<\/span><\/h2>\nA refrigerant is a substance with controlled pressure and phase-change properties. It can evaporate at a low temperature and condense at a higher temperature. These properties allow a heat pump to move thermal energy from a colder source to a warmer heating system.<\/p>\n
Most building heat pumps use a vapour-compression cycle<\/strong>. The refrigerant changes between liquid and vapour as it passes through the system. The compressor provides the electrical work needed to raise the refrigerant\u2019s pressure and temperature.<\/p>\nRefrigerant compared with other heat pump fluids<\/strong><\/p>\n<\/div>\n\n
\n\n\n| Medium<\/th>\n | Where it circulates<\/th>\n | Core purpose<\/th>\n<\/tr>\n<\/thead>\n |
\n\nRefrigerant<\/strong><\/td>\n| Inside the sealed refrigerant circuit<\/td>\n | Absorbs, transports, and releases heat through evaporation and condensation<\/td>\n<\/tr>\n | \nBrine or source fluid<\/strong><\/td>\n| Ground collector, borehole, or indirect source circuit<\/td>\n | Carries heat from the ground or another source to the heat pump<\/td>\n<\/tr>\n | \nHeating water<\/strong><\/td>\n| Radiators, underfloor heating, fan coils, buffer tanks, and hot-water heat exchangers<\/td>\n | Distributes useful heat through the building<\/td>\n<\/tr>\n | \nElectricity<\/strong><\/td>\n| Compressor, pumps, fans, valves, and controls<\/td>\n | Drives the heat pump and its auxiliary components<\/td>\n<\/tr>\n | \nOutdoor air<\/strong><\/td>\n| Across the evaporator of an air-source heat pump<\/td>\n | Supplies environmental heat to the system<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n The refrigerant normally does not enter the building\u2019s heating-water circuit. A heat exchanger separates the two circuits. The same principle separates the refrigerant from a ground-source brine circuit.<\/p>\n<\/div>\n <\/span>What is the core purpose of a refrigerant?<\/span><\/h2>\nThe core purpose of the refrigerant is to transfer heat across a temperature difference<\/strong>. The heat source may be cold compared with the required room-heating or hot-water temperature. The refrigerant makes this transfer possible by changing pressure, temperature, and physical state.<\/p>\nThe refrigerant does not create the environmental heat. It collects and carries that heat. The compressor then enables the heat to be delivered at a more useful temperature.<\/p>\n <\/span>How the refrigerant cycle works<\/span><\/h2>\nStep 1: Evaporation<\/strong><\/p>\nThe low-pressure refrigerant enters the evaporator. It absorbs heat from outdoor air, ground-source brine, groundwater, or another heat source. This heat causes the refrigerant to evaporate.<\/p>\n Step 2: Compression<\/strong><\/p>\nThe compressor draws in the refrigerant vapour. It compresses the vapour to a higher pressure. The refrigerant temperature rises as a result.<\/p>\n Step 3: Condensation<\/strong><\/p>\nThe hot refrigerant passes through the condenser. It releases heat to the heating water or another heat sink. The refrigerant changes back into a liquid as it releases heat.<\/p>\n Step 4: Expansion<\/strong><\/p>\nThe liquid refrigerant passes through an expansion valve. The valve reduces its pressure and temperature. The refrigerant can then enter the evaporator and repeat the cycle.<\/p>\n A reversible heat pump can also provide active cooling. In cooling mode, the system changes the direction of heat transfer. It collects heat from the building and releases it to the outside air, ground, or water source.<\/p>\n <\/span>Why are refrigerants needed?<\/span><\/h2>\nA building may require heating water at 30\u00b0C, 45\u00b0C, 55\u00b0C, or more. The available heat source may be much colder. Outdoor air can be below freezing, while ground or groundwater temperatures remain relatively low.<\/p>\n The refrigerant provides a practical way to bridge this temperature difference. It can evaporate below the source temperature and condense above the required heating-water temperature. The compressor moves the refrigerant between these operating conditions.<\/p>\n Without a suitable refrigerant and refrigerant circuit, a compression heat pump cannot transfer low-temperature environmental heat into a useful heating system.<\/p>\n The practical need for correct refrigerant selection<\/strong><\/p>\nIncorrect system selection can create real operating and business problems:<\/p>\n \n- The heat pump may not deliver the required heating output on the coldest design day.<\/li>\n
