Parametric study of evacuated tube collector solar air heater with inserted baffles on thermal network for low-temperature applications

Abstract

The great challenge in the evacuated tube solar air heater for the industrial application is choosing the optimum thermal networks to get target temperature for the desired air flow rate. In this work, theoretical analysis is done to investigate the influence of the significant design parameters such as evacuated tube length, diameter and number of tubes in a collector on the thermal performance and to design a thermal network model for achieving the desired temperature at specified flow rate of air for industrial process heat applications. Further, establishing an empirical correlation to simplify the thermal network design process. Based on the results of design parametric study, optimal parameters identified for a collector system are 20 numbers of evacuated tubes having dimensions of 1.8 m length, 58 and 47 mm outer and inner diameters. It is noticed that a considerable drop in temperature rise attained in each collector while increasing the number of collectors in series network. The enviro-economic analysis reveals that the overall useful energy gain per annum can be achieved around 8252 kWh which will reduce 17.16 tonne of carbon dioxide emission through the utilization of a thermal network comprising six modules working at 500 kg/h mass flow rate of air. The correlation relates the attainable effective thermal with the non-dimensional operating parameters such as mass flow number, temperature ratio, and number of collectors. The correlation can be used to design a solar evacuated tube thermal network and the proposed solar evacuated tube thermal network can be effectively employed for fulfilling the industrial process heating applications require hot air between 80 and 120 °C.