Sample records for vertical ground-coupled heat

  1. A Simplified Procedure for Sizing Vertical Ground Coupled Heat Pump Heat Exchangers for Residences in Texas

    E-print Network

    O'Neal, D. L.; Gonzalez, J. A.; Aldred, W.

    1994-01-01

    A simplified technique for the sizing of vertical U-tube ground coupled heat pump (GCHP) heat exchangers for Texas climates was developed utilizing a transient simulation model of a ground coupled heat pump and weather and soil data for Texas...

  2. A Modified Analytical Method for Simulating Cyclic Operation of Vertical U-Tube Ground-Coupled Heat Pumps

    E-print Network

    Dobson, M. K.; O'Neal, D. L.; Aldred, W.

    1994-01-01

    solutions inside the soil, and comes closer than previous analytical methods to satisfying the constant heat flux assumption of the original analytical solution. The thermal capacitance effects of the fluid inside the ground-coupled heat exchanger...

  3. Short time step analysis of vertical ground-coupled heat exchangers: The approach of CaRM

    Microsoft Academic Search

    Angelo Zarrella; Massimiliano Scarpa; Michele De Carli

    2011-01-01

    In this paper an improvement of the model CaRM (CApacity Resistance Model) is presented to consider the borehole thermal capacitance, both of the filling material of the borehole and of the heat carrier fluid inside the ground heat exchanger. Several models, numerical and analytical, are available in literature for short time step analyses of ground-coupled heat pump systems. According to

  4. A computational capacity resistance model (CaRM) for vertical ground-coupled heat exchangers

    Microsoft Academic Search

    Michele De Carli; Massimo Tonon; Angelo Zarrella; Roberto Zecchin

    2010-01-01

    Several models are available in literature to simulate ground heat exchangers. In this paper an approach based on electrical analogy is presented, for this reason named CaRM (CApacity Resistance Model). In some cases several information are needed during design: both the borehole and the surrounding ground are affected by thermal exchange. The model here presented allows to consider the fluid

  5. Cooperative heat transfer and ground coupled storage system

    DOEpatents

    Metz, Philip D. (Rocky Point, NY)

    1982-01-01

    A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.

  6. An experimental and analytical study of the transient behavior of vertical u-tube ground-coupled heat pumps in the cooling mode

    E-print Network

    Dobson, Monte Keith

    1991-01-01

    for an ON/OFF Cycle Using Actual and Averaged Heat Input Rate 123 6. 2 Daily Comparison Between GSIM Predictions and Experimental Data from September 3 to September 7 131 LIST OF FIGURES FIGURE PAGE Typical Start-Up Behavior of Capacity and EWT... of Gravity (ft/min2) Cylindrical Integral (dimen sion less) Forced Convection Coefficient (Btu/hr-ft -uF) Free Convection Coefficient (Btu/hr-ft -oF) Enthalpy (B tu/ibm) Thermal Conductivity (Btu/hr-ft- F) Mass (ibm) Mass Flow Rate (Ibm/hr) Nusselt...

  7. A simplified methodology for sizing ground coupled heat pump heat exchangers in cooling dominated climates

    E-print Network

    Gonzalez, Jose Antonio

    1993-01-01

    temperature, ground density, ground thermal conductivity and indoor air temperature were presented. Soil density was not found to be a significant contributor to the performance of ground coupled heat pump (GCHP) heat exchangers. Soil temperature and soil... thermal conductivity were found to be the most important parameters for sizing GCHP heat exchangers. The effects of oversizing or undersizing the heat exchanger were investigated. Oversized heat exchangers provide lower entering water temperatures (EWTs...

  8. Ground-Coupled Heating-Cooling Systems in Urban Areas: How Sustainable Are They?

    ERIC Educational Resources Information Center

    Younger, Paul L.

    2008-01-01

    Ground-coupled heating-cooling systems (GCHCSs) exchange heat between the built environment and the subsurface using pipework buried in trenches or boreholes. If heat pumps in GCHCSs are powered by "green electricity," they offer genuine carbon-free heating-cooling; for this reason, there has been a surge in the technology in recent years.…

  9. Ground coupled heat-pump-system experimental results

    NASA Astrophysics Data System (ADS)

    Metz, P. D.

    1983-06-01

    Since October 1980, a small house in Upton, Long Island, New York has been heated and cooled by a liquid source heat pump using a shallow serpentine earth coil as a heat source/sink. After a brief introduction and system description, system performance data are presented, for the winter of 1981-82 and the summer of 1982, followed by a discussion of these results. The experimental test house is a 104 m(2) (1120 ft(2)) 3 bedroom ranch of energy saving construction with a heating load of 7.8 x 10 to the 6th power J/0C-day (4.1 x 10 to the 3rd power Btu/0F-day). The heat pump used during most of the period reported on here is a commercially available water to air unit sized to just meet the building design heating load with no auxiliary heat. The earth coil contains 155 m (507 ft) of nominal 1-1/2 in. medium density polyethylene pipe, and is approximately 25% ethylene glycol in water, is employed to permit subfreezing earth coil operation. Two independent data acquisition systems, a datalogger microcomputer system backed up by a Btu meter, monitor the space conditioning system performance.

  10. Ground-Coupled Heat Pump Applications and Case Studies

    E-print Network

    Braud, H. J.

    1989-01-01

    The paper presents an overview of ground loops for space-conditioning heat pumps, hot water, ice machines, and water-cooled refrigeration in residential and commercial applications. In Louisiana, a chain of hamburger drive-ins uses total ground...

  11. A Review of Ground Coupled Heat Pump Models Used in Whole-Building Computer Simulation Programs

    E-print Network

    Do, S. L.; Haberl, J. S.

    is the general term that includes the ground coupled heat pump (GCHP), groundwater (GWHP), and surface water (SWHP) heat pump. Although each of these systems utilizes the ground as a heat source/sink, they vary in the different ways the ground temperatures... are delivered to the heat pump. The GCHP system has closed loop GHXs that circulate a fluid through tubes in contact with the ground. GWHP has opened loop GHXs that circulate fluid extracted from wells in the ground or from lakes or bodies of water. SWHP...

  12. Experimental analysis of direct-expansion ground-coupled heat pump systems

    NASA Astrophysics Data System (ADS)

    Mei, V. C.; Baxter, V. D.

    1991-09-01

    Direct-expansion ground-coil-coupled (DXGC) heat pump systems have certain energy efficiency advantages over conventional ground-coupled heat pump (GCHP) systems. Principal among these advantages are that the secondary heat transfer fluid heat exchanger and circulating pump are eliminated. While the DXGC concept can produce higher efficiencies, it also produces more system design and environmental problems (e.g., compressor starting, oil return, possible ground pollution, and more refrigerant charging). Furthermore, general design guidelines for DXGC systems are not well documented. A two-pronged approach was adopted for this study: (1) a literature survey, and (2) a laboratory study of a DXGC heat pump system with R-22 as the refrigerant, for both heating and cooling mode tests done in parallel and series tube connections. The results of each task are described in this paper. A set of general design guidelines was derived from the test results and is also presented.

  13. Numerical Simulation of a Radiant Heating System Using Solar-Ground Coupled Heat Pump with Seasonal Thermal Storage

    Microsoft Academic Search

    Xiao Wang; Maoyu Zheng; Wenyong Zhang

    2010-01-01

    To apply the solar-ground coupled heat pump (SGCHP) in severe cold areas, this paper presents the simulation study on a radiant heating system using SGCHP with seasonal thermal storage. The radiant heating system was installed in a detached house in the suburbs of Harbin (126°46'E, 45°45'N). The unit model of each component was given. The performance and operation characteristics of

  14. Performance and costs of a roof-sized PV\\/thermal array combined with a ground coupled heat pump

    Microsoft Academic Search

    M. Bakker; H. A. Zondag; M. J. Elswijk; K. J. Strootman; M. J. M. Jong

    2005-01-01

    A photovoltaic\\/thermal (PVT) panel is a combination of photovoltaic cells with a solar thermal collector, generating solar electricity and solar heat simultaneously. Hence, PVT panels are an alternative for a combination of separate PV panels and solar thermal collectors. A promising system concept, consisting of 25m2 of PVT panels and a ground coupled heat pump, has been simulated in TRNSYS.

  15. Modeling and Simulation of Solar Seasonal Underground Thermal Storage in a Solar-Ground Coupled Heat Pump System

    Microsoft Academic Search

    Wenyong Zhang; Maoyu Zheng; Xiao Wang

    2010-01-01

    This paper presents a three-dimensional unsteady state fluid-solid coupling mathematical model of multiple ground heat exchangers (GHE) used in a solar-ground coupled heat pump system (SGCHPS). The model was developed with the commercial computational fluid dynamics (CFD) software FLUENT. To simulate the long-term performance of solar seasonal underground thermal storage in SGCHPS, the mathematical models of solar collector and plate

  16. Experimental study of a solar-assisted ground-coupled heat pump system with solar seasonal thermal storage in severe cold areas

    Microsoft Academic Search

    Xiao Wang; Maoyu Zheng; Wenyong Zhang; Shu Zhang; Tao Yang

    2010-01-01

    This paper presents the experimental study of a solar-assisted ground-coupled heat pump system (SAGCHPS) with solar seasonal thermal storage installed in a detached house in Harbin. The solar seasonal thermal storage was conducted throughout the non-heating seasons. In summer, the soil was used as the heat sink to cool the building directly. In winter, the solar energy was used as

  17. A techno-economic comparison of a direct expansion ground-source and a secondary loop ground-coupled heat pump system for cooling in a residential building

    Microsoft Academic Search

    Yonghui Guo; Guoqiang Zhang; Jin Zhou; Jiasheng Wu; Wei Shen

    This paper reports a techno-economic comparison between a direct expansion ground-source heat pump system (DX-GSHP) and a secondary loop ground-coupled heat pump system (SL-GCHP). For this purpose, a DX-GSHP and an SL-GCHP system are designed and installed in parallel for same space cooling load in a demonstrating building in Hunan province, China. The structures of the two systems are described.

  18. EnergyPlus vs DOE-2: The Effect of Ground Coupling on Heating and Cooling Energy Consumption of a Slab-On-Grade Code House in a Cold Climate

    E-print Network

    Andolsun, S.; Culp, C.; Haberl, J.

    -on-grade constructions. This paper extends the previous comparative work by comparing EnergyPlus and DOE-2.1e results for GCHT based on a slab-on- grade code house in a cold climate. Three GCHT models were used in the study. These models were Winkelmann?s (2002...) model in DOE-2.1e, Winkelmann?s model in EnergyPlus and EnergyPlus with its GCHT calculator utility, Slab. INTRODUCTION Ground-coupled heat transfer (GCHT) through concrete floor slabs is a significant component of the total load for heating...

  19. Bubble Enhanced Heat Transfer from a Vertical Heated Surface

    Microsoft Academic Search

    Brian Donnelly; Darina B. Murray; Tadhg S. O'Donovan

    2008-01-01

    A rising bubble in a liquid can greatly enhance heat transfer from heated surfaces by acting like a bluff body, displacing fluid as it moves and via the wake generated by the bubble, increasing the mixing of the liquid. The current research quantifies the effect a single free rising ellipsoidal air bubble has on heat transfer from a vertical heated

  20. Heating system with vapour compressor heat pump and vertical U-tube ground heat exchanger

    NASA Astrophysics Data System (ADS)

    Hanuszkiewicz-Drapa?a, Ma?gorzata; Sk?adzie?, Jan

    2010-10-01

    In the paper a heating system with a vapour compressor heat pump and vertical U-tube ground heat exchanger for small residential house is considered. A mathematical model of the system: heated object - vapour compressor heat pump - ground heat exchanger is presented shortly. The system investigated is equipped, apart from the heat pump, with the additional conventional source of heat. The processes taking place in the analyzed system are of unsteady character. The model consists of three elements; the first containing the calculation model of the space to be heated, the second - the vertical U-tube ground heat exchanger with the adjoining area of the ground. The equations for the elements of vapour compressor heat pump form the third element of the general model. The period of one heating season is taken into consideration. The results of calculations for two variants of the ground heat exchanger are presented and compared. These results concern variable in time parameters at particular points of the system and energy consumption during the heating season. This paper presents the mutual influence of the ground heat exchanger subsystem, elements of vapour compressor heat pump and heated space.

