DRYING PAPER BY IMPINGING JETS OF SUPERHEATED STEAM .2. COMPARISON OFSTEAM AND AIR AS DRYING FLUIDS

The behavior of superheated steam and air as drying fluids during the constant rate period of drying paper under impinging jets was compared in the jet temperature range 20 less-than-or-equal-to T(j) less-than- or-equal-to 465-degrees-C for jet Reynolds numbers of 1000 less-than-o r-equal-to Re(j) less-than-or-equal-to 12000. At equal mass flux, stea m drying is faster than air drying above the inversion temperature of 175-degrees-C. Also, the specific blower power for steam drying is muc h lower than for air drying at temperatures in the range of industrial importance. Superheated steam impingement drying can therefore lead t o important capital investment and energy cost reductions, relative to air drying.