scholarly journals The Influence of Stack Position and Acoustic Frequency on the Performance of Thermoacoustic Refrigerator with the Standing Wave

2017 ◽  
Vol 38 (4) ◽  
pp. 89-107 ◽  
Author(s):  
Jakub Kajurek ◽  
Artur Rusowicz ◽  
Andrzej Grzebielec
Keyword(s):  
Standing Wave ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Acoustic Power ◽  
Working Fluid ◽  
Parallel Plates ◽  
Acoustic Frequency ◽  
Plate Spacing ◽  
Resonance Frequencies ◽  
Thermoacoustic Refrigerator

Abstract Thermoacoustic refrigerator uses acoustic power to transport heat from a low-temperature source to a high-temperature source. The increasing interest in thermoacoustic technology is caused due to its simplicity, reliability as well as application of environmentally friendly working fluids. A typical thermoacoustic refrigerator consists of a resonator, a stack of parallel plates, two heat exchangers and a source of acoustic wave. The article presents the influence of the stack position in the resonance tube and the acoustic frequency on the performance of thermoacoustic refrigerator with a standing wave driven by a loudspeaker, which is measured in terms of the temperature difference between the stack edges. The results from experiments, conducted for the stack with the plate spacing 0.3 mm and the length 50 mm, acoustic frequencies varying between 100 and 400 Hz and air as a working fluid are consistent with the theory presented in this paper. The experiments confirmed that the temperature difference for the stack with determined plate spacing depends on the acoustic frequency and the stack position. The maximum values were achieved for resonance frequencies and the stack position between the pressure and velocity node.

scholarly journals Performance analysis of the thermoacoustic refrigerator with the standing wave and air as a working fluid

2018 ◽  
Vol 44 ◽  
pp. 00063 ◽  
Author(s):  
Jakub Kajurek ◽  
Artur Rusowicz
Keyword(s):  
Temperature Difference ◽  
High Reliability ◽  
Power Input ◽  
Acoustic Power ◽  
Operating Frequency ◽  
Working Fluid ◽  
Resonator Length ◽  
Environmental Friendliness ◽  
The Impact ◽  
Thermoacoustic Refrigerator

Thermoacoustic refrigerator is a new and emerging technology capable of transporting heat from a low-temperature source to a high-temperature source by utilizing the acoustic power input. These devices, operating without hazardous refrigerants and owning no moving components, show advantages of high reliability and environmental friendliness. However, simple to fabricate, the designing of thermoacoustic refrigerators is very challenging. This paper illustrates the impact of significant factors on the performance of the thermoacoustic refrigerator which was measured in terms of the temperature difference generated across the stack ends. The experimental device driven by a commercial loudspeaker and air at atmospheric pressure as a working fluid was examined under various resonator length and operating frequencies. The results indicate that appropriate resonator’s length and operating frequency lead to an increase in the temperature difference created across the stack. The maximum values were achieved for operating frequency equalled to 200 and 300 Hz whereas resonator length corresponded to the half-length of the acoustic wave for these frequencies. The results of experiment also confirm that relationship between these parameters is strongly affected by the stack spacing, which in this research was equalled to 0.4 mm.

scholarly journals Influence of Parallel Plate Stack Spacing on the Temperature Difference of Thermoacoustic Refrigerator by using Helium as a Working Medium

2019 ◽  
Vol 8 (4) ◽  
pp. 2704-2712
Keyword(s):  
Heat Exchanger ◽  
Temperature Difference ◽  
Parallel Plate ◽  
Sheet Material ◽  
Maximum Temperature ◽  
Working Fluid ◽  
Operating Pressure ◽  
Parallel Plates ◽  
Refrigeration System ◽  
Thermoacoustic Refrigerator

