Thermoconvective flow velocity in a high-speed magnetofluid seal after it has stopped

Convective flow is investigated in the high-speed (linear velocity of the shaft seal is more than 1 m/s) magnetofluid shaft seal after it has been stopped. Magnetic fluid is preliminarily heated due to viscous friction in the moving seal. After the shaft has been stopped, nonuniform heated fluid remains under the action of a high-gradient magnetic field. Numerical analysis has revealed that in this situation, intense thermomagnetic convection is initiated. The velocity of magnetic fluid depends on its viscosity. For the fluid with viscosity of 2 × 10 -4 m 2/s the maximum flow velocity within the volume of magnetic fluid with a characteristic size of 1 mm can attain a value of 10 m/s

Influence of the meridional flow and thermomagnetic convection on characteristics of magnetic fluid seal

For the low-speed magnetic fluid seals, the influence of the meridional flow, induced by the shaft rotation, on the distribution of magnetic particles concentration, is studied. Influence of the thermomagnetic convection on the structure of this flow and on the temperature distribution in high-speed magnetic fluid seals is investigated also. The problems were examined by numerical methods. It is discovered that even very slow rotation of the shaft homogenises distribution of the magnetic particles concentration in the seal and thereby enlarges its operation life. For high-speed seals thermomagnetic convection provides the penetration of the fluid flow in the region of the narrow gap and levels off the temperature distribution decreasing its maximum value and thereby enlarges its operation life too. It is found also that the influence of thermomagnetic convection grows with the viscosity increasing

Effect of diffusion of magnetic particles on the parameters of the magnetic fluid seal: A numerical simulation

In the paper, a motion of magnetic nanoparticles in a high gradient magnetic field and its correlation with the characteristics of the magnetic fluid seal are numerically studied. The neutral curve defining a range of parameters, where the liquid keeps fluidity, is found. It is shown that the concentration of particles during the initial time period grows linearly and then the exponent decreases to 0.5 with time. It is found that at a high enough value of magnetic field the area of close-packed particles is formed under the pole tip. Numerical simulation has shown that with some values of the parameters it is possible to decrease the magnetic particles' concentration essentially so that the basic fluid leaks out from the seal under gravity, i.e. the magnetic fluid seal fails. It has appeared that the characteristic time of the described processes depends on the properties of magnetic fluid and on the magnetic field value and has an order from several hours to several years

Thermomagnetic convection in a cylindrical enclosure. Part 1: Zero gravity

The effects of a uniform external magnetic field on the thermomagnetic convection of magnetic fluid in a cylindrical enclosure are numerically studied. It was found that uniform magnetic field can be cause the convection in the non-uniformly heated magnetic fluid in a cylindrical enclosure even in the case of zero gravity. There are two threshold values of fluid magnetization and temperature gradient. Above the first threshold the convective flow is realized as circular flow, above the second one there are two cells in the enclosure. The angle between a magnetic field strength and a temperature gradient is found to be significant factor influencing structure of a convective flow and heat transfer control

Influence of the meridional flow and thermomagnetic convection on characteristics of magnetic fluid seal

For the low-speed magnetic fluid seals, the influence of the meridional flow, induced by the shaft rotation, on the distribution of magnetic particles concentration, is studied. Influence of the thermomagnetic convection on the structure of this flow and on the temperature distribution in high-speed magnetic fluid seals is investigated also. The problems were examined by numerical methods. It is discovered that even very slow rotation of the shaft homogenises distribution of the magnetic particles concentration in the seal and thereby enlarges its operation life. For high-speed seals thermomagnetic convection provides the penetration of the fluid flow in the region of the narrow gap and levels off the temperature distribution decreasing its maximum value and thereby enlarges its operation life too. It is found also that the influence of thermomagnetic convection grows with the viscosity increasin

Effect of diffusion of magnetic particles on the parameters of the magnetic fluid seal: A numerical simulation

In the paper, a motion of magnetic nanoparticles in a high gradient magnetic field and its correlation with the characteristics of the magnetic fluid seal are numerically studied. The neutral curve defining a range of parameters, where the liquid keeps fluidity, is found. It is shown that the concentration of particles during the initial time period grows linearly and then the exponent decreases to 0.5 with time. It is found that at a high enough value of magnetic field the area of close-packed particles is formed under the pole tip. Numerical simulation has shown that with some values of the parameters it is possible to decrease the magnetic particles' concentration essentially so that the basic fluid leaks out from the seal under gravity, i.e. the magnetic fluid seal fails. It has appeared that the characteristic time of the described processes depends on the properties of magnetic fluid and on the magnetic field value and has an order from several hours to several year

Thermoconvective flow velocity in a high-speed magnetofluid seal after it has stopped

Convective flow is investigated in the high-speed (linear velocity of the shaft seal is more than 1 m/s) magnetofluid shaft seal after it has been stopped. Magnetic fluid is preliminarily heated due to viscous friction in the moving seal. After the shaft has been stopped, nonuniform heated fluid remains under the action of a high-gradient magnetic field. Numerical analysis has revealed that in this situation, intense thermomagnetic convection is initiated. The velocity of magnetic fluid depends on its viscosity. For the fluid with viscosity of 2 × 10 -4 m 2/s the maximum flow velocity within the volume of magnetic fluid with a characteristic size of 1 mm can attain a value of 10 m/

Thermomagnetic convection in a cylindrical enclosure. Part 1: Zero gravity

The effects of a uniform external magnetic field on the thermomagnetic convection of magnetic fluid in a cylindrical enclosure are numerically studied. It was found that uniform magnetic field can be cause the convection in the non-uniformly heated magnetic fluid in a cylindrical enclosure even in the case of zero gravity. There are two threshold values of fluid magnetization and temperature gradient. Above the first threshold the convective flow is realized as circular flow, above the second one there are two cells in the enclosure. The angle between a magnetic field strength and a temperature gradient is found to be significant factor influencing structure of a convective flow and heat transfer control