Effect of radiation heat transfer in convective drying of cranberry: Numerical solutions of one and two dimensional heat and mass transfer and comparison of results

Abstract

In this work, a numerical model is developed to analyse the effect of radiation on convective drying of a spherical food product. The spherical object considered was cranberry (Vaccinium macrocarpon). The drying air temperatures considered were 313 K, 323 K, 333 K, 343 K and 348 K. There were four models developed; 1D model without and with radiation term and 2D model without and with radiation term. The governing equations were discretized using the finite difference method with an implicit scheme. The discretized equations were then solved by developing a MATLAB computer code using Gauss-Seidel iterative method. The diffusion coefficient, which is a function of temperature, was used to couple the heat and mass transfer equations simultaneously. Both grid and time independent tests were conducted. The transient temperature and moisture distribution contours were estimated for all four models. The results were compared to identify the effects of radiation term in 1D and 2D codes. A maximum error of 14.97% in temperature profile between without and with radiation model created a maximum error of 6.9% in moisture content. The results were compared with experimental solutions and it was found that a good agreement was noticed with 2D models (maximum error of 10.7%) compared to 1D models (maximum error of 13%). Also, a good match was reported between radiation models developed and experimental results. It is concluded that the radiation term must be added while solving convective drying problems.