Convection Channel Flow Research Articles

Binary diffusion and heat transfer in laminar mixed convection channel flows with uniform wall heat flux: extremely thin film thickness

A detailed numerical study has been performed to investigate the combined heat and mass transfer in laminar mixed convection channel flows with uniform wall heat flux. In an initial effort the liquid film on the channel wall is assumed to be extremely thin in thickness. Major dimensionless groups governing the present problem areGrT,GrMx,Pr,Sc, φ andRe. Results are specifically presented for an air-water system under various conditions. The effects of wall heating flux, the Reynolds number and the relative humidity of the moist air in the ambient on the momentum, heat and mass transfer in the flow are investigated in great detail.

Steady conjugate heat transfer in turbulent channel flows

The characteristics of steady conjugate heat transfer in turbulent channel flow which is uniformly heated over a finite length are numerically studied. The influences of wall thickness, wall-to-fluid conductivity ratio, and Prandtl number on the nondimensional heat flux and the evolution of temperature field are discussed in great detail. Particular attention is paid to study the wall conduction effects on low-Reynolds number turbulent forced convection heat transfer. The results show that the effects of wall conduction on turbulent forced convection channel flow are significant, especially for the cases with larger wall thickness and wall-to-fluid conductivity ratio.

Combined heat and mass transfer in laminar forced convection channel flows

This study is to examine the effects of latent heat transfer associated with the liquid film vaporization on the heat transfer in the laminar forced convection channel flows. Major non-dimensional parameters identified are Pr, Sc, and φ. Results are specifically presented for an air-water system under various conditions. The effects of system temperatures on the heat and mass transfer are investigated in great detail. Results show that the evaporation of the liquid film has significant influences on laminar forced convection heat transfer.

Heat transfer enhancement in a convective field with corona discharge.

An experimental study was conducted to examine the heat transfer enhancement in forced convective channel flow by means of the ionic wind induced between the plate wall and plural negative wire electrodes, which were put at the center line of the channel. A theoretical analysis was also performed on electric, flow, and temperature field taking account of the interactions among these fields. Firstly, the combined flow field where the cellular secondary motion occured owing to the field's interaction was characterized in conjunction with the bulk flow velocity and the electric field strength. Secondly, the enhancement of convective heat transfer rate was recognized, especially under low Reynolds number, and its mechanism was clarified. On the basis of these results, the heat transfer performance was shown in connection with the amount of electric power and pumping power.

A WALL PLUME FED BY THE DISCHARGE OF A VERTICAL CHANNEL

Abstract A finite-difference marching scheme was employed to obtain numerical solutions for a wall plume spawned by the discharge from a vertical, natural convection channel flow. The plume is bounded by an isothermal vertical wall that is the continuation of one of the walls of the channel. The wall-plume solutions were carried out for a range of dimensionless heights of the channel and for a Prandtl number of 0.7. Since the channel height controls the velocity and temperature profiles at the channel exit, it also plays a key role in the development of the wall plume because these profiles serve to initiate the plume. Just downstream of the channel exit, the newly exposed flank of the plume interacts with and is cooled by the ambient fluid, while the wall-adjacent portion of the plume retains its channel heritage. Subsequently, the ambient fluid penetrates deeply into the plume, effectively obliterating its channel origins. Thereafter, the plume approaches a natural convection vertical-plate boundary lay...

Wall conductance effects on convective horizontal channel flow

An exact solution has been found for the fully developed combined free and forced convection flow of electrically conducting fluids between two horizontal conducting walls under a transverse magnetic field. It is found that with the increase of the wall conductance the velocity decreases while the current density and the temperature increase. There is an incipient reversed flow for a critical Grashof number which is positive for the upper wall and negative for the lower wall. The magnitude of the critical Grashof number decreases with the increase of the wall conductance.

Combined forced and free convection MHD channel flow in entrance region

The entrance problem of convective magnetohydrodynamic channel flow between two parallel plates subjected simultaneously to an axial temperature gradient and a pressure gradient is investigated numerically. Both constant heat flux and constant wall temperature cases are considered. The solutions match to the fully developed solutions after a certain entrance length. It is found that an applied transverse magnetic field may reduce the entrance length of the velocity considerably, but has little effect on the temperature development. At high Hartmann number, the velocity entrance length is inversely proportion to M 2 as it was predicted by Shercliff in the absence of free convection. However, a sufficient large free convection may prolong the developing process considerably.

Dissipative effect on convective MHD channel flow

By means of a numerical analysis viscous and Joulean dissipations are considered in a combined forced and free convective MHD flow between two vertical plates that are subjected simultaneously to a pressure and a temperature gradient. It is shown that the dissipations tend to increase the flow rate and decrease the heat transfer, and they destabilize the system when the high temperature is at the lower side.

Effect of wall conductances on convective magnetohydrodynamic channel flow

The problem of convective magnetohydrodynamic channel flow in a vertical channel subjected simultaneously to an axial temperature gradient and a pressure gradient is examined when the thermal and the electrical conductance of the channel walls are arbitrary. The effects of wall conductances on the flow rate and heat transfer are found and discussed. When the vertical temperature gradient is negative, which is the case of heating from below, there exists a critical Rayleigh number at which the fluid becomes unstable. The critical Rayleigh number is also found as a function of the wall conductances.

Combined forced and free convection channel flows in magnetohydrodynamics

characteristic turbulence scale L If the scale I > (CDA)', then the energy builds up in a few scale lengths and then decays rather rapidly. If, however, I 1 is, in every case, proportional to £~. These results are not inconsistent with the currently accepted ideas about turbulent energy decay. The persistence of the large eddies is rather clearly brought out; whereas, at the same time, the small eddies show a tendency to hold on to their energy, as predicted by the Kolmogoroff hypothesis. The implications of the results for the calculation of the radar cross section of turbulent plasmas is the following: if we accept the hypothesis that