Modeling deep-bed grain drying using Comsol Multiphysics

CFD simulations were carried out to predict the convective heat and mass transfer coefficients in the rice bed, and correlations were developed for the convective heat and mass transfer coefficients as a function of drying air flow rate. The developed correlations were used to extend the coupled CFD and diffusion model developed by ElGamal et al. (2013) for thinlayer rice drying to volumetric heat and mass transfer in a deep-bed of rice. All mathematical models were solved using the Comsol Multiphysics® simulation program v4.3 (Comsol Inc, Palo Alto), which uses the finite element method to solve the model equations. The model was used to predict the air temperature, as well as the grain moisture content and temperature at different locations of the dryer during the drying process. The theoretical predictions of moisture and temperature profiles inside a deep-bed of rice were verified by experimental data from literature

Multi-scale model for heat and mass transfer during rice drying

Grain drying is a simultaneous heat and moisture transfer problem. The modeling of such a problem is of significance in understanding and controlling the drying process. The main goal of this study was to predict the heat and mass transfer processes during deep-bed rice drying. To achieve this, first, CFD simulations were carried out to analyze the external flow and temperature fields at steady-state for a control volume of a stationary rice bed. The model was used to predict the convective heat and mass transfer coefficients in the rice bed, and correlations were developed for the convective heat and mass transfer coefficients as a function of drying air flow rate. Then, the coupled CFD and diffusion model developed by ElGamal, Ronsse, Radwan & Pieters (2013) to investigate the heat and mass transfer for thin-layer drying of rice was extended to volumetric heat and mass transfer in a deep-bed of rice using the predicted heat and mass transfer coefficients. All models were solved numerically using the finite element method. The model was used to predict the air temperature, as well as the grain moisture content and temperature at different locations of the dryer during the drying process. The theoretical predictions of moisture and temperature profiles inside a deep-bed of rice were verified by experimental data from literature. The average mean relative deviation values for the prediction of grain moisture content varied between 1.00 to 3.13%

Emerging thermal imaging techniques for seed quality evaluation: Principles and applications

Due to the massive progress occurred in the past few decades in imaging, electronics and computer science, infrared thermal imaging technique has witnessed numerous technological advancement and smart applications in non-destructive testing and quality monitoring of different agro-food produces. Thermal imaging offers a potential non-contact imaging modality for the determination of various quality traits based on the infrared radiation emitted from target foods. The technique has been moved from just an exploration method in engineering and astronomy into an effective tool in many fields for forming unambiguous images called thermograms eventuated from the temperature and thermal properties of the target objects. It depends principally on converting the invisible infrared radiation emitted by the objects into visible two-dimensional temperature data without making a direct contact with the examined objects. This method has been widely used for different applications in agriculture and food science and technology with special applications in seed quality assessment. This article provides an overview of thermal imaging theory, briefly describes the fundamentals of the system and explores the recent advances and research works conducted in quality evaluation of different sorts of seeds. The article comprehensively reviewed research efforts of using thermal imaging systems in seed applications including estimation of seed viability, detection of fungal growth and insect infections, detection of seed damage and impurities, seed classification and variety identification.info:eu-repo/semantics/acceptedVersio

Physico-mechanical Properties of Rough Rice Grain under Different Moisture Conditions

This study was carried out to evaluate some physical and mechanical properties of three Hungarian rice varieties named Dáma, Janka and M488 under different moisture levels to be a useful data for modelling the moisture changes in rough rice storage bins. Rough rice grains were conditioned to moisture contents of 12, 18, 24, and 30% (w.b.). Five mechanical expressions named rupture force (Fr), maximum stress (σmax), grain deformation (D), energy (E) and toughness (T) were extracted from stress–strain curve for all tested varieties as a function of moisture content. Also, some physical properties such as bulk density, true density, porosity and some morphological features of grain were determined as a function of moisture content for tested rough rice grain. The results revealed that the measured physical and mechanical properties are significantly effected by moisture contents for the three tested rice varieties. In general, when the moisture content increased, the rupture force and maximum stress decreased for all investigated grains. However, the deformation, energy and toughness firstly decreased with moisture content increase and after that increased with further increase of moisture content for all rice varieties. On the other hand, the bulk density, true density and porosity do not have a specific trend with increasing moisture content. Moreover, there was a significant difference among the selected rice varieties in terms of their bulk density and porosity at the same moisture content range

