ATLAS meet Thermal Calculations of the Muon Barrel1 Brief history of thermal calculations for the Muon Barrel : Schnejinsk I Problem: program was designed for liquid not gaseous cooling. The effect of thermal expansion not included. Cooling medium was an incompressible liquid of the density of air  unreasonable temperature disributions

ATLAS meet Thermal Calculations of the Muon Barrel2 1999: Group of Daniel Gasser (CERN) New approach: commercial program used. Problem: Complexity of Barrel geometry with narrow passages for air between the chambers. Not enough grid cells to cover the structure AND have sufficient resolution in the passages Got program running with increased passages  good-looking, unrealistic results New concept: make passages partly-transparent for air Emma V. de Castelvi worked on it until end of 2001, then left CERN.

ATLAS meet Thermal Calculations of the Muon Barrel3 2002: Group of Daniel Gasser (CERN) New concept: Modify chamber geometry from flat to cylindrical. This makes computation easier and allows to introduce narrower. New programmer: Leonardo N. V. Goncalves 2003, january Result: better than previous approach, but still too large gaps between chambers

ATLAS meet Thermal Calculations of the Muon Barrel4 2004: new s/w with variable cell size –with 500 k cells of variable size the barrel geometry with it‘s narrow passages between chambers could be realisticly described –large demand of CPU power made usage of GRID necessary –work done by Anna Müller from ST, CERN

ATLAS meet Thermal Calculations of the Muon Barrel5 THERMAL ANALYSIS OF ATLAS MUON DETECTOR – 3 D Global Layout (1) 12 Diffusers at the bottom Extract grids at the top Extract grids at the bottom

ATLAS meet Thermal Calculations of the Muon Barrel6 Power consumption of MDT/RPC

ATLAS meet Thermal Calculations of the Muon Barrel7 Cell domaines for simulation of the Barrel

ATLAS meet Thermal Calculations of the Muon Barrel8 Thermal distribution ~ 32 o C ~ 18 o C

ATLAS meet Thermal Calculations of the Muon Barrel9 Velocity distribution ~ 0.5 m/s

ATLAS meet Thermal Calculations of the Muon Barrel10 See movie of thermal development in the Barrel prepared by Anna Müller !

ATLAS meet Thermal Calculations of the Muon Barrel11 Summary simulation works fine, though not all details of the barrel and surrounding equipment are included in simulation results most worrisome for operation of RPCs, which should operate below 25 deg C TC plans to install water-cooled radiators in upper part of the barrel regions of high air-velocity + turbulences may degrade laser based alignment