REFRIGERANTS
Gliding towards the right choice
Some new refrigerants, such as R452A, R449A, R448A,R513A and R450A have a glide factor which wasn’t present in the older refrigerants they are replacing. Elise Kuntzelmann of La RPF*
talks to Patrice Serre,
application engineer and project manager for Friga Bohn refrigeration products at Lennox Emea about the importance of glide when choosing a product.
EK: What difficulties does a glide temperature refrigerant represent?
PS: The glide generates a variable evaporation temperature. This means that the difference between the return air temperature and evaporating temperatures of the refrigerant at the unit cooler outlet (Delta T) is not constant. In the case of some new refrigerants, these glides can be as much as 6°C. For a -8°C setup point it is possible for the refrigerant to enter the unit cooler as low as -14°C at the exchanger inlet.
The question is how to select a product that should work with a new refrigerant. In other words, how to take into account the Delta T, that is to say the difference between the evaporation temperature evaporator outlet and that of the air.
Unlike R404A, for which there was no glide, opting for the same equipment with a glide refrigerant, represents an overpower generated at the unit cooler.
By selecting an exchanger with a new refrigerant with the same power as R404A, the exchange surface will be much lower. This lower surface area may become restrictive in the case of foods with high moisture content. The freezing on the heat exchanger is faster and the performance will be reduced. By choosing a lower exchange surface, faster freezing involves more frequent defrosting. An electric defrost requires additional heat input into the chamber and therefore to turn the cold more often. It is therefore necessary to adapt the installation according to the type of products preserved.
*
La revue pratique du froid 14 October 2017
Looking at the future, we are being encouraged to work with refrigerants with a GWP of less than 150 such as R455A (about 12K glide) or R454C (about6K glide). But with a 12K glide, this raises questions about the durability of these refrigerants with respect to exchangers.
I also think that the local legislation should evolve the classification of certain refrigerants in the category of flammable. CO2
coefficients to inform end-users. We rely on refrigerant coefficients, which allows us, in te context of exchangers, to modify capacities in a reliable way. This makes it possible to compare different types of products.
EK: What about the water glycol option?
seems to me to be an interesting solution able to circumvent the various disadvantages mentioned.
EK: What does Eurovent certification mean when choosing a product?
PS: We are stakeholders in the Eurovent certification and work to define common
PS: We see a number of centralised glycol- based installations that promote the reduction of refrigerant volumes. There are medium temperature refrigeration systems running on glycol water or CO2
.
This last, condensing on glycol system water to make the low temperature part. It is an economical and more sustainable choice that will allow us to better support refrigerant changes. Microchannel solutions also tend to reduce the amount of refrigerants.
R449A
www.acr-news.com
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