Effects of a novel hybrid turbulator tape on the thermohydraulic performance and irreversibility of a solar air heater

Abstract

Renewable energy from the sun has been a rapidly expanding field in recent years, because to its many advantages as a sustainable, cost-effective, and environmentally friendly power source. Energy drives economic growth and industrialization today. Air heating is a prominent solar energy utilization for space and process heating including washing, desalination, crop drying, and others. To improve energy efficiency, this study examined several designs of novel hybrid tape within an affordable solar-powered air heater. Solar air heaters can improve their heating efficiency by adding additional novel swirl generator. Many research have been done in this subject, however novel geometries are being proposed to better the heat transfer enhancement (HTE)-blowing power penalty tradeoff. Hybrid turbulator tapes are new, and there is no parametric investigation on their advantages. To cover this gap in this research, utilized air as the working fluid to investigate the pressure drop and heat transfer characteristics inside a uniformly heated circular tube with hybrid turbulator tape inserts. The aim was to cover the turbulent flow regime by varying the Reynolds number from 10,104 to 73,788. The thermohydraulic performance with pitch, length, and width ratios is investigated in this work. In comparison to a plain tube, it is observed an average increase of 91% and 39% in the Nusselt number and friction factor, respectively. This indicates a significant improvement in the tube's performance. It is also found that the important thermal performance factor exceeded one for all tape combinations. Novel correlations have also developed. With such encouraging results, using the tested turbulator in a solar air heater for improved performance is feasible.

Keywords

• Turbulent flow
• Heat transfer enhancement
• Hybrid tapes
• Nusselt number
• Friction characteristics