Ammonia refrigerator: how it works and why it still works used

When it comes to refrigeration units, most immediately imagine modern models with freon or isobutane. But there is a technology that has been used for more than a century - ammonia refrigerators. Despite the emergence of new refrigerants, ammonia (NH₃) remains in demand in industrial and some household systems. Why? It's all about its unique physical properties and high efficiency.

In this article we will look at how exactly an ammonia refrigerator works, what processes occur inside the system, and why this refrigerant is still not losing ground. You will learn about the design features, benefits and potential risks, as well as where such refrigerators are used today. If you've ever encountered industrial freezers or old Soviet refrigerators, this information will be especially useful.

Physical Basics: Why Ammonia Cools

To understand how an ammonia refrigerator works, you need to remember the basics of thermodynamics. Cooling occurs due to phase transitions of the refrigerant - the substance that circulates through the system. Ammonia is ideal for this role due to two key properties:

• 🔥 Low boiling point - at atmospheric pressure, ammonia boils already at -33,3°C, which allows heat to be removed even in freezers with ultra-low temperatures.
• ⚡ High heat of evaporation — during the transition from the liquid phase to the gaseous phase, 1 kg of ammonia absorbs about 1370 kJ heat (for comparison: for freon R134a this figure is almost 2 times lower).
• 🔄 Good thermal conductivity — ammonia more efficiently transfers heat through the walls of heat exchangers, which reduces energy losses.

Unlike freons, ammonia does not form explosive mixtures with air (at a concentration of up to 16%), but at This has a high cooling capacity ability to remove a large amount of heat per unit of time. That is why it is often used in industrial refrigeration units, where cooling of large volumes is required.

Interesting fact: ammonia was the first refrigerant used in commercial refrigerators back in 1870s. It was used in the first mechanical refrigeration machines created by Karl von Linde. Despite its toxicity, ammonia remains one of the most energy-efficient refrigerants today.

The design of an ammonia refrigerator: main components

The design of an ammonia refrigerator differs little from classical systems, but has a number of features related to the properties refrigerant. Let's look at the key elements:

1. Compressor - compresses the ammonia gas, increasing its pressure and temperature. Ammonia systems often use piston or screw compressorsdesigned for high loads.
2. Condenser - a heat exchanger where hot ammonia under pressure is cooled and condensed into a liquid. Usually it is a coil with forced airflow.
3. Receiver is a container for storing liquid ammonia before supplying it to the evaporator. In industrial systems it can be equipped with level meters and safety valves.
4. Evaporator — here liquid ammonia boils, taking heat from the refrigeration chamber. In household models, the evaporator is often built into the walls of the freezer.
5. Thermostatic valve (TRV) - doses the supply of refrigerant to the evaporator, maintaining optimal pressure.
6. Automation system - temperature, pressure sensors and relays that control the operation of the compressor and fans.

A special feature of ammonia systems is mandatory presence of emergency valves and leakage sensors, since ammonia is toxic. Industrial installations also provide vapor neutralization systems (for example, water curtains).

Why are capillary tubes not used in ammonia systems?

Unlike freon refrigerators, where the refrigerant is dosed through a thin capillary tube, this is not possible in ammonia systems due to high pressure and the risk of moisture freezing. Instead, thermostatic expansion valves (TEVs) or electronic expansion valves are used, which more precisely control the flow of refrigerant.

Operation principle: cycle of an ammonia refrigerator in steps

The operating cycle of an ammonia refrigerator is based on reverse Carnot cycle and includes four main stages. Let's look at them in detail:

1. Compression (compressor)
   

   Ammonia gas enters the compressor, where it is compressed to pressure 10–15 barand its temperature rises to 70–90°C. This process requires significant energy expenditure, but is necessary for further condensation.

2. Condensation (condenser)
   

   Hot ammonia under high pressure enters the condenser, where it is cooled by a flow of air or water. At the same time, it changes from a gaseous state to a liquid state, giving off heat to the environment. The condensation temperature depends on the type of system, but is usually 30–40°C.

3. Throttling (TRV)
   

   High pressure liquid ammonia passes through a thermostatic expansion valve, where its pressure drops sharply to 2–4 barand the temperature drops to -10…-30°C. This process is called adiabatic expansion.

4. Evaporation (evaporator)
   

   Cold liquid ammonia enters the evaporator, where it boils, absorbing heat from the refrigeration chamber. Gaseous ammonia again enters the compressor, and the cycle repeats.

The key difference from freon systems is higher operating pressures. For example, in household refrigerators with R134a freon, the condensation pressure rarely exceeds 8–10 bar, while in ammonia systems it can reach 20 bar and higher. This places increased demands on the strength of pipelines and connections.

Interestingly, some industrial systems use cascade cyclewhere ammonia operates in the upper stage (high temperature), and in the lower (low temperature) another refrigerant is used, for example CO₂. This allows you to reach temperatures up to -60°C without the risk of ammonia freezing.

