Study On The Solid-liquid Phase Change Heat Transfer Characteristics Of Skeletons With Different Material

Green transformation development brings unprecedented opportunities for the application of energy storage technology.The addition of skeletons to solid-liquid phase change materials is an effective means to improve the heat transfer performance of phase change materials,but there are few studies on the heat transfer of solid-liquid phase change containing skeletons of different materials and structures.In this thesis,a combination of experimental studies and numerical simulations is used to investigate in depth the melting process,temperature variations and local thermal non-equilibrium effects of phase change materials containing skeletons of different materials.In this thesis,a solid-liquid phase change experimental platform is built and the melting process of phase change materials containing different materials and skeletons is observed using experimental research methods.The local thermal non-equilibrium effect during the melting process of materials containing different materials and structural skeletons is analysed by measuring the temperature change of composite phase change materials.The study shows thatThe material and structure of the skeleton significantly affects the melting process and the rate of heat storage of the composite phase change material.Compared with pure phase change materials,the melting time of phase change materials containing metal skeleton is shorter,the solid-liquid phase change interface migrates backward faster,the upper part of the solid-liquid phase change interface migrates backward faster than the lower part,the addition of metal skeleton helps to improve the heat storage rate of composite phase change materials,the greater the thermal conductivity of the skeleton,the faster the heat storage rate of composite phase change materials,while the melting time of paraffin wax containing nylon skeleton is slightly longer than that of pure paraffin wax,the solid-liquid phase change interface migration rate is not as fast as that of phase change materials containing metal skeleton,the heat storage rate of phase change materials containing nylon skeleton is slower,When the skeleton structure in a composite phase change material changes,the melting time,the solid-liquid phase change interface and the heat storage rate all change.For example,the V-shaped aluminium alloy/paraffin wax has a shorter melting time compared to the uniform aluminium alloy/paraffin wax,the solid-liquid phase change interface has a "C" shape,the heat storage rate of the V-shaped aluminium alloy/paraffin wax is greater than that of the uniform aluminium alloy/paraffin wax,and the V-shaped skeleton structure facilitates the melting process of the phase change material in relation to the thermal conductivity of the skeleton.The material and structure of the skeleton affect the temperature change and the local thermal non-equilibrium effect of the composite phase change material.The process of temperature change of the composite phase change material is divided into pre-,mid-and post-phase.In the early stage,the skeleton and the phase change material are heated to a rapid increase in temperature.The greater the thermal conductivity of the skeleton in the composite phase change material,the faster the temperature rise of the composite phase change material,and there will be a delay in the temperature change of the phase change material containing nylon skeleton in the early stage.The skeleton structure in the composite phase change material also changes the temperature rise rate of the phase change material,the better the heat transfer properties of the skeleton structure,the faster the temperature rise of the composite phase change material,for example,the temperature rise rate of phase change materials with a V-shaped skeleton structure is significantly stronger than that of phase change materials with a uniform skeleton structure.The skeleton material and structure have a significant influence on the local thermal non-equilibrium effect within the composite phase change material.The temperature difference between the skeleton and its surrounding paraffin is used to reflect the local thermal non-equilibrium effect.The temperature difference shows a complex trend with time,with multiple peaks and valleys.For example,the maximum temperature difference between V-shaped aluminium alloy/paraffin can reach a peak of 2 ℃.The peak temperature difference is related to the structure of the skeleton and its thermal conductivity,the distance between the heating surfaces and the strength of the natural convection,which can sometimes be negative,mainly because the natural convection in the liquid phase in the solid-liquid phase change region is stronger than the thermal conductivity of the skeleton.