Lexicographic multi-objective optimization of thermoacoustic refrigerator’s stack
- Authors: Tartibu, L.K. , Sun, B. , Kaunda, M.A.E.
- Date: 2015
- Subjects: Thermoacoustic , Stack , Cooling Load , Coefficient of performance , Multi-objective optimization , GAMS
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/17624 , uj:15907 , ISSN: 0947-7411 , Citation: Tartibu, L.K., Sun, B. & Kaunda M.A.E. 2015. Lexicographic multi-objective optimisation of thermoacoustic refrigerator’s stack. Journal of Heat and Mass Transfer. 51(5): 649-660. DOI: 10.1007/s00231-014-1440-z. , DOI: 10.1007/s00231-014-1440-z
- Description: Abstract: This work develops a novel mathematical programming model to optimize the performance of a simple thermoacoustic refrigerator (TAR). This study aims to optimize the geometric parameters namely the stack position, the stack length, the blockage ratio and the plate spacing involved in designing TARs. System parameters and constraints that capture the underlying thermoacoustic dynamics have been used to define the models. The cooling load, the coefficient of performance and the acoustic power loss have been used to measure the performance of the device. The optimization task is formulated as a three-criterion nonlinear programming problem with discontinuous derivatives (DNLP). Since we optimize multiple objectives simultaneously, each objective component has been given a weighting factor to provide appropriate user-defined emphasis. A practical example is given to illustrate the approach. We have determined a design statement of a stack describing how the geometrical parameters describing would change if emphasis is given to one objective in particular. We also considered optimization of multiple objectives components simultaneously and identify global optimal solutions describing the stack geometry using a lexicographic multiobjective optimization scheme. Additionally, this approach illustrates the difference between a design for maximum cooling and best coefficient of performance of a simple TAR.
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Experimental investigation of ceramic substrates in standing wave thermoacoustic refrigerator
- Authors: Alcock, A. C. , Tartibu, L. K. , Jen, T. C.
- Date: 2016
- Subjects: Thermoacoustic , Refrigeration , Ceramic substrates
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/223682 , uj:22499 , Citation: Alcock, A.C., Tartibu, L.K. & Jen, T.C. 2016. Experimental investigation of ceramic substrates in standing wave thermoacoustic refrigerator. International Conference on Sustainable Materials Processing and Manufacturing, SMPM 2017, 23-25 January 2017, Kruger National Park. DOI: 10.1016/j.promfg.2016.12.021. , ISSN: 2351-9789
- Description: Abstract: This work experimentally investigates the performance of ceramic substrates used as stacks in standing wave thermoacoustic coolers. Thermoacoustic technology is proposed in this study as an alternative sustainable solution to current issues with vapour compression refrigerators because of its environmentally friendlier attributes. However, the main hindrance to the expansion of this technology is its current lack of efficiency. Hence, an experimental investigation is conducted in this study. The influence of the geometrical configuration of the stack, described as the heart of the device, is investigated. The device was equipped with different selected low-cost porous materials (ceramic substrates) for performance testing and studies. Porosity, length and position of the ceramic substrates are variables that are considered in order to investigate the performance of the cooler. Eight cordierite honeycomb ceramic substrates with square cross sections and of four different lengths (26 mm, 48 mm, 70 mm and 100 mm) were considered. Five different stack positions, measured from the hot ends of the stack to the pressure antinode in increments of 100 mm, were investigated. Measurement of temperature difference at steady state was used to determine the performance of a particular configuration. Guidance on the design of this sustainable solution for refrigeration and selection of the best geometrical configuration of ceramic substrates are provided. In addition, clarity on the relation between the geometrical configurations and the frequencies of the sound wave is highlighted.
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Experimental investigation of an adjustable thermoacoustically-driven thermoacoustic refrigerator
- Authors: Alcock, A. C. , Tartibu, L. K. , Jen, T. C.
- Date: 2018
- Subjects: Thermoacoustic , Refrigeration , TADTAR
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/281227 , uj:30258 , Citation: Alcock, A.C., Tartibu, L.K. & Jen, T.C. 2018. Experimental investigation of an adjustable thermoacoustically-driven thermoacoustic refrigerator.
- Description: Abstract: An experimental investigation is conducted on a new adjustable thermoacoustically-driven thermoacoustic refrigerator (TADTAR). This refrigerator comprises of a thermoacoustic engine which drives a thermoacoustic refrigerator. This study aims to demonstrate the possibility to alter the TADTAR performance through the adjustment of specific design parameters. An adjustable resonator, which consisted of stacks, spacing couplings and shell-tube heat exchangers was designed and built. Six different honeycomb ceramic stacks were investigated. For each system, three different stack configuration were studied. Measurements of temperature difference across the refrigerator stack and sound pressure levels at steady states were used to determine the performance of the device. Through the adjustment of the length and the insertion of the heat exchanger, the performance of the device with a longer resonator was relatively higher. This study shows that an adjustable resonator successfully alters the frequency output of the thermoacoustic engine to match the frequency required by the thermoacoustic refrigerator and achieve resonance. In addition, this study demonstrates the possibility to change the geometrical configuration of the device and ultimately alter the performance of the TADTAR. Through the adjustment of the length of the resonator, this study shows that a single device could have different operating points. This creates new possibilities to introduce control system able to adjust the geometry of thermoacoustic system while in operation.
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