Development of a multi-scale model for deep-bed drying of rice

The drying behavior of rough rice in a deep bed was analyzed numerically by solving the heat and moisture transfer equations using a novel deep-bed model. The model consisted of two scales. A computational fluid dynamics (CFD) model was used first to predict the convective coefficients of heat and mass transfer between an individual rough rice kernel and air in the rough rice bed. The predicted heat and mass transfer coefficients were then used for coupling the moisture and heat fluxes inside the rough rice kernel with the external convective heat and mass transfers at the kernels' surfaces in a complete rough rice bed model using the Comsol Multiphysics simulation environment. The developed model was used to predict the grain moisture contents and temperatures at different heights in the bed during drying. The theoretical predictions of moisture profiles inside a deep bed of rough rice were validated against experimental data from literature. The results revealed that the mean relative deviation between predicted and experimental values varied between 3.1% and 6.8%. Most importantly, the novel approach used in this study allowed the deep-bed model to predict the moisture and temperature distributions inside the individual rough rice kernels at different heights in the rough rice bed

Incorporation of a solar tracking system for enhancing the performance of solar air heaters in drying apple slices

The main aim of this study was to develop an integrated solar-tracking system to maximize the efficiency of solar heaters manufactured from recyclable aluminum cans (RAC) for optimum drying of apple slices. The results revealed that the thermal efficiency of the solar air heater incorporated with a tracking unit was significantly improved by about 45% compared with the conventional fixed heaters at all tested air flow rates. The highest thermal efficiency of 87.1% of the solar air heater equipped with a tracking unit was achieved at the highest air flow rate of 44 m3h-1. The highest moisture diffusivity (Deff) at the high levels of drying air temperature and flow rate and the highest value of Deff (5.43×10-10 m2s-1) was obtained in the dryer with a tracking system at the highest air flow rate of 44 m3h-1. The drying rate of apple slices under such a tracking module was considerably higher than that of either the traditional fixed system or the ambient sun drying.info:eu-repo/semantics/acceptedVersio

Coupling CFD and diffusion models for analyzing the convective drying behavior of a single rice kernel

The drying behavior of a single rice kernel subjected to convective drying was analyzed numerically by solving heat and moisture transfer equations using a coupled CFD and diffusion model. The transfer coefficients were computed simultaneously with the external flow field and the internal diffusive field of the grain. The model was validated using results of a thin-layer drying experiments from literature. The effects of velocity and temperature of the drying air on the rice kernel were analyzed. It was found that the air temperature was the major variable that affected the drying rate of the rice kernel. The initial drying rates (in first 20 min) were 7%, 12% and 19% per hour at inlet air temperature of 30ºC, 45ºC, and 60ºC, respectively. Important temperature gradients within the grain existed only in the first few minutes of the drying process. The moisture content gradients reached a maximum value of 11.7% [d.b.].mm-1 at approximately 45 min along the short axis in the thickness direction. The variation of the inlet air velocity showed a minor effect on the drying rate of the rice kernel. The heat and mass transfer coefficients varied from 16.57 to 203.46 W•m-2•K-1 and from 0.0160 to 0.1959 m•s-1, respectively. The importance of the computation of the transfer coefficients with the heat and mass transfer model is demonstrated

Genetic Basis of Combining Ability for Various Quantitative Traits Using CMS Lines of Rice (Oryza sativa L.)

