Natural stratification-based cooling characteristics of a microencapsulated phase-change material suspension and its parametric optimization study

doi:10.19799/j.cnki.2095-4239.2024.1185

Abstract

Abstract:

This study exploits the advantages of microencapsulated phase-change material suspensions (MPCMSs), such as excellent flowability, high cooling storage density, and stable thermal behavior during cooling release. By integrating these properties into a natural stratification-based cooling storage system, a three-dimensional transient model of a cylindrical cold storage tank with a pseudo-octagonal diffuser was developed. This study investigates the cooling release and temperature distribution characteristics of MPCMSs with mass fractions of 10%, 20%, and 30% under different flow rates. The effects of the diffuser opening count and diameter on the cooling process were analyzed. An optimization strategy employing nozzle-type diffusers was proposed, and the influence of different diffuser structural parameters on the thermocline thickness, temperature fields in small-opening regions, and outflow velocity was examined.The results demonstrate that using MPCMS as the storage medium in a natural stratification-based system creates a thermocline with a steep temperature gradient at the center and smaller gradients at the sides. Higher mass fractions suppress hot-cold fluid mixing and increase the specific heat capacity in the phase-change region, enhancing the cooling release efficiency and temperature control. For 10% and 20% MPCMS mass fractions, increasing the number of openings, selecting a 10 mm diameter diffuser, and using a new nozzle-type diffuser reduce the thermocline thickness and improve cooling performance. However, at 30% mass fraction, variations in the number of openings and the use of nozzle-type diffusers compared with the original diffuser yield negligible differences in performance. This study provides valuable insights for advancing the application of MPCMS in natural stratification-based cooling systems and offers scientific support for optimizing MPCMS energy storage technology.

Key words: MPCMS, cold storage characteristics, thermocline, diffuser, structural optimization

CLC Number:

TK 02

Yalong CHENG, Kunfeng LIANG, Xun ZHOU, Miaomiao LIU, Gangxin LYU, Yitian SONG. Natural stratification-based cooling characteristics of a microencapsulated phase-change material suspension and its parametric optimization study[J]. Energy Storage Science and Technology, 2025, 14(6): 2256-2269.

Figures/Tables 18

Fig. 1

Fig. 2

Table 1

Table 2

Operating conditions parameters"

参数	质量分数 $ω$
	工况1			工况2			工况3
	10%	20%	30%	10%	20%	30%	10%	20%	30%
流量 $Q$ /(m³/h)	12.56			8.37			6.28
释冷时间 $t$ /h	1			1.5			2
入口流速 $v i n$ /(m/s)	0.61732			0.41153			0.30864
开孔个数	12			12			12
开孔直径/mm	8			8			8

Table 2

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项目名称	数值
入口温度/K	303
出口温度/K	296
重力加速度/(m/s²)	9.81
蓄冷介质	MPCMS
黏度模型	Laminar flow
入口类型	Inlet-velocity
出口类型	Pressure-out

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