Abstract
This paper is concerned with melting of a vertical ice layer adhering to the substrate by using radiating heat source of halogen lamps having a large fraction of short wave beam or nichrome heater having a comparatively large fraction of long wave one. From the present experimental results, it can be seen that the heating of short wave radiation produces a peculiar melting behavior of strongly rough melting-surface due to the internal melting at the grain boundary of ice-surface. On the other hand, for the case of long wave radiation the melting-surface becomes very smooth. The melting rate of clear ice layer by short wave radiation obtained from halogen lamps is smaller than that of cloudy ice layer due to the good penetration of short wave fraction through the clear ice layer. Moreover, the raising of temperature of ice-substrate interface could offer a feasibility of removing ice layer from the structure subject to atmospheric icing. Concludingly, it is clarified that the melting rate of ice layer could be predicted numerically by using the band model of extinction coefficient or absorption coefficient presented in this study.
Zusammenfassung
Diese Arbeit behandelt das Schmelzen einer senkrechten Eisschicht auf einer Unterlage mit Hilfe von Halogen-Lampen mit einem hohen Anteil an kurzen Wellen und Nichromheizern mit einem hohen Anteil an langen Wellen. Aus diesen Versuchen läßt sich ableiten, daß die Heizung durch kurzwellige Strahlung ein eigentümliches Schmelzverhalten mit sehr rauher Oberfläche hervorruft, verursacht durch Schmelzen an den Korngrenzen der Eisoberfläche. Bei langwelliger Heizung wird die Oberfläche sehr glatt. Die Abschmelzrate einer Klareisschicht bei kurzwelliger Heizung durch Halogen-Lampen ist geringer als die einer Opaleisschicht wegen des besseren Eindringens der kurzen Wellen in das klare Eis. Der Temperaturanstieg an der Grenze Eis — Unterlage bietet die Möglichkeit der Enteisung von Bauteilen, die der atmosphärischen Vereisung ausgesetzt sind. Es folgt, daß die Abschmelzrate einer Eisschicht, numerisch vorausberechnet werden kann, indem man das Bandmodell des Extinktions- und des Absorptionskoeffizienten dieser Arbeit verwendet.
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Abbreviations
- A:
-
transmission, defined in equation (4)
- aν :
-
monochromatic absorption coefficient of clear ice
- C:
-
constant
- Eb :
-
monochromatic emissive power
- hi :
-
thickness of ice layer
- hin :
-
initial thickness of ice layer
- hm :
-
thickness of substrate
- k0 :
-
extinction coefficient for h0 → 0
- ks :
-
modified extinction coefficient
- kν :
-
monochromatic extinction coefficient
- Li :
-
latent heat of melting
- n:
-
index number, defined in equation (2)
- \(q_{h_i }\) :
-
heat flux absorbed at surface of substrate
- qr0 :
-
radiant heat flux impinged onto ices-urface
- qri{y}:
-
radiant heat flux in ice layer
- S:
-
distance from initial ice-surface to transient melting-surface
- Tb :
-
temperature of radiating heat source
- Ti :
-
temperature in ice layer
- Tm :
-
temperature in substrate
- T∞ :
-
environmental temperature
- T1 :
-
temperature of surface of ice layer
- T2 :
-
temperature of substrate-surface
- T3 :
-
temperature of back side surface of substrate
- t:
-
time
- y:
-
distance from initial ice-surface
- Z:
-
ratio of backward radiative heat flux to forward one for cloudy ice
- α :
-
heat transfer coefficient
- χi :
-
thermal diffusivity of ice
- χm :
-
thermal diffusivity of substrate
- λi :
-
thermal conductivity of ice
- λm :
-
thermal conductivity of substrate
- υ:
-
wavelength
- υc :
-
critical wavelength
- ρi :
-
density of ice
- σ:
-
Stefan-Boltzmann constant
References
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Seki, N., Sugawara, M. & Fukusako, S. Radiative melting of ice layer adhering to a vertical surface. Warme- und Stoffubertragung 12, 137–144 (1979). https://doi.org/10.1007/BF01002329
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DOI: https://doi.org/10.1007/BF01002329