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MICE Collaboration meeting at Columbia University, New York 12 – 14 June 2003 How Liquid Hydrogen behaves thermally in a Convective Absorber by Wing Lau, Stephanie Yang -- Oxford University

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Cooling performance of the Convective absorber design The MICE absorber adopts a convective cooling design. The heating power of the beam is being cooled by the stagnant pool of liquid hydrogen which contacts directly. The liquid hydrogen is in turn being cooled by the gas helium.

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The analysis are being carried out in two phases. In the first phase, we examine the cooling effect of the absorber without any heat exchange from the gas helium. In this model, the initial temperature of the liquid hydrogen was set at 17K and the containment walls of the absorber is kept at 17 K. Adiabatic boundary conditions were applied, i.e. no heat is exchanged between the outside and the inside of the containment wall. This is a reasonable assumption as there is a layer of vacuum outside the absorber that prevents heat transfer by convection; This work is now completed. We looked at how the liquid hydrogen behaves under a beam power of 60W, 150W and 300W respectively. In our second phase of the analysis, we have included the helium gas a medium of heat exchange. The temperature of the containment wall is no longer specified, but determined by flow and heat carrying capacity of the gas helium. This work is still on going.

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A reminder of what we did on the force – flow Absorber design

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without the inlet and outlet manifoldswith the inlet and outlet manifolds The 3-D models

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model mesh -- over 1.5 million grids Beam modelled as a 10mm tube

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Steady state velocity results

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The CFD model for the Convective absorber design

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The CFD model showing the containment and the beam

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The CFD model showing the close containment

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Results for a beam power of 60 W

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60W beam power

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Results for a beam power of 150 W

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150W beam Power

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Results for a beam power of 300 W

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Temperature result at 300W, LH2,

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Velocity result at 300W, LH2

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The Phase 2 model

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Absorber diameter: 300mm Beam diameter: 10mm, Power: 150W GHe pipe diameter: 15mm, length of pipe is 15mm, inlet velocity: 2m/s Multicomponent: fluid domain: GHe, LH2, fluid sub-domain: beam, solid sub- domain: wall Turbulent Model: K-Epsilon Initial temperature: GHe:17K, LH2: 17K Global Temperature result see next page beam GHe inlets GHe outlets Meshed model LH2 region Solid dividing wall

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naturalConvtn_abs_tst_002.res

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naturalConvtn_abs_tst_004.res

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Simple hand calculation: Given: Specific heat of LH2: 9680 J/kg K LH2 density: 70.79kg/m^3 Volume of absorber window: 0.0196672m^3 Density * volume = 70.79*0.0196672 = 1.392241088kg Cp*1.392241088kg = 13476.8937318 J/K 300W = 300 J/s 300 (J/s) / 13476.8937318 (J/K) = 0.02226K/s For 300W, 2.5K needs 44 secs 60W, 1K needs 2246 secs

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