Performance evaluation of a liquid-sodium thermoacoustic engine with magnetohydrodynamic electricity generation based upon the Swift model

Liquid sodium is an attractive working fluid for thermoacoustic conversion. Herein, a numerical study on a standing-wave thermoacoustic electricity generation system with liquid sodium as the working fluid is presented, based upon the Swift model. The characteristics of the thermoacoustic conversion and the output performance of the system have been investigated. The results show that the sodium engine can reach a power density much higher than the classical gas engine. Due to the strong acoustic coupling between components, the electricity output is significantly affected by the input heating power, the magnetic flux density, and the load ratio. In a typical case, the thermal-to-electric efficiency and the relative Carnot efficiency can reach 4.6% and 7.8%, respectively, with a temperature difference of 563 K and an input heat of 5 kW. More importantly, the output electricity density reaches 150 kW/m3, higher than some commercially available technologies. These results demonstrate the potential of such technology for small-scale electricity generation. Its extremely simple structure without any mechanical moving part endows the system with high reliability and long lifetime, if risks of corrosion and exposure to air and water can be avoided.