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The classic design of a loop heat pipe (LHP) usually includes a cylindrical evaporator design, where the heat generated at the wall has thermal/hydraulic contact with the surface of a cylindrical porous wick structure. Such a design is characterized by good technological and physical bases and a well-proven theory. It is capable to solve many practical tasks. However, also attempts to design a loop heat pipe with flat contacting surfaces between the heated wall and wick are of practical interest for applications for which the effective heat inputs to cylindrical evaporator surface is hardly realizable, or for which mounting surfaces require contact over a flat surface only. World wide there is only limited development of flat evaporator loop heat pipes [1]. Therefore this study can be called a novelty. Besides of technological development the basis for physical modeling of such loop heat pipe should be elaborated.

This paper discusses the thermal modeling activities as a design and development tool for the Tracker Thermal Control System, the mechanically pumped, carbon dioxide thermal management system for the AMS-2 Silicon Tracker. Main modeling topics are: radiator sizing and condenser development, set-point control and pre-heating issues with respect to the spatial and temporal temperature gradient requirements of the Tracker.

This paper will discuss thermal control examples, which were considered to be (very) promising in the past, whose further developments were stopped due to number of reasons, but which currently are regaining attention resulting in a re-start of R&D activities, which must lead to applications in real spacecraft. The various issues are electro-hydrodynamic and electro-osmotic control of heat pipes and of capillary and mechanically pumped single- and two-phase thermal control loops, switching by electro-hydrodynamic, electro-osmotic, and the novel electro-wetting control, vapour pressure driven thermal control loops, thermal-gravitational modelling & scaling, and controlled rotating radial heat pipe joints. The revival of the old activities and the start of novel activities are considered to be important for near-future spacecraft thermal control applications.

Mechanically and capillary pumped two-phase heat transport systems are currently developed to meet the high power and long transport distance requirements of thermal management systems for future spacecraft. Compared to existing single-phase systems, two-phase loops offer important advantages: reduced overall mass and pumping power consumption, virtually isothermal behaviour, adjustable working temperature, insensitivity to variations in heat load and sink temperature, and high flexibility with respect to the location of heat sources within the loop. As two-phase flow and heat transfer in low-gravity environment is expected to (considerably) differ from terrestrial behaviour, the technology of two-phase heat transport systems and their components is to be demonstrated in orbit. Therefore a Dutch-Belgian Two-Phase experiment has been developed within the ESA In-Orbit Technology Demonstration Programme.