(Solved): 15.4. A shell-and-tube exchanger with two tube passes is used to heat ethanol from 60F to 14 ...

15.4. A shell-and-tube exchanger with two tube passes is used to heat ethanol from $60^{?}\mathrm{F}$ to $140^{?}\mathrm{F}$ with steam condensing at $230^{?}\mathrm{F}$ in the shell. ${}^{27a}$ The BWG 14 steel tubes are $\frac{3}{4}$ in. OD. The design overall coefficient (inside area) is $196\mathrm{Btu}/\mathrm{h}?{\mathrm{ft}}^2?{}^{?}\mathrm{F}$, based on an assumed fouling coefficient of $1,000\mathrm{Btu}/\mathrm{h}?{\mathrm{ft}}^2?{}^{?}\mathrm{F}$ and a steam film coefficient of $1,800\mathrm{Btu}/\mathrm{h}?{\mathrm{ft}}^2?{}^{?}\mathrm{F}$. (a) If four tube passes were used, what would be the new overall coefficient? $(b)$ Estimate the new pressure drop if the tube length is unchanged and the calculated $?p$ for two tube passes was $140{\mathrm{lb}}_f/{\mathrm{ft}}^2$.