Linear Stabitlity Analysis of a Supercritical Loop. T'Joen, C., G., A., Rohde, M., & De Paepe, M. In 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics (HEFAT 2012), pages 242-250, 2012. International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics.
abstract   bibtex   
Because of their unique properties, supercritical fluids are becoming increasingly popular for industrial applications. These fluids behave liquid like at low temperatures and gas like at higher temperatures, with a smooth transition in between. This makes them very suited as a solvent for chemical extraction and separation processes. Another important use is as a power fluid. Modern fossil fuel fired power plants all operate using supercritical water, and on a smaller power scale they are considered for organic rankine cycles and refrigeration. As they heat up, the density of a supercritical fluid changes shows a very sharp drop for temperatures close to the critical point. This large density difference can be used as the driving force to circulate the fluid in a loop, rather than using a pump. This idea is similar to natural circulation boiling loops, but the density difference is larger. It adds a layer of inherent safety to a design, as active components such as pumps are no longer required; but also adds an additional complexity: flow instabilities. It is well known from natural circulation boiling systems, that these loops can become unstable under certain conditions (e.g. high power and low flow rate). In this study, a simple supercritical loop is studied to determine the neutral stability boundary. This is done through linear stability analysis: the set of one-dimensional governing equations is first linearised and then the eigenvalues are determined. These describe the response, indicating if it is stable or not. The results indicate that there is a clear unstable area, which can be linked to different types of instabilities.
@inproceedings{
 title = {Linear Stabitlity Analysis of a Supercritical Loop},
 type = {inproceedings},
 year = {2012},
 pages = {242-250},
 issue = {July},
 publisher = {International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics},
 city = {Malta LB  - t2012linear},
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 last_modified = {2018-10-02T09:30:05.765Z},
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 citation_key = {TJoen2012},
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 abstract = {Because of their unique properties, supercritical fluids are becoming increasingly popular for industrial applications. These fluids behave liquid like at low temperatures and gas like at higher temperatures, with a smooth transition in between. This makes them very suited as a solvent for chemical extraction and separation processes. Another important use is as a power fluid. Modern fossil fuel fired power plants all operate using supercritical water, and on a smaller power scale they are considered for organic rankine cycles and refrigeration. As they heat up, the density of a supercritical fluid changes shows a very sharp drop for temperatures close to the critical point. This large density difference can be used as the driving force to circulate the fluid in a loop, rather than using a pump. This idea is similar to natural circulation boiling loops, but the density difference is larger. It adds a layer of inherent safety to a design, as active components such as pumps are no longer required; but also adds an additional complexity: flow instabilities. It is well known from natural circulation boiling systems, that these loops can become unstable under certain conditions (e.g. high power and low flow rate). In this study, a simple supercritical loop is studied to determine the neutral stability boundary. This is done through linear stability analysis: the set of one-dimensional governing equations is first linearised and then the eigenvalues are determined. These describe the response, indicating if it is stable or not. The results indicate that there is a clear unstable area, which can be linked to different types of instabilities.},
 bibtype = {inproceedings},
 author = {T'Joen, C G A and Rohde, M and De Paepe, M},
 booktitle = {9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics (HEFAT 2012)}
}

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