TRANSITION FROM NUCLEATE BOILING TO CONVECTIVE BOILING IN COMPACT HEAT-EXCHANGERS

The boiling of pure fluids has been experimentally studied in several types of compact heat exchanger channels. Plate fin and corrugated hea t exchangers have been studied (seven geometries). Controlling the Bow parameters (mass flux and vapour quality), the heat flux and measurin g the wall temperature, have allowed characterization of the local hea t transfer coefficient. The results clearly show that the dominant mec hanisms occurring could be nucleate or convective boiling. The transit ion between these two mechanisms depends on the flow characteristics a nd also on the channel geometry. Based on these measurements, an objec tive criteria can be established to identify the flow boiling regime. The knowledge of such a criteria is useful if we want to extend the us e of compact heat exchanger to boiling of mixtures(1). (C) 1998 Publis hed by Elsevier Science Ltd and IIR.