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Consideration of Baffle cooling scheme

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## Consideration of Baffle cooling scheme

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**Consideration of Baffle cooling scheme**T. Sekiguchi KEK, IPNS**Introduction**• This document describes general considerations about cooling schemes. • Baffle = Collimator for 1st Horn • A graphite cylinder:fin= 32mm andfout = 400mm length = 1.7m • Heat load: 4.2 kJ/pulse (1.2 kW) due to beam halo and ~1kW from back-scattered pions. g~2kW heat load is expected. gCooling is required. • For calculations, it is assumed that the heat generation is concentrated at the inner surface. 400mm 32mm 1700mm**Consideration of cooling scheme**Cooled by Helium or water? Merits Demerits**Helium flow**10mmfpipe Option #1 (He cooling) • Heat load concentrates on inner part of Baffle gCooling inner surface is efficient. • Helium is transferred to inner cavity with10mmfpipe. • Open circuit • Hand calculation is performed. • Helium initial temperature = 25 ºC • Very high temperature gas blows toward the beam window and the target! g Closed circuit is preferable.**He in**He out Option #2 (He cooling) • Closed circuit. • Helium flow is divided into 6 paths. • 6 holes atfhole=200mm fNot optimized. • 2kW heat flow into 6 holes. g heat flow for each hole = 333W. • Helium temperature rise is reduced since only 600W heat is cooled. • Calculation with realistic model is needed. 10mmf 200mm**Water flow**Option #3 (Water cooling) • Cooling outer surface. • 10 pipes attached on outer surface f Not optimized • 2kW heat flow into 10 pipes. g Heat flow for each pipe = 200W • Heat transfer coeff. is ~ 950W/m2/K with even 1l/min water flow. • Calculations with realistic model is needed. • To reduce the amount of radioactive waste water, the number of pipes and the pipe diameter should be reduced. 10mmfSUS pipe**Summary**• Helium and water cooling are considered. • Calculations with some heat flow assumptions are performed. • In the case of He cooling, closed circuit is preferable since high temperature gas blows the beam window. • We need FEM calculations with • helium or water flows and • expected thermal load distribution. • Cooling scheme should be optimized in the cases of the options #2 and #3.**Table #1 for calculation**Helium properties under 0.1MPa condition.**Table #2 for calculation**Properties of water.**Simple simulations by ANSYS**• Rotational symmetry model of the option #2. • Helium flow ~1g/s (0.167g/s per hole), temperature = 410 ºC Heat conductivity around 400 ºC ~80 W/m/K (const.) adiabatic Heat flow at inner surface ~2kW Heat transfer coeff. ~ 121W/m2/K Temperature @inner surface ~440 ºC Hole diameter =10mm**Simple simulations by ANSYS**• Rotational symmetry model of the option #2. • Helium flow ~1g/s (0.167g/s per hole), temperature = 410 ºC Heat conductivity around 400 ºC ~80 W/m/K (const.) Natural convection ~10W/m2/K Heat flow at inner surface ~2kW Atmospheric temp. ~60 ºC Heat transfer coeff. ~ 121W/m2/K Temperature @inner surface ~360 ºC Hole diameter =10mm**Simple simulations by ANSYS**• Rotational symmetry model of the option #3. • Water flow ~1l/min (16.7g/s), temperature = 27.9 ºC Heat conductivity around 30 ºC ~116 W/m/K (const.) adiabatic Heat flow at inner surface ~2kW Water pipe d=10mm Heat transfer coeff. ~ 2490 W/m2/K Temperature @ inner surface ~33.7 ºC**Simple simulations by ANSYS**• Rotational symmetry model of the option #3. • Water flow ~1l/min (16.7g/s), temperature = 27.9 ºC Atmospheric temp ~60 ºC Heat conductivity around 30 ºC ~116 W/m/K (const.) Natural convection ~10W/m2/K Heat flow at inner surface ~2kW Water pipe d=10mm Heat transfer coeff. ~ 2490 W/m2/K Temperature @ inner surface ~34.2 ºC