Two theoretical criteria represented by Katgerman, and Clyne and Davies for prognosticating hot tearing sensitivity were compared. Both unrefined and grain-refined samples of Al2024 alloy were solidified at various co...Two theoretical criteria represented by Katgerman, and Clyne and Davies for prognosticating hot tearing sensitivity were compared. Both unrefined and grain-refined samples of Al2024 alloy were solidified at various cooling rates ranging from 0.4 to 17.5 °C/s. Thermal analysis was used to detect dendrite coherency point and temperature of eutectic reaction. Curves of solid and liquid fractions were plotted based on Newtonian method to determine hot tearing susceptible areas. The experimental results show that the most susceptible zone in which hot tearing can occur in Al2024 is where Al_2CuMg intermetallic compound forms as a eutectic phase at last stage of mushy-state interval. Also, both criteria are in a good agreement with each other at high cooling rates used in direct-chill casting process while Clyne and Davies＇ model is more acceptable to determine hot tearing tendency from low to medium cooling rates.展开更多
Phase change materials are one of the potential resources to replace fossil fuels in regards of supplying the energy of buildings.Basically,these materials absorb or release heat energy with the help of their latent h...Phase change materials are one of the potential resources to replace fossil fuels in regards of supplying the energy of buildings.Basically,these materials absorb or release heat energy with the help of their latent heat.Phase change materials have low thermal conductivity and this makes it possible to use the physical properties of these materials in the tropical regions where the solar radiation is more direct and concentrated over a smaller area.In this theoretical work,an attempt has been made to study the melting process of these materials by applying constant heat flux and temperature.It was found that by increasing the thickness of phase change materials’layers,due to the melting,more thermal energy is stored.Simultaneously it reduces the penetration of excessive heat into the chamber,so that by increasing the thickness of paraffin materials up to 20 mm,the rate of temperature reduction reaches more than 18%.It was also recognized that increasing the values of constant input heat flux increases buoyancy effects.Increasing the Stefan number from 0.1 to 0.3,increases the temperature by 6%.展开更多
In this study the injective micropolar flow in a porous channel is investigated.The flow is driven by suction or injection on the channel walls,and the micropolar model is used to describe the working fluid.This probl...In this study the injective micropolar flow in a porous channel is investigated.The flow is driven by suction or injection on the channel walls,and the micropolar model is used to describe the working fluid.This problem is mapped into the system of nonlinear coupled differential equations by using Berman's similarity transformation.These are solved for large mass transfer via Adomian decomposition method(ADM).Also the numerical method is used for the validity of this analytical method and excellent agreement is observed between the solutions obtained from ADM and numerical results.Trusting this validity,effects of some other parameters are discussed.It can be seen that increasing in the value of N_(1) have different results in comparison with N_(2).展开更多
In this paper,the errata for a published paper,titled“Application of Adomian decomposition method for micropolar flow in a porous channel,authored by F.Shakeri Aski,Seyed Jalal Nasirkhani,E.Mohammadian,A.Asgari,in th...In this paper,the errata for a published paper,titled“Application of Adomian decomposition method for micropolar flow in a porous channel,authored by F.Shakeri Aski,Seyed Jalal Nasirkhani,E.Mohammadian,A.Asgari,in the journal of Propulsion and Power Research 3(1)(2014)15-21”,were presented.Since micropolar flow in a porous channel attracts considerable research interest,it is necessary to correct the minor typo errors in the boundary conditions of the medium.This should be said that the typo errors have not affected the results because the correct boundary conditions have been applied in the written maple code.There is just a typo error in the written boundary conditions in the paper.展开更多
文摘Two theoretical criteria represented by Katgerman, and Clyne and Davies for prognosticating hot tearing sensitivity were compared. Both unrefined and grain-refined samples of Al2024 alloy were solidified at various cooling rates ranging from 0.4 to 17.5 °C/s. Thermal analysis was used to detect dendrite coherency point and temperature of eutectic reaction. Curves of solid and liquid fractions were plotted based on Newtonian method to determine hot tearing susceptible areas. The experimental results show that the most susceptible zone in which hot tearing can occur in Al2024 is where Al_2CuMg intermetallic compound forms as a eutectic phase at last stage of mushy-state interval. Also, both criteria are in a good agreement with each other at high cooling rates used in direct-chill casting process while Clyne and Davies＇ model is more acceptable to determine hot tearing tendency from low to medium cooling rates.
文摘Phase change materials are one of the potential resources to replace fossil fuels in regards of supplying the energy of buildings.Basically,these materials absorb or release heat energy with the help of their latent heat.Phase change materials have low thermal conductivity and this makes it possible to use the physical properties of these materials in the tropical regions where the solar radiation is more direct and concentrated over a smaller area.In this theoretical work,an attempt has been made to study the melting process of these materials by applying constant heat flux and temperature.It was found that by increasing the thickness of phase change materials’layers,due to the melting,more thermal energy is stored.Simultaneously it reduces the penetration of excessive heat into the chamber,so that by increasing the thickness of paraffin materials up to 20 mm,the rate of temperature reduction reaches more than 18%.It was also recognized that increasing the values of constant input heat flux increases buoyancy effects.Increasing the Stefan number from 0.1 to 0.3,increases the temperature by 6%.
文摘In this study the injective micropolar flow in a porous channel is investigated.The flow is driven by suction or injection on the channel walls,and the micropolar model is used to describe the working fluid.This problem is mapped into the system of nonlinear coupled differential equations by using Berman's similarity transformation.These are solved for large mass transfer via Adomian decomposition method(ADM).Also the numerical method is used for the validity of this analytical method and excellent agreement is observed between the solutions obtained from ADM and numerical results.Trusting this validity,effects of some other parameters are discussed.It can be seen that increasing in the value of N_(1) have different results in comparison with N_(2).
文摘In this paper,the errata for a published paper,titled“Application of Adomian decomposition method for micropolar flow in a porous channel,authored by F.Shakeri Aski,Seyed Jalal Nasirkhani,E.Mohammadian,A.Asgari,in the journal of Propulsion and Power Research 3(1)(2014)15-21”,were presented.Since micropolar flow in a porous channel attracts considerable research interest,it is necessary to correct the minor typo errors in the boundary conditions of the medium.This should be said that the typo errors have not affected the results because the correct boundary conditions have been applied in the written maple code.There is just a typo error in the written boundary conditions in the paper.
