水平管内R1234yf的流动沸腾换热特性

doi:10.16085/j.issn.1000-6613.2021-1823

摘要/Abstract

摘要：

通过实验研究了环境友好型制冷剂R1234yf在内径为0.5mm的水平圆形微通道内的流动沸腾换热特性，测量了不同工况下R1234yf的沸腾换热系数（HTC），并与传统制冷剂R134a进行了对比，分析了质量流速、热流密度和干度对换热系数变化规律的影响。实验条件为：饱和温度(17±1)℃，质量流速1000~2500kg/(m²·s)，热流密度25~143kW/m²。实验结果表明：R1234yf的换热系数随着热流密度的增大而显著增大，而质量流速和干度的影响较小，核态沸腾为其主导换热机制。对比R1234yf和R134a在相同工况下的换热特性，发现两种工质的平均换热系数差别较小，并均随着热流密度增大而逐渐增加，但是R1234yf发生干涸（Dryout）时的热流密度小于R134a。将实验数据与已有文献中的核沸腾主导的经验关联式的预测结果进行了对比，得到了较好的吻合。

关键词: 制冷剂R1234yf, 微通道, 流动沸腾, 关联式

Abstract:

The flow boiling heat transfer characteristics of environmentally friendly refrigerant R1234yf in a 0.5mm horizontal circular microchannel were studied experimentally. The heat transfer coefficients (HTCs) of R1234yf were measured and compared with that of R134a, and the effects of mass flux, heat flux and vapor quality on HTC were analyzed. The saturation temperature was (17±1)℃, and the mass fluxes vary from 1000kg/(m²·s) to 2500kg/(m²·s) with heat fluxes ranging from 25kW/m² to 143kW/m². The experimental results showed that the HTC of R1234yf in 0.5mm microchannel increases with the increase of heat flux, while the mass flux and vapor quality showed a weak influence on it. The trend indicated that nucleate boiling was the dominant mechanism for flow boiling heat transfer. In addition, the heat transfer performance of R1234yf and R134a were compared under the same working conditions. The HTCs of R1234yf and R134a were almost identical and both increased with the increase of heat flux, but the heat flux for the occurrence of dryout of R1234yf was smaller than that of R134a. Finally, the experimental data for the two refrigerants were compared with two nucleate boiling-dominated correlations from literature and good agreements were obtained.

Key words: refrigerant R1234yf, microchannel, flow boiling, correlations

中图分类号:

TK124

冯龙龙, 钟珂, 张羽森, 商庆春, 贾洪伟. 水平管内R1234yf的流动沸腾换热特性[J]. 化工进展, 2022, 41(7): 3502-3509.

FENG Longlong, ZHONG Ke, ZHANG Yusen, SHANG Qingchun, JIA Hongwei. Flow boiling heat transfer characteristics of R1234yf in horizontal microchannel[J]. Chemical Industry and Engineering Progress, 2022, 41(7): 3502-3509.

图/表 12

表1 R1234yf和R134a在饱和温度为17℃时的部分热物性参数

制冷剂	ODP	GWP	饱和压力p_sat/MPa	液体密度ρ_l/kg·m^-3	气体密度ρ_v/kg·m^-3	汽化潜热i_lv/kJ·kg^-1	定压比热容c_p_，l/kJ·kg^-1·K^-1	黏度μ_l/μPa·s	热导率λ_l/mW·m^-2·K^-1	表面张力σ/mN·m^-1
R1234yf	0	4	0.542	1120.3	30.01	151.56	1.3563	169.69	66.011	7.182
R134a	0	1430	0.521	1236.2	25.305	184.89	1.3939	215.24	84.579	9.093

图1 实验装置示意图1—齿轮泵；2—旁通阀；3—冷凝器；4—质量流量计；5—预热段；6—实验段；7—数据采集仪&电脑；8—储液罐；9—干燥过滤器

图2 实验段及热电偶贴附示意图

图3 实验段加热效率

图4 单相Nusselt数与Gnielinski[21]关联式预测值的对比

表2 实验参数的不确定度

测量值		计算参数
参数名	不确定度	参数名	不确定度
m/kg·s	±0.1%	G/kg·m^-2·s^-1	±2.83%
D， L/m	±2%	q/kW·m^-2	±2.12%
U/V， I/A	±0.5%	h/kW·m^-2·K^-1	±6.76%
T（T-type）/℃	±1.17%	x	±0.87%
p/Pa	±0.25%	Q/W	±0.71%

图5 热流密度对局部换热系数的影响

图6 质量流速对局部换热系数的影响

图7 沿程平均换热系数随热流密度的变化

图8 R1234yf与R134a的局部换热系数对比

图9 R1234yf与R134a的平均换热系数对比

图10 换热系数实验结果与模型计算结果的对比

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