Advantages and disadvantages of ammonia refrigerators

Despite its toxicity, ammonia remains a popular refrigerant due to a number of undeniable advantages. However, this technology also has serious limitations. Let's look at the pros and cons:

Advantages

• ⚡ High energy efficiency — ammonia systems consume 15–20% less electricity compared to freon systems with the same cooling capacity.
• 🌍 Environmentally friendly — ammonia does not destroy the ozone layer (ODP = 0) and has minimal global warming potential (GWP = 0).
• 💰 Low cost of refrigerant — ammonia is cheaper than most freons and their substitutes.
• 🔧 Durability — properly designed ammonia systems serve 20–30 years without loss of efficiency.
• ❄️ Work at extremely low temperatures — ammonia is effective even in freezers with a temperature to -50°C.

Disadvantages

• ☠️ Toxicity - when concentrated in the air more than 35 mg/m³ ammonia irritates the mucous membranes, and when 500 mg/m³ can cause pulmonary edema. Ventilation systems are required. and leakage sensors.
• 🔥 Fire hazard — although ammonia is not flammable, at high concentrations (more than 16%) it forms explosive mixtures with air.
• 🛠️ Difficulty of maintenance —repair and refueling of ammonia systems require special equipment and certified specialists.
• 💧 Corrosive activity —ammonia reacts with copper and its alloys, so the systems use steel or aluminum pipelines.
• 🏠 Limited household use —due to toxicity, ammonia is almost not used in modern home refrigerators (with the exception of some industrial models).

It is important to understand that the risks of ammonia are greatly exaggerated in everyday perception. With proper operation and compliance with safety precautions, the likelihood of a leak is minimal. For example, ammonia has been used in industrial refrigeration chambers for more than 100 years, and serious incidents are extremely rare.

Where ammonia refrigerators are used. today

Although ammonia has been almost completely replaced by freons and isobutane in household refrigerators, it still dominates in several key areas:

• 🏭 Food industry - meat processing plants, fisheries, dairy processing plants. Ammonia systems are used for blast freezing and storing food at temperatures up to -40°C.
• 🚢 Refrigerated transport - refrigerators, railway cars and sea containers. Ammonia is valued here for its reliability and ability to operate autonomously.
• ❄️ Ice arenas and skating rinks - ice cooling systems often operate on ammonia due to its high heat capacity.
• 🧪 Pharmaceutics and chemical industry — for storing reagents and medications at ultra-low temperatures.
• 🏢 Central air conditioning systems —in large shopping centers and office buildings, ammonia is used in chillers for water cooling.

In the household segment, ammonia refrigerators are extremely rare today, but you can still find working examples among Soviet equipment, for example:

• Refrigerators "Minsk" (models of the 1960s–1980s)
• "ZIL-Moskvich" (industrial freezers)
• "Saratov" (domestic refrigerators for rural areas)

Why is ammonia not used in modern household refrigerators?

The main reasons are toxicity and strict requirements for tightness. Manufacturers prefer safer refrigerants (for example R600a isobutane), which do not require special precautions. In addition, household refrigerators are designed for smaller sizes. volumes of refrigerant, where the advantages of ammonia are not so noticeable.

Recently there has been a revival of interest in ammonia as an environmentally friendly refrigerant. For example, in Europe and the USA it is being actively introduced in supermarkets instead of freons with high GWP (global warming potential) companies like Danfoss And Emerson are developing new compressors and automation specifically for ammonia systems.

Maintenance: what the owner needs to know

If you operate an ammonia refrigerator (especially an industrial one), it is important to follow several key maintenance rules, unlike freon ones. systems, here errors can lead not only to breakdown, but also to the leakage of toxic gas.

Checking the tightness of connections (every 6 months)

Controlling the oil level in the compressor

Cleaning the condenser from dust and dirt

Testing pressure and temperature sensors

Checking the operation of emergency ventilation

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Particular attention should be paid to the following aspects:

1. Leak control
   

   Ammonia has a pungent odor, so even a small leak can be detected without devices. However, for industrial systems it is mandatory to install gas analyzers. If a leak is detected, you must:

   • Immediately turn off the system.
   • Ventilate the room (ammonia is lighter than air, so it accumulates in the upper part).
   • Use protective equipment (respirator with cartridge KD or BKF).

Refrigerant charging

Ammonia can only be charged using special equipment (for example, gas stations with vacuum pumps). cylinders without a reducer - high pressure can lead to pipeline rupture.

Compressor maintenance

Ammonia is aggressive to conventional compressor oils, so special grades are used (for example, POE oils). They need to be changed every 2000–3000 working hours.

⚠️ Attention: When working with ammonia systems, it is prohibited to use tools made of copper or its alloys (for example, brass keys). forming unstable connections that can cause corrosion and leaks. All fittings and pipelines must be made of steel or aluminum.

