Numerical Simulation on Thermal Performance of Flat and Rib Heat Exchangers Based Solar Food Dryer Under No Load Conditions

Solar dryers are low-cost, energy-efficient, and environmentally friendly devices for drying agricultural products in rural areas of the Himalayan regions. In this study, a two-dimensional model of a flat and rib heat exchanger-based solar food dryer was modeled and solved using Ansys Fluent. The flow was assumed to be two-dimensional, steady, incompressible, and fully developed. The numerical model of the solar dryer was validated with experimental data available from the literature, with less than 5 % deviation of the simulation results. The simulation was performed under no-load conditions for flat and heat exchanger-based solar dryers. Thermodynamic performance of the solar dryers was conducted with 9 l/s, 12 l/s and 15 l/s for 8 hrs. from 09:00 to 17:00 on the 17 th of February 2023 for the weather conditions of Dhulikhel, Nepal. The simulation results showed that the rectangular rib-based heat exchanger, featuring a rib height of 1 mm and a gap of 10 mm, increased the ambient temperature by more than 8 °C throughout the day. The elevated temperature at the outlet on the cold side of the rib-based heat exchanger helped to increase the collector temperature by more than 5 °C. The heat exchanger effectiveness was found to be a maximum of 38 % at 9 l/s for the rib heat exchanger and reduces with increasing airflow. Also, the results showed that numerical simulation can be a reliable method to design and optimize the solar dryer for better thermal performance.