Critical heat flux on a vertical surface in saturated pool boiling at high pressures

Abstract

This paper investigates the CHF in saturated pool boiling of ethanol, R141b, and water on a 7 mm diameter vertical copper surface at high pressures. The pressures are from 0.1 to 3 MPa for ethanol, 0.1 to 1.5 MPa for R141b, and 0.1 to 0.8 MPa for water. The results show that the occurrence of CHF is accompanied by the formation of large vapor masses covering most of the heating surface with all three liquids over the whole range of pressures investigated here. The well-known Kutateladze-type CHF correlation explains the variations in the CHF with pressure well for ethanol and R141b, and underestimates the pressure dependence of the CHF for water. A correlation considering the effect of surface wettability on the CHF agrees fairly well with the CHF for water in the whole range of pressures here, when the temperature dependence of the contact angle determined from available data is incorporated into the correlation. This suggests that it is necessary to consider changes in surface wettability with pressure to be able to predict the CHF of water at high pressures.

Coolability of a Corium Pool in a Debris Bed -- Impact of Debris Size, Steam and Liquid Flowrate, Tilting Angle and Pressure on Critical Heat Flux (CHF)

“…We apply that correlation to a situation where a spherical molten pool of radius R is surrounded by a debris bed of porosity 0.4 and debris size 4mm. Although our results are only available up to 2 bar, the correlation is extended to higher pressure (5 bar): this may be partly justified by the similar correlation found by Sakashita [16] up to 6 bar. The corium pool is discretized in a series of layers of thickness h and the interface between the molten pool and the debris bed is located at a position (R,𝜃) or, equivalently (r,z) where r and z are respectively the radius and the elevation of the layer.…”

“…Sakashita (Fig. 10 of [16]) reports CHF data for water higher than Zuber and Lienard and Dhir predictions assuming P 0.5 dependency. The author explains that this gap is well addressed by taking wettability effects into account.…”

“…As recalled in Sakashita [16], Kutateladze-type CHF correlation indicates that CHF varies as s 0.5 , i.e. as P 0.5 .…”

“…Sakashita [16] studied the CHF dependency on pressure. He and some other authors he cites showed that CHF behavior with pressure agrees quite well for liquids other than water.…”

Molecular Dynamics Study on the Wettability of the Lithium Droplet and Tungsten Surface

“…In some wettability-related studies, most use liquid water as the research object to observe the contact angle, whether experimentally or numerically. For example, Sakashita considered the surface of nickel-plated copper sheets at different temperatures and pressures. Hayashi et al , and Hirose et al researched it near the operating conditions of a pressurized water reactor.…”