Second law analysis for the optimization of plate heat exchangers

The transfer of thermal power in reduced spaces can be attained by plate heat exchangers (PHE), making these devices suitable for different applications. The encumbrance is very limited due to the parallel plates installed with a reduced distance, so the fluids circulate in alternate manner inside the correspondent channel in a counter-current configuration. Appropriate corrugations on the plate surface are provided to improve the thermal transfer, however the frictions with the fluid can increase significantly. In this paper, a second law analysis involving the irreversibilities connected with the thermal transfer and pressure drops was carried out to identify the optimal PHE configuration by means of the minimal entropy generation approach. Because technical solutions employed to improve the thermal transfer among the fluids often determine a pressure drops growth, an optimal configuration can be identified. At this purpose, a quality dimensionless index related to the irreversibilities and determined with a parametric study by varying number of plates, pitch, corrugation angle, fluid flow rates and exchange surface material allowed to identify the optimized PHE.