“Experimental Investigation of Heat Transfer Enhancement through Elliptical Dimples for Divergent Channel”

Mechanical Engineering

An experimental investigation was conducted to determine whether dimples on micro heat exchangers, Turbine blades, Electrical Cooling Systems can increase heat transfer for turbulent airflows. This was accomplished by performing experimental studies using setup which consist of divergent test channel in which Elliptical dimples are milled with aspect ratio (AR=1.5) arrangement (Inline, offline and Smooth) on one side of aluminum plates (Test Section) with a relative depth c/D1=0.33 and relative pitch S/Dm = 1.6.The main physical mechanisms causing the enhancement of heat transfer is the generation and amplification of sufficiently strong longitudinal vortices which are interacting with the thermal boundary layer. Since vortex induced heat transfer enhancement depends strongly on shape and position of Dimples, the subject of ongoing research is to find design strategies for device shape and placement optimization. For those configurations the heat transfer coefficient (h), Nusselt number (Nu), pressure drop (Pd), thermal performance (Tp) and Nusselt number ratio (Nu/Nu_s) were determined experimentally. For Elliptical dimples, heat transfer enhancements (relative to a flat plate) were observed for Reynolds number range from 5000 to 15000 (Reynolds number based on channel height and Velocity of hot air fluid). Also the results are validated analytically for Nusselt number and heat transfer coefficient for smooth horizontal plate. Specifically, this investigation was conducted to determine whether the use of dimples can enhance heat transfer characteristics for Compact Heat Exchangers and turbine blades, Electronic cooling, Biomedical devices, etc. applications. With different types of arrangements such as smooth, inline and offline with variable parameter such as velocity, v = 5 m/sec, v = 10m/sec, v = 15m/sec for this conditions cases are studied and it has been found that the offset arrangement in divergent plate gives optimum solution as compared to other arrangements.

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.