5.35 A DPHX is made of type M copper tubing. The heat exchanger is a 3 × 1 design

(3-std outside tube with a 1-std inside tube). Toluene flows through the inner tube with a volumetric flow rate of 0.5 L/s and an average temperature of 30°C. Water flows in the annulus at a rate of 3 L/s with an average temperature of 60°C. Toluene can be considered an organic liquid and the water can be assumed to be from a city water supply. Determine the following:

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

(W/m2 K).

b. Overall heat transfer coefficient for a clean heat exchanger (W/m2 K).

c. Overall heat transfer coefficient if fouling is considered (W/m2 K).