油浓度对小管径水平内螺纹管内R404A冷凝换热影响的实验研究  

Experimental Study of the Influence of the Oil Concentration on the Condensing Heat Exchange of R404A Inside a Horizontal Tube Internally Threaded With a Small Diameter

作　　者：王学东[1] 柳建华[1] 宋吉[2] 高屹峰[2] 

机构地区：[1]上海理工大学能源与动力工程学院,上海200093 [2]国际铜业协会(中国),上海200020

出　　处：《热能动力工程》2017年第10期29-33,共5页Journal of Engineering for Thermal Energy and Power

基　　金：上海市科委建设项目(13DZ2260900)

摘　　要：研究了强制对流条件下水平内螺纹管内R404A气液两相流冷凝换热特性,主要讨论油浓度对外径为5 mm的内螺纹管内R404A冷凝换热的影响。实验中油浓度变化范围为0~5%,设置入口平均饱和冷凝温度为40℃,质量流密度变化范围为200~400 kg/(m^2·s),热流密度变化范围为5~45 kW/m^2。实验研究表明:油的出现恶化了换热,在油浓度为1%以下时恶化作用可以忽略,但随着油浓度的增加换热恶化作用越来越明显;对于纯R404A和油浓度为1%的R404A-油混合物,冷凝换热系数随着制冷剂蒸汽干度的降低而逐渐减小;对于油浓度为3%和5%的R404A-油混合物,随着制冷剂蒸汽干度的下降,冷凝换热系数先增加然后逐渐减小,在干度为0.7~0.75之间呈现出一个冷凝换热系数的峰值。同一质量流密度下,换热系数惩罚因子会随着干度的增加而减小,即干度越大,换热恶化作用越大;当质量流密度从200 kg/(m^2·s)增加到400 kg/(m^2·s)时,同一油浓度下油对换热系数的恶化作用相对变小。Studied were the condensing heat exchange characteristics of a gas-liquid two-phase flow of R404 A inside a horizontal internally threaded tube under the forced convection condition and mainly discussed was the influence of the oil concentration on the condensing heat exchange of R404 A inside the above-mentioned tube. The oil concentration under the test varied in a range from 0 to 5%,the average value of the saturated condensing temperature set at the inlet was 40 ℃,the mass flow density ranged from 200 kg/m^2 s to 400 kg/m^2 s and the heat flux density from 5 k W/m^2 to 45 k W/m^2. It has been found that the presence of oil will deteriorate the heat exchange and such deterioration can be neglected when the oil concentration is below 1%,however,the deterioration will be more and more obvious with an increase of the oil concentration. For pure R404 A and a R404 A-oil mixture with its oil concentration being 1%,the condensing heat exchange coefficient will gradually decrease with a decrease of the dryness of the steam of the refrigerant. For a R404 A-oil mixture with its oil concentration being 3% and 5% respectively,the condensing heat exchange coefficient will first increase and then gradually decrease with a decrease in the dryness of the steam of the refrigerant. A peak value of the condensing heat exchange coefficient will appear when the foregoing dryness varies between 0. 7 and 0. 75. At a same mass flow density,the heat exchange coefficient penalty factor will decrease with an increase of the foregoing dryness,i. e. the bigger the dryness,the bigger the deterioration role. When the mass flow density increases from 200 kg/m^2 s to 400 kg/m^2 s,the deterioration role played by the oil on the heat exchange coefficient will become relatively small at a same oil concentration.

关 键 词：油浓度 小管径 冷凝换热 R404A 水平内螺纹管 

分 类 号：TK124[动力工程及工程热物理—工程热物理]