Experiments and simulations on flow and heat transfer behavior of Therminol-55 liquid phase heat transfer fluid have been conducted in a ribbed tube with the outer diameter and inner diameter 25.0 and 20.0 mm,pitch an...Experiments and simulations on flow and heat transfer behavior of Therminol-55 liquid phase heat transfer fluid have been conducted in a ribbed tube with the outer diameter and inner diameter 25.0 and 20.0 mm,pitch and rib height of 4.5 and 1.0 mm.respectively.Experimental results show that the heat transfer and thermal performance of Therminol-55 liquid phase heat transfer fluid in the ribbed tube are considerably improved compared to those of the smooth tube.The Nusselt number increase with the increase of Reynolds number.The increase in heat transfer rate of the ribbed tube has a mean value of 2.24 times.Also,the pressure drop results reveal that the average friction factor of the ribbed tube is in a range of 2.4 and 2.8 times over the smooth tube.Numerical simulations of three-dimensional flow behavior of Therminol-55 liquid phase heat transfer fluid are carried out using three different turbulence models in the ribbed tube.The numerical results show that the heat transfer of ribbed tube is improved because vortices are generated behind ribs,which produce some disruptions to fluid flow and enhance heat transfer compared with smooth tube.The numerical results prove that the ribbed tube can improve heat transfer and fluid flow performances of Therminol liquid phase heat transfer fluid.展开更多
Magnetorheological （MR） fluid is a type of a smart material that can control its mechanical properties under a magnetic field. Iron particles in MR fluid form chain structures in the direction of an applied magnetic...Magnetorheological （MR） fluid is a type of a smart material that can control its mechanical properties under a magnetic field. Iron particles in MR fluid form chain structures in the direction of an applied magnetic field, which is known as MR effect, resulting in variation of stiffness, shear modulus, damping and tribological characteristics of MR fluid. As MR effect depends on the density of particles in the fluid or the strength of a magnetic field, the experiments are conducted to evaluate the friction property under reciprocating motion by changing the types of MR fluid and the strength of a magnetic field. The material of aluminum, brass, and steel are chosen for specimen as they are the most common material in mechanical applications. The surfaces of specimen are also observed by optical microscope before and after experiments to compare the surfaces with test conditions. The comparing results show that the friction coefficient increases as the strength of a magnetic field increases in regardless of types of MR fluid or the material. Also the density of particle in MR fluid affects the friction characteristic. The results from this research can be used to improve the performance of mechanical applications using MR fluid.展开更多
A Jeffery-Hamel （J-H） flow model of the non-Newtonian fluid type inside a convergent wedge （inclined walls） with a wall friction is derived by a nonlinear ordinary differential equation with appropriate boundary c...A Jeffery-Hamel （J-H） flow model of the non-Newtonian fluid type inside a convergent wedge （inclined walls） with a wall friction is derived by a nonlinear ordinary differential equation with appropriate boundary conditions based on similarity relationships. Unlike the usual power law model, this paper develops nonlinear viscosity based only on a tangential coordinate function due to the radial geometry shape. Two kinds of solutions are developed, i.e., analytical and semi-analytical （numerical） solutions with suitable assumptions. As a result of the parametric examination, it has been found that the Newtonian normalized velocity gradually decreases with the tangential direction progress. Also, an increase in the friction coefficient leads to a decrease in the normalized Newtonian velocity profile values. However, an increase in the Reynolds number causes an increase in the normalized velocity function values. Additionally, for the small values of wedge semi-angle, the present solutions are in good agreement with the previous results in the literature.展开更多
The steady laminar mixed convection boundary layer flow and heat transfer of a micropolar fluid near the stagnation point on a stretched vertical surface with prescribed skin friction were considered.The governing par...The steady laminar mixed convection boundary layer flow and heat transfer of a micropolar fluid near the stagnation point on a stretched vertical surface with prescribed skin friction were considered.The governing partial differential equations were transformed into a system of ordinary differential equations,which were then solved numerically using the shooting method.Results for the stretching velocity,the local Nusselt number,the temperature,and the velocity profiles are presented for various values of the mixed convection parameter λ and material parameter K when the Prandtl number is equal to 1.Both assisting（heated plate） and opposing（cooled plate） flow regions are considered.It is found that dual solutions exist for both assisting and opposing flows.展开更多
采用粉末冶金模压烧结制备了Ti-15Mo/HA生物复合材料,研究了羟基磷灰石(HA)对复合材料的微观结构、显微硬度及摩擦磨损性能的影响。结果表明,随着HA含量的增加,Ti-15Mo/HA复合材料中的α-Ti增加、β-Ti减少,同时有多种陶瓷相(CaTiO_(3)...采用粉末冶金模压烧结制备了Ti-15Mo/HA生物复合材料,研究了羟基磷灰石(HA)对复合材料的微观结构、显微硬度及摩擦磨损性能的影响。结果表明,随着HA含量的增加,Ti-15Mo/HA复合材料中的α-Ti增加、β-Ti减少,同时有多种陶瓷相(CaTiO_(3)、Ca_(3)(PO_(4))_(2)、CaO等)生成。加入HA生成的多种硬质陶瓷相使得Ti-15Mo/HA复合材料的维氏硬度提高。由于Mo在Ti中的固溶强化和陶瓷相的弥散强化,以及液体的润滑作用,Ti-15Mo/HA复合材料在模拟体液(simulated body fluid,SBF)环境下的摩擦因数和磨损率较低。Ti-15Mo/5HA比其他复合材料具有更好的耐磨性能,其平均摩擦因数为0.42,磨损率约为2.51×10^(-4)mm^(3)/(N·m)。Ti-15Mo合金是黏着磨损和磨粒磨损共同作用,而Ti-15Mo/HA复合材料以磨粒磨损为主,黏着磨损为辅。粉末冶金制备的Ti-15Mo/5HA复合材料显示了良好的耐磨性能,在硬组织替代和修复材料领域具有潜在的应用前景。展开更多
基金Supported by the National Natural Science Foundation of China(11472093 and21276056)
文摘Experiments and simulations on flow and heat transfer behavior of Therminol-55 liquid phase heat transfer fluid have been conducted in a ribbed tube with the outer diameter and inner diameter 25.0 and 20.0 mm,pitch and rib height of 4.5 and 1.0 mm.respectively.Experimental results show that the heat transfer and thermal performance of Therminol-55 liquid phase heat transfer fluid in the ribbed tube are considerably improved compared to those of the smooth tube.The Nusselt number increase with the increase of Reynolds number.The increase in heat transfer rate of the ribbed tube has a mean value of 2.24 times.Also,the pressure drop results reveal that the average friction factor of the ribbed tube is in a range of 2.4 and 2.8 times over the smooth tube.Numerical simulations of three-dimensional flow behavior of Therminol-55 liquid phase heat transfer fluid are carried out using three different turbulence models in the ribbed tube.The numerical results show that the heat transfer of ribbed tube is improved because vortices are generated behind ribs,which produce some disruptions to fluid flow and enhance heat transfer compared with smooth tube.The numerical results prove that the ribbed tube can improve heat transfer and fluid flow performances of Therminol liquid phase heat transfer fluid.
