数值模拟分析自然对流对管壳式相变蓄热装置熔融过程的影响
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摘要
随着能源优化配置和清洁供热的需求越来越高,提高固液相变蓄热的换热效率成为相变蓄热中的重要问题,特别是自然对流影响。本文运用数值模拟方法研究了水平单管管壳式的Ba(OH)2·8H2O蓄热装置中自然对流与无对流对其熔融过程的影响,对熔融过程相界面进行了详细的描述。结果表明,在熔融过程中,对流传热在5min～30min内成为传热主导方式,较高温度的液相材料上升,而较低温度的液相材料下降,从而产生循环对流,使上部区域相较于换热管下部区域先熔融,自然对流加速换热管中上部区域换热效率,但对下部区域换热效率影响较小。总体来说,自然对流使相变材料熔融时间缩短19.23%。
Efficiency promotion of heat transfer has become significant issue for thermal storage with PCM(phase change material),especially natural convection,accompanied with the claim of energy optimization and clean heating supply. This paper using numerical simulation method studied the influence of natural convection on the melting process of the horizontal single-tube heat storage device with Ba(OH)2·8 H2 O-PCM. The phase interface during melting process was investigated with two different conditions-without or with natural convection,which might provide reasonable suggestions for optimization of thermal storage device. The results showed that natural convective heat transfer dominate heat transfer within 5-30 minutes in melting process. The warm liquid PCM rise to the upper district and the cold one descended to the lower district,inducing circulation flow around the heating tube,which contributed that the PCM above the inner tube was melted obviously faster than the below. Natural convection enhanced the heat transfer efficiency of heat exchanger set in the upper and middle region,but had little effect in the bottom region. In general,natural convection shortened the melting time by 19.23%.
Efficiency promotion of heat transfer has become significant issue for thermal storage with PCM(phase change material),especially natural convection,accompanied with the claim of energy optimization and clean heating supply. This paper using numerical simulation method studied the influence of natural convection on the melting process of the horizontal single-tube heat storage device with Ba(OH)2·8 H2 O-PCM. The phase interface during melting process was investigated with two different conditions-without or with natural convection,which might provide reasonable suggestions for optimization of thermal storage device. The results showed that natural convective heat transfer dominate heat transfer within 5-30 minutes in melting process. The warm liquid PCM rise to the upper district and the cold one descended to the lower district,inducing circulation flow around the heating tube,which contributed that the PCM above the inner tube was melted obviously faster than the below. Natural convection enhanced the heat transfer efficiency of heat exchanger set in the upper and middle region,but had little effect in the bottom region. In general,natural convection shortened the melting time by 19.23%.
引文
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[2]Lin,Y. X.,Alva G.,Fang G. Y. Review on thermal performances and applications of thermal energy storage systems with inorganic phase change materials. Energy 165(2018):685-708.
[3]Dincer,I.,Dost,S. A perspective on thermal energy storage systems for solar energy applications.International Journal of Energy Research,20.6(2015):547-557.
[4]Vyshak,N. R.,and Jilani,G. Numerical analysis of latent heat thermal energy storage system. Energy Conversion&Management 48.7(2007):2161-2168.
[5]Prieto,M. M.,and González B. Fluid flow and heat transfer in PCM panels arranged vertically and horizontally for application in heating systems.Renewable Energy 97(2016):331-343.
[6]Tao,Y. B.,and Carey,V. P. Effects of PCM thermophysical properties on thermal storage performance of a shell-and-tube latent heat storage unit. Applied Energy 179(2016):203-210.
[7]Avci,M,Yazici,M. Y. Experimental study of thermal energy storage characteristics of a paraffin in a horizontal tube-in-shell storage unit. Energy Conversion&Management 73.2(2013):271-277.
[8]范宗良，高轩，张飞龙，王刚，李贵贤.Y型纵翅片管式相变蓄热过程模拟[J].甘肃科学学报，2017,29(02):74-78.
[9]王美俊，田松峰，韩强，胥佳瑞，陈曦.管壳式换热器蓄热单元数值模拟与优化[J].节能，2016,35(08):11-15+2.
[10]顾煜炯，张晨，耿直，王敏.新型套管式相变蓄热器结构优化及传热研究[J].热力发电，2018,47(01):33-37.
[11]黄凯良，苌群鹏，宋嘉森，冯国会，姜编，刘康.同心管束式空气型相变蓄热器换热影响因素分析[J].流体机械，2018,46(11):74-78+56.
[12]韩广顺，王培伦，金翼，黄云，丁红胜，丁玉龙.列管式相变蓄热器性能强化的模拟[J].储能科学与技术，2015,4(02):183-188.
[13]梁栋栋.低温蓄热装置优化设计及实验研究[D].广州大学，2018.
[14]盛强，邢玉明，罗恒.八水氢氧化钡相变材料储热性能实验[J].北京航空航天大学学报，2014,40(05):635-638.
[15]毛发，章学来，王友利，陈文朴.八水合氢氧化钡与相变蓄热容器的相容性研究[J].太阳能学报，2017,38(08):2292-2296.
[16]Voller V R,Prakash C. A fixed grid numerical modeling methodology for convection-diffusion mushy region phase-change problems[J].International Journal of Heat and Mass Transfer,1987,30(8):1709-1719.