Experimental study on kinetic to thermal energy conversion with fluid agitation

Abstract

Modern wind turbines are generally used for electricity generation; however, the final form of energy required by many users is thermal energy. Although electrical energy conversion to thermal energy is a high-efficiency process, the efficiency of electricity generation from wind turbines is usually low. In this thesis, a heat generator with fluid agitation is developed and studied. This heat generator converts kinetic energy (e.g. that from a wind turbine) directly to thermal energy through the process of viscous dissipation; this process is achieved through the agitation of the working fluid inside a container. This heat generator uses an optimized flat blade turbine (FBT) impeller and a fully baffled configuration. An electric motor is used to provide the kinetic energy input to the heat generator. A torque sensor, a tachometer, and thermocouples are used to measure the torque, rotational speed (RPM,) and temperature rise in the fluid, respectively. Using the measured quantities, the efficiency of kinetic energy to sensible heat conversion is calculated. Experiments are conducted at different rotational speeds and for different working fluids: distilled water, ethylene glycol, and their respective nanofluids with Al₂O₃ nanoparticles at different concentrations. The experimental results indicate that the heat generator is up to 90% efficient in converting kinetic energy to thermal energy. The temperature rise rate increases with the rotational speed and larger diameter of the impeller. Furthermore, the addition of nanoparticles improves the thermal properties of the fluid, but it does not significantly affect the energy conversion efficiency or the rate of temperature rise in the fluid. A wind turbine can power this heat generator to provide heat to a house or a commercial building. This innovative renewable energy technology would benefit wind rich remote areas with cold weather.