Numerical analysis of flow boiling heat transfer of zeotropic mixtures in mini-channels

doi:10.11949/0438-1157.20250117

Abstract

Abstract:

The flow boiling heat transfer characteristics of zeotropic mixtures in mini-channels are investigated using a numerical approach based on the volume of fluid (VOF) multiphase model, incorporating an improved Lee phase change model. The model's accuracy is validated through comparison with experimental data. Under constant wall temperature conditions, the effects of mass flux [50—1100 kg/(m²·s)], mixture composition (R134a inlet mass fraction 0.1—0.9), and wall temperature (32—70℃) on heat transfer performance are systematically analyzed. The results indicate that at low mass flux, an increase from 50 kg/(m²·s) to 400 kg/(m²·s) enhances the heat transfer coefficient by more than 90%. However, at high mass flux, further increasing to 1100 kg/(m²·s) reduces the heat transfer coefficient by approximately 27%, suggesting a transition in the dominant heat transfer mechanism. At the same time, when the inlet concentration of the low-boiling component R134a increases from 0.1 to 0.3, the heat transfer coefficient decreases by 15% to 45%. Furthermore, at high R134a concentrations, the heat transfer coefficient rises significantly as wall temperature increases from 32℃ to 40℃, after which it stabilizes, reaching a peak near 40℃. These findings provide insights into the underlying transport mechanisms governing zeotropic mixture flow boiling in mini-channels and offer guidance for optimizing thermal management applications.

Key words: zeotropic mixture, mini-channel, boiling, multiphase flow, heat and mass transfer, numerical analysis

摘要：

为研究非共沸工质在小通道内的流动沸腾换热特性，基于VOF多相流模型并结合改进Lee相变模型，研究了非共沸工质（R134a/R245fa）在水平小通道内的流动沸腾换热特性。通过与实验数据对比，验证了模型的可靠性。进一步在恒定壁温条件下，分析了质量流密度[50~1100 kg/(m²·s)]、工质组分配比[R134a入口浓度（质量分数）为0.1~0.9]和加热壁温（32~70℃）对流动沸腾换热性能的影响。结果表明，低质量流密度对传热系数影响明显，在低质量流密度下，当质量流密度从50 kg/(m²·s)上升至400 kg/(m²·s)时，传热系数提高超过90%，在高质量流密度条件下，当质量流密度增大到1100 kg/(m²·s)时，传热系数降低约27%。同时，当低沸点组分R134a入口浓度从0.1升至0.3时，传热系数下降15%~45%；而在高浓度下，当壁温从32℃升到40℃时，传热系数显著提升，随后趋于平稳，最大值出现在40℃左右。研究结果为非共沸工质在小通道内的研究和应用提供支撑。

关键词: 非共沸工质, 小通道, 沸腾, 多相流, 传热传质, 数值分析

CLC Number:

TQ 025.3

Hang ZHOU, Sijing ZHANG, Jian LIU, Xiaosong ZHANG. Numerical analysis of flow boiling heat transfer of zeotropic mixtures in mini-channels[J]. CIESC Journal, 2025, 76(8): 3864-3872.

周航, 张斯婧, 刘剑, 张小松. 小通道内非共沸工质流动沸腾换热数值分析[J]. 化工学报, 2025, 76(8): 3864-3872.

Figures/Tables 12

Fig.1 Schematic diagram of the numerical simulation setup

Fig.2 Variation of average fluid temperature in the tube over time under different grid sizes

Fig.3 Boundary conditions

Fig.4 Comparison of HTC results between numerical simulation and experiment for R134a/R245fa in mini-channels

Fig.5 Effect of mass flux density on the flow boiling heat transfer coefficient (a) and total heat flux density (b) in a mini-channel for R134a/R245fa

Fig.6 Effect of mass flux on flow boiling flow patterns of R134a/R245fa in mini-channels

Fig.7 Effect of mass flux on flow boiling fluid temperature distribution of R134a/R245fa in mini-channels

Fig.8 Effect of component ratio on flow boiling heat transfer coefficient of R134a/R245fa in mini-channels

Fig.9 Effect of component ratio on flow boiling flow patterns of R134a/R245fa in mini-channels

