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Sample records for pool boiling system

  1. Secondary pool boiling effects

    NASA Astrophysics Data System (ADS)

    Kruse, C.; Tsubaki, A.; Zuhlke, C.; Anderson, T.; Alexander, D.; Gogos, G.; Ndao, S.

    2016-02-01

    A pool boiling phenomenon referred to as secondary boiling effects is discussed. Based on the experimental trends, a mechanism is proposed that identifies the parameters that lead to this phenomenon. Secondary boiling effects refer to a distinct decrease in the wall superheat temperature near the critical heat flux due to a significant increase in the heat transfer coefficient. Recent pool boiling heat transfer experiments using femtosecond laser processed Inconel, stainless steel, and copper multiscale surfaces consistently displayed secondary boiling effects, which were found to be a result of both temperature drop along the microstructures and nucleation characteristic length scales. The temperature drop is a function of microstructure height and thermal conductivity. An increased microstructure height and a decreased thermal conductivity result in a significant temperature drop along the microstructures. This temperature drop becomes more pronounced at higher heat fluxes and along with the right nucleation characteristic length scales results in a change of the boiling dynamics. Nucleation spreads from the bottom of the microstructure valleys to the top of the microstructures, resulting in a decreased surface superheat with an increasing heat flux. This decrease in the wall superheat at higher heat fluxes is reflected by a "hook back" of the traditional boiling curve and is thus referred to as secondary boiling effects. In addition, a boiling hysteresis during increasing and decreasing heat flux develops due to the secondary boiling effects. This hysteresis further validates the existence of secondary boiling effects.

  2. Design and test of a compact optics system for the pool boiling experiment

    NASA Technical Reports Server (NTRS)

    Ling, Jerri S.; Laubenthal, James R.

    1990-01-01

    The experiment described seeks to improve the understanding of the fundamental mechanisms that constitute nucleate pool boiling. The vehicle for accomplishing this is an investigation, including tests to be conducted in microgravity and coupled with appropriate analyses, of the heat transfer and vapor bubble dynamics associated with nucleation, bubble growth/collapse and subsequent motion, considering the interrelations between buoyancy, momentum and surface tension which will govern the motion of the vapor and surrounding liquid, as a function of the heating rate at the heat transfer surface and the temperature level and distribution in the bulk liquid. The experiment is designed to be contained within the confines of a Get-Away-Special Canister (GAS Can) installed in the bay of the space shuttle. When the shuttle reaches orbit, the experiment will be turned on and testing will proceed automatically. In the proposed Pool Boiling Experiment a pool of liquid, initially at a precisely defined pressure and temperature, will be subjected to a step imposed heat flux from a semitransparent thin-film heater forming part of one wall of the container such that boiling is initiated and maintained for a defined period of time at a constant pressure level. Transient measurements of the heater surface and fluid temperatures near the surface will be made, noting especially the conditions at the onset of boiling, along with motion photography of the boiling process in two simultaneous views, from beneath the heating surface and from the side. The conduct of the experiment and the data acquisition will be completely automated and self-contained. For the initial flight, a total of nine tests are proposed, with three levels of heat flux and three levels of subcooling. The design process used in the development and check-out of the compact photographic/optics system for the Pool Boiling Experiment is documented.

  3. Pool Boiling Experiment Has Five Successful Flights

    NASA Technical Reports Server (NTRS)

    Chiaramonte, Fran

    1997-01-01

    The Pool Boiling Experiment (PBE) is designed to improve understanding of the fundamental mechanisms that constitute nucleate pool boiling. Nucleate pool boiling is a process wherein a stagnant pool of liquid is in contact with a surface that can supply heat to the liquid. If the liquid absorbs enough heat, a vapor bubble can be formed. This process occurs when a pot of water boils. On Earth, gravity tends to remove the vapor bubble from the heating surface because it is dominated by buoyant convection. In the orbiting space shuttle, however, buoyant convection has much less of an effect because the forces of gravity are very small. The Pool Boiling Experiment was initiated to provide insight into this nucleate boiling process, which has many earthbound applications in steamgeneration power plants, petroleum plants, and other chemical plants. In addition, by using the test fluid R-113, the Pool Boiling Experiment can provide some basic understanding of the boiling behavior of cryogenic fluids without the large cost of an experiment using an actual cryogen.

  4. Pool Boiling Experiment Has Successful Flights

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Pool Boiling Experiment (PBE) is designed to improve understanding of the fundamental mechanisms that constitute nucleate pool boiling. Nucleate pool boiling is a process wherein a stagnant pool of liquid is in contact with a surface that can supply heat to the liquid. If the liquid absorbs enough heat, a vapor bubble can be formed. This process occurs when a pot of water boils. On Earth, gravity tends to remove the vapor bubble from the heating surface because it is dominated by buoyant convection. In the orbiting space shuttle, however, buoyant convection has much less of an effect because the forces of gravity are very small. The Pool Boiling Experiment was initiated to provide insight into this nucleate boiling process, which has many Earthbound applications, such as steam-generation power plants, petroleum, and other chemical plants. Also, by using the test fluid R-113, the Pool Boiling Experiment can provide some basic understanding of the boiling behavior of cryogenic fluids without the large cost of an experiment using an actual cryogen.

  5. Conceptual design for spacelab pool boiling experiment

    NASA Technical Reports Server (NTRS)

    Lienhard, J. H.; Peck, R. E.

    1978-01-01

    A pool boiling heat transfer experiment to be incorporated with a larger two-phase flow experiment on Spacelab was designed to confirm (or alter) the results of earth-normal gravity experiments which indicate that the hydrodynamic peak and minimum pool boiling heat fluxes vanish at very low gravity. Twelve small sealed test cells containing water, methanol or Freon 113 and cylindrical heaters of various sizes are to be built. Each cell will be subjected to one or more 45 sec tests in which the surface heat flux on the heaters is increased linearly until the surface temperature reaches a limiting value of 500 C. The entire boiling process will be photographed in slow-motion. Boiling curves will be constructed from thermocouple and electric input data, for comparison with the motion picture records. The conduct of the experiment will require no more than a few hours of operator time.

  6. Visualization study on pool boiling heat transfer

    NASA Astrophysics Data System (ADS)

    Kamei, Shuya; Hirata, Masaru

    1991-04-01

    The visualized boiling phenomena were observed by means of high speed photographic shadowgraphy using a rotating prism camera (nac HIGH SPEED CAMERA model-16HD) with the speed of about 3500 frames per second. The photographs show that pool boiling heat transfer phenomena are varied for the boiling curve based on the experiments. Experiments have been carried out to investigate pool boiling heat transfer phenomena on a horizontal thin filament in subcooled and saturated distilled water. The experiments were performed for atmospheric pressure,for filament diameters of about 0.3 mm, for region of natural convection to film boiling. The color-film made by high speed movie camera are converted to high speed color video-tape. It is convenient to edit and show the tape for visualization with teaching the students. The high speed color video showed that the successive motion and shape of bubbles during their process of detachment varied with increasing heat flux on the heated surface of a filament. From these results, it was confirmed that the high speed phenomena of boiling by the slow motion video pictures could be estimated clearly.

  7. Electrohydrodynamic Pool Boiling in Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Shaw, Benjamin D.; Stahl, S. L.

    1996-01-01

    This research is concerned with studying the effects of applied electric fields on pool boiling in a reduced-gravity environment. Experiments are conducted at the NASA Lewis 2.2 sec Drop tower using a drop rig constructed at UC Davis. In the experiments, a platinum wire is heated while immersed in saturated liquid refrigerants (FC-72 and FC-87), or water, causing vapor formation at the wire surface. Electric fields are applied between the wire surface and an outer screen electrode that surrounds the wire. Preliminary normal-gravity experiments with water have demonstrated that applied electric fields generated by the rig electronics can influence boiling characteristics. Reduced-gravity experiments will be performed in the summer of 1996. The experiments will provide fundamental data on electric field strengths required to disrupt film boiling (for various wire heat generation input rates) in reduced gravity for a cylindrical geometry. The experiments should also shed light on the roles of characteristic bubble generation times and charge relaxation times in determining the effects of electric fields on pool boiling. Normal-gravity comparison experiments will also be performed.

  8. Steady State Vapor Bubble in Pool Boiling.

    PubMed

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C; Maroo, Shalabh C

    2016-02-03

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics.

  9. Steady State Vapor Bubble in Pool Boiling

    NASA Astrophysics Data System (ADS)

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.

    2016-02-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics.

  10. Steady State Vapor Bubble in Pool Boiling

    PubMed Central

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.

    2016-01-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics. PMID:26837464

  11. Water inventory management in condenser pool of boiling water reactor

    DOEpatents

    Gluntz, Douglas M.

    1996-01-01

    An improved system for managing the water inventory in the condenser pool of a boiling water reactor has means for raising the level of the upper surface of the condenser pool water without adding water to the isolation pool. A tank filled with water is installed in a chamber of the condenser pool. The water-filled tank contains one or more holes or openings at its lowermost periphery and is connected via piping and a passive-type valve (e.g., squib valve) to a high-pressure gas-charged pneumatic tank of appropriate volume. The valve is normally closed, but can be opened at an appropriate time following a loss-of-coolant accident. When the valve opens, high-pressure gas inside the pneumatic tank is released to flow passively through the piping to pressurize the interior of the water-filled tank. In so doing, the initial water contents of the tank are expelled through the openings, causing the water level in the condenser pool to rise. This increases the volume of water available to be boiled off by heat conducted from the passive containment cooling heat exchangers. 4 figs.

  12. Water inventory management in condenser pool of boiling water reactor

    DOEpatents

    Gluntz, D.M.

    1996-03-12

    An improved system for managing the water inventory in the condenser pool of a boiling water reactor has means for raising the level of the upper surface of the condenser pool water without adding water to the isolation pool. A tank filled with water is installed in a chamber of the condenser pool. The water-filled tank contains one or more holes or openings at its lowermost periphery and is connected via piping and a passive-type valve (e.g., squib valve) to a high-pressure gas-charged pneumatic tank of appropriate volume. The valve is normally closed, but can be opened at an appropriate time following a loss-of-coolant accident. When the valve opens, high-pressure gas inside the pneumatic tank is released to flow passively through the piping to pressurize the interior of the water-filled tank. In so doing, the initial water contents of the tank are expelled through the openings, causing the water level in the condenser pool to rise. This increases the volume of water available to be boiled off by heat conducted from the passive containment cooling heat exchangers. 4 figs.

  13. The bubble fossil record: insight into boiling nucleation using nanofluid pool-boiling

    NASA Astrophysics Data System (ADS)

    Huitink, David; Ontiveros, Elvis Efren Dominguez; Hassan, Yassin

    2012-02-01

    Subcooled pool boiling of Al2O3/water nanofluid (0.1 vol%) was investigated. Scanning electron microscopy and energy dispersive X-ray spectroscopy were used to observe surface features of the wire heater where nanoparticles had deposited. A layer of aggregated alumina particles collected on the heated surface, where evidence of fluid shear associated with bubble nucleation and departure was "fossilized" in the fluidized nano-porous surface coating. These structures contain evidence of the fluid forces present in the microlayer prior to departure and provide a unique understanding of boiling phenomena. A unique mode of heat transfer was identified in nanofluid pool boiling.

  14. A fundamental study of nucleate pool boiling under microgravity

    NASA Technical Reports Server (NTRS)

    Ervin, Jamie S.; Merte, Herman, Jr.

    1991-01-01

    An experimental study of incipient boiling in short-term microgravity and with a/g = +/- 1 for pool boiling was performed. Calibrated thin gold films sputtered on a smoothly polished quartz surface were used simultaneously for thermal resistance measurements and heating of the boiling surface. The gold films were used for both transient and quasi-steady heating surface temperature measurements. Two test vessels were constructed for precise measurement and control of fluid temperature and pressure: a laboratory pool boiling vessel for the a/g = +/- experiments and a pool boiling vessel designed for the 131 m free-fall in the NASA Lewis Research Center Microgravity Research Facility for the microgravity tests. Measurements included the heater surface temperature, the pressure near the heating surface, and the bulk liquid temperatures. High speed photography was used in the experiments. With high quality microgravity and the measured initial temperature of the quiescent test fluid, R113, the temperature distribution in the liquid at the moment of boiling inception resulting from an imposed step in heat flux is known with a certainty not possible previously. The types of boiling propagation across the large flat heating surface are categorized; the conditions necessary for their occurrence are described. Explosive boiling propagation with a striking pattern of small scale protuberances over the entire vapor mass periphery not observed previously at low heat flux levels is described. For the heater surface with a/g = -1, a step in the heater surface temperature of short duration was imposed. The resulting liquid temperature distribution at the moment of boiling inception was different from that obtained with a step in heat flux.

  15. A Fundamental Study of Nucleate Pool Boiling Under Microgravity

    NASA Technical Reports Server (NTRS)

    Ervin, Jamie S.; Merte, Herman, Jr.

    1996-01-01

    An experimental study of incipient boiling in short-term microgravity and with a/g = +/- 1 for pool boiling was performed. Calibrated thin gold films sputtered on a smoothly polished quartz surface were used simultaneously for thermal-resistance measurements and heating of the boiling surface. The gold films were used for both transient and quasi-steady heating surface temperature measurements. Two test vessels were constructed for precise measurement and control of fluid temperature and pressure: a laboratory pool boiling vessel for the a/g = +/- 1 experiments and a pool boiling vessel designed for the 131 m free-fall in the NASA Lewis Research Center Microgravity Research Facility for the microgravity tests. Measurements included the heater surface temperature, the pressure near the heating surface, the bulk liquid temperatures. High speed photography (up to 1,000 frames per second) was used in the experiments. With high quality microgravity and the measured initial temperature of the quiescent test fluid, R113, the temperature distribution in the liquid at the moment of boiling inception resulting from an imposed step in heat flux is known with a certainty not possible previously. The types of boiling propagation across the large flat heating surface, some observed here for the first time, are categorized; the conditions necessary for their occurrence are described. Explosive boiling propagation with a striking pattern of small scale protuberances over the entire vapor mass periphery not observed previously at low heat flux levels (on the order of 5 W/cm(exp 2)) is described. For the heater surface with a/g = -1, a step in the heater surface temperature of short duration was imposed. The resulting liquid temperature distribution at the moment of boiling inception was different from that obtained with a step in heat flux.

  16. Pool and flow boiling in variable and microgravity

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1994-01-01

    As is well known, boiling is an effective mode of heat transfer in that high heat flux levels are possible with relatively small temperature differences. Its optimal application requires that the process be adequately understood. A measure of the understanding of any physical event lies in the ability to predict its behavior in terms of the relevant parameters. Despite many years of research the predictability of boiling is currently possible only for quite specialized circumstances, e.g., the critical heat flux and film boiling for the pool boiling case, and then only with special geometries. Variable gravity down to microgravity provides the opportunity to test this understanding, but possibly more important, by changing the dimensional and time scales involved permits more detailed observations of elements involved in the boiling process, and perhaps discloses phenomena heretofore unknown. The focus here is on nucleate boiling although, as will be demonstrated below, under but certain circumstances in microgravity it can take place concurrently with the dryout process. In the presence of earth gravity or forced convection effects, the latter process is usually referred to as film boiling. However, no vapor film as such forms with pool boiling in microgravity, only dryout. Initial results are presented here for pool boiling in microgravity, and were made possible at such an early date by the availability of the Get-Away-Specials (GAS). Also presented here are some results of ground testing of a flow loop for the study of low velocity boiling, eventually to take place also in microgravity. In the interim, variable buoyancy normal to the heater surface is achieved by rotation of the entire loop relative to earth gravity. Of course, this is at the expense of varying the buoyancy parallel to the heater surface. Two questions which must be resolved early in the study of flow boiling in microgravity are (1) the lower limits of liquid flow velocity where buoyancy

  17. Gravity and Heater Size Effects on Pool Boiling Heat Transfer

    NASA Technical Reports Server (NTRS)

    Kim, Jungho; Raj, Rishi

    2014-01-01

    The current work is based on observations of boiling heat transfer over a continuous range of gravity levels between 0g to 1.8g and varying heater sizes with a fluorinert as the test liquid (FC-72/n-perfluorohexane). Variable gravity pool boiling heat transfer measurements over a wide range of gravity levels were made during parabolic flight campaigns as well as onboard the International Space Station. For large heaters and-or higher gravity conditions, buoyancy dominated boiling and heat transfer results were heater size independent. The power law coefficient for gravity in the heat transfer equation was found to be a function of wall temperature under these conditions. Under low gravity conditions and-or for smaller heaters, surface tension forces dominated and heat transfer results were heater size dependent. A pool boiling regime map differentiating buoyancy and surface tension dominated regimes was developed along with a unified framework that allowed for scaling of pool boiling over a wide range of gravity levels and heater sizes. The scaling laws developed in this study are expected to allow performance quantification of phase change based technologies under variable gravity environments eventually leading to their implementation in space based applications.

  18. Electrical design of payload G-534: The Pool Boiling Experiment

    NASA Technical Reports Server (NTRS)

    Francisco, David R.

    1992-01-01

    Payload G-534, the Pool Boiling Experiment (PBE), is a Get Away Special that is scheduled to fly on the shuttle in 1992. This paper will give a brief overall description of the experiment with the main discussion being the electrical design with a detailed description of the power system and interface to the GAS electronics. The batteries used and their interface to the experiment Power Control Unit (PCU) and GAS electronics will be examined. The design philosophy for the PCU will be discussed in detail. The criteria for selection of fuses, relays, power semiconductors and other electrical components along with grounding and shielding policy for the entire experiment will be presented. The intent of this paper is to discuss the use of military tested parts and basic design guidelines to build a quality experiment for minimal additional cost.

  19. Transient nucleate pool boiling in microgravity: Some initial results

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.; Lee, H. S.; Ervin, J. S.

    1994-01-01

    Variable gravity provides an opportunity to test the understanding of phenomena which are considered to depend on buoyancy, such as nucleate pool boiling. The active fundamental research in nucleate boiling has sought to determine the mechanisms or physical processes responsible for its high effectiveness, manifested by the high heat flux levels possible with relatively low temperature differences. Earlier research on nucleate pool boiling at high gravity levels under steady conditions demonstrated quantitatively that the heat transfer is degraded as the buoyancy normal to the heater surfaced increases. Correspondingly, it was later shown, qualitatively for short periods of time only, that nucleate boiling heat transfer is enhanced as the buoyancy normal to the heater surface is reduced. It can be deduced that nucleate pool boiling can be sustained as a quasi-steady process provided that some means is available to remove the vapor generated from the immediate vicinity of the heater surface. One of the objectives of the research, the initial results of which are presented here, is to quantify the heat transfer associated with boiling in microgravity. Some quantitative results of nucleate pool boiling in high quality microgravity (a/g approximately 10(exp -5)) of 5s duration, obtained in an evacuated drop tower, are presented here. These experiments were conducted as precursors of longer term space experiments. A transient heating technique is used, in which the heater surface is a transparent gold film sputtered on a qua rtz substrate, simultaneously providing the mean surface temperature from resistance thermometry and viewing of the boiling process both from beneath and across the surface. The measurement of the transient mean heater surface temperature permits the computation, by numerical means, of the transient mean heat transfer coefficient. The preliminary data obtained demonstrates that a quasi-steady boiling process can occur in microgravity if the bulk

  20. Assessment of a magnet system combining the advantages of cable-in-conduit forced-flow and pool-boiling magnets

    SciTech Connect

    Slack, D.; Hassenzahl, W.; Felker, B.; Chaplin, M.

    1993-10-06

    This paper presents an idea for a magnet system that could be used to advantage in tokamaks and other fusion engineering devices. Higher performance designs, specifically newer tokamaks such as those for the international Tokamak Engineering Reactor (ITER) and Tokamak Physics Experiment (TPX) use Cable in Conduit Conductor (CICC) forced flow coils to advantage to meet field and current density requirements. Pool boiling magnets lack structural integrity to resist high magnetic forces since helium cooling areas must surround each conductor. A second problem is that any leak can threaten the voltage standoff integrity of the magnet system. This is because a leak can result in low-pressure helium gas becoming trapped by limited conductance in the magnet bundle and low-pressure helium has poor dielectric strength. The system proposed here is basically a CICC system, with it`s inherent advantages, but bathed in higher pressure supercritical helium to eliminate the leak and voltage break-down problems. Schemes to simplify helium coolant plumbing with the proposed system are discussed. A brief historical review of related magnet systems is included. The advantages and disadvantages of using higher pressure, supercritical helium in combination with solid electrical insulation in a CICC system are discussed. Related electrical data from some previous works are compiled and discussed.

  1. Infrared thermometry study of nanofluid pool boiling phenomena

    PubMed Central

    2011-01-01

    Infrared thermometry was used to obtain first-of-a-kind, time- and space-resolved data for pool boiling phenomena in water-based nanofluids with diamond and silica nanoparticles at low concentration (<0.1 vol.%). In addition to macroscopic parameters like the average heat transfer coefficient and critical heat flux [CHF] value, more fundamental parameters such as the bubble departure diameter and frequency, growth and wait times, and nucleation site density [NSD] were directly measured for a thin, resistively heated, indium-tin-oxide surface deposited onto a sapphire substrate. Consistent with other nanofluid studies, the nanoparticles caused deterioration in the nucleate boiling heat transfer (by as much as 50%) and an increase in the CHF (by as much as 100%). The bubble departure frequency and NSD were found to be lower in nanofluids compared with water for the same wall superheat. Furthermore, it was found that a porous layer of nanoparticles built up on the heater surface during nucleate boiling, which improved surface wettability compared with the water-boiled surfaces. Using the prevalent nucleate boiling models, it was possible to correlate this improved surface wettability to the experimentally observed reductions in the bubble departure frequency, NSD, and ultimately to the deterioration in the nucleate boiling heat transfer and the CHF enhancement. PMID:21711754

  2. Infrared thermometry study of nanofluid pool boiling phenomena.

    PubMed

    Gerardi, Craig; Buongiorno, Jacopo; Hu, Lin-Wen; McKrell, Thomas

    2011-03-16

    Infrared thermometry was used to obtain first-of-a-kind, time- and space-resolved data for pool boiling phenomena in water-based nanofluids with diamond and silica nanoparticles at low concentration (<0.1 vol.%). In addition to macroscopic parameters like the average heat transfer coefficient and critical heat flux [CHF] value, more fundamental parameters such as the bubble departure diameter and frequency, growth and wait times, and nucleation site density [NSD] were directly measured for a thin, resistively heated, indium-tin-oxide surface deposited onto a sapphire substrate. Consistent with other nanofluid studies, the nanoparticles caused deterioration in the nucleate boiling heat transfer (by as much as 50%) and an increase in the CHF (by as much as 100%). The bubble departure frequency and NSD were found to be lower in nanofluids compared with water for the same wall superheat. Furthermore, it was found that a porous layer of nanoparticles built up on the heater surface during nucleate boiling, which improved surface wettability compared with the water-boiled surfaces. Using the prevalent nucleate boiling models, it was possible to correlate this improved surface wettability to the experimentally observed reductions in the bubble departure frequency, NSD, and ultimately to the deterioration in the nucleate boiling heat transfer and the CHF enhancement.

  3. Infrared thermometry study of nanofluid pool boiling phenomena

    NASA Astrophysics Data System (ADS)

    Gerardi, Craig; Buongiorno, Jacopo; Hu, Lin-Wen; McKrell, Thomas

    2011-12-01

    Infrared thermometry was used to obtain first-of-a-kind, time- and space-resolved data for pool boiling phenomena in water-based nanofluids with diamond and silica nanoparticles at low concentration (<0.1 vol.%). In addition to macroscopic parameters like the average heat transfer coefficient and critical heat flux [CHF] value, more fundamental parameters such as the bubble departure diameter and frequency, growth and wait times, and nucleation site density [NSD] were directly measured for a thin, resistively heated, indium-tin-oxide surface deposited onto a sapphire substrate. Consistent with other nanofluid studies, the nanoparticles caused deterioration in the nucleate boiling heat transfer (by as much as 50%) and an increase in the CHF (by as much as 100%). The bubble departure frequency and NSD were found to be lower in nanofluids compared with water for the same wall superheat. Furthermore, it was found that a porous layer of nanoparticles built up on the heater surface during nucleate boiling, which improved surface wettability compared with the water-boiled surfaces. Using the prevalent nucleate boiling models, it was possible to correlate this improved surface wettability to the experimentally observed reductions in the bubble departure frequency, NSD, and ultimately to the deterioration in the nucleate boiling heat transfer and the CHF enhancement.

  4. Environmental qualification testing of the prototype pool boiling experiment

    NASA Technical Reports Server (NTRS)

    Sexton, J. Andrew

    1992-01-01

    The prototype Pool Boiling Experiment (PBE) flew on the STS-47 mission in September 1992. This report describes the purpose of the experiment and the environmental qualification testing program that was used to prove the integrity of the prototype hardware. Component and box level vibration and thermal cycling tests were performed to give an early level of confidence in the hardware designs. At the system level, vibration, thermal extreme soaks, and thermal vacuum cycling tests were performed to qualify the complete design for the expected shuttle environment. The system level vibration testing included three axis sine sweeps and random inputs. The system level hot and cold soak tests demonstrated the hardware's capability to operate over a wide range of temperatures and gave the project team a wider latitude in determining which shuttle thermal altitudes were compatible with the experiment. The system level thermal vacuum cycling tests demonstrated the hardware's capability to operate in a convection free environment. A unique environmental chamber was designed and fabricated by the PBE team and allowed most of the environmental testing to be performed within the project's laboratory. The completion of the test program gave the project team high confidence in the hardware's ability to function as designed during flight.

  5. Evaluation of commercial enhanced tubes in pool boiling: Topical report

    SciTech Connect

    Jung, C.; Bergles, A.E.

    1989-03-01

    In support of a study of shellside boiling with enhanced tubes, a pool boiling apparatus was developed and used to test single tubes with various structured boiling surfaces in R-113. The basic design of the tube-bundle test section was carried out and certain critical design features were tested experimentally. Copper tubes, 3/4 in. o.d. and 4 in. long, were selected with 1/4 in. diameter cartridge heaters. Four thermocouples were inserted in 3/32 in. diameter, 2 in. long holes. The pool boiling characteristics of a plain tube agree well with previous tests. Wolverine Turbo-B tubes with small, medium, and large features performed identically for a heat flux greater than 20 kW/m/sup 2/. For lower heat flux, however, the Turbo-B S was slightly superior. In general, the Wolverine Turbo-B tubes had more favorable boiling characteristics than the single Wieland Gewa-T tube that was tested. The test procedure is deemed entirely adequate for screening enhanced tubes to see which ones should be used in the tube-bundle test section. Three different ways of mounting the tubes were tested in R-113 at 65/degree/C and 5 bar gage pressure. As all three constructions sealed well, the simplest design is recommended in which a snap ring fixes the tube to the wall and an O-ring seals against the pressure. The general design features of the tube bundle test chamber are also presented. 14 refs.

  6. Nucleate pool boiling in the long duration low gravity environment of the Space Shuttle

    NASA Technical Reports Server (NTRS)

    Hasan, M. M.; Lin, C. S.; Knoll, R. H.; Bentz, M. D.; Meserole, J. S.

    1993-01-01

    The results are presented of an experimental study of nucleate pool boiling performed in the low gravity environment of the space shuttle. Photographic observations of pool boiling in Freon 113 were obtained during the 'Tank Pressure Control Experiment,' flown on the Space Transportation System, STS-43 in August 1991. Nucleate boiling data from large (relative to bubble size) flat heating surfaces (0.1046 by 0.0742 m) was obtained at very low heat fluxes (0.22 to 1.19 kW/sq m). The system pressure and the bulk liquid subcooling varied in the range of 40 to 60 kPa and 3 to 5 C respectively. Thirty-eight boiling tests, each of 10-min duration for a given heat flux, were conducted. Measurements included the heater power, heater surface temperature, the liquid temperature and the system pressure as functions of heating time. Video data of the first 2 min of heating was recorded for each test. In some tests the video clearly shows the inception of boiling and the growth and departure of bubbles from the surface during the first 2 min of heating. In the absence of video data, the heater temperature variation during heating shows the inception of boiling and stable nucleate boiling. During the stable nucleate boiling, the wall superheat varied between 2.8 to 3.8 C for heat fluxes in the range of 0.95 to 1.19 kW/sq m. The wall superheat at the inception of boiling varied between 2 to 13 C.

  7. Effect of surface properties on nucleate pool boiling

    SciTech Connect

    Haze, Ikuya; Tomemori, Hideki; Motoya, Daiju; Osakabe, Masahiro

    1999-07-01

    A series of experiments on nucleate pool boiling was performed by use of an oxygen-free copper rod and platinum wires of different surface properties under both normal gravity condition and microgravity condition. As a result of the experiments, under normal gravity condition, the bubbling on thick cracked silicone-coated surfaces and that on scale surfaces were more vigorous than that on mirror-finished (copper) surfaces, that on bare (Pt) surfaces, that on thin silicone-coated surfaces and that on thick silicone-coated surfaces. The boiling curves on the mirror-finished surface, the bare surface, the thin silicone-coated surface and the thick cracked silicone-coated surface were equal to those predicted by the Rohsenow's correlation. The superheats on the thick silicone-coated surface and the scale surface were larger than those predicted by the Rohsenow's correlation. The boiling curves on the non-cracked silicone-coated surface and the scale surface corrected by those heat resistance were equal to those predicted by the Rohsenow's correlation. The superheat on the thick silicone-coated surface corrected by its heat resistance was smaller than that predicted by the Rohsenow's correlation. The thick cracked silicone-coated surface enhanced the nucleate boiling heat transfer. On the other hand, under microgravity condition, the bubbles stayed around heated surfaces except scale surfaces. The boiling curve on the bare surface under microgravity condition was equal to that under normal gravity condition. The effect of surface properties on the nucleate boiling heat transfer under microgravity condition was equal to that under normal gravity condition.

  8. HORIZONTAL BOILING REACTOR SYSTEM

    DOEpatents

    Treshow, M.

    1958-11-18

    Reactors of the boiling water type are described wherein water serves both as the moderator and coolant. The reactor system consists essentially of a horizontal pressure vessel divided into two compartments by a weir, a thermal neutronic reactor core having vertical coolant passages and designed to use water as a moderator-coolant posltioned in one compartment, means for removing live steam from the other compartment and means for conveying feed-water and water from the steam compartment to the reactor compartment. The system further includes auxiliary apparatus to utilize the steam for driving a turbine and returning the condensate to the feed-water inlet of the reactor. The entire system is designed so that the reactor is self-regulating and has self-limiting power and self-limiting pressure features.

  9. A New Theory of Nucleate Pool Boiling in Arbitrary Gravity

    NASA Technical Reports Server (NTRS)

    Buyevich, Y. A.; Webbon, Bruce W.

    1995-01-01

    Heat transfer rates specific to nucleate pool boiling under various conditions are determined by the dynamics of vapour bubbles that are originated and grow at nucleation sites of a superheated surface. A new dynamic theory of these bubbles has been recently developed on the basis of the thermodynamics of irreversible processes. In contrast to other existing models based on empirically postulated equations for bubble growth and motion, this theory does not contain unwarrantable assumptions, and both the equations are rigorously derived within the framework of a unified approach. The conclusions of the theory are drastically different from those of the conventional models. The bubbles are shown to detach themselves under combined action of buoyancy and a surface tension force that is proven to add to buoyancy in bubble detachment, but not the other way round as is commonly presumed. The theory ensures a sound understanding of a number of so far unexplained phenomena, such as effect caused by gravity level and surface tension on the bubble growth rate and dependence of the bubble characteristics at detachment on the liquid thermophysical parameters and relevant temperature differences. The theoretical predictions are shown to be in a satisfactory qualitative and quantitative agreement with observations. When being applied to heat transfer at nucleate pool boiling, this bubble dynamic theory offers an opportunity to considerably improve the main formulae that are generally used to correlate experimental findings and to design boiling heat removal in various industrial applications. Moreover, the theory makes possible to pose and study a great deal of new problems of essential impact in practice. Two such problems are considered in detail. One problem concerns the development of a principally novel physical model for the first crisis of boiling. This model allows for evaluating critical boiling heat fluxes under various conditions, and in particular at different

  10. Pool boiling from rotating and stationary spheres in liquid nitrogen

    NASA Technical Reports Server (NTRS)

    Cuan, Winston M.; Schwartz, Sidney H.

    1988-01-01

    Results are presented for a preliminary experiment involving saturated pool boiling at 1 atm from rotating 2 and 3 in. diameter spheres which were immersed in liquid nitrogen (LN2). Additional results are presented for a stationary, 2 inch diameter sphere, quenched in LN2, which were obtained utilizing a more versatile and complete experimental apparatus that will eventually be used for additional rotating sphere experiments. The speed for the rotational tests was varied from 0 to 10,000 rpm. The stationary experiments parametrically varied pressure and subcooling levels from 0 to 600 psig and from 0 to 50 F, respectively. During the rotational tests, a high speed photographic analysis was undertaken to measure the thickness of the vapor film surrounding the sphere. The average Nusselt number over the cooling period was plotted against the rotational Reynolds number. Stationary sphere results included local boiling heat transfer coefficients at different latitudinal locations, for various pressure and subcooling levels.

  11. Characteristics of Pool Boiling on Graphite-Copper Composite Surfaces

    NASA Technical Reports Server (NTRS)

    Zhang, Nengli; Chao, David F.; Yang, Wen-Jei

    2002-01-01

    Nucleate pool boiling performance of different liquids on graphite-copper composite (Gr-Cu) surfaces has been experimentally studied and modeled. Both highly wetting fluids, such as freon-113 and pentane, and a moderately wetting fluid (water) were tested on the Gr-Cu surfaces with different graphite-fiber volume fractions to reveal the enhancement effects of the composite surfaces on the nucleate pool boiling. Results of the experiments show that the graphite-fiber volume fraction has an optimum value. The Gr-Cu composite surface with 25 percent graphite-fiber volume (f=0.25) has a maximum enhancement effect on the nucleate boiling heat transfer comparing to the pure copper surface. For the highly wetting fluid, the nucleate boiling heat transfer is generally enhanced on the Gr- Cu composite surfaces by 3 to 6 times shown. In the low heat flux region, the enhancement is over 6 times, but in the high heat flux region, the enhancement is reduced to about 40%. For the moderately wetting fluid (water), stronger enhancement of nucleate boiling heat transfer is achieved on the composite surface. It shown the experimental results in which one observes the nucleate boiling heat transfer enhancement of 5 to 10 times in the low heat flux region and an enhancement of 3 to 5 times in the high heat flux region. Photographs of bubble departure during the initial stage of nucleate boiling indicate that the bubbles detached from the composite surface are much smaller in diameter than those detached from the pure copper surface. Typical photographs are presented.It shows that the bubbles departed from the composite surface have diameters of only O(0.1) mm, while those departed from the pure copper surface have diameters of O(1) mm. It is also found that the bubbles depart from the composite surface at a much higher frequency, thus forming vapor columns. These two phenomena combined with high thermal conductivity of the graphite fiber are considered the mechanisms for such a

  12. Subcooled pool boiling on thin wire in microgravity

    NASA Astrophysics Data System (ADS)

    Zhao, J. F.; Wan, S. X.; Liu, G.; Yan, N.; Hu, W. R.

    2009-01-01

    A new set of experimental data of subcooled pool boiling on a thin wire in microgravity aboard the 22nd Chinese recoverable satellite is reported in the present paper. The temperature-controlled heating method is used. The results of the experiments in normal gravity before and after the flight experiment are also presented, and compared with those in microgravity. The working fluid is degassed R113 at 0.1 MPa and subcooled by 26C nominally. A thin platinum wire of 60μm in diameter and 30 mm in length is simultaneously used as heater and thermometer. It is found that the heat transfer of nucleate pool boiling is slightly enhanced in microgravity comparing with those in normal gravity. It is also found that the correlation of Lienhard and Dhir can predict the CHF with good agreement, although the range of the dimensionless radius is extended by three or more decades above the originally set limit. Three critical bubble diameters are observed in microgravity, which divide the observed vapor bubbles into four regimes with different sizes. Considering the Marangoni effect, a qualitative model is proposed to reveal the mechanism underlying the bubble departure processes, and a quantitative agreement can also be acquired.

  13. A depletable micro-layer model for nucleate pool boiling

    NASA Astrophysics Data System (ADS)

    Sato, Yohei; Niceno, Bojan

    2015-11-01

    A depletable micro-layer model has been developed for the simulation of nucleate pool boiling within the framework of Computational Fluid Dynamics (CFD) modeling using an interface-tracking method. A micro-layer model is required for the CFD simulation to take into account vaporization from the thin liquid film - called the micro-layer - existing beneath a growing vapor bubble on a hot surface. In our model, the thickness of the micro-layer is a variable defined at each discretized fluid cell adjacent to the heat-transfer surface; the layer decreases due to vaporization, and can finally disappear. Compared to existing micro-region models, most of them based on the concept of contact-line evaporation, as originally proposed by Stephan and Busse, and by Lay and Dhir, our model incorporates simplified modeling ideas, but can nonetheless predict the temperature field beneath the growing bubble accurately. The model proposed in this paper has been validated against measurements of pool boiling in water at atmospheric pressure. Specifically, the bubble principal dimensions and the temperature distribution over the heat-transfer surface are in good agreement with experimental data.

  14. Momentum effects in steady nucleate pool boiling during microgravity.

    PubMed

    Merte, Herman

    2004-11-01

    Pool boiling experiments were conducted in microgravity on five space shuttle flights, using a flat plate heater consisting of a semitransparent thin gold film deposited on a quartz substrate that also acted as a resistance thermometer. The test fluid was R-113, and the vapor bubble behavior at the heater surface was photographed from beneath as well as from the side. Each flight consisted of a matrix of three levels of heat flux and three levels of subcooling. In 26 of the total of 45 experiments conditions of steady-state pool boiling were achieved under certain combinations of heat flux and liquid subcooling. In many of the 26 cases, it was observed from the 16-mm movie films that a large vapor bubble formed, remaining slightly removed from the heater surface, and that subsequent vapor bubbles nucleate and grow on the heater surface. Coalescence occurs upon making contact with the large bubble, which thus acts as a vapor reservoir. Recently, measurements of the frequencies and sizes of the small vapor bubbles as they coalesced with the large bubble permitted computation of the associated momentum transfer. The transient forces obtained are presented here. Where these arise from the conversion of the surface energy in the small vapor bubble to kinetic energy acting away from the solid heater surface, they counter the Marangoni convection due to the temperature gradients normal to the heater surface. This Marangoni convection would otherwise impel the large vapor bubble toward the heater surface and result in dryout and unsteady heat transfer.

  15. Pool boiling on a large horizontal flat resistance heater

    SciTech Connect

    Reguillot, F.; Witte, L.; Lienhard, J.; Poniewski, M. Kielce University of Technology, )

    1992-08-01

    Results are presented of experiments on n-pentane/Freon-113 system, carried out to investigate the film-transition boiling region where liquid-solid contacts contribute significantly to the local heat flux, using a large flat horizontal resistance heater mounted on a ceramic insulating substrate. After steady film boiling was reached, the heat flux was decreased and recorded simultaneously with the temperature measured by thermocouples attached to the lower side of the heater surface. It is shown that the observed data on the quasi-linear film boiling regime are better represented by Berenson's (1960) correlation than by Klimenko's (1981) correlation. Burnout values measured for Freon-113 compared reasonably well to available correlations for the flat plate geometry. 10 refs.

  16. Visualization of pool boiling from complex surfaces with internal tunnels

    NASA Astrophysics Data System (ADS)

    Pastuszko, Robert

    2012-04-01

    The paper presents experimental investigations of boiling heat transfer for a system of connected narrow horizontal and vertical tunnels. These extended surfaces, named narrow tunnel structure (NTS), can be applied to electronic element cooling. The experiments were carried out with ethanol at atmospheric pressure. The tunnel external covers were manufactured out of 0.1 mm thick perforated copper foil (hole diameters 0.5 mm), sintered with the mini-fins, formed on the vertical side of the 10 mm high rectangular fins and horizontal inter-fin surface. Visualization studies were conducted with a transparent structured model of joined narrow tunnels limited with the perforated foil. The visualization investigations aimed to formulate assumptions for the boiling model through distinguishing boiling types and defining all phases of bubble growth.

  17. Experimental Investigation of Pool Boiling Heat Transfer Enhancement in Microgravity in the Presence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, C.

    2000-01-01

    The research carried out in the Heat Transfer Laboratory of the Johns Hopkins University was motivated by previous studies indicating that in terrestrial applications nucleate boiling heat transfer can be increased by a factor of 50 when compared to values obtained for the same system without electric fields. Imposing an external electric field holds the promise to improve pool boiling heat transfer in low gravity, since a phase separation force other than gravity is introduced. The influence of electric fields on bubble formation has been investigated both experimentally and theoretically.

  18. Pool boiling of nanoparticle-modified surface with interlaced wettability

    PubMed Central

    2012-01-01

    This study investigated the pool boiling heat transfer under heating surfaces with various interlaced wettability. Nano-silica particles were used as the coating element to vary the interlaced wettability of the surface. The experimental results revealed that when the wettability of a surface is uniform, the critical heat flux increases with the more wettable surface; however, when the wettability of a surface is modified interlacedly, regardless of whether the modified region becomes more hydrophilic or hydrophobic, the critical heat flux is consistently higher than that of the isotropic surface. In addition, this study observed that critical heat flux was higher when the contact angle difference between the plain surface and the modified region was smaller. PMID:22607462

  19. Pool boiling of nanoparticle-modified surface with interlaced wettability.

    PubMed

    Hsu, Chin-Chi; Su, Tsung-Wen; Chen, Ping-Hei

    2012-05-18

    This study investigated the pool boiling heat transfer under heating surfaces with various interlaced wettability. Nano-silica particles were used as the coating element to vary the interlaced wettability of the surface. The experimental results revealed that when the wettability of a surface is uniform, the critical heat flux increases with the more wettable surface; however, when the wettability of a surface is modified interlacedly, regardless of whether the modified region becomes more hydrophilic or hydrophobic, the critical heat flux is consistently higher than that of the isotropic surface. In addition, this study observed that critical heat flux was higher when the contact angle difference between the plain surface and the modified region was smaller.

  20. Pool boiling of nanoparticle-modified surface with interlaced wettability

    NASA Astrophysics Data System (ADS)

    Hsu, Chin-Chi; Su, Tsung-Wen; Chen, Ping-Hei

    2012-05-01

    This study investigated the pool boiling heat transfer under heating surfaces with various interlaced wettability. Nano-silica particles were used as the coating element to vary the interlaced wettability of the surface. The experimental results revealed that when the wettability of a surface is uniform, the critical heat flux increases with the more wettable surface; however, when the wettability of a surface is modified interlacedly, regardless of whether the modified region becomes more hydrophilic or hydrophobic, the critical heat flux is consistently higher than that of the isotropic surface. In addition, this study observed that critical heat flux was higher when the contact angle difference between the plain surface and the modified region was smaller.

  1. Momentum effects in steady nucleate pool boiling during microgravity.

    PubMed

    Merte, Herman

    2004-11-01

    Pool boiling experiments were conducted in microgravity on five space shuttle flights, using a flat plate heater consisting of a semitransparent thin gold film deposited on a quartz substrate that also acted as a resistance thermometer. The test fluid was R-113, and the vapor bubble behavior at the heater surface was photographed from beneath as well as from the side. Each flight consisted of a matrix of three levels of heat flux and three levels of subcooling. In 26 of the total of 45 experiments conditions of steady-state pool boiling were achieved under certain combinations of heat flux and liquid subcooling. In many of the 26 cases, it was observed from the 16-mm movie films that a large vapor bubble formed, remaining slightly removed from the heater surface, and that subsequent vapor bubbles nucleate and grow on the heater surface. Coalescence occurs upon making contact with the large bubble, which thus acts as a vapor reservoir. Recently, measurements of the frequencies and sizes of the small vapor bubbles as they coalesced with the large bubble permitted computation of the associated momentum transfer. The transient forces obtained are presented here. Where these arise from the conversion of the surface energy in the small vapor bubble to kinetic energy acting away from the solid heater surface, they counter the Marangoni convection due to the temperature gradients normal to the heater surface. This Marangoni convection would otherwise impel the large vapor bubble toward the heater surface and result in dryout and unsteady heat transfer. PMID:15644357

  2. Pool boiling heat transfer characteristics of ZrO2 water nanofluids from a flat surface in a pool

    NASA Astrophysics Data System (ADS)

    Chopkar, Manoj; Das, A. K.; Manna, I.; Das, P. K.

    2008-06-01

    Nucleate pool boiling of ZrO2 based aqueous nanofluid has been studied. Though enhancement in nucleate boiling heat transfer has been observed at low volume fraction of solid dispersion, the rate of heat transfer falls with the increase in solid concentration and eventually becomes inferior even to pure water. While surfactants increase the rate of heat transfer, addition of surfactant to the nanofluid shows a drastic deterioration in nucleate boiling heat transfer. Further, the boiling of nanofluid renders the heating surface smoother. Repeated runs of experiments with the same surface give a continuous decrease in the rate of boiling heat transfer.

  3. A fractal study for nucleate pool boiling heat transfer of nanofluids

    NASA Astrophysics Data System (ADS)

    Xiao, Boqi; Jiang, Guoping; Chen, Lingxia

    2010-01-01

    In this paper, a fractal model for nucleate pool boiling heat transfer of nanofluids is developed based on the fractal distribution of nanoparticles and nucleation sites on boiling surfaces. The model shows the dependences of the heat flux on nanoparticle size and the nanoparticle volume fraction of the suspension, the fractal dimension of the nanoparticle and nucleation site, temperature of nanofluids and properties of fluids. The fractal model predictions show that the natural convection stage continues relatively longer in the case of nanofluids. The addition of nanoparticles causes a decrease of the pool nucleate boiling heat transfer. The nucleate pool boiling heat transfer coefficient is decreased by increasing particle concentration. An excellent agreement between the proposed model predictions and experimental data is found. The validity of the fractal model for nucleate pool boiling heat transfer is thus verified.

  4. Experimental analysis of nanofluid pool boiling heat transfer in copper bead packed porous layers

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Wang, Ji

    2016-07-01

    Coupling the nanofluid as working fluid and the copper beads packed porous structure on heating surface were employed to enhance the pool boiling heat transfer by changing the fluid properties with the adjunction of nanoparticles in liquid and altering the heating surface with a bead porous layer. Due to the higher thermal conductivity, the copper beads served as an extended heating surface and the boiling nucleation sites rose, but the flow resistance increased. The CuO-water and SiO2-water nanofluids as well as the pure water were respectively employed as working fluids in the pool boiling experiments. Comparing with the base fluid of water, the higher thermal conductivity and lower surface tension occur in the nanofluids and those favor the boiling heat transfer, but the higher viscosity and density of nanofluids serve as deteriorative factors. So, the concentration region of the nanofluids should be chosen properly. The maximum relative error between the collected experimental data of the pure water on a flat surface and the theoretical prediction of pool boiling using the Rohsenow correlation was less than 12 %. The comparisons of the pool boiling heat transfer characteristics were also conducted between the pure water and the nanofluids respectively on the horizontal flat surface and on the heating surface packed with a copper bead porous layer. Besides, the boiling bubble generation, integration and departure have a great affect on the pool boiling and were recorded with a camera in the bead stacked porous structures at different heat flux.

  5. Transition from Pool to Flow Boiling: The Effect of Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Dhir, Vijay K.

    2004-01-01

    Applications of boiling heat transfer in space can be found in the areas of thermal management, fluid handling and control, power systems, on-orbit storage and supply systems for cryogenic propellants and life support fluids, and for cooling of electronic packages for power systems associated with various instrumentation and control systems. Recent interest in exploration of Mars and other planets, and the concepts of in-situ resource utiliLation on Mars highlights the need to understand the effect of gravity on boiling heat transfer at gravity levels varying from 1>= g/g(sub e) >=10(exp -6). The objective of the proposed work was to develop a mechanistic understanding of nucleate boiling and critical heat flux under low and micro-gravity conditions when the velocity of the imposed flow is small. For pool boiling, the effect of reduced gravity is to stretch both the length scale as well as the time scale for the boiling process. At high flow velocities, the inertia of the liquid determines the time and the length scales and as such the gravitational acceleration plays little role. However, at low velocities and at low gravity levels both liquid inertia and buoyancy are of equal importance. At present, we have little understanding of the interacting roles of gravity and liquid inertia on the nucleate boiling process. Little data that has been reported in the literature does not have much practical value in that it can not serve as a basis for design of heat exchange components to be used in space. Both experimental and complete numerical simulations of the low velocity, low-gravity nucleate boiling process were carried out. A building block type of approach was used in that first the growth and detachment process of a single bubble and flow and heat transfer associated with the sliding motion of the bubble over the heater surface after detachment was studied. Liquid subcooling and flow velocity were varied parametrically. The experiments were conducted at 1 g(sub e

  6. Extended hydrodynamic theory of the peak and minimum pool boiling heat fluxes

    NASA Technical Reports Server (NTRS)

    Linehard, J. H.; Dhir, V. K.

    1973-01-01

    The hydrodynamic theory of the extreme pool boiling heat fluxes is expanded to embrace a variety of problems that have not previously been analyzed. These problems include the prediction of the peak heat flux on a variety of finite heaters, the influence of viscosity on the Taylor and Helmoltz instability mechanisms with application to film boiling and to the peak heat flux in viscous liquids, the formalization of the analogy between high-current-density electrolysis and boiling, and the description of boiling in the low-gravity limit. The predictions are verified with a large number of new data.

  7. Pool Boiling of Ethanol-Water mixture on Nano-Textured Surfaces

    NASA Astrophysics Data System (ADS)

    Yarin, Alexander; Sahu, Rakesh; Sinha-Ray, Sumit; Sinha-Ray, Suman

    2015-03-01

    An experimental and theoretical study of pool boiling of ethanol-water mixtures on nano-textured surfaces was studied. A comparison of pool boiling on bare copper surface with pool boiling on surfaces covered by copper-plated supersonically-blown nanofibers revealed a significant increase in the heat flux in the latter case. Namely, the heat flux on the nano-textured surfaces was about 3-8 times higher than that on the bare copper surfaces, while the surface temperature due to the nano-texture would be lower by about 10 °C at the same heat flux. The significant positive effect of the nano-texture is due to the fact that it facilitates bubble nucleation. Some preliminary results of numerical modeling of boiling process in the framework of the Cahn-Hilliard approach are discussed and several examples of the predictions are given. Supported by NASA, Grant No. NNX13AQ77G.

  8. Experimental Investigation of Pool Boiling Heat Transfer Enhancement in Microgravity in the Presence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, Cila

    1996-01-01

    compared to values obtained for the same system without electric fields. Imposing an external electric field holds the promise to improve pool boiling heat transfer in low gravity, since a phase separation force other than gravity is introduced. The goal of our research is to experimentally investigate the potential of EHD and the mechanisms responsible for EHD heat transfer enhancement in boiling in low gravity conditions.

  9. An experimental apparatus to study nucleate pool boiling of R-114 and oil mixtures

    NASA Astrophysics Data System (ADS)

    Karasabun, M.

    1984-12-01

    In order to study the nucleate pool-boiling performance of R-114pen1 refrigerant and R-114-oil mixtures from enhanced evaporator tube surfaces, an experimental apparatus was designed, constructed and instrumented. The evaporator was made of a T-shaped Pyrex glass container. Boiling occurred from a smooth, hard-copper tube, 15.9 mm in outer diameter, 12.7 mm in inside diameter and 431.8 mm in length. The tube was heated using a cartridge heater, and was instrumented with 8 thermocouples to measure the wall temperature. A Hewlett-Packard 3497A data acquisition/control unit and a 9826A computer were used to collect and process data. The condenser was cooled by an ethylene glycol-water mixture, which was maintained at about -17 C by means of an R-12 refrigeration system. Nine data runs were completed to de-bug the experimental apparatus and to check for reproducibility. During all data runs, especially at higher heat fluxes (greater than 10 kW/sqm), large temperature variations were observed along and around the active boiling length of the test tube. The data were compared with data found in the literature and reasonable agreement was obtained.

  10. Particulate fouling during the pool boiling heat transfer of MWCNT nanofluid

    NASA Astrophysics Data System (ADS)

    Xue, H. Sheng; Fan, Jian R.; Hu, Ya C.; Hong, Rong H.

    2012-05-01

    Pool boiling of multi-walled carbon nanotube (MWCNT) nanofluid was conducted to investigate fouling of a copper surface with a diameter of 12 mm. At low heat flux the fouling curve takes the shape of saw tooth with an asymptotic value. When boiling stretches, dispersant, Gum Arabic fails, MWCNT particles deposit on the heating wall completely. Progressively increasing the heat flux, depositing accelerates, superheat and fouling resistance increase drastically.

  11. A Fundamental Study of Nucleate Pool Boiling Under Microgravity. Final report

    SciTech Connect

    Ervin, J.S.; Merte, H. Jr.

    1996-03-01

    An experimental study of incipient boiling in short-term microgravity and with a/g = {+-} 1 for pool boiling was performed. Calibrated thin gold films sputtered on a smoothly polished quartz surface were used simultaneously for thermal-resistance measurements and heating of the boiling surface. The gold films were used for both transient and quasi-steady heating surface temperature measurements. Two test vessels were constructed for precise measurement and control of fluid temperature and pressure: a laboratory pool boiling vessel for the a/g = {+-} 1 experiments and a pool boiling vessel designed for the 131 m free-fall in the NASA Lewis Research Center Microgravity Research Facility for the microgravity tests. Measurements included the heater surface temperature, the pressure near the heating surface, the bulk liquid temperatures. High speed photography (up to 1,000 frames per second) was used in the experiments. With high quality microgravity and the measured initial temperature of the quiescent test fluid, R113, the temperature distribution in the liquid at the moment of boiling inception resulting from an imposed step in heat flux is known with a certainty not possible previously. The types of boiling propagation across the large flat heating surface, some observed here for the first time, are categorized; the conditions necessary for their occurrence are described. Explosive boiling propagation with a striking pattern of small scale protuberances over the entire vapor mass periphery not observed previously at low heat flux levels (on the order of 5 W/cm(exp 2)) is described. For the heater surface with a/g = {minus}1, a step in the heater surface temperature of short duration was imposed. The resulting liquid temperature distribution at the moment of boiling inception was different from that obtained with a step in heat flux.

  12. Catastrophe characteristics of the condensation and pool boiling phenomena

    NASA Astrophysics Data System (ADS)

    Ma, Xuehu; Xu, Dunqi; Lin, Jifang

    1995-02-01

    Recently, Utaka proposed two types of the transition modes of dropwise condensation, i.e. the continuous and the jumping modes, and presented a criterion for determining the condensation transition mode. Stylianous and Rose proposed two hypotheses, the coalescence-limited transition and the nucleation site saturation transition. Neither Utaka's criterion nor Rose's hypotheses could clearly interpret the physical mechanisms of the transition both from filmwise to dropwise and from dropwise to pseudofilm condensation, and explicitly presented the main factors affecting the transitions. Kalinin hs given a general review of the transition boiling heat transfer. The catastrophe theory will be applied here to eluicidate the complex phenomena of the transitions of the condensation and boiling pattern states.

  13. Dynamics of discrete bubble in nucleate pool boiling on thin wires in microgravity

    NASA Astrophysics Data System (ADS)

    Wan, Shixin; Zhao, Jianfu; Liu, Gang

    2009-03-01

    A space experiment on bubble behavior and heat transfer in subcooled pool boiling phenomenon has been performed utilizing the temperature-controlled pool boiling (TCPB) device both in normal gravity in the laboratory and in microgravity aboard the 22nd Chinese recoverable satellite. The fluid is degassed R113 at 0.1 MPa and subcooled by 26°C nominally. A thin platinum wire of 60 μm in diameter and 30 mm in length is simultaneously used as heater and thermometer. Only the dynamics of the vapor bubbles, particularly the lateral motion and the departure of discrete vapor bubbles in nucleate pool boiling are reported and analyzed in the present paper. It’s found that these distinct behaviors can be explained by the Marangoni convection in the liquid surrounding vapor bubbles. The origin of the Marangoni effect is also discussed.

  14. Nucleate pool boiling: High gravity to reduced gravity; liquid metals to cryogens

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1988-01-01

    Requirements for the proper functioning of equipment and personnel in reduced gravity associated with space platforms and future space station modules introduce unique problems in temperature control; power generation; energy dissipation; the storage, transfer, control and conditioning of fluids; and liquid-vapor separation. The phase change of boiling is significant in all of these. Although both pool and flow boiling would be involved, research results to date include only pool boiling because buoyancy effects are maximized for this case. The effective application of forced convection boiling heat transfer in the microgravity of space will require a well grounded and cogent understanding of the mechanisms involved. Experimental results are presented for pool boiling from a single geometrical configuration, a flat surface, covering a wide range of body forces from a/g = 20 to 1 to a/g = 0 to -1 for a cryogenic liquid, and from a/g = 20 to 1 for water and a liquid metal. Similarities in behavior are noted for these three fluids at the higher gravity levels, and may reasonably be expected to continue at reduced gravity levels.

  15. Effect of nanoparticles on critical heat flux of water in pool boiling heat transfer

    NASA Astrophysics Data System (ADS)

    You, S. M.; Kim, J. H.; Kim, K. H.

    2003-10-01

    The present study is to enhance the critical heat flux (CHF) in pool boiling from a flat square heater immersed in nanofluid (water mixed with extremely small amount of nanosized particles). The test results show that the enhancement of CHF was drastic when nanofluid is used as a cooling liquid instead of pure water. The experiment was performed to measure and compare pool boiling curves of pure water and nanofluid at the pressure of 2.89 psia (Tsat=60 °C) using 1×1 cm2 polished copper surfaces as a boiling surface. The tested nanofluid contains alumina (Al2O3) nanoparticles dispersed in distilled and deionized water. Tested concentrations of nanoparticles range from 0 g/l to 0.05 g/l. The measured pool boiling curves of nanofluids saturated at 60 °C have demonstrated that the CHF increases dramatically (˜200% increase) compared to pure water case; however, the nucleate boiling heat transfer coefficients appear to be about the same.

  16. Electrical design of Space Shuttle payload G-534: The pool boiling experiment

    NASA Technical Reports Server (NTRS)

    Francisco, David R.

    1993-01-01

    Payload G-534, the Pool Boiling Experiment (PBE), is a Get Away Special (GAS) payload that flew on the Space Shuttle Spacelab Mission J (STS 47) on September 19-21, 1992. This paper will give a brief overall description of the experiment with the main discussion being the electrical design with a detailed description of the power system and interface to the GAS electronics. The batteries used and their interface to the experiment Power Control Unit (PCU) and GAS electronics will be examined. The design philosophy for the PCU will be discussed in detail. The criteria for selection of fuses, relays, power semiconductors, and other electrical components along with grounding and shielding policy for the entire experiment are presented. The intent of this paper is to discuss the use of military tested parts and basic design guidelines to build a quality experiment for minimal additional cost.

  17. Pool boiling of water on nano-structured micro wires at sub-atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Arya, Mahendra; Khandekar, Sameer; Pratap, Dheeraj; Ramakrishna, S. Anantha

    2016-09-01

    Past decades have seen active research in enhancement of boiling heat transfer by surface modifications. Favorable surface modifications are expected to enhance boiling efficiency. Several interrelated mechanisms such as capillarity, surface energy alteration, wettability, cavity geometry, wetting transitions, geometrical features of surface morphology, etc., are responsible for change in the boiling behavior of modified surfaces. Not much work is available on pool boiling at low pressures on microscale/nanoscale geometries; low pressure boiling is attractive in many applications wherein low operating temperatures are desired for a particular working fluid. In this background, an experimental setup was designed and developed to investigate the pool boiling performance of water on (a) plain aluminum micro wire (99.999 % pure) and, (b) nano-porous alumina structured aluminum micro wire, both having diameter of 250 µm, under sub-atmospheric pressure. Nano-structuring on the plain wire surface was achieved via anodization. Two samples, A and B of anodized wires, differing by the degree of anodization were tested. The heater length scale (wire diameter) was much smaller than the capillary length scale. Pool boiling characteristics of water were investigated at three different sub-atmospheric pressures of 73, 123 and 199 mbar (corresponding to T sat = 40, 50 and 60 °C). First, the boiling characteristics of plain wire were measured. It was noticed that at sub-atmospheric pressures, boiling heat transfer performance for plain wire was quite low due to the increased bubble sizes and low nucleation site density. Subsequently, boiling performance of nano-structured wires (both Sample A and Sample B) was compared with plain wire and it was noted that boiling heat transfer for the former was considerably enhanced as compared to the plain wire. This enhancement is attributed to increased nucleation site density, change in wettability and possibly due to enhanced pore scale

  18. Pool boiling of water on nano-structured micro wires at sub-atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Arya, Mahendra; Khandekar, Sameer; Pratap, Dheeraj; Ramakrishna, S. Anantha

    2015-10-01

    Past decades have seen active research in enhancement of boiling heat transfer by surface modifications. Favorable surface modifications are expected to enhance boiling efficiency. Several interrelated mechanisms such as capillarity, surface energy alteration, wettability, cavity geometry, wetting transitions, geometrical features of surface morphology, etc., are responsible for change in the boiling behavior of modified surfaces. Not much work is available on pool boiling at low pressures on microscale/nanoscale geometries; low pressure boiling is attractive in many applications wherein low operating temperatures are desired for a particular working fluid. In this background, an experimental setup was designed and developed to investigate the pool boiling performance of water on (a) plain aluminum micro wire (99.999 % pure) and, (b) nano-porous alumina structured aluminum micro wire, both having diameter of 250 µm, under sub-atmospheric pressure. Nano-structuring on the plain wire surface was achieved via anodization. Two samples, A and B of anodized wires, differing by the degree of anodization were tested. The heater length scale (wire diameter) was much smaller than the capillary length scale. Pool boiling characteristics of water were investigated at three different sub-atmospheric pressures of 73, 123 and 199 mbar (corresponding to T sat = 40, 50 and 60 °C). First, the boiling characteristics of plain wire were measured. It was noticed that at sub-atmospheric pressures, boiling heat transfer performance for plain wire was quite low due to the increased bubble sizes and low nucleation site density. Subsequently, boiling performance of nano-structured wires (both Sample A and Sample B) was compared with plain wire and it was noted that boiling heat transfer for the former was considerably enhanced as compared to the plain wire. This enhancement is attributed to increased nucleation site density, change in wettability and possibly due to enhanced pore scale

  19. Lateral Motion and Departure of Vapor Bubbles in Nucleate Pool Boiling on Thin Wires in Microgravity

    NASA Astrophysics Data System (ADS)

    Zhao, J. F.; Wan, S. X.; Liu, G.; Li, Z. D.; Lu, Y. H.; Yan, N.

