Cryogenic fluids density

When only a single phase is present, the system pressure depends on the temperature, the volume, and the quantity of material. Rather large pressures can be produced by completely vaporizing a cryogenic fluid in a closed chamber. For example, using the helium density data of Figure 6, we see that an unyielding container filled initially with liquid at 1 atm (p = 0.125 g/cm ) would experience a pressure of 100 atm at 27°K and about 1000 atm at 270°K if the container were initially half full of liquid, it would experience a pressure of about 50 atm at 27°K (p = 0.0625 g/cm ) and about 400 atm at 270°K. In practice, if the container remained intact, its volume would increase somewhat so that the final density and the pressure would be reduced. 

Table II. Liquid and Vapor Densities of Cryogenic Fluids at One...

VISCOSITIES AND DENSITIES OF CRYOGENIC FLUIDS IN THEIR SATURATED LIQUID STATE. M.S. THESIS. 

For illustration. Figure 1.2 plots the temperature and pressure ranges over which the four fluids exist as liquids between the saturation curve and triple line. Temperature/ pressure (T/P) plots are used throughout the text to illustrate how the LAD performs as a function of the thermodynamic state of the liquid. For comparison. Table 1.1 lists the four primary cryogenic fluids along with thermophysical properties at the NBP saturation conditions relevant in the current work, such as the saturation temperature, heat of vaporization hfg, liquid density pf, kinematic viscosity v, and surface tension j lv- Clearly, advanced systems are required to store, maintain, and transfer such cold liquids. 

Large liquid-rocket-powered missiles are usually tanked to a measured volume. In order to measure the weight tanked, the density must be known. However, the boiling of cryogenic fluids, such as liquid oxygen, causes difficulty in determining the density. 

Two-Phase Systems. The combination of low boiling point and low heat of vaporization increases the possibility that cryogenic fluids become boiling, two phase systems. The influence of this fact upon pumping, liquid density, and level determination are obvious. Any sensor adding energy to the system is in fact creating a vapor-liquid interface at the very point of measurement. 

H. M. Roder, ASRDI Oxygen Technology Survey, Volume V Density and Liquid Level Measurement Instrumentation for the Cryogenic Fluids Oxygen, Hydrogen and Nitrogen, NASA SP-3083, 1974. 

The term rollover is used generally to describe the uncontrolled, spontaneous, penetrative convective self-mixing of two layers of multi-component cryogenic liquids with initially different densities. The fluid dynamics of this mixing phenomenon is incorrectly described by the word rollover. However, the term is in wide use today and is used in this monograph. Rollover is only one of a number of evaporation instabilities with cryogenic liquids, and is accompanied by a massive increase of evaporation rate over a long period of time (Mode A), measured in hours, or short period of time (Mode B), measured in seconds or minutes. 

A second important factor is the difficulty of the experiment. Some measurements, such as liquid densities at ambient temperatures, provide accurate data easily, but in other cases experiments may be difficult or infeasible. Complications that would argue against experiments include high temperatures and/or pressures (or very low temperatures or pressures requiring cryogenic or vacuum equipment) chemicals that are unstable, corrosive, or toxic and chemicals that are not available in sufficient purity or quantity. Some properties, such as high-pressure phase equilibria and the thermal conductivity of polar fluids, are more difficult to measure accurately. A few laboratories do have capabilities for more difficult measurements, so the option of contracting with such a lab for measurements may be considered. 

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