Summary Panel Results A designer needs to think about three primary goals when engineering a piping system. These are:
The GLD Piping System Builder and Computational Fluid Dynamics modules help to ensure that the design achieves all three goals.
GOAL 1: Purging Purge pump requirements are displayed at the bottom of the Overview Tabbed Panel. If the purging flow rate and/or purging pressure drop are too high, installers will not be able to purge the supply-return runout pairs and circuits. Please be sure that your design has a purging flow rate and purging pressure drop that can be handled by available purge pump equipment. If you have questions, contact your local installation resources. GLD performs all purge calculations with water (systems are always purged with water). Furthermore if a design has balancing valves included, note that purging calculations are performed assuming that the balancing valves are all fully open. In general, it is extremely difficult to purge a system that requires a flow rate greater than 150gpm and/or a head loss greater than 100 ft. hd. If your system has purge requirements such as these, it may be worthwhile redesigning the system in the Piping System Builder (larger diameter supply-return runouts, fewer circuits per supply return runout, etc. will help). The system below, for example, will be impossible to purge.
GOAL 2: Energy Transfer To efficiently transfer heat energy between the circulating fluid and the ground, Reynolds numbers must be above a certain minimum value. Typically, designers aim for turbulent flow Reynolds numbers during peak load conditions. If Reynolds numbers are too low, system performance may suffer severely. Conversely, if Reynolds numbers are too high, circulating pumps may be oversized, resulting in much wasted operational energy and excessive operational costs. The Reynolds number range for a system is reported in the Operational Performance section on the Overview tab. Range is defined as the maximum and minimum Reynolds numbers across the circuits in an entire system. In addition to looking for Reynolds numbers that provide turbulent flow, a designer should also be interested in the spread of the Reynolds number range. In general, the tighter the range the better. For example, a range of say 3255 - 3511 is more optimal than a range of 2855 - 4211. The system below has appropriate Reynolds numbers and a beautiful Reynolds number range. The system below has a wide Reynolds number range that should be tightened up, if possible. While a number of design decisions can lead to a wide Reynolds number range, two of the most common factors include external imbalance and internal imbalance.
GOAL 3: Circulation Pump Sizing An undersized circulation pump will not provide the Reynolds numbers necessary to achieve Goal 2. An oversized circulation pump will waste a lot of energy. In general, as of early 2016, many systems use significantly oversized circulation pumps. The circulation pump power for a system is reported in the Power Performance section on the Overview tab. If the design has an associated Peak Load entered for a design, the Piping Module will also report a Pumping Power Score at the top of the Overview tab. The lower the score, the better. And of course, the more stars, the better as well. As can be seen in the image below, this 1200 kBtu/hr (100 ton peak system) with 60 400 ft deep boreholes, requires only a 1.03 hP circulation pump, earning a Pumping Power Score of 1.0 (the lower the better) and five stars. If you have more detailed questions about piping design, we encourage you to experiment with different designs in the Piping System Builder and see how the different design decisions impact System results. Since the design process is fast and easy with these tools, they can act as a superb learning resource. If you are interested in expert training on these tools and the design process, please contact us. |