CF testing pipe & testing plan S. Coelli, D. Giugni, C. Glitza, et al. NIKHEF, July 10th 2009 D. Giugni NIKHEF July 09
Outline Testing plan and activities on the CO2 for the qualification of the TMG on the local supports. Design of the CF testing pipe. Thermal characteristics of the CF pipes. D. Giugni NIKHEF July 09
What are the key parameters? For IBL we should be starting to compare the key parameters for al the layouts considered. Most of them can easily be quantified by means of adequate yard-sticks. Others belong to the production path and its optimization. Let see about those we can quantify: HTC and CHF measurements for the boiling channel. The modules will see the effect of the local variation of the HTC along the channel affected by the axial conductivity. It is therefore important to measure the overall mean HTC on a full length pipe and on the real stave. Thermal figure of merit of the stave. Mainly provides the conductive temperature drop across the stave normalized to the heat flow [C.cm2/W] This is again a combined effect (convection + conductive) that can be evaluated with both a real stave or the so called CF testing pipe. D. Giugni IBL Gen. M. -CERN June 09-
Available pipe sizes We are actually spanning from diameter ranging from 24mm depending upon the coolant and upon the material of the pipes. CF pipes diameter is limited by the production process. At the moment the two ID’s are available : 2.5mm and 3.5mm Ti pipe has a thickness of 120um. The available ID’s are: 1.75, 2.75 and 3.75mm For testing channel 800mm long on CO2 the evident most promising diameters are: CF pipe ID 2.5mm Ti pipe ID 1.75mm Combining these pipes diameters, cooling options and stave design, I came up with a prototyping matrix that also offers the guideline for the thermal qualification: see next slide D. Giugni NIKHEF July 09
Stave and pipe prototyping plan
Mean HTC and measurement of the basic thermal performances In the process of reaching the minimum ID diameter for the CF pipe, we started with 3.5mmID (4OD). The first CF testing pipe has been therefore built with this diameter even if this is not optimized for the CO2. Smaller pipes will come soon. The HTC measurement is generally tricky to perform. On a CF pipe is even more difficult due to the non negligible T drop across the pipe wall. As for the thermal impedance across the materials of the local support, the thermal interfaces between the various parts play a significant rule. The idea is though to have a testing pipe that, potentially, allow an estimate of relevant parameters. Hereafter is what we have built to connect to a CO2 plant: D. Giugni NIKHEF July 09
Design of the CF testing pipe Geometry: 3.5ID; 250um th.; +/-45deg; ~T300 fiber, Vf=45% Transversal conductivity see later Carbon Foam: POCO Conductivity along the pipe axis: K=135 Wm-1K-1 Conductivity across the pipe: K=45 Wm-1K-1 Heat capacity: Cp=0.7 J.g-1K-1 Heaters Total power=100W; R=7.5 Thermal Sensor: TC 19 outside the CF pipe + 19 underneath of the heaters TC type K D. Giugni NIKHEF July 09
CF testing pipe: sensors lay-out D. Giugni NIKHEF July 09
How does it work Given P the power generated by the heaters: DTev (Tinner_pipe- Tevap) ~ HTC DTpipe (Touter_pipe - Tinner_pipe) ~ K pipe DTfoam (Theaters- Touter_pipe) ~ K foam Since it is not possible to stick a sensor on the inner side of the CF pipe, the value of the transversal K is fundamental to know the inner pipe temperature. The correlations in the literature generally foresee lay-ups with unidirectional ply that cannot fit nicely the laminates with braid. In fact, the direction of the fibers in a braid has a radial component that benefits the transversal K. T sensor DT=fm.P Heaters DTev T sensor D. Giugni NIKHEF July 09
The pipe transversal K The pipe K has been measured on a planar laminate made of the same braid material. Two labs have been asked to do the measurement and both of them came with the same value: 0.76W.m-1K-1 Problems comes from the fact that the lamination process for the samples produce a laminate that has a significant fiber volume ratio from the pipe [60% vs. 45%] . Need though to scale it analytically via stretching the standard thermal conduction theory for the laminates. D. Giugni NIKHEF July 09
The pipe transversal K (2) Test sample D. Giugni NIKHEF July 09
Testing plan on CO2 CF 3.5mm ID testing pipe. HTC and CHF Now CF 2.5mm ID testing pipe. HTC and CHF Sept ----------------------------------------------------------------------------------------------- CF 2.5mm double pipe stave. Thermal figure merit Now CF 2.5mm single pipe stave. Thermal figure merit Oct Ti 1.75 monopipe stave Thermal figure merit Oct These measurements must be done cold (-40C) on CO2 system. We want to benefit from the expertise and equipment at NIKHEF. D. Giugni NIKHEF July 09