Refrigerants & Coolants Bartosz Zajaczkowski, PhD Lecture 5

Four groups: HC, HCFC, CFC, HFC Halocarbons Today topics Four groups: HC, HCFC, CFC, HFC Halocarbons R11 R12 R22 R134a R1234yf R-numbering system

THE FOUR GROUPS

There are three groups/combinations/categories of synthetic refrigerants + plus the natural base: HC – HydroCarbons (natural refrigerants that serve as a base for production of synthetic ones) CFC – ChloroFluoroCarbons HCFC – HydroChloroFluoroCarbons HFC - HydroFluoroCarbons

They are two the most basic HC refrigerants that became all synthetic halocarbons. methane R-50 (-161.7°C, 111.4 K) ethane R-170 (-88.6°C)

Hydrocarbons are not used in AC and refrigeration systems due to their dominant characteristic - high flammability. Precautions need to be taken to mitigate the consequences. Hydrocarbons make excellent refrigerants in practice and are very popular in the petrochemical industry, where handling of flammable fluids is customary.

HALOCARBONS

Due to serious limitations of natural refrigerants (incl Due to serious limitations of natural refrigerants (incl. Infamous high flammability of hydrocarbons), researchers (Midgley and his team) investigated the possibility of using synthetic compounds as refrigerants. Synthetic refrigerants are non-flammable and non-toxic, designed to operate within the most convenient temperature range for general refrigeration (-100°C up to 100°C). They are derivatives of two basic hydrocarbons (methane and ethane).

As a result they are basically suitable for almost any application (refrigeration and AC). They are called halogenated hydrocarbons or simply halocarbons because fluorine and chlorine belong to the group of elements (VII) called halogens.

Halogens VII Fluorine and Chlorine are gases. Bromine is a liquid. Iodine and Astatine are solids.

Halocarbons are well known for their environmental issues (ODP and GWP), but there are some other important concerns as well, including: Fluorocarbon refrigerants dissolve natural rubber. Halocarbons break down at high temperature to produce very irritating and toxic compounds (e.g. phosgene COCl2) .

How synthetic refrigerants are made? To make a new refrigerant, hydrogen carbons are removed from either the ethane or methane and replaced with other atoms, e.g. if hydrogen is replaced with fluorine, HC is said to be fluorinated. If it is replaced with chlorine it is chlorinated. When all hydrogen atoms are replaced, the refrigerant is said to be fully halogenated. Any remaining hydrogen atoms mean that the refrigerant is only partially halogenated.

Halogenation

Triangle of elements

CFC (ChloroFluoroCarbons) CFCs contain no hydrogen. All H hydrogen atoms are replaced with F fluorine and C chlorine. CFCs have a very long life in the atmosphere (>75y) and are very harmful to the environment. Since December 1995 all CFCs are banned from use and cannot be produced anymore. The most popular CFC in domestic applications was R-12 (one carbon, two fluorine, two chlorine).

HCFC (HydroChloroFluoroCarbons) HCFC refrigerants still contain hydrogen, therefore they are called partially halogenated. They are characterized by shorter life spans in the atmosphere, therefore they are less harmful to the environment. For residential purposes the most common HCFC refrigerant was R-22 (one carbon, one chlorine, one hydrogen, two fluorine).

HFC (HydroFluoroCarbons) HFC refrigerant does not contain chlorine, therefore it does no harm to the ozone as CFCs. It is only fluorinated. The most popular HFC refrigerant is R-134a, designed as a substitute for the popular but harmful R-12.

R11 R11 (1bar = 24°C) Molecular formula CCl3F Molar mass 137.37 g/mol Appearance Colorless liquid/gas Density 1.494 g/cm3 Melting point -110.48 °C Boiling point 23.77 °C ODP = 1 GWP = 4000

R-11 is a non-corrosive, non-toxic, non-flammable refrigerant. Its low operating pressures and relatively high compressor displacement require use of a centrifugal compressor. Before being banned R-11 was used in air-conditioning for small office buildings, factories, stores, and theaters. The ODP of all other refrigerants is compared to R11.

An example R11 refrigeration cycle on log p-h diagram (T0 = -5°C, Tk = 40°C).

R12 R12 (1bar = -30°C) Molecular formula CCl2F2 Molar mass 120.91 g/mol Appearance – colorless gas with ether-like odor Density 1.486 g/cm³ (−29.8 °C) Melting point −157.7 °C (115.5 K) Boiling point −29.8 °C (243.3 K) ODP = 0.82 GWP = 8100

Refrigerant R12 is said to be the most widely used of all the refrigerants being used for different applications. Similarly to R-11 it is completely safe, in that it is non-toxic, non-flammable, non-explosive. It is very stable and very difficult to break down, even under extreme operating conditions. Refrigerant R-12 condenses at moderate pressures under normal atmospheric conditions. It is suitable for use in high, medium and low temperature applications with all types of compressors. Refrigerant R12 was used in domestic refrigerators and freezers, liquid chillers, dehumidifiers, ice makers, water coolers, water fountains and transport refrigeration…

An example R12 refrigeration cycle on log p-h diagram (T0 = -5°C, Tk = 40°C). 

Comparison of R11 and R12 refrigeration cycle on log p-h diagram (T0 = -5°C, Tk = 40°C).

R12 concentration in the atmosphere

R22 R22 (1bar = -41°C) Molecular formula CHClF2 Molar mass 86.47 g/mol Appearance Colorless gas Density 3.66 kg/m3 at 15°C, gas Melting point -175.42 °C, 98 K, -284 °F Boiling point -40.7 °C, 232 K, -41 °F ODP = 0.05 GWP = 1700 The most popular substitute is R417A

Operating pressures of R22 are higher than for R-12. Developed as a low temperature refrigerant for domestic, commercial and industrial freezers and low temperature systems. It allows an evaporator temperature as low as -70°C. It was widely used in packaged air-conditioners where small compressor displacement is an advantage: Residential and Commercial A/C Medium- and low-temperature commercial refrigeration: food service supermarket display cases food storage and processing ice machines cars and some transport Operating pressures of R22 are higher than for R-12.