The refrigerants are usually provided in the conventional refrigeration system despite the fact that, they produce CFCs and HCFCs, which are hazardous to the environment. However, these disadvantages can be overcome using air or inert gas in the thermoacoustic refrigeration system. The present research involves the effect of spacing of parallel plate stack on the performance of thermoacoustic refrigerator (TAR) in terms of temperature difference (∆T). The entire resonator system as well as other structural parts of the refrigerator are fabricated by using PVC to reduce conduction heat loss. Three parallel plate stacks have been used to study the performance of TAR considering different porosity ratios by varying the gap between the parallel plates (0.28 mm, 0.33 mm and 0.38 mm). The parallel plate stacks are fabricated by using aluminium and mylar sheet material and the working fluid used for the experimental study is helium. The experiments have been carried out with different drive ratios ranging from 0.6% to 1.6% with operating frequencies of 200 – 600 Hz. Also the mean operating pressure used for the experiment is 2 to 10 bar and cooling load of 2 to 10W are considered. The ∆T between the hot heat exchanger and cold heat exchanger is recorded using RTDs and Bruel and Kjaer data acquisition system. Experimental results shows that the lowest temperature measured at cold heat exchanger is -2.1 oC by maintaining the hot heat exchanger temperature at about 32 oC. The maximum temperature difference of 32.90 oC is achieved.

Aerodynamic and Thermal Measurements in a Standing Wave Thermoacoustic Refrigerator

2010 ◽  
Author(s):  
Gaelle Poignand ◽  
Emmanuel Jondeau ◽  
Philippe Blanc-Benon
Keyword(s):  
Heat Transfer ◽  
Standing Wave ◽  
Heat Exchangers ◽  
System Performance ◽  
Heat Fluxes ◽  
Acoustic Energy ◽  
Working Fluid ◽  
Cooling Power ◽  
Thermal Measurements ◽  
Thermoacoustic Refrigerator

Thermoacoustic refrigerators produce a cooling power from an acoustic energy. Over the last decades, these devices have been extensively studied since they are environment-friendly, robust and miniaturizable. Despite all these advantages, their commercialization is limited by their low efficiency. One reason for this limitation comes from the complex thermo-fluid process between the stack and the two heat exchangers which is still not sufficiently understood to allow for optimization. In particular, at high acoustic pressure level, vortex shedding can occur behind the stack as highlight by [Berson & al., Heat Mass Trans, 44, 10151023 (2008)]. The created vortex can affect heat transfer between the stack and the heat exchangers and thus, they can reduce the system performance. In this work, aerodynamic and thermal measurements are both conducted in a standing wave thermoacoustic refrigerator allowing investigation of vortex influence on the system performance. The proposed device consists on a resonator operated at frequency of 200 Hz, with hot and cold heat exchangers placed at the stack extremities. The working fluid is air at ambient temperature and atmospheric pressure. The aerodynamic field behind the stack is described using high-speed Particle Image Velocimetry. This technique allows the acoustic velocity field measurement at a frequency up to 3000 Hz. Thermal measurements consist on the acquisition of both the temperature evolution along the stack and the heat fluxes extracted at the cold heat exchanger. These measurements are performed by specific micro-sensors developed by MEMS technology. The combination of these two measurements should be helpful for the further understanding of the heat transfer between the stack and the heat exchangers.

Coupled Analysis Approach in OTEC System Design

2012 ◽  
Author(s):  
Shan Shi ◽  
John Halkyard ◽  
Nishu Kurup ◽  
Lei Jiang
Keyword(s):  
System Design ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Cold Water ◽  
Large Diameter ◽  
Working Fluid ◽  
Coupled Analysis ◽  
Ammonia Vapor ◽  
Water Pipe ◽  
Floating Platform

