Sedimentation of particles in cooling systems significantly affects thermal performance, leading to reduced efficiency and potential system failures. This study examines the impact of calcium carbonate (CaCO3) particles' sedimentation, with different concentrations and particle sizes, on heat transfer in tubular pipes under laminar flow conditions. The Discrete Element Method (DEM) is employed to investigate particle deposition and its flow behavior under the influence of various forces. Nanoparticles and submicron-sized particles are primarily influenced by Brownian motion and drag forces. To simulate the fluid motion, momentum, continuity, and energy equations are solved using OpenFOAM software. Consequently, a coupled CFD-DEM approach is implemented using the open-source CFDEM software toaccurately describe particle behavior and heat transfer physics. The results of this study show that.a small volume concentration (1.2×10-6 %) of CaCO3 reduces the Nusselt number by 5.5% compared to the Nusselt number without sedimentation in pipe flow, with a total reduction of up to 11% as the volume concentration of CaCO3 increases. © 1993 Association for Computing Machinery. All rights reserved.