In a typical cryogenic heat exchanger, a hot process stream is passed through a series of tubes, which are surrounded by a cool cryogenic fluid. Heat is transferred from the process stream to the cryogenic fluid, which causes the temperature of the process stream to be reduced. The cryogenic fluid is then passed through a series of tubes, where it is heated and then circulated back to the process stream. This process is repeated until the desired temperature of the process stream is reached. 

In the cryogenic industry, heat exchangers are widely used. Some common applications of heat in the cryogenic industry include:

1. LNG production: LNG is a clean energy source that requires low-temperature liquefaction for storage and transportation. Heat exchangers are used to control temperature during liquefaction, transforming gas into liquid.

2. LOX production from air liquefaction: Liquid air (LOX) is an important raw material used for producing oxygen. Heat exchangers are used to control temperature and pressure during production, transforming gas into liquid.

3. Liquid hydrogen production: Liquid hydrogen is an important clean energy source that requires low-temperature liquefaction for storage and transportation. Heat exchangers are used to control temperature and pressure during production, transforming gas into liquid.

4. Air conditioning and refrigeration: Heat exchangers can be used to control temperature in air conditioning and refrigeration systems to ensure comfortable indoor environments and food safety.

In summary, heat exchangers play an important role in the cryogenic industry, helping to control temperature and pressure to ensure the production and storage of clean energy, as well as providing comfortable indoor environments and food safety.