SEARCH · Search NASA

Results for “CPL”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2

All sources NASA NTRS DOE OSTI

NASA NTRS1989

Testing of a controller for a hybrid capillary pumped loop thermal control system

A controller for a series hybrid capillary pumped loop (CPL) system that requires no moving parts does not resrict fluid flow has been tested and has demonstrated improved performance characteristics over a plain CPL system and simple hybrid CPL systems. These include heat load sharing, phase separation, self-regulated flow control and distribution, all independent of most system pressure drop. In addition, the controlled system demonstrated a greater heat transport capability than the simple CPL system but without the large fluid inventory requirement of the hybrid systems. A description of the testing is presented along with data that show the advantages of the system.

Schweickart, Russell↗

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 NTRS1998

An Experimental Study of Pressure Oscillation in a Capillary Pumped Loop with Multiple Evaporators and Condensers

The heat transport capability of a capillary pumped loop (CPL) is limited by the pressure drop that its evaporator wick can sustain. The pressure drop in a CPL is not constant even under seemingly steady operation, but rather exhibits an oscillatory behavior. A hydrodynamic theory based on a mass-spring-dashpot model was previously developed to predict the pressure oscillation in a CPL with a single evaporator and a single condenser. The theory states that the pressure oscillation is a function of physical dimensions of the CPL components and operating conditions. Experimental data agreed very well with theoretical predictions. The hydrodynamic stability theory has recently been extended to predict the pressure oscillations in CPLs with multiple evaporators and multiple condensers. Concurrently, an experimental study was conducted to verify the theory and to investigate the effects of various parameters on the pressure oscillation. Four evaporators with different wick properties were tested using a test loop containing two condenser plates. The test loop allowed the four evaporators to be tested in a single-pump, two-pump or four-pump configuration, and the two condenser plates to be plumbed either in parallel or in series. Test conditions included varying the power input, the reservoir set point temperature, the condenser sink temperature, and the flow resistance between the reservoir and the loop. Experimental results agreed well with theoretical predictions.

Ku, Jen-Tung↗

NASA NTRS1999

Overview of Loop Heat Pipe Operation

Loop heat pipes (LHP's) are two-phase heat transfer devices that utilize the evaporation and condensation of a working fluid to transfer heat, and the capillary forces developed in the porous wicks to circulate the fluid. The LHP was first developed in the former Soviet Union in the early 1980s, about the same time that the capillary pumped loop (CPL) was developed in the United States. The LHP is known for its high pumping capability and robust operation mainly due to the use of fine-pored metal wicks and an integral evaporator/hydro-accumulator design. The LHP technology is rapidly gaining acceptance in aerospace community. It is the baseline design for thermal control of several spacecraft, including NASA's GLAS and Chemistry, ESA's ATLID, CNES' STENTOR, RKA's OBZOR, and several commercial satellites. Numerous LHP papers have been published since the mid-1980's. Most papers presented test results and discussions on certain specific aspects of the LHP operation. LHP's and CPL's show many similarities in their operating principles and performance characteristics. However, they also display significant differences in many aspects of their operation. Some of the LHP behaviors may seem strange or mysterious, even to experienced CPL practitioners. The main purpose of this paper is to present a systematic description of the operating principles and thermal-hydraulic behaviors of LHP'S. LHP operating principles will be given first, followed by a description of the thermal-hydraulics involved in LHP operation. Operating characteristics and important parameters affecting the LHP operation will then be described in detail. Peculiar behaviors of the LHP, including temperature hysteresis and temperature overshoot during start-up, will be explained. For simplicity, most discussions will focus upon LHP's with a single evaporator and a single condenser, but devices with multiple evaporators and condensers will also be discussed. Similarities and differences between LHP's and CPL's will be addressed throughout the paper whenever appropriate.

Ku, Jentung↗

NASA NTRS2002

Airborne Lidar Measurements of Aerosol Optical Properties During SAFARI-2000

The Cloud Physics Lidar (CPL) operated onboard the NASA ER-2 high altitude aircraft during the SAFARI-2000 field campaign. The CPL provided high spatial resolution measurements of aerosol optical properties at both 1064 nm and 532 nm. We present here results of planetary boundary layer (PBL) aerosol optical depth analysis and profiles of aerosol extinction. Variation of optical depth and extinction are examined as a function of regional location. The wide-scale aerosol mapping obtained by the CPL is a unique data set that will aid in future studies of aerosol transport. Comparisons between the airborne CPL and ground-based MicroPulse Lidar Network (MPL-Net) sites are shown to have good agreement.

