Numerical Pipe Flow Model to Demonstrate Laminar Flow in Concentric Double-Pipe Heat Exchangers

This paper presents a numerical model for demonstrating laminar flow behavior within concentric double-pipe heat exchangers. Developed in Python and Engineering Equation Solver (EES), the approach leverages the fundamental energy equation in cylindrical coordinates, capturing both radial and axial variations in fluid temperature. The model addresses fully developed laminar flow in a 1D marching approach. Comparisons between parallel-flow and counterflow configurations highlight the role of fluid properties, geometry, and boundary conditions in governing overall heat transfer performance. The convective heat transfer coefficient is predicted using Nusselt number correlations for annular flow, and these analytical predictions are validated against numerical solutions. Results demonstrate how fluid conductivity and the ratio of inner to outer diameters fundamentally affect the attainable heat exchanger coefficient under laminar conditions. A simplified thermodynamic analysis further quantifies the energy exchange and the log mean temperature difference, complementing the full numerical model. Notably, the counterflow design can improve heat transfer by up to 28.3% compared to its parallel-flow counterpart, illustrating the model’s ability to capture theorized performance trends. A separate study considers the effects of a high viscosity fluid and external convection losses to the ambient as an extension of the model’s capabilities. While the convective heat losses decrease the average temperature in the exchanger by up to 5°C, placing the viscous fluid on the inside can help to compensate for those losses through the heat generated by friction. By using fundamental theory with computational techniques, this framework offers a valuable pedagogical tool for enhancing students’ understanding of heat exchanger design and necessary computations.