Variation of the thermal conductivity of elastomeric foam with pressure

In a previous study, the authors used well-known upper and lower bounds to develop the form of an empirical correlation for the thermal conductivity of foam insulation as a function of ambient pressure. The correlation was in terms of three constants which were determined by performing a nonlinear regression on experimentally measured thermal conductivity values of foam neoprene insulation at varying ambient pressure. In this previous work, the thermal conductivity of neoprene rubber was determined using the three constants, one of which is the reciprocal of the thermal conductivity of air. In the present paper, we show that the three correlation constants can, alternately, be determined by using values of the constituent thermal conductivities (e.g. air and rubber), and the effective thermal conductivity at one pressure only. Previously reported values of the measured effective thermal conductivity of foam neoprene insulation under applied pressure, up to 1.18 MPa, were found to have a maximum difference of about 14% of the values predicted using the correlation. It was also found that the accuracy of the correlation did not depend strongly on the reference pressure used.