Simulation on chill-down behavior and induced thermal stress of a cryogenic tank during LN2 filling

Abstract

In order to illustrate the relevance between the chill-down and the thermal stress characteristics of cryogenic tanks during filling, a unidirectional thermal-structural numerical method is introduced in this paper. Aiming at the filling process of a LN2 tank, the flow field, temperature distribution and the cooling behavior of the tank wall are calculated in detail through a two-dimensional CFD model. Based on the temperature data of CFD calculations, time-ordered static structural analyses of the thermal deformation and thermal stress of the tank wall were conducted by a finite element model. Results show that, the degree of the thermal deformation is positively related to the cooling degree of the tank. The thermal stress concentrated area does not depend on the distribution of the thermal deformation, but is consistent with the position of the liquid level where exists the remarkable temperature gradient. For the bottom filling process of the target tank, the thermal stress is most serious at the beginning filling stage and the maximum appears at the tank bottom. By comparing with the experimental data, this numerical method is verified to be a useful tool for the evaluation, design, and safe operation of cryogenic tanks.