Experiments in Fluids

, 57:146

On the correspondence between flow structures and convective heat transfer augmentation for multiple jet impingement

Research Article

DOI: 10.1007/s00348-016-2232-7

Cite this article as:
Terzis, A. Exp Fluids (2016) 57: 146. doi:10.1007/s00348-016-2232-7
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Abstract

The correspondence between local fluid flow structures and convective heat transfer is a fundamental aspect that is not yet fully understood for multiple jet impingement. Therefore, flow field and heat transfer experiments are separately performed investigating mutual–jet interactions exposed in a self-gained crossflow. The measurements are taken in two narrow impingement channels with different cross-sectional areas and a single exit design. Hence, a gradually increased crossflow momentum is developed from the spent air of the upstream jets. Particle image velocimetry (PIV) and liquid crystal thermography (LCT) are used in order to investigate the aerothermal characteristics of the channel with high spatial resolution. The PIV measurements are taken at planes normal to the target wall and along the centreline of the jets, providing quantitative flow visualisation of jet and crossflow interactions. Spatially resolved heat transfer coefficient distributions on the target plate are evaluated with transient techniques and a multi-layer of thermochromic liquid crystals. The results are analysed aiming to provide a better understanding about the impact of near-wall flow structures on the convective heat transfer augmentation for these complex flow phenomena.

List of symbols

C

Regression coefficient

\(C_\mathrm{D}\)

Discharge coefficient

D

Jet diameter (m)

G

Mass velocity (kg/(m\(^2\) s))

h

Heat transfer coefficient (W/(m\(^2\) K))

L

Length of impingement hole (m)

m

Exponent of Reynolds number

Nu

Nusselt number

n

POD mode number

Q

Vortex identification criterion

Re

Reynolds number

S

Dispersion coefficient

U

Velocity (m/s)

\(u',w'\)

Fluctuating velocities (m/s)

u

Streamwise velocity component (m/s)

w

Vertical velocity component (m/s)

xyz

Coordinate system

X

Streamwise jet spacing (m)

Y

Channel width/spanwise jet spacing (m)

Z

Separation distance (m)

Subscripts

cf

Crossflow

D

Jet diameter

j

Jet

\(\infty \)

Free stream conditions

max

Maximum value

Abbreviations

LCT

Liquid crystal thermography

PIV

Particle image velocimetry

POD

Proper orthogonal decomposition

TLC

Thermochromic liquid crystals

VC

Vortex centre

Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.Institute of Aerospace ThermodynamicsUniversität StuttgartStuttgartGermany