Wall boiling in a vertical annulus: Effect of inlet subcooling and mass flow rate

Abstract

Numerical studies on low flow rate convection boiling in a vertical annulus has been carried out to predict effects of inlet subcooling and mass flow rate. The aspect ratio of vertical annulus is 352 while the annular gap is 3.5 mm. RPI wall boiling model is used for the development of present code and the results are verified with those available in literature. The results show that onset of significant void (OSV) can be delayed to achieve maximum heat transfer by increasing the liquid subcooling and liquid mass flow rate. The average Nusselt number increases almost linearly with increase in the mass flow rate as well as the inlet subcooling. At high heat flux, very high wall temperatures are observed with low subcooling and low mass flow rates. This should be avoided for enhanced safety.