  1. Natural convection heat transfer along vertical rectangular ducts

    Microsoft Academic Search

    M. Ali

    2009-01-01

    Experimental investigations have been reported on steady state natural convection from the outer surface of vertical rectangular\\u000a and square ducts in air. Seven ducts have been used; three of them have a rectangular cross section and the rest have square\\u000a cross section. The ducts are heated using internal constant heat flux heating elements. The temperatures along the vertical\\u000a surface and

  2. Heating system position and vertical microclimate distribution in chrysanthemum greenhouse

    Microsoft Academic Search

    F. L. K. Kempkes; N. J van de Braak

    2000-01-01

    In the cultivation of greenhouse chrysanthemums, the main heating system is often positioned overhead. Under unfavourable conditions, this can lead to unacceptable vertical temperature differences or high relative humidity (RH) in the crop and ultimately to increased risk of diseases. Moreover, the overhead heating pipes will result in higher energy loss compared to a heating system at a lower position.

  3. The vertical structure of ocean heat transport G. Boccaletti,1

    E-print Network

    Marshall, John

    global ocean heat transport can be deduced from estimates of air-sea fluxes [Trenberth and Caron, 2001The vertical structure of ocean heat transport G. Boccaletti,1 R. Ferrari,1 A. Adcroft,2 D is through its poleward heat transport: about 1.5 PW or more than 30% of that accomplished by the ocean

  4. Natural convection in a vertical annular space heated from below

    Microsoft Academic Search

    H. Ozoe; T. Okamoto; S. W. Churchill

    1979-01-01

    Natural convection in an annular space with a vertical axis was investigated by measuring the rate of heat transfer in silicone oil for various thermal inputs. The rate approached heat transfer in infinite horizontal plates with the increased Rayleigh number; the circulation pattern for moderate Reynolds numbers was a symmetrical set of rollcells with axes in the radial direction and

  5. Limitations of Using Uniform Heat Flux Assumptions in Sizing Vertical Borehole Heat Exchanger Fields

    E-print Network

    of the heat flow in the ground is used to predict the temperature rise and fall over time of the fluidLimitations of Using Uniform Heat Flux Assumptions in Sizing Vertical Borehole Heat Exchanger heat exchangers and the surrounding ground are essential for design, optimization and energy analysis

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

    SciTech Connect

    Pastuszko, Robert [Chair of Thermodynamics and Fluids Mechanics, The Kielce University of Technology, Al. Tysiaclecia P.P. 7, 25-314 Kielce (Poland)

    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)

  7. Natural Convection Heat Transfer from Vertical Helical Coils in Oil

    Microsoft Academic Search

    Mohamed E. Ali

    2006-01-01

    An experimental study has been conducted on steady-state natural convection heat transfer from vertical helical coil tubes in heat transfer oil of a Prandtl number range of 250–400. Fifteen coils are used in this experiment. These coils are classified into five groups; each group has a specified coil diameter-to-tube diameter ratio for two, five, and ten turns. The helix coil

  8. Heat transfer analysis of boreholes in vertical ground heat exchangers

    Microsoft Academic Search

    Heyi Zeng; Nairen Diao; Zhaohong Fang

    2003-01-01

    A ground heat exchanger (GHE) is devised for extraction or injection of thermal energy from\\/into the ground. Bearing strong impact on GHE performance, the borehole thermal resistance is defined by the thermal properties of the construction materials and the arrangement of flow channels of the GHEs. Taking the fluid axial convective heat transfer and thermal “short-circuiting” among U-tube legs into

  9. Single thermal plume in locally heated vertical soap films.

    PubMed

    Adami, N; Dorbolo, S; Caps, H

    2011-10-01

    A vertical soap film is maintained by injection of a soap solution from the top. The film is then locally heated. Thermal plumes may be observed to rise in the film, depending on the magnitude of the heating and injected flows. The nearly two-dimensional nature of the system allows to visualize the motion of the plumes using an infrared camera. A model is proposed to describe the growth, emergence, and stationarity of the plumes in the film by taking into account both magnitudes of the heating ?T and injected flow Q. PMID:22181270

  10. Numerical model of mixed convection heat transfer between a series of vertical parallel plates with planar heat sources

    E-print Network

    Watson, James Christopher

    1995-01-01

    Heat transfer between a series of vertical parallel plates with planar heat sources has been studied numerically. The series of plates formed a series of channels, or cooling passages, in which fluid could flow. Heat dissipation from the heat...

  11. Fluid Flow and Heat Transfer of Natural Convection around Heated Vertical Cylinders

    Microsoft Academic Search

    Fumiyoshi Kimura; Tatsuo Tachibana; Kenzo Kitamura; Tsutomu Hosokawa

    2004-01-01

    Natural convective flows of water induced around heated vertical cylinders have been investigated experimentally. Special interests were paid to the influences of cylinder diameter on the turbulent transition and also on the local heat transfer characteristics of the cylinders. The diameters of the cylinders were varied systematically from 10 to 165mm. Visualizations of the flows around the cylinder and of

  12. Heat transfer in vertically aligned phase change energy storage systems

    SciTech Connect

    El-Dessouky, H.T.; Bouhamra, W.S.; Ettouney, H.M.; Akbar, M. [Kuwait Univ., Safat (Kuwait). Dept. of Chemical Engineering

    1999-05-01

    Convection effects on heat transfer are analyzed in low temperature and vertically aligned phase change energy storage systems. This is performed by detailed temperature measurements in the phase change material (PCM) in eighteen locations forming a grid of six radial and three axial positions. The system constitutes a double pipe configuration, where commercial grade paraffin wax is stored in the annular space between the two pipes and water flows inside the inner pipe. Vertical alignment of the system allowed for reverse of the flow direction of the heat transfer fluid (HTF), which is water. Therefore, the PCM is heated from the bottom for HTF flow from bottom to top and from the top as the HTF flow direction is reversed. For the former case, natural convection affects the melting process. Collected data are used to study variations in the transient temperature distribution at axial and radial positions as well as for the two-dimensional temperature field. The data are used to calculate the PCM heat transfer coefficient and to develop correlations for the melting Fourier number. Results indicate that the PCM heat transfer coefficient is higher for the case of PCM heating from bottom to top. Nusselt number correlations are developed as a function of Rayleigh, Stefan, and Fourier numbers for the HTF flow from bottom to top and as a function of Stefan and Fourier numbers for HTF flow from top to bottom. The enhancement ratio for heat transfer caused by natural convection increases and then levels off as the inlet temperature of the HTF is increased.

  13. Convective heat transfer around vertical jet fires: an experimental study.

    PubMed

    Kozanoglu, Bulent; Zárate, Luis; Gómez-Mares, Mercedes; Casal, Joaquim

    2011-12-15

    The convection heat transfer phenomenon in vertical jet fires was experimentally analyzed. In these experiments, turbulent propane flames were generated in subsonic as well as sonic regimes. The experimental data demonstrated that the rate of convection heat transfer increases by increasing the length of the flame. Assuming the solid flame model, the convection heat transfer coefficient was calculated. Two equations in terms of adimensional numbers were developed. It was found out that the Nusselt number attains greater values for higher values of the Rayleigh and Reynolds numbers. On the other hand, the Froude number was analyzed only for the subsonic flames where the Nusselt number grows by this number and the diameter of the orifice. PMID:21962859

  14. Geothermal Energy Utilization via Effective Design of Ground-Coupled

    E-print Network

    Tennessee, University of

    the earth (geo): soil, fluid, rock, and magma ­ Clean ­ Renewable ­ Reliable (average system availability column well #12;Typical Vertical Geothermal Heat Exchangers U-Tubes Others (Florides & Kalogirou, 2007) #12;More on Geothermal Heat Pump · EPA on GHP (1993) ­ GeoExchange (GHP) systems are the most energy

  15. Experimental Study of Natural Convection from Electrically Heated Vertical Cylinders Immersed in Air

    Microsoft Academic Search

    Sad Jarall; Antonio Campo

    2005-01-01

    An experimental study of laminar steady-state natural convection heat transfer from electrically heated vertical cylinders immersed in air has been undertaken. Three stainless steel (316 SS) test sections of different slenderness ratios were employed. Surface temperature profiles along the vertical cylinders were obtained using miniature thermocouples when the cylinders were heated with different power levels resulting in different total wall

  16. Vertical heat flux and lateral mass transport in nonlinear internal waves

    E-print Network

    (2010), Vertical heat flux and lateral mass transport in nonlinear internal waves, Geophys. Res. Lett and heat flux over the shelf. [3] By definition, particle speeds (uw) in NLIWs are com- parable to the waveClick Here for Full Article Vertical heat flux and lateral mass transport in nonlinear internal

  17. Forced convection heat transfer of saturated liquid hydrogen in vertically-mounted heated pipes

    NASA Astrophysics Data System (ADS)

    Tatsumoto, Hideki; Shirai, Yasuyuki; Shiotsu, Masahiro; Hata, Koichi; Naruo, Yoshihiro; Kobayasi, Hiroaki; Inatani, Yoshifumi

    2014-01-01

    Heat transfer from the inner side of vertically-mounted heated pipes to forced flow of saturated liquid hydrogen was measured with a quasi-steady increase of a heat generation rate for wide ranges of flow rate and saturated pressure. The tube heaters have lengths L of 100 mm and 167 mm with the diameter D of 4 mm and lengths of 150 mm and 250 mm with the diameter of 6 mm. The heat fluxes at departure from nucleate boiling (DNB) were higher for higher flow velocity, lower pressures and shorter L/D. The effect of L/D on the DNB heat flux was clarified. It is confirmed that our DNB correlation can describe the experimental data.

  18. Effect of vertical separation distance on laminar natural convective heat transfer over two vertically spaced equitemperature horizontal cylinders

    Microsoft Academic Search

    H. Yuncu; A. Batta

    1994-01-01

    A numerical study of laminar natural convective heat transfer in air from a pair of equitemperature horizontal cylinders placed one above the other in a vertical plane was carried out. Prime attention was focused on how heat transfer characteristics of the upper cylinder are affected by center-to-center separation distance between two cylinders (CCD). The study was limited to Rayleigh number

  19. Pool boiling heat transfer from vertical heater array in liquid nitrogen

    Microsoft Academic Search

    Charlotte J. Chui; M. S. Sehmbey; L. C. Chow; O. J. Hahn

    1995-01-01

    The heat transfer from an array of discrete sources is expected to differ from the behavior of a single heat source due to the interaction between the flow induced by individual heat sources. This study details the results from experiments conducted to study the pool boiling heat transfer characteristics from a vertical heater array with flush-mounted heat sources. The lower

  20. CFD analysis of heat transfer within a bottom heated vertical concentric cylindrical enclosure

    NASA Astrophysics Data System (ADS)

    Hussain Malik, Asif; Shah, Ajmal; Khushnood, Shahab

    2013-06-01

    The CFD analysis of heat transfer within a bottom heated vertical concentric cylindrical enclosure is important with respect to the process in the chemical and process industries. The research work focuses on the CFD analysis of the enclosure with respect to the machines used for the segregation of chemicals in the chemical industries. The CFD simulations are performed to study the effects of inner cylinder material and outer cylinder geometric configurations on the heat transfer mechanism in the enclosure. The CFD simulations are conducted at a bottom disc temperature of 393 K and compared with the published results at a temperature of 433 K. This research study depicts the behavior of bottom heated vertical concentric cylindrical enclosure at different bottom disc temperatures. This study also investigates the heat transfer mechanism of the enclosure using different inner cylinder materials and different configurations of the outer cylinder. In such enclosures a uniform temperature is required for the segregation of chemicals. A more uniform temperature is observed in the enclosure by using aluminum inner cylinder of the bottom disc and using two different diameter outer cylinders as compared to the mild steel and stainless steel.

  1. General Correlations for Laminar and Transition Natural Convection Heat Transfer from Vertical Triangular Cylinders in Air

    Microsoft Academic Search

    M. E. Ali; H. Al-Ansary

    2011-01-01

    Experimental investigations have been reported on steady-state natural convection heat transfer from the outer surface of vertical triangular cylinder in air. Five cylinders have been used with equilateral side lengths of 0.044, 0.06, 0.08, 0.10, and 0.13 m. The cylinders are heated using internal constant heat flux heating elements. The temperatures along the vertical surface and the peripheral directions of

  2. Natural Convection Heat Transfer of a Rectangular Block within a Vertical Enclosure

    Microsoft Academic Search

    Xiaohui Zhang; Mo Yang

    2009-01-01

    A numerical solution of the natural convection heat transfer between two cold and hot isolated vertical plates is presented for different horizontal and vertical location ratios of an enclosure. Results show that: a) flow configurations of cold and hot plates are different; b) the increase of vertical location ratio, toward that corresponding to the enclosure middle value, is considerably diminishing

  3. The Design of Ground-Coupled Heat Pump Systems

    E-print Network

    Parker, J. D.

