Cryogenic Pump Pressure Control via Pre-cooled Gas Injection
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Solution Overview
Problem
Cryogenic pumps, particularly those handling low-density fluids like liquid hydrogen, face challenges in achieving the required suction pressure due to high inlet head losses, leading to inefficiencies and increased compression costs, with existing solutions like supercooling being limited by thermosiphon systems that cause hydrogen to heat up, reducing pumping time.
Innovation Solution
A pressure control system that selectively maintains the tank pressure at or above the saturation pressure of the cryogenic fluid, using a combination of reinjecting cooled fluid from the pump and injecting cooled gas from a high-pressure source, managed by sensors and computation logic to optimize the pressure and prevent cavitation, allowing continuous operation and maximizing hydrogen density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the tank is pressurized using thermosiphon or high-pressure hydrogen from cylinders, then the suction pressure requirement is met, but the liquid hydrogen heats up, reducing the available level of supercooling and pumping time
Solution Approach 1:
The invention introduces a pre-cooling system that cools the hydrogen before it enters the tank. A heat exchanger pre-cools the hydrogen from ambient temperature to a lower temperature (e.g., -40°C to -100°C), and this pre-cooled hydrogen is then injected into the tank to maintain low temperature and extend pumping time while still meeting suction pressure requirements.
2Duration of action of stationary object
If the pump operates with supercooled liquid hydrogen, then the suction pressure requirement is met and pumping time is extended, but the system complexity increases due to additional pressure control mechanisms
Solution Approach 1:
The invention implements a self-regulating pressure control system where sensors continuously monitor the pressure in the tank and suction line, and automatically activate the pre-cooling system or pressure injection system when pressure drops below the required threshold (Psat + NPSH). This automated feedback control maintains optimal conditions without requiring constant manual intervention, extending pumping time while managing system complexity through intelligent automation.
3Stress or pressure
If ambient temperature hydrogen is injected into the tank to maintain pressure, then the suction pressure is maintained, but the liquid hydrogen temperature increases, reducing density and pumping efficiency
Solution Approach 1:
The invention fundamentally changes the temperature parameter of the hydrogen being injected into the tank. Instead of using ambient temperature hydrogen (20-25°C), the system pre-cools the hydrogen to -40°C to -100°C before injection. This parameter change ensures that when hydrogen is added to maintain tank pressure, the liquid hydrogen temperature and density are preserved, maintaining pumping efficiency while still achieving the required suction pressure.
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 solution enables continuous operation of cryogenic hydrogen pumps by maintaining optimal pressure, reducing cavitation, and extending the pumping time by maintaining hydrogen in a supercooled state, thus maximizing output and efficiency while minimizing energy costs.
Implementation Method 1
a pipe connecting a high-pressure gas source to the tank via a cooling member that cools the gas
Implementation Method 2
the cooling member situated in the pipe connecting the high-pressure gas source to the tank comprises a heat exchanger able selectively to place the gas from the high-pressure gas source in a heat-exchange relationship with the cryogenic fluid pumped from the tank
Implementation Method 3
the pipe connecting a high-pressure outlet of the pump to the tank comprises an expansion valve for reinjecting cold gas into the tank
Data Source
AI summary
The invention relates to a device for pumping a cryogenic fluid, consisting of a tank for storing a cryogenic fluid containing cryogenic liquid, a cryogenic pump having an inlet pressure loss, and a suction line connecting the tank to the pump, said pumping device including a system for controlling the pressure in the tank for selectively maintaining said pressure at least equal to the saturation pressure of the stored cryogenic fluid plus the inlet pressure loss of the cryogenic pump and optionally plus the value of the pressure losses owing to the pipes forming the suction line connecting the tank to the pump. The invention is characterized in that the pressure-control system includes a duct connecting a high-pressure outlet of the pump to the tank for selectively returning the pumped cold fluid to the tank, said duct including an expansion valve for returning cold gas to the tank.