Heat Exchange 101

THE BASICS OF MOVING HEAT -

DEFINITIONS -

• BTU - British Thermal Unit, The amount of heat required to raise 1 lb. of water 1 F.

• Coefficient of heat transfer (convective) - A measure of a fluid's ability to transfer (absorb or reject) heat. This is expressed in Btu/hr/area/delta t

• Conduction heat transfer - The transfer (movement) of heat through a solid, or through a fluid (if the fluid is not moving).

• Convection heat transfer - The transfer (movement) of heat through a fluid (gas or liquid) by that fluid flowing to another location.

• Convective heat transfer coefficient - See Coefficient of heat transfer (convective).

• Cp - See specific heat

• Delta t - The difference in temperature.

• Duty - The amount of heat added/subtracted in a heat transfer application (Btu/hr).

• Enthalpy - The heat content of a substance from some reference point.

• Forced convection - Convective heat transfer when the fluid is forced (blown, pumped).

• Heat balance - The heat rejected must equal the heat absorbed.

• k - See Thermal Conductivity.

• Latent Duty - Duty resulting from a change in state (boiling or evaporating and freezing or condensing).

• Natural convection - Convective heat transfer where the difference in density (because of the difference in temperature) is the only driving force to move the fluid.

• Pressure drop - the pressure at the output of a device minus the pressure at the input to a device.

• Sensible Duty - Duty as a result of temperature change.

• Specific heat - the ratio of heat required to raise 1 pound of a substance 1 F to the heat required to raise 1 pound of water 1 F.

• Thermal Conductivity - Resistance to heat flow (Btu·.mass/ft/ F).