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Heat and Mass Transfer

, Volume 49, Issue 11, pp 1637–1646 | Cite as

Transitional boundary layer flow and heat transfer over blocked surfaces with influence of free stream velocity and block height

  • O. YemeniciEmail author
  • Z. A. Firatoglu
Original

Abstract

Velocity, turbulent intensity, static pressure and temperature measurements over the flat plate and blocked surfaces were investigated in a low speed wind tunnel in the presence of free stream velocity and block height. The experiments were carried out for free stream velocities of 5, 7 and 10 m/s encompassing the transitional region and for block heights of 10, 15 and 20 mm forming the different flow samples. A constant-temperature anemometer, a micro-manometer and copper-constant thermocouples were used for measurements of velocity and turbulent intensity, static pressure and temperature, respectively. The results showed that the flow separations and reattachments occurred on the blocked surfaces which enhanced the average heat transfer up to 1.54, 1.71 and 1.84 fold of the flat plate value at 5 m/s for the rising block height, 1.49, 1.68 and 1.80 at 7 m/s, and 1.44, 1.63 and 1.78 at 10 m/s, respectively.

Keywords

Heat Transfer Nusselt Number Turbulent Intensity Flat Plate Heat Transfer Characteristic 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

Cp

Pressure coefficient, dimensionless

h

Convective heat transfer coefficient, W/m2K

h

Block height, mm

H

Shape factor, dimensionless

H

Channel height, mm

K

Thermal conductivity, W/mK

Nu

Nusselt number, dimensionless

P

Pressure, Pa

Pr

Prandtl number, dimensionless

q

Heat flux, W/m2

Rex

Streamwise distance Reynolds number, dimensionless

Reθ

Momentum thickness Reynolds number, dimensionless

ReH

Channel height Reynolds number, dimensionless

s

Block spacing, mm

Tu

Turbulence level, %

T

Temperature, °C

u

Streamwise velocity, m/s

urms

Root mean square velocity, m/s

U

Mean free stream velocity, m/s

w

Block width, mm

W

Channel width, mm

x

Streamwise directions, mm

xl

Unheated starting length, mm

XF

Length of the recirculation region of downstream surface of the first block, mm

XR

Reattachment length of the recirculation region of upstream surface of the last block, mm

XT

Length of the recirculation region of top face of the first block, mm

y

Pitch wise directions, mm

Greek symbols

γ

Intermittency factor, dimensionless

δ

Boundary layer thickness, mm

θ

Momentum thickness, mm

ρ

Density, kg/m3

Subscripts

o

Flow-off

f

Flow-on

in

Inlet

L

Laminar

T

Turbulent

0

Free stream

w

Wall

f

Flat

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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringUniversity of UludagBursaTurkey
  2. 2.Department of Mechanical EngineeringUniversity of HarranSanliurfaTurkey

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