Question

Hot stream Aromatic stream 85 40 85.2 Cold stream Cooling water 20 35 Inlet temperature (°C) Outlet temperature (C) Mass flowrate x heat capacity (KW°C) The fluid properties are as follows Cold stream Cooling water 4193 Hot streanm Heat capacity (Jlkg K) Density (kg/m2) Viscosity (cP) Thermal conductivity (WIm-K) Fouling factor (m2.°C) 2840 750 0.34 0.19 0.00018 1.016 0.594 0.000176 The cooling water is allocated to the tube-side of the exchanger . It is preferable to employ a fixed-tubesheet heat exchanger for the service. 25.4 mm OD tubes (2.1 mm wall thickness) on a 1.25 x OD triangular pitch are available. The thermal conductivity of the tube material is kw-51 Wm.K Consider four (4) tube passes .The maximum tube length that can be employed is 6098 mie.Ls 6.098 m Assume 1-shell pass. The shell diameter should not exceed 1.5 mie. D, s 1.5m Baffle cut is set at 25% and the baffle spacing (b) is assumed to be 0.5 x D' The maximum allowable tube-side and shell-side pressure drops are 70 kPa and 50 kPa . . Total annual cost (TAC) is given as follows TAC-1234+ 131 ) Prube Pshe where A is the area of the exchanger in m, TAC is in Syear, ?? is in Pa, m in kg s and ? in kg/m The standard design procedure for a heat exchanger is given in figure 3.7 of your study guide (pg 56). Critically assess the shortcomings of this method. ( Maximum of 6 lines) 2.2 Provide a mathematical expression for the following constraints o the tube side velocity o the shell-side velocity, and (Hi nt: see page 54 and 64 of your study guide. Note: cooling water in the tubes) 23 Derive an expression for the number of tubes in terms of the tube-side velocity, number of tube passes, mass flowrate and tube inside diameter (Hint see page 63 of your study guide)

Answer 1