Systems and methods for re-condensation of boil-off gas
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Solution Overview
Problem
Cryogenic fluid tanks, such as those on aircraft, face pressure increases due to boil-off gas evaporation, leading to undesirable venting of combustible gases into the atmosphere, which is inefficient and harmful.
Innovation Solution
A system that utilizes a heat exchanger to condense boil-off gas from a first cryogenic fluid using a second cryogenic fluid at a lower temperature, such as liquid nitrogen, and returns the condensed gas to the tank, while using the exhaust gas to purge or inert aircraft components, thereby reducing emissions and tank pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If boil-off gas is vented directly to the atmosphere, then tank pressure is reduced, but harmful emissions increase and fuel is lost
Solution Approach 1:
The patent converts the harmful boil-off gas that would otherwise be vented into a useful resource by condensing it back to liquid form and returning it to the cryogenic tank, thereby eliminating harmful emissions and recovering fuel that would have been lost
Solution Approach 2:
Instead of discarding the boil-off gas to the atmosphere, the system recovers it by condensing the gas back to liquid form and returning it to the cryogenic tank, thus preventing both harmful emissions and fuel loss
2Loss of substance
If a heat exchanger system is added to condense boil-off gas, then emissions are reduced and fuel is conserved, but device complexity increases
Solution Approach 1:
The heat exchanger system serves multiple functions: it condenses boil-off gas to prevent emissions, recovers fuel by returning condensed liquid to the tank, and can be integrated with existing cryogenic tank systems, thereby achieving fuel conservation without proportionally increasing complexity
Solution Approach 2:
The heat exchanger acts as an intermediary device that facilitates the phase change of boil-off gas from gas to liquid form, enabling the recovery and return of fuel to the tank while maintaining a relatively simple system architecture
3Weight of moving object
If cryogenic tank volume is reduced to decrease weight, then aircraft weight is reduced, but boil-off gas management becomes more challenging
Solution Approach 1:
The condensed boil-off gas is returned to the cryogenic tank itself, allowing the tank to serve its own gas management needs and eliminating the requirement for separate storage vessels or complex external gas management systems
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 reduces harmful emissions, conserves fuel, and allows for lighter, more compact cryogenic tank systems with minimal external power requirements, effectively managing boil-off gas and maintaining tank pressure.
Implementation Method 1
the heat exchanger configured to transfer a flow of heat from the boil-off gas stream to a liquid stream of a second cryogenic fluid
Implementation Method 2
condense at least a portion of the boil-off gas stream to a liquid
Implementation Method 3
The second cryogenic fluid may be evaporated as the second cryogenic fluid passes through the second passage
Data Source
Figure 1
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Figure 5
AI summary
A system in one embodiment includes a heat exchanger, a detection unit, and a controller. The heat exchanger includes a first passage and a second passage configured for exchange of heat therebetween. The first passage is configured to receive a boil-off gas stream of a first cryogenic fluid. The second passage is configured to receive a liquid stream of a second cryogenic fluid. The detection unit is configured to detect a characteristic of the boil-off gas stream. The controller is configured to, responsive to information acquired from the detection unit corresponding to the characteristic, control the flow of the second cryogenic fluid to provide sufficient exchange of heat from the boil-off gas stream via the heat exchanger to condense at least a portion of the boil-off gas stream. A liquid stream of the first cryogenic fluid is output from the first passage and returned to a first tank.