The Development of a Sensor to Determine Velocity in Liquid Aluminum

This thesis presents two sensor designs to determine velocity of liquid aluminum. These sensors are referred to as Sensor1 and Sensor2 where the principle of operation is based on forced convective heat transfer. Sensor1 is constructed of one material while Sensor2 is comprised of two materials, the geometry of both is that of a circular cylinder. The immersion of the sensor into the flow can be classified as a circular cylinder in liquid aluminum crossflow. A calculation of the localized Nusselt number acting on the surface of the sensor produces an estimate of the magnitude and direction of velocity. The localized Nusselt number estimate is provided by more than one thermocouple temperature measurement from within the sensor. The Sensor1 and Sensor2 concepts were constructed and tested in flowing liquid aluminum and numerical models were developed to study the heat transfer between the liquid and sensor.A peculiarity of this liquid metal system is that aluminum may solidify and subsequently melt onto the surface of the sensors; the solid aluminum is referred to as shell. The growth of the shell depends on various conditions, one examined in this work is the thermal resistance at the Sensor1-aluminum interface. An enthalpy numerical model is used to show that the thermal resistance at the Sensor1-aluminum interface has an important effect on the solidification and melting times of shell. The numerical model is validated with experimental measurements of localized shell solidification and melting times.To estimate the velocity of liquid aluminum the solidification of shell must be suppressed. By incorporating two materials of drastically different thermal properties, various regions of Sensor2 may be treated as lumped systems, this mathematical treatment provides fast estimates of the localized Nusselt number, hence the velocity can be determined in real-time. The modified Nusselt number estimated by Sensor2 is a sum of the thermal resistance from the thermal boundary layer and thermal resistance at the Sensor2-aluminum interface. By numerically modeling the flow of liquid aluminum over the Sensor2 design and by comparing these results to experimental data, the thermal resistance at the Sensor2-aluminum interface is estimated. A technique to determine the magnitude and direction of velocity from the local Nusselt number of the Sensor2 design is presented.Ph.D