Mixed convection of heat and mass transfer in an isosceles trapezoidal cavity has been studied numerically. Constant heat flux is imposed through four outlets and the grid is insulated. The inclined walls are maintain...Mixed convection of heat and mass transfer in an isosceles trapezoidal cavity has been studied numerically. Constant heat flux is imposed through four outlets and the grid is insulated. The inclined walls are maintained in natural convection while the lower horizontal wall is adiabatic. These conditions reflect the air draft zone of the ASUTO charcoal stove. The governing two-di- mensional flow equations have been solved by using the finite difference method and Thomas’s algorithm. The investigations are conducted for different values of Richardson (R<sub>i</sub>), Reynolds number (R<sub>e</sub>) and inclination angles of sidewalls. The results are presented in terms of streamlines, isotherms, moisture contours. It was found that for Reynolds number (R<sub>e</sub>) equal to 100, the flow pattern is strongly dependent on the inclination angle and Richardson number. Thus, for high Richardson number (R<sub>i</sub>) values (10, 100), the dominance of natural convection over the flow structure decreases with the decreasing of the inclination angle of sidewalls of the cavity. For R<sub>i</sub> = 1, an optimum air draft corresponds to an inclination angle in the vicinity of 22° while for R<sub>i</sub> = 10 or 100 (in dominance of natural convection), the optimum inclination angle for air draft is in the vicinity of 15°.展开更多
This paper describes various aspects of the design methodology and heat transfer calculations for an elevated linear absorber. The absorber is a part of the linear Fresnel reflector solar concentrator system, in which...This paper describes various aspects of the design methodology and heat transfer calculations for an elevated linear absorber. The absorber is a part of the linear Fresnel reflector solar concentrator system, in which hot fluid is generated. The design of the absorber is an inverted trapezoidal air cavity with a glass cover enclosing a multi tube absorber. In a trapezoidal cavity absorber, a set of linear multi tube absorber with plate(named as "plane surface") and without plate(named as "tube surface") underneath are considered. An analytical simulation is done for different gaps between the tubes and for different depths of the cavity. A better design of the absorber is found out to maximize the heat transfer rate supplied to the absorber tube fluid. Also, the experimentally obtained overall heat loss coefficients are compared with the analytical values for the considered arrangements of absorber set up and results are discussed in details.展开更多
We investigate heat and mass transfer in an isosceles trapezoidal cavity, filled with charcoal considered as a granular porous medium. The Darcy-Brinkman-Forchheimer flow model is coupled to the energy and mass equati...We investigate heat and mass transfer in an isosceles trapezoidal cavity, filled with charcoal considered as a granular porous medium. The Darcy-Brinkman-Forchheimer flow model is coupled to the energy and mass equations with the assumption of non-thermal equilibrium. These equations are discretized by the finite volume method with an offset mesh and then solved by the line-by-line method of Thomas. The coupling between pressure and velocity is obtained by Semi-Implicit Method for Pressure Linked Equations. (SIMPLE) algorithm. The results show that the temperature in the cavity increases when the inclination angle of the sides walls decreases. The 15° inclination is selected as being able to offer better thermal performance in the cookstove combustion chamber.展开更多
文摘Mixed convection of heat and mass transfer in an isosceles trapezoidal cavity has been studied numerically. Constant heat flux is imposed through four outlets and the grid is insulated. The inclined walls are maintained in natural convection while the lower horizontal wall is adiabatic. These conditions reflect the air draft zone of the ASUTO charcoal stove. The governing two-di- mensional flow equations have been solved by using the finite difference method and Thomas’s algorithm. The investigations are conducted for different values of Richardson (R<sub>i</sub>), Reynolds number (R<sub>e</sub>) and inclination angles of sidewalls. The results are presented in terms of streamlines, isotherms, moisture contours. It was found that for Reynolds number (R<sub>e</sub>) equal to 100, the flow pattern is strongly dependent on the inclination angle and Richardson number. Thus, for high Richardson number (R<sub>i</sub>) values (10, 100), the dominance of natural convection over the flow structure decreases with the decreasing of the inclination angle of sidewalls of the cavity. For R<sub>i</sub> = 1, an optimum air draft corresponds to an inclination angle in the vicinity of 22° while for R<sub>i</sub> = 10 or 100 (in dominance of natural convection), the optimum inclination angle for air draft is in the vicinity of 15°.
文摘This paper describes various aspects of the design methodology and heat transfer calculations for an elevated linear absorber. The absorber is a part of the linear Fresnel reflector solar concentrator system, in which hot fluid is generated. The design of the absorber is an inverted trapezoidal air cavity with a glass cover enclosing a multi tube absorber. In a trapezoidal cavity absorber, a set of linear multi tube absorber with plate(named as "plane surface") and without plate(named as "tube surface") underneath are considered. An analytical simulation is done for different gaps between the tubes and for different depths of the cavity. A better design of the absorber is found out to maximize the heat transfer rate supplied to the absorber tube fluid. Also, the experimentally obtained overall heat loss coefficients are compared with the analytical values for the considered arrangements of absorber set up and results are discussed in details.
文摘We investigate heat and mass transfer in an isosceles trapezoidal cavity, filled with charcoal considered as a granular porous medium. The Darcy-Brinkman-Forchheimer flow model is coupled to the energy and mass equations with the assumption of non-thermal equilibrium. These equations are discretized by the finite volume method with an offset mesh and then solved by the line-by-line method of Thomas. The coupling between pressure and velocity is obtained by Semi-Implicit Method for Pressure Linked Equations. (SIMPLE) algorithm. The results show that the temperature in the cavity increases when the inclination angle of the sides walls decreases. The 15° inclination is selected as being able to offer better thermal performance in the cookstove combustion chamber.
