Local Heat Transfer and Pressure Drop in a Rotating Two-Pass Ribbed Rectangular Channel

Shou-Shing Hsieh,Hsiu-Cheng Liao

doi:10.1155/s1023621x01000173

Shou-Shing Hsieh, Hsiu-Cheng Liao

Open Access

https://doi.org/10.1155/s1023621x01000173

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Abstract

The influences of rotation and uneven heating condition as well as passage aspect ratio on the local heat transfer coefficient and pressure drop in a rotating, two pass ribroughened (rib heighte/DH≈0.27; rib pitchp/e=8) rectangular channel with a crosssection aspect ratio of 3 was studied for Reynolds numbers from 5000 to 25,000 and rotation numbers from 0 to 0.24. Regionally averaged Nusselt number variations along the duct have been determined over the trailing and leading surfaces for two pass straight channels and U-bend region. Implementing with the data from Hsieh and Liu (1996) forAR=1and 1.5 withp/e=5ande/DH=0.17and 0.20, passage aspect ratio effect was further examined. Furthermore, data for180∘U-bend region with ribroughened turbulator on heat transfer were also measured. It was found that a complicated three-dimensional accelerated flow and secondary flow in this U-bend region caused higher heat transfer on both leading/trailing walls. Enhancement performance ratios are also presented and discussed. Results again indicate a slight decrease in heat transfer coefficient for an increase in passage aspect ratio as compared to those of previous studies.

Highlights

Owing to the increase in the turbine inlet temperature of gas turbine engines, there is an urgent need today to obtain a higher efficiency in the engines of aircraft, ships and many other industrial applications
The results presented in this paper are aimed at studying the local heat transfer and pressure drop in a rotating two-pass ribbed rectangular channel
The convective heat transfer performance inside of a rotating two-pass roughened channel is governed by the ratio of the rotating mean radius to channel hydraulic diameter, Reynolds number, Prandtl number, rotation number, rotational Rayleigh number, channel aspect ratio, wall to fluid density difference ratio, flow direction, and rib geometry and size

Summary

Introduction

Owing to the increase in the turbine inlet temperature of gas turbine engines, there is an urgent need today to obtain a higher efficiency in the engines of aircraft, ships and many other industrial applications. Parallel with the evolution of metal working at high temperatures, several methods of cooling rotor blades have been tried and developed. Cooled blades are widely used in modern engines. Radial channel cooling is a commonly used method. These channels are often designed with two artificially roughened and two smooth walls, and the designer must know the heat transfer coefficient on each of the walls in order to predict the turbine airfoil’s life correctly. It is necessary to know the pressure loss for such a channel.

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