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Question regarding pex heat transfer

Question regarding pex heat transfer

Question regarding pex heat transfer

(OP)
Hello,
I'm trying to do some conductive heat transfer calculations for two types of pex pipe, "normal" pex and insulated pex.  All I need is the heat transfer coefficients  (units: BTU/(hr ft^2 F).  I've done enough google searches to know I must be looking in the wrong place.  Can someone direct me to where I can find spec sheets on various types of Pex.  In addition to the heat transfer coefficient, I'd also need the OD.

thanks
EEPROM

RE: Question regarding pex heat transfer

For such a vague question, let me start by referring you to

http://www.pexflex.net/html/docs/PEXFLEX_Datasheet.pdf

After you read it, ask us more questions. I think you want overall heat transfer coefficients for various pipe sizes w and without insulation.

Also it would help if you stated the application.

 

RE: Question regarding pex heat transfer

Eeprom,

You had an exceedingly stern reaction, especially considering you're asking for advices for free. If you only had glanced to IRstuff's profile on eng-tip community, you'd have seen he's a very active member, who has offered and keeps offering many useful advices. In this case he's just outlined how improper was your enquiry.
 

RE: Question regarding pex heat transfer

Ah, that's what you were looking for.

ASTM F876 – Standard Specification for Crosslinked Polyethylene (PEX) Tubing.

ASTM F877 – Standard Specification for Crosslinked Polyethylene (PEX) Plastic Hot- and Cold-Water Distribution Systems.

ASTM F2080 – Standard Specification for Cold-Expansion Fittings With Metal Compression-Sleeves for Cross-Linked Polyethylene (PEX) Pipe.

CSA B137.5 – Crosslinked Polyethylene (PEX) Tubing Systems for Pressure Applications.

DIN 4726 – Plastic Piping Used in Warm Water Floor Heating (Warmwasser-Fußbodenheizungen und Heizkörperanbindungen - Rohrleitungen aus Kunststoffen).

RE: Question regarding pex heat transfer

All you need is the heat transfer coefficients, which are of course ENTIRELY dependent on the application.  Is this PEX tubing embedded in concrete?  Hanging in free air?  Inside a wall cavity?  Coaxial inside another piece of pipe? Outdoors or indoors?  Is it PEX, or PEX-Al-PEX composite tubing?  What's the operating temperature?  What sort of insulation?  What OD of pipe/tube and insulation?  What thickness of each?

You're looking for more than datasheets, I'm afraid.

RE: Question regarding pex heat transfer

Maybe he meant thermal conductivity (Btu/hr/ft/F), which in the end is almost the same thing as heat transfer coeffcient (Btu/hr/ft^2/F) for someone who makes calculations and take decisions

RE: Question regarding pex heat transfer

(OP)
Ione,
Thank you.  That is what I was looking for.  I appreciate the help.

EE

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