Multi-objective Shape and Flow Optimization of Finned Double-Tube Heat Exchanger Filled with Nanofluid: A CFD and RSM Study

In the present study, the thermal attributes and hydrodynamic characteristics of a finned double-tube heat exchanger involving six design variables ( Re , ( H D ) , ( p D ) , ( t D ) , ∅ p , ( T c T h ) ) were numerically investigated and optimized by simultaneous use of computational fluid dynamics and response surface methodology. Ninety numerical designs proposed based on the face-centered central composite design (FCCD) technique were utilized to generate mathematical regression models of response functions. The accuracy and reliability of the obtained regression models including η t - h , η II , Nu Nu s and Δ p were investigated through analysis of variance (ANOVA). Furthermore, the significance of model terms was also analyzed by considering F values larger than the critical F value for each response functions and a P value smaller than the selected level of significance (i.e. 0.05). Multi-objective shape and flow optimization of the finned double-tube counter-flow heat exchanger was carried out using the composite desirability function approach to maximize the thermo-hydrodynamic performance index, exergetic efficiency and Nusselt number and to minimize the pressure drop across the heat exchanger. The optimum design variables resulting in the highest desirability function (i.e. 0.8886) were found to be Re = 4000 , ( H D ) = 0.154 , ( p D ) = 9.840 , ( t D ) = 8.610 , ∅ p = 0 % , ( T c T h ) = 0.968 , which correspond to the maximum predicted value of η ( t - h ) = 1.193 , η II = 8.367 % , Nu Nu s = 1.771 , Δ p = 7461.1 ( Pa ) . The value of η ( t - h ) can be further increased up to 1.261 where the composite desirability function reaches to 0.8514.