    1985-01-01

    . % IIC P.E. I!= Flgure 6. Thermal Reslstance and Thermal Stablllty In Terms of the Atterberg Limlts (7). 3' POLYETHYLENE (.OR 21, 2' POLVETHYLENE jj WITH 314. CONCENTRIC WITH 314. CONCENTRIC PVC DIP TUBE PVC DIP TUBE In Flgure 6, Salomone def...

  4. Effect of horizontal heat and fluid flow on the vertical temperature distribution in a semiconfining layer

    USGS Publications Warehouse

    Lu, N.; Ge, S.

    1996-01-01

    By including the constant flow of heat and fluid in the horizontal direction, we develop an analytical solution for the vertical temperature distribution within the semiconfining layer of a typical aquifer system. The solution is an extension of the previous one-dimensional theory by Bredehoeft and Papadopulos [1965]. It provides a quantitative tool for analyzing the uncertainty of the horizontal heat and fluid flow. The analytical results demonstrate that horizontal flow of heat and fluid, if at values much smaller than those of the vertical, has a negligible effect on the vertical temperature distribution but becomes significant when it is comparable to the vertical.

  5. Natural convection heat transfer between inner sphere and outer vertically eccentric cylinder

    Microsoft Academic Search

    Wen Ruey Chen

    2010-01-01

    The effects of eccentricity and geometric configuration with a Newtonian fluid have been investigated numerically to determine heat transfer by natural convection between the sphere and vertical cylinder with isothermal boundary conditions. The inner sphere and outer vertical cylinder were heated and cooled in a steady change of temperature. Calculations were carried out systematically for a range of the Rayleigh

  6. Numerical simulations of natural convection heat transfer along a vertical cylinder

    Microsoft Academic Search

    Muhammad Rafique; I. Ahmad; M. Abdul Basit; Romana Begum; Wajid Aziz; Muhammad Farooq; Kamran Rasheed Qureshi

    2011-01-01

    Purpose – The purpose of this paper is to present a numerical solution for the problem of steady laminar flow and heat transfer characteristics of viscous incompressible fluid. Design\\/methodology\\/approach – For this purpose a two dimensional code has been developed to simulate the natural convection heat transfer along a vertical cylinder, for four different geometries: from vertical cylinder in infinite

  7. Effect of Heating System Position on Vertical Distribution of Crop Temperature and Transpiration in Greenhouse Tomatoes

    Microsoft Academic Search

    F. L. K. Kempkes; N. J. Van de Braak; J. C. Bakker

    2000-01-01

    The presence of independently controllable heating systems enables local crop heating to influence the crop development. The position of the heating system also influences energy consumption. A simulation model was developed to predict the effects of the heating system on the vertical distribution of crop temperature and transpiration in a greenhouse tomato crop. The model is based on physical transport

  8. Combined natural and forced convection heat transfer for assisting thermally developing flow in a uniformly heated vertical circular cylinder

    Microsoft Academic Search

    Hussein A. Mohammed; Yasin K. Salman

    2007-01-01

    Combined convection heat transfer in a vertical circular cylinder has been experimentally studied for assisting, thermally developing and thermally fully developed laminar air flows under constant wall heat flux boundary conditions for Reynolds number range from 400 to 1600, and the heat flux is varied from 60 Wm?2 to 400 Wm?2. This paper has examined the effect of the cylinder inclination angle

  9. THE EFFECT OF BARS AND TRANSIENT SPIRALS ON THE VERTICAL HEATING IN DISK GALAXIES

    SciTech Connect

    Saha, Kanak; Tseng, Yao-Huan; Taam, Ronald E., E-mail: kanak@asiaa.sinica.edu.t [Institute of Astronomy and Astrophysics, Academia Sinica-TIARA, Taiwan (China)

    2010-10-01

    The nature of vertical heating of disk stars in the inner as well as the outer region of disk galaxies is studied. The galactic bar (which is the strongest non-axisymmetric pattern in the disk) is shown to be a potential source of vertical heating of the disk stars in the inner region. Using a nearly self-consistent high-resolution N-body simulation of disk galaxies, the growth rate of the bar potential is found to be positively correlated with the vertical heating exponent in the inner region of galaxies. We also characterize the vertical heating in the outer region where the disk dynamics is often dominated by the presence of transient spiral waves and mild bending waves. Our simulation results suggest that the non-axisymmetric structures are capable of producing the anisotropic heating of the disk stars.

  10. Vertical Concentric Tube Ground Couoled Heat Exchangers V. C. Mei and S. K. Fischer*

    E-print Network

    Oak Ridge National Laboratory

    #12;Vertical Concentric Tube Ground Couoled Heat Exchangers V. C. Mei and S. K. Fischer* Abstract exchangers for use in heat-pump applications is described. The experimental apparatus consists. This heat exchanger was placed in a 0.20-m (8-in.) inside-diameter well and backfilled with sand

  11. Bond Graph Model of a Vertical U-Tube Steam Condenser Coupled with a Heat Exchanger

    E-print Network

    Paris-Sud XI, Université de

    Bond Graph Model of a Vertical U-Tube Steam Condenser Coupled with a Heat Exchanger K. Medjaher1+ A and thus the bottom well acts as a heat exchanger. The storage of hydraulic and thermal energies steam condenser; Heat exchanger; Bond graph 1. Introduction Modern process engineering plants

  12. Gas Heat Transfer in a Heated Vertical Channel under Deteriorated Turbulent Heat Transfer Regime

    E-print Network

    Lee, Jeongik

    Passive cooling via natural circulation of gas after a loss of coolant (LOCA) accident is one of the major goals of the Gas-cooled Fast Reactor (GFR). Due to its high surface heat flux and low coolant velocities under ...

  13. Gas heat transfer in a heated vertical channel under deteriorated turbulent heat transfer regime

    E-print Network

    Lee, Jeongik

    2007-01-01

    Passive cooling via natural circulation of gas after a loss of coolant (LOCA) accident is one of the major goals of the Gas-cooled Fast Reactor (GFR). Due to its high surface heat flux and low coolant velocities under ...

  14. 45 (2008-5) Heat Transfer of liquid droplets impinging on vertically aligned SWNTs film

    E-print Network

    Maruyama, Shigeo

    with conventional copper surfaces. Key Words : Single-walled carbon nanotubes, Vertical alignment, Bonding, Liquid-ku, Yokohama, Kanagawa 221-8686 By using a vertically aligned single-walled carbon nanotubes (VA-SWNT) film to a copper block to construct a high-temperature heating surface. Liquid droplets were impinged onto the high

  15. Computer simulation of natural convection heat transfer from an assembly of vertical cylinders of PARR2

    Microsoft Academic Search

    M. Abdul Basit; Muhammad Rafique; Imran R. Chughtai; Mansoor H. Inayat

    2007-01-01

    In this paper a Computer Code COSINAC (Computer Simulation of Natural Convection from Assembly of vertical Cylinders) has been developed to simulate the natural convection heat transfer from an assembly of vertical cylinders of Pakistan Research Reactor-2 (PARR-2), under the steady state reactor operation. The momentum and energy equations in cylindrical co-ordinates, representing the thermal hydraulic behavior of a typical

  16. Estimating heat flux transmission of vertical greenery ecosystem

    Microsoft Academic Search

    C. Y. Jim; Hongming He

    2011-01-01

    Nurturing vegetation on building envelopes provides an innovative and eco-friendly alternative to urban greening especially in compact cities. Whereas the thermal and other benefits of green roofs have been studied intensively, green walls have received scanty attention. This study evaluates the thermodynamic transmission process of the vertical greenery ecosystem. We designed a field experiment to monitor solar radiation and weather

  17. Natural convection heat transfer from a long heated vertical cylinder to an adjacent air gap of concentric and eccentric conditions

    Microsoft Academic Search

    R. Hosseini; A. Rezania; M. Alipour; L. A. Rosendahl

    2011-01-01

    In this work, the natural convection heat transfer from a long vertical electrically heated cylinder to an adjacent air gap\\u000a is experimentally studied. The aspect and diameter ratios of the cylinder are 55.56 and 6.33, respectively. The experimental\\u000a measurements were obtained for a concentric condition and six eccentricities from 0.1 to 0.92 at five different heat fluxes.\\u000a The surface temperature

  18. Natural Convection in a Vertical Annuli with Discrete Heat Sources

    Microsoft Academic Search

    M. Sankar

    2011-01-01

    In this article, we numerically study natural convection heat transfer in a cylindrical annular cavity with discrete heat sources on the inner wall, whereas the outer wall is isothermally cooled at a lower temperature, and the top wall, the bottom wall, and unheated portions of the inner wall are assumed to be thermally insulated. To investigate the effect of discrete

  19. Method and apparatus for determining vertical heat flux of geothermal field

    DOEpatents

    Poppendiek, Heinz F. (LaJolla, CA)

    1982-01-01

    A method and apparatus for determining vertical heat flux of a geothermal field, and mapping the entire field, is based upon an elongated heat-flux transducer (10) comprised of a length of tubing (12) of relatively low thermal conductivity with a thermopile (20) inside for measuring the thermal gradient between the ends of the transducer after it has been positioned in a borehole for a period sufficient for the tube to reach thermal equilibrium. The transducer is thermally coupled to the surrounding earth by a fluid annulus, preferably water or mud. A second transducer comprised of a length of tubing of relatively high thermal conductivity is used for a second thermal gradient measurement. The ratio of the first measurement to the second is then used to determine the earth's thermal conductivity, k.sub..infin., from a precalculated graph, and using the value of thermal conductivity thus determined, then determining the vertical earth temperature gradient, b, from predetermined steady state heat balance equations which relate the undisturbed vertical earth temperature distributions at some distance from the borehole and earth thermal conductivity to the temperature gradients in the transducers and their thermal conductivity. The product of the earth's thermal conductivity, k.sub..infin., and the earth's undisturbed vertical temperature gradient, b, then determines the earth's vertical heat flux. The process can be repeated many times for boreholes of a geothermal field to map vertical heat flux.

  20. Conjugate Natural Convection Heat Transfer in a Vertical Annulus with Internal Circumferential Fins

    Microsoft Academic Search

    M. Molki; M. Faghri

    1994-01-01

    A numerical investigation is carried out to study natural convection heat transfer in a vertical annular enclosure with circumferential fins mounted on the inner cylinder. Heat is generated within the inner solid cylinder, while the top, the bottom, and the outer walls are exposed to convection. The results show that, even though the presence of fins does not alter the

  1. Experimental Study of the Natural-Convection Plume from a Heated Vertical Cylinder

    Microsoft Academic Search

    Irma Welling; Hannu Koskela; Timo Hautalampi

    1998-01-01

    This article describes an experimental study of the natural convection from a vertical cylinder, and gives new data for the velocity and temperature distributions of a heat source with real structure and high heating capacity. Two different instruments, a laser Doppler anemometer and 3D ultrasonic anemometer, were used for velocity measurements. Thermistors were used for temperature measurements. Velocity data were

  2. Laminar natural convection in a laterally heated and upper cooled vertical cylindrical enclosure

    Microsoft Academic Search

    A. Lemembre; J.-P. Petit

    1998-01-01

    Numerical simulation of laminar natural convection in a vertical cylinder is proposed. The cylinder is insulated at the bottom, laterally heated at a uniform heat flux density and cooled at the same flux at the top surface. The influence of the characteristic parameters of the problem on the steady-state solution is analysed (102? Ra ? 106; 0.7? Pr ? 92.5;

  3. An experimental investigation of free convection heat transfer in a vertical cylinder with a hemispherical bottom

    Microsoft Academic Search

    T. S. Hunter II

    1974-01-01

    Transient natural convection heating of a bounded liquid was investigated. The test fluid was in contact with a wall at uniform temperature. An aluminum tank, a vertical cyclinder with a hemispherical bottom, was externally heated by water circulated through a constant temperature bath. Flow phenomena, made visible by an electrochemical process, were photographed. Tests were conducted at three aspect ratios,

  4. Natural convection heat transfer at a vertical surface \\/boundary conditions of the second kind

    Microsoft Academic Search

    O. G. Martynenko; Iu. A. Sokovishin

    1977-01-01

    The problem of natural convection heat transfer at vertical plane and cylindrical surfaces with prescribed heat flux is formulated, and various methods of solution are investigated. The basic equations of natural convection, similarity criteria, and boundary layer equations are derived. Self-similar problems are formulated, and integral methods, asymptotic expansion methods, and finite difference methods of solution are proposed. Numerical calculations

  5. Forced convection heat transfer of subcooled liquid nitrogen in a vertical tube

    Microsoft Academic Search

    H. Tatsumoto; Y. Shirai; K. Hata; T. Kato; M. Futakawa; M. Shiotsu

    2010-01-01

    Experimental research on forced convection heat transfer of subcooled liquid nitrogen ranging from the pressures of 0.3 MPa to its supercritical pressure is carried out for wide ranges of inlet temperature and flow velocity. A stainless steel tube heater with the inner diameter of 5.4 mm and the length of 100 mm is mounted vertically. The heat transfer coefficients in

  6. Fluid flow and convective heat transfer in a vertical porous annulus

    SciTech Connect

    Jiang, P.X.; Wang, B.X.; Luo, D.A.; Ren, Z.P. [Tsinghua Univ., Beijing (China). Dept. of Thermal Engineering

    1996-08-23

    This article presents a numerical study of upward fluid flow and the corresponding convective heat transfer in a vertical porous annulus. The study investigated the effects of the inertia term, thermal dispersion, variable porosity, variable properties, buoyancy, particle diameter, and fluid pressure on the flow and heat transfer. The heat transfer augmentation produced by the porous matrix was also analyzed. It was found that for the conditions studied, the effect of thermal dispersion and variable porosity had to be considered. For Re{sub e} {ge} 5, the flow inertia had nonnegligible influence on the flow field and local heat transfer coefficient near the inlet (x/L {le} 0.02). When Re{sub e} {ge} 400, the flow inertia significantly influenced the overall friction factor in the vertical porous annulus. The porous medium greatly enhanced the heat transfer coefficient and also sharply increased the friction resistance. At supercritical pressures (25 MPa), variable properties significantly influenced the heat transfer.

