Transition of free convection flow inside an inclined parallel walled channel: effects of inclination angle and width of the channel

Transition of free convection flow in an inclined parallel walled channel has been investigated numerically by employing k–ɛ turbulent model. Particular attention is paid on how the inclination angle and width of the channel affect the transition process of the flow developing in the channel. The upper plate of the channel is heated isothermally and facing downward, while the lower one is kept under the adiabatic condition. The inclination angle of the channel is varied from 0° to 85° with respect to its vertical position while the distance separating the two plates is systematically reduced from 0.45 to 0.06 m. Distributions of velocity, turbulent kinetic energy and local heat flux are presented to examine the critical distance and the results obtained show good agreement with experimental data available in the literature

Effect of width and temperature of a vertical parallel plate channel on the transition of the developing thermal boundary layer

Numerical simulations are performed to study the transition of the development of the thermal boundary layer of air along an isothermal heated plate in a large channel which is bounded by an adiabatic plate. In particular, the aim is to investigate the effects of the channel width (b) on the transition of the flow under various plate temperatures. Three different RANS based turbulent k–ε models namely standard, RNG and Realizable with an enhanced wall function are employed in the simulations. The channel width was varied from 0.04 m to 0.45 m and the numerical results of the maximum values of the flow velocity, turbulent kinetic energy were recorded along the vertical axis to examine the critical distance of the developing flow. The results show that the transition delays when the width is increased from 0.04 m to 0.08 m and particularly, the critical distance at b = 0.08 m reaches its maximum with the Grashof number of 2.8 × 1010. However, the critical distance drops when b is increased further from 0.08 m to 0.45 m, indicating an early transition of the flow. The transition remains unaffected by the adiabatic plate when b is greater than 0.45 m. Comparisons of selected numerical results are made with available experimental data of turbulent flow and a satisfied agreement is received

Transition of free convection flow between two isothermal vertical plates

Numerical simulations are performed to study the transition of the development of thermal boundary layer of air along isothermal heated plates in a large channel. In particular, the aim is to investigate the effects of the channel width on the transition of the flow under various plate temperatures. Realizable k–ε turbulence model with an enhanced wall function is employed to obtain the numerical simulations of flow and thermal fields in the channel. The channel width is varied from 0.04 m to 0.45 m and the numerical results of the maximum values of flow velocity, turbulent kinetic energy are recorded along the flow to examine the critical distance of the developing flow. Effects on the transition of the two different types of wall boundary conditions, isothermal and adiabatic, applied to the channel are also examined. The results particularly indicate that the flow transition in the isothermal cases takes later than that in the adiabatic cases

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