Absorption refrigerators running on liquefied gas are a unique engineering solution that allows you to keep food fresh where there is no access to an electrical network. Unlike conventional compressor units, there are no moving mechanical parts, and cooling occurs due to physical and chemical processes.
The main working substance in such systems is most often ammonia, circulating in a closed circuit along with hydrogen and water. It is the heating of this mixture to certain temperatures that starts the evaporation process, which ensures the removal of heat from the refrigeration chamber.
Understanding the principles of operation absorption cycle is necessary for every owner of a motorhome or boat planning to install an autonomous refrigerator. This knowledge will help not only to operate the equipment correctly, but also to quickly diagnose malfunctions if the cooling efficiency decreases.
Physical basis of the absorption cycle
The heart of the system is the heating element, which acts on a concentrated solution of ammonia in water. Under the influence of heat, ammonia begins to actively evaporate, separating from the water and creating high pressure in the upper part of the system. This vapor is then sent to the condenser, where it cools and turns into a liquid state.
The liquid ammonia then enters the evaporator, where it is mixed with hydrogen. Hydrogen in this system it plays the role of an inert carrier gas, reducing the partial pressure of ammonia and allowing it to evaporate at very low temperatures. It is the process of evaporation of ammonia in a hydrogen environment that causes intense heat absorption from the interior of the refrigerator.
⚠️ Attention: Ammonia is toxic and has a pungent odor. Although modern systems are sealed, if a characteristic odor appears, it is necessary to immediately turn off the gas supply and ventilate the room.
After evaporation, the gaseous mixture of ammonia and hydrogen returns to the absorber. There aqueous solution, deprived of ammonia, again absorbs vapor, after which the cycle repeats. The entire process is completely silent, since it does not involve compressors or fans (with the exception of forced ventilation in some models).
Key components of the cooling system
Structurally, a gas refrigerator consists of several main components, each of which performs a critical function. The tightness of the system is the first and main requirement, since any break in the circuit will lead to complete inoperability of the device.
The heater can be gas (burner with wick or electronic ignition) or electric (heating element), which makes such refrigerators universal. Switching between energy sources often occurs automatically or manually through a special mode selector.
- 🔥 Generator —a container where the solution is heated and ammonia and water are separated.
- ❄️ Evaporator —a zone where products are directly cooled due to boiling refrigerant.
- 💧 Absorber —the lower part of the circuit where the lean solution is again saturated with ammonia vapor.
- 🌬️ Dephlegmator —a device for cleaning steam from water impurities before condensation.
All these elements are connected by thin tubes, often made of stainless steel or special alloys that are resistant to corrosion. The quality of welds and connections determines the durability of the entire unit, which can last for decades if treated with care.
Efficiency and dependence on external conditions
It is important to understand that absorption refrigerators are not able to cool below ambient temperature as effectively as compressor refrigerators. Their Efficiency directly depends on the difference in temperature inside the chamber and outside.
If it is hot outside, the system requires more energy to maintain the set mode. Unlike compressor models, which quickly switch on and off, a gas refrigerator operates in a constant mode, maintaining balance.
Particular attention should be paid to ventilation. For gas combustion, a constant supply of oxygen is required, and combustion products must be effectively removed. Impaired air circulation can lead not only to a decrease in efficiency, but also to a dangerous accumulation of carbon monoxide.
Advantages and disadvantages over compressor models
When choosing between absorption and compressor technology, you need to weigh the pros and cons. Gas models win in autonomy and noiselessness, but lose in cooling speed and sensitivity to tilts.
The main advantage is the ability to work for days from one cylinder liquefied gas without connecting to the power supply. This makes them ideal for long-term stops far from civilization.
| Parameter | Absorptive (Gas) | Compressor |
|---|---|---|
| Noise when operation | Completely silent | There is a hum of the compressor |
| Energy consumption | Low (gas) / High (12V) | High |
| Roll sensitivity | High (max 3-5 degrees) | Low (up to 30 degrees) |
| Service life | 15-20 years or more | 7-10 years |
| Cooling speed | Slow (12-24 hours) | Fast (1-2 hours) |
However, it is worth noting that while the car is moving, using gas mode is often prohibited safety rules. In such cases, you have to switch to battery power, which requires the presence of a capacitive batteries or generator.
Rules for safe operation and startup
The first start-up of a new or long-inactive refrigerator should be carried out strictly according to the instructions. It is necessary to check the tightness of the connections and the absence of gas odor in the room before ignition.
The ignition process may take some time, as the system needs to warm up and start circulation. In models with piezo ignition, you must hold the gas supply button for several seconds after the wick ignites.
☑️ Check before starting
⚠️ Attention: It is prohibited to operate the refrigerator on gas if the car is in motion. Use only electric mode (12V/220V) during the trip.
Check the burner flame regularly: it should be smooth and blue. A yellow or orange tint indicates improper combustion of the mixture, which requires cleaning the nozzle or adjusting the air supply.
Maintenance and typical malfunctions
Although the system is considered maintenance-free, it requires periodic attention. The main problem is clogging of the burner jets with combustion products or dust. This can easily be solved by purging or careful cleaning.
Another common problem is the formation of air pockets in the refrigerant circuit. In such cases, the refrigerator may stop cooling, although the burner is working properly.
What to do if the refrigerator stops freezing?
Try turning the refrigerator upside down and gently knocking on the tubes. Sometimes this helps dislodge the gas plug. If this does not help, a professional refill or replacement of the unit is required.
To extend the service life, it is recommended to check the condition of the ventilation ducts on the rear wall once a season. Channels clogged with cobwebs or dirt impair heat transfer and can lead to overheating of the system.
Comparison of models and choice for a motorhome
There are many models from different manufacturers on the modern market. When choosing, you should pay attention not only to the volume, but also to the energy consumption class and type of control.
Electronic control systems allow you to more accurately regulate the temperature and automatically switch between power sources. Mechanical models are easier to repair, but less functional.
The volume of the refrigerator should be selected based on the number of people in the crew and the duration of autonomous stays. You should not chase the maximum volume if you are traveling together - this will only increase gas consumption.
Frequently asked questions (FAQ)
Is it possible to turn on a gas refrigerator on the go?
It is strictly not recommended. In the event of an accident or sudden braking, this can lead to a gas leak and fire. Use power from the car battery while driving.
Why does a refrigerator not cool well in hot weather?
Absorption systems are highly dependent on the ambient temperature. Make sure the refrigerator is level and the ventilation grilles are not closed. Direct sunlight also reduces efficiency.
How often do you need to change the gas in the cylinder?
Consumption depends on the model and the outside temperature. On average, one standard cylinder per 50 liters of chamber volume is enough for 2-3 weeks of continuous operation in the summer.
A gurgling sound is heard - is this normal?
Yes, quiet gurgling or clicking is the normal sound of refrigerant circulating through the pipes. Loud sounds may indicate airing of the system.