Air Cylinder – Zero Grade Air

Air Cylinder: Zero-grade air specialty gas is typically used to zero out a sensor to an ambient air environment, free of unwanted impurities. Zero Air is available in the 34L, 103L, 221L and 550L size disposable calibration gas cylinders. Zero Air is available for immediate delivery. Please call us if you have an urgent requirement.  Air Cylinder – Zero Grade Air calibration gas can accommodate a variety of calibration gas regulators. Please select from the regulator options below. Contact us if you need assistance selecting the appropriate regulator for your specialty Air Cylinder gas application.

Basically, refrigerant gases used in all refrigeration systems are classified as natural and synthetic. Ammonia and carbon dioxide are the most widely used natural refrigerants due to their excellent thermodynamic properties. On the other hand, fluorocarbon-based refrigerants are synthetic substances that began to be developed and produced in the 1930s.

The importance of refrigerant gases in refrigeration systems: Air Cylinder – Zero Grade Air

The thermodynamic properties of refrigerant gases are the essence of the operation of any refrigeration system. Therefore, the design and construction of the compressor, evaporator, condenser, and expansion valve determine the type of refrigerant to be used.

Refrigerants are substances with a high capacity to absorb heat from one place and then dissipate it elsewhere. In this sense, the absorption of heat is carried out by taking advantage of the low temperature that the refrigerant acquires in low-pressure conditions. On the other hand, heat dissipation is carried out thanks to the ease with which the coolant heats up under high-pressure conditions.

In both industrial and domestic and commercial refrigeration, refrigerant gases move through a circuit. This circuit has a low-pressure zone and a high-pressure zone, in which the refrigerant is cooled and heated, respectively.

Natural refrigerant gases

The most important natural refrigerant gases for industrial refrigeration are ammonia (NH3) and carbon dioxide (CO2). In addition, we must also highlight sulfur dioxide (SO2), which was used at the beginning of the 20th century in small refrigeration equipment. Next, we will talk about each of them and also about propane gas.

Ammonia

Since 1876, ammonia has been the most widely used refrigerant for cooling large cold rooms. The ASHRAE classification assigns ammonia the code R-717. This is a highly toxic and corrosive gas. Therefore, refrigeration installations that use this refrigerant must comply with strict safety measures.

With ammonia, temperatures as low as -70 °C can be reached in refrigeration plants by absorption. On the other hand, using mechanical compression systems, temperatures of -40 °C can be reached. Ammonia refrigeration evaporators work at an average pressure of 20 psig, while condensers work at about 155 psig.

On the other hand, the boiling point of ammonia at atmospheric pressure is -33 °C, but the critical temperature is 133 °C. Also, the freezing temperature of ammonia is -78 °C.

Ammonia has an ozone depletion potential (ODP) equal to zero (0). On the other hand, the global warming potential (GWP) of ammonia is also zero. All the mentioned characteristics make ammonia an excellent natural and ecological refrigerant.

Carbon dioxide

Carbon dioxide, also known in the ASHRAE standard as R-744, is a much less toxic and corrosive refrigerant gas than ammonia. However, the use of its thermodynamic qualities is achieved at higher working pressures. Consequently, it requires more robust compressors, evaporators for refrigeration, condensers, and pipes.

CO2-based industrial refrigeration systems work in a subcritical or transcritical regime, although the latter requires relatively more complex installations.

Sulfur dioxide

In the mid-1930s, sulfur dioxide (SO2) was used as a refrigerant gas in small domestic refrigerators. However, it was rapidly displaced by chlorofluorocarbon-based synthetic refrigerant gases. The main causes of such substitution were its high toxicity and corrosivity.

Propane

Propane is a refrigerant gas derived from petroleum and has excellent thermodynamic properties. Its main disadvantage is that it is highly flammable, which requires certain safety conditions in case of leaks. However, it has the advantage of having a very low price.

In the ASHRAE nomenclature, propane is known as R-290 and is widely used in industrial refrigeration systems. In addition, it is a refrigerant gas with a PAO equal to zero and a GWP of just 3. Therefore, it is a very ecological alternative.

Synthetic refrigerant gases – Air Cylinder – Zero Grade Air

By 1930, refrigeration companies understood that natural refrigerants were never going to allow them to expand refrigeration to homes and small businesses. In other words, apart from the high toxicity and corrosiveness of almost all natural refrigerants, their characteristics did not allow compact equipment to be built. Consequently, thanks to great research and development efforts, the first synthetic refrigerants emerged.

At the time, these new coolants were the closest thing to the ideal coolant. In this way, dichlorodifluoromethane (CCl2F2) was created, which is also known in the ASHRAE standard as R-12. However, over the years, it was determined that fluorocarbon-based refrigerants were damaging the ozone layer and contributing to global warming. Consequently, in the Montreal Protocol (1986), its replacement was agreed upon at the global level.
R-12 was replaced by chlorodifluoromethane (HCFC), which is also known as R-22. However, this synthetic refrigerant gas was quickly replaced by a new generation of HFC (hydrofluorocarbon) gases, which cause less harmful effects on the environment.

R-134a, one of the most used HFC gases today: This HFC refrigerant has zero ozone depletion potential (ODP). On the other hand, the global warming potential (GWP) is 1430. When R-134a is used in compressors designed for R-12, mineral oil must be replaced by synthetic oil based on polyester (POE).

R-134a can in turn be replaced by a more modern gas based on hydrofluoro olefins (R-513A). This state-of-the-art refrigerant gas has a GWP of 630, which is much lower than that of R 134a.

R-152a for industrial refrigeration: R-152a is a difluoroethane-based refrigerant gas, which has a GWP of 124 and does not destroy the ozone layer. This refrigerant has thermodynamic properties superior to R-134a and is widely used in chiller-type refrigeration systems.

Zeotropic mixtures of refrigerant gases

All the refrigerants mentioned above are chemically pure substances. Therefore, they have a single boiling and condensation point at a certain pressure and temperature. However, zeotropic refrigerant mixtures are compounds formed by two or more pure refrigerants with different boiling and condensation points. These mixtures form the 400 series of the ASHRAE classification.

The most widely used zeotropic mixtures today are the following: R-404A, R-410A, R-450A, and R-448A. In all of them, the slip produced by the different boiling and condensation points of the substances that make up each mixture is taken into account.