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Geo-Exchange

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Using Seider we find NuD is 854 h is 21673 W/m^2*K Rtot is .613 K/W Therefore the required length is 20,855 meters. This length is impractical. – PowerPoint PPT presentation

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Title: Geo-Exchange


1
Geo-Exchange
Addison Parks and Andy Gerla
2
Summer Time
  • Home walls are mainly heated from
  • the Suns radiation and cooled by the
  • convection of wind.
  • This results in an uncomfortably warm
  • home. Due to green initiatives, it would
  • save money and protect the environment
  • to cool a home through a geo-exchange
  • system rather then a conventional
  • AC Unit.
  • Here we have a home resting on what
  • are called heat pump piles. Fluid
  • circulates through the cooler heat pump
  • piles and then through the home to absorb
  • the heat coming from the outside. That
  • way the outside heat never raises the
  • internal temperature.

Preferred Temperature 72 F
Outside Temperature 92 F
Ground Temperature Constant 60 F
3
Heat Pump Piles
  • The only energy required to run a heat
  • pump pile is the pump situated at the top.
  • The energy required to run the pump is
  • minimal compared to an AC unit. Warm
  • fluid coming from the home circulates
  • down the center of the pipe and then
  • returns to the home passing by the
  • outer wall of the pipe.
  • We will now determine how long
  • the pile will need to be assuming
  • Tm,i 92 F, Tm,o 61 F, r110cm,
  • r212cm, r315cm, and the pipe
  • is made out of a board of glass fiber.

4
Wayne in Ground Pump
  • We will use this Wayne in Ground Pump.
  • This pump does 6120 GPH or .00643 m3/s.
  • Our fluid will be water.

5
Calculations
Table A.3 Glass fiber k0.058
r1.010m r2.012m r3.015m
W
Tm,o 60 F
m K
289 K
Table A.6 Water _at_ 297 K k608.8E-3
W
m K
Ns
µ917E-6
Pr6.3
m3
r2
r3
r1
L
cp1.87kJ/kgK
  • It is determined that the equivalent diameter is
    0.04m
  • The Reynolds number is 202,660 and therefore
    turbulent.
  • Using Seider we find NuD is 854
  • h is 21673 W/m2K
  • Rtot is .613 K/W
  • Therefore the required length is 20,855 meters.
    This length is
  • impractical.

Tm,i 92 F
306 K
6
Corrected Values
  • A more practical situation would be to decrease
  • the size to r15mm, r27mm, r38mm. Then
  • decrease the flow to 1.43 Gallons an hour.
  • This results in the following
  • It is determined that the equivalent diameter is
    0.004m
  • The Reynolds number is 87 and therefore laminar.
  • NuD is 173
  • h is 159 W/m2K
  • Rtot is .509 K/W
  • Therefore the required length is 4 meters.
  • In conclusion, wed determine how much heat comes
  • from the walls and that would determine how many
  • Heat Pump Piles a home would need.

Additional pipes may be needed to remove
internally generated heat.
Pipes to Heat Pump Pile
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