# Latent Heat

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:

\(\large{ Q = m \; Q_l }\) |