Browsing by Author "Anderson, William G."
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Item 3D Printed Wicks for Loop Heat Pipes(2023 International Conference on Environmental Systems, 2023-07-16) Gupta, Rohit; Chen, Chien-Hua; Anderson, William G.This paper describes the development of 3D printed wicks for loop heat pipes. This work is part of an overall effort by Advanced Cooling Technologies, Inc. to develop 3D printed loop heat pipes as a low-cost, rapidly-manufacturable alternative technology to standard loop heat pipes for future high-performance small spacecraft. The wicks were built using laser powder bed fusion of standard 316L SS powder. The build parameters were varied by controlling a custom variable called the energy density to produce an assortment of wicks with different capillary metrics, i.e., porosity, permeability, and maximum pore radius. The variation in the capillary metrics, determined using a combination of capillary flow porometry and mercury intrusion porosimetry, was studied with respect to the energy density. The pore distribution was also studied by analyzing in detail the intrusion curves acquired during mercury intrusion porosimetry. The results from this study can serve as general guidelines for building future 3D printed wicks for loop heat pipes with the desired capillary performance.Item Advanced Passive Thermal Experiment for Hybrid Variable Conductance Heat Pipes and HiK™ Plates on the International Space Station(47th International Conference on Environmental Systems, 2017-07-16) Ababneh, Mohammed T.; Tarau, Calin; Anderson, William G.; Farmer, Jeffery T.; Alvarez-Hernandez, Angel R.; Ortega, StephaniaAs NASA prepares to further expand human and robotic presence in space, it is well known that spacecraft architectures will be challenged with unprecedented thermal environments in deep space. In addition, there is a need to extend the duration of the missions in both cold and hot environments, including cis-lunar and planetary surface excursions. The heat rejection turn–down ratio of the increased thermal loads in the above-mentioned conditions is crucial for minimizing vehicle resources (e.g. power). Therefore, future exploration activities will have the need of thermal management systems that can provide higher reliability and performance, and power and mass reduction. In an effort to start addressing the current technical gaps in thermal management systems, novel new passive thermal technologies have been selected to be included as part of suite of experiments to be tested on the board of the International Space Station (ISS), tentatively in 2017. Advanced Cooling Technologies, Inc. (ACT), together with NASA Marshall Space Flight Center and NASA Johnson Space Center, are working to test and validate hybrid wick VCHP with warm reservoir and HiK™ plates on the ISS under the Advanced Passive Thermal experiment (APTx) project. The APTx consists of two separate payloads that will be tested sequentially: • Payload 1 contains a VCHP/HiK™ plate assembly: a hybrid-wick copper-Monel-water VCHP design consists of a copper evaporator (with sintered wick inside), a monel adiabatic section and a condenser both with grooved wick inside and a NCG reservoir thermally and physically attached to the evaporator. In turn, the VCHP evaporator is mounted on an aluminum HiK™ plate. • Payload 2 contains a HiK™ plate and the ElectroWetting Heat Pipe (EWHP) experiment, developed by the University of Texas at Austin. This paper will cover the results to date for the flight test, which is planned for 2017.Item Development of Flight Demonstration Hot Reservoir Variable Conductance Heat Pipes for Microgravity Testing and Future Lunar Landers and Surface Systems(2023 International Conference on Environmental Systems, 2023-07-16) Lee, Kuan-Lin; Tarau, Calin; Abdelmaksoud, Ramy; Anderson, William G.; Kharangate, Chirag; Kamotani, YasuhiroThe lunar landers and rovers require a reliable tight passive thermal control technology due to their exposure to the ambient's harsh temperature conditions such as the lunar night where the temperature drops to about -280?F (-173.3?C) and lasts for a continuous 14-day period. Advanced Cooling Technologies Inc. (ACT) has devised and demonstrated a hot reservoir variable conductance heat pipe (HR-VCHP) to be an ideal passive variable thermal link between the payloads and the radiator for such lunar landers since HR-VCHP can offer much tighter thermal control capability when compared to a regular cold-biased reservoir VCHP. Under NASA Small Business Technology Transfer (STTR) program, ACT and Case Western Reserve University (CWRU) further matured this technology by introducing a novel fluid management feature that enables a non-condensable gas (NCG) flow to generate inside the device. This flow can maintain the moisture level of the reservoir and lead to more reliable VCHP operation in space. Two flight demonstration units (FDU) of HR-VCHPs with NCG flow are under development: one for microgravity testing on International Space Station (ISS) and another one for lunar lander thermal control applications. The FDU for microgravity testing is made from copper where the working fluid is water while the HR-VCHP for the future lunar landers is made from aluminum where the working fluid is ammonia or propylene. This paper will present a compact HR-VCHP prototype description, reliability testing results, and the development status of two FDUs.Item Hybrid Heat Pipes for Planetary Surface and High Heat Flux Applications(45th International Conference on Environmental Systems, 2015-07-12) Ababneh, Mohammed T.; Tarau, Calin; Anderson, William G.Novel hybrid wick Constant Conductance Heat Pipes (CCHPs) were developed to solve the high heat flux limitation for future highly integrated electronics. In addition to carrying power over long distances in space, the hybrid CCHP evaporator can also operate against an adverse tilt on the planetary surface for Lunar and Martian landers and rovers. These hybrid heat pipes will be capable of operating at the higher heat flux requirements expected in NASA’s future spacecraft and instruments such as on the next generation of polar rovers and equatorial landers. The thermal transport