1993-07-01

High Capacity Grooved Heat Pipes 932303

In the frame of an ESA technology program, the development of a High Capacity Grooved Heat Pipe (HGP), based on the thermal requirements of the next generation of telecommunication satellites, was contracted to SABCA.
Different promising concepts and methods of groove technology were reviewed. A trade-off and design study was performed on potential HGP concepts, taking into account theoretical performances (on earth and in micro-gravity), ease of manufacturing and of assembly as well as the heat pipe working reliability and priming capability.
The two finally selected concepts were aluminium extruded heat pipes (outer diameter of 25 mm, vapour core diameter of 15 mm), based on a multi re-entrant grooves concept or on a mixed rectangular/re-entrant grooves concept.
The acceptance test program, to which these two heat pipes had been submitted, included leak, proof and burst tests as well as classical thermal tests (maximum heat transport capacity, maximum tilt capability, start-up, priming, gas plug/ageing, bending influence, sensitivity to non-condensible gas, non-uniform heat input).
The test results showed for the multi re-entrant grooves HGP heat pipe good confidence and the fulfilment of the required specifications on heat transport capacity and on tilt capability: the experimental maximum heat transport capability was found to be around 1500 Watt-metres (horizontally at a vapour temperature of 20°C) for a required 600 Watt-metres while the maximum tilt capability had been measured between 18 mm (at a vapour temperature of 20°C).
Based on the HGP concept, two down-scaled versions (outer diameter of 15 mm and of 20 mm) had been developed and tested in order to analyze the impact of the size on the performance of this heat pipe design.
In the frame of an ESA parabolic flight campaign, the three versions of the HGP heat pipes (15 mm, 20 mm, 25 mm) were submitted to various heat loads, going for some of them to their maximum heat transport capacities. This parabolic flight, which led to useful data on the maximum performances and/or on their operating behaviour of these heat pipes in micro-gravity environment, is briefly presented and its results described.
The next step in this technology program, currently on-going, is the full qualification of this newly developed re-entrant groove heat pipe design according to the ESA requirements.

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