REFRIGERANTS
term option, it should be noted that these stocks are finite. Therefore, this should only be viewed as a temporary solution until a more permanent solution can be implemented.
Future options When assessing of what to do with existing F-Gas refrigeration plant, it is often desirable to retain the equipment and consider what options are available to allow for continued operation up to 2030 and beyond. One option is conversion of the refrigerant gas to a lower GWP alternative, examples of which can be found in figure B. As part of any refrigerant conversion work it is important to consider the following: Replacement of thermostatic expansion valves (TEVs) with electronic expansion valves (EEVs) - Many of the new lower GWP refrigerants are a blend of chemicals that evaporate over a temperature range, often referred to as ‘glide’. This may differ from the existing fluid, which is likely to evaporator at a constant temperature. It is recommended to replace traditional TEVs with EEVs to provide
better control of refrigeration flow around the system and reduce the risk of liquid passing from evaporators back to the compressor and causing damage. This modification requires replacement of the valve itself, a new control panel or panel modifications to incorporate the new controller(s) and site wiring between the controller(s) and the EEVs. There is an added benefit when using EEVs in terms of improving system efficiency, especially when coupled with floating head pressure control.
Change in cooling capacity and power consumption - When converting to a new refrigerant there is the potential for a change in system cooling duty and/or power consumption. This is due to differences in the characteristics of the new refrigerant (e.g. specific heat, mass flow and operating pressures). An assessment should be undertaken when planning the works
to ensure there is sufficient capacity and power available after the conversion to meet the existing cooling demand.
Compressor discharge temperature - Introducing a new refrigerant to an existing system can lead to an increase in compressor discharge temperature. This has the potential to damage the compressor itself, add personnel safety concerns due to the elevated temperature and possible problems with oil cooling. A simple assessment can be carried out using the compressor supplier’s selection software to ensure that this issue is avoided. This may involve further modifications to the system and avoiding the use of a particular refrigerant.
Modifications to refrigerant leak detection – When changing refrigerant, the existing leak detection system need to be modified/ recalibrated. This could include the replacement of detection system ‘heads’ and/or the recalibration of the system for the new refrigerant characteristics.
Increased operating pressure – A replacement refrigerant may operate with higher working pressures than the gas it’s replacing. This may require modifications to system components such as pressure relief valves and even the pipework itself. Assessment of future working pressures is essential to ensure safe operation after conversion and should be carried out before work commences.
Assessment of flammability – Many HFC refrigeration systems were not subject to assessments relating to ignition or explosion risk when originally installed. However, a growing number of replacement refrigerants are classified as mildly flammable (A2L)- see figure B. This means they are unlikely to be suitable as replacement fluids for existing
www.acr-news.com systems without significant modifications.
The way of minimising a refrigerant’s contribution towards global warming is to utilise a natural fluid, such as ammonia or carbon dioxide. These low cost gases have been used for over a hundred years. Ammonia has a
GWP of zero and CO2 has a GWP of one. Neither are subject to the F-Gas Regulation and so purchasing of any natural refrigerant equipment can be seen as a long-term investment. With the introduction of the F-Gas Regulation, it has become necessary to monitor refrigeration equipment containing HFC for leakage, to limit the potential environmental impact caused by a release into the atmosphere.
The regulation is a positive step in terms of ever-growing
environmental awareness but also bring additional responsibilities on parties who are tasked with ensuring conformance to the regulation. It is hoped that the information provided in this article provides refrigeration plant owners and operators with a greater understanding of how the F-Gas Regulation affects their business and what should be considered when for the future.
Figure B. March 2020 41
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60
