HEAT PIPES FOR CONTROL

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					HEAT PIPES FOR CONTROL

    CAN THEY BE USED IN
    CHEMICAL REACTORS?
             David Reay


        16TH PIN MEETING, RUNCORN,   1
             9 SEPTEMBER 2008
A Sodium Heat Pipe I Made Some
Time Ago Introduces the Concept




          16TH PIN MEETING, RUNCORN,   2
               9 SEPTEMBER 2008
And this is Developed into an ‘Active
    Feedback Controlled VCHP’




Which controls the source (reactor) temperature to
+-1Deg.C

                  16TH PIN MEETING, RUNCORN,         3
                       9 SEPTEMBER 2008
Back to Basics - Thermosyphons & Heat
         Pipes: What are they?




                                  Conventional heat pipe schematic. (1) HP
                                  case, (2) porous wick, (3) vapour channel,
                                  (4) vapour, and (5) liquid.

       Thermosyphon
 (Gravity-assisted liquid
 transport)

                        16TH PIN MEETING, RUNCORN,                         4
                             9 SEPTEMBER 2008
A Little Bit of History


                                Perkins Tubes used
                                to transfer heat from a
                                hot air stream to a
                                cold one – gas-gas
                                heat recovery.



                        The Perkins tube is a
                        thermosyphon – relies on
                        gravity for liquid return




   16TH PIN MEETING, RUNCORN,                             5
        9 SEPTEMBER 2008
  The Perkins Oven – use coal to bake
bread without getting soot on the dough!




             16TH PIN MEETING, RUNCORN,   6
                  9 SEPTEMBER 2008
Closer to Chemical Engineering – safety
                first!




            16TH PIN MEETING, RUNCORN,    7
                 9 SEPTEMBER 2008
The current version of the Perkins Heat
              Exchanger




            16TH PIN MEETING, RUNCORN,    8
                 9 SEPTEMBER 2008
Heat Pipe Working Fluids


                              Fluids can cover
                              temperature ranges
                              appropriate to most
                              reactors.
                              Liquid metals used – eg
                              sodium.




     16TH PIN MEETING, RUNCORN,                         9
          9 SEPTEMBER 2008
Comparison of fluid performance


                                Merit number compares
                                relative heat transport
                                capability of different
                                working fluids.


                                Strong function of latent
                                heat, surface tension,
                                viscosity




        16TH PIN MEETING, RUNCORN,                          10
             9 SEPTEMBER 2008
Limitation to heat transport are several

                                  Capillary limit affected by
                                  orientation of heat pipe &
                                  wick design.
                                  The wick is a passive
                                  pump.


                                  Sonic limit occurs when
                                  fluid density high (eg at low
                                  T)




            16TH PIN MEETING, RUNCORN,                            11
                 9 SEPTEMBER 2008
Types of Heat Pipe




  16TH PIN MEETING, RUNCORN,   12
       9 SEPTEMBER 2008
Applications as a Function of Heat Pipe
               Features




            16TH PIN MEETING, RUNCORN,    13
                 9 SEPTEMBER 2008
                    Isothermalisation


Isothermalisation – or
evening out of
temperatures, is an
inherent feature that
may benefit reactors




                         16TH PIN MEETING, RUNCORN,   14
                              9 SEPTEMBER 2008
Variable Conductance HP in a Reactor
             (Nuclear)




           16TH PIN MEETING, RUNCORN,   15
                9 SEPTEMBER 2008
  Benefits in Chemical Reactors
Catalysts have been put on heat pipes, with surface reactions.
The heat pipe is in ideal way of heat removal/input to the
catalyst thereon.




                 16TH PIN MEETING, RUNCORN,                      16
                      9 SEPTEMBER 2008
More possible benefits in Reactors




          16TH PIN MEETING, RUNCORN,   17
               9 SEPTEMBER 2008
Chinese Chemical Heat Pipe Reactor




          16TH PIN MEETING, RUNCORN,   18
               9 SEPTEMBER 2008
VCHP Concepts – Passive Control




         16TH PIN MEETING, RUNCORN,   19
              9 SEPTEMBER 2008
VCHP – Passive Feedback Control




         16TH PIN MEETING, RUNCORN,   20
              9 SEPTEMBER 2008
VCHP – Active Feedback Control – as
           shown earlier




          16TH PIN MEETING, RUNCORN,   21
               9 SEPTEMBER 2008
As with the SDR, rotation aids heat
   transfer and fluid transport


                                       Used for cooling
                                       rotating
                                       machinery




          16TH PIN MEETING, RUNCORN,                      22
               9 SEPTEMBER 2008
Other rotating variants




    16TH PIN MEETING, RUNCORN,   23
         9 SEPTEMBER 2008
                    In Conclusion
• The heat pipe, in its several variants, has many
  interesting heat transfer features.
• The heat pipe/thermosyphon could act to isothermalise
  reactor vessels, minimising uneven reaction rates.
• The ability to passively control temperatures at its
  evaporator could contribute to minimise excursions in
  endo- or exothermic reactions.
• The application of active feedback control can lead to
  precise temperature control.

• Newcastle University is able to collaborate with potential
  partners in bringing the technology into the marketplace.

                    16TH PIN MEETING, RUNCORN,             24
                         9 SEPTEMBER 2008
Common wastewater treatment




       16TH PIN MEETING, RUNCORN,   25
            9 SEPTEMBER 2008

				
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