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The paper presents an economic optimization of a STHX with two commonly adopted (i.e., Kern and Bell-Delaware) and one rarely explored (i.e., Wills-Johnston) methods. A detailed numerical code concerning thermal, hydraulic, exergy, and economic analysis of STHX is developed for all three methods. Normalized sensitivity analysis, parametric study, and Genetic Algorithm are used to ascertain the most influential parameters and optimize the total cost. It is observed that the calculations made using the Wills-Johnston method were reasonably close to the Bell-Delaware method. While the Kern method showed a significant deviation in the shell side calculations because of the several assumptions in this method. The parametric analysis showed that increasing the mass flow rate and the number of baffles increased the operating cost because of an exponential increase in the pressure drops. Finally, the optimization reduced the heat transfer area by ~26.4%, capital cost by ~20%, operational cost by ~50%, total cost by ~22%, and the stream cost by ~21%.

Gasketed plate heat exchangers (PHXs) are frequently used as preheaters in thermal water desalination systems to preheat the intake seawater by recovering heat from the brine and distillate streams. The detailed design and analysis of PHXs as a preheater is not available in the desalination related studies. Rather, the heat transfer coefficients are calculated by simple empirical equations. The current study provides a comprehensive design procedure and analysis of these preheaters. In this regard, a numerical model is developed to investigate the thermal–hydraulic performance of PHXs under various operating conditions. First, the code is validated against the experimental data and then the effect of input parameters is studied. The results show that the feed flow rate and plate chevron angle are very important parameters for the heat transfer coefficient and pressure drop in PHXs. It is shown that the salinity does not affect the HX performance; however, the study also showed that the selection of fouling resistance is critical and it considerably disturbs the design parameters that govern the heat exchanger cost. Finally, the sensitivity analysis is presented to identify the most sensitive input parameters for the thermal–hydraulic performance of the heat exchanger.