  7. HEAT TRANSFER CORRELATION FOR TWO PHASE FLOW IN VERTICAL PIPES USING ARTIFICIAL NEURAL NETWORK

    Microsoft Academic Search

    A. J. Ghajar; L. M. Tam; H. K. Tam

    In many industrial applications, such as the flow of natural gas and oil in flowlines and wellbores, the knowledge of nonboiling two-phase, two-component (liquid and permanent gas) heat transfer is required. Several heat transfer correlations for forced convective heat transfer during gas-liquid two-phase flow in vertical pipes have been published over the past 40 years. These correlations were developed based

  8. Estimation of the average surface heat flux over an inhomogeneous terrain from the vertical velocity variance

    NASA Technical Reports Server (NTRS)

    Eilts, M. D.; Sundara-Rajan, A.; Evans, R. J.

    1987-01-01

    An indirect method of estimating the surface heat flux from observations of vertical velocity variance at the lower mid-levels of the convective atmospheric boundary layer is described. Comparison of surface heat flux estimates with those from boundary-layer heating rates is good, and this method seems to be especially suitable for inhomogeneous terrain for which the surface-layer profile method cannot be used.

  9. Natural-convection heat transfer to air from a vertical array of two horizontal circular cylinders

    Microsoft Academic Search

    Masafumi Kurayama; Eiji Harada; Hirotaka Konno; X. Li

    1994-01-01

    An experimental study was conducted of steady-state natural-convection heat transfer to air from two horizontal cylinders arranged in a vertical line. Variation of heat-transfer coefficients of both cylinders with cylinder spacing and surface temperature is presented, and it is shown that the heat transfer around the upper cylinder was strongly affected by the buoyant plume induced by the lower cylinder.

  10. Experimental study of low Prandtl number natural convection in an array of uniformly heated vertical cylinders

    Microsoft Academic Search

    J. C. Dutton; J. R. Welty

    1975-01-01

    An experimental program was conducted to study natural convection heat ; transfer in an array of uniformly heated vertical cylinders in mercury. The ; cylinders were arranged in an equilateral triangular pattern, and three bundle ; spacings, P\\/D = 1.5, 1.3, and 1.1, were studied. The heat transfer results are ; presented as local Nusselt number--modified Grashof number correlations. The

  11. Computer cooling using a two phase minichannel thermosyphon loop heated from horizontal and vertical sides and cooled from vertical side

    NASA Astrophysics Data System (ADS)

    Bieli?ski, Henryk; Mikielewicz, Jaros?aw

    2010-10-01

    In the present paper it is proposed to consider the computer cooling capacity using the thermosyphon loop. A closed thermosyphon loop consists of combined two heaters and a cooler connected to each other by tubes. The first heater may be a CPU processor located on the motherboard of the personal computer. The second heater may be a chip of a graphic card placed perpendicular to the motherboard of personal computer. The cooler can be placed above the heaters on the computer chassis. The thermosyphon cooling system on the use of computer can be modeled using the rectangular thermosyphon loop with minichannels heated at the bottom horizontal side and the bottom vertical side and cooled at the upper vertical side. The riser and a downcomer connect these parts. A one-dimensional model of two-phase flow and heat transfer in a closed thermosyphon loop is based on mass, momentum, and energy balances in the evaporators, rising tube, condenser and the falling tube. The separate two-phase flow model is used in calculations. A numerical investigation for the analysis of the mass flux rate and heat transfer coefficient in the steady state has been accomplished.

  12. Heat transfer during melting around an isothermal vertical cylinder

    Microsoft Academic Search

    P. R. Souza Mendes; A. C. Jr. Pinho Brasil

    1987-01-01

    Research on alternative energy resources has intensified during the past few decades as a consequence of the alarming increase in energy cost. Effective thermal energy storage systems have become a true necessity, especially in solar energy applications. Using the phase change of some materials in thermal energy storage systems is advantageous in various ways. For example, the heat capacity of

  13. Heat transfer due to film condensation on vertical fluted tubes

    NASA Astrophysics Data System (ADS)

    Garg, V. K.; Marto, P. J.

    1984-07-01

    An analysis of film condensation on a vertical fluted tube has been made considering gravitational and surface tension effects over the entire fluted surface, and using surface-oriented coordinates. For the first time surface tension effects are determined, as they should, from the shape of the condensate-vapor interface rather than the shape of the flute. Two-dimensional conduction within the condensate film as well as in the fluted tube is considered. A finite-difference solution of the highly non-linear partial differential equation for the film thickness is coupled with a finite-element solution of the condition problem. The procedure has been tested on a sinusoidal flute with amplitude to pitch ratio approx. 0.2. A linear extrapolation, on a log-log basis, of our results shows good comparison with experimental data.

  14. Experimental study of natural convection heat transfer from vertical array of isothermal horizontal elliptic cylinders

    Microsoft Academic Search

    T. Yousefi; M. Ashjaee

    2007-01-01

    Laminar free convection heat transfer from vertical array of horizontal isothermal elliptic cylinders with vertical major axis has been experimentally investigated. Experiments were carried out using Mach–Zehnder interferometer with the cylinder spacing from two to five cylinder major axis and at Rayleigh numbers in the range between 103 and 2.5×103. The effects of cylinder spacing and Rayleigh number on the

  15. Experimental study of natural convection heat transfer from vertical array of isothermal horizontal elliptic cylinders

    Microsoft Academic Search

    T. Yousefi; M. Ashjaee

    2007-01-01

    Laminar free convection heat transfer from vertical array of horizontal isothermal elliptic cylinders with vertical major axis has been experimentally investigated. Experiments were carried out using Mach-Zehnder interferometer with the cylinder spacing from two to five cylinder major axis and at Rayleigh numbers in the range between 10³ and 2.5 x 10³. The effects of cylinder spacing and Rayleigh number

  16. Heat transfer by natural convection from a uniformly heated vertical circular pipe with different entry restriction configurations

    Microsoft Academic Search

    Hussein A. Mohammed; Yasin K. Salman

    2007-01-01

    Natural convection heat transfer for laminar air flow in a vertical circular pipe by using the boundary condition of constant wall heat flux in the ranges of RaL from 1.1×109 to 4.7×109 has been experimentally investigated. The experimental set up was designed for determining the effect of different configurations of restriction placed in the bottom position at the entry of

  17. Convection Heat and Mass Transfer in an Electrical Conducting Power Law Flow over a Heated Vertical Porous Plate

    Microsoft Academic Search

    B. I. Olajuwon

    2010-01-01

    This paper investigates convection heat and mass transfer flow in an electrically conducting power law fluid past a vertical porous plate in presence of a transverse magnetic field, thermal radiation, and thermal diffusion. The non–linear partial differential equations governing the flow are transformed into ordinary differential equations using the usual similarity method and the resulting similarity equations are solved numerically

  18. Experimental Investigation of Free-Convection Heat Transfer in Vertical Tube at Large Grashof Numbers

    NASA Technical Reports Server (NTRS)

    Eckert, E R G; Diaguila, A J

    1955-01-01

    Report presents the results of an investigation conducted to study free-convection heat transfer in a stationary vertical tube closed at the bottom. The walls of the tube were heated, and heated air in the tube was continuously replaced by fresh cool air at the top. The tube was designed to provide a gravitational field with Grashof numbers of a magnitude comparable with those generated by the centrifugal field in rotating-blade coolant passages (10(8) to 10(13)). Local heat-transfer coefficients in the turbulent-flow range and the temperature field within the fluid were obtained.

  19. Experimental study of natural convective heat transfer in a vertical hexagonal sub channel

    SciTech Connect

    Tandian, Nathanael P.; Umar, Efrizon; Hardianto, Toto; Febriyanto, Catur [Faculty of Mechanical and Aerospace Engineering, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132 (Indonesia); Nuclear Technology Center for Materials and Radiometry, National Nuclear Energy Agency, Bandung (Indonesia); Faculty of Mechanical and Aerospace Engineering, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132 (Indonesia); Nuclear Energy Regulation Agency, Jakarta (Indonesia)

    2012-06-06

    The development of new practices in nuclear reactor safety aspects and optimization of recent nuclear reactors, including the APWR and the PHWR reactors, needs a knowledge on natural convective heat transfer within sub-channels formed among several nuclear fuel rods or heat exchanger tubes. Unfortunately, the currently available empirical correlation equations for such heat transfer modes are limited and researches on convective heat transfer within a bundle of vertical cylinders (especially within the natural convection modes) are scarcely done. Although boundary layers around the heat exchanger cylinders or fuel rods may be dominated by their entry regions, most of available convection correlation equations are for fully developed boundary layers. Recently, an experimental study on natural convective heat transfer in a subchannel formed by several heated parallel cylinders that arranged in a hexagonal configuration has been being done. The study seeks for a new convection correlation for the natural convective heat transfer in the sub-channel formed among the hexagonal vertical cylinders. A new convective heat transfer correlation equation has been obtained from the study and compared to several similar equations in literatures.

  20. The transfer of heat and mass to a vertical plate under frosting conditions

    E-print Network

    Poth, Louis Joseph

    1960-01-01

    THE TRAESFPIR OF HEAT . 'ND NASH 10 A VERTICAL PLATE UNDER FROSTING CONDITIONS A Thesis Louis Joseph Poth, Jr. Submitted to the Graduate School of the Agricultural and Nechanioal College of Texas in partial fulfili ment of the requirements... of the Husselt-Grashof correlation for heat transfer. coefficient of saturation temper ture and concen- tration gradient correlation, for small temper- ature difference. ooefficient of frost specific gravity-thermal oonductivity correlation. coefficient...

