Investigation of the process of cooling cryogenic pipelines with liquid hydrogen to optimize firing tests of rocket engines

Purpose. Development of a mathematical model that adequately describes the non-stationary process of cooling long cryogenic pipelines with liquid hydrogen and makes it possible to determine optimal operating parameters that ensure minimal refrigerant consumption in preparation for firing tests of liquid rocket engines. Methods. A vacuum-insulated pipe made of cryogenic steel with a total length of 272.5 m, with a bore diameter of 96 mm and a wall thickness of 2 mm was used as the modeling object. The total weight of the shut-off equipment located on the main line is 246 kg. Liquid supercooled hydrogen with an inlet temperature of 19 K is supplied to the pipeline under an excess pressure of 0.2 MPa. The ambient temperature is 293 K. Results. In this paper, we propose a model for cooling long insulated pipelines when liquid water flows through them, which makes it possible to determine the flow parameters at various points in time and estimate the time when the main line enters operating mode. Based on the proposed model, an automated algorithm was developed for calculating the cooling process of a long pipeline with cryogenic components, which makes it possible to obtain data for constructing the temperature fields of the pipeline walls and the flow of transported cryoproducts at various time points, as well as to determine the time when the main line enters operation and the moment of the onset of a stationary single-phase flow. The results of the calculation are in good agreement with the experimental data. Conclusion. Using this model under various initial and boundary conditions, it is possible to work out the optimal mode of real physical processes and achieve minimal losses of cryogenic components with minimal time spent in preparing bench systems for fire tests, as one of the stages of the production cycle of liquid propellants in mechanical engineering.