Pool boiling heat transfer characteristics of twisted tube in flooded evaporator

doi:10.3969/j.issn.0438-1157.2013.04.003

Abstract

Abstract: The objective of this paper is to study the pool boiling heat transfer characteristics of twisted tubes in a flooded evaporator.The twisted tubes are processed from common circular evaporating tubes with an outer diameter of 15.88 mm.The outer and inner diameters, wall thickness and length of the twisted tube are 19.50, 11.28, 1.09, and 3310 mm, respectively.With the same number of tubes, the twisted tube flooded evaporator(TFE) requires smaller heat exchange area than the common flooded evaporator(FE).The pool boiling heat transfer coefficients outside tubes, tube side Reynolds number Re_i, wall superheat T_sup, saturation temperature of refrigerant T_sat and heat flux q_b are considered as the key parameters.The results show that pool boiling heat transfer coefficient increases with Re_i, T_sat and q_b and decreases as T_sup increases.The case study shows that the overall heat transfer coefficient of TFE is about 1.15 times that of FE with the same heat capacity.It is proved that the application of TFE in the water-cooled screw chiller is feasible.

Key words: pool boiling, twisted tube, flooded evaporator, water-cooled screw chiller

摘要： 对螺旋扁管在满液式蒸发器中的池沸腾传热进行了实验研究。螺旋扁管由外径为15.88 mm的圆形满蒸管加工而得,其外径、壁厚以及长度分别为19.50 mm×11.28 mm、1.09 mm和3310 mm。通过实验研究了管程Reynolds数Re_i、制冷剂饱和温度T_sat、管壁过热度T_sup以及热通量q_b对于池沸腾传热性能的影响。结果表明,随着Re_i、T_sat和q_b的增加,螺旋扁管满液式蒸发器以及原有满液式蒸发器的沸腾传热性能都随之增强,而随着T_sup的增加,两者的沸腾传热性能却呈下降趋势。同时,对装有两种满液式蒸发器的螺杆式冷水机组分别进行了测试,结果表明在换热量相同的条件下,螺旋扁管满液式蒸发器比原有蒸发器的总传热系数提高了15%左右,证明螺旋扁管满液式蒸发器在螺杆式冷水机组中的应用是可行的。

关键词: 池沸腾, 螺旋扁管, 满液式蒸发器, 螺杆式冷水机组

CLC Number:

TB657.5

ZHU Dongsheng, ZHOU Jicheng, HUO Zhengqi, LI Jun, LI Yan. Pool boiling heat transfer characteristics of twisted tube in flooded evaporator[J]. CIESC Journal, 2013, 64(4): 1151-1156.

朱冬生, 周吉成, 霍正齐, 李军, 李燕. 满液式蒸发器中螺旋扁管的池沸腾传热[J]. 化工学报, 2013, 64(4): 1151-1156.

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