How to enable surface evaporation

Vijayaraj.B

I' m working to simulate a drying of biomass product whih has a very high moisture content. For this I m using Speciecs model in Fluent.I have selected abosulute pressure.The bottom plate is heated to a higher temperature..Above the biomass layer hot air at a temperature of 100'C is made to flow at a velocity of 1m/sec.I have defined 4 species in the problem,ie Air,LiquidWater, waterVapour and Biomass. Since it is a drying problem the moisture present in the biomass should be evaporated and is to be carried along the air which is flowing over the biomass layer.Hence the relative humidity of the air should increase.But when I run the above said problem,evaporation of the liquid does not take place .Hence to activate the evaporation of fluid from the biomass to the air what should I do. Kindly send me your suggestiions.