| Along with the rapid development of space technology, the requirement for thermal insulating technology has become stronger, and the materials which are closely related to thermal insulating technology have become the key research in the thermal insulation field. Although the existing thermal insulating materials are improved constantly, they still can not meet increasingly stringent insulating environment and requirements. Therefore, it is an eternal topic to strengthen the properties of existing thermal insulating materials and search for new efficient materials.The significance of thermal insulation in various fields is treated and an integrated introduction of investigation and development for thermal insulation technology and thermal insulating materials is summarized in this paper firstly. A kind of ZrO2 hollow sphere thermal insulating materials with excellent performance is presented on the basic of an summarization of the mechanism of thermal insulating materials and the approach to improve the performance of thermal insulating materials, which can control the conduction, convection and radiation effectively. The theoretical models to estimate the thermal conductivity are summarized, and a point-contact hollow sphere model which accords with the microstructure of ZrO2 materials, and large numbers of numerical simulation are proceed to analyze the effect of porosity, size of pore etc on the thermal conductivity, and also the effect of conduction, convection and radiation is analyzed to find approach to control them. Finally, compare the result of theoretical models, numerical simulation and experiment to indicate the applicable bound for theoretical models and numerical simulation respectively: it is found that the theoretical model is suited for low temperature, and numerical simulation is a feasible method to calculate thermal conductivity which is fit for any temperature.ZrO2 hollow sphere is applied to exhaust pipe of engine on the basic of above study, and then STAR-CD is employed to analyze the influence of the thickness of thermal insulating materials, emissivity, vacuum and the fashion of thermal insulation on the effect of thermal insulation. An optimal scheme of thermal insulation is presented and compared to the former scheme. It is found that the scheme with excellent effect of thermal insulation makes the efficiency of thermal insulation increase 31.7% and the heat loss reduce 91.4% which provides theoretical basis and idea for stringent thermal insulation designing. |
