| Description |
Ground source thermal energy transport systems have the potential to improve the efficiency of space heating. Two such systems, a thermosiphon and a vertical U-tube system, were installed in a housing unit in Park City, Utah with the aim of assessing performance. From temperature measurements, the heating Coefficient of Performance (COP) for the U-tube system was determined to be around 3. When taking into consideration only space heating, because of the poor performance of the U-tube system and the relatively inexpensive cost of natural gas, the high installation cost of this particular U-tube GSHP will not be recouped in energy cost savings. COP was not used to assess the thermosiphon, but the heat transfer rate per unit length associated with the thermosiphon was found to be approximately 2.3 times greater than that of the U-tube system. Transient temperature measurements led to the development of a conceptual heat transfer model that described the convective heat transfer between flowing groundwater and the thermal grout sealing each piping network. Using this model, a method was developed to infer the convective heat transfer coefficient of each system directly from temperature measurements along the outside of each piping network without directly measuring groundwater velocity. From this method, the heat transfer coefficient for the U-tube was accurately found to be between 8 and 14.4 W/m2-K. |
