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Efficient Method for Thermal Conductivity Measurement in Spine QA/QC

Discover the quick and clean Ballistic Method by H.-G. Moser at MPI, Munich, for measuring thermal conductivity in spines. This method ensures robust and reproducible results, with insights on calibration and verification processes. Evaluate the impact of different power levels on measurements and ensure a fast response for accurate results.

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Efficient Method for Thermal Conductivity Measurement in Spine QA/QC

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  1. A quick and clean method to measure thermal conductivity Application: QA and QC of spines Standard Method: DT between heat source and heat sink Disadvatage: depends on thermal coupling of heaters, sensors etc.... H.-G. Moser MPI, Munich

  2. Ballistic Method heater pt100 pt100 T T t t Measure reponse T(t): time constant depends on c/ck (c: specific heat, ck: thermal conductivity) H.-G. Moser MPI, Munich

  3. Ballistic Method heater pt100 pt100 X=0 L t=0: T0 t>0: Tr T(t,x)=Tr-(Tr-T0)Sciexp(-ei²at/L²)cos[ei(x-L)/L] ei=p/2, 3/2 p , 5/2 p ci=4 sin(ei)/[2ei sin(2ei)] a=ck/cr H.-G. Moser MPI, Munich

  4. TPG bar 12 cm Theoretical solution for T=const boundary condition! H.-G. Moser MPI, Munich

  5. Measurements In practice: use heater (constant power) instead of constant temperature bath Spine is a composite object => Calibration necessary H.-G. Moser MPI, Munich

  6. TPG/Cu Ln[(T-Tmin)/(Tmin-Tmax)] Copper bar TPG bar H.-G. Moser MPI, Munich

  7. Effect of different power One practical problem is bad reproducibility of the coupling heater/sample (and sensor/sample) Can be checked by varying the heater power 1.7, 3.2, 6.6 W Ln[(T-Tmax)/(Tmin-Tmax)] H.-G. Moser MPI, Munich

  8. Conclusions Time constant (almost) independent of heater power, coupling of heaters and sensors Fast response: small effect of ambient temperature Robust and reproducible measurement of Ck -> develop a simple QC setup for spine H.-G. Moser MPI, Munich

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