Heat-release stability of single tank molten salt heat storage system based on continuous regulation of heat exchange area

doi:10.19799/j.cnki.2095-4239.2021.0353

Abstract

Abstract:

When a coil heat exchanger is placed in a single-tank molten-salt heat storage system, the heat release power of the system decreases with an increase in the heat release time. To achieve stable heat release, in this study, the influence of the change in the heat exchange area on the heat release power of single-tank heat storage systems was examined by experiment using low-melting-point molten salt and air as the heat extraction mediums. By continuously adjusting the heat exchanger area, the outlet temperature of the heat exchanger could be stabilized at the set target value for a long time, and the heat release power could be stabilized. Experimental analysis demonstrated that continuous adjustment of the heat transfer area with a stable heat release is preferred, and the stable heat release time accounts for ～98% of the total heat release time. By continuously adjusting the heat exchange area, stable outlet temperature and heat release power could be obtained.

Key words: molten salt, heat exchange area, heat release power, outlet temperature

CLC Number:

TK 124

Xiaotong CHEN, Yuanwei LU, Cong HE, Wenbing SONG, Yuting WU, Guichun YANG. Heat-release stability of single tank molten salt heat storage system based on continuous regulation of heat exchange area[J]. Energy Storage Science and Technology, 2021, 10(5): 1753-1759.

Figures/Tables 13

Fig. 1

Table 1

Physical parameters of molten salt"

参数	数值
熔点/℃	85.4
分解温度/℃	612
密度/(kg·m^-3)	$ρ s = 2083.486 - 0.7484 T$
比热容/(J·℃^-1)	$c p s = 1450 + 0.345 T$
导热系数/(W·℃^-1)	$λ s = 0.5082 + 1.167 × 10 - 4 T$
潜热/(kJ·kg^-1)	106.9

Table 1

Fig. 2

Table 2

Setting formulas of different setting methods"

整定方法	K_p	T_i	T_d
C-c法	$K p = T 1 K τ (43 + τ 4 T 1)$	$T i = τ (32 T 1 + 6 τ) 13 T 1 + 8 τ$	$T d = 4 T 1 τ 11 T 1 + 2 τ$
Lopze法	$K p = 1.357 K (τ T 1) - 0.947$	$T i = 1.176 T 1 τ T 1 0.738$	$T d = 0.381 (τ T 1) 0.995$
Mcp法	$K p = 1 K 4 T 1 + τ 3 64 τ T 1 2 - 1$	$T i = 1024 T 1 3 τ 2 4 T 1 + τ 4 T 1 + τ 3 64 τ T 1 2 - 1$	$T d = 4 T 1 + τ 2 10.67 T 1 - T 1 - τ 4 T 1 + τ 3 64 τ T 1 2 - 1$
Z-N法	$K p = 1.2 T 1 K τ$	$T i = 2 T 1$	$T d = T 1 2$

Table 2

Fig. 3

Table 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9

Fig. 10

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整定方法	K_p	T_i	T_d
C-c法	1.702	37.369	6.218
Lopze法	1.345	52.467	13.117
Mcp法	0.845	24.691	0.282
Z-N法	1.036	36.377	7.679

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