Numerical Simulation On Properties Of Phase Change Thermal Stotage Wiht Perforated Serrated Fin

With the rapid development of global industry,the exploitation and consumption of large sum of energy bring us not only the problem of energy shortages,but also a world problem of serious environmental pollution.Therefore,seeking for new clean energy and developing new thermal storage technology as well as raising energy utilization efficiency become the priority of the development of each country.With the large potential for development,solar energy thermal power generation techniques is a major manner to relieve the resource scarcity and environmental pollution and other problems;however the problem of energy storage restricts the development of solar energy.Thermal storage techniques can relieve the mismatching of energy supply on time and space due to factors like day and night alteration,among which phase-changing thermal storage techniques become the key point of domestic and international researches because of its advantages like big intensity of thermal storage,easy control of process and constant temperature during phase change,etc.This thesis studies the properties of high-temperature fin plate type phase change thermal storage with perforated serrated fin basing on the theory of phase change thermal storage.Take Solar Salt(40%KNO3-60%NaNO3)as the phase change material and high-temperature heat transfer oil(T66)as the thermal carrier.Adopting CFD stimulation calculations,this thesis studies the influences of thermal carrier entrance parameter and fin geometric parameter and natural convection caused by gravity to the thermal properties of phase change thermal storage.The main contents and conclusions of the study are as follows:(1)Introduce the study background and significance of the topic and review the existing situation and development trends of domestic and international phase change thermal storage.Theoretically,introduce the principle and thermal transfer model of phase change thermal storage and analyze the solutions of numerical methods on thermal transfer problems and interpret the sifting principle of high-temperature phase change materials.(2)Establish the three-dimensional model of fin plate type high-temperature phase change thermal storage and analyze the influence of thermal carrier entrance parameter to thermal storage.The stimulated result shows that the greater temperature difference between the phase change material and entrance temperature,the faster the entrance speed is,the faster the thermal storage speed is.With the entrance temperature gap of thermal storage reaching a certain extent,the thermal property of thermal storage may also reaches the limit.Therefore,always rising the temperature of the thermal carrier will also lead to the waste of heat.(3)Through comparative analysis of the influence of the shape,bore diameter and thickness of perforated serrated fin to the thermal storage and releasing speed,the simulated result turned out that: compared with square and triangle bores serrated fin,serrated fin with round bore has the fast thermal storage and releasing speed;and the size of bore poses a larger influence to the thermal storage and releasing speed while the smaller the bore diameter is,the faster the thermal storage and releasing speed is;the influence of the thickness of the fin plate to the thermal storage and releasing speed is relatively small,the thicker the plate is,the larger the flowing resistance is,as a result,the less the filling quantity of phase change material is,which further reduces the overall thermal storage volume.(4)Using numerical simulation and studying the influence of natural convection to the properties of thermal storage and releasing through changing the direction of gravity,the simulation result turns out that when the direction of gravity is X(Putting vertically),the large zoom of natural convection formed by liquefied phase change material makes the speed of thermal storage and releasing reaching the fastest.Though the existence of natural convection promotes the smelting and solidification of phase change material,the influence of natural convection in melting process is larger than that in solidification process.