- The unit may need excessive compressor power at high flow temperatures.<\/li>\n
- The available installation area may not meet the required safety distances.<\/li>\n
- A split system may introduce unnecessary on-site refrigerant connections.<\/li>\n
- A high-GWP refrigerant may create regulatory, supply, and lifecycle risks.<\/li>\n
- An uncommon refrigerant may have limited local service support.<\/li>\n
- A large refrigerant charge may increase direct emission consequences.<\/li>\n
- A poor match between refrigerant and compressor may reduce efficiency or component life.<\/li>\n
- An unapproved refrigerant conversion may damage the compressor, seals, lubricant, or heat exchangers.<\/li>\n<\/ul>\n
The German Environment Agency states that there is no single perfect refrigerant for every application. The correct choice depends on the specific system, operating conditions, construction requirements, energy use, environmental impact, availability, and legal framework.<\/p>\n <\/span>Key features of heat pump refrigerants<\/span><\/h2>\nA refrigerant must be assessed through several connected properties. No single value provides a complete evaluation.<\/p>\n<\/div>\n \n \n\n\n| Feature<\/th>\n | What it describes<\/th>\n | Why it matters<\/th>\n<\/tr>\n<\/thead>\n | \n\nPhase-change behaviour<\/strong><\/td>\n| How the substance evaporates and condenses<\/td>\n | Controls heat absorption and heat release<\/td>\n<\/tr>\n | \nPressure-temperature relationship<\/strong><\/td>\n| The pressure required at each operating temperature<\/td>\n | Affects compressor design, pipework, and component strength<\/td>\n<\/tr>\n | \nOperating envelope<\/strong><\/td>\n| The permitted combination of source, sink, and discharge temperatures<\/td>\n | Determines whether the heat pump can meet design conditions<\/td>\n<\/tr>\n | \nThermodynamic performance<\/strong><\/td>\n| How effectively the fluid supports heat transfer<\/td>\n | Influences capacity and energy efficiency<\/td>\n<\/tr>\n | \nCritical temperature<\/strong><\/td>\n| The temperature above which normal condensation is no longer possible<\/td>\n | Important for high-temperature applications<\/td>\n<\/tr>\n | \nVolumetric capacity<\/strong><\/td>\n| Heating or cooling capacity per volume of refrigerant vapour<\/td>\n | Influences compressor size and circuit dimensions<\/td>\n<\/tr>\n | \nSafety class<\/strong><\/td>\n| Toxicity and flammability classification<\/td>\n | Determines product and installation safety measures<\/td>\n<\/tr>\n | \nGlobal warming potential<\/strong><\/td>\n| Climate effect if refrigerant reaches the atmosphere<\/td>\n | Influences direct emissions and regulation<\/td>\n<\/tr>\n | \nOzone depletion potential<\/strong><\/td>\n| Potential effect on the ozone layer<\/td>\n | Helps exclude ozone-depleting substances<\/td>\n<\/tr>\n | \nTemperature glide<\/strong><\/td>\n| Temperature change during phase change in some blends<\/td>\n | Affects heat-exchanger and service design<\/td>\n<\/tr>\n | \nMaterial compatibility<\/strong><\/td>\n| Compatibility with metals, seals, plastics, and lubricants<\/td>\n | Supports reliability and component life<\/td>\n<\/tr>\n | \nCharge quantity<\/strong><\/td>\n| Mass of refrigerant inside the equipment<\/td>\n | Affects safety calculations and potential direct emissions<\/td>\n<\/tr>\n | \nChemical stability<\/strong><\/td>\n| Resistance to breakdown under operating conditions<\/td>\n | Supports long-term reliability<\/td>\n<\/tr>\n | \nAvailability and serviceability<\/strong><\/td>\n| Access to refrigerant, components, skills, and recovery services<\/td>\n | Affects downtime and lifecycle cost<\/td>\n<\/tr>\n | \nRegulatory durability<\/strong><\/td>\n| Likelihood that the system remains supportable under future rules<\/td>\n | Reduces stranded-asset and replacement risk<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n These features are interdependent. A low-GWP refrigerant may require additional flammability controls. A non-flammable refrigerant may operate at very high pressure. A technically efficient fluid may still be unsuitable for a specific room, product category, or output temperature.<\/p>\n<\/div>\n <\/span>Detailed explanation of refrigerant features<\/span><\/h2>\nPhase-change behaviour<\/h3>\nDefinition:<\/strong> Phase-change behaviour describes how a refrigerant changes between liquid and vapour.