Heat Transfer and Fluid Flow Over a Flat Plate - PowerPoint PPT Presentation

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Heat Transfer and Fluid Flow Over a Flat Plate

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Heat Transfer and Fluid Flow Over a Flat Plate MANE 4020 Fall 2005 Convection Heat Transfer It quantifies the energy transfer between a fluid at one temperature ... – PowerPoint PPT presentation

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Title: Heat Transfer and Fluid Flow Over a Flat Plate


1
Heat Transfer and Fluid Flow Over a Flat Plate
MANE 4020 Fall 2005
2
Fluid Problem Friction and Boundary layer
U0
U?
U(y)
d(x)
xo
Shear stress
U(x,0)0
Boundary layer thickness dy , U(y)/ U? 0.99
3
Measurement of the Velocity Profile
U
4
Skin Friction Coefficient
Skin Friction Correlations
Laminar flow
Turbulent flow
Skin Friction Measurement
From
(difficult to get u near to wall)
5
Boundary layer models
1/7th Power Law
More exact expression
y ? 5
y ? 30
6
Boundary layer models
7
Convection Heat Transfer
  • It quantifies the energy transfer between a fluid
    at one temperature flowing over a solid object at
    a different temperature.
  • - q is the heat flux (J/s m2 W/m2)
  • - DT is the difference between fluid temperature
    (in the freestream) and the solid wall
    temperature
  • A is the surface area of the solid.
  • q is the total heat transfer from a surface
    (Watts).

8
Two common questions of any convective heat
transfer problem
  • Given the distribution of surface temperature as
    a function of position along a surface, what is
    the distribution of local heat flux?
  • Given the distribution of local surface heat flux
    as a function of position along a surface, what
    is the distribution of surface temperature?

Tfluid
Tsolid
9
Fluid flow and heat transfer over flat plate - A
complex problem
Rex U? x/n is the criterion for the
Turbulent/Laminar Rexgt105 for the flat plate
flow Red gt2300, for the pipe flow
10
Dimensionless heat transfer coefficient (Stanton
)
Laminar flow can be derived
Turbulent flow - experimental
h is the property of flow Pr is the property of
fluid
11
St decreases with the increase of Re. St
increases when the flow becomes turbulent flow.
12
Measurement of heat transfer coefficient (I)
13
Measurement of heat transfer coefficient (II)
T?
T?
Rrad
Rconv
Tplate
Rcond
Tblack
14
The plate is constructed of four layers of
materials Four, 2 in. wide Ni-Chrome heating
strips which are embedded in fiberglass and epoxy
resin 3/8 in. balsa wood 5/8 in.
plywood 1/8 in. plywood.
15
Measurement of heat transfer coefficient (III)
Qo VI
h
16
Structure of Wind Tunnel
Wind supply Blower /Fan (quantity supply)
Settling chamber (quality supply)
Honeycomb, Mesh Screen
To reduce turbulence
17
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