基金Supported by Basic Science Research Program of National Research Foundation of Korea,Ministry of Education,Science and Technology of the Korean(Grant No.NRF-2015R1D1A1A09060901)Ministry of Science,ICT and Future Planning,Korea,under Convergence Information Technology Research Center(Grant No.IITP-2015-H8601-15-1003) supervised by Institute for Information&Communications Technology PromotionAdvanced Technology Center R&D Program funded by the Ministry of Trade,Industry&Energy of Korea(Grant No.10048876)
文摘Magnetorheological （MR） fluid is a type of a smart material that can control its mechanical properties under a magnetic field. Iron particles in MR fluid form chain structures in the direction of an applied magnetic field, which is known as MR effect, resulting in variation of stiffness, shear modulus, damping and tribological characteristics of MR fluid. As MR effect depends on the density of particles in the fluid or the strength of a magnetic field, the experiments are conducted to evaluate the friction property under reciprocating motion by changing the types of MR fluid and the strength of a magnetic field. The material of aluminum, brass, and steel are chosen for specimen as they are the most common material in mechanical applications. The surfaces of specimen are also observed by optical microscope before and after experiments to compare the surfaces with test conditions. The comparing results show that the friction coefficient increases as the strength of a magnetic field increases in regardless of types of MR fluid or the material. Also the density of particle in MR fluid affects the friction characteristic. The results from this research can be used to improve the performance of mechanical applications using MR fluid.
文摘A Jeffery-Hamel （J-H） flow model of the non-Newtonian fluid type inside a convergent wedge （inclined walls） with a wall friction is derived by a nonlinear ordinary differential equation with appropriate boundary conditions based on similarity relationships. Unlike the usual power law model, this paper develops nonlinear viscosity based only on a tangential coordinate function due to the radial geometry shape. Two kinds of solutions are developed, i.e., analytical and semi-analytical （numerical） solutions with suitable assumptions. As a result of the parametric examination, it has been found that the Newtonian normalized velocity gradually decreases with the tangential direction progress. Also, an increase in the friction coefficient leads to a decrease in the normalized Newtonian velocity profile values. However, an increase in the Reynolds number causes an increase in the normalized velocity function values. Additionally, for the small values of wedge semi-angle, the present solutions are in good agreement with the previous results in the literature.
基金the financial supports received in the form of fundamental research grant scheme (FRGS)the financial supports received in the form of research university grant (GUP)
文摘The steady laminar mixed convection boundary layer flow and heat transfer of a micropolar fluid near the stagnation point on a stretched vertical surface with prescribed skin friction were considered.The governing partial differential equations were transformed into a system of ordinary differential equations,which were then solved numerically using the shooting method.Results for the stretching velocity,the local Nusselt number,the temperature,and the velocity profiles are presented for various values of the mixed convection parameter λ and material parameter K when the Prandtl number is equal to 1.Both assisting（heated plate） and opposing（cooled plate） flow regions are considered.It is found that dual solutions exist for both assisting and opposing flows.
文摘采用粉末冶金模压烧结制备了Ti-15Mo/HA生物复合材料,研究了羟基磷灰石(HA)对复合材料的微观结构、显微硬度及摩擦磨损性能的影响。结果表明,随着HA含量的增加,Ti-15Mo/HA复合材料中的α-Ti增加、β-Ti减少,同时有多种陶瓷相(CaTiO_(3)、Ca_(3)(PO_(4))_(2)、CaO等)生成。加入HA生成的多种硬质陶瓷相使得Ti-15Mo/HA复合材料的维氏硬度提高。由于Mo在Ti中的固溶强化和陶瓷相的弥散强化,以及液体的润滑作用,Ti-15Mo/HA复合材料在模拟体液(simulated body fluid,SBF)环境下的摩擦因数和磨损率较低。Ti-15Mo/5HA比其他复合材料具有更好的耐磨性能,其平均摩擦因数为0.42,磨损率约为2.51×10^(-4)mm^(3)/(N·m)。Ti-15Mo合金是黏着磨损和磨粒磨损共同作用,而Ti-15Mo/HA复合材料以磨粒磨损为主,黏着磨损为辅。粉末冶金制备的Ti-15Mo/5HA复合材料显示了良好的耐磨性能,在硬组织替代和修复材料领域具有潜在的应用前景。
