Häufige Kältemitteltypen in Kälher verwendet

Refrigerants in chillers operate within a refrigeration cycle, typically vapor-compression or absorption, where they transition between liquid and gas states to move heat from the process to the environment. The choice of refrigerant depends on factors like cooling capacity, environmental impact, safety, cost, and system design. While no single refrigerant is perfect for every scenario, several stand out as widely used in chiller plants due to their efficiency and adaptability. The global push to reduce greenhouse gas emissions and ozone depletion has led to phase-outs of older refrigerants, driving innovation in low-global warming potential (GWP) and zero-ozone depletion potential (ODP) alternatives.

Common Refrigerant Types and Their Characteristics

Below is a detailed breakdown of the most prevalent refrigerants in chiller systems, organized by type, properties, and applications. This section includes a table for clarity and covers both current and historical usage, reflecting the transition to sustainable options.

Water (R718)

• Properties: Water is a natural refrigerant with excellent thermal conductivity, a high heat absorption capacity, and a boiling point of 212°F (100°C) at standard pressure.
• Vorteile: It’s non-toxic, widely available, cost-effective, and environmentally friendly, with no ODP or GWP. Its abundance makes it a low-cost solution for large systems.
• Drawbacks: Its efficiency is sensitive to ambient temperatures, and it can corrode system components, raising maintenance costs. Water is impractical for vapor-compression chillers due to its high boiling point and is mainly used in absorption chillers with a heat source like steam or hot water.
• Anwendungen: Commonly found in large-scale absorption chillers for industrial processes where waste heat is available, such as in chemical plants or district cooling systems. It’s less common in vapor-compression systems due to operational limitations.

R134A (HFC)

• Properties: A hydrofluorocarbon (HFC) with stable thermal characteristics, low toxicity, and a boiling point of -15°F (-26°C). It’s non-corrosive and non-flammable.
• Vorteile: Widely used due to its reliability and minimal ODP, making it a safer alternative to older refrigerants like R12. It’s effective in medium-temperature cooling and compatible with existing systems.
• Drawbacks: Its GWP of 1,430 contributes to greenhouse gas emissions, leading to a phase-down under agreements like the Kigali Amendment to the Montreal Protocol. It’s also being replaced in some regions due to environmental concerns.
• Anwendungen: Popular in automotive air conditioning, commercial chillers, and industrial systems, though its use is declining in favor of lower-GWP options. It’s often found in medium-sized chillers for HVAC applications.

R407C (HFC Blend)

• Properties: A blend of R32, R125, and R134a, with a boiling point of -46°F (-43°C) and a GWP of 1,774.
• Vorteile: Lower cooling capacity than R410A but less expensive and more environmentally friendly than R22, with zero ODP. It’s often used as a retrofit for R22 systems, offering compatibility with existing equipment.
• Drawbacks: Still has a significant GWP, and its performance is slightly less robust than R410A, requiring careful system design.
• Anwendungen: Used as an R22 retrofit in air conditioning and medium-sized industrial chillers, particularly in regions transitioning away from HCFCs.

R404A (HFC Blend)

• Properties: A blend of R125, R143a, and R134a, with a boiling point of -51°F (-46°C) and a GWP of 3,922.
• Vorteile: Effective for low- and medium-temperature applications, serving as a replacement for older CFCs and HCFCs. It offers high efficiency in cold storage and freezer systems.
• Drawbacks: Extremely high GWP limits its future use, with phase-outs accelerating globally under environmental regulations. It’s also more expensive to handle due to its environmental impact.
• Anwendungen: Found in commercial refrigeration and some industrial chillers, particularly cold storage, but being supplanted by alternatives like R448A due to regulatory pressure.

R717 (Ammonia)

• Properties: A halogen-free refrigerant with a boiling point of -28°F (-33°C) and the highest heat absorption capacity per volume among common refrigerants.
• Vorteile: Highly efficient, with stable thermal properties, a GWP of 0, and no ODP. Its strong odor aids in leak detection, and it’s cost-effective for large systems.
• Drawbacks: Toxic and flammable, requiring careful handling and robust safety measures. It’s corrosive to copper, limiting material choices and increasing installation costs.
• Anwendungen: Dominant in large industrial chiller plants, such as food processing, cold storage, and chemical manufacturing, where its efficiency outweighs safety concerns. It’s particularly suited for systems with large cooling loads.

