水平微圆管内R22和R410a凝结换热试验

Experimental Investigation on Condensation Heat Transfer of R22 and R410a in Microtubes

R410a是被广泛看好的一种R22替代物,研究R410a的凝结换热特性对于开发适用此类制冷工质的凝结换热设备具有重要意义。搭建了微细尺度凝结换热试验台,测量了饱和温度为40℃、质量流速为200～1000 kg/(m^2·s)、干度为0.2～0.8条件下R22和R410a在内径为0.941 mm不锈钢圆管内的凝结换热系数,分析了质量流速和干度对凝结换热的影响,并把试验数据与被广泛应用于传统大管道的SHAH(1979)和AKERS(1959)关联式进行了对比。试验与分析结果表明,凝结换热系数随着质量流速和干度的增大而增大,在高干度区更加明显,表明在高干度区切应力的作用增强;两个关联式均不能准确预测试验数据,最大偏差超过60%;与R22相比,R410a的凝结换热系数在较低质量流速时低于R22,在中高质量流速时与R22相当。

R410a is known as one of the substitutes of R22. Studying the pressure drop of R410a during condensing process is important for designing high efficient condensation heat transfer equipments using R410a as refrigerant. Test fig for condensation heat transfer in micro-scale is established and condensation heat transfer coefficients of R22 and R410a in stainless round tube with the inner diameter of 0.941 mm are measured at a saturate temperature of 40℃, with mass flux varying from 200-1 000 kg/（m^2·s）, over the quality 0.2-0.8. The effects of mass flux and vapor quality were analyzed and present experiment data were compared with SHAH （1979） correlation and AKERS（1959） correlation which are based on experiment data from conventional tubes and widely used. The experimental and analytical results showed that condensation heat transfer coefficients increased with mass flux and vapor quality and obviously faster in high vapor quality region, which indicated that vapor shear force played more important role. The two correlations both can＇t predict present experiment data accurately especially in high vapor quality region with the biggest error of 60%. Condensation heat transfer coefficients of R410a are lower than that of R22 at low mass flux and vapor quality but nearly equivalent at intermediate or more higher mass flux.