N. Voudouris et K. Hayakawa, SIMULTANEOUS DETERMINATION OF THERMAL-CONDUCTIVITY AND DIFFUSIVITY OFFOODS USING A POINT HEAT-SOURCE PROBE - A THEORETICAL-ANALYSIS, Lebensmittel-Wissenschaft + Technologie, 27(6), 1994, pp. 522-532
A computerized mathematical model was developed to examine theoretical
ly the applicability of a continuous point heat source method for simu
ltaneous determination of thermal conductivity (k) and thermal diffusi
vity (alpha) of foods by developing proper data reduction methods. A p
robe of composite structure as well as an overall finite contact condu
ctance coefficient between the probe and the food was assumed. Glycero
l and agar gel were used as reference materials to obtain a mean effec
tive distance 'r' from the point heat source to the temperature sensor
location that is needed in the determination. Estimated k for 15 diff
erent foods was in good agreement with values obtained from the litera
ture (2.5% maximum deviation), whereas the agreement for alpha was rea
sonably good only for foods with large alpha values. A small overall t
hermal contact conductance coefficient introduced an error of 46% in k
and 35% in alpha determination. The minimum food size for accurate de
termination of thermal transport properties was 22 mm height x 8 mm ra
dius, but was further reduced to 17 mm x 5 mm when the heater dimensio
ns were decreased by a factor of four.