Nonlinear temperature field near the stack ends of a standing-wave thermoacoustic refrigerator

Measurement of density fluctuations using digital holographic interferometry in a standing wave thermoacoustic oscillator

“…10 confirm previous experimental [11,18,21], numerical [11,21] or analytical [13] studies, whose main conclusions state that there exists complicated heat and mass transport phenomena next to the ends of a stack. However, a new point here is that we measured density fluctuations (instead of velocity or temperature fluctuations), but also that the device we studied is a self-sustained thermoacoustic oscillator (instead of a stack at room temperature submitted to an acoustic wave by an external sound source), which notably means that there exists also a steep temperature gradient at the location where measurement are processed.…”

“…Also, while the model predicts that entrance effects extend up to %2.5 mm, the experiments show that the entrance effects extend up to %6 mm. Such an extension of the impact of entrance effects beyond the distance 2u has already been reported by Berson et al [21] both numerically and experimentally (from the measurement of T 0 using cold wire anemometry), and can be explained (at least partially) by accounting for the axial conduction within the fluid in Eq. (12).…”

“…It is also interesting to analyze the spectral components of density fluctuations, notably because previous theoretical [13] and experimental [21] studies have shown that the stack termination should be responsible for higher harmonics generation in temperature fluctuations (even if pressure fluctuations should be monochromatic). It is therefore expected that the latter impact on temperature fluctuations should also modify the spectral content of density fluctuations.…”

“…Laser Doppler Velocimetry and Particle Image Velocimetry provide information about the gas parcel velocity and have been used previously to characterize acoustic streaming [14][15][16][17] or vortex shedding processes [18][19][20], while cold wire anemometry [21] has been used to characterize the nonlinear temperature fluctuations in the vicinity of the stack termination. In this paper, attention is focused on the development of another measurement method allowing to get information about density http://dx.doi.org/10.1016/j.expthermflusci.2015.09.012 0894-1777/Ó 2015 Elsevier Inc. All rights reserved.…”

Influence of magnetic field on the periodically oscillating fluid inside a porous medium attached to a thick solid plate

“…These advantages include no moving components, low maintenance cost, environmental friendly working medium (e.g., inert gases), and the use of low potential energy input sources [2]. Therefore, thermoacoustic related research topics have caught the attention of numerous researchers over the past few decades [2][3][4][5][6][7]. The temperature gradient, required to run a thermoacoustic system, can be developed using any low potential sources of energy; for example, solar energy [8], waste heat from automotive engine [9], and industrial waste heat [10].…”