Structural Analysis And Numerical Simulation Of Thermal Storage Equipment On Mid-low Temperature Phase Change Material

With the rapid development of industry, heat storage energy such as solar, wasteheat and geothermal energy and fully utilized are becoming increasingly important,More attention has been paid to research on the heat storage techniques. Because ofits large energy storage per unit volume and substantially constant temperature in theheat storage process, heat storage with Phase change materials （PCMs） has beenresearch hot spot at present. Two critical technologies for latent heat storage are theenergy storage materials and the heat storage structure. Usually, the phase changematerials except metals have relatively poor heat conduction performance, whichslow the storage/release heat during PCM’s melting and the solidification processand limit the development of phase-change thermal storage technology. Therefore, itis necessary taking effective heat transfer enhancement to improve the heat transfercoefficient of phase change thermal storage. The method often used is adding fins tothe PCMs side of phase change thermal storage structure. Barium hydroxideoctahydrate（Ba（OH）₂·8H₂O）, paraffic, low melting point alloy SnZn were used onbehalf of the mid-low temperature phase change materials with annular finned tubesheat exchanger structure for the study of heat transfer enhancement effect on the heatstorage structure.The mathematical models of Ba（OH）₂·8H₂O heat storage device with annularfinned tubes were established in this paper. Heat storage/Discharge process of theheat storage device were simulated by using FLUENT software,distribution of liquidrate and temperature,different measuring point temperature change rule and PCMheat/heat quantity were simulated. In order to obtain universal results, impact ofparameters such as fin height and fins spacing on heat effect were analyzed.Compared to PCM phase change process with smooth surface tube heat storage unit,the best design parameters of cylindrical Ba（OH）₂·8H₂O heat storage device weredetermined. Eventually,16mm heat tube diameter and80mm PCM encapsulationdiameter were used in heat storage unit with annular finned tube.13%heat storagetime shorten than the same volume under no finned heat exchange tube. The total heatstorage for the Ba（OH）₂·8H₂O heat storage device is2.34×10⁵kJ. It provides reference basis for the application of the mid-temperature heat storage device in thefield of energy utilization.For paraffin heat storage devices, fin structure added in PCM side and lowannular fins added in fluid side for the low melting point alloy SnZn snake-tube heatexchanger. Single tube mathematical model was built, impact of parameters such asfin height and fins spacing on heat effect were analyzed. The best design parametersof the two heat storage devices were determined. A two-dimensional mathematicalmodel of PCM overall heat storage device that heat exchange pipe diameter is16mmwas built to simulate distribution of temperature field, interface moving rule,temperature change of different measuring point, PCM heat storage/release and so on.Eventually paraffin finned tube heat exchanger structure was confirmed which heatexchange tube spacing is80mm and total amount of stored heat is1.142×10⁴kJ;Adding low rib strengthening heat transfer device in heat exchange tube to Sn-9Znheat storage device, corresponding to the total heat storage is2.76×10⁴kJ, and thisprovid reference value in engineering applications.