Comparison of CHF data for water and R-134a using the fluid-to-fluid modeling methods

The CHF experiments in tubes and annulus cooled with HFC-134a have been performed. The objective of this study is to provide the applicable ranges of the existing fluid-to-fluid modeling techniques of CHF for HFC-134a. The HFC-134a and water CHF data have been compared by applying the Ahmad and the Katto modeling parameters. The flow parameter ranges of the HFC-134a CHF data used in the comparison are pressures of 1.40 ∼2.66 MPa (equivalent 8.58 ∼ 15.46 MPa in water), mass fluxes of 150 ∼ 3500 kg/m2s and inlet qualities of -0.448 ∼ -0.09. The water CHF data in annulus that were obtained from the experiments in the same geometry with the test section in the HFC-134a experiments were used. For mass fluxes from 710 to 3500 kg/m2s in tubes, the CHF data for HFC-134a and water fall closely on the same curve for the dimensionless CHF vs. the Ahmad and the Katto modeling parameters. For mass fluxes below 600 kg/m2s in annulus, the dimensionless CHFs as a function of the Ahmad and the Katto modeling parameters show a large difference between the HFC-134a and water. The Katto and the Ahmad modeling parameters cannot be correlated with the dimensionless CHF data for HFC-134a and water on the same curve in low mass flux and high quality conditions. (author)