A study of the transient effects of thermoacoustic convection heat transfer in air

An experimental study of Thermoacoustic Convection (TAC) heat transfer in air is presented. The experimental apparatus consisted of an insulated rectangular box with a foil heating element attached to the upper endplate. The heating element was connected to a DC power source. The endplate opposite the heating element could be removed to facilitate experimentation in open, as well as enclosed, containers. Thermocouples were placed along the length of the container to measure the transient air temperature. The enclosed apparatus could be evacuated to experimentally measure the effect of radiation absorption by the thermocouples. The presence of air around the thermocouple was found to have a cooling effect on it. It was proposed that the magnitude of this cooling effect be evaluated as a means of determining if a forced convective cooling process was taking place. Once this was found to be the case, the Nusselt number for each thermocouple bead in air was determined for specific points in time. These values were presented as an indication of the relative magnitudes of air movement within the container. The results were examined for insight into the transient and spatial variation of Nusselt number (and, therefore, air movement) within the container. Results were presented for both enclosed and open container geometries to observe any affect of cavity configuration on TAC. The results confirm the existence of TAC. Notable spatial and transient variations of the air movement indicative of TAC were observed. In addition, significant differences were found between experimentation in open and enclosed container geometries.