A low-energy research house with an FHX in Oak Ridge, Tennessee, was chosen for validation of the numerical model.
Figure 7 shows the conceptual layout of the house with the designed FHX loop.
Both heat pumps were connected to a common FHX in the house.
ORNL has instrumented the FHX and heat pumps and collects data on water inlet and outlet temperatures, pipe surface temperatures at various points, soil temperatures both within the trenches and at undisturbed locations, heat flux across the foundation walls, and other variables of interest.
A non-uniform grid consisting of approximately 13,000 cells is utilized, with cell spacing fine around the FHX pipes as well as heat transfer surfaces, and increasing toward the edges of the domain.
The FHX system model also includes a simple heat pump model.
The model has several limitations based on un-modeled phenomena such as moisture transport in the soil and snow accumulation; these things are ignored in the current FHX model.