Optimizing Energy Transfer in Heat Exchangers With CNT‐Embedded Coaxial Cylinders: A Numerical and Statistical Study by Keller‐Box Method

ABSTRACT This study explores the enhancement of cooling efficiency in heated coaxial cylinders using carbon nanotube nanoparticles. It provides insights into improving that cooling mechanism by incorporating hybrid nanofluids, specifically SWCNTs+water and MWCNTs+water, saturated in a Darcy‐Forchheimer porous medium placed between coaxial cylinders. The inner cylinder stretches under convective boundary conditions, while the outer surface remains stationary with a constant surface temperature. The purpose is to examine the controlled parameters that help the system maintain heat transport and reduce skin drag. Using Xue's model, the analysis compares the two nanofluid suspensions’ momentum and thermal transport properties. The Keller‐box method in MATLAB is utilized to solve the problem, and regression analysis with ‐statistics and P ‐value is performed using ND‐Solve in Mathematica. Graphical illustrations are presented to comprehensively understand the dynamic behavior of SWCNTs+water and MWCNTs+water suspensions. It is concluded that the stretching cylinder shows a dominant impact compared to the stretching sheet, leading to higher skin friction values due to better momentum transfer. Increasing volume fraction lowered the heat transport rate due to decreased thermal distribution. ‐statistics showed that radiation had a more dominant effect than the Biot number on the predicted Nusselt number for both SWCNTs+water and MWCNTs+water suspensions.