Numerical study of transient characteristics of a standing-wave thermoacoustic heat engine

Understanding of transient fluid flow and heat transfer characteristics within thermoacoustic devices is crucial to improve their start up processes and subsequently the achievable efficiencies. The present numerical study investigates the transient features of a standing-wave quarter-wavelength thermoacoustic heat engine composed of hot and cold heat exchangers, a stack, and a resonator. The non-linear fluid dynamical as well as energy equations are solved on the structured grids by resolving viscous and thermal boundary layers using OpenFOAM software. Full discretization of governing equations captured nonlinear features of flow at high pressure amplitudes which are typically ignored by the linear theory. The results show the existence of acoustic streaming phenomenon in the system due to the interaction of Stokes boundary layer adjacent to the solid regions which can lead to undesirable convective heat transport and as a result the reduction of the system efficiency.