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Results for “Capillary Two-Phase System”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Modeling the use of a binary mixture as a control scheme for two-phase thermal systems

Two-phase thermal loops using mechanical pumps, capillary pumps, or a combination of the two have been chosen as the main heat transfer systems for the space station. For these systems to operate optimally, the flow rate in the loop should be controlled in response to the vapor/liquid ratio leaving the evaporator. By substituting a mixture of two non-azeotropic fluids in place of the single fluid normally used in these systems, it may be possible to monitor the temperature of the exiting vapor and determine the vapor/liquid ratio. The flow rate would then be adjusted to maximize the load capability with minimum energy input. A FLUINT model was developed to study the system dynamics of a hybrid capillary pumped loop using this type of control and was found to be stable under all the test conditions.

Benner, S. M.↗
NASA NTRS1985

Thermal management of high power space based systems

Conventional techniques of using a portion of the spacecraft skin for radiation of waste heat will be inadequate for high powered payloads (50 to 100 kWe) due to the lack of sufficient area. A Shuttle type system using a pumped single phase fluid loop could be scaled up to higher power but this type of system would require excessive pump power and weight. A pumped two-phase heat transfer loop has a much lower pumping requirement due to the higher latent heat of vaporization of the fluid in comparison to the sensible heat it can absorb through a temperature change. Concepts for an evaporator and a condenser for a pumped two-phase system are described. The condenser uses capillary grooves and a separate pumped condensate return line to achieve high heat transfer coefficients and stable operation due to the separation of the vapor and liquid flows. The cold plate evaporator uses wicks to contain the liquid and transport it to the heated surface. It can also function as a condenser for warming components. Control concepts for the cold plate are discussed. Concepts for deployment or erection of large space radiators are also considered.

Hwangbo, H.↗
NASA NTRS1983

Concept evaluation of four thermal utility systems for low orbit spacecraft

Attention is given to the design features and comparative performance of four two-phase heat transport systems under consideration by NASA as long term space mission devices for the collection, transportation and rejection of waste heat from spacecraft components over the zero-100 C temperature range. The system types are: a mechanically pumped two-phase loop, a capillary pumped loop, an osmotic pumped loop, and a loop employing a biomorph pump. The principal advantage of a capillary pumped loop is that it is a passive system with few moving parts that inherently possesses high reliability. The working fluid recommended for use in such a thermal utility is NH3, which has the requisite combination of high latent heat of vaporization and high surface tension.

Peterson, G. P.↗
NASA NTRS1987

Verification of an analytic modeler for capillary pump loop thermal control systems

A number of computer programs have been written to model two-phase heat transfer systems for space use. These programs support the design of thermal control systems and provide a method of predicting their performance in the wide range of thermal environments of space. Predicting the performance of one such system known as the capillary pump loop (CPL) is the intent of the CPL Modeler. By modeling two developed CPL systems and comparing the results with actual test data, the CPL Modeler has proven useful in simulating CPL operation. Results of the modeling effort are discussed, together with plans for refinements to the modeler.

Schweickart, R. B.↗
NASA NTRS1972

Closed-cycle power supply for fluidic control systems

Power supply utilizes small quantities of two-phase fluid of suitable thermodynamic properties for circulation in a capillary-pumped heat transfer loop. Fluid is vaporized in evaporator, passed through fluidic system load, condensed, pumped by multistage capillary pump, and returned to the evaporator.

Fiet, O.↗
NASA NTRS1990

Capillary Pumped Loop Modeler

Capillary Pumped Loop (CPL) Modeler computer program is amalgamation of software that mathematically models performance of CPL system and its environment. Two-phase heat-transport device capable of transferring heat loads efficiently over large distance with little temperature differential. Utilizes surface-tension forces established in fine-pore capillary wick to circulate working fluid, requiring no external pumpling power. Predicts steady-state or quasi-steady behavior of CPL embedded in spacecraft or other thermal environment. Also predicts location of liquid/vapor interface in each condenser. Written in VAX/VMS FORTAN 77.

