Research On Testing Method Of The Fabric Unsteady-State Thermal Insulation Properties

The thermal property of textiles is an important parameter related to human body comfort, and extensive research work has been done in this area. Many studies of thermal properties, which carried out so far are mainly concentrated on the static state, but few researches on the unsteady-state thermal properties have been done. In high temperature environments, the temperature of fabric and object protected by fabric will increase gradually until it reaches heat balance. In that case, it belongs to typical unsteady state heat transfer process. It is unfit for this case that test by tradition static method. In meeting that case, a new unsteady state method of thermal insulation test is adopted. And unsteady stare heat transmitting properties of fabric is studied systematically in this thesis. The main contents are as follows:1. Put an electron numerical thermometer's probe, enwrapped by fabric, in close to a static state, constant temperature (180℃) condition, and record the probe's temperature timely, and then the data are analyzed.2. Through analyzing the combined convection and radiation heat transfer coefficient between the fabric or probe's surface and thesurroundings. Simulate this heat transfer process by a long cylinder model, one dimension transfer heat by radial, with instant convective heat transfer coefficient. And the fabric's unsteady state heat resistance factor is developed. It can describe the fabric's thermophysical properties. And then it can describe the fabric's unsteady state heat transfer properties.3. Compared and analyzed the testing curve , and then the evaluation induces, which sign the testing results, are developed, include the difference of critical time, the difference of critical temperature, the unsteady state thermal insulation factor, the initial unsteady state heat transfer characteristics value, the fabric's unsteady state thermal protection coefficient. These induces describe the fabric's thermal resistance properties during the unsteady heat transfer process. The unsteady state thermal insulation factors don't manifest fabric's insulation property as a result like some tradition induces, but as a process.4. Choose fourteen fabrics, for research the relative between the thermal insulation properties and the number of layers or different combination. Measured properties of monolayer double deck and the fabric's different combination by the unsteady state heat transfer and warmth retention testing methods, and the data are analyzed, illustrated, and compared. Through regression analysis, the results show: There is some correlarions between these induce acquired by the unsteady state and static method, demonstrating between these induces there is intrinsic dependence.5. Measured the thermal insulation properties as a function of the number of layers and thickness. The static heat preservation ratio just increases to twice, but the unsteady state thermal protection coefficientincreases to near four times when the fabric add to near four times. And it proves that it unfit for fabric's unsteady state thermal properties by static method.ZHANG Yao (Textile Engineering) Supervised by Prof. ZHU Sukang...