Estimation of Temperature-Dependent Effective Thermal Conductivity and Specific Heat of Thermally Bonded High Bulk Nonwoven Exposed to Sub-Zero Temperature

Abstract

In this work, temperature-dependent effective thermal conductivity and specific heat of high bulk thermally bonded polyester nonwovens (composed of 4 fibres viz. 1.4 denier solid, 3 denier hollow, 6 denier hollow and 15 denier hollow individually) are estimated for the sub-zero condition where the temperature drops up to 213 K (−60 °C). Experiments are performed in a custom made climatic chamber for measurement of the transient sensor temperature data placed at a different location inside the fibre web. The test chamber can achieve and maintain the temperature in the range of 213 K - 310 K. The properties are estimated using theoretical relations available in the literature. Heat transfer through the fibre web is assumed to be a one-dimensional coupled conduction-radiation problem. Effective thermal conductivity is calculated at a different ambient temperature ranging from 213 K to 273 K and specific heat is calculated at an ambient temperature of 213 K. Experimental temperature profiles compares well with numerical temperature profiles and thus justifies the numerical methodology adopted in this work. It can be seen from the results that effective thermal conductivity and specific heat decreases with a decrease in temperature which is favourable in providing more insulation in an extremely cold climate.