Ku, Jentung↗
NASA NTRS1983

Thermal management system technology development for space station applications

A short discussion of the history to date of the NASA thermal management system technology development program is presented, and the current status of several ongoing studies and hardware demonstration tasks is reported. One element of technology that is required for long-life, high-power orbital platforms/stations that is being developed is heat rejection and a space-constructable radiator system. Aspects of this project include high-efficiency fin concepts, a heat pipe quick-disconnect device, high-capacity heat pipes, and an alternate interface heat exchanger design. In the area of heat acquisition and transport, developments in a pumped two-phase transport loop, a capillary pumped transport loop using the concept of thermal utility are reported. An example of a thermal management system concept is provided.

Rankin, J. G.↗
NASA NTRS1988

Pumped two-phase heat transfer loop

A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes several independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.

Edelstein, Fred↗
NASA NTRS1991

A Local Condensation Analysis Representing Two-phase Annular Flow in Condenser/radiator Capillary Tubes

NASA's effort for the thermal environmental control of the Space Station Freedom is directed towards the design, analysis, and development of an Active Thermal Control System (ATCS). A two phase, flow through condenser/radiator concept was baselined, as a part of the ATCS, for the radiation of space station thermal load into space. The proposed condenser rejects heat through direct condensation of ATCS working fluid (ammonia) in the small diameter radiator tubes. Analysis of the condensation process and design of condenser tubes are based on the available two phase flow models for the prediction of flow regimes, heat transfer, and pressure drops. The prediction formulas use the existing empirical relationships of friction factor at gas-liquid interface. An attempt is made to study the stability of interfacial waves in two phase annular flow. The formulation is presented of a stability problem in cylindrical coordinates. The contribution of fluid viscosity, surface tension, and transverse radius of curvature to the interfacial surface is included. A solution is obtained for Kelvin-Helmholtz instability problem which can be used to determine the critical and most dangerous wavelengths for interfacial waves.

Karimi, Amir↗
NASA NTRS1987

Pumped two-phase heat transfer loop

A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes a plurality of independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.

Edelstein, Fred↗
NASA NTRS1991

The enhanced capillary pumped loop flight experiment, a prototype of the EOS platform thermal control system

The CAPL shuttle flight experiment will provide micro-gravity verification of the prototype capillary pumped loop (CPL) thermal control system for EOS. The design of the experiment is discussed with particular emphasis on the new technology areas in ammonia two-phase reservoir design and heat pipe heat exchanger development. The thermal and hydrodynamic analysis techniques and results are also presented, including pressure losses, fluid flow, and on-orbit heat rejection capability. CAPL experiment results will be presented after the flight, currently planned for 1993.

Butler, D.↗
NASA NTRS1992

The Capillary Pumped Loop Flight Experiment (CAPL): A pathfinder for EOS

The CAPL shuttle flight experiment will provide microgravity verification of the prototype capillary pumped loop (CPL) thermal control system for EOS. The design of the experiment is discussed with particular emphasis on the new technology areas in ammonia two-phase reservior design and heat pipe heat exchanger development. The thermal and hydrodynamic analysis techniques and results are also presented, including pressure losses, fluid flow, and non-orbit heat rejection capability. CAPL experiment results will be presented after the flight, presently planned for 1993.

Butler, D.↗
NASA NTRS1988

A new linearized theory of laminar film condensation of two phase annular flow in a capillary pumped loop

Future large space based facilities, such as Space Station, will require energy management systems capable of transporting tens of kilowatts of heat over a hundred meters or more. This represents better than an order of magnitude improvement over current technology. Two-phase thermal systems are currently being developed to meet this challenge. Condensation heat transfer plays a very important role in this system. The present study attempts an analytic solution to the set of linearized partial differential equations. The axial velocity and temperature functions were found to be Bessel functions which have oscillatory behavior. This result agrees qualitatively with the experimental evidence from tests at both NASA Goddard Space Flight Center and elsewhere.

