6 research outputs found
NUMERICAL INVESTIGATION OF THE SOLAR CHIMNEY PERFORMANCE WITH THE INTERMEDIATE ABSORBING WALL
The design of air conditioning systems is one of the effective factors in optimizing energy consumption in residential and commercial buildings. In this study, the performance of a solar chimney with different solar thermal flux on it and the use of an absorbent wall in the chimney have been investigated. Increasing the air temperature adjacent to the absorbing wall has the effect of thermosyphon in the chimney that ultimately leads to continuous air movement inside the chimney. In most of the proposed designs for these chimneys, the absorbing wall is one of the sidewalls. With sunlight warming up the wall, the air flows into the chimney. By heating the absorbing wall and increasing the temperature gradient, some heat in this wall will be lost through the conduction phenomenon in the wall thickness to the outside or inside the building. In the proposed scheme, the absorbing wall is located in the middle of the chimney and since the optimum width for the chimney is between 0.2m and 0.3m, in the proposed scheme, the distance between each wall and the intermediate absorbing wall is equal to 0.25m. In order to simulate the flow field, the equations of mass, momentum, and energy conservation are solved in the two-dimensional form with constant, incompressible, and turbulent flow assumptions simultaneously. To solve the equations, an academic code based on Fortran's language and SIMPLE algorithm is used. Due to the nature of the turbulent flow of air within the solution field, the turbulent model is used because of the good performance of this model in simulating boundary layer flows with high reciprocating gradients. The
intensity and concentration of heat transfer and geometric parameters related
to the solar chimney, such as the entrance area, the thickness and length of the absorbing wall, and the location of the absorbing wall in the amount of discharged air flow have been investigated and the optimal values for maximum air discharge have been extracted. Moreover the absorbent wall partitioning is presented as a novel solution to increase the thermosyphon phenomenon in the solar chimney
Natural convective heat transfer of magnetite/graphite slurry under a magnetic field
This paper presents a numerical analysis of the natural convective heat transfer of magnetite/graphite slurry non-Newtonian ferrofluid in a square enclosure under a variable external magnetic field. A heat source with variable temperature distribution is located at the bottom of the enclosure. The left and right walls of the enclosure are at a relatively low temperature. The top wall and part of the bottom wall are thermally insulated. Experimental results are used to obtain the non-Newtonian behavior of graphite slurry and to obtain the properties of its temperature function. The governing equations take into account the effects of ferrohydrodynamics, magnetohydrodynamics, and non-Newtonian fluid behavior. The effects of the Rayleigh number, magnetic number, and Hartmann number on the heat transfer and fluid flow are studied. The results show that, at low Rayleigh numbers, the increase in the Hartmann number does not have any effect on the heat transfer. At high Rayleigh numbers, the heat transfer decreases as the Hartmann number increases. This decrease becomes less significant at higher Rayleigh numbers. The results also show that the strength of the applied magnetic field (the Kelvin force) should reach a certain value (Mn∗f≥104) so that it can affect the heat transfer