  1. Conjugate Effects on Steady Laminar Natural Convection Heat Transfer in Vertical Eccentric Annuli

    Microsoft Academic Search

    Maged A. I. El-Shaarawi; Esmail M. A. Mokheimer; Ahmad Jamal

    2005-01-01

    Combined conduction-free convection heat transfer in vertical eccentric annuli is numerically investigated using finite-difference technique. Numerical results are presented for a fluid of Prandtl number 0.7 in an annulus of radius ratio 0.5 and dimensionless eccentricity 0.5. The conjugation effect on the induced flow rate and the total heat absorbed in the annulus is presented for the case of one

  2. Developing Flow of Mixed Convection in a Vertical Rectangular Duct with One Heating Wall

    Microsoft Academic Search

    Chin-Hsiang Cheng; Chun-Jen Weng

    1993-01-01

    Heat transfer and flow patterns of laminar mixed confection in the developing region of a vertical rectangular duct with one heating wall have been investigated numerically in this study. The parabolic boundary layer model is adopted to predict the three-dimensional buoyancy-assisted flow field. Governing equations art solved by using the SIMPI.KC method coupled with a forward marching, implicit finite difference

  3. Comparison of two vertical condensation obturation techniques: Touch 'n Heat modified and System B

    Microsoft Academic Search

    G. K. Silver; R. M. Love; D. G. Purton

    1999-01-01

    Abstract Silver GK, Love RM and Purton DG. Comparison of two vertical condensation,obturation,techniques:,Touch,’n Heat modified and System B. International Endodontic Journal, 32, 287?295, 1999. Aim,The aims,of this study were,firstly to compare

  4. Thermal convection in a uniformly heated fluid between vertical parallel plates

    Microsoft Academic Search

    Brent Ellerbroek; Alexander Kolin

    1979-01-01

    In this paper an approximation is presented for the velocity of convection currents resulting when an electrically conducting liquid sheet between two closely spaced vertical parallel plates joined at the edges is uniformly heated by an electric current flowing parallel to the plates. A quantitative analysis of the velocity distribution is examined in the context of its importance to thermal

  5. Experimental study of natural convection heat transfer from an enclosed assembly of thin vertical cylinders

    Microsoft Academic Search

    Muhammad Arshad; Mansoor Hameed Inayat; Imran Rafiq Chughtai

    2011-01-01

    Steady state heat transfer by natural convection was investigated experimentally from an enclosed assembly of thin vertical cylinders at high Rayleigh numbers. The published literature lacks any information regarding such a study in the turbulent boundary layer regime. All the available literature is for the laminar region for an enclosed assembly. The enclosed assembly consisted of a 3 × 3 array of

  6. Natural convection in vertical annuli: A numerical study for constant heat flux on the inner wall

    Microsoft Academic Search

    J. A. Khan; R. Kumar

    1989-01-01

    A numerical investigation has been conducted to evaluate the effects of diameter ratio and aspect ratio in natural convection of gases within vertical annuli. The inner cylinder is maintained at uniform heat flux and the outer cylinder at constant temperature. The horizontal top and bottom walls are insulated. Detailed result of ⤠15, 1 ⤠A ⤠10, and 100

  7. Heat transfer analysis in a two-side heated smooth square vertical channel with adverse and favorable mixed convection

    SciTech Connect

    Dutta, S.; Zhang, X.; Khan, J.A.; Bell, D.

    1997-07-01

    Experimental heat transfer measurements and analysis for mixed convection in a vertical square channel are presented. The flow direction is changed with respect to the earth's gravity field by selectively opening and closing the flow control valves. Desired flow directions are selected such that buoyancy assists or opposes the bulk flow direction pressure gradient. The heating condition is asymmetric. Most previous experiments used symmetrically heated circular tubes. Present configuration shows significant increase in the Nusselt number in both assisted and opposed flow conditions. In general, opposed flow shows higher heat transfer coefficients. Unlike symmetric heating conditions, Nusselt number ratio is observed to be increasing with increasing Gr/Re or Gr/Re{sup 2} ratios for both assisted and opposed flow conditions.

  8. Heat transfer in vertical Bridgman growth of oxides - Effects of conduction, convection, and internal radiation

    NASA Technical Reports Server (NTRS)

    Brandon, S.; Derby, J. J.

    1992-01-01

    In the present investigation of crystalline phase internal radiation and heat conduction during the vertical Bridgman growth of a YAG-like oxide crystal, where transport through the melt is dominated by convection and conduction, heat is also noted to be conducted through ampoule walls via natural convection and enclosure radiation. The results of a quasi-steady-state axisymmetric Galerkin FEM indicate that heat transfer through the system is powerfully affected by the optical absorption coefficient of the crystal. The coupling of internal radiation through the crystal with conduction through the ampoule walls promotes melt/crystal interface shapes that are highly reflected near the ampoule wall.

  9. Effects of water vapor condensation on the convection heat transfer of wet flue gas in a vertical tube

    Microsoft Academic Search

    L. Jia; X. F. Peng; Y. Yan; J. D. Sun; X. P. Li

    2001-01-01

    The annular thin film condensation of water vapor in wet flue gas flowing through a vertical tube was studied theoretically and experimentally. Especially discussions were conducted on the effects induced by condensation of small amount of water vapor (10–20% fraction) on convection heat transfer in a vertical tube. The convection heat transfer was enhanced by the condensation of the condensable

  10. Boiling heat transfer in a vertical microchannel: Local estimation during flow boiling with a non intrusive method

    E-print Network

    Boiling heat transfer in a vertical microchannel: Local estimation during flow boiling with a non the results of experimental and numerical studies concerning boiling heat transfer inside vertical of boiling flows in microscale's geometry, it is vital to quantify these transfers. To achieve this goal

  11. Experimental research on heat transfer of natural convection in vertical rectangular channels with large aspect ratio

    SciTech Connect

    Lu, Qing; Qiu, Suizheng; Su, Guanghui [State Key Laboratory of Multi Phase Flow in Power Engineering, Xi'an JIaotong University, Xi'an, Shaanxi 710049 (China); School of Nuclear Science and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 (China); Tian, Wenxi; Ye, Zhonghao [School of Nuclear Science and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 (China)

    2010-01-15

    This work presents the experimental research on the steady laminar natural convection heat transfer of air in three vertical thin rectangular channels with different gap clearance. The much higher ratio of width to gap clearance (60-24) and the ratio of length to gap clearance (800-320) make the rectangular channels similar with the coolant flow passage in plate type fuel reactors. The vertical rectangular channels were composed of two stainless steal plates and were heated by electrical heating rods. The wall temperatures were detected with the K-type thermocouples which were inserted into the blind holes drilled in the steal plates. Also the air temperatures at the inlet and outlet of the channel were detected. The wall heat fluxes added to the air flow were calculated by the Fourier heat conduction law. The heat transfer characteristics were analyzed, and the average Nusselt numbers in all the three channels could be well correlated with the Rayleigh number or the modified Rayleigh number in a uniform correlation. Furthermore, the maximum wall temperatures were investigated, which is a key parameter for the fuel's integrity during some accidents. It was found that even the wall heat flux was up to 1500 W/m{sup 2}, the maximum wall temperature was lower than 350 C. All this work is valuable for the plate type reactor's design and safety analysis. (author)

  12. Enhancing heat transfer rates from closed-sided, open-topped heat exchangers, each having vertical rectangular fins extending upwards from a horizontal base

    Microsoft Academic Search

    K. Jambunathan; S. D. Probert; M. J. Shilston

    1984-01-01

    The almost two-dimensional steady-state rates of heat loss from arrays of uniformly-spaced vertical rectangular fins, extending upwards--in otherwise stagnant air--from horizontal heated bases, have been measured. (The vertical air gaps between the fins were closed at their sides, by insulated vertical end-barriers.) The effects of various combinations of height, thickness and spacing of the fins, for different base temperatures (in

  13. Experimental study on flow boiling heat transfer of LNG in a vertical smooth tube

    NASA Astrophysics Data System (ADS)

    Chen, Dongsheng; Shi, Yumei

    2013-10-01

    An experimental apparatus is set up in this work to study the upward flow boiling heat transfer characteristics of LNG (liquefied natural gas) in vertical smooth tubes with inner diameters of 8 mm and 14 mm. The experiments were performed at various inlet pressures from 0.3 to 0.7 MPa. The results were obtained over the mass flux range from 16 to 200 kg m-2 s-1 and heat fluxes ranging from 8.0 to 32 kW m-2. The influences of quality, heat flux and mass flux, tube diameter on the heat transfer characteristic are examined and discussed. The comparisons of the experimental heat transfer coefficients with the predicted values from the existing correlations are analyzed. The correlation by Zou et al. [16] shows the best accuracy with the RMS deviation of 31.7% in comparison with the experimental data.

  14. Boiling Heat Transfer of a Refrigerant Flowing Vertically Downward in a Mini-channel

    NASA Astrophysics Data System (ADS)

    Miyata, Kazushi; Mori, Hideo; Ohishi, Katsumi; Hamamoto, Yoshinori

    Experiments were performed on boiling heat transfer of a refrigerant R-410A flowing vertically downward in a copper rectangular tube and a triangular tube of 1.04 mm and 0.88 mm inside hydraulic diameter, respectively,for the development of a high-performance heat exchanger using small tubes or multi-port extruded tubes for air conditioning systems. Local heat transfer coefficients were measured in a range of mass fluxes from 30 to 200kg/(m2s), heat fluxes from 1 to 20 kW/m2 and quality from 0.05 to 1 at the evaporation temperature of 10 °C.Characteristics of the heat transfer coefficient and dryout quality were clarified by comparing the measurements with the data for the circular tube of 1.0 mm inside diameter previously obtained.

  15. Transient heat and mass transfer by natural convection from vertical surfaces in porous media

    NASA Astrophysics Data System (ADS)

    Cheng, Ching-Yang

    2000-06-01

    A study on the transient heat and mass transfer from vertical plates embedded in fluid saturated porous media is conducted. The wall temperature and concentration are power functions of the dimensionless streamwise coordinate. Results for the heat and mass transfer rates are obtained for different values of the Lewis number, the buoyancy ratio, the power-law exponent and the ratio of porosity and heat capacity ratio. The transient local Nusselt number at X = 1 is found to be almost independent of the ratio of porosity and heat capacity ratio, while the transient local Sherwood number at X = 1 tends to increase as the ratio of porosity and heat capacity ratio is increased. Moreover, increasing the power-law exponent increases the transient local Nusselt and Sherwood numbers.

  16. Constructal multi-scale package of vertical channels with natural convection and maximal heat transfer density. CONSTRUCTAL DESIGN: THE GENERATION OF MULTI-SCALE HEAT

    E-print Network

    Kihm, IconKenneth David

    transfer density. CONSTRUCTAL DESIGN: THE GENERATION OF MULTI-SCALE HEAT AND FLUID FLOW STRUCTURES-scale structures in natural convection with the objective of maximizing the heat transfer density, or the heat transfer rate per unit of volume§ . The flow volume is filled with vertical equidistant heated blades

  17. Downflow heat transfer in a heated ribbed vertical annulus with a cosine power profile

    Microsoft Academic Search

    J. L. Anderson; K. G. Condie; T. K. Larson

    1991-01-01

    Experiments designed to investigate downflow heat transfer in a heated, ribbed annulus test section simulating one of the annular coolant channels of a Savannah River Plant production reactor Mark 22 fuel assembly have been conducted at the Idaho National Engineering Laboratory. The inner surface of the annulus was constructed of aluminum and was electrically heated to provide an axial cosine

  18. Vertical heat transfer in the Arctic Ocean: The role of double-diffusive mixing

    NASA Astrophysics Data System (ADS)

    Sirevaag, Anders; Fer, Ilker

    2012-07-01

    Microstructure profiles collected in the central Amundsen Basin are analyzed in order to quantify the role of double-diffusive mixing for vertical heat transfer from the Atlantic layer. In the profiles, a persistent, but laterally incoherent thermohaline staircase structure is identified in the 200-260 m depth range. The staircase contains homogeneous layers with average height of 1.3 m and thin, high-gradient interfaces with average temperature and salinity jumps of about 0.065°C and 0.015, respectively. When inferred from a commonly used diffusive convection parameterization, the average vertical heat flux within the staircase is 0.6 W m-2. This is one order of magnitude larger than the molecular diffusion alone and of the same order as the overall heat loss from the Atlantic layer in the deep basins of the Arctic Ocean. The parameterization is evaluated using observed turbulent heat fluxes and is found to overestimate diffusive convective fluxes with up to an order of magnitude, especially for weak thermal forcing (small temperature jumps in staircase). Staircases coexist with thermohaline intrusions in the vertical temperature and salinity profiles. Lomonosov Ridge is identified as a potential region for formation of intrusions. It is found that salt fingering is the dominant process during intrusion growth whereas diffusive convection is the dominant process in maintaining the intrusions at steady state in the deep basins.

  19. 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.

  20. Thermal performances of different types of underground heat exchangers

    Microsoft Academic Search

    Xinguo Li; Yan Chen; Zhihao Chen; Jun Zhao

    2006-01-01

    An experiment system with different types of U-vertical ground coupled heat exchanger (UGCHE) in situ was set up, for example, single or double U-pipes with sandstone backfills, and single U-pipe with cement backfills. Experiments on the thermal performance of UGCHE were carried out in different conditions, such as different inlet temperature, flow rate, soil types, backfill materials, number of U-pipes

  1. Vertical heat flux and lateral mass transport in nonlinear internal waves

    NASA Astrophysics Data System (ADS)

    Shroyer, E. L.; Moum, J. N.; Nash, J. D.

