Research On Heat Exchange Device Based On Cascade Phase Change Energy Storage

Phase change heat storage technology has many advantages such as high heat storage density and constant temperature during heat storage and release.It has become a research hotspot in the field of medium and low temperature heat storage.The use of phase change latent heat storage technology for industrial waste heat is mainly focused on: the selection of phase change materials,the enhancement of the thermal conductivity of phase change materials,the analysis of the phase change heat transfer process,the structural design of the phase change heat storage device,and the enhancement of the heat transfer process.Organic phase change materials have the advantages of non-toxic,non-corrosive,no overcooling and phase separation during the phase change process,but at the same time have the problem of low thermal conductivity,which reduces the heat exchange efficiency of the phase change materials.Based on this factor,this research will study the thermal conductivity enhancement methods of hybrid phase change materials made of three different types of organic materials.Paraffin wax,stearic acid,and a mixture of paraffin and stearic acid are used as phase change materials,and high thermal conductivity material powders are used as additives to prepare composite phase change materials.Research on high thermal conductivity material powders as enhancers to enhance the thermal conductivity of composite phase change materials The effect of thermal properties and thermal physical parameters test.The experiment determined that the first stage of the cascade phase change heat exchanger,the second and third stage phase change materials were 70%(10% paraffin + 90% stearic acid):30% graphite,70%(90% paraffin)+10% stearic acid): 30% graphite and 70%(50% paraffin+50% stearic acid): 30% graphite.A fin-tube type cascaded phase-change energy storage heat exchange device is designed,which adopts ring-shaped fins and is equipped with three-stage phase-change material.The heat energy stored in the three-stage phase-change material is converted and output by the heat-carrying fluid water in the tube.Establish a two-dimensional heat transfer model,use ANSYS Fluent numerical simulation software to simulate the heat transfer characteristics of the heat exchange device during melting and heat storage,and analyze the effect of changing the fin height,fin spacing and fin thickness on the phase change material PCM-1,PCM-2 and PCM-3 melting process liquid comparison and temperature field changes over time.The simulation analysis results show that: compared with the bare tube type cascade phase change energy storage heat exchanger,the finned tube type cascade phase change energy storage heat exchanger can significantly increase the melting rate of the phase change materials of each part of the heat exchanger and reduce the phase change The time required for the material to completely melt.Increasing the height of the fin,increasing the thickness of the fin,and reducing the fin spacing are effective ways to reduce the melting and heat storage time of the heat exchanger.Among them,the fin height and the fin spacing are the main influencing factors,and the fin spacing is the secondary factor.By changing the composition ratio of the three-stage phase-change material in the cascade phase-change energy storage heat exchanger,five sets of heat exchanger structure working conditions are set up,and numerical simulations are carried out.From the phase change material liquid phase change and temperature The field change explores the influence of different PCM composition ratios on the heat transfer performance of the cascade phase change heat device.The results show that the cascade phase change energy storage heat exchange device with 5 PCM composition ratios has a good heat storage effect,and the heat flux density curve is stable.Comparing the liquid phase ratio change curves under the five PCM composition ratios,the time required for the melting and heat storage of the cascade phase change energy storage heat exchange device is the shortest when the composition ratio is 3:2:1.Therefore,in the design of cascade phase change heat accumulators,a PCM composition ratio of 3:2:1 is more conducive to rapid heat storage in the accumulator.