Industrial solar drying system: modeling and design optimization of plate slotted fin-and-tube heat exchanger

Abstract

Drying is one of the most energy-intensive stages in clay bricks manufacturing where fuel or another conventional energy source is used to heat the air before blowing it on the wet bricks. In order to reduce the energy consumption and decrease the carbon footprint of construction materials, thermal solar heat represents a promising and suitable energy source for this industrial application. In this paper, the utilization of solar energy in clay bricks drying process through compact cross flow water-to-air heat exchanger is investigated. Considering the intermittent profile of solar radiations, modeling and experimental validation of a water-to-air heat exchanger thermo-flow characteristics estimation at variable hot fluid temperature is performed. An agreement of more than 97% between numerical results and experimental measurements is demonstrated. Additionally, in order to improve the industrial solar drying system efficiency, an optimization of the heat exchanger geometric parameters is carried out based on the performance evaluation criterion and the required drying temperature in clay bricks manufacturing. According to findings, the recommended configuration for a constant heat transfer volume of 0.05 m3 is characterized by tube diameter, longitudinal and transverse pitches of 18 mm, fin spacing of 2.9 mm and fin thickness of 0.6 mm. This configuration is able to increase the heat exchanger performance evaluation criterion by around 53% compared to the baseline configuration. The annual thermal performance of the solar dryer is evaluated via dynamic simulation via the TRNSYS software and shows that the optimal configuration improves the drying temperature by more than 16%.