Experimental Study on Critical Heat Flux (CHF) in a R134a Cooled Vertical Tube at High Pressures

An experimental study of critical heat flux (CHF) in a R134a cooled vertical tube was performed with a wide set of parameters. The experiments were conducted at 2.8, 3.3, 3.8 and 4 MPa, mass fluxes of 500-4000 kg/m²s and inlet temperatures of 23-81 °C in a uniformly heated tube with 10 mm inside diameter and a heating length of 2495 mm. The parametric trends of CHF show a general agreement with previous understanding in water. The experimental results were compared with the correlation of Katto & Ohno. It was found that the correlation can predict the present experimental results well except for low mass fluxes, but even at high pressures near the critical pressure. Scaling laws were applied to convert the experimental results to water equivalent conditions. The comparison with the water standard CHF look-up table shows a good agreement. Therefore R134a can be used as a modeling fluid for predicting CHF in water for the investigated geometric and parametric conditions.