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					               Cryogenics Research Program
                           Steven Van Sciver, PI
      National High Magnetic Field Laboratory at Florida State University

   Primary mission:
     – To carry out experimental and analytical research on liquid helium and other
       cryogens so that they can be better applied in the cooling of large
       superconducting magnet systems.
   Research & Development Support:
     – Liquid Helium Fluid Dynamics Studies: DOE/HEP
     – Visualization Studies of Heat and Mass Transfer in Forced Flow He II: NSF-
       Thermal Sciences
     – FSU for supplement to Visualization Studies (FSU - Research Foundation)
   Other Cryogenics Work at the NHMFL
     – Cryogenic systems for the NHMFL: 900 MHz NMR magnet cryostat
     – Design of cryogenic systems for HTS transformer (Korea/CAPS)




                   DOE HEP Review 5/30/2002
              Presentation Content


   Introduce the FSU-NHMFL Cryogenics group
   Describe R&D facilities
   Review current research activities supported by DOE-HEP
    – He II Heat pulse propagation experiment
    – High Reynolds number forced flow He II
    – Cryogenic instrumentation development
   Briefly discuss other related research activities
    – Flow visualization studies
   Future plans (What happens next?)
    – He II two phase flow visualization




             DOE HEP Review 5/30/2002
          NHMFL-FSU Cryogenics Group


    Faculty:                                    Graduate Students:
      – Steve Van Sciver (Professor/PI)           –   David Hilton (Physics)
      – Ho Myung Chang (Visiting Professor)       –   Silvie Fuzier (ME)
    Staff:                                       –   Zhang Tao (ME)
      – Dogan Celik (Post doc)                    –   Yeon Suk Choi (ME)
      – Kurt Cantrell (Engineer)                  –   Wu Ting (ME)
      – Scott Maier (Technician)                 Undergraduate students
                                                  – Cary Henry (FSU-ME)
                                                  – Tom Adams (FSU-ME)
underlined persons are supported by DOE-HEP         (NSF REU)




                 DOE HEP Review 5/30/2002
 DOE/HEP funded graduate students & post docs

Past Graduate Students:                     Past Postdocs and Visitors
   John Weisend (PhD, 1989):                Dwight Kingsbury (Post doc, 1991-5)
     – SLAC Cryogenics group (since 1999)        – Florida DOT
   D. Scott Holmes (PhD, 1989):             Bertrand Baudouy (Post doc 1997-8)
     – Lake Shore Cryotronics (left:1999)        – CEA/Saclay
   Xiaodong Huang (PhD, 1994):              Xiang Yu (Post doc 1998-2002)
     – Financial Analyst                         – DESY Hamburg
   Yuenian Huang (PhD, 1994):               Mike Smith (Scientist 1995-2000)
     – FNAL Technical Division (since            – KLA-Tencor (2000- present)
        1996)                                Matthieu Dalban-Canassy - Visiting
   John Panek (PhD, 1998)                     French student
     – Goddard Space Flight Center           Arnaud Gilibert - Visiting French
                                               student




                 DOE HEP Review 5/30/2002
Facilities for Cryogenics Research at the NHMFL

   Liquid Helium Flow Facility (LHFF)
     – 5 m long, 20 cm ID horizontal cryogenic vessel with vertical reservoirs at
       either end containing circulation pumps and other hardware.
     – Presently being upgraded to include viewing ports for visualization studies.
   Cryogenic Helium Experimental Facility (CHEF).
     – 3 m long, 60 cm ID cryogenic vessel with N2 and He temperature thermal
       shields equipped with a high volume flow bellows pump capable of up to 5
       liters/s forced flow LHe.
     – CHEF is being used to study high Reynolds number liquid helium flow.
   Cryogenic Particle Image Velocimetry (PIV) facility.
     – Apparatus to perform micro-scale imaging studies of flow fields in liquid
       helium and other cryogenic fluids.
     – A cryogenic vessel with optical windows, dual-head pulse Nd:YAG laser and
       image processing and analysis equipment.
         www.magnet.fsu.edu/magtech/research/cryogenics.html




