ABSTRACT

A solar dryer integrated with a simple bed rock was designed and constructed with locally available materials to dry tomatoes and pepper. The dryer was composed of solar collector, drying chamber, back up heater and airflow system all integrated together. The back-up heater provided alternative heating during cloudy weather conditions or at night when solar radiations were low. The dryer was designed based on climatic conditions of Ikale summit located in Ikale, Ekiti Nigeria. The average ambient conditions were 26°C air temperatures and 83% relative humidity with daily global solar radiation incident on horizontal surface of about 600W/M. This study describes the design considerations and results of calculations of design parameters. A minimum of 3 .77 solar collector area was required to dry a batch of 1kg tomatoes and pepper vegetables in 8 hours under force convection from the initial moisture content of 84.7% to final moisture content of 10.1% wet basis. Using similarity laws a dryer with collector area of I.78 was fabricated and used in experimental drying tests under varied heat source conditions namely; solar, bed rock and a combination of solar and bed rock. Solar assisted dryer system efficiency was estimated at 70%.