Abstract

Micro-heat-sinks for Space Applications
Co-Authors: Sergey Zhdanov, Luca Chignoli, Gianpietro Elvio Cossali

During space missions, the problems related to the thermal conditioning of devices, to the personnel comfort and to the thermo-mechanical stresses are known and essential. Furthermore for a space mission certain priorities are particularly important, such as the small dimension and the lightness of thermal equipments. Another specific problem is the handling of liquids in microgravity. Due to the presence of high temperature gradients, which straightforwardly implies significant heating/cooling powers, these constraints are difficult to implement. Miniaturized heat exchangers and sinks for passive elements, such as heat pipes, may have a large industrial diffusion for electronic component cooling, in propulsion and in the power production for micro-satellites, spacecrafts and airplanes. Given the great value of the ratio between exchanging surface and volume of these systems, the specific thermal power per unit volume can reach extremely high values (the value of 100 W/cm2 may be a possible target). One of the main problems of the micro-heat-sinks, given the minimum internal diameter of the microtubes, is represented by considerable pressure drop. This leads to an inadequate equipment size for the pumping system and to the difficulty to use passive components. The usage of polymeric additives or of surfactants can have relevant effects on the reduction of the friction coefficient. Particular properties of microduct internal surfaces (in particular the solid surface wettability) could decrease the pressure drop, making their application even more efficient. The low wettability of certain material, together with low density, elasticity and mechanical resistance, suggest that the development of a new technology for heat exchangers, based on a sheet of microtubes, could be of great interest for space and terrestrial applications. The paper describes the main use of microtechnologies for the thermal control in space and some hints for new specific components for next missions and micro-satellites.

Brief Bio

Dr. Marengo received his Masters degree in Energetics at the Politecnico of Milan with a thesis about "Drop Impingement on Liquid Film" in 1996. He taught in high schools for a short period and then, in 1993, started the Ph.D. studies at the Politecnico of Milan. He was awarded first by the Deutscher Akademischer Austauschdienst (DAAD) and then by the European Community TMR Program with a 10+20 months scholarship to work in Germany, at the Institut of Fluidmechanics of Prof. Durst in Erlangen. He continued his Ph.D. studies in Erlangen, becoming in 1996 university researcher by Prof. Tropea in the same University. In 1998 he was research assistant at the University of Darmstadt (Germany) and appointed head of the research group of "Liquid Interfaces and Spray". From 1998 to 2002 he has been research assistant of Thermodynamics and Heat Transfer at the University of Bergamo. He taught as assistant for the courses of "Numerical Methods in Chemical Engineering", of "Fluidmechanics (laboratory)", of "Technical Physics (Thermodynamics and Heat Transfer)" and of "Heat Transfer". Since 2000 he is Contract Professor of Thermodynamics and Heat Transfer. Since 2002 Marco Marengo is Associate Professor of Thermal Physics and Heat Transfer. He is European Newsletter Editor for ILASS Europe and SOCRATES Tutor for the Engineering Faculty in Bergamo. He is active in many industrial contracts. He published more than 50 scientific papers and presentations about liquid sprays, drop impact on solid dry and wetted surfaces, diesel injection, laser anemometry, building physics and micr .