                 DOE HEP Review 5/30/2002
DOE/HEP: Liquid Helium Fluid Dynamics Studies

 Current Research Activities
    Transient heat transfer in He II (D. Hilton)
      – Fundamental understanding of He II turbulence
      – Application: transient cooling of high Jc superconductors
    High Reynolds number He II heat and mass transfer (S. Fuzier, T. Wu)
      – Steady pressure drop at high velocity
      – Heat transport by forced convection and counterflow
      – Drag coefficient on sphere in He II
    Flow visualization studies (D. Celik)
      – Planning underway for flow visualization in two phase He II at high Reynolds
        number
    Instrumentation development (Cryogenics group)
      – Capacitive level gauge (DESY/AMI collaboration)
      – Pressure transducer, high speed thermometry, laser heating




               DOE HEP Review 5/30/2002
Transient heat transfer in He II (D. Hilton)

Goal: Study highly (t < 1 ms) transient heat transfer in He II for
        stability of high current density conductors
 Experiment:
    – Measure limits to energy transport in He II by 2nd sound thermal shock
    – Study development of mutual friction turbulent condition following the
      thermal shock pulse
    – Directly measure the development of quantum turbulence in He II
      by 2nd sound resonance attenuation
    – Increase understanding of the limits to He II pulse heat transport
   Status
    – Experiment complete and student is preparing dissertation
    – Papers submitted to PRL and LT-23
    – Plans to incorporate technology in forced flow experiments




             DOE HEP Review 5/30/2002
               Experimental Schematic

                 dt                                  T(t)
                                                                                                  He II
     Heater                                u
                                                                                                  Bath



   Second sound pulse propagates at u = c2 ≈ 20 m/s
   Heat content of pulse is ∫rCdT• c2dt [J/m2]
   Trailing edge of pulse is attenuated due to turbulence buildup in the
    He II
    Thermometer measures T(t)
                                                                      527.1

                                                     mm 84 = z²

    Compare ∆Ep to ∆E = Q• dt
                                                                                  2   m/Wk 0 02         027.1





                                                                                                                ]K[ erutarepmeT
                                                                                  2   m/Wk 0 01
                                                                                                        517.1


                                                                                                        017.1


                                                                                                        507.1


                                                                                                        007.1
                                               0.3     8.2        6.2       4.2       2.2         0.2

                DOE HEP Review 5/30/2002                           ]sm[ em iT
                       Experimental test section


                                                       Thermometers
                                                                                 Heater




                                        Second sound
                                         resonators


Graduate student, David Hilton,
preparing second sound
thermal shock experiment
                                     The channel is 178 mm long, with a 19.1 mm x 12.7 mm
                                     interior cross-section.

                        DOE HEP Review 5/30/2002
          Fraction of heat pulse received




                         Energy Transport Fraction [-]
   Energy transport fraction
    versus initial pulse energy                                                                 y = 339 x
                                                                                                r = 0.98
                                                                                                            -1.30


    for SSS pulses in He II.
                                                         1.00
   Solid line is a fit for ∆E ≥
    100 J/m2. The slope is
    ∆E-1.3 indicating that                                          T A = 1.70 K
    energy transport is                                             ²z = 127.0 mm

    maximum around 100 J/m2
   Dashed line is a power law                           0.10
    fit to comparable data
    acquired by Shimazaki,
    Iida, and Murakami
                                                                1        10              100                        1000

                                                                    Initial Pulse Energy [J/m    2]




                  DOE HEP Review 5/30/2002
Second Sound Attenuation Measurement

                                                 dt T(t)                            T(t)             T(t)
                                                                                                                           He II
                                                                                                                           Bath

                                                         Q(t)                       Q(t)            Q(t)
                                     Channel Transverse Cavity Spectrum
                                       Second Sound Resonance Peaks
                                                                                                Amplitude of resonance peak is
                         0.15                                                                  attenuated by local turbulence
                                                 n = 12
                                                                        n = 14
                         0.10
                                                                                 n = 16

                                                                                                            ∆T(z)=∆T0exp(-z)
Thermometer Signal [-]




                         0.05

                         0.00
                                                                                               where (m-1) is the attenuation
                         -0.05                                                                 coefficient
                         -0.10

