The Development And Application Of A Guard Hot Plate Designed For Thermal-Conductivity Measurements At High Temperature

In order to solve the problem of energy consumption in buildings,research and promotion of low thermal conductivity insulation materials has become an important task in the development of science and technology.As one of the important thermal physical parameters of various thermal insulation materials,thermal conductivity not only measures the thermal insulation effect of thermal insulation materials,but also plays an extremely important role in the selection of heat transfer equipment and thermal calculation in the heat transfer process.In this paper,based on the principle of one-dimensional steady state,a set of thermal conductivity measuring instruments applied in the middle and high temperature range was developed by using the double sample guard hot plate method.The accuracy and repeatability of the experimental device at different temperatures were verified by measuring the thermal conductivity reference plate of the national standard thermal insulation material.The experimental device was used to measure the thermal conductivity of ceramic fiber board and polyurethane foam board at different temperatures.Uncertainty analysis of the thermal conductivity of ceramic fiberboard at different temperatures further illustrates the accuracy and applicability of the measurement device.The main work completed in this article are:1.Several methods for measuring thermal conductivity and the basic principle of guard plate method measurement were summarized,and the factors affecting thermal conductivity measurement were analyzed.At the same time,the research status of high temperature guard hot plate method thermal conductivity instrument at home and abroad is reviewed.2.Based on the basic principle of one-dimensional steady state and the use of protective hot plate method to measure thermal conductivity,a set of automatic temperature controlled high temperature hot plate method thermal conductivity measuring instrument is designed according to national standards.Through the calculation of the formula,the heating power of the main board,shield and cold plate is determined.According to the specification,the materials of the surrounding insulation are determined.The thickness of the insulation layer,the temperature of the outermost layer,and the heat exchange with the outdoor are determined through theoretical calculations.3.After explaining the various components of the core test system,the temperature control system and software test system of the whole device are introduced.The voltage and current signals in the power measurement signals in the temperature control system were calibrated using Agilent multimeters.Finally,the operation interface of the test software is described.4.In order to further improve the accuracy of the device,the cube model is established through the software to simulate whether the thickness of the insulation layer is appropriate.At the same time,the temperature distribution of the hot plate and the influence of the joints on the temperature of the main shield were simulated.The cylinder model was established through the software to simulate the effect of platinum resistance on temperature measurement after the temperature measurement hole is coated with the thermal conductive glue compared with before the thermal conductive glue is applied.5.The thermal conductivity of the national standard thermal insulation reference board,ceramic fiber board and polyurethane foam board was measured using the experimental device.The measured data was analyzed to obtain the accuracy and the repeatability of the device.Comparing the calculated thermal conductivity with the experimentally measured thermal conductivity,the components that make up the heat loss are obtained.Through experimental analysis,the uncertainty of the device measuring ceramic fibers at different temperatures is calculated.