This equation is expressed for a straight tube of any arbitrary crosssection
and can be safely applied to a helical coiled tube provided
that _S0
gen is computed on the basis of unit center-line length of the
tube. In Eq. (18), the first part of the quantity on right hand side
originates for heat transfer, while the second part arises due to friction.
From Eq. (18), it is apparent that high Stanton number leads to
decrease the heat transfer share of _S0
gen, while a greater friction factor
has the significant effect of enhancing the entropy generation
rate due to viscous effects. Eq. (18) is demonstrated as follows: