The design of triple concentric tube heat exchanger (TCTHE) requires heat transfer coefficient (HTC) values for all three fluid streams as input parameters. The fluid through intermediate tube transfers heat to other fluids simultaneously. The present study applies a concept of thermal resistance network and quadratic equation is developed for computing HTC of intermediate fluid for TCTHE under adiabatic condition. ‘Oil ISO VG 22’ is taken as intermediate fluid and is cooled by using water as inner and outer cooling fluid in the present work. The HTCs of inner and outer cooling fluids are calculated from the well-established empirical correlations available in the literature. CAD modelling is done using Catia V5 and simulation is carried out using STAR CCM+ CFD software. The results of the method are compared with those obtained from mathematical models in the literature as well as results from CFD analysis are validated. © 2022 Informa UK Limited, trading as Taylor & Francis Group.