Experimental Study on Water Evaporation Enhanced by Surface Heating

The average evaporation flux was significantly higher while water was heated at a flat surface by two aligned heating elements than that while the water surface was heated 5 mm below in the designed experiments under the similar conditions. The observation is contrary to the Stefan condition. A thermodynamic model is derived from the Gibbs dividing-surface approximation at a flat evaporating surface to demonstrate that an interfacial flow can enhance the evaporation by transporting energy from a high temperature position to a low temperature position. The measures showed that the interfacial liquid temperature was up to 6.9°C higher around the heating wires than that at the centerline between two heating wires as water was heated at the interface. The induced interfacial flow can transport the energy to maintain the evaporation by overtaking the negative thermal conduction to the interface globally.