Heat Transfer of Fibrous Insulation Battings

Abstract

Abstract : Heat losses by convection, conduction, and radiation through battings made of solid and hollow regular fibers (fiber diameter D sub f = 25- micrometers), fine fibers (12-micrometers D sub f 15-micrometers), and microfibers (D sub f 10 micrometers) have been investigated by using laboratory-scale heat flow apparatus and heat transfer analysis. It is found that these heat losses are interrelated functions of batting thickness, batting bulk-density, and fiber diameter. Natural convective heat loss is found to be negligible for all the battings. Conductive heat loss is essentially inversely proportional to batting thickness and relatively independent of fiber properties. Radiative heat loss is found to decrease with increasing bulk density and decreasing fiber diameter. Hence, microfiber battings can be thinner than battings made from other fibers to provide similar thermal insulation. On the basis of the same bulk density and batting thickness, microfibers can provide a maximum of about 25% and 10% higher clo values than regular and fine fibers, respectively. In view of the low radiative heat loss of microfibers and the high resilience of regular fibers, they should be combined to form economical composite battings. In addition, reflective battings made from reflective layers and low bulk-density fibers should also be pursued for applications where laundering is not required.