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Research Papers: Conduction

Thermal Insulators' Performances in Simulated Mars Environment

[+] Author and Article Information
Diego Scaccabarozzi

e-mail: diego.scaccabarozzi@polimi.it

Marco Tarabini

Politecnico di Milano,
Polo Territoriale di Lecco,
Via G. Previati 1/c,
Lecco 23900, Italy

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 8, 2012; final manuscript received August 6, 2013; published online October 25, 2013. Assoc. Editor: Bruce L. Drolen.

J. Heat Transfer 136(1), 011302 (Oct 25, 2013) (6 pages) Paper No: HT-12-1489; doi: 10.1115/1.4025367 History: Received September 08, 2012; Revised August 06, 2013

This paper describes the experimental characterization of the thermal insulation properties of a multilayer insulator (MLI) and of an aerogel. Materials characterization was performed to optimize the thermal control design of a small interferometer devoted to planetary observation. In order to simulate the Martian environment, tests were performed in a carbon dioxide atmosphere, with pressures between 10 and 104 Pa and temperatures from 193 to 353 K. MLI was tested at different levels of layers compression to investigate thermal insulation changes deriving from the constraining of the mechanical structure. The thermal conductivity was measured with a purposely designed guarded hot plate apparatus. Results showed that the aerogel exhibits a lower thermal conductivity for gas pressures larger than 100 Pa and that the layer compression of the MLIs does not affect the heat conduction for gas pressures above 103 Pa.

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Figures

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Fig. 1

Sketch of the hot guarded apparatus with two specimens configuration

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Fig. 2

Sketch of the test setup to measure material conductivity

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Fig. 3

Thermal image of the cold disk in stationary condition. White crosses with temperature values are located in the inner area where an average temperature of 38 °C and a standard deviation of 0.7 °C are obtained.

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Fig. 4

Thermal conductivity uncertainty as a function of the equivalent cold and inner disk temperatures; CO2 conductivity is used as reference value

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Fig. 5

Relative contributions to the thermal conductivity uncertainty of temperatures Ti and Tceq (light gray-circles and black-squares mark lines), heat flow rate Qt (dark gray-triangle line), sample area A and thickness t (light gray-square and black-diamond lines).Worst case with Ti and Tceq set to 333 K and 303 K.

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Fig. 6

Thermal conductivity in air, hot case configuration. MLI behaviors are shown with continuous black and gray dashed lines, light gray continuous line is used for aerogel, dashed black line represents air thermal conductivity at normal pressure, i.e., 25.7 10−3 W m−1 K−1. Relative uncertainties are shown with the same gray code.

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Fig. 7

Thermal conductivity in CO2 atmosphere, hot case configuration. Continuous black, dark and light gray show MLI conductivities with 8, 6, and 4 mm thicknesses. Dark gray dashed line describes aerogel behavior and black dashed curve shows CO2 reference thermal conductivity at normal pressure, i.e., 15 10−3 W m−1 K−1.

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Fig. 8

Thermal conductivity in CO2 atmosphere, cold case configuration. Continuous black, dark, and light gray show MLI thermal conductivities with 8, 6, and 4 mm thicknesses. Dark gray dashed line describes aerogel behavior and black dashed one shows CO2 reference thermal conductivity.

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