CFD Letters 16, Issue 12 (2024) 97-112 97 CFD Letters Journal homepage: https://semarakilmu.com.my/journals/index.php/CFD_Letters/index ISSN: 2180-1363 Numerical Investigation of Thermal Performance for Turbulent Water Flow through Dimpled Pipe Ansam Adil Mohammed 1,* , Mahmoud Sh. Mahmoud 1 , Suha K Jebir 1 , Ahmed F. Khudheyer 1 1 Mechanical Engineering Department, College of Engineering, Al‐Nahrain University, Baghdad, Iraq ARTICLE INFO ABSTRACT Article history: Received 4 January 2024 Received in revised form 8 February 2024 Accepted 10 March 2024 Available online 31 July 2024 Dimples are tiny indentations on the surfaces of the body that enhance heat transfer and alter fluid flow characteristics on or within the body. Numerical investigations were conducted to analyse the heat transfer and flow characteristics in a cross- combined dimple tube in the range of Reynolds numbers from 6000 to 14000. The finite volume method recognised a novel enhancement model utilising methods for composite-form surfaces. Compared to a smooth tube working similarly, the effects significantly improve the heat transfer index, performance evaluation criteria, and friction factor. A three-dimensional simulation was conducted to clarify the underlying process by which dimples affect thermal performance. The simulation findings suggest that the dimples effectively enhance heat transfer by altering the temperature distribution and increasing the temperature gradient within the central area of the dimple section. A concave surface profile disrupts the flow and prevents the formation of a stable boundary layer, promoting the mixing of hot and cold fluids. Furthermore, the study investigates how geometric characteristics impact thermal and hydraulic efficiencies, emphasising that larger dimples improve overall thermo-hydraulic performance. Specifically, the heat transfer enhancement achieved an average increase of 17.3%, ranging from 18.03% to 38.6%, surpassing that of the traditional smooth tube. Keywords: dimple tube; heat transfer coefficient; Nusselt number; friction factor 1. Introduction Heat transmission is an inherent process that occurs naturally. Heat exchangers are utilised to transport heat efficiently and cost-effectively. Studying the performance of thermal devices is a crucial area of focus in engineering. Enhancing heat transport is crucial for sustained energy expansion. Researchers have persisted in their investigations of heat transfer enhancement in the literature. Several researchers have focused on improving heat transfer by utilising intricate geometric designs to induce secondary fluid motion and boost the velocity of heat transmission as shown in the previous studies [1-4]. From a financial and industrial standpoint, a significant imperative exists to enhance the efficiency of a heating and cooling switch system that may be installed by Al-Qalamchi and Adil [5]. Augmenting * Corresponding author. E-mail address: ansam.a.mohammed@nahrainuniv.edu.iq (Ansam Adil Mohammed) https://doi.org/10.37934/cfdl.16.12.97112