requirements for future spacecraft missions continue to increase, while at the same time the heat acquisition areas have trended downward, thereby increasing the incident heat flux from 5-10W/cm2 to the projected > 50W/cm2. This exceeds the performance of standard axial groove CCHPs and loop heat pipes (LHPs). Aluminum/ammonia and stainless steel/ammonia hybrid CCHPs to demonstrate high heat flux capability and for planetary (Lunar and Martian) rovers and landers were designed, fabricated and tested. The CCHPs had a sintered powder metal wick in the evaporator and axial grooves in the adiabatic and condenser regions The hybrid wick high heat flux aluminum/ammonia CCHP transported a heat load of 175 watts with heat flux input of 53W/cm2 at 0.1 inch adverse elevation. This demonstrates an improvement in heat flux capability of 3 times over the standard axial groove CCHP design. The hybrid wick high heat flux stainless steel/ammonia CCHP transported a heat load of 165 watts with heat flux input of 51W/cm2 at 0.1 inch adverse elevation. The Thermal Link planetary aluminum/ammonia CCHP transported approximately 202 watts at a 4.2° adverse inclination before dryout, exceeding the 150W target. Also the Thermal Link planetary aluminum/ammonia CCHP was tested for maximum transport power at three different adverse elevations to extrapolate zero-g power. The maximum power at zero-g is 288 watts, exceeding the 150W target. The X-ray micrographs for the interface between the sintered powder metal wick and the axial grooves in the stainless steel hybrid CCHP shows much better contact in comparison to the aluminum CCHP because of the successful internal sintering technique developed during this project.Item Launch Vehicle Avionics Passive Thermal Management(44th International Conference on Environmental Systems, 2014-07-13) Anderson, William G.; Corday, Cameron; DeChristopher, Mike; Hartenstine, John R.; Maxwell, Taylor; Schwendeman, Carl; Tarau, CalinA passive thermal management system was designed to cool avionics on a launch vehicle for 3 different thermal modes. Prior to launch, the heat sink for the avionics is purge duct flow. During the 10 minute launch period, the thermal energy is stored in phase change material (PCM). On orbit, the heat sink is a radiator. The system consists of 1. A high conductivity thermal shelf, 2. A PCM thermal storage system, 3. Heat pipes to conduct the heat from the shelf to the heat sinks, 4. Fins to reject the heat to the purge duct, and 5. A radiator to reject the heat on orbit. A unique aspect of the system design is the avionics shelf, which contains embedded heat pipes. While the electronics locations are fixed before manufacturing with encapsulated high conductivity material, this design allows the avionics boxes to be positioned anywhere. A second benefit is the much higher thermal effective thermal conductivity, which can approach 2500 W/m K in long systems. A low-cost, simplified version of the system to fabricated to verify the design during ground testing, consisting of the high conductivity plate, the heat pipe, and the purge duct sink. The general performance matched expectations, except that the overall ΔT was higher than expected, due to the thermal interface materials. This can be improved with a better material.Item Multiple Loop Heat Pipe Radiator for Variable Heat Rejection in Future Spacecraft(45th International Conference on Environmental Systems, 2015-07-12) Velson, Nathan Van; Tarau, Calin; DeChristopher, Mike; Anderson, William G.As NASA refocuses its human mission ambitions to colder areas of exploration beyond Low Earth Orbit, the need for improved variable heat rejection thermal control systems increases. To account for large variations in heat loads and environment temperatures, a thermal control system with a large turndown ratio is required. This paper presents a variable heat rejection system that uses multiple Loop Heat Pipes (LHPs) to reject large heat loads from a single-phase pumped loop, with high turndown ratios. A novel method of LHP control through local flow rate modulation of the single-phase fluid is developed and demonstrated. Systematic Thermal Desktop modeling of multiple LHP systems was performed to demonstrate the potential of this method. A modeled 2.5 kW three LHP system was shown to have a turndown ratio of 10:1 at a sink temperature of -41°C K and a turndown of 1.5:1 at a sink temperature of -269°C. Finally, an experimental study of a two-LHP system was performed to support the conclusions of the modeling effort.Item Two-Phase Thermal Switch for Spacecraft Passive Thermal Management(45th International Conference on Environmental Systems, 2015-07-12) Velson, Nathan Van; Tarau, Calin; Anderson, William G.Future manned and unmanned spacecraft will venture far beyond the relatively benign environment of low Earth orbit. The combination of extreme environments and high turndown requirements present a significant challenge for spacecraft thermal control systems. Thermal switches are among the thermal control devices that will be required to dissipate a wide range of heat loads in widely varying environments. A novel two-phase passive thermal switch technology has been developed and demonstrated. This technology uses the condensing vapor of a saturated two-phase working fluid to both transfer the heat and provide the contact pressure for the heat transfer surfaces of the switch. The switching mechanism is passively triggered by the temperature of the heat source. In addition to the On/Off capability of a thermal switch, the technology serves as a variable thermal link while in the On condition to maintain a heat source set point temperature. This set point temperature is determined by the design of the switch. In this paper, the principles of operation of the two-phase thermal switch are presented. A prototype switch was built and tested over a range of conditions. The set point temperature was determined for a range of enclosure gas counter pressures, and the maintenance of a heat source set point temperature is demonstrated. The performance of the unoptimized prototype switch is characterized and shown to have a nominal On thermal conductance of 0.7 W/K and an On/Off conductance ratio of 20.