球形容器内石蜡非约束融化特性实验

doi:10.11949/j.issn.0438-1157.20181341

摘要/Abstract

摘要：

通过可视化实验研究了球内受空隙影响的石蜡（RT27）非约束融化过程，探讨了球直径、加热温度、初始温度以及相变材料（PCM）填充率对球内非约束融化特性的影响。通过对PCM固液界面演化、固相运动等融化行为的观察发现，受球内空隙影响，非约束融化过程会出现固相PCM先漂浮后下沉的融化模式。进一步的量化结果表明：增大球直径，固相PCM漂浮时间先增大后减小，总融化时间则持续增大；提升加热温度和初始温度，固相PCM漂浮时间和总融化时间减小；增大PCM填充率，固相漂浮时间和总融化时间先增大后减小。最后，通过对实验数据的无量纲化分析，提出了无量纲总融化时间（受Rayleigh数、Stefan数、PCM填充率、无量纲初始温度影响）关系式。

关键词: 相变, 多相流, 传热, 热能存储, 非约束融化, 空隙, 球形容器

Abstract:

A visualization experiment is conducted to investigate the unconstrained melting process of phase change material (PCM, paraffin RT27) with void in a spherical container. Factors including the spherical container diameter, the heating temperature, the initial temperature and the filling ratio of PCM are discussed. Melting behaviors including the solid-liquid interface evolution and the solid PCM motion are revealed, in which a melting mode of floating melting following by close-contact melting is observed due to the existence of void in the spherical container. The quantitative results show that as the spherical container diameter increases, the floating melting time increase first and then decreases, while the total melting time shows a continually increasing trend. Increasing heating temperature or increasing initial temperature will decrease the floating melting time and total melting time. With the increases of PCM filling ratio, the PCM floating melting time and the total melting time increase first and then decrease. Finally, a dimensionless total melting time correlation in terms of Rayleigh number, Stefan number, filling ratio of PCM and dimensionless initial temperature is proposed.

Key words: phase change, multiphase flow, heat transfer, thermal energy storage, unconstrained melting, void, spherical container

中图分类号:

TK 124

高泽世, 姚元鹏, 吴慧英. 球形容器内石蜡非约束融化特性实验[J]. 化工学报, 2019, 70(7): 2480-2487.

Zeshi GAO, Yuanpeng YAO, Huiying WU. Experiment on the unconstrained melting of paraffin in spherical containers[J]. CIESC Journal, 2019, 70(7): 2480-2487.

图/表 12

图1 球形相变单元内锥形孔隙剖面图[31]

Fig.1 Sectional view of cone-shaped void in spherical phase change unit[31]

图2 球形容器内PCM非约束融化实验系统

Fig.2 Experimental setup for unconstrained melting of PCM inside spherical container

表1 RT27热物性参数[27]

Table 1 Thermophysical properties of RT27[27]

热物性参数	数值
密度 (固相), ρ_s/（kg/m³）	880
密度 (液相), ρ_l/（kg/m³）	760
热导率 (固相), λ_s/(W/(m·℃))	0.24
热导率 (液相), λ_l/(W/(m·℃))	0.15
比热容 (固相), c_s/(kJ/(kg·℃))	2.4
比热容 (液相), c_l/(kJ/(kg·℃))	1.8
热膨胀系数 (液相), β/℃^-1	5×10^-4
运动黏度, ν/(m²/s)	5×10^-6
潜热, L/(kJ/kg)	179
相变温度, T_m/℃	27

表2 球形容器样品

Table 2 Spherical container samples

直径/mm	PCM质量,M₀/g	球壳质量/g
20.05	2.787	1.331
30.70	10.861	2.397
40.75	26.522	4.219
50.10	48.990	9.840
60.10	79.996	13.093
70.30	131.592	14.627

图3 蓄热球内非约束融化过程(D = 40.75 mm, Th = 37℃, Ti = 7℃, ε = 0.90)

Fig.3 Unconstrained melting process in a sphere(D = 40.75 mm, Th = 37℃, Ti= 7℃, ε=0.90)

图4 固相PCM漂浮及下沉过程示意图

Fig.4 Schematic diagram of floating and sinking of solid PCM

图5 漂浮融化时间（a）和总融化时间（b）随直径以及加热温度的变化

Fig.5 Variation of float melting time (a) and total melting time (b) with diameter and heating temperature

图6 漂浮融化时间（a）和总融化时间（b）随PCM填充率的变化

Fig.6 Variation of float melting time (a) and total melting time (b) with PCM filling ratio

图7 漂浮融化时间（a）和总融化时间（b）随初始温度的变化

Fig.7 Variation of float melting time (a) and total melting time (b) with initial temperature

表3 无量纲参数相对误差汇总

Table 3 Errors of dimensionless parameters

参数	相对误差/%
Ra	8
Ste	2.8
S_i	2.8
Fo	7.1
ε	0.1

图8 无量纲总融化时间和无量纲漂浮融化时间关系式

Fig.8 Correlation between dimensionless total melting time and dimensionless floating melting time

图9 无量纲总融化时间关系式

Fig.9 Correlation of dimensionless total melting time

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