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Thread: R22 Temp To Pressure Formula
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16-03-2008, 04:18 PM #1
R22 Temp To Pressure Formula
I am trying to write a computer program that calculates the pressure of R22 from a given temp, just like a p/t chart.
I have searche the web an have not been able to find a formula. Does anyone know what this formula is?
Thanks
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16-03-2008, 05:49 PM #2
Re: R22 Temp To Pressure Formula
Find a set of tables for the refrigerant you want to use. Then plug the data into an Excel spreadsheet. One column for temperature and another for pressure. Then you can curve fit the data so that your program calculates the pressure from the temperature input from the instruments.
You may have to turn on the Data Analysis option in Excel, but it's in there. Look in the Help section (F1) and search for curve fitting or regression as the topic.
The temperature to pressure works out quite well, but going from pressure to temperature with this method is a little dicey.Last edited by US Iceman; 16-03-2008 at 05:50 PM. Reason: spelling
If all else fails, ask for help.
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16-03-2008, 05:53 PM #3
Re: R22 Temp To Pressure Formula
Interesting problem. I made a heat pump where i wished to read out the condensing and evaporator temperature on the PLC from a pressure transducer. I was looking for a formula that i could program the plc with so it could convert pressure to temperature. I wasnt able to find a formula.
I doubt there exists a simple formula. At least if it should give an accurate result. If someone has a formula, simple or complicated, i'm also very interested in it.
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16-03-2008, 05:56 PM #4
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16-03-2008, 10:06 PM #5
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16-03-2008, 10:51 PM #6
Re: R22 Temp To Pressure Formula
I know some compressor calculation software uses formulas and not tables to calculate capasity. Danfoss does this. You can read out the formula as well as the values for each compressor that you put in the formula (an universal formula but different values put into that formula dependent on which compressor to calculate). I tried to make a formula myself a couple year ago, but I didnt have enough time to have a serious try. Maybe i should try one more time.
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17-03-2008, 12:22 AM #7
Re: R22 Temp To Pressure Formula
If you figure it out, let me know. It is not a linear formula, or it would be fairly easy.
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17-03-2008, 01:32 AM #8
Re: R22 Temp To Pressure Formula
Originally Posted by lwarrenIf all else fails, ask for help.
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17-03-2008, 02:07 AM #9
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17-03-2008, 05:06 AM #10
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17-03-2008, 08:21 AM #11
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17-03-2008, 10:59 AM #12
Re: R22 Temp To Pressure Formula
Ok, here it is:
abbc://yyy.refrigerants.dupont.com/Suva/en_US/pdf/h16419.pdf
This is actually the formula for pressure from temperature, which is what I asked for. However, I actually need to convert pressure back to temp so I will have to try to figure out how to redo the formula.
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17-03-2008, 11:21 AM #13
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Re: R22 Temp To Pressure Formula
I think that any high school pupil good in mathematics can do that for you easy. Al relationships and constants are there, and it should be easy to derive formula for temperature.
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17-03-2008, 01:50 PM #14
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17-03-2008, 01:51 PM #15
Re: R22 Temp To Pressure Formula
Hi.
Where I use to work we used a program called MSR32.
We connected 2 pressure transducers and had a ability to run 38 thermocouples through 2 data loggers. There is a formula but I neglected to write any down. Our visiting
engineer wrote them into the program.
So sorry mate. Give Solkane in germany a call. One of there engineers could help.
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17-03-2008, 02:47 PM #16
Re: R22 Temp To Pressure Formula
My math is pretty rusty, but Im sure I can eventually figure it out. If I get it figured out I will post it, but if someone beats me to it please post the formula.
Hey SteinarN, I found the formula, why don't you figure out how to reverse it for temp? LOL!
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17-03-2008, 02:52 PM #17
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17-03-2008, 03:16 PM #18
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17-03-2008, 03:56 PM #19
Re: R22 Temp To Pressure Formula
Instead of rewriting the equation why not use a loop in the program? Use the pressure as an input and continue the loop until the temperature is within 0.001 of the results.
If all else fails, ask for help.
