Abstract
A new approach to the model of natural convection from a horizontal, isothermal round plate and a simplified analytical solution of this model have been presented. In this model two separate regions with different fluid motions have been distinguished. In the first region, inside the boundary layer, the fluid flows concentrically towards the centre of the plate, while in the second one (stagnation region) the fluid is motionless. The presented theory has been verified experimentally.
Zusammenfassung
Ein neuer Lösungsweg für das Modell der freien Konvektion an einer isothermen, kreisförmigen, horizontalen Platte und eine vereinfachte analytische Lösung für dieses Modell werden hier vorgestellt. An diesem Modell wird zwischen zwei Bereichen mit verschiedenen Fluidbewegungen unterschieden. Im ersten Bereich, innerhalb der Grenzschicht, strömt das Fluid konzentrisch in Richtung Plattenmitte, während im zweiten Bereich (Stau-Bereich) die Flüssigkeit in Ruhe ist. Diese Theorie wurde experimentell überprüft.
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Abbreviations
- a=λ/c p ·ϱ :
-
thermal diffusivity
- A :
-
cross-section area (Fig. 2)
- A1:
-
control surface of the plate
- c p :
-
specific heat at constant pressure of the fluid
- D :
-
diameter of the plate
- F :
-
coefficient of boundary layer shape, def. (12)
- g :
-
gravitational acceleration
- h :
-
thickness of the tested fluid in experimental devices
- H :
-
height of a fluid column (see Fig. 3)
- i :
-
specific enthalpy
- K,K1:
-
constants (Eqs. 16 and 26)
- m :
-
mass flux
- Nu D =αD/λ :
-
Nu R =αR/λ — Nusselt numbers
- p :
-
pressure
- \(\dot q\) :
-
heat flux density
- Q :
-
heat flux
- R :
-
radius of the plate
- Ra D =g β ΔTD 3/(ν a):
-
Ra R =g β ΔTR 3/(ν α)Rayleigh numbers
- s :
-
radius of the free buoyant stream (see Fig. 2)
- s 1 :
-
radius of stagnation region
- T :
-
temperature
- W :
-
velocity
- x :
-
length of the boundary layer
- x :
-
horizontal coordinate to the surface
- y :
-
vertical coordinate to the surface
- α :
-
heat transfer coefficient
- β :
-
coefficient of volumetric expansion
- δ :
-
thickness of boundary layer
- δ s :
-
thickness of boundary layer at region of its transformation
- θ :
-
dimensionless temperature
- Δ :
-
difference
- λ :
-
thermal conductivity
- ν :
-
kinematic viscosity
- ϱ :
-
fluid density
- Φ :
-
coefficient defined by Eq. (35)
- cr:
-
critical
- w :
-
related to the wall
- x :
-
related to thex direction or to fluid properties inside boundary layer
- y :
-
related to they direction
- ∞:
-
fluid ambient condition
References
Lewandowski, W. M.; Kubski, P.: Methodical investigation of free convection from vertical and horizontal plates. Wärme-Stoffübertrag. 17 (1983) 147–157
Lewandowski, W. M.: Systematyczne badania przejmowania ciepła od płyty poziomej do ciezy w przestrzeni nieograniczonej w warunkach konwekcji natualnej (Systematic investigations of heat transfer from a horizontal plate to a fluid in an unlimited space in the conditions of natural convection) (1908), Doctor's Thesis, Techn. Univ. of Gdańsk
Lewandowski, W. M.: Wymiana ciepła od płaskich powierzchni w warunkach laminarnej konwekcji swobodnej (Heat transfer from flat surfaces under conditions of laminar free convection), Zesz. Nauk, Polit. Gdańsk, t. Mechanika-53, 412, 1–90
Lewandowski, W. M.; Kubski, P.: Effect of the use of the balance and gradient methods as a result of experimental investigation of natural convection action with regard to the conception and construction of measuring apparatus. Wärme-Stoffübertrag. 18 (1984) 247–256
Lewandowski, W. M.: The mechanism of natural convection heat transfer from isothermal vertical, horizontal and inclined plates. Arch. Thermod. 4 (1986) 235–255
Schmidt, E.; Beckman, W.: Das Temperatur- und Geschwindigkeitsfeld von einer wärmeabgebenden senkrechten Platte bei natürlicher Konvektion. Techn. Mech. Thermodyn. (1930) 341–391
Schmidt, E.: Forschung. 3 (1932) 181
Jaluria, Y.: Natural convection heat and mass transfer. Oxford: Pergamon 1980
Rotem, Z.; Claassen, L.: Natural convection above unconfined horizontal surfaces. J. Fluid Mech. 38 (1969) 173–192
Schmidt, E.: Proc. IV. Intern. Congr. for Applied Mech., Cambridge, (1934) 92–98
Fujii, T.; Imura, H.: Natural convection heat transfer from a plate with arbitrary inclination. Int. J. Heat Mass Transfer 15 (1972) 755–765
Kierkus, W.: An analysis of laminar free convection flow and heat transfer about an inclined isothermal plate. Int. J. Heat Mass Transfer 11 (1968) 241–253
Chen, T. S.; Tien, H. C.; Armaly, B. F.: Natural convection on horizontal and vertical plates with variable surface temperature or heat flux. Int. J. Heat Mass Transfer 29 (1986) 1465–1478
Chang, Keun-Shik; Han, Jn-Cheol: Natural convective heat transfer over inclined short plates. Communications in Applied Numerical Methods (1988) 665–673
Kubski, P.: Błonowa wymiana ciepła (Film heat transfer), Mat. Symp. Wym. Ciepła i Masy, Jabłonna (1979)
Takeuchi, M.; Heya, N.; Kimura, T.: Numerical analysis of natural convection from an upward-facing horizontal surface. Heat Transf. Japanese Research, 15 (1986) 17–30
Yu, W.-S.; Lin, H.-T.: Free convection heat transfer from an isothermal plate with arbitrary inclination. Wärme-Stoffübertrag. 23 (1988) 203–211
Goldstein, R. J.; Kei-Shun, Lau: Laminar natural convection from a horizontal plate and the influence of plate edge extensions. J. Fluid Mech. 129 (1983) 55–75
Takeuchi, M.; Ota, Y.; Tanaka, Y.: Laminar natural convection heat transfer from a flat plate in a thermally stratified fluid. Trans. Jap. Soc. Mech. Engers. 40 (1974) 1046
Kamal-Eldin, H.; Salah, A. M.: Natural convection from isothermal flat surfaces. Int. J. Heat Mass. Transfer. 13 (1970) 1873.
Al-Arabi, M., El-Riedy, M.: Natural convection heat transfer from isothermal horizontal plates of different plates of different shapes. Int. J. Heat Mass. Transfer 19 (1976) 1399
Ling, F. F.: A simple laboratory apparatus for measurements of natural convection heat transfer over a flat plate in vertical, inclined and horizontal positions. Int. J. Mech. Eng. Educ. 11 (1982) 245
Churchill, S. W.: Free convection around immersed bodies. Singlephase Convective Heat Transfer. New York: Hemisphere 1983
Singh, P.: Narayan, K. A.: Free convection heat transfer over a horizontal plate at low Prandtl number. Canadian J. Chem. Eng. 67 (1989) 507–512
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Lewandowski, W.M., Kubski, P. & Khubeiz, J.M. Natural convection heat transfer from round horizontal plate. Wärme- und Stoffübertragung 27, 281–287 (1992). https://doi.org/10.1007/BF01589965
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DOI: https://doi.org/10.1007/BF01589965