Conversion Calculator for Units of
THERMAL CONDUCTANCE
(Heat Transfer Coefficient)
Type in size . . .
select units . . .
watts/m² °K
Btu/ft² sec. °F
Btu/ft² hour °F
Btu/ft² sec. °C
Btu/ft² hour °C
calories/cm² sec. °K
calories/m² hour °K
watts/cm² °K
watts/m² °K
kW/m² °K
MW/m² °K
kcal/m² sec. °K
kcal/m² hour °K
then press
Else
Values are shown to . . .
3
4
5
6
7
8
9
significant figures
.
Btu / ft.² sec. °F
watts / cm² °K
Btu / ft.² hour °F
watts / m² °K
Btu / ft.² sec. °C
kW / m² °K
Btu / ft.² hour °C
MW / m² °K
calories / cm² sec. °K
kcal / m² sec. °K
calories / m² hour °K
kcal / m² hour °K
°K
can be replaced by
°C
in all of the above since those degrees are the same size.
ft.
is foot, and
kcal
is kilocalories.
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.
THERMAL CONDUCTANCE
Also known as Heat Transfer Coefficient
It is a measure of the rate at which heat energy flows through a surface. A typical use for this is in a building, when assessing the heat which is lost through the external walls.
It is measured by the amount of energy which flows through a unit area, in unit time, when there is a unit temperature difference between the two sides of the surface. So, a logical expectation of its units would be something like *joules per square metre per second per degree kelvin* or J/m² s °K
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 °F
However, when looking at the SI units it will be seen that there appears to be no unit of time. So what has happened?
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 Conductance to
watts/sq.metre degree kelvin [W/m² °K]
So, more correctly, the definition should not refer to 'energy which flows' but to 'power which flows' and leave out the reference to 'unit time'.