On the oscillatory instability of closed-loop thermosyphons
Abstract
The stability of natural convection flows in single-phase closed-loop thermosyphons is investigated. The thermosyphons considered in the present analysis are fluid-filled tubes bent into rectangular shapes. The fluid is heated over the lower horizontal segment and cooled over the upper horizontal segment. Analytical and numerical solutions are presented for a range of loop aspect ratios and radii for both laminar and turbulent flows. It is found that the steady-state results for thermosyphons with different aspect ratios and radii can be expressed in terms of a single dimensionless parameter. When this parameter is less than a critical value, the flow is always stable. Above this critical point, oscillatory instability exists for a narrow range of a friction parameter. The calculated neutral stability conditions show that the flow is least stable when the aspect ratio of the loop approaches unity. The frequency of the convection-induced oscillation is slightly higher than the angular frequency of a fluid particle traveling along the loop.
- Publication:
-
ASME Journal of Heat Transfer
- Pub Date:
- November 1985
- Bibcode:
- 1985ATJHT.107..826C
- Keywords:
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- Convective Flow;
- Convective Heat Transfer;
- Flow Stability;
- Free Convection;
- Pipe Flow;
- Thermosiphons;
- Laminar Flow;
- Oscillating Flow;
- Temperature Distribution;
- Turbulent Flow;
- Fluid Mechanics and Heat Transfer