Handbook of air conditioning and refrigeration / Shan K

Action and Measures
REFRIGERANTS, REFRIGERATION CYCLES, AND REFRIGERATION SYSTEMS 9.11
3.1 percent in the Copenhagen amendments. The Copenhagen amendments had been ratified by 58
parties.
The impact of CFCs on the ozone layer poses a serious threat to human survival. The following
measures are essential:
Conversions and Replacements. Use alternative refrigerants (substitutes) to replace the CFCs in
existing chillers and direct-expansion (DX) systems. During the conversion of the CFC to
non–ozone depletion alternative refrigerants, careful analysis should be conducted of capacity, efficiency,
oil miscibility, and compatibility with existing materials after conversion. For many refrigeration
systems that already have a service life of more than 15 years, it may be cost-effective to
buy a new one using non-CFC refrigerant to replace the existing refrigeration package.
● HFC-134a and HCFC-22 are alternative refrigerants to replace CFC-12.
● HCFC-123, and HFC-245ca are alternative refrigerants to replace CFC-11 in large chillers.
It is important to realize that HCFC-123 and HCFC-22 themselves are interim refrigerants and will
be restricted in consumption beginning in 2004. HCFC-123 has a very low global warming potential and
is widely used in centrifugal chillers. HCFC-22 is widely used in small and medium-size DX systems.
● HFC-134a, HFC-407C, and HFC-410A are alternative refrigerants to replace HCFC-22. HFC-
407C is a near-azeotropic refrigerant of HFC-32/HFC-125/HFC-134a (23/25/52) [means
(23%/25%/525)], and HFC-410A also a near-azeotropic refrigerant of HFC-32/HFC-125 (50/50).
● HFC-245ca or another new HFC possibly developed before 2004 will be the hopeful alternative
to replace HCFC-123.
In supermarkets, CFC-502 is a blend of HCFC-22/CFC-115 (48.8/51.2).
● HFC-404A, HFC-507, and HFC-410A are alternative refrigerants to replace CFC-502. HFC-
404A is a near-azeotropic refrigerant of HFC-125/HFC-143a/HFC-134a(44/52/4); and HFC-
507 is an azeotropic refrigerant of HFC-125/HFC-143a (45/55).
Reducing Leakage and Preventing Deliberate Venting. To reduce the leakage of refrigerant from
joints and rupture of the refrigeration system, one must detect the possible leakage, tighten the
chillers, improve the quality of sealing material, and implement preventive maintenance.
Prevent the deliberate venting of CFCs and HCFCs and other refrigerants during manufacturing,
installation, operation, service, and disposal of the products using refrigerants.
Avoid CFC and HCFC emissions through recovery, recycle, and reclaiming. According to
ASHRAE Guideline 3-1990, recovery is the removal of refrigerant from a system and storage in an
external container. Recycle involves cleaning the refrigerant for reuse by means of an oil separator
and filter dryer. In reclamation, refrigerant is reprocessed for new product specifications.
To avoid the venting of CFCs and HCFCs and other refrigerants, an important step is to use an
ARI-certified, portable refrigerant recovering/recycling unit to recover all the liquid and remaining
vapor from a chiller or other refrigeration system. An outside recovery/reclaiming service firm may
also be employed. A typical refrigerant recovery unit is shown in Fig. 9.2. It includes a recovery
cylinder, a vacuum pump or compressor, a water-cooled condenser, a sight glass, a shutoff float
switch, necessary accessories, pipes, and hoses.
To recover refrigerant from a chiller that has been shut down involves two phases: liquid recovery
and vapor recovery. Liquid recovery is shown in Fig. 9.2a. The vacuum pump or compressor
in the recovery unit creates a low pressure in the recovery cylinder. Liquid refrigerant is then
extracted from the bottom of the chiller into the recovery cylinder. If the recovery cylinder is not
large enough, the shutoff float switch ceases to operate the vacuum pump or compressor when the