Name Quiz 10
Q.1 The exponential function is only exactly zero when the argument goes to infinity.
This is a result of approximating the system as having no thermal gradients.
But from a
practical point of view the exponential has reached 99% of the change when the argument
is 5 so when time is five times bigger than (hA)/(
ρ
c
p
V) the system is effectively reached
thermal equilibrium.
Q. 2 Lumped system is appropriate when Bi<0.1
Q.3 THIS HAS A TYPO – both dimensionless heat transfer coefficient and
dimensionless time can exceed 1
Q.4 There are three charts for each geometry to give each of the functions described.
Q.5 That is what
"
T
t
=
#
2
T
x
2
means.
Q.6 The square root of the product of the thermal diffusivity and elapsed time has units of
distance (m) and is the distance that has begun to approach the temperature of the
surrounding – see the write up on erfc on Blackboard.
Q.7 see page 748
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 Spring '08
 Landau
 Dynamics, Heat, Mass Transfer, Heat Transfer, #, 11.94%, CpV, 10 0%

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