Thermodynamics is air ducts, dew point

AI Thread Summary
The airflow inside an air conditioning duct, particularly when cooled, behaves more like constant pressure rather than constant volume. This is important for accurately determining the dew point of the air flow. While there is a small pressure differential created by the fan, it is negligible in the context of the overall airflow. Therefore, for practical purposes, assuming constant pressure is a valid approximation. Understanding this distinction is crucial for HVAC system analysis and performance evaluation.
rolan91602
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Can anyone confirm if the flow of air inside an air conditioning duct, when cooled, behaves as constant volume as compared to constant pressure? I am trying to determine the dew point of the flow and, depending of how it behaves inside the duct, this value will depend on if it is at constant voulume or constant pressure. I think it is at constant volume. Please confirm.
 
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The duct is open on both ends. There is going to be a small pressure differential due to the fan, required to move the air, but it's going to be almost insignificant. To a good approximation, you can assume constant pressure.
 
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