Modeling the Moisture Dependent Thermal Properties of Multiplier Onion (Allium Cepa L. var Aggregatum)

Abstract

The thermal properties of multiplier onion namely thermal conductivity, thermal diffusivity and specific heat were determined in the moisture range of 80.87 to 88.84 % w.b. Thermal conductivity was determined using a line heat source transient heat transfer method whereas the thermal diffusivity was determined by Dickerson method using the thermal diffusivity probe. The thermal conductivity and specific heat of onion increased whereas the thermal diffusivity decreased with increase in moisture content. The thermal conductivity, thermal diffusivity and specific heat of onion ranged from 0.17 ± 0.01 to 0.53 ± 0.03 W/mK, 4.32 x 10-7 ± 0.58 to 2.01 x 10-7 ± 0.11 m2/s and 1.01 to 5.75 J/kg.K, respectively. Mathematical modeling was done using the linear regression analysis to predict the specific heat of onions. Among the different models developed, the empirical equation which involved the thermal diffusivity and moisture content predicted the specific heat of onion with a R2 of 0.974.

Termalne osobine luka, kao što su: toplotna provodljivost, toplotna difuzija i specifična toplota su određivane u opsegu vlage od 80.87 do 88.84%. Toplotna provodljivost je određena metodom prolaznog prenosa toplote dok je toplotna difuzija određena Dickerson metodom, korišćenjem toplotne difuzione sonde. Toplotna provodljivost i specifična toplota crnog luka porasle su dok je toplotna difuzija smanjena sa povećanjem sadržaja vlage. Toplotna provodljivost, toplotna difuzija i specifična toplota crnog luka u rasponu od 0,17 ± 0,01 na 0,53 ± 0,03 V/mK , 4.32 h 10-7 ± 0,58 do 2,01 k 10-7 ± 0,11 m2/s i 1,01 do 5,75 J/kg.K , redom. Matematičko modeliranje je urađeno pomoću linearne regresione analize predviđene specifične toplote luka. Među različitim razvijenim modelima, empirijska jednačina koja uključuje toplotnu difuziju i sadržaj vlage predvidela je specificnu toplotu crnog luka sa R2 od 0,974 .