Microwave Drying Conditions Research Articles

Thin layer drying kinetics of Gundelia tournefortii L.

The literature surveyed revealed that the drying kinetics of Gundelia tournefortii has not been investigated. In this study, mathematical modeling of the thin layer drying kinetics of G. tournefortii is investigated for both the microwave and open sun drying conditions. Five different microwave power levels ranging from 90 to 800W were used for the microwave drying. Solar radiation for the open sun drying varied from 350 to 1100W/m2. Drying took place in the falling rate period. Increasing the microwave power caused a significant decrease in drying time. The experimental moisture loss data were fitted to the 14 thin layer drying models. Among the models proposed, the Midilli model precisely represented the microwave drying behavior of G. tournefortii with the coefficient of determination higher than 0.996 and mean square of deviation (χ2), root mean square error (RMSE) and mean bias error (MBE) lower than 1.82×10−4, 12×10−3 and 1.4×10−4, respectively for all the microwave drying conditions studied. Values of drying constant (k) were in the range of 0.0098–0.2943min−1 and the effective moisture diffusivities (Deff) of G. tournefortii ranged from 5.5×10−8 to 3.5×10−7m2/s. The values of k and Deff increased with the increase of microwave power level. The logarithmic model was found to best describe the open sun drying kinetics of G. tournefortii. The effective diffusivity of G. tournefortii under the sun drying condition was determined as 2.48×10−10m2/s.

Experimental study on microwave drying of Chinese and Indonesian low-rank coals

Drying characteristics of low rank coals in a local microwave oven operating at 2.45 GHz were investigated. Effects of coal particle size, microwave power level, and coal sample size on drying characteristics were studied. Weight losses and temperature history of the samples were measured during drying. Drying rates were then obtained vs. drying time and moisture content. It was found that drying rate was increased with increasing coal particle size showing different trends from conventional drying methods reported in the literature. It was also observed that drying rate increased with increasing power output of the microwave oven or with decreasing coal sample weight. Effects of coal ash content and coal type were also investigated by comparing Chinese and Indonesian low rank coals. Ash content seems to be the governing factor in determining the drying characteristics for coal samples with small particle sizes. Drying mechanism of coals under microwave drying conditions was also discussed.

Analysis of heat and mass transfer during microwave drying of food products

Microwave (MW) drying is a rapid dehydration technique that can be applied to specific foods. Increasing concerns over product quality and production costs have motivated the researchers to investigate and the industry to adopt microwave drying technology. The advantages of microwave drying include the following: shorter drying time, improved product quality, and flexibility in producing a wide variety of dried products. Drying is influenced by heat and mass transfer between drying airflow and product, as well as the complex moisture transport processes which take place in the product.. This paper presents an analytical approach for the drying of potato. The laws of moisture content change in the food product as a function of mass transfer are used for the theoretical approach. The study gives a brief description of efforts made to obtain basic drying parameters under different microwave drying conditions. This computational method can be used as a tool for microwave drying of potato slabs more efficiency.

Modeling of Moisture Diffusion in Microwave Drying of Hardwood

A one-dimensional mathematical model was developed to predict temperature and moisture content profiles in red maple (Acer rubrum L.) and white oak (Quercus alba) during microwave drying. The model was solved using the finite element analysis with MATLAB software. The predictions for temperature and moisture content agreed favorably well with the experimental data. The diffusion coefficients of the red maple and the white oak in microwave drying conditions were calculated and analyzed. Equations of the diffusion coefficient in longitudinal and transverse directions based on input microwave power level are presented in this article. In microwave drying of hardwood, the red maple was heated more efficiently than the white oak because of higher absorbing efficiency of the microwave power.