Flow Boiling and Pressure Drop Measurements for R134a/Oil Mixtures Part 2: Evaporating in a Plain Tube.
Intube flow boiling experiments for refrigerant R-134a mixed with a lubricating oil are reported for a plain, horizontal tube. The tests were run at a nominal inlet pressure of 3.4 bar over a wide range of vapor qualities at mass velocities of 100, 200, and 300 kg/m2s (73.5, 147 and 220.5 thousands of lb/h ft2) for inlet oil concentrations from 0-5 wt.% oil. At low to intermediate vapor qualities (0.2 <x< 0.60), the oil tended to increase the local boiling coefficient while significant deterioration in boiling performance occurred at high vapor qualities for the higher concentrations. As opposed to similar tests with a microfin tube, no evidence of oil holdup inside the plain tube test sections was noted. However, the effect of flow pattern appears to be important while also the effect of local physical properties on the heat transfer coefficient at high vapor qualities was confirmed.
Record created on 2005-08-08, modified on 2016-08-08