Relationship of vapour pressure and Dew Point

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SUMMARY

The discussion centers on calculating Molal Humidity and Relative Humidity for moist air at 32 degrees Celsius with a dew point of 26 degrees Celsius and an atmospheric pressure of 100.7 kPa. The formula for Molal Humidity is defined as Molal Humidity = Pi / (Ptot - Pi), and for Relative Humidity as Relative Humidity = Pi / Pvap. The user calculated a Molal Humidity of 3.45% by substituting the vapor pressure from a pressure table as the partial pressure, which was confirmed as correct by another participant.

PREREQUISITES
  • Understanding of vapor pressure and dew point concepts
  • Familiarity with humidity calculations
  • Knowledge of atmospheric pressure measurements
  • Ability to use equations for Molal and Relative Humidity
NEXT STEPS
  • Research the relationship between vapor pressure and dew point temperature
  • Learn how to use psychrometric charts for humidity calculations
  • Explore advanced humidity measurement techniques
  • Study the impact of temperature on relative humidity
USEFUL FOR

Students in meteorology, environmental science, and HVAC professionals who require a deeper understanding of humidity calculations and their implications in real-world applications.

miniradman
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Homework Statement


Moist air at 32 degrees C has a dew point of 26 degrees C. The total or atmospheric pressure
is 100.7kPa.

find the:
Molal Humidity
Relative Humidity

Homework Equations


Molal Humidity = \frac{P_{i}}{P_{tot} - P_{i}}
Relative Humidity = \frac{P_{i}}{P_{vap}}


The Attempt at a Solution


I'm thinking I can simply sub in the vapour pressure for the dew point (looking at a pressure table) straight in as the partial pressure for molal humidity.

I got an answer of 3.45%, using equation for molal humidity. I have no answers for this particular question, so I'm not sure if this is correct.
 
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miniradman said:

Homework Statement


Moist air at 32 degrees C has a dew point of 26 degrees C. The total or atmospheric pressure
is 100.7kPa.

find the:
Molal Humidity
Relative Humidity

Homework Equations


Molal Humidity = \frac{P_{i}}{P_{tot} - P_{i}}
Relative Humidity = \frac{P_{i}}{P_{vap}}


The Attempt at a Solution


I'm thinking I can simply sub in the vapour pressure for the dew point (looking at a pressure table) straight in as the partial pressure for molal humidity.

I got an answer of 3.45%, using equation for molal humidity. I have no answers for this particular question, so I'm not sure if this is correct.
Looks correct.

Chet
 

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