含油R32管内流动沸腾换热特性测试及关联式开发

doi:10.11949/0438-1157.20210838

摘要/Abstract

摘要：

R32作为低温室效应制冷剂得到广泛应用，空调器中循环的介质是制冷剂与润滑油的混合物，掌握R32-润滑油混合物的流动沸腾特性是R32空调器优化设计的关键。本文的目的是参照空调器实际运行工况，测试R32-润滑油混合物的管内流动沸腾换热特性，开发传热系数关联式。新搭建了具有防爆功能的R32-润滑油混合物管内换热性能测试台，采用换热管为7 mm铜管，测试的质流密度200~400 kg/(m²·s)、干度0.2~0.7、油浓度0~5%。实验结果表明，R32-润滑油混合物管内流动沸腾传热系数随质流密度的增大而增大；在中低干度下传热系数随油浓度的增大而增大，在高干度下随油浓度增大先增大后减小并于3%油浓度处取得最大值。基于混合物物性与流型开发了传热系数关联式，预测值与85%的实验数据的误差在±20%内。

关键词: R32, 润滑油, 流动, 蒸发, 传热, 关联式

Abstract:

As a low GWP refrigerant, R32 is widely used in room air-conditioners in which the working fluid is the mixture of refrigerant and lubricating oil. In order to optimize R32 air conditioner, it is necessary to know the flow boiling heat transfer characteristic of R32-oil mixture. The purpose of this paper is to test the flow boiling heat transfer characteristics of R32-oil mixture inside tubes and develop a new correlation of heat transfer coefficient according to the actual working conditions of air conditioners. A new experiment rig with explosion-proof function was set up to test the heat transfer performance of R32-oil mixture inside tubes. Copper tube with 7 mm outer diameter was chosen as the test section, and the test conditions include the mass flux ranged from 200 to 400 kg/(m²·s), the vapor quality ranged from 0.2 to 0.7 and the oil concentration ranged from 0 to 5%. The test results indicated that, the heat transfer coefficient of R32-oil mixture increases with the increase of mass flux; moreover, the presence of oil enhances the heat transfer at the range of low and intermediate vapor qualities; there is a peak of local heat transfer coefficient at about 3% oil concentration at higher vapor qualities. A new heat transfer coefficient correlation of R32-oil mixture inside 7 mm smooth tube was developed based on the mixture properties and the flow pattern, and it agrees with 85% of experimental data within deviation of ±20%.

Key words: R32, lubricating oil, flow, evaporation, heat transfer, correlation

中图分类号:

TK 124

李广, 庄大伟, 谢丽懿, 丁国良, 郑立宇, 龙春仙, 江波. 含油R32管内流动沸腾换热特性测试及关联式开发[J]. 化工学报, 2022, 73(2): 612-621.

Guang LI, Dawei ZHUANG, Liyi XIE, Guoliang DING, Liyu ZHENG, Chunxian LONG, Bo JIANG. Experimental investigation and correlation development of flow boiling heat transfer characteristics of R32-oil mixture inside tube[J]. CIESC Journal, 2022, 73(2): 612-621.

图/表 10

图1 实验台示意图1—压缩机;2—压缩机油分离器;3—气动调节阀;4—球阀;5—过冷器;6—制冷剂储液罐;7—制冷剂质量流量计;8—单向止回阀;9—预热器;10—测试段;11—过热器;12—电热水器;13—油分离器组;14—气液分离器;15—储油罐;16—高压油泵;17—微型调节阀;18—油质量流量计;19—针阀;20—冷水机组;21—水箱;22—水泵;23—体积流量计

Fig.1 Schematic diagram of experimental apparatus

图2 测试段示意图

Fig.2 Schematic diagram of test section

表1 实验工况

Table 1 Test conditions of the experimental rig

项目	数值
蒸发温度/℃	-5、5、15
干度	0.2、0.4、0.6、0.7
质流密度/(kg/(m²·s))	200、300、400
管径/mm	7
润滑油浓度/%	0、1、3、5

表2 参数测量仪器及精度

Table 2 Measuring instrument and uncertainties

测量参数	测量仪器	测量范围	测量精度
制冷剂温度	5TC-TT-K-36型热电偶	-10~25℃	±0.05℃
冷取水温度	5TC-TT-K-36型热电偶	5~10℃	±0.05℃
加热水温度	5TC-TT-K-36型热电偶	30~50℃	±0.05℃
制冷剂压力	CX3051/G/HT/5M压力变送器	1500 kPa	±0.1%
润滑油压力	CX3051/G/HT/5M压力变送器	3000 kPa	±0.5%
制冷剂压降	3051S2CD3A2E12A1AB4K5M5压差变送器	0~50 kPa	±0.04%
制冷剂质量流量	E+H科式流量计	5.1~17.1 g/s	±0.05%
润滑油质量流量	OVAL科式流量计	0~0.257 g/s	±0.015%
冷却水体积流量	LWGY-12BAGS1/U/NE/NT体积流量计	0.48~39.6 L/min	±0.5%
加热水体积流量	LWGY-12BAGS1/U/NE/NT体积流量计	0.48~39.6 L/min	±0.5%

图3 蒸发温度15℃ R32-润滑油混合物传热系数随干度和油浓度的变化

Fig.3 Heat transfer coefficient of R32-oil mixture plotted as a function of oil concentration and vapor quality at 15℃ evaporation temperature

图4 蒸发温度5℃ R32-润滑油混合物传热系数随干度和油浓度的变化

Fig.4 Heat transfer coefficient of R32-oil mixture plotted as a function of oil concentration and vapor quality at 5℃ evaporation temperature

图5 蒸发温度-5℃ R32-润滑油混合物传热系数随干度和油浓度的变化

Fig.5 Heat transfer coefficient of R32-oil mixture plotted as a function of oil concentration and vapor quality at -5℃ evaporation temperature

图6 液膜厚度示意图

Fig.6 Schematic diagram of liquid thickness

图7 C和n值拟合结果

Fig.7 Determination of the parameters C and n from the experimental results for R32-oil mixture

图8 传热系数拟合结果与实验结果对比

Fig.8 Predicted αtp,r,o of new correlation vs. experiment αtp,r,o of R32-oil mixture

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