Heat transfer in magnetic fluids at low Reynolds number

Graduation date: 1981This study was concerned with the flow of a magnetic self-propelled\ud ferrohydrodynamic fluid in a horizontal circular tube subjected\ud to axially varying temperature and magnetic field. The first\ud phase of the study involved the analytical solution to the governing\ud equations for the velocity and temperature profiles within the fully\ud developed flow region of the duct when subjected to linearly varying\ud axial temperature and magnetic field. The results showed the problem\ud to be similar to gravity-induced natural convection flows even though\ud the variables are different. The Nusselt number was found to be a\ud function of a magnetic Rayleigh number.\ud The second part of the study consisted of an experimental investigation\ud at the thermal entry region of flow caused by a change in\ud tube wall heat flux and a numerical solution to the governing equations\ud for the same problem. Because of the low pyromagnetic coefficient\ud of the water-based Lignosite fluid used in the study, only low\ud Reynolds number flows were obtained. It was found that a hot-wire\ud anemometer could be used for velocity measurements if the overheat\ud ratio was maintained at a low value and measurements were made within\ud a region of constant magnetic field strength. The experimentally\ud and numerically obtained velocity and temperature profiles generally\ud agreed in magnitude and shape but a shift in maximum velocity point\ud location was observed. This shift was attributed to experimental\ud errors and to physical properties of the magnetic fluid that were\ud approximated due to lack of information