Energy and exergy analysis of a water bed-infrared dryer coupled with a photovoltaic-thermal collector

Abstract

Orange is a perishable fruit that is dried to increase its shelf-life. The main challenge of industrial dryers is their high energy consumption, which accounts for about 12% to 20% of the energy demands of the industry. In the present study, a continuous water bed-infrared dryer equipped with a photovoltaic-thermal (PV-T) collector was presented for orange fruit drying. The designed dryer comprised two main units: the PV-T air collector and the water bed-infrared dryer. The PV-T collector was considered to simultaneously generate electricity and heat required for the hot airflow inside the dryer. The effects of the hot water flow rate (0.05, 0.1, and 0.15 L/min) and the product thickness (3, 5, and 7 mm) on solar heat fraction, final moisture content of the dried oranges, and energy and exergy efficiencies of the dryer were investigated using the factorial test based on a randomized complete block design experiment. The average solar heat fraction increased by 35.1% with increasing the thickness from 3 to 7 mm, and increased by 29.8% with increasing the water flow rate from 0.05 to 0.15 L/min. Rising the water flow rate in the studied range reduced the final moisture content by about 14.7%. The average solar heat fraction, final moisture content as well as energy and exergy efficiencies of the dryer were obtained 0.26-0.61, 9.1%-16.04% wet basis (wb), 26.35%-35.63%, and 3.42%-12.9%, respectively. The best operating condition suggested based on the highest solar heat fraction, energy and exergy efficiencies, and the lowest final moisture content, was the 3-mm slice thickness of orange and the water flow rate of 0.15 L/min. Practical Applications The main challenge of industrial dryers is their high energy consumption. In the present study, to increase energy efficiency in water bed dryers, a heat source of infrared radiation was deployed on top of the product surface, and a PV-T collector was used to generate electricity and hot airflow simultaneously. We experimentally investigated the changes in heat fraction of solar energy, final moisture content of dried oranges, and energy and exergy efficiencies of the designed continuous water bed-infrared dryer equipped with PV-T collector at different operating conditions.