Description

Cryogenic technology is an indispensable part of an industrialized society and its importance is constantly growing. Until a few decades ago, cryogenic technology was essentially limited to special applications in medicine, aerospace, superconducting magnets and diagnostics, but the spectrum has expanded substantially to include the division of food, energy transport and energy storage, for example LNG (at ≈ 110 Kelvin) and 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 of less than 120 Kelvin and covers a wide range of liquid and gaseous fluids such as helium (4.2 Kelvin), hydrogen (20 Kelvin) and natural gas (LNG 110 Kelvin).

The operation of cryogenic institutions requires basic knowledge of the heat and phase transition of fluids in order to be able to map energy-efficient processes and plan machinery. This requires basic knowledge from various disciplines of apparatus engineering, plant process engineering and measurement technology, with particular 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 appropriately taken into account in the measurement, regulation and control technology. The safety technology of cryogenic systems also differs from that of conventional piping or chemical carrier networks. Cryogenic systems can, for example, build up high pressures in the event of heat loss, so suitable measures must be taken into account at the planning stage

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

Targets

The target of the lecture is to convey the basics of refrigeration and the liquefaction of fluids with a boiling temperature below 120 K. For this purpose, the essential principles of thermodynamics, phase change and heat transfer mechanisms must be understood and the essential components of such a low-temperature system must be able to be balanced.

The relationship between the thermal and mechanical material parameters at cryogenic temperatures and the physical processes is established. Practical examples are used to illustrate the influence on the design.

The basic structure of cryostats is explained in detail and illustrated using 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.

Contents

• Introduction to cryogenic technology
   
• Circuit processes and methods of refrigeration (Joule-Thompson/Brayton/Claude/Stirling)
• Cryogenic operating media
• Examples of cryogenic applications and their components (bath, forced and contact cooling)
   
• Thermal insulation (vacuum, super insulation) and thermal shields
• Storage and transfer of cryogenic fluids (e.g. cans, trucks, pipelines, ships)
• Requirements for measurement/control/safety technology in cryogenic environments
• Specific design features for cryostat systems

• Influence of low temperatures on metallic alloys and composite materials
• Requirements and qualification of structural and functional materials for the cryogenic temperature range
• Equipment for material characterization at low temperatures

Prior knowledge:

Confident handling of the knowledge of physics, heat and mass transfer and design theory taught in the Bachelor's program

Workload: 20 lecture hours + 6 practical units + approx. 96 follow-up hours = 120 hours