An example R22 refrigeration cycle on log p-h diagram (T0 = -5°C, Tk = 40°C) 1bar ~ -40°C.

Operating pressure of R12 and R22 on log p-h diagram (T0 = -5°C, Tk = 40°C).

Comparison between heat of evaporation of R12 and R22.

Comparison between densities (liquid and vapour) of R22 and R12.

R22 can still be used in small heat pump systems, but new systems have not been manufactured for use in the EU since late 2003. From 2010 on only recycled or saved stocks of R22 can be used, as it is no longer manufactured.

R134a R134a (1bar = -26°C) Molecular formula C2H2F4 Molar mass 102.03 g/mol Appearance Colorless gas Density 4.25 kg/m³, gas Melting point -103.3°C (169.85 K) Boiling point -26.3°C (246.85 K) ODP = 0 GWP = 1430 Replacement for R11 & R12 (not a drop-in)

It is used inmany segments of the refrigeration industry, most notably in: automotive air conditioning, appliances, small stationary equipment, medium-temperature supermarket cases, and industrial and commercial chillers One of the most widely used refrigerant in blends (component of other refrigerants), foam blowing agent, fire suppressant and propellant in metered-dose inhalers and aerosols.

R-134a is the most direct substitute and replacement for R-12 in higher temperature applications. However it is not a direct drop-in substitute. Some retrofitting is required, e.g. gaskets have to be changed and the oil has to be removed.

An example R134a refrigeration cycle on log p-h diagram (T0 = -5°C, Tk = 40°C) 1bar ~ -26°C.

Comparison of R134a and R12 refrigeration cycle on log p-h diagram (T0 = -5°C, Tk = 40°C).

Comparison between heat of evaporation of R134a and R12.

Comparison between densities (liquid and vapour) of R134a and R12.

R134a, with a GWP (100 years) of 1430 is extensively used in refrigeration and air conditioning. Now it has been banned in Europe for new mobile air conditioners according to Directive, 2006/ 40/EC.

R1234yf R1234yf - near drop-in replacement for R134a. Chemical formula C3H2F4 Molar mass 114 g/mol Appearance colorless gas Density 1.1 g/cm3 at 25 °C (liquid); Boiling point −30 °C (−22 °F; 243 K) ODP 0 GWP 4

Comparison of R134a and R12 refrigeration cycle on log p-h diagram (T0 = -5°C, Tk = 40°C).

Comparison between heat of evaporation of R134a and R1234yf.

Comparison between densities (liquid and vapour) of R134a and R1234yf.

R: Read paragraphs 1, 4 and 5 (but you are welcome to read everything) R: Read paragraphs 1, 4 and 5 (but you are welcome to read everything). J. Navarro-Esbrí, J.M. Mendoza-Miranda, A. Mota-Babiloni, A. Barragán-Cervera, J.M. Belman-Flores, Experimental analysis of R1234yf as a drop-in replacement for R134a in a vapor compression system, International Journal of Refrigeration, Volume 36, Issue 3, May 2013, Pages 870-880, ISSN 0140-7007, Estimated reading time 20-30 minutes. http://www.sciencedirect.com/science/article/pii/S014070071200357X

R-NUMBERING SYSTEM

The R-numbering system was developed by DuPont (company founded in 1802 by Eleuthère Irénée du Pont) and systematically identifies the molecular structure of refrigerants made with a single halogenated hydrocarbon. R   b  C-  H+  F The meaning of the codes is as follows: b – (Thousands digit) — Number of double bonds in the molecule. This is omitted when zero, and in practice is rarely used, since most candidate compounds are unstable. C (Hundreds digit) — The number of carbon atoms minus one. Omitted for methyl and halides, which have only one carbon atom. H (Tens digit) — One plus the number of hydrogen atoms per molecule. F (Rightmost digit) — Number of fluorine atoms per molecule.

Additional rules: A suffix with a capital B and a number indicates the number of bromine atoms, when present. This is VERY rarely used. A suffix of a lower-case letter a, b, or c indicates unbalanced isomers (1, 2 or 3). Remaining bonds not accounted for are occupied by chlorine atoms. Simple examples: R22 - 1 carbon atom, 1 hydrogen atom, 2 fluorine atoms and the reminder: 1 chlorine atom. R134a - 2 carbon atoms, 2 hydrogen atoms, 4 fluorine atoms,  a means that isomer is unbalanced by 1 atom. R1234yf -1 double bond, 3 carbon atoms, 2 hydrogen atoms, 4 fluorine atoms, yf means that this is an isomer (one of seven)

Blends having the same pure components but with different compositions are identified with upper case letter that follows the number (ex R 404A, R407C). Refrigerants having the form R-4xxx are zeotropic blends of two or more refrigerants, while those with the form R-5xxx are azeotropes. Example R407... 407A R-32/125/134a (20.0/40.0/40.0) 407B R-32/125/134a (10.0/70.0/20.0) 407C R-32/125/134a (23.0/25.0/52.0) 407D R-32/125/134a (15.0/15.0/70.0) 407E R-32/125/134a (25.0/15.0/60.0) 407F R-32/125/134a (30.0/30.0/40.0)

Inorganic compounds are assigned a number in the 700 series Inorganic compounds are assigned a number in the 700 series. Identification numbers are formed by adding the relative molecular mass of components to 700.