Cryogenic refrigeration involves cooling materials to extremely low temperatures below -153°C using compressed gases like nitrogen and oxygen. It is achieved through a refrigeration cycle where a gas is compressed, cooled, expanded to condense and cool a material. Applications include producing rocket fuels, MRI machines, food storage and preservation, and cooling superconductors. Refrigerators receive star ratings from 1-5 stars based on their energy efficiency, with 5-star models using the most efficient compressors like inverters.

1. KRISHNA DHONDGE
Production & Industrial Engineering

2. What is Cryogenic Refrigeration
 Cryogenics is the cooling of materials to extremely low temperatures using
highly condensed gases.
 Cryogenics involves refrigeration at temperatures below 120 K (-153°C). These
low temperatures, which are not natural on earth, make it possible to liquefy
gases such as methane, oxygen, nitrogen and hydrogen.
 Cryogenic temperatures are generally achieved through a refrigeration cycle.
First, the gaseous refrigerant (green) is compressed and heated in a
compressor.
 While cryogenics usually involves temperature below the freezing point of
liquid nitrogen yet above that of absolute zero, researchers have achieved
temperatures below absolute zero (so-called negative Kelvin temperatures).

3.  Cryogenic refrigeration uses very low temperature refrigerants, especially liquid
nitrogen and solid or liquid carbon dioxide. Liquid nitrogen is produced off-site
at large air separation plants and is transported to food processing plants in
insulated tanks.
 At a food manufacturing facility, the liquid nitrogen or solid carbon dioxide may
be used to chill another refrigerant or will be used to directly chill the product.
 There are several applications of cryogenics. It is used to produce cryogenic
fuels for rockets, including liquid hydrogen and liquid oxygen (LOX). The
strong electromagnetic fields needed for nuclear magnetic resonance (NMR)
are usually produced by supercooling electromagnets with cryogens. Magnetic
resonance imaging (MRI) is an application of NMR that uses liquid
helium. Infrared cameras frequently require cryogenic cooling. Cryogenic
freezing of food is used to transport or store large quantities of food.
 A cryogenic rocket engine is a rocket engine that uses a cryogenic
fuel and oxidizer, that is, both its fuel and oxidizer are gases liquefied and
stored at very low temperatures.

5. How cryogenic Refrigeration is done
 Cryogenic temperatures are generally achieved through a refrigeration cycle.
First, the gaseous refrigerant (green) is compressed and heated in a
compressor.
 Next, the compressed refrigerant (red) is cooled. The heat from this cooling
process is used in the compressor.
 The refrigerant then travels through an expansion valve, cooling to the point of
condensation. This condensed refrigerant now comes in contact with the
material to be cooled, bringing the temperature of the material down to
cryogenic temperatures.
 As it cools the material, the liquid refrigerant is in turn reheated and undergoes
the cycle again.

6. Application of Cryogenic Refrigeration
 Cryogenics is used in a variety of applications. It can be used to produce
cryogenic fields for rockets, in MRI machines that use liquid helium and require
cryogenic cooling, storing large quantities of food, special effects fog, recycling,
freezing blood and tissue samples, and even cooling superconductors
 Cryosurgery. A type of surgery that uses cryogenic temperatures to eliminate
unwanted tissue or tumors.
 Cryoelectronics. The ultra-frozen temperatures that cryogenic fluids can
provide offer the ability for electrons in materials to move freely with little
resistance.
 Food Preservation. To preserve packaged foods such as produce, the food
items
 Transportation of Gases. Cryogenics is also used to transport gases that are
not typically cryogenic.

7. How star ratings are given to Refrgerator
 A 5 Star fridge will have more efficient compressors, like inverter compressors
 Every refrigerator has an energy efficiency star rating awarded according to the
conditions laid down by the Bureau of Energy Efficiency.
 One star means that the fridge is inefficient and consumes a lot of energy, while
five stars are given to the most energy-efficient appliance.
 Which means a 3 star rated refrigerator will consume about 100-150 units more than a 4 star
and similarly a 4 star rated refrigerator will consume 100-150 units more than a 5 star per year.