Turbulent flow and heat transfer enhancement in rectangular channels with novel cylindrical grooves

Turbulent flow characteristics and heat transfer performances in square channels with different cylindrical-shaped grooves are analyzed and compared numerically in this research. The novel groove geometries are conventional cylindrical grooves with rounded transitions to the adjacent flat surfaces and with modifications to their bases. The objective of this work is to determine optimal configuration for augmenting heat transfer rates with minimal pressure drop penalties. The paper documents also provide the flow details near the groove surface. All turbulent fluid flow and heat transfer results are obtained using computation fluid dynamics with a verified v²f turbulence closure model. Five rectangular channels with different cylindrical groove shapes are computed. Heat transfer enhancement and flow details are analyzed and compared with results for conventional cylindrical groove geometry and for conventional square ribs. This investigation shows that the conventional cylindrical grooves have similar overall heat transfer enhancement with conventional square ribs, but the pressure loss penalty is much decreased from square rib values. The rounded transition of the grooves has a large advantage over conventional cylindrical grooved surfaces in both enhancing heat transfer and reducing pressure loss penalty. For the rounded-transition grooves, recirculating flows inside the groove are reduced and reattachment develops more smoothly and the separating zone is reduced compared with the flow over the conventional cylindrical groove. The velocity magnitude in the near-wall region of grooved surface is much larger compared with that over a ribbed surface, which essentially causes the larger heat transfer enhancement for the groove surfaces. The design for the rounded transitions is shown to improve the overall thermal performance for channel internal cooling.