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In this work, we study the unsteady free convection boundary-layer flow of a nanofluid along a stretching sheet with thermal radiation in the presence of magnetic field. To obtain non-similar equations, continuity, momentum, energy, and concentration equations have been non-dimensionalized by usual transformation. The non-similar solutions are considered here which depend on the magnetic parameter M, radiation parameter R, Prandtl number P r , Eckert number E c , Lewis number L e , Brownian motion parameter N b , thermophoresis parameter N t , and Grashof number G r . The obtained equations have been solved by an explicit finite difference method with stability and convergence analysis. The velocity, temperature, and concentration profiles are discussed for different time steps and for the different values of the parameters of physical and engineering interest.

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This numerical analysis presents the airside performance of a wavy fin-and-tube heat exchanger having 4 row configurations considering steady, incompressible and 3D flow using Commercial CFD Code ANSYS CFX 12.0. Results are presented in the form of friction factor (f), Colburn factor (j) and efficiency index (j/f). The numerical procedure has been validated by comparison with published numerical and experimental results and good agreement has been observed. A series of numerical calculations have been carried out in order to analyze the influence of various geometric characteristics on different fields as well as on the heat transfer and pressure drop and efficiency within a heat exchanger. The effects of longitudinal pitch (Ll), transverse pitch (Lt), Fin Pitch (Fp), wavy angle (Wa) and inlet flow angle (α) on wavy fin-and-tube heat exchanger are studied. Different inlet flow angles such as 0 , + 17.5˚, -17.5˚, +35˚ and -35˚ are employed normal to the face of the heat exchanger in order to investigate the performance of inlet flow angles. There is a strong correlation between the response of the flow efficiency, pressure drop and heat transfer performance to these parameters.

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