McGill, M. J.↗

NASA NTRS2002

Cloud Physics Lidar: Instrument Description and Initial Measurement Results

The Cloud Physics Lidar (CPL) is a new custom-built instrument for the NASA ER-2 high-altitude aircraft. The CPL can provide multiwavelength measurements of cirrus, subvisual cirrus, and aerosols with high temporal and spatial resolution. Its state-of-the-art technology gives it a high repetition rate, and photon-counting detection, and includes a low-pulse-energy laser. The CPL was first deployed at the Southern African Regional Science Initiative's 2000 field campaign during August and September 2000. This paper provides an overview of the instrument and initial data results to illustrate the measurement capability of the CPL.

McGill, Matthew↗

NASA NTRS2004

Classification of Particle Shapes from Lidar Depolarization Ratios in Convective Ice Clouds Compared to in situ Observations During CRYSTAL-FACE

This manuscript describes a method to class@ cirrus cloud ice particle shape using lidar depolarization measurements as a basis for segregating different particle shape regimes. Measurements from the ER-2 Cloud Physics Lidar (CPL) system during CRYSTAL-FACE provide the basis for this work. While the CPL onboard the ER-2 aircraft was providing remote sensing measurements of cirrus clouds, the Cloud Particle Imager (CPI) onboard the WB-57 aircraft was flying inside those same clouds to sample particle sizes. The results of classifying particle shapes using the CPL data are compared to the in situ measurements made using the CPI , and there is found to be good agreement between the particle shape inferred from the CPL data and that actually measured by the CPI. If proven practical, application of this technique to spaceborne observations could lead to large-scale classification of cirrus cloud particle shapes.

Noel, Vincent↗

NASA NTRS2004

Use of Probability Distribution Functions for Discriminating Between Cloud and Aerosol in Lidar Backscatter Data

In this paper we describe the algorithm hat will be used during the upcoming Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission for discriminating between clouds and aerosols detected in two wavelength backscatter lidar profiles. We first analyze single-test and multiple-test classification approaches based on one-dimensional and multiple-dimensional probability density functions (PDFs) in the context of a two-class feature identification scheme. From these studies we derive an operational algorithm based on a set of 3-dimensional probability distribution functions characteristic of clouds and aerosols. A dataset acquired by the Cloud Physics Lidar (CPL) is used to test the algorithm. Comparisons are conducted between the CALIPSO algorithm results and the CPL data product. The results obtained show generally good agreement between the two methods. However, of a total of 228,264 layers analyzed, approximately 5.7% are classified as different types by the CALIPSO and CPL algorithm. This disparity is shown to be due largely to the misclassification of clouds as aerosols by the CPL algorithm. The use of 3-dimensional PDFs in the CALIPSO algorithm is found to significantly reduce this type of error. Dust presents a special case. Because the intrinsic scattering properties of dust layers can be very similar to those of clouds, additional algorithm testing was performed using an optically dense layer of Saharan dust measured during the Lidar In-space Technology Experiment (LITE). In general, the method is shown to distinguish reliably between dust layers and clouds. The relatively few erroneous classifications occurred most often in the LITE data, in those regions of the Saharan dust layer where the optical thickness was the highest.

Liu, Zhaoyan↗

NASA NTRS2005

A Comparison of High Spectral Resolution Infrared Cloud-Top Pressure Altitude Algorithms Using S-HIS Measurements

This paper presents a comparison of cloud-top altitude retrieval methods applied to S-HIS (Scanning High Resolution Interferometer Sounder) measurements. Included in this comparison is an improvement to the traditional CO2 Slicing method. The new method, CO2 Sorting, determines optimal channel pairs to apply the CO2 Slicing. Measurements from collocated samples of the Cloud Physics Lidar (CPL) and Modis Airborne Simulator (MAS) instruments assist in the comparison. For optically thick clouds good correlation between the S-HIS and lidar cloud-top retrievals are found. For tenuous ice clouds there can be large differences between lidar (CPL) and S-HIS retrieved cloud-tops. It is found that CO2 Sorting significantly reduces the cloud height biases for the optically thin cloud (total optical depths less then 1.0). For geometrically thick but optically thin cirrus clouds large differences between the S-HIS infrared cloud top retrievals and the CPL detected cloud top where found. For these cases the cloud height retrieved by the S-HIS cloud retrievals correlated closely with the level the CPL integrated cloud optical depth was approximately 1.0.

Holz, Robert E.↗

NASA NTRS1986

Functional and performance tests of two capillary pumped loop engineering models

This paper presents the results of the functional and performance tests for two capillary pumped loop (CPL) engineering models. Both CPL systems are aluminum/ammonia transport systems which contain eight parallel evaporators and six parallel condensers in a single loop. Tests conducted include the transport limit, heat load shearing between evaporators, liquid inventory/temperature control by the reservoir, pressure priming under heat load, diode function of condensers, and isolation of a single deprimed evaporator. Consistent performance results were obtained for both systems. Transport capabilities of up to 70 kw-m with individual evaporators managing up to 1.7 kw, with a corresponding input heat flux of 15w/sq cm, were demonstrated. These tests demonstrated the ability of a CPL system to operate over a wide range of conditions and thus established the viability of these systems for high power thermal management of large spacecraft, such as the NASA Space Station.

