Tubular SiSiC structures for high temperature applications · Tubular SiSiC structures for high...
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Tubular SiSiC structures for high temperature applications Ehsan Rezaei 1,2 , Maurizio Barbato 1 , Sandro Gianella 3 , Sophia Haussener 2 , Alberto Ortona 1 1 MEMTI-SUPSI, 6928, Manno, Switzerland 2 Institute of Mechanical Engineering, EPFL, 1015 Lausanne, Switzerland 3 EngiCer SA,Viale Pereda 22, Balerna 6828, Switzerland Conclusions • Preliminary tests were successfully performed on empty tubes and tubes filled with random foams. • The LTNE model is formulated using literature data on permeability and heat transfer parameters of similar foams. • More experiments will be performed using the high temperature testing setup. New heat transfer and permeability parameters will be obtained from these tests, which will be used for further simulations. Acknowledgement In cooperation with CTI Swiss Competence Centers for Energy Research (SCCER Heat and Electricity Storage). Introduction Silicon infiltrated SiC (SiSiC) is a ceramic material for applications in harsh environments such as burners, recuperators and heat storage systems. It has wide industrial applications due to its high mechanical and chemical stability in elevated temperatures as well as its excellent thermal shock resistance. In high temperatures, above 1000°C, three main factors may limit the performance of SiSiC: bead formation due to melting of silicon, severe oxidation especially in presence of water vapor and high thermally induced stresses. The first two factors are investigated earlier for various SiSiC lattices [1]. This work focuses on the thermal behavior of SiSiC lattices, which will be used as the base for future works on thermal stress analysis of these materials. Experimental setup A specific test rig was designed and assembled to accomplish high temperatures (max 1600°C) measurements of heat exchange capabilities of the tubular porous materials under study in this work. For tube heating, a special furnace was commissioned to the Xerion Company (Freiberg, D). This furnace is able to provide high thermal power densities in a limited zone. To provide a laminar flow to the gasses entering the hot zone, an expansion chamber coupled with a pipe of a sufficient length were utilized. Preliminary test are successfully performed on empty tubes and tubes filled with random foams. The furnace temperature was set to 1280°C. High temperature measurement apparatus. 1 2 3 4 outlet furnace inlet DAQ/controller Tubular heat exchangers The samples are SiSiC tubes filled in the middle with a porous foam. SiSiC tubes were acquired from the porous ceramic manufacturer (EngiCer). They consists of a SiC alfa powders bound by silicon which was melt infiltrated at high temperature. 5 cm 10 cm As received Si-SiC random foam sample side view (left) and top view (right). As received Si-SiC tube sample side view Numerical model An axisymmetric LTNE (local thermal non-equilibrium) model has been applied using COMSOL Multiphysics. Steady state condition is considered with a laminar air flow at the inlet of the tube. Similar to the experiments, the tube is filled in the middle part with a porous medium. The transport properties for the porous medium have been taken from literature based on detailed pore-level simulations [2]. The LTNE axisymmetric model with the boundary conditions. References [1] Rezaei, E., Haussener, S., Gianella, S., & Ortona, A. (2016). Early-stage oxidation behavior at high temperatures of SiSiC cellular architectures in a porous burner. Ceramics International, 42(14), 16255-16261. [2] Haussener, S., Coray, P ., LipiĹ, W., Wyss, P ., & Steinfeld, A. (2010). Tomography-based heat and mass transfer characterization of reticulate porous ceramics for high-temperature processing. Journal of Heat Transfer, 132(2), 023305. Results Solid (left) and fluid (right) phase temperatures in the center line of the porous medium for different pore nominal diameters. The results clearly show the greater heat transfer capabilities of the tubes filled with porous medium compared with empty tube. Samples with smaller cell size show to be more effective. However small cell sizes leads to higher temperature variations in the solid foam which causes higher thermally induced stresses. Air temperature distribution (°C) in the center line of empty tube (left) and tube filled with a foam with 5 pores per inch (right) z r 1300 20 z r 1300 20
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Transcript of Tubular SiSiC structures for high temperature applications · Tubular SiSiC structures for high...
