Mathematical modeling of thermal stratification in a double wall cryogenic propellant tank with different insulations using one-dimensional flow over vertical plate approximation

Abstract

The aerodynamic sidewall heating is an inevitable phenomenon happening in a cryogenic propellant tank during a space mission. The propellant tanks of the launch vehicle are designed as an integral part of the vehicle structure. It is designed so that it has to withstand the internal fluid pressure and support the vehicle's static and dynamic launch loads. The propellant state inside the propellant tank will be at their boiling temperature or subcooled condition so that chances of formation of stratification and self-pressurization are higher with minimal heat infiltration itself. The propellant condition varies due to stratification, and it is essential to keep the state of propellant in a predefined state for the successful operation of the cryogenic engine. This paper discusses about the mathematical modeling of the thermal stratification phenomenon in a cryogenic propellant tank. A 1-D computer program is developed based on the available correlation of natural convection flow over a vertical flat plate to predict a double-walled cylindrical cryogenic storage tank's stratification parameters. The model can predict stratification at various types of insulation such as foam, vacuum, MLI, and different cryogens; hydrogen, nitrogen, and oxygen. The importance of gravity condition on the evolution of stratification is studied using the model. Different gravity conditions ranging from 10−4 go to 10−1 go on stratification evolution are carried out. Under 10−1 go, the time required for reaching the stratified layer to tank bottom in a cylindrical tank is obtained as 1347 s. As the gravity value decreases further from 10−2 go to 10−4 go, the time required increases 1.59 times, 2.99 times, and 8.09 times.