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17-03-2008, 04:11 PM #20
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17-03-2008, 04:38 PM #21
Re: R22 Temp To Pressure Formula
It has been some time since I have looked at curve fitting the pressure to temperature. I seem to remember the accuracy was not too good, but then... how good would you need it to be?
If all else fails, ask for help.
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17-03-2008, 04:52 PM #22
Re: R22 Temp To Pressure Formula
The temperature to pressure formula from Du Pont has an average deviation of 0,11%. I would be happy if i got +-0,5C in deviation. I'ts just for information, not a part of the regulation of the heat pump.
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17-03-2008, 05:24 PM #23
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Re: R22 Temp To Pressure Formula
I send this formula to my cousin who is doctor of mathematic science and professor of mathematic at Zagreb university. I expect his answer in few days.
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17-03-2008, 05:52 PM #24
Re: R22 Temp To Pressure Formula
Originally Posted by SteinarNIf all else fails, ask for help.
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17-03-2008, 07:46 PM #25
Re: R22 Temp To Pressure Formula
which of the formulas in the document do you want reversing as I will see what I can sort out?
Ian
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17-03-2008, 07:55 PM #26
Re: R22 Temp To Pressure Formula
Ian,
The equation he is looking for is reverse of the temperature to pressure equation with all of the log base 10 fun stuff.
They are trying to get the saturation temperature from the pressure.If all else fails, ask for help.
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17-03-2008, 08:04 PM #27
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17-03-2008, 08:29 PM #28
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17-03-2008, 08:49 PM #29
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17-03-2008, 09:13 PM #30
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17-03-2008, 09:40 PM #31
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Re: R22 Temp To Pressure Formula
Yes I am aware, but you quoting me and replying to me!
And I knew what we (in fact Iwarren) want from this formula ( picture in my post no.27) and I said, that I send that formula to my cousin (post 23) to derive what you stated in post 28
What a mess.
I see now, you looking in linear mode and I looking in hybrid mode.
Correcting this mess....
Corrected!Last edited by nike123; 17-03-2008 at 09:48 PM. Reason: cleaning of mess
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17-03-2008, 09:57 PM #32
Re: R22 Temp To Pressure Formula
You guys just found one of the interesting features of this forum. I typically use the last post first view so I can read the most current post first.
When someone refers to a post use the post number, not by relative location or we will have a big mess!!!If all else fails, ask for help.
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17-03-2008, 10:36 PM #33
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17-03-2008, 10:40 PM #34
Re: R22 Temp To Pressure Formula
This also has me confused; if you look at the Units and Factors for that equation it says that
T = temperature in deg. R = deg. F + 459.69 deg.
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17-03-2008, 11:01 PM #35
Re: R22 Temp To Pressure Formula
Hi all
maybe to see this:
http://www.fchart.com/ees.shtml#1.1
http://www.fchart.com/eesdemo.shtml
http://www.fchart.com/eesexmpl.shtml
hope this is of some help
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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18-03-2008, 01:01 AM #36
Re: R22 Temp To Pressure Formula
When you are doing gas law or thermodynamic calculations you have to use absolute pressure and temperature.
This means your pressure transducer has to be absolute pressure (which you use in the equation) and then subtract 14.69 psi from it for gauge pressure (unless you are in a vacuum) for the display.
The same thing applies to temperature. You have to add 459.69 to your temperature readings then plug it into the equation (or subtract depending on what you are doing).
And you thought this was going to be easy???If all else fails, ask for help.
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18-03-2008, 01:02 AM #37
Re: R22 Temp To Pressure Formula
Hi Josip,
EES is what I use for most information and calculations. It is a very good program, but a little expensive.If all else fails, ask for help.
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25-03-2008, 01:09 AM #38
Re: R22 Temp To Pressure Formula
Hey nike123, did your cousin ever figure out how re work that formula for temperature?
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25-03-2008, 08:45 AM #39
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25-03-2008, 09:32 PM #40
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28-03-2008, 10:12 PM #41
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Re: R22 Temp To Pressure Formula
Today I have conversation with my cousin and only he could came up with this problem is that he and his colleagues cannot derive formula from this one, and he advise me to take approach with Excel as one with most likely useful for your goal.
