scholarly journals Numerical Modeling and Performance Evaluation of Standing Wave Thermoacoustic Refrigerators with a Multi-Layered Stack

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4360
Author(s):  
Umar Nawaz Bhatti ◽  
Salem Bashmal ◽  
Sikandar Khan ◽  
Rached Ben-Mansour
Keyword(s):  
Standing Wave ◽  
Numerical Study ◽  
Temperature Drop ◽  
Acoustic Power ◽  
Heat Energy ◽  
Coefficient Of Performance ◽  
Material Layer ◽  
And Performance ◽  
Stacked Material ◽  
Thermoacoustic Refrigerators

Thermoacoustic refrigerators have huge potential to replace conventional refrigeration systems as an alternative clean refrigeration technology. These devices utilize conversion of acoustic power and heat energy to generate the desired cooling. The stack plays a pivotal role in the performance of Standing Wave Thermoacoustic Refrigerators (SWTARs), as the heat transfer takes place across it. Performance of stacks can be significantly improved by making an arrangement of different materials inside the stack, resulting in anisotropic thermal properties along the length. In the present numerical study, the effect of multi-layered stack on the refrigeration performance of a SWTAR has been evaluated in terms of temperature drop across the stack, acoustic power consumed and device Coefficient of Performance (COP). Two different aspects of multi-layered stack, namely, different material combinations and different lengths of stacked layers, have been investigated. The combinations of four stack materials and length ratios have been investigated. The numerical results showed that multi-layered stacks produce lower refrigeration temperatures, consume less energy and have higher COP value than their homogeneous counterparts. Among all the material combinations of multi-layered stack investigated, stacks composed of a material layer with low thermal conductivity at the ends, i.e., RVC, produced the best performance with an increase of 26.14% in temperature drop value, reduction in the acoustic power consumption by 4.55% and COP enhancement of 5.12%. The results also showed that, for a constant overall length, an increase in length of side stacked material layer results in an increase in values of both temperature drop and COP.

Effects of the Optimized Resonator Dimensions on the Performance of the Standing-Wave Thermoacoustic Refrigerator

2016 ◽  
Vol 819 ◽  
pp. 63-68
Author(s):  
Mawahib Hassan El-Fawal ◽  
Normah Mohd-Ghazali ◽  
Mohd Shafiek Yaccob
Keyword(s):  
Standing Wave ◽  
Cooling System ◽  
Small Diameter ◽  
Acoustic Power ◽  
Diameter Ratio ◽  
Coefficient Of Performance ◽  
Resonator Length ◽  
Environmentally Safe ◽  
And Performance ◽  
Thermoacoustic Refrigerator

Thermoacoustic refrigerator is an alternative cooling system, which is environmentally safe due to the absence of any refrigerants. The resonator tube of the system is of great importance; its design and dimensions influence the design and performance of the entire refrigerator. This work describes the design of the stack and the resonator along with the influence of its dimensions on the performance of the standing-wave thermoacoustic refrigerator. The resonator consists of two tubes, one larger than the other, characterized by the diameter ratio of the smaller over the larger diameter. A Lagrange multiplier method is used as a technique to optimize the coefficient of performance (COP) of the system. Results show that the resonator small diameter tube dissipates a minimum acoustic power at a diameter ratio of 0.46, which is 17 percent less than the published values. Moreover, the results show that the resonator length increases gradually with the increase of the mean design temperature which leads to the increase of the total acoustic power dissipated by the resonator, reducing the COP of the standing-wave thermoacoustic refrigerator.

scholarly journals Review of investigations in eco-friendly thermoacoustic refrigeration system

2017 ◽  
Vol 21 (3) ◽  
pp. 1335-1347 ◽  
Author(s):  
Ashish Raut ◽  
Uday Wankhede
Keyword(s):  
Research And Development ◽  
Ecological Impact ◽  
Acoustic Power ◽  
Heat Energy ◽  
Optimization Techniques ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Improve Heat Transfer ◽  
Thermoacoustic Effect ◽  
Thermoacoustic Refrigeration

To reduce greenhouse gas emissions, internationally research and development is intended to improve the performance of conventional refrigeration system also growth of new-fangled refrigeration technology of potentially much lesser ecological impact. This paper gives brief review of research and development in thermoacoustic refrigeration also the existing situation of thermoacoustic refrigeration system. Thermoacoustic refrigerator is a novel sort of energy conversion equipment which converts acoustic power into heat energy by thermoacoustic effect. Thermoacoustic refrigeration is an emergent refrigeration technology in which there are no moving elements or any environmentally injurious refrigerants during its working. The concept of thermoacoustic refrigeration system is explained, the growth of thermoacoustic refrigeration, various investigations into thermoacoustic refrigeration system, various optimization techniques to improve coefficient of performance, different stacks and resonator tube designs to improve heat transfer rate, various gases, and other parameters like sound generation have been reviewed.

