Journal of Thermal Science

, Volume 23, Issue 2, pp 169–176

A comparative study of the local heat transfer distributions around various surface mounted obstacles

  • Robert Wyssmann
  • Dirk Ullmer
  • Alexandros Terzis
  • Peter Ott
Article

DOI: 10.1007/s11630-014-0692-8

Cite this article as:
Wyssmann, R., Ullmer, D., Terzis, A. et al. J. Therm. Sci. (2014) 23: 169. doi:10.1007/s11630-014-0692-8

Abstract

In many engineering applications, heat transfer enhancement techniques are of vital importance in order to ensure reliable thermal designs of convective heat transfer applications. This study examines experimentally the heat transfer characteristics on the base plate around various surface mounted obstacles. Local convection coefficients are evaluated in the vicinity of each individual protruding body with great spatial resolution using the transient liquid crystal technique. Five different obstacles of constant height-to-hydraulic diameter ratio (∼1.3) are considered. These include: a cylinder, a square, a triangle, a diamond and a vortex generator of delta wing shape design. The experiments were carried out over a range of freestream Reynolds numbers, based on the hydraulic diameter of each obstacle, varying from 4,000 to 13,000. The results indicate a negligible effect of the flow speed on the heat transfer topological structure and a considerable effect of the obstacle geometry on the level and distribution of heat transfer enhancement.

Keywords

surface obstacles heat transfer enhancement transient liquid crystal technique 

Nomenclature

c J/(kg K)

specific heat

d m

hydraulic diameter

h W/(m2 K)

heat transfer coefficient

H m

obstacle height

k W/(m K)

thermal conductivity

Re

Reynolds number

t s

time

T K

temperature

U m/s

velocity

VG

vortex generator

x,y,z

coordinate system

Greek

a m

obstacle side

ρ kg/m3

density

µ kg/(m s)

dynamic viscosity

Subscripts

i

initial conditions

freestream conditions

g

hot gas conditions

LC

liquid crystals

ref

flat plate (no obstacle)

Copyright information

© Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Robert Wyssmann
    • 1
  • Dirk Ullmer
    • 1
  • Alexandros Terzis
    • 1
  • Peter Ott
    • 1
  1. 1.Group of Thermal Turbomachinery (GTT)École Polytechnique Fédérale de Lausanne (EPFL) SCI-STI-POLausanneSwitzerland

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