The amount of heat (Btu) transmitted in 1 hour through 1 sq. ft. of a homogenous material 1 in. thick for a difference in temperature of 1o F. between two surfaces of the material. 
The amount of heat (Btu) transmitted in 1 hour through 1 sq. ft. of a homogenous material 1 in. thick for a difference in temperature of 1o F. between two surfaces of the material. 
Related Terms 
INTERFACE RESISTANCE

CALCINE

RADIATIONAll warm bodies emit light (electromagnetic radiation, mostly infrared). When this radiation is absorbed or emitted by a body, heat is transferred and termed 'heat transfer by radiation'. Such heat transfer requires a line of sight (view factor) and is proportional to the fourth power of the absolute temperature difference between bodies and the emissivity of the bodies. 
MEAN TEMPERATURE DIFFERENCEIn heat exchange calculations, a pseudo average temperature difference between the warmer and colder fluids at inlet and outlet conditions. 
FIVEFOURTHS POWER LAWThe proposition that the rate of heat loss from a body by free convection is proportional to the fivefourths power of the difference between the temperature of the body and that of its surroundings. 
INSULATIONA material of low thermal conductivity used to reduce heat loss. 
FILM COEFFICIENTFor a fluid confined in a vessel, the rate of flow of heat out of the fluid, per unit area of vessel wall divided by the difference between the temperature in the interior of the fluid and the temperature at the surface of the wall. Also known as convection coefficient. 
SECOND LAW OF THERMODYNAMICSHeat will flow only from material at higher temperature to material at lower temperature. 
CALLENDAR AND BARNES' CONTINUOUSFLOW CALORIMETERA calorimeter in which the heat to be measured is absorbed by water flowing through a tube at a constant rate, and the quantity of heat is determined by the rate of flow and the temperature difference between water at ends of the tube. 
HEATTRANSFER COEFFICIENTThe amount of heat which passes through a unit area of a medium or system in a unit time when the temperature difference between the boundaries of the system is 1 degree. 
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