Water Tempature through Pipe
Water Tempature through Pipe
(OP)
Can anyone give me some guidance on approximately how much water temperature could increase through an 8-inch metalic pipe (above ground) if the water is coming out of a bore well over a distance of say 4Klm. Outside temperature would be a maximum of 50c (water coming out of bore well would be apprx 30c).
RE: Water Tempature through Pipe
Lying on the surface or on supports with free flow all around the pipe?
Solar radiation or just air somehow?
Any insulation?
Any painting? Colour?
Wind speed assumed ?( increases the heat input into the pipe if above ground )
If the flow is at least 1-2 m/sec, my best estimate without Solar radiation would be 35 to 40C at the end.
If you're getting Solar radiation as well, then it could be higher than 50C.
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RE: Water Tempature through Pipe
To support effectively provide technical information about the piping /insulation/ wind and of course flow rate.
We cannot read your mind.
Steel pipe, DN 8", water Velocity 1.5 m/s, 30 C, air velocity 3m/s,50 C, emissivity pipe 0.8, no insulation > temperature outlet about 36 C
Pierre
RE: Water Tempature through Pipe
Over an incremental length dL of pipe traversed, heat absorbed per sec dQ = S x 0.8 x .7 x pi x D x dL
Heat absorbed by Mass of water traversing through pipe per sec, dQ = dL/dt . pi. (D2/4). rho. Cp. dT
Equating the 2 expressions and simplifying, D/4 . rho . Cp. dT/dt = S . 0.56, which can be integrated easily for the total traversal time. So for 4000m at 1.5m/sec, t = 4000/1.5 = 2670secs, and T-30 = 5.8degC, for Cp = 4180J/kg/degC. So T = 36degC. You can adjust the traversal time t if your water velocity is not 1.5m/sec.
Natural or forced convection from hot air to pipe is small at low wind velocity in comparison and neglected.
RE: Water Tempature through Pipe
Remember - More details = better answers
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RE: Water Tempature through Pipe
The answer will be about 43 C, all other parameters being the same.
Pierre
RE: Water Tempature through Pipe
So combined should be somewhere between 40 to 45C. Less at night time of course....
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Also: If you get a response it's polite to respond to it.
RE: Water Tempature through Pipe
I am heading to the site this week to get more information.
I'm assuming the pipe is elevated above ground but it may be a HDPE pipe
RE: Water Tempature through Pipe
RE: Water Tempature through Pipe
Would a chiller help to bring down the temperature to 35c?
RE: Water Tempature through Pipe
If this is HDPE, watch for both thermal expansion - PE is 10 times that of steel and more importantly the allowable design pressure goes down and shouldn't exceed 50C surface temp.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Water Tempature through Pipe
"Total Solar radiation S is 900w/m2 max in the infra red."
Of the total, only 50% is in the infrared and capable of heating. Remaining is UV and visible light. So, including a 0.5 multiplier on the RHS to S, temp rise would be 2.9degC and not 5.8degC. Exit temp = 33degC. Note the influence of water flowrate on the exit temp ( lower flowrate = higher traversal time = higher exit temp). So the highest temp you'd get is when water flow is at its minimum. Read the calc carefully and adjust where required to suit your conditions.
RE: Water Tempature through Pipe
RE: Water Tempature through Pipe
TTFN (ta ta for now)
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RE: Water Tempature through Pipe
https://www.fondriest.com/environmental-measuremen...
From your graph, since reflectance is the complement of emissivity for opaque materials (where transmissivity = 0), we can say, for UV stabilised black HDPE, e = 1-0.1 = 0.9 over the IR wavelength range ( assuming r remains at 0.1 in the far infrared also). And absorptivity is more or less = emissivity for most materials (Kirchoff's Law approximation). And 0.9 inferred from this graph is close enough to the 0.8 value used previously in the calcs.
RE: Water Tempature through Pipe
If the visible reflectance is less than 100%, then visible light is absorbed, and that equates to heat; even white PVC is not 100% reflective in the visible, so it will get heat from visible light
TTFN (ta ta for now)
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RE: Water Tempature through Pipe
In the chapter on radiation in Perry, it says for polished metals, emittance in the infra red results from free electron excitation, while bound electron excitation dominates at emission in the shorter wavelengths, including within the visible range of 0.4micron to 0.7micron. And the converse must also be true for absorptance I guess.
So temp rise is 5.8degC at 1.5m/sec water velocity even for UV stabilised HDPE pipe.
RE: Water Tempature through Pipe