The effect of double-diffuse convectionadmin / April 2, 2019
The effect of double-diffuse convection, a combination of heat and mass transfer, could destroy the stability of a system’s flow. Nearly laminated, the non-convective zone acts as a mass and thermal insulator for the lower convective zone. The non- convective zone needs precautions to prevent convection and sustain stability. Currents could be caused by the movement of the laminated layers disturbing the pond, hence reducing the storage sufficiency of the pond. The addition of porous media in the lower convective zone of the laminated solar pond limits the instability of the pond. Salinity Gradient Solar Ponds are containers with specific amounts of salinity concentrations that increases with deepness. It starts with a low value of salinity at the UCZ and then to a value near saturation at the LCZ. In order to avoid natural convection to some extent, the concentration gradient of the NCZ should be great enough. As soon as a critical temperature (depending on the parameters of the pond) is reached, convection starts occurring. This phenomenon ascends with time and it then leads to the distortion of the interface between the LCZ and NCZ, hence affecting the storage process adversely. The stability of the gradient zone plays an important role in the productivity of energy collection. The reduction of the thickness of the NCZ is caused by the despoliation of the boundaries of the UCZ and LCZ leading to the pond’s destruction. The despoliations in the UCZ are caused mainly by convection and wind and by the perpendicular difference in temperature when the pond’s floor is intensely heated from isolation in the LCZ. It might be possible that the rate of erosion of the velocity in the NCZ be suppressed by managing the difference in temperature in the LCZ to a smaller value. This could be done by the absorption of the reserved heat in the storage zone (LCZ). Porous medium could be introduced in the LCZ to slow down the vortices created in the LCZ. The advantages of the porous medium are: it does not affect the structure of the interface of the upper layer, causes a reduction in temperature increase in the LCZ, reduces instability by reducing the difference in temperature in the solar pond, and causes an increase in the stability of the NCZ, hence increasing the pond’s stability. Galvanized steel was used as a material for the fabrication of the solar pond and polystyrene foam was used for insulation.