Tubular SiSiC structures for high temperature applications
Ehsan Rezaei1,2, Maurizio Barbato1, Sandro Gianella3, Sophia Haussener2, Alberto Ortona1
1MEMTI-SUPSI, 6928, Manno, Switzerland 2Institute of Mechanical Engineering, EPFL, 1015 Lausanne, Switzerland
3EngiCer SA, Viale Pereda 22, Balerna 6828, Switzerland
Conclusions!• Preliminary tests were successfully performed on empty tubes and tubes
filled with random foams. • The LTNE model is formulated using literature data on permeability and
heat transfer parameters of similar foams. • More experiments will be performed using the high temperature testing
setup. New heat transfer and permeability parameters will be obtained from these tests, which will be used for further simulations.
Acknowledgement!In cooperation with CTI Swiss Competence Centers for Energy Research (SCCER Heat and Electricity Storage).
Introduction!Silicon infiltrated SiC (SiSiC) is a ceramic material for applications in harsh environments such as burners, recuperators and heat storage systems. It has wide industrial applications due to its high mechanical and chemical stability in elevated temperatures as well as its excellent thermal shock resistance. In high temperatures, above 1000°C, three main factors may limit the performance of SiSiC: bead formation due to melting of silicon, severe oxidation especially in presence of water vapor and high thermally induced stresses. The first two factors are investigated earlier for various SiSiC lattices [1]. This work focuses on the thermal behavior of SiSiC lattices, which will be used as the base for future works on thermal stress analysis of these materials.
Experimental setup A specific test rig was designed and assembled to accomplish high temperatures (max 1600°C) measurements of heat exchange capabilities of the tubular porous materials under study in this work. For tube heating, a special furnace was commissioned to the Xerion Company (Freiberg, D). This furnace is able to provide high thermal power densities in a limited zone. To provide a laminar flow to the gasses entering the hot zone, an expansion chamber coupled with a pipe of a sufficient length were utilized. Preliminary test are successfully performed on empty tubes and tubes filled with random foams. The furnace temperature was set to 1280°C.
High temperature measurement apparatus.
1 2 3
4
outlet furnace inlet DAQ/controller
Tubular heat exchangers!The samples are SiSiC tubes filled in the middle with a porous foam. SiSiC tubes were acquired from the porous ceramic manufacturer (EngiCer). They consists of a SiC alfa powders bound by silicon which was melt infiltrated at high temperature.
5 cm
10 cm
As received Si-SiC random foam sample side view (left) and top view (right).
As received Si-SiC tube sample side view
Numerical model!An axisymmetric LTNE (local thermal non-equilibrium) model has been applied using COMSOL Multiphysics. Steady state condition is considered with a laminar air flow at the inlet of the tube. Similar to the experiments, the tube is filled in the middle part with a porous medium. The transport properties for the porous medium have been taken from literature based on detailed pore-level simulations [2].
The LTNE axisymmetric model with the boundary conditions.
References [1] Rezaei, E., Haussener, S., Gianella, S., & Ortona, A. (2016). Early-stage oxidation behavior at high temperatures of SiSiC cellular architectures in a porous burner. Ceramics International, 42(14), 16255-16261. [2] Haussener, S., Coray, P., LipiĹ, W., Wyss, P., & Steinfeld, A. (2010). Tomography-based heat and mass transfer characterization of reticulate porous ceramics for high-temperature processing. Journal of Heat Transfer, 132(2), 023305.
Results!
Solid (left) and fluid (right) phase temperatures in the center line of the porous medium for different pore nominal diameters.
The results clearly show the greater heat transfer capabilities of the tubes filled with porous medium compared with empty tube. Samples with smaller cell size show to be more effective. However small cell sizes leads to higher temperature variations in the solid foam which causes higher thermally induced stresses.
Air temperature distribution (°C) in the center line of empty tube (left) and tube filled with a foam with 5 pores per inch (right)
z
r 1300
20 z
r 1300
20
