Specific features of transient processes and shape of the c urve of boiling on surfaces with porous coatings

The effect of the most important factors, determining the shape of boiling curve on porous surfaces has been studied. Experimental studies of boiling processes are realized on horizontal upward turned surfaces with porous coatings of different types at boundary conditions of the second type (q=const) under conditions of natural convection. The experiments are carried out under pressures from 0.02 to 3.1 MPa with water (moistening angle is approximately 40 deg). The change of thermal loading is realized in steps. When studying stationary regimes of boiling the reaching of new stationary states after each laoding increase is recorded according to coincidence of indices of three thermocouples, which are fixed in the sublayer, for 20-40 min after the sublayer temperature stops growing. Boiling curves and diagrams of loading change rate effect on the shape of water boiling curves on surfaces with porous coatings and on smooth surfaces are presented. The experimental results show that physics of boiling on porous surfaces is very specific and thermal processes in the case differ considerably from the processes taking place during boiling on smooth surfaces. None of the published theoretical models of heat exchange process during boiling on surfaces with porous coatings does not tae into account and explain the effects detected