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*1.5*
for -ln[1-{1-exp(-5.67Pr x )}0.671t
h2--------------------------------------------------(55)
{ 1 - exp(-5.67-Pr x )}0.33
*1•5*
for -ln[1-{1-exp(-5.67Pr x)}0•67] > t
h* -----------------------2 *(56)
v76 { 1 - exp(-t )}
The transient heat transfer coefficient-calculated by Eqs.(55) and (56)
* * 0.33
is shown in Fig.7 in h vs x Pr plot.
In view of Eqs.(52) and (55), the ratio between asymptotic transient
heat transfer coefficient and steady state one is given by
h aPr0•17*. a
_a = 1.78x* (57)
h stNust{ 1 - exp(-5.67 Pr x1.5)}0.33 •
The value of h a/hst calculated by Eq.(57) for Pr = 1 is shown in Fig.4.
II. 6 TURBULENT FLOW FOR Pr > 1
For a turbulent flow, the velocity field is represented by turbulent
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