Hydrothermal behaviour of hybrid nanofluid flow in a shell-and conical coil tube heat exchanger; numerical approach

The present work considers a shell-and-coil heat exchanger, and the hybrid nanofluid's flow and heat transfer inside the proposed thermal system are numerically evaluated. The coil tube has a conical pattern and is oriented horizontally inside the shell. Three water-based hybrid nanofluids are considered here as heat transfer fluids. A commercial CFD code that uses the finite volume method performs the numerical analysis. The regime of fluid flow is turbulent in both coil and shell sections. The validation analysis of the present numerical model was performed using the experimental results of the reference, and accordingly, the accuracy of the present numerical model was proved. This work includes two sectors. In the first part, the volume concentration of the considered hybrid nanofluid was kept constant, and the influence of the hybrid nanofluid kind on the hydrothermal behaviour of the shell-conical-coil heat exchanger was evaluated numerically. In this section, three hybrid nanofluids, (i) Water/MgO-TiO2, (ii) Water/MOS2-CuO, and (iii) Water/Ag-HEG, were employed. Also, for all suggested hybrid nanofluids, the volume concentration of both employed nanoparticles are equal to each other, φ1= φ2. The obtained outcomes depicted that between various considered heat transfer fluids, the Water/MgO-TiO2 model displayed the most outstanding thermal performance value in all the investigated Dean numbers, and the model Water/MOS2-CuO was in second place. Moreover, the maximum thermal performance for the hybrid nanofluid was obtained at φ1 = φ2 = 0.7. The Ag-HEG/Water and MgO-TiO2/Water hybrid nanofluids have the lowest and maximum thermal performance at the lowest considered Dean number among the evaluated hybrid nanofluids. As a result, the MgO-TiO2/Water hybrid nanofluid has roughly 18.95% higher thermal performance than the Ag-HEG/Water hybrid nanofluid. Furthermore, the MgO-TiO2/Water and Ag-HEG/Water hybrid nanofluids have the highest and lowest thermal performance at the highest considered Dean number, respectively. Consequently, the MgO-TiO2/Water hybrid nanofluid exhibits approximately 39.22% higher thermal performance than the Ag-HEG/Water hybrid nanofluid. The MgO-TiO2/Water hybrid nanofluid has the highest and lowest thermal performance at the lowest Dean number, with ϕ1 = ϕ2 = 0.7 and ϕ1 = ϕ2 = 0.3, respectively. The ϕ1 = ϕ2 = 0.7 model has a thermal performance that is approximately 39.28% greater than the ϕ1 = ϕ2 = 0.3 model at the lowest regarded Dean number. At the highest regarded Dean number, the MgO-TiO2/Water hybrid nanofluid with ϕ1 = ϕ2 = 0.3 exhibits a lower thermal performance than the model ϕ1 = ϕ2 = 0.7 by about 14.28%.