Thin Layer Drying and Modelling of Poultry Litter Briquettes

Solar Energy, 2008

Solar dryers use free and renewable energy sources, reduce drying losses (as compared to sun drying) and show lower operational costs than the artificial drying, thus presenting an interesting alternative to conventional dryers. This work proposes to study the feasibility of a solar chimney to dry agricultural products. To assess the technical feasibility of this drying device, a prototype solar chimney, in which the air velocity, temperature and humidity parameters were monitored as a function of the solar incident radiation, was built. Drying tests of food, based on theoretical and experimental studies, assure the technical feasibility of solar chimneys used as solar dryers for agricultural products. The constructed chimney generates a hot airflow with a yearly average rise in temperature (compared to the ambient air temperature) of 13 ± 1°C. In the prototype, the yearly average mass flow was found to be 1.40 ± 0.08 kg/s, which allowed a drying capacity of approximately 440 kg.

2019

A solar powered air inflated grain dryer was developed at Indian Agricultural Research Institute, New Delhi. The developed dryer works on principle of greenhouse effect. The thin layer drying experiments were carried out by drying the freshly harvested paddy in the developed dryer and sun drying. The time required for drying of paddy up to milling moisture content of 14% in the developed dryer ranged from 7.5-9 hours and 11-12.8 hours in sun drying respectively. The drying curves obtained from the experiments were fitted to eight commonly used thin layer drying models. The selected models were compared based on coefficient of determination (R) and Root mean square error (RMSE). The page model (R2=0.9954 and RMSE = 0.007245) had the best fit for the drying of paddy in the developed dryer. Wang and Singh model (R2=0.995 and RMSE = 0.0064) followed by approximation of diffusion model were other models which suitably described the drying kinetics of paddy in the dryer. Sun drying of pad...

2012

Drying of carrots slices and different size carrot cubes layer was investigated in a laboratory dryer with a heater with thermostat. The thin carrots slices layer drying process was studied with small heated air flow by convection. Based on the experimental data, the drying time and temperature dependent drying rate was calculated and presented. Using the proposed methodology, different size (10x10x10 mm; 15x15x15 mm) carrot cube layer drying coefficients, depended on the drying time, were determined. Using the drying rate, the layer of carrot slices drying was simulated and receiving results compared with the experimental data. The obtained measurement results are in high correlation with calculations. The average difference between the calculation and measurement did not exceed 1 %. A mathematical model for thick, porous medium layers, containing small particles, drying is presented. This model contains a system of partial differential equations including the matter and environmen...

Agricultural Engineering International Cigr Journal, 2015

This study presents the thin layer drying behavior of unripe plantain slices (Musa paradisiaca) in a developed biomass cabinet dryer. The developed dryer provided an environment with an optimum operating temperature between 50℃-70℃ meant for drying agricultural materials. The use of thin layer drying mechanisms and equations contribute to better understanding of drying food materials. The thin layer drying behaviour of agricultural products was identified based on the mathematical models which describe the heat and mass transfer phenomena of the products. In order to select a suitable drying model, fourteen different thin layer drying models were fitted to experimental data. Fick's second law was used to calculate the moisture diffusivity with some simplifications. The results were compared for their goodness of fit in terms of correlation coefficient (R2), reduced chi square (χ2), root mean square error (RMSE), and mean bias error (MBE). Effective moisture diffusivity values of unripe plantain slices during drying were-56.8 x 10-1,-2.60 x 10-1 and-6.84 x 10-1 m2/s for charcoal at 5, 10 and 15 mm thicknesses. Midilli and Kucuk, Modified Henderson and Wangh and Singh models were most suitable to describe the drying behavior of unripe plantain at 5, 10 and 15 mm thicknesses respectively when dried with charcoal and there were good agreements between the experimental and predicted variables.

Songklanakarin Journal of Science and Technology

Wet Paddy (KDML 105 variety) was dried under different process conditions applying a pilot scale experimental gas-fired infrared dryer. The infrared radiation is expressed in terms of peak wavelength of infrared emitter, and the initialmoisture content of paddy were varied to study the drying behavior. Five existing mathematical models describing thin layer drying have been investigated. The experimental results were compared considering their goodness of fit in terms of coefficientof determination, R2, root mean square deviation, RMSD, and Chi-square, c2. The available thin layer drying models were fitted to the drying data resulting in the Modified Page Model being chosen, with a high average value of R2 =0.9952.This model was considered to be best fitted over other models, because it gave the lowest RMSD and c2 values, which were compared between the observed and predicted moisture ratios. A combined regression equation was developed to predictthe drying parameters k and n, which...

