Cryogenics the refrigeration technology


Cryogenics is a complicated taxonomic category falling beneath the refrigeration technology. So, let’s take a short summary on refrigeration and air-con. It’s essentially concerning taking energy from a given volume (low temperature) and throwing it into the atmosphere (high temperature) however, consistent with the foundations of nature it’s not possible (at least while not doing a little work on the system). To prove this, we are able to merely prove the converse wrong. in {an exceedingly |in a very} glass of heat water place an square block, if energy is transferred from the cold object to the upper temperature, then which means the square block must transfer a number of its heat to the nice and cozy water, which might imply that the square block becomes colder and also the heat water becomes hotter that as we tend to might imagine isn’t what happens. Thus however do refrigerators keep cool objects cold?

It is achieved by neatly breaking down the energy transfer into smaller steps. 1st a cool refrigerant (which is cooler than the cold space) is more matured the walls of the white goods. The refrigerant absorbs the warmth from the cold house since it’s at a lower temperature and becomes hotter. this is often compressed (either by a mechanical device or a pump) inflicting a pressure increase resulting in an extra temperature increase. Next it’s more matured another set of tubes (condenser) so it loses a number of its heat to the atmosphere (since it’s at a better temperature than the atmosphere). it’s cooled down all over again once it’s skilled true gone through| had| undergone |saw |felt |responded  to| suffered} an expander and also the entire cycle is perennial. Thus though it appears like nature is being betrayed, in reality, it ne’er is. Currently that we’ve got designed the inspiration, allow us to look additional ahead into the sphere of cryogen.

Fig :Typical single stage vapor compression refrigeration

While refrigeration deals with the accomplishment of low temperatures, physics takes it a step additional managing very low temperatures, going below -1500C. primarily these involve temperatures at that otherwise usually gasified substances like element, Oxygen, Hydrogen, Helium, etc. area unit was liquids. it’s derived from the Greek words “Kryos” that means frost and “Genic” aiming to turn out. A unremarkably used refrigerant like LOX (Liquid Oxygen) needs a temperature of -1830C to alter into the liquid section and element at -2690C. in line with the second law of natural philosophy, there’s a barrier towards to the lower finish of the metric below that a temperature can’t be earned. this is often called the “absolute zero” and is capable a price of -273.150C or within the temperature scale, 0 K. this is often not possible to achieve since it might need infinite quantity of energy to achieve this state. At such low temperatures, atoms and molecules behave otherwise than at traditional attributable to quantum mechanical effects. for instance, liquid element at a temperature of concerning 2K has zero consistency and might advance the walls of a instrumentality, this is often known as a superfluid. sure materials once treated with cryogens exhibit special properties, like once metals area unit cooled at those temperatures they behave as super conductors. refrigerant Liquids area unit used extensively within the region, food, medicine, natural philosophy and energy industries.


Such low temperatures can’t be measured exploitation the traditional mercury and alcohol thermometers since they freeze a lot of before that. Special temperature sensing devices exploitation special materials like Pt (up to 20K temperature) and doped semiconducting material (up to 1K Temperature). These materials area unit used resistance temperature sensing devices and want the suitable standardization. These area unit typically utilized in mixtures as primary and secondary sensing devices.


Fig :Typical single stage vapor compression refrigeration

Generation of the refrigerant temperatures involves the method of phase change of gases. There area unit many various ways of liquefying gases however they work on an equivalent principle. Air is extracted and compressed to nice extent inflicting it to heat up. it’s then allowed to come back all the way down to temperature keeping the pressure constant. it’s then additional cooled through a device to a lower temperature. this is often currently swollen (pressure lowered) back to air pressure. This growth causes speedy cooling and a few portion of the air is liquefied. The cool gases area unit sent to the start of the warmth money dealer to cool down the incoming propellant from the primary stage. The liquefied air is distilled to separate the elements like atomic number 8, Nitrogen, Argon, etc. Lighter gases like element can even be achieved however adding stages of growth, i.e. the cold gases from the primary stage are additional depressurized in steps to supply a lower temperature.


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