Acoustic wave motion along a narrow cylindrical duct in the presence of an axial mean flow and temperature gradient

2000 ◽  
Vol 107 (4) ◽  
pp. 1859-1867 ◽  
Author(s):  
Keith S. Peat ◽  
Ray Kirby
Keyword(s):  
Temperature Gradient ◽  
Acoustic Wave ◽  
Wave Motion ◽  
Mean Flow ◽  
Cylindrical Duct

General Solution of Acoustic Wave Equation for Circular Reversing Chamber with Temperature Gradient

1991 ◽  
Vol 113 (4) ◽  
pp. 543-550 ◽  
Author(s):  
Yang-Hann Kim ◽  
Jae Woong Choi
Keyword(s):  
Wave Equation ◽  
Temperature Gradient ◽  
General Solution ◽  
Acoustic Wave ◽  
Transmission Loss ◽  
Rigid Wall ◽  
Acoustic Wave Equation ◽  
Mean Flow ◽  
Helmholtz Resonators ◽  
Twisting Angle

A general solution for transmission loss in a circular reversing chamber with the effects of temperature gradient, offset, and twisting angle variations of inlet/outlet ports is obtained by using the mode matching technique. The assumptions included in the solution method are division of the reversing chamber into segments, continuity of pressure and velocity at the boundaries of adjacent elements, constant temperature along each segment, and rigid wall boundary condition. Furthermore, the general solution can reduce to the existing solution of acoustic wave equation for a reversing chamber when no mean flow of exhaust gas and temperature gradient are present. The numerical simulation results based upon the obtained governing equation have the same trough frequencies and shapes of transmission loss curves as the experimental results performed on various types of reversing chambers. From these simulations, it is determined that the diameter of the reversing chamber dictates that cutoff frequencies in the transmission loss curves, and its length controls the number of standing waves in the chamber. Reversing chambers exhibit the acoustic characteristics of simple expansion chambers when the ratios of length over diameter are small. Even for limiting cases, i.e., Helmholtz resonators and close ended pipes, simulations produce the predicted results derived by other existing theories for silencers.

Technical Note. Influence of Material Used for the Regenerator on the Properties of a Thermoacoustic Heat Pump

2013 ◽  
Vol 38 (4) ◽  
pp. 565-570 ◽  
Author(s):  
Bartłomiej Kruk
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Acoustic Wave ◽  
Heat Pump ◽  
Sound Wave ◽  
Heat Exchangers ◽  
Heat Pumps ◽  
Technical Note ◽  
New Materials ◽  
Modern Technologies

Abstract Research in termoacoustics began with the observation of the heat transfer between gas and solids. Using this interaction the intense sound wave could be applied to create engines and heat pumps. The most important part of thermoacoustic devices is a regenerator, where press of conversion of sound energy into thermal or vice versa takes place. In a heat pump the acoustic wave produces the temperature difference at the two ends of the regenerator. The aim of the paper is to find the influence of the material used for the construction of a regenerator on the properties of a thermoacoustic heat pump. Modern technologies allow us to create new materials with physical properties necessary to increase the temperature gradient on the heat exchangers. The aim of this paper is to create a regenerator which strongly improves the efficiency of the heat pump.

scholarly journals An Efficient Scheme for Onboard Reduction of Moored χpod Data

2017 ◽  
Vol 34 (11) ◽  
pp. 2533-2546 ◽  
Author(s):  
Johannes Becherer ◽  
James N. Moum
Keyword(s):  
Heat Flux ◽  
Temperature Gradient ◽  
Fast Response ◽  
Flow Speed ◽  
Mean Flow ◽  
Temperature Variance ◽  
Efficient Scheme ◽  
Linear Accelerometer

AbstractA scheme for significantly reducing data sampled on turbulence devices (χpods) deployed on remote oceanographic moorings is proposed. Each χpod is equipped with a pitot-static tube, two fast-response thermistors, a three-axis linear accelerometer, and a compass. In preprocessing, voltage means, variances, and amplitude of the subrange (inertial-convective subrange of the turbulence) of the voltage spectrum representing the temperature gradient are computed. Postprocessing converts voltages to engineering units, in particular mean flow speed (and velocity), temperature, temperature gradient, and the rate of destruction of the temperature variance χ from which other turbulence quantities, such as heat flux, are derived. On 10-min averages, this scheme reduces the data by a factor of roughly 24 000 with a small (5%) low bias compared to complete estimates using inertial-convective subrange scaling of calibrated temperature gradient spectra.

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