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MEASUREMENT OF TOTAL HEMISPHERICAL EMITTANCE OF SOLIDS USING A STEADY-STATE CALORIMETRIC METHOD Mario MISALE, Giovanni

MEASUREMENT OF TOTAL HEMISPHERICAL EMITTANCE OF SOLIDS USING A STEADY-STATE CALORIMETRIC METHOD Mario MISALE, Giovanni TANDA DITEC, University of Genoa, Italy.

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MEASUREMENT OF TOTAL HEMISPHERICAL EMITTANCE OF SOLIDS USING A STEADY-STATE CALORIMETRIC METHOD Mario MISALE, Giovanni

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  1. MEASUREMENT OF TOTAL HEMISPHERICAL EMITTANCE OF SOLIDS USING A STEADY-STATE CALORIMETRIC METHOD Mario MISALE, Giovanni TANDA DITEC, University of Genoa, Italy

  2. Radiative properties of materials (emittance, absorptance, reflectance) are important in engineering devices operating in high vacuum and/or high temperature conditions Prediction of these properties is feasible only in special conditions Experimental investigation is mandatory, especially when surface finishing conditions vary in use

  3. An apparatus for the measurement of total hemispherical emittance of solids has been developed • The measurement is based on the steady-state calorimetric technique: • the sample is electrically heated and exchanges heat with the surrounding only by thermal radiation • qel = V·i = As(Ts4 - T4) • Requirements • high vacuum (< 10-5 mbar) • care in the sample and container design • careful estimation of heat losses

  4. q = qel qgas qk = (Ts4T4) /[ (1 s)/ sAs+1/AsFs,+(1)/A] s = [ As(Ts4 T4) / q  C]1C=(1)As/(A)0 As H=9 cm, W=5 cm, t = 7 mm

  5. Conduction/radiation losses through wires T Ts d2T/dx2 = c0(T4T4) T x qk= -kdT/dx]x=0 Ts = 400 K, T= 300 K, s=0.05, qk=13.9% qelTs = 700 K, qk=10.2% qel Ts = 400 K, T= 300 K, s=0.3, qk=2.7% qelTs = 700 K, qk=1.9% qel Ts = 400 K, T= 300 K, s=0.7, qk=1.1% qelTs = 700 K, qk=0.8% qel

  6. Uncertainty analysis • s = [ As(Ts4 T4) / q  C]1q = qel qgas qk • s = c1 qel / [  As(Ts4 T4) ]c1 = (qel qgas qk)/qel 2 % qk /qk =50% c1 /c1 = 1-11% Ts=0.6-3 K,T=0.9-2 K Ts = 400 K, T= 300 K, s=0.05,  s%=11.5% Ts = 700 K,  s%=8.9% Ts = 400 K, T= 300 K, s=0.1,  s%=6.0% Ts = 700 K,  s%=4.6% Ts = 400 K, T= 300 K, s=0.3,  s%=3.3% Ts = 700 K,  s%=2.6% Ts = 400 K, T= 300 K, s=0.7,  s%=2.2% Ts = 700 K,  s%=2.2%

  7. Samples: Aluminium (Anticorodal 6063) #2 #1 Surface conditions: as-received (#1), sandblasted (#2), black anodised (#3) #3

  8. Results #2 #3 #1

  9. Future developments dTs/d = [sAs(Ts4 T4) + qk ] / (ms cp,s + mhcp,h )

  10. Conclusions An experimental apparatus for the measurement of total hemispherical emittance of solids has been presented Results for ordinarily polished, sandblasted and black anodised Aluminium alloy samples (Anticorodal 6063) were presented, in the 350-630 K temperature range Results were in close agreement with literature data Recorded emittance values covered a wide range (0.05 to 0.82), providing the suitability of the technique for any surface condition Simultaneous specific heat measurements can be easily performed during the cooling transient of samples

  11. END OF PRESENTATION THANK YOU FOR YOUR ATTENTION !

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