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Abstract
Pool boiling critical heat flux (CHF) has been measured for pentane, hexane, methanol, FC-72, FC-87, and R113 on a 25.4 mm diameter smooth brass horizontal surface at five different reduced pressures ranging from 0.01to 0.24. The CHF data are compared with various established CHF models as well as the new mechanistic CHF lift-off model recently proposed by the authors. The dependence of CHF on pressure is examined, and it is found that the lift-off model gives a reasonably good prediction of changes in CHF with step changes in the reduced pressure. The R113 and FC-72 boiling curves suggest that a partially wetting transition boiling regime is encountered just prior to CHF.
Highlights
Critical heat flux (CHF) is the maximum heat flux that can be applied to a boiling system while operating in the nucleate boiling heat transfer regime
In the early work of Guan et al (2011) pool boiling curves and critical heat flux (CHF) data were measured for pentane, hexane, and FC-72 at three different pressures
Horizontal saturated pool boiling curves and CHF are measured for pentane, hexane, methanol, FC-72, FC-87, and R113 at five different operating pressures ranging from 100 to 450 kPa
Summary
Critical heat flux (CHF) is the maximum heat flux that can be applied to a boiling system while operating in the nucleate boiling heat transfer regime. Once the applied heat flux exceeds CHF, a vapor film will blanket the heating surface and create substantial resistance to heat transfer. Haramura and Katto (1983) postulated that CHF occurs when the heat flux is sufficient to fully evaporate the liquid macro layer, and their well known model takes the form, q"CHF , Ka tto q"CHF , Zu b er. Guan et al (2011) introduced a new horizontal pool boiling CHF model that is based on a liquid macrolayer lift-off mechanism. The liquid macrolayer lift-off model introduced by Guan, et al (2011) unifies the horizontal CHF mechanism with that for both flow boiling and vertical pool boiling
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