In this dissertation, entropy generation minimisation techniques are used to numerically investigate the minimum entropy generation due to heat transfer and fluid friction in a number of different heat exchangers. Twenty-seven different industrial-types of heat exchangers with power ratings ranging between 100 and 800 kW were analyzed. This was done due to their large energy consumption and inefficiencies associated with their operation. Through numerical optimisation it was possible to conclude that the main variables that affected entropy generation were the steam inlet temperature, followed by the tube-side diameter for the given sample set. The main mechanism contributing to entropy generation was the effect of fluid friction, although this was only the case at smaller tube diameters. By using the principles of entropy generation minimization the entropy generated of each heat exchanger could be reduced by between 2% and 64%. By using the principles of the entropy generation minimisation technique, the optimal diameter could be determined that yielded results within 1% of the global minimum entropy generation. / Dissertation (MEng)--University of Pretoria, 2015. / Mechanical and Aeronautical Engineering / MEng / Unrestricted