                                                                                                Attenuation coefficient, , is a
                                     ²z = 101.6 mm
                         -0.15       L = 13.3 mm

                                                                                               measure of turbulence density
                                     T A = 1.71 K
                         -0.20
                                 2         3         4          5       6          7       8   (votrex line length/volume)
                                                       Heater Sweep
                                                      Frequency [kHz]


                                               DOE HEP Review 5/30/2002
              Second Sound Attenuation

                                                                       Excess attenuation versus time
     12                                                                at one position, revealing the
                                                                       induced turbulence generated
                                                                       by the pulse.
     10
]
-1




                   Pulse
      8           arrival

      6
                                                                       The vertical line marks the 2nd
                                               Peak
                                            turbulence                 sound pulse arrival time.
      4

      2                           200 kW/m 2 Power Flux Density        The curve is a fit, based on
                                                                       the leaky capacitor model (LCM)
                                       250 µs Square Pulse
                                 101.6 mm Above Primary Heater
      0                                 1.70 K LHe Ambient

     -2
          0   5             10         15         20      25      30

                                  Time [ms]




                      DOE HEP Review 5/30/2002
                Leaky Capacitor Model
     1            RF             2




     +                                                                                     2
                                                           t  t 0                
                                                 = a  
                                                  (t)     exp          exp t  t 0 
                                                                                        
                                                                                          
           CS           CT                 RD

                                                            D            G    


     0


 Cs is source capacitor containing charge (heat pulse) and Ct is the tank
    capacitor initially at zero potential.
   Charge is transferred to Ct at a time constant determined by G ≈ RfCt.
   The tank capacitor is the leaky capacitor, with the drain resistor, RD.
   The energy density of the tank capacitor, determined in part by the
    potential at 2 squared, leads the LCM fit equation.




                DOE HEP Review 5/30/2002
    Instrumentation 2nd Sound Experiment

These experiments require heat transfer                                                                    SFT 3.3 - SF
                                                                                                          Calibration Plot
  and thermometry to operate on a time                                                               Decreasing Temperature

  scale < 1 ms.                                                                100


 Heater development (nichrome, 15 to 35                                        80         B




                                                   SFT Static Resistance [ž]
  nm thick) on quartz                                                           60

 Several kinds of thermometry                                                  40                                     µ 0H c [G]         T c [K]     s [-]

    – Graphite (Pentel pencil lead, B-hardness)                                 20
                                                                                                                A
                                                                                                                B
                                                                                                                           70
                                                                                                                           500
                                                                                                                                          2.47
                                                                                                                                          1.65
                                                                                                                                                          15
                                                                                                                                                          11
      on ground G-10 substrate                                                                       A
                                                                                                                    Ag (67.5 nm) / Sn (100 nm)

    – Sn (Ag) thin film on s-glass 6 mm diameter
                                                                                 0                                      SiO 2 Filament (6 µm)
                                                                                                                                IE = 100 µA

      fiber, (Proximity effect superconductor)                                 -20
                                                                                     1.5       2.0        2.5        3.0            3.5             4.0        4.5
   2nd Sound resonators combined these                                                              LHe Ambient Te mpe rature [K]

    technologies




                  DOE HEP Review 5/30/2002
         Forced flow He II experiments
Goal: to extend the pressure drop and heat transfer in
forced flow He II to higher Reynolds numbers
(Re > 107 and u > 20 m/s, velocity of 2nd sound in He II)*

 Pressure drop measurements
     - Measure ∆P for smooth tube and deduce friction factor
     - Study Joule-Thomson effect (dT/dP) for He II
     - Observe cavitation effect by monitor of absolute pressure
   Heat transfer experiments
     - Steady-state, local heat transfer in He II (u > 1 m/s)
     - Transient, local heat transfer
     - Principal question: is the Mutual friction interaction in He II dependent
     on overall fluid velocity. This should manifest itself in a deviation in
     temperature profile from calculation extrapolated from low velocity data



        *   Previous maximum u < 5 m/s


              DOE HEP Review 5/30/2002
         Pressure drop and Joule-Thomson effect
      in forced flow He II at high Reynolds numbers

