Case Studies in Thermal Engineering (Dec 2021)
Buoyancy driven second grade nano boundary layers over a catalytic surface with reaction rate, heat of reaction and activation energy at boundary
Abstract
The present article aims to explore the characteristics of catalytic surface reactions on free convection non-Newtonian nanofluid boundary layers which are driven by buoyancy force. The non-Newtonian behavior of the fluid is modeled using a Cauchy stress tensor which includes pressure, dynamic viscosity, two normal stress moduli and two Rivlin-Ericksen tensors. The Buongiorno model is utilized to model the nanofluid behavior. The exothermic surface reactions are considered by Arrhenius kinetics at the wall. The boundary conditions are designed with one-step, non-isothermal and first order reactions. Furthermore, the flow phenomenon is assumed with elastic deformation effects. To carry out a parametric study, the governing equations and boundary conditions were transformed into a non-dimensional form with essential parameters. The impacts of exothermic reactions in the flow region are explored using heat of reaction, reaction rate and activation energy parameters which occurred in the boundary. The flow behaviors are clearly analyzed with a numerical experiment. The results are plotted for momentum, thermal and concentration boundary layers, skin friction, dimensionless wall temperature and dimensionless wall concentration. The numerical values of dimensionless wall temperature and wall concentration are presented. It is found that the heat of reaction raises the temperature and concentration profiles significantly due to the catalytic surface reactions and it shows a slight enhancement in the velocity profile. Both activation energy and reaction rate constant retard all the nanofluid profiles and have a significant role on the temperature and concentration profiles. The surface reaction and the buoyancy parameters show a significant variation inside the boundary layer flow region of second grade nanofluid.
