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11-03-2010, 11:22 AM #1
Working on the international system. Im confused
Hey how u doing?
I’m moving soon from US to down under and I’m trying to get my mind used to work in the international metric system so I have a couple of question and I 'd appreciate for your help.
Ok I know that temp is measure with C Celsius instead of F. But I've been reading some posts and articles on the net and when they talk about subcooling or superheat they talk about "K" ???
For example this is from an article “liquid subcool values of say 1K to 3K”. What do they mean by this?? Is this 1 kelvin to 3 kelvin? Why are they using Kelvin instead of Celsius?
I’ve seen also that in some articles they use celsious and Kelvin interchangeably.
But 23 C are not the same as 23 K, are they?? I thought that C=K-273
Can someone help me to digest this please.
I have 2 more questions.
1. What unit is used in Aussie to measure refrigerant pressure? Psi??
2. How is airflow measured in Aussie? CFM??
Thanks.
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11-03-2010, 11:41 AM #2
Re: Working on the international system. Im confused
Forget about American units of measure. They aren't used anywhere else except sometimes in Canada. Pressure is recorded in bar or kpa. Degrees Kelvin is an absolute scale starting at -273 C but one degree C difference is the same as 1 degree K. Air flow is recorded in cubic meters per second or per hour. Water flow is recorded in litres per second or lcubic meters per hour. refrigeration effect and motor power are in kW. The best way is to start using the international units & don't try to convert everything. The calculations are way easier & you'll fit in and become comfortable much faster.
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11-03-2010, 12:10 PM #3
Re: Working on the international system. Im confused
Hi, elgue
Welcome to RE forums ....
you can find and learn a lot by searching RE forums....
use key words like superheat, subcooling, measuring units, Kelvin etc...
read this thread:
http://www.refrigeration-engineer.co...ad.php?t=23821
of course, welcome back with any new doubt you have
good luck down under....
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
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11-03-2010, 08:00 PM #4
Re: Working on the international system. Im confused
Here is si units
http://www.gordonengland.co.uk/conversion/thermcon.htmMy wife used to say you never listen to a word I say at least I think that what she said
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11-03-2010, 08:12 PM #5
Re: Working on the international system. Im confused
Charlie,B”H
Engineers like to work in bars.
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11-03-2010, 09:05 PM #6
Re: Working on the international system. Im confused
Even though K normally stands for Kelvin, people use the term K on the end of a number to express temperature differences.
For example Saturated Condensing temp of 56DegC and the actual temperature of the liquid line is 48DegC, this would give you 8DegC subcooling or 8K ( temperature difference.The difference between genius and stupidity is that genius has its limits.
Marc
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11-03-2010, 09:08 PM #7
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12-03-2010, 12:35 AM #8
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14-03-2010, 07:28 AM #9
Re: Working on the international system. Im confused
Hey Thanks to everyboby for taking the time to answer my questions.
Does anyone know where I can find a P/T chart on the web for Celsius and bar or Kpa??? I've been trying to find one and all I find are P/T charts with F and Psi.
By the way any good HVACR book (basics) with the SI system you would recomend?
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14-03-2010, 08:39 AM #10
Re: Working on the international system. Im confused
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14-03-2010, 09:04 AM #11
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14-03-2010, 12:55 PM #12
Re: Working on the international system. Im confused
here's a PT guide for the "400" refrigerants. I have one for ammonia, R22 & R507 but it's too big to upload
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14-03-2010, 06:39 PM #13
Re: Working on the international system. Im confused
Try this
http://fridgetech.com/calculators/My wife used to say you never listen to a word I say at least I think that what she said
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