Numerical investigations of flow and energy fields near a thermoacoustic couple

Abstract

The flow field and the energy transport near thermoacoustic couples are simulated using a 2D full Navier-Stokes solver. The thermoacoustic couple plate is maintained at a constant temperature; plate lengths, which are ''short'' and ''long'' compared with the particle displacement lengths of the acoustic standing waves, are tested. Also investigated are the effects of plate spacing and the amplitude of the standing wave. Results are examined in the form of energy vectors, particle paths, and overall entropy generation rates. These show that a net heat-pumping effect appears only near the edges of thermoacoustic couple plates, within about a particle displacement distance from the ends. A heat-pumping effect can be seen even on the shortest plates tested when the plate spacing exceeds the thermal penetration depth. It is observed that energy dissipation near the plate increases quadratically as the plate spacing is reduced. The results also indicate that there may be a larger scale vortical motion outside the plates which disappears as the plate spacing is reduced.

Generalization of the thermoacoustic form functions for evaluating the transverse temperature gradient effect

“…The cited thermo-fluid processes occurring in stack ends are beyond the scope of the standard linear theory [19,21] because it's based on the uniform transverse time-average temperature [17]. Moreover, the experimental observations are retrieved by numerical investigations [5,8,17]. It confirms that the net heat exchange between fluid and wall takes place at distance from the stack ends not exceeding the peak to peak particle displacement.…”

“…In fact, more adequate computational fluid dynamic methods are used to solve unsteady compressible Navier-Stokes equations or the low Mach equivalent equations [3,5,8,10,11,24]. Alternatively, simpler methods are also used and are in good agreement with experiments [12,17].…”

A Comprehensive Empirical Correlation for Finned Heat Exchangers with Parallel Plates Working in Oscillating Flow

“…Hence, for the heat exchanger types A and B, the obtained magnitudes have orders of B1 > B2 > B3 and A1 > A2 > A3. Numerical simulation by Ishikawa et al [21] showed that the net heat From the response surfaces with fixed various parameters, it is noted that l/d h , as a geometrical parameter, has a negative influence on the Nusselt number. The rise of l/d h leads to a dramatic weakening in the heat transfer performance.…”

“…Hence, for the heat exchanger types A and B, the obtained magnitudes have orders of B1 > B2 > B3 and A1 > A2 > A3. Numerical simulation by Ishikawa et al [21] showed that the net heat transfer rate between solid and fluid states mainly occurred on the inlet and outlet faces of the heat exchanger with parallel plates. When the fin length is increased, the heat flux on inlet and outlet faces can be positive or negative, leading to a decrease in the net heat flux.…”

“…Hence, for the heat exchanger types A and B, the obtained magnitudes have orders of B1 > B2 > B3 and A1 > A2 > A3. Numerical simulation by Ishikawa et al [21] showed that the net heat Table 1. It can be seen from the figures that, when the Reynolds number and Valensi number are both a controlled constant, the Nusselt number decreases as l/dh is increased, reflected in the response surface illustrated in Figure 4.…”