Effects of rotation number on heat transfer and fluid flow in a three-pass serpentine passage with lateral outflow

The purpose of this study is to experimentally and numerically investigate the effects of rotation number on heat transfer and fluid flow in a three-pass serpentine passage with lateral outflow. In the present study, the rotation number varies from 0 to 0.09, and the inlet Reynolds number is 5000. The heat transfer coefficient distribution of the three-pass serpentine passage is measured using the transient liquid crystal technique. The current work fills the research gap of the effect of rotation number on heat transfer distribution in a three-pass serpentine passages with lateral outflow. The results of this study show that the span-wise-averaged Nusselt numbers in the region of l/d < 16 and l/d > 33.6 increase monotonically with the rotation number increasing, particularly in l/d = 6.4, with a maximum increase of 58.5%. However, the rotation reduces the Nusselt numbers of the middle passage by between 2.6 and 7.3% when the rotation number increases from 0 to 0.06. The area-averaged Nusselt numbers rapidly decrease in the area of A_i = 4; this phenomenon is more obvious at higher rotation numbers, and the maximum decrease is 34.6%. The pressure coefficient in the region of l/d < 14 tends to increase gradually along the flow direction when Ro = 0.09. The rotation changes the flow direction and shrinks the vortex size in the lateral-outflow passage. Accordingly, the pressure coefficient rapidly increases by 74.1% in the lateral-outflow passage when Ro = 0.06 and Ro = 0.09.