R410A (HFC Blend)

• Properties: A blend of R32 and R125, non-flammable, with a boiling point of -61°F (-52°C) and a GWP of 2,088.
• Vorteile: High cooling capacity and efficiency, making it a common replacement for R22 in air conditioning and chillers. It operates at higher pressures, enhancing heat transfer.
• Drawbacks: High GWP drives its phase-down, and it requires higher operating pressures than some alternatives, increasing system costs.
• Anwendungen: Widely used in commercial HVAC chillers and smaller industrial systems, though transitioning to lower-GWP options is underway, especially with upcoming bans in some regions by 2025.

R744 (Carbon Dioxide, CO2)

• Properties: A natural refrigerant with a boiling point of -109°F (-78°C) at standard pressure, non-flammable, and non-toxic in low concentrations.
• Vorteile: Environmentally friendly with a GWP of 1 and zero ODP. It’s abundant and performs well in transcritical cycles, offering high heat transfer efficiency.
• Drawbacks: Requires high-pressure systems (up to 4,000 psi), increasing installation and maintenance costs. Leaks in confined spaces can displace oxygen, posing safety risks.
• Anwendungen: Increasingly used in commercial refrigeration, such as supermarket chillers, and industrial systems where sustainability is a priority, particularly in Europe and North America.

Hydrocarbons (e.g., R290 – Propane, R600a – Isobutane)

• Properties: Natural refrigerants with low boiling points (e.g., R290 at -44°F/-42°C), excellent thermodynamic properties, and minimal environmental impact (GWP < 4, ODP = 0).
• Vorteile: High efficiency, low cost, and eco-friendly, making them viable for sustainable cooling. They are gaining popularity as replacements for HFCs.
• Drawbacks: Highly flammable, requiring specialized safety systems and limiting their use in densely populated areas or large industrial settings.
• Anwendungen: Used in domestic refrigeration and some industrial chillers, particularly in regions prioritizing green solutions, like Europe, and in smaller systems where safety measures are manageable.

R123 (HCFC-123)

• Properties: A hydrochlorofluorocarbon (HCFC) with a boiling point of 82°F (28°C), used historically in low-pressure centrifugal chillers.
• Vorteile: Effective for low-pressure systems and compatible with older equipment.
• Drawbacks: Ozone-depleting with a GWP of 77, leading to its phase-out under the Montreal Protocol. Production ceased in developed countries by 2020.
• Anwendungen: Found in legacy chillers, now being retrofitted or replaced with alternatives like R245fa or R1233zd.

R1233zd

• Properties: A low-GWP refrigerant (GWP = 4.5) with a boiling point of 50°F (10°C), classified as A1 (low toxicity, non-flammable).
• Vorteile: Environmentally friendly with zero ODP and low toxicity, making it a sustainable choice for new systems.
• Drawbacks: Requires system redesign for compatibility and is less established in the market compared to HFCs.
• Anwendungen: Used in new low-pressure chillers as a sustainable alternative to older HCFCs, gaining traction in modern designs.

R514A (HCFC Blend)

• Properties: A blend of HFOs with a GWP of 7, classified as B1 (slightly flammable).
• Vorteile: Low GWP and zero ODP, offering a sustainable option for low-pressure chillers.
• Drawbacks: Its flammability requires safety considerations, limiting its use in certain environments.
• Anwendungen: Used in low-pressure chillers as an alternative to R123, particularly in new equipment designs.

The following table summarizes the key properties and applications of these refrigerants for easy reference:

Selecting the Right Refrigerant

Choosing a refrigerant involves balancing efficiency, safety, cost, and environmental impact:

• Cooling Requirements: High-capacity needs favor ammonia or R410A; low-temperature applications may use R404A or hydrocarbons.
• Environmental Regulations: Opt for low-GWP options like R744 or R717 to meet standards like the Kigali Amendment, which is driving phase-downs of high-GWP HFCs.
• System Design: High-pressure refrigerants (e.g., R744, R410A) need robust components; water and ammonia suit absorption systems, while HFCs fit vapor-compression setups.
• Sicherheit: Non-toxic, non-flammable options like R134A or R744 are safer in populated areas, while ammonia requires strict handling due to toxicity.
• Kosten: Water and hydrocarbons are economical upfront, but installation and maintenance costs vary (e.g., high for R744 due to pressure requirements).

Abschluss

The most common refrigerant types used in chillers include water (in absorption systems), R134a, R407C, R404A, ammonia (R717), R410A, CO2 (R744), and hydrocarbons like R290, alongside newer options like R1233zd and R514A. However, due to environmental regulations and sustainability goals, there is a clear shift toward low-GWP refrigerants such as CO2, ammonia, and HFOs. When selecting a refrigerant, factors like cooling capacity, environmental impact, safety, cost, and regulatory compliance must be carefully considered to optimize chiller performance while meeting modern standards.