• Raudenský, Miroslav
• Chabičovský, Martin
• Kotrbáček, Petr

Abstract

Spray cooling is a common cooling method in the steel industry and especially in the heat treatment and quenching of steel products and components. The water is sprayed on the hot surface by the nozzle which transforms the water stream into droplets. Sprays can provide very high cooling rates with the benefit of the regulation of the cooling process. The proper cooling regime is crucial for obtaining required mechanical properties after quenching. The spray cooling of hot steel surfaces (presence of boiling) is influenced by several parameters. They can be divided into two groups. The first group deals with spray parameters like water impact density, water temperature, water additives and droplets size. The second group relates to cooled surface: temperature, velocity, roughness and presence of scales. The key factors are the water impact density and cooled surface temperature. Number of factors makes the numerical prediction of the cooling intensity (heat transfer coefficient) complicated and so the laboratory measurement which includes mentioned factors is a way how to obtain exact value of the heat trůansfer coefficient for spray cooling of hot surfaces. The exact knowledge of the temperature dependent heat transfer coefficient is crucial for numerical simulations of the cooling process which allows proper design (sizing) of spray quenching units. This paper describes non-stationary spray cooling laboratory measurement and deals with factors influencing the spray cooling. The influence of each factor is experimentally investigated and the influence on the heat transfer coefficient is described.

Topics

• density
• impedance spectroscopy
• surface
• simulation
• steel
• quenching