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Choosing a refrigerator is not necessarily an easy exercise. We are looking for efficiency, but also silence, and economy, while we juggle with the more or less relevant technologies of each other. Among those that may be good to understand is the linear compressor.
Some manufacturers display technologies with more or less explicit names on the technical data sheets of their products. In the field of refrigeration, you may come across the term linear compressor. What does it mean, how does it work, does it make any real sense in practice? Technical decryption in the land of the Eskimos...
A linear compressor signed LG, which performs a back and forth movement.
Does your refrigerator consume too much? Is it too noisy? Is it 15°C in the vegetable drawer? Maybe it's time to change it! But maybe you've already thought about it... and were a bit confused when you arrived at your appliance retailer. Nothing could be more normal, it is not easy to sort out the marketing arguments and those that really focus on the good of your food, your ears, or even that of the environment.
Among the terms that you may encounter, "linear compressor" belongs to those that are not insignificant. Indeed, the compressor is one of the centerpieces of the refrigerator, if not the most important.
But already, why a compressor?
In a refrigerator, it's all about pressure. Indeed, the machine does not generate cold, as one might think, but plays with the pressure – and therefore the temperature – of a gas. A cycle which is initiated by the compressor, which compresses the gas in order to impose a sharp rise in temperature, often up to 60°C. The condenser, this long pipe that winds behind the refrigerator, is then responsible for evacuating part of this heat, a step that allows the gas to return to a liquid state.
Subsequently, in the regulator, or rather at its outlet, the liquid then loses pressure, dropping violently in temperature (-20°C). It then enters the evaporator, from where it absorbs the heat contained in the refrigerator. It thus heats up and regains its gaseous state just before passing through the compressor again, which will compress it so that the condenser can evacuate as much heat as possible, etc., etc.
Responsible for both the bulk of the noise and the bulk of the consumption of a refrigerator, the compressor is therefore, so to speak, the "motor" of a refrigerator.
Compressor, Ok, but why linear?
Traditionally, the compressors fitted to our refrigerators are set in motion using a connecting rod-crank system, a concept which has not failed to prove its worth, but which, in this context, has a small drawback: to make the machine, the presence of an arm is necessary; however, who says arms, says joints, and therefore points of friction. In fact, the energy efficiency of the device is therefore not optimal, especially since the power is in principle not adjustable.
A "classic" compressor. We guess the connecting rod-crank system.
Indeed, the conventional compressor starts when the temperature inside the refrigerator is too high, and stops when it is satisfactory. The result is the noise we all know, which can be a little annoying in some cases.
However, there is a new generation of compressors that work differently, the so-called inverter compressors, used, for example, by Samsung. These do not obey an operating logic conditioned by too high a temperature, for the simple and good reason that they do not stop operating, but adapt the power according to needs. Thus, for example, they can deliver 30% of the available power as long as the door is closed, then switch to 80% just after a long opening of the refrigerator.
Finally, the linear compressor is an extension of this technology. In fact, not content with being an inverter compressor itself, it is not based on a crank system, but, as its name suggests, on a linear motor. In practice, this means the disappearance of the connecting rod (of the arm) and of the friction points linked to the latter, thus virtually leaving a single and unique friction point, that of the piston. A system which, in theory, significantly increases energy efficiency compared to a "classic" compressor, since it combines adaptation and reduced friction.
Including. But where do we find that?
The linear compressor is an LG technology and the Korean intends to exploit it exclusively. Not possible, therefore, to find a Samsung stamped refrigerator bearing the label of this technology.
On the other hand, the latter is not the prerogative of high-end models, since it is quite possible to find a linear compressor in a handset of medium size at a reasonable price (500 to 600 €).
But while almost all US-made handsets or refrigerators made by LG can apparently accommodate a linear compressor, we note, however, that this does not seem to be the case with smaller appliances. Indeed, small refrigerators, in the so-called "table top" format, are thus deprived of a linear compressor.
Concretely, what is the benefit for the consumer?
Presented in this way, the linear compressor seems rather attractive. Indeed, LG lends it several advantages over the competition, both in terms of energy efficiency, noise and reliability. What is it in reality? Are promises kept?
On the energy efficiency side, if refrigerators equipped with a linear compressor do not stand out for their incredibly low consumption, it is clear that they are rather a group of very good students. Difficult, however, to confirm or deny the promised gain (20%). If the friction is indeed reduced and if LG ensures that its system takes advantage of it to adjust the power with unprecedented precision, the fact is that most of the models equipped have adopted at the same time the ventilated cold, reputed to be more energy intensive than the static cold from our old refrigerators. We can therefore only observe that the equipment/consumption ratio remains very good, even if devices rated A++ and A+++ remain relatively rare.
Regarding noise, LG highlights a gain of 1 to 2 dB. Here too, it is difficult to verify whether the promise is kept, but we observe that the Korean products equipped with a linear compressor are rather within a correct average, with announced sound levels which are barely above 40 dB(A ). Its other products (not equipped with linear compressors), on the other hand, do not really belong to the best students, with many models displaying a rather passable 43 dB(A). We can therefore, by contrast, consider that there has indeed been progress.
Finally, the simplification of the compressor mechanism should, logically, bring a gain in reliability. This generation of linear compressors being quite recent, since finalized in 2009, it is however impossible to judge this technology with hindsight. As for the repairers contacted by us, there are a few breakdowns, but nothing unacceptable, with figures that can be described as anecdotal. Reliability to be confirmed over the long term, therefore.