    A space experiment on bubble behavior and heat transfer in subcooled pool boiling phenomenon has been performed utilizing the temperature-controlled pool boiling (TCPB) device both in normal gravity in the laboratory and in microgravity aboard the 22nd Chinese recoverable satellite. The fluid is R113 at 0.lMPa and subcooled by 26°C nominally. A thin platinum wire of 60µm in diameter and 30mm in length is simultaneously used as heater and thermometer. Only the lateral motion and the departure of discrete vapor bubbles in nucleate pool boiling are reported and analyzed in the present paper. A scale analysis on the Marangoni convection surrounding a bubble in the process of subcooled nucleate pool boiling leads to formulas of the characteristic velocity of the lateral motion and its observability. The predictions consist with the experimental observations. Considering the Marangoni effect, a new qualitative model is proposed to reveal the mechanism underlying the bubble departure processes and a quantitative agreement can also be acquired.

  20. Pool boiling on surfaces with mini-fins and micro-cavities

    NASA Astrophysics Data System (ADS)

    Pastuszko, Robert; Piasecka, Magdalena

    2012-11-01

    The experimental studies presented here focused on pool boiling heat transfer on mini-fin arrays, mini-fins with perforated covering and surfaces with micro-cavities. The experiments were carried out for water and fluorinert FC-72 at atmospheric pressure. Mini-fins of 0.5 and 1 mm in height were uniformly spaced on the base surface. The copper foil with holes of 0.1 mm in diameter (pitch 0.2/0.4 mm), sintered with the fin tips, formed a system of connected perpendicular and horizontal tunnels. The micro-cavities were obtained through spark erosion. The maximal depth of the craters of these cavities was 15 - 30 μm and depended on the parameters of the branding-pen settings. At medium and small heat fluxes, structures with mini-fins showed the best boiling heat transfer performance both for water and FC-72. At medium and high heat fluxes (above 70 kW/m2 for water and 25 kW/m2 for FC-72), surfaces with mini-fins without porous covering and micro-cavities produced the highest heat transfer coefficients. The surfaces obtained with spark erosion require a proper selection of geometrical parameters for particular liquids - smaller diameters of cavities are suitable for liquids with lower surface tension (FC-72).

  1. Comparison of pool boiling heat transfer for different tunnel-pore surfaces

    NASA Astrophysics Data System (ADS)

    Pastuszko, Robert

    2014-03-01

    Complex experimental investigations of boiling heat transfer on structured surfaces covered with perforated foil were performed. Experimental data were discussed for three kinds of enhanced surfaces: tunnel structures (TS), narrow tunnel structures (NTS) and mini-fins with the copper wire net (NTS-L). The experiments were carried out with water, ethanol, R-123 and FC-72 at atmospheric pressure. The TS and NTS surfaces were manufactured out of perforated copper foil (hole diameters: 0.3, 0.4, 0.5 mm) sintered with the mini-fins, formed on the vertical side of the 5 and 10 mm high rectangular main fins and horizontal inter-fin surface. The NTS-L surfaces were formed by mini-fins of 0.5 and 1 mm height uniformly spaced on the base surface. The wire mesh with an aperture of 0.32, 0.4 and 0.5 mm sintered with the fin tips formed a system of connected perpendicular horizontal tunnels. The tunnel width was 0.6 - 1.0 - 1.5 mm and the depth was 0.5 or 1.0 mm. The effects of the Bond number and dimensionless parameters for three kinds of enhanced structures on heat transfer ratio at nucleate pool boiling were examined.

  2. Heat Transfer Performances of Pool Boiling on Metal-Graphite Composite Surfaces

    NASA Technical Reports Server (NTRS)

    Zhang, Nengli; Chao, David F.; Yang, Wen-Jei

    2000-01-01

    Nucleate boiling, especially near the critical heat flux (CHF), can provide excellent economy along with high efficiency of heat transfer. However, the performance of nucleate boiling may deteriorate in a reduced gravity environment and the nucleate boiling usually has a potentially dangerous characteristic in CHF regime. That is, any slight overload can result in burnout of the boiling surface because the heat transfer will suddenly move into the film-boiling regime. Therefore, enhancement of nucleate boiling heat transfer becomes more important in reduced gravity environments. Enhancing nucleate boiling and critical heat flux can be reached using micro-configured metal-graphite composites as the boiling surface. Thermocapillary force induced by temperature difference between the graphite-fiber tips and the metal matrix, which is independent of gravity, will play an important role in bubble detachment. Thus boiling heat transfer performance does not deteriorate in a reduced-gravity environment. Based on the existing experimental data, and a two-tier theoretical model, correlation formulas are derived for nucleate boiling on the copper-graphite and aluminum-graphite composite surfaces, in both the isolated and coalesced bubble regimes. Experimental studies were performed on nucleate pool boiling of pentane on cooper-graphite (Cu-Gr) and aluminum-graphite (Al-Gr) composite surfaces with various fiber volume concentrations for heat fluxes up to 35 W per square centimeter. It is revealed that a significant enhancement in boiling heat transfer performance on the composite surfaces is achieved, due to the presence of micro-graphite fibers embedded in the matrix. The onset of nucleate boiling (the isolated bubble regime) occurs at wall superheat of about 10 C for the Cu-Gr surface and 15 C for the Al-Gr surface, much lower than their respective pure metal surfaces. Transition from an isolated bubble regime to a coalesced bubble regime in boiling occurs at a superheat of

  3. Pool boiling of dielectric liquids on porous graphite and extended copper surfaces

    NASA Astrophysics Data System (ADS)

    Parker, Jack L.

    This work investigated pool boiling of the dielectric liquids HFE-7100 and FC-72 on plane copper and porous graphite and on copper surfaces with corner pins. The work investigated the effects of surface orientation and liquid subcooling and, for the copper surfaces with corner pins, the effect of surface roughness. In addition, investigations were made studying the heat transfer by natural convection and nucleate boiling, as well as the effects of liquid subcooling (up to 30 K) and surface inclination (0°--upward facing, to 180°--downward facing) on nucleate boiling heat transfer and Critical Heat Flux (CHF). The results are applicable to direct immersion cooling by nucleate boiling of high power computer chips dissipating 50 - 100 W/cm2 while maintaining the junction temperature for the chips below the recommended values (˜85 °C). Pool boiling experiments are performed with degassed HFE-7100 and FC-72 liquids using uniformly heated 10 x 10 mm porous graphite and copper surfaces with corner pins. The measured footprint temperatures and thermal power removed from the surfaces are used to construct the pool boiling curves and determine the critical heat flux and corresponding surface superheat. Results are compared with those obtained on plane copper of same heated footprint area. The obtained CHF values are also compared with those reported in the open literature for plane, micro-porous, and macro-structured surfaces. Digital photographs and video are obtained to help explain and interpret the results. For the first time, natural convection correlations for dielectric liquids on plane, porous, and copper with corner pins developed. These correlations are important to electronic cooling in the stand-by mode when the heat dissipation by the chips is only a few watts. Results show that the power removed by natural convection from surfaces with corner pins is 67% more than from plane Si and Cu surfaces at the same surface superheat. Using porous graphite and copper

  4. Experimental analysis of bubble growth, departure and interactions during pool boiling on artificial nucleation sites

    SciTech Connect

    Siedel, S.; Cioulachtjian, S.; Bonjour, J.

    2008-09-15

    The present work describes experimental results of pentane pool boiling, simplified to the cases of boiling on a single or on two adjacent nucleation sites. Bubbles growths have been recorded by a high speed camera under various wall superheat conditions. Bubble volume has been plotted as a function of time, and an experimental growth law has been proposed. Oscillations were observed during growth, showing the interaction of one bubble with the preceding bubble released from the same nucleation site. Lateral coalescence has been visualized and the images have brought to the fore the capillary effects on the distortion of the interface. (author)

  5. Apparatus for draining lower drywell pool water into suppresion pool in boiling water reactor

    DOEpatents

    Gluntz, Douglas M.

    1996-01-01

    An apparatus which mitigates temperature stratification in the suppression pool water caused by hot water drained into the suppression pool from the lower drywell pool. The outlet of a spillover hole formed in the inner bounding wall of the suppression pool is connected to and in flow communication with one end of piping. The inlet end of the piping is above the water level in the suppression pool. The piping is routed down the vertical downcomer duct and through a hole formed in the thin wall separating the downcomer duct from the suppression pool water. The piping discharge end preferably has an elevation at or near the bottom of the suppression pool and has a location in the horizontal plane which is removed from the point where the piping first emerges on the suppression pool side of the inner bounding wall of the suppression pool. This enables water at the surface of the lower drywell pool to flow into and be discharged at the bottom of the suppression pool.

  6. Experimental Investigation of Pool Boiling Heat Transfer Enhancement in Microgravity in the Presence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, Cila

    1999-01-01

    In boiling high heat fluxes are possible driven by relatively small temperature differences, which make its use increasingly attractive in aerospace applications. The objective of the research is to develop ways to overcome specific problems associated with boiling in the low gravity environment by substituting the buoyancy force with the electric force to enhance bubble removal from the heated surface. Previous studies indicate that in terrestrial applications nucleate boiling heat transfer can be increased by a factor of 50, as compared to values obtained for the same system without electric fields. The goal of our research is to experimentally explore the mechanisms responsible for EHD heat transfer enhancement in boiling in low gravity conditions, by visualizing the temperature distributions in the vicinity of the heated surface and around the bubble during boiling using real-time holographic interferometry (HI) combined with high-speed cinematography. In the first phase of the project the influence of the electric field on a single bubble is investigated. Pool boiling is simulated by injecting a single bubble through a nozzle into the subcooled liquid or into the thermal boundary layer developed along the flat heater surface. Since the exact location of bubble formation is known, the optical equipment can be aligned and focused accurately, which is an essential requirement for precision measurements of bubble shape, size and deformation, as well as the visualization of temperature fields by HI. The size of the bubble and the frequency of bubble departure can be controlled by suitable selection of nozzle diameter and mass flow rate of vapor. In this approach effects due to the presence of the electric field can be separated from effects caused by the temperature gradients in the thermal boundary layer. The influence of the thermal boundary layer can be investigated after activating the heater at a later stage of the research. For the visualization experiments a

  7. Investigation of change in surface morphology of heated surfaces upon pool boiling of magnetic fluids under magnetic actuation

    NASA Astrophysics Data System (ADS)

    Shojaeian, Mostafa; Yildizhan, Melike-Mercan; Coşkun, Ömer; Ozkalay, Ebrar; Tekşen, Yiğit; Gulgun, Mehmet Ali; Funda Yagci Acar, Havva; Koşar, Ali

    2016-09-01

    Nanofluids are becoming a significant candidate for new generation coolants to be used in industrial applications. In order to reduce clustering and sedimentation of nanoparticles and improve the heat transfer performance simultaneously, magnetic fluids prepared with magnetic Fe3O4 nanoparticles dispersed in water, which were placed in a pool and were exposed to varying magnetic fields to actuate nanoparticles in the system. The effect of magnetic actuation on boiling heat transfer characteristics and on the surface morphology of the pool was examined. An average enhancement of 29% in boiling heat transfer was achieved via magnetic actuation with rather low magnetic field (magnetic flux densities up to 11 mT) densities. Furthermore, it was observed that magnetic actuation significantly prevented the deposition and sedimentation of the nanoparticles in the pool. Otherwise, significant destabilization of nanoparticles causing aggregation and heavy sedimentation was present as a result of the performed surface analysis. Even though magnetic actuation reduced the sedimentation on the macroscale, the deposition of a thick and porous film occurred onto the pool floor, increasing the surface roughness.

  8. Circumferential temperature distribution during nucleate pool boiling outside smooth and modified horizontal tubes

    SciTech Connect

    Dominiczak, Przemyslaw R.; Cieslinski, Janusz T.

    2008-10-15

    In the work an approach to avoid a circumferential temperature distribution existing during nucleate pool boiling on a horizontal cylinder within low heat flux densities is presented. The idea of the approach is local heat transfer enhancement by a porous layer application on a part of the heating surface. An experiment on nucleate pool boiling heat transfer from horizontal cylinders to saturated R141b and water under atmospheric pressure is reported. Experiments have been conducted using stainless steel tubes with the outside diameter between 8 mm and 23 mm with the active length of 250 mm. The outside surface of the tubes was smooth or partially coated with a porous metallic layer. In particular, measurements of inside circumferential temperature distribution have been performed. (author)

  9. Experimental study of the characteristics and mechanism of pool boiling CHF enhancement using nanofluids

    NASA Astrophysics Data System (ADS)

    Kim, Hyungdae; Kim, Moohwan

    2009-05-01

    The pool boiling critical heat flux (CHF) performance of aqueous nanofluids was investigated using various nanoparticles of TiO2, Al2O3, and SiO2. The usage of a nanofluid as a working fluid can significantly enhance the pool boiling CHF, which was found to be strongly dependent on the kind of nanoparticle, as well as its concentration. A nanoparticle surface coating was observed on the heating surface after the experiment. The CHF of pure water on the nanoparticle-coated surface was higher than that of nanofluids for all cases. This revealed that the cause of the CHF enhancement using nanofluids is due to the fact that the heater surface is modified by the nanoparticle deposition. The mechanism of CHF enhancement due to the nanoparticle coating was discussed, relating it to surface wettability, surface roughness, and maximum capillary wicking height of the nanoparticle-coated surface.

  10. Bubble Departure from Metal-Graphite Composite Surfaces and Its Effects on Pool Boiling Heat Transfer

    NASA Technical Reports Server (NTRS)

    Chao, David F.; Sankovic, John M.; Motil, Brian J.; Yang, W-J.; Zhang, Nengli

    2010-01-01

    The formation and growth processes of a bubble in the vicinity of graphite micro-fiber tips on metal-graphite composite boiling surfaces and their effects on boiling behavior are investigated. It is discovered that a large number of micro bubbles are formed first at the micro scratches and cavities on the metal matrix in pool boiling. By virtue of the non-wetting property of graphite, once the growing micro bubbles touch the graphite tips, the micro bubbles are sucked by the tips and merged into larger micro bubbles sitting on the end of the tips. The micro bubbles grow rapidly and coalesce to form macro bubbles, each spanning several tips. The necking process of a detaching macro bubble is analyzed. It is revealed that a liquid jet is produced by sudden break-off of the bubble throat. The composite surfaces not only have higher temperatures in micro- and macrolayers but also make higher frequency of the bubble departure, which increase the average heat fluxes in both the bubble growth stage and in the bubble departure period. Based on these analyses, the enhancement mechanism of pool boiling heat transfer on composite surfaces is clearly revealed.

  11. Transient Pool Boiling Critical Heat Flux of FC-72 Under Saturated Conditions

    SciTech Connect

    Fitri, Sutopo P.; Katsuya Fukuda; Qiusheng Liu; Jongdoc Park

    2006-07-01

    In this study, the steady-state and transient critical heat fluxes (CHFs) in pool boiling were measured on 1.0 mm diameter horizontal cylinders of gold and platinum heaters under saturated conditions due to transient heat inputs, Q{sub 0}exp(t/t), in a pool of Fluorinert FC-72. Heaters were heated by electric current with the periods, t, ranged from 10 ms to 20 s, and the pressures ranged from atmospheric up to around 1.2 MPa. The steady-state CHFs measured are dependent on pressure and almost agree with the values obtained by Kutateladze's correlation based on hydrodynamic instability (HI) model. It was considered that the boiling inception and the direct transition during the steady-state period occur by the pre-pressure of {approx}1.2 MPa. The trend of typical transient CHFs were clearly divided into the first, second, and third groups for long, short, and intermediate periods, respectively. The direct transition processes to film boiling without nucleate boiling for the short periods obtained from both heaters were confirmed due to the heterogeneous spontaneous nucleation (HSN) in flooded cavities on the cylinder surface. The empirical correlations to express each of corresponding CHFs measured on both heaters for the short periods are presented in this paper. (authors)

  12. Measurement of Key Pool BOiling Parameters in nanofluids for Nuclerar Applications

    SciTech Connect

    Bang, In C; Buongiorno, Jdacopo; Hu, Lin-wen; Wang, Hsin

    2007-01-01

    Nanofluids, colloidal dispersions of nanoparticles in a base fluid such as water, can afford very significant Critical Heat Flux (CHF) enhancement. Such engineered fluids potentially could be employed in reactors as advanced coolants in safety systems with significant safety and economic advantages. However, a satisfactory explanation of the CHF enhancement mechanism in nanofluids is lacking. To close this gap, we have identified the important boiling parameters to be measured. These are the properties (e.g., density, viscosity, thermal conductivity, specific heat, vaporization enthalpy, surface tension), hydrodynamic parameters (i.e., bubble size, bubble velocity, departure frequency, hot/dry spot dynamics) and surface conditions (i.e., contact angle, nucleation site density). We have also deployed a pool boiling facility in which many such parameters can be measured. The facility is equipped with a thin indium-tin-oxide heater deposited over a sapphire substrate. An infra-red high-speed camera and an optical probe are used to measure the temperature distribution on the heater and the hydrodynamics above the heater, respectively. The first data generated with this facility already provide some clue on the CHF enhancement mechanism in nanofluids. Specifically, the progression to burnout in a pure fluid (ethanol in this case) is characterized by a smoothly-shaped and steadily-expanding hot spot. By contrast, in the ethanol-based nanofluid the hot spot pulsates and the progression to burnout lasts longer, although the nanofluid CHF is higher than the pure fluid CHF. The presence of a nanoparticle deposition layer on the heater surface seems to enhance wettability and aid hot spot dissipation, thus delaying burnout.

  13. Measurement of Key Pool Boiling Parameters in Nanofluids for Nuclear Applications

    NASA Astrophysics Data System (ADS)

    Bang, In Cheol; Buongiorno, Jacopo; Hu, Lin-Wen; Wang, Hsin

    Nanofluids, colloidal dispersions of nanoparticles in a base fluid such as water, can afford very significant Critical Heat Flux (CHF) enhancement. Such engineered fluids potentially could be employed in reactors as advanced coolants in safety systems with significant safety and economic advantages. However, a satisfactory explanation of the CHF enhancement mechanism in nanofluids is lacking. To close this gap, we have identified the important boiling parameters to be measured. These are the properties (e.g., density, viscosity, thermal conductivity, specific heat, vaporization enthalpy, surface tension), hydrodynamic parameters (i.e., bubble size, bubble velocity, departure frequency, hot/dry spot dynamics) and surface conditions (i.e., contact angle, nucleation site density). We have also deployed a pool boiling facility in which many such parameters can be measured. The facility is equipped with a thin indium-tin-oxide heater deposited over a sapphire substrate. An infra-red high-speed camera and an optical probe are used to measure the temperature distribution on the heater and the hydrodynamics above the heater, respectively. The first data generated with this facility already provide some clue on the CHF enhancement mechanism in nanofluids. Specifically, the progression to burnout in a pure fluid (ethanol in this case) is characterized by a smoothly-shaped and steadily-expanding hot spot. By contrast, in the ethanol-based nanofluid the hot spot pulsates and the progression to burnout lasts longer, although the nanofluid CHF is higher than the pure fluid CHF. The presence of a nanoparticle deposition layer on the heater surface seems to enhance wettability and aid hot spot dissipation, thus delaying burnout.

  14. Environmental qualification testing of payload G-534, the Pool Boiling Experiment

    NASA Technical Reports Server (NTRS)

    Sexton, J. Andrew

    1992-01-01

    Payload G-534, the prototype Pool Boiling Experiment (PBE), is scheduled to fly on the STS-47 mission in September 1992. This paper describes the purpose of the experiment and the environmental qualification testing program that was used to prove the integrity of the hardware. Component and box level vibration and thermal cycling tests were performed to give an early level of confidence in the hardware designs. At the system level, vibration, thermal extreme soaks, and thermal vacuum cycling tests were performed to qualify the complete design for the expected shuttle environment. The system level vibration testing included three axis sine sweeps and random inputs. The system level hot and cold soak tests demonstrated the hardware's capability to operate over a wide range of temperatures and gave wider latitude in determining which shuttle thermal attitudes were compatible with the experiment. The system level thermal vacuum cycling tests demonstrated the hardware's capability to operate in a convection free environment. A unique environmental chamber was designed and fabricated by the PBE team and allowed most of the environmental testing to be performed within the hardware build laboratory. The completion of the test program gave the project team high confidence in the hardware's ability to function as designed during flight.

  15. Pool boiling heat transfer of deionized and degassed water in packed-perforated copper beads

    NASA Astrophysics Data System (ADS)

    Wen, Mao-Yu; Jang, Kuang-Jang; Ho, Ching-Yen

    2016-11-01

    Nucleate pool boiling with porous media made of perforated copper beads as the enhanced structure is conducted in saturated, deionized and degassed water. Data are taken at an atmospheric pressure (saturation temperature of 100 °C) and at heat fluxes from 4500 to 72,300 W/m2 while increasing the heat flux. The bead-packed structure is heated on the bottom. The layer of loose particles on the heated surface is free to move under the action of bulk liquid convection and vapor nucleation. The effects of the weight (number), size and layers of the free particles are experimentally explored using copper particles for different copper bead diameters which were 2, 3, 4 and 5 mm. The boiling enhancement is closely related to the particle weight, size and layers, and the heat flux applied. The results show that free particles are presented to have a distinct advantage in boiling heat transfer, resulting in an average increase in the heat transfer coefficient of 126 % relative to the flat plate without particles. In order to obtain insight into the fluid boiling phenomena, flow visualization is also made to observe the detailed fluid boiling characteristics of the copper particles present. The visualizations show that bubble nucleation preferentially occurs at the narrow corner cavities formed between the free particles and the heated surface.

  16. Pool boiling heat transfer of water/ γ-alumina micro-fluids around the horizontal cylinder

    NASA Astrophysics Data System (ADS)

    Nikkhah, V.; Hormozi, F.

    2016-04-01

    A set of experiments was performed to quantify the pool boiling heat transfer coefficient of water/ γ-alumina micro-fluids at mass concentration ranged from 0.1 to 0.4 % of micro-particles with mean size of 1-2 μm. To stabilize the prepared micro-fluid, pH control, stirring and adding the SDS as a surfactant were carried out. Also, thermal conductivity of micro-fluids are measured using KD2 decagon pro. Results showed that micro-fluids have relatively higher thermal conductivity rather than the base fluids. According to the results, there are two distinguishable heat transfer regions namely natural convection and nucleate boiling regions. Influence of some operating parameters such as heat flux, mass concentration of micro-particles and surface fouling resistance on the pool boiling heat transfer coefficient were experimentally studied and briefly discussed. Results demonstrated a significant deterioration of heat transfer coefficient of micro-fluids in comparison with the base fluid over the extended time (1000 min of operation) in nucleate boiling region, while in natural convection region, enhancement of heat transfer coefficient is registered. According to the results, heat transfer coefficient is strongly controlled by/ γ-alumina concentration due to the deposition of micro-particles on the heating section. Rectilinear changes of scale formation with time in term of fouling resistance were clearly seen at regions, where natural convection is a dominant heat transfer mechanism and also for higher heat fluxes at nucleate boiling heat transfer region.

  17. Theoretical modeling of CHF for near-saturated pool boiling and flow boiling from short heaters using the interfacial lift-off criterion

    SciTech Connect

    Mudawar, I.; Galloway, J.E.; Gersey, C.O.

    1995-12-31

    Pool boiling and flow boiling were examined for near-saturated bulk conditions in order to determine the critical heat flux (CHF) trigger mechanism for each. Photographic studies of the wall region revealed features common to both situations. At fluxes below CHF, the vapor coalesces into a wavy layer which permits wetting only in wetting fronts, the portions of the liquid-vapor interface which contact the wall as a result of the interfacial waviness. Close examination of the interfacial features revealed the waves are generated from the lower edge of the heater in pool boiling and the heater`s upstream region in flow boiling. Wavelengths follow predictions based upon the Kelvin-Helmholtz instability criterion. Critical heat flux in both cases occurs when the pressure force exerted upon the interface due to interfacial curvature, which tends to preserve interfacial contact with the wall prior to CHF, is overcome by the momentum of vapor at the site of the first wetting front, causing the interface to lift away from the wall. It is shown this interfacial lift-off criterion facilitates accurate theoretical modeling of CHF in pool boiling and in flow boiling in both straight and curved channels.

  18. Enhancement of pool boiling from a vertical rod using guide disks

    SciTech Connect

    Whitehouse, J.C.

    1992-11-01

    This report provides experimental and theoretical investigation of the boiling process which used a system of evenly spaced disks to constrain the path of bubbles from point origin to point of collapse. The experiments identified five distinct heat-transfer regimes, two of which (flange and strobe) are unique to this geometry and cannot be explained by conventional heat-transfer correlations. Bubble and wave models developed for flange and strobe boiling, respectively, predict these phenomena with reasonable success.

  19. Enhancement of pool boiling from a vertical rod using guide disks

    SciTech Connect

    Whitehouse, J.C.

    1992-01-01

    This report provides experimental and theoretical investigation of the boiling process which used a system of evenly spaced disks to constrain the path of bubbles from point origin to point of collapse. The experiments identified five distinct heat-transfer regimes, two of which (flange and strobe) are unique to this geometry and cannot be explained by conventional heat-transfer correlations. Bubble and wave models developed for flange and strobe boiling, respectively, predict these phenomena with reasonable success.

  20. Numerical Simulation on Single Bubble Pool Boiling with Influence of Heater Thermal Capacity

    NASA Astrophysics Data System (ADS)

    Zhao, Jian-Fu; Zhang, Liang; Li, Zhen-Dong

    The model of single bubble pool boiling is used to simulate nucleate pool boiling phenomenon in the present paper. Local convection and heat transfer around a single vapour bubble which is growing from a nucleus bubble planted artificially on the surface of heaters with different thicknesses, as well as transient heat conduction inside the heater’s wall, are simulated numerically with sharp interface representation. Multi-cycle simulation is adopted to eliminate the effect of un-physical initial conditions. It’s found that the thermal response of wall is found to affect the bubble growth and boiling heat transfer. During the process of bubble growth, a sharp temperature drop inside the solid wall is evident near the contact line underneath the growing bubble because of the strong evaporation in micro-region. The temperature and heat flux profiles change with the move of the contact line, and twice sharp temperature drops at a certain location are observed, which correspond to the expanding and recoiling processes, respectively. During the waiting period after the bubble detached from the wall, the temperature field is recovered by heat conduction inside the solid wall. As a part of preparation of the SOBER project onboard the Chinese recoverable satellite SJ-10, which will be launched in the end of 2015, the gravity influence is also studied.

  1. Critical Heat Flux in Pool Boiling on Metal-Graphite Composite Surfaces

    NASA Technical Reports Server (NTRS)

    Zhang, Nengli; Yang, Wen-Jei; Chao, David F.; Chao, David F. (Technical Monitor)

    2000-01-01

    A study is conducted on high heat-flux pool boiling of pentane on micro-configured composite surfaces. The boiling surfaces are copper-graphite (Cu-Gr) and aluminum-graphite (Al-Gr) composites with a fiber volume concentration of 50%. The micro-graphite fibers embedded in the matrix contribute to a substantial enhancement in boiling heat-transfer performance. Correlation equations are obtained for both the isolated and coalesced bubble regimes, utilizing a mathematical model based on a metal-graphite, two-tier configuration with the aid of experimental data. A new model to predict the critical heat flux (CHF) on the composites is proposed to explain the fundamental aspects of the boiling phenomena. Three different factors affecting the CHF are considered in the model. Two of them are expected to become the main agents driving vapor volume detachment under microgravity conditions, using the metal-graphite composite surfaces as the heating surface and using liquids with an unusual Marangoni effect as the working fluid.

  2. Bubble Behavior in Subcooled Pool Boiling of Water under Reduced Gravity

    NASA Astrophysics Data System (ADS)

    Suzuki, Koichi; Suzuki, Motohiro; Takahash, Saika; Kawamura, Hirosi; Abe, Yoshiyuki

    2003-01-01

    Subcooled pool boiling of water was conducted in reduced gravity performed by a parabolic flight of aircraft and a drop-shaft facility. A small stainless steel plate was physically burned out in the subcooled water by AC electric power during the parabolic flight. Boiling bubbles grew with increasing heating power but did not detached from the heating surface. The burnout heat fluxes obtained were 200 ~ 400 percent higher than the existing theories. In the ground experiment, boiling bubbles were attached to the heating surface with a flat plate placed over the heating surface, and the experiment was performed by the same heating procedure as practiced under the reduced gravity. Same burnout heat fluxes as under the reduced gravity were obtained by adjusting the plate clearance to the heating surface. As the heating time extended longer than the reduced gravity duration, the burnout heat fluxes decreased gradually and became constant. Contact area of bubbles with heating surface was observed using a transparent heating surface in microgravity performed by a drop-shaft facility. The contact area of bubbles increased significantly at the start of microgravity. It is suggested by the experimental results that the boiling bubbles expand rapidly in the high heat flux region and the rapid evaporation of liquid layer remained between the bubbles and the heating surface raises up the critical heat flux higher than the existing theories in microgravity.

  3. EHD enhancement of pool and in-tube boiling of alternate refrigerants

    NASA Astrophysics Data System (ADS)

    Ohadi, M. M.; Dessiatoun, S.; Singh, A.; Fanni, M. A.

    1993-08-01

    The electrohydrodynamic (EHD) is an active heat transfer augmentation technique which utilizes the effect of secondary motions generated through the application of an electrostatic potential to a dielectric fluid. Net result is better momentum and heat transfer between the fluid and the heat transfer wall through destabilization of the thermal boundary layer and better mixing of the fluid adjacent to the heat transfer surface. EHD enhancement of refrigerant/refrigerant oil mixtures heat transfer using the electrohydrodynamic (EHD) technique is the subject of a three-year experimental investigation in a project funded by the U.S. Department of Energy, effective June 1, 1993. For the interim period between November 1992 and June 1993 when the DOE funds became available, the Air-Conditioning and Refrigeration Technology Institute (ARTI) provided partial funding for our EHD research program with the aim of accomplishing three major tasks: (1) conduct a comprehensive search of the literature on EHD-enhanced, in-tube and external boiling heat transfer enhancement of alternate refrigerants; (2) design, fabricate, and instrument an in-tube, EHD-enhanced boiling/condensation test rig and perform preliminary testing of the setup; and (3) conduct experiments and document new findings on EHD-enhanced external boiling of alternate refrigerants/refrigerant mixtures in an existing pool boiling test rig apparatus. Description of tasks performed are described and results are discussed.

  4. Single-bubble dynamics in pool boiling of one-component fluids.

    PubMed

    Xu, Xinpeng; Qian, Tiezheng

    2014-06-01

    We numerically investigate the pool boiling of one-component fluids with a focus on the effects of surface wettability on the single-bubble dynamics. We employed the dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)], a diffuse-interface model for liquid-vapor flows involving liquid-vapor transition in nonuniform temperature fields. We first perform simulations for bubbles on homogeneous surfaces. We find that an increase in either the contact angle or the surface superheating can enhance the bubble spreading over the heating surface and increase the bubble departure diameter as well and therefore facilitate the transition into film boiling. We then examine the dynamics of bubbles on patterned surfaces, which incorporate the advantages of both hydrophobic and hydrophilic surfaces. The central hydrophobic region increases the thermodynamic probability of bubble nucleation while the surrounding hydrophilic region hinders the continuous bubble spreading by pinning the contact line at the hydrophobic-hydrophilic intersection. This leads to a small bubble departure diameter and therefore prevents the transition from nucleate boiling into film boiling. With the bubble nucleation probability increased and the bubble departure facilitated, the efficiency of heat transfer on such patterned surfaces is highly enhanced, as observed experimentally [Int. J. Heat Mass Transfer 57, 733 (2013)]. In addition, the stick-slip motion of contact line on patterned surfaces is demonstrated in one-component fluids, with the effect weakened by surface superheating.

  5. Wettability influence on the onset temperature of pool boiling: Experimental evidence onto ultra-smooth surfaces.

    PubMed

    Bourdon, B; Bertrand, E; Di Marco, P; Marengo, M; Rioboo, R; De Coninck, J

    2015-07-01

    In this article we study systematically the effect of wettability on the onset of boiling on the same nanometrically smooth surface. By grafting different monolayers of molecules, we were able to explore the wettability from the equilibrium static contact angle, θ0=0° to θ0=110°, without changing the surface topography. The superheat temperature at the onset of pool boiling was measured and eventually a non-classical trend of TONB as a function of wettability was observed. The nucleation site densities for the different grafting cases were also measured by image analysis. Moreover, we propose a novel theoretical interpretation to this phenomenon linking nucleation and the molecular diffusion coefficient. MD simulation results support this approach.

  6. Experimental studies on CHF enhancement in pool boiling with CuO-water nanofluid

    NASA Astrophysics Data System (ADS)

    Hegde, Ramakrishna N.; Rao, Shrikantha S.; Reddy, R. P.

    2012-06-01

    Critical heat flux enhancement (CHF) in pool boiling with CuO nanofluids was experimentally studied using a 36 gauge NiCr wire at atmospheric pressure. Experimentation included (1) subjecting the wire surface to multiple heating cycles with constant volume concentration of CuO nanofluid and (2) subjecting the wire surface to a single heating cycle with different volume concentrations of CuO nanofluid. Boiling of nanofluid in both the cases resulted in nanoparticle deposition and subsequent smoothing of the wire surface. To substantiate the nanoparticle deposition and its effect on critical heat flux, investigation was done by studying the surface roughness and SEM images of the wire surface. The experimental results show the evidence of nanoparticle deposition on the wire surface and its effect on CHF enhancement.

  7. Alkali metal pool boiler life tests for a 25 kWe advanced Stirling conversion system

    NASA Technical Reports Server (NTRS)

    Anderson, W. G.; Rosenfeld, J. H.; Noble, J.

    1991-01-01

    The overall operating temperature and efficiency of solar-powered Stirling engines can be improved by adding an alkali metal pool boiler heat transport system to supply heat more uniformly to the heater head tubes. One issue with liquid metal pool boilers is unstable boiling. Stable boiling is obtained with an enhanced boiling surface containing nucleation sites that promote continuous boiling. Over longer time periods, it is possible that the boiling behavior of the system will change. An 800-h life test was conducted to verify that pool boiling with the chosen fluid/surface combination remains stable as the system ages. The apparatus uses NaK boiling on a - 100 + 140 stainless steel sintered porous layer, with the addition of a small amount of xenon. Pool boiling remained stable to the end of life test. The pool boiler life test included a total of 82 cold starts, to simulate startup each morning, and 60 warm restarts, to simulate cloud cover transients. The behavior of the cold and warm starts showed no significant changes during the life test. In the experiments, the fluid/surface combination provided stable, high-performance boiling at the operating temperature of 700 C. Based on these experiments, a pool boiler was designed for a full-scale 25-kWe Stirling system.

  8. Boils

    MedlinePlus

    ... the boil is very bad or comes back. Antibacterial soaps and creams cannot help much once a ... following may help prevent the spread of infection: Antibacterial soaps Antiseptic (germ-killing) washes Keeping clean (such ...

  9. Boiling induced nanoparticle coating and its effect on pool boiling heat transfer on a vertical cylindrical surface using CuO nanofluids

    NASA Astrophysics Data System (ADS)

    Hegde, Ramakrishna N.; Rao, Shrikantha S.; Reddy, R. P.

    2012-09-01

    Experiments were performed to study boiling induced nanoparticle coating and its influence on pool boiling heat transfer using low concentrations of CuO- nanofluid in distilled water at atmospheric pressure. To investigate the effect of the nanoparticle coated surface on pool boiling performance, two different concentrations of CuO nanofluids (0.1 and 0.5 g/l) were chosen and tests were conducted on a clean heater surface in nanofluid and nanoparticle coated surface in pure water. For the bare heater tested in CuO nanofluid, CHF was enhanced by 35.83 and 41.68 % respectively at 0.1 and 0.5 g/l concentration of nanofluid. For the nanoparticle coated heater surface obtained by boiling induced coating using 0.1 and 0.5 g/l concentration of nanofluid and tested in pure water, CHF was enhanced by 29.38 and 37.53 % respectively. Based on the experimental investigations it can be concluded that nanoparticle coating can also be a potential substitute for enhancing the heat transfer in pure water. Transient behaviour of nanofluid was studied by keeping heat flux constant at 1,000 and 1,500 kW/m2 for 90 min in 0.5 g/l concentration. The boiling curve shifted to the right indicating degradation in boiling heat transfer due to prolonged exposure of heater surface to nanofluid. Experimental outcome indicated that pool boiling performance of nanofluid could be a strong function of time and applied heat flux. The longer the duration of exposure of the heater surface, the higher will be the degradation in heat transfer.

  10. Pool film boiling from rotating and stationary spheres in liquid nitrogen. [for SSME turbopump ball bearings

    NASA Technical Reports Server (NTRS)

    Cuan, Winston M.; Schwartz, Sidney H.

    1988-01-01

    Results are presented for a preliminary experiment involving a saturated pool boiling at 1 atm from rotating 2 and 3 inch diameter spheres which were immersed in LN2. Additional results are presented for a stationary 2 inch diameter sphere quenched in LN2, which were obtained with a more versatile and complete experimental apparatus. The speed of the rotational tests varied from 0 to 10,000 rpm. The stationary experiments parametrically varied pressure and subcooling levels from 0 to 600 psig and from 0 to 50 F, respectively. During the rotational tests, a high speed photographic analysis was undertaken to measure the thickness of the vapor film surrounding the sphere.

  11. Analytical model of the time variation of liquid film thickness under saturation pool boiling bubbles

    SciTech Connect

    Yajima, Takeshi; Yabe, Akira; Takahashi, Katsuyuki; Maki, Hiroshi

    1999-07-01

    Zuber's and Katto's models have been proposed for explaining the mechanism of burnout heat flux. But these are static models, and do not account for the EHD (Electro-hydrodynamical) effects. The authors therefore determined the dynamic burnout heat flux mechanisms by measuring the EHD enhancement effect and by measuring the time-dependent thickness of the thin liquid film under pool boiling bubbles. They found that the time variation of the liquid film thickness is controlled by the surface tension around the edge of the bubbles and by the repeated supply and discharge of liquid from the thin liquid film region under the bubbles.

  12. Effect of ionic additive on pool boiling critical heat flux of titania/water nanofluids

    NASA Astrophysics Data System (ADS)

    Jung, Jung-Yeul; Kim, Hyungdae; Kim, Moo Hwan

    2013-01-01

    TiO2/water nanofluids were prepared and tested to investigate the effects of an ionic additive (i.e., nitric acid in this study) on the critical heat flux (CHF) behavior in pool boiling. Experimental results showed that the ionic additive improved the dispersion stability but reduced the CHF increase in the nanofluid. The additive affected the self-assembled nanoparticle structures formed on the heater surfaces by creating a more uniform and smoother structure, thus diminishing the CHF enhancement in nanofluids.

  13. Cryogenic Boil-Off Reduction System Testing

    NASA Technical Reports Server (NTRS)

    Plachta, David W.; Johnson, Wesley L.; Feller, Jeffery

    2014-01-01

    The Cryogenic Boil-Off Reduction System was tested with LH2 and LOX in a vacuum chamber to simulate space vacuum and the temperatures of low Earth orbit. Testing was successful and results validated the scaling study model that predicts active cooling reduces upper stage cryogenic propulsion mass for loiter periods greater than 2 weeks.

  14. Cryogenic Propellant Boil-Off Reduction System

    NASA Astrophysics Data System (ADS)

    Plachta, D. W.; Christie, R. J.; Carlberg, E.; Feller, J. R.

    2008-03-01

    Lunar missions under consideration would benefit from incorporation of high specific impulse propellants such as LH2 and LO2, even with their accompanying boil-off losses necessary to maintain a steady tank pressure. This paper addresses a cryogenic propellant boil-off reduction system to minimize or eliminate boil-off. Concepts to do so were considered under the In-Space Cryogenic Propellant Depot Project. Specific to that was an investigation of cryocooler integration concepts for relatively large depot sized propellant tanks. One concept proved promising—it served to efficiently move heat to the cryocooler even over long distances via a compressed helium loop. The analyses and designs for this were incorporated into NASA Glenn Research Center's Cryogenic Analysis Tool. That design approach is explained and shown herein. Analysis shows that, when compared to passive only cryogenic storage, the boil-off reduction system begins to reduce system mass if durations are as low as 40 days for LH2, and 14 days for LO2. In addition, a method of cooling LH2 tanks is presented that precludes development issues associated with LH2 temperature cryocoolers.

  15. Pool boiling with high heat flux enabled by a porous artery structure

    NASA Astrophysics Data System (ADS)

    Bai, Lizhan; Zhang, Lianpei; Lin, Guiping; Peterson, G. P.

    2016-06-01

    A porous artery structure utilizing the concept of "phase separation and modulation" is proposed to enhance the critical heat flux of pool boiling. A series of experiments were conducted on a range of test articles in which multiple rectangular arteries were machined directly into the top surface of a 10.0 mm diameter copper rod. The arteries were then covered by a 2.0 mm thickness microporous copper plate through silver brazing. The pool wall was fabricated from transparent Pyrex glass to allow a visualization study, and water was used as the working fluid. Experimental results confirmed that the porous artery structure provided individual flow paths for the liquid supply and vapor venting, and avoided the detrimental effects of the liquid/vapor counter flow. As a result, a maximum heat flux of 610 W/cm2 over a heating area of 0.78 cm2 was achieved with no indication of dryout, prior to reaching the heater design temperature limit. Following the experimental tests, the mechanisms responsible for the boiling critical heat flux and performance enhancement of the porous artery structure were analyzed.

  16. Cryogenic Boil-Off Reduction System Testing

    NASA Technical Reports Server (NTRS)

    Plachta, David W.; Johnson, Wesley L.; Feller, Jeffrey R.

    2014-01-01

    Cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LO2) are a part of NASA's future space exploration due to the high specific impulse that can be achieved using engines suitable for moving 10's to 100's of metric tons of payload mass to destinations outside of low earth orbit. However, the low storage temperatures of LH2 and LO2 cause substantial boil-off losses for missions with durations greater than several days. The losses can be greatly reduced by incorporating high performance cryocooler technology to intercept heat load to the propellant tanks and by the integration of self-supporting multi-layer insulation. The active thermal control technology under development is the integration of the reverse turbo- Brayton cycle cryocooler to the propellant tank through a distributed cooling network of tubes coupled to a shield in the tank insulation and to the tank wall itself. Also, the self-supporting insulation technology was utilized under the shield to obtain needed tank applied LH2 performance. These elements were recently tested at NASA Glenn Research Center in a series of three tests, two that reduced LH2 boil-off and one to eliminate LO2 boil-off. This test series was conducted in a vacuum chamber that replicated the vacuum of space and the temperatures of low Earth orbit. The test results show that LH2 boil-off was reduced 60% by the cryocooler system operating at 90K and that robust LO2 zero boil-off storage, including full tank pressure control was achieved.

  17. Investigations on heat transfer enhancement in pool boiling with water-CuO nano-fluids

    NASA Astrophysics Data System (ADS)

    Hegde, Ramakrishna N.; Rao, Shrikantha S.; Reddy, R. P.

    2012-04-01

    The main focus of the present work is to investigate Critical Heat Flux (CHF) enhancement using CuO nanofluid relative to CHF of pure water. To estimate the effect of nanoparticles on the CHF, pool boiling CHF values were measured for various volume concentrations of CuO nanofluid and compared with pure water. CHF enhancement of 130% was recorded at 0.2 % by volume of CuO nano-fluids. Surface roughness of the heater surface exposed to three measured heating cycles indicated surface modifications at different volume concentrations of nanofluid. SEM image of the heater surface revealed porous layer build up, which is thought to be the reason for CHF enhancement.

  18. Generalized multidemensional propagation velocity equations for pool-boiling superconducting windings

    SciTech Connect

    Christensen, E.H.; O'Loughlin, J.M.

    1984-09-01

    Several finite difference, finite element detailed analyses of propagation velocities in up to three dimensions in pool-boiling windings have been conducted for different electromagnetic and cryogenic environments. Likewise, a few full scale simulated winding and magnet tests have measured propagation velocities. These velocity data have been correlated in terms of winding thermophysical parameters. This analysis expresses longitudinal and transverse propagation velocities in the form of power function regression equations for a wide variety of windings and electromagnetic and thermohydraulic environments. The generalized velocity equations are considered applicable to well-ventilated, monolithic conductor windings. These design equations are used piecewise in a gross finite difference mode as functions of field to predict the rate of normal zone growth during quench conditions. A further check of the validity of these predictions is available through total predicted quench durations correlated with actual quench durations of large magnets.

  19. Thermal singularity and contact line motion in pool boiling: Effects of substrate wettability.

    PubMed

    Taylor, M T; Qian, Tiezheng

    2016-03-01

    The dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)] is employed to model the growth of a single vapor bubble in a superheated liquid on a flat homogeneous substrate. The bubble spreading dynamics in the pool boiling regime has been numerically investigated for one-component van der Waals fluids close to the critical point, with a focus on the effect of the substrate wettability on bubble growth and contact line motion. The substrate wettability is found to control the apparent contact angle and the rate of bubble growth (the rate of total evaporation), through which the contact line speed is determined. An approximate expression is derived for the contact line speed, showing good agreement with the simulation results. This demonstrates that the contact line speed is primarily governed by (1) the circular shape of interface (for slow bubble growth), (2) the constant apparent contact angle, and (3) the constant bubble growth rate. It follows that the contact line speed has a sensitive dependence on the substrate wettability via the apparent contact angle which also determines the bubble growth rate. Compared to hydrophilic surfaces, hydrophobic surfaces give rise to a thinner shape of bubble and a higher rate of total evaporation, which combine to result in a much faster contact line speed. This can be linked to the earlier formation of a vapor film and hence the onset of boiling crisis.

  20. Thermal singularity and contact line motion in pool boiling: Effects of substrate wettability

    NASA Astrophysics Data System (ADS)

    Taylor, M. T.; Qian, Tiezheng

    2016-03-01

    The dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007), 10.1103/PhysRevE.75.036304] is employed to model the growth of a single vapor bubble in a superheated liquid on a flat homogeneous substrate. The bubble spreading dynamics in the pool boiling regime has been numerically investigated for one-component van der Waals fluids close to the critical point, with a focus on the effect of the substrate wettability on bubble growth and contact line motion. The substrate wettability is found to control the apparent contact angle and the rate of bubble growth (the rate of total evaporation), through which the contact line speed is determined. An approximate expression is derived for the contact line speed, showing good agreement with the simulation results. This demonstrates that the contact line speed is primarily governed by (1) the circular shape of interface (for slow bubble growth), (2) the constant apparent contact angle, and (3) the constant bubble growth rate. It follows that the contact line speed has a sensitive dependence on the substrate wettability via the apparent contact angle which also determines the bubble growth rate. Compared to hydrophilic surfaces, hydrophobic surfaces give rise to a thinner shape of bubble and a higher rate of total evaporation, which combine to result in a much faster contact line speed. This can be linked to the earlier formation of a vapor film and hence the onset of boiling crisis.

  1. Thermal singularity and contact line motion in pool boiling: Effects of substrate wettability.

    PubMed

    Taylor, M T; Qian, Tiezheng

    2016-03-01

    The dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)] is employed to model the growth of a single vapor bubble in a superheated liquid on a flat homogeneous substrate. The bubble spreading dynamics in the pool boiling regime has been numerically investigated for one-component van der Waals fluids close to the critical point, with a focus on the effect of the substrate wettability on bubble growth and contact line motion. The substrate wettability is found to control the apparent contact angle and the rate of bubble growth (the rate of total evaporation), through which the contact line speed is determined. An approximate expression is derived for the contact line speed, showing good agreement with the simulation results. This demonstrates that the contact line speed is primarily governed by (1) the circular shape of interface (for slow bubble growth), (2) the constant apparent contact angle, and (3) the constant bubble growth rate. It follows that the contact line speed has a sensitive dependence on the substrate wettability via the apparent contact angle which also determines the bubble growth rate. Compared to hydrophilic surfaces, hydrophobic surfaces give rise to a thinner shape of bubble and a higher rate of total evaporation, which combine to result in a much faster contact line speed. This can be linked to the earlier formation of a vapor film and hence the onset of boiling crisis. PMID:27078445

  2. Effect of subcooling and wall thickness on pool boiling from downward-facing curved surfaces in water

    SciTech Connect

    El-Genk, M.S.; Glebov, A.G.

    1995-09-01

    Quenching experiments were performed to investigate the effects of water subcooling and wall thickness on pool boiling from a downward-facing curved surface. Experiments used three copper sections of the same diameter (50.8 mm) and surface radius (148 mm), but different thickness (12.8, 20 and 30 mm). Local and average pool boiling curves were obtained at saturation and 5 K, 10 K, and 14 K subcooling. Water subcooling increased the maximum heat flux, but decreased the corresponding wall superheat. The minimum film boiling heat flux and the corresponding wall superheat, however, increased with increased subcooling. The maximum and minimum film boiling heat fluxes were independent of wall thickness above 20 mm and Biot Number > 0.8, indicating that boiling curves for the 20 and 30 thick sections were representative of quasi steady-state, but not those for the 12.8 mm thick section. When compared with that for a flat surface section of the same thickness, the data for the 12.8 mm thick section showed significant increases in both the maximum heat flux (from 0.21 to 0.41 MW/m{sup 2}) and the minimum film boiling heat flux (from 2 to 13 kW/m{sup 2}) and about 11.5 K and 60 K increase in the corresponding wall superheats, respectively.

  3. Bubble Behavior and Heat Transfer of Nucleate Pool Boiling on Micro-Pin-Finned Surface in Microgravity

    NASA Astrophysics Data System (ADS)

    Wei, Jin-Jia; Xue, Yan-Fang; Zhao, Jian-Fu; Li, Jing

    2011-01-01

    Nucleate pool boiling on micro-pin-finned surface structure is proposed for efficiently cooling electronic components with high heat flux in microgravity, and was verified by experiments performed utilizing the drop tower Beijing. Micro-pin-fins with the dimensions of 50 × 60 μm2 (thickness × height) and the space of 50 μm were fabricated on the chip surface by the dry etching technique. FC-72 was used as the working fluid. Nucleate pool boiling of FC-72 on a smooth surface was also tested for comparison. Unlike much obvious deterioration of heat transfer of nucleate pool boiling on the smooth surface in microgravity, constant heater surface temperature of nucleate pool boiling for the micro-pin-finned surface was observed, even though a large coalesced bubble completely covered the surface under microgravity condition. The performance of high efficient heat transfer on micro-pin-finned surface is independent of the gravity, which stems from the sufficient supply of fresh liquid to the heater surface due to the capillary forces.

  4. Effects of nanoparticle layering on nanofluid and base fluid pool boiling heat transfer from a horizontal surface under atmospheric pressure

    NASA Astrophysics Data System (ADS)

    White, Steven B.; Shih, Albert J.; Pipe, Kevin P.

    2010-06-01

    Previous heat transfer studies of nanofluids have shown that suspended nanoparticles can affect thermal properties within a fluid and furthermore can affect surface roughness by depositing on a heater surface. Pool boiling studies of nanofluids have demonstrated either enhanced or diminished heat transfer, yet have been unable to distinguish the contributions of increased surface roughness and suppression of bubble transport by suspended particles because they have used base fluids on a clean boiling surface as a comparison. We resolve this uncertainty by studying the boiling performance of a surface exposed to a series of boiling tests that alternate between water and a water-based nanofluid with suspended 40 nm ZnO nanoparticles. We find that the performance for the water tests increases significantly, showing a 62% enhancement after four cycles. This increase correlates well with a surface roughness model for boiling that uses atomic force microscopy-measured surface data to quantify the layering of nanoparticles in intervening nanofluid boiling tests. We find that the performance of the ZnO nanofluid initially shows a 24% enhancement versus water on a clean (unroughened) surface, but then steadily declines in later tests as nanoparticle layering occurs, showing a measured trend that is opposite that of water. We ascribe this decrease to the suppression of bubble formation and motion by the suspended particles. The results demonstrate that the effect of increased surface roughness due to nanoparticle layering can be twofold, greatly enhancing boiling for the base fluid and slightly decreasing performance for the nanofluid.

  5. Zero Boil-Off System Testing

    NASA Technical Reports Server (NTRS)

    Plachta, David W.; Johnson, Wesley L.; Feller, Jeffrey R.

    2015-01-01

    Cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LO2) are a part of NASA's future space exploration due to their high specific impulse for rocket motors of upper stages suitable for transporting 10s to 100s of metric tons of payload mass to destinations outside of low earth orbit and for their return. However, the low storage temperatures of LH2 and LO2 cause substantial boil-off losses for missions with durations greater than several months. These losses can be eliminated by incorporating high performance cryocooler technology to intercept heat load to the propellant tanks and modulating the cryocooler to control tank pressure. The active thermal control technology being developed by NASA is the reverse turbo-Brayton cycle cryocooler and its integration to the propellant tank through a distributed cooling tubing network coupled to the tank wall. This configuration was recently tested at NASA Glenn Research Center, in a vacuum chamber and cryoshroud that simulated the essential thermal aspects of low Earth orbit, its vacuum and temperature. Testing consisted of three passive tests with the active cryocooler system off, and 7 active tests, with the cryocooler powered up. The test matrix included zero boil-off tests performed at 90 full and 25 full, and several demonstrations at excess cooling capacity and reduced cooling capacity. From this, the tank pressure response with varied cryocooler power inputs was determined. This test series established that the active cooling system integrated with the propellant tank eliminated boil-off and robustly controlled tank pressure.

  6. Transient pool boiling heat transfer due to increasing heat inputs in subcooled water at high pressures

    SciTech Connect

    Fukuda, K.; Shiotsu, M.; Sakurai, A.

    1995-09-01

    Understanding of transient boiling phenomenon caused by increasing heat inputs in subcooled water at high pressures is necessary to predict correctly a severe accident due to a power burst in a water-cooled nuclear reactor. Transient maximum heat fluxes, q{sub max}, on a 1.2 mm diameter horizontal cylinder in a pool of saturated and subcooled water for exponential heat inputs, q{sub o}e{sup t/T}, with periods, {tau}, ranging from about 2 ms to 20 s at pressures from atmospheric up to 2063 kPa for water subcoolings from 0 to about 80 K were measured to obtain the extended data base to investigate the effect of high subcoolings on steady-state and transient maximum heat fluxes, q{sub max}. Two main mechanisms of q{sub max} exist depending on the exponential periods at low subcoolings. One is due to the time lag of the hydrodynamic instability which starts at steady-state maximum heat flux on fully developed nucleate boiling (FDNB), and the other is due to the heterogenous spontaneous nucleations (HSN) in flooded cavities which coexist with vapor bubbles growing up from active cavities. The shortest period corresponding to the maximum q{sub max} for long period range belonging to the former mechanism becomes longer and the q{sub max}mechanism for long period range shifts to that due the HSN on FDNB with the increase of subcooling and pressure. The longest period corresponding to the minimum q{sub max} for the short period range belonging to the latter mechanism becomes shorter with the increase in saturated pressure. On the contrary, the longest period becomes longer with the increase in subcooling at high pressures. Correlations for steady-state and transient maximum heat fluxes were presented for a wide range of pressure and subcooling.

  7. Enhancement of Pool Boiling Heat Transfer and Control of Bubble Motion in Microgravity Using Electric Fields - BCOEL

    NASA Technical Reports Server (NTRS)

    Herman, Cila; Iacona, Estelle; Acquaviva, Tom; Coho, Bill; Grant, Nechelle; Nahra, Henry; Sankaran, Subramanian; Taylor, Al; Julian, Ed; Robinson, Dale; VanZandt, Dave

    2001-01-01

    The BCOEL project focuses on improving pool boiling heat transfer and bubble control in microgravity by exposing the fluid to electric fields. The electric fields induce a body force that can replace gravity in the low gravity environment, and enhance bubble removal from thc heated surface. A better understanding of microgravity effects on boiling with and without electric fields is critical to the proper design of the phase-change-heat-removal equipment for use in space-based applications. The microgravity experiments will focus on the visualization of bubble formation and shape during boiling. Heat fluxes on the boiling surface will be measured, and, together with the measured driving temperature differences, used to plot boiling curvcs for different electric field magnitudes. Bubble formation and boiling processes were found to be extremely sensitive to g-jitter. The duration of the experimental run is critical in order to achieve steady state in microgravity experiments. The International Space Station provides conditions suitable for such experiments. The experimental appararus to be used in the study is described in the paper. The apparatus will be tested in the KC-135 first, and microgravity experiments will be conducted on board of the International Space Station using the Microgravity Science Glovebox as the experimental platform.

  8. Enhancement of Pool Boiling Heat Transfer and Control of Bubble Motion in Microgravity Using Electric Fields (BCOEL)

    NASA Technical Reports Server (NTRS)

    Herman, Cila; Iacona, Estelle; Acquaviva, Tom; Coho, Bill; Grant, Nechelle; Nahra, Henry; Taylor, Al; Julian, Ed; Robinson, Dale; VanZandt, Dave

    2001-01-01

    The BCOEL project focuses on improving pool boiling heat transfer and bubble control in microgravity by exposing the fluid to electric fields. The electric fields induce a body force that can replace gravity in the low gravity environment, and enhance bubble removal from the heated surface. A better understanding of microgravity effects on boiling with and without electric fields is critical to the proper design of the phase-change-heat-removal equipment for use in spacebased applications. The microgravity experiments will focus on the visualization of bubble formation and shape during boiling. Heat fluxes on the boiling surface will be measured, and, together with the measured driving temperature differences, used to plot boiling curves for different electric field magnitudes. Bubble formation and boiling processes were found to be extremely sensitive to g-jitter. The duration of the experimental run is critical in order to achieve steady state in microgravity experiments. The International Space Station provides conditions suitable for such experiments. The experimental apparatus to be used in the study is described in the paper. The apparatus will be tested in the KC-135 first, and microgravity experiments will be conducted on board of the International Space Station using the Microgravity Science Glovebox as the experimental platform.

  9. Zero Boil-Off System Testing

    NASA Technical Reports Server (NTRS)

    Plachta, D. W.; Johnson, W. L.; Feller, J. R.

    2015-01-01

    Cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LO2) are a part of NASA's future space exploration plans due to their high specific impulse for rocket motors of upper stages. However, the low storage temperatures of LH2 and LO2 cause substantial boil-off losses for long duration missions. These losses can be eliminated by incorporating high performance cryocooler technology to intercept heat load to the propellant tanks and modulating the cryocooler temperature to control tank pressure. The technology being developed by NASA is the reverse turbo-Brayton cycle cryocooler and its integration to the propellant tank through a distributed cooling tubing network coupled to the tank wall. This configuration was recently tested at NASA Glenn Research Center in a vacuum chamber and cryoshroud that simulated the essential thermal aspects of low Earth orbit, its vacuum and temperature. This test series established that the active cooling system integrated with the propellant tank eliminated boil-off and robustly controlled tank pressure.

  10. Zero boil-off system testing

    NASA Astrophysics Data System (ADS)

    Plachta, D. W.; Johnson, W. L.; Feller, J. R.

