Experimental Study of Heat Transfer and Pressure Loss in Channels with Miniature V Rib-Dimple Hybrid Structure

Abstract

In order to increase the thermal efficiency, gas turbines are designed to operate at higher temperature, which requires a highly efficient cooling structure. The dimples and ribs are effective structures to enhance the convective heat transfer in the cooling channels, which are commonly used in the gas turbine blade internal cooling and combustion chamber cooling. Despite a large number of the literature about the study of the heat transfer performance of the dimples or ribs respectively, few studies dealt with the flow and heat transfer characteristics of a hybrid structure with the ribs and dimples. In the present paper, a novel hybrid cooling structure with miniature Vshaped ribs and dimples is presented, and the flow structure, pressure loss and heat transfer characteristics of a cooling channel with the rib-dimple hybrid structure are investigated. The heat transfer characteristics are obtained using a transient liquid crystal thermography technique. The rib-dimples with three different rib heights of 0.6 mm,1.0 mm and 1.5 mm and with the dimple depth of 4mm are studied in rectangular channels within the Reynolds number range from 10,000 to 60,000. The experimental study showed that the Nusselt numbers of the channels with the rib-dimples are significantly higher than those of the channel with pure dimples. The friction factor increases rapidly with the height of V ribs. The V ribs increase the flow disturbance in the front half of the dimples, leading to an increase of the flow turbulent kinetic energy, increasing the flow mixing dramatically, and breaking out the flow recirculation zone in the front half of the dimples. Therefore the V rib-dimple hybrid structure on the cooling channel surface provides much larger heat transfer enhancement capability than the conventional dimples.

Computer Flow Simulation and Verification for Turbine Blade Channel Formed by the C-90-22 A Profile

“…friction losses: these are directly related to the formation of a boundary layer on the concave and convex parts of a profile and its interaction with the main flow [14]; -edge losses: these are related to the convergence of flows with different velocities behind the trailing edge [15]; -wave losses: these occur only in supersonic flows; when the Mach number is greater than the critical value, a supersonic region is formed on the blade surface ending with shock waves [16];…”

“…friction losses: these are directly related to the formation of a boundary layer on the concave and convex parts of a profile and its interaction with the main flow [14]; -edge losses: these are related to the convergence of flows with different velocities behind the trailing edge [15]; -wave losses: these occur only in supersonic flows; when the Mach number is greater than the critical value, a supersonic region is formed on the blade surface ending with shock waves [16]; (2) end losses: these are related to the formation of a boundary layer on the end surfaces and with the generation of vortices due to the medium flow from a concave surface to a convex one [17,18]. Fluid dynamic processes occurring in blade channels, as well as in pipes, depend on both geometric and operating parameters.…”

Coupled behavior of shape memory alloy-based morphing spacecraft radiators: experimental assessment and analysis

“…In this equation, σ is defined as the Stefan-Boltzmann constant, while A i is the area of surface i and i j F  is the radiation transfer factor from surface i to surface j [27][28][29][30]. The radiation transfer factor is itself a function of the orientation of surface i relative to surface j and the emissivities of both surfaces.…”

Effect of Boundary Conditions and Turbulence Treatment on the Simulated Performance of a Ribbed Heat Exchanger

“…Liu et al [18] studied different truncated ribs configurations, obtained as the fractal evolution of continuous ribbed channels. Rao and Zhang [19] combined V-shaped ribs and dimples to improve the heat transfer in cooling channels representative of the ones used in gas turbine engines. Kaewchoothong et al [20] performed both experimental tests and numerical simulations on a square channel equipped with ribs on two opposite surfaces.…”