Laminar flow heat transfer enhancement in square and rectangular channels having: (1) A wire-coil, axial and spiral corrugation combined with helical screw-tape with and without oblique teeth and a (2) spiral corrugation combined with twisted tapes with oblique teeth

A survey of the developments in heat transfer studies of non-linear inelastic as well as elastic fluids in tubes is given. Experimental findings concerning heat transfer enhancement characteristics of viscoelastic aqueous polymer solutions are very significant. Specifically, it is reported that heat transfer results for viscoelastic aqueous polymer solutions are drastically higher than those found for water in laminar flow in rectangular ducts. A number of investigators suggested that the high experimental heat transfer values were due to secondary flows resulting from the elasticity of the fluids. In this context recent results concerning the fully developed thermal field in constant pressure gradient driven laminar flow of a class of viscoelastic fluids characterized by single mode, non-affine constitutive equations in straight pipes of arbitrary contour ∂D is reviewed. Heat transfer enhancement due to shear-thinning is identified together with the enhancement due to the inherent elasticity of the fluid. The latter is the result of secondary flows in the cross-section. Increasingly large enhancements are computed with increasing elasticity of the fluid as compared to its Newtonian counterpart. Large enhancements are possible even with dilute fluids. Isotherms for the temperature field are presented and discussed for several non-circular contours such as the ellipse and the equilateral triangle together with heat transfer behavior in terms of the Nusselt number Nu.

Download Full-text

Heat transfer enhancement for laminar flow in tubes using curved delta wing vortex generator inserts

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2016.06.120 ◽

2016 ◽

Vol 106 ◽

pp. 1415-1426 ◽

Cited By ~ 34

Author(s):

P.W. Deshmukh ◽

S.V. Prabhu ◽

R.P. Vedula

Keyword(s):

Heat Transfer ◽

Laminar Flow ◽

Heat Transfer Enhancement ◽

Delta Wing ◽

Vortex Generator ◽

Transfer Enhancement

Download Full-text

Design of a Microfin Array Heat Sink Using Flow-Induced Vibration to Enhance the Heat Transfer Rate in the Laminar Flow Regime

10.1115/imece2001/mems-23886 ◽

2001 ◽

Author(s):

Jeung Sang Go ◽

Geunbae Lim ◽

Hayong Yun ◽

Sung Jin Kim ◽

Inseob Song

Keyword(s):

Heat Transfer ◽

Laminar Flow ◽

Heat Transfer Enhancement ◽

Flow Regime ◽

Heat Transfer Rate ◽

Heat Sink ◽

Transfer Rate ◽

Transfer Enhancement ◽

Air Velocity ◽

Flow Induced Vibration

Abstract This paper presented design guideline of the microfin array heat sink using flow-induced vibration to increase the heat transfer rate in the laminar flow regime. Effect of the flow-induced vibration of a microfin array on heat transfer enhancement was investigated experimentally by comparing the thermal resistances of the microfin array heat sink and those of a plain-wall heat sink. At the air velocities of 4.4m/s and 5.5 m/s, an increase of 5.5% and 11.5% in the heat transfer rate was obtained, respectively. The microfin flow sensor also characterized the flow-induced vibration of the microfin. It was determined that the microfin vibrates with the fundamental natural frequency regardless of the air velocity. It was also shown that the vibrating displacement of the microfin is increased with increasing air velocity and then saturated over a certain value of air velocity. Based on the numerical analysis of the temperature distribution resulted from microfin vibration and experimental results, a simple heat transfer model (heat pumping model) was proposed to understand the heat transfer mechanism of a microfin array heat sink. Under the geometric and structural constraints, the maximum heat transfer enhancement was obtained at the intersection of the minimum thickness of the microfin and constraint of the bending angle.

Download Full-text