    2016-03-01

    Cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LO2) are a part of NASA's future space exploration plans due to their high specific impulse for rocket motors of upper stages. However, the low storage temperatures of LH2 and LO2 cause substantial boil-off losses for long duration missions. These losses can be eliminated by incorporating high performance cryocooler technology to intercept heat load to the propellant tanks and modulating the cryocooler temperature to control tank pressure. The technology being developed by NASA is the reverse turbo-Brayton cycle cryocooler and its integration to the propellant tank through a distributed cooling tubing network coupled to the tank wall. This configuration was recently tested at NASA Glenn Research Center in a vacuum chamber and cryoshroud that simulated the essential thermal aspects of low Earth orbit, its vacuum and temperature. This test series established that the active cooling system integrated with the propellant tank eliminated boil-off and robustly controlled tank pressure.

  11. Enhancement of Heat Transfer with Pool and Spray Impingement Boiling on Microporous and Nanowire Surface Coatings

    SciTech Connect

    Thiagarajan, S. J.; Wang, W.; Yang, R.; Narumanchi, S.; King, C.

    2010-09-01

    The DOE National Renewable Energy Laboratory (NREL) is leading a national effort to develop next-generation cooling technologies for hybrid vehicle electronics. The goal is to reduce the size, weight, and cost of power electronic modules that convert direct current from batteries to alternating current for the motor, and vice versa. Aggressive thermal management techniques help to increase power density and reduce weight and volume, while keeping chip temperatures within acceptable limits. The viability of aggressive cooling schemes such as spray and jet impingement in conjunction with enhanced surfaces is being explored. Here, we present results from a series of experiments with pool and spray boiling on enhanced surfaces, such as a microporous layer of copper and copper nanowires, using HFE-7100 as the working fluid. Spray impingement on the microporous coated surface showed an enhancement of 100%-300% in the heat transfer coefficient at a given wall superheat with respect to spray impingement on a plain surface under similar operating conditions. Critical heat flux also increased by 7%-20%, depending on flow rates.

  12. Experimental investigation and mechanism of critical heat flux enhancement in pool boiling heat transfer with nanofluids

    NASA Astrophysics Data System (ADS)

    Kamatchi, R.; Venkatachalapathy, S.; Nithya, C.

    2016-11-01

    In the present study, reduced graphene oxide (rGO) is synthesized from graphite using modified Hummer and chemical reduction methods. Various characterizations techniques are carried out to study the in-plane crystallite size, number of layers, presence of functional groups and surface morphology. Different concentrations of 0.01, 0.1, and 0.3 g/l of rGO/water nanofluids are prepared by dispersing the flakes in DI water. The colloidal stability of 0.3 g/l concentration is measured after 5 days using Zetasizer and found to be stable. The rGO/water nanofluids are then used to study the effect on the enhancement of critical heat flux (CHF) in pool boiling heat transfer. Results indicate an enhancement in CHF ranging from 145 to 245 % for the tested concentrations. The mechanisms of CHF enhancement are analyzed based on surface wettability, surface roughness, and porous layer thickness. The macrolayer dryout model sufficiently supports the mechanism of CHF enhancement of thin wire with rGO deposits, which is not reported yet.

  13. Pool boiling enhancement through bubble induced convective liquid flow in feeder microchannels

    NASA Astrophysics Data System (ADS)

    Jaikumar, A.; Kandlikar, S. G.

    2016-01-01

    Bubbles departing from the nucleation sites induce a liquid flow from the bulk to the heated surface during pool boiling. Alternating the nucleating regions with non-nucleating regions facilitates separate liquid-vapor pathways for departing vapor bubbles and returning liquid. We explored an additional enhancement through liquid feeder channels on the heater surface directing the returning liquid towards the nucleating region. The nucleating bubbles were confined to the nucleating region as the returning liquid flow induced strong convective currents over the non-nucleating regions. In the best performing configuration, the nucleating regions were 0.5 mm wide, separated by non-nucleating regions of width 2.125 mm, which corresponded to the bubble departure diameter. The non-nucleating regions contained 0.5 mm wide feeder channels directing liquid towards the nucleating region. High speed images indicated distinct vapor columns over the nucleating regions with liquid channeled through the feeder channels. At higher heat fluxes, the strong liquid currents established over the feeder channels suppressed any undesirable nucleation in them keeping the separated vapor-liquid pathways functional. This enhancement technique resulted in a critical heat flux of 394 W/cm2 at a wall superheat of 5.5 °C which translated to a heat transfer coefficient of 713 kW/m2 °C. The additional surface area and high heat transfer coefficient due to microchannel flow in feeder channels, and the unobstructed surface available for the bubbles to expand over the prime heat transfer surface area before departing were seen to be responsible for their superior performance.

  14. Pool boiling of enhanced heat transfer surfaces in refrigerant-oil mixtures and aqueous calcium sulfate solutions

    SciTech Connect

    Curcio, L.A.; Somerscales, E.F.

    1994-08-01

    Pool boiling data of structured surfaces in R113/3GS oil mixtures show a general decrease in heat transfer with oil concentration, degradation in performance of all surfaces at 10% oil, no change in enhancement of the structured surfaces over plain surface, and restoration of performance of the enhanced surfaces upon cleaning in denatured alcohol. Fouling data of structured surfaces in pool boiling of sat. aq. CaSO{sub 4} solution show that effects of fouling (wall superheat changes, deposit weight) are more pronounced at 80 kW/m{sup 2} than at 10 kW/m{sup 2} heat flux; precipitation fouling show an effect within the first 2 h exposure. High flux surfaces have lower deposition weight than other surfaces; thus the deposition rate may depend strongly on wall superheat. The numerous nucleation sites of the enhanced surfaces provide more turbulent motion near the boiling surface than for the plain surface; thus the removal rate should be greater for an enhanced surface, although no removal of a deposit was ever observed.

  15. Nucleate pool boiling heat transfer characteristics of TiO{sub 2}-water nanofluids at very low concentrations

    SciTech Connect

    Suriyawong, Adirek; Wongwises, Somchai

    2010-11-15

    A study of nucleate pool boiling heat transfer of TiO{sub 2}-water nanofluids is experimentally conducted. Nanofluids with various concentrations of 0.00005, 0.0001, 0.0005, 0.005, and 0.01 vol.% are employed. Horizontal circular plates made from copper and aluminium with different roughness values of 0.2 and 4 {mu}m are used as heating surfaces. The experiments are performed to explore the effects of nanofluids concentration as well as heating surface material and roughness on nucleate pool boiling characteristics and the heat transfer coefficient under ambient pressure. The results show that based on the copper heated surface which is tested with a concentration of 0.0001 vol.%, higher nucleate pool boiling heat transfer coefficient is obtained when compared with the base fluid. A 15% increase is obtained for the surface roughness of 0.2 {mu}m and a 4% increase is obtained for roughness of 4 {mu}m. For concentrations higher than 0.0001 vol.%, however, the higher the concentration, the lower the heat transfer coefficient. In the case of aluminium heated surface, the corresponding heat transfer coefficients are larger than for the copper surface by around 30% with a roughness of 0.2 {mu}m and around 27% with a roughness of 4 {mu}m. Moreover, the results also indicate that the heat transfer coefficient obtained based on a roughness of 4 {mu}m is higher than that for a roughness of 0.2 {mu}m by around 12% for aluminium and by around 13% for copper. (author)

  16. Pool boiling of water-Al2O3 and water-Cu nanofluids on horizontal smooth tubes

    PubMed Central

    2011-01-01

    Experimental investigation of heat transfer during pool boiling of two nanofluids, i.e., water-Al2O3 and water-Cu has been carried out. Nanoparticles were tested at the concentration of 0.01%, 0.1%, and 1% by weight. The horizontal smooth copper and stainless steel tubes having 10 mm OD and 0.6 mm wall thickness formed test heater. The experiments have been performed to establish the influence of nanofluids concentration as well as tube surface material on heat transfer characteristics at atmospheric pressure. The results indicate that independent of concentration nanoparticle material (Al2O3 and Cu) has almost no influence on heat transfer coefficient while boiling of water-Al2O3 or water-Cu nanofluids on smooth copper tube. It seems that heater material did not affect the boiling heat transfer in 0.1 wt.% water-Cu nanofluid, nevertheless independent of concentration, distinctly higher heat transfer coefficient was recorded for stainless steel tube than for copper tube for the same heat flux density. PMID:21711741

  17. Pool boiling of water-Al2O3 and water-Cu nanofluids on horizontal smooth tubes.

    PubMed

    Cieslinski, Janusz T; Kaczmarczyk, Tomasz Z

    2011-03-15

    Experimental investigation of heat transfer during pool boiling of two nanofluids, i.e., water-Al2O3 and water-Cu has been carried out. Nanoparticles were tested at the concentration of 0.01%, 0.1%, and 1% by weight. The horizontal smooth copper and stainless steel tubes having 10 mm OD and 0.6 mm wall thickness formed test heater. The experiments have been performed to establish the influence of nanofluids concentration as well as tube surface material on heat transfer characteristics at atmospheric pressure. The results indicate that independent of concentration nanoparticle material (Al2O3 and Cu) has almost no influence on heat transfer coefficient while boiling of water-Al2O3 or water-Cu nanofluids on smooth copper tube. It seems that heater material did not affect the boiling heat transfer in 0.1 wt.% water-Cu nanofluid, nevertheless independent of concentration, distinctly higher heat transfer coefficient was recorded for stainless steel tube than for copper tube for the same heat flux density.

  18. Pool boiling of water-Al2O3 and water-Cu nanofluids on horizontal smooth tubes

    NASA Astrophysics Data System (ADS)

    Cieslinski, Janusz T.; Kaczmarczyk, Tomasz Z.

    2011-12-01

    Experimental investigation of heat transfer during pool boiling of two nanofluids, i.e., water-Al2O3 and water-Cu has been carried out. Nanoparticles were tested at the concentration of 0.01%, 0.1%, and 1% by weight. The horizontal smooth copper and stainless steel tubes having 10 mm OD and 0.6 mm wall thickness formed test heater. The experiments have been performed to establish the influence of nanofluids concentration as well as tube surface material on heat transfer characteristics at atmospheric pressure. The results indicate that independent of concentration nanoparticle material (Al2O3 and Cu) has almost no influence on heat transfer coefficient while boiling of water-Al2O3 or water-Cu nanofluids on smooth copper tube. It seems that heater material did not affect the boiling heat transfer in 0.1 wt.% water-Cu nanofluid, nevertheless independent of concentration, distinctly higher heat transfer coefficient was recorded for stainless steel tube than for copper tube for the same heat flux density.

  19. Migration of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling

    PubMed Central

    2011-01-01

    The migration characteristics of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling were investigated experimentally. Four types of carbon nanotubes with the outside diameters from 15 to 80 nm and the lengths from 1.5 to 10 μm were used in the experiments. The refrigerants include R113, R141b and n-pentane. The oil concentration is from 0 to 10 wt.%, the heat flux is from 10 to 100 kW·m-2, and the initial liquid-level height is from 1.3 to 3.4 cm. The experimental results indicate that the migration ratio of carbon nanotube increases with the increase of the outside diameter or the length of carbon nanotube. For the fixed type of carbon nanotube, the migration ratio decreases with the increase of the oil concentration or the heat flux, and increases with the increase of the initial liquid-level height. The migration ratio of carbon nanotube increases with the decrease of dynamic viscosity of refrigerant or the increase of liquid phase density of refrigerant. A model for predicting the migration ratio of carbon nanotubes in the refrigerant-based nanofluid pool boiling is proposed, and the predictions agree with 92% of the experimental data within a deviation of ±20%. PMID:21711730

  20. Migration of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling

    NASA Astrophysics Data System (ADS)

    Peng, Hao; Ding, Guoliang; Hu, Haitao

    2011-12-01

    The migration characteristics of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling were investigated experimentally. Four types of carbon nanotubes with the outside diameters from 15 to 80 nm and the lengths from 1.5 to 10 μm were used in the experiments. The refrigerants include R113, R141b and n -pentane. The oil concentration is from 0 to 10 wt.%, the heat flux is from 10 to 100 kW·m-2, and the initial liquid-level height is from 1.3 to 3.4 cm. The experimental results indicate that the migration ratio of carbon nanotube increases with the increase of the outside diameter or the length of carbon nanotube. For the fixed type of carbon nanotube, the migration ratio decreases with the increase of the oil concentration or the heat flux, and increases with the increase of the initial liquid-level height. The migration ratio of carbon nanotube increases with the decrease of dynamic viscosity of refrigerant or the increase of liquid phase density of refrigerant. A model for predicting the migration ratio of carbon nanotubes in the refrigerant-based nanofluid pool boiling is proposed, and the predictions agree with 92% of the experimental data within a deviation of ±20%.

  1. Migration of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling.

    PubMed

    Peng, Hao; Ding, Guoliang; Hu, Haitao

    2011-03-14

    The migration characteristics of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling were investigated experimentally. Four types of carbon nanotubes with the outside diameters from 15 to 80 nm and the lengths from 1.5 to 10 μm were used in the experiments. The refrigerants include R113, R141b and n-pentane. The oil concentration is from 0 to 10 wt.%, the heat flux is from 10 to 100 kW·m-2, and the initial liquid-level height is from 1.3 to 3.4 cm. The experimental results indicate that the migration ratio of carbon nanotube increases with the increase of the outside diameter or the length of carbon nanotube. For the fixed type of carbon nanotube, the migration ratio decreases with the increase of the oil concentration or the heat flux, and increases with the increase of the initial liquid-level height. The migration ratio of carbon nanotube increases with the decrease of dynamic viscosity of refrigerant or the increase of liquid phase density of refrigerant. A model for predicting the migration ratio of carbon nanotubes in the refrigerant-based nanofluid pool boiling is proposed, and the predictions agree with 92% of the experimental data within a deviation of ±20%.

  2. Review of the influence of nanoparticles on thermal conductivity, nucleate pool boiling and critical heat flux

    NASA Astrophysics Data System (ADS)

    Kshirsagar, Jagdeep M.; Shrivastava, Ramakant

    2015-03-01

    Nanofluids, the fluid suspensions of nonmaterials, have shown many interesting properties and the unique features offer unprecedented potential for many applications. Research on nanofluids has progressed rapidly since its enhanced thermal conductivity was first noted, about a decade ago, though much debate and inconsistency have been reported. Insufficient understanding of the formulation, mechanism of nanofluids further limits their applications [1-34]. Inconsistent data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers [35-43] have noted an enhancement in the critical heat flux during nanofluid boiling. Some researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux augmentation. In the review, the future developments of these technologies are discussed. In order to be able to put the nanofluid heat transfer technologies into practice, fundamental of these studies are greatly needed to comprehend the physical mechanisms.

  3. Radioisotope Power System Pool Concept

    NASA Technical Reports Server (NTRS)

    Rusick, Jeffrey J.; Bolotin, Gary S.

    2015-01-01

    Advanced Radioisotope Power Systems (RPS) for NASA deep space science missions have historically used static thermoelectric-based designs because they are highly reliable, and their radioisotope heat sources can be passively cooled throughout the mission life cycle. Recently, a significant effort to develop a dynamic RPS, the Advanced Stirling Radioisotope Generator (ASRG), was conducted by NASA and the Department of Energy, because Stirling based designs offer energy conversion efficiencies four times higher than heritage thermoelectric designs; and the efficiency would proportionately reduce the amount of radioisotope fuel needed for the same power output. However, the long term reliability of a Stirling based design is a concern compared to thermoelectric designs, because for certain Stirling system architectures the radioisotope heat sources must be actively cooled via the dynamic operation of Stirling converters throughout the mission life cycle. To address this reliability concern, a new dynamic Stirling cycle RPS architecture is proposed called the RPS Pool Concept.

  4. Review of nucleation and incipient boiling under pool and forced convection conditions

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1987-01-01

    An overview of liquid-vapor nucleation is given. The result of thermodynamic equilibrium across curved liquid-vapor interfaces is presented. The extension of this to include the interaction with idealizations of surface cavities is made to demonstrate how superheat requirements for nucleation will be affected by surface roughness, flow velocity and buoyancy. Experimental measurements of high liquid superheats and nucleation delay times are presented as examples of homogeneous nucleation. Examples of nucleation and boiling on smooth glass substrates and on metal surfaces with various surface roughnesses are presented.

  5. The effect of Bond number on pool boiling for mini-fin surfaces and different working fluids

    NASA Astrophysics Data System (ADS)

    Strąk, Ewelina; Pastuszko, Robert

    2016-03-01

    Experimental nucleate pool boiling data were collected for structures in the form of extended surfaces sintered with perforated foil. The article describes experimental investigations for two kinds of surfaces: smooth and mini-fins with sintered perforated foil (MFP). The MFP surfaces were manufactured out of perforated copper foil (pore diameters: 0.05 - 0.3 mm) sintered with the mini-fins, uniformly spaced on the base surface. The experiments were carried out at atmospheric pressure for four kinds of the fluids: water, ethanol, FC-72 and Novec 649. The results for these working fluids were compared in terms of the Bond number and other dimensionless parameters. For all working fluids, the heat transfer coefficients obtained for the MFP surfaces were from 2 to 5 times higher than those for the smooth surface. Using a regression analysis with reference to selected physical properties and several characteristic dimensions, it was possible to develop a correlation for the Nusselt number.

  6. Subcooled Pool Boiling Heat Transfer Mechanisms in Microgravity: Terrier-improved Orion Sounding Rocket Experiment

    NASA Technical Reports Server (NTRS)

    Kim, Jungho; Benton, John; Kucner, Robert

    2000-01-01

    A microscale heater array was used to study boiling in earth gravity and microgravity. The heater array consisted of 96 serpentine heaters on a quartz substrate. Each heater was 0.27 square millimeters. Electronic feedback loops kept each heater's temperature at a specified value. The University of Maryland constructed an experiment for the Terrier-Improved Orion sounding rocket that was delivered to NASA Wallops and flown. About 200 s of high quality microgravity and heat transfer data were obtained. The VCR malfunctioned, and no video was acquired. Subsequently, the test package was redesigned to fly on the KC-135 to obtain both data and video. The pressure was held at atmospheric pressure and the bulk temperature was about 20 C. The wall temperature was varied from 85 to 65 C. Results show that gravity has little effect on boiling heat transfer at wall superheats below 25 C, despite vast differences in bubble behavior between gravity levels. In microgravity, a large primary bubble was surrounded by smaller bubbles, which eventually merged with the primary bubble. This bubble was formed by smaller bubbles coalescing, but had a constant size for a given superheat, indicating a balance between evaporation at the base and condensation on the cap. Most of the heaters under the bubble indicated low heat transfer, suggesting dryout at those heaters. High heat transfer occurred at the contact line surrounding the primary bubble. Marangoni convection formed a "jet" of fluid into the bulk fluid that forced the bubble onto the heater.

  7. Pool boiling of R-114/oil mixtures from single tubes and tube bundles. Master's thesis

    SciTech Connect

    Murphy, T.J.

    1987-09-01

    An apparatus was designed, fabricated, and operated for the testing of horizontal tube bundles for boiling of R-114 with various concentrations of oil. Preliminary data were taken on the top tube in the bundle, with and without the other tubes in operation. Results showed up to a 37% increase in the boiling heat-transfer coefficient as a result of the favorable bundle effect. In a separate single-tube apparatus, three enhanced tubes were tested at a saturation temperature of 2.2 C with oil mass concentrations of 0, 1, 2, 3, 6 and 10%. The tubes were: 1) a finned tube with 1024 fins per meter, 2) a finned tube with 1575 fins per meter and 3) a Turbo-B tube. These tubes resulted in enhancement ratios in pure refrigerant of 2.8, 3.8 and 5.2, respectively, at a practical heat flux of 30 kW/sq. meter. With 3% oil, these ratios were decreased to 2.6, 3.5 and 5, while with 10% oil, these ratios were further reduced to 2.6, 3.2 and 4.7, respectively. Based on these results, the use of Turbo-B tubes is expected to result in significant savings in weight and size of evaporators over the finned tubes presently in use on board some naval vessels.

  8. Transport processes in boiling and two-phase systems, including near-critical fluids

    NASA Technical Reports Server (NTRS)

    Hsu, Y.-Y.; Graham, R. W.

    1976-01-01

    Aspects of pool boiling are considered, taking into account nucleate boiling, the nucleate boiling mechanism, film boiling, and the transition between nucleate and film boiling. The characteristics of two-phase flow are also investigated, giving attention to two-phase flow parameters and equations, the flow pattern in two-phase flow, the pressure drop in two-phase flow, heat transfer in two-phase flow, two-phase flow dynamics, the boiling crisis in two-phase flow, the critical flow rate, the propagation of the pressure pulse and the sonic velocity in two-phase media, instrumentation for two-phase flow, and geometry and field effects on boiling and two-phase flow. Near-critical fluids are also considered.

  9. Viscous hydrodynamic instability theory of the peak and minimum pool boiling heat fluxes

    NASA Technical Reports Server (NTRS)

    Dhir, V. K.

    1972-01-01

    Liquid viscosity was included in the Bellman-Pennington theory of the Taylor wave in a liquid vapor interface. Predictions of the most susceptible wavelength, and of the wave frequency, were made as a function of a liquid viscosity parameter and the Bond number. The stability of a gas jet in a viscous liquid was studied and the result is used to predict the peak heat flux on large horizontal heaters. Experimental measurements of the dominant Taylor wave and its growth rate were made during the film boiling of cyclohexanol on cylindrical heaters. The results bear out the predictions quite well. The thickness of the vapor blanket surrounding a cylindrical heater was measured and a correlation suggested. The effect of large fluxes of vapor volume on the dominant wavelength was also noted. Theoretical results of the peak heat flux are compared with the experimental data, and the effect of finite geometry of flat plate heaters on the peak heat flux is also discussed.

  10. Dynamical Behavior of Discrete Bubble and Heat Transfer of Nucleate Pool Boiling in Short-Term Microgravity

    NASA Astrophysics Data System (ADS)

    Zhao, Jian-Fu

    2012-07-01

    Boiling in microgravity is an increasing significant subject of investigation. Motivation for the study comes not only from many potential space applications due to its high efficiency to transfer high heat flux with liquid-vapor phase change, but also from powerful platform of microgravity to reveal the mechanism of heat transfer underneath the phenomenon of boiling. In the present paper, the growth of a discrete bubble during nucleate pool boiling and heat transfer in short-term microgravity is studied experimentally utilizing the drop tower Beijing. A P-doped N-type square silicon chip with the dimensions of 10x10x0.5 mm ^{3} was used as the heater. Two 0.25-mm diameters copper wires for power supply was soldered to the side surfaces of the chip at the opposite ends. The normal resistant of the chip is 75 Ω. The chip was heated by using Joule effect. A D.C. power supply of constant current was used to input energy to the heater element. A 0.12-mm diameter, T-type thermocouple adhered on the centre of the backside of the chip was used for the measurement of wall temperature, while two other T-type thermocouples were used for the bulk liquid temperature. FC-72 was used as working fluid. The concentration of air was determined by using Henry law as 0.0046 moles gas/mole liquid. The pressure and the bulk liquid temperature in the boiling chamber were nominally 102.0 kPa and 12.0 °C, respectively. The shapes of the bubbles were recorded using a high speed camera at a speed of 250 fps with a shutter speed of 1/2000 s. Based on the image manipulation, the effective diameter of the discrete bubble is obtained. The experiments were conducted utilizing the drop tower Beijing, which can provide a short-term microgravity condition. The residual gravity of 10 ^{-2 ... -3} g _{0} can be maintained throughout the short duration of 3.6 s. To avoid the influence of natural convection in normal gravity environment, the heating switched on at the release of the drop capsule

  11. Evaluation of a passive containment cooling system for a simplified BWR (boiling water reactor)

    SciTech Connect

    Otonari, J.; Arai, K. ); Oikawa, H.; Nagasaka, H. )

    1989-11-01

    Simplified boiling water reactors (BWRs) are characterized for the adoption of a passive containment cooling system (PCCS) and a passive emergency core cooling system (ECCS). TOSPAC, which had been developed as the preliminary design code for several PCCS concepts, was compared with TRAC for verification. TOSPAC analyses were also performed to show the effectiveness of the isolation condenser (IC) as a PCCS over a wide range of break spectra. The selected reference plant for the analysis is a natural circulation BWR plant with 1,800-MW(thermal) power. The ECCS consists of a gravity-driven cooling system (GDCS) and depressurization valves. The IC and drywell cooler are considered for the PCCS. The IC units and drywell coolers are placed in the IC pool and GDCS pool, respectively.

  12. Pool boiler heat transport system for a 25 kWe advanced Stirling conversion system

    NASA Technical Reports Server (NTRS)

    Anderson, W. G.; Rosenfeld, J. H.; Saaski, E. L.; Noble, J.; Tower, L.

    1990-01-01

    Experiments to determine alkali metal/enhanced surface combinations that have stable boiling at the temperatures and heat fluxes that occur in the Stirling engine are reported. Two enhanced surfaces and two alkali metal working fluids were evaluated. The enhanced surfaces were an EDM hole covered surface and a sintered-powder-metal porous layer surface. The working fluids tested were potassium and eutectic sodium-potasium alloy (NaK), both with and without undissolved noncondensible gas. Noncondensible gas (He and Xe) was added to the system to provide gas in the nucleation sites, preventing quenching of the sites. The experiments demonstrated the potential of an alkali metal pool boiler heat transport system for use in a solar-powered Stirling engine. The most favorable fluid/surface combination tested was NaK boiling on a -100 +140 mesh 304L stainless steel sintered porous layer with no undissolved noncondensible gas. This combination provided stable, high-performance boiling at the operating temperature of 700 C. Heat fluxes into the system ranged from 10 to 50 W/sq cm. The transition from free convection to nucleate boiling occurred at temperatures near 540 C. Based on these experiments, a pool boiler was designed for a full-scale 25-kWe Stirling system.

  13. Evaluation of the Safety Systems in the Next Generation Boiling Water Reactor

    NASA Astrophysics Data System (ADS)

    Cheng, Ling

    The thesis evaluates the safety systems in the next generation boiling water reactor by analyzing the main steam line break loss of coolant accident performed in the Purdue university multi-dimensional test assembly (PUMA). RELAP5 code simulations, both for the PUMA main steam line break (MSLB) case and for the simplified boiling water reactor (SBWR) MSLB case have been utilized to compare with the experiment data. The comparison shows that RELAP5 is capable to perform the safety analysis for SBWR. The comparison also validates the three-level scaling methodology applied to the design of the PUMA facility. The PUMA suppression pool mixing and condensation test data have been studied to give the detailed understanding on this important local phenomenon. A simple one dimensional integral model, which can reasonably simulate the mixing process inside suppression pool have been developed and the comparison between the model prediction and the experiment data demonstrates the model can be utilized for analyzing the suppression pool mixing process.

  14. Phase relations and adiabats in boiling seafloor geothermal systems

    USGS Publications Warehouse

    Bischoff, J.L.; Pitzer, Kenneth S.

    1985-01-01

    Observations of large salinity variations and vent temperatures in the range of 380-400??C suggest that boiling or two-phase separation may be occurring in some seafloor geothermal systems. Consideration of flow rates and the relatively small differences in density between vapors and liquids at the supercritical pressures at depth in these systems suggests that boiling is occurring under closed-system conditions. Salinity and temperature of boiling vents can be used to estimate the pressure-temperature point in the subsurface at which liquid seawater first reached the two-phase boundary. Data are reviewed to construct phase diagrams of coexisting brines and vapors in the two-phase region at pressures corresponding to those of the seafloor geothermal systems. A method is developed for calculating the enthalpy and entropy of the coexisting mixtures, and results are used to construct adiabats from the seafloor to the P-T two-phase boundary. Results for seafloor vents discharging at 2300 m below sea level indicate that a 385??C vent is composed of a brine (7% NaCl equivalent) in equilibrium with a vapor (0.1% NaCl). Brine constitutes 45% by weight of the mixture, and the fluid first boiled at approximately 1 km below the seafloor at 415??C, 330 bar. A 400??C vent is primarily vapor (88 wt.%, 0.044% NaCl) with a small amount of brine (26% NaCl) and first boiled at 2.9 km below the seafloor at 500??C, 520 bar. These results show that adiabatic decompression in the two-phase region results in dramatic cooling of the fluid mixture when there is a large fraction of vapor. ?? 1985.

  15. Characteristics of Transient Boiling Heat Transfer

    SciTech Connect

    Liu, Wei; Monde, Masanori; Mitsutake, Y.

    2002-07-01

    In this paper, one dimensional inverse heat conduction solution is used for a measurement of pool boiling curve. The experiments are performed under atmospheric pressure for copper, brass, carbon steel and gold. Boiling curves, including unsteady transition boiling region, are found can be traced fairly well from a simple experiment system by solving inverse heat conduction solution. Boiling curves for steady heating and transient heating, for heating process and cooling process are compared. Surface behavior around CHF point, transition boiling and film-boiling regions are observed by using a high-speed camera. The results show the practicability of the inverse heat conduction solution in tracing boiling curve and thereby supply us a new way in boiling heat transfer research. (authors)

  16. 77 FR 36014 - Initial Test Program of Emergency Core Cooling Systems for Boiling-Water Reactors

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-15

    ... COMMISSION Initial Test Program of Emergency Core Cooling Systems for Boiling-Water Reactors AGENCY: Nuclear...-1277, ``Initial Test Program of Emergency Core Cooling Systems for Boiling- Water Reactors.'' This... testing features of emergency core cooling systems (ECCSs) for boiling-water reactors (BWRs)....

  17. Design of a pool boiler heat transport system for a 25 kWe advanced Stirling conversion system

    NASA Technical Reports Server (NTRS)

    Anderson, W. G.; Rosenfeld, J. H.; Noble, J.; Kesseli, J.

    1991-01-01

    The overall operating temperature and efficiency of solar-powered Stirling engines can be improved by adding a heat transport system to more uniformly supply heat to the heater head tubes. One heat transport system with favorable characteristics is an alkali metal pool boiler. An alkali metal pool boiler heat transport system was designed for a 25-kW advanced Stirling conversion system (ASCS). Solar energy concentrated on the absorber dome boils a eutectic mixture of sodium and potassium. The alkali metal vapors condense on the heater head tubes, supplying the Stirling engine with a uniform heat flux at a constant temperature. Boiling stability is achieved with the use of an enhanced boiling surface and noncondensible gas.

  18. Numerical simulation and experimental validation of the dynamics of multiple bubble merger during pool boiling under microgravity conditions.

    PubMed

    Abarajith, H S; Dhir, V K; Warrier, G; Son, G

    2004-11-01

    Numerical simulation and experimental validation of the growth and departure of multiple merging bubbles and associated heat transfer on a horizontal heated surface during pool boiling under variable gravity conditions have been performed. A finite difference scheme is used to solve the equations governing mass, momentum, and energy in the vapor liquid phases. The vapor-liquid interface is captured by a level set method that is modified to include the influence of phase change at the liquid-vapor interface. Water is used as test liquid. The effects of reduced gravity condition and orientation of the bubbles on the bubble diameter, interfacial structure, bubble merger time, and departure time, as well as local heat fluxes, are studied. In the experiments, multiple vapor bubbles are produced on artificial cavities in the 2-10 micrometer diameter range, microfabricated on the polished silicon wafer with given spacing. The wafer was heated electrically from the back with miniature strain gage type heating elements in order to control the nucleation superheat. The experiments conducted in normal Earth gravity and in the low gravity environment of KC-135 aircraft are used to validate the numerical simulations.

  19. The Effect of Coating Thickness and Roughness of Nucleate Pool Boiling Heat Transfer on Nanoparticle Coated Surface

    NASA Astrophysics Data System (ADS)

    Das, Sudev; Bhaumik, Swapan

    2016-04-01

    The influence of coating thickness and surface roughness on pool boiling heat transfer is experimentally studied over a range of surface roughness values with varied coating thickness with water at atmospheric pressure. Test surfaces used in this experiment are namely, untreated surface (Ra = 0.0899 µm), polished surface (Ra = 0.0493 µm), TiO2 nanoparticle coated surface with a roughness (Ra) ranging from 0.0338 to 0.289 µm. The surfaces were characterized with respect to contact angle, surface roughness and coating thickness. The contact angle, surface roughness and coating thickness were measured by sessile drop method, optical surface profiler and instrument thickness monitor respectively. Heat fluxes observed ranged from 52.63 to 144.73 W/cm2. Different trends were observed in the Heat Transfer Coefficient (HTC) with respect to the surface roughness and coating thickness values on the same set of heat flux. The HTC was found to increase with increasing the roughness values for untreated and polish surface but nanoparticle coated surfaces displayed different trend in HTCs. The HTC was found to increase with increasing coating thickness with all wall superheat.

  20. Thermal behavior of aqueous iron oxide nano-fluid as a coolant on a flat disc heater under the pool boiling condition

    NASA Astrophysics Data System (ADS)

    Salari, E.; Peyghambarzadeh, S. M.; Sarafraz, M. M.; Hormozi, F.; Nikkhah, V.

    2016-04-01

    This paper experimentally focuses on the pool boiling heat transfer characteristics of gamma Fe3O4 aqueous nano-fluids on a flat disc heater. The nano-fluid used in this research was prepared using two-step method and was stabilized using nonylphenol ethoxylate nonionic surfactant, pH setting, and sonication process as well. Influence of different operating parameters such as heat flux (0-1546 kW/m2), mass concentration of nano-fluids (weight concentration 0.1-0.3 %), bubble formation, critical heat flux (1170 kW/m2 for water, 1230 kW/m2 (wt% = 0.1), 1320 kW/m2 (wt% = 0.2), 1450 kW/m2 (wt% = 0.3) and fouling on pool boiling heat transfer coefficient of nano-fluid as a thermal performance index were experimentally investigated and briefly discussed. Results demonstrated that the pool boiling heat transfer coefficient increases with increasing the mass concentration and the applied heat flux. In addition, the rate of bubble formation is significantly intensified at higher heat fluxes and subsequently, larger bubbles detach the surface due to the intensification of bubble coalescence. In terms of fouling formation, it can be stated that fouling of nano-fluids is a strong function of time and rate of deposition is increased over the extended time while the pool boiling heat transfer coefficient was not decreased over the time, as porous deposited layer on the surface are detached from the surface by bubble interactions. In terms of critical heat flux, capillary action of the deposited layer was found to be the main reason responsible for increasing the critical heat flux as liquid is stored inside the porous deposited layer, which enhances the surface toleration against the critical heat flux crisis.

  1. EHD enhancement of pool and in-tube boiling of alternate refrigerants. Final report, 15 January 1993--15 June 1993

    SciTech Connect

    Ohadi, M.M.; Dessiatoun, S.; Singh, A.; Fanni, M.A.

    1993-08-01

    The Electrohydrodynamic (EHD) is an active heat transfer augmentation technique which utilizes the effect of secondary motions generated through the application of an electrostatic potential to a dielectric fluid. Net result is better momentum and heat transfer between the fluid and the heat transfer wall through destabilization of the thermal boundary layer and better mixing of the fluid adjacent to the heat transfer surface. EHD enhancement of refrigerant/refrigerant oil mixtures heat transfer using the Electrohydrodynamic (EHD) technique is the subject of a three-year experimental investigation in a project funded by the US Department of Energy, effective June 1, 1993. For the interim period between November 1992 and June 1993 when the DOE funds became available, the Air-Conditioning and Refrigeration Technology Institute (ARTI) provided partial funding for our EHD research program with the aim of accomplishing three major tasks: (1) conduct a comprehensive search of the literature on EHD-enhanced, in-tube and external boiling heat transfer enhancement of alternate refrigerants; (2) Design, fabricate, and instrument an in-tube, EHD-enhanced boiling/condensation test rig and perform preliminary testing of the setup; (3) conduct experiments and document new findings on EHD-enhanced external boiling of alternate refrigerants/refrigerant mixtures in an existing pool boiling test rig apparatus. Description of Tasks performed are described and results are discussed.

  2. Energy pooling upconversion in organic molecular systems.

    PubMed

    LaCount, Michael D; Weingarten, Daniel; Hu, Nan; Shaheen, Sean E; van de Lagemaat, Jao; Rumbles, Garry; Walba, David M; Lusk, Mark T

    2015-04-30

    A combination of molecular quantum electrodynamics, perturbation theory, and ab initio calculations was used to create a computational methodology capable of estimating the rate of three-body singlet upconversion in organic molecular assemblies. The approach was applied to quantify the conditions under which such relaxation rates, known as energy pooling, become meaningful for two test systems, stilbene-fluorescein and hexabenzocoronene-oligothiophene. Both exhibit low intramolecular conversion, but intermolecular configurations exist in which pooling efficiency is at least 90% when placed in competition with more conventional relaxation pathways. For stilbene-fluorescein, the results are consistent with data generated in an earlier experimental investigation. Exercising these model systems facilitated the development of a set of design rules for the optimization of energy pooling. PMID:25793313

  3. The Gibbs Energy Basis and Construction of Boiling Point Diagrams in Binary Systems

    ERIC Educational Resources Information Center

    Smith, Norman O.

    2004-01-01

    An illustration of how excess Gibbs energies of the components in binary systems can be used to construct boiling point diagrams is given. The underlying causes of the various types of behavior of the systems in terms of intermolecular forces and the method of calculating the coexisting liquid and vapor compositions in boiling point diagrams with…

  4. Aging study of boiling water reactor high pressure injection systems

    SciTech Connect

    Conley, D.A.; Edson, J.L.; Fineman, C.F.

    1995-03-01

    The purpose of high pressure injection systems is to maintain an adequate coolant level in reactor pressure vessels, so that the fuel cladding temperature does not exceed 1,200{degrees}C (2,200{degrees}F), and to permit plant shutdown during a variety of design basis loss-of-coolant accidents. This report presents the results of a study on aging performed for high pressure injection systems of boiling water reactor plants in the United States. The purpose of the study was to identify and evaluate the effects of aging and the effectiveness of testing and maintenance in detecting and mitigating aging degradation. Guidelines from the United States Nuclear Regulatory Commission`s Nuclear Plant Aging Research Program were used in performing the aging study. Review and analysis of the failures reported in databases such as Nuclear Power Experience, Licensee Event Reports, and the Nuclear Plant Reliability Data System, along with plant-specific maintenance records databases, are included in this report to provide the information required to identify aging stressors, failure modes, and failure causes. Several probabilistic risk assessments were reviewed to identify risk-significant components in high pressure injection systems. Testing, maintenance, specific safety issues, and codes and standards are also discussed.

  5. Dryout and Rewetting in the Pool Boiling Experiment Flown on STS-72 (PBE-2 B) and STS-77 (PBE-2 A)

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.; Lee, Ho Sung; Keller, Robert B.

    1998-01-01

    Experiments were conducted in the microgravity of space in which a pool of liquid (R-113), initially at a precisely defined pressure and temperature, is subjected to a step imposed heat flux from a semi-transparent thin-film heater forming part of one wall of the container such that boiling is initiated and maintained for a defined period of time at a constant pressure level. A total of nine tests were conducted at three levels of heat flux and three levels of subcooling in each of the two space experiments in a GAS canister on the STS-77, -72, respectively. Three (3) modes of propagation of boiling across the heater surface and subsequent vapor bubble growths were observed, in addition to the two (2) modes observed in the previous microgravity pool boiling space flights on STS-47, -57, and -60. Of particular interest were the extremely dynamic or "explosive" growths, which were determined to be the consequence of the large increase in the liquid-vapor interface area associated with the appearance of a corrugated or rough interface. Predictions of circumstances for its onset have been carried out. Assumptions were necessary regarding the character of disturbances necessary for the instabilities to grow. Also, a new vapor bubble phenomena was observed in which small vapor bubbles migrated toward a larger bubble, eventually coalescing with this larger bubble. The heat transfer was enhanced approximately 30% as a result of these migrating bubbles, which is believed to be a vapor bubble manifestation of Marangoni convection and/or molecular momentum effects, sometimes referred to as vapor recoil. The circumstances of heat flux and liquid subcooling necessary to produce heater surface dryout for an initially stagnant liquid subjected to an imposed heat flux have been more closely identified.

  6. Experimental and Thermalhydraulic Code Assessment of the Transient Behavior of the Passive Condenser System in an Advanced Boiling Water Reactor

    SciTech Connect

    S.T. Revankar; W. Zhou; Gavin Henderson

    2008-07-08

    The main goal of the project was to study analytically and experimentally the condensation heat transfer for the passive condenser system such as GE Economic Simplified Boiling Water Reactor (ESBWR). The effect of noncondensable gas in condenser tube and the reduction of secondary pool water level to the condensation heat transfer coefficient was the main focus in this research. The objectives of this research were to : 1) obtain experimental data on the local and tube averaged condensation heat transfer rates for the PCCS with non-condensable and with change in the secondary pool water, 2) assess the RELAP5 and TRACE computer code against the experimental data, and 3) develop mathematical model and ehat transfer correlation for the condensation phenomena for system code application. The project involves experimentation, theoretical model development and verification, and thermal- hydraulic codes assessment.

  7. POOL WATER TREATMENT AND COOLING SYSTEM DESCRIPTION DOCUMENT

    SciTech Connect

    V. King

    2000-06-19

    The Pool Water Treatment and Cooling System is located in the Waste Handling Building (WHB), and is comprised of various process subsystems designed to support waste handling operations. This system maintains the pool water temperature within an acceptable range, maintains water quality standards that support remote underwater operations and prevent corrosion, detects leakage from the pool liner, provides the capability to remove debris from the pool, controls the pool water level, and helps limit radiological exposure to personnel. The pool structure and liner, pool lighting, and the fuel staging racks in the pool are not within the scope of the Pool Water Treatment and Cooling System. Pool water temperature control is accomplished by circulating the pool water through heat exchangers. Adequate circulation and mixing of the pool water is provided to prevent localized thermal hotspots in the pool. Treatment of the pool water is accomplished by a water treatment system that circulates the pool water through filters, and ion exchange units. These water treatment units remove radioactive and non-radioactive particulate and dissolved solids from the water, thereby providing the water clarity needed to conduct waste handling operations. The system also controls pool water chemistry to prevent advanced corrosion of the pool liner, pool components, and fuel assemblies. Removal of radioactivity from the pool water contributes to the project ALARA (as low as is reasonably achievable) goals. A leak detection system is provided to detect and alarm leaks through the pool liner. The pool level control system monitors the water level to ensure that the minimum water level required for adequate radiological shielding is maintained. Through interface with a demineralized water system, adequate makeup is provided to compensate for loss of water inventory through evaporation and waste handling operations. Interface with the Site Radiological Monitoring System provides continuous

  8. Pool power control in remelting systems

    DOEpatents

    Williamson, Rodney L.; Melgaard, David K.; Beaman, Joseph J.

    2011-12-13

    An apparatus for and method of controlling a remelting furnace comprising adjusting current supplied to an electrode based upon a predetermined pool power reference value and adjusting the electrode drive speed based upon the predetermined pool power reference value.

  9. Effect of liquid spreading due to nano/microstructures on the critical heat flux during pool boiling

    NASA Astrophysics Data System (ADS)

    Ahn, Ho Seon; Jo, Hang Jin; Kang, Soon Ho; Kim, Moo Hwan

    2011-02-01

    It is well known that nanoparticles deposited on a heating surface during nanofluid boiling can change the characteristics of the heating surface and increase the critical heat flux (CHF) dramatically. We considered a new approach to investigate the nanoparticle surface effect on CHF enhancement using surfaces modified with artificial micro/nanostructures similar to deposited nanoparticle structures. We examined the effect of the surface wettability and liquid spreading ability on the CHF. The results demonstrated that the CHF enhancement on the modified surfaces was a consequence of both the improved surface wettability and the liquid spreading ability of the artificial micro/nanostructures.

  10. Experience with solar systems for heating swimming pools in Germany

    SciTech Connect

    Croy, R.; Peuser, F.A. )

    1994-07-01

    The results of the demonstration programme [open quotes]Efficient Use of Energy in Swimming Pool Construction[close quotes] has had a positive effect on the dissipation of solar systems for swimming pools. Infrared measurements show how a homogeneous flow can be achieved in the absorber field. The fact that solar systems are acceptable can be clearly in evidence that the behaviour of visitors to purely solar-heated pools with variable water temperature does not differ in principle from conventionally-heated pools with constant temperature. Economic considerations of the operation show that swimming pool solar systems are competitive with conventional heating systems.

  11. Performance Study and Dynamic Optimization Design for Thread Pool Systems

    SciTech Connect

    Dongping Xu

    2004-12-19

    Thread pools have been widely used by many multithreaded applications. However, the determination of the pool size according to the application behavior still remains problematic. To automate this process, in this thesis we have developed a set of performance metrics for quantitatively analyzing thread pool performance. For our experiments, we built a thread pool system which provides a general framework for thread pool research. Based on this simulation environment, we studied the performance impact brought by the thread pool on different multithreaded applications. Additionally, the correlations between internal characterizations of thread pools and their throughput were also examined. We then proposed and evaluated a heuristic algorithm to dynamically determine the optimal thread pool size. The simulation results show that this approach is effective in improving overall application performance.

  12. A novel role of three dimensional graphene foam to prevent heater failure during boiling.

    PubMed

    Ahn, Ho Seon; Kim, Ji Min; Park, Chibeom; Jang, Ji-Wook; Lee, Jae Sung; Kim, Hyungdae; Kaviany, Massoud; Kim, Moo Hwan

    2013-01-01

    We report a novel boiling heat transfer (NBHT) in reduced graphene oxide (RGO) suspended in water (RGO colloid) near critical heat flux (CHF), which is traditionally the dangerous limitation of nucleate boiling heat transfer because of heater failure. When the heat flux reaches the maximum value (CHF) in RGO colloid pool boiling, the wall temperature increases gradually and slowly with an almost constant heat flux, contrary to the rapid wall temperature increase found during water pool boiling. The gained time by NBHT would provide the safer margin of the heat transfer and the amazing impact on the thermal system as the first report of graphene application. In addition, the CHF and boiling heat transfer performance also increase. This novel boiling phenomenon can effectively prevent heater failure because of the role played by the self-assembled three-dimensional foam-like graphene network (SFG).

  13. A Novel Role of Three Dimensional Graphene Foam to Prevent Heater Failure during Boiling

    PubMed Central

    Ahn, Ho Seon; Kim, Ji Min; Park, Chibeom; Jang, Ji-Wook; Lee, Jae Sung; Kim, Hyungdae; Kaviany, Massoud; Kim, Moo Hwan

    2013-01-01

    We report a novel boiling heat transfer (NBHT) in reduced graphene oxide (RGO) suspended in water (RGO colloid) near critical heat flux (CHF), which is traditionally the dangerous limitation of nucleate boiling heat transfer because of heater failure. When the heat flux reaches the maximum value (CHF) in RGO colloid pool boiling, the wall temperature increases gradually and slowly with an almost constant heat flux, contrary to the rapid wall temperature increase found during water pool boiling. The gained time by NBHT would provide the safer margin of the heat transfer and the amazing impact on the thermal system as the first report of graphene application. In addition, the CHF and boiling heat transfer performance also increase. This novel boiling phenomenon can effectively prevent heater failure because of the role played by the self-assembled three-dimensional foam-like graphene network (SFG). PMID:23743619

  14. The Parable of the Boiled System Safety Professional: Drift to Failure

    NASA Technical Reports Server (NTRS)

    Shivers, C. Herbert

    2011-01-01

    Recall from the Parable of the Boiled Frog, that tossing a frog into boiling water causes the frog to jump out and hop away while placing a frog in suitable temperature water and slowly bringing the water to a boil results in the frog boiling due to not being aware of the slowly increasing danger, theoretically, of course. System safety professionals must guard against allowing dangers to creep unnoticed into their projects and be ever alert to notice signs of impending problems. People have used various phrases related to the idea, most notably, latent conditions, James Reason in Managing the Risks of Organizational Accidents (1, pp 10-11), Drift to Failure, Sydney Dekker (2, pp 82-86) in Resilience Engineering: Chronicling the Emergence of Confused Consensus in Resilience Engineering: Concepts and Precepts, Hollnagel, Woods and Leveson, and normalization of deviance, Diane Vaughan in The Challenger Launch Decision: Risky Technology, Culture, and Deviance at NASA (3). Reason also said, If eternal vigilance is the price of liberty, then chronic unease is the price of safety (1, p 37). Our challenge as system safety professionals is to be aware of the emergence of signals that warn us of slowly eroding safety margins. This paper will discuss how system safety professionals might better perform in that regard.

  15. Experimental study of void behavior in a suppression pool of a boiling water reactor during the blowdown period of a loss of coolant accident

    NASA Astrophysics Data System (ADS)

    Rassame, Somboon

    The possible failure of an Emergency Core Cooling System (ECCS) train due to a large amount of entrained gas in the ECCS pump suction piping in a Loss of Coolant Accident (LOCA) is one of the potential engineering problems faced in a Boiling Water Reactor (BWR) power plant. To analyze potential gas intrusion into the ECCS pump suction piping, the study of void behavior in the Suppression Pool (SP) during the LOCA is necessary. The void fraction distribution and void penetration are considered as the key parameters in the problem analysis. Two sets of experiments, namely, steady-state tests and transient tests were conducted using the Purdue University Multi-Dimensional Integral Test Assembly for ESBWR application (PUMA-E) to study void behavior in the SP during the blowdown. The design of the test apparatus used is based on the scaling analysis from a prototypical BWR containment (MARK-I) with consideration of the downcomer size, the SP water level, and the downcomer water submergence depth. Several instruments were installed to obtain the required experimental data, such as inlet gas volumetric flow, void fraction, pressure, and temperature. For the steady-state tests, the air was injected through a downcomer pipe in the SP in order to simulate the physical phenomena in the SP during the initial blowdown of LOCA. Thirty tests were performed with two different downcomer sizes (0.076 and 0.102 m), various air volumetric flow rates or flux (0.003 to 0.153 m3/s or 0.5 to 24.7 m/s), initial downcomer void conditions (fully filled with water, partially void, and completely void) and air velocity ramp rates (one to two seconds). Two phases of the experiment were observed, namely, the initial phase and the quasi-steady phase. The initial phase produced the maximum void penetration depth; and the quasi-steady phase showed less void penetration with oscillation in the void penetration. The air volumetric flow rate was found to have a minor effect on the void fraction

  16. Zero Boil-Off System Design and Thermal Analysis of the Bimodal Thermal Nuclear Rocket

    SciTech Connect

    Christie, Robert J.; Plachta, David W.

    2006-01-20

    Mars exploration studies at NASA are evaluating vehicles that incorporate Bimodal Nuclear Thermal Rocket (BNTR) propulsion which use a high temperature nuclear fission reactor and hydrogen to produce thermal propulsion. The hydrogen propellant is to be stored in liquid state for periods up to 18 months. To prevent boil-off of the liquid hydrogen, a system of passive and active components are needed to prevent heat from entering the tanks and to remove any heat that does. This report describes the design of the system components used for the BNTR Crew Transfer Vehicle and the thermal analysis performed. The results show that Zero Boil-Off (ZBO) can be achieved with the electrical power allocated for the ZBO system.

  17. Boils (Furunculosis)

    MedlinePlus

    ... resulting from the deep infection of a hair follicle. The infection is usually caused by a type ... germ gain entry into and infect the hair follicle, resulting in a boil. Boils may resolve with ...

  18. Pressure suppression containment system for boiling water reactor

    DOEpatents

    Gluntz, Douglas M.; Nesbitt, Loyd B.

    1997-01-01

    A system for suppressing the pressure inside the containment of a BWR following a postulated accident. A piping subsystem is provided which features a main process pipe that communicates the wetwell airspace to a connection point downstream of the guard charcoal bed in an offgas system and upstream of the main bank of delay charcoal beds which give extensive holdup to offgases. The main process pipe is fitted with both inboard and outboard containment isolation valves. Also incorporated in the main process pipe is a low-differential-pressure rupture disk which prevents any gas outflow in this piping whatsoever until or unless rupture occurs by virtue of pressure inside this main process pipe on the wetwell airspace side of the disk exceeding the design opening (rupture) pressure differential. The charcoal holds up the radioactive species in the noncondensable gas from the wetwell plenum by adsorption, allowing time for radioactive decay before the gas is vented to the environs.

  19. Pressure suppression containment system for boiling water reactor

    DOEpatents

    Gluntz, D.M.; Nesbitt, L.B.

    1997-01-21

    A system is disclosed for suppressing the pressure inside the containment of a BWR following a postulated accident. A piping subsystem is provided which features a main process pipe that communicates the wetwell airspace to a connection point downstream of the guard charcoal bed in an offgas system and upstream of the main bank of delay charcoal beds which give extensive holdup to offgases. The main process pipe is fitted with both inboard and outboard containment isolation valves. Also incorporated in the main process pipe is a low-differential-pressure rupture disk which prevents any gas outflow in this piping whatsoever until or unless rupture occurs by virtue of pressure inside this main process pipe on the wetwell airspace side of the disk exceeding the design opening (rupture) pressure differential. The charcoal holds up the radioactive species in the noncondensable gas from the wetwell plenum by adsorption, allowing time for radioactive decay before the gas is vented to the environs. 3 figs.

  20. Boiling Fluids Behave Quite Differently in Space

    NASA Video Gallery

    The boiling process is really different in space, since the vapor phase of a boiling liquid does not rise via buoyancy. Spacecraft and Earth-based systems use boiling to efficiently remove large am...

  1. Dynamic analysis of the condensate feedwater system in boiling water reactor plants

    SciTech Connect

    Tanji, J.; Omori, T.

    1982-05-01

    The computer code, CONFAC, has been developed for dynamic analysis of the condensate feedwater system in boiling water reactor plants. This code simulates the hydrodynamics in the piping system, the pump dynamics, and the feedwater controller in order to clarify the system transient characteristics in such cases as pump trip incidents. Code verification was performed by comparison between analytical results and actual plant operational data. Satisfactory agreement was obtained. With the code, appropriate pump start/stop interlocks were estimated for preventing pump cavitation in pump trip incidents.

  2. Carbon dynamics in peatland pool systems: the role of light

    NASA Astrophysics Data System (ADS)

    Pickard, Amy; Heal, Kate; McLeod, Andy; Dinsmore, Kerry

    2016-04-01

    Open-water pools are widespread in peatlands and are considered to represent biogeochemical hotspots within the peatland landscape. However the contribution of pool systems to wider peatland C cycling has not been quantified fully and there is a lack of knowledge of the role of photochemical processes in such environments. In this study, light exposure experiments were conducted in two contrasting pools to test the reactivity of aquatic C. The first study site was located at Cross Lochs (CL), Forsinard, in the Flow Country of Northern Scotland, in a 412 m2 pool characterised by low dissolved organic carbon (DOC) concentrations (˜15 mg C L-1). The second site was located at Red Moss of Balerno (RM), a raised bog in central Scotland, in a 48 m2 pool with high DOC concentrations (˜35 mg C L-1). Experiments took place over 9 days in situ at each pool in mid-summer 2015, with 500 mL water samples contained in bags transparent to sunlight and in opaque control bags. After field exposure, optical, chemical and stable C isotope analyses were conducted on the samples. Significant differences in biogeochemical cycling of DOC were detected between the two systems, with DOC losses as a percentage of the total C pool 15% higher at RM than at CL after light exposure. The mean DOC concentration of light exposed samples at RM declined steeply initially, with 83% observed DOC degradation occurring by day 3 of the experiment. Total losses of 7.9 mg DOC L-1were observed in light exposed samples at RM, along with decreasing E4:E6 ratios, suggesting that material remaining at the end of the experiment was humified. Depletion of DOC was positively correlated with production of CO2 at both sites, with concentrations of up to 4.3 mg CO2-C L-1 recorded at RM. Stable C isotope signatures at both sites were altered under light treatment, as demonstrated by the production of enriched δ13C-DOC (+0.46 ‰ relative to opaque bags) and depleted δ13C-DIC (-0.97 ‰ relative to opaque bags) at

  3. Carbon dynamics in peatland pool systems: the role of light

    NASA Astrophysics Data System (ADS)

    Pickard, Amy; Heal, Kate; McLeod, Andy; Dinsmore, Kerry

    2016-04-01

    Open-water pools are widespread in peatlands and are considered to represent biogeochemical hotspots within the peatland landscape. However the contribution of pool systems to wider peatland C cycling has not been quantified fully and there is a lack of knowledge of the role of photochemical processes in such environments. In this study, light exposure experiments were conducted in two contrasting pools to test the reactivity of aquatic C. The first study site was located at Cross Lochs (CL), Forsinard, in the Flow Country of Northern Scotland, in a 412 m2 pool characterised by low dissolved organic carbon (DOC) concentrations (˜15 mg C L‑1). The second site was located at Red Moss of Balerno (RM), a raised bog in central Scotland, in a 48 m2 pool with high DOC concentrations (˜35 mg C L‑1). Experiments took place over 9 days in situ at each pool in mid-summer 2015, with 500 mL water samples contained in bags transparent to sunlight and in opaque control bags. After field exposure, optical, chemical and stable C isotope analyses were conducted on the samples. Significant differences in biogeochemical cycling of DOC were detected between the two systems, with DOC losses as a percentage of the total C pool 15% higher at RM than at CL after light exposure. The mean DOC concentration of light exposed samples at RM declined steeply initially, with 83% observed DOC degradation occurring by day 3 of the experiment. Total losses of 7.9 mg DOC L‑1were observed in light exposed samples at RM, along with decreasing E4:E6 ratios, suggesting that material remaining at the end of the experiment was humified. Depletion of DOC was positively correlated with production of CO2 at both sites, with concentrations of up to 4.3 mg CO2-C L‑1 recorded at RM. Stable C isotope signatures at both sites were altered under light treatment, as demonstrated by the production of enriched δ13C-DOC (+0.46 ‰ relative to opaque bags) and depleted δ13C-DIC (-0.97 ‰ relative to opaque

  4. CLASSIFICATION OF THE MGR POOL WATER TREATMENT AND COOLING SYSTEM

    SciTech Connect

    J.A. Ziegler

    1999-08-31

    The purpose of this analysis is to document the Quality Assurance (QA) classification of the Monitored Geologic Repository (MGR) pool water treatment and cooling system structures, systems and components (SSCs) performed by the MGR Safety Assurance Department. This analysis also provides the basis for revision of YMP/90-55Q, Q-List (YMP 1998). The Q-List identifies those MGR SSCs subject to the requirements of DOE/RW-0333P, ''Quality Assurance Requirements and Description'' (QARD) (DOE 1998).

  5. A Low Cost, Self Acting, Liquid Hydrogen Boil-Off Recovery System

    NASA Technical Reports Server (NTRS)

    Pelfrey, Joy W.; Sharp, Kirk V. (Technical Monitor)

    2001-01-01

    The purpose of this research was to develop a prototype liquid hydrogen boll-off recovery system. Perform analyses to finalize recovery system cycle, design detail components, fabricate hardware, and conduct sub-component, component, and system level tests leading to the delivery of a prototype system. The design point and off-design analyses identified cycle improvements to increase the robustness of the system by adding a by-pass heat exchanger. Based on the design, analysis, and testing conducted, the recovery system will liquefy 31% of the gaseous boil off from a liquid hydrogen storage tank. All components, including a high speed, miniature turbocompressor, were designed and manufacturing drawings were created. All hardware was fabricated and tests were conducted in air, helium, and hydrogen. Testing validated the design, except for the turbocompressor. A rotor-to-stator clearance issue was discovered as a result of a concentricity tolerance stack-up.

  6. Aging assessment of the boiling-water reactor (BWR) standby liquid control system. Phase 1

    SciTech Connect

    Orton, R.D.; Johnson, A.B.; Buckley, G.D.; Larson, L.L.

    1992-10-01

    Pacific Northwest Laboratory conducted a Phase I aging assessment of the standby liquid control (SLC) system used in boiling-water reactors. The study was based on detailed reviews of SLC system component and operating experience information obtained from the Nuclear Plant Reliability Database System, the Nuclear Document System, Licensee Event Reports, and other databases. Sources dealing with sodium pentaborate, borates, boric acid, and the effects of environment and corrosion in the SLC system were reviewed to characterize chemical properties and corrosion characteristics of borated solutions. The leading aging degradation concern to date appears to be setpoint drift in relief valves, which has been discovered during routine surveillance and is thought to be caused by mechanical wear. Degradation was also observed in pump seals and internal valves. In general, however, the results of the Phase I study suggest that age-related degradation of SLC systems has not been serious.

  7. Aging assessment of the boiling-water reactor (BWR) standby liquid control system

    SciTech Connect

    Orton, R.D.; Johnson, A.B.; Buckley, G.D.; Larson, L.L.

    1992-10-01

    Pacific Northwest Laboratory conducted a Phase I aging assessment of the standby liquid control (SLC) system used in boiling-water reactors. The study was based on detailed reviews of SLC system component and operating experience information obtained from the Nuclear Plant Reliability Database System, the Nuclear Document System, Licensee Event Reports, and other databases. Sources dealing with sodium pentaborate, borates, boric acid, and the effects of environment and corrosion in the SLC system were reviewed to characterize chemical properties and corrosion characteristics of borated solutions. The leading aging degradation concern to date appears to be setpoint drift in relief valves, which has been discovered during routine surveillance and is thought to be caused by mechanical wear. Degradation was also observed in pump seals and internal valves. In general, however, the results of the Phase I study suggest that age-related degradation of SLC systems has not been serious.

