The cooled surface is at least partly covered with a porous sorbent material. The design of a cryopump has to combine cryogenic aspects and technological vacuum considerations in a unique manner, as the generation of low temperature itself presupposes the existence of vacuum conditions and vice versa. Thus, the cryopump is by its physical principle a high-vacuum pump. Besides straightforward parameters, such as pressure and temperature, the performance cryopump is very much governed by the complex interaction between gas particles and cooled sorbent surface.

  • The Cryopump is the pump type that provides the highest pumping speeds, especially when operated in situ of the vacuum recipient.

  • A typical cryopump consists of a cryogenic refrigerator producing refrigeration at two temperature stages. Each stage in turn cools an extended surface cryopanel onto which the gases will freeze. The first stage of the refrigerator, shown at right, usually operates in the range of 50-75 K (Kelvin) and is used to cool the outer cryopanel and louvers across the inlet opening of the cryopump. Water vapor will freeze out onto these panels.

  • The second, or cold stage, of the refrigerator, shown at left, usually operates between 10-20 K and is used to cool the inner cryopanels. Gases such as nitrogen, oxygen and argon will freeze onto these panels. Lastly, any gases that have not yet frozen onto a panel will be adsorbed (a process known as cryosorption) into charcoal, which is located on the underside of the second stage cryopanel.

  • A cryopump will accumulate large amounts of solid water, air, argon, nitrogen, and oxygen before it has to be defrosted, as illustrated at right. Pumping speeds decrease very little while these thick layers of cryodeposits are built up, and the refrigerator’s temperature changes very little. Typically, water can be allowed to accumulate on the louver until approximately half of the louver is blocked. Solid nitrogen and argon can accumulate in layers that are several centimeters thick on the outside of the cold panel. Typically, the thickness is only limited by their coming into contact with a warmer surface. The rated amount of hydrogen that can be adsorbed is usually based on the assumption that the accumulated hydrogen will result

  • The major types of Heat Exchanger equipment are:

  • Shell and Tube type

  • Finned tube type

  • Bare tube type

  • Plate and frame type.

  • Spiral type

  • Plate Coil type

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