Thermal and hydraulic performance of circular tube with innovative wire mesh inserts: An experimental study

This study focuses on the design, development, and experimental investigation of novel porous inserts within a circular tube to assess thermo-hydraulic performance. Two innovative wire mesh insert configurations were introduced: wire mesh twisted tape (WMTT) and circular ring wire mesh (CRWM). The research also explores the influence of varying porosities such as 8, 10, 18 and 20 (pores per inch) PPI and impact of notch on thermal-hydraulic characteristics. Experiments were conducted using water as the working fluid at five different mass flow rates (0.04-0.2kg/s) and three different heater power levels of 400, 600 and 800 W under controlled conditions. The study examines key performance parameters such as the Nusselt number, friction factor, and performance evaluation criteria (PEC) to compare the performance of different insert configurations. Initial tests were performed using WMTT-8 PPI, CRWM-10 PPI, and a plain tube under varying mass flow rates and heater power conditions. The findings indicate that the CRWM-10 PPI configuration consistently exhibits higher Nusselt numbers and friction factors across all experimental conditions. Specifically, the CRWM-10 PPI insert achieved a maximum enhancement of 41.5% in the Nusselt number and a 165% increase in the friction factor compared to the plain tube. Based on the PEC analysis, CRWM-10 PPI demonstrated superior thermal-hydraulic performance over WMTT-8 PPI. Further, research on different porosities was concentrated with CRWM inserts due to their superior performance over WMTT. The CRWM-18 PPI configuration exhibited a 7.6% and 1.9% higher PEC than CRWM-10 and 20 PPI, respectively. To balance heat transfer enhancement and pressure drop, notches were introduced in CRWM-18 PPI. Findings indicate that insert with notch contribution is almost similar to insert without a notch in improving the Nusselt number but reduces the friction factor by approximately 12.7%, leading to a 1.3% increase in PEC. The outcome of this study shows the potential of CRWM inserts as an efficient technique to improve the performance of the circular tube, which can be incorporated into the absorber tube of a solar parabolic trough collector.