Ph.D Thesis Colloquium

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Cryogenics refers to the field of science and engineering below 123 K (-150 ºC).  Also it deals with the production, utilization and maintenance of the same. Below 123 K, the so called “Permanent gases” such as Argon, Oxygen, Nitrogen, Hydrogen and Helium can be liquefied. Because of their low boiling point and latent heat of vaporization, special storage and transfer systems are needed for storing these cryogens for end applications. Hence, it is necessary to use insulated cryogenic transfer lines to minimize the evaporation losses and enable maximum fluid collection during the transfer of the cryogens.

Flexible transfer lines are manoeuvrable, easy to handle and can take care differences in the heights between the storage and receiver tanks when compared to rigid transfer lines. On the other hand, the design and fabrication of flexible cryogenic transfer lines is more cumbersome than those of rigid transfer lines. To the best of our knowledge, the procedure available to design and develop a flexible transfer line is scanty in the open literature.  The work presented here perhaps tries to fill the gap by detailing the theoretical background for the development of the super-insulated vacuum jacketed flexible cryogenic transfer lines, such as the determination of wall thicknesses, estimation of heat loads by different modes of heat transfer and pressure drop estimations for both single and two-phase flows through the transfer lines and the possible studies on two phase flow through the transfer lines.

Hence, to start with, a quick disassemble type flexible transfer line of 20.5 mm ID, 62 mm OD and 3 m long has been designed and fabricated. Studies on cool-down, heat transfer and pressure drop has been carried out towards optimizing the various critical parameters such as numbers of Multi-layer Insulations (MLI) and spacer distances. Studies also have been carried out for measuring the void fraction and flow phenomenon in the developed flexible transfer line. Simple and cost effective capacitance and diode sensors have been developed and integrated in-line to the developed transfer line for measuring the void fraction and the flow pattern. Based on the studies and the expertise gained in the development of 3 m long flexible transfer line, a 5 m long flexible transfer line of 35 mm ID and 102 mm OD with Bayonet joints has been developed for the specific application of national importance. Studies have been performed towards the performance evaluation of the above transfer line.

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