Comparative study on mixing rules of vapor-liquid equilibrium for R290/R245fa

doi:10.11949/0438-1157.20241420

Abstract

Abstract:

R290/R245fa constitutes a non-azeotropic refrigerant pair suitable for auto-cascade ejector refrigeration cycles. However, the scarcity of experimental data and significant discrepancies among prediction models pose challenges. To enhance the accuracy of vapor-liquid equilibrium (VLE) data calculations for the R290/R245fa binary mixture, this paper utilizes the Peng-Robinson (PR) equation in conjunction with three mixing rules: the van der Waals (VDW), Wong-Sandler (WS), and Modified Huron-Vidal first-order (MHV1) mixing rules. Additionally, it employs the UNIFAC (Dortmund) activity coefficient model to evaluate the VLE properties of the mixture. The results indicate that the MHV1 mixing rule exhibits superior computational accuracy for low-pressure systems compared to the WS and VDW mixing rules. Considering the impact of hydrogen bonding forces among fluorinated hydrocarbon molecules on the vapor-liquid phase composition, the optimal model modifies the area and volume parameters of fluorine-containing groups within the activity coefficient model. This modification reduces the average relative deviation of pressure to 0.7937% and lowers the absolute deviation of the vapor-phase component to 0.0018. The prediction results demonstrate that the accuracy of the modified model is comparable to that of REFPROP 10.0, with a relative deviation of pressure between the modified model and REFPROP 10.0 amounting to 0.7051%, and an absolute deviation of the vapor-phase component of 0.0025.Finally, utilizing the modified parameters, the phase diagram for the R290/R245fa mixed refrigerant is plotted within the temperature range of 243.15 K to 283.15 K.

Key words: binary mixtures, activity coefficient, vapor-liquid equilibria, hydrocarbon, hydrogen bond

摘要：

R290/R245fa是一组适用于自动复叠喷射制冷循环的非共沸制冷剂，然而，现有文献中关于其实验数据稀缺，且各预测模型间存在显著偏差。为提升R290/R245fa混合工质汽液相平衡的计算精度，选取了PR方程，并结合VDW、WS、MHV1三种混合规则以及UNIFAC（Dortmund）活度系数模型，对该二元混合工质的汽液相平衡特性进行了评估。结果表明，在低压体系下，MHV1混合规则的计算精度优于WS和VDW混合规则。基于最优模型，考虑了氢键在氟代烃分子间的作用力对气液相组成的影响。通过修正活度系数模型中含氟基团的面积参数和体积参数，压力相对偏差降低至0.7937%，气相组分绝对偏差降低至0.0018。计算结果显示，修正后的模型与REFPROP 10.0模型的精度相当，其压力平均相对偏差为0.7051%，气相组分的绝对偏差则为0.0025。最后绘制了R290/R245fa混合工质在243.15~283.15 K温度范围内的相图。

关键词: 二元混合物, 活度系数, 汽液平衡, 碳氢化合物, 氢键

CLC Number:

TK 123

Hao DING, Lin WANG, Hao LIU. Comparative study on mixing rules of vapor-liquid equilibrium for R290/R245fa[J]. CIESC Journal, 2025, 76(S1): 9-16.

丁昊, 王林, 刘豪. R290/R245fa汽液相平衡混合规则对比研究[J]. 化工学报, 2025, 76(S1): 9-16.

Figures/Tables 8

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序号	基团	R_k	Q_k	a_mn				b_mn
1	CH₃	0.6325	1.0608	0	0	342	342	0	0	-1.679	-1.679
2	CH₂	0.6325	0.7081	0	0	342	342	0	0	-1.679	-1.679
3	CF₃	1.284	1.266	-484.3	-484.3	0	0	2.467	2.467	0	0
4	CHF₂	1.284	1.098	-484.3	-484.3	0	0	2.467	2.467	0	0

序号	基团	R_k	Q_k	a_mn				b_mn
1	CH₃	0.6325	1.0608	0	0	342	342	0	0	-1.679	-1.679
2	CH₂	0.6325	0.7081	0	0	342	342	0	0	-1.679	-1.679
3	CF₃	1.284	1.266	-484.3	-484.3	0	0	2.467	2.467	0	0
4	CHF₂	1.284	1.098	-484.3	-484.3	0	0	2.467	2.467	0	0

温度/K	实验数据点数N_p	模型一计算压力p_cal	模型一气相组分y	模型二计算压力p_cal	模型二气相组分y	模型三计算压力p_cal	模型三气相组分y
298.18	16	AARD(p)	100ARD(y)	AARD(p)	100ARD(y)	AARD(p)	100ARD(y)
298.18	16	1.79%	0.4938	1.53%	1.18	1.25%	1.0940
313.22	16	AARD(p)	100ARD(y)	AARD(p)	100ARD(y)	AARD(p)	100ARD(y)
313.22	16	2.27%	0.7964	2.86%	1.22	2.03%	1.1064

温度/K	实验数据点数N_p	模型一计算压力p_cal	模型一气相组分y	模型二计算压力p_cal	模型二气相组分y	模型三计算压力p_cal	模型三气相组分y
298.18	16	AARD(p)	100ARD(y)	AARD(p)	100ARD(y)	AARD(p)	100ARD(y)
298.18	16	1.79%	0.4938	1.53%	1.18	1.25%	1.0940
313.22	16	AARD(p)	100ARD(y)	AARD(p)	100ARD(y)	AARD(p)	100ARD(y)
313.22	16	2.27%	0.7964	2.86%	1.22	2.03%	1.1064

主基团	序号	子基团	R_k	Q_k
CH₂	1	CH₃	0.6325	1.0608
CH₂	2	CH₂	0.6325	0.7081
CF₂	3	CF₃	1.5932	1.5330
CF₂	4	CHF₂	1.1623	1.4002