7 refrigerators

The magnetic refrigeration is a couple of years old concept . Used in cryogenics and astronautics, the magnetic refrigeration was waiting for its D-day to enter also the household refrigerators market. As far as I know, the D-day still has not come…

What´s gadolinium and how the magnetic refrigerator will work (if it will work)

Gadolinium may be a substance you have never heard of before. Anyway, it is there sitting on the 64th place in the Mendeleev´s periodic table of elements.
It is often used as an intravenous contrast agent to improve the images obtained by Magnetic Resonance Imaging (products like MultiHance, Omniscan, Gadovist contain gadolinium).

When Gadolinium is put into a magnetic field, it heats up (the so called positive magnetocaloric effect). When demagnetised, it cools down (negative magnetocaloric effect). And that is the whole secret of magnetic refrigerators.

Magnetic refrigerators save energy

Such gadolinium-based magnetic refrigerator would loose almost no energy during the cooling cycle. This is it´s main advantage compared to standard vapor-cycle compressor refrigerators where the energy loss is huge during compression and expansion of the cooling agent. Therefore magnetic refrigerators are expected to consume up to 50% less power than the standard fridges.

The compressor fridge

The compressor sucks the fumes from the evaporator and pressures them so that they get liquid in the refrigerator condensator part. The condensator grid (the grid your fridge has in its back part) emits the portion of the heat to the outer space of the room.

The cooling agnet - being pushed towards the sluice - expands and is driven to the evaporator again consuming all the temperature available in the limited refrigerator inner space (cooling it pretty down).

The absorption fridge

The absorption refrigerator uses the properties of some fluids (like water) to (first) catch the gasses around and (later) to loose them while consuming the temperature from the mixture and the space around.

The cooling agent is (usually) evaporated in the evaporator and it takes the warmth off the fridge inner space.

The vapors are condensed in the absorber part of the refrigerator, the temperature is exchanged with the environment and the cooling agent gets the form of the gass and is lead to the condensator where it liquefies again.

How to distinguish the compressor and the absorption refrigerator at the first glance (hearing)

Simply, the compressor fridge makes the noise, while the absorption one (the valve compressor doesn´t work) is quiet …

From the very beginnings, people noticed that the food lasts longer if it is stored in cooler place.

Who invented the refrigerator?

To cool the foodstuffs, the first refrigerators used the natural ice. Around 1755, scottish physician William Cullen used a simple box with larger blocks of ice to keep the inner temperature low.

In the 1790 an English manufacture produced the first refrigerator for commercial purposes – it was a box with double walls where the space between these walls was filled with chopped ice.

This invention (system of walls with the interim space filled with ice) was patented by French physician Focard-Chateau later in 1801.

From natural to synthetic ice

In 1834, Jacob Perkins patented his method of freezing the water with ether vapors and the first true refrigerator (opposed to a simple ice-box) was built.

In 1873, german Carl von Linde used for the very same purpose the ammonia gas but due to the synthetic ice refrigerators unreliability these inventions have never been really adopted and people massively used the double-walls ice-filled refrigerators by 1920s.

The compression refrigerators vs the absorption refrigerators

The evaporation at low temperatures is the idea behind the up-to-date refrigerators. In 1922, two Swedish inventors, von Platen and Muntens found out that if they dissolve the ether in water and the heat the mixture, the ether will evaporize. To do so it will use the temperature of the water-ether mixture. At the end we get the ether in the form of the gas and the ice as the evaporation of the ether consumed all the heat from the mixture.

Von Platen and Muntens sold their patent to Axel Green, founder of Electrolux who converted it into commercially successful fridge used literally by masses.

The first refirgerators used gas flame to heat the ether or ammonia refrigerant and when the gas burning unit was replaced by electrical heating unit and the potential danger of conflagration was eliminated, there were no other obstacles to stop the triumph of modern refrigerators.

After the IIWW, both Siemens and Electrolux who were leaders in fridge production started to produce the compressor refrigerators.

The cooling system here was driven by electro-compressor sucking the cooling agent (first ammonia and later freons). This agent was heated under pressure (portion of the heat was directioned to the condensator grid in the back part of the fridge), liquified and then expanded in the inner part of the cooling system. There the fluid started evaporate rapidly consuming all the temperature from the inner space of the ferigerator, cooling it down.

The refrigerators are able to keep the inner temperature between 0 and 10 Celsius degree which is low enough to store the foodstuff fresh for about 1 week.