Refrigeration & Climate Pumps
Nowadays, it is impossible to imagine our daily life without industrial refrigeration technology. Be it for frozen foods, freeze-dried fruits and vegetables, or temperature-controlled cold storages and state-of-the-art plant or server cooling, modern refrigerants and high-tech installations can be found in all areas. At the same time, the requirements on availability, safety and leak tightness have increased significantly in recent years.
Pumps for refrigerants
The machines and systems in refrigeration technology are subject to continuous change. For example, the introduction of the new ‘F-gas regulation’ has resulted in refrigerants such as ammonia (R717, NH3) and carbon dioxide (R744, CO2) to become more and more popular. Here, the requirements on leak tightness and dimensioning of components increase with the vapor pressure of the refrigerants. Reliability and simple handling of the pumps are also of great importance when it comes to delivering water or water-glycol mixtures.
Application areas for pumps of refrigeration technology
Pumps are used in refrigeration technology at a variety of different locations. In large systems, for example, pumps deliver the refrigerant (e.g. ammonia, carbon dioxide) to the individual evaporators. Due to the high vapor pressure of the refrigerants and the low temperatures (where icing is a risk), hermetic pumps, which do not feature a shaft seal, have become widely accepted for use in this area – such as the canned motor pump, a special design of the radial pump. The refrigerant vapor becomes compressed and cooled in the compressor circuit so that the medium condenses and is returned to the reservoir as a liquid. In many cases, ‘cold’ is also delivered to the consumers by means of heat transfer fluids, such as oil, water or water-glycol mixtures. These media are transported by pumps – often over a widespread supply network – to the locations to be cooled.
Application examples for pumps in the refrigeration & climate area
· Space cooling
· Cold storages
· Plant cooling
· Server cooling
· Freeze drying
· Deep freezing
· Refrigerating plants
· Ground freezing systems
· Cryogenic applications
· Air conditioning / industrial air-conditioning systems
Possible refrigerants / refrigerating agents for refrigeration technology
· Ammonia (NH3)
· Carbon dioxide (CO2)
· Water-glycol mixtures
Successful application examples
Liquid ammonia (NH3) is a modern refrigerant. When pumping from the reservoir, attention must be paid to a low NHSH value and technical leak tightness. Mostly hermetic pumps are used here.
Carbon dioxide, also known as R744 or CO2, is a refrigerant with great future potential. Because of its high vapour pressure, it is necessary to ensure a suitable design of the components and pumps.
The most commonly used liquid for distributing heat and cold is water. Water is often mixed with glycol to prevent it from freezing. The centrifugal pump is the most common technology used to pump these media. Mechanical seals are the preferred choice in simple designs. But with higher demands on system availability and MTBF (e.g. mobile application on trains or in difficult-to-access offshore applications), hermetic pumps are increasingly being used.
Many modern electronic components generate a large amount of heat and must therefore be cooled to ensure trouble-free operation. A water-glycol mixture, used most commonly, is pumped through an air cooler which then cools the components. Seal-less (hermetic) pumps have proven themselves in mobile systems. This technology is also often applied to cool transformers by using oil and conveying it through the air coolers.
Oils are generally used for refrigerant transport in deep-freeze and freeze-drying applications. These oils are still viscous at low temperatures, which makes centrifugal pumps suitable for use with them. Hermetic pumps are often required at low temperatures in order to avoid damage due to ice build-up and to ensure high system availability.
Centrifugal pumps with special designs and materials have proven themselves for very low temperatures. Stainless steel or aluminium, for example, are used as pump materials. The pump and motor often form a unit (canned motor).
“The pumping of cryogenic liquids, which are increasingly used in special refrigeration technology, requires special pump designs. Very high demands are placed on the static seals and materials, and the motor technology has to be adapted (liquid-cooled motor).”
In absorption refrigeration systems, a substance in a solution (e.g. ammonia or lithium bromide) is used as the refrigerant. In the continuous process, which often takes place in a vacuum, centrifugal pumps convey the solution in the media. Hermetic centrifugal pumps are generally used because the processes take place in a vacuum and the used media must not be released into the environment.