Measurement of Coupled Heat and Moisture Transfer Coefficients for Selected Vegetables

Two experimental devices. Capped Column and Open Column, were used to measure four heat and mass transfer coefficients of four vegetables: potato, yam. butterquash and turnip. Two classical coefficients, thermal conductivity. KT, and moisture diffusivity. DM, and two coupled coefficients. moisture gradient induced heat transfer coefficient, KM, and temperature gradient induced moisture migration coefficient Dr(or δT=DT/DM), were measured. The mean measured values of KT obtained for potato, yam, buttersquash and turnip were 0.50, 0.58, 0.54 and 0.51 W/m-K, respectively. The mean measured values of KM for potato, yam. buttersquash and turnip were 117.1, 32.8, 41.0 and 190.8 W/m, respectively, of δT were 0.00059, 0.00065, 0.00024and 0.00047 per degree K, respectively and of DM were 1.32×10-9, 1.16×10-9, and 1.58×10-4 m2/s, respectively. Smaller interocellular spaces seemed to have a positive effect on the thermal conductivity. Moisture content and size of intercellular spaces both seemed to have positive effect on KM. The value of δT was lower for vegetables with higher moisture content which is consistent with the results reported in literature. The value of DM seemed to be positively affected by both the porosity and the size of the intercellular spaces in the test vegetables.