Fig.10 Effect of wall temperature on flow boiling heat transfer coefficient of R134a/R245fa in mini-channels

Fig.11 Effect of wall temperature on flow boiling flow patterns of R134a/R245fa in mini-channels

Fig.12 Effect of wall temperature on flow boiling fluid temperature distribution of R134a/R245fa in mini-channels

References 34

[1]	Kadam S T, Kumar R. Twenty first century cooling solution: microchannel heat sinks[J]. International Journal of Thermal Sciences, 2014, 85: 73-92.
[2]	Zheng N, Wei J J, Zhao L. Analysis of a solar Rankine cycle powered refrigerator with zeotropic mixtures[J]. Solar Energy, 2018, 162: 57-66.
[3]	Richardson E S. Thermodynamic performance of new thermofluidic feed pumps for organic rankine cycle applications[J]. Applied Energy, 2016, 161: 75-84.
[4]	Wang J L, Zhao L, Wang X D. A comparative study of pure and zeotropic mixtures in low-temperature solar Rankine cycle[J]. Applied Energy, 2010, 87(11): 3366-3373.
[5]	Guo C, Wang J, Du X Z, et al. Experimental flow boiling characteristics of R134a/R245fa mixture inside smooth horizontal tube[J]. Applied Thermal Engineering, 2016, 103: 901-908.
[6]	Dang C, Jia L, Zhang X, et al. Experimental investigation on flow boiling characteristics of zeotropic binary mixtures (R134a/R245fa) in a rectangular micro-channel[J]. International Journal of Heat and Mass Transfer, 2017, 115: 782-794.
[7]	Dang C, Jia L, Peng Q, et al. Experimental study on flow boiling heat transfer for pure and zeotropic refrigerants in multi-microchannels with segmented configurations[J]. International Journal of Heat and Mass Transfer, 2018, 127: 758-768.
[8]	代宝民. CO₂/低GWP工质二元混合物微小通道内流动换热机理的研究[D]. 天津: 天津大学, 2015.
	Dai B M. Research on heat transfer mechanism of CO₂/low-GWP refrigerant binary mixtures flowing in micro- and mini-channels[D]. Tianjin: Tianjin University, 2015.
[9]	Azzolin M, Bortolin S, Del Col D. Flow boiling heat transfer of a zeotropic binary mixture of new refrigerants inside a single microchannel[J]. International Journal of Thermal Sciences, 2016, 110: 83-95.
[10]	In S, Baek S, Jin L X, et al. Flow boiling heat transfer of R123/R134a mixture in a microchannel[J]. Experimental Thermal and Fluid Science, 2018, 99: 474-486.
[11]	Bamorovat Abadi G, Yun E, Kim K C. Flow boiling characteristics of R134a and R245fa mixtures in a vertical circular tube[J]. Experimental Thermal and Fluid Science, 2016, 72: 112-124.
[12]	Azzolin M, Berto A, Bortolin S, et al. Condensation of ternary low GWP zeotropic mixtures inside channels[J]. International Journal of Refrigeration, 2019, 103: 77-90.
[13]	Deng H, Rossato M, Fernandino M, et al. A new simplified model for condensation heat transfer of zeotropic mixtures inside horizontal tubes[J]. Applied Thermal Engineering, 2019, 153: 779-790.
[14]	Mastrullo R, Mauro A W, Napoli G, et al. Flow boiling of azeotropic and non-azeotropic mixtures. Effect of the glide temperature difference on the nucleate boiling contribution: assessment of methods[J]. Journal of Physics: Conference Series, 2020, 1599(1): 012053.
[15]	Chen J Y, Bao L L, Xu W C, et al. Experimental study on flow boiling heat transfer characteristics of zeotropic mixture R1233zd(E)/R1234yf in horizontal tube[J]. Applied Thermal Engineering, 2024, 254: 123942.
[16]	Qi Z L, Jia L, Dang C, et al. Heat transfer enhancement for flow boiling of zeotropic mixtures with regulating liquid mass transfer resistance[J]. International Journal of Heat and Fluid Flow, 2024, 107: 109402.
