Passive flow direction biasing of cryogenic thermosiphon
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Solution Overview
Problem
Existing thermosiphon cooling devices for superconducting magnets in MRI systems do not guarantee counter-flow in the heat exchanger, leading to reduced heat transfer efficiency and making it difficult to control flow directions, especially when geometrical placement in a gravity field is not feasible.
Innovation Solution
Incorporating passive one-way valves in the primary and secondary coolant circuits to ensure counter-flow in the heat exchanger by allowing flow in specific directions and blocking opposite directions, ensuring efficient heat exchange and reliable startup of the thermosiphon cooling system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive thermosiphon flow is used in the secondary cooling circuit, then startup can be performed with only gas helium, but the flow direction in the heat exchanger cannot be controlled to guarantee counter-flow
Solution Approach 1:
The system uses passive one-way valves that automatically control flow direction based on pressure differentials during operation. The valves self-regulate to ensure counter-flow in the heat exchanger without requiring external control systems, maintaining the advantage of passive thermosiphon startup while adding flow direction control
Solution Approach 2:
The patent introduces one-way valves that change the flow parameters dynamically based on operating conditions. During startup, the system operates in passive thermosiphon mode with gas helium, and the valves automatically adjust to maintain proper flow directions as the system transitions to operational phases
2Reliability
If geometric placement is used to control flow direction in gravity field, then counter-flow can be achieved, but the system becomes complex and less adaptable when geometric placement is not feasible
Solution Approach 1:
The patent replaces the mechanical/geometric placement system with a valve-based flow control system. Instead of relying on gravitational field and geometric orientation to control flow directions, the system uses passive one-way valves that control flow based on pressure differentials, making the system adaptable to various geometric configurations
Solution Approach 2:
Rather than using gravity and geometry to drive flow in the desired direction, the patent inverts the approach by using valves to restrict flow in unwanted directions, thereby guiding flow in the desired counter-flow pattern through prohibition rather than promotion
3Productivity
If heat exchange efficiency is improved through counter-flow, then heat transfer performance increases, but the system requires precise flow direction control that is difficult to achieve
Solution Approach 1:
The passive one-way valves automatically maintain the flow directions necessary for counter-flow heat exchange. The valves self-regulate based on pressure differentials, ensuring that the primary and secondary coolant circuits flow in opposite directions through the heat exchanger, thereby maintaining high heat transfer efficiency without requiring external control
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
The solution provides improved and reliable startup of the thermosiphon cooling system, ensuring efficient heat exchange by guaranteeing counter-flow in the heat exchanger, even when geometrical placement is not feasible, and maintaining hermetically sealed primary and secondary cooling circuits using helium as the working fluid.
Implementation Method 1
A first passive one way valve is disposed on the first flow loop and is oriented to allow flow in an allowed direction of flow in the first flow loop and to block flow in an opposite blocked direction of flow in the first flow loop
Implementation Method 2
The combination of flow in the allowed direction of flow in the first flow loop and flow in the allowed direction of flow in the second flow loop produces counter-flow in the heat exchanger
Implementation Method 3
The approach has advantages over more conventional LHe immersion. The thermosiphon approach enables startup without a large supply of LHe
Implementation Method 4
promoting passive thermosiphon flow in the secondary cooling circuit
Implementation Method 5
As the primary coolant circuit cools the working gas helium, it transitions to a two-phase mixture of gas and liquid helium (LHe)
Data Source
AI summary
A cooling device (40) includes a heat exchanger (50), a first flow loop (52) connecting a cold sink (42, 44, 46) and the heat exchanger, and a second flow loop (54) connecting a hot sink (20) and the heat exchanger. A first passive one way valve (62) disposed on the first flow loop is oriented to allow flow in an allowed direction of flow (F1) and to block flow in the opposite direction. A second passive one way valve (64) disposed on the second flow loop is oriented to allow flow in an allowed direction of flow (F2) and to block flow in the opposite direction. The allowed directions of flow produce counter-flow in the heat exchanger. In an illustrative embodiment, the hot sink is comprises a cryogenic magnet coil (20) and the hot sink is a cold head (42, 44) and liquid helium tank (46).