Fluid-to-Fluid modelling of CHF at High-Pressure subcooled water conditions

An experiment was carried out to obtain data on critical heat flux (CHF) in an 8-mm vertical heated tube cooled with Refrigerant (R-134a) at high-pressure subcooled and low-quality conditions. Parametric trends of the CHF data were examined and have been shown consistent with those obtained in experiments with water flow. Variations of CHF depends mainly on local flow conditions and the length effect appears to be diminished at length-to-diameter (L/D) ratios from 30 to 200. The Katto scaling law has been shown applicable for transforming R-134a CHF values into water CHF values at subcooled and low-quality conditions. The R-134a CHF data have been transformed using the Katto fluid-to-fluid scaling law and assessed against the water CHF values obtained from the 2006 CHF look-up table (LUT-2006). The results showed that the LUT-2006 is conservative and need further development.