When deciding to purchase a heat pump, we usually pay attention to its parameters. While we are mostly interested in the heating power of a device and its price, we are rarely interested in other features of a heat pump. One of the worthwhile aspects when selecting a heat pump is the refrigerant used in its housing. Let’s take a closer look at what’s inside a heat pump and what the refrigerants, hidden under cryptic symbols, actually are.
What are refrigerants?
A refrigerant, also known as a cooling agent, is a thermodynamic medium involved in the process of heat exchange in a piece of cooling equipment or heat pump. The mechanism behind refrigerants is simple – by bringing the medium to its boiling point under low pressure and low temperature in a cooling system made of copper, the refrigerant absorbs the generated heat and then releases it during liquefication under a higher pressure and temperature. The origins of refrigerants date back to the 1930s. Back then, Jacob Perkins invented a steam-powered, compressor-based cooling device, thus laying the cornerstone for today’s refrigeration industry.
Although the perfect refrigerant should be safe for people and the environment, cause no corrosion and also provide good thermodynamic properties, a medium like this only exists in our imagination. Until now scientists have not been successful in discovering a substance that would be able to meet all of the abovementioned requirements. Nevertheless, new combinations and substances are being tested all the time to identify the refrigerant that would be closest to perfection.
Refrigerants in heat pumps
While there are currently heat pumps operating with various working media in the market, several of these may be considered the most popular. Those commonly used in household solutions surely include hydrofluorocarbons, also referred to as fluorinated greenhouse gases. These include:
- R410A – a near azeotropic blend of R32 (50%) and R125 (50%);
- R134a – so-called tetrafluoroethane;
- R407C – a noncombustible, zeotropic blend of R32 (23%), R125 (25%) and R134A. Apart from the above, the following agents are becoming ever more popular:
- R32 – i.e. difluoromethane, popular, among others, in air-conditioners;
- R1234ze – trans-1,3,3,3-tetrafluoro-1-propene, featuring a low GWP value;
There are also natural agents, which are attracting more and more interest. R290, that is propane, as well as R744, that is carbon dioxide (CO2), are among those worth mentioning.
Does the type of the refrigerant applied matter?
The question seems natural – if heat pumps and cooling equipment available in the market offer such an extensive range of refrigerants, does it matter what substance is inside the air-conditioner or heat pump? It turns out that this actually is an important matter to consider. All refrigerants may be divided into specific groups, based on their combustibility or toxicity. Substance combustibility is marked with digits, where 1 designates noncombustible agents, 2 designates combustible agents, 2L designates moderately combustible agents, while 3 designates readily combustible or explosive agents. Toxicity is designated with the letter A (low toxicity) or B (high toxicity). And so, for example, propane (R290) is a combustible agent, which means that the manufacturer is required to adhere to additional safety measures for users of equipment operating on this agent. In contrast, R410A and R134a are refrigerants that belong to the group A1, which are both noncombustible and have a low toxicity, making them safe for the user. These two critical aspects are important when designing equipment that requires the use of a refrigerant.