Evaporation Enthalpy Formula |
||
|
\( Q \;=\; m \cdot h_{fg} \) (Evaporation Enthalpy) \( m \;=\; \dfrac{ Q }{ h_{fg} } \) \( h_{fg} \;=\; \dfrac{ Q }{ m } \) |
||
| Symbol | English | Metric |
| \( Q \) = Total Heat Required for Evaporation | \(Btu\;/\;lbm\) | \(kJ\;/\;kg\) |
| \( m \) = Liquid Mass | \(lbm\) | \(kg\) |
| \( h_{fg} \) = Specific Enthalpy of Vaporization | \(Btu\;/\;lbm\) | \(kJ\;/\;kg\) |
Evaporation enthalpy, abbreviated as Q, also called enthalpy of vaporization or latent heat of vaporization, is the amount of energy required to convert a substance from its liquid phase to its vapor phase at a constant temperature and pressure. This process occurs at the substance’s boiling point under a given pressure, and the energy is needed to overcome the intermolecular forces that hold the liquid molecules together. Unlike sensible heat, which changes the temperature of a substance, the enthalpy of evaporation does not change the temperature but instead facilitates the phase transition. The energy absorbed during this process is stored as potential energy in the vapor molecules, allowing them to exist in the gaseous state. The evaporation enthalpy is specific to each substance and depends on factors like temperature and pressure.
Evaporation Enthalpy Formula |
||
|
\( Q \;=\; n \cdot \Delta H_{vap} \) (Evaporation Enthalpy) \( n \;=\; \dfrac{ Q }{ \Delta H_{vap} } \) \( \Delta H_{vap} \;=\; \dfrac{ Q }{ n } \) |
||
| Symbol | English | Metric |
| \( Q \) = Total Heat Required for Evaporation | \(Btu\;/\;lbm\) | \(kJ\;/\;kg\) |
| \( n \) = Number of Moles of the Substance | \(dimensionless\) | \(dimensionless\) |
| \( \Delta H_{vap} \) = Mole Enthalpy of Vaporization | \(Btu\;/\;lbm-mol\) | \(kJ\;/\;mol\) |