Consideration of Baffle cooling scheme

1
Consideration of Baffle cooling scheme

• T. Sekiguchi
• KEK, IPNS

2
Introduction

• This document describes general considerations
  about cooling schemes.
• Baffle Collimator for 1st Horn
• A graphite cylinder fin 32mm and fout 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.
• g Cooling is required.
• For calculations, it is assumed that the heat
  generation is concentrated at the inner surface.

400mm
32mm
1700mm
3
Consideration of cooling scheme

• Cooled by Helium or water?

Water cooling Helium cooling
More efficient cooling g High heat transfer coefficient Reduce radioactive waste water
Radioactive waste water Open circuit is not preferable Temperature rise is very high with low Helium flow rate
Merits
Demerits
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Option 1 (He cooling)

• Heat load concentrates on inner part of Baffle
• g Cooling inner surface is efficient.
• Helium is transferred to inner cavity with 10mmf
  pipe.
• 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 mass flow rate (g/s) 1 2 10
THe_at_exit (ºC) 410 218 64
Reynolds number 560 1400 9240
Heat transfer coefficient (W/m2/K) 37.9 30.1 142.5
DT between He and surface (ºC) 309 389 82.2
Tmax at graphite (ºC) 719 607 146
5
Option 2 (He cooling)
He in
He out

• Closed circuit.
• Helium flow is divided into 6 paths.
• 6 holes at fhole200mm f Not 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
(Total) He mass flow rate (g/s) 1 2 10
THe_at_exit (ºC) 410 218 64
Reynolds number 590 1500 9650
Heat transfer coefficient (W/m2/K) 121.2 96.4 485.9
DT between He and surface (ºC) 51.5 64.7 12.8
Tmax at graphite (ºC) 466 286 80
6
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.

10mmf SUS pipe
Water flow rate (l/min) 1 2 10
Twater_at_exit (ºC) 27.9 26.4 25.3
Reynolds number 2490 4970 24900
Heat transfer coefficient (W/m2/K) 950 2250 10300
DT between water and surface (ºC) 7.9 3.3 0.7
Tmax at graphite (ºC) 40.0 33.9 30.2
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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.

8
Supplements
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Table 1 for calculation
Helium properties under 0.1MPa condition.
Temp (K) Density (kg/m3) Specific heat (kJ/kg/K) Viscosity coeff. (mPas) Heat conductivity (mW/m/K) Prandtlnumber
100 0.487 5.195 9.77 72.0 0.705
200 0.244 5.193 15.35 115.0 0.693
300 0.163 5.193 19.93 152.7 0.678
400 0.122 5.193 24.29 188.2 0.670
500 0.098 5.193 28.36 221.2 0.666
600 0.081 5.193 32.21 252.3 0.663
700 0.070 5.193 35.89 278.0 0.67
800 0.061 5.193 39.43 304.0 0.67
1000 0.049 5.193 46.16 354.0 0.68
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Table 2 for calculation
Properties of water.
Temp (K) Density (kg/m3) Specific heat (kJ/kg/K) Viscosty coeff. (mPas) Heat conductivity (mW/m/K) Prandtl number
273 999.8 4.217 1791.4 561.9 13.44
280 999.9 4.199 1435.4 576.0 10.46
290 998.9 4.184 1085.3 594.3 7.641
300 996.6 4.179 854.4 610.4 5.850
310 993.4 4.179 693.7 624.5 4.642
320 989.4 4.180 577.2 636.9 3.788
330 984.8 4.184 489.9 647.6 3.165
340 979.4 4.188 422.5 656.8 2.694
350 973.6 4.194 369.4 664.6 2.331
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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 _at_inner surface 440 ºC
Hole diameter 10mm
12
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 _at_inner surface 360 ºC
Hole diameter 10mm
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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 d10mm
Heat transfer coeff. 2490 W/m2/K
Temperature _at_ inner surface 33.7 ºC
14
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 d10mm
Heat transfer coeff. 2490 W/m2/K
Temperature _at_ inner surface 34.2 ºC