Heat only flows from warm to cold. For this reason, there are refrigerants which, at low temperatures and pressures, absorb energy from a hotter source and thereby evaporate. The refrigerants also have to release this energy again. This takes place through an increase in pressure and temperature as a result of a compression process, which means that the refrigerant can give off energy to a colder environment. The gas is then released in a throttle, which reduces the temperature and pressure to the level at which it can absorb energy.
If these work steps follow in a cycle, then heat is permanently withdrawn from the heat source, e.g. goods to be cooled, and they cool down.
However, these refrigerants can only cover certain temperature differences, which is why there are many different refrigerants that can be connected in series, so to speak, this is called cascading. Unfortunately, no refrigerant is perfect, so every refrigerant has advantages and also disadvantages in another respect. The following points are of particular importance when assessing refrigerants:
The harmfulness of refrigerants on the greenhouse effect is expressed by the GWP (Global Warming Potential), the GWP describes the harmfulness of one kilo of refrigerant to the harmfulness of one kilo of CO2.
Some refrigerants have toxic or flammable properties.
Many refrigerants do not have good thermodynamic properties, which means that the energy required to transport the heat increases.
To find the optimal refrigerant for the process, many factors have to be considered. Over the years, a refrigeration machine often costs many times its initial cost. The running costs of refrigerant loss, repair costs, maintenance and safety checks are often neglected.
The harmfulness of various refrigerants on the climate has been proven. In 1987, for example, a group of refrigerants that banned CFCs was banned. This grouping contains chlorine molecules that have been shown to contribute to the enlargement of the ozone hole.
Today, however, global warming is a problem for future generations. With the replacement of CFCs, new refrigerants had to be produced. This is how HFCs were brought to market. The HFCs do not damage the ozone layer, but they do contribute significantly to the greenhouse effect. The contribution to the greenhouse effect of a refrigerant is called GWP (Global Warming Potential). The GWP value is a mass-oriented comparison of one kilo of refrigerant to one kilo of CO2, where CO2 has the value 1.
The F-gas regulation has already led to a reduction in the amount of HFCs, which is leading to availability problems and price increases. From January 1, 2020, there will be a ban on the construction of stationary refrigeration systems with refrigerants exceeding the GWP value of 2500. For deep-freeze applications below -50 ° C there is currently an exception in the F-gas regulation. This includes, for example, R23 (GWP: 14800), the price of which has already risen sharply. This exemption is currently being discussed and could be abolished with the next revision of the F-gas regulation.
In order to avoid such problems, it is important to find out about the refrigerant to be used in advance. Cold air machines offer a particularly friendly alternative to harmful refrigerants; the refrigerant air is completely harmless to people and the environment.
Percentage reduction of the HFC refrigerants available on the market over the period 2015-2030
Source: Federal Environment Agency