Conversion Calculator for Units of
HEAT FLUX DENSITY
(Heat Flow Rate Intensity)
Type in size . . .
select units . . .
watts/m²
watts/sq.in.
watts/sq.ft.
kilowatts/sq.ft.
Btu/sq.ft. sec.
Btu/sq.ft. min.
Btu/sq.ft. hour
watts/cm²
watts/m²
kilowatts/m²
calories/cm² sec.
kilocalories/m² min.
kilocalories/m² hour
then press
Else
Values are shown to . . .
3
4
5
6
7
8
9
significant figures
.
watts / sq.in.
watts / cm²
watts / sq.ft.
watts / m²
kilowatts / sq.ft.
kilowatts / m²
Btu / sq.ft. sec.
calories / cm² sec.
Btu / sq.ft. min.
kilocalories / m² min.
Btu / sq.ft. hour.
kilocalories / m² hour
watts / m²
is the same as
joules / m² second
sq.in.
and
sq.ft.
are square inch and square foot respectively.
sec.
and
min.
are the second and minute (of time) respectively.
The values of the
Btu
and
calorie
are those of the International Table.
Very large and very small numbers appear in e-Format and are not spaced.
Unvalued zeros on all numbers have been suppressed.
Caution
NO guarantee as to the accuracy of these values is given.
And they should be checked against some other source.
HEAT FLUX DENSITY
Also known as Heat Flow Rate Intensity
This is a measure of the rate at which heat energy flows into or out of a surface.
It is expressed simply as the amount of energy which flows through a unit area, in unit time. So, a logical expectation of its units would be something like *joules per square metre per second* or J/m² s
And, looking the 'older' types of units listed in the calculator it will be seen that they are of that form, like Btu/ft² sec
However, (as explained above in Thermal Conductance) when looking at the SI units it will be seen that there appears to be no unit of time. Why?
In the SI the units *joule/second* are equal to (are the definition of) a watt (which is a measure of power) and that fact has been used in reducing the units for Flux Density to
watts/sq.metre [W/m²]
A typical example of the use of this measure is in working out anticipated ground temperatures as a result of the Sun's heat falling on the Earth's surface.