Condensate Load from Heating Air

on . Posted in Fluid Dynamics

Condensate load from heating air is the amount of water vapor that condenses into liquid water when air is heated.  When air is heated, its capacity to hold moisture increases.  The condensate load is the moisture that exceeds the air's capacity to hold water vapor, leading to the formation of liquid water.

Brief explanation of the process

  • Heating Air  -  When air is heated, its temperature rises.  As the temperature increases, the air's capacity to hold moisture also increases.
  • Moisture Content  -  Air contains water vapor, which is moisture in a gaseous form.  The amount of water vapor air can hold depends on its temperature; warmer air can hold more moisture.
  • Saturation Point  -  The saturation point is the maximum amount of water vapor that air can hold at a given temperature.  When air reaches its saturation point, further heating or addition of moisture will cause the excess moisture to condense into liquid water.
  • Condensation  -  If the air is heated beyond its saturation point or encounters a colder surface, the excess moisture condenses into liquid water.  This liquid water is what is referred to as condensate.

The condensate load can be a consideration in various systems, such as HVAC systems.  Excessive condensate can lead to issues such as mold growth, corrosion, and damage to equipment.  Therefore, managing condensate is an important aspect of designing and maintaining heating systems.  It's important to note that the specific condensate load will depend on factors such as the initial moisture content of the air, the temperature to which the air is heated, and the relative humidity.  Engineers and designers often take these factors into account when designing heating systems to ensure efficient operation and to prevent issues related to excess condensate.


Condensate Load from Heating Air formula

\( m_c =  60 \; c_a \; \gamma_a  \; Q_a \;\left( T_{out} - T_{in}  \right) \;/\; Q_{ls} \) 
Symbol English Metric
\( m_c \) = condensate load \(lbm\) \(kg\)
\( c_a \) = air specific heat \(Btu \;/\; lbm-F\) \(kJ \;/\; kg-K\)
\( \gamma_a \)  (Greek symbol gamma) = air specific weight \(lbf \;/\; ft^3\) \(N \;/\; m^3\)
\( Q_a \) = air flow rate \(ft^3 \;/\; sec\) \(m^3 \;/\; s\)
\( T_{out} \) = air outlet temperature \(F\) \(K\)
\( T_{in} \) = air inlet temperature \(F\) \(K\)
\( Q_{ls}   \) = steam latent heat \(Btu \;/\; lbm\) \(kJ \;/\; kg\)


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Tags: Pipe Sizing Heat Air HVAC Condensate