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re: r-value conversions (was: solar heating, empirical measu(r)ements & experience)
17 may 1996
alan braggins wrote:
>> nick@vu-vlsi.ee.vill.edu (nick pine) writes:
[someone else wrote...]
>> > is it true that 1 watt = 3.412 btu/hr? if so, have i got it right that
>> > r-1 (international) degc.m^2/w = r-5.678 (us) degf.hr.ft^2/btu?
>>
>> i think so.
let me try this step by step, with a calculator.
a 1 m x 1 m wall with a metric r-value of 1 will pass 1 watt of heat
if the temperature difference is 1 c.
so a 10.76 ft^2 wall will pass 3.41 btu/hr of heat if the temperature
difference is 1.8 f. ok?
so that wall will pass 3.41/1.8 btu/hr with a temperature difference if 1 f.
and a 1 ft^2 wall like that will pass 3.41/1.8/10.76 = 0.176 btu/hr.
(numerically the same as the metric r-value of an r1 window...)
so that wall has a us r-value of 5.68.
>% /usr/bin/units
>you have: kelvin m2 / watt
>you want: rankine hour ft2 / btu
> * 1.752557e+00
>
>you have: m2 / watt
>you want: hour ft2 / btu
> * 3.154603e+00
>
>either i'm wrong about rankine being to fahrenheit as kelvin is to
>celsius, i'm misunderstanding units output, or you have used 9/5
>where you should have used 5/9.
i've never used that unix function, altho it looks useful.
anyone know the name of the one that turns tabs into spaces?
>> or would those be degrees k, in that particular alphabetical procession?
>
>for temperature _differences_, kelvin is the same as degrees centigrade.
but you must call it by the right name, no? :-)
nick
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