Cryogenic Helium Experimental                           LEVEL CONTROL

 Facility (CHEF).
                                                        BELLOWS AND
                                                            UAT
                                                        ACT OR



                                            CAN SUPPLY OF HELIUM



                             INST      AT
                                 RUMENT ION MODULE
                                              PRESSURE TRANSDUCER




         SHIELDS AT 77 AND 4.2 K       He RETURN LINE                   AL EST
                                                              EXPERIMENT T SECTION
                                                                                     Graduate student Sylvie Fuzier
                                                                                     operating High Reynolds number
               Instrumented test section ID = 9.8 mm, L = 1.2 m                     helium flow experiment.
               Maximum u ≈ 20 m/s; ReD ≈ 3 x 107


                          DOE HEP Review 5/30/2002
Schematic pressure drop experiment

                                       Shown is complete flow loop ready
                                       for installation in CHEF.

                                       The experimental test section
                                       consists of a 1.2 m long SS tube,
                                       9.8 mm ID instrumented with
                                       pressure transducers and
                                       thermometry.

                                       Pressure transducers are Validyne ∆P
                                       and operate at liquid helium temp.




               T                                T

 mHe

                                  ∆p
                                               ∆p
       DOE HEP Review 5/30/2002
Pressure drop across 1 m test section


                                Pressure drop does not
                                scale with rn
                                                       5.6
                                T (K)     rn  rT T 
                                                  
                                1.7 K     0.25r

                                1.85 K    0.4r

                                2K        0.62r




     DOE HEP Review 5/30/2002
Friction Factor (f) vs. Reynolds No.

                                                L
                                  p  2 f        ru 2
                                               dH

                                   Von Karman-Nikuradse

                               1
                                  1.737 * lnRe* f  0.396
                                f

                                   Colebrook, e = 1.4 x 10-4
                                  1             e   1.25
                                      4 log     
                                   f          3.7D Re f

                                                    rdv
                                    Where, Re 
                                                    n




    DOE HEP Review 5/30/2002
                   Joule-Thomson effect
                               T                                     T

mHe                                                                           T  T  1
                                                                               
                                                       ∆p                     p h rC p
                    0.1                                              ∆p

                   0.09
                                                                          1.7 K
                   0.08
                                                                          1.85 K
                   0.07
                                                                          2K
      delt T (K)




                   0.06                                                   1.7 K JT
                   0.05                                                   1.85 K JT
                   0.04                                                   2 K JT
                                                                          1.7 K JT integ
                   0.03
                                                                          1.85 K JT integ
                   0.02
                                                                          2 K JT integ
                   0.01
                     0
                          0            10                  20   30
                                            delt P (kPa)

                          DOE HEP Review 5/30/2002
Steady-State heat transfer experiment
                     T        T     T T   T       T     T   T
   mHe
                                     H



               u = 0.5 m/s                                          u = 4 m/s




                                                                1

                                          dT d  1 dT          3
    He II energy equation rvC                               q ( x)
                                          dx dx  f (T ) dx 
         DOE HEP Review 5/30/2002
Transient Heat Transfer Calculations
 Calculated temperature profiles for instantaneous pulse heat at x = 0.
 Mutual friction interaction assumed to be independent of velocity.

                       80
                                                                     t=0.01s
                       70
                                                V = 10 m/s           t=0.02s
                       60                       Q = 0.1 J/cm2        t=0.03s
                                                                     t=0.04s
  deltT (mK)




                       50
                                                                     t=0.05s
                       40
                       30
                       20

                       10
                        0
               -10          0        10           20      30    40             50
                                                x (cm)


                     DOE HEP Review 5/30/2002
      Project status and future work
   Remaining task to complete transient heat transfer
    experiment (Test section is under construction)




    – Preliminary data expected by summer (two ICEC-19 Abstracts)
   Future work to combine 2nd sound attenuation experiment
    with high Reynolds number forced flow
    – Measure attenuation at high velocity (u ≈ 20 m/s)
    – Possible link between counterflow and classical turbulence
    – Modeling of combined heat and mass transfer in high Re regime




             DOE HEP Review 5/30/2002
Drag Coefficient on a Sphere in Flowing He II*
 Goal: To investigate whether drag on bluff objects is
 anomalous in He II regime

