DRYING WITH SUPERHEATED STEAM:MAXIMUM DRYING RATE AS A LINEAR FUNCTION OF PRESSURE

摘要

Drying with superheated steam as heating agent is controlled through three operativernvariables, the steam temperature, the recycle velocity, and the system pressure. Once thernother conditions are fixed, there is an optimum pressure at which drying rate reaches itsrnmaximum value. The exact optimum conditions can be found through a differentialrnmass and energy balance over the heat exchange area, resulting in two equations. Thernfirst one, to calculate the drying rate as function of the operating conditions and thernsecond one to find the values of those conditions which make the operation optimum.rnFinally, this paper shows that the relationship between maximum drying rate andrnpressure can be rewritten in a unique linear equation. Experiments were performed in arnmodel system to obtain a family of drying rates vs. pressure curves, and in accordancernwith the predicted behaviour, it was observed that all maximum drying rates lay on arnstraight line.