Relative Humidity: Find Optimum Off Coil Air Temp.

In summary: Additionally, the mixed air temperature of 78°F db and 65°F wb will result in an off-coil air temperature of approximately 56.5°F db, though this estimate may be slightly off. The corresponding relative humidity levels for this off-coil air temperature cannot be determined without additional information. In summary, the total load in the conditioned space is 320 mBh with a sensible heat ratio of 0.90. 20% of the blower air volume will be used for ventilation. The space setpoint is 75°F db, 45% relative humidity, and the outdoor air is 90°F db, 78°F wb.
  • #1
rthomas0010
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the total load in the conditioned space is equal to 320 mBh with a sensible heat ratio equal to 0.90. Outside air equal to 20% of the blower air volume will be used for ventilation. The space setpoint is 75°F db, 45% relative humidity. The outdoor air is 90°F db, 78°F wb.



What relative humidity level will be maintained if the off coil dry bulb temperature is 5°F warmer than the optimum off coil air temperature? _____%
What relative humidity level will be maintained if the off coil dry bulb temperature is 5°F cooler than the optimum off coil air temperature? _____%


Mixed air temperature is 78°F db, 65°F wb. I believe the off coil air temperature maybe 56.5°F db, but that might be a little off. What are those relative humidity levels?

1. Homework Statement have been given



2. Homework Equations is not known by me



3. The Attempt at a Solution has been unsuccessful. Any and all assistance will be appreciated. Thank you.
 
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  • #2
The relative humidity levels will depend on the off-coil dry bulb temperature. If the off-coil dry bulb temperature is 5°F warmer than the optimum off-coil air temperature, the relative humidity level will be lower than 45%. If the off-coil dry bulb temperature is 5°F cooler than the optimum off-coil air temperature, the relative humidity level will be higher than 45%.
 

What is relative humidity?

Relative humidity is the measurement of water vapor present in the air compared to the maximum amount of water vapor that can be present at a given temperature. It is expressed as a percentage and is an important factor in determining the comfort level and health of individuals.

What is the relationship between relative humidity and off coil air temperature?

Off coil air temperature is the temperature of the air that has passed through the cooling coil in an air conditioning system. Relative humidity is affected by this temperature because as the air cools, its ability to hold water vapor decreases, resulting in an increase in relative humidity.

Why is it important to find the optimum off coil air temperature for relative humidity?

Finding the optimum off coil air temperature is important because it directly affects the relative humidity of the air. If the temperature is too high, the air will not be cooled enough and the relative humidity will remain high, leading to discomfort and potential health issues. On the other hand, if the temperature is too low, the air may become too dry, causing skin and respiratory problems.

How is the optimum off coil air temperature for relative humidity determined?

The optimum off coil air temperature is determined through a process called psychrometrics, which takes into account the temperature, humidity, and pressure of the air. By using psychrometric charts or equations, the optimum off coil air temperature can be calculated for a specific relative humidity level.

What are the benefits of maintaining the optimum off coil air temperature for relative humidity?

Maintaining the optimum off coil air temperature for relative humidity can result in improved comfort, as well as better indoor air quality. It can also help prevent the growth of mold and bacteria, which thrive in high humidity environments. Additionally, it can save energy and reduce costs by ensuring the air conditioning system is running efficiently.

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