A double-loop-type traveling-wave thermoacoustic refrigerator driven by a multistage traveling-wave engine was constructed. To reduce the onset temperature for thermoacoustic oscillations and achieve a refrigerator temperature of −100 °C, three etched stainless steel mesh regenerators were installed close to the sweet spot within the prime mover loop and one regenerator was fixed in the refrigerator loop. The maximum measured COP of the whole system at-50°C, was 0.029. Gas oscillations occurred when the hot temperature of the regenerator in the prime mover loop exceeded 85 °C. On the other hand, refrigeration (−42.3 °C) was observed when the hot heat exchanger temperature reached 90 °C, which is lower than the boiling point of water. Furthermore, the refrigerator achieved a minimum cold temperature of −107.4 °C when the hot temperature was 270 °C.
Computational fluid dynamics (CFD) simulations have become prevalent tools in the numerical modeling of complex thermoacoustic phenomena. The basic problem concerning a CFD simulation of a complete system is the computational cost. To overcome this problem, a CFD simulation tool using an impedance matching boundary (IMB) condition has been developed to analyze the characterization of the flow field in a looped-tube travelling-wave thermoacoustic engine. The thermodynamic processes were simulated using a two-dimensional numerical solution for the compressible Navier-Stokes equations. By imposing an impedance matching boundary condition, flow fields around the regenerator and heat-exchanger plates were simulated. The boundary condition being defined as an acoustic load which was derived from experimental data. From the simulations, features of the flow field such as nonlinear vortex generation around the regenerator and heat-exchanger plates were observed that were not present in the analytical solutions. Furthermore, the temperature oscillations were obtained around regenerator plates, and the operating mechanism of a looped-tube travelling-wave thermoacoustic engine was characterized both qualitatively and quantitatively. The CFD tool was validated by obtaining good agreement when comparing results with those from experimental data and analytical solutions. As a result, it was concluded that CFD
Numerical study is conducted to investigate the fluid-structure interaction around a static circular cylinder in two and three dimensional simulations. The cylinder with an elastic surface is fixed in uniform flow at Reynolds number 1000. The objective is to investigate the influence of elastic surface on the fluid forces around the cylinder. The continuity equation, Navier-Stokes equations and Poisson equation are solved by Marker and cell method. The elastic wall is treated by a mass-spring-damper force model that is solved with fluid forces referred from the flow simulation. As a result, it is obtained that the elastic surface at the back side of cylinder (Model D) decreases the drag force on the cylinder.
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