Numerical modeling of no vent filling of a cryogenic tank with thermodynamic vent system augmented injector

Abstract

This paper describes a computational procedure to simulate the chilldown and No Vent Filling of a cryogenic tank with a Thermodynamic Vent System (TVS) assisted injector. During No Vent Filling with a TVS augmented injector, the cryogenic liquid coming from a supply tank is divided into two streams prior to entering the target tank; a small portion of the liquid is allowed to pass through a Joule-Thomson valve to produce a mixture of cold liquid and vapor that is used to cool the second stream that carries the bulk of the incoming fluid before it is injected into the tank. The cold stream is also used to cool the surface of the injector, further helping to reduce the tank pressure before it exits to a vacuum. The Generalized Fluid System Simulation Program (GFSSP), a general-purpose flow network code, has been used to simulate the chill and fill process and compare with the test data. The numerical model accounts for a) different regimes of pool boiling heat transfer that occur during tank chilldown, b) condensation of vapor around spray droplets, at the interface of the cooled injector and ullage, and at the liquid–vapor interface, and c) compression of ullage vapor by the rising liquid level. The observed discrepancy between test and predictions for tank pressure is within 20% and tank filling time is within 4%.