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Steady and Transient Critical Heat Fluxes on a Horizontal Cylinder in a Pool of Freon-113
Katasuya Fukuda and Qiusheng Liu

The study of steady and transient boiling heat transfer caused by an exponentially increasing heat input with time is important to the safety evaluation of reactivity accidents in water cooled nuclear reactors. Steady and transient critical heat fluxes were measured on 1.0 mm diameter horizontal cylinders with different surface conditions in a pool of Freon-113 for exponentially increasing heat inputs. The periods of exponentially increasing heat inputs ranged from about 20 ms to 20 s, and the pressures ranged from atmospheric up to 1082 kPa under saturated and subcooled conditions. Following results were obtained. (1) Steady critical heat flux under high pressure is dependent only on the degree of subcooling. (2) Transient critical heat flux can be classified into three regions, and also in every region, when system pressure is fixed, it is dependent on the degree of subcooling. (3) Steady and transient critical heat flux are influenced by the surface state.

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