Ku, J.↗

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 NTRS1986

Design of an advanced two-phase capillary cold plate

The functional principles and implementation of capillary pumped loop (CPL) two phase heat transport system for various elements of the Space Station program are described. Circulation of the working fluid by the surface-tension forces in a fine-pore capillary wick is the core principle of CPL systems. The liquid, usually NH3 at the moment, is changed into a vapor by heat absorption at one end of the loop, and the vapor is carrried back along the wick by the surface tension within the wick. NASA specifications and the results of mechanical and thermal tests for prototype cold plate and the capillary pump designs are outlined. The CPL is targeted for installation on free-flying platforms, attached payloads, and power subsystem thermal control systems.

Chalmers, D. R.↗

NASA NTRS1988

Exploratory study of temperature oscillations related to transient operation of a Capillary Pumped Loop heat pipe

An analytical study has been conducted for better understanding of a peculiar transient behavior which was displayed in testing of a Capillary Pumped Loop (CPL) heat pipe system. During several test runs of this CPL system varying degrees of surface temperature oscillations occurred in the inlet line of the evaporators. Although several theories have been forwarded to explain this observed phenomenon, a satisfactory understanding of causes of these oscillations is still missing. The present investigation derives the conditions which lead to such oscillatory temperature behavior in evaporator inlet section of the mentioned CPL system. Stability characteristics of these temperature oscillations were investigated.

Kiper, A. M.↗

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 NTRS1990

Development and integration of the capillary pumped loop GAS and Hitchhiker flight experiments

The Capillary Pumped Loop (CPL) is a thermal control system with high density heat acquisition and transport capability. A small spaceflight version of the CPL was built and flown as a GAS experiment on STS 51-D in April 1985 and STS 51-G in June 1985, and as a Hitchhiker-G experiment on STS 61-C in January 1986. The purpose of the experiments was to demonstrate the capability of a capillary pumped system under microgravity conditions for use in the thermal control of large scientific instruments, advanced orbiting spacecraft, and space station components. The development, integration, and test activities of the CPL are described.

Butler, D.↗

NASA NTRS1992

A prototype heat pipe heat exchanger for the capillary pumped loop flight experiment

A Capillary Pumped Two-Phase Heat Transport Loop (CAPL) Flight Experiment, currently planned for 1993, will provide microgravity verification of the prototype capillary pumped loop (CPL) thermal control system for EOS. CAPL employs a heat pipe heat exchanger (HPHX) to couple the condenser section of the CPL to the radiator assembly. A prototype HPHX consisting of a heat exchanger (HX), a header heat pipe (HHP), a spreader heat pipe (SHP), and a flow regulator has been designed and tested. The HX transmits heat from the CPL condenser to the HHP, while the HHP and SHP transport heat to the radiator assembly. The flow regulator controls flow distribution among multiple parallel HPHX's. Test results indicated that the prototype HPHX could transport up to 800 watts with an overall heat transfer coefficient of more than 6000 watts/sq m-deg C. Flow regulation among parallel HPHX's was also demonstrated.

Ku, Jentung↗

NASA NTRS1992

Two-phase/two-phase heat exchanger simulation analysis

The capillary pumped loop (CPL) system is one of the most desirable devices to dissipate heat energy in the radiation environment of the Space Station providing a relatively easy control of the temperature. A condenser, a component of the CPL system, is linked with a buffer evaporator in the form of an annulus section of a double tube heat exchanger arrangement: the concentric core of the double tube is the condenser; the annulus section is used as a buffer between the conditioned space and the radiation surrounding but works as an evaporator. A CPL system with this type of condenser is modeled to simulate its function numerically. Preliminary results for temperature variations of the system are shown and more investigations are suggested for further improvement.

Kim, Rhyn H.↗

NASA NTRS1994

Experimental and theoretical studies of capillary-pumped loop heat pipes

An experimental investigation of capillary-pumped loop (CPL) head pipes with single and multiple evaporators designed to develop and validate a computer model to predict the performance of CPL heat pipes over a wide range of conditions is discussed. The results of a literature search and review and a numerical study to determine the effects of geometric design parameters on the CPL heat pipe pressure drop and heat transfer characteristics are described. Vapor groove geometry and the use of circular versus rectangular evaporators were studied.

Obot, N. T.↗