Heat Transfer
Overall heat transfer co-efficient for cooling of hydrocarbons by water is about

50 -100 BTU/hr. ft.2°F
50 -100 W/m² . °K
1000 - 1500 BTU/hr. ft.2°F
50 -100 Kcal/hr.m².°C

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Heat Transfer
Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the

Temperature of the fin end
Constant temperature equal to that of the base
Surrounding temperature
Average temperature of the fin

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Heat Transfer
In sub-cooled boiling,

Temperature of the heating surface is less than the boiling point of the liquid
Temperature of the heating surface is more than the boiling point of the liquid
Very large vapour space is necessary
Bubbles from heating surface are absorbed by the mass of the liquid

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