   Force flow He II in channels behaves classically in terms of friction
  factor and JT effect (e.g. High Reynolds number experiments).
   Drag over bluff body (sphere) is dominated by form factors rather than
  skin friction.
   Flow around sphere is a well characterized ―classical‖ problem to test
  He II fundamentals
   Experiment
       - The form drag on a sphere in flowing He I and He II calculated
       from the observed pressure distribution over the surface
       - Possibility of temperature dependence to the critical phenomena



        *Work supported in part by DOE-HEP and NHMFL

              DOE HEP Review 5/30/2002
    Pressure measurement scheme




                                        P ()  P0
 Coefficient of pressure : C P                     10 mm sphere mounted
                                         1           within the test section. The
                                            rU 2     1 mm strut supports the
                                         2           sphere and transmits
                                                     surface pressure to an
 Drag coefficient : C  2 C ( ) cos sin  d
                      d     p                       external sensor.




             DOE HEP Review 5/30/2002
                Pressure coefficient (Cp) vs. angle

 Pressure distribution for various temperatures at Re = 2.2  105

         1.5

                                                                                       Profile show supercritical
                    Re = 2.2 * 10E5                                     1.7 K
                                                                        1.9 K
           1                                                            2.1 K
                                                                                      behavior above the laminar-
         0.5
                                                                                      turbulent transition
                                                   Separation                          Boundary layer separation
 C
     P     0                                                                          occurs at 110 degrees.
                                                                                       Small differences in temp.
                                                                                      dependence
         -0.5


          -1


         -1.5
                0         30          60         90        120    150           180
                                      Azimuthal Angle [Degrees]



                               DOE HEP Review 5/30/2002
              Drag coefficient vs. temperature

                                                                   CD in He II increase with
        0.7                                                       decreasing temperature.
                                                      Re=1.1*E5
                                                      Re=2.0*E5

                                                                   CD is the largest at 1.6 K
        0.6                                           Re=2.2*E5
                                                      Re=3.3*E5

                                                                  decreasing monotonically to
                                                      Re=5.6*E5
                                                      T
        0.5
                                                                  the value in He I.
C       0.4
    D



                                                                   Extrapolation CD in He II
                                                                  to T coincide with app.
        0.3


        0.2                                                       constant values in He I.

        0.1
               1.6   1.8       2        2.2     2.4        2.6
                              Temperature [K]




                           DOE HEP Review 5/30/2002
Drag coefficient vs. normal fluid Reynolds number



                                                                         The data correlate more
        0.6
                                                    Cd_2.54K

        0.5
                                                    Cd_2.1K
                                                    Cd_2.0K             closely with one curve if
                                                    Cd_1.9K
                                                    Cd_1.8K             plotted vs. Ren = (rn/r)Re
                                                                         Scaling shift CD(min) to
        0.4                                         Cd_1.7K
                                                    Cd_1.6K

                                                                        approx. same value of Ren
                                                    Smooth
C       0.3
                                                                        for each temperature.
    D




        0.2                                                              Normal fluid appears to
                                                                        play a role in turbulent
                                                                        transition.
        0.1


         0
                   4          5                 6                   7
              10         10                10                  10
                                  Re
                                       n




                       DOE HEP Review 5/30/2002
          Project status and future work


 Observations on drag coefficient:
 CD measured for 2 x 104 < Re < 4 x 105 between 1.6 K  T 2.1 K
 Appears to scale with normal fluid Reynolds number.
 Drag crisis is governed by the location of the boundary layer separation
which could depend on the normal fluid density.

