SF-98-05-2 -- Development of Design Tools for Ground-Source Heat Pump Piping ✓ Most Recent

High-density polyethylene (HDPE) piping systems with thermal fusion joints have several attractive characteristics when applied to ground-source heat pump (GSHP) systems. However, engineers may not have access to GSHP piping and fitting head loss data or to easy-to-use tools for piping design/pump sizing. Some GSHP systems have been conservatively designed with pumps that are grossly oversized. Systems have been installed in which the pump energy use exceeds heat pump energy. In some cases, engineers completely avoid the use of GSHPs because they are not comfortable with the low level of sophistication and the difficulty of using current GSHP design tools. A project has been undertaken to measure head loss in common GSHP fittings and pipe design and to develop a set of easy-to-use and accurate piping design tools. These tools will not only give designers more confidence but will reduce the cost of GSHPs by reducing oversizing and piping complexity that has been common in some installations. The results of this project are presented in a format similar to the tools currently used by practicing HVAC design engineers. Tables for fitting equivalent lengths and k-factors have been developed. Log-log plots of head loss vs. flow rate and liquid velocity are presented in a format similar to the plots appearing in the 1993 ASHRAE Handbook--Fundamentals. These tables and charts for HDPE piping components complement existing charts and tables for traditional piping systems.

Units: Dual