Bend Geometries in Internal Cooling Channels for Improved Thermal Performance

The pressure drop and heat transfer in a two pass internal cooling channel with two different bend geometries is experimentally studied with the goal of improving the thermal performance factor (TPF) in the coolant channel. The geometries studied are (1) a baseline U-bend geometry with a rectangular divider wall, (2) a symmetrical bulb at the end of the divider wall, and (3) a combination of the symmetrical bulb and a bow on the opposite outer wall leading to a shaped flow contraction and expansion in the bend. Tests are conducted for four Reynolds number ranging from 10,000 to 55,000. The symmetrical bulb eliminates the separation due to the sharp turn and makes the heat transfer distribution in the bend portion more uniform. This modification reduces the bend pressure drop by 37% and augments the TPF by nearly 29% compared to the baseline case. The combination of bulb and bow case increases the local heat transfer in the bend region significantly, and reduces the bend pressure drop by nearly 27% leading to an augmentation of the TPF of 32% compared to the baseline case. These improvements in TPF point to the benefits of using the improved bend designs in internal cooling channels.