www.dlr.de Folie 1 Measuring Optical and Thermal Properties of High Temperature Receivers Johannes Pernpeintner, Thomas Fend 4 th SFERA Summerschool, May 15-16, 2013, Burg Hornberg
www.dlr.de Folie 2 Part I: Thermal properties of receivers for SOLAR TOWER TECHNOLOGY Thomas Fend Part II: Optical and thermal properties of tube receivers for PARABOLIC TROUGH TECHNOLOGY Johannes Pernpeitner
www.dlr.de Folie 3 Why Solar Tower Technology? Efficiency limited by thermal engine Higher temperatures higher efficiencies Higher losses athighertemperatures Higher concentration ratio
www.dlr.de Folie 4 Solar Tower Technology: Example
www.dlr.de Folie 5 Receivers for Solar Tower Technology volumetric receivers tube receivers direct medium receivers
www.dlr.de Folie 6 Tube Receivers absorption on outer tube surface transport of heat through tube wall to a medium media: liquid salt, liquid metal, water, air thermal resistance non homogeneous heating tube surface temperature is higher than medium temperature
www.dlr.de Folie 7 Tube Receivers Solar Two absorption on outer tube surface transport of heat through tube wall to a medium media: liquid salt, liquid metal, water, air thermal resistance non homogeneous heating tube surface temperature is higher than medium temperature
www.dlr.de Folie 8 Tube Receivers Gemasolar absorption on outer tube surface transport of heat through tube wall to a medium media: liquid salt, liquid metal, water, air thermal resistance non homogeneous heating tube surface temperature is higher than medium temperature Source: torresolenergy
www.dlr.de Folie 9 Tube Receivers PS10/PS20 absorption on outer tube surface transport of heat through tube wall to a medium media: liquid salt, liquid metal, water, air thermal resistance non homogeneous heating tube surface temperature is higher than medium temperature Source: desertec UK
www.dlr.de Folie 10 Volumetric Receivers Radiation absorbed in the porous volume of the receiver Front temperature lower than medium temperature Medium: air, pressurized air
www.dlr.de Folie 11 Volumetric Receivers Radiation absorbed in the porous volume of the receiver Front temperature lower than medium temperature Medium: air, pressurized air 2mm 0.8 mm
www.dlr.de Folie 12 Volumetric Receivers Radiation absorbed in the porous volume of the receiver Front temperature lower than medium temperature Medium: air, pressurized air Solar Tower Jülich Tower: 60m 2153 Heliostats (8.2 m²) 22.7 m² receiver aperture 1 h thermal storage 500 C/ 30 bar 1.5 MW el turbine
www.dlr.de Folie 13 Thermal Performance Prediction
www.dlr.de Folie 14 Thermal Performance Prediction Absorption
www.dlr.de Folie 15 Thermal Performance Prediction Absorption Conductive resistance in tube wall
www.dlr.de Folie 16 Thermal Performance Prediction Absorption Conductive resistance in tube wall Convective resistance
www.dlr.de Folie 17 Thermal Performance Prediction Absorption Conductive resistance in tube wall Convective resistance tables standard techniques optimization of process by geometry and thermal properties of the employed material
www.dlr.de Folie 18 Thermal Performance Prediction: Heat Transfer Enhancing Concepts Increased heat transfer surface Enhanced heat transfer by gradation in radial direction Thermal properties of porous material needed Proposed in Korean/Swiss/German project CMC4CSP
www.dlr.de Folie 19 Thermal Performance Prediction: Volumetric Receiver Conductive resistance and Convective resistance in porous volume Advanced experimental techniques necessary if non uniform pore geometries are used
www.dlr.de Folie 20 Thermal Performance Prediction Conductive resistance and Convective resistance in porous volume Advanced experimental techniques necessary if non uniform pore geometries are used
www.dlr.de Folie 21 Thermal Performance Prediction Conductive resistance and Convective resistance in porous volume Advanced experimental techniques necessary if non uniform pore geometries are used
www.dlr.de Folie 22 Thermal Conductivity of Porous Materials Transient Plane Source Technique + Measurement of characteristic volumes + mesurement yields effective thermal conductivity effective thermal diffusivity heat capacity
www.dlr.de Folie 23 Thermal Conductivity of Porous Materials Transient Plane Source Technique + Measurement of characteristic volumes + mesurement yields effective thermal conductivity effective thermal diffusivity heat capacity
www.dlr.de Folie 24 Effective Thermal Conductivity of Porous Materials: Metal Foams Nickel base alloy
www.dlr.de Folie 25 Convective Resistance in Porous Volume two phase approach in continuum model Additional term in energy equations of solid and fluid phase eff m C P 2 T A dt dx S F v A v ( T S T F ) 0 ( T T ) S F 0 A v : volumetric convective heat transfer coefficient
www.dlr.de Folie 26 Experimental Set-Up for Volumetric Convective Heat Transfer Coefficient Av: AAF-method 1 Heat Element Absorber sample Air Insulation DT(t,0) x=0 x=l T(t,0) T(t,L) DT(t,L) Air flow with alternating temperature profile induced Porous sample causes phase shift and amplitude attenuation Av determined t Df t 1. ) Alternating Air flow method after Younis and Viskanta
www.dlr.de Folie 27 Experimental Set-Up for Volumetric Convective Heat Transfer Coefficient Av: AAF-method Heat Element Absorber sample Cordierite 20 ppi CB SiC 45 ppi Air Insulation x=0 x=l T(t,0) T(t,L) SSiC 10 ppi 10 mm DT(t,0) DT(t,L) t Df t
www.dlr.de Folie 28 Experimental Set-Up for Volumetric Convective Heat Transfer Coefficient Av: AAF-method Heat Element Air Absorber sample 10 8 6 y = 0,42x 0,62 76 all 45 76 all 20 76 all 10 Nu 4 y = 0,15x 0,62 Insulation DT(t,0) x=0 x=l T(t,0) T(t,L) DT(t,L) 2 0 y = 0,08x 0,62 0 50 100 150 200 Re t Df t
www.dlr.de Folie 29 Experimental Set-Up for Volumetric Convective Heat Transfer Coefficient Av: AAF-method Heat Element Air Absorber sample 10 8 6 y = 0,42x 0,62 76 all 45 76 all 20 76 all 10 Nu 4 y = 0,15x 0,62 Insulation DT(t,0) x=0 x=l T(t,0) T(t,L) DT(t,L) 2 0 y = 0,08x 0,62 0 50 100 150 200 Re t Df t Nu 1.1 4.8 n PPI Re 0.62
www.dlr.de Folie 30 Experimental Set-Up for Volumetric Convective Heat Transfer Coefficient Av: AlAv-method 1 sample beamer IR camera mass flow measurement blower 1. ) AlphaAv method after Brendelberger et al.
www.dlr.de Folie 31 Experimental Set-Up for Volumetric Convective Heat Transfer Coefficient Av: AlAv-method
www.dlr.de Folie 32 The AlAv-method: Results on Metal Foams
www.dlr.de Folie 33 Conclusions For the prediction of the thermal performance of high temperature components characteristic quantities are needed Transient plane Source Technique for thermal conductivity measurement AAF and AlAV method for volumetric convective heat transfer properties