Direct Simulations of Thermoacoustic Heat Exchangers (original) (raw)
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Numerical Simulation of a Thermoacoustic Refrigerator
Journal of Computational Physics, 1996
harmful refrigerants such as CFCs. Another advantage of these devices is the very small number of moving parts A low Mach-number compressible flow model for the simulation of acoustically driven flow in a thermoacoustic stack is constructed. required, potentially making them highly reliable.
Numerical Simulation of Stack-Heat Exchangers Coupling in a Thermoacoustic Refrigerator
AIAA Journal, 2004
The Navier-Stokes equations for an unsteady and compressible flow are solved numerically to investigate the flow near the stack of a thermoacoustic refrigerator. The computational domain is a resonator "slice" including the resonator end but not the source. An incoming wave is introduced into the domain using the method of characteristics. Also included in the domain is a stack plate and two heat exchangers. The effects of the acoustic Mach number and geometrical parameters on refrigerator performance is investigated. Of special interest are some nonlinear temperature oscillations, which are not predicted by linear models and are due to acoustic propagation, and coupling between the stack plate and the heat exchangers. It is shown that the maximum heat pumping occurs for a stack/heat exchanger separation that is of the order of one particle displacement amplitude.
Numerical Simulation of Thermoacoustic Refrigerator
2011
Thermoacoustic is a technology that uses high-amplitude sound waves in a pressurized gas generating a hot and cold region, therefore this device can be used as a heat pump or a refrigerator. This device has the advantage of no ozonedepleting or toxic coolant and few moving parts, because this refrigerator is a system that operates using sound waves to transport heat, therefore its refrigerator is more economic and better for the environment. This refrigerator consists mainly of a closed tube with a stack of a number of parallel plates, and two heat exchangers and a loudspeaker that sustains an acoustic standing wave in the resonator tube. This paper aims to study the performance of a thermoacoustic refrigerator, using the numeric analyze (Ansys –CFX ®), this results is the transient time, and the experimental analyze, was the results at the state steady. The numeric results showed evolution at temperature, pressure and velocity flows are discussed and compared.
Numerical simulation of a thermodynamic refrigerator
ESAIM: Proceedings, 1996
harmful refrigerants such as CFCs. Another advantage of these devices is the very small number of moving parts A low Mach-number compressible flow model for the simulation of acoustically driven flow in a thermoacoustic stack is constructed. required, potentially making them highly reliable.
Theoretical evaluation of stack-based thermoacoustic refrigerators
International Journal of Air-Conditioning and Refrigeration
Standing wave thermoacoustic refrigerator uses stack, is the heart of the thermoacoustic cooling system. The porous stack in the resonator tube develops temperature difference across the stack for heat pumping upon loudspeaker sound interaction of oscillating gas. In this paper, the optimization of stack-heat exchangers system and resonator is discussed using linear thermoacoustic theory for better COP and cooling power of refrigerator. The loudspeaker is assumed to provide the required acoustic power with the back volume gas spring system. Helium and air are chosen because of their better thermophysical properties and cost, compared to other competent gases. The 200 mm diameter stack is optimized for the temperature difference of 28 K. The theoretical results of the optimized refrigerator models are compared with the DeltaEC simulation results for deriving conclusions. DeltaEC predicts the cooling power and COP of 349 W at 0.998 for helium, and 139 W at 1.133 for air, respectively.
ASME 2019 International Mechanical Engineering Congress and Exposition, 2019
Thermo-acoustic refrigeration could potentially become an alternative option to current traditional refrigeration systems provided that the issue related to its efficiency is addressed. One of the incentives for developing this technology is the opportunity it establishes with respect to the use of a sustainable heat source to induce cooling. Many existing works have pointed out the relationship between the geometrical configuration of the device and its performance. Mainly, the stack geometry and position have been the focus of these previous works. In this work, a standing-wave ThermoAcoustically-Driven Thermo-Acoustic Refrigerator with an adjustable resonator has been developed. Hence the device is made of two portions, joined with an adjustable duct, namely a simple standing-wave thermo-acoustic engine that converts heat into a sound wave and a simple thermo-acoustic refrigerator where heat pumping takes place. The Design Environment for Low-amplitude ThermoAcoustic Energy Conversion (DELTAEC) was used to model and analyze the influence of the adjustment of the resonator on the cooling performance. Parameters like the temperature difference across the stack, the frequency of the acoustic sound wave generated, the cooling power and the coefficient of performance have been studied. The initial results reported in this study show the possibility to change the performance of practical TADTAR by adjusting the resonator length.
