Estimation of the thermal contact resistance between potato granules and steel

The sample resistance of a metal junction filled with a layer of a food material was obtained by the classical method of measuring the axial temperature profile in two metal cylinders above and below the sample under pressure. The results reported here represent a first estimate of the sample resistance of potato granule layers constrained between steel counterfaces. Its value increased as expected with increasing sample thickness. The sample resistance was in the range 0.7–2.5 K W −1 and decreased slightly with increasing temperature from 30 to 90 °C but varied only slightly with sample density in the range 1020–1470 kg m −3. The extrapolated lower bound contact resistance for a single steel-potato granule interface was of the order 0.15–0.65 K W −1. The value of the thermal conductivity derived from the variation of sample resistance with thickness was overestimated compared to other measurements using a line source technique.