  8. Regulation of power pools and system operators: An international comparison

    SciTech Connect

    Barker, J. Jr.; Tenenbaum, B.; Woolf, F.

    1997-12-31

    This paper focuses on the governance and regulation of power pools outside the United States. The current governance and regulatory arrangements for four power pools, as developed in pool documents and government regulations and laws, are compared and contrasted. The power pools analyzed are located in England and Wales, Australia, Canada, and Scandinavia. Topics discussed in relation to these pools are the effects of structure on governance, how each pool has dealt with a number of basic governance decisions, how the pools monitor the markets, ways in which regulators and other institutions control pools, and self-governance issues.

  9. Thermoplastic fusion bonding using a pressure-assisted boiling point control system.

    PubMed

    Park, Taehyun; Song, In-Hyouk; Park, Daniel S; You, Byoung Hee; Murphy, Michael C

    2012-08-21

    A novel thermoplastic fusion bonding method using a pressure-assisted boiling point (PABP) control system was developed to apply precise temperatures and pressures during bonding. Hot embossed polymethyl methacrylate (PMMA) components containing microchannels were sealed using the PABP system. Very low aspect ratio structures (AR = 1/100, 10 μm in depth and 1000 μm in width) were successfully sealed without collapse or deformation. The integrity and strength of the bonds on the sealed PMMA devices were evaluated using leakage and rupture tests; no leaks were detected and failure during the rupture tests occurred at pressures greater than 496 kPa. The PABP system was used to seal 3D shaped flexible PMMA devices successfully.

  10. Tunable molten oxide pool assisted plasma-melter vitrification systems

    DOEpatents

    Titus, Charles H.; Cohn, Daniel R.; Surma, Jeffrey E.

    1998-01-01

    The present invention provides tunable waste conversion systems and apparatus which have the advantage of highly robust operation and which provide complete or substantially complete conversion of a wide range of waste streams into useful gas and a stable, nonleachable solid product at a single location with greatly reduced air pollution to meet air quality standards. The systems provide the capability for highly efficient conversion of waste into high quality combustible gas and for high efficiency conversion of the gas into electricity by utilizing a high efficiency gas turbine or an internal combustion engine. The solid product can be suitable for various commercial applications. Alternatively, the solid product stream, which is a safe, stable material, may be disposed of without special considerations as hazardous material. In the preferred embodiment, the arc plasma furnace and joule heated melter are formed as a fully integrated unit with a common melt pool having circuit arrangements for the simultaneous independently controllable operation of both the arc plasma and the joule heated portions of the unit without interference with one another. The preferred configuration of this embodiment of the invention utilizes two arc plasma electrodes with an elongated chamber for the molten pool such that the molten pool is capable of providing conducting paths between electrodes. The apparatus may additionally be employed with reduced use or without further use of the gases generated by the conversion process. The apparatus may be employed as a net energy or net electricity producing unit where use of an auxiliary fuel provides the required level of electricity production. Methods and apparatus for converting metals, non-glass forming waste streams and low-ash producing inorganics into a useful gas are also provided. The methods and apparatus for such conversion include the use of a molten oxide pool having predetermined electrical, thermal and physical

  11. Experimental investigation into effects of ultrasonic vibration on pool boiling heat transfer performance of horizontal low-finned U-tube in TiO2/R141b nanofluid

    NASA Astrophysics Data System (ADS)

    Chang, Tong-Bou; Wang, Zi-Long

    2016-01-01

    An experimental investigation was performed into the pool boiling heat transfer performance of a low-finned U-tube immersed in TiO2/R141b nanofluid with four different nanoparticle loadings (0, 0.0001, 0.001, and 0.01 vol%). The energy-dispersive X-ray spectrometry results revealed that some of the TiO2 nanoparticles adhered to the heated surface during boiling, and therefore increased the thermal resistance. The heat transfer performance of the nanofluids with particle loadings of 0.0001, 0.001 and 0.01 vol% was thus found to be reduced by around 10, 20 and 50 %, respectively, compared to that of pure R141b refrigerant. Accordingly, an ultrasonic vibration crusher was used to inhibit the formation of the TiO2 nano-sorption layer on the U-tube surface. The ultrasonic vibration suppressed the deposition of TiO2 nanoparticles and improved the heat transfer performance of the nanofluids as a result. Of the four working fluids, the nanofluid with a particle loading of 0.0001 vol% yielded the optimal heat transfer performance (i.e., a heat transfer coefficient around 30 % higher than that of pure R141b refrigerant.)

  12. Experimental investigation into effects of ultrasonic vibration on pool boiling heat transfer performance of horizontal low-finned U-tube in TiO2/R141b nanofluid

    NASA Astrophysics Data System (ADS)

    Chang, Tong-Bou; Wang, Zi-Long

    2016-11-01

    An experimental investigation was performed into the pool boiling heat transfer performance of a low-finned U-tube immersed in TiO2/R141b nanofluid with four different nanoparticle loadings (0, 0.0001, 0.001, and 0.01 vol%). The energy-dispersive X-ray spectrometry results revealed that some of the TiO2 nanoparticles adhered to the heated surface during boiling, and therefore increased the thermal resistance. The heat transfer performance of the nanofluids with particle loadings of 0.0001, 0.001 and 0.01 vol% was thus found to be reduced by around 10, 20 and 50 %, respectively, compared to that of pure R141b refrigerant. Accordingly, an ultrasonic vibration crusher was used to inhibit the formation of the TiO2 nano-sorption layer on the U-tube surface. The ultrasonic vibration suppressed the deposition of TiO2 nanoparticles and improved the heat transfer performance of the nanofluids as a result. Of the four working fluids, the nanofluid with a particle loading of 0.0001 vol% yielded the optimal heat transfer performance (i.e., a heat transfer coefficient around 30 % higher than that of pure R141b refrigerant.)

  13. Passive containment cooling system with drywell pressure regulation for boiling water reactor

    DOEpatents

    Hill, P.R.

    1994-12-27

    A boiling water reactor is described having a regulating valve for placing the wetwell in flow communication with an intake duct of the passive containment cooling system. This subsystem can be adjusted to maintain the drywell pressure at (or slightly below or above) wetwell pressure after the initial reactor blowdown transient is over. This addition to the PCCS design has the benefit of eliminating or minimizing steam leakage from the drywell to the wetwell in the longer-term post-LOCA time period and also minimizes the temperature difference between drywell and wetwell. This in turn reduces the rate of long-term pressure buildup of the containment, thereby extending the time to reach the design pressure limit. 4 figures.

  14. Passive containment cooling system with drywell pressure regulation for boiling water reactor

    DOEpatents

    Hill, Paul R.

    1994-01-01

    A boiling water reactor having a regulating valve for placing the wetwell in flow communication with an intake duct of the passive containment cooling system. This subsystem can be adjusted to maintain the drywell pressure at (or slightly below or above) wetwell pressure after the initial reactor blowdown transient is over. This addition to the PCCS design has the benefit of eliminating or minimizing steam leakage from the drywell to the wetwell in the longer-term post-LOCA time period and also minimizes the temperature difference between drywell and wetwell. This in turn reduces the rate of long-term pressure buildup of the containment, thereby extending the time to reach the design pressure limit.

  15. Microheater Array Boiling Experiment

    NASA Technical Reports Server (NTRS)

    Kim, Jungho; McQuillen, John; Balombin, Joe

    2002-01-01

    By conducting pool boiling tests in microgravity, the effect of buoyancy on the overall boiling process and the relative magnitude of other phenomena can be assessed. Data from KC-135 and sounding rocket experiments indicate little effect of gravity on boiling heat transfer at wall superheats below 25 C, despite vast differences in bubble behavior between gravity levels. In microgravity, a large primary bubble, surrounded by smaller satellite bubbles, moved over the surface, occasionally causing nucleation. Once formed, the primary bubble size remained constant for a given superheat, indicating evaporation at the bubble base is balanced with condensation on the bubble cap. The primary bubble's size increased with wall superheat. Most heaters under the primary bubble had low heat transfer rates, suggesting liquid dryout. Strong Marangoni convection developed in microgravity, forming a 'jet' into the bulk liquid that forced the bubble onto the heater. An experiment is being designed for the. Microgravity Science Glovebox. This experiment uses two 96 element microheater arrays, 2.7 and 7.0 mm in size. These heaters are individually controlled to operate at a constant temperature, measuring local heat fluxes as a function of time and space. Most boiling experiments operate at constant wall heat flux with larger heaters, allowing only time and space-averaged measurements. Each heater is about the bubble departure size in normal gravity, but significantly smaller than the bubble departure size in reduced gravity.

  16. Boiling incipience and convective boiling of neon and nitrogen

    NASA Technical Reports Server (NTRS)

    Papell, S. S.; Hendricks, R. C.

    1977-01-01

    Forced convection and subcooled boiling heat transfer data for liquid nitrogen and liquid neon were obtained in support of a design study for a 30 tesla cryomagnet cooled by forced convection of liquid neon. This design precludes nucleate boiling in the flow channels as they are too small to handle vapor flow. Consequently, it was necessary to determine boiling incipience under the operating conditions of the magnet system. The cryogen data obtained over a range of system pressures, fluid flow rates, and applied heat fluxes were used to develop correlations for predicting boiling incipience and convective boiling heat transfer coefficients in uniformly heated flow channels. The accuracy of the correlating equations was then evaluated. A technique was also developed to calculate the position of boiling incipience in a uniformly heated flow channel. Comparisons made with the experimental data showed a prediction accuracy of plus or minus 15 percent

  17. Boiling incipience and heat transfer on smooth and enhanced surfaces

    SciTech Connect

    Shakir, S.

    1987-01-01

    A comprehensive experimental study in nucleate pool boiling of binary mixtures was carried out to investigate the effects of mixture composition on boiling incipient and deactivation superheats and heat-transfer coefficients. All experiments were performed at a pressure of 1.01 bar on conventional smooth surfaces and an enhanced surface (High Flux of Union Carbide Corporation). Contact angles were also measured for the same mixtures on the smooth surfaces of brass and copper. The incipience and deactivation of boiling sites on the enhanced surface occurred at much lower wall superheats than on the smooth ones. For the mixture systems investigated, the incipient superheats were observed to be higher than the corresponding deactivation superheats. The classical boiling nucleation criterion was found to be inadequate in predicting the measured incipient superheats. The boiling-heat-transfer coefficients obtained on the smooth surfaces showed a deterioration when compared with the values obtained from a simple linear mixing law between the single-component values. The enhanced surface-heat-transfer coefficients for boiling of the same mixtures showed both positive and negative deviations from the linear mixing law between the pure component values.

  18. Design of inventory pools in spare part support operation systems

    NASA Astrophysics Data System (ADS)

    Mo, Daniel Y.; Tseng, Mitchell M.; Cheung, Raymond K.

    2014-06-01

    The objective of a spare part support operation is to fulfill the part request order with different service contracts in the agreed response time. With this objective to achieve different service targets for multiple service contracts and the considerations of inventory investment, it is not only important to determine the inventory policy but also to design the structure of inventory pools and the order fulfilment strategies. In this research, we focused on two types of inventory pools: multiple inventory pool (MIP) and consolidated inventory pool (CIP). The idea of MIP is to maintain separated inventory pools based on the types of service contract, while CIP solely maintains a single inventory pool regardless of service contract. Our research aims to design the inventory pool analytically and propose reserve strategies to manage the order fulfilment risks in CIP. Mathematical models and simulation experiments would be applied for analysis and evaluation.

  19. Boiling incipience and convective boiling of neon and nitrogen

    NASA Technical Reports Server (NTRS)

    Papell, S. S.; Hendricks, R. C.

    1977-01-01

    Forced convection and subcooled boiling heat transfer data for liquid nitrogen and liquid neon were obtained in support of a design study for a 30 tesla cryomagnet cooled by forced convection of liquid neon. The cryogen data obtained over a range of system pressures, fluid flow rates, and applied heat fluxes were used to develop correlations for predicting boiling incipience and convective boiling heat transfer coefficients in uniformly heated flow channels. The accuracy of the correlating equations was then evaluated. A technique was also developed to calculate the position of boiling incipience in a uniformly heated flow channel. Comparisons made with the experimental data showed a prediction accuracy of + or - 15 percent.

  20. Fundamental study of molten pool depth measurement method using an ultrasonic phased array system

    NASA Astrophysics Data System (ADS)

    Mizota, Hirohisa; Nagashima, Yoshiaki; Obana, Takeshi

    2015-07-01

    The molten pool depth measurement method using an ultrasonic phased array system has been developed. The molten pool depth distribution is evaluated by comparing the times taken by the ultrasonic wave to propagate through a molten pool and a solid-phase and through only the solid-phase near the molten pool. Maximum molten pool depths on a flat type-304 stainless-steel plate, formed with a gas tungsten arc welding machine for different welding currents from 70 to 150 A, were derived within an error of ±0.5 mm.

  1. EHD enhancement of nucleate boiling. [Electrohydrodynamic

    SciTech Connect

    Cooper, P. )

    1990-05-01

    This paper describes: (a) an experimental investigation into the effect of an electric field applied to pool boiling of Freon (R114) on a finned tube and (b) a theoretical model of electrically enhanced nucleate boiling applicable to simple surfaces only. Experimental results have shown electrohydrodynamic (EHD) enhancement of heat transfer to be manifest in two ways: (1) elimination of boiling hysteresis, (2) augmentation of nulceate boiling heat transfer coefficients by up to an order of magnitude. These effects were also observed in electrically enhanced boiling of Freon/oil mixtures. A new analytical model is described whereby EHD nucleate boiling data from previous studies (employing simple apparatus comprising heated wires with concentric cylinder electrodes) have been correlated for the first time using the concept of an electrical influence number. This dimensionless parameter is based upon the relationship between applied electric field intensity and changes in bubble departure diameter at a heat transfer surface.

  2. MODULAR AND FULL SIZE SIMPLIFIED BOILING WATER REACTOR DESIGN WITH FULLY PASSIVE SAFETY SYSTEMS

    SciTech Connect

    M. Ishii; S. T. Revankar; T. Downar; Y. Xu, H. J. Yoon; D. Tinkler; U. S. Rohatgi

    2003-06-16

    OAK B204 The overall goal of this three-year research project was to develop a new scientific design of a compact modular 200 MWe and a full size 1200 MWe simplified boiling water reactors (SBWR). Specific objectives of this research were: (1) to perform scientific designs of the core neutronics and core thermal-hydraulics for a small capacity and full size simplified boiling water reactor, (2) to develop a passive safety system design, (3) improve and validate safety analysis code, (4) demonstrate experimentally and analytically all design functions of the safety systems for the design basis accidents (DBA) and (5) to develop the final scientific design of both SBWR systems, 200 MWe (SBWR-200) and 1200 MWe (SBWR-1200). The SBWR combines the advantages of design simplicity and completely passive safety systems. These advantages fit well within the objectives of NERI and the Department of Energy's focus on the development of Generation III and IV nuclear power. The 3-year research program was structured around seven tasks. Task 1 was to perform the preliminary thermal-hydraulic design. Task 2 was to perform the core neutronic design analysis. Task 3 was to perform a detailed scaling study and obtain corresponding PUMA conditions from an integral test. Task 4 was to perform integral tests and code evaluation for the DBA. Task 5 was to perform a safety analysis for the DBA. Task 6 was to perform a BWR stability analysis. Task 7 was to perform a final scientific design of the compact modular SBWR-200 and the full size SBWR-1200. A no cost extension for the third year was requested and the request was granted and all the project tasks were completed by April 2003. The design activities in tasks 1, 2, and 3 were completed as planned. The existing thermal-hydraulic information, core physics, and fuel lattice information was collected on the existing design of the simplified boiling water reactor. The thermal-hydraulic design were developed. Based on a detailed integral

  3. Pool Purification

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Caribbean Clear, Inc. used NASA's silver ion technology as a basis for its automatic pool purifier. System offers alternative approach to conventional purification chemicals. Caribbean Clear's principal markets are swimming pool owners who want to eliminate chlorine and bromine. Purifiers in Caribbean Clear System are same silver ions used in Apollo System to kill bacteria, plus copper ions to kill algae. They produce spa or pool water that exceeds EPA Standards for drinking water.

  4. 76 FR 22444 - Privacy Act; System of Records: State-52, Parking Permit and Car Pool Records

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-21

    ... Act; System of Records: State-52, Parking Permit and Car Pool Records Summary: Notice is hereby given that the Department of State proposes to amend an existing system of records, Parking Permit and Car... will retain the name ``Parking Permit and Car Pool Records.'' It is also proposed that the...

  5. Characterization of pool thermal stratification in the San Joaquin River system

    NASA Astrophysics Data System (ADS)

    Butler, N. L.; Hunt, J. R.

    2013-12-01

    Temperature is a critical water quality parameter for Chinook salmon (Oncorhynchus tshawystcha) and is a potentially limiting factor for the successful reintroduction of Chinook into the San Joaquin River system. When ambient stream water temperatures exceed salmon thermal tolerances, salmon seek out cooler water in pools as thermal refuge. While current models of the San Joaquin River can estimate ambient surface water temperature, vertical variations in pool temperature are unknown and not modeled. This study measured river pool thermal stratification in the San Joaquin River system to assess available thermal refuge and identify the key drivers of thermal stratification in this system. During July 2012, daytime vertical water temperature profiles were measured in 53 river pools to survey the prevalence of thermal stratification in the San Joaquin River system from the Mariposa Bypass to the its confluence with the Merced River. Between September and November 2012 six of the pools that exhibited thermal stratification during July were instrumented with water temperature sensor arrays and piezometers. The water temperature sensor arrays were constructed by attaching sensors at regular intervals to the exterior of a PVC pipe to measure the vertical water temperature in the pool and into the sediment. Additionally, piezometers determined pool water head along with pressure head at two different depths into the sediment. Sensor arrays were setup for a minimum of two weeks at each site with sensors recording data every 15 minutes. Thermal stratification occurred in 82% of the 53 pools surveyed in the San Joaquin River during July. Pool depths ranged from 0.64 m to 6.37 m with an average depth of 2.09 m. Differences in vertical water temperature ranged from less than 3 °C to 11.4 °C with an average water temperature difference of 4.2 °C. Vertical water temperature differences did not correlate with pool depth. In the six pools instrumented for two weeks, thermal

  6. Geysering in boiling channels

    SciTech Connect

    Aritomi, Masanori; Takemoto, Takatoshi; Chiang, Jing-Hsien

    1995-09-01

    A concept of natural circulation BWRs such as the SBWR has been proposed and seems to be promising in that the primary cooling system can be simplified. The authors have been investigating thermo-hydraulic instabilities which may appear during the start-up in natural circulation BWRs. In our previous works, geysering was investigated in parallel boiling channels for both natural and forced circulations, and its driving mechanism and the effect of system pressure on geysering occurrence were made clear. In this paper, geysering is investigated in a vertical column and a U-shaped vertical column heated in the lower parts. It is clarified from the results that the occurrence mechanism of geysering and the dependence of system pressure on geysering occurrence coincide between parallel boiling channels in circulation systems and vertical columns in non-circulation systems.

  7. A Study of Nucleate Boiling with Forced Convection in Microgravity

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1999-01-01

    The ultimate objective of basic studies of flow boiling in microgravity is to improve the understanding of the processes involved, as manifested by the ability to predict its behavior. This is not yet the case for boiling heat transfer even in earth gravity, despite the considerable research activity over the past 30 years. The elements that constitute the nucleate boiling process - nucleation, growth, motion, and collapse of the vapor bubbles (if the bulk liquid is subcooled) - are common to both pool and flow boiling. It is well known that the imposition of bulk liquid motion affects the vapor bubble behavior relative to pool boiling, but does not appear to significantly influence the heat transfer. Indeed, it has been recommended in the past that empirical correlations or experimental data of pool boiling be used for design purposes with forced convection nucleate boiling. It is anticipated that such will most certainly not be possible for boiling in microgravity, based on observations made with pool boiling in microgravity. In earth gravity buoyancy will act to remove the vapor bubbles from the vicinity of the heater surface regardless of how much the imposed bulk velocity is reduced, depending, of course, on the geometry of the system. Vapor bubbles have been observed to dramatically increase in size in pool boiling in microgravity, and the heat flux at which dryout took place was reduced considerably below what is generally termed the critical heat flux (CHF) in earth gravity, depending on the bulk liquid subcooling. However, at heat flux levels below dryout, the nucleate pool boiling process was enhanced considerably over that in earth gravity, in spite of the large vapor bubbles formed in microgravity and perhaps as a consequence. These large vapor bubbles tended to remain in the vicinity of the heater surface, and the enhanced heat transfer appeared to be associated with the presence of what variously has been referred to as a liquid microlayer between the

  8. Flow Boiling and Condensation Experiment

    NASA Video Gallery

    The Flow Boiling and Condensation Experiment is another investigation that examines the flow of a mixture of liquids and the vapors they produce when in contact with hot space system equipment. Coo...

  9. Fuzzy Pool Balance: An algorithm to achieve a two dimensional balance in distribute storage systems

    NASA Astrophysics Data System (ADS)

    Wu, Wenjing; Chen, Gang

    2014-06-01

    The limitation of scheduling modules and the gradual addition of disk pools in distributed storage systems often result in imbalances among their disk pools in terms of both disk usage and file count. This can cause various problems to the storage system such as single point of failure, low system throughput and imbalanced resource utilization and system loads. An algorithm named Fuzzy Pool Balance (FPB) is proposed here to solve this problem. The input of FPB is the current file distribution among disk pools and the output is a file migration plan indicating what files are to be migrated to which pools. FPB uses an array to classify the files by their sizes. The file classification array is dynamically calculated with a defined threshold named Tmax that defines the allowed pool disk usage deviations. File classification is the basis of file migration. FPB also defines the Immigration Pool (IP) and Emigration Pool (EP) according to the pool disk usage and File Quantity Ratio (FQR) that indicates the percentage of each category of files in each disk pool, so files with higher FQR in an EP will be migrated to IP(s) with a lower FQR of this file category. To verify this algorithm, we implemented FPB on an ATLAS Tier2 dCache production system. The results show that FPB can achieve a very good balance in both free space and file counts, and adjusting the threshold value Tmax and the correction factor to the average FQR can achieve a tradeoff between free space and file count.

  10. Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants

    NASA Astrophysics Data System (ADS)

    Yoshida, Suguru; Fujita, Yasunobu

    The current state of knowledge on heat transfer to boiling refrigerants (halogenated hydrocarbons) in a pool and flowing inside a horizontal tube is reviewed with an emphasis on information relevant to the design of refrigerant evaporators, and some recommendations are made for future research. The review covers two-phase flow pattern, heat transfer characteristics, correlation of heat transfer coefficient, influence of oil, heat transfer augmentation, boiling from tube-bundle, influence of return bend, burnout heat flux, film boiling, dryout and post-dryout heat transfer.

  11. Saguaro: A distributed operating system based on pools of servicers

    NASA Astrophysics Data System (ADS)

    Andrews, G. R.; Schlichting, R. D.

    1985-03-01

    The progress achieved during the first year of the integrated Saguaro distributed operating system project is presented. The major accomplishments were the completion of the initial design and preliminary implementation of several system components, the subsequent refinement of the user interface and the file system, and the investigation into the use of a universal type system to type data and specify interfaces in the operating system.

  12. Boiling of the interface between two immiscible liquids below the bulk boiling temperatures of both components.

    PubMed

    Pimenova, Anastasiya V; Goldobin, Denis S

    2014-11-01

    We consider the problem of boiling of the direct contact of two immiscible liquids. An intense vapour formation at such a direct contact is possible below the bulk boiling points of both components, meaning an effective decrease of the boiling temperature of the system. Although the phenomenon is known in science and widely employed in technology, the direct contact boiling process was thoroughly studied (both experimentally and theoretically) only for the case where one of liquids is becoming heated above its bulk boiling point. On the contrary, we address the case where both liquids remain below their bulk boiling points. In this paper we construct the theoretical description of the boiling process and discuss the actualisation of the case we consider for real systems.

  13. Boiling of the interface between two immiscible liquids below the bulk boiling temperatures of both components.

    PubMed

    Pimenova, Anastasiya V; Goldobin, Denis S

    2014-11-01

    We consider the problem of boiling of the direct contact of two immiscible liquids. An intense vapour formation at such a direct contact is possible below the bulk boiling points of both components, meaning an effective decrease of the boiling temperature of the system. Although the phenomenon is known in science and widely employed in technology, the direct contact boiling process was thoroughly studied (both experimentally and theoretically) only for the case where one of liquids is becoming heated above its bulk boiling point. On the contrary, we address the case where both liquids remain below their bulk boiling points. In this paper we construct the theoretical description of the boiling process and discuss the actualisation of the case we consider for real systems. PMID:25403831

  14. Automatic Welding System of Aluminum Pipe by Monitoring Backside Image of Molten Pool Using Vision Sensor

    NASA Astrophysics Data System (ADS)

    Baskoro, Ario Sunar; Kabutomori, Masashi; Suga, Yasuo

    An automatic welding system using Tungsten Inert Gas (TIG) welding with vision sensor for welding of aluminum pipe was constructed. This research studies the intelligent welding process of aluminum alloy pipe 6063S-T5 in fixed position and moving welding torch with the AC welding machine. The monitoring system consists of a vision sensor using a charge-coupled device (CCD) camera to monitor backside image of molten pool. The captured image was processed to recognize the edge of molten pool by image processing algorithm. Neural network model for welding speed control were constructed to perform the process automatically. From the experimental results it shows the effectiveness of the control system confirmed by good detection of molten pool and sound weld of experimental result.

  15. How Does Water Boil?

    NASA Astrophysics Data System (ADS)

    Zahn, Dirk

    2004-11-01

    Insight into the boiling of water is obtained from molecular dynamics simulations. The process is initiated by the spontaneous formation of small vacuum cavities in liquid water. By themselves, these defects are very short lived. If, however, several cavities occur at close distances, they are likely to merge into larger vacuum holes. At the liquid-vapor interfaces, single or small groups of water molecules tend to leave the liquid surface. Once the system is propagated beyond the transition state, these evaporation events outnumber the competing reintegration into the hydrogen-bonded network.

  16. Design, Construction, and Qualification of a Microscale Heater Array for Use in Boiling Heat Transfer

    NASA Technical Reports Server (NTRS)

    Rule, T. D.; Kim, J.; Kalkur, T. S.

    1998-01-01

    Boiling heat transfer is an efficient means of heat transfer because a large amount of heat can be removed from a surface using a relatively small temperature difference between the surface and the bulk liquid. However, the mechanisms that govern boiling heat transfer are not well understood. Measurements of wall temperature and heat flux near the wall would add to the database of knowledge which is necessary to understand the mechanisms of nucleate boiling. A heater array has been developed which contains 96 heater elements within a 2.5 mm square area. The temperature of each heater element is held constant by an electronic control system similar to a hot-wire anemometer. The voltage that is being applied to each heater element can be measured and digitized using a high-speed A/D converter, and this digital information can be compiled into a series of heat-flux maps. Information for up to 10,000 heat flux maps can be obtained each second. The heater control system, the A/D system and the heater array construction are described in detail. Results are presented which show that this is an effective method of measuring the local heat flux during nucleate and transition boiling. Heat flux maps are obtained for pool boiling in FC-72 on a horizontal surface. Local heat flux variations are shown to be three to six times larger than variations in the spatially averaged heat flux.

  17. Boiling Experiment Facility for Heat Transfer Studies in Microgravity

    NASA Technical Reports Server (NTRS)

    Delombard, Richard; McQuillen, John; Chao, David

    2008-01-01

    Pool boiling in microgravity is an area of both scientific and practical interest. By conducting tests in microgravity, it is possible to assess the effect of buoyancy on the overall boiling process and assess the relative magnitude of effects with regards to other "forces" and phenomena such as Marangoni forces, liquid momentum forces, and microlayer evaporation. The Boiling eXperiment Facility is now being built for the Microgravity Science Glovebox that will use normal perfluorohexane as a test fluid to extend the range of test conditions to include longer test durations and less liquid subcooling. Two experiments, the Microheater Array Boiling Experiment and the Nucleate Pool Boiling eXperiment will use the Boiling eXperiment Facility. The objectives of these studies are to determine the differences in local boiling heat transfer mechanisms in microgravity and normal gravity from nucleate boiling, through critical heat flux and into the transition boiling regime and to examine the bubble nucleation, growth, departure and coalescence processes. Custom-designed heaters will be utilized to achieve these objectives.

  18. Analysis of an open-air swimming pool solar heating system by using an experimentally validated TRNSYS model

    SciTech Connect

    Ruiz, Elisa; Martinez, Pedro J.

    2010-01-15

    In the case of private outdoor swimming pools, seldom larger than 100 m{sup 2}, conventional auxiliary heating systems are being installed less and less. Solar heating is an option to extend the swimming season. The temperature evolution of an open-air swimming pool highly depends on the wind speed directly on the water surface, which at the same time is influenced by the surroundings of the pool. In this paper, the TRNSYS model of a private open-air pool with a 50-m{sup 2} surface was validated by registering the water temperature evolution and the meteorological data at the pool site. Evaporation is the main component of energy loss in swimming pools. Six different sets of constants found in literature were considered to evaluate the evaporative heat transfer coefficient with the purpose of finding the most suitable one for the TRNSYS pool model. In order to do that, the evolution of the pool water temperature predicted by the TRNSYS pool model was compared with the experimentally registered one. The simulation with TRNSYS of the total system, including the swimming pool and the absorber circuit integrated into the existing filter circuit, provided information regarding the increase of the pool temperature for different collector areas during the swimming season. This knowledge, together with the economic costs, support the decision about the absorber field size. (author)

  19. A review on boiling heat transfer enhancement with nanofluids.

    PubMed

    Barber, Jacqueline; Brutin, David; Tadrist, Lounes

    2011-04-04

    There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement.

  20. A review on boiling heat transfer enhancement with nanofluids

    PubMed Central

    2011-01-01

    There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement. PMID:21711794

  1. A review on boiling heat transfer enhancement with nanofluids

    NASA Astrophysics Data System (ADS)

    Barber, Jacqueline; Brutin, David; Tadrist, Lounes

    2011-12-01

    There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement.

  2. Film boiling heat transfer from a sphere in natural and forced convection of freon-113

    SciTech Connect

    Dix, D.; Orozco, J. )

    1990-01-01

    Boiling heat transfer fluxes were measured on a 3.84-cm hollow copper sphere, in both forced convection and pool boiling, as a function of angular position in Freon 113. This paper reports on forced-convection tests run at speeds of 0.5 to 1.9 m/s. These tests were conducted in the stable film boiling region of the boiling curve. Significant heat transfer rates were measured in the vapor wake region of the sphere for flow film boiling. Video observations of the boiling process revealed that the flow film boiling vapor removal mechanism consisted of periodic formation and detachment of a vapor wake in the rear of the sphere. For pool boiling it was found that the heated surface had a uniform rate of energy dissipation in the stable film boiling regime, whereas in forced convection the film boiling rate was dependent on angular position. Pool film boiling tests also showed multiple humps (more than one maximum heat flux) in the boiling curve when the liquid was subcooled.

  3. Cryogenic Boiling and Two-Phase Flow during Pipe Chilldown in Earth and Reduced Gravity

    NASA Astrophysics Data System (ADS)

    Yuan, Kun; Ji, Yan; Chung, J. N.; Shyy, Wei

    2008-01-01

    For many industrial, medical and space technologies, cryogenic fluids play indispensable roles. An integral part of the cryogenic transport processes is the chilldown of the system components during initial applications. In this paper, we report experimental results for a chilldown process that is involved with the unsteady two-phase vapor-liquid flow and boiling heat transfer of the cryogen coupled with the transient heat conduction inside pipe walls. We have provided fundamental understanding on the physics of the two-phase flow and boiling heat transfer during cryogenic quenching through experimental observation, measurement and analysis. Based on the temperature measurement of the tube wall, the terrestrial cryogenic chilldown process is divided into three stages of film boiling, nucleate boiling and single-phase convection that bears a close similarity to the conventional pool boiling process. In earth gravity, cooling rate is non-uniform circumferentially due to a stratified flow pattern that gives rise to more cooling on the bottom wall by liquid filaments. In microgravity, there is no stratified flow and the absence of the gravitational force sends liquid filaments to the central core and replaces them by low thermal conductivity vapor that significantly reduces the heat transfer from the wall. Thus, the chilldown process is axisymmetric, but longer in microgravity.

  4. Modeling step-pool systems in steep streams by a cellular automaton sandpile model

    NASA Astrophysics Data System (ADS)

    Saletti, M.; Molnar, P.; Hassan, M. A.; Zimmermann, A. E.; Fraccarollo, L.

    2013-12-01

    Alluvial step-pool systems in gravel-bed rivers have been widely studied in the last decades in both field and flume experiments. The focus has been on step formation, the geometry of step-pool sequences, the spatial and temporal variation in step properties, and the hydraulics of flow over steps. Scientists have focused on the conditions under which step-pool sequences form, remain stable and eventually collapse (Church and Zimmermann, 2007; Curran 2007). Step-pool systems are usually stable for very long periods, in which the macro-morphology does not change, even if single step-pool units may change during small flood events. Step structures typically collapse during intense flood events, with return times of 20÷50 years. These breakdown events produce an avalanche-like pulse of sediment and a rearrangement in the channel morphology. Despite a rich literature on the processes of step formation and collapse, the modeling thereof is still in its infancy. It has been proposed by Church and Zimmermann (2007) that step formation is ruled mainly by random location of big boulders along the channel--these grains act as keystones which block smaller particles and create a channel-spanning step. The nonlinear threshold-driven processes of jamming and collapse, together with the stochastic nature of bedload transport and the random location of the keystones, makes it impossible to model the step-pool system in a deterministic way. Instead, we hypothesize that step-pool systems during intense sediment transport events behave like open, dynamical and dissipative systems close to a critical state, and we adopt the modeling framework of self-organized criticality (Bak et al., 1988) in this description. To test our hypothesis we developed a cellular automaton model based on ideas of the simple sandpile model in 1-D and 2-D. Grains are added at the top of a channel randomly, they pass through the channel and form bed structures, and ultimately exit the channel at the

  5. A Low Cost, Self-Acting, Liquid Hydrogen Boil-Off Recovery System

    NASA Technical Reports Server (NTRS)

    Pelfrey, Joy w.

    2000-01-01

    PROJECT SUMMARY. 1 PROJECT OBJECTIVES. Detail Design. Final Analysis. Hardware Procurement. Component Tests. System Tests..Prototype Tests. 2. WORK PERFORMED. Detail Design. Final Analysis. Hardware Procurement. Component Tests. System Tests. Prototype Tests. 3. Results obtained. Detail Design. Final Analysis. Hardware Procurement. Component Tests. System Tests. Prototype Tests. 5. TECHNICAL MERIT AND FEASIBILITY ASSESSMENT. 6. APPENDIX A: SIZE DETAIL DRAWINGS. 7. APPENDIX B: CONSULTANTS SENSITIVITY STUDY. 8. APPENDIX C: CONSULTANTS REPORT. ROTORDYNAMIC ANALYSIS 9. SF298 REPORT DOCUMENTATION PAGE.

  6. Effect of Magnetic Fields on the Boiling Heat Transfer Characteristics of Nanofluids

    NASA Astrophysics Data System (ADS)

    Naphon, Paisarn

    2015-11-01

    The main focus of the present study is to investigate the effect of magnetic fields on the pool boiling heat transfer characteristics on the cylindrical surface of nanofluids. The nanofluids with suspended TiO2 nanoparticles in the base fluid refrigerant R141b are used as the working fluid. Effects of magnetic field strength, nanoparticle concentration, and boiling pressure on the pool boiling heat transfer coefficient and the boiling bubble characteristics are considered. In this study, magnetic fields with strengths of 5.0× 10^{-4} T, 7.5× 10^{-4} T, and 10.0× 10^{-4} T are applied to exert a force on the boiling surface with permanent magnets. According to the experimental results, it is found that the magnetic fields have a significant effect on the pool boiling heat transfer enhancement with a maximum enhancement of 27.91 %.

  7. Science communication and vernal pool conservation: a study of local decision maker attitudes in a knowledge-action system.

    PubMed

    McGreavy, Bridie; Webler, Thomas; Calhoun, Aram J K

    2012-03-01

    In this study, we describe local decision maker attitudes towards vernal pools to inform science communication and enhance vernal pool conservation efforts. We conducted interviews with town planning board and conservation commission members (n = 9) from two towns in the State of Maine in the northeastern United States. We then mailed a questionnaire to a stratified random sample of planning board members in August and September 2007 with a response rate of 48.4% (n = 320). The majority of survey respondents favored the protection and conservation of vernal pools in their towns. Decision makers were familiar with the term "vernal pool" and demonstrated positive attitudes to vernal pools in general. General appreciation and willingness to conserve vernal pools predicted support for the 2006 revisions to the Natural Resource Protection Act regulating Significant Vernal Pools. However, 48% of respondents were unaware of this law and neither prior knowledge of the law nor workshop attendance predicted support for the vernal pool law. Further, concerns about private property rights and development restrictions predicted disagreement with the vernal pool law. We conclude that science communication must rely on specific frames of reference, be sensitive to cultural values, and occur in an iterative system to link knowledge and action in support of vernal pool conservation.

  8. A rule-based expert system for automatic control rod pattern generation for boiling water reactors

    SciTech Connect

    Lin, L.S.; Lin, C. )

    1991-07-01

    This paper reports on an expert system for generating control rod patterns that has been developed. The knowledge is transformed into IF-THEN rules. The inference engine uses the Rete pattern matching algorithm to match facts, and rule premises and conflict resolution strategies to make the system function intelligently. A forward-chaining mechanism is adopted in the inference engine. The system is implemented in the Common Lisp programming language. The three-dimensional core simulation model performs the core status and burnup calculations. The system is successfully demonstrated by generating control rod programming for the 2894-MW (thermal) Kuosheng nuclear power plant in Taiwan. The computing time is tremendously reduced compared to programs using mathematical methods.

  9. Simulation of the tropical Pacific warm pool with the NCAR Climate System Model

    SciTech Connect

    Kiehl, J.T.

    1998-06-01

    The simulation of the tropical western Pacific warm pool is explored with the NCAR Climate System Model (CSM). The simulated sea surface temperatures in the Pacific basin have biases that are similar to other coupled model simulations in this region. In particular, an excessive cold tongue of water extends across the Pacific basin, with warm water on either side of this cold tongue. The warm pool region is also too cold. This cold bias exists in spite of an overestimate in surface net energy flux into this region. To understand the source of this bias in SST, simulations from the uncoupled and fully coupled models are analyzed in terms of biases in surface energy budget. These analyses suggest that the strong constraint of little ocean heat transport out of the warm pool region forces a change in SST gradient that leads to an increase in the atmospheric zonal wind. This increase in zonal wind causes an increase in latent heat flux in the warm pool region. The increase in latent heat flux is required to offset a significant bias in net surface solar flux. The bias in surface solar flux is due to an underestimate of model cloud shortwave absorption.

  10. Evaporation, Boiling and Bubbles

    ERIC Educational Resources Information Center

    Goodwin, Alan

    2012-01-01

    Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The…

  11. Liquid crystal thermography in boiling heat transfer

    SciTech Connect

    Klausner, J.F.; Mei, R.; Chen, W.C.

    1995-12-31

    The utilization of liquid crystal thermography to study heterogeneous boiling phenomena has gained popularity in recent years. In order not to disturb the nucleation process, which occurs in the microstructure of the heating surface, the crystals are applied to the backside of a thin heater. This work critically examines the ability of liquid crystal thermography to quantitatively capture the thermal field on the boiling surface. The thermal field identified experimentally through liquid crystal thermography is compared against that computed in the vicinity of a growing vapor bubble using a simulation which considers the simultaneous heat transfer between three phases: the solid heater, the liquid microlayer, and the growing vapor bubble. The temperature history beneath a growing vapor bubble elucidates the high frequency response required to capture the transient thermal fields commonly encountered in boiling experiments. Examination of the governing equations and numerical results reveal that due to the heater thermal inertia, the temperature variation on the bottom of the heater is significantly different than that on the boiling surface. In addition, the crystals themselves have a finite spatial resolution and frequency response which filter out much of the microscale phenomenon associated with boiling heat transfer. Analysis of existing pool and flow boiling liquid crystal thermographs indicate that the typical spacial resolution is on the order of 0.25 mm and the response time is on the order of 5 ms which are insufficient to resolve the fine spacial and temporal details of the heating surface thermal field. Thus the data obtained from liquid crystal thermography applied to boiling heat transfer must be cautiously interpreted.

  12. Swimming Pools.

    ERIC Educational Resources Information Center

    Ministry of Housing and Local Government, London (England).

    Technical and engineering data are set forth on the design and construction of swimming pools. Consideration is given to site selection, pool construction, the comparative merits of combining open air and enclosed pools, and alternative uses of the pool. Guidelines are presented regarding--(1) pool size and use, (2) locker and changing rooms, (3)…

  13. System for reducing heat losses from indoor swimming pools by use of automatic covers. Report No. 3

    SciTech Connect

    Not Available

    1994-09-30

    This progress report covers the period July 1, 1994 through September 30, 1994, and summarizes continuing work on developing deloyable covers for indoor swimming pools. This work includes design and development of motor controllers to deploy and roll up pool covers, reels, cover material of polyethylene and foam filled laminates, and plans for field deployment of a system, where energy savings can be monitored.

  14. Transition to Film Boiling in Microgravity: Influence of Subcooling

    NASA Astrophysics Data System (ADS)

    Zhao, Jian-Fu; Li, Jing; Yan, Na; Wang, Shuang-Feng

    2010-07-01

    The transition process to film pool boiling in microgravity is studied experimentally aboard the Chinese recoverable satellite SJ-8. A quasi-steady heating method is adopted, in which the heating voltage is controlled to increase exponentially with time. Small, primary bubbles are formed and slid on the surface, which coalesce with each other to form a large coalesced bubble. Two ways are observed for the transition from nucleate to film boiling at different subcoolings. At high subcooling, the coalesced bubble with a smooth surface grows slowly. It is then difficult for the coalesced bubble to cover the whole heater surface, resulting in a special region of transition boiling in which nucleate boiling and local dry areas can coexist. In contrast, strong oscillation of the coalesced bubble surface at low subcooling may cause rewetting of local dry areas and activation of more nucleate sites, resulting in an abrupt transition to film boiling.

  15. Aspects of subcooled boiling

    SciTech Connect

    Bankoff, S.G.

    1997-12-31

    Subcooled boiling boiling refers to boiling from a solid surface where the bulk liquid temperature is below the saturation temperature (subcooled). Two classes are considered: (1) nucleate boiling, where, for large subcoolings, individual bubbles grow and collapse while remaining attached to the solid wall, and (2) film boiling, where a continuous vapor film separates the solid from the bulk liquid. One mechanism by which subcooled nucleate boiling results in very large surface heat transfer coefficient is thought to be latent heat transport within the bubble, resulting from simultaneous evaporation from a thin residual liquid layer at the bubble base, and condensation at the polar bubble cap. Another is the increased liquid microconvection around the oscillating bubble. Two related problems have been attacked. One is the rupture of a thin liquid film subject to attractive and repulsive dispersion forces, leading to the formation of mesoscopic drops, which then coalesce and evaporate. Another is the liquid motion in the vicinity of an oscillating contact line, where the bubble wall is idealized as a wedge of constant angle sliding on the solid wall. The subcooled film boiling problem has been attacked by deriving a general long-range nonlinear evolution equation for the local thickness of the vapor layer. Linear and weakly-nonlinear stability results have been obtained. A number of other related problems have been attacked.

  16. Bubble departure in the direct-contact boiling field with a continuous liquid-liquid interface

    SciTech Connect

    Kadoguchi, Katsuhiko

    2007-01-15

    Behavior of vapor bubbles was experimentally investigated in the boiling field where a volatile liquid layer of per-fluorocarbon PF5050 (boiling point 306K) was directly in contact with an immiscible hot liquid layer of water above it. Heat was supplied to the continuous liquid-liquid interface by the impingement of the downward hot water jet. Vapor bubbles were generated not only from this continuous interface but from a large number of PF5050 droplets floating on it. According to precise observation, incipience of boiling did not occur at the liquid-liquid interface but in the PF5050 liquid close to the interface in both cases of continuous and dispersed interfaces. As a result, the bubbles broke up the thin PF5050 liquid film above them and rose up into the water layer. This bubble departure phenomenon, which does not occur in the ordinary pool boiling field on the solid heating wall, is very important to evaluate the heat transfer performance in the present direct-contact boiling system. For modeling this behavior, sizes of the bubbles were measured at the moment just after they were released into the water pool. Volumes of the bubbles were larger in the case of departing from the continuous liquid-liquid interface than from the droplets. This tendency could be explained by taking into account the buoyancy force acting on unit area of the thin PF5050 liquid film above the bubble before departure, which was one of the most important parameters for the liquid film breakdown. (author)

  17. Bubble Dynamics, Two-Phase Flow, and Boiling Heat Transfer in Microgravity

    NASA Technical Reports Server (NTRS)

    Chung, Jacob N.

    1998-01-01

    This report contains two independent sections. Part one is titled "Terrestrial and Microgravity Pool Boiling Heat Transfer and Critical heat flux phenomenon in an acoustic standing wave." Terrestrial and microgravity pool boiling heat transfer experiments were performed in the presence of a standing acoustic wave from a platinum wire resistance heater using degassed FC-72 Fluorinert liquid. The sound wave was created by driving a half wavelength resonator at a frequency of 10.15 kHz. Microgravity conditions were created using the 2.1 second drop tower on the campus of Washington State University. Burnout of the heater wire, often encountered with heat flux controlled systems, was avoided by using a constant temperature controller to regulate the heater wire temperature. The amplitude of the acoustic standing wave was increased from 28 kPa to over 70 kPa and these pressure measurements were made using a hydrophone fabricated with a small piezoelectric ceramic. Cavitation incurred during experiments at higher acoustic amplitudes contributed to the vapor bubble dynamics and heat transfer. The heater wire was positioned at three different locations within the acoustic field: the acoustic node, antinode, and halfway between these locations. Complete boiling curves are presented to show how the applied acoustic field enhanced boiling heat transfer and increased critical heat flux in microgravity and terrestrial environments. Video images provide information on the interaction between the vapor bubbles and the acoustic field. Part two is titled, "Design and qualification of a microscale heater array for use in boiling heat transfer." This part is summarized herein. Boiling heat transfer is an efficient means of heat transfer because a large amount of heat can be removed from a surface using a relatively small temperature difference between the surface and the bulk liquid. However, the mechanisms that govern boiling heat transfer are not well understood. Measurements of

  18. Odd-Boiled Eggs

    ERIC Educational Resources Information Center

    Kaminsky, Kenneth; Scheman, Naomi

    2010-01-01

    At a Shabbat lunch in Madrid not long ago, the conversation turned to the question of boiling eggs. One of the guests mentioned that a Dutch rabbi he knew had heard that in order to make it more likely that boiled eggs be kosher, you should add an egg to the pot if the number you began with was even. According to the laws of Kashruth, Jews may not…

  19. Mutagen formation in a model beef boiling system. III. Purification and identification of three heterocyclic amine mutagens-carcinogens

    SciTech Connect

    Taylor, R.T.; Fultz, E.; Knize, M.

    1985-01-01

    An extensively boiled supernatant/sub 2/ (S/sub 2/) fraction from beef round steak contains two major Salmonella frameshift mutagens, designated as HPLC peaks A and B. These same mutagens arise, but in different proportions, when S/sub 2/ is boiled with creatine phosphate (CP), and they are produced in much greater quantities from a boiled mixture of S/sub 2/ + L-tryptophan (Trp) + CP + FeSO/sub 4/ (S/sub 2//sup */). A third mutagen, peak C, is also generated in the S/sub 2//sup */ mixture. Mutagen peaks A, B, and C were purified to homogeneity and shown by their absorption spectra, mass fragmentation patterns, and other data to be 2-amino-3-methylimidazo(4,5-f)quinoline (IQ), 3-amino-1-methyl-5H-pyrido(4,3-b)-indole (Trp-P-2), and 3-amino-1,4-dimethyl-5H-pyrido(4,3-b)indole (Trp-P-1), respectively. This is the first demonstration that IQ, Trp-P-2, and Trp-P-1 can form under aqueous conditions at 100/sup 0/C from reactions between low molecular weight precursors that are present in meat juice. Further simplification of and studies with the S/sub 2/ fraction of beef muscle should provide relevant information about the mechanisms of frameshift mutagen formation during the cooking of meats and fish.

  20. Enhanced Boiling on Micro-Configured Composite Surfaces Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Zhang, Nengli; Chai, An-Ti

    1999-01-01

    In order to accommodate the growing thermal management needs of future space platforms, several two-phase active thermal control systems (ATCSs) have evolved and were included in the designs of space stations. Compared to the pumped single-phase liquid loops used in the conventional Space Transportation System and Spacelab, ATCSs offer significant benefits that may be realized by adopting a two-phase fluid-loop system. Alternately, dynamic power systems (DPSs), based on the Rankine cycle, seem inevitably to be required to supply the electrical power requirements of expanding space activities. Boiling heat transfer is one of the key technologies for both ATCSs and DPSs. Nucleate boiling near critical heat flux (CHF) can transport very large thermal loads with much smaller device size and much lower pumping power. However, boiling performance deteriorates in a reduced gravity environment and operation in the CHF regime is precarious because any slight overload will cause the heat transfer to suddenly move to the film boiling regime, which in turn, will result in burnout of the heat transfer surfaces. New materials, such as micro-configured metal-graphite composites, can provide a solution for boiling enhancement. It has been shown experimentally that this type of material manifests outstanding boiling heat transfer performance and their CHF is also extended to higher values. Due to the high thermal conductivity of graphite fiber (up to 1,200 W/m-K in the fiber direction), the composite surfaces are non-isothermal during the boiling process. The composite surfaces are believed to have a much wider safe operating region (a more uniform boiling curve in the CHF regime) because non-isothermal surfaces have been found to be less sensitive to variations of wall superheat in the CHF regime. The thermocapillary forces formed by the temperature difference between the fiber tips and the metal matrix play a more important role than the buoyancy in the bubble detachment, for the

  1. Experimental Investigation on the Effects of Coolant Concentration on Sub-Cooled Boiling and Crud Deposition on Reactor Cladding at Prototypical PWR Operating Conditions

    SciTech Connect

    Schultis, J., Kenneth; Fenton, Donald, L.

    2006-10-20

    Increasing demand for energy necessitates nuclear power units to increase power limits. This implies significant changes in the design of the core of the nuclear power units, therefore providing better performance and safety in operations. A major hindrance to the increase of nuclear reactor performance especially in Pressurized Deionized water Reactors (PWR) is Axial Offset Anomaly (AOA)--the unexpected change in the core axial power distribution during operation from the predicted distribution. This problem is thought to be occur because of precipitation and deposition of lithiated compounds like boric acid (H{sub 2}BO{sub 3}) and lithium metaborate (LiBO{sub 2}) on the fuel rod cladding. Deposited boron absorbs neutrons thereby affecting the total power distribution inside the reactor. AOA is thought to occur when there is sufficient build-up of crud deposits on the cladding during subcooled nucleate boiling. Predicting AOA is difficult as there is very little information regarding the heat and mass transfer during subcooled nucleate boiling. An experimental investigation was conducted to study the heat transfer characteristics during subcooled nucleate boiling at prototypical PWR conditions. Pool boiling tests were conducted with varying concentrations of lithium metaborate (LiBO{sub 2}) and boric acid (H{sub 2}BO{sub 3}) solutions in deionized water. The experimental data collected includes the effect of coolant concentration, subcooling, system pressure and heat flux on pool the boiling heat transfer coefficient. The analysis of particulate deposits formed on the fuel cladding surface during subcooled nucleate boiling was also performed. The results indicate that the pool boiling heat transfer coefficient degrades in the presence of boric acid and lithium metaborate compared to pure deionized water due to lesser nucleation. The pool boiling heat transfer coefficients decreased by about 24% for 5000 ppm concentrated boric acid solution and by 27% for 5000 ppm

  2. Explosive Boiling at Very Low Heat Fluxes: A Microgravity Phenomenon

    NASA Technical Reports Server (NTRS)

    Hasan, M. M.; Lin, C. S.; Knoll, R. H.; Bentz, M. D.

    1993-01-01

    The paper presents experimental observations of explosive boiling from a large (relative to bubble sizes) flat heating surface at very low heat fluxes in microgravity. The explosive boiling is characterized as either a rapid growth of vapor mass over the entire heating surface due to the flashing of superheated liquid or a violent boiling spread following the appearance of single bubbles on the heating surface. Pool boiling data with saturated Freon 113 was obtained in the microgravity environment of the space shuttle. The unique features of the experimental results are the sustainability of high liquid superheat for long periods and the occurrence of explosive boiling at low heat fluxes (0.2 to 1.2 kW/sq m). For a heat flux of 1.0 kW/sq m a wall superheat of 17.9 degrees C was attained in ten minutes of heating. This was followed by an explosive boiling accompanied with a pressure spike and a violent bulk liquid motion. However, at this heat flux the vapor blanketing the heating surface could not be sustained. Stable nucleate boiling continued following the explosive boiling.

  3. NaK pool-boiler bench-scale receiver durability test: Test results and materials analysis

    SciTech Connect

    Andraka, C.E.; Goods, S.H.; Bradshaw, R.W.; Moreno, J.B.; Moss, T.A.; Jones, S.A.

    1994-06-01

    Pool-boiler reflux receivers have been considered as an alternative to heat pipes for the input of concentrated solar energy to Stirling-cycle engines in dish-Stirling electric generation systems. Pool boilers offer simplicity in design and fabrication. The operation of a full-scale pool-boiler receiver has been demonstrated for short periods of time. However, to generate cost-effective electricity, the receiver must operate Without significant maintenance for the entire system life, as much as 20 to 30 years. Long-term liquid-metal boiling stability and materials compatibility with refluxing NaK-78 is not known and must be determined for the pool boiler receiver. No boiling system has been demonstrated for a significant duration with the current porous boiling enhancement surface and materials. Therefore, it is necessary to simulate the full-scale pool boiler design as much as possible, including flux levels, materials, and operating cycles. On-sun testing is impractical because of the limited test time available. A test vessel was constructed with a porous boiling enhancement surface. The boiling surface consisted of a brazed stainless steel powder with about 50% porosity. The vessel was heated with a quartz lamp array providing about go W/CM2 peak incident thermal flux. The vessel was charged with NaK-78. This allows the elimination of costly electric preheating, both on this test and on fullscale receivers. The vessel was fabricated from Haynes 230 alloy. The vessel operated at 750{degrees}C around the clock, with a 1/2-hour shutdown cycle to ambient every 8 hours. The test completed 7500 hours of lamp-on operation time, and over 1000 startups from ambient. The test was terminated when a small leak in an Inconel 600 thermowell was detected. The test design and data are presented here. Metallurgical analysis of virgin and tested materials has begun, and initial results are also presented.

  4. Thermosyphon boiling in vertical channels

    NASA Astrophysics Data System (ADS)

    Bar-Cohen, A.; Schweitzer, H.

    The thermal characteristics of ebullient cooling systems for VHSIC and VLSI microelectronic component thermal control are studied by experimentally and analytically investigating boiling heat transfer from a pair of flat, closely spaced, isoflux plates immersed in saturated water. A theoretical model for liquid flow rate through the channel is developed and used as a basis for correlating the rate of heat transfer from the channel walls. Experimental results for wall temperature as a function of axial location, heat flux, and plate spacing are presented. The finding that the wall superheat at constant imposed heat flux decreases as the channel is narrowed is explained with the aid of a boiling thermosiphon analysis which yields the mass flux through the channel.

  5. Fundamental Boiling and RP-1 Freezing Experiments

    NASA Technical Reports Server (NTRS)

    Goode, Brian

    2002-01-01

    The prestart thermal conditioning of the hardware in LOX (liquid oxygen) systems involve heat transfer between LOX and metal where boiling plays a large role. Information is easily found on nucleate boiling, maximum heat flux, minimum heat flux and film boiling for common fluids like water. After looking at these standard correlations it was felt more data was needed for the cool down side transition boiling for the LN2 and LOX. In particular interest is the film boiling values, the temperature at which transition begins and the slope as peak heat flux is approached. The ultimate goal is an array of boiling heat transfer coefficient as a function of surface temperature which can be used in the chilldown model of the feed system, engine and bleed system for X-34. The first experiment consisted of an actual MC-1 LOX Impeller which had been machined backwards, that was instrumented with 17 surface thermocouples and submerged in liquid nitrogen. The thermocouples were installed on metal thicknesses varying from the thin inducer to the thick hub.

  6. Cryptococcal meningitis in systemic lupus erythematosus patients: pooled analysis and systematic review.

    PubMed

    Fang, Wenjie; Chen, Min; Liu, Jia; Hagen, Ferry; Ms, Abdullah; Al-Hatmi; Zhang, Peilian; Guo, Yun; Boekhout, Teun; Deng, Danqi; Xu, Jianping; Pan, Weihua; Liao, Wanqing

    2016-01-01

    Cryptococcal meningitis is an important fungal infection among systemic lupus erythematosus patients. We conducted a pooled analysis and systematic review to describe the epidemiological and clinical profile of cryptococcal meningitis in systemic lupus erythematosus patients. From two hospitals in China and nine literature databases, cases and prevalence data were collected for pooled analysis and meta-analysis, respectively. Categorical variables of cases were compared using a χ(2)-test on the statistical program of SAS. A multiple regression analysis was performed to ascertain independent predictors significantly correlated with prognosis. Meta-analysis was conducted by the statistical program of R. The prevalence of cryptococcal meningitis in systemic lupus erythematosus patients was 0.5%. Patients were predominantly females and adults. A prednisone equivalent of more than 30 mg/day before infection was associated with higher mortality (odds ratio (OR)=9.69 (1.54, 60.73)). In all, 36.8-38.9% patients showed low lupus activity when they developed the crytococcal infection. Moreover, 38.2% of the patients were misdiagnosed. The estimated case-fatality rate was 23.6%. Our results suggest that more emphasis should be placed to further understand lupus-related cryptococcal meningitis and to develop better prophylaxis and management strategies to combat this condition. PMID:27599471

  7. The Relationship Between the Color Characteristics of the RGB Colorimetric System and the Physicochemical Properties of Petroleums and high Boiling Hydrocarbon Distillates

    NASA Astrophysics Data System (ADS)

    Dolomatov, M. Yu.; Yarmuhametova, G. U.

    2016-09-01

    An interrelation was established between physicochemical properties of oils and high boiling hydrocarbon distillates and their solutions' color characteristics defi ned in the RGB colorimetric system using a standard radiation source CIE D65. It was shown that by using color characteristics of solutions of the specifi ed objects, it was possible to determine their relative density, molecular mass, activation energy of viscous fl ow, and the coking value. Research results were confi rmed by statistical data processing using the methods of multivariate regression and correlation analysis.

  8. Pool impacts of Leidenfrost drop

    NASA Astrophysics Data System (ADS)

    Darbois Texier, Baptiste; Maquet, Laurent; Dorbolo, Stephane; Dehandschoewercker, Eline; Pan, Zhao; Truscott, Tadd

    2015-11-01

    This work concerns the impact of a droplet made of a volatile liquid (typically HFE) on a pool of an other liquid (typically silicone oil) which temperature is above the boiling point of the drop. Depending on the properties of the two liquids and the impacting conditions, four different regimes are observed. For low impacting speeds, the droplet bounces on the surface of the bath and finally levitates above it in a Leidenfrost state. Such a regime occurs as soon as the pool temperature exceeds the boiling point of the drop. This observation means that there is no threshold in temperature for a Leidenfrost effect on a liquid surface contrary to the case of a solid substrate. For intermediate impacting velocities, the pinch-off of the surface of the pool entraps the drop in the liquid bulk. The entrapped drop is separated from the pool by a layer of its own vapour in a similar way of antibulles. For increasing impacting speeds, the vapour layer between the drop and the pool does not hold during the pinch-off event. The contact of the drop with the hot liquid provokes a sudden and intense evaporation. At very large impacting speeds, the drop rapidely contacts the pool, spreads and finally induces a hemi-spherical cavity. In the end, these four different regimes are summarized in a Froud-Weber diagram which boundaries are discussed.

  9. Enhanced boiling heat transfer in horizontal test bundles

    SciTech Connect

    Trewin, R.R.; Jensen, M.K.; Bergles, A.E.

