Heat and mass transfer for a small diameter thermosyphon with low fill ratio
Thermosyphons of smaller dimensions are more commonly sought after as electronics cooling devices. The interactions of the tube wall and working fluid become more significant as the dimension of a thermosyphon is reduced, particularly for high surface tension fluids such as water. This paper aims to...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2020-02-01
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| Series: | International Journal of Thermofluids |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2666202719300102 |
| _version_ | 1819298029990051840 |
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| author | Anthony J. Robinson Kate Smith Turlough Hughes Sauro Filippeschi |
| author_facet | Anthony J. Robinson Kate Smith Turlough Hughes Sauro Filippeschi |
| author_sort | Anthony J. Robinson |
| collection | DOAJ |
| description | Thermosyphons of smaller dimensions are more commonly sought after as electronics cooling devices. The interactions of the tube wall and working fluid become more significant as the dimension of a thermosyphon is reduced, particularly for high surface tension fluids such as water. This paper aims to experimentally investigate a water-charged, small diameter (8 mm) thermosyphon as it operates with a low (25%) filling ratio for a relatively long evaporator length of 200 mm. High speed videography provides in-situ flow pattern visualization at different heat input power. The boiling regimes for each level of heat flux are determined by analyzing the flow patterns from the high-speed video footage. The interdependence of the flow regimes and the heat and mass transfer mechanisms is evaluated using the measured wall temperature variations and derived thermosyphon performance metrics, such as the average heat transfer coefficients and thermal resistances. It was observed that the heat and mass transport was dominated by Geyser-type boiling at lower heat fluxes with associated low heat transfer coefficients in the evaporator and condenser. With increasing thermal power, less liquid was observed to return to the evaporator resulting in more aggressive boiling events which improved the heat transfer coefficients in both the evaporator and condenser. For all power levels tested, the dominant thermal resistance was found to be that associated with the condenser. The ultimate failure of the thermosyphon was a result of liquid hold-up in the condenser section and subsequent falling liquid film and evaporator dryout. |
| first_indexed | 2024-12-24T05:23:25Z |
| format | Article |
| id | doaj.art-ac3b3663afe3428b9c472b82b4c506f0 |
| institution | Directory Open Access Journal |
| issn | 2666-2027 |
| language | English |
| last_indexed | 2024-12-24T05:23:25Z |
| publishDate | 2020-02-01 |
| publisher | Elsevier |
| record_format | Article |
| series | International Journal of Thermofluids |
| spelling | doaj.art-ac3b3663afe3428b9c472b82b4c506f02022-12-21T17:13:24ZengElsevierInternational Journal of Thermofluids2666-20272020-02-011100010Heat and mass transfer for a small diameter thermosyphon with low fill ratioAnthony J. Robinson0Kate Smith1Turlough Hughes2Sauro Filippeschi3Department of Mechanical and Manufacturing Engineering, Trinity College Dublin, Dublin D2, Ireland; Corresponding author.Department of Mechanical and Manufacturing Engineering, Trinity College Dublin, Dublin D2, IrelandDepartment of Mechanical and Manufacturing Engineering, Trinity College Dublin, Dublin D2, IrelandDepartment of Energy, Systems, Land and Constructions Engineering, University of Pisa, Pisa, ItalyThermosyphons of smaller dimensions are more commonly sought after as electronics cooling devices. The interactions of the tube wall and working fluid become more significant as the dimension of a thermosyphon is reduced, particularly for high surface tension fluids such as water. This paper aims to experimentally investigate a water-charged, small diameter (8 mm) thermosyphon as it operates with a low (25%) filling ratio for a relatively long evaporator length of 200 mm. High speed videography provides in-situ flow pattern visualization at different heat input power. The boiling regimes for each level of heat flux are determined by analyzing the flow patterns from the high-speed video footage. The interdependence of the flow regimes and the heat and mass transfer mechanisms is evaluated using the measured wall temperature variations and derived thermosyphon performance metrics, such as the average heat transfer coefficients and thermal resistances. It was observed that the heat and mass transport was dominated by Geyser-type boiling at lower heat fluxes with associated low heat transfer coefficients in the evaporator and condenser. With increasing thermal power, less liquid was observed to return to the evaporator resulting in more aggressive boiling events which improved the heat transfer coefficients in both the evaporator and condenser. For all power levels tested, the dominant thermal resistance was found to be that associated with the condenser. The ultimate failure of the thermosyphon was a result of liquid hold-up in the condenser section and subsequent falling liquid film and evaporator dryout.http://www.sciencedirect.com/science/article/pii/S2666202719300102Flow regimesFlow visualizationHeat transferReflux Thermosyphon |
| spellingShingle | Anthony J. Robinson Kate Smith Turlough Hughes Sauro Filippeschi Heat and mass transfer for a small diameter thermosyphon with low fill ratio International Journal of Thermofluids Flow regimes Flow visualization Heat transfer Reflux Thermosyphon |
| title | Heat and mass transfer for a small diameter thermosyphon with low fill ratio |
| title_full | Heat and mass transfer for a small diameter thermosyphon with low fill ratio |
| title_fullStr | Heat and mass transfer for a small diameter thermosyphon with low fill ratio |
| title_full_unstemmed | Heat and mass transfer for a small diameter thermosyphon with low fill ratio |
| title_short | Heat and mass transfer for a small diameter thermosyphon with low fill ratio |
| title_sort | heat and mass transfer for a small diameter thermosyphon with low fill ratio |
| topic | Flow regimes Flow visualization Heat transfer Reflux Thermosyphon |
| url | http://www.sciencedirect.com/science/article/pii/S2666202719300102 |
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