Drying characteristics of paddy in an integrated dryer

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 ...

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...

Foods

The effect of hybrid infrared-convective (IRC), microwave (MIC) and infrared-convective-microwave (IRCM) drying methods on thermodynamic (drying kinetics, effective moisture diffusivity coefficient (Deff), specific energy consumption (SEC)) and quality (head rice yield (HRY), color value and lightness) characteristics of parboiled rice samples were investigated in this study. Experimental data were fitted into empirical drying models to explain moisture ratio (MR) variations during drying. The Artificial Neural Network (ANN) method was applied to predict MR. The IRCM method provided shorter drying time (reduce percentage = 71%) than IRC (41%) and microwave (69%) methods. The Deff of MIC drying (6.85 × 10−11–4.32 × 10−10 m2/s) was found to be more than the observed in IRC (1.32 × 10−10–1.87 × 10−10 m2/s) and IRCM methods (1.58 × 10−11–2.31 × 10−11 m2/s). SEC decreased during drying. Microwave drying had the lowest SEC (0.457 MJ/kg) compared to other drying methods (with mean 28 MJ/kg...

2017

Drying characteristics of paddy in STR dryer was studied at three air velocities 1.0, 1.5, 2.0 and 3.0 ms -1 respectively. Drying of paddy occurred in falling rate period. It was observed that duration of drying of paddy from 14.5 to 8 % moisture content (w.b.) was 4–6 h depending upon the source of energy used. In order to select a suitable drying curve five drying models (Exponential, Henderson and Pabis, Page, Logarithmic and Power law) were fitted to the experimental moisture ratio data. Among the mathematical models investigated, Page model best described the drying behaviour of paddy with highest coefficient of determination (r 2 ) values and least chi-square, χ 2 , mean bias error (MBE) and root mean square error (RMSE) values. Among all the drying models, Page model adequately described the drying behaviour of paddy using electrical heating source.

Agricultural Engineering International: The CIGR Journal, 2018

This paper investigated the effect of the components of fluidized bed dryer with two thermal sources of heater and infrared such as air temperature at three levels (40, 50 and 60°C) equivalent to radiation intensity of 0.031, 0.042 and 0.053 W.cm -3 in infrared dryer, final moisture content of dried Tarom and Shirudi varieties at three levels (8-9%, 9-10% and 10-11% (d.b.)) and air velocity of 4.5 ms -1 on the milling characteristic and drying time. To this end, stepwise regression was used for selecting the best models for each dependent variable in terms of the independent variables and genetic algorithm was used for optimizing the parameters of dryer with simultaneous consideration of cracked and fractured grains, milling recovery, degree of milling and drying time. The results indicated that quadratic model was best fitted with the experimental data. The results of design of experiments exhibited the infrared fluidized bed dryer was the better option as compared to the warm air ...

Food and Bioproducts Processing, 2012

The objective of this study was to develop a drying equation for predicting the thin layer drying kinetics of dried Thai Hom Mali paddy using different drying gases. Thai Hom Mali paddy cv. Khao Dok Mali 105 with initial moisture content of 32% dry basis was dried in a heat pump dryer at 0.4 m/s fixed superficial velocity, 60% fixed evaporator bypass air ratio, and varied drying temperatures of 40, 50, 60 and 70 • C using hot air, CO 2 and N 2 gases as drying media. Drying rate was not affected by drying gases but increased with drying temperatures. Moisture ratios, at any given time during the drying process, were compared among various models, namely, Newton, Page, Modified Page I, Henderson and Pabis, two-term, approximation of diffusion, and Midilli. The effect of drying air temperatures on the coefficients of the best moisture ratio model was determined by single step regression method. The R 2 coefficient, root mean square error (RMSE) and chi-square (2) were criteria for selecting the best model. The study found that the Midilli model was the best model for describing the drying behavior of Thai Hom Mali paddy in every evaluated drying gas. It should be possible to predict the moisture content of a product with a generalized model that shows the effect of drying air temperature on the model constants and coefficients.

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.

Current Journal of Applied Science and Technology, 2020

A Static flat-bed batch dryer was developed for drying paddy from harvesting moisture content (20-22%) to 12% for safe storage. The dryer mainly consisted of Blower, Heating chamber, Plenum chamber and drying chamber. Twenty kg paddy was dried in the developed dryer at two different inlet air flow rate (1 m 3 /min. and 1.26 m 3 /min). The machine has a capacity of 20 kg and temperature of drying air was 60 and 55°C respectively. The moisture content was recorded at every 15 minutes interval and moisture ratio plots were generated. The experimental data were fit in 8 different thin-layer drying models and statistical parameters along with the model constants were obtained. It was found that the Wang and Singh model with the highest values for R 2 and the least values of RMSE in selected drying conditions has the best fit. Henderson & Pabis and Newton models were also found suitable for describing the drying kinetics of paddy in the developed dryer.

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 Thermal Analysis and Calorimetry, 2020

In the present work, the first and second laws of thermodynamics were used to perform energy and exergy analyses for deep bed drying of paddy in a convective dryer. Also, the equivalent specific CO 2 emission was assessed. Drying experiments were carried out at drying air temperatures of 40, 50 and 60 °C, and air flow rates of 0.008, 0.012 and 0.017 m 3 s -1 . Energy utilization, energy utilization ratio and energy efficiency were obtained to be in the range of 0.061-0.1412 kJ s -1 , 22.41-46.81% and 4.37-8.56%, respectively. Exergy loss decreased continually with drying time and the average values ranged from 0.019 to 0.081 kJ s -1 . Exergy efficiency varied in the range of 32.44-66.91%. Energy and exergy efficiency was improved at low temperature-low flow rate and high temperature-high flow rate, respectively. The results of environmental analysis declared that specific CO 2 emission ranged from 3.83 to 8.42 kg CO 2 kg -1 water where high temperature-low flow rate drying air reduced the footprint. Semi-industrial drying • Rough rice • Energy utilization • Exergy efficiency • CO 2 emission * Mohsen Beigi