    1994-08-01

    Two-phase flow boiling from bundles of horizontal tubes with smooth and enhanced surfaces has been investigated. Experiments were conducted in pure refrigerant R-113, pure R-11, and mixtures of R-11 and R-113 of approximately 25, 50, and 75% of R-113 by mass. Tests were conducted in two staggered tube bundles consisting of fifteen rows and five columns laid out in equilateral triangular arrays with pitch-to-diameter ratios of 1.17 and 1.5. The enhanced surfaces tested included a knurled surface (Wolverine`s Turbo-B) and a porous surface (Linde`s High Flux). Pool boiling tests were conducted for each surface so that reference values of the heat transfer coefficient could be obtained. Boiling heat transfer experiments in the tube bundles were conducted at pressures of 2 and 6 bar, heat flux values from 5 to 80 kW/m{sup 2}s, and qualities from 0% to 80%, Values of the heat transfer coefficients for the enhanced surfaces were significantly larger than for the smooth tubes and were comparable to the values obtained in pool boiling. It was found that the performance of the enhanced tubes could be predicted using the pool boiling results. The degradation in the smooth tube heat transfer coefficients obtained in fluid mixtures was found to depend on the difference between the molar concentration in the liquid and vapor.

  10. Radiolysis of boiling water

    NASA Astrophysics Data System (ADS)

    Yang, Shuang; Katsumura, Yosuke; Yamashita, Shinichi; Matsuura, Chihiro; Hiroishi, Daisuke; Lertnaisat, Phantira; Taguchi, Mitsumasa

    2016-06-01

    γ-radiolysis of boiling water has been investigated. The G-value of H2 evolution was found to be very sensitive to the purity of water. In high-purity water, both H2 and O2 gases were formed in the stoichiometric ratio of 2:1; a negligible amount of H2O2 remained in the liquid phase. The G-values of H2 and O2 gas evolution depend on the dose rate: lower dose rates produce larger yields. To clarify the importance of the interface between liquid and gas phase for gas evolution, the gas evolution under Ar gas bubbling was measured. A large amount of H2 was detected, similar to the radiolysis of boiling water. The evolution of gas was enhanced in a 0.5 M NaCl aqueous solution. Deterministic chemical kinetics simulation elucidated the mechanism of radiolysis in boiling water.

  11. A DNA pooling based system to detect Escherichia coli virulence factors in fecal and wastewater samples

    PubMed Central

    Luz María Chacón, J; Lizeth Taylor, C; Carmen Valiente, A; Irene Alvarado, P; Ximena Cortés, B

    2012-01-01

    The availability of a useful tool for simple and timely detection of the most important virulent varieties of Escherichia coli is indispensable. To this end, bacterial DNA pools which had previously been categorized were obtained from isolated colonies as well as selected in terms of utilized phenotype; the pools were assessed by two PCR Multiplex for the detection of virulent E. coli eaeA, bfpA, stx1, stx2, ipaH, ST, LT, and aatA genes, with the 16S gene used as DNA control. The system was validated with 66 fecal samples and 44 wastewater samples. At least one positive isolate was detected by a virulent gene among the 20 that were screened. The analysis of fecal samples from children younger than 6 years of age detected frequencies of 25% LT positive strains, 8.3% eae, 8.3% bfpA, 16.7% ipaH, as well as 12.5 % aatA and ST. On the other hand, wastewater samples revealed frequencies of 25.7% eaeA positive, 30.3% stx1, 15.1% LT and 19.7% aatA. This study is an initial step toward carrying out epidemiological field research that will reveal the presence of these bacterial varieties. PMID:24031959

  12. Energy Storage for Power Systems Applications: A Regional Assessment for the Northwest Power Pool (NWPP)

    SciTech Connect

    Kintner-Meyer, Michael CW; Balducci, Patrick J.; Jin, Chunlian; Nguyen, Tony B.; Elizondo, Marcelo A.; Viswanathan, Vilayanur V.; Guo, Xinxin; Tuffner, Francis K.

    2010-04-01

    Wind production, which has expanded rapidly in recent years, could be an important element in the future efficient management of the electric power system; however, wind energy generation is uncontrollable and intermittent in nature. Thus, while wind power represents a significant opportunity to the Bonneville Power Administration (BPA), integrating high levels of wind resources into the power system will bring great challenges to generation scheduling and in the provision of ancillary services. This report addresses several key questions in the broader discussion on the integration of renewable energy resources in the Pacific Northwest power grid. More specifically, it addresses the following questions: a) how much total reserve or balancing requirements are necessary to accommodate the simulated expansion of intermittent renewable energy resources during the 2019 time horizon, and b) what are the most cost effective technological solutions for meeting load balancing requirements in the Northwest Power Pool (NWPP).

  13. Modelling Napl Dissolution from Lens and Pools Under Varying Flowfields in Heterogeneous Subsurface Systems

    NASA Astrophysics Data System (ADS)

    Prakash, P.; Nambi, I. M.

    2011-12-01

    Non- Aqueous Phase Liquids (NAPLs) such as chlorinated organic solvents are major sources of groundwater contamination throughout the world. The non-uniform distribution of these contaminants as NAPL pools and residual NAPL zones introduce additional spatial heterogeneity in the hydrological parameters such as porosity and permeability. Bench scale dissolution studies were carried out and a conceptual contaminant transport model was developed to predict the downstream NAPL concentrations in aqueous phase. The dissolution studies were carried out in a bench scale 2-D sand tank reactor for multiple NAPL configurations and various initial NAPL saturations. A complex heterogeneous subsurface system mimicking NAPL as residuals, NAPL as lens and NAPL as pools was created by embedding more than one NAPL contaminated zone of coarse sand within a clean NAPL free zone of fine sand. Dissolved NAPL concentrations were measured along the downstream of NAPL source zone. A 2-D conceptual contaminant transport model was developed and validated which successfully accounts for NAPL interphase mass transfer limitation under varying flow fields in a saturated heterogeneous subsurface systems. The analysis of multiple lens experimental data revealed that initial NAPL saturations and relative permeability have significant effect in altering mass transfer characteristics which affects the efficacy of any remedial effort to decontaminate groundwater. Non equilibrium concentrations of NAPL were observed near the source zone during dissolution from high initial NAPL saturations, whereas tailing concentrations with steep decline from equilibrium state were seen at later times. The rate limited conditions occurred much earlier under heterogeneous soil conditions when compared to those observed by researchers under homogeneous soil conditions. This behavior was attributed to the large changes in aqueous permeability fields occurring with the progress of dissolution process. Mathematical

  14. Legionella species colonization of water distribution systems, pools and air conditioning systems in cruise ships and ferries

    PubMed Central

    Goutziana, Georgia; Mouchtouri, Varvara A; Karanika, Maria; Kavagias, Antonios; Stathakis, Nikolaos E; Gourgoulianis, Kostantinos; Kremastinou, Jenny; Hadjichristodoulou, Christos

    2008-01-01

    Background Legionnaires' disease continues to be a public health concern in passenger ships. This study was scheduled in order to investigate Legionella spp. colonization of water distribution systems (WDS), recreational pools, and air-conditioning systems on board ferries and cruise ships in an attempt to identify risk factors for Legionella spp. colonization associated with ship water systems and water characteristics. Methods Water systems of 21 ferries and 10 cruise ships including WDS, air conditioning systems and pools were investigated for the presence of Legionella spp. Results The 133 samples collected from the 10 cruise ships WDS, air conditioning systems and pools were negative for Legionella spp. Of the 21 ferries WDS examined, 14 (66.7%) were legionellae-positive. A total of 276 samples were collected from WDS and air conditioning systems. Legionella spp. was isolated from 37.8% of the hot water samples and 17.5% of the cold water samples. Of the total 96 positive isolates, 87 (90.6%) were L. pneumophila. Legionella spp. colonization was positively associated with ship age. The temperature of the hot water samples was negatively associated with colonization of L. pneumophila serogroup (sg) 1 and that of L. pneumophila sg 2 to 14. Increases in pH ≥7.8 and total plate count ≥400 CFU/L, correlated positively with the counts of L. pneumophila sg 2 to 14 and Legionella spp. respectively. Free chlorine of ≥0.2 mg/L inhibited colonization of Legionella spp. Conclusion WDS of ferries can be heavily colonized by Legionella spp. and may present a risk of Legionnaires' disease for passengers and crew members. Guidelines and advising of Legionnaires' disease prevention regarding ferries are needed, in particular for operators and crew members. PMID:19025638

  15. Sodium reflux pool-boiler solar receiver on-sun test results

    NASA Astrophysics Data System (ADS)

    Andraka, C. E.; Moreno, J. B.; Diver, R. B.; Moss, T. A.

    1992-06-01

    The efficient operation of a Stirling engine requires the application of a high heat flux to the relatively small area occupied by the heater head tubes. Previous attempts to couple solar energy to Stirling engines generally involved directly illuminating the heater head tubes with concentrated sunlight. In this study, operation of a 75-kW(sub t) sodium reflux pool-boiler solar receiver has been demonstrated and its performance characterized on Sandia's nominal 75-kW(sub t) parabolic-dish concentrator, using a cold-water gas-gap calorimeter to simulate Stirling engine operation. The pool boiler (and more generally liquid-metal reflux receivers) supplies heat to the engine in the form of latent heat released from condensation of the metal vapor on the heater head tubes. The advantages of the pool boiler include uniform tube temperature, leading to longer life and higher temperature available to the engine, and decoupling of the design of the solar absorber from the engine heater head. The two-phase system allows high input thermal flux, reducing the receiver size and losses, therefore improving system efficiency. The receiver thermal efficiency was about 90 percent when operated at full power and 800 C. Stable sodium boiling was promoted by the addition of 35 equally spaced artificial cavities in the wetted absorber surface. High incipient boiling superheats following cloud transients were suppressed passively by the addition of small amounts of xenon gas to the receiver volume. Stable boiling without excessive incipient boiling superheats was observed under all operating conditions. The receiver developed a leak during performance evaluation, terminating the testing after accumulating about 50 hours on sun. The receiver design is reported here along with test results including transient operations, steady-state performance evaluation, operation at various temperatures, infrared thermography, x-ray studies of the boiling behavior, and a postmortem analysis.

  16. Sodium reflux pool-boiler solar receiver on-sun test results

    SciTech Connect

    Andraka, C E; Moreno, J B; Diver, R B; Moss, T A

    1992-06-01

    The efficient operation of a Stirling engine requires the application of a high heat flux to the relatively small area occupied by the heater head tubes. Previous attempts to couple solar energy to Stirling engines generally involved directly illuminating the heater head tubes with concentrated sunlight. In this study, operation of a 75-kW{sub t} sodium reflux pool-boiler solar receiver has been demonstrated and its performance characterized on Sandia's nominal 75-kW{sub t} parabolic-dish concentrator, using a cold-water gas-gap calorimeter to simulate Stirling engine operation. The pool boiler (and more generally liquid-metal reflux receivers) supplies heat to the engine in the form of latent heat released from condensation of the metal vapor on the heater head tubes. The advantages of the pool boiler include uniform tube temperature, leading to longer life and higher temperature available to the engine, and decoupling of the design of the solar absorber from the engine heater head. The two-phase system allows high input thermal flux, reducing the receiver size and losses, therefore improving system efficiency. The receiver thermal efficiency was about 90% when operated at full power and 800{degree}C. Stable sodium boiling was promoted by the addition of 35 equally spaced artificial cavities in the wetted absorber surface. High incipient boiling superheats following cloud transients were suppressed passively by the addition of small amounts of xenon gas to the receiver volume. Stable boiling without excessive incipient boiling superheats was observed under all operating conditions. The receiver developed a leak during performance evaluation, terminating the testing after accumulating about 50 hours on sun. The receiver design is reported here along with test results including transient operations, steady-state performance evaluation, operation at various temperatures, infrared thermography, x-ray studies of the boiling behavior, and a postmortem analysis.

  17. Boiling effect in liquid nitrogen directly cooled Yb³⁺:YAG laser.

    PubMed

    Sakurai, Toshimitsu; Chosrowjan, Haik; Furuse, Hiroaki; Taniguchi, Seiji; Kitamura, Toshiyuki; Fujita, Masayuki; Ishii, Shinya; Izawa, Yasukazu

    2016-02-20

    Liquid nitrogen (LN2) behavior on the surface of excited Yb(3+):YAG is investigated using fluorometry. From the time-resolved temperature variations and integrated fluorescence spectra intensity on this directly cooled Yb(3+):YAG surface, we observe a phase transition of LN2 from nucleate boiling to film boiling. As a result of this pool boiling, good beam quality should occur when the temperature and heat flux at an excited surface of Yb(3+):YAG are below 95 K and 15.8  W/cm2, respectively. That is, the LN2 should remain in a steady state of nucleate boiling to produce good beam quality using pool boiling.

  18. Liquid metal boiling inception

    NASA Technical Reports Server (NTRS)

    Sabin, C. M.; Poppendiek, H. F.; Mouritzen, G.; Meckel, P. T.; Cloakey, J. E.

    1972-01-01

    An experimental study of the inception of boiling in potassium in forced convection is reported. The boiler consisted of a 0.19-inch inside diameter, niobium-1% zirconium boiler tube approximately six feet long. Heating was accomplished by direct electrical tube wall conduction. Experiments were performed with both all-liquid fill and two-phase fill startup sequences and with a range of flow rates, saturation temperatures, inert gas levels, and fill liquid temperatures. Superheat of the liquid above the equilibrium saturation temperature was observed in all the experiments. Incipient boiling liquid superheat ranged from a few degrees to several hundred. Comparisons of these data with other data and with several analytical treatments are presented.

  19. System for reducing heat losses from indoor swimming pools by use of automatic covers. Report No. 1

    SciTech Connect

    Not Available

    1994-04-25

    This is a progress report for the period October 1, 1993 through March 31, 1994, for a project to develop cover systems for indoor swimming pools with the objective of reducing energy consumption. Effort has included evaluation of cover materials, development of brakes to tension deployment ropes, better limit of motion switches, reel systems, drive systems for the take up spool, and drive tensioning systems.

  20. Lifeguard Training: Principles and Administration. A Manual for Developing and Administering Lifeguard Systems for Pools and Beaches. Second Edition, Revised.

    ERIC Educational Resources Information Center

    Howes, Gordon T., Ed.; Hill, Rolland, Ed.

    This manual for developing and administering lifeguard systems for pools and beaches is divided into three sections. Section 1, "Personnel," suggests prerequisites for lifeguard training, personal health, fitness and inservice training, and preventive lifeguarding. Section 2, "Operations," discusses the following: a) water conditions of surf…

  1. Enhanced Boiling on Micro-Configured Composite Surfaces Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Two experimental setups: High Heat Flux Pool Boiling Setup and Optical system of Measuring Contact Angle and Spreading Parameters were established and a series of experiments was conducted. The experimental work on the nucleate boiling performance of both Freon-113 and water on the composite surfaces has been finished and the results show that the composite surface with 25% volume fraction of graphite fibers in the copper matrix has the best enhancing performance. Stronger enhancement was obtained for water compared to Freon-113. The wall superheat initiating boiling was reduced 40% and 35% and the heat flux of the nucleate boiling was augmented up to ten times and 6.7 times, respectively. A bubble departure model has been presented to explain the enhancement mechanism of the boiling heat transfer on the composite surfaces. A powerful optical method to measure contact angle and spreading parameters of liquids on solid surfaces, including both transparent and non-transparent substrates, has been developed and successfully used in the measurements for various liquid-solid systems. The experimental work on identification of profiles near three-phase line by laser shadowgraphy method has been finished and the characteristics of the three-phase line for different liquid-solid systems were unveiled, which is very important to understand the mechanism of boiling under microgravity conditions. The four basic patterns of sessile profile were discovered through caustics and caustic-diffraction analysis by applying wave theory in shadowgraphy technology, which contributes to clearly explain the different characteristics of wetting and spreading of various liquids on a solid surface, and therefore to further understand the bubble departure mechanisms. A new working pattern of heat pipes using working fluids with positive surface-tension gradient against temperature was discovered and analyzed, and then the new heat pipe systems using this kind of working fluids have been

  2. The Underwater Spectrometric System Based on CZT Detector for Survey of the Bottom of MR Reactor Pool - 13461

    SciTech Connect

    Potapov, Victor; Safronov, Alexey; Ivanov, Oleg; Smirnov, Sergey; Stepanov, Vyacheslav

    2013-07-01

    The underwater spectrometer system for detection of irradiated nuclear fuel on the pool bottom of the reactor was elaborated. During the development process metrological studies of CdZnTe (CZT) detectors were conducted. These detectors are designed for spectrometric measurements in high radiation fields. A mathematical model based on the Monte Carlo method was created to evaluate the capability of such a system. A few experimental models were realized and the characteristics of the spectrometric system are represented. (authors)

  3. Boiling on Microconfigured Composite Surfaces Enhanced

    NASA Technical Reports Server (NTRS)

    Chao, David F.

    2000-01-01

    Boiling heat transfer is one of the key technologies for the two-phase active thermal-control system used on space platforms, as well as for the dynamic power systems aboard the International Space Station. Because it is an effective heat transfer mode, boiling is integral to many space applications, such as heat exchangers and other cooling devices. Nucleate boiling near the critical heat flux (CHF) can transport very large thermal loads with a much smaller device and much lower pumping power than for single-phase heat exchangers. However, boiling performance sharply deteriorates in a reduced-gravity environment, and operation in the CHF regime is somewhat perilous because of the risk of burnout to the device surface. New materials called microconfigured metal-graphite composites can enhance boiling. The photomicrograph shows the microconfiguration (x3000) of the copper-graphite (Cu-Gr) surface as viewed by scanning electronic microscope. The graphite fiber tips appear as plateaus with rugged surfaces embedded in the copper matrix. It has been experimentally demonstrated that this type of material manifests excellent boiling heat transfer performance characteristics and an increased CHF. Nonisothermal surfaces were less sensitive to variations of wall superheat in the CHF regime. Because of the great difference in conductivity between the copper base and the graphite fiber, the composite surfaces have a nonisothermal surface characteristic and, therefore, will have a much larger "safe" operating region in the CHF regime. In addition, the thermocapillary forces induced by the temperature differences between the fiber tips and the metal matrix play an important role in bubble detachment, and may not be adversely affected in a reduced-gravity environment. All these factors indicate that microconfigured composites may improve the reliability and economy (dominant factors in all space applications) of various thermal components found on spacecraft during future

  4. Natural convection in a uniformly heated pool

    SciTech Connect

    Tzanos, C.P.

    1996-05-01

    In the event of a core meltdown accident, to prevent reactor vessel failure from molten corium relocation to the reactor vessel lower head, the establishment of a coolable configuration has been proposed by flooding with water the reactor cavity. In Reference 3, it was shown that for the heavy-water new production reactor (NPW-HWR) design, this strategy, e.g., the rejection of decay heat to a containment decay heat removal system by boiling of water in the reactor cavity, could keep the reactor vessel temperature below failure limits. The analysis of Ref. 3 was performed with the computer code COMMIX-1AR/P, and showed that natural convection in the molten-corium pool was the dominant mechanism of heat transfer from the pool to the wall of the reactor vessel lower head. To determine whether COMMIX adequately predicts natural convection in a pool heated by a uniform heat source, in Ref. 4, the experiments of free convection in a semicircular cavity of Jahn and Reineke were analyzed with COMMIX. It was found that the Nusselt (Nu) number predicted by COMMIX was within the spread of the experimental measurements. In the COMMIX analysis of Ref. 4, the semicircular cavity was treated as symmetric. The objective of the work presented in this paper was to extend the COMMIX validation analysis of Ref. 4 by removing the assumption of symmetry and expanding the analysis up to the highest Rayleigh (Ra) number that leads to a steady state. In conclusion, this work shows that the numerical predictions of natural convection in an internally heated pool bounded by a curved bottom are in reasonably good agreement with experimental measurements.

  5. Boiling heat transfer enhancement in subsurface horizontal and vertical tunnels

    SciTech Connect

    Pastuszko, Robert

    2008-09-15

    Complex experimental investigations of boiling heat transfer on structured surfaces covered with perforated foil were taken up. Experimental data were discussed for two kinds of enhanced surfaces formed by joined horizontal and vertical tunnels: tunnel structures (TS) and narrow tunnel structures (NTS). The experiments were carried out with water, ethanol and R-123 at atmospheric pressure. The TS and NTS surfaces were manufactured out of perforated copper foil of 0.05 mm thickness (hole diameters: 0.3, 0.4, 0.5 mm) sintered with the mini-fins, formed on the vertical side of the 5 mm high rectangular fins and horizontal inter-fin surface. The effects of hole (pore) diameters, tunnel pitch for TS and tunnel width for NTS on nucleate pool boiling were examined. Substantial enhancement of heat transfer coefficient was observed. The investigated surfaces showed boiling heat transfer coefficients similar to those of existing structures with subsurface tunnels, but at higher heat fluxes range. (author)

  6. 46 CFR 154.705 - Cargo boil-off as fuel: General.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Pressure and Temperature Control § 154.705 Cargo boil-off as fuel: General. (a) Each cargo boil-off fuel system under § 154.703(c) must meet §§ 154.706 through 154.709. (b) The piping in the cargo boil-off fuel... 46 Shipping 5 2012-10-01 2012-10-01 false Cargo boil-off as fuel: General. 154.705 Section...

  7. 46 CFR 154.705 - Cargo boil-off as fuel: General.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Pressure and Temperature Control § 154.705 Cargo boil-off as fuel: General. (a) Each cargo boil-off fuel system under § 154.703(c) must meet §§ 154.706 through 154.709. (b) The piping in the cargo boil-off fuel... 46 Shipping 5 2014-10-01 2014-10-01 false Cargo boil-off as fuel: General. 154.705 Section...

  8. 46 CFR 154.705 - Cargo boil-off as fuel: General.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Pressure and Temperature Control § 154.705 Cargo boil-off as fuel: General. (a) Each cargo boil-off fuel system under § 154.703(c) must meet §§ 154.706 through 154.709. (b) The piping in the cargo boil-off fuel... 46 Shipping 5 2013-10-01 2013-10-01 false Cargo boil-off as fuel: General. 154.705 Section...

  9. Acoustic emission feedback control for control of boiling in a microwave oven

    DOEpatents

    White, Terry L.

    1991-01-01

    An acoustic emission based feedback system for controlling the boiling level of a liquid medium in a microwave oven is provided. The acoustic emissions from the medium correlated with surface boiling is used to generate a feedback control signal proportional to the level of boiling of the medium. This signal is applied to a power controller to automatically and continuoulsly vary the power applied to the oven to control the boiling at a selected level.

  10. Interactions Between the Nighttime Valley-Wind System and a Developing Cold-Air Pool

    NASA Astrophysics Data System (ADS)

    Arduini, Gabriele; Staquet, Chantal; Chemel, Charles

    2016-10-01

    The Weather Research and Forecast numerical model is used to characterize the influence of a thermally-driven down-valley flow on a developing cold-air pool in an idealized alpine valley decoupled from the atmosphere above. Results for a three-dimensional (3D) valley, which allows for the formation of a down-valley flow, and for a two-dimensional (2D) valley, where the formation of a down-valley flow is inhibited, are analyzed and compared. A key result is that advection leads to a net cooling in the 2D valley and to a warming in the 3D valley, once the down-valley flow is fully developed. This difference stems from the suppression of the slope-flow induced upward motions over the valley centre in the 3D valley. As a result, the downslope flows develop a cross-valley circulation within the cold-air pool, the growth of the cold-air pool is reduced and the valley atmosphere is generally warmer than in the 2D valley. A quasi-steady state is reached for which the divergence of the down-valley flow along the valley is balanced by the convergence of the downslope flows at the top of the cold-air pool, with no net contribution of subsiding motions far from the slope layer. More precisely, the inflow of air at the top of the cold-air pool is found to be driven by an interplay between the return flow from the plain region and subsidence over the plateaux. Finally, the mechanisms that control the structure of the cold-air pool and its evolution are found to be independent of the valley length as soon as the quasi-steady state is reached and the down-valley flow is fully developed.

  11. Optimization of UA of heat exchangers and BOG compressor exit pressure of LNG boil-off gas reliquefaction system using exergy analysis

    NASA Astrophysics Data System (ADS)

    Kochunni, Sarun Kumar; Ghosh, Parthasarathi; Chowdhury, Kanchan

    2015-12-01

    Boil-off gas (BOG) generation and its handling are important issues in Liquefied natural gas (LNG) value chain because of economic, environment and safety reasons. Several variants of reliquefaction systems of BOG have been proposed by researchers. Thermodynamic analyses help to configure them and size their components for improving performance. In this paper, exergy analysis of reliquefaction system based on nitrogen-driven reverse Brayton cycle is carried out through simulation using Aspen Hysys 8.6®, a process simulator and the effects of heat exchanger size with and without related pressure drop and BOG compressor exit pressure are evaluated. Nondimensionalization of parameters with respect to the BOG load allows one to scale up or down the design. The process heat exchanger (PHX) requires much higher surface area than that of BOG condenser and it helps to reduce the quantity of methane vented out to atmosphere. As pressure drop destroys exergy, optimum UA of PHX decreases for highest system performance if pressure drop is taken into account. Again, for fixed sizes of heat exchangers, as there is a range of discharge pressures of BOG compressor at which the loss of methane in vent minimizes, the designer should consider choosing the pressure at lower value.

  12. Initial fuel temperature effects on burning rate of pool fire.

    PubMed

    Chen, Bing; Lu, Shou-Xiang; Li, Chang-Hai; Kang, Quan-Sheng; Lecoustre, Vivien

    2011-04-15

    The influence of the initial fuel temperature on the burning behavior of n-heptane pool fire was experimentally studied at the State Key Laboratory of Fire Science (SKLFS) large test hall. Circular pool fires with diameters of 100mm, 141 mm, and 200 mm were considered with initial fuel temperatures ranging from 290 K to 363 K. Burning rate and temperature distributions in fuel and vessel wall were recorded during the combustion. The burning rate exhibited five typical stages: initial development, steady burning, transition, bulk boiling burning, and decay. The burning rate during the steady burning stage was observed to be relatively independent of the initial fuel temperature. In contrast, the burning rate of the bulk boiling burning stage increases with increased initial fuel temperature. It was also observed that increased initial fuel temperature decreases the duration of steady burning stage. When the initial temperature approaches the boiling point, the steady burning stage nearly disappears and the burning rate moves directly from the initial development stage to the transition stage. The fuel surface temperature increases to its boiling point at the steady burning stage, shortly after ignition, and the bulk liquid reaches boiling temperature at the bulk boiling burning stage. No distinguished cold zone is formed in the fuel bed. However, boiling zone is observed and the thickness increases to its maximum value when the bulk boiling phenomena occurs.

  13. Electrically Driven Liquid Film Boiling Experiment

    NASA Technical Reports Server (NTRS)

    Didion, Jeffrey R.

    2016-01-01

    This presentation presents the science background and ground based results that form the basis of the Electrically Driven Liquid Film Boiling Experiment. This is an ISS experiment that is manifested for 2021. Objective: Characterize the effects of gravity on the interaction of electric and flow fields in the presence of phase change specifically pertaining to: a) The effects of microgravity on the electrically generated two-phase flow. b) The effects of microgravity on electrically driven liquid film boiling (includes extreme heat fluxes). Electro-wetting of the boiling section will repel the bubbles away from the heated surface in microgravity environment. Relevance/Impact: Provides phenomenological foundation for the development of electric field based two-phase thermal management systems leveraging EHD, permitting optimization of heat transfer surface area to volume ratios as well as achievement of high heat transfer coefficients thus resulting in system mass and volume savings. EHD replaces buoyancy or flow driven bubble removal from heated surface. Development Approach: Conduct preliminary experiments in low gravity and ground-based facilities to refine technique and obtain preliminary data for model development. ISS environment required to characterize electro-wetting effect on nucleate boiling and CHF in the absence of gravity. Will operate in the FIR - designed for autonomous operation.

  14. Loss of spent fuel pool cooling PRA: Model and results

    SciTech Connect

    Siu, N.; Khericha, S.; Conroy, S.; Beck, S.; Blackman, H.

    1996-09-01

    This letter report documents models for quantifying the likelihood of loss of spent fuel pool cooling; models for identifying post-boiling scenarios that lead to core damage; qualitative and quantitative results generated for a selected plant that account for plant design and operational practices; a comparison of these results and those generated from earlier studies; and a review of available data on spent fuel pool accidents. The results of this study show that for a representative two-unit boiling water reactor, the annual probability of spent fuel pool boiling is 5 {times} 10{sup {minus}5} and the annual probability of flooding associated with loss of spent fuel pool cooling scenarios is 1 {times} 10{sup {minus}3}. Qualitative arguments are provided to show that the likelihood of core damage due to spent fuel pool boiling accidents is low for most US commercial nuclear power plants. It is also shown that, depending on the design characteristics of a given plant, the likelihood of either: (a) core damage due to spent fuel pool-associated flooding, or (b) spent fuel damage due to pool dryout, may not be negligible.

  15. Fragment structure from vapor explosions during the impact of molten metal droplets into a liquid pool

    NASA Astrophysics Data System (ADS)

    Kouraytem, Nadia; Li, Er Qiang; Vakarelski, Ivan Uriev; Thoroddsen, Sigurdur

    2015-11-01

    High-speed video imaging is used in order to look at the impact of a molten metal drop falling into a liquid pool. The interaction regimes are three: film boiling, nucleate boiling or vapor explosion. Following the vapor explosion, the metal fragments and different textures are observed. It was seen that, using a tin alloy, a porous structure results whereas using a distinctive eutectic metal, Field's metal, micro beads are formed. Different parameters such as the metal type, molten metal temperature, pool surface tension and pool boiling temperature have been altered in order to assess the role they play on the explosion dynamics and the molten metal's by product.

  16. Geographic Information Systems-Transportation ISTEA management systems server-net prototype pooled fund study: Phase B summary

    SciTech Connect

    Espinoza, J. Jr.; Dean, C.D.; Armstrong, H.M.

    1997-06-01

    The Geographic Information System-Transportation (GIS-T) ISTEA Management Systems Server Net Prototype Pooled Fund Study represents the first national cooperative effort in the transportation industry to address the management and monitoring systems as well as the statewide and metropolitan transportation planning requirements of the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA). The Study was initiated in November 1993 through the Alliance for Transportation Research and under the leadership of the New Mexico State Highway and Transportation Department. Sandia National Laboratories, an Alliance partner, and Geographic Paradigm Computing. Inc. provided technical leadership for the project. In 1992, the Alliance for Transportation Research, the New Mexico State Highway and Transportation Department, Sandia National Laboratories, and Geographic Paradigm Computing, Inc., proposed a comprehensive research agenda for GIS-T. That program outlined a national effort to synthesize new transportation policy initiatives (e.g., management systems and Intelligent Transportation Systems) with the GIS-T server net ideas contained in the NCHRP project {open_quotes}Adaptation of GIS to Transportation{close_quotes}. After much consultation with state, federal, and private interests, a project proposal based on this agenda was prepared and resulted in this Study. The general objective of the Study was to develop GIS-T server net prototypes supporting the ISTEA requirements for transportation planning and management and monitoring systems. This objective can be further qualified to: (1) Create integrated information system architectures and design requirements encompassing transportation planning activities and data. (2) Encourage the development of functional GIS-T server net prototypes. (3) Demonstrate multiple information systems implemented in a server net environment.

  17. Stabilization of freon 113 subcooled boiling in forced convection

    SciTech Connect

    Gentile, D.; Benejean, R.; Llory, M.

    1985-09-01

    A simple electronic feedback system allowing to perform tests in subcooled boiling of Freon 113 in the transition region, where systems directly heated by Joule effect are unstable, is presented. A short, electrically heated tube is used where the current is controlled by the measure of the wall temperature. First experiments highlight a hysteresis phenomenon depending on whether the temperature difference between the wall and the boiling liquid is increased or decreased, and the influence of surface conditions on the shape of the boiling curve.

  18. When water does not boil at the boiling point.

    PubMed

    Chang, Hasok

    2007-03-01

    Every schoolchild learns that, under standard pressure, pure water always boils at 100 degrees C. Except that it does not. By the late 18th century, pioneering scientists had already discovered great variations in the boiling temperature of water under fixed pressure. So, why have most of us been taught that the boiling point of water is constant? And, if it is not constant, how can it be used as a 'fixed point' for the calibration of thermometers? History of science has the answers.

  19. Boiling heat transfer enhancement of water on tubes in compact in-line bundles

    NASA Astrophysics Data System (ADS)

    Liu, Zhen-Hua; Qiu, Yu-Hao

    2006-01-01

    In desalinization devices and some heat exchangers making use of low-quality heat energy, both wall temperatures and wall heat fluxes of the heated tubes are generally quite low; hence they cannot cause boiling in flooded tube-bundle evaporators with common large tube spacing. However, when the tube spacing is very small, the incipient boiling in restricted spaces can generate and results in higher heat transfer than that of pool boiling at the same heat flux. This study investigated experimentally the effects of tube spacing, positions of tubes and test pressures on the boiling heat transfer of water in restricted spaces of the compact in-line bundles consisting of smooth horizontal tubes. The experimental results show that tube spacing and tube position have significant effects on the boiling heat transfer in a compact tube bundle. There is an optimum tube spacing that provides the largest heat transfer coefficient at the same heat flux.

  20. Functionally Pooled models for the global identification of stochastic systems under different pseudo-static operating conditions

    NASA Astrophysics Data System (ADS)

    Sakellariou, J. S.; Fassois, S. D.

    2016-05-01

    The problem of identifying a single global model for stochastic dynamical systems operating under different conditions is considered within a novel Functionally Pooled (FP) identification framework. Within it a specific value of a measurable scheduling variable characterizes each operating condition that has pseudo-static effects on the dynamics. The FP framework incorporates parsimonious FP models capable of fully accounting for cross correlations among the operating conditions, functional pooling for the simultaneous treatment of all data records, and statistically optimal estimation. Unlike seemingly related Linear Parameter Varying (LPV) model identification leading to suboptimal accuracy in this context, the postulated FP model estimators are shown to achieve optimal statistical accuracy. An application case study based on a simulated railway vehicle under various mass loading conditions serves to illustrate the high achievable accuracy of FP modelling and the improvements over local models employed within LPV-type identification.

  1. Thermal analysis of five unglazed solar collector systems for the heating of outdoor swimming pools

    SciTech Connect

    Molineaux, B.; Lachal, B.; Guisan, O. )

    1994-07-01

    The performance and behavior of five unglazed solar collector installations, devoted to the heating of five outdoor swimming pools located in Switzerland, is studied on the basis of experimental data collected in 1988. Due to the low temperatures involved, hourly efficiencies often exceed 80%. The mean daily collector efficiency is of the order of 60% in optimal conditions and is in good agreement with the G3 simulation program.

  2. The Physics of Boiling at Burnout

    NASA Technical Reports Server (NTRS)

    Theofanous, T. G.; Tu, J. P.; Dinh, T. N.; Salmassi, T.; Dinh, A. T.; Gasljevic, K.

    2000-01-01

    The basic elements of a new experimental approach for the investigation of burnout in pool boiling are presented. The approach consists of the combined use of ultrathin (nano-scale) heaters and high speed infrared imaging of the heater temperature pattern as a whole, in conjunction with highly detailed control and characterization of heater morphology at the nano and micron scales. It is shown that the burnout phenomenon can be resolved in both space and time. Ultrathin heaters capable of dissipating power levels, at steady-state, of over 1 MW/square m are demonstrated. A separation of scales is identified and it is used to transfer the focus of attention from the complexity of the two-phase mixing layer in the vicinity of the heater to a micron-scaled microlayer and nucleation and associated film-disruption processes within it.

  3. The influence of three-dimensional capillary-porous coatings on heat transfer at liquid boiling

    NASA Astrophysics Data System (ADS)

    Surtaev, A. S.; Pavlenko, A. N.; Kalita, V. I.; Kuznetsov, D. V.; Komlev, D. I.; Radyuk, A. A.; Ivannikov, A. Yu.

    2016-04-01

    The process of heat transfer at pool boiling of liquid (Freon R21) on tubes with three-dimensional plasma-deposited capillary-porous coatings of various thicknesses has been experimentally studied. Comparative analysis of experimental data showed that the heat transfer coefficient for a heater tube with a 500-μm-thick porous coating is more than twice as large as that in liquid boiling on an otherwise similar uncoated tube. At the same time, no intensification of heat exchange in the regime of bubble boiling is observed on a tube with a 100-μm-thick porous coating.

  4. Critical heat flux for free convection boiling in thin rectangular channels

    SciTech Connect

    Cheng, Lap Y.; Tichler, P.R.

    1991-01-01

    A review of the experimental data on free convection boiling critical heat flux (CHF) in vertical rectangular channels reveals three mechanisms of burnout. They are the pool boiling limit, the circulation limit, and the flooding limit associated with a transition in flow regime from churn to annular flow. The dominance of a particular mechanism depends on the dimensions of the channel. Analytical models were developed for each free convection boiling limit. Limited agreement with data is observed. A CHF correlation, which is valid for a wide range of gap sizes, was constructed from the CHFs calculated according to the three mechanisms of burnout. 17 refs., 7 figs.

  5. Cooling of hot bubbles by surface texture during the boiling crisis

    NASA Astrophysics Data System (ADS)

    Dhillon, Navdeep; Buongiorno, Jacopo; Varanasi, Kripa

    2015-11-01

    We report the existence of maxima in critical heat flux (CHF) enhancement for pool boiling on textured hydrophilic surfaces and reveal the interaction mechanism between bubbles and surface texture that governs the boiling crisis phenomenon. Boiling is a process of fundamental importance in many engineering and industrial applications but the maximum heat flux that can be absorbed by the boiling liquid (or CHF) is limited by the boiling crisis. Enhancing the CHF of industrial boilers by surface texturing can lead to substantial energy savings and reduction in greenhouse gas emissions on a global scale. However, the fundamental mechanisms behind this enhancement are not well understood, with some previous studies indicating that CHF should increase monotonically with increasing texture density. However, using pool boiling experiments on a parametrically designed set of plain and nano-textured micropillar surfaces, we show that there is an optimum intermediate texture density that maximizes CHF and further that the length scale of this texture is of fundamental significance. Using imbibition experiments and high-speed optical and infrared imaging, we reveal the fundamental mechanisms governing the CHF enhancement maxima in boiling crisis. We acknowledge funding from the Chevron corporation.

  6. Film boiling of mercury droplets

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Schoessow, G. J.; Chmielewski, C. E.

    1975-01-01

    Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting; therefore, these data can be compared to film boiling theory. Diffusion from the upper surface of the drop appears as a dominant mode of mass transfer from the drop. A closed-form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.

  7. Film boiling of mercury droplets

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Schoessow, G. J.; Chmielewski, C. E.

    1975-01-01

    Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting; therefore, these data can be compared to film boiling theory. For these data, diffusion from the upper surface of the drop is a dominant mode of mass transfer from the drop. A closed-form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.

  8. Development of a water boil-off spent-fuel calorimeter system. [To measure decay heat generation rate

    SciTech Connect

    Creer, J.M.; Shupe, J.W. Jr.

    1981-05-01

    A calorimeter system was developed to measure decay heat generation rates of unmodified spent fuel assemblies from commercial nuclear reactors. The system was designed, fabricated, and successfully tested using the following specifications: capacity of one BWR or PWR spent fuel assembly; decay heat generation range 0.1 to 2.5 kW; measurement time of < 12 h; and an accuracy of +-10% or better. The system was acceptance tested using a dc reference heater to simulate spent fuel assembly heat generation rates. Results of these tests indicated that the system could be used to measure heat generation rates between 0.5 and 2.5 kW within +- 5%. Measurements of heat generation rates of approx. 0.1 kW were obtained within +- 15%. The calorimeter system has the potential to permit measurements of heat generation rates of spent fuel assemblies and other devices in the 12- to 14-kW range. Results of calorimetry of a Turkey Point spent fuel assembly indicated that the assembly was generating approx. 1.55 kW.

  9. Natural convection in a uniformly heated pool

    SciTech Connect

    Tzanos, C.P.

    1996-12-31

    To prevent reactor vessel failure from molten corium relocation to the reactor vessel lower head in the event of a core meltdown accident, the establishment of a coolable configuration has been proposed by flooding the reactor cavity with water. In Ref. 3, it was shown that for the heavy-water new production reactor (NPW-HWR) design, this strategy (e.g., the rejection of decay heat to a containment decay heat removal system by boiling of water in the reactor cavity) could keep the reactor vessel temperature below failure limits. The analysis of Ref. 3 was performed with the COMMIX-IAR/P computer code and showed that natural convection in the molten-corium pool was the dominant mechanism of heat transfer from the pool to the wall of the reactor vessel lower head. COMMIX is a general-purpose thermal-hydraulics code based on finite differencing by the first-order upwind scheme. To determine whether COMMIX adequately predicts natural convection in a pool heated by a uniform heat source, in Ref. 4, the experiments of free convection in a semicircular cavity of Jahn and Reineke were analyzed with COMMIX in Ref. 5. It was found that the Nusselt number predicted by COMMIX was within the spread of the experimental measurements. In the COMMIX analysis of Ref. 5, the semicircular cavity was treated as symmetric. The objective of this paper was to extend the COMMIX validation analysis of Ref. 5 by removing the assumption of symmetry and expanding the analysis from the highest Rayleigh number of the experiments of Ref. 4 to the highest Rayleigh number that leads to a steady state.

  10. System for reducing heat losses from indoor swimming pools by use of automatic covers. Technical progress report No. 4, October 1, 1994--December 31, 1994

    SciTech Connect

    Not Available

    1995-01-15

    The principal developments during the fifth quarter of the project (October - December 1994) have been as follows. (1) Design fabrication and bench testing of new 24-v controller employing automatic photocell shut-off of motor. (2) Design, fabrication and bench testing of new 42-v controller employing automatic stop-ball and limit-switch shut-off of motor. (3) Design, fabrication, installation, operation and adjustment of prototype improved pool cover system in Denver. (4) Continued planning of installation, demonstration and evaluation of improved pool cover system at the Denver Skyland Recreation Center. (5) Improved mounting brackets. (6) Preparation of a comprehensive paper on swimming pool evaporation rates.

  11. RENO-CC: A new system to fuel lattice design in boiling water reactors using neural networks

    SciTech Connect

    Ortiz, J. J.; Perusquia, R.; Hernandez, J. L.

    2006-07-01

    We show a new system to optimize fuel lattices in BWRs named RENO-CC. The system employs a multi state recurrent neural network (MSRNN) for optimizing a fuel lattice pin-by-pin {sup 235}U enrichment distribution. Local Power Peaking Factor (LPPF) and k-infinite (k{sub {infinity}}) are involved in the MSRNN energy function. Both parameters are calculated by the 2D HELIOS transport code for lattice burn-up. Through the iterative process the MSRNN decreases PPF value while k{sub {infinity}}, is kept in a rank of values, at the beginning of lattice life (BOL). The iterative process ends after 20 iterations. If PPF is not lower than limit, RENO-CC applies a fuzzy logic rule in order to recommend if the fuel lattice has an acceptable LPPF value and it might eventually be used in a fuel load. When a fuel lattice is obtained it can be used into a fuel assembly. And eventually, this fuel assembly would be used in the process of fuel load and control rod patterns optimization. So, a 3D core reactor calculation must decide if such a lattice design can fulfill the operation conditions into the reactor core. Preliminary results are shown in this paper. (authors)

  12. Wastewater treatment in a compact intensified wetland system at the Badboot: a floating swimming pool in Belgium.

    PubMed

    Van Oirschot, D; Wallace, S; Van Deun, R

    2015-09-01

    The Badboot (Dutch for swimming pool boat) is a floating swimming pool located in the city center of Antwerp in Belgium. The overall design consists of a recycled ferry boat that serves as a restaurant and next to that a newly built ship that harbours an Olympic size swimming pool, sun decks, locker rooms with showers, and a party space. A major design goal of the project was to make the ship as environmentally friendly as possible. To avoid discharge of contaminated waste water in the Antwerp docks, the ship includes onsite treatment of wastewater in a compact constructed wetland. The treatment wetland system was designed to treat wastewater from visitor locker rooms, showers, toilets, two bars, and the wastewater from the restaurant kitchen. Due to the limited space on board the ship, only 188 m(2) could be allocated to a wetland treatment system. As a result, part of the design included intensification of the wetland treatment process through the use of Forced Bed Aeration, which injects small quantities of air in a very uniform grid pattern throughout the wetland with a mechanical air compressor. The system was monitored between August 2012 and March 2013 (with additional sampling in the autumn of 2014). Flows and loads to the wetland were highly variable, but removal efficiency was extremely high; 99.5 % for chemical oxygen demand (COD), 88.6 % for total nitrogen and 97.2 % for ammonia. The treatment performance was assessed using a first-order, tanks-in-series model (the P-k-C* model) and found to be roughly equivalent to similar intensified wetlands operating in Germany. However, treatment performance was substantially better than data reported on passive wetlands, likely as a result of intensification. Even with mechanically assisted aeration, the total oxygen delivered to the treatment wetlands was insufficient to support conventional nitrification and denitrification, so it is likely that alternate nitrogen removal pathways, such as anammox, are

  13. Hydrologic Connection Between Geysers and Adjacent Thermal Pools, Two Examples: El Tatio, Chile and Yellowstone, USA

    NASA Astrophysics Data System (ADS)

    Munoz Saez, C.; Fauria, K.; Manga, M.; Hurwitz, S.; Namiki, A.

    2014-12-01

    Geyser eruption cycles can be influenced by adjacent and distant thermals sources, suggesting a hydraulic connection through permeable pathways. Diffusion of fluid pressure can be responsible for the communication between geysers. In this study we examine the processes linking two different geysers with adjacent thermal pools. The first was Vega Rinconada, located at El Tatio geyser field, Chile, where we measured temperature inside the conduit between the ground surface and a depth of seven meters, at one-meter intervals. The second was Lone Star Geyser in Yellowstone National Park, where we measured temperature of the overflow water at the base of the cone. Concurrently, we measured temperature and the water level in pools adjacent to both geysers. We found common elements in both geyser - pool systems: First, water temperature in both adjacent pools was below the boiling point and cooler than water in the geysers. Second, changes in pool water levels were correlated with eruptions of the geysers. During the quiescent period of the geysers, the water level increased in adjacent pools, while water level in the pools deceased during eruptions. Additionally, measurements inside of the conduit in Vega Rinconada Geyser showed that water temperature increased in the deepest part of the conduit during eruptions, while water temperature decreased in the shallow part of the geyser conduit (~1 to 2 m). These drops in temperature in the shallow conduit were coincident with the drop in water level in the adjacent pool. This suggests that after the initiation of an eruption, water may drain from the pool to the geyser. Furthermore, we observed a temperature drop of 3oC in the shallow conduit immediately preceding the end of an eruption. This suggests that flow from the pool to geyser contributes to eruption shut off. Our observations of geyser-pool systems indicate a hydrologic connection between the geysers and their adjacent pools. In the case of Vega Rinconada, cold water

  14. Boiling behavior of sodium-potassium alloy in a bench-scale solar receiver

    NASA Astrophysics Data System (ADS)

    Moreno, J. B.; Andraka, C. E.; Moss, T. A.

    During 1989-90, a 75-kW(sub t) sodium reflux pool-boiler solar receiver was successfully demonstrated at Sandia National Laboratories. Significant features of this receiver include the following: (1) boiling sodium as the heat transfer medium, and (2) electric-discharge-machined (EDM) cavities as artificial nucleation sites to stabilize boiling. Since this first demonstration, design of a second-generation pool-boiler receiver that will bring the concept closer to commercialization has begun. For long life, the new receiver uses Haynes Alloy 230. For increased safety factors against film boiling and flooding, it has a refined shape and somewhat larger dimensions. To eliminate the need for trace heating, the receiver will boil the sodium-potassium alloy NaK-78 instead of sodium. To reduce manufacturing costs, it will use one of a number of alternatives to EDM cavities for stabilization of boiling. To control incipient-boiling superheats, especially during hot restarts, it will contain a small amount of inert gas. Before the new receiver design could be finalized, bench-scale tests of some of the proposed changes were necessary. A series of bench-scale pool boilers were built from Haynes Alloy 230 and filled with NaK-78. Various boiling-stabilizer candidates were incorporated into them, including laser-drilled cavities and a number of different sintered-powder-metal coatings. These bench-scale pool boilers have been operated at temperatures up to 750 C, heated by quartz lamps with incident radiant fluxes up to 95 W/sq cm. The effects of various orientations and added gases have been studied. Results of these studies are presented.

  15. 47 CFR 97.523 - Question pools.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Question pools. 97.523 Section 97.523... SERVICE Qualifying Examination Systems § 97.523 Question pools. All VECs must cooperate in maintaining one question pool for each written examination element. Each question pool must contain at least 10 times...

  16. 47 CFR 97.523 - Question pools.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Question pools. 97.523 Section 97.523... SERVICE Qualifying Examination Systems § 97.523 Question pools. All VECs must cooperate in maintaining one question pool for each written examination element. Each question pool must contain at least 10 times...

  17. 47 CFR 97.523 - Question pools.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Question pools. 97.523 Section 97.523... SERVICE Qualifying Examination Systems § 97.523 Question pools. All VECs must cooperate in maintaining one question pool for each written examination element. Each question pool must contain at least 10 times...

  18. 47 CFR 97.523 - Question pools.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Question pools. 97.523 Section 97.523... SERVICE Qualifying Examination Systems § 97.523 Question pools. All VECs must cooperate in maintaining one question pool for each written examination element. Each question pool must contain at least 10 times...

  19. 47 CFR 97.523 - Question pools.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Question pools. 97.523 Section 97.523... SERVICE Qualifying Examination Systems § 97.523 Question pools. All VECs must cooperate in maintaining one question pool for each written examination element. Each question pool must contain at least 10 times...

  20. Carbon concentrations and transformations in peatland pools

    NASA Astrophysics Data System (ADS)

    Chapman, Pippa; Holden, Joseph; Baird, Andrew; Turner, Edward; Dooling, Gemma; Billett, Mike; McKenzie, Rebecca; Leith, Fraser; Dinsmore, Kerry

    2016-04-01

    Peatland pools may act as important features for aquatic and gaseous carbon production, transformation and release. Peatland restoration often results in new pools being created. Here we compare aquatic carbon concentrations in nearby natural and artificial pool systems monitored at three sites in northern Scotland over a three-year period. We found significant differences in pool water carbon concentrations between pool types with larger dissolved organic carbon (DOC) and dissolved carbon dioxide (CO2) in artificial pools. The differences were strong for all sites and occurred in all seasons. Importantly, the DOC outflows from natural pools were markedly lower than the DOC flowing into natural pools showing that processes in these pools were transforming and removing the DOC. These effects were not found in the artificial pools. Data on the composition of the DOC (absorbance ratios, specific ultraviolet absorbance) suggested that natural pools tended to have DOC that had been processed, and was older (radiocarbon dating) while the DOC in artificial pools was young and had not undergone much biochemical processing. Slope position was an important factor influencing pool DOC with those pools with a longer upslope contributing area and collecting water with a longer hillslope residence time having larger DOC concentrations. Dissolved methane (CH4) concentrations were not significantly different between pool types but the concentrations were always above atmospheric levels with values ˜ 200 times atmospheric concentrations not uncommon. Dissolved CO2 concentrations in the artificial pools were extremely large; typically ˜20 times atmospheric levels while those in natural pools were typically only just above atmospheric levels. The pools were strong sources of CH4 and CO2 evasion from the peat system. The smaller size of the artificial pools means that more of their CO2 is stored in the water until it reaches the stream system, while the larger natural pools have

  1. The post-transcriptional regulatory system CSR controls the balance of metabolic pools in upper glycolysis of Escherichia coli.

    PubMed

    Morin, Manon; Ropers, Delphine; Letisse, Fabien; Laguerre, Sandrine; Portais, Jean-Charles; Cocaign-Bousquet, Muriel; Enjalbert, Brice

    2016-05-01

    Metabolic control in Escherichia coli is a complex process involving multilevel regulatory systems but the involvement of post-transcriptional regulation is uncertain. The post-transcriptional factor CsrA is stated as being the only regulator essential for the use of glycolytic substrates. A dozen enzymes in the central carbon metabolism (CCM) have been reported as potentially controlled by CsrA, but its impact on the CCM functioning has not been demonstrated. Here, a multiscale analysis was performed in a wild-type strain and its isogenic mutant attenuated for CsrA (including growth parameters, gene expression levels, metabolite pools, abundance of enzymes and fluxes). Data integration and regulation analysis showed a coordinated control of the expression of glycolytic enzymes. This also revealed the imbalance of metabolite pools in the csrA mutant upper glycolysis, before the phosphofructokinase PfkA step. This imbalance is associated with a glucose-phosphate stress. Restoring PfkA activity in the csrA mutant strain suppressed this stress and increased the mutant growth rate on glucose. Thus, the carbon storage regulator system is essential for the effective functioning of the upper glycolysis mainly through its control of PfkA. This work demonstrates the pivotal role of post-transcriptional regulation to shape the carbon metabolism.

  2. Heat Transfer in Boiling Dilute Emulsion with Strong Buoyancy

    NASA Astrophysics Data System (ADS)

    Freeburg, Eric Thomas

    Little attention has been given to the boiling of emulsions compared to that of boiling in pure liquids. The advantages of using emulsions as a heat transfer agent were first discovered in the 1970s and several interesting features have since been studied by few researchers. Early research focuses primarily on pool and flow boiling and looks to determine a mechanism by which the boiling process occurs. This thesis looks at the boiling of dilute emulsions in fluids with strong buoyant forces. The boiling of dilute emulsions presents many favorable characteristics that make it an ideal agent for heat transfer. High heat flux electronics, such as those seen in avionics equipment, produce high heat fluxes of 100 W/cm2 or more, but must be maintained at low temperatures. So far, research on single phase convection and flow boiling in small diameter channels have yet to provide an adequate solution. Emulsions allow the engineer to tailor the solution to the specific problem. The fluid can be customized to retain the high thermal conductivity and specific heat capacity of the continuous phase while enhancing the heat transfer coefficient through boiling of the dispersed phase component. Heat transfer experiments were carried out with FC-72 in water emulsions. FC-72 has a saturation temperature of 56 °C, far below that of water. The parameters were varied as follows: 0% ≤ epsilon ≤ 1% and 1.82 x 1012 ≤ RaH ≤ 4.42 x 1012. Surface temperatures along the heated surface reached temperature that were 20 °C in excess of the dispersed phase saturation temperature. An increase of ˜20% was seen in the average Nusselt numbers at the highest Rayleigh numbers. Holography was used to obtain images of individual and multiple FC-72 droplets in the boundary layer next to the heated surface. The droplet diameters ranged from 0.5 mm to 1.3 mm. The Magnus effect was observed when larger individual droplets were injected into the boundary layer, causing the droplets to be pushed

  3. Boiling and nonboiling heat transfer to electrolyte solutions

    SciTech Connect

    Najibi, S.H.; Mueller-Steinhagen, H.; Jamialahmadi, M.

    1996-10-01

    Heat transfer to electrolyte solutions is a common engineering problem in the chemical and petrochemical industries. Nevertheless, only a few experimental investigations of heat transfer to electrolyte solutions can be found in the literature. To improve design of heat transfer equipment and to understand fouling characteristics, it is important to know the clean heat transfer coefficient of electrolyte solutions, and whether heat transfer to electrolyte solutions can be predicted with models found for less complicated fluids. A wide range of experiments were performed to determine the effects of various dissolved salts on forced-convective, pool boiling, and subcooled flow-boiling heat transfer. The effect of dissolved salts on bubble size and nucleation site density were also investigated. The measured heat transfer coefficients are compared with recommended correlations for the different heat transfer modes.

  4. Analysis of Free Amino Acid Pools in Fungal Mycelia

    PubMed Central

    Heathcote, J. G.; Davies, D. M.; Haworth, C.

    1972-01-01

    Free amino acid pools derived from three different types of fungal mycelia have been analyzed by the method of Heathcote and Haworth by using thinlayer chromatography. The preliminary extraction was carried out with boiling water and interfering proteins; peptides and salts were first removed by means of an ion-retardation resin. As far as determined, the results obtained represent the first quantitative analysis of fungal amino acid pools. PMID:4622829

  5. System for reducing heat losses from indoor swimming pools by use of automatic covers. Final report, October 1, 1993--September 30, 1995

    SciTech Connect

    1996-01-01

    This final report is an account of the principal activities of Lof Energy Systems, Inc. in a two-year project funded by the Energy Related Inventions Program (ERIP) of the U.S. Department of Energy. The primary objective has been the development of a fully practical and economical system for saving energy in indoor swimming pools by use of motorized covers. The goal is wide-spread use of a fully developed product, in institutional swimming pools. Four major tasks, depicted in the accompanying Performance Schedule, have been completed, and one other has been initiated and its completion committed. Principal accomplishments have been the selection and improvement of cover materials and designs, lengthening and strengthening of reels and improvements in motorized components and their control, design and installation of pool covers in full scale demonstration and evaluation of fully developed commercial system, preparation and dissemination of manuals and reports, finalization of arrangements for Underwriters Laboratory certification of products, and final report preparation and submission. Of greatest significance has been the successful demonstration of the fully developed system and the verification and reporting by an energy consultant of the large savings resulting from pool cover use. Probably the best evidence of success of the DOE-ERIP project in advancing this invention to a commercial stage is its acceptance for sale by the Lincoln Equipment Company, a national distributor of swimming pool supplies and equipment. A copy of the relevant page in the Lincoln catalog is included in this report as Annex A. Representatives of that company now offer Tof motorized pool cover systems to their pool owner customers. In addition to the plans for securing UL certification the company expects to continue making design improvements that can increase system reliability, durability, and cost-effectiveness.

  6. An Experimental Study of Boiling in Reduced and Zero Gravity Fields

    NASA Technical Reports Server (NTRS)

    Usiskin, C. M.; Siegel, R.

    1961-01-01

    A pool boiling apparatus was mounted on a counterweighted platform which could be dropped a distance of nine feet. By varying the size of the counterweight, the effective gravity field on the equipment was adjusted between zero and unity. A study of boiling burnout in water indicated that a variation in the critical heat flux according to the one quarter power of gravity was reasonable. A consideration of the transient burnout process was necessary in order to properly interpret the data. A photographic study of nucleate boiling showed how the velocity of freely rising vapor bubbles decreased as gravity was reduced. The bubble diameters at the time of breakoff from the heated surface were found to vary inversely as gravity to the 1/3.5 power. Motion pictures were taken to illustrate both nucleate and film boiling in the low gravity range.

  7. Thermohydrodynamics of boiling in binary compressible fluids.

    PubMed

    Liu, Jiewei; Do-Quang, Minh; Amberg, Gustav

    2015-10-01

    We numerically study the thermohydrodynamics of boiling for a CO(2) + ethanol mixture on lyophilic and lyophobic surfaces in both closed and open systems, based on a diffuse interface model for a two-component system. The corresponding wetting boundary conditions for an isothermal system are proposed and verified in this paper. New phenomena due to the addition of another component, mainly the preferential evaporation of the more volatile component, are observed. In the open system and the closed system, the physical process shows very different characteristics. In the open system, except for the movement of the contact line, the qualitative features are rather similar for lyophobic and lyophilic surfaces. In the closed system, the vortices that are observed on a lyophobic surface are not seen on a lyophilic surface. More sophisticated wetting boundary conditions for nonisothermal, two-component systems might need to be further developed, taking into account the variations of density, temperature, and surface tension near the wall, while numerical results show that the boundary conditions proposed here also work well even in boiling, where the temperature is nonuniform.

  8. Boiling Temperature and Reversed Deliquescence Relative Humidity Measurements for Mineral Assemblages in the NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O System

    SciTech Connect

    Rard, J A; Staggs, K J; Day, S D; Carroll, S A

    2005-12-01

    Boiling temperature measurements have been made at ambient pressure for saturated ternary solutions of NaCl + KNO{sub 3} + H{sub 2}O, NaNO{sub 3} + KNO{sub 3} + H{sub 2}O, and NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O over the full composition range, along with those of the single salt systems. Boiling temperatures were also measured for the four component NaCl + NaNO{sub 3} + KNO{sub 3} + H{sub 2}O and five component NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O mixtures, where the solute mole fraction of Ca(NO{sub 3}){sub 2}, x(Ca(NO{sub 3}){sub 2}), was varied between 0 and 0.25. The maximum boiling temperature found for the NaCl + KNO{sub 3} + H{sub 2}O system is {approx} 134.9 C; for the NaNO{sub 3} + KNO{sub 3} + H{sub 2}O system is {approx} 165.1 C at x(NaNO{sub 3}) {approx} 0.46 and x(KNO{sub 3}) {approx} 0.54; and for the NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O system is 164.7 {+-} 0.6 C at x(NaCl) {approx} 0.25 and x(Ca(NO{sub 3}){sub 2}) {approx} 0.75. The NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O system forms molten salts below their maximum boiling temperatures, and the temperatures corresponding to the cessation of boiling (dry out temperatures) of these liquid mixtures were determined. These dry out temperatures range from {approx} 300 C when x(Ca(NO{sub 3}){sub 2}) = 0 to {ge} 400 C when x(Ca(NO{sub 3}){sub 2}) = 0.20 and 0.25. Mutual deliquescence/efflorescence relative humidity (MDRH/MERH) measurements were also made for the NaNO{sub 3} + KNO{sub 3} and NaCl + NaNO{sub 3} + KNO{sub 3} salt mixture from 120 to 180 C at ambient pressure. The NaNO{sub 3} and NaCl + NaNO{sub 3} + KNO{sub 3} salt mixture has a MDRH of 26.4% at 120 C and 20.0% at 150 C. This salt mixture also absorbs water at 180 C, which is higher than expected from the boiling temperature experiments. The NaCl + NaNO{sub 3} + KNO{sub 3} salt mixture was found to have a MDRH of 25.9% at 120 C and 10.5% at 180 C. The investigated mixture

  9. Subcooled forced convection boiling of trichlorotrifluoroethane

    NASA Technical Reports Server (NTRS)

    Dougall, R. S.; Panian, D. J.