SIMULATION STUDIES ON THE THERMOACOUSTIC COOLING
IAEME Publication, 2014
Cooling by an acousticwave is one of the attractive areas of research in the field of cry coolers and refrigeration. Towards the development of such systems, simulation can be carried out by several methods. We present here the simulation studies of thermo acoustically driven standing wave refrigerator and traveling wave thermoacoustic prime mover for the pulse tube refrigeration using the procedures of Computational Fluid Dynamics (CFD). The CFD analysis is carried out using Ansys Fluent, incorporating the necessary boundary conditions, for different operating and geometric parameters. The study indicates that the working fluid has an influence on the system frequency and on the pressure amplitude. The results obtained by CFD are compared with those obtained using experiments wherever possible and they are in good agreement.
Designing and Manufacturing a Thermoacoustic Refrigerator
2020
The objective of this design project is to demonstrate and apply the physics of the thermoacoustic effect by designing and building a device called a thermoacoustic refrigerator. The thermoacoustic effect is the ability to use sound waves to impose a thermal gradient, thus creating a heating or cooling effect. The thermoacoustic effect was achieved by sending sound waves from a speaker down a tube which created standing waves that generated a thermal gradient across a stack. Heat exchangers remove the excess heat at the hot end of the stack and thus the tube cools. The system is composed of an acoustic driver, stack, and two different heat exchangers, all housed in a resonance tube. The working fluid that was used during the initial tests was unpressurized air, with a goal to progress to pressurized helium. The maximum cooling found was a temperature difference of 3.1 ⁰C. Tests with pressurized helium were not possible due to critical failures of a gasket and various speakers. With ...
Experimental study and analysis of a thermoacoustically driven thermoacoustic refrigerator
Sādhanā, 2020
Experimental investigations are performed on a half-wavelength standing wave type thermoacoustically driven thermoacoustic refrigerator also known as TADTAR. Present TADTAR device conceived to be a quarter wavelength standing wave type thermoacoustic engine (TAE) coupled to a quarter wavelength standing wave thermoacoustic refrigerator (TAR). A TAE generates acoustic work using heat, and this produced acoustic work is directly fed to TAR where a useful cooling effect is developed. The study here aims to project the enhancement in the performance of a TADTAR system by using better geometric choices and operating conditions. In the present work, by keeping the engine part unaltered, parametric variations on the refrigerator side are performed. Two geometric parameters namely resonator length and TAR stack position and one operating parameter, working gas, have been varied at three distinct choices. The performance of TADTAR is examined for three output parameters of TADTAR namely frequency of oscillations, pressure amplitude, and temperature difference across TAR stack. The present study should be useful for assisting select these parameters for starting the designing of a TADTAR. It also helps in concluding in a more generalized way the dependence of the above-said output of TADTAR on the varying parameters. This paper shows that longer resonator and HeAr mixture as working gas among the choices is better for a TADTAR system for achieving better performance. It also highlights the potential existence of a unique position for a stack length for a TADTAR to attain maximum performance in terms of the temperature difference across the TAR stack. The present paper reports the maximum temperature difference of 16.3 K across the TAR stack.
Thermoacoustic Refrigerators and Heat Pumps: New Insights for A High Performance
Thermoacoustic refrigerators and heat pumps are considered one of the important emerging green technologies. They are based on the use of acoustic pressure waves to supply cooling or heating effects. The oscillating gas interaction with a solid wall called the stack generates thermoacoustic effects. This study presents the effects of the operating conditions and geometric parameters on the temperature difference across the stack and the coefficient of performance of a thermoacoustic heat pump at different cooling loads. The design steps of these systems were also demonstrated. Theoretical study of the operation conditions and geometric parameters was presented using "DeltaEC". The results showed that higher harmonics are less desirable for thermoacoustic phenomena as they lower the temperature difference across the stack. Further insights into the effects of amplitude pressure, mean pressure and stack geometries were also demonstrated. This study helps to establish the concepts and design steps for thermoacoustic refrigerators and heat pumps.