Speaker
Description
Stable operation of helium cryogenic system and low heat loads are of paramount importance. In order to achieve the required pressure stability and heat loads, all sources of possible disturbances have to be eliminated at the design phase and latest during the commissioning activities. One of such disturbances is thermally driven oscillations (TAO), which could occur when a local heat source is presented or continuous transition from cold to warm temperatures exists. Unfortunately, theoretical background of TAO for helium systems, originally developed by Nikolaus Rott, is relative complicated for practical implementations, and also contains ideal conditions, like smooth tube without frictional contribution to flow. Moreover, TAO occurrence has a statistical character, so in some properly designed systems, these oscillations could also occur and countermeasures must be taken. In the open literature sources, TAO are extensively measured, though thorough result comparisons would be helpful. Additionally, the systematic discussion of all countermeasures is still missing. In the present paper, a short review on available theoretical and experimental results related to the TAOs is given. Several practical tips for the designing as well as review on countermeasures during cryogenic system operation are presented.