Air - Heating, Cooling, Mixing, Humidifying or Dehumidifying Processes

Calculator for common air conditioning processes including heating, cooling, mixing, humidifying and dehumidifying air using psychrometric principles and heat/moisture balances.

Process TypeInitial StateFinal StateDescription
Heating AirState A (dry bulb temp, humidity)State B (higher dry bulb temp, same humidity)Air is heated along a constant specific humidity line. Enthalpy increases while humidity ratio remains constant.
Mixing AirState A + State C (different conditions)State B (mixture point)Two air streams mix. Result depends on volume ratio. Uses heat balance: mA·hA + mC·hC = (mA + mC)·hB
Cooling & DehumidifyingState A (above dew point)State B (below dew point)Air cools and moisture condenses on cold surface. If temperature > Dew Point: constant humidity line. If temperature < Dew Point: moisture reduces (xA - xB condenses).
Humidifying with Steam/WaterState A (lower humidity)State B (higher humidity)Water or steam added. Adiabatic process follows constant enthalpy line. Temperature slightly decreases (saturated steam: <1°C change).

Process Equations

Heat Balance for Mixing

$$m_A h_A + m_C h_C = (m_A + m_C) h_B$$

Where:

  • $m$ = mass of air (kg)
  • $h$ = specific enthalpy (J/kg)

Moisture Balance for Mixing

$$m_A x_A + m_C x_C = (m_A + m_C) x_B$$

Where:

  • $x$ = specific humidity (kg H₂O/kg dry air)

Key Concepts

  • Mollier Diagram: Visualization tool showing air state changes
  • Dew Point Temperature: Temperature at which condensation begins
  • Specific Humidity: Mass of water vapor per unit mass of dry air
  • Adiabatic Process: Process without heat transfer
  • Fog Formation: Occurs when mixing point falls below saturation line
Air - Heating, Cooling, Mixing, Humidifying or Dehumidifying Processes | MEPKit Engineering Tools | MEPKit