Latent Heat

Written by Jerry Ratzlaff on . Posted in Thermodynamics

matter phasesLatent heat, abbreviated as \(Q_l\), is the energy absorbed or released by a substance during a constant temperature or phase change from a solid to liquid, liquid to gas or vise versa.


Latent Heat Formulas

\(\large{ Q_l = \frac{Q}{m}  }\)   
\(\large{ Q_l = 0.68 \; cfm \; \Delta gr  }\) (HVAC) btu/hr


 Units English Metric
\(\large{ Q_l }\)  = latent heat of a substance \(\large{\frac{Btu}{lbm}}\) \(\large{\frac{kJ}{kg}}\)
\(\large{ cfm }\)  = cubic feet per minute \(\large{\frac{ft^3}{min}}\) \(\large{\frac{m^3}{min}}\)
\(\large{ \Delta gr }\)  = grains/lb differential \(\large{\frac{gr}{lbm}}\) \(\large{\frac{mg}{kg}}\)
\(\large{ m }\) = mass of the substance \(\large{lbm}\) \(\large{kg}\)
\(\large{ Q }\) = amount of energy transferred for the phase change \(\large{lbf-ft}\) \(\large{J}\)

Solve for:

\(\large{ Q = m \; Q_l }\)   


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Tags: Equations for Heat Equations for HVAC Equations for Soil