Journal of food engineering, 2005

This paper presents a periodical analysis of multi-tray crop drying attached to an inclined multi-pass solar air heater with in-built thermal storage. The performance of multi-tray drying integrated with a solar air heater was evaluated for drying of the paddy crop. A parametric ...

Drying has important influences on agricultural products' quality and storage. Drying characteristics of different agricultural products vary. Temperature and velocity of drying airflow affect greatly drying quality and drying efficiency of agricultural products. Two types of solar drying systems for different drying temperature requirement were designed and characterized in this paper: solar air drying system with plate air collector and solar parabolic trough concentrating drying system. In solar air drying system with plate air collector, the drying oven has two ventilation modes. With top inlet and bottom outlet ventilation mode, the overall temperature in drying oven is relatively high, however large vertical temperature difference exists in drying oven. With bottom inlet and top outlet ventilation mode, the temperature in drying oven is uniformity, however relatively low. In notoginseng drying experiment, the drying time is shortened to half of that in nature drying. The average thermal efficiency is 66.5%. The solar trough concentrating drying system utilizes a low cost and reliable V-type metal cavity to collect solar irradiation. In the system, the heat conducting oil can be heated to 230℃, and the air flow from heat exchanger reaches above 200℃. The tobacco shred drying experiments verifies that the drying temperature of the system meets the tobacco shred drying requirement. Solar trough concentrating drying system matchts the drying temperature scope of 80℃~200℃.

This paper presents the energy parameters of corn drying in a convective crop dryer powered by exhaust gas waste heat. The empirical study was applied for drying 1,500 g batch size of an indigenous variety of maize grains (corn kernels). The study considered the impact of the drying air temperature and velocity on the energy indices (total and specific energy consumption, electric and thermal energy demand), drying rate, of the crop dryer, and the moisture diffusion coefficient of the studied samples. Tests were run at varying drying air temperatures (50, 55, and 60 °C) and air velocities (1.0, 1.5, and 2.0 m/s). Results obtained show that the drying parameters had a noticeable influence on the rates of heat transfer and moisture diffusion in the maize samples. The average drying rates varied between 0.83 and 1.4 g/min, whereas drying duration ranged from 305 to 515 min. The thermal efficiency of the drying process ranged from 4.23% to 8.07%. Its values had a direct relationship with the drying air temperature and an inverse relationship with the drying air velocity. The specific energy consumption, which varied between 129.95 and 227.63 kWh/kg increased with increasing air temperature and velocity. Drying air temperature had an inverse effect on the values of the electric energy consumption of the dryer system at constant air velocity. The maximum and minimum thermal energy values were obtained as 97.12 and 55.4 kWhr, respectively. The activation energy and moisture diffusion coefficient values were in the range of 31.75 to 41.05 kJ/mol and 5.77 ×10 − 11 to 1.11 ×10 − 10 m 2 /s, respectively for the studied drying conditions. Prospects for commercial applications as well as recommendations for additional studies were stated.

An integrated dryer comprising three different air heating sources such as solar, biomass and electrical was developed for drying of paddy. Drying kinetics of paddy (long grain variety PR-ll8 procured from PAU, Ludhiana) in the dryer using single as well as combined heating sources was studied at different air temperatures. Drying of paddy occurred in falling rate period. It was observed that duration of drying of paddy from 22% to l3% moisture content (wet basis) was 5-9 hours depending upon the source of energy used. In order to select a suitable drying curve, six thin layer-drying models (Newton, Page, Modified Page, Henderson and Pabis, Logarithmic and Wang and Singh) were fitted to the experimental moisture ratio data. Among the mathematical models investigated, Wang and Singh model best described the drying behaviour of paddy using solar, biomass and combined heating sources with highest correlation coefficient (r2) values and least chi-square, (X2\, mean bias error (MBE) and ...

Precision control of drying conditions is very important in conducting thin-layer drying experiment on agricultural products. For control of drying it is necessary to determine drying kinetics, and obtain the moisture change during the drying process. In order to carry out the experiments a generalpurpose fully automated thin-layer dryer was designed and tested. Experiments on the drying kinetics of paddy (Fajr variety) were conducted at five drying air temperatures, ranging from 30 to 70 C o , in four air velocities, ranging from 0.25 to 1.0 m/s. During the drying the mass loss of samples measured continuously with a digital balance. Drying curves obtained from the experimental data were fitted to nine thin layer models. Results showed that two-term model predicts moisture change in drying with higher accuracy than other models.