Influence of Crossflow-Induced Swirl and Impingement on Heat Transfer in a Two-Pass Channel Connected by Two Rows of Holes

Detailed heat transfer distributions are presented inside a two-pass coolant square channel connected by two rows of holes on the divider walls. The enhanced cooling is achieved by a combination of impingement and crossflow-induced swirl. Three configurations are examined where the crossflow is generated from one coolant passage to the adjoining coolant passage through a series of straight and angled holes and a two-dimensional slot placed along the dividing wall. The holes/slots deliver the flow from one passage to another. This is typically achieved in a conventional design by a 180 deg U-bend. Heat transfer distributions will be presented on the sidewalls of the passages. A transient liquid crystal technique is applied to measure the detailed heat transfer coefficient distributions inside the passages. Results for the three-hole supply cases are compared with the results from the traditional 180 deg turn passage for three channel flow Reynolds numbers ranging between 10,000 and 50,000. Results show that the new feed system, from first pass to second pass using crossflow injection holes, produces significantly higher Nusselt numbers on the second pass walls. The heat transfer enhancements in the second pass of these channels are as much as two to three times greater than that obtained in the second pass for a channel with a 180 deg turn. Results are also compared with channels that have only one row of discharge holes.