    2010-04-01

    Comprehensive observations of velocity, density, and turbulent dissipation permit quantification of the nonlinear internal wave (NLIW) contribution to vertical heat flux and lateral mass transport over New Jersey's shelf. The effect of NLIWs on the shelf heat budget was significant. On average, heat flux in NLIWs was 10 times larger than background at the pycnocline depth. NLIWs were present at midshelf <10% of the time, yet we estimate that they contributed roughly one-half the heat flux across the pycnocline during the observation period, which was characterized by weak to moderate winds. Lateral transport distances due to the leading 3 waves in NLIW packets were typically $\\rm{O(100 m) but ranged several kilometers. The month-averaged daily onshore transport (per unit alongshelf dimension) by NLIWs is estimated as 0.3 m2s-1. This is comparable to a weak downwelling wind, but sustained over an entire month.

  2. Effect of surfactant on evaporative heat transfer coefficients in vertical film forced convection

    E-print Network

    Shah, Basit Husain

    1972-01-01

    of satisfactory pre- cision, provided known precautions are taken. Mankowich has attr1buted major causes of poor precision, when measuring sur- face tensions of aqueous solutions of surfactants by due du Nouy method, to insufficient 'aging' time with the ring...EFFECT OF SURFACTANT ON EVAPORATIVE HEAT TRANSFER COEFFICIENTS IN VERTICAL FILM FORCED CONVECTION A Thesis by BASIT HUSAIN SHAH Submitted to the Graduate College of Texas A8M University in partial fulfillment of the requirement for the degree...

  3. Rayleigh-Benard Convection in a Vertical Cylinder Heated from Below with a Nonuniform Temperature

    Microsoft Academic Search

    Gang Luo; Pratap Vanka

    2001-01-01

    Rayleigh-Benard convection in a vertical cylinder heated from below with a uniform bottom wall temperature has been studied extensively. At low aspect ratios, the flow starts as an axisymmetric pattern and gradually becomes non-axisymmetric when the Rayleigh number is increased. For aspect ratios around and greater than unity, the first stable flow pattern is a non-axisymmetric mode at all Rayleigh

  4. Effect of Using Porous Inserts on Natural Convection Heat Transfer Between Two Concentric Vertical Cylinders

    Microsoft Academic Search

    Suhil Kiwan; Mohammed Sabty Alzahrany

    2008-01-01

    A numerical simulation of the steady-state, laminar, axisymmetric, natural convection heat transfer in the annulus between two concentric vertical cylinders using porous inserts is studied. A finite volume code is used to numerically solve the sets of governing equations. The Darcy-Brinkman-Forchheimer model along with Boussinesq approximation is used to solve for the flow in the porous region. The Navier-Stokes equation

  5. Transient natural convection along vertical cylinder with Heat and Mass transfer

    Microsoft Academic Search

    P. Ganesan; H. P. Rani

    1998-01-01

    A numerical solution for the transient natural convection flow over a vertical cylinder under the combined buoyancy effect\\u000a of heat and mass transfer is presented. The velocity, temperature and concentration profiles, local and average skin-friction,\\u000a Nusselt number and Sherwood number are shown graphically. It is observed that time taken to reach steady state increases with\\u000a Schmidt number and decreases as

  6. Augmentation of heat transfer in a bubble agitated vertical rectangular channel

    NASA Astrophysics Data System (ADS)

    Mitra, Asish; Dutta, Tapas Kumar; Ghosh, Dibyendu Narayan

    2012-04-01

    This paper presents the results of an experimental study of convective heat transfer between three parallel vertical plates symmetrically spaced with and without bubble agitation to ascertain the degree of augmentation of the heat transfer coefficients due to agitation. The centre plate was electrically heated, while the other side plates were water-cooled forming two successive parallel vertical rectangular channels of dimensions 20 cm × 3.5 cm × 35 cm (length W, gap L, height H) each. At the bottom of the hot and cold plates air spargers were fitted. Water/ethylene glycol (100%) was used to fill the channels. The superficial gas velocity ranged from 0.0016 to 0.01 m/s. Top, bottom and sides of the channels were open to the water/ethylene glycol in the chamber which is the novel aspect of this study. Experimental data have been correlated as under: Natural convective heat transfer: Nu = 0.60 Gr 0.29, r = 0.96, ? = 0.186, 1.17 E6 < Gr < 1.48 E7; Bubble agitated heat transfer: St = 0.11( ReFrPr 2)-0.23, r = 0.82, ? = 0.002, 1.20 E-2 < ( ReFrPr 2) < 1.36 E2.

  7. Influence of Heating Rate on Subcooled Flow Boiling Critical Heat Flux in a Short Vertical Tube

    NASA Astrophysics Data System (ADS)

    Hata, Koichi; Shiotsu, Masahiro; Noda, Nobuaki

    The subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3m/s), the inlet subcoolings (?Tsub, in=130 to 161K), the inlet pressure (Pin=812 to 1315kPa), the dissolved oxygen concentration (O2=5.88 and 7.34ppm) and the increasing heat input (Q0exp(t/?), ?=38.1ms to 8.3s) are systematically measured by the experimental water loop installed the pressurizer. The SUS304 tube of test tube inner diameter (d=6mm), heated length (L=60mm), L/d=10 and wall thickness (?=0.5mm) with the rough finished inner surface (Surface roughness, Ra=3.18µm) is used in this work. The CHF data for high heating rate were compared with the quasi steady state ones previously obtained and the values calculated by the steady state CHF correlations against outlet and inlet subcoolings. Transient CHF correlation against inlet subcooling has been given based on the experimental data for wide exponentially increasing heat input (Q0exp(t/?), ?=38.1ms to 8.3s). The influence of heating rate on CHF was investigated into details and the dominant mechanism of subcooled flow boiling critical heat flux for high heating rate was discussed.

  8. Unsteady Boundary Layer Flow and Heat Transfer of a Casson Fluid past an Oscillating Vertical Plate with Newtonian Heating

    PubMed Central

    Hussanan, Abid; Zuki Salleh, Mohd; Tahar, Razman Mat; Khan, Ilyas

    2014-01-01

    In this paper, the heat transfer effect on the unsteady boundary layer flow of a Casson fluid past an infinite oscillating vertical plate with Newtonian heating is investigated. The governing equations are transformed to a systems of linear partial differential equations using appropriate non-dimensional variables. The resulting equations are solved analytically by using the Laplace transform method and the expressions for velocity and temperature are obtained. They satisfy all imposed initial and boundary conditions and reduce to some well-known solutions for Newtonian fluids. Numerical results for velocity, temperature, skin friction and Nusselt number are shown in various graphs and discussed for embedded flow parameters. It is found that velocity decreases as Casson parameters increases and thermal boundary layer thickness increases with increasing Newtonian heating parameter. PMID:25302782

  9. Influence of fluid-property variation on turbulent convective heat transfer in vertical annular channel flows.

    SciTech Connect

    D. M. McEligot; J. H. Bae; J. Y. Yoo; H. Choi; James R. Wolf

    2005-10-01

    Influence of strongly-varying properties of supercritical-pressure fluids on turbulent convective heat transfer is investigated using direct numerical simulation. We consider thermally-developing upward flows in a vertical annular channel where the inner wall is heated with a constant heat flux and the outer wall is insulated. CO2 is chosen as the working fluid at a pressure to 8 Mpa, and the inlet Reynolds number based on the channel hydraulic diameter and the bulk velocity is Re0 = 8900. It is shown that turbulent convective heat transfer characteristics of supercritical flow are significantly different from those of constant-property flow mainly due to spatial and temporal variations of fluid density. Non-uniform density distribution causes fluid particles to be accelerated either by expansion or buoyancy force near the heated wall, while temporal density fluctuations change the transport characteristics of turbulent heat and momentum via the buoyancy production terms arising from the correlations such as p1u1x, p1u1r and p1h1. Among various turbulence statistics, the streamwise turbulent heat flux shows a very peculiar transitional behavior due to the buoyancy effect, changing both in sign and magnitude. Consequently, a non-monotonic temperature distribution is developed in the flow direction, causing severe impairment of heat transfer in supercritical flows.

  10. Experimental study of mixed convection heat transfer in vertical helically coiled tube heat exchangers

    SciTech Connect

    Ghorbani, N. [School of Mechanical Engineering, University of Leeds, Leeds, England (United Kingdom); Taherian, H. [Department of Engineering Technology and Industrial Distribution, Texas A and M University, College Station, TX (United States); Gorji, M. [Department of Mechanical Engineering, Babol Noushirvani University of Technology, Babol (Iran); Mirgolbabaei, H. [Department of Mechanical Engineering, Islamic Azad University, Jouybar branch, Jouybar (Iran)

    2010-10-15

    In this study the mixed convection heat transfer in a coil-in-shell heat exchanger for various Reynolds numbers, various tube-to-coil diameter ratios and different dimensionless coil pitch was experimentally investigated. The experiments were conducted for both laminar and turbulent flow inside coil. Effects of coil pitch and tube diameters on shell-side heat transfer coefficient of the heat exchanger were studied. Different characteristic lengths were used in various Nusselt number calculations to determine which length best fits the data and several equations were proposed. The particular difference in this study in comparison with the other similar studies was the boundary conditions for the helical coils. The results indicate that the equivalent diameter of shell is the best characteristic length. (author)

  11. Self Heating Effects of High Power SOI Vertical DMOS Transistor with Lateral Drain Contacts

    NASA Astrophysics Data System (ADS)

    Pinardi, Kuntjoro; Heinle, Ulrich; Bengtsson, Stefan; Olsson, Jörgen

    Self heating effects in silicon-on-insulator (SOI) high power Vertical Diffused MOS (VDMOS) transistors have been investigated by electro-thermal simulations. Unlike other conventional VDMOS devices, here we work on a modified VDMOS transistor with drain contacts at the surface. In this work we study two different aspects of this transistor namely: (1) Effect of self heating on the device performance and (2) effect of the elevated temperature on the device characteristics. Our simulation results indicate that the temperature distribution is concentrated at the drift region under the gate area and spreads down toward the drain area. The self heating effect gives a notable effect on our newly proposed VDMOS in the on-state (when Vg > Vt), and the breakdown point decreases. As we increase the ambient temperature the breakdown point decreases further.

  12. Natural convection on a vertical plate in a saturated porous medium with internal heat generation

    NASA Astrophysics Data System (ADS)

    Guedda, M.; Sriti, M.; Achemlal, D.

    2014-08-01

    The main goal of this paper is to re-exam a class of exact solutions for the two-dimensional free convection boundary layers induced by a heated vertical plate embedded in a saturated porous medium with an exponential decaying heat generation. The temperature distribution of the plate has been assumed to vary as a power of the axial coordinate measured from the leading edge of the plate and subjected to an applied lateral mass flux. The boundary layer equations are solved analytically and numerically using a fifth-order Runge-Kutta scheme coupled with the shooting iteration method. As for the classical problem without internal heat generation, it is proved that multiple (unbounded) solutions arise for any and for any suction/injection parameter. For such solutions, the asymptotic behavior as the similarity variable approaches infinity is determined.

  13. Buoyant instabilities in downward flow in a symmetrically heated vertical channel

    SciTech Connect

    Evans, G. [Sandia National Lab., Livermore, CA (United States); Greif, R. [Univ. of California, Berkeley, CA (United States)

    1996-07-01

    This study of the downward flow of nitrogen in a tall, partially heated vertical channel (upstream isothermal at T{sub in}*, heated region isothermal at T{sub s}* downstream adiabatic) shows the strong effects of buoyancy even for small temperature differences. Time-dependent oscillations including periodic flow reversals occur along the channel walls. Although the flow and heat transfer are asymmetric, the temperature and axial component of velocity show symmetric reflections at two times that are half a period apart and the lateral component of velocity shows antisymmetric reflections at the two times. There is strong interaction between the downward flow in the central region of the channel and the upward flow along the heated channel walls. At the top of the heated region, the upward buoyant flow turns toward the center of the channel and is incorporated into the downward flow. Along the channel centerline there are nonmonotonic variations of the axial component of velocity and temperature and a large lateral component of velocity that reverses direction periodically. Results are presented for Re = 219.7 and Gr/Re{sup 2} = 1.83, 8.0, and 13.7. The heat transfer and the frequency of the oscillations increases and the flow and temperature fields become more complex as Gr/Re{sup 2} increases. The results have applications to fiber drying, food processing, crystal growth, solar energy collection, cooling of electronic circuits, ventilation, etc.

