Vertical flow boiling of refrigerant R134a in small channels

This article presents an experimental study of ascendant forced flow boiling in mini-channels with refrigerant R134a. A flat aluminium multi-port extruded tube composed of 11 parallel rectangular channels (3.28 mm × 1.47 mm) with hydraulic diameter of 2.01 mm was used. Mass flux ranged from 90 to 295 kg/m2 s and heat flux from 6.0 to 31.6 kW/m2. Two working pressures, 405 and 608 kPa, were tested. Inlet subcooling varied from 1 to 17 K. Heat transfer was found to be greater than that previously reported in the literature for conventional tubes, while dry-out occurred at low qualities.