[17]	Patra C K, Bhattacharya A, Das P K. Heat transfer characteristics of acetone and methanol flow boiling in parallel microchannel heat sink: a parametric study and assessment of predictive correlations[J]. Applied Thermal Engineering, 2025, 270: 126217.
[18]	Szczukiewicz S, Magnini M, Thome J R. Proposed models, ongoing experiments, and latest numerical simulations of microchannel two-phase flow boiling[J]. International Journal of Multiphase Flow, 2014, 59: 84-101.
[19]	ANSYS Inc. ANSYS FLUENT Theory Guide[M]. Canonsburg, PA: ANSYS Inc., 2009.
[20]	Lee J, O'Neill L E, Lee S, et al. Experimental and computational investigation on two-phase flow and heat transfer of highly subcooled flow boiling in vertical upflow[J]. International Journal of Heat and Mass Transfer, 2019, 136: 1199-1216.
[21]	Li K, Liu Y C, Wen J, et al. A numerical model for the flow condensation of the binary zeotropic mixture[J]. International Communications in Heat and Mass Transfer, 2022, 130: 105767.
[22]	Lee W H. Computational Methods for Two-Phase Flow and Particle Transport[M]. Singapore: World Scientific, 2013.
[23]	杨志强, 贺波, 刘鹏飞. R14和R23及其非共沸混合物在水平管内沸腾换热特性的模拟研究[J]. 制冷技术, 2024, 44(1): 31-38.
	Yang Z Q, He B, Liu P F. Simulation of boiling heat transfer characteristics of pure refrigerants of R14 and R23 and their zeotropic mixtures inside horizontal tube[J]. Chinese Journal of Refrigeration Technology, 2024, 44(1): 31-38.
[24]	Revellin R, Dupont V, Ursenbacher T, et al. Characterization of diabatic two-phase flows in microchannels: flow parameter results for R-134a in a 0.5mm channel[J]. International Journal of Multiphase Flow, 2006, 32(7): 755-774.
[25]	Lee W H. A Pressure Iteration Scheme for Two-Phase Flow Modeling[M]. Washington D.C.: Hemisphere Publishing, 1980.
[26]	Luo Y, Li W, Zhang J Z, et al. Analysis of thermal performance and pressure loss of subcooled flow boiling in manifold microchannel heat sink[J]. International Journal of Heat and Mass Transfer, 2020, 162: 120362.
[27]	Luo Y, Zhang J Z, Li W. A comparative numerical study on two-phase boiling fluid flow and heat transfer in the microchannel heat sink with different manifold arrangements[J]. International Journal of Heat and Mass Transfer, 2020, 156: 119864.
[28]	Fang C, David M, Rogacs A, et al. Volume of fluid simulation of boiling two-phase flow in a vapor-venting microchannel[J]. Frontiers in Heat and Mass Transfer, 2010, 1(1): 1-11.
[29]	Wong K C, Chong J H. Hydrodynamics and heat transfer prior to onset of nucleate boiling in a rectangular microchannel heat sink[J]. International Communications in Heat and Mass Transfer, 2015, 64: 34-41.
[30]	Luo Y, Li J Y, Zhou K, et al. A numerical study of subcooled flow boiling in a manifold microchannel heat sink with varying inlet-to-outlet width ratio[J]. International Journal of Heat and Mass Transfer, 2019, 139: 554-563.
[31]	Kim J, Cho J Y, Lee J S. Flow boiling enhancement by bubble mobility on heterogeneous wetting surface in microchannel[J]. International Journal of Heat and Mass Transfer, 2020, 153: 119631.
[32]	Qu W L, Mudawar I. Flow boiling heat transfer in two-phase micro-channel heat sinks ( Ⅰ ) : Experimental investigation and assessment of correlation methods[J]. International Journal of Heat and Mass Transfer, 2003, 46(15): 2755-2771.
[33]	Li W, Zhou K, Li J Y, et al. Effects of heat flux, mass flux and two-phase inlet quality on flow boiling in a vertical superhydrophilic microchannel[J]. International Journal of Heat and Mass Transfer, 2018, 119: 601-613.
[34]	Yang B, Wang P, Bar-Cohen A. Mini-contact enhanced thermoelectric cooling of hot spots in high power devices[J]. IEEE Transactions on Components and Packaging Technologies, 2007, 30(3): 432-438.