  14. Natural convection heat transfer of nanofluids along a vertical plate embedded in porous medium.

    PubMed

    Uddin, Ziya; Harmand, Souad

    2013-01-01

    The unsteady natural convection heat transfer of nanofluid along a vertical plate embedded in porous medium is investigated. The Darcy-Forchheimer model is used to formulate the problem. Thermal conductivity and viscosity models based on a wide range of experimental data of nanofluids and incorporating the velocity-slip effect of the nanoparticle with respect to the base fluid, i.e., Brownian diffusion is used. The effective thermal conductivity of nanofluid in porous media is calculated using copper powder as porous media. The nonlinear governing equations are solved using an unconditionally stable implicit finite difference scheme. In this study, six different types of nanofluids have been compared with respect to the heat transfer enhancement, and the effects of particle concentration, particle size, temperature of the plate, and porosity of the medium on the heat transfer enhancement and skin friction coefficient have been studied in detail. It is found that heat transfer rate increases with the increase in particle concentration up to an optimal level, but on the further increase in particle concentration, the heat transfer rate decreases. For a particular value of particle concentration, small-sized particles enhance the heat transfer rates. On the other hand, skin friction coefficients always increase with the increase in particle concentration and decrease in nanoparticle size. PMID:23391481

  15. Critical heat flux performance of hypervapotrons proposed for use in the ITER divertor vertical target

    SciTech Connect

    Youchison, D.L.; Marshall, T.D.; McDonald, J.M.; Lutz, T.J.; Watson, R.D. [Sandia National Labs., Albuquerque, NM (United States); Driemeyer, D.E. Kubik, D.L.; Slattery, K.T.; Hellwig, T.H. [McDonnell Douglas Aerospace, St. Louis, MO (United States)

    1997-09-01

    Task T-222 of the International Thermonuclear Experimental Reactor (ITER) program addresses the manufacturing and testing of permanent components for use in the ITER divertor. Thermalhydraulic and critical heat flux performance of the heat sinks proposed for use in the divertor vertical target are part of subtask T-222.4. As part of this effort, two single channel, medium scale, bare copper alloy, hypervapotron mockups were designed, fabricated, and tested using the EB-1200 electron beam system. The objectives of the effort were to develop the design and manufacturing procedures required for construction of robust high heat flux (HHF) components, verify thermalhydraulic, thermomechanical and critical heat flux (CHF) performance under ITER relevant conditions, and perform analyses of HHF data to identify design guidelines and failure criteria and possibly modify any applicable CHF correlations. The design, fabrication, and finite element modeling of two types of hypervapotrons are described; a common version already in use at the Joint European Torus (JET) and a new attached fin design. HHF test data on the attached fin hypervapotron will be used to compare the CHF performance under uniform heating profiles on long heated lengths with that of localized, highly peaked, off nominal profiles.

  16. Natural convection heat transfer of nanofluids along a vertical plate embedded in porous medium

    PubMed Central

    2013-01-01

    The unsteady natural convection heat transfer of nanofluid along a vertical plate embedded in porous medium is investigated. The Darcy-Forchheimer model is used to formulate the problem. Thermal conductivity and viscosity models based on a wide range of experimental data of nanofluids and incorporating the velocity-slip effect of the nanoparticle with respect to the base fluid, i.e., Brownian diffusion is used. The effective thermal conductivity of nanofluid in porous media is calculated using copper powder as porous media. The nonlinear governing equations are solved using an unconditionally stable implicit finite difference scheme. In this study, six different types of nanofluids have been compared with respect to the heat transfer enhancement, and the effects of particle concentration, particle size, temperature of the plate, and porosity of the medium on the heat transfer enhancement and skin friction coefficient have been studied in detail. It is found that heat transfer rate increases with the increase in particle concentration up to an optimal level, but on the further increase in particle concentration, the heat transfer rate decreases. For a particular value of particle concentration, small-sized particles enhance the heat transfer rates. On the other hand, skin friction coefficients always increase with the increase in particle concentration and decrease in nanoparticle size. PMID:23391481

  17. A vertical resonance heating model for X- or peanut-shaped galactic bulges

    NASA Astrophysics Data System (ADS)

    Quillen, Alice C.; Minchev, Ivan; Sharma, Sanjib; Qin, Yu-Jing; Di Matteo, Paola

    2014-01-01

    We explore a second-order Hamiltonian vertical resonance model for X-shaped or peanut-shaped galactic bulges. The X- or peanut-shape is caused by the 2:1 vertical Lindblad resonance with the bar, with two vertical oscillation periods per orbital period in the bar frame. We examine N-body simulations and find that due to the bar slowing down and disc thickening during bar buckling, the resonance and associated peanut-shape moves outward. The peanut-shape is consistent with the location of the 2:1 vertical resonance, independent of whether the bar buckled or not. We estimate the resonance width from the potential m = 4 Fourier component and find that the resonance is narrow, affecting orbits over a narrow range in the angular momentum distribution, dL/L ˜ 0.05. As the resonance moves outward, stars originally in the mid-plane are forced out of the mid-plane and into orbits just within the resonance separatrix. The height of the separatrix orbits, estimated from the Hamiltonian model, is approximately consistent with the peanut-shape height. The peanut- or X-shape is comprised of stars in the vicinity of the resonance separatrix. The velocity distributions from the simulations illustrate that low-inclination orbits are depleted within resonance. Within resonance, the vertical velocity distribution is broad, consistent with resonant heating caused by the passage of the resonance through the disc. In the Milky Way bulge, we relate the azimuthally averaged mid-plane mass density near the vertical resonance to the rotation curve and bar pattern speed. At an estimated vertical resonance galactocentric radius of ˜1.3 kpc, we confirm a mid-plane density of ˜5 × 108 M? kpc-3, consistent with recently estimated mass distributions. We find that the rotation curve, bar pattern speed, 2:1 vertical resonance location, X-shaped tips and mid-plane mass density, are all self-consistent in the Milky Way galaxy bulge.

  18. Downflow heat transfer in a heated ribbed vertical annulus with a cosine power profile

    SciTech Connect

    Anderson, J.L.; Condie, K.G.; Larson, T.K.

    1991-10-01

    Experiments designed to investigate downflow heat transfer in a heated, ribbed annulus test section simulating one of the annular coolant channels of a Savannah River Plant production reactor Mark 22 fuel assembly have been conducted at the Idaho National Engineering Laboratory. The inner surface of the annulus was constructed of aluminum and was electrically heated to provide an axial cosine power profile and a flat azimuthal power shape. Data presented in this report are from the ECS-2c series, which was a follow on series to the ECS-2b series, conducted specifically to provide additional data on the effect of different powers at the same test conditions, for use in evaluation of possible power effects on the aluminum temperature measurements. Electrical powers at 90%, 100%, and 110% of the power required to result in the maximum aluminum temperature at fluid saturation temperature were used at each set of test conditions previously used in the ECS-2b series. The ECS-2b series was conducted in the same test rig as the previous ECS-2b series. Data and experimental description for the ECS-2b series is provided in a previous report. 18 refs., 25 figs., 3 tabs.

  19. Potential vertical movement of large heat-generating waste packages in salt.

    SciTech Connect

    Clayton, Daniel James; Martinez, Mario J.; Hardin, Ernest L.

    2013-05-01

    With renewed interest in disposal of heat-generating waste in bedded or domal salt formations, scoping analyses were conducted to estimate rates of waste package vertical movement. Vertical movement is found to result from thermal expansion, from upward creep or heave of the near-field salt, and from downward buoyant forces on the waste package. A two-pronged analysis approach was used, with thermal-mechanical creep modeling, and coupled thermal-viscous flow modeling. The thermal-mechanical approach used well-studied salt constitutive models, while the thermal-viscous approach represented the salt as a highly viscous fluid. The Sierra suite of coupled simulation codes was used for both approaches. The waste package in all simulations was a right-circular cylinder with the density of steel, in horizontal orientation. A time-decaying heat generation function was used to represent commercial spent fuel with typical burnup and 50-year age. Results from the thermal-mechanical base case showed approximately 27 cm initial uplift of the package, followed by gradual relaxation closely following the calculated temperature history. A similar displacement history was obtained with the package density set equal to that of salt. The slight difference in these runs is attributable to buoyant displacement (sinking) and is on the order of 1 mm in 2,000 years. Without heat generation the displacement stabilizes at a fraction of millimeter after a few hundred years. Results from thermal-viscous model were similar, except that the rate of sinking was constant after cooldown, at approximately 0.15 mm per 1,000 yr. In summary, all calculations showed vertical movement on the order of 1 mm or less in 2,000 yr, including calculations using well-established constitutive models for temperature-dependent salt deformation. Based on this finding, displacement of waste packages in a salt repository is not a significant repository performance issue.

  20. The Sensitivity of Shortwave Radiative Forcing and Heating Rates to the Aerosol Vertical Profile

    NASA Astrophysics Data System (ADS)

    Schmid, B.; Guan, H.; McComiskey, A.; McFarlane, S.; Kuzmanoski, M.; Pilewskie, P.; Magi, B.

    2007-12-01

    We are investigating the sensitivity of the shortwave aerosol radiative forcing and the heating rate profile to the vertical profile of aerosol optical properties (extinction, single-scattering albedo, and asymmetry parameter), solar geometry and surface albedo for clear-sky conditions. Total uncertainties in modeled local diurnally averaged direct radiative forcing (DRF) at the surface and top of the atmosphere (TOA) due to uncertainties in the input parameters mentioned above range from 0.2 to 1.3 W m-2 (42 to 20%) depending on location (from tropical to polar sites), solar zenith angle, surface reflectance, aerosol type, and aerosol optical depth. The largest contributor to total uncertainty in DRF is usually single scattering albedo; however decreasing measurement uncertainties for any property would increase accuracy in DRF. Comparison of two radiative transfer models (RRTM_SW and SBDART) suggests the contribution of modeling error is small compared to the total uncertainty although comparable to uncertainty arising from some individual properties. In this presentation we are assessing the results not only at TOA and the surface but throughout the vertical profile. As inputs, we are using slightly idealized case studies from SAFARI-2000 (Southern Africa), ACE-Asia (Sea of Japan, 2001), ARM Aerosol IOP (Oklahoma, 2003), and RADAGAST (Niger, 2006). These case studies encompass a wide range of aerosols including marine, local and transported smoke, dust, and pollution aerosols. Initial results indicate that the shape of the aerosol extinction profile has very little impact on TOA and surface forcing. However, as long as the aerosol is not purely scattering (i.e single-scattering albedo < 1), the shape of the extinction profile is important for the vertical profiles of forcing and heating rates. In contrast, the shape of the aerosol absorption profile has a slight impact on TOA and surface forcing but is the main driver for the forcing and heating rate profiles. Unfortunately, the vertical profile of aerosol absorption is a quantity that is currently measured with rather large uncertainties only. We also show actual measurements of up and down-welling spectral flux profiles from the 2003 ARM Aerosol IOP and our attempts at deriving heating rate profiles from these.

  1. Characterization of heat loads from mitigated and unmitigated vertical displacement events in DIII-D

    SciTech Connect

    Hollmann, E. M.; Moyer, R. A. [University of California-San Diego, La Jolla, California 92093 (United States)] [University of California-San Diego, La Jolla, California 92093 (United States); Commaux, N.; Jernigan, T. J. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)] [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Eidietis, N. W.; Humphreys, D. A.; Strait, E. J.; Wesley, J. C. [General Atomics, San Diego, California 92186 (United States)] [General Atomics, San Diego, California 92186 (United States); Lasnier, C. J. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Pitts, R. A.; Sugihara, M. [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul Lez Durance (France)] [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul Lez Durance (France); Watkins, J. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)

    2013-06-15

    Experiments have been conducted on the DIII-D tokamak to study the distribution and repeatability of heat loads and vessel currents resulting from vertical displacement events (VDEs). For unmitigated VDEs, the radiated power fraction appears to be of order 50%, with the remaining power dominantly conducted to the vessel walls. Shot-to-shot scatter in heat loads measured at one toroidal location is not large (<±50%), suggesting that toroidal asymmetries in conducted heat loads are not large. Conducted heat loads are clearly observed during the current quench (CQ) of both mitigated and unmitigated disruptions. Significant poloidal asymmetries in heat loads and radiated power are often observed in the experiments but are not yet understood. Energy dissipated resistively in the conducting walls during the CQ appears to be small (<5%). The mitigating effect of neon massive gas injection (MGI) as a function of MGI trigger delay has also been studied. Improved mitigation is observed as the MGI trigger delay is decreased. For sufficiently early MGI mitigation, close to 100% radiated energy and a reduction of roughly a factor 2 in vessel forces is achieved.

