Results 1 to 9 of 9
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07-12-2005, 12:55 AM #1
How do you size a txv when you are the OEM
In our production we use a 1/4 ton valve in a 3/8" 24 tube 30"coil, we also use a 1/4 ton valve in a 1/2" 20 tube 88" coil. The same valve for a coil more than 3 times the size. Are we just guessing? How does one calculate the right valve. Thanks, Ken
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07-12-2005, 01:26 AM #2
Re: How do you size a txv when you are the OEM
Is this a finned-tube air cooling coil?
It may have to do with pressure drop through the coil(s) and the heat transfer capacity of each coil.
The 1/2" tube is 3 times as long, but the 1/2" tube is a lot larger ID than a 3/8".
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07-12-2005, 07:16 AM #3
Re: How do you size a txv when you are the OEM
I say it all comes down to subcooling
design the system around subcoolingThe primary function of the design engineer is to make things difficult for the fabricator and impossible for the serviceman.
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07-12-2005, 01:33 PM #4
Re: How do you size a txv when you are the OEM
Originally Posted by kengineering
In order to size the correct TEV first you have to know the refrigeration capacity. Secondly the evaporating temperature. Thirdly the pressure drop across valve which is the condensing pressure minus evaporating pressure and plus the different pressure drops in the liquid line and after TEV. Then with these three values you will refer to the TEV catalogue and select the correct size.
CheersEven Einstein Asked Questions
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07-12-2005, 02:07 PM #5
Re: How do you size a txv when you are the OEM
review these links... they should help to explain the question about TXV selection.
http://www.sporlan.com/10-9.pdf
http://www.sporlan.com/10-10.pdf
The Sporlan website is a great place to spend some time reading!!!
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07-12-2005, 10:48 PM #6
Re: How do you size a txv when you are the OEM
Thanks again for all the response. I will check out the Sporlan pages. The example in question is a finned fan coil for a open air screen self select type beverage cooler. In this case it is for R22 and desired temp is 38-40*f. Ken
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08-12-2005, 02:41 PM #7
Re: How do you size a txv when you are the OEM
Select your TXV according to your compressor capacity.
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09-12-2005, 12:11 AM #8
Re: How do you size a txv when you are the OEM
design around subcooling is and interesting idea. When migyt i get more information. Ken
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09-12-2005, 12:36 AM #9
Re: How do you size a txv when you are the OEM
Ken,
If you look through the Sporlan selection and application information in the literature you will see subcooling increases the TXV capacity.
The reduced liquid temperature increases the net refrigerating effect per pound of refrigerant circulated in the system.
You can also have too much subcooling... If the liquid temperature is below the evaporating temperature, the liquid will not evaporate/boil in the coil.
Too much of something is not better...Last edited by US Iceman; 09-12-2005 at 08:02 PM. Reason: text editing
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