ANALYSIS OF HEAT AND MASS TRANSFER DURING MICROWAVE DRYING OF FOOD PRODUCTS
Abstract - 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.
Prepare sample into required dimension
Record the sample weights at predetermined time interval
Calculate the moisture content using Eq (1)
Non-Dimensionalize the moisture content value
Determine Lag factor (G) and drying coefficient (k) by regressing the dimensionless moisture content
Calculate the Biot number and μ1 value
Determine moisture diffusivity (D)
Based on the results of this study, the following conclusions were drawn.
1) Drying took place mainly in the falling rate period followed by a constant rate period after a short heating period.
2) The drying rate increases with increasing the microwave power or sample diameter.
3) An increase in slab diameter results an increase in the drying coefficient It is because of sudden and volumetric heating, generating high pressure inside the potato samples, resulted in boiling and bubbling of the samples.
4) At low microwave power (90 W), the drying coefficient increases slightly with increase in sample diameter.
5) The variable power had most significant effect on the drying capability.
6) Drying constant increases with an increase in microwave power which is obviously expected.
7) Below the microwave power of 270 W the drying constants for thicker samples are numerically lower than those for thinner plates. This could possibly due to increasing internal resistance to mass transfer. However, beyond a microwave power of 270 W, the trend is reversed. This is because that in high level, the effect of microwave power is more than the effect of increasing internal resistance to mass transfer.
8) In order to maximize the benefits of microwave drying, further studies are required at lower power outputs with different microwave power cycles.
9) In further studies, more comprehensive experimental application of the method should be considered to attain a better understanding drying process of potato slabs as a function of time. Moreover, the influence of various sizes of potato slabs can be studied using this approach.
Attachment:- ANALYSIS OF HEAT AND MASS TRANSFER.pdf