Geo-Exchange

1. Geo-Exchange Addison Parks and Andy Gerla

2. Summer Time • Home walls are mainly heated from • the Sun’s 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, r1=10cm, • r2=12cm, r3=15cm, 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 m^3/s. • Our fluid will be water.

5. Calculations Table A.3 Glass fiber k=0.058 r1=.010m r2=.012m r3=.015m W Tm,o= 60 ̊ F m ̊ K = 289 ̊ K Table A.6 Water @ 297 ̊ K k=608.8E-3 W m ̊ K Ns µ=917E-6 Pr=6.3 m3 r2 r3 r1 L cp=1.87kJ/kg*K • 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/m^2*K • 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 r1=5mm, r2=7mm, r3=8mm. 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/m^2*K • Rtot is .509 K/W • Therefore the required length is 4 meters. • In conclusion, we’d 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