Ocean Thermal Energy Conversion (OTEC) technologies based on floating platforms generate electrical energy by utilizing the temperature difference between the deep ocean water and the surface water. One typical offshore floating OTEC system uses the temperature difference to drive a heat engine, utilizing a closed-loop Rankine cycle with a working fluid such as ammonia (NH3). Cold water is pumped through a large flexible pipe from approximately 1000m depth to heat exchangers which condense the ammonia vapor. Warm water from the surface is pumped through heat exchangers to evaporate the liquid ammonia to drive the turbine. An OTEC floating platform could be a semisubmersible, a spar, or other typical offshore hull form with a taut or a catenary mooring system. As opposed to oil and gas production platforms, the OTEC system consists of a large diameter cold water pipe (CWP) which will participate in the global performance of the floating platform. Its unique behavior also includes the contribution of CWP entrained water which behaves differently in lateral and vertical directions due to its open bottom design. The hydrodynamic behavior of the large scale cold water pipe is an important consideration in the system design and analysis. The study presented in this work includes the application of a fully coupled analysis program with an accurate cold water pipe dynamic model in OTEC floating system analysis. The study could be useful for future guidance and reference on OTEC floating platform designs.

Study of a small-scale standing-wave thermoacoustic engine

2009 ◽  
Vol 224 (1) ◽  
pp. 133-141 ◽  
Author(s):  
S Jung ◽  
K I Matveev
Keyword(s):  
Standing Wave ◽  
Acoustic Pressure ◽  
Acoustic Power ◽  
Vitreous Carbon ◽  
Working Fluid ◽  
Small Scale ◽  
Balance Theory ◽  
Reticulated Vitreous Carbon ◽  
Thermoacoustic Engine ◽  
Atmospheric Air

This article reports experimental and modelling results obtained with a small-scale standing-wave thermoacoustic engine. Reticulated vitreous carbon is used as the stack material and atmospheric air as the working fluid. The engine is tested with resonators of variable lengths in the range 57–124 mm. The engine starts generating sound at temperature differences of 200–300 °C between the hot and cold parts of the system. The acoustic pressure amplitudes up to 2 kPa are measured inside the resonator in the excited regimes. A simplified energy-balance theory adequately predicts a trend in the temperature difference for the sound onset, while underestimating actual values. Model estimations show that the stack-generated acoustic power reaches 100 mW at the stack-based efficiencies of several per cent.

scholarly journals Experimental Investigation on the Thermoacoustic Effect in Easily Accessible Porous Materials

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 83
Author(s):  
Jakub Kajurek ◽  
Artur Rusowicz
Keyword(s):  
Experimental Investigation ◽  
Porous Materials ◽  
Standing Wave ◽  
Atmospheric Pressure ◽  
Acoustic Power ◽  
High Porosity ◽  
Parallel Plates ◽  
Thermoacoustic Effect ◽  
Wave Device ◽  
Made In

Thermoacoustic devices are the systems which use acoustic power to transport heat through a stack in a resonance tube. The stack is one of the most important parts of the thermoacoustic systems. It can have different geometries, like parallel plates, circular pores, or pin arrays. However, the fabrication of stacks with regular geometries is sometimes impractical due to material and assembly costs. These problems can be solved by using stack fabricated with random and easily accessible porous materials. In this paper an experimental investigation on the thermoacoustic effect in easily accessible porous materials is presented. The measurements with the stacks were made in a standing wave device filled with air at atmospheric pressure. The reported results confirm that some of the materials with high porosity can be an alternative to a traditional stack geometries and materials.

scholarly journals High-Temperature Particle Flow Testing in Parallel Plates for Particle-to-Supercritical CO2 Heat Exchanger Applications

2020 ◽  
Author(s):  
Hendrik F. Laubscher ◽  
Kevin J. Albrecht ◽  
Clifford K. Ho
Keyword(s):  
High Temperature ◽  
Heat Exchanger ◽  
Supercritical Co2 ◽  
Cost Effective ◽  
Particle Flow ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Parallel Plates ◽  
Design Work ◽  
Plate Spacing