He told me that he will try to came up with some useful solution in near future and that he will discuss this problem with his colleagues.
I will keep you posted with development on this mater.
It seems that you make some shock in mathematical community.
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29-03-2008, 07:19 PM #42
Re: R22 Temp To Pressure Formula
Are you searching for a computer program that has the ability to convert R22 temperature to pressure correlation? If so I have it. We can convert this in F to PSIG or in C to KPA. Operates on Windows based computers with Windows .net Framework 2.0 as pre-requisite operating system. We can also convert this same calculation for 28 other Refrigerants. For blends we output both Dew Point and Bubble Point readouts.
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29-03-2008, 07:30 PM #43
Re: R22 Temp To Pressure Formula
I'm searching for a formula to incorporate in a PLC program for conversion from pressure to temperature. Do you have such a formula mcjo tech?
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29-03-2008, 09:17 PM #44
Re: R22 Temp To Pressure Formula
StienerN
If you could please explain your application and applications needs it would help me to understand what it is you may require. Is it the formula you require? Our software does not have a basic formula. Or is it just a program that is capable of these correlations? If it is something that there would be a demand for I am sure we could produce some custom software for this application.
Joe
ExactCharge Industries,Inc.
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29-03-2008, 09:29 PM #45
Re: R22 Temp To Pressure Formula
I've made a large heat pump controlled by a PLC with a HMI panel conected. It is installed HP and LP tranducers conected to the PLC, so it is possible to read out the pressures. But I would like it to be possible to read out the condensing and evaporator temperatures also. Thats the reason I need the formula to convert from pressures to temperatures, a formula which can be incorporated in the existing PLC program.
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29-03-2008, 10:11 PM #46
Re: R22 Temp To Pressure Formula
Thanks,
I understand you application now. Our software for Pressure/Temperature correlations is not formula based but rather logic based so we would not be able to help in your application. I am sure that there is a formula which can accomplish your needs but we do the correlations by different means. Sorry we could not be of more help.
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30-03-2008, 12:01 PM #47
Re: R22 Temp To Pressure Formula
Hi,
I believe that formula is not simple, having 4 non linear basic formulas to calculate properties charts.... in other hand if its so why to loose the time to make charts .... just give few formulas and we can calculate what we need
..... when you read those articles with so many equations, interpolations....information
http://www.imst-art.com/ficherosdesc/interpolation.pdf
http://nii.nist.gov/srd/REFPROP7doc1.pdf (1.69MB)
http://potomac.nist.gov/srd/PDFfiles/REFPROP8.PDF
Originally Posted by US Iceman
Originally Posted by SteinarN
Originally Posted by lwarren
..... seems using properties charts and normal programing procedures is inevitable process
.... of course I can be wrong.... just my 2pence
Best regards, JosipLast edited by Josip; 30-03-2008 at 01:13 PM. Reason: add link
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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30-03-2008, 12:19 PM #48
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30-03-2008, 01:24 PM #49
Re: R22 Temp To Pressure Formula
Hi, nike123
what to say.... good luck
maybe to use one of those ... close to CoolPack
http://www.et.web.mek.dtu.dk/WinDali...nDali_2.10.ZIP
http://www.et.web.mek.dtu.dk/WinDali/Files/WinDali.pdf
http://www.et.web.mek.dtu.dk/WinDali...fEqns_3.10.ZIP
all above is here...
http://www.et.web.mek.dtu.dk/WinDali/Index.html
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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30-03-2008, 04:08 PM #50
Re: R22 Temp To Pressure Formula
Well it seems everyone is insisting on doing this the hard way. Try this...
Temp=-8.13681513E+01+3.20065359E+00*Press-3.81813098E-02*Press^2+2.96408154E-04*Press^3-1.29284314E-06*Press^4+2.90447694E-09*Press^5-2.61193736E-12*Press^6
Temp = °F (saturation temperature)
Press = psia (valid for range of 10 psia to 315 psia)
It may not be exact to 4 decimal places but it should be close enough.
Edit: this applies to R-22 only!!Last edited by US Iceman; 30-03-2008 at 04:10 PM. Reason: added note
If all else fails, ask for help.
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