Humidity distribution affected by freely exposed water surfaces: Simulations and experimental verification

Accurate models for the water vapor flux at a water-air interface are required in various scientific, reliability and civil engineering aspects. Here, a study of humidity distribution in a container with air and freely exposed water is presented. A model predicting a spatial distribution and time evolution of relative humidity based on statistical rate theory and computational fluid dynamics is developed. In our approach we use short-term steady-state steps to simulate the slowly evolving evaporation in the system. Experiments demonstrate considerably good agreement with the computer modeling and allow one to distinguish the most important parameters for the model.

Figure 1

Schematic of the geometric model input.

Figure 2

Mesh used for the simulation of the setup containing the large water vessel.

Figure 3

Initial profile of the relative humidity for the simulation with a large water vessel. Color scale shows RH.

Figure 4

Schematic top view of the experimental setup.

Figure 5

Change of RH with time for different sensor positions in the setup with the small vessel.

Figure 6

Change of RH with time for different sensor positions in the setup with the large vessel.

Figure 7

Simulated RH after 4000 s for the case of sheer diffusion with a large water vessel. Color scale shows RH.

Figure 8

Experimental and modeled dependencies of RH on time for the setup with the small vessel and sensor positions (1) and (2). For the experimental curves, deviations due to the uncertainty of the sensor are shown as vertical bars.

Figure 9

Experimental and modeled dependencies of RH on time for the setup with the large vessel and sensor positions (1) and (2). For the experimental curves, deviations due to the uncertainty of the sensor are shown as vertical bars.

Figure 10

Modeled dependencies of RH on time for the cases of no convection ($u_0$ = 0 cm/s) and small convection velocities shown in the panel. The modeling is carried out for the setup with the small vessel at sensor position (2).

Figure 11

Modeled dependencies of RH on time for the case of convection with $u_0$ = 2 cm/s. For both sensor positions the simulation is done with time evolving (change in flow) and steady flows. See text for details.

Figure 12

Experimental and modeled dependencies of RH on time for the setup with the large vessel. For the experimental curves, deviations due to the uncertainty of the sensor are shown as vertical bars. The simulated curves are based on the model including convection.

Figure 13

Simulated RH after 4000 s with $u_0=1$ cm/s for the case of the setup with the large water vessel. Color scale shows RH and the arrows indicate air flow.