scholarly journals Optimization of Microwave Coupled Hot Air Drying for Chinese Yam Using Response Surface Methodology

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 745 ◽  
Author(s):  
Hanyang Wang ◽  
Dan Liu ◽  
Haiming Yu ◽  
Donghai Wang ◽  
Jun Li
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Power Density ◽  
Air Temperature ◽  
Microwave Power ◽  
Slice Thickness ◽  
Air Velocity ◽  
Hot Air Drying ◽  
Air Drying ◽  
Hot Air

The effect of microwave coupled hot air drying on rehydration ratio (RR) and total sugar content (TSC) of Chinese yam was investigated. Single factor test and response surface methodology were used for process parameter optimization with hot air temperature, hot air velocity, slice thickness, and microwave power density as variables and RR and TSC of dried products as responses. The effect of variables on RR followed the order: slice thickness > hot air temperature > microwave power density > hot air velocity. The effect of variables on TSC followed the order: slice thickness > microwave power density > hot air velocity > hot air temperature. The optimized process parameters were hot air velocity of 2.5 m/s, hot air temperature of 61.7 °C, slice thickness of 8.5 mm, and microwave power density of 5.9 W/g. Under the optimal conditions, the predicted values of RR and TSC were 1.90 g/g and 5.74 g/100 g, respectively, which is very close to corresponding actual values (1.83 g/g and 5.72 g/100 g). The desirability of 0.913 further validated the effectiveness of the model. The findings from this work may apply to other agricultural products.

scholarly journals Optimisation of energy consumption of a solar-electric dryer during hot air drying of tomato slices

2019 ◽  
Vol 50 (3) ◽  
pp. 150-158 ◽  
Author(s):  
Nnaemeka R. Nwakuba
Keyword(s):  
Energy Consumption ◽  
Air Temperature ◽  
High Energy ◽  
Slice Thickness ◽  
Air Velocity ◽  
Hot Air Drying ◽  
Air Drying ◽  
Hot Air ◽  
Drying Conditions ◽  
Desirability Index

High-energy demand of convective crop dryers has prompted study on optimisation of dryer energy consumption for optimal and cost effective drying operation. This paper presents response surface optimisation of energy consumption of a solar-electric dryer during hot air drying of tomato slices. Drying experiments were conducted with 1 kg batch of tomato samples using a 33 central composite design of Design Expert 7.0 Statistical Package. Three levels of air velocity (1.0, 1.5 and 2.0 ms–1), slice thickness (10, 15 and 20 mm) and air temperature (50, 60 and 70°C) were used to investigate their effects on energy consumption. A quadratic model was obtained with a high coefficient of determination (R2) of 0.9825. The model was validated using the statistical analysis of the experimental parameters and normal probability plot of the energy consumption residuals. Results obtained indicate that the process parameters had significant quadratic effects (P<0.05) on the energy consumption. The energy consumption varied between 5.42 kWh and 99.78 kWh; whereas the specific energy consumption varied between 5.53 kWhkg–1 and 150.61 kWhkg–1. The desirability index method was applied in predicting the ideal energy consumption and drying conditions for tomato slices in a solar-electric dryer. At optimum drying conditions of 1.94 ms–1 air velocity, 10.36 mm slice thickness and 68.4°C drying air temperature, the corresponding energy consumption was 5.6 8kWh for maximum desirability index of 0.989. Thermal utilisation efficiency (TUE) of the sliced tomato samples ranged between 15 ≤TUE ≤58%. The maximum TUE value was obtained at 70°C air temperature, 1.0 ms–1 air velocity and 10 mm slice thickness treatment combination, whereas the minimum TUE was obtained at 50°C air temperature, 2.0 ms–1 air velocity and 20 mm slice thickness. Recommendation and prospect for further improvement of the dryer system were stated.

scholarly journals Optimization of energy consumption of a solar-electric dryer during hot air drying of tomato slices

2019 ◽  
Author(s):  
Nnaemeka R. Nwakuba
Keyword(s):  
Energy Consumption ◽  
Air Temperature ◽  
High Energy ◽  
Utilization Efficiency ◽  
Slice Thickness ◽  
Hot Air Drying ◽  
Air Drying ◽  
Hot Air ◽  
Drying Conditions ◽  
Desirability Index

