{"id":38438,"date":"2024-03-26T16:47:25","date_gmt":"2024-03-26T16:47:25","guid":{"rendered":"https:\/\/www.alicat.com\/?post_type=article&p=38438"},"modified":"2026-01-26T16:39:32","modified_gmt":"2026-01-26T16:39:32","slug":"absolutdruckregelung-absoluttemperaturregelung","status":"publish","type":"support","link":"https:\/\/www.alicat.com\/de\/support\/absolute-pressure-control-absolute-temperature-control\/","title":{"rendered":"Aufrechterhaltung kryogener Temperaturen mit Druckregelung"},"content":{"rendered":"\n[et_pb_section fb_built=”1″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_row _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_heading title=”Maintaining cryogenic temperatures with pressure control” _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”]

Cryogens are substances that liquefy at or below 120 K under standard pressure (760 Torr). They are commonly used in applications to keep liquefied substances at extremely cold temperatures, including cryopreservation, rocket propulsion, and medical imaging.<\/p>\n

Two of the most well-know cryogens are liquid nitrogen and helium. Liquid nitrogen is commonly used for cold storage and flash freezing in lab settings, and is near the upper end of the cryogen temperature spectrum. Helium is particularly notable for its proximity to absolute zero (0 K). It is typically at 3-4 K, with variations depending on the specific isotope<\/a> and the ambient pressures.<\/p>\n

Challenge: Mitigating loss of cryogenic gases<\/h2>\n

The equilibrium temperature of a cryogen is highly dependent on pressure, as demonstrated in figure 1. Because of this, tight control of absolute pressure enables tight control of absolute temperature.<\/p>\n

In cryopreservation applications, researchers must prevent the loss of the cryogen due to evaporation and pressure fluctuations. This is challenging, as atmospheric pressure often fluctuates by as much as \u00b125 Torr.<\/p>\n

Imagine a researcher using a 100 L dewar of liquid helium. A pressure decrease of 25 Torr will result in the vaporization of 0.874 liquid liters, generating 25 standard cubic feet (or ~700 standard liters) of helium gas. This is approximately $25 worth of liquid helium. Over a period of years, the helium vaporization may quickly amount to thousands of dollars in unnecessary loss.<\/p>\n

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Figure 1: Interdependence of temperature and pressure for common cryogens.<\/em><\/h6>[\/et_pb_text][et_pb_text _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”]

In cryopreservation applications, researchers must prevent the loss of the cryogen due to evaporation and pressure fluctuations. This is challenging, as atmospheric pressure often fluctuates by as much as \u00b125 Torr.<\/p>\n

Imagine a researcher using a 100 L dewar of liquid helium. A pressure decrease of 25 Torr will result in the vaporization of 0.874 liquid liters, generating 25 standard cubic feet (or ~700 standard liters) of helium gas. This is approximately $25 worth of liquid helium. Over a period of years, the helium vaporization may quickly amount to thousands of dollars in unnecessary loss.<\/p>\n

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In an extreme example, pressure fluctuations in propellant storage tanks at NASA\u2019s John F. Kennedy space center resulted in boiloff of 650 kg of liquid hydrogen each day \u2013 estimated in 2001 to cost $625,000 each year!<\/h3>[\/et_pb_text][et_pb_text _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”]

<\/strong><\/h2>\n

Solution:<\/strong> Tightly regulating headspace pressure<\/h2>\n

Pressure meters\/controllers therefore play critical roles in cryogenic temperature control, including:<\/p>\n