Investigation of thermodynamics performance of a heat exchanger-incorporated solar dryer equipped with double-pass flat, v-corrugated, and low-e coated collectors for drying applications

In this study, a solar dryer incorporating a flat plate heat exchanger to recover heat from exhaust air was investigated to explore the usability of different types of collectors in the system. Their usability was further evaluated through economic and environmental analyses. Moreover, the thermodynamic performance of the solar dryers was evaluated under two weather conditions in Nepal. Apple drying experiments were conducted for 8 h from 09:00 to 17:00 from February to April 2023 on solar dryers and with open sun drying (OSD) in Dhulikhel, Nepal. The results showed that the low emissivity (low-e) coated aluminum collector was more efficient in terms of collector efficiency and drying rate than collectors with flat or v-corrugated GI absorbers. The average collector efficiency and drying rate were found to be 89 % and 107 g/(h x m2) using the low-e coated aluminum collectors, while the values were 50 % and 84 g/(h x m2) for the GI sheet collector. The results indicated a slight improvement in the performance of v-corrugated collectors, with values of 53 % and 89 g/(h x m2). The drying rate for OSD was found to be 78 g/(h x m2), which was lower than for the dryers with all collectors used in this study. In terms of economic analysis, the dryer equipped with the low-e coated collector was found to be superior, with a payback time of 1.61 years compared to the dryers with flat or v-corrugated GI collectors. Reducing the thermal losses due to radiation by using the low-e coated absorber was shown to be more important than increasing the absorber area using v-corrugated GI sheets.