Experimental study on heat storage performance of a double-fin rectangular phase change energy storage unit

doi:10.19799/j.cnki.2095-4239.2023.0627

Abstract

Abstract:

This study aims to investigate the influence of different boundary temperatures on the heat storage performance of the phase change energy storage unit (PCESU) by conducting visual experiments on the melting process of phase change material (PCM) in a double-fin rectangular PCESU at different boundary temperatures. The analysis involves examining the melting behavior and heat transfer process based on the observation of the solid–liquid interface, PCM temperature, and liquid fraction. The results show that during the late melting stage, solid PCM accumulated at the right-bottom of the PCESU, extending the heat storage time, with the melting time ratio of the PCM at this stage exceeding 30%. With the increase of boundary temperature, the shape of the solid-liquid interface remains considerably constant, with temperature distribution variation being similar. However, the evolution process of the solid-liquid interface accelerates, and natural convection is enhanced, leading to a 60% increase in the nonuniformity of the temperature distribution in the PCM. Moreover, the phase transition temperature increases by a maximum of 2.9 ℃. The results demonstrate that when the boundary temperature increases from 50 ℃ to 73 ℃, the complete melting time is shortened by 510 min. Lower the boundary temperature, greater the $F o S t e$ , indicating that increasing the boundary temperature has a pronounced effect on heat transfer enhancement of the PCM at a lower boundary temperature.

Key words: double-fin, rectangular phase change energy storage unit, boundary temperature, melting process, natural convection

CLC Number:

TK 02

Yibin LUO, Wenchao DUAN, Jinghao YAN, Jie LI, Xiaoqin SUN, Shuguang LIAO. Experimental study on heat storage performance of a double-fin rectangular phase change energy storage unit[J]. Energy Storage Science and Technology, 2024, 13(2): 405-415.

Figures/Tables 22

Fig. 1

Fig. 2

Table 1

Thermal properties of experimental materials"

(a) 石蜡热物性参数表
热物性	参数
相变温度区间/℃	37~45
密度/(k $/$ m³)	961(s)/893(l)
导热系数/[W/(m $·$ ℃)]	0.31(s)/0.21(l)
比热容/[kJ/(kg $·$ ℃)]	2.12(s)/1.98(l)
相变潜热/(kJ/kg)	220.5
动力黏度/(Pa $·$ s)	0.00787
体积热膨胀系数/℃^-1	0.0008

Table 1

Table 2

Fig. 3

Table 3

Fig. 4

Table 4

Uncertainty analysis of the main parameters"

实验参数	温度	长度	图像分辨率	液相率	换热量
不确定度	$±$ 1 ℃	$±$ 1mm	$±$ 1.0%	4.2%	7.5%

Table 4

Fig. 5

Fig. 6

Fig. 7

Table 5

Melting time ratio of the dead space εat different boundary temperatures"

参数	M1(T_w=50 ℃)	M2(T_w=55 ℃)	M3(T_w=64 ℃)	M4(T_w=69 ℃)	M5(T_w=73 ℃)
熔化死角完全熔化用时 $t d e a d$	280 min	190 min	130 min	100 min	90 min
石蜡完全熔化用时 $t t o t a l$	720 min	460 min	310 min	250 min	210 min
熔化死角用时比 $ε$	38.89%	39.13%	32.26%	40.00%	42.86%

Table 5

Fig. 8

Fig. 9

Table 6

Average temperature difference in the midperpendicular plane of M5"

温差平均值	对应测点	M5(T_w=73 ℃)
$T 1 j ¯$ / $T 2 j ¯$	(T11、T12、T13)/(T21、T22、T23)	1.96 ℃
$T 2 j ¯$ / $T 3 j ¯$	(T21、T22、T23)/(T31、T32、T33)	3.23 ℃
$T i 1 ¯$ / $T i 2 ¯$	(T11、T21、T31)/(T12、T22、T32)	1.50 ℃
$T i 2 ¯$ / $T i 3 ¯$	(T12、T22、T32)/(T13、T23、T33)	1.54 ℃

Table 6

Fig. 10

Fig. 11

Table 7

Fig. 12

Table 8

Fig. 13

Fig. 14

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(a)硅胶加热片主要参数
尺寸/mm×mm	输入电压/V	电阻/Ω	可承受温度范围/℃	测量精度
120 x 120	220	10	-50～250	±1%
(b)温控器主要参数
电源规格	温度探头	控温温度范围/℃	工作环境温度/℃	测量精度
110~240 VAC 50/60 Hz	K型热电偶	-20～300	-10～60	±1%

温差平均值	M1(T_w=73 ℃)	M2(T_w=69 ℃)	M3(T_w=64 ℃)	M4(T_w=55 ℃)	M5(T_w=50 ℃)
T1j/T2j	1.96 ℃	1.68 ℃	1.21 ℃	0.66 ℃	0.28 ℃
T2j/T3j	3.23 ℃	2.60 ℃	2.16 ℃	1.84 ℃	1.17 ℃
Ti1/Ti3	3.04 ℃	3.03 ℃	2.84 ℃	2.46 ℃	1.90 ℃

实验	相变温度
M1(T_w=73 ℃)	44.1~44.7 ℃
M2(T_w=69 ℃)	43.2~44.0 ℃
M3(T_w=64 ℃)	42.9~43.6 ℃
M4(T_w=55 ℃)	41.9~42.8 ℃
M5(T_w=50 ℃)	41.0~42.0 ℃

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