Hsu, Y. K.↗
NASA NTRS1986

Capillary pumped loop GAS and Hitchhiker flight experiments

Flight experiments of a capillary pumped loop (CPL) aboard the Space Shuttle on both the Get Away Special (GAS) and Hitchhiker-G (H/H-G) carriers are described. These tests have shown that a two-phase heat transfer loop utilizing a wicking material as the system pumping mechanism can operate successfully in a zero-g environment. The CPL operating modes demonstrated were start-up, heat load sharing/natural priming, liquid inventory and temperature control via the reservoir, dryout recovery, and isolation of a single pump deprime. Also investigated were high and low power limits, and inlet subcooling requirements. In these CPL flight experiments, successful system operation was demonstrated at input power levels up to 560 watts and inlet subcooling below 2 C.

Ku, J.↗
NASA NTRS1987

Investigation of thermal-fluid mechanical characteristics of the capillary pump and the pumped two-phase loop

This first semi-annual report summarized progress made on NASA Goddard Space Flight Center (GSFC) Grant NAG 5-834 during the period September 1, 1986 to February 28, 1987. The goal of the project is to gain a better understanding of the transient behavior of the Capillary Pump Loop (CPL) developed and tested by the GSFC. The investigation is directed toward development of analytical models to represent the transient thermal-fluid mechanic processes occurring in different parts of the CPL engineering model. Evaluation of the available test data has been the starting point for the investigation. Based on results of this evaluation, supplementary tests will be conducted by using a CPL test system already operational in the Heat Transfer laboratory of the university. Of particular interest is the oscillatory behavior of the CPL engineering model exhibited during some of the earlier test runs conducted at NASA-GSFC and Johnson Space Center (JSC).

Kiper, Ali M.↗
NASA NTRS1992

Advanced two-phase heat transfer systems

Future large spacecraft, such as the Earth Observing System (EOS) platforms, will require a significantly more capable thermal control system than is possible with current 'passive' technology. Temperatures must be controlled much more tightly over a larger surface area. Numerous heat load sources will often be located inside the body of the spacecraft without a good view to space. Power levels and flux densities may be higher than can be accommodated with traditional technology. Integration and ground testing will almost certainly be much more difficult with such larger, more complex spacecraft. For these and similar reasons, the Goddard Space Flight Center (GSFC) has been developing a new, more capable thermal control technology called capillary pumped loops (CPL's). CPL's represent an evolutionary improvement over heat pipes; they can transport much greater quantities of heat over much longer distances and can serve numerous heat load sources. In addition, CPL's can be fabricated into large cold plates that can be held to tight thermal gradients. Development of this technology began in the early 1980's and is now reaching maturity. CPL's have recently been baselined for the EOS-AM platform (1997 launch) and the COMET spacecraft (1992 launch). This presentation describes this new technology and its applications. Most of the viewgraphs are self descriptive. For those that are less clear additional comments are provided.

Swanson, Theodore D.↗
NASA NTRS1991

Two-Phase Bidirectional Heat Exchanger

Heat exchanger transfers heat from one two-phase thermal loop to another. Condenses vapor in one loop while evaporating liquid in other. Transfers heat with very small drops in temperature and pressure, and efficiently joins heat pipes thermally without mixing of their working fluids. Several such heat exchangers used to build long, complex multiloop heat-control systems. Exchanger bidirectional: transfers heat in reverse, condensing on normally evaporating side, and vice versa. Can warm equipment it normally cools, without using auxiliary heater. In reverse transfer, wicks on evaporating side supply liquid continuously by capillary action; reverse-flow pump not needed. Design modified for other working fluids and larger heat-transfer rates.

Kroliczek, Edward↗