## Thermal Analysis for ATLAS Detector

#2134

Calculations of Thermal Regime of ATLAS Facility

**Tech Area / Field**

- PHY-NGD/Fluid Mechanics and Gas Dynamics/Physics

**Status****8** Project completed

**Registration date****27.03.2001**

**Completion date****20.09.2004**

**Senior Project Manager**

Malakhov Yu I

**Leading Institute**

State Unitary Enterprise STRELA, Russia, Chelyabinsk reg., Snezhinsk

**Collaborators**

- Lawrence Livermore National Laboratory, USA, CA, Livermore

**Project summary**

The objective of the project is to calculate free-convection heat exchange in the ATLAS facility cavern taking into account the latest data received from CERN on the heat loads (heat release in tile-calorimeter, on the surface of the muon chambers, in the electronic racks and heat discharge in the toroidal cryostats). The project will also include calculations to study how different parameters influence heat exchange (heat exchange inside the muon chambers; how blocking of the air circulation between the inner chambers influences heat exchange with free convection). Special attention will be given to the temperature study in the cross-section of the detector (2D geometry) located at 2 meters from the point where two beams collide.

It is supposed to run basic calculations using commercial code (CFX). The calculation results will be compared to those obtained with other codes: Star CD (calculations will be run by CERN experts); SINARA-2D code developed at RFNC-VNIITF [2] and the codes implementing the method of heat balance [3].

Thermal calculations performed under the project will facilitate better understanding of the thermal mode of ATLAS facility and help generate practical recommendations for manufacture and assembly of the facility equipment (first of all, the muon chambers).

SINАRА-2D code was developed to calculate some emergency processes in nuclear reactors. The code models the flow of multi-component compressible and almost incompressible medium including strength and elastic-plastic properties, linear and non-linear heat conduction, etc. SINARA-2D code employs implicit finite-difference schemes to solve differential equations describing physical processes. Numerical algorithms for solving heat conduction and gas dynamic equations are based on ROMB technique developed at RFNC-VNIITF for the large deformation problems [4-8].

Since SINARA-2D was initially developed to solve the problems of another class, it is supposed to modify its algorithms and modules in the interests of convection calculations. For this purpose it is supposed to benefit from the expertise of RFNC-VNIITF’s experts in the sophisticated 2D calculations and development of algorithms for solving the equations of heat conduction and hydrodynamics. To solve effectively the problems of convection heat and mass transfer, it is necessary to improve the preciseness of the scheme taking into account the convection flows of mass, momentum and energy at the grid movement with respect to the medium. Some efforts will be needed to adapt difference scheme to model almost incompressible medium in convection problems. Radiation heat exchange will be included if necessary.

*Reference:*

1. Atlas Muon Spectrometer Technical Design Report, CERN/LHCC 97-22, 5 June 1997.

2. User manual for calculation of the differential equations. Russian Federal Nuclear Center VNIITF, 1987.

3. Gadzhiev A.D., Gadzhieva V.V., Lebedev S.N.etc. The SINARA software package for mathematical simulation of dynamics of emergency processes in nuclear power installations on fast neutron reactor. The pre-print of Russian Federal Nuclear Center VNIITF, N 130, 1998.

4. Gadzhiev A.D., Pisarev V.N. The implicit finite - difference method ROMB for numerical solution of equations of gas dynamics with heat conduction. The Journal of Computational mathematics and mathematical physics, 1979, v.19, № 5, p.1288-1303.

5. Gadzhiev A.D., Pisarev V.N., Shestakov А.А. The method for numerical solution of two-dimensional problems of heat conductivity on the non-orthogonal grids. The Journal of Computational mathematics and mathematical physics, 1982, v.22, № 2, p. 339-347.

6. Pisarev V.N. "ROMB" scheme parametrical family for two-dimensional equation of heat conductivity. VANT, 1992, 3, p. 42-48.

7. Gadzhiev A.D., Lebedev S.N. The implicit finite-difference methods “RID” for the numerical solution of gas dynamic equations. VANT, s. Methods and Codes of the numerical solution of the problems of the mathematical physics. 1987, 1, p. 49-52.

8. Gadzhiev A.D, Kuzmin S.Yu, Lebedev S.N., Pisarev V.N. The implicit finite - difference method ROMB for numerical solution of two-dimensional equations of gas dynamics on arbitrary Eulerian-Lagrangian grids. The pre-print of Russian Federal Nuclear Center VNIITF, N 94, 1996.

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