REFRIGERANTS is that any new or existing
products must have no ability to deplete ozone so R22 and any R22 containing blends are the past. A major problem with regulations on HFCs emanating from the Authorities – and the EU in particular under the F Gas regulations – is that they focus entirely on the direct Global Warming Potential (GWP) of a refrigerant and do not take into account the Total Equivalent Warming Impact (TEWI) of a system. But energy efficiency – and therefore lower emissions of CO2 – should surely be the key determinant factor in the selection of any refrigerant rather than their individual direct GWP. In short, F Gas is a crude, inefficient and simplistic way of regulating refrigerants. We shall have to wait and see if F Gas will still apply to the UK at the end of the transition period in December but the likelihood is that the UK will contin ue to be regulated by similar regulations at the very least, if not F Gas itself
The headline attraction of so- called natural refrigerants such as ammonia, hydrocarbons and CO2 is their description of being ‘natural’. In fact these products are not natural at all but in reality substantially manufactured in chemical plants. Of course, their GWPs are low which is also a prime attraction but there are offsetting problems including flammability, toxicity, high pressure and require higher capital
In the case of CO investment.
2, there is
the additional problem of lower efficiency due to its low critical temperature. But there is a new family of chemicals called hydrofluoro-olefins (HFOs) which either in isolation or in combination with other components have the very real potential of providing refrigerant compounds which have very low GWPs and are either non- flammable or of low flammability (A2L ASHRAE safety classification). Hydrofuoro-olefins (HFOs), has been developed by the fluorochemical manufacturers which could provide the basis for
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a practical and lower cost solution. HFOs have very low atmospheric lifetimes which result in GWPs below 10 and often below 1, that is, similar to CO2. Essentially, HFOs are not suitable direct replacements for low boiling refrigerants but can be blended with HFCs to provide replacement blends combining low GWPs, non-flammability, or low flammability, with equal or higher efficiencies.
The acr industry has been accustomed to fluids with low temperature glides or azeotropes, for example R22, R404A, R507, R410A, but practical experience since the 1990s has shown that blends with wide glides (eg R407C) have not presented problems in RAC installations, so new HFO/HFC blends such as R448A, R449A, R470A, R470B clearly point the way to a lower GWP and safe future.
We wrote in this magazine a year ago that the development of blends with GWP less than 400 provides a practical, stable, energy efficient, non-flammable, low toxicity and low-cost way forward to replacing refrigerants such as R404A, R507 and R410A. In order to retrofit such blends into an existing installation, then of course any refrigerant has to be non-flammable.
In the particular case of
equipment using R404A and R507 at low evaporating temperatures of ca 350C for example, it gets progressively more difficult to
match their key properties of energy efficiency, non-flammability, low toxicity, low GWP. Reducing the GWP even further risks flammability, although it may be possible to drive the GWP even lower without compromising performance.
But the key point here is that, by signalling that a direct GWP limit of max 400 would be acceptable for at least the next 10 years, particularly in the case of replacing both R404A and R507, the authorities would provide more stability and certainty in the market. After all, there are some countries which have not made the transition to HFCs yet and are still operating largely on R22.
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