Abstract Realizing cost-effective, dispatchable, renewable energy production using concentrated solar power (CSP) relies on reaching high process temperatures to increase the thermal-to-electrical efficiency. Ceramic based particles used as both the energy storage medium and heat transfer fluid is a promising approach to increasing the operating temperature of next generation CSP plants. The particle-to-supercritical CO2 (sCO2) heat exchanger is a critical component in the development of this technology for transferring thermal energy from the heated ceramic particles to the sCO2 working fluid of the power cycle. The leading design for the particle-to-sCO2 heat exchanger is a shell-and-plate configuration. Currently, design work is focused on optimizing the performance of the heat exchanger through reducing the plate spacing. However, the particle channel geometry is limited by uniformity and reliability of particle flow in narrow vertical channels. Results of high temperature experimental particle flow testing are presented in this paper.

Quantitative Visualization of the Thermoacoustic Effect

2010 ◽  
Author(s):  
Cila Herman
Keyword(s):  
Energy Conversion ◽  
Temperature Difference ◽  
Holographic Interferometry ◽  
High Speed ◽  
Noble Gases ◽  
Temperature Fields ◽  
Working Fluid ◽  
Parallel Plates ◽  
Acoustic Standing Wave ◽  
Thermoacoustic Effect

Thermoacoustic energy conversion was introduced into engineering systems during the past three decades as a new, alternative, environmentally safe energy conversion technology. It uses noble gases and mixtures of noble gases as working fluids rather than hazardous refrigerants required for the vapor compression cycle. A thermoacoustic system can operate both as a prime mover/engine (a temperature gradient and heat flow imposed across the stack lead to the generation of acoustic work/sound in the resonator) and, when reversing the thermodynamic cycle, as a refrigerator (acoustic work is used to pump heat from the low temperature reservoir and release it into a higher temperature ambient). Energy transport in thermoacoustic systems is based on the thermoacoustic effect. Using an acoustic driver, the working fluid in the resonance tube is excited to generate an acoustic standing wave. When introducing a stack of parallel plates of length Δx into the acoustic field at a suitable location, a temperature difference ΔT develops along the stack plates. This temperature difference is caused by the thermoacoustic effect. In this paper the thermoacoustic effect is visualized using real-time holographic interferometry combined with high-speed cinematography. In holographic interferometry both temperature and pressure variations impact the refractive index and both of these variations are present in our thermoacoustic system. In our analysis temperature variations are uncoupled from pressure variations to quantitatively visualize the oscillating temperature fields around the stack plate.

Experimental Investigation on the Performance of the Air-based Standing Wave Thermoacoustic Refrigerator using Heat Pipe as Heat Exchangers

2020 ◽  
Vol 28 (01) ◽  
pp. 2050007
Author(s):  
Praitoon Chaiwongsa ◽  
Somchai Wongwises
Keyword(s):  
Heat Exchanger ◽  
Standing Wave ◽  
Thermoelectric Module ◽  
Heat Pipes ◽  
Acoustic Power ◽  
Coefficient Of Performance ◽  
Cooling Load ◽  
Heat Absorber ◽  
Cooling Loads ◽  
Thermoacoustic Refrigerator

The coefficient of performance (COP) and relative coefficient of performance (COPR) of the standing wave thermoacoustic refrigerator (SWTAR) were investigated. The components of the SWTAR are a resonator tube, a stainless-steel bowl-shaped resonator cone, a commercial loudspeaker, a spiral stack, a cold side heat exchanger (CSHX) with miniature heat pipes (MHPs) and a hot side heat exchanger (HSHX). An operating frequency of 163[Formula: see text]Hz was used in this study, with an acoustic power (AP) supply of 10, 20 and 30[Formula: see text]W. Cooling loads were heat provided from a thermoelectric module (TEM) by joining the hot side of the TEM to the copper heat absorber and transferring heat to the CSHX through MHPs. The COP of the SWTAR increased with increasing cooling load. The slopes of the COP curves decreased with increasing AP. The COPR of the SWTAR increased with increasing cooling load until it was approximately 30% of AP.

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