Line × Tester experiment was carried out at the Experimental Farm of Rice Research and Training Center (RRTC), Sakha, Kafrelsheikh, Egypt during three growing seasons to evaluate the performance of 21 F1 hybrids along with their parents. Three cytoplasmic male sterile lines, two wild abortive (Wild Abortive); IR69625A, IR70368A and one (Kalinga) K17A as female were tested with seven cultivars/lines as testers. The analysis of variance detected that, highly significant variations among genotypes (parental lines with their crosses) for all traits in both seasons and in their combined analysis. Two hybrid combinations; IR69625A×Giza178 and IR69625A×Giza179 were recorded the best values for grain yield under both seasons and their combined. General combining ability (GCA) and specific combining ability (SCA) effects of genotypes for the studied traits were estimated. The results indicated that, K17A (female) and Giza 179 (male) were the best combiner for early heading date and could be useful to breed early maturing rice cultivars. The CMS line IR69625A and Giza178, Giza179 gave highly significant and positive GCA value and so appeared to be good parental lines combiner in hybrid combinations for high grain yield/plant. The positive values of GCA mean increased for grain yield/plant, which could be useful in breeding programs for high yield potential rice cultivars. The hybrid combination IR69625A×Giza179 showed highly significant and positive SCA estimates under both seasons and their combined. In conclusion, it is clear that this hybrid seemed promising hybrid for earliness and high grain yield under Egyptian conditions

Thermal Degradation of Bioactive Compounds during Drying Process of Horticultural and Agronomic Products: A Comprehensive Overview

Over the last few decades, many researchers have investigated in detail the characteristics of bioactive compounds such as polyphenols, vitamins, flavonoids, and glycosides, and volatile compounds in fruits, vegetables and medicinal and aromatic plants that possess beneficial properties, as well as consumer acceptance and preference. The main aim of this article is to provide an updated overview of recent research endeavors related to the effects of the drying process on the major bioactive/effective compounds in agricultural products. Particular emphasis was placed on details related to the changes occurring in vitamin C, polyphenols, flavonoids, glycosides and volatile compounds, as well as the antioxidant activity. An analysis of the degradation mechanisms of these compounds showed that vitamin C, phenols, flavonoids and glycosides react with oxygen during the convective drying process under high drying temperatures, and the reaction rate results in degradation in such bioactive compounds due to high reducibility. On the other hand, high temperature results in a short drying time, thus minimizing the degradation of bioactive compounds. The reviewed research works addressing this trend revealed that the ideal drying temperatures for retaining vitamin C, polyphenols, flavonoids, glycosides, volatile compounds and their antioxidant activity were 50–60 °C, 55–60 °C, 60–70 °C, 45–50 °C, 40–50 °C and 50–70 °C, respectively. In conclusion, to maintain plant bioactive components, convective drying at relatively low drying temperatures is strongly recommended

Gastric carcinoma at Tanta Cancer Center: A comparative retrospective clinico-pathological study of the elderly versus the non-elderly

Background and aims: To study the clinico-pathological features, treatments and outcomes of gastric carcinoma (GC) in the elderly (⩾65 years) and the non-elderly Egyptian patients. Methods: This retrospective cohort study included 168 patients with histologically confirmed GC treated at Tanta Cancer Center between 2003 and 2007. Results: Compared to the non-elderly, elderly patients had significantly higher proportion of tumors involving the cardia (p = 0.034) and of adenocarcinoma NOS histology (p = 0.032). Treatments were largely comparable in the two groups. Response to palliative chemotherapy was achieved in 44.4% of the elderly and 25.5% of the non-elderly patients (p = 0.417). The median overall survival (OS), disease-free survival (DFS) and progression-free survival (PFS) were 6, 17 and 3 months, respectively. The median OS was 4 months in the elderly compared to 9 months in the non-elderly (p = 0.005). The median DFS was 4 months in the elderly compared to 20 months in the non-elderly (p = 0.004). The median PFS was 2 months in the elderly compared to 3 months in the non-elderly (p = 0.685). In multivariate analysis, poor performance status was an independent predictor of poor OS, DFS and PFS. Non-curative or no surgery and lack of chemotherapy use were independent predictors of poor OS. Age was an independent predictor of poor DFS. Conclusions: Compared to the non-elderly, GC in the elderly has similar clinico-pathological characteristics and exhibits comparable outcomes with the same treatment options. Treatments should be tailored to each patient