Fuyuko Fukuyoshi

Development of An Experimental Small Loop Heat Pipe with Polytetrafluoroethylene Wicks

This paper reports the development of an experimental small loop heat pipe with polytetrafluoroethylene (PTFE) wicks. Three kinds of PTFE porous materials were fabricated, and their wick properties were evaluated. It was clarified that the peak pore radii of the PTFE porous materials ranged from 0.8 to 2:2 � m, and their porosities ranged from 27 to 50%. A small loop heat pipe with PTFE wicks was designed using these properties, and an experimental small loop heat pipe, for which the wick in an evaporator is exchangeable, was fabricated. The experimental loop was tested with 1.2 and 2:2 � m PTFE wicks under atmospheric conditions. The test result with a 2:2 � mPTFEwickshowedahighoperatingtemperature,possiblyduetovaporleakfromtheevaporatorgroovesto the compensation chamber. The test results with the 1:2 � m PTFE wick showed a lower operating temperature, lower thermal resistance, and stable operation of the loop heat pipe.

BepiColombo/MMO Thermal Control System

The thermal control system (TCS) of BepiColombo/MMO (Mercury Magnetospheric Orbiter) is presented. MMO is a spin-stabilized spacecraft due to the scientific requirements. The spin axis is pointed nearly perpendicular to the Mercury revolution plane. The harsh environment near Mercury (0.31AU from the Sun at perihelion) imposes 11 solar constant irradiation on MMO spacecraft, while its thermal control system is required to maintain the onboard equipment and the spacecraft structure in proper temperature range during the entire mission phases. The MMO is controlled by means of passive thermal design technique and some components are controlled by means of combined method of passive and active techniques. The passive thermal control elements are Optical Solar Reflector (OSR), thermal shield, paints, films, and Multi Layer Insulation blankets (MLI). All external surfaces should be electrical conductive due to scientific requirement. Although we have adopted conventional thermal control devices as much as possible, we have been obliged to develop a new component and new devices intended for high temperature environment : High Gain Antenna (HGA), High Temperature MLI (HT-MLI), High Temperature Conductive White Paint, and so on. The developments and tests of newly developed components and devices are presented as well as the selection of conventional thermal control materials and devices. MMO Thermal Test Model (TTM) will be tested three times elaborately; the thermal balance test (TBT) with 1 solar constant solar simulator at the Tsukuba Space Center (TKSC) in November-December 2009, the TBT with IR panels at ISAS (Institute of Space and Astronautical Science) in February 2010, and the TBT at ESTEC in September-October 2010.

BepiColombo/MMO Thermal Test Model Testing

Lessons learned and results from BepiColombo/Mercury Magnetospheric Orbiter (MMO) thermal test model testing are presented. The MMO Thermal Test Model (TTM) was elaborately tested in four Thermal Balance Tests (TBTs): TBT with a 1 solar constant simulator at the Tsukuba Space Center in November 2009, TBT with infrared panels at the Institute of Space and Astronautical Science in February 2009, TBT with a 10 solar constant simulator at the European Space Research and Technology Centre (ESTEC) in October 2010, and TBT of the MMO TTM and MOSIF TTM composite at ESTEC in December 2010. This last MOSIF-MMO test was conducted by the European Space Agency.

Development of An Experimental Small Loop Heat Pipe with PTFE Wick

This paper reports development of an experimental small LHP with PTFE wick. PTFE porous materials with 0.8 – 2.2 μm pore radius were fabricated and the basic properties were evaluated. An experimental small LHP with the PTFE wicks was designed and tested in an atmospheric condition. A PTFE wick with 1.2 μm pore radius was used to demonstrate the loop performance. The test results showed excellent operating characteristics of the LHP.

Improvement in Operating Characteristics of a Small Loop Heat Pipe with Active Control of a Reservoir

This paper reports test results of active control of heat transfer performance of a small loop heat pipe (LHP) with a thermoelectric converter (TEC) in an atmospheric condition. The TEC is attached to a reservoir of the LHP to control the operating temperature by heating and cooling using a bipolar power supply. Tests were conducted by varying the evaporator power, the reservoir set point temperature, and the condenser sink temperature. The test results showed that the TEC is able to control the LHP operating with small electric power. The test results also demonstrated enhancement of the start-up success by maintaining a constant reservoir temperature during the start-up process. Forced shut-off of the loop operation by rapid heating of the reservoir was also demonstrated.

Thermal Performance of a Miniature Loop Heat Pipe for Spacecraft Thermal Control System

The Loop Heat Pipes (LHPs) are robust, self-starting and a passive two-phase thermal control system that uses the latent heat of vaporization of an internal working fluid to transfer heat from an evaporator (the heat source) to a condenser (the heat sink). The circulation of the working fluid is accomplished by capillary pressure gradients in a fine porous wick with very small pores. LHPs are rapidly gaining acceptance in the aerospace community and several terrestrial applications are emerging as well. In the present study, a miniature LHP is investigated the thermal performance for spacecraft thermal control system. Tests will be conducted including start-up, low power, power ramp up, high power, rapid power change, and rapid sink temperature change. Finally, we want to demonstrate the potential of LHP to become the next-generation heat transfer device to cool terrestrial devices such as advanced electronic which have high power dissipations. First of all, this paper presents the influence of the gravitational forces on the LHP performance. The present tests performed under steady state condition with three different orientations (horizontal, gravity-assisted, anti-gravity).Copyright