Hydrogen Dispensing Unit Pressure Relief via Block and Bleed Valves
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Solution Overview
Problem
Hydrogen dispensing units face pressure increases due to residual trapped hydrogen in transfer lines, which can exceed design limits, potentially causing equipment failures or misinterpretation by pressure transducers, and existing pressure relief valves are not reliable for frequent use.
Innovation Solution
A method involving a hydrogen dispensing unit that cools hydrogen before dispensing, measures pressure in conduits, and uses a combination of block and bleed valves to vent hydrogen when pressure exceeds a selected threshold, thereby managing pressure and preventing equipment damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If hydrogen is cooled in the heat exchanger prior to dispensing, then the hydrogen temperature is reduced for safe dispensing, but the residual trapped hydrogen in the transfer lines becomes excessively cold and its pressure drops below safe operating limits
Solution Approach 1:
The patent applies preliminary action by heating the residual trapped hydrogen in the transfer lines after dispensing to compensate for the excessive cooling effect. The controller activates the heater to raise the temperature of residual hydrogen before pressure measurement, ensuring accurate pressure readings and preventing false low-pressure conditions that would occur if the cold residual hydrogen were measured immediately after cooling.
2Stress or pressure
If pressure relief valves are used to relieve excessive pressure in residual hydrogen, then the pressure is reduced to safe levels, but the valves fail to completely reseal after relieving pressure
Solution Approach 1:
The patent replaces the mechanical pressure relief valve system with an active thermal management system. Instead of using passive mechanical relief valves that fail to seal, the system uses heaters controlled by a controller to actively manage the temperature and pressure of residual hydrogen, maintaining pressure within safe operating limits without compromising valve sealing integrity.
3Temperature
If the dispensing unit sits idle with cooled residual hydrogen in the transfer lines, then the hydrogen remains at low temperature, but the pressure increases beyond design pressure limits
Solution Approach 1:
The patent implements feedback control by continuously monitoring the pressure of residual hydrogen in the transfer lines with a pressure sensor and using a controller to activate heaters when pressure exceeds predetermined thresholds. This closed-loop feedback system dynamically adjusts heating to maintain pressure within safe operating limits, preventing over-pressurization during idle periods while preserving the cooling benefits during dispensing.
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 method effectively reduces pressure in transfer lines, preventing equipment failures and ensuring reliable operation by safely venting excess hydrogen, thus maintaining equipment within safe pressure limits.
Implementation Method 1
the hydrogen dispensing unit (1) comprising a heat exchanger (106) to cool the hydrogen prior to the hydrogen being dispensed into the receiving vessel (118 or 218)
Implementation Method 2
opening and subsequently closing the block valve (108 or 208) when the pressure of the first quantity of hydrogen equals or exceeds a selected pressure thereby removing a fraction of the first quantity of hydrogen from the first one or more conduits (130, 132, 232, 233)
Implementation Method 3
As the hydrogen dispension unit sits idle waiting to refuel another vehicle, the temperature of the residual trapped hydrogen will increase resulting in a pressure increase in the lines
Data Source
AI summary
Method of operating a hydrogen dispensing where pressure relief is provided through block and bleed valves. After dispensing hydrogen from a dispensing station where the hydrogen is cooled during dispensing, trapped hydrogen remains in the transfer lines. During the idle time between refueling vehicles, the temperature of the trapped hydrogen increases resulting in an increase in the pressure of the trapped hydrogen. Block and bleed valves operate to relieve the pressure in the transfer lines.