摘要:

Space transportation systems require high‐performance thermal protection and fluid management techniques for systems ranging from cryogenic fluid management devices to primary structures and propulsion systems exposed to extremely high temperatures, as well as for other space systems such as cooling or environment control for advanced space suits and integrated circuits. Although considerable developmental effort is being expended to bring potentially applicable technologies to a readiness level for practical use, new and innovative methods are still needed. One such method is the concept ofAdvanced Micro Cooling Modules(AMCMs), which are essentially compact two‐phase heat exchangers constructed of microchannels and designed to remove large amounts of heat rapidly from critical systems by incorporating phase transition. The development of AMCMs requires fundamental technological advancement in many areas, including: (1) development of measurement methods/systems for flow‐pattern measurement/identification for two‐phase mixtures in microchannels; (2) development of a phenomenological model for two‐phase flow which includes the quantitative measure of flow patterns; and (3) database development for multiphase heat transfer/fluid dynamics flows in microchannels. This paper focuses on the results of experimental research in the phenomena of two‐phase flow in microchannels. The work encompasses both an experimental and an analytical approach to incorporating flow patterns for air‐water mixtures flowing in a microchannel, which are necessary tools for the optimal design of AMCMs. Specifically, the following topics are addressed: (1) design and construction of a sensitive test system for two‐phase flow in microchannels, one which measures ac and dc components of in‐situ physical mixture parameters including spatial concentration using concomitant methods; (2) data acquisition and analysis in the amplitude, time, and frequency domains; and (3) analysis of results including evaluation of data acquisition techniques and their validity for application in flow pattern determination. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649551

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The mass, power, and volume energy savings of two‐phase systems for future spacecraft creates many advantages over current single‐phase systems. Current models of two‐phase phenomena such as pressure drop, void fraction, and flow regime prediction are still not well defined for space applications. Commercially available two‐phase modeling software has been developed for a large range of acceleration fields including reduced‐gravity conditions. Recently, a two‐phase experiment has been flown to expand the two‐phase database. A model of the experiment was created in the software to determine how well the software could predict the pressure drop observed in the experiment. Of the simulations conducted, the computer model shows good agreement of the pressure drop in the experiment to within 30&percent;. However, the software does begin to over‐predict pressure drop in certain regions of a flow regime map indicating that some models used in the software package for reduced‐gravity modeling need improvement. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649552

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

In the temperature range of 450–700 K, there are currently no working fluids that have been validated for heat pipes and loop heat pipes, with the exception of water in the lower portion of the range. This paper reviews a number of potential working fluid including several organic fluids, mercury, sulfur/iodine, and halides. Physical property data are used where available, and estimated where unavailable using standard methods. The halide salts appear to possess attractive properties, with good liquid transport factors, and suitable vapor pressures. Where nuclear radiation is not a consideration, other potential working fluids are aniline, naphthalene, toluene, and phenol. The limited available life test data available suggests that toluene, naphthalene, and some of the halides are compatible with stainless steel, while the other fluids have not been tested. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649553

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Under a contract (No.F33615‐00‐C‐5009) with the U.S. Air Force Materials Lab, Cytec Carbon Fibers, LLC is conducting a program to identify high risk, high payoff thermal management applications for the insertion of high thermal conductivity carbon composite materials in future space and military aircraft. The program involves the identification of relevant design requirements, the design of components for thermal management applications utilizing the most appropriate high conductivity carbon composite material solution, the fabrication of prototype test articles, performance and characterization tests on the prototype articles, and test data correlation of measured results. The final step in the program requires end‐user acceptance or qualification testing of the designed components. Within this program, several different satellite and military aircraft thermal management applications have been selected and are currently in various stages of development. This paper will provide a summary list of the selected applications, a description of the thermal management materials employed, and a technical overview of some example projects. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649554

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

This paper presents a systematic analysis of fluid flow and heat transfer in a liquid hydrogen storage vessel for both earth and space applications. The study considered a cylindrical tank with elliptical top and bottom. The tank wall is made of aluminum and a multi‐layered blanket of cryogenic insulation (MLI) has been attached on the top of the aluminum. The tank is connected to a cryocooler to dissipate the heat leak through the insulation and tank wall into the fluid within the tank. The cryocooler has not been modeled; only the flow in and out of the tank to the cryocooler system has been included. The primary emphasis of this research has been the fluid circulation within the tank for different fluid distribution scenario and for different level of gravity to simulate potential earth and space based applications. The equations solved in the liquid region included the conservation of mass, conservation of energy, and conservation of momentum. For the solid region only the heat conduction equation was solved. The steady‐state velocity, temperature, and pressure distributions were calculated for different inlet positions, inlet velocities, and for different gravity values. The above simulations were carried out for constant heat flux and constant wall temperature cases. It was observed that a good flow circulation could be obtained when the cold entering fluid was made to flow in radial direction and the inlet opening was placed close to the tank wall. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649555

