Modeling the thin-layer drying process of Granny Smith apples: Application in an indirect solar dryer

Abstract

The thin-layer drying kinetics of Granny Smith apples is determined by thermogravimetric analysis of the drying process at constant temperatures ranging from 20 C to 50 C, using intervals of 5 C. The experimental drying curves obtained in the TGA were fitted to the Wang-Singh equation, which was found to describe precisely the drying process. A novel model, capable of predicting the evolution of the moisture ratio of Granny Smith apples during the drying process and under variable drying temperatures, was proposed. The model was validated with experimental TGA measurements of the drying of apples at variable temperatures, typical of solar drying, obtaining maximum deviations for the drying time of less than 1.5%. Once validated, the model proposed was also applied to the drying of Granny Smith apples in an indirect solar dryer. The comparison of the model prediction with the experimental measurements of the drying of apples at variable drying conditions conducted in a lab-scale solar dryer showed a proper agreement, with low deviations (less than 10%) due to the thermal inertia of the samples.

Solar dryers for tropical food preservation: Thermophysics of crops, systems and components

“…Static equilibrium moisture contents determination is preferred for examining stored crops whereas dynamic methods used for crop samples taken from dryers in operation (Bala, 2003). Several theoretical, semi-theoretical and empirical models for the moisture equilibrium isotherms of agricultural crops produces have proposed to determine the relationship between equilibrium moisture content and equilibrium relative humidity (Brunauer et al, 1938;Day and Nelson, 1965;Henderson, 1952;Thomson et al, 1968;Chen and Clayton, 1971;Pfost et al, 1976;Iglesias et al, 1976;Chen and Morey, 1989;Soysal and Öztekin, 2001;Blanco-Cano et al, 2016a). There is no universal equation that represents accurately the moisture equilibrium isotherms of all agricultural crop products.…”

Continuous and intermittent microwave‐vacuum drying of apple: Drying kinetics, protein, mineral content, and color

“…Granny Smith apple drying have been investigated previously such as freeze (An et al, ), convective (Cruz, Guiné, & Gonçalves, ), and indirect solar (Blanco‐Cano, Soria‐Verdugo, Garcia‐Gutierrez, & Ruiz‐Rivas, ) drying methods. The aim of this research was to study the effects of continuous and intermittent microwave‐vacuum drying on the drying kinetics on “Granny Smith” apples, to describe the moisture removal behavior according to Page's model, to investigate color changes and to observe the changes in the levels of minerals and protein compounds.…”

Karbon Fiber Destekli Kabin Kurutucuda Farklı Sıcaklıklarda Elma Dilimlerinin Kurutulmasının İncelenmesi: Kurutma Karakteristikleri ve Performans Değerlendirmesi

“…Gıdaların ince tabaka kurutulmasının matematiksel modellemesi pratik ve doğru sonuçlar vermektedir [4]. Elmanın dilimler halinde konvektif [11][12][13], konvektif silikon [14], mikrodalga [15] kurutucularda, kızılötesi kurutucu [16], güneş enerjisi destekli kurutucu [17][18], ısı pompalı kurutucu [18] gibi kurutucularda kurutulmasının ince tabaka modelleri ile başarı ile incelendiği çalışmalara literatürde rastlanmaktadır. Yeni bir ısıtma kaynağı tasarımı içeren karbon fiber destekli kurutucularda, yüksek sıcaklıklarda çalışabilen, enerji verimliliği yüksek olduğu belirtilen karbon fiber destekli ısıtma ortamları kullanılmakta ve kombine ısı aktarım mekanizmaları (taşınım, iletim, ışınım) yoluyla gıda maddesinin ısınması sağlanmaktadır [19][20][21][22][23][24].…”