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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. :D:D
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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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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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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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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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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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Re: R22 Temp To Pressure Formula
Hi, :)
I believe that formula is not simple, having 4 non linear basic formulas to calculate properties charts:rolleyes:.... in other hand if its so why to loose the time to make charts :confused:.... 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
Quote:
Originally Posted by US Iceman
EES is what I use for most information and calculations.:cool: It is a very good program, but a little expensive.
..... agree with you, after reading above articles I understood why EES are so expensive;) a lot of efforts.... but definitely worth that money....
Quote:
Originally Posted by SteinarN
.....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.
.... why not use those pressures and in the same row show adjacent temperature for that pressure according to charts... then install another two temperature probes and make possible to read suction and discharge superheat what is more important ....
Quote:
Originally Posted by lwarren
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?
.... seems we cannot help much...when you read above articles I believe you will realize why, but still you can use the same way....
..... seems using properties charts and normal programing procedures is inevitable process;)
.... of course I can be wrong.... just my 2pence
Best regards, Josip :)
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Re: R22 Temp To Pressure Formula
Quote:
Originally Posted by
SteinarN
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.
I downloaded software Wolframs Mathematica today and I am going to install it, and try to came up with something.:)
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Re: R22 Temp To Pressure Formula
Hi, nike123 :)
Quote:
Originally Posted by
nike123
I downloaded software Wolframs Mathematica today and I am going to install it, and try to came up with something.:)
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 :)
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Re: R22 Temp To Pressure Formula
Well it seems everyone is insisting on doing this the hard way. :confused: 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!!
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Re: R22 Temp To Pressure Formula
Is this formula derived from Excel, Iceman?
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Re: R22 Temp To Pressure Formula
Quote:
Originally Posted by SteinarN
Is this formula derived from Excel, Iceman?
Hi,
No it was generated with the EES program Josip mentioned in one of his posts. There will be some minor deviations in the data since this is very hard to curve fit.
To see if it meets the requirements the equation can be plugged into Excel and copied down a column. Put the pressures in a column to feed the equation and then check the generated numbers (temperature) to the pressures in a PT chart.
This should be within 0.5 degree (in F scale) or less as an approximate average. At the low end (around -25°F and below) the deviation jumps up to about 1-2°.
It's not exact, but it should be close enough.;)
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Re: R22 Temp To Pressure Formula
Hi, US Iceman :)
Quote:
Originally Posted by
US Iceman
Well it seems everyone is insisting on doing this the hard way. :confused: Try this...
.....Edit: this applies to R-22 only!!
.... seems it is in our nature :confused:
.... then again convert it to *C :D
Thanks US Iceman, (that sausage is too loooong) I will stick with charts ...faster and seems even more accurate.....
Best regards, Josip :)
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Re: R22 Temp To Pressure Formula
Wow, I never figured it would be this hard to get this formula. I would certainly never have even got close to figuring this out.
If your formula is as close as you say UsIceman, that will be more than close enough for me.
Thanks everyone for all of your help.
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Re: R22 Temp To Pressure Formula
You can get something comparable to this using Excel also. I just happen to use EES more often and can get it done faster.
I could probably fine tune the equation for better accuracy if the range were not so large. There are other ways of doing this also, but this was the fastest, since I'm working for free!:D
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Re: R22 Temp To Pressure Formula
Looks like a simple Polynomial equation to 5 places :D
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Re: R22 Temp To Pressure Formula
US Iceman-
Well I am sure it is something I am doing wrong, but I cannot get your formula to come out right. I have even entered it in several online formula calculators and it does not come out right there either.
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Re: R22 Temp To Pressure Formula
mmmmmmmmmmmm nice
thanks a lot josip nice websites
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Re: R22 Temp To Pressure Formula
Quote:
Originally Posted by lwarren
US Iceman-
Well I am sure it is something I am doing wrong, but I cannot get your formula to come out right. I have even entered it in several online formula calculators and it does not come out right there either.
I checked it before it was posted.:(
If you copied the equation into a cell in Excel an adjacent cell would be the pressure in psia. For example, copy the equation into cell A4.
=-81.3681513+3.20065359*A3-0.0381813098*A3^2+0.000296408154*A3^3-0.00000129284314*A3^4+0.00000000290447694*A3^5-2.61193736E-12*A3^6
A3 would be the input pressure in psia. The value calculated in cell A4 would be the saturation temperature for that pressure listed in cell A3.
If the equation is not working then you are either using gauge pressure or the decimal point was in the wrong position in interpreting the engineering notion used in the earlier post.
Copy the equation above and try it again.;)
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Re: R22 Temp To Pressure Formula
Quote:
Originally Posted by
US Iceman
I checked it before it was posted.:(
=((-81.3681513)+(3.20065359*A3)-(0.0381813098*A3^2)+(0.000296408154*A3^3)-(0.00000129284314*A3^4)+(0.00000000290447694*A3^5)-(2.61193736E-12*A3^6))
A3 would be the input pressure in psia. The value calculated in cell A4 would be the saturation temperature for that pressure listed in cell A3.
Copy the equation above and try it again.;)
It just needed some brackets adding US Iceman. Works fine now. Straight forward Polynomial :D
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Re: R22 Temp To Pressure Formula
Ooops.
Well, that's another possibility also frank. I did not think about operator precedent.
In Excel the equation worked just fine as posted, but the precedence of the math operations (addition, subtraction, etc.) could have been over ridden and caused some real issues also.
