The use of Carbon dioxide (R744) as a refrigerant declined for a number of
reasons, including
changes in technology and the introduction of fluorocarbon refrigerants, which were seen
as ‘safety refrigerants’.
Properties
A) Carbon dioxide has an ozone depletion potential (OPD) of zero and a global warming
potential (GWP) of 1.
B) It is generally regarded as a cheap and easily available refrigerant, and many regard
it as an ideal refrigerant.
C) Carbon dioxide is non-toxic. It has low toxicity and is non-flammable.
D) Carbon dioxide is colorless, odorless and is also heavier than air.If enough carbon
dioxide builds up in an enclosed space it will begin to displace oxygen and can cause
asphyxiation in anyone present within the space. As carbon dioxide is colorless and
odorless, a person in the space will not be able to tell unless proper detectors and
alarms are installed.
E) As a refrigerant, carbon dioxide operates at a higher pressure than fluorocarbons and
other refrigerants. While this presents design challenges it can usually be overcome in
systems designed specifically in suction and discharge tubing.
F) Carbon dioxide is not compatible with commonly used refrigeration system lubricants.It
is not suited for use with polyol ester (POE) and poly vinyl ether (PVE) lubricants, and
it has only limited applications with poly alkylene glycol (PAG) lubricants.
Safety Issues
A) Some restrictions are placed on the size of the refrigerant charge, with additional
allowances made for systems with detectors and alarms fitted, and as carbon dioxide is
heavier than air the standard requires “suitable precautions” to be taken to prevent the
undue accumulation of refrigerant in occupied spaces in the event of a leak.
B) As with fluorocarbon refrigerants, the standard also requires the system to be designed
to withstand the refrigerant’s maximum operating pressure.
C) The International Institute of Refrigeration (IIR) identified carbon dioxide’s high
working pressure as the main drawback to its use.
Thermodynamic Properties
1) Carbon dioxide is colorless. At low concentrations, the gas is odorless. At higher
concentrations it has a sharp, acidic odor.
2) At standard temperature and pressure, the density of carbon dioxide is around 1.98
kg/m3, about 1.5 times that of air.
3) Carbon dioxide has no liquid state at pressures below 5.1 standard atmospheres (520
kPa). At 1 atmosphere the gas deposits directly to a solid at temperatures below −78.5 °C
and the solid sublimes directly to a gas above −78.5 °C. In its solid state, carbon
dioxide is commonly called dry ice.
4) Liquid carbon dioxide forms only at pressures above 5.1 atm; the triple point of carbon
dioxide is about 518 kPa at −56.6 °C.The critical point is 7.38 MPa at 31.1 °C.
Corporate Acceptance
Coca Cola company stated that the company’s preliminary field tests proved the technology
to be reliable, in real life circumstances the equipment often used less energy than
equivalent equipment using HFC as a refrigerant.
Till 2006, the company was market testing a range of drinks fridges and vending machines
using carbon dioxide refrigerants.
changes in technology and the introduction of fluorocarbon refrigerants, which were seen
as ‘safety refrigerants’.
Properties
A) Carbon dioxide has an ozone depletion potential (OPD) of zero and a global warming
potential (GWP) of 1.
B) It is generally regarded as a cheap and easily available refrigerant, and many regard
it as an ideal refrigerant.
C) Carbon dioxide is non-toxic. It has low toxicity and is non-flammable.
D) Carbon dioxide is colorless, odorless and is also heavier than air.If enough carbon
dioxide builds up in an enclosed space it will begin to displace oxygen and can cause
asphyxiation in anyone present within the space. As carbon dioxide is colorless and
odorless, a person in the space will not be able to tell unless proper detectors and
alarms are installed.
E) As a refrigerant, carbon dioxide operates at a higher pressure than fluorocarbons and
other refrigerants. While this presents design challenges it can usually be overcome in
systems designed specifically in suction and discharge tubing.
F) Carbon dioxide is not compatible with commonly used refrigeration system lubricants.It
is not suited for use with polyol ester (POE) and poly vinyl ether (PVE) lubricants, and
it has only limited applications with poly alkylene glycol (PAG) lubricants.
Safety Issues
A) Some restrictions are placed on the size of the refrigerant charge, with additional
allowances made for systems with detectors and alarms fitted, and as carbon dioxide is
heavier than air the standard requires “suitable precautions” to be taken to prevent the
undue accumulation of refrigerant in occupied spaces in the event of a leak.
B) As with fluorocarbon refrigerants, the standard also requires the system to be designed
to withstand the refrigerant’s maximum operating pressure.
C) The International Institute of Refrigeration (IIR) identified carbon dioxide’s high
working pressure as the main drawback to its use.
Thermodynamic Properties
1) Carbon dioxide is colorless. At low concentrations, the gas is odorless. At higher
concentrations it has a sharp, acidic odor.
2) At standard temperature and pressure, the density of carbon dioxide is around 1.98
kg/m3, about 1.5 times that of air.
3) Carbon dioxide has no liquid state at pressures below 5.1 standard atmospheres (520
kPa). At 1 atmosphere the gas deposits directly to a solid at temperatures below −78.5 °C
and the solid sublimes directly to a gas above −78.5 °C. In its solid state, carbon
dioxide is commonly called dry ice.
4) Liquid carbon dioxide forms only at pressures above 5.1 atm; the triple point of carbon
dioxide is about 518 kPa at −56.6 °C.The critical point is 7.38 MPa at 31.1 °C.
Corporate Acceptance
Coca Cola company stated that the company’s preliminary field tests proved the technology
to be reliable, in real life circumstances the equipment often used less energy than
equivalent equipment using HFC as a refrigerant.
Till 2006, the company was market testing a range of drinks fridges and vending machines
using carbon dioxide refrigerants.
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