 Future Activities
 More precise pressure transducer has developed in order to extend our
measurement over a wider range of Reynolds number.
 Possibility to use flow visualization techniques




               DOE HEP Review 5/30/2002
    New Pressure Transducer




 Collaboration with the University of Oregon Physics Department, C. Swanson
 Requires high accuracy capacitance measurement



          DOE HEP Review 5/30/2002
                      Pressure Transducer Calibration Curve


                     47.808
                                  4.2 K                                        Temp. : 1.7 K < T < 4.2 K
                                  2.54 K
                                  2.1 K

                                                                               Deviation : 5.7710-6 [pF]
                     47.804       1.9 K
                                  1.7 K
  Capacitance (Pf)
Capacitance [pF]




                                                                               Accuracy :  0.05 [Pa]
                     47.800


                                                                               Advantages:
                                                                              - About 10x increased sensitivity
                     47.796
                                                                              and minimal zero drift compared
                                           C = 47.794 + 5.986 10-5 P         to Validyne
                                                                              - Calibration not temperature
                     47.792                                                    dependent
                              0       50          100         150       200

                                              Pressure [Pa]




                                  DOE HEP Review 5/30/2002
       Other NHMFL Cryogenics Activities

   Visualization studies of He II heat and mass transfer (T. Zhang)
    – Particle Image Velocimetry (PIV) in He II
    – Supported by NSF (Thermal Sciences) & FSU (Research Foundation)
   900 MHz NMR cryostat design (NHMFL funds)
    – 1.8 K He II cryostat for 40 MJ magnet (K. Cantrell)
   Cryogenic Cooling System for HTS Transformer
    – High efficiency cryostat for Navy & utility applications (Y. Choi)
    – Korean Cooperative Science Program (H. M. Chang, 50% cost share)
    – Also supported by FSU Center for Advanced Power Systems (CAPS)




               DOE HEP Review 5/30/2002
Particle-Image-Velocimetry Measurement in He II*

   Application of Particle Image Velocimetry (PIV) to study flow
    fields in He II (other cryogens)
   First application of PIV to counterflow heat transport in He II
   Requirements of technique
    – Pulse laser and optical cryostat with image collection system
    – Neutral density particles (d ≈ 10 mm)
   Also received Program enhancement grant from FSU to apply
    this technique to forced flow liquid helium
    – Modification of LHFF underway to provide optical access.




           *Work supported by NSF-Thermal Sciences
               DOE HEP Review 5/30/2002
Background - PIV fundamentals




1. Flow seeding and image capture            2. Image subdivided into Interrogation
                                             Regions




                                                       3. Correlation process

  4. Result - whole view of velocity field

           DOE HEP Review 5/30/2002
        PIV Experiment Setup


                                                                         QuickTime™ and a
                                                                    Photo - JPEG decompressor
                                                                  are needed to see this picture.



                                        Beam expanding
                                        optics
                  Laser sheet
Optical port
                                                Dual laser head

                                                                   Computer


                      CCD camera


 Beam dump



                                              Synchronizer
               Figure 17 Optical cryostat with PIV setup




               DOE HEP Review 5/30/2002
     Options for neutral density particles

1. Hollow glass spheres. These can be obtained in
   close to neutral density, but there is a large
   variation in size and individual particle density.
   Selection is possible, but tedious
2. Solid H2-D2 particles (or H2 + other higher density
   < mm particles). We have been injecting fine spray
   of liquid H2 into LHe to produce particles.
3. Solid particles of higher density (d ≈ 0.3 mm, SiO2),
   but fine enough to be easily moved by eddy
   currents




                 DOE HEP Review 5/30/2002
    Counterflow Channel

                                       Valve stem



                                           Particle seeder

  Support structure
                                              Guide tube

                                            Screen

                                           Channel extension (G-10)

                                       Transparent flow channel
50 mm
                                            Film heater



  Channel developed for first experiment


  DOE HEP Review 5/30/2002
Results of counterflow experiments

         30 mm




   Step Heat Pulse; q = 560 mW/cm2
                                     q (t)
   Elapsed time = 335 ms
                                             t



       DOE HEP Review 5/30/2002
Comparing PIV results with analysis
 PIV analysis results of velocity distribution:
   — Most region of flow field has a velocity in the range of
     17-28 mm/s which gives a mean velocity of 22 mm/s
   — Calculated velocity of normal fluid:


                                    40 mm/s
 Reasons for this discrepancy:
   — Slip velocity for hollow glass spheres is from 2.9 mm/s
     (20 µm) to 18.13 mm/s (50 µm)
   — Heat diffusion process would also affect local velocity of
     normal fluid                                                 g




               DOE HEP Review 5/30/2002
        Status of PIV Experiments

   Preliminary results gave qualitative agreement with
    counterflow analysis
   Need to improve techniques for neutral density particle
    injection and particle characteristics
   Experiments scheduled for summer 2002
   Abstract submitted to ICEC 19
   Continue to develop neutral particle generation techniques
   Fall 2002 we will begin to introduce PIV techniques to
    forced flow experiments in modified LHFF




           DOE HEP Review 5/30/2002
Visualization experiments in He II two phase flow

Goal: to visually observe flow states in He
  II/vapor two phase and quantitatively
  measure flow conditions in each phase.

