Did you know that CO2 is NOT dangerous? -G. Pisano-
Truly,
every refrigerant is able to harm if not properly handled. But actually
one of the feature which drives the fear toward carbon dioxide is
exactly the one which is bringing the largest benefit: high pressure is
frightening but is also the quality providing stunning heat transfer
properties when CO2 is used into a refrigeration system.
However
high pressure shall not be frightening at all, because with an
appropriate design a CO2 system is simple and safe, like every other
system. And, though is working with higher pressures, a CO2 system uses
smaller or similar pipe wall thickness to other systems, too! Do you
dare to unbelieve this? Just consider the following example.
Let’s
pretend I am the owner of a supermarket chain and I am planning to open
a new small size point of sales requiring a total of 50kW refrigeration
capacity, with 50 meters overall pipe length. When thinking about
choosing R404A, my engineers have dimensioned the evaporators return
lines to the machinery room with a 50 mm pipe diameter featuring 1,5 mm
wall thickness. Doing the same exercise with CO2 leads to a 20 mm pipe
diameter and a 1 mm wall thickness. And guess what? I will give a ring
to my friend Peter Barlow, to let him calculate the pipe hoop stress
induced by both systems (R404A and CO2) obviously using the same
material: interesting enough, he informed me that both examples lead to
same hoop stress, around 40 Mpa, which is well below the maximum
allowable stress for the given pipe material.
So, why bother about high pressure? Simply follow basic engineering rules and get the best out of CO2!
