Numerical analysis of the flow pathlines in thermo-acoustic couples
- Authors: Tartibu, L.K. , Kunene, T.
- Date: 2019
- Subjects: Thermo-acoustic , Heat transfer , Stack
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/401870 , uj:33606 , Citation: Tartibu, L.K. & Kunene, T. 2019. Numerical analysis of the flow pathlines in thermo-acoustic couples.
- Description: Abstract: Thermo-acoustic systems use a high amplitude sound-wave for refrigeration or electricity generation without the drawbacks of expensive construction, adverse environmental impact or high maintenance cost. The effective conversion of energy occurs within the “stack” considered as the heart of the system. The time-averaged rate of heat transfer across the edges of the stack is a good indicator of an effective performance. Hence, studying the effect of the geometry of the stack edges together with their locations is useful. Furthermore, current manufacturing practices make it possible to develop diverse stack edges, resulting in an improved efficiency of the heat transfer. For effective modelling of the heat transfer rate, a second-order, double-precision discretization of state variables and a laminar viscous model was used. A numerical model was developed using the commercial code FLUENT. The evolution of the flow vortices at different drive ratio was analyzed. Two edges shapes were considered namely rectangular and rounded edges. Using numerical analysis, this study has pointed out that stack edge profiles has a significant effect on the overall performance of thermo-acoustic systems. Rounding the stack edge profile appears to be beneficial for the system performance. This study point out the link between the non-linearity observed in thermo-acoustic systems, the flow streaming and the mean vorticity at the stack edges.
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Maximum cooling and maximum efficiency of thermoacoustic refrigerators
- Authors: Tartibu, L.K.
- Date: 2016
- Subjects: Thermoacoustic refrigerator, , Stack , Cooling load
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/92045 , uj:20178 , Citation: Tartibu, L.K. 2016. Maximum cooling and maximum efficiency of thermoacoustic refrigerators.
- Description: Abstract: This work provides valid experimental evidence on the difference between design for maximum cooling and maximum efficiency for thermoacoustic refrigerators. In addition, the influence of the geometry of the honeycomb ceramic stack on the performance of thermoacoustic refrigerators is presented as it affects the cooling power. Sixteen cordierite honeycomb ceramic stacks with square cross sections having four different lengths of 26 mm, 48 mm, 70 mm and 100 mm are considered. Measurements are taken at six different locations of the stack hot ends from the pressure antinode, namely 100 mm, 200 mm, 300 mm, 400 mm, 500 mm and 600 mm respectively. Measurement of temperature difference across the stack ends at steady state for different stack geometries are used to compute the cooling load and the coefficient of performance. The results obtained with atmospheric air showed that there is a distinct optimum depending on the design goal.
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Maximum cooling and maximum efficiency of thermoacoustic refrigerators
- Authors: Tartibu, L.K.
- Date: 2015
- Subjects: Thermoacoustic refrigerator , Stack , Cooling Load , Coefficient of performance
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/17735 , uj:15918 , ISSN: 0947-7411 , Citation: Tartibu, L.K. 2015. Maximum cooling and maximum efficiency of thermoacoustic refrigerators. Journal of Heat and Mass Transfer, 51(7): 901-1050. DOI: 10.1007/s00231-015-1599-y. , DOI: 10.1007/s00231-015-1599-y
- Description: Abstract: This work provides valid experimental evidence on the difference between design for maximum cooling and maximum efficiency for thermoacoustic refrigerators. In addition, the influence of the geometry of the honeycomb ceramic stack on the performance of thermoacoustic refrigerators is presented as it affects the cooling power. Sixteen cordierite honeycomb ceramic stacks with square cross sections having four different lengths of 26 mm, 48 mm, 70 mm and 100 mm are considered. Measurements are taken at six different locations of the stack hot ends from the pressure antinode, namely 100 mm, 200 mm, 300 mm, 400 mm, 500 mm and 600 mm respectively. Measurement of temperature difference across the stack ends at steady state for different stack geometries are used to compute the cooling load and the coefficient of performance. The results obtained with atmospheric air showed that there is a distinct optimum depending on the design goal.
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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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Impact of ceramic substrates geometry on the performance of simple thermo-acoustic engines
- Authors: Tartibu, L. K.
- Date: 2018
- Subjects: Thermo-acoustic engine , Ceramic substrate , Stack
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/281021 , uj:30225 , Citation: Tartibu, L.K. 2018. Impact of ceramic substrates geometry on the performance of simple thermo-acoustic engines.
- Description: Abstract: This work experimentally examines the influence of the stack geometry and position on the performance of thermo-acoustic engines (TAE). Twenty cordierite honeycomb ceramic stacks with square pores and five different lengths (7 mm, 13 mm, 17 mm, 22 mm and 25 mm) were considered. Measurements were taken at seven different locations of the stack hot ends from the pressure antinode (closed end), namely 52 mm, 72 mm, 92 mm,112 mm, 132 mm, 152 mm and 172 mm respectively. The temperature difference across the stack and radiated sound pressure level at steady state are considered indicators of the performance of the device...
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A sustainable solution for refrigeration using Thermo-acoustic technology
- Authors: Tartibu, L.K.
- Date: 2016
- Subjects: Thermo-acoustic refrigerator , Stack , Honeycomb ceramic
- Language: English
- Type: Conference proceedings
- Identifier: http://ujcontent.uj.ac.za8080/10210/390307 , http://hdl.handle.net/10210/217019 , uj:21586 , Citation: Tartibu, L.K. 2016. A sustainable solution for refrigeration using Thermo-acoustic technology.
- Description: Abstract: This work explores the use of thermo-acoustic coolers as alternative technology for refrigeration. A valid experimental evidence on the influence of the geometry of the honeycomb ceramic stack on the performance of thermosacoustic refrigerators is described. Sixteen cordierite honeycomb ceramic stacks with square cross sections having four different lengths of 26 mm, 48 mm, 70 mm and 100 mm are considered. Measurements are taken at six different locations of the stack hot ends from the pressure antinode, namely 100 mm, 200 mm, 300 mm, 400 mm, 500 mm and 600 mm respectively. Measurement of temperature difference across the stack ends at steady state for different stack geometries are used to measure the performance of the device. The results with atmospheric air demonstrates the influence of the stack geometry on the cooling power and shows that some its geometrical parameters are interdependent.
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