Alternatives refrigerant with GWP <5 This section details alternatives natural or hydrocarbons refrigerants with a GWP lower than 5 and ODP of 0, which are gaining momentum such as: Ammonia, Propane, C02 and Water.
AMMONIA (R 717)
GWP : 0 ; ODP : 0
General Description
Ammonia (NH3) is a natural refrigerant approximately 15-20% more efficient than its HCFC counterparts, low cost and abundant. It is an irritant to eyes and skin, has a strong odour which makes leaks easily detectable and requires safety measures in internal plant room containing chillers. It is one of the first refrigerant used in the history of refrigeration. It is not a pollutant; in fact, it is a fertiliser. Ammonia corrodes copper, therefore in canâ&#x20AC;&#x2122;t be used in VRF systems and cannot operate in hermetic compressors (i.e. compressors where the motor is in an enclosure under refrigerant pressure) because the copper windings on the motor would corrode. Ammonia chillers require external motor (i.e. centrifugal compressors). The ammonia molecule is small, therefore the prevention of leakage along the shaft between compressor and motor is difficult
Technical Use
Used in a lot of low temperature applications like CO2, where HFOs are not the best fit. Its high efficiency allows for the reduction in heat exchange surface area, smaller pipe sizes and refrigerant charges. New products are in development to overcome the problem of compatibility ammonia / copper, this include semi hermetic compressor (i.e. the copper in outside the refrigerant circuit); Hermetic compressors with aluminium motor windings (not subject to ammonia corrosion) and separating hood compressors (i.e. permanent magnets rotors located in a pressurised enclosure) with stator externally (i.e. the copper windings are outside the refrigerant circuit)
Drawbacks
Toxicity and flammability, which can be deadly if it exceeds 300 ppm. R-717 is classified in the B2 safety group (for toxicity and flammability) in ASHRAE Standard 34-2010
Usage recommendations
Used in large refrigeration/chiller plants or in small packaged chillers. Requires sprinklers in internal plant rooms
Commercial Availability
Star Refrigeration, Azena, Evapco, Budzar Industries, and GEA
PROPANE (R 290)
GWP : 4 ; ODP : 0
General Description
Natural hydrocarbon refrigerant - used in many parts of our daily life, such as refrigerators, air conditioning or even hairspray
Technical Use
Works with high flow temperatures (75oC in hot water from heat pump is possible) so improves COPs at higher flow temp Safety measures must be implemented in heat pump and after-sales service processes, similar to Gas boilers Spark free tools needed
Drawbacks
Highly Flammable and risk of suffocation. Moreover, it is a by-product of natural gas processing and petroleum refining, therefore linked to the oil industry
Usage recommendations
Suitable for large refrigeration/chiller plants or in small packaged chillers
Commercial Availability
Vaillant (aro Therm heat pumps), Gree (Asa), Dimplex (Edel). Not very common in the US so far
Refrigerants & Environmental Impacts
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