Flow and heat transfer performance of steam cooling in V-shaped ribbed channels

The distributions of Nusselt number (Nu) for steam cooling on V-shaped rib roughness channel with different rib angles were measured by an infrared camera for a Reynolds number (Re) range of (6.0 to 17.7)×103. The results show that the heat transfer performance in the region following the upwind side of V-shaped ribs is greatly enhanced. With the rib angle decreasing, the heat transfer performance of steam cooling in the channel increases. The 45° V-shaped rib roughness channel has the best heat transfer performance in all investigated objects. The flow characteristics and pressure loss of steam flow for all investigated channels were also studied by the CFD method and compared with those of air flow in the similar operating conditions. It is concluded that the secondary flow in ribbed channels is induced by the V-shaped rib turbulator. The cooler flow in the core region of the channel provides a supplement to the area, which results in a thermal boundary layer thinning in that region. Therefore the heat transfer performance is enhanced for the V-shaped rib roughness channel. In the same Reynolds number conditions, the pressure loss coefficients for steam flow and air flow are nearly the same, however, the heat transfer performance of steam flow is obviously higher than that of air flow. ©, 2015, Shanghai Jiao Tong University. All right reserved.