    1972-01-01

    Experimental heat-transfer data were obtained for the forced-convection boiling of trichlorotrifluoroethane (R-113 or Freon-113) in a vertical annular test annular test section. The 97 data points obtained covered heat transfer by forced convection, local boiling, and fully-developed boiling. Correlating methods were obtained which accurately predicted the heat flux as a function of wall superheat (boiling curve) over the range of parameters studied.

  10. Numerical simulation of boiling water reactor ventclearing hydrodynamics

    SciTech Connect

    Nichols, B.D.; Hirt, C.W.

    1980-02-01

    Pressure suppression pools used in nuclear reactors are subject to hydrodynamic processes involving complicated free surface configurations. A new numerical method, SOLA-VOF, developed to handle such problems is described and evaluated through comparisons with laboratory test data. Results from numerous computations provide a detailed understanding of the hydrodynamic phenomena associated with boiling water reactor vent-clearing processes. In addition, calculations show the sensitivity of the results to variations in the water vapor content, vent submergence depth, vent orifice size, and to the influence of fluid-structure interactions.

  11. Simulating soil C stability with mechanistic systems models: a multisite comparison of measured fractions and modelled pools

    NASA Astrophysics Data System (ADS)

    Robertson, Andy; Schipanski, Meagan; Sherrod, Lucretia; Ma, Liwang; Ahuja, Lajpat; McNamara, Niall; Smith, Pete; Davies, Christian

    2016-04-01

    Agriculture, covering more than 30% of global land area, has an exciting opportunity to help combat climate change by effectively managing its soil to promote increased C sequestration. Further, newly sequestered soil carbon (C) through agriculture needs to be stored in more stable forms in order to have a lasting impact on reducing atmospheric CO2 concentrations. While land uses in different climates and soils require different management strategies, the fundamental mechanisms that regulate C sequestration and stabilisation remain the same. These mechanisms are used by a number of different systems models to simulate C dynamics, and thus assess the impacts of change in management or climate. To evaluate the accuracy of these model simulations, our research uses a multidirectional approach to compare C stocks of physicochemical soil fractions collected at two long-term agricultural sites. Carbon stocks for a number of soil fractions were measured at two sites (Lincoln, UK; Colorado, USA) over 8 and 12 years, respectively. Both sites represent managed agricultural land but have notably different climates and levels of disturbance. The measured soil fractions act as proxies for varying degrees of stability, with C contained within these fractions relatable to the C simulated within the soil pools of mechanistic systems models1. Using stable isotope techniques at the UK site, specific turnover times of C within the different fractions were determined and compared with those simulated in the pools of 3 different models of varying complexity (RothC, DayCent and RZWQM2). Further, C dynamics and N-mineralisation rates of the measured fractions at the US site were assessed and compared to results of the same three models. The UK site saw a significant increase in C stocks within the most stable fractions, with topsoil (0-30cm) sequestration rates of just over 0.3 tC ha-1 yr-1 after only 8 years. Further, the sum of all fractions reported C sequestration rates of nearly 1

  12. Saguaro: a distributed operating system based on pools of servers. Annual report, 1 January 1984-31 December 1986

    SciTech Connect

    Andrews, G.R.

    1986-03-03

    Prototypes of components of the Saguaro distributed operating system were implemented and the design of the entire system refined based on the experience. The philosophy behind Saguaro is to support the illusion of a single virtual machine while taking advantage of the concurrency and robustness that are possible in a network architecture. Within the system, these advantages are realized by the use of pools of server processes and decentralized allocation protocols. Potential concurrency and robustness are also made available to the user through low-cost mechanisms to control placement of executing commands and files, and to support semi-transparent file replication and access. Another unique aspect of Saguaro is its extensive use of type system to describe user data such as files and to specify the types of arguments to commands and procedures. This enables the system to assist in type checking and leads to a user interface in which command-specific templates are available to facilitate command invocation. A mechanism, channels, is also provided to enable users to construct applications containing general graphs of communication processes.

  13. Investigation of Body Force Effects on Flow Boiling Critical Heat Flux

    NASA Technical Reports Server (NTRS)

    Zhang, Hui; Mudawar, Issam; Hasan, Mohammad M.

    2002-01-01

    The bubble coalescence and interfacial instabilities that are important to modeling critical heat flux (CHF) in reduced-gravity systems can be sensitive to even minute body forces. Understanding these complex phenomena is vital to the design and safe implementation of two-phase thermal management loops proposed for space and planetary-based thermal systems. While reduced gravity conditions cannot be accurately simulated in 1g ground-based experiments, such experiments can help isolate the effects of the various forces (body force, surface tension force and inertia) which influence flow boiling CHF. In this project, the effects of the component of body force perpendicular to a heated wall were examined by conducting 1g flow boiling experiments at different orientations. FC-72 liquid was boiled along one wall of a transparent rectangular flow channel that permitted photographic study of the vapor-liquid interface at conditions approaching CHF. High-speed video imaging was employed to capture dominant CHF mechanisms. Six different CHF regimes were identified: Wavy Vapor Layer, Pool Boiling, Stratification, Vapor Counterflow, Vapor Stagnation, and Separated Concurrent Vapor Flow. CHF showed great sensitivity to orientation for flow velocities below 0.2 m/s, where very small CHF values where measured, especially with downflow and downward-facing heated wall orientations. High flow velocities dampened the effects of orientation considerably. Figure I shows representative images for the different CHF regimes. The Wavy Vapor Layer regime was dominant for all high velocities and most orientations, while all other regimes were encountered at low velocities, in the downflow and/or downward-facing heated wall orientations. The Interfacial Lift-off model was modified to predict the effects of orientation on CHF for the dominant Wavy Vapor Layer regime. The photographic study captured a fairly continuous wavy vapor layer travelling along the heated wall while permitting liquid

  14. ATWS Analysis with an Advanced Boiling Curve Approach within COBRA 3-CP

    SciTech Connect

    Gensler, A.; Knoll, A.; Kuehnel, K.

    2007-07-01

    In 2005 the German Reactor Safety Commission issued specific requirements on core coolability demonstration for PWR ATWS (anticipated transients without scram). Thereupon AREVA NP performed detailed analyses for all German PWRs. For a German KONVOI plant the results of an ATWS licensing analysis are presented. The plant dynamic behavior is calculated with NLOOP, while the hot channel analysis is performed with the thermal hydraulic computer code COBRA 3-CP. The application of the fuel rod model included in COBRA 3-CP is essential for this type of analysis. Since DNB (departure from nucleate boiling) occurs, the advanced post DNB model (advanced boiling curve approach) of COBRA 3-CP is used. The results are compared with those gained with the standard BEEST model. The analyzed ATWS case is the emergency power case 'loss of main heat sink with station service power supply unavailable'. Due to the decreasing coolant flow rate during the transient the core attains film boiling conditions. The results of the hot channel analysis strongly depend on the performance of the boiling curve model. The BEEST model is based on pool boiling conditions whereas typical PWR conditions - even in most transients - are characterized by forced flow for which the advanced boiling curve approach is particularly suitable. Compared with the BEEST model the advanced boiling curve approach in COBRA 3-CP yields earlier rewetting, i.e. a shorter period in film boiling. Consequently, the fuel rod cladding temperatures, that increase significantly due to film boiling, drop back earlier and the high temperature oxidation is significantly diminished. The Baker-Just-Correlation was used to calculate the value of equivalent cladding reacted (ECR), i.e. the reduction of cladding thickness due to corrosion throughout the transient. Based on the BEEST model the ECR value amounts to 0.4% whereas the advanced boiling curve only leads to an ECR value of 0.2%. Both values provide large margins to the 17

  15. The myth of the boiling point.

    PubMed

    Chang, Hasok

    2008-01-01

    Around 1800, many reputable scientists reported significant variations in the temperature of pure water boiling under normal atmospheric pressure. The reported variations included a difference of over 1 degree C between boiling in metallic and glass vessels (Gay-Lussac), and "superheating" up to 112 degrees C on extracting dissolved air out of water (De Luc). I have confirmed most of these observations in my own experiments, many of which are described in this paper. Water boils at the "boiling point" only under very particular circumstances. Our common-sense intuition about the fixedness of the boiling point is only sustained by our limited experience.

  16. Computations of Boiling in Microgravity

    NASA Technical Reports Server (NTRS)

    Tryggvason, Gretar; Jacqmin, David

    1999-01-01

    The absence (or reduction) of gravity, can lead to major changes in boiling heat transfer. On Earth, convection has a major effect on the heat distribution ahead of an evaporation front, and buoyancy determines the motion of the growing bubbles. In microgravity, convection and buoyancy are absent or greatly reduced and the dynamics of the growing vapor bubbles can change in a fundamental way. In particular, the lack of redistribution of heat can lead to a large superheat and explosive growth of bubbles once they form. While considerable efforts have been devoted to examining boiling experimentally, including the effect of microgravity, theoretical and computational work is limited to very simple models. In this project, the growth of boiling bubbles is studied by direct numerical simulations where the flow field is fully resolved and the effects of inertia, viscosity, surface deformation, heat conduction and convection, as well as the phase change, are fully accounted for. The proposed work is based on previously funded NASA work that allowed us to develop a two-dimensional numerical method for boiling flows and to demonstrate the ability of the method to simulate film boiling. While numerical simulations of multi-fluid flows have been advanced in a major way during the last five years, or so, similar capability for flows with phase change are still in their infancy. Although the feasibility of the proposed approach has been demonstrated, it has yet to be extended and applied to fully three-dimensional simulations. Here, a fully three-dimensional, parallel, grid adaptive code will be developed. The numerical method will be used to study nucleate boiling in microgravity, with particular emphasis on two aspects of the problem: 1) Examination of the growth of bubbles at a wall nucleation site and the instabilities of rapidly growing bubbles. Particular emphasis will be put on accurately capturing the thin wall layer left behind as a bubble expands along a wall, on

  17. 10 CFR 36.63 - Pool water purity.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Pool water purity. 36.63 Section 36.63 Energy NUCLEAR... § 36.63 Pool water purity. (a) Pool water purification system must be run sufficiently to maintain the conductivity of the pool water below 20 microsiemens per centimeter under normal circumstances. If pool...

  18. 10 CFR 36.63 - Pool water purity.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Pool water purity. 36.63 Section 36.63 Energy NUCLEAR... § 36.63 Pool water purity. (a) Pool water purification system must be run sufficiently to maintain the conductivity of the pool water below 20 microsiemens per centimeter under normal circumstances. If pool...

  19. 10 CFR 36.63 - Pool water purity.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 1 2013-01-01 2013-01-01 false Pool water purity. 36.63 Section 36.63 Energy NUCLEAR... § 36.63 Pool water purity. (a) Pool water purification system must be run sufficiently to maintain the conductivity of the pool water below 20 microsiemens per centimeter under normal circumstances. If pool...

  20. 48 CFR 9.703 - Contracting with individual pool members.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... individual pool members. 9.703 Section 9.703 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Defense Production Pools and Research and Development Pools 9.703 Contracting with individual pool members. (a) Pool members may submit...

  1. 48 CFR 9.702 - Contracting with pools.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 1 2014-10-01 2014-10-01 false Contracting with pools. 9... PLANNING CONTRACTOR QUALIFICATIONS Defense Production Pools and Research and Development Pools 9.702 Contracting with pools. (a) Except as specified in this subpart, a pool shall be treated the same as any...

  2. 48 CFR 9.703 - Contracting with individual pool members.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... individual pool members. 9.703 Section 9.703 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Defense Production Pools and Research and Development Pools 9.703 Contracting with individual pool members. (a) Pool members may submit...

  3. 48 CFR 9.703 - Contracting with individual pool members.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... individual pool members. 9.703 Section 9.703 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Defense Production Pools and Research and Development Pools 9.703 Contracting with individual pool members. (a) Pool members may submit...

  4. 48 CFR 9.702 - Contracting with pools.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 1 2013-10-01 2013-10-01 false Contracting with pools. 9... PLANNING CONTRACTOR QUALIFICATIONS Defense Production Pools and Research and Development Pools 9.702 Contracting with pools. (a) Except as specified in this subpart, a pool shall be treated the same as any...

  5. 48 CFR 9.702 - Contracting with pools.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 1 2012-10-01 2012-10-01 false Contracting with pools. 9... PLANNING CONTRACTOR QUALIFICATIONS Defense Production Pools and Research and Development Pools 9.702 Contracting with pools. (a) Except as specified in this subpart, a pool shall be treated the same as any...

  6. 48 CFR 9.703 - Contracting with individual pool members.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... individual pool members. 9.703 Section 9.703 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Defense Production Pools and Research and Development Pools 9.703 Contracting with individual pool members. (a) Pool members may submit...

  7. 48 CFR 9.702 - Contracting with pools.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 1 2011-10-01 2011-10-01 false Contracting with pools. 9... PLANNING CONTRACTOR QUALIFICATIONS Defense Production Pools and Research and Development Pools 9.702 Contracting with pools. (a) Except as specified in this subpart, a pool shall be treated the same as any...

  8. 48 CFR 9.703 - Contracting with individual pool members.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... individual pool members. 9.703 Section 9.703 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Defense Production Pools and Research and Development Pools 9.703 Contracting with individual pool members. (a) Pool members may submit...

  9. 48 CFR 9.702 - Contracting with pools.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Contracting with pools. 9... PLANNING CONTRACTOR QUALIFICATIONS Defense Production Pools and Research and Development Pools 9.702 Contracting with pools. (a) Except as specified in this subpart, a pool shall be treated the same as any...

  10. Swimming Pool Safety

    MedlinePlus

    ... insist that the following rules are followed: Keep toys away from the pool when the pool is ... after each use. No tricycles or other riding toys at poolside. No electrical appliances near the pool. ...

  11. Pooling data from fatality analysis reporting system (FARS) and generalized estimates system (GES) to explore the continuum of injury severity spectrum.

    PubMed

    Yasmin, Shamsunnahar; Eluru, Naveen; Pinjari, Abdul R

    2015-11-01

    Fatality Analysis Reporting System (FARS) and Generalized Estimates System (GES) data are most commonly used datasets to examine motor vehicle occupant injury severity in the United States (US). The FARS dataset focuses exclusively on fatal crashes, but provides detailed information on the continuum of fatality (a spectrum ranging from a death occurring within thirty days of the crash up to instantaneous death). While such data is beneficial for understanding fatal crashes, it inherently excludes crashes without fatalities. Hence, the exogenous factors identified as critical in contributing (or reducing) to fatality in the FARS data might possibly offer different effects on non-fatal crash severity levels when a truly random sample of crashes is considered. The GES data fills this gap by compiling data on a sample of roadway crashes involving all possible severity consequences providing a more representative sample of traffic crashes in the US. FARS data provides a continuous timeline of the fatal occurrences from the time to crash - as opposed to considering all fatalities to be the same. This allows an analysis of the survival time of victims before their death. The GES, on the other hand, does not offer such detailed information except identifying who died in the crash. The challenge in obtaining representative estimates for the crash population is the lack of readily available "appropriate" data that contains information available in both GES and FARS datasets. One way to address this issue is to replace the fatal crashes in the GES data with fatal crashes from FARS data thus augmenting the GES data sample with a very refined categorization of fatal crashes. The sample thus formed, if statistically valid, will provide us with a reasonable representation of the crash population. This paper focuses on developing a framework for pooling of data from FARS and GES data. The validation of the pooled sample against the original GES sample (unpooled sample) is carried

  12. Pooling data from fatality analysis reporting system (FARS) and generalized estimates system (GES) to explore the continuum of injury severity spectrum.

    PubMed

    Yasmin, Shamsunnahar; Eluru, Naveen; Pinjari, Abdul R

    2015-11-01

    Fatality Analysis Reporting System (FARS) and Generalized Estimates System (GES) data are most commonly used datasets to examine motor vehicle occupant injury severity in the United States (US). The FARS dataset focuses exclusively on fatal crashes, but provides detailed information on the continuum of fatality (a spectrum ranging from a death occurring within thirty days of the crash up to instantaneous death). While such data is beneficial for understanding fatal crashes, it inherently excludes crashes without fatalities. Hence, the exogenous factors identified as critical in contributing (or reducing) to fatality in the FARS data might possibly offer different effects on non-fatal crash severity levels when a truly random sample of crashes is considered. The GES data fills this gap by compiling data on a sample of roadway crashes involving all possible severity consequences providing a more representative sample of traffic crashes in the US. FARS data provides a continuous timeline of the fatal occurrences from the time to crash - as opposed to considering all fatalities to be the same. This allows an analysis of the survival time of victims before their death. The GES, on the other hand, does not offer such detailed information except identifying who died in the crash. The challenge in obtaining representative estimates for the crash population is the lack of readily available "appropriate" data that contains information available in both GES and FARS datasets. One way to address this issue is to replace the fatal crashes in the GES data with fatal crashes from FARS data thus augmenting the GES data sample with a very refined categorization of fatal crashes. The sample thus formed, if statistically valid, will provide us with a reasonable representation of the crash population. This paper focuses on developing a framework for pooling of data from FARS and GES data. The validation of the pooled sample against the original GES sample (unpooled sample) is carried

  13. Design of hydrotherapy exercise pools.

    PubMed

    Edlich, R F; Abidin, M R; Becker, D G; Pavlovich, L J; Dang, M T

    1988-01-01

    Several hydrotherapy pools have been designed specifically for a variety of aquatic exercise. Aqua-Ark positions the exerciser in the center of the pool for deep-water exercise. Aqua-Trex is a shallow underwater treadmill system for water walking or jogging. Swim-Ex generates an adjustable laminar flow that permits swimming without turning. Musculoskeletal conditioning can be accomplished in the above-ground Arjo shallow-water exercise pool. A hydrotherapy pool also can be custom designed for musculoskeletal conditioning in its shallow part and cardiovascular conditioning in a deeper portion of the pool. Regardless of the type of exercise, there is general agreement that the specific exercise conducted in water requires significantly more energy expenditure than when the same exercise is performed on land. PMID:3192611

  14. THE OUTDOOR POOL

    PubMed Central

    Craster, Charles V.

    1919-01-01

    That almost any bit of water will serve for a wading pool seems to be the idea in practice. Dr. Craster has tested such pools and finds that they need to be as well constructed as bathing pools and as well cared for. Chlorination is necessary when they can not otherwise be controlled. ImagesPOOL I.POOL II.POOL III.p826-a PMID:18010192

  15. Interactions between pool geometry and hydraulics

    USGS Publications Warehouse

    Thompson, D.M.; Nelson, J.M.; Wohl, E.E.

    1998-01-01

    An experimental and computational research approach was used to determine interactions between pool geometry and hydraulics. A 20-m-long, 1.8-m-wide flume was used to investigate the effect of four different geometric aspects of pool shape on flow velocity. Plywood sections were used to systematically alter constriction width, pool depth, pool length, and pool exit-slope gradient, each at two separate levels. Using the resulting 16 unique geometries with measured pool velocities in four-way factorial analyses produced an empirical assessment of the role of the four geometric aspects on the pool flow patterns and hence the stability of the pool. To complement the conclusions of these analyses, a two-dimensional computational flow model was used to investigate the relationships between pool geometry and flow patterns over a wider range of conditions. Both experimental and computational results show that constriction and depth effects dominate in the jet section of the pool and that pool length exhibits an increasing effect within the recirculating-eddy system. The pool exit slope appears to force flow reattachment. Pool length controls recirculating-eddy length and vena contracta strength. In turn, the vena contracta and recirculating eddy control velocities throughout the pool.

  16. Flow Boiling Critical Heat Flux in Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Mudawar, Issam; Zhang, Hui; Hasan, Mohammad M.

    2004-01-01

    This study provides systematic method for reducing power consumption in reduced gravity systems by adopting minimum velocity required to provide adequate CHF and preclude detrimental effects of reduced gravity . This study proves it is possible to use existing 1 ge flow boiling and CHF correlations and models to design reduced gravity systems provided minimum velocity criteria are met

  17. Mechanism of enhancement/deterioration of boiling heat transfer using stable nanoparticle suspensions over vertical tubes

    NASA Astrophysics Data System (ADS)

    Narayan, G. Prakash; Anoop, K. B.; Das, Sarit K.

    2007-10-01

    Boiling heat transfer using nanofluids has been a subject of a few investigations in the past few years and incongruous results have been reported in literature regarding the same. Conflicting explanations for deterioration of pool boiling heat transfer coefficient at higher concentrations (4-16wt%) have been presented by various researchers. Recently, a few works have reported a significant enhancement in pool boiling heat transfer coefficient at lower concentrations (0.32-1.25wt%) and the physical reasons for this have not been explained. The present work is aimed at removing these ambiguities. Experiments have been carried out by using stable water based nanofluids containing alumina nanoparticles (average sizes of 47 and 150nm) with vertical tubular heaters of various surface roughnesses (48, 98, and 524nm). It has been observed that with the rough heater (Ra=524nm), heat transfer is significantly enhanced and the enhancement reaches ˜70% at a particle loading of 0.5wt%. With the smooth heater (Ra=48nm), heat transfer is significantly deteriorated and the heat flux reduction reaches ˜45% at a particle loading of 2wt%. Further, it has been observed that a parameter which is the ratio of average size of the particle to the average roughness value of the heater can explain the reported controversy in the pool boiling behavior of these suspensions.

  18. Experiments of ECCS strainer blockage and debris settling in suppression pools

    SciTech Connect

    Hecker, G.E.; Johnson, A.B.; Murthy, P.; Padmanabhan

    1996-03-01

    If a rupture occurs in a nuclear power station pipe that leads to or from the reactor pressure vessel, the resultant Loss of Coolant Accident (LOCA) would initiate a chain of events involving complex flow phenomena. In a Boiling Water Reactor (BWR), the steam or liquid pipe break pressurizes the dry well, forcing the inert containment gases and steam through downcomers into the suppression pool, thoroughly mixing any particulates and pipe insulation debris carried with the gas flow to the pool. As the steam flow decreases, its unsteady condensation at the end of the downcomers (Condensation Oscillation and Chugging) produces continued water motion in the suppression pool and downcomers. During the blowdown event, high pressure and then low pressure pumps automatically start injecting water from the suppression pool into the reactor to keep its temperature under control. Proper functioning of this Emergency Core Cooling System (ECCS) is critical for the first 30 minutes or so, before operators have time to consider and align alternative sources of cooling water. A major concern for proper operation of the ECCS is the effect of fragmented insulation and plant particulates on the head loss at pump suction strainers. Sufficient loss could exceed the NPSH margin, causing cavitation with a resultant loss of pump capacity and longevity. The bead loss increases with the mass of debris accumulated on the pump strainers, which in turn is dependent on the debris concentration versus time in the suppression pool. This paper describes two sets of experiments that quantified the strainer head loss. One set of experiments considered the mixing and settling of fibrous insulation debris and fine iron oxide particles in the suppression pool during and after chugging. These tests used a reduced scale facility which duplicated the kinetic energy per unit water volume to define the concentration of the actual materials in the pool versus time.

  19. Eucalyptus tolerance mechanisms to lanthanum and cerium: subcellular distribution, antioxidant system and thiol pools.

    PubMed

    Shen, Yichang; Zhang, Shirong; Li, Sen; Xu, Xiaoxun; Jia, Yongxia; Gong, Guoshu

    2014-12-01

    Guanglin 9 (Eucalyptus grandis × Eucalyptus urophlla) and Eucalyptus grandis 5 are two eucalyptus species which have been found to grow normally in soils contaminated with lanthanum and cerium, but the tolerance mechanisms are not clear yet. In this study, a pot experiment was conducted to investigate the tolerance mechanisms of the eucalyptus to lanthanum and cerium. Cell walls stored 45.40-63.44% of the metals under lanthanum or cerium stress. Peroxidase and catalase activities enhanced with increasing soil La or Ce concentrations up to 200 mg kg(-1), while there were no obvious changes in glutathione and ascorbate concentrations. Non-protein thiols concentrations increased with increasing treatment levels up to 200 mg kg(-1), and then decreased. Phytochelatins concentrations continued to increase under La or Ce stress. Therefore, the two eucalyptus species are La and Ce tolerant plants, and the tolerance mechanisms include cell wall deposition, antioxidant system response, and thiol compound synthesis. PMID:25303462

  20. Computer simulation of the non-steady-state radioactive labelling of a system of metabolite pools with constant rates of influx and efflux.

    PubMed

    England, P J

    1970-05-01

    The derivation is given of the general case of a differential equation describing the labelling of a single metabolite pool that is subjected to constant rates of influx of radioactive material when the pool size is itself changing at constant rate. A programme, written in ALGOL, is briefly described that solves a set of these differential equations, and that can be used to simulate the radioactive labelling of a system of metabolite pools. A copy of the programme, together with examples of input and output, has been deposited as Supplementary Publication no. SUP 50001 at the National Lending Library for Science and Technology, Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1970), 116, 7.

  1. 7 CFR 1001.7 - Pool plant.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Pool plant. 1001.7 Section 1001.7 Agriculture... Handling Definitions § 1001.7 Pool plant. Pool plant means a plant, unit of plants, or system of plants as specified in paragraphs (a) through (f) of this section, but excluding a plant described in paragraph (h)...

  2. 7 CFR 1124.7 - Pool plant.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 9 2011-01-01 2011-01-01 false Pool plant. 1124.7 Section 1124.7 Agriculture... Regulating Handling Definitions § 1124.7 Pool plant. Pool plant means a plant, unit of plants, or a system of plants as specified in paragraphs (a) through (f) of this section, but excluding a plant specified...

  3. 7 CFR 1030.7 - Pool plant.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 9 2011-01-01 2011-01-01 false Pool plant. 1030.7 Section 1030.7 Agriculture... Handling Definitions § 1030.7 Pool plant. Pool plant means a plant, unit of plants, or system of plants as specified in paragraphs (a) through (f) of this section, but excluding a plant specified in paragraph (h)...

  4. 7 CFR 1001.7 - Pool plant.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 9 2011-01-01 2011-01-01 false Pool plant. 1001.7 Section 1001.7 Agriculture... Handling Definitions § 1001.7 Pool plant. Pool plant means a plant, unit of plants, or system of plants as specified in paragraphs (a) through (f) of this section, but excluding a plant described in paragraph (h)...

  5. 7 CFR 1033.7 - Pool plant.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Pool plant. 1033.7 Section 1033.7 Agriculture... Handling Definitions § 1033.7 Pool plant. Pool plant means a plant, unit of plants, or system of plants as specified in paragraphs (a) through (f) of this section, or a plant specified in paragraph (j) of...

  6. 7 CFR 1033.7 - Pool plant.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 9 2011-01-01 2011-01-01 false Pool plant. 1033.7 Section 1033.7 Agriculture... Handling Definitions § 1033.7 Pool plant. Pool plant means a plant, unit of plants, or system of plants as specified in paragraphs (a) through (f) of this section, or a plant specified in paragraph (j) of...

  7. 7 CFR 1032.7 - Pool plant.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 9 2011-01-01 2011-01-01 false Pool plant. 1032.7 Section 1032.7 Agriculture... Handling Definitions § 1032.7 Pool plant. Pool plant means a plant, unit of plants, or system of plants as specified in paragraphs (a) through (f) of this section, or a plant specified in paragraph (i) of...

  8. 7 CFR 1032.7 - Pool plant.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Pool plant. 1032.7 Section 1032.7 Agriculture... Handling Definitions § 1032.7 Pool plant. Pool plant means a plant, unit of plants, or system of plants as specified in paragraphs (a) through (f) of this section, or a plant specified in paragraph (i) of...

  9. Experimental investigation of nucleate boiling and thin-film evaporation on enhanced silicon surfaces

    NASA Astrophysics Data System (ADS)

    Malla, Shailesh

    The present work consists of two major studies. The first study investigates the effects of surface energy or wettability on nucleate pool boiling and the second study investigates the thin-film evaporative cooling for near junction thermal management. For the first study, effects of surface energy or wettability on critical heat flux (CHF) and boiling heat transfer (BHT) of smooth heated surfaces was studied in saturated pool boiling of water at 1 atm. For this purpose hydrophilic and hydrophobic surfaces were created on one side of 1cm x 1cm double-side polished silicon substrates. A resistive heating layer was applied on the opposite side of each substrate. The surface energies of the created surfaces were characterized by measuring the static contact angles of water sessile drops. To provide a wide range of surface energies, surfaces were made of Teflon (hydrophobic), bare silicon (hydrophilic) and aluminum oxide (most hydrophilic). The measured contact angles on these surfaces were ˜108, ˜57 and ˜13 degrees respectively. The results of pool boiling tests on these surfaces clearly illustrate the connection between surface energy and CHF. CHF was shown to linearly decrease with contact angle increase, from ˜125 W/cm2 on aluminum oxide (most hydrophilic) to nearly one tenth of this value on Teflon (hydrophobic). The most hydrophilic surface also produced increasingly better BHT than plain silicon and Teflon as heat flux increased. However, below ˜5 W/cm2 the hydrophobic surface demonstrated better heat transfer due to earlier onset of nucleate boiling, reducing surface superheats by up to ˜5 degrees relative to the other two surfaces. Above ˜5 W/cm2 the BHT of the hydrophobic surface rapidly deteriorated as superheat increased towards the value at CHF. To further understand the effect of surface energy on pool boiling performance, the growth and departure of bubbles from single nucleating sites on each surface were analyzed from high-speed video recordings

  10. Simulation of Thermal Stratification in BWR Suppression Pools with One Dimensional Modeling Method

    SciTech Connect

    Haihua Zhao; Ling Zou; Hongbin Zhang

    2014-01-01

    The suppression pool in a boiling water reactor (BWR) plant not only is the major heat sink within the containment system, but also provides the major emergency cooling water for the reactor core. In several accident scenarios, such as a loss-of-coolant accident and extended station blackout, thermal stratification tends to form in the pool after the initial rapid venting stage. Accurately predicting the pool stratification phenomenon is important because it affects the peak containment pressure; the pool temperature distribution also affects the NPSHa (available net positive suction head) and therefore the performance of the Emergency Core Cooling System and Reactor Core Isolation Cooling System pumps that draw cooling water back to the core. Current safety analysis codes use zero dimensional (0-D) lumped parameter models to calculate the energy and mass balance in the pool; therefore, they have large uncertainties in the prediction of scenarios in which stratification and mixing are important. While three-dimensional (3-D) computational fluid dynamics (CFD) methods can be used to analyze realistic 3-D configurations, these methods normally require very fine grid resolution to resolve thin substructures such as jets and wall boundaries, resulting in a long simulation time. For mixing in stably stratified large enclosures, the BMIX++ code (Berkeley mechanistic MIXing code in C++) has been developed to implement a highly efficient analysis method for stratification where the ambient fluid volume is represented by one-dimensional (1-D) transient partial differential equations and substructures (such as free or wall jets) are modeled with 1-D integral models. This allows very large reductions in computational effort compared to multi-dimensional CFD modeling. One heat-up experiment performed at the Finland POOLEX facility, which was designed to study phenomena relevant to Nordic design BWR suppression pool including thermal stratification and mixing, is used for

  11. Swimming pools soak up the sun

    SciTech Connect

    Cuoghi, D.; Hesse, P.; Schiller, T.

    1996-05-01

    Solar pool heaters survived the boom and bust solar years of the 1970s and 1980s. Today they are even popular and cost-effective in parts of the country where many people think solar is impractical. This article discusses the following topics: how solar pool heaters work; types of solar pool heater collectors; collector and pump sizing; collector siting and mounting; systems costs and economics; pool covers. 3 figs.

  12. Hysteresis of boiling for different tunnel-pore surfaces

    NASA Astrophysics Data System (ADS)

    Pastuszko, Robert; Piasecka, Magdalena

    2015-05-01

    Analysis of boiling hysteresis on structured surfaces covered with perforated foil is proposed. Hysteresis is an adverse phenomenon, preventing high heat flux systems from thermal stabilization, characterized by a boiling curve variation at an increase and decrease of heat flux density. Experimental data were discussed for three kinds of enhanced surfaces: tunnel structures (TS), narrow tunnel structures (NTS) and mini-fins covered with the copper wire net (NTS-L). The experiments were carried out with water, R-123 and FC-72 at atmospheric pressure. A detailed analysis of the measurement results identified several cases of type I, II and III for TS, NTS and NTS-L surfaces.

  13. Designing pooling systems for noisy high-throughput protein-protein interaction experiments using boolean compressed sensing.

    PubMed

    Mourad, Ramy; Dawy, Zaher; Morcos, Faruck

    2013-01-01

    Group testing, also known as pooling, is a common technique used in high-throughput experiments in molecular biology to significantly reduce the number of tests required to identify rare biological interactions while correcting for experimental noise. Central to the group testing problem are 1) a pooling design that lays out how items are grouped together into pools for testing and 2) a decoder that interprets the results of the tested pools, identifying the active compounds. In this work, we take advantage of decoder guarantees from the field of compressed sensing (CS) to address the problem of efficient and reliable detection of biological interaction in noisy high-throughput experiments. We also use efficient combinatorial algorithms from group testing as well as established measurement matrices from CS to create pooling designs. First, we formulate the group testing problem in terms of a Boolean CS framework. We then propose a low-complexity l1-norm decoder to interpret pooling test results and identify active compounds. We demonstrate the robustness of the proposed l1-norm decoder in simulated experiments with false-positive and false-negative error rates typical of high-throughput experiments. When benchmarked against the current state-of-the-art methods, the proposed l1-norm decoder provides superior error correction for the majority of the cases considered while being notably faster computationally. Additionally, we test the performance of the l1-norm decoder against a real experimental data set, where 12,675 prey proteins were screened against 12 bait proteins. Lastly, we study the impact of different sparse pooling design matrices on decoder performance and show that the shifted transversal design (STD) is the most suitable among the pooling designs surveyed for biological applications of CS. PMID:24407306

  14. Corium quench in deep pool mixing experiments

    SciTech Connect

    Spencer, B.W.; McUmber, L.; Gregorash, D.; Aeschlimann, R.; Sienicki, J.J.

    1985-01-01

    The results of two recent corium-water thermal interaction (CWTI) tests are described in which a stream of molten corium was poured into a deep pool of water in order to determine the mixing behavior, the corium-to-water heat transfer rates, and the characteristic sizes of the quenched debris. The corium composition was 60% UO/sub 2/, 16% ZrO/sub 2/, and 24% stainless steel by weight; its initial temperature was 3080 K, approx.160 K above the oxide phase liquidus temperature. The corium pour stream was a single-phase 2.2 cm dia liquid column which entered the water pool in film boiling at approx.4 m/s. The water subcooling was 6 and 75C in the two tests. Test results showed that with low subcooling, rapid steam generation caused the pool to boil up into a high void fraction regime. In contrast, with large subcooling no net steam generation occurred, and the pool remained relatively quiescent. Breakup of the jet appeared to occur by surface stripping. In neither test was the breakup complete during transit through the 32 cm deep water pool, and molten corium channeled to the base where it formed a melt layer. The characteristic heat transfer rates measured 3.5 MJ/s and 2.7 MJ/s during the fall stage for small and large subcooling, respectively; during the initial stage of bed quench, the surface heat fluxes measured 2.4 MW/m/sup 2/ and 3.7 MW/m/sup 2/, respectively. A small mass of particles was formed in each test, measuring typically 0.1 to 1 mm and 1 to 5 mm dia for the large and small subcooling conditions, respectively. 9 refs., 13 figs., 1 tab.

  15. Development of Flow Boiling and Condensation Experiment on the International Space Station- Normal and Low Gravity Flow Boiling Experiment Development and Test Results

    NASA Technical Reports Server (NTRS)

    Nahra, Henry K.; Hall, Nancy R.; Hasan, Mohammad M.; Wagner, James D.; May, Rochelle L.; Mackey, Jeffrey R.; Kolacz, John S.; Butcher, Robert L.; Frankenfield, Bruce J.; Mudawar, Issam; Konichi, Chris; Hyounsoon, Lee

    2013-01-01

    Flow boiling and condensation have been identified as two key mechanisms for heat transport that are vital for achieving weight and volume reduction as well as performance enhancement in future space systems. Since inertia driven flows are demanding on power usage, lower flows are desirable. However, in microgravity, lower flows are dominated by forces other than inertia (like the capillary force). It is of paramount interest to investigate limits of low flows beyond which the flow is inertial enough to be gravity independent. One of the objectives of the Flow Boiling and Condensation Flight Experiment sets to investigate these limits for flow boiling and condensation. A two-phase flow loop consisting of a Flow Boiling Module and two Condensation Modules has been developed to experimentally study flow boiling condensation heat transfer in the reduced gravity environment provided by the reduced gravity platform. This effort supports the development of a flow boiling and condensation facility for the International Space Station (ISS). The closed loop test facility is designed to deliver the test fluid, FC-72 to the inlet of any one of the test modules at specified thermodynamic and flow conditions. The zero-g-aircraft tests will provide subcooled and saturated flow boiling critical heat flux and flow condensation heat transfer data over wide range of flow velocities. Additionally, these tests will verify the performance of all gravity sensitive components, such as evaporator, condenser and accumulator associated with the two-phase flow loop. We will present in this paper the breadboard development and testing results which consist of detailed performance evaluation of the heater and condenser combination in reduced and normal gravity. We will also present the design of the reduced gravity aircraft rack and the results of the ground flow boiling heat transfer testing performed with the Flow Boiling Module that is designed to investigate flow boiling heat transfer and

  16. Use of a microchip flow-chamber system as a screening test for platelet storage pool disease.

    PubMed

    Minami, Hiroaki; Nogami, Keiji; Ogiwara, Kenichi; Furukawa, Shoko; Hosokawa, Kazuya; Shima, Midori

    2015-08-01

    Platelet storage pool disease (SPD) is a platelet function disorder characterized by a reduction in the number or content of α-granules, dense granules, or both, and is diagnosed by specialized tests. Patients with SPD often present with prolonged bleeding time (BT), but the sensitivity and reproducibility of this test have limitations, often resulting in false negatives. It has recently been reported that an automated microchip flow-chamber system (T-TAS(®)) is useful in the assessment of anti-platelet therapy, and could have potential as a screening test for SPD. We examined the utility of T-TAS in three individuals from one family diagnosed with δ-SPD. The propositus had a mildly prolonged BT, and the standard tests for platelet function were close to the normal range. Whole blood samples were anti-coagulated with hirudin and applied to T-TAS microchips coated with collagen (PL-chips) at shear rates of 1000 and 2000 s(-1). Platelet thrombus formation (PTF) was monitored with a pressure sensor. Markedly depressed PTF was observed in all cases at both shear rates. These findings indicate that T-TAS is highly sensitive to the defect in these patients with SPD, and may represent a good candidate screening test for a wide range of platelet function disorders. PMID:26072294

  17. Use of a microchip flow-chamber system as a screening test for platelet storage pool disease.

    PubMed

    Minami, Hiroaki; Nogami, Keiji; Ogiwara, Kenichi; Furukawa, Shoko; Hosokawa, Kazuya; Shima, Midori

    2015-08-01

    Platelet storage pool disease (SPD) is a platelet function disorder characterized by a reduction in the number or content of α-granules, dense granules, or both, and is diagnosed by specialized tests. Patients with SPD often present with prolonged bleeding time (BT), but the sensitivity and reproducibility of this test have limitations, often resulting in false negatives. It has recently been reported that an automated microchip flow-chamber system (T-TAS(®)) is useful in the assessment of anti-platelet therapy, and could have potential as a screening test for SPD. We examined the utility of T-TAS in three individuals from one family diagnosed with δ-SPD. The propositus had a mildly prolonged BT, and the standard tests for platelet function were close to the normal range. Whole blood samples were anti-coagulated with hirudin and applied to T-TAS microchips coated with collagen (PL-chips) at shear rates of 1000 and 2000 s(-1). Platelet thrombus formation (PTF) was monitored with a pressure sensor. Markedly depressed PTF was observed in all cases at both shear rates. These findings indicate that T-TAS is highly sensitive to the defect in these patients with SPD, and may represent a good candidate screening test for a wide range of platelet function disorders.

  18. Boils

    MedlinePlus

    ... Sections of the JAOCD JAOCD Archive Published Members Online Dermatology Journals Edit This Favorite Name: Category: Share: Yes ... 2/2017 2017 AOCD Spring Current Concepts in Dermatology Meeting more Latest News ... Surveys About AOCD The AOCD was recognized in ...

  19. Marangoni Effects in the Boiling of Binary Fluid Mixtures

    NASA Technical Reports Server (NTRS)

    Ahmed, Sayeed; Carey, Van P.; Motil, Brian

    1996-01-01

    Results of very recent experimental studies indicate that during nucleate boiling in some binary mixture, Marangoni effects augment the gravity driven flow of liquid towards the heated surface. With gravity present, it is impossible to separate the two effects. The reduced gravity environment gives an unique opportunity to explore th role of Marangoni effects on the boiling mechanisms free of gravitational body forces that obscure the role of such effects. However, recent experimental results suggest that under reduced gravity conditions, Marangoni effects is the dominant mechanism of vapor-liquid exchange at the surface for some binary mixture. To further explore such effects, experiments have been conducted with water/2-propanol mixtures at three different concentrations under normal gravity with different orientations of the heater surface and under reduce gravity aboard the DC-9 aircraft at NASA Lewis Research Center. The system pressure was sub atmospheric (approx. 8 kP at 1g(n)) and the bulk liquid temperature varied from low subcooling to near saturation. The molar concentrations of 2-propanol tested were 0.015, 0.025, and 0.1. Boiling curves were obtained both for high gravity (approx. 2g(n)) and reduce gravity (approx. 0.01g(n)). For each concentration of 2-propanol, the critical heat flux has been determined in the flight experiments only for reduced gravity conditions. Comparison of boiling curves and CHF obtained under l-g(n) an reduced gravity indicates that boiling mechanism in this mixtures is nearly independent of gravity. The results also indicate that the Marangoni mechanism is strong enough in these mixtures to sustain the boiling under reduced gravity conditions.

  20. CHIMNEY FOR BOILING WATER REACTOR

    DOEpatents

    Petrick, M.

    1961-08-01

    A boiling-water reactor is described which has vertical fuel-containing channels for forming steam from water. Risers above the channels increase the head of water radially outward, whereby water is moved upward through the channels with greater force. The risers are concentric and the radial width of the space between them is somewhat small. There is a relatively low rate of flow of water up through the radially outer fuel-containing channels, with which the space between the risers is in communication. (AE C)

  1. Boiling significantly promotes photodegradation of perfluorooctane sulfonate.

    PubMed

    Lyu, Xian-Jin; Li, Wen-Wei; Lam, Paul K S; Yu, Han-Qing

    2015-11-01

    The application of photochemical processes for perfluorooctane sulfonate (PFOS) degradation has been limited by a low treatment efficiency. This study reports a significant acceleration of PFOS photodegradation under boiling condition compared with the non-boiling control. The PFOS decomposition rate increased with the increasing boiling intensity, but declined at a higher hydronium level or under oxygenation. These results suggest that the boiling state of solution resulted in higher effective concentrations of reactants at the gas-liquid interface and enhanced the interfacial mass transfer, thereby accelerating the PFOS decomposition. This study broadens our knowledge of PFOS photodegradation process and may have implications for development of efficient photodegradation technologies. PMID:26117498

  2. Boiling significantly promotes photodegradation of perfluorooctane sulfonate.

    PubMed

    Lyu, Xian-Jin; Li, Wen-Wei; Lam, Paul K S; Yu, Han-Qing

    2015-11-01

    The application of photochemical processes for perfluorooctane sulfonate (PFOS) degradation has been limited by a low treatment efficiency. This study reports a significant acceleration of PFOS photodegradation under boiling condition compared with the non-boiling control. The PFOS decomposition rate increased with the increasing boiling intensity, but declined at a higher hydronium level or under oxygenation. These results suggest that the boiling state of solution resulted in higher effective concentrations of reactants at the gas-liquid interface and enhanced the interfacial mass transfer, thereby accelerating the PFOS decomposition. This study broadens our knowledge of PFOS photodegradation process and may have implications for development of efficient photodegradation technologies.

  3. Lattice Boltzmann modeling of boiling heat transfer: The boiling curve and the effects of wettability

    SciTech Connect

    Li, Q.; Kang, Q. J.; Francois, M. M.; He, Y. L.; Luo, K. H.

    2015-03-03

    A hybrid thermal lattice Boltzmann (LB) model is presented to simulate thermal multiphase flows with phase change based on an improved pseudopotential LB approach (Li et al., 2013). The present model does not suffer from the spurious term caused by the forcing-term effect, which was encountered in some previous thermal LB models for liquid–vapor phase change. Using the model, the liquid–vapor boiling process is simulated. The boiling curve together with the three boiling stages (nucleate boiling, transition boiling, and film boiling) is numerically reproduced in the LB community for the first time. The numerical results show that the basic features and the fundamental characteristics of boiling heat transfer are well captured, such as the severe fluctuation of transient heat flux in the transition boiling and the feature that the maximum heat transfer coefficient lies at a lower wall superheat than that of the maximum heat flux. Moreover, the effects of the heating surface wettability on boiling heat transfer are investigated. It is found that an increase in contact angle promotes the onset of boiling but reduces the critical heat flux, and makes the boiling process enter into the film boiling regime at a lower wall superheat, which is consistent with the findings from experimental studies.

  4. Lattice Boltzmann modeling of boiling heat transfer: The boiling curve and the effects of wettability

    DOE PAGESBeta

    Li, Q.; Kang, Q. J.; Francois, M. M.; He, Y. L.; Luo, K. H.

    2015-03-03

    A hybrid thermal lattice Boltzmann (LB) model is presented to simulate thermal multiphase flows with phase change based on an improved pseudopotential LB approach (Li et al., 2013). The present model does not suffer from the spurious term caused by the forcing-term effect, which was encountered in some previous thermal LB models for liquid–vapor phase change. Using the model, the liquid–vapor boiling process is simulated. The boiling curve together with the three boiling stages (nucleate boiling, transition boiling, and film boiling) is numerically reproduced in the LB community for the first time. The numerical results show that the basic featuresmore » and the fundamental characteristics of boiling heat transfer are well captured, such as the severe fluctuation of transient heat flux in the transition boiling and the feature that the maximum heat transfer coefficient lies at a lower wall superheat than that of the maximum heat flux. Moreover, the effects of the heating surface wettability on boiling heat transfer are investigated. It is found that an increase in contact angle promotes the onset of boiling but reduces the critical heat flux, and makes the boiling process enter into the film boiling regime at a lower wall superheat, which is consistent with the findings from experimental studies.« less

  5. Evaluation of correlations of flow boiling heat transfer of R22 in horizontal channels.

    PubMed

    Zhou, Zhanru; Fang, Xiande; Li, Dingkun

    2013-01-01

    The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels.

  6. Bubble dynamics, two-phase flow, and boiling heat transfer in a microgravity environment

    NASA Technical Reports Server (NTRS)

    Chung, Jacob N.

    1994-01-01

    The two-phase bubbly flow and boiling heat transfer in microgravity represents a substantial challenge to scientists and engineers and yet there is an urgent need to seek fundamental understanding in this area for future spacecraft design and space missions. At Washington State University, we have successfully designed, built and tested a 2.1 second drop tower with an innovation airbag deceleration system. Microgravity boiling experiments performed in our 0.6 second Drop Tower produced data flow visualizations that agree with published results and also provide some new understanding concerning flow boiling and microgravity bubble behavior. On the analytical and numerical work, the edge effects of finite divergent electrode plates on the forces experienced by bubbles were investigated. Boiling in a concentric cylinder microgravity and an electric field was numerically predicted. We also completed a feasibility study for microgravity boiling in an acoustic field.

  7. Evaluation of correlations of flow boiling heat transfer of R22 in horizontal channels.

    PubMed

    Zhou, Zhanru; Fang, Xiande; Li, Dingkun

    2013-01-01

    The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels. PMID:23956695

  8. Direct Numerical Simulation of Boiling Multiphase Flows: State-of-the-Art, Modeling, Algorithmic and Computer Needs

    SciTech Connect

    Nourgaliev R.; Knoll D.; Mousseau V.; Berry R.

    2007-04-01

    The state-of-the-art for Direct Numerical Simulation (DNS) of boiling multiphase flows is reviewed, focussing on potential of available computational techniques, the level of current success for their applications to model several basic flow regimes (film, pool-nucleate and wall-nucleate boiling -- FB, PNB and WNB, respectively). Then, we discuss multiphysics and multiscale nature of practical boiling flows in LWR reactors, requiring high-fidelity treatment of interfacial dynamics, phase-change, hydrodynamics, compressibility, heat transfer, and non-equilibrium thermodynamics and chemistry of liquid/vapor and fluid/solid-wall interfaces. Finally, we outline the framework for the {\\sf Fervent} code, being developed at INL for DNS of reactor-relevant boiling multiphase flows, with the purpose of gaining insight into the physics of multiphase flow regimes, and generating a basis for effective-field modeling in terms of its formulation and closure laws.

  9. Flash boiling from carbon foams for high-heat-flux transient cooling

    NASA Astrophysics Data System (ADS)

    Engerer, J. D.; Fisher, T. S.

    2016-07-01

    Flash boiling of a liquid pool results in an event characterized by rapid phase change and, as a result, high rates of expansion and cooling. Because of the potential advantages of such characteristics for convective heat transfer, flash boiling is considered here for the purpose of cooling transient heat loads. The event has the positive characteristics mentioned as well as rapid response (˜10 ms) and high initial rates of phase change, and then quickly decays to a steady-state regime analogous to pool boiling. The performance of the cooling mechanism is evaluated using an objective function derived from the effect of temperature on the efficiency of optical transmission in a diode-pumped solid-state laser. Statistical surrogate models based on the experimental results are used to predict optimal run conditions. Experiments using these predicted parameters show that flash boiling can maintain device temperature to within ±6.1 °C through a pulsed 5 s heat flux of 68 W cm-2 and to within ±1.4 °C for a heat flux of 39 W cm-2.

  10. Suppression Pool Mixing and Condensation Tests in PUMA Facility

    SciTech Connect

    Ling Cheng; Kyoung Suk Woo; Mamoru Ishii; Jaehyok Lim; Han, James

    2006-07-01

    Condensation of steam with non-condensable in the form of jet flow or bubbly flow inside the suppression pool is an important phenomenon on determining the containment pressure of a passively safe boiling water reactor. 32 cases of pool mixing and condensation test have been performed in Purdue University Multi-Dimensional Integral Test Assembly (PUMA) facility under the sponsor of the U.S. Nuclear Regulatory Commission to investigate thermal stratification and pool mixing inside the suppression pool during the reactor blowdown period. The test boundary conditions, such as the steam flow rate, the noncondensable gas flow rate, the initial water temperature, the pool initial pressure and the vent opening submergence depth, which covers a wide range of prototype (SBWR-600) conditions during Loss of Coolant Accident (LOCA) were obtained from the RELAP5 calculation. The test results show that steam is quickly condensed at the exit of the vent opening. For pure steam injection or low noncondensable injection cases, only the portion above the vent opening in the suppression pool is heated up by buoyant plumes. The water below the vent opening can be heated up slowly through conduction. The test results also show that the degree of thermal stratification in suppression pool is affected by the vent opening submergence depth, the pool initial pressure and the steam injection rate. And it is slightly affected by the initial water temperature. From these tests it is concluded that the pool mixing is strongly affected by the noncondensable gas flow rate. (authors)

  11. Direct numerical simulations of EHD-enhanced film boiling

    NASA Astrophysics Data System (ADS)

    Sharifi, Payam; Esmaeeli, Asghar

    2007-11-01

    Boiling is one of the most efficient modes of heat exchange. Yet, in applications involving boiling in micro-devices or under microgravity conditions it is extremely desirable to enhance the heat transfer rate even further to increase the efficiency of these systems. An enhancement mechanism that is particularly attractive is the one due to application of an electric field to the bulk of fluid. Here, the dielectric mismatch between the liquid and vapor phases results in convective flows and, therefore, a higher heat transfer coefficient. While the enhancement of heat and mass transfer by electric field has been known for decades, a fundamental understanding of the problem is still lacking primarily due to difficulties in conduct of experimental and theoretical studies. The current advances in development of numerical methods for direct simulations of multiphase flows, however, have opened up enormous possibilities for detailed understanding of this problem. Such simulations can make it possible to capture the highly unsteady dynamics of the boiling flows. Here, we present a front tracking algorithm in conjunction with a leaky-dielectric electrohydrodynamic (EHD) model to study EHD-enhanced film boiling on horizontal surfaces. The goal is to compare the average wall Nusselt number at different strengths of the electric field and to correlate the macroscopic behavior of the flow with the dynamics of the phase boundary.

  12. Large-scale Generation of Patterned Bubble Arrays on Printed Bi-functional Boiling Surfaces.

    PubMed

    Choi, Chang-Ho; David, Michele; Gao, Zhongwei; Chang, Alvin; Allen, Marshall; Wang, Hailei; Chang, Chih-hung

    2016-01-01

    Bubble nucleation control, growth and departure dynamics is important in understanding boiling phenomena and enhancing nucleate boiling heat transfer performance. We report a novel bi-functional heterogeneous surface structure that is capable of tuning bubble nucleation, growth and departure dynamics. For the fabrication of the surface, hydrophobic polymer dot arrays are first printed on a substrate, followed by hydrophilic ZnO nanostructure deposition via microreactor-assisted nanomaterial deposition (MAND) processing. Wettability contrast between the hydrophobic polymer dot arrays and aqueous ZnO solution allows for the fabrication of heterogeneous surfaces with distinct wettability regions. Heterogeneous surfaces with various configurations were fabricated and their bubble dynamics were examined at elevated heat flux, revealing various nucleate boiling phenomena. In particular, aligned and patterned bubbles with a tunable departure frequency and diameter were demonstrated in a boiling experiment for the first time. Taking advantage of our fabrication method, a 6 inch wafer size heterogeneous surface was prepared. Pool boiling experiments were also performed to demonstrate a heat flux enhancement up to 3X at the same surface superheat using bi-functional surfaces, compared to a bare stainless steel surface. PMID:27034255

  13. Large-scale Generation of Patterned Bubble Arrays on Printed Bi-functional Boiling Surfaces

    PubMed Central

    Choi, Chang-Ho; David, Michele; Gao, Zhongwei; Chang, Alvin; Allen, Marshall; Wang, Hailei; Chang, Chih-hung

    2016-01-01

    Bubble nucleation control, growth and departure dynamics is important in understanding boiling phenomena and enhancing nucleate boiling heat transfer performance. We report a novel bi-functional heterogeneous surface structure that is capable of tuning bubble nucleation, growth and departure dynamics. For the fabrication of the surface, hydrophobic polymer dot arrays are first printed on a substrate, followed by hydrophilic ZnO nanostructure deposition via microreactor-assisted nanomaterial deposition (MAND) processing. Wettability contrast between the hydrophobic polymer dot arrays and aqueous ZnO solution allows for the fabrication of heterogeneous surfaces with distinct wettability regions. Heterogeneous surfaces with various configurations were fabricated and their bubble dynamics were examined at elevated heat flux, revealing various nucleate boiling phenomena. In particular, aligned and patterned bubbles with a tunable departure frequency and diameter were demonstrated in a boiling experiment for the first time. Taking advantage of our fabrication method, a 6 inch wafer size heterogeneous surface was prepared. Pool boiling experiments were also performed to demonstrate a heat flux enhancement up to 3X at the same surface superheat using bi-functional surfaces, compared to a bare stainless steel surface. PMID:27034255

  14. The science of pooling

    SciTech Connect

    Gilbert, E.

    1995-10-01

    The pooling of data from radon studies is described. Pooling refers to the analysis of original data from several studies, not meta-analysis in which summary measures from published data are analyzed. A main objective for pooling is to reduce uncertainty and to obtain more precise estimates of risk than would be available from any single study.

  15. 48 CFR 232.470 - Advance payment pool.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 3 2012-10-01 2012-10-01 false Advance payment pool. 232... Items 232.470 Advance payment pool. (a) An advance payment pool agreement— (1) Is a means of financing... addition to any other advance payment pool agreement at a single contractor location when it is...

  16. 48 CFR 232.470 - Advance payment pool.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 3 2014-10-01 2014-10-01 false Advance payment pool. 232... Items 232.470 Advance payment pool. (a) An advance payment pool agreement— (1) Is a means of financing... addition to any other advance payment pool agreement at a single contractor location when it is...

  17. 48 CFR 232.470 - Advance payment pool.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 3 2013-10-01 2013-10-01 false Advance payment pool. 232... Items 232.470 Advance payment pool. (a) An advance payment pool agreement— (1) Is a means of financing... addition to any other advance payment pool agreement at a single contractor location when it is...

  18. 48 CFR 232.470 - Advance payment pool.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 3 2011-10-01 2011-10-01 false Advance payment pool. 232... Items 232.470 Advance payment pool. (a) An advance payment pool agreement— (1) Is a means of financing... addition to any other advance payment pool agreement at a single contractor location when it is...

  19. 48 CFR 232.470 - Advance payment pool.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Advance payment pool. 232... Items 232.470 Advance payment pool. (a) An advance payment pool agreement— (1) Is a means of financing... addition to any other advance payment pool agreement at a single contractor location when it is...

