January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Undulator Hall Power Dissipation

What is it and where does the heat go?

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Contents

• Air Flow• Average heating• Localized heating

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Air Flow

• From West to East only– air is recirculated and brought back through a large

duct in the Undulator Hall to the West end– same direction as beam

• Constant flow rate 20,000 cfm• Low average velocity, ≈ 1 mph

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Flow Characteristics

• Turbulent Flow --- Reynolds number for tunnel cross-section ( H= 21.5 ft) is 180,000.

• Low velocity --- ≈ 1 mph.

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Temperature Control

• Only one zone for temperature control– just one temperature variable can be adjusted

• Temperature control– Input temperature at discharge into the Undulator

Hall will be held within ± 1 F at 68 F, with “Process Heat Load” up to 8.5 kW.

– The “Process Heat Load” is from the present and future undulator system equipment and doesn’t include lighting or environmental heating/cooling sources.

– Note 8.5 kW is 50 W/m of tunnel and 65 W/m of undulator line

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Sources of Heating/Cooling

• Access– People, equipment brought in, leakage of air

• Undulator System – See next slide

• Tunnel walls and floor– Initial warm up, seasonal variations, moisture

• Utilities– Lighting, exit signs, power lines, chilled and hot water lines, phone/data/fire/pps

• Other systems– DL2/Vertical Bend magnet wires

• Many different time scales: quasi-static to random

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Undulator System Heating LoadsF.O. Radiation Loss SystemPhotodiode Radiation Loss

SystemCamera MotorsCamerasQuad magnetsCorrector magnetsQuad and Corrector WiresBPM RF ReceiversBFM Sensor electronicsHLSWPMCable Drops

MPS Link BoxesVacuum PumpsMagnet Water Lines Convective loadQuad Power LinesUCM Rack and ContentsTranslation MotorsCAM MotorsUndulator Motion IOCDiagnostic MotorsDiagnostic Motor IOCPhotomultiplier

Current Estimate for Total Undulator System Load

11 kW. . . (85 W/m of undulator line)

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Estimated Temperature Profile

• Total temperature rise of 1.0 deg C

• The temperature rise will increase with time as the tunnel warms up and additional heat loads are added.

• Probably want to offset discharge temperature 1 F to get mean at 68 F.

WEST EAST

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Localized Heating

• Warm air from local heat sources will completely mix with tunnel air within a few (<10) tunnel diameters

• Locally heated air persists in boundary layers which grow in size and mix with the main tunnel air stream.

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Forced Air Flow Around Racks or Pedestals

• Laminar layer forms around obstacle, eddies form downstream of it.

• ReD for support pedestals is about 30,000 so it will have same type of flow From Kreith, pg 406

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Free Convection Air Flow Around Racks

• warmed air forms a thin boundary layer next to rack and rises

• air velocity at top of rack ~2 ft per s

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Localized Heating Estimate

• 4-5 deg C air rises from the rack sides, more or less vertically, and warms a portion of the grider and segment

• Heat flows through the girder and segment and back into the air.

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Temperature averaging

• Effects of short term air temperature changes can be significantly averaged out.

• Example: Undulator segment– Measured response time constant ≈ 16 hrs. For

temperature changes at period of 24 hr, = 0.26 hr-

1, there is about a factor of 4 reduction in the response of the undulator temperature.€

˜ T Device (ω) =˜ T Air(ω)

1− iωτ

January 22, 2008 Undulator System Meeting J. Welchwelch@slac.stanford.edu

Conclusions

• Tunnel air temperature will rise by 1 deg C or more along the tunnel length due to power dissipation– Undulator system is the dominate heat source

• Localized heating was semi-quantitatively investigated– 150 W racks placed under the segmentswill warm

adjacent air 3-4 deg C– Warmed air will rise and flow directly onto the girder

and undulator segment