Concavity Enhanced Heat Transfer in an Internal Cooling Passage

Abstract

The present study evaluates an innovative approach for enhancement of surface heat transfer in a channel using concavities, rather than protruding elements. Serving as a vortex generator, a concavity is expected to promote turbulent mixing in the flow bulk and enhance the heat transfer. Using a transient liquid crystal imaging system, local heat transfer distribution on the surface roughened by an staggered array based on two different shapes of concavities, i.e. hemispheric and tear-drop shaped, have been obtained, analyzed and compared. The results reveal that both concavity configurations induce a heat transfer enhancement similar to that of continuous rib turbulators, about 2.5 times their smooth counterparts 10,000 ≤ Re ≤ 50,000. In addition, both concavity arrays reveal remarkably low pressure losses that are nearly one-half the magnitudes incurred with protruding elements. In turbine cooling applications, the concavity approach is particularly attractive in reducing system weight and ease of manufacturing.

Forced Convection Heat Transfer Analysis through Dimpled Surfaces with Different Arrangements

“…Fouling rate reduction b. Cost reduction c. weight reduction etc [11], however, much of the research work either experimental or numerical is on spherical dimples of uniform diameter [7,12]. It is also seen that most of the research is confined to flow in the channel i.e.…”

“…Afanasyev et al [6] carried an experimental to study the heat transfer characteristics of flow over a flat plate having spherical dimples and reported an increment of 30-40% in the heat transfer rate with a minimum pressure drop. Chyu et al [7] conducted an experiment to study local heat transfer coefficient distribution in a channel having dimples of spherical & tear drop type. They observed a considerable increase in the distribution of local heat transfer coefficient everywhere on these dimple surfaces as compared to flat surface.…”

An Experimental Study on Heat Transfer Enhancement of Flat Plates Using Dimples

“…No significant effect on the hydrodynamics of flow was observed in their study. Chyu et al [5] used tear drop type dimples along with hemispherical dimples to study the heat transfer characteristics of air flow in the channel. They observed a considerable increment in the heat transfer rate for the surfaces having dimples (About 2.5 times then their smooth surfaces).…”

Forced Convection Heat Transfer Analysis of Square Shaped Dimples on Flat Plates

“…They observed an increase of 30-40% in the heat transfer rate with no significant effect on the hydrodynamics of flow. In an another study, Chyu et al [5] used the transient liquid crystal imaging system to analyze and compare tear drop type and hemispherical dimples to study the heat transfer distribution in the channel. He observed a considerable increment in the heat transfer rate for the surfaces having dimples (about 2.5 times their smooth counterparts 10,000 ≤ Re ≤ 50,000).…”

“…From the literature, it is very much clear that dimples (vortex generators) have high potential to enhance the heat transfer along with the production of lower pressure drop penalties. The other advantages include low weight and cost and low fouling rates [9], However, most of the researchers conducted numerical or experimental work on spherical dimples of uniform diameter [5,10]. Also most of the research is confined to flow in the channel with a very few studies on external flow [10].So the main aim of this project is to experimentally study the effect of square dimples under external laminar forced flow conditions.…”