  20. Modeling acid-gas generation from boiling chloride brines

    PubMed Central

    2009-01-01

    Background This study investigates the generation of HCl and other acid gases from boiling calcium chloride dominated waters at atmospheric pressure, primarily using numerical modeling. The main focus of this investigation relates to the long-term geologic disposal of nuclear waste at Yucca Mountain, Nevada, where pore waters around waste-emplacement tunnels are expected to undergo boiling and evaporative concentration as a result of the heat released by spent nuclear fuel. Processes that are modeled include boiling of highly concentrated solutions, gas transport, and gas condensation accompanied by the dissociation of acid gases, causing low-pH condensate. Results Simple calculations are first carried out to evaluate condensate pH as a function of HCl gas fugacity and condensed water fraction for a vapor equilibrated with saturated calcium chloride brine at 50-150°C and 1 bar. The distillation of a calcium-chloride-dominated brine is then simulated with a reactive transport model using a brine composition representative of partially evaporated calcium-rich pore waters at Yucca Mountain. Results show a significant increase in boiling temperature from evaporative concentration, as well as low pH in condensates, particularly for dynamic systems where partial condensation takes place, which result in enrichment of HCl in condensates. These results are in qualitative agreement with experimental data from other studies. Conclusion The combination of reactive transport with multicomponent brine chemistry to study evaporation, boiling, and the potential for acid gas generation at the proposed Yucca Mountain repository is seen as an improvement relative to previously applied simpler batch evaporation models. This approach allows the evaluation of thermal, hydrological, and chemical (THC) processes in a coupled manner, and modeling of settings much more relevant to actual field conditions than the distillation experiment considered. The actual and modeled distillation

  1. Modeling acid-gas generation from boiling chloride brines

    SciTech Connect

    Zhang, Guoxiang; Spycher, Nicolas; Sonnenthal, Eric; Steefel, Carl

    2009-11-16

    This study investigates the generation of HCl and other acid gases from boiling calcium chloride dominated waters at atmospheric pressure, primarily using numerical modeling. The main focus of this investigation relates to the long-term geologic disposal of nuclear waste at Yucca Mountain, Nevada, where pore waters around waste-emplacement tunnels are expected to undergo boiling and evaporative concentration as a result of the heat released by spent nuclear fuel. Processes that are modeled include boiling of highly concentrated solutions, gas transport, and gas condensation accompanied by the dissociation of acid gases, causing low-pH condensate. Simple calculations are first carried out to evaluate condensate pH as a function of HCl gas fugacity and condensed water fraction for a vapor equilibrated with saturated calcium chloride brine at 50-150 C and 1 bar. The distillation of a calcium-chloride-dominated brine is then simulated with a reactive transport model using a brine composition representative of partially evaporated calcium-rich pore waters at Yucca Mountain. Results show a significant increase in boiling temperature from evaporative concentration, as well as low pH in condensates, particularly for dynamic systems where partial condensation takes place, which result in enrichment of HCl in condensates. These results are in qualitative agreement with experimental data from other studies. The combination of reactive transport with multicomponent brine chemistry to study evaporation, boiling, and the potential for acid gas generation at the proposed Yucca Mountain repository is seen as an improvement relative to previously applied simpler batch evaporation models. This approach allows the evaluation of thermal, hydrological, and chemical (THC) processes in a coupled manner, and modeling of settings much more relevant to actual field conditions than the distillation experiment considered. The actual and modeled distillation experiments do not represent

  2. Outbreak of boils in an Alaskan village

    PubMed Central

    Landen, Michael G; McCumber, Barbara J; Asay, Elvin D; Egeland, Grace M

    2000-01-01

    Objective To determine whether taking steam baths was associated with furunculosis and to evaluate possible risk factors for the occurrence of boils during a large outbreak in Alaska. Design A cohort study of village residents, a case-control study, and assessment of environmental cultures taken from steam baths. Setting Village in southwestern Alaska. Participants 1 adult member from 77 of the 92 house-holds in the village was interviewed; 115 residents with at least one boil occurring between January 1 and December 12, 1996 were considered to be cases; 209 residents without a boil acted as the control group. All 459 village residents were included in the cohort study. Main outcome measure Rate of infection among all residents and residents who regularly took steam baths, risk factors for infection, and relative risk of infection. Results 115 people (25%) had had at least one boil. Men were more likely to have had a boil than women (relative risk 1.5; 95% confidence interval 1.1 to 2.2). The highest rate of infection was among people ages 25-34 years (32/76; 42%). No children younger than 2 years had had boils. Boils were associated with using a steam bath (odds ratio 8.1; 3.3 to 20.1). Among those who used a steam bath, the likelihood of developing boils was reduced by routinely sitting on a towel while bathing, which women were more likely to do, and bathing with fewer than 8 people. Of the 93 samples taken from steam baths, one Staphylococcus aureus isolate was obtained from a bench in an outer dressing room. Conclusion Using a steam bath was associated with developing boils in this outbreak in a village in Alaska. People should be advised to sit on towels while using steam baths. PMID:10778372

  3. Boiling and Evaporation on Micro/nanoengineered Surfaces

    NASA Astrophysics Data System (ADS)

    Dai, Xianming

    Two-phase transport is widely used in energy conversion and storage, energy efficiency and thermal management. Surface roughness and interfacial wettability are two major impact factors for two-phase transport. Micro/nanostructures play important roles in varying the surface roughness and improving interfacial wettability. In this doctoral study, five types of micro/nanoengineered surfaces were developed to systematically study the impacts of interfacial wettability and flow structures on nucleate boiling and capillary evaporation. These surfaces include: 1) superhydrophilic atomic layer deposition (ALD) coatings; 2) partially hydrophobic and partially hydrophilic composite interfaces; 3) micromembrane-enhanced hybrid wicks; 4) superhydrophilic micromembrane-enhnaced hybrid wicks, and 5) functionalized carbon nanotube coated micromembrane-enhnaced hybrid wicks. Type 1 and 2 surfaces were developed to investigate the impacts of intrinsic superhydrophilicity and hydrophobic-hydrophilic composite wettability on nucleate boiling. Superhydrophilicity was achieved by depositing nano-thick ALD TiO 2 coatings, which were used to enable intrinsically superhydrophilic boiling surfaces on the microscale copper woven meshes. Critical heat flux (CHF) was substantially increased because of the superwetting property and delayed local dryout. Carbon nanotube (CNT) enabled partially hydrophobic and partially hydrophilic interfaces were developed to form ideal cavities for nucleate boiling. The hydrophobic-hydrophilic composite interfaces were synthesized from functionalized multiwall carbon nanotubes (FMWCNTs) by introducing hydrophilic functional groups on the surfaces of pristine MWCNTs. The nanoscale FMWCNTs with heterogeneous wettabilities were coated on the micromeshes to form hierarchical surfaces, which effectively increase the heat transfer coefficient (HTC) and CHF of pool boiling. To enhance capillary evaporation, micromembrane-enhanced capillary evaporating surfaces, i

  4. 13 CFR 120.611 - Pools backing Pool Certificates.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Pools backing Pool Certificates... Secondary Market Certificates § 120.611 Pools backing Pool Certificates. (a) Pool characteristics. As set forth in the Program Guide, each Pool must have: (1) A minimum number of guaranteed portions of...

  5. 13 CFR 120.611 - Pools backing Pool Certificates.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 13 Business Credit and Assistance 1 2014-01-01 2014-01-01 false Pools backing Pool Certificates... Secondary Market Certificates § 120.611 Pools backing Pool Certificates. (a) Pool characteristics. As set forth in the Program Guide, each Pool must have: (1) A minimum number of guaranteed portions of...

  6. 13 CFR 120.611 - Pools backing Pool Certificates.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 13 Business Credit and Assistance 1 2011-01-01 2011-01-01 false Pools backing Pool Certificates... Secondary Market Certificates § 120.611 Pools backing Pool Certificates. (a) Pool characteristics. As set forth in the Program Guide, each Pool must have: (1) A minimum number of guaranteed portions of...

  7. 13 CFR 120.611 - Pools backing Pool Certificates.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 13 Business Credit and Assistance 1 2013-01-01 2013-01-01 false Pools backing Pool Certificates... Secondary Market Certificates § 120.611 Pools backing Pool Certificates. (a) Pool characteristics. As set forth in the Program Guide, each Pool must have: (1) A minimum number of guaranteed portions of...

  8. 13 CFR 120.611 - Pools backing Pool Certificates.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Pools backing Pool Certificates... Secondary Market Certificates § 120.611 Pools backing Pool Certificates. (a) Pool characteristics. As set forth in the Program Guide, each Pool must have: (1) A minimum number of guaranteed portions of...

  9. Criticality in the slowed-down boiling crisis at zero gravity.

    PubMed

    Charignon, T; Lloveras, P; Chatain, D; Truskinovsky, L; Vives, E; Beysens, D; Nikolayev, V S

    2015-05-01

    Boiling crisis is a transition between nucleate and film boiling. It occurs at a threshold value of the heat flux from the heater called CHF (critical heat flux). Usually, boiling crisis studies are hindered by the high CHF and short transition duration (below 1 ms). Here we report on experiments in hydrogen near its liquid-vapor critical point, in which the CHF is low and the dynamics slow enough to be resolved. As under such conditions the surface tension is very small, the experiments are carried out in the reduced gravity to preserve the conventional bubble geometry. Weightlessness is created artificially in two-phase hydrogen by compensating gravity with magnetic forces. We were able to reveal the fractal structure of the contour of the percolating cluster of the dry areas at the heater that precedes the boiling crisis. We provide a direct statistical analysis of dry spot areas that confirms the boiling crisis at zero gravity as a scale-free phenomenon. It was observed that, in agreement with theoretical predictions, saturated boiling CHF tends to zero (within the precision of our thermal control system) in zero gravity, which suggests that the boiling crisis may be observed at any heat flux provided the experiment lasts long enough. PMID:26066249

  10. Criticality in the slowed-down boiling crisis at zero gravity.

    PubMed

    Charignon, T; Lloveras, P; Chatain, D; Truskinovsky, L; Vives, E; Beysens, D; Nikolayev, V S

    2015-05-01

    Boiling crisis is a transition between nucleate and film boiling. It occurs at a threshold value of the heat flux from the heater called CHF (critical heat flux). Usually, boiling crisis studies are hindered by the high CHF and short transition duration (below 1 ms). Here we report on experiments in hydrogen near its liquid-vapor critical point, in which the CHF is low and the dynamics slow enough to be resolved. As under such conditions the surface tension is very small, the experiments are carried out in the reduced gravity to preserve the conventional bubble geometry. Weightlessness is created artificially in two-phase hydrogen by compensating gravity with magnetic forces. We were able to reveal the fractal structure of the contour of the percolating cluster of the dry areas at the heater that precedes the boiling crisis. We provide a direct statistical analysis of dry spot areas that confirms the boiling crisis at zero gravity as a scale-free phenomenon. It was observed that, in agreement with theoretical predictions, saturated boiling CHF tends to zero (within the precision of our thermal control system) in zero gravity, which suggests that the boiling crisis may be observed at any heat flux provided the experiment lasts long enough.

  11. Criticality in the slowed-down boiling crisis at zero gravity

    NASA Astrophysics Data System (ADS)

    Charignon, T.; Lloveras, P.; Chatain, D.; Truskinovsky, L.; Vives, E.; Beysens, D.; Nikolayev, V. S.

    2015-05-01

    Boiling crisis is a transition between nucleate and film boiling. It occurs at a threshold value of the heat flux from the heater called CHF (critical heat flux). Usually, boiling crisis studies are hindered by the high CHF and short transition duration (below 1 ms). Here we report on experiments in hydrogen near its liquid-vapor critical point, in which the CHF is low and the dynamics slow enough to be resolved. As under such conditions the surface tension is very small, the experiments are carried out in the reduced gravity to preserve the conventional bubble geometry. Weightlessness is created artificially in two-phase hydrogen by compensating gravity with magnetic forces. We were able to reveal the fractal structure of the contour of the percolating cluster of the dry areas at the heater that precedes the boiling crisis. We provide a direct statistical analysis of dry spot areas that confirms the boiling crisis at zero gravity as a scale-free phenomenon. It was observed that, in agreement with theoretical predictions, saturated boiling CHF tends to zero (within the precision of our thermal control system) in zero gravity, which suggests that the boiling crisis may be observed at any heat flux provided the experiment lasts long enough.

  12. Zero Boil Off Cryogen Storage for Future Launchers

    NASA Technical Reports Server (NTRS)

    Valentian, D.; Plachta, D.; Kittel, P.; Hastings, L. J.; Salerno, Louis J.; Arnold, James O. (Technical Monitor)

    2001-01-01

    be to actively cool the shield in the hydrogen tank to reduce the parasitic losses. This would allow the use of less expensive, presently available coolers (80 K vs. 20 K) and potentially simplify the system by requiring only a single compressor on the pad amd a single disconnect line. The compressor could be a hefty commercial unit, with only the cold head requiring expensive flight development and qualification. While this is actually a reduced boil off configuration rather than a zero-boil off case, if the cryogen loss could be cut significantly, the increase in hold time and reduced need for draining and refilling the propellant tanks could meet the vehicle operations needs in the majority of instances.Bearing in mind the potential benefits of ZBO, NASA AMES and SNECMA Moteurs decided to exchange their technical views on the subject. This paper will present a preliminary analysis for a multi-mission module using a fairly low thrust cryogenic engine and ZBO during cruise. Initial mass is 5.5. tons (in ETO). The cryogenic engine will be used near each periapsis in order to minimize the AV requirement. The payload obtained by this propulsion system is compared to a classical storable bipropellant propulsion system for several cases (e. g. Mars lander, Jupiter orbiter, Saturn orbiter). For the Jupiter and Saturn cases, the power source could be an RTG or a large parabolic mirror illuminating a solar panel. It is shown -that - due to its much larger specific impulse - the cryogenic ZBO solution provides much higher payloads, especially for exploration missions involving landing on planets, asteroids, comets, or other celestial bodies.

  13. Why Is NASA Boiling Fluids in Space?

    NASA Video Gallery

    Convection and buoyancy work differently in space than on Earth. Learn how NASA uses this information and applies it to everyday life. Boiling fluids in space is easier than it is on Earth. Learn m...

  14. 21 CFR 872.6710 - Boiling water sterilizer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Boiling water sterilizer. 872.6710 Section 872...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered device that consists of a container for boiling...

  15. 21 CFR 872.6710 - Boiling water sterilizer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Boiling water sterilizer. 872.6710 Section 872...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered device that consists of a container for boiling...

  16. 21 CFR 872.6710 - Boiling water sterilizer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Boiling water sterilizer. 872.6710 Section 872...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered device that consists of a container for boiling...

  17. 21 CFR 872.6710 - Boiling water sterilizer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Boiling water sterilizer. 872.6710 Section 872...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered device that consists of a container for boiling...

  18. 21 CFR 872.6710 - Boiling water sterilizer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Boiling water sterilizer. 872.6710 Section 872...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered device that consists of a container for boiling...

  19. SUPERHEATING IN A BOILING WATER REACTOR

    DOEpatents

    Treshow, M.

    1960-05-31

    A boiling-water reactor is described in which the steam developed in the reactor is superheated in the reactor. This is accomplished by providing means for separating the steam from the water and passing the steam over a surface of the fissionable material which is not in contact with the water. Specifically water is boiled on the outside of tubular fuel elements and the steam is superheated on the inside of the fuel elements.

  20. High flux film and transition boiling

    SciTech Connect

    Witte, L.C.

    1993-02-01

    An investigation was conducted on the potential for altering the boiling curve through effects of high velocity and high subcooling. Experiments using water and Freon-113 flowing over cylindrical electrical heaters in crossflow were made to see how velocity and subcooling affect the boiling curve, especially the film and transition boiling regions. We sought subcooling levels down to near the freezing points of these two liquids to prove the concept that the critical heat flux and the minimum heat flux could be brought together, thereby averting the transition region altogether. Another emphasis was to gain insight into how the various boiling regions could be represented mathematically on various parts of heating surface. Motivation for the research grew out of a realization that the effects of very high subcooling and velocity might be to avert the transition boiling altogether so that the unstable part of the boiling curve would not limit the application of high flux devices to temperatures less than the burnout temperatures. Summaries of results from the study are described. It shows that the potential for averting, the transition region is good, and points the way to further research that is needed to demonstrate the potential.

  1. High flux film and transition boiling

    NASA Astrophysics Data System (ADS)

    Witte, L. C.

    1993-02-01

    An investigation was conducted on the potential for altering the boiling curve through effects of high velocity and high subcooling. Experiments using water and Freon-113 flowing over cylindrical electrical heaters in crossflow were made to see how velocity and subcooling affect the boiling curve, especially the film and transition boiling regions. We sought subcooling levels down to near the freezing points of these two liquids to prove the concept that the critical heat flux and the minimum heat flux could be brought together, thereby averting the transition region altogether. Another emphasis was to gain insight into how the various boiling regions could be represented mathematically on various parts of the heating surface. Motivation for the research grew out of a realization that the effects of very high subcooling and velocity might be to avert the transition boiling altogether so that the unstable part of the boiling curve would not limit the application of high flux devices to temperatures less than the burnout temperatures. Summaries of results from the study are described. It shows that the potential for averting the transition region is good and points the way to further research that is needed to demonstrate the potential.

  2. Cold pool dissipation

    NASA Astrophysics Data System (ADS)

    Grant, Leah D.; Heever, Susan C.

    2016-02-01

    The mechanisms by which sensible heat fluxes (SHFs) alter cold pool characteristics and dissipation rates are investigated in this study using idealized two-dimensional numerical simulations and an environment representative of daytime, dry, continental conditions. Simulations are performed with no SHFs, SHFs calculated using a bulk formula, and constant SHFs for model resolutions with horizontal (vertical) grid spacings ranging from 50 m (25 m) to 400 m (200 m). In the highest resolution simulations, turbulent entrainment of environmental air into the cold pool is an important mechanism for dissipation in the absence of SHFs. Including SHFs enhances cold pool dissipation rates, but the processes responsible for the enhanced dissipation differ depending on the SHF formulation. The bulk SHFs increase the near-surface cold pool temperatures, but their effects on the overall cold pool characteristics are small, while the constant SHFs influence the near-surface environmental stability and the turbulent entrainment rates into the cold pool. The changes to the entrainment rates are found to be the most significant of the SHF effects on cold pool dissipation. SHFs may also influence the timing of cold pool-induced convective initiation by altering the environmental stability and the cold pool intensity. As the model resolution is coarsened, cold pool dissipation is found to be less sensitive to SHFs. Furthermore, the coarser resolution simulations not only poorly but sometimes wrongly represent the SHF impacts on the cold pools. Recommendations are made regarding simulating the interaction of cold pools with convection and the land surface in cloud-resolving models.

  3. Influence of the heater material on the critical heat load at boiling of liquids on surfaces with different sizes

    NASA Astrophysics Data System (ADS)

    Anokhina, E. V.

    2010-05-01

    Data on critical heat loads q cr for the saturated and unsaturated pool boiling of water and ethanol under atmospheric pressure are reported. It is found experimentally that the critical heat load does not necessarily coincide with the heat load causing burnout of the heater, which should be taken into account. The absolute values of q cr for the boiling of water and ethanol on copper surfaces 65, 80, 100, 120, and 200 μm in diameter; tungsten surface 100 μm in diameter; and nichrome surface 100 μm in diameter are obtained experimentally.

  4. Heat transfer from internally heated hemispherical pools

    SciTech Connect

    Gabor, J.D.; Ellsion, P.G.; Cassulo, J.C.

    1980-01-01

    Experiments were conducted on heat transfer from internally heated ZnSO/sub 4/-H/sub 2/O pools to the walls of hemispherical containers. This experimental technique provides data for a heat transfer system that has to date been only theoretically treated. Three different sizes of copper hemispherical containers were used: 240, 280, 320 mm in diameter. The pool container served both as a heat transfer surface and as an electrode. The opposing electrode was a copper disk, 50 mm in diameter located at the top of the pool in the center. The top surface of the pool was open to the atmosphere.

  5. Bench-scale screening tests for a boiling sodium-potassium alloy solar receiver

    SciTech Connect

    Moreno, J.B.; Moss, T.A.

    1993-06-01

    Bench-scale tests were carried out in support of the design of a second-generation 75-kW{sub t} reflux pool-boiler solar receiver. The receiver will be made from Haynes Alloy 230 and will contain the sodium-potassium alloy NaK-78. The bench-scale tests used quartz-lamp-heated boilers to screen candidate boiling-stabilization materials and methods at temperatures up to 750{degree}C. Candidates that provided stable boiling were tested for hot-restart behavior. Poor stability was obtained with single 1/4-inch diameter patches of powdered metal hot-press-sintered onto the wetted side of the heat-input area. Laser-drilled and electric-discharge-machined cavities in the heated surface also performed poorly. Small additions of xenon, and heated-surface tilt out of the vertical dramatically improved poor boiling stability; additions of helium or oxygen did not. The most stable boiling was obtained when the entire heat-input area was covered by a powdered-metal coating. The effect of heated-area size was assessed for one coating: at low incident fluxes, when even this coating performed poorly, increasing the heated-area size markedly improved boiling stability. Good hot-restart behavior was not observed with any candidate, although results were significantly better with added xenon in a boiler shortened from 3 to 2 feet. In addition to the screening tests, flash-radiography imaging of metal-vapor bubbles during boiling was attempted. Contrary to the Cole-Rohsenow correlation, these bubble-size estimates did not vary with pressure; instead they were constant, consistent with the only other alkali metal measurements, but about 1/2 their size.

  6. Bench-scale screening tests for a boiling sodium-potassium alloy solar receiver

    NASA Astrophysics Data System (ADS)

    Moreno, J. B.; Moss, T. A.

    1993-06-01

    Bench-scale tests were carried out in support of the design of a second-generation 75-kW(sub t) reflux pool-boiler solar receiver. The receiver will be made from Haynes Alloy 230 and will contain the sodium-potassium alloy NaK-78. The bench-scale tests used quartz lamp heated boilers to screen candidate boiling stabilization materials and methods at temperatures up to 750 degree C. Candidates that provided stable boiling were tested for hot-restart behavior. Poor stability was obtained with single 1/4-inch diameter patches of powdered metal hot press sintered onto the wetted side of the heat-input area. Laser-drilled and electric discharge machined cavities in the heated surface also performed poorly. Small additions of xenon, and heated-surface tilt out of the vertical, dramatically improved poor boiling stability; additions of helium or oxygen did not. The most stable boiling was obtained when the entire heat-input area was covered by a powdered-metal coating. The effect of heated-area size was assessed for one coating: at low incident fluxes, when even this coating performed poorly, increasing the heated-area size markedly improved boiling stability. Good hot-restart behavior was not observed with any candidate, although results were significantly better with added xenon in a boiler shortened from 3 to 2 feet. In addition to the screening tests, flash-radiography imaging of metal-vapor bubbles during boiling was attempted. Contrary to the Cole-Rohsenow correlation, these bubble-size estimates did not vary with pressure; instead they were constant, consistent with the only other alkali metal measurements, but about 1/2 their size.

  7. [Functional distinction of secreting pools of the pancreas and participation of the pancreatic ductal system in the development of the pancreatic secret properties].

    PubMed

    Korot'ko, G F; Voskanian, S E; Gladkiĭ, E Iu; Makarova, T M; Bulgakov, V A

    2002-08-01

    Acute experiments on dogs with separate secretion of the pancreatic enzymes, either stimulated or inhibited, from two lobes of pancreas, and investigation into the character of kinetics of the secretion from 5-7 ductal pools of the pancreas showed the functional specifics, with the device of ductal valves and microdepot of a secret of the pancreas ductal system playing an important role. The conclusion is made that the final secret of pancreas removed to the duodenum is a product of a secret-motor activation of non-equipotentional microregions of the gland, being the components of an intervisceral dynamical mosaic.

  8. Dynamics of Vapour Bubbles in Nucleate Boiling. 1; Basic Equations of Bubble Evolution

    NASA Technical Reports Server (NTRS)

    Buyevich, Yu A.; Webbon, Bruce W.; Callaway, Robert (Technical Monitor)

    1995-01-01

    We consider the behaviour of a vapour bubble formed at a nucleation site on a heated horizontal wall. There is no forced convection of an ambient liquid, and the bubble is presumably separated from the wall by a thin liquid microlayer. The energy conservation law results in a variational equation for the mechanical energy of the whole system consisting of the bubble and liquid. It leads to a set of two strongly nonlinear equations which govern bubble expansion and motion of its centre of mass. A supplementary equation to find out the vapour temperature follows from consideration of heat transfer to the bubble, both from the bulk of surrounding liquid and through the microlayer. The average thickness of the microlayer is shown to increase monotonously with time as the bubble meniscus spreads along the wall. Bubble expansion is driven by the pressure head between vapour inside and liquid far away from the bubble, with due allowance for surface tension and gravity effects. It is resisted by inertia of liquid being placed into motion as the bubble grows. The inertia originates also a force that presses the bubble to the wall. This force is counteracted by the buoyancy and an effective surface tension force that tends to transform the bubble into a sphere. The analysis brings about quite a new formulation of the familiar problem of bubble growth and detachment under conditions of nucleate pool boiling.

  9. 10 CFR 36.33 - Irradiator pools.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... purification system designed to be capable of maintaining the water during normal operation at a conductivity..., irradiator pools must either: (1) Have a water-tight stainless steel liner or a liner metallurgically... water level that could allow water to drain out of the pool. Pipes that have intakes more than 0.5...

  10. 10 CFR 36.33 - Irradiator pools.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... purification system designed to be capable of maintaining the water during normal operation at a conductivity..., irradiator pools must either: (1) Have a water-tight stainless steel liner or a liner metallurgically... water level that could allow water to drain out of the pool. Pipes that have intakes more than 0.5...

  11. Designing and Evaluating Health Systems Level Hypertension Control Interventions for African-Americans: Lessons from a Pooled Analysis of Three Cluster Randomized Trials

    PubMed Central

    Pavlik, Valory N.; Chan, Wenyaw; Hyman, David J.; Feldman, Penny; Ogedegbe, Gbenga; Schwartz, Joseph E.; McDonald, Margaret; Einhorn, Paula; Tobin, Jonathan N.

    2015-01-01

    Objectives African-Americans (AAs) have a high prevalence of hypertension and their blood pressure (BP) control on treatment still lags behind other groups. In 2004, NHLBI funded five projects that aimed to evaluate clinically feasible interventions to effect changes in medical care delivery leading to an increased proportion of AA patients with controlled BP. Three of the groups performed a pooled analysis of trial results to determine: 1) the magnitude of the combined intervention effect; and 2) how the pooled results could inform the methodology for future health-system level BP interventions. Methods Using a cluster randomized design, the trials enrolled AAs with uncontrolled hypertension to test interventions targeting a combination of patient and clinician behaviors. The 12-month Systolic BP (SBP) and Diastolic BP (DBP) effects of intervention or control cluster assignment were assessed using mixed effects longitudinal regression modeling. Results 2,015 patients representing 352 clusters participated across the three trials. Pooled BP slopes followed a quadratic pattern, with an initial decline, followed by a rise toward baseline, and did not differ significantly between intervention and control clusters: SBP linear coefficient = −2.60±0.21 mmHg per month, p<0.001; quadratic coefficient = 0.167± 0.02 mmHg/month, p<0.001; group by time interaction group by time group x linear time coefficient=0.145 ± 0.293, p=0.622; group x quadratic time coefficient= −0.017 ± 0.026, p=0.525). Results were similar for DBP. The individual sites did not have significant intervention effects when analyzed separately. Conclusion Investigators planning behavioral trials to improve BP control in health systems serving AAs should plan for small effect sizes and employ a “run-in” period in which BP can be expected to improve in both experimental and control clusters. PMID:25808682

  12. Effect of Running Parameters on Flow Boiling Instabilities in Microchannels.

    PubMed

    Zong, Lu-Xiang; Xu, Jin-Liang; Liu, Guo-Hua

    2015-04-01

    Flow boiling instability (FBI) in microchannels is undesirable because they can induce the mechanical vibrations and disturb the heat transfer characteristics. In this study, the synchronous optical visualization experimental system was set up. The pure acetone liquid was used as the working fluid, and the parallel triangle silicon microchannel heat sink was designed as the experimental section. With the heat flux ranging from 0-450 kW/m2 the microchannel demand average pressure drop-heater length (Δp(ave)L) curve for constant low mass flux, and the demand pressure drop-mass flux (Δp(ave)G) curve for constant length on main heater surface were obtained and studied. The effect of heat flux (q = 188.28, 256.00, and 299.87 kW/m2), length of main heater surface (L = 4.5, 6.25, and 8.00 mm), and mass flux (G = 188.97, 283.45, and 377.94 kg/m2s) on pressure drops (Ap) and temperatures at the central point of the main heater surface (Twc) were experimentally studied. The results showed that, heat flux, length of the main heater surface, and mass flux were identified as the important parameters to the boiling instability process. The boiling incipience (TBI) and critical heat flux (CHF) were early induced for the lower mass flux or the main heater surface with longer length. With heat flux increasing, the pressure drops were linearly and slightly decreased in the single liquid region but increased sharply in the two phase flow region, in which the flow boiling instabilities with apparent amplitude and long period were more easily triggered at high heat flux. Moreover, the system pressure was increased with the increase of the heat flux.

  13. Effect of Running Parameters on Flow Boiling Instabilities in Microchannels.

    PubMed

    Zong, Lu-Xiang; Xu, Jin-Liang; Liu, Guo-Hua

    2015-04-01

    Flow boiling instability (FBI) in microchannels is undesirable because they can induce the mechanical vibrations and disturb the heat transfer characteristics. In this study, the synchronous optical visualization experimental system was set up. The pure acetone liquid was used as the working fluid, and the parallel triangle silicon microchannel heat sink was designed as the experimental section. With the heat flux ranging from 0-450 kW/m2 the microchannel demand average pressure drop-heater length (Δp(ave)L) curve for constant low mass flux, and the demand pressure drop-mass flux (Δp(ave)G) curve for constant length on main heater surface were obtained and studied. The effect of heat flux (q = 188.28, 256.00, and 299.87 kW/m2), length of main heater surface (L = 4.5, 6.25, and 8.00 mm), and mass flux (G = 188.97, 283.45, and 377.94 kg/m2s) on pressure drops (Ap) and temperatures at the central point of the main heater surface (Twc) were experimentally studied. The results showed that, heat flux, length of the main heater surface, and mass flux were identified as the important parameters to the boiling instability process. The boiling incipience (TBI) and critical heat flux (CHF) were early induced for the lower mass flux or the main heater surface with longer length. With heat flux increasing, the pressure drops were linearly and slightly decreased in the single liquid region but increased sharply in the two phase flow region, in which the flow boiling instabilities with apparent amplitude and long period were more easily triggered at high heat flux. Moreover, the system pressure was increased with the increase of the heat flux. PMID:26353523

  14. 3-Bromopyruvate induces rapid human prostate cancer cell death by affecting cell energy metabolism, GSH pool and the glyoxalase system.

    PubMed

    Valenti, Daniela; Vacca, Rosa A; de Bari, Lidia

    2015-12-01

    3-bromopyruvate (3-BP) is an anti-tumour drug effective on hepatocellular carcinoma and other tumour cell types, which affects both glycolytic and mitochondrial targets, depleting cellular ATP pool. Here we tested 3-BP on human prostate cancer cells showing, differently from other tumour types, efficient ATP production and functional mitochondrial metabolism. We found that 3-BP rapidly induced cultured androgen-insensitive (PC-3) and androgen-responsive (LNCaP) prostate cancer cell death at low concentrations (IC(50) values of 50 and 70 μM, respectively) with a multimodal mechanism of action. In particular, 3-BP-treated PC-3 cells showed a selective, strong reduction of glyceraldeide 3-phosphate dehydrogenase activity, due to the direct interaction of the drug with the enzyme. Moreover, 3-BP strongly impaired both glutamate/malate- and succinate-dependent mitochondrial respiration, membrane potential generation and ATP synthesis, concomitant with the inhibition of respiratory chain complex I, II and ATP synthase activities. The drastic reduction of cellular ATP levels and depletion of GSH pool, associated with significant increase in cell oxidative stress, were found after 3-BP treatment of PC-3 cells. Interestingly, the activity of both glyoxalase I and II, devoted to the elimination of the cytotoxic methylglyoxal, was strongly inhibited by 3-BP. Both N-acetylcysteine and aminoguanidine, GSH precursor and methylglyoxal scavenger, respectively, prevented 3-BP-induced PC-3 cell death, showing that impaired cell antioxidant and detoxifying capacities are crucial events leading to cell death. The provided information on the multi-target cytotoxic action of 3-BP, finally leading to PC-3 cell necrosis, might be useful for future development of 3-BP as a therapeutic option for prostate cancer treatment. PMID:26530987

  15. Boiling heat transfer enhancement of nanofluids on a smooth surface with agitation

    NASA Astrophysics Data System (ADS)

    Kong, Xin; Qi, Baojin; Wei, Jinjia; Li, Wei; Ding, Jie; Zhang, Yonghai

    2016-02-01

    The pool boiling heat transfer performance on a smooth silicon chip surface with agitation was experimentally investigated in this study. The nanofluids (Ag/alcohol) of 0.02 % volume concentration and ethyl alcohol with purification over 99.9 % were the two contrast working fluids. For each group, subcoolings of 40, 50 and 60 K were conducted under atmospheric pressure. To enhance the heat transfer performance, an agitating device was fixed above the top of the chip. The experimental results indicated that nanofluids could enhance the heat transfer performance especially in the nucleate boiling region. The heat transfer coefficient was significantly increased with nanofluids, while the critical heat flux (CHF) was nearly not changed. In the agitation Reynolds number of 20,300, the heat transfer performance of nanofluids was significantly enhanced in the convection region, and the CHF was increased by more than 25 % for all groups. This boiling phenomenon was observed for both nanofluids and alcohol groups. Meanwhile, the boiling curves of different liquid subcoolings in the nucleate region were quite similar to each other under agitation.

  16. Effect of surface micro-texture on bubble dynamics and boiling critical heat flux

    NASA Astrophysics Data System (ADS)

    Dhillon, Navdeep; Buongiorno, Jacopo; Varanasi, Kripa

    2014-11-01

    We present results of an experimental study on the effect of surface texture on the dynamics of bubble growth and departure in pool boiling of water and correlate them to the measured values of critical heat flux (CHF) on these surfaces. Although it is well known that surface roughness or micro-texture has a significant impact on macroscale boiling parameters such as boiling heat transfer coefficient (HTC) and CHF, the physics underlying these processes is not well understood. Using high speed optical and infrared (IR) imaging, we explored the mechanism of single bubble growth and departure on micro-textured surfaces fabricated using photolithography techniques. Interestingly, we observed that the introduction of the micro-texture not only completely changed bubble dynamics and boiling surface thermal characteristics but there was a clear correlation between the micro-texture parameters and the salient bubble characteristics such as the departure diameter and frequency. To explain these results, we propose a physical model based on micro-texture-induced surface microflows supplementing the conventional bubble growth and departure theory based on buoyancy and capillary pinning forces, and verify it using CHF measurements. Funding for this project is provided by Chevron Corp.

  17. A microgravity boiling and convective condensation experiment

    NASA Technical Reports Server (NTRS)

    Kachnik, Leo; Lee, Doojeong; Best, Frederick; Faget, Nanette

    1987-01-01

    A boiling and condensing test article consisting of two straight tube boilers, one quartz and one stainless steel, and two 1.5 m long glass-in-glass heat exchangers, on 6 mm ID and one 10 mm ID, was flown on the NASA KC-135 0-G aircraft. Using water as the working fluid, the 5 kw boiler produces two phase mixtures of varying quality for mass flow rates between 0.005 and 0.1 kg/sec. The test section is instrumented at eight locations with absolute and differential pressure transducers and thermocouples. A gamma densitometer is used to measure void fraction, and high speed photography records the flow regimes. A three axis accelerometer provides aircraft acceleration data (+ or - 0.01G). Data are collected via an analog-to-digital conversion and data acquisition system. Bubbly, annular, and slug flow regimes were observed in the test section under microgravity conditions. Flow oscillations were observed for some operating conditions and the effect of the 2-G pullout prior to the 0-G period was observed by continuously recording data throughout the parabolas. A total fo 300 parabolas was flown.

  18. Enhancements of Nucleate Boiling Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Zhang, Nengli; Chao, David F.; Yang, W. J.

    2000-01-01

    This paper presents two means for enhancing nucleate boiling and critical heat flux under microgravity conditions: using micro-configured metal-graphite composites as the boiling surface and dilute aqueous solutions of long-chain alcohols as the working fluid. In the former, thermocapillary force induced by temperature difference between the graphite-fiber tips and the metal matrix plays an important role in bubble detachment. Thus boiling-heat transfer performance does not deteriorate in a reduced-gravity environment. In the latter cases, the surface tension-temperature gradient of the long-chain alcohol solutions turns positive as the temperature exceeds a certain value. Consequently, the Marangoni effect does not impede, but rather aids in bubble departure from the heating surface. This feature is most favorable in microgravity. As a result, the bubble size of departure is substantially reduced at higher frequencies. Based on the existing experimental data, and a two-tier theoretical model, correlation formulas are derived for nucleate boiling on the copper-graphite and aluminum-graphite composite surfaces, in both the isolated and coalesced bubble regimes. In addition, performance equations for nucleate boiling and critical heat flux in dilute aqueous solutions of long-chain alcohols are obtained.

  19. 3. POOL, DAM, AND INTAKE TO PIPELINE LEADING TO FISH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. POOL, DAM, AND INTAKE TO PIPELINE LEADING TO FISH WHEEL, LOOKING WEST-NORTHWEST. - Santa Ana River Hydroelectric System, Bear Creek Diversion Dam & Confluence Pool, Redlands, San Bernardino County, CA

  20. 2. CONFLUENCE POOL, DETAIL OF TUNNEL PORTAL WITH WATER ENTERING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. CONFLUENCE POOL, DETAIL OF TUNNEL PORTAL WITH WATER ENTERING FROM SANTA ANA RIVER. VIEW TO NORTHEAST. - Santa Ana River Hydroelectric System, Bear Creek Diversion Dam & Confluence Pool, Redlands, San Bernardino County, CA

  1. 1. WATER ENTERING CONFLUENCE POOL FROM BEAR CREEK AT LEFT, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. WATER ENTERING CONFLUENCE POOL FROM BEAR CREEK AT LEFT, AND FROM SANTA ANA RIVER THROUGH TUNNEL #0 AT RIGHT. VIEW TO NORTHEAST. - Santa Ana River Hydroelectric System, Bear Creek Diversion Dam & Confluence Pool, Redlands, San Bernardino County, CA

  2. A model for calculation of RCS pressure during reflux boiling under reduced inventory conditions and its assessment against PKL data. [Reactor Cooling Systems (RCS)

    SciTech Connect

    Palmrose, D.E. ); Mandl, R.M. )

    1991-01-01

    There has been recent interest in the United States concerning the loss of residual heat removal system (RHRS) under reduced coolant inventory conditions for pressurized water reactors. This issue is also of interest in the Federal Republic of Germany and an experiment was performed in the integral PKL-HI experimental facility at Siemens-KWU to supply applicable data. Recently, an NRC-sponsored effort has been undertaken at the Idaho-National Engineering Laboratory to identify and analyze the important thermal-hydraulic phenomena in pressurized water reactors following the long term loss-of-RHRS during reduced inventory operation. The thermal-hydraulic response of a closed reactor coolant system during such a transient is investigated in this report. Some of the specific processes investigated include: reflux condensation in the steam generators, the corresponding pressure increase in the reactor coolant system, and void fraction distributions on the primary side of the system. Mathematical models of these and other physical processes Experiment B4.5.

  3. Swimming pool. View of aisle between swimming pool and seating ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Swimming pool. View of aisle between swimming pool and seating area. Non-original spa pool is partially visible on right. - Jewish Community Center of San Francisco, 3200 California Street, San Francisco, San Francisco County, CA

  4. 13 CFR 120.1704 - Pool Loans eligible for Pooling.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ..., construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered by... zoos—712130 (“Zoos and Botanical Gardens”). (b) SBA review of a Pool Loan prior to pool formation....

  5. 13 CFR 120.1704 - Pool Loans eligible for Pooling.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ..., construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered by... zoos—712130 (“Zoos and Botanical Gardens”). (b) SBA review of a Pool Loan prior to pool formation....

  6. 13 CFR 120.1704 - Pool Loans eligible for Pooling.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ..., construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered by... zoos—712130 (“Zoos and Botanical Gardens”). (b) SBA review of a Pool Loan prior to pool formation....

  7. 13 CFR 120.1704 - Pool Loans eligible for Pooling.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ..., construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered by... zoos—712130 (“Zoos and Botanical Gardens”). (b) SBA review of a Pool Loan prior to pool formation....

  8. 13 CFR 120.1704 - Pool Loans eligible for Pooling.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ..., construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered by... zoos—712130 (“Zoos and Botanical Gardens”). (b) SBA review of a Pool Loan prior to pool formation....

  9. The extent of the influence and flux estimation of volatile mercury from the aeration pool in a typical coal-fired power plant equipped with a seawater flue gas desulfurization system.

    PubMed

    Sun, Lumin; Feng, Lifeng; Yuan, Dongxing; Lin, Shanshan; Huang, Shuyuan; Gao, Liangming; Zhu, Yong

    2013-02-01

    Before being discharged, the waste seawater from the flue gas desulfurization system of coal-fired power plants contains a large amount of mercury, and is treated in aeration pools. During this aeration process, part of the mercury enters the atmosphere, but only very limited impact studies concerning this have been carried out. Taking a typical Xiamen power plant as an example, the present study targeted the elemental mercury emitted from the aeration pool. Concentrations of dissolved gaseous mercury as high as 1.14 ± 0.17 ng·L(-1) were observed in the surface waste seawater in the aeration pool, and gaseous elemental mercury (GEM) as high as 10.94 ± 1.89 ng·m(-3) was found in the air above the pool. To investigate the area affected by this GEM through air transfer, the total mercury in the dust and topsoil samples around the aeration pool were analyzed. Much higher values were found compared to those at a reference site. Environmental factors other than solar radiation had limited influence on the concentrations of the mercury species in the pool. A simulation device was built in our laboratory to study the flux of mercury from the aeration pool into the air. The results showed that more than 0.59 kg of mercury was released from the aeration pool every year, occupying 0.3% of the total mercury in the waste seawater. The transfer of mercury from water to air during the aeration pool and its environmental influence should not be ignored.

  10. The extent of the influence and flux estimation of volatile mercury from the aeration pool in a typical coal-fired power plant equipped with a seawater flue gas desulfurization system.

    PubMed

    Sun, Lumin; Feng, Lifeng; Yuan, Dongxing; Lin, Shanshan; Huang, Shuyuan; Gao, Liangming; Zhu, Yong

    2013-02-01

    Before being discharged, the waste seawater from the flue gas desulfurization system of coal-fired power plants contains a large amount of mercury, and is treated in aeration pools. During this aeration process, part of the mercury enters the atmosphere, but only very limited impact studies concerning this have been carried out. Taking a typical Xiamen power plant as an example, the present study targeted the elemental mercury emitted from the aeration pool. Concentrations of dissolved gaseous mercury as high as 1.14 ± 0.17 ng·L(-1) were observed in the surface waste seawater in the aeration pool, and gaseous elemental mercury (GEM) as high as 10.94 ± 1.89 ng·m(-3) was found in the air above the pool. To investigate the area affected by this GEM through air transfer, the total mercury in the dust and topsoil samples around the aeration pool were analyzed. Much higher values were found compared to those at a reference site. Environmental factors other than solar radiation had limited influence on the concentrations of the mercury species in the pool. A simulation device was built in our laboratory to study the flux of mercury from the aeration pool into the air. The results showed that more than 0.59 kg of mercury was released from the aeration pool every year, occupying 0.3% of the total mercury in the waste seawater. The transfer of mercury from water to air during the aeration pool and its environmental influence should not be ignored. PMID:23305917

  11. Results from Boiling Temperature Measurements for Saturated Solutions in the Systems NaCl + KNO{sub 3} + H{sub 2}O, NaNO{sub 3} + KNO{sub 3} + H{sub 2}O, and NaCl + NaNO{sub 3} + KNO{sub 3} + H{sub 2}O

    SciTech Connect

    Rard, J A

    2004-10-04

    Boiling temperature measurements have been made for saturated ternary solutions of NaCl + KNO{sub 3} + H{sub 2}O and NaNO{sub 3} + KNO{sub 3} + H{sub 2}O over the full solute mole fraction range, along with the limiting binary solutions NaCl + H{sub 2}O, NaNO{sub 3} + H{sub 2}O, and KNO{sub 3} + H{sub 2}O. Boiling temperatures have also been measured for the quaternary NaCl + NaNO{sub 3} + KNO{sub 3} + H{sub 2}O mixtures with KNO{sub 3}:NaNO{sub 3} mole ratios of 1.01 and 1.19, which corresponding to the eutectic ratio and a near-eutectic ratio for the NaNO{sub 3} + KNO{sub 3} + H{sub 2}O subsystem. The maximum boiling temperature found for the NaCl + KNO{sub 3} + H{sub 2}O system is 134 C and for the NaNO{sub 3} + KNO{sub 3} + H{sub 2}O system is 160 C, but boiling temperatures as high as 196 C were measured the NaCl + NaNO{sub 3} + KNO{sub 3} + H{sub 2}O system. These mixture compositions correspond to the major mineral assemblages that are predicted to control the deliquescence relative humidity of salts found by leaching dust samples from the proposed nuclear repository at Yucca Mountain, Nevada.

  12. Rhizobins, a Group of Peptides in the Free-Amino-Acid Pool of the Soybean-Rhizobium System

    PubMed Central

    Garay, Andrew S.; Ahlgren, Joy A.; Gonzalez, Mark A.; Stasney, Mark A.; Madtes, Paul C.

    1986-01-01

    Free-living Rhizobium (according to Bergey's Manual of Systematic Bacteriology, [1984, The Williams & Wilkins Co., Baltimore], Bradyrhizobium) japonicum was found to release a peptide into the nutrient media. Soybean nodules contained this peptide and exuded it into the soil. The name “rhizobin A” is suggested for this peptide. Nodules also contained another peptide, rhizobin B, as well as an unidentified, ninhydrin-positive compound, rhizobin C. The three peptides were confined to the free-amino-acid pool of the soluble fraction and eluted consecutively from a cation-exchange column. Rhizobin A was isolated in a highly purified form; its molecular mass was approximately 1,600 daltons as determined by Sephadex gel filtration and mass spectrometry. The amino-acid composition could be determined only approximately, because a long time was necessary for acid hydrolysis, possibly due to unusual linkages. The rhizobin concentration in soybean nodules continually increased during 50 days of growth, from 2 to approximately 400 μg/g (fresh weight). When combined nitrogen was added to nodulated soybean and subsequently removed, nitrogenase activity, nodulation, and nodule growth first decreased and then recovered. The relative amount of rhizobin A followed a similar pattern. Rhizobins were not detected in the roots, stems, and leaves of nodulated soybean plants. They were present in Lupinus nodules, but absent in alder nodules. PMID:16347004

  13. NUCLEAR SUPERHEATER FOR BOILING WATER REACTOR

    DOEpatents

    Holl, R.J.; Klecker, R.W.; Graham, C.B.

    1962-05-15

    A description is given of a boiling water reactor having a superheating region integral with the core. The core consists essentially of an annular boiling region surrounding an inner superheating region. Both regions contain fuel elements and are separated by a cylindrical wall, perforations being provided in the lower portion of the cylindrical wall to permit circulation of a common water moderator between the two regions. The superheater region comprises a plurality of tubular fuel assemblies through which the steam emanating from the boiling region passes to the steam outlet. Each superheater fuel assembly has an outer double-walled cylinder, the double walls being concentrically spaced and connected together at their upper ends but open at the bottom to provide for differential thermal expansion of the inner and outer walls. Gas is entrapped in the annulus between the walls which acts as an insulating space between the fissionable material inside and the moderator outside. (AEC)

  14. Thermodynamics of Flow Boiling Heat Transfer

    NASA Astrophysics Data System (ADS)

    Collado, F. J.

    2003-05-01

    Convective boiling in sub-cooled water flowing through a heated channel is essential in many engineering applications where high heat flux needs to be accommodated. It has been customary to represent the heat transfer by the boiling curve, which shows the heat flux versus the wall-minus-saturation temperature difference. However it is a rather complicated problem, and recent revisions of two-phase flow and heat transfer note that calculated values of boiling heat transfer coefficients present many uncertainties. Quite recently, the author has shown that the average thermal gap in the heated channel (the wall temperature minus the average temperature of the coolant) was tightly connected with the thermodynamic efficiency of a theoretical reversible engine placed in this thermal gap. In this work, whereas this correlation is checked again with data taken by General Electric (task III) for water at high pressure, a possible connection between this wall efficiency and the reversible-work theorem is explored.

  15. Experimental and analytical study of a boiling collector in thermal siphon operation

    SciTech Connect

    Silva, M. da; Eugenia, M.

    1992-01-01

    The purpose of this study is to analytically and experimentally evaluate the performance of a boiling solar collector in thermal siphon operation so that, in future work, solar collectors can be optimized for boiling operation. A new procedure, based on boiling heat transfer fundamentals, is developed to estimate the rate of energy gain in the collector. The temperature of the absorber plate is determined from the simultaneous solution of the rate of energy absorbed by the collector and the rate of energy used in boiling as a function of vapor bubble density, the energy required for bubble formation, and the volumetric flow rate through the collector. Since the volumetric flow rate could not be predicted theoretically, experimentally estimated values are used in the numerical calculation. This model is an improvement over previous models which assume that the total mass flow rate that flows through the collector boils, when in reality just a small percent of this mass flow boils and most of it is recirculated. To validate the analytical model, the thermal efficiency and the absorber plate temperature of two collector-condenser systems are experimentally determined. Measurements with both a conventional sheet with tube and a waffled flat plate collector indicate the importance of collector geometry. The two-phase thermal siphon system operates at practically the same thermal efficiency as the hydronic single-phase system, but it uses one less pump, the net rate of useful energy transfer in the two-phase system is higher than in the single-phase system. When boiling collectors are designed for two-phase operation, they may out-perform hydronic collectors.

  16. Boiling as household water treatment in Cambodia: a longitudinal study of boiling practice and microbiological effectiveness.

    PubMed

    Brown, Joseph; Sobsey, Mark D

    2012-09-01

    This paper focuses on the consistency of use and microbiological effectiveness of boiling as it is practiced in one study site in peri-urban Cambodia. We followed 60 randomly selected households in Kandal Province over 6 months to collect longitudinal data on water boiling practices and effectiveness in reducing Escherichia coli in household drinking water. Despite > 90% of households reporting that they used boiling as a means of drinking water treatment, an average of only 31% of households had boiled water on hand at follow-up visits, suggesting that actual use may be lower than self-reported use. We collected 369 matched untreated and boiled water samples. Mean reduction of E. coli was 98.5%; 162 samples (44%) of boiled samples were free of E. coli (< 1 colony-forming unit [cfu]/100 mL), and 270 samples (73%) had < 10 cfu/100 mL. Storing boiled water in a covered container was associated with safer product water than storage in an uncovered container.

  17. Boiling as Household Water Treatment in Cambodia: A Longitudinal Study of Boiling Practice and Microbiological Effectiveness

    PubMed Central

    Brown, Joseph; Sobsey, Mark D.

    2012-01-01

    This paper focuses on the consistency of use and microbiological effectiveness of boiling as it is practiced in one study site in peri-urban Cambodia. We followed 60 randomly selected households in Kandal Province over 6 months to collect longitudinal data on water boiling practices and effectiveness in reducing Escherichia coli in household drinking water. Despite > 90% of households reporting that they used boiling as a means of drinking water treatment, an average of only 31% of households had boiled water on hand at follow-up visits, suggesting that actual use may be lower than self-reported use. We collected 369 matched untreated and boiled water samples. Mean reduction of E. coli was 98.5%; 162 samples (44%) of boiled samples were free of E. coli (< 1 colony-forming unit [cfu]/100 mL), and 270 samples (73%) had < 10 cfu/100 mL. Storing boiled water in a covered container was associated with safer product water than storage in an uncovered container. PMID:22826487

  18. The boiling point of stratospheric aerosols.

    NASA Technical Reports Server (NTRS)

    Rosen, J. M.

    1971-01-01

    A photoelectric particle counter was used for the measurement of aerosol boiling points. The operational principle involves raising the temperature of the aerosol by vigorously heating a portion of the intake tube. At or above the boiling point, the particles disintegrate rather quickly, and a noticeable effect on the size distribution and concentration is observed. Stratospheric aerosols appear to have the same volatility as a solution of 75% sulfuric acid. Chemical analysis of the aerosols indicates that there are other substances present, but that the sulfate radical is apparently the major constituent.

  19. CONTINUOUS ANALYZER UTILIZING BOILING POINT DETERMINATION

    DOEpatents

    Pappas, W.S.

    1963-03-19

    A device is designed for continuously determining the boiling point of a mixture of liquids. The device comprises a distillation chamber for boiling a liquid; outlet conduit means for maintaining the liquid contents of said chamber at a constant level; a reflux condenser mounted above said distillation chamber; means for continuously introducing an incoming liquid sample into said reflux condenser and into intimate contact with vapors refluxing within said condenser; and means for measuring the temperature of the liquid flowing through said distillation chamber. (AEC)

  20. BOILING SLURRY REACTOR AND METHOD FO CONTROL

    DOEpatents

    Petrick, M.; Marchaterre, J.F.

    1963-05-01

    The control of a boiling slurry nuclear reactor is described. The reactor consists of a vertical tube having an enlarged portion, a steam drum at the top of the vertical tube, and at least one downcomer connecting the steam drum and the bottom of the vertical tube, the reactor being filled with a slurry of fissionabie material in water of such concentration that the enlarged portion of the vertical tube contains a critical mass. The slurry boils in the vertical tube and circulates upwardly therein and downwardly in the downcomer. To control the reactor by controlling the circulation of the slurry, a gas is introduced into the downcomer. (AEC)

  1. Pools for the Handicapped.

    ERIC Educational Resources Information Center

    American School and University, 1979

    1979-01-01

    Three institutions in Ohio now stress hydrotherapy and water recreation as important parts of individual educational programs for the handicapped. Specially designed and adapted pools provide freedom of movement and ego building as well as physical education and recreation. (Author)

  2. Vitamin D Pooling Project

    Cancer.gov

    The Vitamin D Pooling Project of Rarer Cancers brought together investigators from 10 cohorts to conduct a large prospective epidemiologic study of the association between vitamin D status and seven rarer cancers.

  3. Weld pool phenomena

    SciTech Connect

    David, S.A.; Vitek, J.M.; Zacharia, T.; DebRoy, T.

    1994-09-01

    During welding, the composition, structure and properties of the welded structure are affected by the interaction of the heat source with the metal. The interaction affects the fluid flow, heat transfer and mass transfer in the weld pool, and the solidification behavior of the weld metal. In recent years, there has been a growing recognition of the importance of the weld pool transport processes and the solid state transformation reactions in determining the composition, structure and properties of the welded structure. The relation between the weld pool transport processes and the composition and structure is reviewed. Recent applications of various solidification theories to welding are examined to understand the special problems of weld metal solidification. The discussion is focussed on the important problems and issues related to weld pool transport phenomena and solidification. Resolution of these problems would be an important step towards a science based control of composition, structure and properties of the weld metal.

  4. Swimming pool granuloma

    MedlinePlus

    Aquarium granuloma; Fish tank granuloma ... Risks include exposure to swimming pools, salt water aquariums, or ocean fish. ... Wash hands and arms thoroughly after cleaning aquariums. Or, wear rubber gloves when cleaning.

  5. A simplified model of decontamination by BWR steam suppression pools

    SciTech Connect

    Powers, D.A.

    1997-05-01

    Phenomena that can decontaminate aerosol-laden gases sparging through steam suppression pools of boiling water reactors during reactor accidents are described. Uncertainties in aerosol properties, aerosol behavior within gas bubbles, and bubble behavior in plumes affect predictions of decontamination by steam suppression pools. Uncertainties in the boundary and initial conditions that are dictated by the progression of severe reactor accidents and that will affect predictions of decontamination by steam suppression pools are discussed. Ten parameters that characterize boundary and initial condition uncertainties, nine parameters that characterize aerosol property and behavior uncertainties, and eleven parameters that characterize uncertainties in the behavior of bubbles in steam suppression pools are identified. Ranges for the values of these parameters and subjective probability distributions for parametric values within the ranges are defined. These uncertain parameters are used in Monte Carlo uncertainty analyses to develop uncertainty distributions for the decontamination that can be achieved by steam suppression pools and the size distribution of aerosols that do emerge from such pools. A simplified model of decontamination by steam suppression pools is developed by correlating features of the uncertainty distributions for total decontamination factor, DF(total), mean size of emerging aerosol particles, d{sub p}, and the standard deviation of the emerging aerosol size distribution, {sigma}, with pool depth, H. Correlations of the median values of the uncertainty distributions are suggested as the best estimate of decontamination by suppression pools. Correlations of the 10 percentile and 90 percentile values of the uncertainty distributions characterize the uncertainty in the best estimates. 295 refs., 121 figs., 113 tabs.

  6. Study of the depression of incipient boiling temperature and the enhancement of critical heat flux induced by ultrasonic wave on horizontal plate facing upward and downward

    SciTech Connect

    Ohtake, Hiroyasu; Koizumi, Yasuo

    1999-07-01

    The effects of an ultrasonic wave on nucleate-boiling heat transfer, focusing on depression of the incipient boiling temperature and enhancement of the critical heat flux (CHF) on horizontal plate facing upward and downward, were examined. Experiments were conducted using a copper thin film and saturated R-113 liquid for a pool condition at 0.10 MPa. The incipient boiling temperature was depressed by the ultrasonic wave incidence up to 10K in reheating experiments where the heat transfer surface had been immersed in the liquid following the previous boiling experiment. On the other hand, it was minimally affected when the boiling experiment started immediately after the test surface was immersed into the liquid. These results were considered to be related to the number of active nucleation sites available. The decrease of the incipient boiling temperature as the power of the ultrasonic wave was increased, however, did not depend on the frequency. It was pointed out that the depression of the incipient boiling temperature was caused by the local pressure increase caused by the ultrasonic wave incidence. The CHF was increased by the ultrasonic wave incidence up to a factor of five and increased by the ultrasonic wave incidence up to a factor of five and increased with the power of the ultrasonic wave. The enhancement of the CHF was caused by acoustic flow near the heating surface: the coalesce bubble on the heating surface was collapsed by the acoustic flow.

  7. Boiling Heat Transfer Measurements on Highly Conductive Surfaces Using Microscale Heater and Temperature Arrays

    NASA Technical Reports Server (NTRS)

    Kim, J.; Bae, S. W.; Whitten, M. W.; Mullen, J. D.; Quine, R. W.; Kalkur, T. S.

    1999-01-01

    Two systems have been developed to study boiling heat transfer on the microscale. The first system utilizes a 32 x 32 array of diodes to measure the local temperature fluctuations during boiling on a silicon wafer heated from below. The second system utilizes an array of 96 microscale heaters each maintained at constant surface temperature using electronic feedback loops. The power required to keep each heater at constant temperature is measured, enabling the local heat transfer coefficient to be determined. Both of these systems as well as some preliminary results are discussed.

  8. To pool or not to pool

    SciTech Connect

    Powell, J.

    1998-07-01

    In world electricity markets, third party access to transmission and distribution networks on non-discriminatory terms is available to generators and retail suppliers. Some market participants may believe that they are able to negotiate better terms and more market share through bilateral contracts than they would be able to obtain in a pool. Hence such companies will either argue against the development of a pool or seek to make membership of it optional. These companies are therefore seeking to ensure their continued ability to exercise their market power. Inevitably, those companies who would suffer in this form of market will advocate a more transparent arrangement where the market power of other organizations is curbed. The physical nature of the country and plant is also an important factor. Hydro-electric plant can, within water limitations, react very quickly to changing demand. These plant do not therefore require elaborate operating schedules hence market prices can be set ignoring physical plant characteristics. The ability of fossil fuel plant to respond is highly dependent on the operating condition of the plant. These generators need to plan their operations well in advance hence prices cannot be set in complete disregard of the generating plants' ability to meet the resulting schedule. The development of competitive markets is not, however, solely driven by commercial issues. Political and economic considerations such as stranded assets and the protection of indigenous industries, such as coal mines, can greatly influence the nature of the markets. Most countries have accepted the wisdom of having some form of pool. The choice of market mechanism will therefore be driven by: Physical constraints of the country infrastructure and plant; Market power of participants; and Political pressures on the Government. Of these factors political pressures tend to carry the greatest influence.

  9. An Investigation of Graduate Scientists' Understandings of Evaporation and Boiling.

    ERIC Educational Resources Information Center

    Goodwin, Alan; Orlik, Yuri

    2000-01-01

    Uses a video presentation of six situations relating to the evaporation and boiling of liquids and the escape of dissolved gases from solution and investigates graduate scientists' understanding of the concepts of boiling and evaporation. (Author/YDS)

  10. The Plausibility of Boiling Geysers on Triton

    NASA Technical Reports Server (NTRS)

    Duxbury, N. S.; Brown, R. H.

    1995-01-01

    A mechanism is suggested and modeled whereby there may be boiling geysers on Triton. The geysers would be of nitrogen considering that Voyager detected cryovolcanic activity, that solid nitrogen conducts heat much less than water ice, and that there is internal heat on Triton.

  11. Classic and Hard-Boiled Detective Fiction.

    ERIC Educational Resources Information Center

    Reilly, John M.

    Through an analysis of several stories, this paper defines the similarities and differences between classic and hard-boiled detective fiction. The characters and plots of three stories are discussed: "The Red House" by A. A. Milne; "I, The Jury" by Mickey Spillane; and "League of Frightened Men" by Rex Stout. The classic detective story is defined…

  12. Big Bubbles in Boiling Liquids: Students' Views

    ERIC Educational Resources Information Center

    Costu, Bayram

    2008-01-01

    The aim of this study was to elicit students' conceptions about big bubbles in boiling liquids (water, ethanol and aqueous CuSO[subscript 4] solution). The study is based on twenty-four students at different ages and grades. The clinical interviews technique was conducted to solicit students' conceptions and the interviews were analyzed to…

  13. Combined shared and distributed memory ab-initio computations of molecular-hydrogen systems in the correlated state: Process pool solution and two-level parallelism

    NASA Astrophysics Data System (ADS)

    Biborski, Andrzej; Kądzielawa, Andrzej P.; Spałek, Józef

    2015-12-01

    An efficient computational scheme devised for investigations of ground state properties of the electronically correlated systems is presented. As an example, (H2)n chain is considered with the long-range electron-electron interactions taken into account. The implemented procedure covers: (i) single-particle Wannier wave-function basis construction in the correlated state, (ii) microscopic parameters calculation, and (iii) ground state energy optimization. The optimization loop is based on highly effective process-pool solution - specific root-workers approach. The hierarchical, two-level parallelism was applied: both shared (by use of Open Multi-Processing) and distributed (by use of Message Passing Interface) memory models were utilized. We discuss in detail the feature that such approach results in a substantial increase of the calculation speed reaching factor of 300 for the fully parallelized solution. The scheme elaborated in detail reflects the situation in which the most demanding task is the single-particle basis optimization.

  14. 48 CFR 873.114 - Best value pool.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 5 2014-10-01 2014-10-01 false Best value pool. 873.114... SUPPLEMENTARY REGULATIONS SIMPLIFIED ACQUISITION PROCEDURES FOR HEALTH-CARE RESOURCES 873.114 Best value pool... solicitation. These vendors constitute the best value pool. This determination is within the sole discretion...

  15. 48 CFR 252.232-7000 - Advance payment pool.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 3 2014-10-01 2014-10-01 false Advance payment pool. 252... Provisions And Clauses 252.232-7000 Advance payment pool. As prescribed in 232.412-70(a), use the following clause: Advance Payment Pool (DEC 1991) (a) Notwithstanding any other provision of this contract,...

