The following is a thermal, mechanical and hydraulic design response report to a heat exchanger problem where ethylene glycol and a poor quality feed of water are put through a shell and tube exchanger with the objective of cooling the ethylene glycol feed. A shell and tube exchanger was chosen over several other exchangers due to its high efficient performance and its relative ease of maintenance in processing these fluids.
From the data given and specific heat capacity researched for ethylene glycol, a MatLab script was constructed to calculate values from a range of formulae for a variety of variables including the initial duty, which was calculated to be 1486.1 KW. It was chosen, that as water is a more corrosive fluid and has a higher operating pressure, the water should pass through tubes made of stainless steel, which are easier to clean, and the ethylene glycol through the shell side. From here the Log Mean Temperature Difference (LMTD), Heat Transfer Coefficient (U = 714) and Total Interfacial Heat Transfer Area (A = 40.16m2) and a Reynolds number were all calculated using MatLab. A number of 336 tubes for the exchanger were established and it was concluded that a 1-4 Shell Tube design was most appropriate with tubes of inner diameter 15.05mm and an outer diameter of 19.05mm with a triangular pitch of 23.81mm giving a pipe thickness of 4mm. Using Kern’s method (Coulson & Richardson, 2005). Chemical Engineering Design, a baffle cut of 25% was required leading to a tube side pressure drop of 0.45 bar and a shell side pressure drop of 0.44 bar.
The report investigates further design specifications and other important data as well as calculations of how these specifications were achieved.
Introduction
The objective of this problem was to design a heat exchanger for the transfer of heat between a relatively warmer Ethylene Glycol fluid stream and a cooler water stream using a shell and tube heat exchanger. Shell and Tube heat