The Research On The Symmetric Hotplate For Measuring Fabric Thermal Resistance

Heat transfer performance is one of the most critical factors of textiles and clothing comfort, is also one of the most important determinant of the development and trade of functional fabrics and garments, while thermal resistance is used to describe the thermal comfort of fabric as an important indicator. There are a lot of standards and instruments to determinate dry thermal resistance of textile materials at home and abroad, each standard has a corresponding apparatus. However, they are very much the same:the hot-plate with the same structure to simulate the heat transfer form of "one-dimensional steady temperature field", all that need to make some experiments to operate with an blank hot-plate and a sample experimental data. However, a large number of experiments found that:The set temperature of the test panel and the actual temperature of the boards are different, there is heat exchange between guard plate and test plate, it will cause system errors for these devices.This thesis is started from basic theory and put forward a new idea of instrument structure, and then providing a new structure reference and research orientation for the measurement of thermal resistance. Research idea is that the steel test plate hanging in the air controlled by a LabVIEW virtual instrument in the constant temperature and humidity chamber, attaching the temperature sensor to the outer surface of the steel test plate. Thus heat can be generated directly from the inner plate and transfer toward the direction perpendicular to the plate to throughout the fabric. It not only omits the guard plate and eliminates the heat exchange with the test board, but also eliminates a test plate temperature inequality ranging from under to surface as system problem.Firstly, write LabVIEW control program and produce experimental apparatus, then put 10 fabric with different thickness on the boards which are test device of steel, two guarded hot-plate at the same time for the thermal resistance measurement, and finally analyze the data of thermal resistance for the three groups (Measured from steel test board devices and two groups of experimental with guarded hot-plate) through the SPSS software. If the array has no significant difference, the experimental results prove that devices are reasonable, but also prove that this idea is feasible, the theory is correct. Therefore, to continue correcting and researching in this direction is meaningful.Setup of the experimental apparatus for this paper comply with the design idea, Lab VIEW control program can effectively run and measure corresponding parameter to calculate the thermal resistance. Finally, data analysis shows that:The data were obtained with device and two sets of experiment, which trend is very similar, but the corresponding values are quite different. It is not difficult to find the blank experimental data and fabric experimental data (especially the 10# fabric) measured by the other two instruments are quite different. The air thermal resistance value measured by the fabric guarded hot-plate is not absolute one, instead the relative value adjusted according to specific sample. And the blank experimental data between YG (B)-606D guarded hot-plate and YG-606E guarded hot-plate is pretty different, and also the ins and outs of YG (B)-606D blank experimental data exist big difference, forming self-negative. The air thermal resistance measured by guarded hot-plate is not credible. Furthermore, some relevant experimental results by Weina Chang prove air thermal resistance measured by the device is valid, in line with theory and practice.Additionally, data error is caused partly by uneven temperature of the test plate. The heat transfer toward multi-direction is a larger important reason for fabric thermal resistance, it will make the value different. Guard plate of fabric guarded hot-plate is not only to ensure that the temperature between the guard plates and test plate equal, preventing horizontal heat transfer from test plate, it can also replenish heat loss of the surface of test plate to form a dynamic equilibrium. But these reasons are only to affect the accuracy of results. It is not enough to make the results where is an order of magnitude difference in fabric experiments.