DRYING PAPER BY IMPINGING JETS OF SUPERHEATED STEAM .1. CONSTANT DRYING RATE IN SUPERHEATED STEAM

Over a wide range of operating conditions, the drying of paper by impinging jets of superheated steam proceeds by a constant rate period followed by a falling rate period. The constant drying rate, investigated here in the jet temperature range 150 less-than-or-equal-to T(j) less-than-or-equal-to 465-degrees-C and over jet Reynolds numbers of 1000 less-than-or-equal-to Re(j) less-than-or-equal-to 12000, is predicted within +/- 12% by a heat transfer expression using Martin's (1977) correlation for the heat transfer coefficient corrected for mass transfer by the Couette flow approximation factor, and a property ratio to account for the large temperature difference between the jet and the paper.