Effect of Rarefied Atmospheres on Natural Convection over Very Thin Wires

Date

2020-07-31

Journal Title

Journal ISSN

Volume Title

Publisher

2020 International Conference on Environmental Systems

Abstract

The direct usage of some measuring instruments based on heat transfer designed for Earth’s atmosphere, such as very thin thermocouples, is unclear when used on other planets or in rarefied atmospheres where the pressure is in the order of the millibar. In these conditions the Knudsen number based on the instrument characteristic length is no longer very small, and the application of traditional empirical correlations to predict heat transfer does not account for this effect or sometimes these correlations could only be applied over narrow Raleigh number or aspect ratio diameter/length range. An experiment has been designed to study the effect of the heat transfer in conditions of free convection at low pressures, which can be expressed in terms of Knudsen number. For this purpose, very thin wires have been tested inside a chamber with air at several pressures between 0.03 millibars and atmospheric pressure in order to simulate rarefied atmospheres. The position of the wires inside the chamber was horizontal and vertical. The wires were heated electrically and their temperature was established by means of the relation between temperature and electrical resistivity measured by the 4-wires method. The presented data are corrected including radiation and material conduction effects.

Description

Lilian Peinado, Instituto Universitario de Microgravedad Ignacio Da Riva - Universidad Politécnica de Madrid, ES
Victor Muntean, Escuela Técnica Superior de Ingeniería Aeronáutica y del Espacio - Universidad Politécnica de Madrid, ES
Isabel Pérez-Grande, Instituto Universitario de Microgravedad Ignacio Da Riva - Universidad Politécnica de Madrid, ES
ICES203: Thermal Testing
The proceedings for the 2020 International Conference on Environmental Systems were published from July 31, 2020. The technical papers were not presented in person due to the inability to hold the event as scheduled in Lisbon, Portugal because of the COVID-19 global pandemic.

Keywords

Rarefied atmosphere, Heat transfer, Natural convection, Mars atmosphere

Citation