Description

Cryogenic technology is an indispensable part of an industrialized society with continuous growing importance. Until a few decades ago cryo-technology was essentially limited to specific applications in medicine, aerospace, superconducting magnets, and diagnostics, today the spectrum has expanded substantially including food-sector, energy transport, and energy storage, for example LNG (at ≈ 110 Kelvin) or liquid hydrogen (at ≈ 20 Kelvin). It is foreseeable that the operation of cryogenic infrastructures will be of central importance to society.

The term cryogenics describes the techniques for generating and operating systems with fluids at temperatures below 120 Kelvin and covers a wide range of liquids as well as gaseous cryogens such as helium (4.2 Kelvin), hydrogen (20 Kelvin) up to natural gas (LNG 110 Kelvin). 

The operation of cryo-plants requires fundamental knowledge of the heat and phase transition of fluids in order to be able to map energetically efficient processes and plan them technically. This requires basic knowledge from various disciplines of systems engineering, process technology, and metrology with special consideration of low temperatures. The effects of low temperatures not only influence the design and dimensioning of components and piping, but also affect the dynamics of cryogenic systems and must be taken into account accordingly in process measuring and control technology. The safety engineering of cryogenic systems also differs from that of conventional piping or chemical carrier networks. For example, high pressures can build up in cryogenic systems in the event of a thermal collapse, so suitable measures must be taken into account at the planning stage.

Another aspect in the realization of cryogenic plants is the consideration of the specific material properties at low temperatures, which differ from those of conventional engineering. Thermal and mechanical parameters for further design can be derived from the thermodynamic relationships as well as the microstructural properties. In addition to metallic alloys, composite materials are also considered as structural and functional materials.

Scope

The aim of the lecture is to teach the basics of refrigeration and liquefaction of fluids with a boiling temperature below 120 K. For this purpose, the essentials of thermodynamics, phase transitions and heat transfer mechanisms must be understood and it should be possible to balance the main components of such a cryogenic system.

The relationship of thermal and mechanical material properties at cryogenic temperatures to the physical background is established. Practical examples are used to illustrate the influence on the design.

The basic design of cryostats is explained in detail and illustrated by examples. The essential design principles and standard components of the measurement and control technology, as well as the essential standards and safety devices are explained.

Content

• Introduction to cryo-technology
  
  
• Thermodynamic process and technology of cryogenic generation (Joule-Thompson/Brayton/Claude/Stirling)
• Cryogenic fluids
• Examples of cryogenic applications and their components (bath-, forced-flow-, contact cooling)
  
  
• Thermal insulation (vacuum-, super-insulation) and thermal shields
• Storage and transfer of cryogenic fluids (e.g. canister, truck, pipeline, ship)
• Requirements for process measuring and control technology within cryogenic environment
• Specific design features for cryostat systems

• Impact of low temperature on metallic alloys and composite materials
• Requirements and qualification of structural and functional materials for cryogenic temperature regime
• Equipment for material characterization at low temperature