Refrigerant Selection for Hot Climates
When you choose an air conditioning or refrigeration system you also choose a refrigerant. When you choose a refrigerant you choose energy efficiency. Refrigerant selection is the primary determinant of air conditioning and refrigeration equipment efficiency. A wise choice can save you a lot of money.
To make a wise choice when choosing a refrigerant you need to ask about its critical temperature.
What is the Critical Temperature of a Refrigerant?
Conventional refrigeration cycles can only operate efficiently using fluids well below critical temperature. Refrigerant R22 has a critical temperature of 96 degrees Celsius. Whereas R410 and R32 (the HFCs designed to replace R22) have a critical temperature of only 71 degrees Celsius. Therefore R410a and R32 will not work efficiently in very hot climates such as Australia and the Middle East because the temperatures in those places rise to over 50 degrees Celsius in the shade in summer. (And up to 70 degrees on a roof in the direct sun)
The critical temperature of a refrigerant is the temperature above which a refrigerant gas (vapour) cannot be liquefied, irrespective of pressure. This process normally takes place in the condenser. The refrigeration compressor pumps hot gas (vapour) into the condenser coil. The air passing through the condenser coil removes the heat from the hot gas (vapour) and it changes state to a liquid. The refrigerant moves along the closed refrigeration system as a liquid to continue the cycle.
Why is the Critical Temperature of a Refrigerant Important?
The performance of an air conditioning or refrigeration system decreases with increasing outdoor temperatures. Refrigerants with a low critical (design) temperature experience a larger degradation of cooling capacity.
The critical temperature of the refrigerant should be as high as possible above the condensing temperature in order to have a greater heat transfer at a constant temperature. If this is not taken care of, then you will have excessive power consumption by the air conditioning or refrigeration system. You may also experience equipment failure due to the excess pressures and temperature build up within the operational air conditioning or refrigeration system.
Is there a solution?
Hydrocarbon Refrigerants have very high critical temperatures and reject heat more than 50% faster than chemical refrigerants. They have been tried and tested over many years in extreme weather conditions. They are indeed an ideal solution for the replacement of HCFCs and HFCs (chemical refrigerants) in extremely hot climates.
The application of flammable hydrocarbon refrigerants can be done safely as with any other type of refrigerant. (By trained engineers and technicians). Several Australian Companies have over 15 years’ experience working with hydrocarbon refrigerants in extremely hot climate conditions. There is no reason to choose extremely harmful and inefficient fluorocarbon refrigerants when solutions are readily available using natural refrigerants for the majority of applications.