Abstract
The essentials of the theory of fractals and chaos are reviewed and then applied to the problem of density-wave oscillations in a boiling channel. It is shown that these mathematical techniques give valuable new insight into nonlinear thermal-hydraulic oscillations.
Zusammenfassung
Die entscheidenden Formeln der Fraktal- und Chaostheorie wurden nochmals aufgezeigt und anschließend auf das Problem der zeitlich veränderten Dichtewellen in einem Siedekanal angewandt. Es wurde gezeigt, daß beide mathematische Verfahren einen wertvollen neuen Einblick in nicht lineare thermisch-hydraulische Schwingungen geben.
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Abbreviations
- A x−s :
-
Heated channel cross sectional area
- A R :
-
Riser cross sectional area
- c pf :
-
Liquid specific heat
- D :
-
Channel diameter
- D c :
-
Correlation dimension
- E :
-
Energy
- f :
-
Friction coefficient
- g :
-
Gravity
- h :
-
Specific enthalpy
- h fg :
-
Latent heat of vaporization
- h f :
-
Liquid enthaly
- K :
-
Loss coefficient
- L :
-
Channel length
- M :
-
Mass
- M 2 :
-
Two-phase mass in the heated channel
- N s :
-
Number of nodes in the subcooled region
- N R :
-
Number of nodes in the riser
- P H :
-
Heated perimeter
- p :
-
Pressure
- Δp :
-
Pressure drop
- q″:
-
Heat flux
- q :
-
Total power
- t :
-
Time
- u :
-
Velocity
- v f :
-
Specific voluje of the liquid
- v fg :
-
Liquid to vapor specific volume difference
- w :
-
Mass flow rate
- z :
-
Space variable
- β :
-
Liquid thermal expansion coefficient, − 1/ϱ ∄ϱ/∄T
- δ x :
-
Perturbation,x(t)−x 0
- ϱ :
-
Density
- ϱ f :
-
Liquid density
- Ω :
-
Characteristic frequency
- λ :
-
Boiling boundary
- a :
-
Acceleration head
- ch:
-
Channel
- D :
-
Downcomer
- e :
-
Channel exit
- ext:
-
External
- f :
-
Friction head
- i :
-
Channel inlet
- I :
-
Inertial head
- g :
-
Gravity head
- n :
-
nth subcooled node
- ref:
-
Reference value
- R :
-
Riser
- 2φ :
-
Two-phase
- 0:
-
Steady-state
- \(N_{p{\text{ch}}} = \frac{{q_0 }}{{w_0 }}\frac{{v_{fg} }}{{h_{fg} v_f }}\) :
-
(Phase change number)
- \(N_{{\text{sub}}} = \frac{{(h_f - h_i )}}{{h_{fg} }}\frac{{v_{fg} }}{{v_f }}\) :
-
(Subcooling number)
- \(Fr = \frac{{u_{i_c }^2 }}{{gL_H }}\) :
-
(Froude number)
- Λ =fL/2D :
-
(Friction number)
- \(b = \frac{{\beta h_{fg} v_f }}{{c_{pf} v_{fg} }}\) :
-
(Thermal expansion number)
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Dedicated Prof. Dr.-Ing. F. Mayinger's 60th birthday
t + =t/v
\(v{\text{ }} = {\text{ }}\frac{{N_{sub} }}{{N_{pch} }}\frac{L}{{u_{i_0 } }} = \lambda _0 /u_{i_0 }\)
M + =M/(ϱ f LA x−s)
z + =z/L
A + R =A R/A x−s
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Lahey, R.T. An application of fractal and chaos theory in the field of two-phase flow & heat transfer. Wärme- und Stoffübertragung 26, 351–363 (1991). https://doi.org/10.1007/BF01591668
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DOI: https://doi.org/10.1007/BF01591668