Types of refrigerant
Ammonia (NH3)
Ammonia is the primary and most widely used refrigerant worldwide in industrial refrigeration applications. It is mainly used in large installations such as deep-freeze stores, slaughterhouses, breweries, central refrigeration in the chemical industry and ice rinks. Cascade systems where CO2 and ammonia are used in parallel are becoming increasingly popular.
Advantages And Disadvantages
The advantages of ammonia are its large specific enthalpy of vaporisation, its environmentally friendly properties and many years of experience as a refrigerant. Ammonia counts as natural refrigerant because of its low GWP. Difficulties arise especially from the toxic, odor-intensive effect of ammonia and the material incompatibility with copper and brass. The installation costs increase due to the higher safety requirements.
Properties
- R717
- Global Warming Potential (GWP): 0
- Density (0 °C): 638.6 kg/m3
- Spec. heat (0 °C): 4.616 kJ/kgK
- Vapor pressure (0 °C): 0.429 Mpa / 60 pisa
Recommended pump series
Carbon dioxide (CO2)
Carbon dioxide is increasingly used as a refrigerant. Particularly popular are supermarket refrigeration and industrial refrigeration systems. CO2 is used in different forms, subcritical in cascade systems, transcritical in pure CO2 systems or as a secondary fluid.
Advantages and Disadvantages
The advantages of carbon dioxide are high environmental compatibility (natural refrigerant) the particularly good heat transfer coefficient and a low compression-to-pressure ratio. Due to the significantly better ratio compared to ammonia, the volumetric efficiency is higher which means that systems can be built more compact. Disadvantages are the proximity of the operating range at the triple point and critical point, as well as the high operating pressures required for efficient operation. The high pressure requirements lead to high system costs.
Properties
- R744
- Global Warming Potential (GWP): 1
- Density (0 °C): 927.4 kg/m3
- Spec. heat (0 °C): 2.542 kJ/kgK
- Vapor pressure (0 °C): 3.485 Mpa / 500 psia
Recommended pump series
Hydrocarbons (HC)
Hydrocarbons are also frequently used as refrigerants, in particular propane, isobutane and propene. Isobutane and propane can be found in many household refrigerators for example. Propane refrigeration systems can also be found in supermarkets.
Advantages and Disadvantages
Hydrocarbons are used due to their good thermodynamic properties and the high similarity with HCFCs in terms of pressure conditions. Propane, for example, has properties similar to HCFC chlorofluoromethane (R22). In addition The disadvantages are the high flammability and the increased requirements for explosion protection.
Properties
- Propane R290
- Global Warming Potential (GWP): 3
- Density (0 °C): 528.7 kg/m3
- Spec. heat (0 °C): 2.503 kJ/kgK
- Vapor pressure (0 °C): 0.474 Mpa / 5 psia
Recommended pump series
Water / Water glycol (H2O)
Water is one of the most common refrigerants worldwide. Water-glycol mixtures are based on a combination of water and glycol, such as ethylene glycol, which acts as anti-freeze and anti-corrosion agent. The mixture may have a different composition depending on the required temperature range. The freezing point can be lowered to –50 °C. Typical applications are cooling inverters in rail vehicles.
Advantages and Disadvantages
Advantages of water / water glycol mixtures lie in the low-cost procurement, the worldwide availability, the non-toxic material property and the high specific heat capacity of water. Due to its environmentally friendly properties, water / water glycol mixtures count as natural refrigerants. However, there are difficulties due to the required compressor power. Compared to an ammonia compressor with the same cooling capacity, a compressor for water has to suck in and compress a volume flow that is up to 300 times as large. This is the reason why the water refrigeration system takes up a very large space.
Properties
- R718 (Water)
- Global Warming Potential (GWP): 0 (*pure water)
- Density (0 °C): 999.7 kg/m3
- Spec. heat (0 °C): 4.195 kJ/kgK
- Vapor pressure (0 °C): 0.001 MPa
Recommended pump series
Hydrofluorcarbons (HFC)
For a long time, Hydrofluorcarbons such as R404A have been used in a wide variety of refrigeration applications. Since January 1, 2020, many HFCs have been banned from the F-Gas Regulation to reduce global warming effects. The regulation prohibits the use of refrigerants with a Global Warming Potential (GWP) of over 2500 in stationary refrigeration systems. However, they can still be used in low-temperature applications below –50 °C.
Advantages and Disadvantages
A popular HFC is the refrigerant R404A, which particularly impresses with its high volumetric cooling capacity. This allows to build refrigeration systems comparatively small. In addition, R404A has long been considered a good alternative for the conventional refrigerants R22 and R502. Due to the high global warming effect, the use of HFCs such as R404A has been severely restricted in Europe. There are more than one alternative for R404A; R-32, R407A or natural refrigerants.
Properties
- R404A
- Global Warming Potential (GWP): 3920
- Density (0 °C): 1,150.0 kg/m3
- Spec. heat (0 °C): 1.357 kJ/kgK
- Vapor pressure (0 °C): 0.61 MPa
Recommended pump series
Silicone oil
Silicone oils such as type Baysilone KT3 are used in particular for low-temperature applications below –50 °C. A typical application are freeze-drying systems which are used for example in the pharmaceutical industry or biotechnology. The systems are used at operating temperatures from –60 °C to –90 °C.
Advantages and Disadvantages
Silicone oils are used as refrigerants, particularly in the low temperature range. Baysilone KT3 is characterized by a low pour point < –100 °C, high thermal stability and low vapor pressures for example. In addition, the silicone oil is not corrosive. However, silicone oils are very expensive compared to other refrigerants.
Properties
- Silicone oil Baysilone KT3
- Type: Linear polydimethyl siloxanes
- Density (–60 °C): 980 kg/m3
- Spec. heat (–60 °C): 1.54 kJ/kgK
- Viscosity (–60 °C): 25 mm2/s