Evaluation of Heat Transfer Kinetics on Layers of Air-Rich Soft Materials in Their Natural State

Air-rich soft materials are widely used in textile products, such as clothes and towels, because they exhibit good heat-retaining properties. Quantification of the heat-retaining properties of materials is necessary for product design engineering. Here, the behavior of heat transfer in the layer structure of the material is evaluated to formulate its kinetics. Such evaluation can address the barriers to appropriate design. The heat transfer kinetics of the multilayered structure of the materials are evaluated by assessing the surface temperature of the outer layers. The evaluation equation for kinetics is formulated by applying the fundamental relationship of heat transfer, which is represented by thermal conductivity and the heat transfer coefficient. In the experimental evaluation, a simple wind tunnel was developed using a blower, hot plate, and digital radiation temperature sensor. The temperature of the hot plate was set at three levels. In the evaluation of surface temperature, the quantity of infrared ray was measured using the digital radiation temperature sensor, because it could be used without mechanically influencing the specimen. The surface temperature of the materials was measured by changing the number of layers from one to eight. In the evaluation of heat transfer kinetics, some properties of the conductivity and the transfer were identified by the formulated relationship for the kinetics of the layered structure and the numerical technique of inverse analysis. It was found that the heat conductivity of the material and heat conductivities between the layers can be identified by the examination of surface temperature variation caused by the change in the number of layers. Then, the crush effect of air-rich structures can be assessed by compressing the material and then analyzing the behavior change in heat transfer caused by the crush. The difference between the observed results and those obtained without the crush of air-rich structure was significant. Thus, we concluded that the physical properties of heat transfer in a multilayered structure of air-rich soft materials can be identified using the surface temperature change in the material resulting from the number of layers. Therefore, it is important to measure its behavior without the crush of the air-rich structure to evaluate the most natural state of the material appropriately.