5.34 A DPHX is made of a 6-nom sch 40 commercial steel outer pipe and a 5-nom sch 40S stainless steel inner pipe. The fluid in the annular space is cyclohexane that has a volumetric flow rate of 120 gpm and an average temperature of 60°F.

The fluid in the inner tube is water at an average temperature of 180°F and flowing at 320 gpm. Cyclohexane is an organic liquid and the water can be assumed to be distilled water. The thermal conductivity of the stainless steel inner pipe is 9.5 Btu/h·ft·°F. Determine the following:

a. Convective heat transfer coefficients in the inner pipe and the annulus

(Btu/h·ft2·°F).

b. Overall heat transfer coefficient for the case of a clean heat exchanger

(Btu/h·ft2·°F).

c. Overall heat transfer coefficient if fouling is considered (Btu/h·ft2·°F).