Unexpected effects of incident radiant energy on evaporation of Water condensate

While water evaporation and condensation are of fundamental importance to our environment, many features remain under investigation. In this study, we explored the water-condensation circle (WCC) formed on the inner surface of Petri dish lids covering containers of water. We found that they progressively diminished in diameter. Surprisingly, the diminution rate could be affected by objects placed beneath the bottom of the container. For systems that were not in thermal equilibrium with the environment (i.e., warm water in the Petri-dish container), thermal conductivity of the materials played the dominant role. Heat transfer from the water in the container to the material beneath affected the temperature of the water and thus the water evaporation, which changed the humidity in the Petri dish and hence the WCC diminution rate. Yet, when no temperature differences existed between the system and the environment, radiant energy emitted by the materials placed beneath the container was a determining factor. This is unexpected. Common materials placed outside chambers of water are not expected to impact evaporation rates.