ABSTRACT
Airless drying appears to be a technique for energy conservation in drying as it enables the energy lost to the atmosphere with the water vapor in the exhaust gases in conventional air dryers to be recycled. Because ∼85% of the thermal energy in the water vapor produced by drying is the latent energy, only the remaining 15% can be potentially recovered, as the dew point at which the latent energy could be recovered from the vapor-air mixture at the typical dryer exhaust is ∼40°C and therefore not industrially useful. Hence, replacing hot air in convective drying by water vapor as it is in airless drying would offer substantial energy savings, typically from 40 to 90%, depending on process conditions (Anonymous, 1994; Stubbing, 1994a-1994c, 1999). An example of an energy audit for a conventional and an airless dryer is given in Table 8.1 (Heat-Win Ltd, Bitterley, U.K.).
