Magnetocaloric anemometry. A novel concept for fluid flow measurement

Abstract

Colloidal magnetic fluids (ferrofluids) and its significance with regard to fluid flow measurement is discussed. This concept -which can properly be called as magnetocaloric anemometry, blikewise than hot-wire anemometry takes advantage of the thermal dependence of the electrical resistance of some metals to measure the flow speed, it takes advantage of the thermal dependence of magnetization of superparamagnetic materials. Because the magnetic field is measured by Hall- sensors which are very sensitive to magnetic variations, and because the very small relaxation times of superparamagnetics materials upon variations of the magnetic field, therefore, magnetocaloric anemometers could offer a high sensibility and resolution fluid flow measurement matched only by hot wire anemometry but eliminating its handicaps, namely, high fragility, low durability and need for continuous maintenance which all in all translates into a high cost technology. The mathematical basis of the concept as well as first preliminary experimental data for magnetocaloric anemometry constitute the core of the present work. Additional R&D is required in order to arrive at a reliable practical design for magnetocaloric anemometers.