Influence of physical properties of working fluids on leakage and diffusion characteristics of refrigerant in limited space

doi:10.11949/0438-1157.20221046

Abstract

Abstract:

A new generation of environmentally friendly working fluids such as R290 and R32 will cause certain safety hazards if they leak due to their explosive characteristics, while the leakage of widely used working fluids such as R22 will also aggravate the greenhouse effect, thereby lead to deterioration of the global climate. Thus, it is necessary to study the leakage, diffusion and deposition of working fluid. In this paper, the numerical simulation of the leakage and diffusion process of working fluids with different physical properties is carried out. In the simulation, the Species component transport model is used to study the concentration of the working fluids under the leakage hole in the limited space, and the influence of the physical properties such as density and viscosity on the leakage and diffusion process. The results show that in the space under the leakage hole, density has a great influence on the concentration distribution of the working fluids, followed by viscosity. The higher the density, the greater the mass fraction of working fluid in the space under the leakage hole. The higher the viscosity, the worse the fluidity of the working fluid, and the greater the mass fraction in the space under the leakage hole. In the whole space, the greater the density of the working fluid, the easier it is to diffuse to the middle and lower part of the room and form a higher mass fraction. The greater the viscosity of the working fluid, the easier it is to entrain with the surrounding air.

Key words: physical properties of working fluids, refrigerant, leakage, limited space, diffusion

摘要：

新一代环境友好型工质如R290、R32等由于其燃爆特性，一旦发生泄漏会造成一定的安全隐患，而仍使用较为广泛的工质如R22等一旦发生泄漏同样会加剧温室效应，从而造成全球气候环境恶化。开展工质的泄漏扩散沉积等相关特性的研究十分必要。针对工质在泄漏扩散过程中由于物性的差异造成的泄漏扩散开展了数值模拟研究，模拟中采用Species组分输运模型，考虑密度、黏度等工质物性参数的差异，对工质在泄漏孔下方、泄漏有限空间内的浓度变化，以及密度、黏度等物性对泄漏扩散过程的影响进行了研究。结果表明：泄漏孔下方区域，密度对工质的浓度分布影响较大，其次是黏度；密度越大，工质在泄漏孔下方区域质量分数越大；黏度越大，工质流动性越差，在泄漏孔下方区域质量分数越大。整个有限空间内，工质的密度越大，越易于向空间的中下部区域扩散并形成较高的质量分数；工质的黏度越大，越易于与周围空气发生卷吸作用。

关键词: 工质物性, 制冷剂, 泄漏, 有限空间, 扩散

CLC Number:

TB 64

Peixu ZHOU, Yalun LI, Gongran YE, Yuan ZHUANG, Xilei WU, Zhikai GUO, Xiaohong HAN. Influence of physical properties of working fluids on leakage and diffusion characteristics of refrigerant in limited space[J]. CIESC Journal, 2023, 74(2): 953-967.

周培旭, 李亚伦, 叶恭然, 庄园, 吴曦蕾, 郭智恺, 韩晓红. 有限空间内工质物性对制冷剂泄漏扩散特性的影响[J]. 化工学报, 2023, 74(2): 953-967.

Figures/Tables 26

Fig.1 Schematic diagram of working fluids leakage process of the improved model

Table 1 Critical flow mass flow rates of common working fluids at room temperature（25℃） with leakage aperture of 3 mm

工质	泄漏压力/MPa	泄漏速率/(g/s)
R717	0.998	1.308
R290	0.948	2.018
R1234yf	0.68	3.191
R22	1.04	2.902
R32	1.68	2.394
R744	6.41	2.001

Fig.2 Room model of leakage simulation

Table 2 Grid size settings

泄漏孔尺寸/m	空间尺寸/m	网格质量	网格数/个
0.0005	0.2	0.835	66469
0.0005	0.1	0.845	301558
0.0001	0.08	0.847	600119
0.0001	0.06	0.849	1324453
0.0001	0.05	0.850	2232378

Fig.3 Grid division of 5 sizes

Fig.4 Grid independence test

Fig.5 Comparison between simulated data and experimental data

Table 3 Physical properties of common working fluids at room temperature and pressure （25℃，0.1 MPa）

工质	T/K	p/MPa	密度/ (kg/m³)	比定压热容/ (kJ/(kg·K))	热导率/ (mW/(m·K))	黏度/ (μPa·s)	动量扩散系数μ/ρ	热扩散系数λ/(ρc_p )
R717 (7664-41-7)	298	0.1	0.69	2.16	25.16	10.08	14.52	16.75
R290 (74-98-6)	298	0.1	1.81	1.68	18.29	8.12	4.49	6.01
R1234yf (754-12-1)	298	0.1	4.71	0.90	13.83	11.46	2.44	3.25
R22 (75-45-6)	298	0.1	3.54	0.66	10.57	12.62	3.56	2.13
R32 (75-10-5)	298	0.1	2.13	0.85	12.51	12.61	5.93	6.95
R744 (14485-07-5)	298	0.1	1.79	0.85	16.62	14.91	8.35	10.95

Fig.6 Contours of leakage process of working fluids in limited space

Fig.7 Contours of concentration distribution of different working fluids under the leakage hole at t=30 s

Fig.8 Concentration distribution of different working fluids at the monitor points under the leakage hole

Fig.9 Concentration distribution of working fluids with large density difference at the monitor points under the leakage hole

Fig.10 Comparison of concentration distribution of R744 and R290 under the leakage hole at different heights

Fig.11 Contours of diffusion process of working fluids in limited space

Fig.12 Contours of concentration distribution of different working fluids at the intersecting surface of the center of the leakage hole (Z=0.115 m) during diffusion process

Table 4 Layouts of monitoring points

序号	X/m	Y/m	Z/m	序号	X/m	Y/m	Z/m	序号	X/m	Y/m	Z/m
点1	1.0	0.7	0.7	点10	2.0	0.7	0.7	点19	3.0	0.7	0.7
点2	1.0	0.7	1.4	点11	2.0	0.7	1.4	点20	3.0	0.7	1.4
点3	1.0	0.7	2.1	点12	2.0	0.7	2.1	点21	3.0	0.7	2.1
点4	1.0	1.4	0.7	点13	2.0	1.4	0.7	点22	3.0	1.4	0.7
点5	1.0	1.4	1.4	点14	2.0	1.4	1.4	点23	3.0	1.4	1.4
点6	1.0	1.4	2.1	点15	2.0	1.4	2.1	点24	3.0	1.4	2.1
点7	1.0	2.1	0.7	点16	2.0	2.1	0.7	点25	3.0	2.1	0.7
点8	1.0	2.1	1.4	点17	2.0	2.1	1.4	点26	3.0	2.1	1.4
点9	1.0	2.1	2.1	点18	2.0	2.1	2.1	点27	3.0	2.1	2.1

Fig.13 Layout of monitor points in the room

Fig.14 Concentration distribution of different working fluids at different monitor points at the same time

Fig.15 Concentration distribution of working fluids at the monitor points in the lower part of the room

Fig.16 Concentration distribution of working fluids at the monitor points in the middle part of the room

Fig.17 Concentration distribution of working fluids at the monitor points in the upper part of the room

Fig.18 Contours of deposition process of working fluids in limited space

Fig.19 Contours of concentration distribution of different working fluids at the intersecting surface of the center of the leakage hole (Z=0.115 m) during deposition process

Fig.20 Concentration curve of R22 at different heights

Fig.21 Concentration of different working fluids with the change of height at the end of leakage process

Fig.22 Concentration of different working fluids with the change of height after the deposition process

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