How Does Room Temperature and Humidity Affect Water Evaporation Rates?

In summary, the HVAC man is conducting an experiment to determine the rate of evaporation of undisturbed water in a controlled environment. The room is a small, unheated basement room with a constant temperature of 50F and 40% relative humidity. A 12 cup coffee carafe filled with water was left in the room for 18 days and only experienced a 3/8" drop in water level, indicating a slow rate of evaporation. The goal is to compare this result with a formula for predicting evaporation rates. However, it is unclear if the room's humidity is being maintained at 40% or if it is becoming more saturated.
  • #1
tinkeringone
15
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HVAC man here, still tinkering with humidification. Trying to get a baseline on the rate of evaporation of undisturbed water in a full container in a room with a fixed RH & temperature and no air currents. It's a cool (unheated) very small, room in my basement with a door on it. The room has been at a constant 50F & 40% RH. Used a 12 cup (untapered, i.e. perfectly cylindrical) coffee carafe and filled it with water (with no lid on it). It's 5 1/2" in diameter and 4 1/2" deep. In 18 days, the water level has dropped a measly 3/8". So it's kinda like watching grass grow.

I tried to make this as empirically simple as possible to create a "worst-case" scenario for a rate of evaporation, and to see if I could compare it to a simple formula for predicting the rate of evaporation.

Can anyone recommend a formula to compare the results of my current experiment with?
 
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  • #2
It is not clear whether the bulk humidity in the room is being maintained at 40%, or whether the air is being allowed to become more saturated.
 

1. What factors affect the rate of evaporation?

The rate of evaporation is affected by several factors including temperature, humidity, wind speed, surface area, and air pressure. Higher temperatures, lower humidity, faster wind speeds, larger surface areas, and lower air pressure can all increase the rate of evaporation.

2. How does temperature affect the rate of evaporation?

As temperature increases, the kinetic energy of water molecules also increases, causing them to move faster and escape into the air more quickly. This leads to a higher rate of evaporation.

3. What role does humidity play in the rate of evaporation?

Humidity refers to the amount of water vapor present in the air. When the air is already saturated with water vapor, it becomes more difficult for additional water molecules to evaporate into the air. Therefore, higher humidity levels can decrease the rate of evaporation.

4. How does wind speed impact the rate of evaporation?

Wind speed can increase the rate of evaporation by removing the water vapor that accumulates near the surface, allowing more water molecules to escape into the air. Additionally, wind can also bring in drier air, creating a lower humidity environment that promotes faster evaporation.

5. Why does surface area affect the rate of evaporation?

The larger the surface area of water, the more water molecules are exposed to the air, increasing the chances of evaporation. This is why larger bodies of water such as oceans and lakes have higher rates of evaporation compared to smaller bodies of water like ponds or puddles.

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