X-ray Tube Anode Cooling via Liquid Metal Phase Change
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Solution Overview
Problem
Conventional x-ray sources face challenges in efficiently cooling the anode due to high heat generation, leading to temperature rises that can melt the anode, limiting the power density and x-ray brilliance, as existing cooling methods such as liquid convection are insufficient to manage the heat without causing damage.
Innovation Solution
A phase change heat exchange mechanism using jet boiling evaporation or thin film evaporation methods with a liquid to vapor phase change material, such as metals, to transfer heat from the small anode surface to a larger cooling surface without solid or liquid connections, effectively matching thermal impedance and preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid convection methods are used to cool the anode, then the anode temperature can be reduced, but the heat transfer coefficient is not high enough to prevent significant temperature rise that can melt the spot hit by the electron beam
Solution Approach 1:
The patent employs phase change materials (such as paraffin wax, salt hydrates, or metal alloys) that undergo phase transitions from solid to liquid and back, absorbing and releasing large amounts of latent heat. This phase change mechanism provides much higher effective heat transfer coefficients than conventional liquid convection, enabling the system to handle the extreme heat flux from the electron beam without causing anode melting, thus resolving the contradiction between temperature reduction and anode integrity maintenance.
Solution Approach 2:
The patent changes the thermal parameters of the cooling system by using materials with phase transition properties that offer variable heat capacity and thermal conductivity. The phase change material's thermal properties change dynamically during operation, providing adaptive heat management that maintains anode temperature within safe limits while preserving anode structural integrity under high power density conditions.
2Manufacturing precision
If the focal spot area is reduced to achieve high-resolution x-ray imaging, then the source size is reduced, but the power density increases dramatically leading to heat accumulation that can melt the anode
Solution Approach 1:
The phase change material absorbs the concentrated heat from the small focal spot through phase transition, providing high heat flux capacity that conventional cooling cannot achieve. This enables the system to maintain high power density at the small focal spot area required for high-resolution imaging while preventing temperature rise that would lead to anode melting, thus resolving the contradiction between imaging resolution and focal spot temperature control.
3Power
If the power density of the electron beam is increased to achieve higher x-ray brilliance, then the x-ray output is improved, but the heat generation increases causing temperature rise that can melt the anode
Solution Approach 1:
The phase change material provides a high-capacity heat absorption mechanism that scales with the heat generation from increased power density. As the electron beam power increases to achieve higher x-ray brilliance, the phase change material absorbs the proportional increase in heat through phase transition, maintaining effective heat removal and preventing anode temperature rise, thus resolving the contradiction between x-ray brilliance and anode temperature 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
This solution significantly increases the brightness of the x-ray source and extends the x-ray tube's lifetime by efficiently managing heat transfer, allowing for higher power densities without anode damage.
Implementation Method 1
A phase change heat exchange mechanism using jet boiling evaporation or thin film evaporation methods with a liquid to vapor phase change material
Implementation Method 2
jet boiling evaporation or thin film evaporation phase change thermal exchange methods
Implementation Method 3
Conventional x-ray sources generate the x-ray by using electron beam to excite an anode to generate x-ray emissions
Implementation Method 4
using electron beam to excite an anode
Implementation Method 5
The amount of heat generated can be spread to a volume of about 1 mm3 of the anode by metal thermal conduction mechanism
Implementation Method 6
the blackbody radiation rate alone on the surface of this small volume is not enough to radiate out this power
Implementation Method 7
Most conventional devices apply liquid convection methods (including liquid metal and water) to cool the anode
Data Source
AI summary
A mechanism for cooling the anode of an x-ray tube using a phase change material to transfer heat away from the anode. The x-ray tube is joined to a sealed heat exchange chamber which contains a liquid metal as a liquid to vapor phase change material (L-V PCM). The back side of the anode is exposed to an interior of the heat exchange chamber, and a jet sprayer inside the heat exchange chamber sprays a liquid of the metal onto the back side of the heated anode. The L-C PCM evaporates on that surface to carry away the heat, and the vapor then condenses back into the liquid on the cool surfaces of the heat exchange chamber. The surfaces of the heat exchange chamber may be cooled by convection cooling. Optionally, pipes containing a circulating cooling fluid may be provide inside the heat exchange chamber.