Device and system for monitoring the conditions of a thermal fluid, and method for said monitoring

A device for monitoring the conditions of a thermal fluid, comprising:

• an inner tube with a length L1 and an outer diameter D1, and
• an outer tube with a length L2, wherein the outer tube comprises a central portion with an inner diameter D2 and ends the inner diameter D1 of which gradually decreases towards the narrowest part thereof having a diameter De, wherein the inner diameter De is smaller than the inner diameter D2,
• wherein the inner tube is arranged coaxially inside the outer tube, the length L1 of the inner tube is greater than the length L2 of the outer tube, and the inner diameter De substantially coincides with the outer diameter D1, such that a substantially airtight chamber is formed between the outer tube and the inner tube,
• wherein the device comprises connection means located on the outside of the outer tube, the connection means being configured for establishing a fluidic communication with the substantially airtight chamber and for coupling a vacuum pump,
• wherein the inner tube is configured for transporting the thermal fluid, and the outer tube is made of metal, and
• wherein the outer tube has a hydrogen permeability coefficient less than the permeability coefficient of the inner tube.