸腾过程的摩擦压降略大于R134a,如质流密度为500 kg/(m^2·s)时,R1234ze(E)的平均摩擦压降值比R134a大8.4%左右。最后,将实验结果同四种摩擦压降经验关联式进行比较分析。
文摘In this paper, the simulation approach and exergy analysis of multi-stage compression high tempera- ture heat pump （HTHP） systems with R1234ze（Z） working fluid are conducted. Both the single-stage and multi-stage compression cycles are analyzed to compare the system performance with 120℃ pressurized hot water supply based upon waste heat recovery. The exergy destruction ratios of each component for different stage compression systems are compared. The results show that the exergy loss ratios of the compressor are bigger than that of the evaporator and the condenser for the single-stage compres- sion system. The multi-stage compression system has better energy and exergy etticiencies with the increase of compression stage number. Compared with the single- stage compression system, the coefficient of performance （COP） improvements of the two-stage and three-stage compression system are 9.1% and 14.6%, respectively. When the waste heat source temperature is 60℃, the exergy efficiencies increase about 6.9% and 11.8% for the two-stage and three-stage compression system respec- tively.
文摘为了解新型环保工质R1234ze(E)微小通道内的冷凝换热及阻力特性,提出采用VOF(volume of fluid)模型对R1234ze(E)和R134a(Tsat=40℃)在水平微细圆管(Dh=1mm)内的冷凝过程进行数值模拟研究,探讨质量流量、干度以及物性对管内冷凝换热和阻力性能的影响。结果表明,R1234ze(E)和R134a的换热系数和压降都随质量流速和干度的增大而增大。相同情况下,R1234ze(E)换热系数小于R134a,但压降大于R134a。R1234ze(E)的液膜厚度平均要比R134a薄15.7%。当气液两相都为湍流,有效热导率对不同工质在水平圆管内的冷凝换热性能有重要影响。R1234ze(E)在管内的液膜分布特性整体上和R134a相似。现有的关联式对R1234ze(E)的压降都存在一定的低估,平均绝对误差都在30%左右。
文摘泡沫金属具有超大比表面积和高热导率,将其填充于换热管内可用于制冷空调系统的强化传热。研究了R1234ze(E)在泡沫金属管内的流动沸腾换热和压降特性。实验工况为:干度0.1~0.9,质流密度90~180 kg·m^(-2)·s^(-1),热通量12.4~18.6 k W·m^(-2)。测试样件为泡沫铜填充管,孔密度为10~40 PPI、孔隙率为90%~95%。实验结果表明,R1234ze(E)比R410A的传热系数低2%~10%,两相压降低30%~42%;当干度大于0.8时,低质流密度下泡沫金属管内传热系数随干度的增加增幅更大;泡沫金属在强化流动沸腾换热的同时,造成压降显著增加,换热影响因子的范围为1.23~2.90,压降影响因子的范围为6~45。开发了适用于R1234ze(E)的泡沫金属管内流动沸腾换热和压降关联式,传热系数和两相压降的预测值与95%的实验值误差分别在±15%和±25%以内。
