1.A double-pipe heat exchanger is constructed of a copper (k = 380 W/m 0C) inner tube of internal diameter Di = 1.2 cm and external diameter Do=1.6 cm and an outer tube of diameter 3.0 cm. The convection heat transfer coefficient is reported to be hi =700 W/m20C on the inner surface of the tube and ho= 1400 W/m2 0C on its outer surface. For a fouling factor Rf,i= 0.0005 m2 0C/W on the tube side and Rf,o= 0.0002 m2 0C/W on the shell side, determine (a) the thermal resistance of the heat exchanger per unit length and (b) the overall heat transfer coefficients Ui and Uo based on the inner and outer surface areas of the tube, respectively.
