A literature review carried out by the authors reveals that that a CFD analysis has not been the focus of attention to evaluate the efficacy of turbulators for improving the thermal performance of solar air heaters. A three dimensional CFD analysis is carried out in the present work to augment the performance of solar air heater. Arc shaped wire turbulators (with forward and reverse curvature aligned with flow direction), V-shaped wire turbulators (with forward and reverse geometry with respect to the flow direction) and Straight turbulators are used in this study to improve the flow turbulence and thereby enhance the convective heat transfer to air. The numerical results are validated with experimental results for model without turbulator to calibrate the numerical methodology. The numerical results show that turbulators whether curved or straight are useful in enhancing the heat transfer rates. The Arc shaped turbulators have been found to provide better heat transfer coefficient value compared to that of straight and V-shape turbulators. Also interestingly, Reverse arc turbulators seems to provide better heat transfer coefficient value compared to forward arc turbulators. Further, V-angle has no significant effect for both forward and reverse V-turbulator configurations.

Thermosyphon unglazed solar flat plate collectors have been widely used all over the world to harness solar energy for generating hot water for various applications. This is mainly due to the passive nature of the system besides being simple in design. However, flat plate collectors are associated with higher heat losses from the surface leading to lower thermal performance. Hence, there is a dire need to optimize the thermal design aspects of the flat plate collector in order to achieve higher thermal performance. In this paper, the results of a full three dimensional CFD simulation of thermosyphon flow in an unglazed solar flat plate collector are presented. It is observed from the parametric study that there are interesting trends for the temperature distribution of the absorber plate and loop water for various simulated solar heat flux inputs. This analysis also brings out the effect of various simulated heat fluxes on the mass flow rates in the collector loop. The results of this CFD simulation study provide an insight into the behavior of the thermosyphon solar flat plate collector under various operating conditions and hence will be further helpful to undertake optimization for enhanced thermal performance of the collector.

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Gas Metal Arc Welding (GMAW) is a welding process where an electrode wire is continuously fed from an automatic wire feeder through a conduit and welding gun to the base metal, where a weld pool is created. The formation of droplet and transfer of droplet are governed by the conservation equations. This study on GMAW aims to simulate transient behavior of welding arc and shielding gas flow. Computational Fluid Dynamics (CFD) is used as a tool to understand multifaceted physics involved in GMAW process. A two dimensional axisymmetric model is prepared to reduce computational time. The heat transfer and fluid flow in the arc column were studied based on the transient distributions of velocity, turbulence, voltage, current density, and temperature. An interactive coupling between welding arc, plasma, current and temperature were considered. The assumed steady state and laminar gas flow in traditional models studied so for does not reflect the real distributions in the welding process. Hence influence of the welding arc on the shielding gas flow and vice versa was taken up for study. From the study it is found that as the arc is struck, the shielding gas is accelerated towards axis. When the plasma reaches towards workpiece, axial momentum of gases is changed to radial momentum and flows away from the workpiece. The shielding gas also carries current from electrode to workpiece which helps in reducing spatter of the arc and hence concentrated arc is obtained