The potential of propane as a refrigerant

With F-gas restrictions on fluorinated refrigerants tightening, the focus is falling on alternatives that could play a mainstream role in the future. Propane is a proven refrigerant with low GWP and excellent efficiency. Kevin Glass, Managing Director of BITZER UK, highlights its potential.

Propane is back in the spotlight as a major potential alternative refrigerant for the future. Harnessing it safely depends on correct application and handling, and mitigating the known risks through effective system design and operation.

Designated R290, propane is a colourless, odourless gas that belongs to the hydrocarbon family. It is a highly efficient refrigerant and has gained popularity in recent years due to its excellent thermodynamic properties and low environmental impact.

Its low global warming potential (GWP) of 3 and zero ozone depletion potential (ODP) make it a viable alternative to conventional refrigerants with high GWP values. It can be used in several refrigeration and air conditioning applications, including commercial, residential, and industrial settings.

It is commonly used in small-scale systems, such as refrigerators, freezers, and packaged air conditioning units. However, it can also be used in larger commercial and industrial refrigeration applications, such as food storage and processing, the chemical industry, and cold storage.
Flammable refrigerants

Under ISO 817, refrigerants are classified into categories A and B: category A includes non-toxic substances, and category B includes toxic refrigerants. Flammability is classified under four groups, where 1 is non-flammable, 2L is flammable with slow flame spread, 2 is flammable, and 3 highly flammable. 

Within the A3 classification, the most important substances used as refrigerants are hydrocarbons such as propane, propene (R1270), isobutane (R600a), butane (R600) and ethane (R170). All have a long history in refrigeration and air conditioning and provided a model for the development of many of the new synthetic refrigerants.

By definition, group A3 refrigerants are highly flammable. They can be ignited at concentrations as low as 2% and as high as 10% in air. Within this range, ignition can be achieved by the spark of a light switch, a steel tool falling on a concrete floor or statically charged work clothes, resulting in deflagration or explosion. Combustion products are mainly carbon dioxide and water, and in themselves harmless.

Effectively mitigating and managing the flammability risk is the key to the safe application of propane, and other hydrocarbon refrigerants.

Application

Use of flammable refrigerants has a long history in household appliances and commercial refrigeration. Towards the end of the 19th century, the use of non-toxic, highly flammable hydrocarbons became widespread due to their good thermodynamic properties, along with ammonia, sulphur dioxide and carbon dioxide.

Propane is well suited to use in commercial refrigeration, air conditioning and heat pump applications. Boiling at -42°C, it can cover evaporating temperatures of -40°C and higher. When propane is compressed, it is possible to achieve usefully large temperature ranges.

R290 has a high cooling capacity, which means it can remove a large amount of heat in a short amount of time. It also has a high coefficient of performance (COP), reducing the amount of energy used to create a given cooling effect and cutting running costs. With rising energy prices, this is obviously highly attractive.

Pressure levels and refrigerating capacity with propane are similar to R22, and its temperature behaviour is as favourable as R134a, combining these excellent properties of the two refrigerants without their environmental downsides.

There are no particular problems with materials compatibility. In contrast to ammonia, copper materials can be used, allowing propane to be used in semi-hermetic and hermetic compressors. Common mineral oils can be used as a lubricant over a wide application range, while polyol ester (POE) and polyalpha olefin (PAO) lubricants offer even more favourable properties.

Safety

Propane-based refrigeration systems must be designed and installed with safety features that minimise the risk of fire and explosion. Such features may include (but are not limited to) pressure relief valves, flame arrestors, and leak detection systems. 

System design must comply with all relevant regulations and standards relating to maximum permitted charge size for the specific application, and mandatory risk mitigation measures.
Detailed guidance on using propane and other flammable refrigerants is provided by REFCOM in its Guidance Note: https://www.refcom.org.uk/media/1157/bra-guide-to-flammable-refrigerants-issue-1-oct-12.pdf

Only suitably qualified and trained operatives are permitted to handle R-290 as a refrigerant, which in the UK means successful completion of the City & Guilds 6187-21 hydrocarbon handling qualification. Safe handling includes use of appropriate personal protective equipment (PPE) such as goggles, a portable gas detector and anti-electrostatic gloves.

When installing propane-based refrigeration systems, it is essential to follow all relevant local and national codes and standards. This ensures safe installation, operation, and maintenance. Post-installation, regular inspections are important to ensure continued safe and efficient operation.

Support and efficient system components

BITZER has a comprehensive support programme for system designers and installers working with flammable refrigerants. This includes guidelines on safe application, and a practical training program held at the SCHAUFLER Academy in Germany (see below).

On the equipment side, our specialist high performance compressors and system components are approved for use with flammable refrigerants such as R290, in a wide range of refrigeration, air conditioning and heat pump applications.

These include reciprocating compressors and compact screw compressors for air conditioning or process cooling, and system components such as oil separators, liquid receivers, condensers, and evaporators.

BITZER offers a comprehensive product portfolio for use with flammable refrigerants, such as the CSH compact screw compressor

To further enhance efficiency, Ecoline reciprocating compressors can be supplied with mechanical capacity control to match output to cooling load.

By using an IQ module, it is also possible to connect propane systems to the BITZER Digital Network (BDN) for detailed performance analysis and remote diagnosis, saving time and money and helping to support safety.

Future outlook

In many applications, propane is a viable alternative to conventional refrigerants with high GWP values, offering high cooling capacity, high efficiency, and low environmental impact.

As the world moves towards more sustainable and environmentally acceptable solutions, use of propane as a refrigerant is expected to increase, particularly in commercial and industrial applications.

The evolving regulatory framework will obviously play a key role, as F-gas regulations limit use of traditional fluids and restrictions on the use of alternatives such as flammable refrigerants are reviewed to permit greater use, subject to effective risk mitigation.

With significant research and development under way, new and improved propane-based refrigeration systems are expected to become available, providing even more efficient and cost-effective cooling solutions.

Training

Regular refresher training is recommended for system designers, installers and maintenance staff working with flammable refrigerants such as propane.

The SCHAUFLER Academy in Rottenburg-Ergenzingen, pictured above, provides both onsite and remote courses designed to equip operatives with the knowledge and skills needed to work safely and efficiently.

For more details: www.trainings-events.bitzer.de

BITZER guidance on propane systems is provided here: www.bitzer.de/shared_media/documentation/at-660-1.pdf?P=/doc/&N=at-660-1.pdf

BITZER Refrigerant Report Online

This annually updated report has become a key reference for refrigeration professionals working across many disciplines. It provides current, reliable information on all commonly used refrigerants and those showing potential for the future. 

The latest version (Issue 21) has been significantly expanded and includes up to date information on properties, specifications and regulations, as well as a quick reference table with filter function for refrigerants.

Access the report here: www.bitzer.de/shared_media/html/a-500-501/en-GB/index.html#index_content