Energy Balance Between Heat In-leaks and Boil-off Rates

2 Energy Balance Between Heat In-leaks and Boil-off Rates 

Heat in-leak, kW = Normal BOR, kg/sxLatent heat of evaporation, kJ/kg 

If for any reason, the BOR falls below the total heat in-leak, the thermal energy flow into and out of the liquid is not balanced and the surplus energy flow is stored in the liquid as superheat or thermal overfill. This surplus energy remains in the liquid and builds up with time. It can only be released by evaporation of some of the now superheated liquid via one of the unstable evaporation phenomena described below. These uncontrolled evaporation phenomena constitute a hazard which increases with time, and with the scale of the storage container and with the volume of liquid being stored. 

The observed puffs of vapour from a laboratory sized container of LNG represent a major uncontrolled vapour release in a 100 m diameter tank. 

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