Basics of Loop Heat Pipe Temperature Control

Nikitkin, Michael; Kotlyarov, Evgeny; Serov, G. P.

doi:10.4271/1999-01-2012

Cited by 13 publications

(4 citation statements)

References 8 publications

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“…The CCHP and LHP are versatile capillary two-phase heat transfer devices which can transport large amounts of heat over long distances with very small temperature differences [1][2][3][4]. In addition, the LHP can provide very tight temperature control for instruments [5,6]. Both CCHPs and LHPs have extensive flight heritage: CCHPs are used in almost every contemporary satellite, and LHPs are used in many NASA spacecraft and commercial satellites [7][8][9][10][11][12][13].…”

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confidence: 99%

Thermal Performance of ATLAS Laser Thermal Control System Demonstration Unit

Robinson

Patel

et al. 2013

44th AIAA Thermophysics Conference

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The second Ice, Cloud, and Land Elevation Satellite mission currently planned by National Aeronautics and Space Administration will measure polar ice topography and canopy height using the Advanced Topographic Laser Altimeter System (ATLAS). The ATLAS comprises two lasers; but only one will be used at a time. Each laser will generate between 125W and 250W of heat, and each laser has its own optimal operating temperature that must be maintained within ±1 o C accuracy by the Laser Thermal Control System (LTCS) consisting of a constant conductance heat pipe (CCHP), a loop heat pipe (LHP) and a radiator. The heat generated by the laser is acquired by the CCHP and transferred to the LHP, which delivers the heat to the radiator for ultimate rejection. The radiator can be exposed to temperatures between -71 o C and -93 o C. The two lasers can have different operating temperatures varying between +15 o C and +30 o C, and their actual operating temperatures are not known while the LTCS is being designed and built. Major challenges of the LTCS include: 1) A single thermal control system must maintain the laser at 15 o C with 250W heat load and -71 o C radiator sink temperature, and maintain the laser at +30 o C with 125W heat load and -93 o C radiator sink temperature. Furthermore, the LTCS must be qualification tested to maintain the ATLAS between +10 o C and +35 o C. 2) The LTCS must be shut down to ensure that the ATLAS can be maintained above its lowest desirable temperature of -2 o C during the survival mode. No software control algorithm for LTCS can be activated during survival and only thermostats can be used. 3) The radiator must be kept above -65 o C to prevent ammonia from freezing using no more than 135W of heater power. 4) The LHP reservoir control heater power is limited to 15W with a 70% duty cycle. 5) The voltage of the power supply can vary between 26 Vdc and 34 Vdc during the spacecraft lifetime. A design analysis shows that a single LTCS can satisfy these requirements. However, shutdown of the LHP is particularly challenging and the shutdown heater must be wired in series with two reservoir thermostats and two CCHP thermostats at different set points. An LTCS demonstration unit has been tested to verify these performance characteristics experimentally prior to proceeding to the final LTCS design and fabrication. Test results showed that the LHP shutdown scheme would be able to shut down the LHP as designed and the reservoir control heater can maintain the ATLAS mass simulator within the ±1 o C accuracy under various combinations of the heat load, sink temperature, and power supply voltage.

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confidence: 99%

Thermal Performance of ATLAS Laser Thermal Control System Demonstration Unit

Robinson

Patel

et al. 2013

44th AIAA Thermophysics Conference

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“…For spacecraft applications requiring a narrow temperature range, regulating the LHP operating temperature becomes necessary. There are various ways to control the LHP operating temperature, depending upon the requirement on the tightness of the temperature control and the availability of the spacecraft power [12][13] . Nevertheless, all temperature control methods use the same underlying principal, i.e.…”

Section: Introductionmentioning

confidence: 99%

Loop Heat Pipe Transient Behavior Using Heat Source Temperature for Set Point Control with Thermoelectric Converter on Reservoir

Paiva

Mantelli

2011

9th Annual International Energy Conversion Engineering Conference

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The LHP operating temperature is governed by the saturation temperature of its reservoir. Controlling the reservoir saturation temperature is commonly done by cold biasing the reservoir and using electrical heaters to provide the required control power. With this method, the loop operating temperature can be controlled within ±0.5K or better. However, because the thermal resistance that exists between the heat source and the LHP evaporator, the heat source temperature will vary with its heat output even if the LHP operating temperature is kept constant. Since maintaining a constant heat source temperature is of most interest, a question often raised is whether the heat source temperature can be used for LHP set point temperature control. A test program with a miniature LHP was carried out to investigate the effects on the LHP operation when the control temperature sensor was placed on the heat source instead of the reservoir. In these tests, the LHP reservoir was cold-biased and was heated by a control heater. Test results show that it was feasible to use the heat source temperature for feedback control of the LHP operation. In particular, when a thermoelectric converter was used as the reservoir control heater, the heat source temperature could be maintained within a tight range using a proportional-integral-derivative or on/off control algorithm. Moreover, because the TEC could provide both heating and cooling to the reservoir, temperature oscillations during fast transients such as loop startup could be eliminated or substantially reduced when compared to using an electrical heater as the control heater.Nomenclature/Acronym/Symbol CC = compensation chamber EH = electrical heater EVAP = evaporator LHP = loop heat pipe PID = proportional-integral-derivative TEC = thermoelectric converter TM = thermal mass

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“…The set point and regulation point of PRVs are fixed and cannot be modified during the LHP operation unless the pressure of the control gas behind the bellows is controlled. Different techniques are proposed to control the gas pressure using a phase change material (PCM) in [30] and heater in [29] and [31].…”

Section: Lhp Control Methodsmentioning

confidence: 99%

“… is the pressure drop coefficient of each bend and it can be obtained by multiplying the contribution of each bend property as described in Eq. (30). These properties consist of the bend angle ( ), the relative bend radius ( ) and the relative bend roughness ( ).…”

Section: Bend Correlationsmentioning

confidence: 99%

Transient Mathematical Modelling of Loop Heat Pipes and Experimental Validation

Jazebizadeh¹

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Basics of Loop Heat Pipe Temperature Control

Cited by 13 publications

References 8 publications

Thermal Performance of ATLAS Laser Thermal Control System Demonstration Unit

Thermal Performance of ATLAS Laser Thermal Control System Demonstration Unit

Loop Heat Pipe Transient Behavior Using Heat Source Temperature for Set Point Control with Thermoelectric Converter on Reservoir

Transient Mathematical Modelling of Loop Heat Pipes and Experimental Validation

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