SPARES & ACCESSORIES
Regenerative turbine pumps and refrigerant processing
By Stephen Basclain, business development manager for Ebsray. R
efrigerants play a vital role in society, providing the proper temperatures to keep products in an ideal state for short or long periods of time. They can be found in a variety of industrial equipment, such as refrigerators, air conditioners, freezers and dehumidifiers. Refrigerants are specialty gas liquids produced at a dedicated manufacturing facility before they are transferred to an industrial plant that requires refrigeration. They are stored in large chillers, which must be continuously operational. The importance of refrigerants to the world is apparent: Without them, society is unable to function at the same capacity as it does today. But transferring refrigerants to all corners of the world is not as simple as handing it off from one person to the next. They require the proper equipment for processing and transfer and not just any pumping technology is capable of processing refrigerants effectively. While many different technologies can be used, there is a clear choice that stands above the rest – regenerative turbine pumps. Regenerative turbine pumps function as a superb solution to the demands of processing refrigerants. They can maintain high pressures while handling low viscosities fluids and aren’t susceptible to cavitation damage. This article will examine the capabilities of regenerative turbine pumps and why they work well over other pumping technologies when handling refrigerants. A closer look at regenerative turbine pumps Though considered rotodynamic, regenerative turbine pumps have close parallels to positive displacement (PD) pumps. Regenerative turbine pumps provide multi-stage performance from a single-stage impeller designed to optimize performance. This allows the pump to create high differential pressures at low flow rates. Regenerative turbine pumps function using a rotating, non-contact, free-wheeling impeller disc that has around 60 small cells on its periphery. When the liquid enters the suction port, the impeller obtains it and accelerates around the narrow hydraulic channel surrounding the cells. Kinetic energy carries the liquid rapidly around the channel. This motion within one revolution builds energy and pressure. The pump technology name stems from its function – the continuous regeneration of small liquid cells creates the differential pressure capability of the pump. Regenerative turbine pumps have the versatility to transfer liquids at high pressure and low flow, while also processing entrained vapours or liquids at or near their boiling point. These conditions limit most pump technologies, causing
28 July 2022 •
www.acr-news.com
performance issues, cavitation, vibration and noise. But regenerative turbine pumps don’t falter from those conditions. Specifically, regenerative turbine pumps can handle viscosities of 0.1 to 50 cSt with differential pressures up to 20 bar (300 psi) and have a maximum allowable working pressure of up to 493 psi (34 bar) to enable handling liquids with high vapour pressures. Typical regenerative turbine pumps generate flow rates up to 200 L/min (52.8 gpm), though some variations can operate with flow rates above that amount. Some newer iterations of this technology can reach peak flow rates as high as – and potentially higher than – 600 L/min (158.5 gpm).
This pump technology thrives because of its design. The
spiral motion, as well as its speed, diminishes the chances for cavitation and pulsation by smoothing the fluid and collapsing the vapour bubbles immediately when they form. Vibration and noise problems also don’t occur in most situations because the pump operates with a smooth flow and a hydraulically balanced design. Refrigerants aren’t the only application where
regenerative turbine pumps excel. This technology functions optimally in applications known for having low viscosity fluids, such as aerosol filling, as well as LPG and Autogas distribution. Other applications include vapourizer feed, cylinder filing, boiler feed water and ammonia transfer and distribution.
Compared with side-channel pumps As previously stated, as well as their resemblance to PD pumps in some aspects of performance, regenerative turbine pumps also have similarities to side-channel pumps. Examples of this are that both pumps can self-prime and perform optimally under poor suction conditions. The differences come from the size of the pump and ease of maintenance. Side-channel pumps are designed to have a larger footprint, mainly due to having multiple pumping stages. Side-channel pumps can have as many as four to eight stages to meet the duty parameters of a particular application. With that many stages, side-channel pumps and their large footprint become more complex to accommodate an installation’s demands. Regenerative turbine pumps, which feature a single- stage, can match the performance of the side-channel pump, while also functioning at two-pole speeds. Side- channel pumps typically operate at four-pole speed.
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