Heat Transfer
HEAT TRANSFER TERMINOLOGY
HEAT TRANSFER TERMINOLOGY
To understand and communicate in the thermal science field, certain terms and
expressions must be learned in heat transfer.
EO 1.1
DESCRIBE the difference between heat and temperature.
EO 1.2
DESCRIBE the difference between heat and work.
EO 1.3
DESCRIBE the Second Law of Thermodynamics and
how it relates to heat transfer.
EO 1.4
DESCRIBE the three modes of heat transfer.
EO 1.5
DEFINE the following terms as they relate to heat
transfer:
a.
Heat flux
b.
Thermal conductivity
c.
Log mean temperature difference
d.
Convective heat transfer coefficient
e.
Overall heat transfer coefficient
f.
Bulk temperature
Heat and Temperature
In describing heat transfer problems, students often make the mistake of interchangeably using
the terms heat and temperature. Actually, there is a distinct difference between the two.
Temperature is a measure of the amount of energy possessed by the molecules of a substance.
It is a relative measure of how hot or cold a substance is and can be used to predict the direction
of heat transfer. The symbol for temperature is T. The common scales for measuring
temperature are the Fahrenheit, Rankine, Celsius, and Kelvin temperature scales.
Heat is energy in transit. The transfer of energy as heat occurs at the molecular level as a result
of a temperature difference. Heat is capable of being transmitted through solids and fluids by
conduction, through fluids by convection, and through empty space by radiation. The symbol
for heat is Q. Common units for measuring heat are the British Thermal Unit (Btu) in the
English system of units and the calorie in the SI system (International System of Units).
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