  16. 48 CFR 873.114 - Best value pool.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 5 2012-10-01 2012-10-01 false Best value pool. 873.114... SUPPLEMENTARY REGULATIONS SIMPLIFIED ACQUISITION PROCEDURES FOR HEALTH-CARE RESOURCES 873.114 Best value pool... solicitation. These vendors constitute the best value pool. This determination is within the sole discretion...

  17. 48 CFR 252.232-7000 - Advance payment pool.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 3 2011-10-01 2011-10-01 false Advance payment pool. 252... Provisions And Clauses 252.232-7000 Advance payment pool. As prescribed in 232.412-70(a), use the following clause: Advance Payment Pool (DEC 1991) (a) Notwithstanding any other provision of this contract,...

  18. 48 CFR 873.114 - Best value pool.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 5 2013-10-01 2013-10-01 false Best value pool. 873.114... SUPPLEMENTARY REGULATIONS SIMPLIFIED ACQUISITION PROCEDURES FOR HEALTH-CARE RESOURCES 873.114 Best value pool... solicitation. These vendors constitute the best value pool. This determination is within the sole discretion...

  19. 48 CFR 252.232-7000 - Advance payment pool.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 3 2013-10-01 2013-10-01 false Advance payment pool. 252... Provisions And Clauses 252.232-7000 Advance payment pool. As prescribed in 232.412-70(a), use the following clause: Advance Payment Pool (DEC 1991) (a) Notwithstanding any other provision of this contract,...

  20. 48 CFR 873.114 - Best value pool.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 5 2011-10-01 2011-10-01 false Best value pool. 873.114... SUPPLEMENTARY REGULATIONS SIMPLIFIED ACQUISITION PROCEDURES FOR HEALTH-CARE RESOURCES 873.114 Best value pool... solicitation. These vendors constitute the best value pool. This determination is within the sole discretion...

  1. 48 CFR 252.232-7000 - Advance payment pool.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Advance payment pool. 252... Provisions And Clauses 252.232-7000 Advance payment pool. As prescribed in 232.412-70(a), use the following clause: Advance Payment Pool (DEC 1991) (a) Notwithstanding any other provision of this contract,...

  2. 48 CFR 873.114 - Best value pool.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Best value pool. 873.114... SUPPLEMENTARY REGULATIONS SIMPLIFIED ACQUISITION PROCEDURES FOR HEALTH-CARE RESOURCES 873.114 Best value pool... solicitation. These vendors constitute the best value pool. This determination is within the sole discretion...

  3. 48 CFR 28.304 - Risk-pooling arrangements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Risk-pooling arrangements... CONTRACTING REQUIREMENTS BONDS AND INSURANCE Insurance 28.304 Risk-pooling arrangements. Agencies may establish risk-pooling arrangements. These arrangements are designed to use the services of the...

  4. 48 CFR 228.304 - Risk-pooling arrangements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Risk-pooling arrangements..., DEPARTMENT OF DEFENSE GENERAL CONTRACTING REQUIREMENTS BONDS AND INSURANCE Insurance 228.304 Risk-pooling... Insurance Rating Plan, as a risk-pooling arrangement to minimize the cost to the Government of...

  5. Blanketing effect of expansion foam on liquefied natural gas (LNG) spillage pool.

    PubMed

    Zhang, Bin; Liu, Yi; Olewski, Tomasz; Vechot, Luc; Mannan, M Sam

    2014-09-15

    With increasing consumption of natural gas, the safety of liquefied natural gas (LNG) utilization has become an issue that requires a comprehensive study on the risk of LNG spillage in facilities with mitigation measures. The immediate hazard associated with an LNG spill is the vapor hazard, i.e., a flammable vapor cloud at the ground level, due to rapid vaporization and dense gas behavior. It was believed that high expansion foam mitigated LNG vapor hazard through warming effect (raising vapor buoyancy), but the boil-off effect increased vaporization rate due to the heat from water drainage of foam. This work reveals the existence of blocking effect (blocking convection and radiation to the pool) to reduce vaporization rate. The blanketing effect on source term (vaporization rate) is a combination of boil-off and blocking effect, which was quantitatively studied through seven tests conducted in a wind tunnel with liquid nitrogen. Since the blocking effect reduces more heat to the pool than the boil-off effect adds, the blanketing effect contributes to the net reduction of heat convection and radiation to the pool by 70%. Water drainage rate of high expansion foam is essential to determine the effectiveness of blanketing effect, since water provides the boil-off effect. PMID:25194555

  6. Blanketing effect of expansion foam on liquefied natural gas (LNG) spillage pool.

    PubMed

    Zhang, Bin; Liu, Yi; Olewski, Tomasz; Vechot, Luc; Mannan, M Sam

    2014-09-15

    With increasing consumption of natural gas, the safety of liquefied natural gas (LNG) utilization has become an issue that requires a comprehensive study on the risk of LNG spillage in facilities with mitigation measures. The immediate hazard associated with an LNG spill is the vapor hazard, i.e., a flammable vapor cloud at the ground level, due to rapid vaporization and dense gas behavior. It was believed that high expansion foam mitigated LNG vapor hazard through warming effect (raising vapor buoyancy), but the boil-off effect increased vaporization rate due to the heat from water drainage of foam. This work reveals the existence of blocking effect (blocking convection and radiation to the pool) to reduce vaporization rate. The blanketing effect on source term (vaporization rate) is a combination of boil-off and blocking effect, which was quantitatively studied through seven tests conducted in a wind tunnel with liquid nitrogen. Since the blocking effect reduces more heat to the pool than the boil-off effect adds, the blanketing effect contributes to the net reduction of heat convection and radiation to the pool by 70%. Water drainage rate of high expansion foam is essential to determine the effectiveness of blanketing effect, since water provides the boil-off effect.

  7. Boiling Water at Hot Creek - The Dangerous and Dynamic Thermal Springs in California's Long Valley Caldera

    USGS Publications Warehouse

    Farrar, Christopher D.; Evans, William C.; Venezky, Dina Y.; Hurwitz, Shaul; Oliver, Lynn K.

    2007-01-01

    The beautiful blue pools and impressive boiling fountains along Hot Creek in east-central California have provided enjoyment to generations of visitors, but they have also been the cause of injury or death to some who disregarded warnings and fences. The springs and geysers in the stream bed and along its banks change location, temperature, and flow rates frequently and unpredictably. The hot springs and geysers of Hot Creek are visible signs of dynamic geologic processes in this volcanic region, where underground heat drives thermal spring activity.

  8. When Regional becomes Local: Linking Regional Seismicity to Perturbations at the Boiling Lake, Dominica

    NASA Astrophysics Data System (ADS)

    Robertson, D.; Joseph, E. P.; Fournier, N.

    2015-12-01

    Dominica is one of 11 volcanically active islands located along the Eastern Caribbean arc. The Boiling Lake-Valley of Desolation area is part of a volcano-hydrothermal system on the island and was identified as the most likely location for a future eruption (Lindsay et. al, 2005). The last phreatic eruption on the island took place within the Boiling Lake-Valley of Desolation area in 1997. In addition to these eruptions the Boiling Lake has undergone six brief periods of physical and chemical instabilities during its 150 years of recorded history. The latest period occurred in 2004-2005 when the Boiling Lake experienced erratic disruptions in geothermal activity. It repeatedly emptied and refilled before returning to its long term stable state. Given such long term stability, a significant, but historically infrequent, perturbation is required to upset the Lake's dynamic equilibrium. Prior to 2004-2005, the factor(s) triggering the instabilities have not been identified. The current work is part of a multi-scale approach at understanding volcano-hydrothermal systems from a geophysical perspective, which incorporates modeling and observed data. Here, the author briefly introduces the multi-scale approach and then focuses on the role of regional earthquakes as possible triggers of the Lake's disruptions. This is discussed in terms of seismic events, induced stress-fields, faults systems and hydrodynamic changes. Finally the author reports on a number of significant events which may define the long elusive perturbation affecting the Boiling Lake.

  9. Numerical Modeling of Propellant Boil-Off in a Cryogenic Storage Tank

    NASA Astrophysics Data System (ADS)

    Majumdar, A. K.; Steadman, T. E.; Maroney, J. L.; Sass, J. P.; Fesmire, J. E.

    2008-03-01

    A numerical model to predict boil-off of stored propellant in large spherical cryogenic tanks has been developed. Accurate prediction of tank boil-off rates for different thermal insulation systems was the goal of this collaborative effort. The Generalized Fluid System Simulation Program, which integrates flow analysis and conjugate heat transfer for solving complex fluid system problems, was used to create the model. Calculation of tank boil-off rate requires simultaneous simulation of heat transfer processes among liquid propellant, vapor ullage space, and tank structure. The reference tank for the boil-off model was the 850,000 gallon liquid hydrogen tank at Launch Complex 39B (LC-39B) at Kennedy Space Center, which is under study for future infrastructure improvements to support the Constellation program. The methodology employed in the numerical model was validated using a sub-scale model and tank. Experimental test data from a 1/15th scale version of the LC-39B tank using both liquid hydrogen and liquid nitrogen were used to anchor the analytical predictions of the sub-scale model. Favorable correlations between sub-scale model and experimental test data have provided confidence in full-scale tank boil-off predictions. These methods are now being used in the preliminary design for other cases including future launch vehicles.

  10. Numerical Modeling of Propellant Boil-Off in a Cryogenic Storage Tank

    NASA Technical Reports Server (NTRS)

    Majumdar, A. K.; Steadman, T. E.; Maroney, J. L.; Sass, J. P.; Fesmire, J. E.

    2007-01-01

    A numerical model to predict boil-off of stored propellant in large spherical cryogenic tanks has been developed. Accurate prediction of tank boil-off rates for different thermal insulation systems was the goal of this collaboration effort. The Generalized Fluid System Simulation Program, integrating flow analysis and conjugate heat transfer for solving complex fluid system problems, was used to create the model. Calculation of tank boil-off rate requires simultaneous simulation of heat transfer processes among liquid propellant, vapor ullage space, and tank structure. The reference tank for the boil-off model was the 850,000 gallon liquid hydrogen tank at Launch Complex 39B (LC- 39B) at Kennedy Space Center, which is under study for future infrastructure improvements to support the Constellation program. The methodology employed in the numerical model was validated using a sub-scale model and tank. Experimental test data from a 1/15th scale version of the LC-39B tank using both liquid hydrogen and liquid nitrogen were used to anchor the analytical predictions of the sub-scale model. Favorable correlations between sub-scale model and experimental test data have provided confidence in full-scale tank boil-off predictions. These methods are now being used in the preliminary design for other cases including future launch vehicles

  11. Flow boiling with enhancement devices for cold plate coolant channel design

    NASA Technical Reports Server (NTRS)

    Boyd, Ronald D.

    1991-01-01

    Future space exploration and commercialization will require more efficient heat rejection systems. For the required heat transfer rates, such systems must use advanced heat transfer techniques. Forced two phase flow boiling heat transfer with enhancements falls in this category. However, moderate to high quality two phase systems tend to require higher pressure losses. This report is divided into two major parts: (1) Multidimensional wall temperature measurement and heat transfer enhancement for top heated horizontal channels with flow boiling; and (2) Improved analytical heat transfer data reduction for a single side heated coolant channel. Part 1 summarizes over forty experiments which involve both single phase convection and flow boiling in a horizontal channel heated externally from the top side. Part 2 contains parametric dimensionless curves with parameters such as the coolant channel radius ratio, the Biot number, and the circumferential coordinate.

  12. Flow-Boiling Critical Heat Flux Experiments Performed in Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Hasan, Mohammad M.; Mudawar, Issam

    2005-01-01

    Poor understanding of flow boiling in microgravity has recently emerged as a key obstacle to the development of many types of power generation and advanced life support systems intended for space exploration. The critical heat flux (CHF) is perhaps the most important thermal design parameter for boiling systems involving both heatflux-controlled devices and intense heat removal. Exceeding the CHF limit can lead to permanent damage, including physical burnout of the heat-dissipating device. The importance of the CHF limit creates an urgent need to develop predictive design tools to ensure both the safe and reliable operation of a two-phase thermal management system under the reduced-gravity (like that on the Moon and Mars) and microgravity environments of space. At present, very limited information is available on flow-boiling heat transfer and the CHF under these conditions.

  13. Modeling and numerical simulation of oscillatory two-phase flows, with application to boiling water nuclear reactors

    SciTech Connect

    Rosa, M.P.; Podowski, M.Z.

    1995-09-01

    This paper is concerned with the analysis of dynamics and stability of boiling channels and systems. The specific objectives are two-fold. One of them is to present the results of a study aimed at analyzing the effects of various modeling concepts and numerical approaches on the transient response and stability of parallel boiling channels. The other objective is to investigate the effect of closed-loop feedback on stability of a boiling water reactor (BWR). Various modeling and computational issues for parallel boiling channels are discussed, such as: the impact of the numerical discretization scheme for the node containing the moving boiling boundary on the convergence and accuracy of computations, and the effects of subcooled boiling and other two-phase flow phenomena on the predictions of marginal stability conditions. Furthermore, the effects are analyzed of local loss coefficients around the recirculation loop of a boiling water reactor on stability of the reactor system. An apparent paradox is explained concerning the impact of changing single-phase losses on loop stability. The calculations have been performed using the DYNOBOSS computer code. The results of DYNOBOSS validation against other computer codes and experimental data are shown.

  14. Vernal Pool Lessons and Activities.

    ERIC Educational Resources Information Center

    Childs, Nancy; Colburn, Betsy

    This curriculum guide accompanies Certified: A Citizen's Step-by-Step Guide to Protecting Vernal Pools which is designed to train volunteers in the process of identifying vernal pool habitat so that as many of these pools as possible can be certified by the Massachusetts Natural Heritage and Endangered Species Program. Vernal pools are a kind of…

  15. Detection of a variable intracellular acid-labile carbon pool in Thalassiosira weissflogii (Heterokontophyta) and Emiliania huxleyi (Haptophyta) in response to changes in the seawater carbon system.

    PubMed

    Isensee, Kirsten; Erez, Jonathan; Stoll, Heather M

    2014-02-01

    Accumulation of an intracellular pool of carbon (C(i) pool) is one strategy by which marine algae overcome the low abundance of dissolved CO2 (CO2 (aq) ) in modern seawater. To identify the environmental conditions under which algae accumulate an acid-labile C(i) pool, we applied a (14) C pulse-chase method, used originally in dinoflagellates, to two new classes of algae, coccolithophorids and diatoms. This method measures the carbon accumulation inside the cells without altering the medium carbon chemistry or culture cell density. We found that the diatom Thalassiosira weissflogii [(Grunow) G. Fryxell & Hasle] and a calcifying strain of the coccolithophorid Emiliania huxleyi [(Lohmann) W. W. Hay & H. P. Mohler] develop significant acid-labile C(i) pools. C(i) pools are measureable in cells cultured in media with 2-30 µmol l(-1) CO2 (aq), corresponding to a medium pH of 8.6-7.9. The absolute C(i) pool was greater for the larger celled diatoms. For both algal classes, the C(i) pool became a negligible contributor to photosynthesis once CO2 (aq) exceeded 30 µmol l(-1) . Combining the (14) C pulse-chase method and (14) C disequilibrium method enabled us to assess whether E. huxleyi and T. weissflogii exhibited thresholds for foregoing accumulation of DIC or reduced the reliance on bicarbonate uptake with increasing CO2 (aq) . We showed that the C(i) pool decreases with higher CO2 :HCO3 (-) uptake rates.

  16. Soil respiration, labile carbon pools, and enzyme activities as affected by tillage practices in a tropical rice-maize-cowpea cropping system.

    PubMed

    Neogi, S; Bhattacharyya, P; Roy, K S; Panda, B B; Nayak, A K; Rao, K S; Manna, M C

    2014-07-01

    In order to identify the viable option of tillage practices in rice-maize-cowpea cropping system that could cut down soil carbon dioxide (CO2) emission, sustain grain yield, and maintain better soil quality in tropical low land rice ecology soil respiration in terms of CO2 emission, labile carbon (C) pools, water-stable aggregate C fractions, and enzymatic activities were investigated in a sandy clay loam soil. Soil respiration is the major pathway of gaseous C efflux from terrestrial systems and acts as an important index of ecosystem functioning. The CO2-C emissions were quantified in between plants and rows throughout the year in rice-maize-cowpea cropping sequence both under conventional tillage (CT) and minimum tillage (MT) practices along with soil moisture and temperature. The CO2-C emissions, as a whole, were 24 % higher in between plants than in rows, and were in the range of 23.4-78.1, 37.1-128.1, and 28.6-101.2 mg m(-2) h(-1) under CT and 10.7-60.3, 17.3-99.1, and 17.2-79.1 mg m(-2) h(-1) under MT in rice, maize, and cowpea, respectively. The CO2-C emission was found highest under maize (44 %) followed by rice (33 %) and cowpea (23 %) irrespective of CT and MT practices. In CT system, the CO2-C emission increased significantly by 37.1 % with respect to MT on cumulative annual basis including fallow. The CO2-C emission per unit yield was at par in rice and cowpea signifying the beneficial effect of MT in maintaining soil quality and reduction of CO2 emission. The microbial biomass C (MBC), readily mineralizable C (RMC), water-soluble C (WSC), and permanganate-oxidizable C (PMOC) were 19.4, 20.4, 39.5, and 15.1 % higher under MT than CT. The C contents in soil aggregate fraction were significantly higher in MT than CT. Soil enzymatic activities like, dehydrogenase, fluorescein diacetate, and β-glucosidase were significantly higher by 13.8, 15.4, and 27.4 % under MT compared to CT. The soil labile C pools, enzymatic activities, and

  17. Vertical boil propagation from a submerged estuarine sill

    NASA Astrophysics Data System (ADS)

    Chickadel, C. Chris; Horner-Devine, Alexander R.; Talke, Stefan A.; Jessup, Andrew T.

    2009-05-01

    Surface disruptions by boils during strong tidal flows over a rocky sill were observed in thermal infrared imagery collected at the Snohomish River estuary in Washington State. Locations of boil disruptions and boil diameters at the surface were quantified and are used to test an idealized model of vertical boil propagation. The model is developed as a two-dimensional approximation of a three-dimensional vortex loop, and boil vorticity is derived from the flow shear over the sill. Predictions of boil disruption locations were determined from the modeled vertical velocity, the sill depth, and the over-sill velocity. Predictions by the vertical velocity model agree well with measured locations (rms difference 3.0 m) and improve by using measured velocity and shear (rms difference 1.8 m). In comparison, a boil-surfacing model derived from laboratory turbulent mixed-layer wakes agrees with the measurements only when stratification is insignificant.

  18. Thread Pool Interface (TPI)

    2008-04-01

    Thread Pool Interface (TpI) provides a simple interface for running functions written in C or C++ in a thread-parallel mode. Application or library codes may need to perform operations thread-parallel on machines with multicore processors. the TPI library provides a simple mechanism for managing thread activation, deactivation, and thread-parallel execution of application-provided subprograms.

  19. The Future of Pooling.

    ERIC Educational Resources Information Center

    Young, Peter C.; Fone, Martin

    1997-01-01

    Discusses seven propositions underlying the strategies that insurance pools can, will, and must pursue: (1) risk management versus risk financing; (2) elimination of windfall advantages; (3) the maintenance of market-dominant status; (4) cost leadership; (5) client focus; (6) innovation and diversification; and (7) leadership challenges. A sidebar…

  20. Melting point, boiling point, and symmetry.

    PubMed

    Abramowitz, R; Yalkowsky, S H

    1990-09-01

    The relationship between the melting point of a compound and its chemical structure remains poorly understood. The melting point of a compound can be related to certain of its other physical chemical properties. The boiling point of a compound can be determined from additive constitutive properties, but the melting point can be estimated only with the aid of nonadditive constitutive parameters. The melting point of some non-hydrogen-bonding, rigid compounds can be estimated by the equation MP = 0.772 * BP + 110.8 * SIGMAL + 11.56 * ORTHO + 31.9 * EXPAN - 240.7 where MP is the melting point of the compound in Kelvin, BP is the boiling point, SIGMAL is the logarithm of the symmetry number, EXPAN is the cube of the eccentricity of the compound, and ORTHO indicates the number of groups that are ortho to another group.

  1. Unorthodox bubbles when boiling in cold water.

    PubMed

    Parker, Scott; Granick, Steve

    2014-01-01

    High-speed movies are taken when bubbles grow at gold surfaces heated spotwise with a near-infrared laser beam heating water below the boiling point (60-70 °C) with heating powers spanning the range from very low to so high that water fails to rewet the surface after bubbles detach. Roughly half the bubbles are conventional: They grow symmetrically through evaporation until buoyancy lifts them away. Others have unorthodox shapes and appear to contribute disproportionately to heat transfer efficiency: mushroom cloud shapes, violently explosive bubbles, and cavitation events, probably stimulated by a combination of superheating, convection, turbulence, and surface dewetting during the initial bubble growth. Moreover, bubbles often follow one another in complex sequences, often beginning with an unorthodox bubble that stirs the water, followed by several conventional bubbles. This large dataset is analyzed and discussed with emphasis on how explosive phenomena such as cavitation induce discrepancies from classical expectations about boiling.

  2. Enhanced Droplet Control by Transition Boiling

    PubMed Central

    Grounds, Alex; Still, Richard; Takashina, Kei

    2012-01-01

    A droplet of water on a heated surface can levitate over a film of gas produced by its own evaporation in the Leidenfrost effect. When the surface is prepared with ratchet-like saw-teeth topography, these droplets can self-propel and can even climb uphill. However, the extent to which the droplets can be controlled is limited by the physics of the Leidenfrost effect. Here, we show that transition boiling can be induced even at very high surface temperatures and provide additional control over the droplets. Ratchets with acute protrusions enable droplets to climb steeper inclines while ratchets with sub-structures enable their direction of motion to be controlled by varying the temperature of the surface. The droplets' departure from the Leidenfrost regime is assessed by analysing the sound produced by their boiling. We anticipate these techniques will enable the development of more sophisticated methods for controlling small droplets and heat transfer. PMID:23056912

  3. Distributed Technologies in a Data Pool

    NASA Astrophysics Data System (ADS)

    Keiser, K.; Conover, H.; Graves, S.; He, Y.; Regner, K.; Smith, M.

    2004-12-01

    A Data Pool is an on-line repository providing interactive and programmatic access to data products through a variety of services. The University of Alabama in Huntsville has developed and deployed such a Data Pool in conjunction with the DISCOVER project, a collaboration with NASA and Remote Sensing Systems. DISCOVER provides long-term ocean and climate data from a variety of passive microwave satellite instruments, including such products as sea-surface temperature and wind, air temperature, atmospheric water vapor, cloud water and rain rate. The Data Pool provides multiple methods to access and visualize these products, including conventional HTTP and FTP access, as well as data services that provide for enhanced usability and interoperability, such as GridFTP, OPeNDAP, OpenGIS-compliant web mapping and coverage services, and custom subsetting and packaging services. This paper will focus on the distributed service technologies used in the Data Pool, which spans heterogeneous machines at multiple locations. For example, in order to provide seamless access to data at multiple sites, the Data Pool provides catalog services for all data products at the various data server locations. Under development is an automated metadata generation tool that crawls the online data repositories regularly to dynamically update the Data Pool catalog with information about newly generated data files. For efficient handling of data orders across distributed repositories, the Data Pool also implements distributed data processing services on the file servers where the data resides. Ontologies are planned to support automated service chaining for custom user requests. The UAH Data Pool is based on a configurable technology framework that integrates distributed data services with a web interface and a set of centralized database services for catalogs and order tracking. While this instantiation of the Data Pool was implemented to meet the needs of the DISCOVER project, the framework was

  4. Fundamental Study of Local Heat Transfer in Forced Convective Boiling of Ammonia on Vertical Flat Plate

    NASA Astrophysics Data System (ADS)

    Kim, Jeong-Hun; Arima, Hirofumi; Ikegami, Yasuyuki

    In the present study, the fundamental experiments that investigate characteristics of local heat transfer in forced convective boiling on vertical flat plate with 2-mm channel height are taken to realize plate type compact evaporator for OTEC or STEC. The experiments are performed with ammonia as the working fluid. The experiments are also carried out with the following test conditions; saturated pressure = 0.7, 0.8, 0.9 MPa, mass flux = 7.5, 10, 15 kg/(m2•s), heat flux = 15, 20, 25 kW/m2 and inlet quality = 0.1 ~ 0.4 [-]. The result shows that the wall superheated temperature of forced convective boiling is lower than that of pool boiling. And the heat transfer coefficient increases with an increase in quality and the decrease in the local heat flux and saturated pressure for prescribed experimental conditions. However, local heat transfer coefficients are not affected by mass fluxes in the prescribed experimental conditions. An empirical correlation that can predict the local heat transfer coefficient on vertical flat plate within experimental conditions is also proposed.

  5. Surface wetting and bubble dynamics of dielectric fluids boiling in high electric fields

    NASA Astrophysics Data System (ADS)

    Dhillon, Navdeep; Love, Christopher; Mahmoudi, Seyed Reza; Varanasi, Kripa

    2014-11-01

    We present results of an experimental study on the effect of high electric fields on the nature of bubble formation and departure in nucleate pool boiling of dielectric fluids. Despite some past studies looking at the application of electric fields to enhance boiling performance, the exact mechanism of interaction of these fields with the fluid/surface is not well understood. In this study, we employed high-speed optical and infrared (IR) imaging to observe changes in wetting behavior of the fluid on the solid surface and the mode of bubble formation and departure under applied electric fields. The experimental results point towards a liquid film stabilization effect of the applied electric field on the boiling surface. Both the bubble departure size and surface dry spot dynamics is visibly altered under the effect of the electric field. These effects can be attributed to the development of surface charges on the bubble microlayer adjacent to the liquid-vapor contact line, which affect the liquid receding and surface rewetting mechanisms. Funding for this project is provided by Chevron Corp.

  6. European simplified boiling water reactor (ESBWR) plant

    SciTech Connect

    Posta, B.A.; Goldenberg, E.A.; Sawhney, P.S.; Rao, A.S.

    1996-07-01

    This paper covers innovative ideas which made possible the redesign of the US 660-MW Simplified Boiling Water Reactor (SBWR) Reactor Island for a 1,200-MW size reactor while actually reducing the building cost. This was achieved by breaking down the Reactor Island into multiple buildings separating seismic-1 from non-seismic-1 areas, providing for better space utilization, shorter construction schedule, easier maintainability and better postaccident accessibility.

  7. Improved access to histopathology using a digital system could increase the organ donor pool and improve allocation.

    PubMed

    Neil, Desley A H; Roberts, Ian S D; Bellamy, Christopher O C; Wigmore, Stephen J; Neuberger, James M

    2014-08-01

    Improvements in digital slide scanners have reached a stage that digital whole slide images (WSIs) can be used for diagnostic purposes. A digital system for histopathology, analogous to the systems used in radiology, would allow the establishment of networks of subspecialist histopathologists to provide a regional, national or even international rota to support out of hours histopathology for emergency frozen sections, urgent paraffin sections and to generally improve efficiencies with the provision of histopathology services. Such a system would promote appropriate organ utilization by allowing rapid characterization of unexpected lesions in the donor to determine whether donation should occur and further characterization of the organ, such as the degree of fibrosis in the kidney or steatosis in the liver, to determine whether the organ should be used. If introduced across Europe, this would promote safe and effective exchange of organs and support a cost efficient use of pathologist expertise. This review article outlines current issues with the provision of an urgent out of hours histopathology service and focuses on how such a service has the potential to increase organ donors, improve allocation, sharing and the use of available donor organs.

  8. Pool boiling on thin heaters: The role of thermal interaction among vapor stems

    SciTech Connect

    Sadasivan, P.; Unal, C.; Nelson, R.

    1993-10-01

    We examine the issue of thermal interactions within a heater as a possible explanation for conflicting critical heat flux data on thin heaters, as reported by various investigators. While heater thermal properties have been considered in previous studies, the focus of this study is the interaction between the thermal transport process within the heater and the distribution of nucleation sites on the heater surface. It is shown that the spatial distribution of stems on the heater surface, as well as the size distribution of these stems, can affect the average surface temperatures. Such interactions are greater as the heater thickness decreases.

  9. Welding pool measurement using thermal array sensor

    NASA Astrophysics Data System (ADS)

    Cho, Chia-Hung; Hsieh, Yi-Chen; Chen, Hsin-Yi

    2015-08-01

    Selective laser melting (SLM) is an additive manufacturing (AM) technology that uses a high-power laser beam to melt metal powder in chamber of inert gas. The process starts by slicing the 3D CAD data as a digital information source into layers to create a 2D image of each layer. Melting pool was formed by using laser irradiation on metal powders which then solidified to consolidated structure. In a selective laser melting process, the variation of melt pool affects the yield of a printed three-dimensional product. For three dimensional parts, the border conditions of the conductive heat transport have a very large influence on the melt pool dimensions. Therefore, melting pool is an important behavior that affects the final quality of the 3D object. To meet the temperature and geometry of the melting pool for monitoring in additive manufacturing technology. In this paper, we proposed the temperature sensing system which is composed of infrared photodiode, high speed camera, band-pass filter, dichroic beam splitter and focus lens. Since the infrared photodiode and high speed camera look at the process through the 2D galvanometer scanner and f-theta lens, the temperature sensing system can be used to observe the melting pool at any time, regardless of the movement of the laser spot. In order to obtain a wide temperature detecting range, 500 °C to 2500 °C, the radiation from the melting pool to be measured is filtered into a plurality of radiation portions, and since the intensity ratio distribution of the radiation portions is calculated by using black-body radiation. The experimental result shows that the system is suitable for melting pool to measure temperature.

  10. Fundamental Boiling and RP-1 Freezing Experiments

    NASA Technical Reports Server (NTRS)

    Goode, Brian; Turner, Larry D. (Technical Monitor)

    2001-01-01

    This paper describes results from experiments performed to help understand certain aspects of the MC-1 engine prestart thermal conditioning procedure. The procedure was constrained by the fact that the engine must chill long enough to get quality LOX at the LOX pump inlet but must be short enough to prevent freezing of RP-1 in the fuel pump. A chill test of an MC-1 LOX impeller was performed in LN2 to obtain data on film boiling, transition boiling and impeller temperature histories. The transition boiling data was important to the chill time so a subsequent experiment was performed chilling simple steel plates in LOX to obtain similar data for LOX. To address the fuel freezing concern, two experiments were performed. First, fuel was frozen in a tray and its physical characteristics were observed and temperatures of the fuel were measured. The result was physical characteristics as a function of temperature. Second was an attempt to measure the frozen thickness of RP-1 on a cold wall submerged in warm RP-1 and to develop a method for calculating that thickness for other conditions.

  11. Boiling incipience in a reboiler tube

    SciTech Connect

    Ali, H.; Alam, S.S. )

    1991-03-01

    This heating surface and liquid temperature distributions were experimentally obtained to identify the boiling incipience conditions in a single vertical tube thermosiphon reboiler with water, acetone, ethanol, and ethylene glycol as test liquids. The test section was an electrically heated stainless steel tube of 25.56-mm i.d. and 1900 mm long. The uniform heat flux values were used in the range of 3800--40 000 W/m{sup 2}, while inlet liquid subcooling were varied from 0.2 to 45.5{degrees} C. The liquid submergence was maintained around 100, 75, 50 and 30%. All the data were generated at 1-atm pressure. The maximum superheats attained around boiling incipience were taken from the wall temperature distributions and correlated with heat flux and physical properties of liquids using the expression of Yin and Abdelmessih. The heated sections required for onset of fully developed boiling with net vapor generation were determined assuming a thermal equilibrium model. In this paper a dimensionless correlation relating these values with heat flux, liquid subcooling, and submergence is proposed.

  12. Boiling Lake of Dominica, West Indies: High-temperature volcanic crater lake dynamics

    NASA Astrophysics Data System (ADS)

    Fournier, N.; Witham, F.; Moreau-Fournier, M.; Bardou, L.

    2009-02-01

    The Boiling Lake of Dominica has exhibited stable high-temperature behavior for at least 150 a. This stability is punctuated by occasional crises involving rapid filling and draining of the lake and changes in water temperature. The most recent such crisis occurred in December 2004 to April 2005. Using the results of previous theoretical and experimental work on analogue models, we present a combined thermal, hydrological, and fluid mechanical model of the Boiling Lake. This reveals that the lake appears to be suspended above the local water table by a constant supply of rising steam bubbles sourced from the boiling of groundwater near an igneous intrusion. The bubbles condense in the Boiling Lake, maintaining the temperature at ˜90°C. The geometry of the lake-conduit system provides a mechanism for instability, with a denser liquid lake overlying a bubbly fractured permeable conduit. Following a sufficiently large perturbation, the whole lake rapidly drains until the surface is at the local water table level. The persistent gas supply then reinitiates filling. We propose that local seismic activity may have caused shock nucleation of bubbles within the conduit and triggered the instability of the Boiling Lake.

  13. Boiling heat transfer of nanofluids--special emphasis on critical heat flux.

    PubMed

    Kim, Sung Joong; Kim, Hyungdae

    2013-11-01

    As innovative nanotechnology-based heat-transfer media, nanofluids have evoked considerable interest among researchers owing to their improved thermal properties as well as their extendable applications to various high-power thermal systems. This paper presents a comprehensive review of recent research developments and patents pertaining to nanofluid boiling heat transfer. Nanofluids definitely offer a wide range of potential improvements in boiling heat-transfer performance. However, experimental data available from different studies are currently beset by numerous contradictions, suggesting that the fundamental mechanisms of nanofluid boiling heat transfer are not yet well understood. Consequently application of these technologies has been limited in some aspects. Only a small number of patents related to nanofluid boiling heat transfer have thus far been reported in the literature. Based on the present review, future technological development and research requirements in this area are outlined in line with technical challenges. To utilize nanofluid boiling heat-transfer technologies for practical applications, more systematic and fundamental studies are required to understand the physical mechanisms involved.

  14. Parametric study of boiling heat transfer in porous media

    SciTech Connect

    Shi, B.; Jones, B.G.; Pan, C.

    1996-04-01

    Detailed numerical modeling and parametric variation studies were conducted on boiling heat transfer processes in porous deposits with emphasis on applications associated with light water nuclear power reactor systems. The processes of boiling heat transfer in the porous corrosion deposits typically involve phase changes in finite volumetric regions in the porous media. The study examined such processes in two porous media configurations, without chimneys (homogeneous porous structures) and with chimneys (heterogeneous porous structures). A 1-D model and a 2-D model were developed to simulate two-phase flows with phase changes, without dry-out, inside the porous media for both structural configurations. For closure of the governing equations, an empirical correlation of the evaporation rate for phase changes inside the porous media was introduced. In addition, numerical algorithms were developed to solve the coupled nonlinear equations of mass, momentum, energy, capillary pressure, and evaporation rate. The distributions of temperature, thermodynamic saturation, liquid pressure, vapor pressure, liquid velocity, and vapor velocity were predicted. Furthermore, the effects of heat flux, system pressure, porosity, particle diameter, chimney population density, chimney radius, and crud thickness on the all superheat, critical heat flux, and minimum saturation were examined. The predictions were found to be in good agreement with the available experimental results.

  15. Design inputs document: Boiling behavior during flow instability

    SciTech Connect

    Coutts, D.A.

    1991-12-31

    The coolant flow in a nuclear reactor core under normal operating conditions is kept as a subcooled liquid. This coolant is evenly distributed throughout the multiple flow channels with a uniform pressure profile across each coolant flow channel. If the coolant flow is reduced, the flow through individual channels will also decrease. A decrease in coolant flow will result in higher coolant temperatures if the heat flux is not reduced. When flow is significantly decreased, localized boiling may occur. This localized boiling can restrict coolant flow and the ability to transfer heat out of the reactor system. The maximum operating power for the reactor may be limited by how the coolant system reacts to a flow instability. One of the methods to assure safe operation during a reducing flow instability, is to operate at a power level below that necessary to initiate a flow excursion. Several correlations have been used to predict the conditions which precede a flow excursion. These correlations rely on the steady state behavior of the coolant and are based on steady state testing. This task will evaluate if there are any deviations between the actual transient flow excursion behavior and the flow excursion behavior based on steady state correlations (ONB, OSV, and CHF). Correlations will be developed which will allow a comparison between the time to excursive behavior predicted using steady state techniques and the actual time to excursive behavior.

  16. Simulation of decay heat removal by natural convection in a pool type fast reactor model-ramona-with coupled 1D/2D thermal hydraulic code system

    SciTech Connect

    Kasinathan, N.; Rajakumar, A.; Vaidyanathan, G.; Chetal, S.C.

    1995-09-01

    Post shutdown decay heat removal is an important safety requirement in any nuclear system. In order to improve the reliability of this function, Liquid metal (sodium) cooled fast breeder reactors (LMFBR) are equipped with redundant hot pool dipped immersion coolers connected to natural draught air cooled heat exchangers through intermediate sodium circuits. During decay heat removal, flow through the core, immersion cooler primary side and in the intermediate sodium circuits are also through natural convection. In order to establish the viability and validate computer codes used in making predictions, a 1:20 scale experimental model called RAMONA with water as coolant has been built and experimental simulation of decay heat removal situation has been performed at KfK Karlsruhe. Results of two such experiments have been compiled and published as benchmarks. This paper brings out the results of the numerical simulation of one of the benchmark case through a 1D/2D coupled code system, DHDYN-1D/THYC-2D and the salient features of the comparisons. Brief description of the formulations of the codes are also included.

  17. A study of flow boiling phenomena using real time neutron radiography

    NASA Astrophysics Data System (ADS)

    Novog, David Raymond

    The operation and safety of both fossil-fuel and nuclear power stations depend on adequate cooling of the thermal source involved. This is usually accomplished using liquid coolants that are forced through the high temperature regions by a pumping system; this fluid then transports the thermal energy to another section of the power station. However, fluids that undergo boiling during this process create vapor that can be detrimental, and influence safe operation of other system components. The behavior of this vapor, or void, as it is generated and transported through the system is critical in predicting the operational and safety performance. This study uses two advanced penetrating radiation techniques, Real Time Neutron Radiography (RTNR), and High Speed X-Ray Tomography (HS-XCT), to examine void generation and transport behavior in a flow boiling system. The geometries studied were tube side flow boiling in a cylindrical configuration, and a similar flow channel with an internal twisted tape swirl flow generator. The heat transfer performance and pressure drop characteristics were monitored in addition to void distribution measurements, so that the impact of void distribution could be determined. The RTNR and heat transfer pipe flow studies were conducted using boiling Refrigerant 134a at pressures from 500 to 700 kPa, inlet subcooling from 3 to 12°C and mass fluxes from 55 to 170kg/m 2-s with heat fluxes up to 40 kW/m2. RTNR and HS-XCT were used to measure the distribution and size of the vapor phases in the channel for cylindrical tube-side flow boiling and swirl-flow boiling geometries. The results clearly show that the averaged void is similar for both geometries, but that there is a significant difference in the void distribution, velocity and transport behavior from one configuration to the next. Specifically, the void distribution during flow boiling in a cylindrical-tube test section showed that the void fraction was largest near the tube center and

  18. Contamination of Groundwater Systems in the US and Canada by Enteric Pathogens, 1990–2013: A Review and Pooled-Analysis

    PubMed Central

    Hynds, Paul Dylan; Thomas, M. Kate; Pintar, Katarina Dorothy Milena

    2014-01-01

    Background Up to 150 million North Americans currently use a groundwater system as their principal drinking water source. These systems are a potential source of exposure to enteric pathogens, contributing to the burden of waterborne disease. Waterborne disease outbreaks have been associated with US and Canadian groundwater systems over the past two decades. However, to date, this literature has not been reviewed in a comprehensive manner. Methods and Principal Findings A combined review and pooled-analysis approach was used to investigate groundwater contamination in Canada and the US from 1990 to 2013; fifty-five studies met eligibility criteria. Four study types were identified. It was found that study location affects study design, sample rate and studied pathogen category. Approximately 15% (316/2210) of samples from Canadian and US groundwater sources were positive for enteric pathogens, with no difference observed based on system type. Knowledge gaps exist, particularly in exposure assessment for attributing disease to groundwater supplies. Furthermore, there is a lack of consistency in risk factor reporting (local hydrogeology, well type, well use, etc). The widespread use of fecal indicator organisms in reported studies does not inform the assessment of human health risks associated with groundwater supplies. Conclusions This review illustrates how groundwater study design and location are critical for subsequent data interpretation and use. Knowledge gaps exist related to data on bacterial, viral and protozoan pathogen prevalence in Canadian and US groundwater systems, as well as a need for standardized approaches for reporting study design and results. Fecal indicators are examined as a surrogate for health risk assessments; caution is advised in their widespread use. Study findings may be useful during suspected waterborne outbreaks linked with a groundwater supply to identify the likely etiological agent and potential transport pathway. PMID:24806545

  19. Boiling radial flow in fractures of varying wall porosity

    SciTech Connect

    Barnitt, Robb Allan

    2000-06-01

    The focus of this report is the coupling of conductive heat transfer and boiling convective heat transfer, with boiling flow in a rock fracture. A series of experiments observed differences in boiling regimes and behavior, and attempted to quantify a boiling convection coefficient. The experimental study involved boiling radial flow in a simulated fracture, bounded by a variety of materials. Nonporous and impermeable aluminum, highly porous and permeable Berea sandstone, and minimally porous and permeable graywacke from The Geysers geothermal field. On nonporous surfaces, the heat flux was not strongly coupled to injection rate into the fracture. However, for porous surfaces, heat flux, and associated values of excess temperature and a boiling convection coefficient exhibited variation with injection rate. Nucleation was shown to occur not upon the visible surface of porous materials, but a distance below the surface, within the matrix. The depth of boiling was a function of injection rate, thermal power supplied to the fracture, and the porosity and permeability of the rock. Although matrix boiling beyond fracture wall may apply only to a finite radius around the point of injection, higher values of heat flux and a boiling convection coefficient may be realized with boiling in a porous, rather than nonporous surface bounded fracture.

  20. Low-boiling-point solvent additives can also enable morphological control in polymer solar cells

    SciTech Connect

    Mahadevapuram, Rakesh C.; Carr, John A.; Chen, Yuqing; Bose, Sayantan; Nalwa, Kanwar S.; Petrich, Jacob W.; Chaudhary, Sumit

    2013-11-02

    Processing organic photovoltaic (OPV) blend solutions with high-boiling-point solvent additives has recently been used for morphological control in bulk-heterojunction OPV cells. Here we show that even low-boiling-point solvents can be effective additives. When P3HT:PCBM OPV cells were processed with a low-boiling-point solvent tetrahydrafuran as an additive in parent solvent o-dichlorobenzene, charge extraction increased leading to fill factors as high as 69.5%, without low work-function cathodes, electrode buffer layers or thermal treatment. This was attributed to PCBM demixing from P3HT domains and better vertical phase separation, as indicated by photoluminescence lifetimes, hole mobilities, and shunt leakage currents. Dependence on solvent parameters and applicability beyond P3HT system was also investigated. (C) 2013 Elsevier B.V. All rights reserved.

  1. Enhancement of critical heat flux in nucleate boiling of nanofluids: a state-of-art review

    PubMed Central

    2011-01-01

    Nanofluids (suspensions of nanometer-sized particles in base fluids) have recently been shown to have nucleate boiling critical heat flux (CHF) far superior to that of the pure base fluid. Over the past decade, numerous experimental and analytical studies on the nucleate boiling CHF of nanofluids have been conducted. The purpose of this article is to provide an exhaustive review of these studies. The characteristics of CHF enhancement in nanofluids are systemically presented according to the effects of the primary boiling parameters. Research efforts to identify the effects of nanoparticles underlying irregular enhancement phenomena of CHF in nanofluids are then presented. Also, attempts to explain the physical mechanism based on available CHF theories are described. Finally, future research needs are identified. PMID:21711949

  2. The effect of TGF-β1 polymorphism on systemic sclerosis: a systematic review and pooled analysis of available literature.

    PubMed

    Wan, Ya-nan; Wang, Yu-jie; Yan, Jun-wei; Li, Xiang-pei; Tao, Jin-hui; Wang, Bing-xiang; Peng, Wen-jia; Wang, Jing

    2013-11-01

    Transforming growth factor-β1 (TGF-β1) plays an important role in the pathogenesis of systemic sclerosis (SSc). To investigate whether TGF-β1 gene promoter polymorphisms were associated with the susceptibility of SSc, we performed a meta-analysis based on all available studies through PubMed, Elsevier Science Direct, Embase, and Chinese Biomedical, China National Knowledge Infrastructure and Google Scholar with the last report up to March 15, 2013. Crude odds ratios with 95% confidence intervals were used to estimate the strength of the association. A fixed or random effects model was adopted according to heterogeneity test. Heterogeneity among studies was evaluated using I (2) . Meta-regression was used to explore potential sources of between-study heterogeneity. Publication bias was estimated using Begg's and Egger's test. Totally, seven papers with 663 SSc patients and 908 healthy controls were subjected to the final analysis. These studies encompass seven for TGF-β1 codon 10, three for codon 25 and three for -509C/T. We failed to detect any association of these promoter polymorphism with SSc susceptibility. For TGF-β1 codon 10 polymorphism, subgroup analyses by race, genotype testing method and classification of SSc were further performed. Similarly, no association was observed. Significant heterogeneity was detected among the studies in all genetic models of TGF-β1 codon 10 polymorphism. Publication bias was absent. Taken together, our meta-analysis did not provided an evidence of confirming association between TGF-β1 (codon 10, codon 25, -509C/T) gene polymorphism and SSc. Nevertheless, due to smaller sample sizes, larger sample studies including different ethnic groups should be considered in future to confirm our results.

  3. Design and Testing of Vacuum Breaker Check Valve for Simplified Boiling Water Reactor

    SciTech Connect

    Ishii, M.; Xu, Y.; Revankar, S.T.

    2002-07-01

    A new design of the vacuum breaker check valve was developed to replace the mechanical valve in a simplified boiling water reactor. Scaling and design calculations were performed to obtain the geometry of new passive hydraulic vacuum breaker check valve. In order to check the valve performance, a RELAP5 model of the simplified boiling water reactor system with the new valve was developed. The valve was implemented in an integral facility, PUMA and was tested for large break loss of coolant accident. (authors)

  4. Boiling in variable gravity under the action of an electric field: results of parabolic flight experiments

    NASA Astrophysics Data System (ADS)

    Di Marco, P.; Raj, R.; Kim, J.

    2011-12-01

    Results from the variable gravity pool boiling experiments performed during the 52nd ESA parabolic flight campaign are reported in this paper. During a typical parabola, the gravity acceleration changes from 1.8gE (high gravity) to ~0gE (low gravity) and finally back to 1.8gE. The two high gravity periods and the microgravity period are each roughly maintained for 20 seconds while the transition from high gravity to low gravity and vice versa occurs over a period of 3-5 seconds. Use of the high feedback frequency microheater array allowed quasi-steady boiling data over the continuous range of gravity levels (0gE-1.8gE). The experimental apparatus consisted of a boiling chamber with a 7×7 mm2 microheater array in a 10×10 configuration. Each heater in the array was individually controlled to maintain a constant temperature. The array could be operated in a full configuration or a selectively powered reduced set of 3×3 heaters. Experiments were performed with FC-72 as the test fluid, the pressure was maintained at a constant value between 1 and 1.13 atm and the subcooling ranged from 27 to 11 K. An external electric field was imposed over the boiling surface by means of a grid consisting of 4 rods, laid parallel to the surface; voltages up to 10 kV were applied. The electric field was effective in reducing the size of the detaching bubbles, and increasing the heat transfer compared to the values in low-g, although its effectiveness decayed as the heat flux/superheat increased. The current results compared well with previous results obtained in the ARIEL apparatus that was operated in orbital flight.

  5. System for reducing heat losses from indoor swimming pools by use of automatic covers. [Quarterly] report No. 5, January 1, 1995--March 31, 1995

    SciTech Connect

    1995-05-01

    To maintain comfortable and healthful temperatures in an indoor swimming pool, heat must be continually supplied to the pool water and to fresh air-that must be brought in for ventilation. Nearly all the heat added to the water is lost by evaporation into the air above the water surface. That very moist air must then be removed and replaced with relatively dry outdoor air that requires heating during most of the year. The cost of natural gas for supplying heat in a typical institutional pool is $10,000 to $25,000 Per Year. When the pool is not being used, typically half to two-thirds of the time, evaporation and the resulting heat demands can be eliminated by placing impervious covers on the water surface. On a schedule of use such as at Skyland, the pool can be covered and evaporation suppressed about two-thirds of the time, thereby saving about ten thousand dollars per year. Determination of the actual savings achieved by use of pool covers is the principal objective of this project. The program goal is the development of the technology and tools for achieving major reductions in the nation`s waste of energy.

  6. Allergic to Pool Water

    PubMed Central

    2012-01-01

    To identify the allergy problem of a 36-year old swimming instructor, who experiences heavy itching and rashes whenever she comes in contact with pool water. Patch tests were performed with European standard series and materials from the work floor. A positive patch test to aluminum chloride and flocculant was observed. Occupational dermatitis is, based on a contact allergy to aluminum chloride in the flocculant. PMID:22993713

  7. Development and Capabilities of ISS Flow Boiling and Condensation Experiment

    NASA Technical Reports Server (NTRS)

    Nahra, Henry; Hasan, Mohammad; Balasubramaniam, R.; Patania, Michelle; Hall, Nancy; Wagner, James; Mackey, Jeffrey; Frankenfield, Bruce; Hauser, Daniel; Harpster, George; Nawrocki, David; Clapper, Randy; Kolacz, John; Butcher, Robert; May, Rochelle; Chao, David; Mudawar, Issam; Kharangate, Chirag R.; O'Neill, Lucas E.

    2015-01-01

    An experimental facility to perform flow boiling and condensation experiments in long duration microgravity environment is being designed for operation on the International Space Station (ISS). This work describes the design of the subsystems of the FBCE including the Fluid subsystem modules, data acquisition, controls, and diagnostics. Subsystems and components are designed within the constraints of the ISS Fluid Integrated Rack in terms of power availability, cooling capability, mass and volume, and most importantly the safety requirements. In this work we present the results of ground-based performance testing of the FBCE subsystem modules and test module which consist of the two condensation modules and the flow boiling module. During this testing, we evaluated the pressure drop profile across different components of the fluid subsystem, heater performance, on-orbit degassing subsystem, heat loss from different modules and components, and performance of the test modules. These results will be used in the refinement of the flight system design and build-up of the FBCE which is manifested for flight in late 2017-early 2018.

  8. Swimming Pools and Molluscum Contagiosum

    MedlinePlus

    ... Travelers' Health: Smallpox & Other Orthopoxvirus-Associated Infections Poxvirus Swimming Pools Recommend on Facebook Tweet Share Compartir The ... often ask if molluscum virus can spread in swimming pools. There is also concern that it can ...

  9. Managing swimming, spa, and other pools to prevent infection.

    PubMed

    Dadswell, J V

    1996-02-01

    Many different kinds of recreational and therapeutic pools now exist and all have the potential to transmit infection. This paper offers a brief review of reports of pool associated infections, along with short descriptions of the different kinds of pool and of the disinfection and filtration systems designed to minimise the possible transmission of infection by pool water. An outline of pool monitoring is included together with the rationale of microbiological testing and current microbiological guidelines. Good management is important; a well managed pool with an adequate disinfectant level, a pH value within the recommended range, regular filter backwashing, and satisfactory microbiological parameters will not present a significant infection risk. If management or design is poor, conditions can occur in which bathers become infected. Most infections reported in association with pools happen in these circumstances. PMID:8777444

  10. Characterisation of the Permafrost Carbon Pool

    USGS Publications Warehouse

    Kuhry, P.; Grosse, G.; Harden, J.W.; Hugelius, G.; Koven, C.D.; Ping, C.-L.; Schirrmeister, L.; Tarnocai, C.

    2013-01-01

    The current estimate of the soil organic carbon (SOC) pool in the northern permafrost region of 1672 Petagrams (Pg) C is much larger than previously reported and needs to be incorporated in global soil carbon (C) inventories. The Northern Circumpolar Soil Carbon Database (NCSCD), extended to include the range 0–300 cm, is now available online for wider use by the scientific community. An important future aim is to provide quantitative uncertainty ranges for C pool estimates. Recent studies have greatly improved understanding of the regional patterns, landscape distribution and vertical (soil horizon) partitioning of the permafrost C pool in the upper 3 m of soils. However, the deeper C pools in unconsolidated Quaternary deposits need to be better constrained. A general lability classification of the permafrost C pool should be developed to address potential C release upon thaw. The permafrost C pool and its dynamics are beginning to be incorporated into Earth System models, although key periglacial processes such as thermokarst still need to be properly represented to obtain a better quantification of the full permafrost C feedback on global climate change.

  11. Pressure drop, heat transfer, critical heat flux, and flow stability of two-phase flow boiling of water and ethylene glycol/water mixtures - final report for project "Efficent cooling in engines with nucleate boiling."

    SciTech Connect

    Yu, W.; France, D. M.; Routbort, J. L.

    2011-01-19

    Because of its order-of-magnitude higher heat transfer rates, there is interest in using controllable two-phase nucleate boiling instead of conventional single-phase forced convection in vehicular cooling systems to remove ever increasing heat loads and to eliminate potential hot spots in engines. However, the fundamental understanding of flow boiling mechanisms of a 50/50 ethylene glycol/water mixture under engineering application conditions is still limited. In addition, it is impractical to precisely maintain the volume concentration ratio of the ethylene glycol/water mixture coolant at 50/50. Therefore, any investigation into engine coolant characteristics should include a range of volume concentration ratios around the nominal 50/50 mark. In this study, the forced convective boiling heat transfer of distilled water and ethylene glycol/water mixtures with volume concentration ratios of 40/60, 50/50, and 60/40 in a 2.98-mm-inner-diameter circular tube has been investigated in both the horizontal flow and the vertical flow. The two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux of the test fluids were determined experimentally over a range of the mass flux, the vapor mass quality, and the inlet subcooling through a new boiling data reduction procedure that allowed the analytical calculation of the fluid boiling temperatures along the experimental test section by applying the ideal mixture assumption and the equilibrium assumption along with Raoult's law. Based on the experimental data, predictive methods for the two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux under engine application conditions were developed. The results summarized in this final project report provide the necessary information for designing and implementing nucleate-boiling vehicular cooling systems.

  12. Water boiling inside carbon nanotubes: toward efficient drug release.

    PubMed

    Chaban, Vitaly V; Prezhdo, Oleg V

    2011-07-26

    We show using molecular dynamics simulation that spatial confinement of water inside carbon nanotubes (CNTs) substantially increases its boiling temperature and that a small temperature growth above the boiling point dramatically raises the inside pressure. Capillary theory successfully predicts the boiling point elevation down to 2 nm, below which large deviations between the theory and atomistic simulation take place. Water behaves qualitatively different inside narrow CNTs, exhibiting transition into an unusual phase, where pressure is gas-like and grows linearly with temperature, while the diffusion constant is temperature-independent. Precise control over boiling by CNT diameter, together with the rapid growth of inside pressure above the boiling point, suggests a novel drug delivery protocol. Polar drug molecules are packaged inside CNTs; the latter are delivered into living tissues and heated by laser. Solvent boiling facilitates drug release.

  13. Results from Boiling Temperature Measurements for Saturated Solutions in the Systems NaCl + Ca(NO3)2 + H2O, NaNO3 + KNO3 + H2O, and NaCl + KNO3 + H2O, and Dry Out Temperatures for NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O

    SciTech Connect

    Rard, J A

    2005-11-29

    Boiling temperature measurements have been made for saturated ternary solutions of NaCl + KNO{sub 3} + H{sub 2}O and NaNO{sub 3} + KNO{sub 3} + H{sub 2}O at three selected salt ratios and for NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O over the full composition range. The maximum boiling temperature found for the NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O system is 164.7 {+-} 0.6 C, and the composition is estimated to occur at x(Ca(NO{sub 3}){sub 2}) {approx} 0.25. Experiments were also performed for the five component NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O mixtures with the molar ratio of NaCl:NaNO{sub 3}:KNO{sub 3} held essentially constant at 1:0.9780:1.1468 as the solute mole fraction of Ca(NO{sub 3}){sub 2}, x(Ca(NO{sub 3}){sub 2}), was varied between 0 and 0.25. The NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O system forms low melting mixtures and thus boiling temperatures for saturated were not determined. Instead, the temperatures corresponding to the cessation of boiling (i.e., dry out temperatures) of these liquid mixtures were determined. These dry out temperatures range from {approx} 300 C when x(Ca(NO{sub 3}){sub 2}) = 0 to {ge} 400 C when x(Ca(NO{sub 3}){sub 2}) = 0.20 and 0.25. The investigated mixture compositions correspond to some of the major mineral assemblages that are predicted to control the deliquescence relative humidity of salts formed by leaching dust samples from the proposed nuclear repository at Yucca Mountain, Nevada.

  14. Explosive boiling of metals upon irradiation by a nanosecond laser pulse

    SciTech Connect

    Mazhukin, V I; Demin, M M; Shapranov, A V; Samokhin, A A

    2014-04-28

    A repeated effect of explosive boiling has been found in metals exposed to a nanosecond laser pulse in the framework of molecular dynamic simulations combined with a continuum description of a conduction band electrons system. This effect can be used, in particular, as a marker of approaching critical parameters of the region in the irradiated matter. (letters)

  15. 46 CFR 154.706 - Cargo boil-off as fuel: Fuel lines.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... atmospheric pressure. Continuous gas detection must be installed to detect leaks in the ventilated space. The... Equipment Cargo Pressure and Temperature Control § 154.706 Cargo boil-off as fuel: Fuel lines. (a) Gas fuel... must be a double-walled piping system with the annular space containing an inert gas at a...

  16. 46 CFR 154.706 - Cargo boil-off as fuel: Fuel lines.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... atmospheric pressure. Continuous gas detection must be installed to detect leaks in the ventilated space. The... Equipment Cargo Pressure and Temperature Control § 154.706 Cargo boil-off as fuel: Fuel lines. (a) Gas fuel... must be a double-walled piping system with the annular space containing an inert gas at a...

  17. 46 CFR 154.706 - Cargo boil-off as fuel: Fuel lines.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... atmospheric pressure. Continuous gas detection must be installed to detect leaks in the ventilated space. The... Equipment Cargo Pressure and Temperature Control § 154.706 Cargo boil-off as fuel: Fuel lines. (a) Gas fuel... must be a double-walled piping system with the annular space containing an inert gas at a...

  18. 46 CFR 154.706 - Cargo boil-off as fuel: Fuel lines.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... atmospheric pressure. Continuous gas detection must be installed to detect leaks in the ventilated space. The... Equipment Cargo Pressure and Temperature Control § 154.706 Cargo boil-off as fuel: Fuel lines. (a) Gas fuel... must be a double-walled piping system with the annular space containing an inert gas at a...

  19. 46 CFR 154.706 - Cargo boil-off as fuel: Fuel lines.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... atmospheric pressure. Continuous gas detection must be installed to detect leaks in the ventilated space. The... Equipment Cargo Pressure and Temperature Control § 154.706 Cargo boil-off as fuel: Fuel lines. (a) Gas fuel... must be a double-walled piping system with the annular space containing an inert gas at a...

  20. Effect of boiling in water of barley and buckwheat groats on the antioxidant properties and dietary fiber composition.

    PubMed

    Hęś, Marzanna; Dziedzic, Krzysztof; Górecka, Danuta; Drożdżyńska, Agnieszka; Gujska, Elżbieta

    2014-09-01

    In recent years, there has been an ever-increasing interest in the research of polyphenols obtained from dietary sources, and their antioxidative properties. The purpose of this study was to determine the effect of boiling buckwheat and barley groats on the antioxidant properties and dietary fiber composition. Antioxidative properties were investigated using methyl linoleate model system, by assessing the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity and metal chelating activity. The results were compared with butylated hydroxytoluene (BHT). Raw barley and buckwheat groats extracts showed higher DPPH scavenging ability compared to boiled barley and buckwheat groats extracts. Raw barley groats extract exhibited higher antioxidant activity than boiled groats extract in the methyl linoleate emulsion. Higher chelating ability in relation to Fe (II) ions was observed for boiled groats extracts as compared to raw groats extracts. BHT showed small antiradical activity and metal chelating activity, while showing higher antioxidative activity in emulsion system. The analysis of groats extracts using HPLC method showed the presence of rutin, catechin, quercetin, gallic, p-hydroxybenzoic, p-coumaric, o-coumaric, vanillic, sinapic, and ferulic acids. Differences in the content of dietary fiber and its fractions were observed in the examined products. The highest total dietary fiber content was detected in boiled buckwheat groats, while the lowest - in boiled barley groats. The scientific achievements of this research could help consumers to choose those cereal products available on the market, such as barley and buckwheat groats, which are a rich source of antioxidative compounds and dietary fiber.