It is always fun trying to find these sort of errors in Excel. They will absolutely drive you nuts. However, one way of watching this is in the formula bar in Excel. When you place the cursor in the formula bar, the brackets change to different colors to show the matching bracket location.;)
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Re: R22 Temp To Pressure Formula
When you look in the 7th segment (2.61193736E-12*A3^6) you can note that your eqation has an Error-12 but when you copy and paste the formula into Excel (or OpenOffice Calc which I've just started using) the error disappears
Don't ask me to explain that one though ;)
Anyone else use OpenOffice?
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Re: R22 Temp To Pressure Formula
E-12 is simply engineering notation. The negative 12 simply means the decimal point should move 12 places to the left. In effect the number becomes very small.
If the notion had shown E12, the decimal point moves 12 places to the right. Therefore the number gets very large.
I suspect this is what the Doh! was all about, but thought I should mention this for others who might not be familiar with this.;)
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Re: R22 Temp To Pressure Formula
Thanks guys for your time and help, and special thanks to you US Iceman for producing the formula.
I will give it another try.
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Re: R22 Temp To Pressure Formula
How can I send you the invoice?:eek:
Just kidding.:p
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Re: R22 Temp To Pressure Formula
Quote:
Originally Posted by
US Iceman
I suspect this is what the Doh! was all about, but thought I should mention this for others who might not be familiar with this.;)
No my friend, this was because I clicked on the reply button twice and double posted. :)
Thanks for the explanation of the E-12 though - as they say, you learn something everyday.
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Re: R22 Temp To Pressure Formula
Ok, let me ask some more stupid questions because I am still not getting this to work right. Your first posted equation is like 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
Your second posted equation starts out like this:
Temp=-81.3681513E The decimal has moved one place to the right. I tried it with both with unsucessful results, but which one is correct?
Keep in mind I am trying to put this in a custom application that is java based, not excel.
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Re: R22 Temp To Pressure Formula
-8.13681513E+01 = -81.3681513
3.20065359E+00 = 3.20065359
3.81813098E-02 = 0.0381813098
2.96408154E-04 = 0.000296408154
etc, etc.
If you are doing this like above, then the simple answer may be Java can't do math equations like this, or, something else is wrong with how the equation is being formatted in the code.
This works in Excel, it works in Visual basic or any other code I have worked in, but I can't comment about Java. Sorry.
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Re: R22 Temp To Pressure Formula
Fair enough, just wanted to make sure I had all of the entries correct.
If anyone is up on java here is the formula so far:
double a = -81.3681513;
double b = 3.20065359;
double c = 0.0381813098;
double d = 2;
double e = 0.000296408154;
double f = 3;
double g = 0.00000129284314;
double h = 4;
double i = 0.00000000290447694;
double j = 5;
double k = 0.000000000000261193736;
double l = 6;
double aa = (b*A3);
double bb = (a+aa);
double cc = (c*A3);
double dd = Math.pow(cc,d);
double ee = (bb-dd);
double ff = (e*A3);
double gg = Math.pow(ff,f);
double hh = (ee+gg);
double ii = (g*A3);
double jj = Math.pow(ii,h);
double kk = (hh-jj);
double ll = (i*A3);
double mm = Math.pow(ll,j);
double nn = (kk+mm);
double oo = (k*A3);
double pp = Math.pow(oo,l);
double qq = (nn-pp);
getOut().setValue(qq);
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Re: R22 Temp To Pressure Formula
Well through the help of someone much smarter than me, It is finally working in my program. It is very accurate from 0- 300 psia,and psig.
Thanks to all who contributed here.
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Re: R22 Temp To Pressure Formula
my plc has two types of tables inside
1 for linear and one for 10 points.
and yes i did use the formulas and checked them against the ashrae books.
the formula of iceman is the one described in ashrae.
because calculating is difficult in a plc and specially when converting from one type to the other now i am using tables again. is faster as the calculation and as we only use a small portion of the big graph better precision as the formula.
i do have all these formulas in SI not in us sorry
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Re: R22 Temp To Pressure Formula
I have figured out a formula to convert absolute bar to degree Kelvin for R404 a. It is mostly within 0,5C accuracy between -47C and +18C. It is probably possible to get it even more accurate and extend the scale by adding several more + or - (P upx x x.x)
P is the pressure in absolute Bars. The result is degree Kelvin.
The formula looks like this:
Log(P;5)x32+226,2+(P up1.8x0.58)-(P up3x0.0187)
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Re: R22 Temp To Pressure Formula
ASHRAE published the Equations of State for refrigerants. It is a lot easier to look there rather than doing curve fitting to data.\ unless you like the math and computer exercise.
Ken
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Re: R22 Temp To Pressure Formula
I couldn't find the ASHRAE publication. I didn't find a curve fitting function in my open office calc either.
However after I realised I had to start with a log function it's actually quite easy to extend and adjust the formula.
I have time to spare and I sometimes enjoy ponder on different mathematical challenges. And this time I did learn something in the end :)
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Re: R22 Temp To Pressure Formula
I searched and it may no longer be produced. I have an old copy somewhere....but can't locate it. Try contacting the refrigerant vendors as they did have this data available at one time as well.
Ken
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Re: R22 Temp To Pressure Formula
I do have all the formulas in my computer for most of the refrogerants.
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Re: R22 Temp To Pressure Formula
shooter, could you share the R404A formula with me?