How an ammonia refrigerator works: device, diagram and features

Ammonia refrigerators are a rare but unique type of refrigeration equipment that is still used in industry, camping, and even in some household models. Unlike conventional compressor systems, they operate on the basis absorption cycle, where the chemical reaction between ammonia, water and hydrogen plays a key role. Such refrigerators have no moving parts (except for a possible fan), which makes them virtually silent and extremely reliable.

If you have ever encountered refrigerators for motorhomes, gas refrigerators for a summer residence, or industrial installations with a thermal drive, then most likely it was an ammonia system. In this article we will analyze operating principle of an ammonia refrigeratorits design, advantages over compressor analogues, as well as the nuances of operation and safety. We will pay special attention to why such refrigerators are still relevant, despite the spread of inverter compressors.

What is an ammonia refrigerator and where is it used

An ammonia refrigerator is refrigeration equipment in which refrigerant ammonia appears (NH₃), and cooling occurs due to absorption-diffusion cycle. Unlike compressor systems, where freon is compressed mechanically, here the process is based on dissolution of ammonia in water and its subsequent release during heating.

Such refrigerators are widely used in:

• 🚐 Motorhomes and campers —due to the ability to operate on gas, electricity or even solar panels.
• 🏕️ Summer cottages —where there is no stable power supply, but there is access to gas or firewood.
• 🏭 Industry —for cooling large volumes (for example, in the chemical or food industry).
• 🚢 Marine transport —where vibration resistance and minimal maintenance are important.

One of the most famous manufacturers of such refrigerators is Electrolux (series Absorption), as well as brands Dometic and Norcold, specializing in camping equipment. In everyday life, ammonia refrigerators are less common due to the high cost and specifics of operation, but in niche segments they remain indispensable.

The design of an ammonia refrigerator: main components

The design of an ammonia refrigerator is significantly different from a compressor refrigerator. Instead of a motor, condenser and evaporator, a system of tubes and filled tanks is used here. Let's consider the key elements: ammonia solution. Let's look at the key elements:

1. Generator (boiler) — here ammonia is released from an aqueous solution when heated (from gas, electricity or another heat source).
2. Condenser — ammonia vapor is cooled and condenses into liquid.
3. Evaporator —liquid ammonia evaporates, taking heat from the fridge compartment.
4. Absorber —here the ammonia dissolves again in water, completing the cycle.
5. Heat exchanger - improves the efficiency of the process by preheating a weak solution in front of the generator.

Some models are also present hydrogen cylinder, which maintains the required pressure in the system. For example, refrigerators Dometic RM use just such a circuit with hydrogen, which makes it possible to do without a pump.

Important: there is no freon in ammonia refrigerators, which means they do not harm the ozone layer. This is one of the key advantages over outdated compressor systems on R-12 or R-22.

Principle of operation: how ammonia cools a refrigerator

The cooling process in an ammonia refrigerator can be divided into four main stages, which are repeated cyclically. Let's look at them in more detail:

1. Generation of ammonia steam

In generator (aka boiler) the aqueous ammonia solution is heated to boiling temperature. Because ammonia boils at a lower temperature than water, it begins to evaporate, separating from the solution. The heat source can be:

• 🔥 Gas burner (in camping models).
• ⚡ Electric heating element (in household refrigerators).
• ☀️ Solar collector (in environmentally friendly systems).

2. Ammonia condensation

Ammonia vapor rises into condenserwhere it is cooled by air or water and turns into liquid. This process is accompanied by the release of heat, so the back wall of the refrigerator can be warm.

3. Evaporation and cooling

Liquid ammonia enters evaporatorwhere, due to a sharp drop in pressure, it turns back into gas, absorbing heat from the fridge compartment. It is this stage that provides cooling.

4. Absorption (absorption) of ammonia

Ammonia gas enters absorber, where it dissolves in water, forming a weak aqueous ammonia solution. This solution then enters the generator again, and the cycle repeats.

Why is hydrogen used in the system?

In some ammonia refrigerators (for example, Dometic RM2351hydrogen is added to the system. It performs two functions:

1. Maintains the necessary pressure for ammonia circulation without a pump.

2. Improves heat transfer in the evaporator, increasing cooling efficiency.

Without hydrogen, an additional pump would be required, which would complicate the design.

Advantages and disadvantages of ammonia refrigerators

Like any technology, absorption refrigerators have their pros and cons. Let's take a closer look at them to understand whether such a refrigerator is suitable for your needs.

✅ Advantages

• 🔇 Complete noiselessness —no compressor, vibrations or moving parts (except for the fan in some models).
• 🔄 Durability —service life can exceed 20 years with proper operation.
• ⚡🔥 Power versatility - work from gas, electricity, solar panels or even wood heating.
• 🌍 Environmentally friendly - ammonia does not destroy the ozone layer (unlike freons R-12 or R-134a).
• 🛠️ Minimal maintenance —do not require refilling with freon or changing the oil.

