Thermal aspects of open sun drying of various crops

Open sun drying (OSD) is the most common method of crop drying in developing countries. Despite several disadvantages, it is widely practiced because it is a simple way of drying. Crop temperature, temperature around the crop, solair temperature, and rate of moisture evaporation are the important parameters in OSD. The thermal behavior of OSD of green chillies, green pea, white gram (kabuli chana), onions, potatoes, and cauliflower was studied. The heat transfer analysis which is mainly dependent on the rate of moisture transfer has also been extended during drying process. A mathematical model has been developed to predict the crop temperature, rate of moisture removal, and solair temperature for a steady state condition. The rate of moisture transfer for potato slices and cauliflower was significantly higher than that in other crops. A fair agreement was observed between predicted and experimental results with coefficient of correlations ranging from 0.8936 to 0.7520, 0.9792–0.4172, and 0.9986–0.9942 for crop temperature, temperature above the crop surface, and rate of the moisture removal during drying, respectively except potato slices.

[1]  S. Sokhansanj,et al.  Moisture transport caused by natural convection in grain stores , 1990 .

[2]  P. J. Lunde.  Solar thermal engineering: Space heating and hot water systems , 1980 .

[3]  I. Dincer.  An exact modelling for thermal diffusivities of solid objects exposed to heating , 1995 .

[4]  L. Diamante,et al.  Mathematical modelling of the thin layer solar drying of sweet potato slices , 1993 .

[5]  Luis Saravia,et al.  RELATIONSHIP BETWEEN A SOLAR DRYING MODEL OF RED PEPPER AND THE KINETICS OF PURE WATER EVAPORATION (I) , 1997 .

[6]  Ibrahim Dincer,et al.  Moisture Loss from Wood Products During Drying—Part I: Moisture Diffusivities and Moisture Transfer Coefficients , 1998 .

[7]  R. D. Gibson.  Theory and problems of heat transfer, (schaum's outline series): McGraw-Hill, New York (1978) , 1979 .

[8]  R. K. Goyal,et al.  Effect of thermal storage on the performance of a deep bed drying system , 1999 .

[10]  Steven C. Chapra,et al.  Numerical Methods for Engineers , 1986 .

[11]  M. S. Sodha,et al.  An analytical and experimental study of open sun drying and a cabinet tyre drier , 1985 .

[12]  G. N. Tiwari,et al.  Evaluation of convective heat transfer coefficient in crop drying under open sun drying conditions , 2001 .

[13]  I. Dincer,et al.  A modelling study for moisture diffusivities and moisture transfer coefficients in drying of solid objects , 1996 .

[14]  I. Dincer,et al.  Determination of moisture diffusivities and moisture transfer coefficients for wooden slabs subject to drying , 1996, Wood Science and Technology.