EFFECT OF DEFLECTION ANGLE ON FLOW AND HEAT TRANSFER IN A ROTATING U-CHANNEL

In this work, the effect of spanwise deflection of a rotating smooth U-channel on flow and heat transfer characteristics is investigated through numerical simulation. Seven deflected U-channel with different angles are adopted, including alpha=90 degrees, 60 degrees, 30 degrees, 0 degrees, -30 degrees, -60 degrees, -90 degrees, and three rotation numbers vary from 0 to 0.29. Using verified numerical method, the flow pattern, detailed and overall heat transfer characteristics and flow friction factor are analyzed. Results show that the deflection angle will enhance the heat transfer in turning section and outlet passage, which can be attributed to the enhancement of flow impact and more complex vortex structure. The deflection of U-channel would generate a Coriolis force at turning section and thus interact with the centrifugal force to change the vortices, which makes the U-channel with negative deflection angle has higher heat transfer enhancement and larger movement of peak Nu number. Compared with positive deflection angle, the negative deflection angle has higher thermal performance and the maximum emerges at alpha=-30 degrees since the U-channel can generate larger heat transfer enhancement with smaller flow loss increase. Besides, the rotation will enhance the local and overall thermal performance of the U-channel, and the effect of deflection angle on the thermal performance of U-channel keep the same at different rotations numbers.