CFD modeling of sloshing-induced pressure drop inside LH 2 storage tanks used in maritime applications

Passive zero-boil-off storage of liquid hydrogen for long-time space missions

A numerical analysis study on the characteristics of evaporation in liquid hydrogen tank with vacuum layer according to changes in heat flux and vacuum pressure

Accurate evaluation of thermo-fluid dynamic characteristics in tanks is critically important for designing liquid hydrogen tanks for small-scale hydrogen liquefiers to minimize heat leakage into the liquid and ullage. Due to the high costs, most future liquid hydrogen storage tank designs will have to rely on predictive computational models for minimizing pressurization and heat leakage. Therefore, in this study, to improve the storage efficiency of a small-scale hydrogen liquefier, a three-dimensional CFD model that can predict the boil-off rate and the thermo-fluid characteristics due to heat penetration has been developed. The prediction performance and accuracy of the CFD model was validated based on comparisons between its results and previous experimental data, and a good agreement was obtained. To evaluate the insulation performance of polyurethane foam with three different insulation thicknesses, the pressure changes and thermo-fluid characteristics in a partially liquid hydrogen tank, subject to fixed ambient temperature and wind velocity, were investigated numerically. It was confirmed that the numerical simulation results well describe not only the temporal variations in the thermal gradient due to coupling between the buoyance and convection, but also the buoyancy-driven turbulent flow characteristics inside liquid hydrogen storage tanks with different insulation thicknesses. In the future, the numerical model developed in this study will be used for optimizing the insulation systems of storage tanks for small-scale hydrogen liquefiers, which is a cost-effective and highly efficient approach.

Investigation on the pressurized discharge performance from a liquid oxygen tank under different injected gas temperatures

Using the concept of superconducting suspension of the inner tank in an outer vessel, the authors have designed and constructed a prototype of a liquid-hydrogen storage tank for automotive application. In contrast to the earlier model with planar design of the bearing, they used a rotationally symmetric arrangement with the inner tank suspended over a central frame bar. The bearing consists of superconducting rings fixed to the central tube of the inner tank and a system of permanent magnets mounted on the frame bar. No additional cooling of the superconductors (YBaCuO rings prepared by a modified multi-seeding process and Bi-2212 rings prepared by the melt cast process) is required. For suspension of the tank in the warm state above Tc, they used newly developed actuators with main springs made of shape-memory alloy. When the tank is filled with liquid hydrogen, the actuators release the tank, thereby providing absolutely passive activation of the bearing.

The motion of the liquid-carrying ship under waves is simultaneously affected by the external wave moment and the sloshing moment of the internal tank, which makes the motion of the ship more complicated. In order to explore the influence of tank sloshing on the ship motion response, the motion of the ship model with tanks at different wavelengths were simulated based on the CFD software. This paper is based on the finite volume method (FVM) to solve the RANS (Reynolds averaged Navier-Stokes) equation for numerical simulation, and the VOF (volume of fluid) method was used to capture the free surface. Using the VOF method, it is necessary to ensure that the mesh at the free surface is sufficiently fine. Based on the above conditions, the pitching motion and rolling motion of the liquid carrier in the head sea condition and the transverse wave condition were simulated, respectively. The results showed that the sloshing of the tank has little influence on the pitching motion but has a greater influence on the rolling motion. When the liquid loading rates were 0, 0.8, 0.9, and 0.98, the pitch angle changes of the ship under different wavelengths were basically the same. However, when the liquid loading rates were 0, 0.4, and 0.8, the roll angle of the ship varied greatly under different wavelengths. By simulating the roll free decay motion of the liquid carrier (the loading rates were 0, 0.2, 0.4, 0.6, 0.8 and 0.98), it was found that the essence of the sloshing effect of the tank is to change the amplitude of the ship’s rolling motion by changing the natural frequency of the ship’s rolling motion. The closer the incident wave frequency is to the natural frequency of the roll of the liquid carrier, the greater the roll amplitude of the ship.

