Design, modeling and analysis of efficient multi-rack tray solar cabinet dryer coupled with north wall reflector

An innovative design of front loaded multi-rack tray (MRT) solar cabinet dryer is presented having optimally inclined reflective north wall (RNW) which utilizes reflected component of the solar radiation in addition to the beam radiation for efficient drying particularly in winter when conventional dryer does not perform well at higher latitudes (>30 degrees N). A modified global solar radiation capture model coupled with RNW is presented to determine the effect of RNW on its performance. A thermal model is also developed for chamber air temperature (T-ch) and crop surface temperature (T-c) with experimental validation and solved using Modified Euler's method using FREEMAT software with experimental validation at Ludhiana climate (30.56 degrees N) India. Use of RNW enhances the radiation capture by 37.58%, 31.57% and 23.24% at 30 degrees, 40 degrees and 50 degrees N latitude respectively in winter. Daily average efficiency q(avg) with RNW was 5% and 4.35% higher under natural and forced convection modes respectively as compared to without using RNW. By using RNW, 4-7 degrees C and 2-5 degrees C higher T-ch was observed as compared to when RNW was not used under natural and forced convection modes respectively. Total reduction in drying time for carrot drying was observed to be 20% and 15% under natural and forced convection modes respectively. Predicted and experimental values for T-ch were successfully validated with root mean square error (RMSE) ranging between 2.6 and 4.9. Uncertainty was found to be 20.5 out of which 19.3 was internal and 1.2 external which indicates the accuracy of observed data to determine the performance of solar dryer.