   Introduce video imaging and PIV
    capability into LHFF experiments
   Measurements of single and two phase
    flow
    – Flow regimes, instabilities
    – Quantitative velocity field measurements
   Comparison to modeling (DESY)




               DOE HEP Review 5/30/2002
LHFF with Flow Visualization Capability



                                               linear
                                              actuator




                                    laser
                       LN2
                                                           LHe
     LHe                                       bellows
                                                pump




                                            experimental
                                               region
           particle seeder camera   5m



       DOE HEP Review 5/30/2002
              Two-Phase Flow Visualization

 Investigate two phase flow                                                                Radiation
    regimes                                                       Pitot Tube                Shield
   Quantitative measurements                                                               T≈4K
     — Velocities of two phases                                        ∆P


     — Interfacial phenomena           Light Source
                                                        Flow Channel
                                                                               Vapor Anemometer
 Instrumentation for                  (LED or Laser)
    measurement of fluid flow                                      Vapor
     — Anemometer or Pitot tube
         for vapor velocity                                        He II
     —   PIV for liquid velovity and
                                                                                           CCD Camera
         interfacial studies
     —   High speed video for                                 Optical windows
         qualitative observations




                    DOE HEP Review 5/30/2002
Status of 2 Phase Flow Visualization


   Modify LHFF to allow visualization experiments
    – Cryostat vendor, due to NHMFL July 2002
    – Facility upgrading (instrumentation, PIV hardware)
   Preliminary design of visualization test section underway
   Need to develop particle seeding techniques for LHFF




             DOE HEP Review 5/30/2002
                              Summary

   Development of data base and physical understanding of He II
    benefits future accelerator development
     – Linear collider (if superconducting) will probably utilize He II cooling (e.g.
       TESLA)
     – VLHC will probably also use He II cooling for high field accelerator
       magnets
   Liquid helium fluid dynamics and heat transfer is an ideal topic for
    educating professional cryogenic engineers
     – Skills include: vacuum, cryostat design, instrumentation and measurement
       technique
   We have an extensive research agenda for future work
   Benefit from interaction with HEP accelerator technology community




                DOE HEP Review 5/30/2002
      Laser heating experiment schematic


   Nd:YAG laser with pulse                                                    Transient
                                                                               Recorder
    width of 3-5 ns
                                                                    Co-axial
   Wavelength 532 nm (green)                      5A
                                                                     cable
                                                  Power
   Energy/pulse up to 120 mJ
                                                  supply
   variable attenuator
   Spot size is 5 mm diameter                                                    Labview
                                                                                  Computer


                                               Optical
                                               windows

                                                                                      Laser
                    QuickTime™ and a
               Photo - JPEG decompressor
             are needed to see this picture.




                                                           Sample
               DOE HEP Review 5/30/2002
             Thermal diffusion time


    Characteristic diffusion
    time, D ≈ d2/
    –   D ≈ 1 ns @ 2 K
    –   D ≈ 10 ms @ 100 K



           He II




             DOE HEP Review 5/30/2002
Sample voltage vs. time




DOE HEP Review 5/30/2002
Determination of the Heat Transfer Coefficient


    Pulse drives sample into film boiling
    Audible noise from boiling
    Recovery time determined by rate of heat loss

                           dT
                       mC     = hA(T - Tb )
                           dt
     – For constant heat transfer coefficient, h, cooling rate has a
       characteristic time  = mC/hA

                                                              d(∆T)/dt
                            T0
                                          ∆T      ∆T0
                           dT
     – Then, h ≈ mC/Aeff      dt       0



                                                           time


             DOE HEP Review 5/30/2002

				
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