Page 442 - Handbook of Energy Engineering Calculations
P. 442
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k = 0.86 (cs /M )
An important compound for which the Weber equation does not work well
is water (the calculated thermal conductivity is less than the actual value).
Figure 12 gives the physical-property factor for water (as a function of fluid
temperature) that is to be substituted in the equations for sensible-heat
transfer with water, or for condensing with steam.
FIGURE 12 Physical-property factors for water and steam vs
temperature. (Chemical Engineering.)
If the thermal conductivity is known, it is best to obtain a pseudomolecular
weight by:
3 4
M = 0.636(c/k) S
This value is substituted in the applicable equation to solve for the
physical-property factor.
Tube pitch for both triangular and square-pitch arrangements is assumed to
be 1.25 times the tube diameter. This is a standard pitch used in the majority
of shell-and-tube heat exchanges. Slight deviations do not appreciably affect
results.
Shell diameter is related to the number of tubes (nN ) by the empirical
PT
equation:
