Heat Transfer and Friction in Rectangular Convergent and Divergent Channels with Ribs
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The local heat transfer and pressure drop of developed turbulent flows in the stationary ribbed rectangular convergent/divergent channels have been investigated experimentally. The rectangular convergent/divergent channels with one-sided ribbed surface only have the inclination angles of 0.72 deg and 1.43 deg at which the ribbed wall is manufactured with a fixed rib height e=0 mm and the ratio of rib spacing (p) to height e=10. The measurement was conducted within the range of Reynolds numbers from 15,000 to 89,000. Because of the streamwise flow acceleration or deceleration, the local heat transfer characteristics of the rectangular divergent/convergent channels are quite different from those of the square straight channel. Thermal performance of the ribbed rectangular divergent/convergent channels is compared with the ribbed square straight channel under three constraints: identical mass flow rate, identical pumping power, and identical pressure drop. The comparison shows that among the four channels of C1 (Dho?Dhi-0.67), C2 (Dho?Dhi-0.86), D1 (Dho?Dhi 1.16), and D2 (Dho?Dhi 1.49), the divergent channel of D2 has the highest thermal performance at the identical mass flow rate, and the divergent channel of D1 has the highest at the identical pumping power and static pressure drop. 2013 by the American Institute of Aeronautics and Astronautics, Inc.