Experimental investigation of a parabolic greenhouse dryer improved with copper oxide nano-enhanced latent heat thermal energy storage unit

Solar dryers are clean and sustainable systems for preserving agricultural products. In this research, three different active greenhouse dryers, which are grouped in direct solar drying systems, have been designed, fabricated, and experimentally surveyed. Different from other works, this research contains an experimental investigation on nano-embedded thermal storage-assisted greenhouse drying system. Major goal of this study is to analyze the impact of utilizing nano-enhanced thermal energy storage unit on the performance of a greenhouse dryer. In this context, tunnel-type parabolic greenhouse dryers with paraffin wax thermal storage unit (PGD-TES) and nano-enhanced paraffin wax thermal storage unit (PGD-NeTES) have been tested and compared with a conventional parabolic greenhouse dryer (PGD). Copper oxide (CuO) nanoparticles have been employed to upgrade the thermal effectiveness of the thermal storage unit. Tests have been done in two flow rates, which are 0.009 and 0.014 kg/s. Utilizing nano-enhanced modification decreased drying time approximately between 35% and 58% in comparison to the conventional dryer. According to the results, average specific energy consumption values were attained in the ranges of 2.10 to 2.48, 1.93 to 2.09, and 1.63 to 1.89 kWh/kg, respectively, for PGD, PGD-TES, and PGD-NeTES. Also, exergy efficiency was improved by 36% by utilizing the nano-enhanced thermal energy storage system.