geothermal design software
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   Geothermal Definitive Design Soil Conditions


GEO®Hourly Advantages:
  • Unique Zone Hourly Analysis
  • Realistic Heat Pump Operation
  • Proper Size Zone Heat Pumps
  • Energy Model - Zones
  • Intelligent Triple Hourly Zone Analysis
  • Lower the First Cost
  • Easy Analysis Optimization
  • Hybrid Design Integration
  • Patents No. 9,443,043 and No.9,852,243

Soil Thermal Conductivity

 ◦   GEO®Hourly Definitive Design Software uses the thermal conductivity of the soil or rocks as the primary heat property and the measurement of soils or rocks ability to conduct heat. Soil conductivity is one of the key element in the design length of an in-ground heat exchanger. The heat conduction rate to the rate of thermal storage (diffusivity) in the ground is used to calculate the grounds thermal resistance. Analyzing the heat flow resistance of the ground surrounding the borehole and the borehole resistance which is the placement of the U-bend piping and the grout in the borehole can be represented by a heat transfer equation that can calculate the variable heat rate in an in-ground heat exchanger ground loop.

Borehole Resistance

 ◦   Borehole Thermal Resistance is the heat property and a measurement of the combined heat flow resistance of the in-ground heat exchanger consisting of the U-bend Hdpe pipe, the placement of the U-bend pipe configuration in the borehole, and the grout surrounding the U-bend pipe in the borehole. The total heat rate results from combining these elements. Borehole Thermal Resistance is a key element in the operating heat rate transfers to the in-ground heat exchanger that determines the required design length.
 ◦   Borehole Resistance calculations used in the GEO®Hourly software is derived from rigorous detailed design methods following studies from reports by IGSHPA in 2012, and U.S. DOE research reported in 2013.

U-Bend Pipe and Configuration Layout

 ◦   In a borehole, water circulates in U-bend pipes connecting the heat pump and the in-ground heat exchanger making a closed loop. The U-bend heat exchanger pipe size and the U-bend heat exchanger Hdpe location pipe configuration layout in the borehole both contribute to the thermal resistance in the borehole.
 ◦   In an U-bend heat exchanger pipe using a single U-bend pipe for the circulating fluid flows down one leg of the U-bend and up the other. Double U-bend heat exchanger pipes can divide the flow between the two U-bend in parallel flow to reduce the flow resistance. Studies sponsored by the DOE shows that the Borehole resistance for double U-bend heat exchanger is lower than single U-Bends resulting in a significant length reduction in the in-ground heat exchanger.
 ◦  The U-bend Hdpe pipe placed in the borehole creates a heat exchanger between the pipe and the borehole wall. This placement contributes to thermal resistance in the borehole. Single U-bend heat exchanger pipe can use a spacer that holds the pipe near the borehole wall that lower the thermal resistance. Double U-bend heat exchanger pipe position the pipe near the outside borehole wall and based on research have a lower resistance than single U-bend pipe resulting in reduce heat exchanger length.

Grout Conductivity

 ◦   The conductivity of the grout surrounding the heat exchanger pipe has a heat property that measures the grouts ability to conduct heat. Boreholes need to be environmentally safe and need to be sealed from aquifer that may seep into the borehole. This sealing method is called grouting the borehole with a bentonite slurry that swells and forms a good seal of the borehole after it is injected into the borehole alongside the U-bend piping. There is a heat conductivity problem with of the bentonite slurry because it will insulate the borehole yielding a very poor conductivity. Graphite or silica sand can be added to the bentonite slurry to raise the conductivity to a a higher conductivity level that is an acceptable value making an Enhanced grout.
 ◦   An enhanced grout is always recommended when sealing the borehole because it provides better heat transfer in the borehole compared to just plain bentonite and will provide more economical Project. All of the element of the borehole including the grouting, U-bend pipe configuration, and U-bend pipe placement are all important elements used to determine the borehole resistance and are a combined heat rate for determining the length of the in-ground heat exchanger systems.