# Latent Heat

Written by Jerry Ratzlaff on . Posted in Thermodynamics

Latent 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

### Where:

 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:

 $$\large{ Q = m \; Q_l }$$