If you do not have experience working with ammonia refrigerators, do not try to repair them yourselfcontact only certified specialists who are authorized to work with ammonia refrigerators. hazardous substances. In Russia, such services are provided by companies with a Rostechnadzor license to operate chemically hazardous facilities.

Safety: how to minimize risks during operation

Ammonia is not only an effective refrigerant, but also a dangerous substance if handled incorrectly. cause harm to health and even lead to accidents. However, following simple safety rules reduces risks to a minimum.

Precautionary measures

• 🚪 Ventilation of the room. data-i="248">3 air changes per hour - ammonia refrigerators must be installed in well-ventilated areas with forced exhaust. Standards require at least 3 air changes per hour.
• 🛡️ Protective means — when servicing systems, use:
  • Respirator with cartridge KD (from ammonia) or BKF (universal).
  • Safety glasses with a sealed fit.
  • Nitrile rubber gloves (ammonia destroys latex).
• 🚨 Emergency systems — in industrial installations the following are required:
  • Gas leak sensors with alarms.
  • Automatic refrigerant cut-off valves.
  • Backup power supplies for ventilation.
• 📋 Documentation — keep a maintenance log, where you record:
  • Pressure in the system (normal: condensation 10–15 bar, evaporation 2–4 bar).
  • Boiling and condensation temperatures.
  • Dates of leak testing.

⚠️ Attention: If liquid ammonia gets on your skin, immediately rinse the affected area with plenty of water during 15 minutes and seek medical help. Do not use ointments or creams - they can worsen a chemical burn. Ammonia dissolves in water, forming an alkali (NH₄OH), which destroys skin proteins.

In domestic conditions (for example, when operating an old Soviet refrigerator using ammonia), it is enough to follow three simple rules:

1. Do not store open containers with acids (vinegar, citric acid) in the refrigerator - if leaked, ammonia can react with them, releasing toxic gases.
2. Regularly check the condition of the rubber door seals - their wear can lead to increased load on the system and risk leaks.
3. Do not place the refrigerator near heat sources (radiators, stoves) - overheating of the condenser increases the pressure in the system.

FAQ: Frequently asked questions about ammonia refrigerators

Is it possible to independently convert a freon refrigerator to ammonia?

No, this is technically impossible and extremely dangerous. Ammonia and freon systems differ:

• Pipeline materials (ammonia requires steel or aluminum, freon requires copper).
• Types of compressor oils (ammonia is incompatible with mineral oils used in freon systems).
• Working pressures (ammonia systems are designed for higher loads).

Any attempt to replace the refrigerant without a complete reconstruction of the system will lead to corrosion, leaks and equipment failure.

How to determine that ammonia is used in the refrigerator and not freon?

There are several signs:

• The nameplate (information plate) indicates the refrigerant R717 (this is the designation of ammonia in refrigeration technology).
• The pipelines are made of steel or aluminum (for freon systems they are usually copper).
• If there is a leak there is a strong smell (freons have no odor).
• The refrigerator is older than 1990 and made in the Soviet Union (for example, "Minsk-15", "Saratov-2").

If you are not sure, do not try to open system - contact a specialist.

What to do if there is a smell of ammonia coming from an ammonia refrigerator?

Follow the algorithm:

1. Immediately unplug the refrigerator.
2. Open the windows and doors for ventilation premises.
3. If the smell is strong, leave the room and call emergency services (telephone 112).
4. Do not turn on the refrigerator until the leak is eliminated - ammonia can ignite at a concentration above 16%.
5. To neutralize vapors, you can use a weak solution of acetic or citric acid (but not near the source leaks!).

After eliminating the leak, be sure to check the system for leaks using a nitrogen test.

Why are ammonia refrigerators still used if they are dangerous?

Despite the risks, ammonia remains in demand thanks to:

• Energy efficiency — ammonia systems consume 15–20% less electricity.
• Environmental friendliness - ammonia does not harm the ozone layer and has zero GWP.
• Low cost - ammonia is cheaper than freons in 5–10 times.
• Reliability - properly designed systems operate for decades without loss of efficiency.

Modern technologies (automation, leakage sensors, hermetic compressors) reduce risks to a minimum. For example, in Europe, more than 80% of industrial refrigeration systems operate on ammonia.

Is it possible to use an ammonia refrigerator at home?

Theoretically it is possible, but in practice it is impractical and dangerous. Household ammonia refrigerator:

• Requires a special permit for operation (in Russia - Rostechnadzor license).
• Requires professional maintenance (refueling, repairs).
• Has a high risk of leakage if used incorrectly.
• Incompatible with modern smart home systems.

Exception - old Soviet models (for example, "Minsk" or "ZIL"), which still work in some homes. But even they are recommended to be gradually replaced with modern freon or isobutane refrigerators.