CbE
120B
Heat Transfer
Turbulent Flow Heat Transfer
Analyzing heat transfer with turbulent flow, we are stuck in a bad place analytically.
We cannot begin to solve the equations
of
motion for an isothermal flow, much less for a
flow with changing temperature. To develop the necessary engineering relations between
the Nussett's number, Reynolds' number and other measurable characteristics
of
turbulent
flow, we use analogies to give us the relevant parameters to describe the situation:
Reynolds stated two mechanisms contribute
to
the transport
of
heat:
1)
Internal diffusion
of
the fluid when at rest
2)
Eddies caused by bulk motion which continually brings fresh fluid into
contact with the surface.
H=At+Bpvt
t = temperature difference
p = density
v = bulk velocity
A,B = constants
H = heat transmitted
I
areatime
An analogous equation was written for fluid friction
R=A'v
+B'
p v
2
Reynold's intuition led
to
the belief
A
a
A'
B
a
B'
or
h
a
f
Consider bulk flow through a pipe at fluid temperature tb and pipe temperature ts. the four
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 Winter '10
 Zasadinski
 Fluid Dynamics, Turbulent Flow, fluid temperature tb

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