A numerical study based on the finite volume method has been performed to study the three-dimension natural convection in a parallelogrammic top side opened cavity filled nanofluid with partially heated square at the ...A numerical study based on the finite volume method has been performed to study the three-dimension natural convection in a parallelogrammic top side opened cavity filled nanofluid with partially heated square at the bottom side.Results are obtained for different governing parameters such as nanoparticle concentration (φ) from 0 to 0.05,inclination angle of the back and front walls (α) from 5° to 75°,Rayleigh number from 10^3 to 10^5,and length of heater changer from 0.1 to 1.The main finding from the obtained result showed that the inclination angle and nanoparticle volume fraction affect the flow structure and enhance the heat transfer.展开更多
This study presents a contribution to the development of a model for vegetable oil droplets vaporization, with a particular focus on the influence of the experimental set-up for their use as fuel in diesel engines. Tw...This study presents a contribution to the development of a model for vegetable oil droplets vaporization, with a particular focus on the influence of the experimental set-up for their use as fuel in diesel engines. Two systems were considered: an open-environment system obtained through a hot gas flow, and a closed-environment system. Vaporization was conducted under identical conditions, with the results subsequently compared. The findings indicate that, for temperatures between 473 K and 673 K, droplets behaviour in both systems presents only a heating and expansion phase. For temperatures above 673 K, the behaviour of the droplets differs between the devices. In the open environment device, a linear reduction in droplets diameter is observed following the transient phase, suggesting stationary vaporization and enabling the calculation of a vaporization constant and the well-known D2 law is respected. In the closed-environment device, puffing, micro-explosions and gas ejections are observed, and it is not possible to determine vaporization constant and D2 law is not respected. The results demonstrate the necessity of developing a model for the thermal decomposition of vegetable oil before attempting to create a model for the vaporization of these oils. In order to achieve this, it is essential to construct an experimental setup that more closely emulates the real conditions within the combustion chamber of a diesel engine, taking into account the variables of pressure, temperature and the heating process.展开更多
In this study,mixed convection heat transfer and fluid flow is numerically investigated in an open system enclosure containing a heated obstacle.Effects of the positions of both obstacles and fluid flow outlet on the ...In this study,mixed convection heat transfer and fluid flow is numerically investigated in an open system enclosure containing a heated obstacle.Effects of the positions of both obstacles and fluid flow outlet on the flow field and heat transfer within the enclosure were studied.Richardson number ranging from 0.1 to 10 was examined for a constant Grashof number at different Reynolds numbers in both base fluid and fluid mixed with Cu nanoparticles(0 to 4%of volume fractions).It is found that the obstacle and outlet position as well as the Richardson number greatly affect the flow field and heat transfer rate.The maximum heat transfer rate occurs for Richardson number 0.1,when the outlet and obstacle position are located at the bottom of the right side of the enclosure(P3)and near right side of the enclosure(8 H),respectively.Also,the heat transfer rate is higher when the obstacle is placed close to the inlet(2 H)and outlet(8 H)compared to the center of the enclosure(5 H).It is shown that although the change of volume fraction of nanofluid does not have significant effect on the flow pattern,however,it enhances the heat transfer rate through improving the effective thermo-physical properties of the base fluid.展开更多
文摘A numerical study based on the finite volume method has been performed to study the three-dimension natural convection in a parallelogrammic top side opened cavity filled nanofluid with partially heated square at the bottom side.Results are obtained for different governing parameters such as nanoparticle concentration (φ) from 0 to 0.05,inclination angle of the back and front walls (α) from 5° to 75°,Rayleigh number from 10^3 to 10^5,and length of heater changer from 0.1 to 1.The main finding from the obtained result showed that the inclination angle and nanoparticle volume fraction affect the flow structure and enhance the heat transfer.
文摘This study presents a contribution to the development of a model for vegetable oil droplets vaporization, with a particular focus on the influence of the experimental set-up for their use as fuel in diesel engines. Two systems were considered: an open-environment system obtained through a hot gas flow, and a closed-environment system. Vaporization was conducted under identical conditions, with the results subsequently compared. The findings indicate that, for temperatures between 473 K and 673 K, droplets behaviour in both systems presents only a heating and expansion phase. For temperatures above 673 K, the behaviour of the droplets differs between the devices. In the open environment device, a linear reduction in droplets diameter is observed following the transient phase, suggesting stationary vaporization and enabling the calculation of a vaporization constant and the well-known D2 law is respected. In the closed-environment device, puffing, micro-explosions and gas ejections are observed, and it is not possible to determine vaporization constant and D2 law is not respected. The results demonstrate the necessity of developing a model for the thermal decomposition of vegetable oil before attempting to create a model for the vaporization of these oils. In order to achieve this, it is essential to construct an experimental setup that more closely emulates the real conditions within the combustion chamber of a diesel engine, taking into account the variables of pressure, temperature and the heating process.
文摘In this study,mixed convection heat transfer and fluid flow is numerically investigated in an open system enclosure containing a heated obstacle.Effects of the positions of both obstacles and fluid flow outlet on the flow field and heat transfer within the enclosure were studied.Richardson number ranging from 0.1 to 10 was examined for a constant Grashof number at different Reynolds numbers in both base fluid and fluid mixed with Cu nanoparticles(0 to 4%of volume fractions).It is found that the obstacle and outlet position as well as the Richardson number greatly affect the flow field and heat transfer rate.The maximum heat transfer rate occurs for Richardson number 0.1,when the outlet and obstacle position are located at the bottom of the right side of the enclosure(P3)and near right side of the enclosure(8 H),respectively.Also,the heat transfer rate is higher when the obstacle is placed close to the inlet(2 H)and outlet(8 H)compared to the center of the enclosure(5 H).It is shown that although the change of volume fraction of nanofluid does not have significant effect on the flow pattern,however,it enhances the heat transfer rate through improving the effective thermo-physical properties of the base fluid.
