A numerical investigation on turbulent convective flow characteristics over periodic grooves of different curvatures

Abstract

Heat transfer augmentation is an essential requirement in all heat transfer devices, such as heat exchangers used in biomedical applications, electronic cooling, solar air heaters, nuclear reactor cores, and gas turbine blade cooling etc. Extended surfaces, protrusions, dimples, internal ribs or, grooves are among the few which are incorporated in the last three decades with the goal of heat transfer augmentation for the better performance of the thermal device. However, considering the usefulness, its relative scarcity in literature, and other advantages of grooved surfaces, we have considered this as a method of heat transfer augmentation here. This makes its necessary to investigate the physics due to turbulence and thermal behavior over periodic grooves (or, ribs) is the prime importance of the present paper. In this work, numerical simulations of turbulent forced convection are carried out by introducing curvatures at sharp corners of a periodic grooved channel at the lower wall. A heat source of constant magnitude is supplied in the bottom wall while the upper wall is insulated. Computations were performed using k-epsilon(RNG) model in RANS formulation implemented in finite volume-based solver in the commercial package ANSYS Fluent 19.2. The simulations are performed over varying Reynolds numbers of 6000-36000 where ratio of the height of the channel and breadth of the groove, groove pitch ratio, and depth ratio kept constant as 1, 2, and 0.5 respectively. Assessment of coefficient of heat transfer, frictional losses, and magnitude of heat enhancement are systematically carried out over varying radius of curvatures on grooves. The insertion of curvatures improves the overall heat transfer by a reasonable magnitude of 12% with an overall 5% increment in the magnitude of heat transfer enhancement. Further, the magnitude of heat transfer increases with increase in curvature radius.