Modeli i termodinmačke osobine tankih kriški paradajza sušenog vrelim vazduhom

The drying kinetics and determination of thermodynamic properties of sliced tomato samples during hot air drying in a hybrid solar-electric crop dryer were presented. One kilogram batch of freshly harvested tomato samples were sliced to 10 mm thickness and dried at varying air velocities (1.0, 1.5 and 2.0 ms-1) and temperatures (50, 55, 60, 65, and 70oC) using the hybrid mode. In order to choose the best drying model, eight thin-layer mathematical models were fitted to the experimental data. The high values of coefficient of determination, R2 and the low values of reduced sum of squares error (SSE) and root mean square error (RMSE) indicated that the Midilli et al. model adequately described the drying process of tomato slices, with its highest R2 (0.9999), lowest SSE (0.1136) and lowest value of RMSE (0.0212) at 70oC temperature and 2.0 ms-1 air velocity. Arrhenius model was used to represent the drying constant as a function of temperature. The effective moisture diffusivity increased with increase in temperature and air velocity; with the highest value obtained at air velocity of 2.0 ms-1 and temperature of 70oC, whereas it was lowest at air velocity of 1.0 ms-1 and temperature of 50oC. The mean activation energy required to dry 1kg batch of 10 mm sliced tomato samples was 39.34 kJmol-1. Enthalpy and Gibbs free energy values were found to decrease with increasing drying temperature as well as the entropy which also exothermically decreased with temperature. Recommendations for further studies were stated.Prikazana je kinetika sušenja i određivanje termodinamičkih osobina uzoraka narezanog paradajza tokom sušenja toplim vazduhom u solarnoj sušari. 1 kg svežih uzoraka paradajza su rezane na debljinu 10 mm i sušene na različitim brzinama vazduha (1,0, 1,5 i 2,0 ms-1) i temperaturama (50, 55, 60, 65 i 70 °C) hibridnim načinom sušenja. Da bi se izabrao najbolji model sušenja, urađeno je 8 tanko-slojnih matematičkih modela sa eksperimentalnim podacima. Visoke vrednosti koeficijenta determinacije, R2 i male vrednosti smanjene sume kvadrata greške (SSE) i kvadratne greške (RMSE) ukazuju da su Midilli i sar. model adekvatno opisali proces sušenja narezanog paradajza, sa najvišim R2 (0.9999), najnižim SSE (0.1136) i najnižom vrednosti RMSE (0.0212) pri temperaturi od 70°C i brzinom vazduha 2.0 ms-1. Arrenius model predstavlja konstantu sušenja kao funkciju temperature. Efikasna difuzivnost vlage se povećava sa povećanjem temperature i brzine vazduha; sa najvećom vrednošću dobijenom brzinom vazduha od 2,0 ms-1 i temperaturom od 70oC, dok je bila najmanja brzina vazduha od 1,0 ms-1 i temperatura od 50oC. Srednja energija aktivacije koja je potrebna za sušenje 1kg šarže od 10 mm rezanih uzoraka paradajza bila je 39,34 kJmol-1. Utvrđeno je da se smanjuju vrednosti slobodne energije Enthalpy i Gibbs sa povećanom temperaturom sušenja, kao i entropijom koja je takođe ekzotermno smanjena sa temperaturom. Navedene su preporuke za dalje istraživanje