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Heat transport is the same phenomena like mass transfer, momentum transfer
and electrical conduction. Similar rate equations, where flow is proportional to a

potential difference.
Potential difference → temperature difference

Heat is typically given the symbol Q, and is expressed in joules (J) in SI units. The
rate of heat transfer is measured in watts (W), equal to joules per second, and is

I
denoted by Q . The heat flow, or the rate of heat transfer per unit area, is measured in
2
watts per area (W/m ), and uses q for the symbol. Table shows the common SI units

used for heat, heat transfer rates, heat flow and given the symbol of its.

Units for Heat Measurements

SI Units

Thermal Energy (Q) 1 J

I
Heat Transfer Rate (Q ) 1 J/s or 1 W
2
Heat flow (q) 1 W/m

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