R134a在水平内微翅管管内凝结换热的实验研究

对制冷剂R134a在水平强化换热管管内的凝结换热性能进行了实验研究。实验管为两种内微翅管,分别命名为A管和B管。实验件采用套管结构,强化内管外表面和外管内表面之间(管间)走乙二醇水溶液。实验过程中管内冷凝温度为51℃,管间乙二醇水溶液的流速为3.35 m/s,乙二醇水溶液的进口温度根据制冷剂的质量流速做相应调整,以保证试件出口制冷剂有一定的过冷度。实验结果表明:两种水平强化管的管内冷凝换热系数均随着制冷剂质量流速的增加而增大,在制冷剂质量流速从300 kg/(m2.s)增加到700kg/(m2.s)时,A管的管内冷凝换热系数比B管高1.87%到6.28%,而B管的制冷剂流动阻力比A管高9.56%到11.05%,A管的结构优于B管。

Experimental Study of the Condensation Heat Exchange of Coolant R134a in a Horizontal Inner-micro-finned Tube

Experimentally studied was the condensation heat exchange performance of coolant R134a in a horizontal intensified heat exchange tube.The test tubes were two types of inner-micro-finned tube,designated as tube A and B respectively.The test pieces adopted a tube-in-tube structure with the glycol water solution passing through the passage between the outer surface of the intensified heat exchange tube and the inner surface of the outer tube(between tubes).During the test,the condensation temperature inside the tube was 51 ℃ and the flow speed of the glycol water solution between tubes was 3.35 m/s.The inlet temperature of the glycol water solution was adjusted according to the mass flow speed of the coolant to ensure a supercooling degree of the coolant at the outlet of the test piece.The test results show that both in-tube condensation heat exchange coefficients of the two types of horizontal intensified heat exchange tube will increase with an increase of the mass flow speed of the coolant.When the mass flow speed of the coolant increases from 300 kg/(m2·s) to 700 kg/(m2·s),the in-tube condensation heat exchange efficient of tube A is 1.87% to 6.28% higher than that of tube B while the flow resistance of the coolant in tube B is 9.56% to 11.05% higher than that in tube A.Therefore,the structure of tube A is superior to that of tube B.