Heat Transfer Investigation of Laminar Flow Mixed Convection of Nanofluids in a Uniformly Heated Horizontal Annulus: A Combination of Theoretical-Based and Experimental-Based Models of Thermal Conductivity and Viscosity

This present study is intended for a CFD analysis of hydrodynamic and thermal characteristics of water-based fluid containing TiO2 or CuO nanoparticles flowing in laminar regime in a 3D uniformly heated horizontal annulus utilizing several. Four distinct models have been developed using various combinations (A, B, C and D) of the available theorical-based and experimental-based thermal conductivity and viscosity correlations. A CFD-Fortran code based on the finite volume technique was elaborated for the numerical solution of the mathematical model of the problem. The implications of Grashof number, volume fraction, and type of nanoparticle on isovelocity, isotherms, mean and wall temperatures, Nusselt number, heat transfer coefficient, pressure drop, and thermal performance evaluation criteria are explored using these different models. The results demonstrate that the Nusselt number and heat transfer coefficient of all developed models improve with the addition of nanoparticles. For 2% of nanoparticles’ concentration, the largest enhancement was reached for model D by about 23.5% with respect to the based liquid, while the smallest enhancement was obtained for model B by about 1.16%. The highest Performance Evaluation Criteria (PEC) are attained by employing model D by about 1.263, followed by model C by about 1.074.