An experimental study on CHF in pool boiling system with SA508 test heater under atmospheric pressure

In this study, pool boiling CHF experiments under atmospheric pressure with SA508 test heater was performed. SA508 is the material of the reactor pressure vessel in a nuclear power plant. Therefore, the CHF behavior of SA508 material is important for the reactor pressure vessel integrity at accident, but there are few studies about that. SA508 material showed very different CHF behavior from other cases (stainless steel). It showed very higher CHF value and the test heater surface was changed significantly. This test heater surface change is due to corrosion of SA508, and the rate of corrosion increases with boiling time. The corrosion product is analyzed as magnetite (Fe3O4), and magnetite has been used as one of nanofluid for CHF enhancement. The size of magnetite produced on the test heater surface is 20–140 nm, that is, it is nanoscale. Therefore, the CHF enhancement mechanism of SA508 material is similar to the case using other test heater (like stainless steel) with magnetite nanofluid. Additives like TSP, Al2O3 and CNT nanoparticles are also tested, but they did not show the CHF enhancement effect. In case of TSP, it showed CHF decrease effect due to preventing effect on SA508 corrosion.

► Pool boiling CHF experiment was performed with several fluids under atmospheric pressure.
► The test specimen (50 mm × 10 mm × 0.7 mm) is made of SA508 Grade 3 Class 1.
► SA508 showed much higher CHF value than SS304.
► Corrosion of SA508 is the reason of the CHF enhancement.
► All additives showed little CHF enhancement effects.