❌ Disadvantages

• 💰 High cost — ammonia refrigerators are 1.5–2 times more expensive than compressor refrigerators.
• ⏳ Slow cooling —it takes 6–12 hours to reach operating temperature (versus 1–2 hours for compressor units).
• 🔥 Depending on heat —at low ambient temperatures (below +10°C) efficiency decreases.
• ☠️ Danger of ammonia leakage —if the system is damaged, a strong odor is possible, and in high concentrations ammonia is toxic.
• 📉 Low efficiency —for 1 kW of cooling, 2–3 kW of heat is spent (for compressor units this figure is better).

Safety: what to do in case of an ammonia leak

Ammonia (NH₃) is a caustic substance with a pungent odor, which in high concentrations can cause pulmonary edema or chemical reactions burn. However, in household refrigerators its quantity is minimal (usually no more than 300 grams), so a serious leak is unlikely. However, it is important to know the safety rules:

⚠️ Attention: If you smell a strong smell of ammonia near the refrigerator, immediately disconnect it from the power supply, open the windows and leave the room for 15-20 minutes. Ammonia is heavier than air and can accumulate at the bottom.

Signs of an ammonia leak:

• 👃 Pungent odor (reminiscent of ammonia or urine).
• 🌫️ The appearance of white “smoke” (with a large leak, ammonia reacts with moisture in the air).
• 🥶 The refrigerator stops cooling, despite the heater running.

Actions in the event of a leak:

1. Disconnect the refrigerator from all power sources (gas, electricity).
2. Ventilate the room for 30–60 minutes.
3. Do not turn on the refrigerator until the fault is resolved.
4. Contact the service center - Independent repair of ammonia systems is prohibited due to the toxicity of the refrigerant.

Comparison of ammonia and compressor refrigerators

To understand which refrigerator is better to choose, let’s compare the key parameters of ammonia and compressor systems:

Ammonia refrigerators are justified where reliability and autonomy is important (camping, dacha, industry), and compressor refrigerators - where necessary efficiency and cooling rate (city apartments, offices).

Operating rules: how to extend the life of a refrigerator

Ammonia refrigerators are unpretentious, but require compliance with several rules in order to last as long as possible. Here are the key recommendations:

Install the refrigerator strictly according to the level (distortions disrupt the circulation of the solution)|

Clean the heat exchanger from dust every 6 months|

Do not place the refrigerator in a room with a temperature below +10°C|

Check the door tightness (wear of the seal increases the load on the system)|

When left idle for a long time (in winter), store the refrigerator in a warm room -->

What not to do:

• ❄️ Defrosting ice with a knife or metal objects - it can be damaged evaporator.
• 🔥 Use an open fire next to the refrigerator (except for models designed for this).
• 🔌 Connect to an unstable power supply without a stabilizer —voltage surges can damage the heating element.

⚠️ Attention: If the refrigerator does not cool, do not try to “overclock” it by increasing the temperature of the heater. This may cause the generator to overheat and leak ammonia. First, check the tightness of the door and the cleanliness of the heat exchanger.

FAQ: Frequently asked questions about ammonia refrigerators

❓ Is it possible to repair an ammonia refrigerator yourself?

No, repair of ammonia systems should only be carried out by a certified specialist. Ammonia is toxic, and special equipment is required to fill or solder the tubes. Independent repair attempts can lead to a leak or explosion (if soldering is incorrect).

❓ Why does an ammonia refrigerator cool poorly in winter?

Absorption refrigerators depend on the ambient temperature. When below +10°C efficiency drops because:

• The circulation of the solution in the heat exchanger worsens.
• Ammonia evaporates worse in the evaporator.

Solution: use a refrigerator in a heated room or choose models with an electrically heated generator.

❓ What gas is used in ammonia refrigerators for campers?

In most camping models (for example, Dometic RM or Norcold DE-0041) is used propane-butane mixture (the same as in gas cylinders for stoves). Some models support connection to 12V or 220V.

❓ How long does it take for an ammonia refrigerator to cool down?

Depending on the model and ambient temperature:

• First cooling to +5°C - 6–12 hours.
• Maintaining temperature - cycles of 2–4 hours (heating/cooling).

This is significantly longer than that of compressor refrigerators, but the process is completely silent.

❓ Is it possible to transport an ammonia refrigerator lying down?

No, Ammonia refrigerators can only be transported in an upright position (or at an angle of no more than 45°). When transported lying down, the solution may enter the evaporator, which will lead to:

• Clogged tubes.
• A drop in cooling efficiency.
• Potential damage heat exchanger.

After transportation, the refrigerator must stand 2-3 hours before turning on.