The effect of the structure of rigid polyurethane foams
blown with a hydrocarbon blowing agent on foam's apparent thermal conductivity
Polimery 2001, No 9, 631
SummaryThe apparent thermal conductivity (λy) was measured (Fig. 1) in rigid polyurethane foams (RPURF) blown with a new type blowing agent, viz., a mixture of pentanes (as an alternative to freons), over a broad range of apparent foam densities (ρ) (Figs. 2, 3). At low ρ, the λy vs. ρ curves exhibited a minimum. Several equations are presented, based on reported theoretical models, which allow to predict Ie for PUR foams (Tab le 1). The values predicted for a given foam varied considerably. The equations developed for foams blown with freons were tested in terms of their usefulness to predict λy for pentanes-blown foams. The RPURF experimental λy-data were consistent only with the λy-data calculated from equation (4) based on the Glicksman model (Fig. 7). Contributions of individual heat transfer modes (conduction in gas phase, conduction in solid phase, radiation) to the overall heat transfer through the foam were estimated in relation to RPURF density (Fig. 8).