ISSN Online: 2688-7231
ISBN Online: 978-1-56700-524-0
Proceedings of the 26thNational and 4th International ISHMT-ASTFE Heat and Mass Transfer Conference December 17-20, 2021, IIT Madras, Chennai-600036, Tamil Nadu, India
Effect of Circumferential Grooves on Two-phase Flow in the Parabolic Trough Solar Collector
The temperature distribution in the absorber wall of the parabolic trough solar collector (PTSC) affects its thermal efficiency and structural stability. The stratified flow regime in the direct steam generation (DSG) process induces a high temperature gradient. The creation of grooves around the circumference at the inner surface of conventional plane absorber tubes improves the heat transfer (HT) as well as reduces the temperature gradient around the circumference of the absorber by increasing the wetted area and turbulence. In this study, the thermal-hydraulic modeling and heat transfer analysis of grooved absorber tubes are presented. The modeling and simulations are performed in ANSYS Fluent 2021R1 commercial software. The hydraulic radius and pitch of grooves are 1 mm 6 mm respectively. The boundary conditions considered are as: operating pressures 60 bar and 100 bar; DNI 750 W/m2; mass flow rates (MFR) 0.4 kg/s and 0.6 kg/s. The heat exchange between absorber and fluid by various mechanisms have been compared. It has been found that evaporation heat transfer increases significantly when the grooves are incorporated. The temperature distribution of the absorber surface in the circumferential and radial directions have been analysed. A slight decrement in the absorber temperature of 2 to 3 K is observed with a groove radius of 1 mm as compared to conventional plane absorber. Further, it has been noticed that the pressure loss increased by 7.56 times and 8 times as compared to the non-grooved absorber tubes, respectively, for MFRs of 0.4 kg/s and 0.6 kg/s at operating pressure of 100 bar. The increment in the fluid mixture velocity is around 0.27 m/s at operating pressure of 100 bar.