Cryogenic Liquid Density Probe Using Saturation Pressure
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Solution Overview
Problem
Current technologies for measuring the density of cryogenic liquids face challenges due to low operating temperatures, non-linearity, calibration difficulties, and electrical safety concerns, especially for flammable liquids like hydrogen.
Innovation Solution
A probe assembly with a manifold and elongated bulb, connected to a vacuum jacket pipe, uses a pressure transmitter to detect the saturation pressure of the liquid, allowing for accurate density calculation through polynomial equations and lookup tables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RTDs are used for measuring density of cryogenic liquids, then density measurement is possible, but operational issues occur at liquid hydrogen temperatures
Solution Approach 1:
The patent replaces electrical measurement systems (RTDs) with a mechanical/physical system based on saturation pressure measurement. The elongated bulb contains liquid hydrogen that evaporates to create vapor pressure, which is measured by a pressure transmitter. This substitution eliminates electrical components from direct contact with cryogenic liquid hydrogen, resolving the operational reliability issue while maintaining measurement capability through the relationship between saturation pressure and density.
Solution Approach 2:
The patent changes the measurement parameter from temperature-based (RTD) to pressure-based (saturation pressure). By measuring the saturation pressure of liquid hydrogen vapor in the elongated bulb and using polynomial equations to convert this pressure to density, the system achieves reliable cryogenic measurement without the operational issues of temperature-based electrical sensors.
2Measurement precision
If Cryogenic Platinum probes are used for flowing liquid density measurement, then density measurement is possible, but they are not linear at hydrogen temperatures and require calibration
Solution Approach 1:
The patent replaces platinum resistance probes with a saturation pressure measurement system. The elongated bulb allows liquid hydrogen to evaporate and establish saturation pressure, which is directly related to temperature and density through well-defined thermodynamic relationships. This eliminates the non-linearity and calibration issues of platinum probes by using a system where the measurement parameter (saturation pressure) has a more direct and predictable relationship with density.
Solution Approach 2:
The elongated bulb acts as a self-regulating system where liquid hydrogen automatically evaporates to maintain saturation conditions. The system self-adjusts to the ambient temperature and pressure conditions, providing a stable measurement reference that does not require external calibration, unlike platinum probes that exhibit non-linear behavior at hydrogen temperatures.
3Adaptability or versatility
If electrical components are used for flowing liquid density measurement, then measurement functionality is achieved, but electrical safety issues arise for flammable liquids
Solution Approach 1:
The patent extracts electrical components from the cryogenic liquid environment. The pressure transmitter is positioned outside the liquid hydrogen flow path, measuring pressure through the wall of the elongated bulb or via a connection that does not require electrical components to be in direct contact with the flammable liquid. This separation eliminates the electrical safety hazard while preserving measurement functionality through the saturation pressure-density relationship.
Solution Approach 2:
The elongated bulb acts as an intermediary between the cryogenic liquid hydrogen and the measurement system. It contains the liquid hydrogen and allows saturation pressure to be transmitted to the pressure transmitter without requiring electrical components to contact the liquid. This intermediary structure enables measurement functionality while eliminating the harmful electrical safety factor.
4Measurement precision
If diode technologies are used for density measurement, then very accurate measurement is achieved, but packaging challenges occur
Solution Approach 1:
The patent replaces diode technology with a saturation pressure measurement system using an elongated bulb. This substitution achieves accurate density measurement through thermodynamic relationships while avoiding the packaging challenges of diode technologies. The elongated bulb design is mechanically simple and can be easily integrated into existing liquid hydrogen flow paths without complex packaging requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Provides robust and accurate density measurement of cryogenic liquids, including hydrogen, while addressing electrical safety and calibration issues, enabling precise flow rate determination.
Implementation Method 1
the chamber containing a pressurized vapor... detecting a pressure of the pressurized vapor after the bulb is placed within the passage
Implementation Method 2
the vapor and the liquid are the same fluid... detecting a pressure within the chamber
Implementation Method 3
a first annular space is formed, where the annular space is at least partially evacuated of air
Data Source
AI summary
A probe assembly for determining a saturation pressure of a liquid includes a manifold having at internal passage and an elongated bulb defining a chamber and having a distal tip portion and a proximal portion. The bulb is secured to the manifold at the proximal end portion with the chamber in fluid communication with the internal passage. A charging port is selectively in fluid communication with the internal passage of the manifold. A pressure transmitter is configured to detect a pressure within the chamber of the elongated bulb.