High-energy demand of convective crop dryers has prompted study on optimization of dryer energy consumption for optimal and cost effective drying operation. This paper presents response surface optimization of energy consumption of a solar-electric dryer during hot air drying of tomato slices. Drying experiments were conducted with 1kg batch of tomato samples using a 33Central Composite Design (CCD) of Design Expert 7.0 Statistical Package. Three levels of air velocity (1.0, 1.5 and 2.0ms–1), slice thickness (10, 15 and 20mm) and air temperature (50, 60 and 70oC) were used to investigate their effects on energy consumption. A quadratic model was obtained with a high coefficient of determination (R2) of 0.9825. The model was validated using the statistical analysis of the experimental parameters and normal probability plot of the energy consumption residuals. Results obtained indicate that the process parameters had significant quadratic effects (p < 0.05) on the energy consumption. The energy consumption varied between 5.42kWh and 99.78kWh; whereas the specific energy consumption varied between 5.53kWhkg–1and 150.61kWhkg–1. The desirability index method was applied in predicting the ideal energy consumption and drying conditions for tomato slices in a solar-electric dryer. At optimum drying conditions of 1.94ms–1air velocity, 10.36mm slice thickness and 68.4oC drying air temperature, the corresponding energy consumption was 5.68kWh for maximum desirability index of 0.989. Thermal utilization efficiency (TUE) of the sliced tomato samples ranged between 15 ≤ TUE ≤ 58%. The maximum TUE value was obtained at 70oC air temperature, 1.0ms–1air velocity and 10mm slice thickness treatment combination, whereas the minimum TUE was obtained at 50oC air temperature, 2.0ms–1air velocity and 20mm slice thickness. Recommendation and prospect for further improvement of the dryer system were stated.

scholarly journals Effective moisture diffusivity during hot air solar drying of tomato slices

2016 ◽  
Vol 62 (No. 1) ◽  
pp. 15-23 ◽  
Author(s):  
H. Samimi Akhijani ◽  
A. Arabhosseini ◽  
M.H. Kianmehr
Keyword(s):  
Moisture Diffusivity ◽  
Effective Moisture Diffusivity ◽  
Slice Thickness ◽  
Solar Drying ◽  
Air Velocity ◽  
Hot Air Drying ◽  
Chi Square ◽  
Air Drying ◽  
Hot Air ◽  
Effective Moisture

Mathematical modelling and effective moisture diffusivity of tomato (Lycopersicon esculentum) was studied during hot air solar drying. An experimental solar dryer with a swivel collector was used for experiments. The collector followed the solar radiation using a precious sensor. Drying experiments were performed in a thin layer hot air drying at slice thicknesses of 3, 5 and 7 mm and air velocities of 0.5, 1 and 2 m/s. The experimental data were fitted to different mathematical moisture ratio models and the Page model was selected as the best model according to correlation coefficient R<sup>2</sup>, chi-square &chi;<sup>2</sup> and root mean square error (RMSE) parameters. The maximum values of moisture diffusivity was&nbsp;6.98 &times; 10<sup>&ndash;9</sup> m<sup>2</sup>/s at air velocity of 2 m/s and slice thickness of 7 mm while the minimum value of the moisture diffusivity was 1.58 &times; 10<sup>&ndash;9</sup> m<sup>2</sup>/s at air velocity of 0.5 m/s and slice thickness of 3 mm.

Microwave Assisted Convective Air Drying of Sugarloaf Pineapples (Ananas Comosus)

2021 ◽  
Vol 37 (5) ◽  
pp. 763-774
Author(s):  
Ernest Ekow Abano
Keyword(s):  
Air Temperature ◽  
Microwave Power ◽  
Moisture Diffusivity ◽  
Hot Air Drying ◽  
Drying Time ◽  
Air Drying ◽  
Microwave Assisted ◽  
Hot Air ◽  
Effective Moisture ◽  
Drying Conditions

HighlightsMicrowave pretreatment before drying reduced drying time significantly.Microwave-assisted drying increased the effective moisture diffusivity coefficient.Microwave pretreatment before convective hot-air drying improved quality parameters.The Middili et al. (2002) model best fitted the microwave-assisted drying of sugarloaf pineapples.Abstract. This study’s objective was to provide the optimum drying conditions to produce quality dried sugarloaf pineapples using microwave pretreatments before the conventional hot air drying. For this, the effect of microwave power (385 to 697 W), microwave time (2 to 4 min), and air temperature (50°C to 70°C) on the drying kinetics and quality of sugarloaf pineapple were evaluated using the Box Behnken response surface methodology. To reach a 17.44±0.09% kg/kg dry matter moisture content, we found the optimum drying conditions for sugarloaf pineapples to be 697 W microwave power for 2.26 min before convective hot air drying at a temperature of 64.75°C. The predicted drying time, ascorbic acid content, and browning index were 13.68 h, 20.89 mg/100 g, and 0.099 Abs unit at this optimum condition, respectively. The pineapple slices’ effective moisture removal rate pretreated with microwave before drying was higher than the control and was between 6.42 × 10-10 m2/s and 11.82 × 10-10 m2/s while ones without a microwave were between 3.54 × 10-10 m2/s and 8.78 × 10-10 m2/s for drying at air temperature between 50°C and 70°C. It was discovered that the Midilli et al. (2002) model was the most appropriate thin layer model for microwave-assisted drying of sugarloaf pineapples. The pineapple slices’ drying rate potential generally increased with microwave power and pretreatments time but not the corresponding increase in the air temperature. Drying time for microwave-assisted drying was in the range of 11 to 20 h, while the ones without microwaves were between 18 and 24 h. Therefore, microwaves should be considered a pretreatment step to the industrial production of sugarloaf pineapple to reduce drying time and produce better quality products. Keywords: Drying, Hot air, Microwave, Moisture diffusivity, Sugarloaf pineapple.

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