Thermohydraulics of quenches and helium recovery in the LHC prototype magnet strings

Chorowski, M.; Lebrun, Philippe; Serio, L.; Weelderen, R. van

doi:10.1016/s0011-2275(98)00015-0

Cited by 18 publications

(9 citation statements)

References 8 publications

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“…Based on experimental data gathered from String 1 [1] and String 2 [2] the heat flux to the helium in the cold mass after a sector quench was estimated (Figure 2a). The heat flux will reach the highest value during the first second and it will rapidly go down to 3.7 MW.…”

Section: Helium Flow From Cold Mass To Header D After a Sector Quenchmentioning

confidence: 99%

Flow and thermo-mechanical analysis of the LHC sector helium relief system

Chorowski¹,

Fydrych²,

Riddone

2005

Proceedings of the Twentieth International Cryogenic Engineering Conference (ICEC20)

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A simultaneous resistive transition of a LHC magnet sector, which may occasionally occur, will cause rapid helium outflow from magnet cryostats to a special relief system composed of long pipes, buffer volumes and accessories. The paper presents some safety and operational aspects of this system. The results show helium dynamic property distributions along the pipes as well as FEM calculations of thermo-structural stresses in the pipe walls.Presented at the 20th International Cryogenic Engineering Conference (ICEC20) A simultaneous resistive transition of a LHC magnet sector, which may occasionally occur, will cause rapid helium outflow from magnet cryostats to a special relief system composed of long pipes, buffer volumes and accessories. The paper presents some safety and operational aspects of this system. The results show helium dynamic property distributions along the pipes as well as FEM calculations of thermo-structural stresses in the pipe walls.

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Section: Helium Flow From Cold Mass To Header D After a Sector Quenchmentioning

confidence: 99%

Flow and thermo-mechanical analysis of the LHC sector helium relief system

Chorowski¹,

Fydrych²,

Riddone

2005

Proceedings of the Twentieth International Cryogenic Engineering Conference (ICEC20)

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“…To identify the modelling elements for the simulation of the LHC String 2 we have followed the approach described in [12] and [13]. Each magnet has been modelled as two volumes, of which the first represents the helium in intimate contact with the superconducting coil, heated during a quench, while the second volume represents the rest of the helium contained in the cold mass, between the iron laminations, in the end-caps and in the internal pipings.…”

Section: Example Of Applicationmentioning

confidence: 99%

“…The total helium inventory in a cold mass is approximately 20 l/m [12]. We have taken for the 15-m long dipoles a total volume of 315 l, and for the short-straight sections 186 l. Of this volume, 3 % was assigned to the helium in proximity of the coil and 97 % to the rest of the cold mass.…”

Section: Example Of Applicationmentioning

confidence: 99%

Flower, a model for the analysis of hydraulic networks and processes

Bottura

Rosso²

2003

Cryogenics

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We have developed in the past years a model that describes hydraulic networks that are typical of the cryogenic interconnection of superconducting magnets. The original model, called Flower, was used mostly to provide consistent boundary conditions for the operation of a magnet. The main limitations were associated with the number and nature of modelling elements available, and to the maximum size of the model that could be solved. Here we present an improvement of the model largely relaxing the above limitations by the addition of new modelling elements, such as parallel flow heat exchangers, and by a significant improvement in the numerics of the solver, using sparse matrix storage and solution techniques. We finally show a typical application to the case of a magnet quench in the LHC string. AbstractWe have developed in the past years a model that describes hydraulic networks that are typical of the cryogenic interconnection of superconducting magnets. The original model, called Flower, was used mostly to provide consistent boundary conditions for the operation of a magnet. The main limitations were associated with the number and nature of modelling elements available, and to the maximum size of the model that could be solved. Here we present an improvement of the model largely relaxing the above limitations by the addition of new modelling elements, such as parallel flow heat exchangers, and by a significant improvement in the numerics of the solver, using sparse matrix storage and solution techniques. We finally show a typical application to the case of a magnet quench in the LHC string.

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“…As elaborated in [6] the quench process of an individual magnet can be divided into two main phases. In the first phase until about 300 ms after initiating the quench of D3, the temperature of its coils increases to about 100 K. Liquid helium in close contact with the coil is heated, quickly vapourizes and expands, thereby compressing the remaining bulk helium of D3 and the rest of the string to a peak value of about 8 bar.…”

Section: Measurementsmentioning

confidence: 99%

“…The time constant for the de-excitation is about 100 s for the dipole magnet circuit and about 45 s for each of the quadrupole magnet circuits. The evolution of the helium in the cold mass of the quenched magnet has been observed and then described with a mathematical model based on energy conservation [6]. The thermohydraulics of a magnet resistive transition is governed by two main processes: initially a fast adiabatic compression of the bulk of helium by the rapidly expanding portion of helium in the vicinity of the coil.…”

Section: Introductionmentioning

confidence: 99%

Modelling of helium-mediated quench propagation in the LHC prototype test string-1

et al. 2000

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The Large Hadron Collider (LHC) prototype test string-1, hereafter referred to as the string, is composed of three ten-meter long prototype dipole magnets and one six-meter long prototype quadrupole magnet. The magnets are immersed in a pressurized static bath of superfluid helium that is maintained at a pressure of about 1 bar and at a temperature of about 1.9 K. This helium bath constitutes one single hydraulic unit, extending along the 42.5 m of the string length. We have measured the triggering of quenches of the string magnets due to the quenching of a single dipole magnet located at the string's extremity; i.e. "quench propagation". Previously reported measurements enabled to establish that in this configuration the quench propagation is mediated by the helium and not by the inter-magnet busbar connections [1], [2]. We present a model of helium mediated quench propagation based on the qualitative conclusions of these two previous papers, and on additional information gained from a dedicated series of quench propagation measurements that were not previously reported. We will discuss the specific mechanisms and their main parameters involved at different time scales of the propagation process, and apply the model to make quantitative predictions. The Large Hadron Collider (LHC) prototype test string-1, hereafter referred to as the string, is composed of three ten-meter long prototype dipole magnets and one sixmeter long prototype quadrupole magnet. The magnets are immersed in a pressurized static bath of superfluid helium that is maintained at a pressure of about 1 bar and at a temperature of about 1.9 K. This helium bath constitutes one single hydraulic unit, extending along the 42.5 m of the string length. We have measured the triggering of quenches of the string magnets due to the quenching of a single dipole magnet located at the string's extremity; i.e. "quench propagation". Previously reported measurements enabled to establish that in this configuration the quench propagation is mediated by the helium and not by the inter-magnet busbar connections [1], [2]. We present a model of helium mediated quench propagation based on the qualitative conclusions of these two previous papers, and on additional information gained from a dedicated series of quench propagation measurements that were not previously reported. We will discuss the specific mechanisms and their main parameters involved at different time scales of the propagation process, and apply the model to make quantitative predictions.

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Thermohydraulics of quenches and helium recovery in the LHC prototype magnet strings

Cited by 18 publications

References 8 publications

Flow and thermo-mechanical analysis of the LHC sector helium relief system

Flow and thermo-mechanical analysis of the LHC sector helium relief system

Flower, a model for the analysis of hydraulic networks and processes

Modelling of helium-mediated quench propagation in the LHC prototype test string-1

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