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Requirements for cooling and power consumption in space platforms are subject to significantly greater constraints than the requirements for terrestrial applications. Existing cooling systems incorporate various mechanisms including thermoelectric (Peltier) cooling elements, radiative cooling, and phase‐change compressor‐based systems. This paper outlines an alternative mechanism currently in development called “thermotunneling”. This mechanism exploits electron tunneling across a vacuum gap of ∼10nm to effect a temperature differential with high efficiency. When complete, these devices (“Cool Chips”) are expected to offer a compact, lightweight, low maintenance and highly efficient (in excess of 50&percent; of Carnot Efficiency) thermal management solution ideally suited for the needs of aerospace applications. This article was originally published with an incorrect list of authors which is now corrected. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649556

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Loop heat pipes (LHPs) have been extensively investigated and considered for the thermal control of satellites and other space equipments, but some geometric limitations, as well as the use of hazardous working fluids must be considered. Focusing on such concerns, a LHP was designed and built to accomplish certain requirements towards its future application in space missions. The designing procedure had to consider some limitations, such as a reduced scale capillary evaporator and the use of an alternative working fluid. Thus, an experimental LHP was built and tested for acetone as the working fluid to manage up to 70 W of heat transfer rate. The experimental results showed a good thermal management performance of the proposed LHP for the imposed limitations to its design. The proposed LHP presented to be a reliable thermal management device for applying in future space missions, especially when considering the use of a less hazardous working fluid. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649557

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The primary objective of the Mars Exploration Rover (MER) 2003 Project focused on the search for evidence of water on Mars. The launch of two identical flight systems occurred in June and July of 2003. The roving science vehicles are expected to land on the Martian surface in early and late January of 2004, respectively. The flight system design inherited many successfully features and approaches from the Mars Pathfinder Mission. This included the use of a mechanically‐pumped fluid loop, known as the Heat Rejection System (HRS), to transport heat from the Rover to radiators on the Cruise Stage during the quiescent trek to Mars. While the heritage of the HRS was evident, application of this system for MER presented unique and difficult challenges with respect to hardware implementation. We will discuss these hardware challenges in each HRS hardware element: the integrated pump assembly, cruise stage HRS, lander HRS, and Rover HRS. These challenges span the entire development cycle including fabrication, assembly, and test. We will conclude by citing the usefulness of this system during launch operations, where in particular, the flight hardware inside the Rover was thermally conditioned by the HRS since there was no other effective means of maintaining its temperature. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649558

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Future space nuclear power systems will require large radiators to dissipate excess thermal energy. Such radiators may be composed of carbon‐carbon composite fins made from high thermal conductivity graphite fibers or may be a more traditional honeycomb structure with face sheets composed of a suitable high temperature metal. In either case, the surface of the radiator must have a high emittance at the desired operating temperature, envisioned to be in the range of 400 to 900 K, and must be durable for the length of the mission, envisioned to be ten years. Existing thermal control paints and coatings may be applicable at the low end of the envisioned temperature range, but may not be applicable at elevated temperatures. Hence, other avenues of emittance enhancement need to be explored. Previous work has identified a number of promising technologies that may be useful for enhancing the emittance of candidate surfaces, including texturing the radiator surface via sand blasting, oxidation at elevated temperature, and exposure to atomic oxygen. This paper will review existing candidate thermal control paints and coatings to identify their strengths and weaknesses and will review other promising technologies that have been proposed in the past few years to enhance the emittance of radiator surfaces. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649559

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

If a conventional spacecraft propellant management device (PMD) of the screened channel type were employed with a cryogenic liquid, vapor bubbles generated within the channel by heat transfer could “dry out” the channel screens and thereby cause the channels to admit large amounts of vapor from the tank into the liquid outflow. This paper describes a new tapered channel design that passively ‘pumps’ bubbles away from the outlet port and vents them into the tank. A predictive mathematical model of the operating principle is presented and discussed. Scale‐model laboratory tests were conducted and the mathematical model agreed well with the measured rates of bubble transport velocity. Finally, an example of the use of the predictive model for a realistic spacecraft application is presented. The model predicts that bubble clearing rates are acceptable even in tanks up to 2 m in length. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649560

出版商:AIP    

年代:1904

数据来源: AIP