Relative Humidity more than 100%

In summary, the conversation discusses the concept of relative humidity and its implications when it exceeds 100%. The speaker suggests that this can occur in simulations but is very unlikely in real world conditions. They also mention the use of a membrane humidifier and the issue of exceeding 100% RH in humid air due to high partial pressures of water vapor. The speaker questions the accuracy of the measurement and the potential impact of air movement on saturation pressures.
  • #1
nishith17
2
0
In a calculation I am getting relative humidity more than 100%. What does it suggests?
I know this means liquid water is also present in addition to saturated vapour. How should I calculate liquid water content then? Do I have to calculate activity first? Also what happens when I am considering diffusion of water vapour to a dry side (through a membrane)? Does liquid water present will evaporate to compensate drop in partial pressure of water vapour (considering total pressure remains constant)?
 
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  • #2
It's raining.
 
  • #3
nigarbageh17 said:
In a calculation I am getting relative humidity more than 100%. What does it suggests?
I know this means liquid water is also present in addition to saturated vapour. How should I calculate liquid water content then? Do I have to calculate activity first? Also what happens when I am considering diffusion of water vapour to a dry side (through a membrane)? Does liquid water present will evaporate to compensate drop in partial pressure of water vapour (considering total pressure remains constant)?

You haven’t said what your calculations were based on. If they were based on a simulation, it is entirely possible for the relative humidity to exceed 100%. If they were based on actual real world air conditions, then it is still possible, but very unlikely. Water droplets condense on foreign particles, such as dust, that are suspended in the air. Without such particles, condensation becomes difficult, and relative humidity’s as high as 800 % have been recorded in extremely clean air under laboratory conditions. In real life conditions, with all the combustion products and pollution that is present in the air, it is very unlikely that relative humidity will ever exceed 100%.
 
  • #4
I did calculations for a membrane humidifier. I am having dry air on one side and on other inlet I have humid air. The problem is that I am getting >100% RH in humid air. Partial pressure of water vapour is more than saturation pressure at that temperature
 
  • #5
nigarbageh17 said:
I did calculations for a membrane humidifier. I am having dry air on one side and on other inlet I have humid air. The problem is that I am getting >100% RH in humid air. Partial pressure of water vapour is more than saturation pressure at that temperature

Saturation vapor pressures are compiled for still air. If your air is in movement, it is entirely possible that your partial pressures should exceed the saturation pressure by a small amount. What is the magnitude of your excess vapor pressure? Is the RH being calculated or is it being measured? Keep in mind that all measurements are subject to measurement errors.
 

1. What does it mean when relative humidity is more than 100%?

When relative humidity is more than 100%, it means that the air is holding more water vapor than it can hold at its current temperature. This can happen when the air is cooled, causing the water vapor to condense into liquid water, or when there is an influx of moisture into the air.

2. Can relative humidity ever be more than 100%?

Yes, relative humidity can be more than 100% in certain conditions, such as during fog or when there is a sudden increase in moisture in the air. However, it is not possible for relative humidity to stay above 100% for extended periods of time.

3. How is relative humidity calculated?

Relative humidity is calculated using the ratio of the amount of water vapor present in the air to the maximum amount of water vapor that could be present at a given temperature. This value is then multiplied by 100 to get the relative humidity percentage.

4. What is the ideal relative humidity for human comfort?

The ideal relative humidity for human comfort is between 30-60%. When the relative humidity is too low, it can cause dryness in the air and on the skin, while high relative humidity can make the air feel sticky and uncomfortable.

5. How does relative humidity affect weather patterns?

Relative humidity plays a crucial role in weather patterns. High relative humidity can lead to the formation of clouds and precipitation, while low relative humidity can result in clear skies and dry conditions. It also affects the effectiveness of evaporation and transpiration, which are important processes in the water cycle.

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