HI Pump FAQs
Data Center Cooling & Wastewater Pump Selection
| IMAGE 1: Grit removal system and pump (Image courtesy of the Hydraulic Institute)
How are pumps used in data centers for cooling?
The growth of advanced cloud computing systems for AI is increasing cooling requirements, resulting in cooling being one of the most critical considerations for a new data center. Pumps play a vital role in cooling these systems by circulating heat transfer liquids that cool the equipment. Liquid cooling can more effectively transfer heat than air due to a much higher volumetric heat capacity; therefore, liquid cooling is advantageous for larger heat loads because it can reduce the footprint and overall cooling energy consumption.
Liquid cooling applications vary widely for data centers but range from various closed-loop heat transfer systems to full immersion of the electronics in dielectric fluids. Each requires a pump of specific design to meet the application requirement; therefore, the type and size of pumps used will depend on the specific application. Lastly, data center cooling requirements—and the technologies and methods used to cool them—are constantly evolving, so it is a difficult task to provide an all-inclusive overview.
The Hydraulic Institute is working to publish some consensus information and guidance on the topic of data center cooling. A committee was recently launched with the purpose of writing a paper that addresses liquid cooling applications such as hybrid air/water cooling, direct-to-chip cooling, immersion cooling and two-phase cooling.
For more information on pump application guidelines and selection of pumps for specific applications, refer to guidebooks available at pumps.org.
How do wastewater properties affect pump selection for the application?
The properties of the wastewater stream are a primary consideration in the pump type selected, and they will impact performance, reliability and maintenance requirements. Wastewater streams often contain varying concentrations of solids, chemicals, biological materials and other contaminants that can influence hydraulic performance and component wear.
When evaluating a wastewater stream, fluid characteristics must be considered, such as:
- Solids concentration and particle size
- Abrasiveness of the solid or the tendency for it to tangle together
- Temperature, specific gravity, pH and viscosity
Wastewater streams and their makeup vary greatly. For example, influent of wastewater to a treatment plant is mostly water that contains inorganic and organic solids, but later in the preliminary treatment process, there are wastewater streams that have considerably more solids that are dense and abrasive, such as grit removal applications. Comparing the requirements for these applications provides a distinct contrast that illustrates how the wastewater streams affect pump design.
Wastewater Influent
The pumps used in an influent lift station must be of the solids-handling type and be capable of passing solids that may include household and commercial solids; large solids; stringy material (rags, hair, etc.); woven materials; sanitary waste; plastic scraps; food waste; sticks, leaves and abrasive materials (sand, grit, stones and pieces of metal); and other inorganic and organic solids. Stringy materials and rags can bind together, creating a large mass that can potentially lead to clogging issues in the pump and associated piping.
Grit Removal
Downstream in the treatment process, after passing through the screens that remove large solids such as sticks, rags and plastic bottles, the wastewater flow enters a grit removal system that separates the grit, sand, gravel and other heavy material that was not separated by the screening. This material is removed to reduce abrasive wear on the downstream components and so that it does not settle in downstream basins or channels. The materials removed by the grit removal system are collected and may be transferred to a classifier, optional washer, cyclone and dewatering system. The collected grit is then either disposed of in a landfill or recycled when permitted and practical.
To support this, a grit transfer pump (Image 1) is required. To limit abrasive wear, the grit transfer pump is commonly a recessed impeller type or other abrasion-resistant solids-handling design. There are several special considerations that need to be addressed when pumping grit slurries. Some include pump sizing, pipeline velocity, pipeline routing, wear/abrasion of the pump and associated piping, preventing the plugging of the grit piping and preventing compaction and solidification of the grit in the storage hoppers and pipelines.
When comparing these two wastewater applications and streams, it is evident pumps with different design objectives are required. The influent pumps will be designed to pass a certain solids size, while the grit removal pump will be designed to pass a high concentration of abrasive solids. The contrast in application and wastewater properties leads to important differences in the pump design to achieve optimal functionality and performance.
For more information on wastewater pumping applications, the wastewater stream and the pump types used for the application, refer to the Wastewater Treatment Plant Pumps: Guidelines for Selection, Application and Operation guidebook at pumps.org.
HI Pump FAQs® is produced by the Hydraulic Institute as a service to pump users, contractors, distributors, reps and OEMs.
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