Sizing the Ground Heat Exchanger

There are several information sources on sizing ground heat exchangers, such as the International Ground Source Heat Pump Association Installation Guide. There are also manufacturers' manuals and several software programs you can use to facilitate the design calculations.

These sources include needed design engineering data, such as:

  • Pipe size and thermal resistance data,
  • Minimum gpm fluid flow in pipe for turbulence,
  • Pressure drop design equations,
  • Fluid properties of viscosity and density,
  • Piping feet of head loss at different flow rates in feet per 100 feet,
  • Pipe and Soil/Field resistance,
  • Earth temperature data for various locations, and
  • Other soil data, thermal properties, and general characteristics.

The general steps in the design are:

  1. Selecting the ground heat exchanger layout,
  2. Checking the minimum fluid velocity,
  3. Designing for air removal so all potential air traps are designed out, and
  4. Sizing the ground heat exchanger length.