Teja Purohitam Narasimha Siva, Gugulothu Santhosh Kumar, Sastry Gadepalli Ravikiran, Burra Bhasker, Bhurat Swapnil Sureshchandra
Department of Mechanical Engineering, National Institute of Technology Andhra Pradesh, Tadepalligudem, India.
Department of Mechanical Engineering, GITAM University, Visakhapatnam, India.
Environ Sci Pollut Res Int. 2022 Jul;29(34):50937-50950. doi: 10.1007/s11356-021-15485-y. Epub 2021 Jul 22.
Thermal energy conversion and storage plays a vital role in numerous sectors like industrial processing, residential and mass cooking processes, thermal management in buildings, chemical heating, and drying applications. It will also useful in waste heat recovery operations in industrial/thermal power stations. The effect of AlO nanoparticle volume fraction (0%, 2%, and 5%) in a paraffin phase change material (PCM) and heater location (Bottom and Sidewall) in a 2D square thermal energy storage system have been numerically analyzed in this study. Transient thermal analysis has been carried out in ANSYS Fluent R18.1 for 500, 1000, and 3000 s. Laminar flow conditions with an enthalpy porosity model are used to study the solidification and melting behavior of nano-PCM. A Grid independence test has been conducted and selected an optimum number of elements as 115538. The results revealed that the addition of nanoparticles in PCM improves its thermal characteristics. The variation of liquid fraction and temperature profile with time has been recorded, and this is due to Rayleigh-Benard convection. At a given time, the melting rate increases with an increase in nanoparticle concentration up to 2% insertion after that the melting fraction reduces for both bottom wall and sidewall heating. This is mainly due to viscous domination with the increase in physical characteristics like density and viscosity of the fluid. Also, the melting rate in the case of sidewall heating augmented more than the bottom wall heating due to negligible buoyancy effects in former than later. The outcome of this analysis helps to find out the optimum volume concentration of nanoparticles to maximize the thermal energy storage applications.
热能转换与存储在众多领域发挥着至关重要的作用，如工业加工、住宅及大规模烹饪过程、建筑物的热管理、化学加热以及干燥应用等。它在工业/热力发电站的余热回收操作中也很有用。本研究对二维方形热能存储系统中，石蜡相变材料（PCM）中AlO纳米颗粒体积分数（0%、2%和5%）以及加热器位置（底部和侧壁）的影响进行了数值分析。在ANSYS Fluent R18.1中进行了500、1000和3000秒的瞬态热分析。采用带有焓孔隙率模型的层流条件来研究纳米PCM的凝固和熔化行为。进行了网格独立性测试，并选择了115538个最佳单元数。结果表明，在PCM中添加纳米颗粒可改善其热特性。记录了液体分数和温度分布随时间的变化，这是由于瑞利-贝纳德对流所致。在给定时间，熔化速率随着纳米颗粒浓度增加至2%而增加，之后对于底部壁面和侧壁加热，熔化分数均降低。这主要是由于随着流体密度和粘度等物理特性的增加，粘性起主导作用。此外，由于侧壁加热情况下的浮力效应比底部壁面加热时可忽略不计，所以侧壁加热时的熔化速率增加得比底部壁面加热时更多。该分析结果有助于找出纳米颗粒的最佳体积浓度，以最大限度地提高热能存储应用。
