چكيده به لاتين
Applying the magnetic field causes significant changes in the rheological and thermal properties of magnetorheological (MR) fluids. One of the thermal properties of MR fluids that changes due to the magnetic field, is thermal conductivity. As a result of magnetic field application, magnetic particles are joined together in the direction of the applied magnetic field and this chain formation arrangement is the most important factor affecting the rheological and thermal properties of MR fluids. In this thesis, the effect of magnetic field on the chain formation of dispersed particles and then the effects of particle chains on the thermal conductivity of magnetorheological fluid were investigated using two experimental methods and CFD simulation. The MR fluid used contains dispersed iron carbonyl particles within the 22H hydraulic fluid. In the experimental section, the transient hot wire (THW) method was used to measure the thermal conductivity of MR fluid, and in the simulation section, coupling of CFD and FTCS methods were used to calculate the thermal conductivity of the fluid, that the results of simulation are in a good agreement with the experimental results. It has been observed that the thermal conductivity changes in MR fluids are anisotropic, such that if the direction of the applied magnetic field is parallel to the temperature gradient direction, the increase in the applied field will increase the thermal conductivity of the magnetorheological fluid, but in the perpendicular direction state, as the applied field increases, the thermal conductivity of the magnetorheological fluid decreases. Numerically, for MR fluid with dispersed particle volume fraction of 15% at magnetic field of 14mT, when the magnetic field and temperature gradient directions are parallel, thermal conductivity increases by 105%, but in perpendicular state, thermal conductivity decreases by 23%. It was also found that by increasing the volume fraction and decreasing the size of dispersed particles, as well as by decreasing the viscosity and increasing the base fluid temperature, the anisotropic changes of the thermal conductivity of MR fluids are enhanced.
