A 1-shell-pass and 8-tube-passes heat exchanger is used to heat glycerin (cp = 0.60 Btu/lbm(oF) from 65oF to 140oF by hot water (cp = 1.0 Btu/ lbm(oF) that enters the thin-walled 0.5-in-diameter tubes at 175oF and leaves at 120oF. The total length of the tubes in the heat exchanger is 500 ft. The convection heat transfer coefficient is 4 Btu/h(ft2(oF on the glycerin (shell) side and 50 Btu/h(ft2(oF on the water (tube) side. Determine the rate of heat transfer in the heat exchanger?
(a) Before any fouling occurs and
(b) After fouling with a fouling factor of 0.002 Btu/h(ft2(oF /Btu on the outer surfaces of the tubes.