Adiabatic Flash of Liquified Gas Release
Liquified gases such as ammonia or chlorine are often stored in cylinders or vessels at ambient temperatures and pressures well above atmospheric pressure. When such a liquified gas is released into the ambient atmosphere, the resultant reduction of pressure causes some of the liquified gas to vaporize immediately. This is known as "adiabatic flashing" and the following equation, derived from a simple heat balance, is used to predict how much of the liquified gas is vaporized.
| where: | |
| X | = weight percent vaporized |
|---|---|
| HsL | = source liquid enthalpy at source temperature and pressure, J/kg |
| HaV | = flashed vapor enthalpy at atmospheric boiling point and pressure, J/kg |
| HaL | = residual liquid enthalpy at atmospheric boiling point and pressure, J/kg |
If the enthalpy data required for the above equation is unavailable, then the following equation may be used.
| where: | |
| X | = weight percent vaporized |
|---|---|
| cp | = source liquid specific heat, J/(kg °C) |
| Ts | = source liquid absolute temperature, K |
| Tb | = source liquid absolute atmospheric boiling point, K |
| H | = source liquid heat of vaporization at atmospheric boiling point, J/kg |
Read more about this topic: Accidental Release Source Terms
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