Second law analysis of pillow plate heat exchanger to enhance thermal performance and its simulation studies

A relatively novel concept in plate heat exchangers is Pillow Plate Heat Exchanger (PPHX), which has demonstrated promising potential in heat transfer efficiency. However, the concept leads to a higher pressure drop compared to controversial models, and still, the effects of its geometrical parameters and operational conditions on efficiency are not clarified, comprehensively. In this study, a PPHX is designed and simulated to clarify the major reasons for pressure drop and entropy generation. In this regard, a 3D model of PPHX by considering conjugate heat transfer is developed and numerically investigated by using ANSYS Fluent. The calculations are accomplished for a wide range of Re numbers (103\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${10}^{3}$$\end{document} to 2.1×104\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$2.1\times {10}^{4}$$\end{document}) consisting of both laminar and turbulent flow regimes. The results are presented in terms of frictional coefficient, Colburn factor, heat transfer coefficient, entropy generation and second law efficiency for different welding spot diameters. It is observed that while increasing the diameter causes a higher pressure drop, it lowers heat transfer and irreversibility. Up to 12% variation in the efficiency is obtained for considered diameters. Meanwhile, although entropy generation due to temperature variation plays a major role in total entropy, entropy generation due to pressure drop has shown an exponential increment as the Re number increases.