A Numerical Investigation on Thermal Transport Phenomena during Solar Drying of a Potato Slice

This study presents a numerical investigation of transport phenomena during the solar drying of a potato slice. The associated transport phenomena are modelled using appropriate boundary conditions and the conservative mass and energy diffusion equations. A simple solar surface-heating model is introduced as the novelty of this study. The governing equations are discretized using the finite volume method (FVM) and the Crank-Nicolson scheme. The discretized equations are then solved using the TDMA method by developing a numerical code in FORTRAN, along with a comprehensive grid-independent study and validation against existing literature. This study evaluates the evaporation rate, heat and mass transfer coefficients, and temperature and water content distributions within the potato slice as it dries under solar irradiation over a sunny day. An average evaporation rate of 9.8 g/m 2 ·s persists over 1 hr, reaching a steady value of 0.41 g/m 2 ·s. Corresponding sets for the heat and mass transfer coefficients are (1.12×10 4 , 73.66) W/m 2 ·°C and (7.95×10 -6 , 5.18×10 -7 ) m/s, respectively. On a sunny day, after 12 hr of solar drying, 82.6% of the total water content evaporates from a 4 mm-thick potato slice with a maximum temperature attainment of 96.76 °C. A parametric study is also conducted. It has been found that a thin slice of potato dries quickly. An additional 4% increase in total evaporation is observed when the slice thickness is reduced to 2 mm; in contrast, a 3% reduction in total evaporation is observed when the slice thickness is increased to 6 mm. The drying process is significantly affected by the inlet air temperature passing over the potato slice; however, its flow rate has an insignificant effect. A 2% reduction in total evaporation is observed when the air flow temperature increases by 30 °C. Such information supports the design of a direct solar-drying system and indirectly helps farmers to prevent food waste.