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Coolant tube

Coolant tube description/claims

1. Field of the Invention

The invention concerns a coolant tube with a tube jacket.

2. Description of the Prior Art

For explosion or rupture protection it is known to make coolant tubes of metal. In such a known coolant tube, a cooling medium (for example a high-voltage insulation oil) is transported by means of a pump into a cooling circuit between a cooling unit and a heat-emitting apparatus, for example a high-power x-ray radiator.

Depending on the maximum heat quantity to be dissipated, the possible cooling capacity must be deigned correspondingly. High flow speeds of the cooling medium occur at maximum cooling capacity, which leads to a corresponding friction of the cooling medium on the inside of the tube jacket, causing the tube jacket to become electrostatically charged. This electrostatic charging can lead to a blow-out of the tube jacket and therefore to a leakage of the coolant tube. Often only a creeping coolant loss that is not promptly noticed occurs given a small leak.

If a decomposition in which gas is released occurs in the coolant during its operation time, this can lead to a saturation of the cooling medium. If the coolant also serves as insulation, the insulation properties of the coolant corresponding degrade due to the decomposition reactions.

An object of the present invention is to provide a coolant tube of the aforementioned type that ensures optimal cooling by the employed coolant during its entire operation time.

This object is achieved by a coolant tube according to the invention that has a tube jacket formed of a plastic (synthetic) material that has a high diffusion coefficient for gas and contains at least one electrically conductive additive.

In the present invention the term “plastic material” is not limited to a material that consists only of a single plastic. Rather, this term also encompass a plastic matrix composed of multiple different plastics or a compound material that does not necessarily have to consist exclusively of plastics, for example.

In the coolant tube according to the invention, gases that are released given a decomposition of the coolant can escape the coolant tube due to the possibility to diffuse through the tube jacket. A saturation of the cooling medium with gases (which cooling medium is directed in the coolant tube according to the invention) is thereby reliably prevented. The insulation properties of the cooling medium are thus not negatively affected.

In the inventive coolant tube, an electrically conductive connection is produced between the tube jacket (which contains at least one electrically conductive additive) and a connection armature (likewise electrically conductive) arranged on the outside of the coolant tube or tube jacket, this electrically conductive connection leads to a potential compensation or equilibration between the inside of the tube jacket (which electrostatically charges due to the friction of the cooling medium) and the connection armature.

A leak of the coolant tube with the unwanted after-effects is thereby reliably avoided.

The plastic material advantageously has a diffusion coefficient (diffusion constant) of at least approximately 3 m2 for the gas escaping from the cooling medium. Compared to a tube jacket made from metal (the difference coefficient of hydrogen in iron is 124·10−13 m2/s), the gases that are released given a decomposition of the coolant can therefore immediately leave the coolant tube after their formation. A saturation of the cooling medium (which cooling medium is directed in the coolant tube) with gas thus does not arise, so the insulation properties of the cooling medium are not negatively affected.

If the coolant tube is part of a cooling circuit in a high-power x-ray radiator, the generated x-ray radiation decomposes the high-voltage insulation oil in the cooling circuit and hydrogen (H2) thereby arises. This can lead to a saturation of the high-voltage insulation oil with hydrogen. If the cooling medium also serves for insulation with regard to the high voltage applied at the x-ray radiator, the insulation properties of the high-voltage insulation oil are then correspondingly worsened by the decomposition reactions.

A diffusion coefficient of approximately 14.7 m2/s has proven to be entirely sufficient for hydrogen gas (H2). A plastic material that exhibits a diffusion coefficient of approximately 14.7 m2/s is, for example, polytetrafluorethylene (PTFE), which is also known under the trade name Teflon®.

Depending on the geometric dimensions of the coolant tube and/or depending on the manufacturing method of the tube jacket, the following electrically conductive additives are suitable for an embedding in the plastic material, for example: graphite powder, metal powder, graphite particles and metal particles. Further suitable, electrically conductive additives are graphite fibers and metal fibers as well as electrically conductive wire cloth. In the framework of the invention the electrically conductive additives cited as examples can be introduced into the plastic material either alternatively or in an arbitrary combination. An adaptation of the tube jacket to the respective application case with regard to its electrical conductivity is thereby possible in a simple manner in the coolant tube according to the invention.

In the event that the plastic material is exposed to particularly high mechanical loads, according to an embodiment of the inventive coolant tube an intermediate layer can be at least partially arranged between the tube jacket and the protective jacket. If gas escape is anticipated, for a metallic protective jacket this intermediate layer must be a woven-type of layer (for example steel mesh) in order to not prevent the diffusion of the gas escaping from the cooling medium.

In particular given a protective jacket made from a metallic weave, for mechanical protection of the tube jacket it is advantageous to arrange an intermediate layer at least partially between the tube jacket and the protective jacket, which intermediate layer is fashioned as a plastic weave, for example.

• Provisional Patent
• Utility Patent

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