CFD ANALYSIS OF VELOCITY AND THERMAL PERFORMANCE IN A COUNTER-FLOW DOUBLE-TUBE HEAT EXCHANGER

The study carries out numerical investigation on the velocity and thermal performance of a counter flow double-tube heat exchanger through the use of Computational Fluid Dynamics (CFD).Three different arrangements smooth tube, spherical element inserts, and double helical baffle are subjected to a thorough examination in terms of their impact on flow, temperature, heat transfer, and overall thermal efficiency.A solvent's three-dimensional CFD model is created in ANSYS Fluent through the application of the finite volume method and the realizable 𝑘-𝜀 turbulence model, as well as under steady-state conditions.Ag-MoS₂ nanofluid gets the role of the hot fluid inside the tube while, in the annulus, water flows as the cold one.The simulations are run at different Reynolds numbers by adjusting hot fluid speed from 0.2 to 0.65 m/s and keeping the inlet temperature of the hot fluid at 350 K and that of the cold one at 300 K. Model validation against available literature shows a good match in the Nusselt number and also in the temperature change.The analysis reveals that an increase in Reynolds number leads to an increase in turbulence and heat transfer coefficients for all setups.The least studied design, the double-helical-baffle configuration, performs the best with a maximum hot fluid temperature drop of 13.936 K and the highest heat transfer rates of 2152.434W for the hot fluid and 50,774.038W for the cold fluid.The logarithmic mean temperature difference is inversely related to Reynolds number while the overall heat transfer coefficient is directly related, thus confirming the improved thermal effectiveness.The results are suggesting that the right geometry alteration along with the optimized flow conditions can be a game-changer in thermally empowering counter-flow double-tube heat exchangers manifold.