Analysis of Exergy and energy in shell and helically coiled finned tube heat exchangers and design optimization

Abstract

In the present study, numerical method is established to analyze the effect of fin geometry and the inlet mass flow rate of the shell, on the Exergy loss in the newly design cylindrical shell and the helically coiled finned tube heat exchangers with an internal core inside the shell. The inlet fluid of coil side is the hot water with the temperature of 70 °C and the velocity equal to 1 m/s. While, the inlet fluid of the shell side is the dry cold air with the temperature of 10 °C and the velocity equal to 1–4 m/s. For validation of the model, the coil and shell side Nusselt number and the friction factor of the coil side is compared with the previous experimental correlations and an acceptable agreement is observed. Results indicate that, with the increase of the inlet mass flow rate of the shell side, fins height and number, NTU, heat transfer and the fan work the Exergy loss increases. Furthermore, it was found, the Exergy loss is always equal to 23.4% of the heat transfer rate. At the end of this work, two correlations are proposed to obtain the optimal values of the operational and geometrical characteristics of the heat exchanger.