Cryogenic Hydrogen Tank Withdrawal Control Near the Two-Phase Boundary
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Solution Overview
Problem
Existing cryogenic pressure tanks in vehicles face challenges such as pressure buildup due to heat input during idle periods, leading to hydrogen liquefaction and inaccurate measurement of remaining hydrogen, which can result in insufficient supply to consumers and mechanical stress on the tank.
Innovation Solution
A method for controlling hydrogen withdrawal from cryogenic pressure tanks involving two phases: an adiabatic phase to reduce pressure and an active heat input phase to maintain a suitable thermodynamic state, with a switchover pressure level ensuring accurate measurement and preventing liquefaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If hydrogen is withdrawn rapidly from a nearly full cryogenic pressure tank to reduce pressure quickly, then the buffer before maximum permissible pressure is increased, but the thermodynamic state of stored hydrogen approaches or reaches the two-phase boundary causing hydrogen to transition into liquid phase and reducing availability as gaseous hydrogen
Solution Approach 1:
The patent applies parameter changes by monitoring temperature and pressure parameters to detect when the two-phase boundary is approached. When this threshold is detected, the control system adjusts the withdrawal rate or introduces heat to maintain hydrogen in the gaseous phase, ensuring reliable hydrogen availability while still achieving sufficient pressure reduction for long idle periods.
Solution Approach 2:
The patent implements feedback control by continuously monitoring temperature and pressure parameters during hydrogen withdrawal. The control system uses this feedback to dynamically adjust the withdrawal rate or apply heat input to prevent hydrogen from transitioning to liquid phase, thereby maintaining reliability while enabling extended idle times.
2Duration of action of moving object
If hydrogen is withdrawn rapidly to reduce pressure quickly, then the distance to maximum permissible pressure is increased, but temperature measurement accuracy becomes insufficient near the two-phase boundary making it impossible to determine remaining tank contents
Solution Approach 1:
The patent introduces temperature and pressure sensors as intermediaries to monitor the thermodynamic state of hydrogen during withdrawal. These sensors provide critical information about proximity to the two-phase boundary, enabling the control system to adjust operations to maintain accurate measurement conditions and determine remaining tank contents reliably.
Solution Approach 2:
The system uses feedback from temperature and pressure measurements to detect when the two-phase boundary is approached. This feedback enables the control system to adjust the withdrawal rate or apply heat to maintain conditions where temperature measurement remains accurate, thereby preserving the ability to determine remaining hydrogen contents.
3Measurement precision
If conventional temperature measurement methods are used with mounting probes or cables, then temperature can be measured on the tank wall, but thermal bridges are created that distort the measurement by promoting heat transfer to the stored hydrogen
Solution Approach 1:
The patent extracts the temperature measurement function from the traditional probe/cable mounting approach that creates thermal bridges. Instead, the system uses non-intrusive temperature sensing methods that measure temperature without creating thermal pathways into the hydrogen, thereby eliminating the thermal bridge effect while maintaining measurement precision.
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
This approach ensures reliable measurement of remaining hydrogen, reduces mechanical stress, and maintains pressure within safe limits, preventing unexpected depletion and enhancing the efficiency and reliability of hydrogen supply.
Implementation Method 1
controlling the hydrogen withdrawal from the cryogenic pressure tank in a first phase such that the withdrawal is essentially adiabatic
Implementation Method 2
controlling the hydrogen withdrawal from the cryogenic pressure tank in a second phase such that the withdrawal occurs with the active input of heat into the hydrogen stored in the cryogenic pressure tank
Data Source
Figure 1
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AI summary
A method (200) for controlling the withdrawal of cryogenic hydrogen from a cryogenic pressure tank (16) is provided. The method (200) comprises controlling (202) the withdrawal of the hydrogen from the cryogenic pressure tank (18) in a first phase (402) such that the withdrawal is essentially adiabatic, and controlling (204) the withdrawal of the hydrogen from the cryogenic pressure tank (18) in a second phase (406) such that the withdrawal takes place with the active input of heat into the hydrogen stored in the cryogenic pressure tank (18). The method (200) further comprises determining (206) a switching pressure level (404) which depends on a minimum measurement accuracy to be maintained for a quantity measurement of the hydrogen stored in the cryogenic pressure tank (18), and setting (208) the switching pressure level (404) as a threshold of the control for a transition from the first phase (402) to the second phase (406).