IntermediateTopic 38 of 105Thermodynamics & Fluids
Air conditioning and psychrometrics
Charts of humid air describe humidity, enthalpy and cooling loads.
In depth
Humid-air properties: dry-bulb temperature, relative humidity, humidity ratio ω, dew point, wet-bulb, specific enthalpy. The psychrometric chart shows processes: sensible heating, cooling and dehumidification, humidification, evaporative cooling, mixing. HVAC loads determined by enthalpy changes.
Key points
- Dew point is saturation T
- Sensible heat ratio
- Comfort zone
ExampleCooling air below its dew point condenses water on the coil.
What is Air conditioning and psychrometrics?
Charts of humid air describe humidity, enthalpy and cooling loads.
Why is it important to understand air conditioning and psychrometrics?
Psychrometric charts describe moist air, which is needed for air conditioning, drying and any process where humidity matters.
What is the dew point?
The temperature at which moist air becomes saturated when cooled at constant pressure, so water condenses below this temperature.
What does relative humidity mean?
The ratio of the actual water vapour pressure to the saturation pressure at the same temperature, expressed as a percentage.
How is Air conditioning and psychrometrics used in practice?
Typical applications include finding the dew point of room air to check for condensation on a window, sizing the cooling coil needed to dehumidify a building and calculating the moisture added in a humidifier for a textile mill.
What should I learn before Air conditioning and psychrometrics?
Study "Refrigerants" first (topic 37 of 105 in Thermodynamics & Fluids). It covers the groundwork this topic builds on.
What are the key points of Air conditioning and psychrometrics?
Dew point is saturation T. Sensible heat ratio. Comfort zone.
Can you give an example of Air conditioning and psychrometrics?
Cooling air below its dew point condenses water on the coil.
What comes after Air conditioning and psychrometrics?
The next topic is "Combustion", which builds directly on this one.
How difficult is Air conditioning and psychrometrics?
It is classed as Intermediate in Thermodynamics & Fluids (topic 38 of 105). It is an intermediate topic. Work through the beginner topics in Thermodynamics & Fluids first.