Exergetic performance of the helically coiled tube heat exchangers: Comparison the sector-by-sector with tube in tube types

The exergy analysis is performed for the flow of fluid and transfer of thermal energy inside the sector-by-sector (SBS) and tube-in-tube (TIT) types of the helically coiled heat exchangers (HCTHs). The turbulent transfer of thermal energy for each side of the heat exchangers is simulated using the Realizable K-epsilon model. The model is verified by comparing the current work values of the Nusselt numbers with the values obtained using the previous empirical correlations. New equations are suggested for the estimation of the exergy efficiency and the coefficient of the exergy performance as functions of the both sides Reynolds numbers, dimensionless coil diameter and pitch. These heat exchangers performance are compared using these equations. It was concluded that, if the dimensionless coil diameter is doubled, the exergy efficiency decreases by 21.8%, 25.7% and 21.1% and the coefficient of the exergy performance decreases by 8%, 9.3% and 14.8% for the heat exchangers with semi-circle cross section, quadrant-circle cross section and the TIT heat exchangers, respectively. Furthermore, the application of the SBS heat exchangers with semi-circle and quadrant-circle cross sections are highly recommended instead of the common TIT types. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University.