Solar dryer performance simulation: Experimental and numerical study

In this study, effect of solar irradiation and suction head on an indirect cabinet solar dryer performance is investigated experimentally and numerically. In this regard, a specific experimental apparatus consisting a collector, heaters and adjustable chimney is fabricated to measure the air flow velocity and temperature at collector outlet in various irradiance (300, 400, 500, 600, 800, and 1,000 W/m(2)) and chimney height (1.85, 2.05, 2.25, and 2.55 m). In addition to the above abilities of experimental setup, more accurate thermal and hydraulic results are achieved. The obtained results are useful to the field since there are many defects in available simulations of collector. Some of the defects concerns incomplete prediction of thermal losses to the environment, ignoring secondary flows and vortices formed by velocity increment through the collector, etc. In the present study, computational fluid dynamics (CFD) is used for modeling the drying chamber utilizing the pressure jump method and simulating the mass transfer phenomenon by a heat source. The results for the studied case (grape as to-be-dried product) as an example, show that the solar irradiation augmentation leads to the temperature and velocity increment while the suction head increment leads to an increasing-decreasing behavior for the temperature. It is also demonstrated that by increasing the solar irradiation from 300 to 1,000 W/m(2), the thermal efficiency of the collector and drying chamber increase from 42.92% to 64.31% and 10.08% to 15.15% respectively and the drying time of grapes reduces from 216 hr to 143 hr. Practical Applications The present study experimentally and numerically investigates a solar dryer for the specific application of grape drying although it can be applied for drying a wide types of fruits. The experimental part of the accomplished research is similar with solar chimney in a way that the present experimental results can be used for solar chimneys too. Based on the obtained results, the drying time as well as the air flow has been improved by applying the suggested drying method.