Does anyone on the list know how to convert insulation specs like R134a +
R141b into something meaningful like how many degrees does it lose / hr at
any given ambient temp?
It can't be done from that information, and the answer to your question is
very complicated. Here is an attempt to reduce the complicated to the
simple. You should understand this procedure will leave out some important
details.
-
R134a and R141b must be some kind of standards concerning the heat
transfer propertries of the materials in question -- like motor oils meeting
the API CH-4 standard. The oil companies must know all the various
properties, but the consumer only needs to know the product meets the
standard. The listed standards will likely have several properties besides
heat transfer properties.
-
All normal building material heat transfer properties are related to BTU
per-hour-per-degree-F difference on the two sides of the material, but at
the lowest level they are not expressed that way. Their heat transfer
properties are expressed in unites of resistance to heat transfer. The sum
of the resistance of all the material that makes up the wall is given the
symbol R, and that is used to compute the heat transfer coefficient, U.
-
U tells us how many BTU will pass through each square foot of the wall
when the temperature difference across the wall is one-degree F. U = 1/R.
-
You must remember that BTUs of heat are related to temperature only
through the specific heat of the substance. Just knowing the number of BTUs
of heat that passes through the walls of a container doesn't tell you what
happens to the temperature inside the container. To estimate what happens
to the temperature, we need to know the specific heat of the stuff inside
the container.
The specific heat of water is 1 and the specific heat of normal air is 0.24.
It takes one BTU to raise (or lower) one pound of water one degree F. That
means that getting a good answer to your question is complex beyond all
expectation.
-
Because all the stuff above is so complicated, it isn't often referred
to. To try to make things simple, most materials are related to there R
(Resistance) values, and for similar applications, you can assume that a
material's insulating properties is directly related to its R value. That
is, a material with whose R value is 20 will insulate twice as good as a
material whose R value is 10.
-
Somewhere you can find just what the R values for R134a and R141b are.
Then you can use those values when comparing other material.
Real simple, isn't it? Good Luck!
CaptnWil, Ret
40 Pier Pointe
New Bern NC 28562
(252) 636-3601
captnwil@coastalnet.com
> Does anyone on the list know how to convert insulation specs like R134a +
> R141b into something meaningful like how many degrees does it lose / hr at
> any given ambient temp?
It can't be done from that information, and the answer to your question is
very complicated. Here is an attempt to reduce the complicated to the
simple. You should understand this procedure will leave out some important
details.
1. R134a and R141b must be some kind of standards concerning the heat
transfer propertries of the materials in question -- like motor oils meeting
the API CH-4 standard. The oil companies must know all the various
properties, but the consumer only needs to know the product meets the
standard. The listed standards will likely have several properties besides
heat transfer properties.
2. All normal building material heat transfer properties are related to BTU
per-hour-per-degree-F difference on the two sides of the material, but at
the lowest level they are not expressed that way. Their heat transfer
properties are expressed in unites of resistance to heat transfer. The sum
of the resistance of all the material that makes up the wall is given the
symbol R, and that is used to compute the heat transfer coefficient, U.
3. U tells us how many BTU will pass through each square foot of the wall
when the temperature difference across the wall is one-degree F. U = 1/R.
4. You must remember that BTUs of heat are related to temperature only
through the specific heat of the substance. Just knowing the number of BTUs
of heat that passes through the walls of a container doesn't tell you what
happens to the temperature inside the container. To estimate what happens
to the temperature, we need to know the specific heat of the stuff inside
the container.
The specific heat of water is 1 and the specific heat of normal air is 0.24.
It takes one BTU to raise (or lower) one pound of water one degree F. That
means that getting a good answer to your question is complex beyond all
expectation.
5. Because all the stuff above is so complicated, it isn't often referred
to. To try to make things simple, most materials are related to there R
(Resistance) values, and for similar applications, you can assume that a
material's insulating properties is directly related to its R value. That
is, a material with whose R value is 20 will insulate twice as good as a
material whose R value is 10.
6. Somewhere you can find just what the R values for R134a and R141b are.
Then you can use those values when comparing other material.
****
Real simple, isn't it? Good Luck!
CaptnWil, Ret
40 Pier Pointe
New Bern NC 28562
(252) 636-3601
captnwil@coastalnet.com
