Evaporation waves in flashing processes

An experimental study on the inception and propagation of evaporation waves in adiabatic flashing of Refrigerant 11 has been performed in glass tubes with diameters 32 mm less than or equal to d less than or equal to 252 mm. The formation of evaporation waves was observed at superheats 35 K less than or equal to Delta theta(max)less than or equal to 50 K and at depressurization rates as low as Delta p/Delta t approximate to 1 bar/s. Additional experiments with metallic inserts as:starters in the test tubes indicate, that the presence of metal/liquid contacts decreases the necessary superheat for the formation of evaporation waves and increases the propagation velocity of the wave along the metallic surface into the superheated liquid. (C) 2000 Elsevier Science Ltd. All rights reserved.