<\/p>\nPurpose:<\/strong> The phase change allows the fluid to absorb or release a large amount of heat within a compact circuit.<\/p>\nBenefit:<\/strong> The heat pump can transfer substantial thermal energy without circulating an extremely large fluid volume.<\/p>\nExample:<\/strong> The refrigerant evaporates in the outdoor unit of an air-source heat pump and condenses while heating the building water.<\/p>\nPressure-temperature relationship<\/h3>\nDefinition: <\/strong>Each refrigerant has a specific relationship between saturation pressure and temperature.<\/p>\nPurpose:<\/strong> This relationship allows engineers to create a low-temperature evaporation condition and a higher-temperature condensation condition.<\/p>\nBenefit:<\/strong> The heat pump can operate between the available source temperature and the required heating-water temperature.<\/p>\nExample:<\/strong> On a cold winter day, the refrigerant must evaporate below the outdoor-coil temperature while condensing above the required flow temperature.<\/p>\nOperating envelope<\/h3>\nDefinition:<\/strong> The operating envelope defines the permitted source temperatures, condensing temperatures, pressures, and compressor conditions.<\/p>\nPurpose:<\/strong> It prevents operation outside the limits of the refrigerant, compressor, lubricant, motor, and other components.<\/p>\nBenefit:<\/strong> Correct operation protects efficiency and equipment life.<\/p>\nExample:<\/strong> A renovation project should verify heating capacity and compressor limits at the actual winter design temperature and required radiator flow temperature.<\/p>\nCritical temperature and high-temperature capability<\/h3>\nDefinition:<\/strong> Critical temperature is the temperature above which a fluid no longer has a normal liquid-vapour phase boundary.<\/p>\nPurpose:<\/strong> It helps determine how a refrigerant behaves at high heat-sink temperatures.<\/p>\nBenefit:<\/strong> It supports the selection of systems for domestic hot water, radiators, process heat, or district heating.<\/p>\nExample:<\/strong> A heat pump designed for a 70\u00b0C flow temperature needs a refrigerant circuit, compressor, and controls that are validated for that complete operating condition.<\/p>\nA high theoretical temperature capability does not guarantee efficient operation. Compressor discharge temperature, pressure ratio, heat-exchanger approach temperatures, source temperature, and control strategy remain important. Product data at defined test conditions provides more useful evidence than the refrigerant name alone.<\/p>\n Thermodynamic efficiency<\/h3>\nDefinition:<\/strong> Thermodynamic properties describe how the refrigerant stores, transports, absorbs, and releases energy.<\/p>\nPurpose:<\/strong> They help the system achieve useful heating output with limited compressor work.<\/p>\nBenefit:<\/strong> A suitable fluid can support good coefficient of performance and seasonal efficiency.<\/p>\nExample:<\/strong> A refrigerant may perform well in a purpose-designed system but poorly if used in components designed for another fluid.<\/p>\nEfficiency is a system result. The refrigerant influences efficiency, but it does not determine efficiency alone. Compressor modulation, fan and pump power, heat-exchanger size, defrost control, source temperature, flow temperature, hydraulic design, and installation quality also matter.<\/p>\n Volumetric heating capacity<\/h3>\nDefinition:<\/strong> Volumetric capacity describes how much heating or cooling capacity a refrigerant can provide for a given vapour volume.<\/p>\nPurpose:<\/strong> It helps engineers size the compressor, pipework, valves, and heat exchangers.<\/p>\nBenefit:<\/strong> A suitable volumetric capacity can support compact equipment and stable control.<\/p>\nExample:<\/strong> Two refrigerants may deliver similar heating output but require different compressor displacement and circuit dimensions.<\/p>\nSafety classification<\/h3>\nDefinition:<\/strong> Refrigerant safety classes describe toxicity and flammability.<\/p>\nPurpose:<\/strong> They create a common basis for product design, charge limits, room requirements, ventilation, ignition-source control, installation, and servicing.<\/p>\nBenefit: <\/strong>The correct safety concept allows refrigerants with different properties to be used responsibly.<\/p>\n | | | | | | | | | | | | | | | | | | | | | |