A numerical study of microtube geometry effect on flow boiling using the volume of fluid method

A numerical simulation of tube geometry effect on the performance of regenerators in Organic Rankine Cycle systems using the Volume of Fluid method

Influence of slosh baffles on thermodynamic performance in liquid hydrogen tank

Pressure build-up in a liquid hydrogen storage tank when subject to fire attack – a numerical study with validation

This paper presents an overview of the use of flow visualization in micro- and mini-channel geometries for the development of pressure drop and heat transfer models during condensation of refrigerants. Condensation flow mechanisms for round, square and rectangular tubes with hydraulic diameters in the range 1–5 mm for 0 < x < 1 and 150 kg/m2-s and 750 kg/m2-s were recorded using unique experimental techniques that permit flow visualization during the condensation process. The effect of channel shape and miniaturization on the flow regime transitions was documented. The flow mechanisms were categorized into four different flow regimes: intermittent flow, wavy flow, annular flow, and dispersed flow. These flow regimes were further subdivided into several flow patterns within each regime. It was observed that the intermittent and annular flow regimes become larger as the tube hydraulic diameter is decreased, at the expense of the wavy flow regime. These maps and transition lines can be used to predict the flow regime or pattern that will be established for a given mass flux, quality and tube geometry. These observed flow mechanisms, together with pressure drop measurements, are being used to develop experimentally validated models for pressure drop during condensation in each of these flow regimes for a variety of circular and noncircular channels with 0.4 < Dh < 5 mm. These flow regime-based models yield substantially better pressure drop predictions than the traditionally used correlations that are primarily based on air-water flows for large diameter tubes. Condensation heat transfer coefficients were also measured using a unique thermal amplification technique that simultaneously allows for accurate measurement of the low heat transfer rates over small increments of refrigerant quality and high heat transfer coefficients characteristic of microchannels. Models for these measured heat transfer coefficients are being developed using the documented flow mechanisms and the corresponding pressure drop models as the basis.

Condensation Flow Mechanisms in Microchannels: Basis for Pressure Drop and Heat Transfer Models

The failure of liquid hydrogen (LH2) tank thermal insulation can lead to excessive heating of the stored hydrogen, causing it to boil and triggering safety mechanisms such as a pressure relief valve or a burst disc to prevent catastrophic vessel failure. This study investigates the boil-off behavior inside LH2 tanks using lumped parameter modeling. A non-equilibrium storage tank equipped with a pressure relief valve or burst disc is modeled, accounting for convection and different boiling regimes, flash evaporation during pressure drop when rupture activated. The model is validated against NASA and BMW experimental data. Furthermore, the study analyzes the LH2 tank under various thermal scenarios, including normal operation, loss of vacuum due to air ingress or ice formation, and an engulfing fire scenario combined with vacuum failure. The findings provide critical insights and methodologies for the safety evaluation and robust design of cryogenic hydrogen tank.

A mathematical model for the pre-cooling process was established to solve the problems of the long pre-cooling time and uncertain parameters of cryogenic propellant tanks. The pre-cooling parameters of a 300 m3 liquid hydrogen tank at several cooling rates were calculated and analyzed. The results show that the liquid hydrogen flow required to pre-cool the gas in the tank, tank wall, accessories, and interlayer thermal insulation materials increases first and then decreases and that the liquid hydrogen flow needed to offset the heat leakage gradually increases with the temperature reduction. When the average cooling rate rose from 0.1 K/min to 1 K/min, the pre-cooling time was shortened from 2730 min to 273 min, and the consumption of liquid hydrogen decreased from 2115 kg to 2091 kg. Among the various heat loads, the inner tank wall and accessories consumed the most significant proportion of liquid hydrogen, accounting for 87.84% to 88.61%. The cooling capacity was derived from the liquid hydrogen’s evaporation and the cryogenic hydrogen gas’s heating process, of which the liquid hydrogen accounted for 23.00%. Considering the principle of safe operation, it is recommended that stepped pre-cooling in two or three stages based on the maximum cooling rate is conducted.

CFD investigation on thermodynamic characteristics in liquid hydrogen tank during successive varied-gravity conditions