The set up consists of a glass column. Water is fed at the top of the column along the walls to make the column a wetted wall column. Hot air from heating chamber with known humidity is allowed to pass through the column vertically upward and evaporation in the liquid film around the wall takes place. The flow rates of water and air can be independently varied to simulate different conditions. Instrumentation is provided to measure the dry and wet bulb temperatures at air inlet and outlet.