Flow Reversal of Fully Developed Mixed Convection in a Vertical Channel with Chemical Reaction

The present analysis is concerned with the criteria for the onset of flow reversal of the fully developed mixed convection in a vertical channel under the effect of the chemical reaction. The governing equations and the critical values of the buoyancy force are solved and calculated numerically via MAPLE. Parameter zones for the occurrence of reversed flow are presented. The exothermic chemical reaction is found to enhance the flow reversal and made flow reversal possible for symmetrical walls temperature. 1. Introduction The study of combined and free convection flow in a heated vertical parallel-plate channel has received considerable attention because of its wide range of applications such as geothermal reservoir, cooling of nuclear reactors, thermal insulation, energy storage, and conservation, chemical, food, and metallurgical industries, and petroleum reservoirs. A combined forced and natural convective flow puts on the situation where an externally driven flow joins with an native buoyant flow and when both are prominent. One of the earliest studies on mixed convection in a vertical channel with uniform wall temperatures had been studied analytically by Tao [1]. Then Habchi and Acharya [2] studied mixed convection in a vertical channel with asymmetric walls heating, where one plate is heated and the other is adiabatic. Fully developed flow was revisited by Aung and Worku [3] and Cheng et al. [4]. They analyzed effects of various boundary conditions and different constant temperature parameters on buoyancy-aided flow. Recently, Pop et al. [5] studied the mixed convection in a vertical channel with chemical reaction and found that dual solutions exist for both velocity and temperature. The high buoyancy force due to a differentially heated wall combined with an upward flow leads to a high fluid flow adjacent to the walls that can precipitate a downward flow (i.e., reversal flow) emanating from the open top of the channel in order to augment the increased upward flow. Experiment on the appearance of flow reversal was conducted by Sparrow et al. [6] for free convection in a one-sided heated vertical channel. Aung and Worku [3] and Cheng et al. [4] studied analytically the occurrence flow reversal for the mixed convection. Criteria for the onset of flow reversal in terms of the Grashof to Reynolds number ratio were developed. Criteria for the occurrence of this flow, adjacent to the colder wall under effects of concentration, and magnetic field including internal heating, micropolar as well as thermophoretic, were presented by [7–9] and [10, 11],