Why oxides intensify spray cooling?

Why oxides intensify spray cooling?

Abstract

Spray cooling is a typical technique used in heat treatment and other metallurgical processes where controlled temperature regimes are required. Cooling intensity is primarily affected by spray parameters as pressure and coolant impingement density. It is not frequently reported but even thin layers of oxides can significantly modify the cooling intensity. This effect is dominant in the cooling of steel surfaces at high surface temperatures. Experimental investigation comparing the cooling of scale-free surfaces and oxidized surfaces show a difference in 50-80% in the cooling intensity. Even a scale layer of several microns can significantly modify the cooling intensity. A low thermal conductivity of the oxides makes the cooling more intensive. The paper provides experimental evidence of this fact and explains the mechanism of spray cooling with boiling. The Leidenfrost phenomenon and change in surface temperature provides key to the explanation why the hot surface covered by the oxides is frequently cooled more intensively than the clean surface.

Spray cooling is a typical technique used in heat treatment and other metallurgical processes where controlled temperature regimes are required. Cooling intensity is primarily affected by spray parameters as pressure and coolant impingement density. It is not frequently reported but even thin layers of oxides can significantly modify the cooling intensity. This effect is dominant in the cooling of steel surfaces at high surface temperatures. Experimental investigation comparing the cooling of scale-free surfaces and oxidized surfaces show a difference in 50-80% in the cooling intensity. Even a scale layer of several microns can significantly modify the cooling intensity. A low thermal conductivity of the oxides makes the cooling more intensive. The paper provides experimental evidence of this fact and explains the mechanism of spray cooling with boiling. The Leidenfrost phenomenon and change in surface temperature provides key to the explanation why the hot surface covered by the oxides is frequently cooled more intensively than the clean surface.

scale cooling, cooling intensification, experimental research

scale cooling, cooling intensification, experimental research

RAUDENSKÝ, M.; HNÍZDIL, M.; KOTRBÁČEK, P.

2013

18.12.2012

Paris

The 30th International Steel Industry Conference in Paris

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