基于MgSO4 的热化学储能特性数值研究

doi:10.19799/j.cnki.2095-4239.2024.0851

摘要/Abstract

摘要：

为研究热化学材料MgSO₄的储能特性，基于反应动力学，建立二维多孔介质MgSO₄·7H₂O/MgSO₄的储热/放热模型，分析了储热、放热单元内传热传质过程中单元反应速率、温度分布和水蒸气浓度分布，并讨论了入口空气温度(T_in )和入口空气速度(U_in )对单元储热特性和热效率的影响。结果表明，对于储热过程， T_in 每增加10 ℃，储热量增加约3.13%，而U_in 每增加0.125 m/s，储热量增加约0.97%，T_in 的增大使得单元热传递速率加快，水蒸气压力更快达到平衡压力，反应速率也随之增加；U_in 的增加，加快了水蒸气的传输速率且增强了单元内的对流换热，强化了其动力学特性，提升了反应速率，导致储热量增加。对于放热过程，单元热效率的变化趋势与储热量相反。T_in 每增加2.5 ℃，热效率降低约0.93%；U_in 每增加0.1 m/s，热效率降低约0.58%。T_in 的增大，提高了反应单元平衡压力，降低了单元反应速率，减弱了放热单元的温升效应；U_in 的增加，提高了水蒸气的输送速率和单元内对流换热，单元内的水蒸气压力得到了提升，最终导致反应速率和热效率的降低。因此，本文为研究MgSO₄的热化学储能特性提供了理论依据和参考。

关键词: MgSO₄·7H₂O, 传热传质, 多孔介质, 热化学储能

Abstract:

A charging/discharging model of the two-dimension porous medium MgSO₄·7H₂O/MgSO₄ is built based on reaction kinetics to study the energy storage properties of the thermochemical material MgSO₄. Reaction rate, temperature distribution and water vapor concentration distribution during heat and mass transfer process in the charging/discharging unit are analyzed. The effects of inlet air temperature (T_in ) and inlet air velocity (U_in ) on the characteristics of the unit and thermal efficiency are analyzed.The results show that, for the charging process, heat storage increases by approximately 3.13% for every 10 ℃ increase in T_in . While heat storage increases by approximately 0.97% for every 0.125 m/s increase in U_in . The increase in T_in results in a faster rate of unit heat transfer and the water vapor pressure reaches equilibrium pressure more quickly. Consequently, the rate of reaction increases. The increase in U_in accelerates the water vapor transport rate and enhances the convective heat transfer within the unit, strengthening its kinetic properties and increasing the reaction rate, leading to an increase in the heat storage capacity.For the discharging process, the trend in unit thermal efficiency is the opposite of the heat storage capacity. Thermal efficiency decreases by approximately 0.93% for every 2.5 ℃ increase in T_in . While heat storage decreases by approximately 0.58% for every 0.1 m/s increase in U_in . The increase in T_in increases the equilibrium pressure of the unit and decreases the unit reaction rate, reducing temperature rise effect of the unit. The increase in U_in increases the rate of water vapor transport and convective heat transfer of the unit, increasing the water vapor pressure. Ultimately, the reaction rate and thermal efficiency are decreased. This study provides a theoretical basis and reference for the thermochemical energy storage properties of MgSO₄.

Key words: MgSO₄·7H₂O, heat and mass transfer, porous medium, thermochemical energy storage

中图分类号:

TK 02

徐书彧, 王燕. 基于MgSO₄ 的热化学储能特性数值研究[J]. 储能科学与技术, doi: 10.19799/j.cnki.2095-4239.2024.0851.

Shuyu XU, Yan WANG. Numerical study of thermochemical energy storage characteristics based on MgSO₄[J]. Energy Storage Science and Technology, doi: 10.19799/j.cnki.2095-4239.2024.0851.

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参数	物理意义[单位]	数值	参数	物理意义[单位]	数值
M_v	水蒸气摩尔质量[g/mol]	18.02	λ_h	MgSO₄·7H₂O导热系数[W/m·K]	0.48
M_h	MgSO₄·7H₂O摩尔质量 [g/mol]	246	λ_deh	MgSO₄导热系数[W/m·K]	0.48
M_deh	MgSO₄摩尔质量[g/mol]	120	A_f	频率因子[1·s^-1]	167000
C_h	MgSO₄·7H₂O比热容[J/kg·K]	1546	E_a	活化能[kJ/mol]	55
C_deh	MgSO₄比热容[J/kg·K]	800	R	理想气体常数	8.314
k_h	MgSO₄·7H₂O渗透率[m²]	5.44×10^-11	p_ref	参考压力[Pa]	101325
k_deh	MgSO₄渗透率[m²]	7×10^-11	D_g	气体扩散系数[m²/s]	2.82×10^-5
ρ_h	MgSO₄·7H₂O密度[kg/m³]	1680	∆H_r	反应焓[kJ/mol]	411
ρ_deh	MgSO₄密度[kg/m³]	2660	∆S_r	反应熵[J/mol/K]	1041
Ψ	化学计量数	6

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基于MgSO₄ 的热化学储能特性数值研究

Numerical study of thermochemical energy storage characteristics based on MgSO₄

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