Vapor Emission Calculations In A Flash

hen a liquid being pumped under pressure leaks into a room accidentally, it often will also “flash” vapor into the room’s atmosphere. Calculating this flash can be important in incident reporting (e.g., heated Clean-in-Place (CIP) solution leaks), or in determining unnecessary heat loads to a refrigerated space (e.g., due to condensate return or hot water leaks). The following formula is used to calculate the amount of flash:

Where: F = flash vapor (lb/hr) L = liquid flow (lb/hr) (See "Rules of Thumb" (below) for calculating liquid flow.)

Consider, for example, a 180°F water-based CIP solution leaking from a pipe at 60 psig through a 1/32” hole into a 40°F room.

Using the formula from the "Rules of Thumb" for calculating liquid flow, consider K? of 1.0 and sp.gr of 1.0...

L = 9519 * 1 * ( π/4 * 1/32 * 1/32 ) *√(1*60) = 56.5 lb/hr

Using the formula for heat content, specific heat of water is considered as 1 btu/lb °F

This leak results in 7.4 lb/hr of CIP solution vapor flashing into room’s atmosphere.