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，本工作为研究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 a two-dimensional porous medium MgSO₄·7H₂O/MgSO₄ was developed using reaction kinetics to investigate the energy storage characteristics of MgSO₄as a thermochemical material. This study examined the reaction rate, temperature distribution, and water vapor concentration distribution during heat and mass transfer in charging/discharging units. This study also examined the influence of inlet air temperature (T_in) and inlet air velocity (U_in) on unit performance and thermal efficiency. The results indicate that during the charging process, heat storage increases by approximately 3.13% for every 10 ℃ increase in T_in and by approximately 0.97% for every 0.125 m/s increase in U_in. An increase in T_in accelerates the rate of unit heat transfer and enables the water vapor pressure to reach equilibrium faster, subsequently increasing the reaction rate. Similarly, an increase in U_in enhances the water vapor transport rate and improves the convective heat transfer within the unit, thereby enhancing the kinetic properties and increasing the reaction rate, which leads to an increase in the heat storage capacity. Conversely, during the discharge process, the unit thermal efficiency exhibited an inverse relationship with heat storage capacity. The thermal efficiency decreased by approximately 0.93% for every 2.5 ℃ increase in T_in, whereas heat storage decreased by approximately 0.58% for every 0.1 m/s increase in U_in. An increase in T_in increases the equilibrium pressure of the unit and decreases its unit reaction rate, thereby reducing the effect of temperature rise of the unit. Furthermore, an increase in U_in increases the rate of water vapor transport and convective heat transfer of the unit, which subsequently increases the water vapor pressure. Ultimately, the reaction rate and thermal efficiency decreased. This study offers a theoretical foundation and practical reference for understanding the thermochemical energy storage characteristics 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, 2024, 13(12): 4299-4309.

Shuyu XU, Yan WANG. Numerical study of thermochemical energy storage characteristics of MgSO₄[J]. Energy Storage Science and Technology, 2024, 13(12): 4299-4309.

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

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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 of MgSO₄

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