buried pipes heat transfer

[snowpit]

say we have two buried pipes [1" id poly.} buried in 5" thick concrete floor,supply and return with ethylene glycol 50% circulating inside the pipes at 18F [5 usgpm], the pipes are 1.75" from top of pipe to concetre surface, at 4" on centres btw pipes , my question if we vary the flow and the centres to 3.5" how this will impact the heat transfer coefficient and proper method of calculation. we are trying to freeze the water sprayed on top of the concrete say 1-1/2" thick ice to make

 

[IRstuff]

At what air temp and ground temp?


TTFN

Eng-Tips Policies FAQ731-376

 

[Yorkman]

Usually slowing down a glycol fluid will adversly affect the mass rate of heat transfer at the chiller. You may expierence shut downs on low evap. pressure cutout, or low leaving solution temperature. These operating safeties may need to be lowered if you slow down the rate of circulation. This is probably not an issue if this project is in the design stage verses an esablished system. The 2006 ASHRAE Refrigeration Handbook has a chapter(#35)on the design and load calculations for ice rinks that might be helpful.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[snowpit]

buried pipes heat transfer

IRstuff (Aerospace)

At what air temp and ground temp?

The concrete temperature is 25F
Air temperature at the surface , 60F, 45F WB

Thanks

 

[sterl]

The people who could answer this question definitively and with lots of field measure would be Toromont Industries (Cimco) in Toronto...But lets assume for a moment you are their competitor.

50% Eg through 1" Poly Pipe at 4" Centers at 5-GPM per tube for a full size rink is a BIG pump, 3-GPM/Tube would be more like ordinary. Big component of the heat XFER to an ice sheet is radiant, so knowing the air conditions near the ice surface will yield a reasonable number for required HT if the sheet is in the dark; but the intensity of color TF lighting is a big heat load on a pro-style rink.

The basic answer is:

42 Btu/sq ft. of Concrete Surface on 4" Centers; 47 at 3-1/2" Centers: Nominal 18 deg. (in) to 20-plus (out). Both at 3-gpm per tube and 1" Thick ice. Obviously lower brine temps required to support Thick Ice.

 

[BigInch]

You may want to see thread378-177790

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[snowpit]

Hi Sterl

How did you arrive to those load figures, what method of
calculation you used

42 Btu/sq ft. of Concrete Surface on 4" Centers; 47 at 3-1/2" Centers

Thanks