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.

scholarly journals Heat Pump Bridge Analysis Using the Modified Energy Transfer Diagram

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 137
Author(s):  
Florian Schlosser ◽  
Heinrich Wiebe ◽  
Timothy G. Walmsley ◽  
Martin J. Atkins ◽  
Michael R. W. Walmsley ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Heat Pump ◽  
Heat Recovery ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Combined Application ◽  
Recovery Potential ◽  
Composite Curve ◽  
And Performance ◽  
The Individual

Heat pumps are the key technology to decarbonise thermal processes by upgrading industrial surplus heat using renewable electricity. Existing insight-based integration methods refer to the idealised Grand Composite Curve requiring the full exploitation of heat recovery potential but leave the question of how to deal with technical or economic limitations unanswered. In this work, a novel Heat Pump Bridge Analysis (HPBA) is introduced for practically targeting technical and economic heat pump potential by applying Coefficient of Performance curves into the Modified Energy Transfer Diagram (METD). Removing cross-Pinch violations and operating heat exchangers at minimum approach temperatures by combined application of Bridge Analysis increases the heat recovery rate and reduce the temperature lift to be pumped at the same time. The insight-based METD allows the individual matching of heat surpluses and deficits of individual streams with the capabilities and performance of different market-available heat pump concepts. For an illustrative example, the presented modifications based on HPBA increase the economically viable share of the technical heat pump potential from 61% to 79%.

scholarly journals Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 125
Author(s):  
Eduardo Freitas ◽  
Pedro Pontes ◽  
Ricardo Cautela ◽  
Vaibhav Bahadur ◽  
João Miranda ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Model ◽  
Heat Dissipation ◽  
Numerical Study ◽  
Pool Boiling ◽  
Temperature Drop ◽  
Surface Cooling ◽  
Average Temperature ◽  
Gold Silver

This study addresses the combination of customized surface modification with the use of nanofluids, to infer on its potential to enhance pool-boiling heat transfer. Hydrophilic surfaces patterned with superhydrophobic regions were developed and used as surface interfaces with different nanofluids (water with gold, silver, aluminum and alumina nanoparticles), in order to evaluate the effect of the nature and concentration of the nanoparticles in bubble dynamics and consequently in heat transfer processes. The main qualitative and quantitative analysis was based on extensive post-processing of synchronized high-speed and thermographic images. To study the nucleation of a single bubble in pool boiling condition, a numerical model was also implemented. The results show an evident benefit of using biphilic patterns with well-established distances between the superhydrophobic regions. This can be observed in the resulting plot of the dissipated heat flux for a biphilic pattern with seven superhydrophobic spots, δ = 1/d and an imposed heat flux of 2132 w/m2. In this case, the dissipated heat flux is almost constant (except in the instant t* ≈ 0.9 when it reaches a peak of 2400 W/m2), whilst when using only a single superhydrophobic spot, where the heat flux dissipation reaches the maximum shortly after the detachment of the bubble, dropping continuously until a new necking phase starts. The biphilic patterns also allow a controlled bubble coalescence, which promotes fluid convection at the hydrophilic spacing between the superhydrophobic regions, which clearly contributes to cool down the surface. This effect is noticeable in the case of employing the Ag 1 wt% nanofluid, with an imposed heat flux of 2132 W/m2, where the coalescence of the drops promotes a surface cooling, identified by a temperature drop of 0.7 °C in the hydrophilic areas. Those areas have an average temperature of 101.8 °C, whilst the average temperature of the superhydrophobic spots at coalescence time is of 102.9 °C. For low concentrations as the ones used in this work, the effect of the nanofluids was observed to play a minor role. This can be observed on the slight discrepancy of the heat dissipation decay that occurred in the necking stage of the bubbles for nanofluids with the same kind of nanoparticles and different concentration. For the Au 0.1 wt% nanofluid, a heat dissipation decay of 350 W/m2 was reported, whilst for the Au 0.5 wt% nanofluid, the same decay was only of 280 W/m2. The results of the numerical model concerning velocity fields indicated a sudden acceleration at the bubble detachment, as can be qualitatively analyzed in the thermographic images obtained in this work. Additionally, the temperature fields of the analyzed region present the same tendency as the experimental results.

scholarly journals Thermoacoustic-Stirling Heat Pump for Domestic Applications

2010 ◽  
Author(s):  
Srinivas Vanapalli ◽  
M. E. H. Tijani ◽  
Simon Spoelstra
Keyword(s):  
Performance Analysis ◽  
The Netherlands ◽  
Heat Pump ◽  
Linear Motor ◽  
Energy Resources ◽  
Coefficient Of Performance ◽  
Energy Usage ◽  
Domestic Heating ◽  
Work Input ◽  
And Performance

Domestic heating contributes to a significant amount of energy usage in the Netherlands. Due to scare energy resources, attention to develop new and efficient technologies is increasing. At ECN, a burner driven heat pump employing thermoacoustic technology is being developed for possible applications in households and offices. The desired temperature lift is from 10 °C to 80 °C. As a first step the heat pump is driven by a linear motor. Measurements and performance analysis of the heat pump are presented in this paper. The heat pump has a coefficient of performance which is the ratio of heat produced to the work input of 1.38 when operating between 10 °C to 80 °C. The performance relative to maximum possible Carnot value is 26.5%.

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