Characterisation and optimisation of flexible transfer lines for liquid helium. Part II: Thermohydraulic modelling. (October 2016)

• Record Type: Journal Article
• Authors: Dittmar, N.; Haberstroh, Ch.; Hesse, U.; Krzyzowski, M.
• Is Part Of: Cryogenics. Volume 79(2016)
• Page Start: 53
• Page End: 62
• Publication Date: 2016-10
• Subjects: Liquid helium -- Cryogenic transfer line -- Cryogenic heat transfer -- Two-phase pressure drop; 00-01 -- 99-00; Low temperature engineering -- Periodicals; Low temperature research -- Periodicals; 536.56
• DOI: 10.1016/j.cryogenics.2016.07.014
• Languages: English
• ISSNs: 0011-2275

Abstract

Highlights: A thermohydraulic code for flexible liquid helium transfer lines has been developed. The thermohydraulic code covers the heat leak and the two-phase pressure drop. The code has been validated with experimental data, resulting in deviations of less than 15%. Design charts for flexible liquid helium transfer lines were calculated based on the thermohydraulic code. Abstract: In part one of this publication experimental results for a single-channel transfer line used at liquid helium (LHe) decant stations are presented. The transfer of LHe into mobile dewars is an unavoidable process since the places of storage and usage are generally located apart from each other. The experimental results have shown that reasonable amounts of LHe evaporate due to heat leak and pressure drop. Thus, generated helium cold gas has to be collected and reliquefied, demanding a huge amount of electrical energy. Although this transfer process is common in cryogenic laboratories, no existing code could be found to model it. Therefore, a thermohydraulic model has been developed to model the LHe flow at operating conditions using published heat transfer and pressure drop correlations. This paper covers the basic equations used to calculate heat transfer and pressure drop, as well as the validation of the thermohydraulic code, and its application within the optimisation process. The final transfer line design features reduced heat leak and pressure drop values based on a combined measurement and modelling campaign in the range of 0.112 < p in < 0.148 MPa, 190 < G < 450 kg/(m 2 s), and 0.04 < x out < 0.12.