  2. Combined forced and buoyancy-induced convective heat transfer in a partially closed vertical channel

    SciTech Connect

    Angirasa, D.; Mahajan, R.L. [Univ. of Colorado, Boulder, CO (United States). Dept. of Mechanical Engineering

    1995-05-01

    This paper reports a numerical study of mixed convection flow over a horizontal surface in a partially closed adiabatic symmetric vertical channel. For low Rayleigh numbers, the forced flow enhances the buoyant convective heat transfer rates. For higher Rayleigh numbers, complex interactions arise between the buoyancy-dominated wall layer and the forced flow convection. The shearing between the buoyancy-dominated wall layer and the forced flow over it induces a stagnation region and a pair of weak recirculating cells in the middle of the channel above the horizontal surface. This effectively reduces heat transfer rates. Nusselt number data are presented for a wide range of Rayleigh and Reynolds numbers. Finally, the effect of the inlet height of forced flow on the transport is discussed.

  3. The CAV program for numerical evaluation of laminar natural convection heat transfer in vertical rectangular cavities

    NASA Astrophysics Data System (ADS)

    Novak, Milos H.; Nowak, Edwin S.

    1993-12-01

    To analyze the laminar natural convection heat transfer and fluid flow distribution in vertical rectangular cavities with or without inner partitions, the personal computer finite difference program entitled CAV is used. The CAV program was tested successfully for slender cavities with aspect ratios as high as R = H/ L = 90 and for the Grashof numbers, based on the cavity height, up to GrH = 3 x10 9. To make the CAV program useful for a number of applications, various types of boundary conditions can also be imposed on the program calculations. Presented are program applications dealing with the 2-D numerical analysis of natural convection heat transfer in very slender window cavities with and without small inner partitions and recommendations are made for window design.

  4. Effect of rolling motion on critical heat flux for subcooled flow boiling in vertical tube

    SciTech Connect

    Hwang, J. S.; Park, I. U.; Park, M. Y.; Park, G. C. [Dept. of Energy Systems Engineering, Seoul National Univ., 599 Gwanak-Ro, Gwanak-Gu, Seoul, 151-744 (Korea, Republic of)

    2012-07-01

    This paper presents defining characteristics of the critical heat flux (CHF) for the boiling of R-134a in vertical tube operation under rolling motion in marine reactor. It is important to predict CHF of marine reactor having the rolling motion in order to increase the safety of the reactor. Marine Reactor Moving Simulator (MARMS) tests are conducted to measure the critical heat flux using R-134a flowing upward in a uniformly heated vertical tube under rolling motion. MARMS was rotated by motor and mechanical power transmission gear. The CHF tests were performed in a 9.5 mm I.D. test section with heated length of 1 m. Mass fluxes range from 285 to 1300 kg m{sup -2}s{sup -1}, inlet subcooling from 3 to 38 deg. C and outlet pressures from 13 to 24 bar. Amplitudes of rolling range from 15 to 40 degrees and periods from 6 to 12 sec. To convert the test conditions of CHF test using R-134a in water, Katto's fluid-to-fluid modeling was used in present investigation. A CHF correlation is presented which accounts for the effects of pressure, mass flux, inlet subcooling and rolling angle over all conditions tested. Unlike existing transient CHF experiments, CHF ratio of certain mass flux and pressure are different in rolling motion. For the mass fluxes below 500 kg m{sup -2}s{sup -1} at 13, 16 (region of relative low mass flux), CHF ratio was decreased but was increased above that mass flux (region of relative high mass flux). Moreover, CHF tend to enhance in entire mass flux at 24 bar. (authors)

  5. Energy and heat fluxes due to vertically propagating Yanai waves observed in the equatorial Indian Ocean

    NASA Astrophysics Data System (ADS)

    Smyth, W. D.; Durland, T. S.; Moum, J. N.

    2015-01-01

    current measurements in the equatorial Indian Ocean in October and November of 2011 revealed oscillations in the meridional velocity with amplitude ˜0.10m/s. These were clearest in a layer extending from ˜300 to 600 m depth and had periods near 3 weeks. Phase propagation was upward. Measurements from two sequential time series at the equator, four meridional transects and one zonal transect are used to identify the oscillation as a Yanai wave packet and to establish its dominant frequency and vertical wavelength. The Doppler shift is accounted for, so that measured wave properties are translated into the reference frame of the mean zonal flow. We take advantage of the fact that, in the depth range where the wave signal was clearest, the time-averaged current and buoyancy frequency were nearly uniform with depth, allowing application of the classical theoretical representation of vertically propagating plane waves. Using the theory, we estimate wave properties that are not directly measured, such as the group velocity and the zonal wavelength and phase speed. The theory predicts a vertical energy flux that is comparable to that carried by midlatitude near-inertial waves. We also quantify the wave-driven meridional heat flux and the Stokes drift.

  6. Melting of a solid adjacent to a heated vertical cylinder with or without subcooling of the solid

    Microsoft Academic Search

    R. G. Kemink

    1981-01-01

    Experiments were performed to provide quantitative heat transfer data corresponding to the problem of melting about a heated vertical cylinder embedded in a solid phase change material. The phase change material employed was 99 percent pure n-eicosane paraffin having an experimentally determined melting point of 36.4 C. Experiments were conducted with the solid phase either at the melting point or

  7. Explicit formulas for laminar natural convection heat transfer along vertical cylinders with power-law wall temperature distribution

    Microsoft Academic Search

    José L. Muñoz-Cobo; José M. Corberán; Sergio Chiva

    2003-01-01

    Natural convection heat transfer coefficients for vertical cylinders with variable surface temperature distribution must be found by complex numerical integration of the corresponding system of governing differential equations. Its evaluation for practical heat transfer calculations is always based on more or less complex correlations fitted to numerical or experimental results. This paper presents alternative approximate formulas for the calculation of

  8. The vertical structure of cloud radiative heating over the Indian subcontinent during summer monsoon

    NASA Astrophysics Data System (ADS)

    Johansson, E.; Devasthale, A.; L'Ecuyer, T.; Ekman, A. M. L.; Tjernström, M.

    2015-02-01

    Every year the monsoonal circulation over the Indian subcontinent gives rise to a variety of cloud types that differ considerably in their ability to heat or cool the atmosphere. These clouds in turn affect monsoon dynamics via their radiative impacts, both at the surface and in the atmosphere. New generation of satellites carrying active radar and lidar sensors are allowing realistic quantification of cloud radiative heating (CRH) by resolving the vertical structure of the atmosphere in an unprecedented detail. Obtaining this information is a first step in closing the knowledge gap in our understanding of the role that different clouds play as regulators of the monsoon and vice versa. Here, we use collocated CloudSat-CALIPSO data sets to understand following aspects of cloud-radiation interactions associated with Indian monsoon circulation. (1) How does the vertical distribution of CRH evolve over the Indian continent throughout monsoon season? (2) What is the absolute contribution of different clouds types to the total CRH? (3) How do active and break periods of monsoon affect the distribution of CRH? And finally, (4) what are the net radiative effects of different cloud types on surface heating? In general, the vertical structure of CRH follows the northward migration and the retreat of monsoon from May to October. It is found that the alto- and nimbostratus clouds intensely warm the middle troposphere and equally strongly cool the upper troposphere. Their warming/cooling consistently exceeds ±0.2 K day-1 (after weighing by vertical cloud fraction) in monthly mean composites throughout the middle and upper troposphere respectively, with largest impact observed in June, July and August. Deep convective towers cause considerable warming in the middle and upper troposphere, but strongly cool the base and inside of the tropical tropopause layer (TTL). Such cooling is stronger during active (-1.23 K day-1) monsoon conditions compared to break periods (-0.36 K day-1). The contrasting warming effect of high clouds inside the TTL is found to be double in magnitude during active conditions compared to break periods. It is further shown that stratiform clouds (combining alto- and nimbostratus clouds) and deep convection significantly cool the surface with net radiative effect in the order of -100 and -400 W m-2, respectively, while warming the atmosphere in the order of 40 and 150 W m-2. While deep convection produces strong cooling at the surface during active periods of monsoon, the importance of stratiform clouds, on the other hand, increases during break periods. The contrasting CREs in the atmosphere and at surface, and during active and break conditions, have direct implications for monsoonal circulation.

  9. Mixed Convection with Conduction and Surface Radiation from a Vertical Channel with Discrete Heating

    NASA Astrophysics Data System (ADS)

    Londhe, S. D.; Rao, C. G.

    2013-10-01

    A numerical investigation into fluid flow and heat transfer for the geometry of a vertical parallel plate channel subjected to conjugate mixed convection with radiation is attempted here. The channel considered has three identical flush-mounted discrete heat sources in its left wall, while the right wall that does not contain any heat source acts as a sink. Air, assumed to be a radiatively non-participating and having constant thermophysical properties subject to the Boussinesq approximation, is the cooling agent. The heat generated in the left wall gets conducted along it and is later dissipated by mixed convection and radiation. The governing equations, considered in their full strength sans the boundary layer approximations, are converted into vorticity-stream function form and are then normalized. These equations along with pertinent boundary conditions are solved through finite volume method coupled with Gauss-Seidel iterative technique. The effects of modified Richardson number, surface emissivity, thermal conductivity and aspect ratio on local temperature distribution along the channel, maximum channel temperature and relative contributions of mixed convection and radiation have been thoroughly studied. The prominence of radiation in the present problem has been highlighted.

  10. Critical heat flux performance of hypervapotrons proposed for use in the ITER divertor vertical target

    NASA Astrophysics Data System (ADS)

    Youchison, Dennis L.; Marshall, Theron D.; McDonald, Jimmie M.; Lutz, Thomas J.; Watson, Robert D.; Driemeyer, Daniel E.; Kubik, David L.; Slattery, Kevin T.; Hellwig, Theodore H.

    1997-12-01

    Task T-222 of the International Thermonuclear Experimental Reactor (ITER) program addresses the manufacturing and testing of permanent components for use in the ITER divertor. Thermal-hydraulic and critical heat flux performance of the heat sinks proposed for use in the divertor vertical target are part of subtask T-222.4. As part of this effort, two single channel, medium-scale, bare copper alloy, hypervapotron mock-ups were designed by Sandia National Laboratories and McDonnell Douglas Aerospace (MDA), fabricated at MDA and tested at Sandia' Plasma Materials Test Facility using the EB-1200 electron beam system. The objectives of our effort were to develop the design and manufacturing procedures required for construction of robust HHF components, verify thermal-hydraulic, thermomechanical and CHF performance under ITER relevant conditions, and perform analyses of HHF data to identify design guidelines, failure criteria and possibly modify any applicable CHF correlations. This paper describes the design, fabrication and finite elements modeling of two types of hypervapotrons, a common version already in use at JET and a new attached- fin design. HHF test data on the attached-fin hypervapotron will be used to compare the CHF performance under uniform heating profiles on long heated lengths to that of localized, highly peaked, off-nominal profiles.

  11. The study and development of the empirical correlations equation of natural convection heat transfer on vertical rectangular sub-channels

    NASA Astrophysics Data System (ADS)

    Kamajaya, Ketut; Umar, Efrizon; Sudjatmi, K. S.

    2012-06-01

    This study focused on natural convection heat transfer using a vertical rectangular sub-channel and water as the coolant fluid. To conduct this study has been made pipe heaters are equipped with thermocouples. Each heater is equipped with five thermocouples along the heating pipes. The diameter of each heater is 2.54 cm and 45 cm in length. The distance between the central heating and the pitch is 29.5 cm. Test equipment is equipped with a primary cooling system, a secondary cooling system and a heat exchanger. The purpose of this study is to obtain new empirical correlations equations of the vertical rectangular sub-channel, especially for the natural convection heat transfer within a bundle of vertical cylinders rectangular arrangement sub-channels. The empirical correlation equation can support the thermo-hydraulic analysis of research nuclear reactors that utilize cylindrical fuel rods, and also can be used in designing of baffle-free vertical shell and tube heat exchangers. The results of this study that the empirical correlation equations of natural convection heat transfer coefficients with rectangular arrangement is Nu = 6.3357 (Ra.Dh/x)0.0740.

  12. Unsteady MHD natural convection from a heated vertical porous plate in a micropolar fluid with Joule heating, chemical reaction and radiation effects

    Microsoft Academic Search

    Ali J. Chamkha; R. A. Mohamed; Sameh E. Ahmed

    2011-01-01

    The effects of Joule-heating, chemical reaction and thermal radiation on unsteady MHD natural convection from a heated vertical\\u000a porous plate in a micropolar fluid are analyzed. The partial differential equations governing the flow and heat and mass transfer\\u000a have been solved numerically using an implicit finite-difference scheme. The case corresponding to vanishing of the anti-symmetric\\u000a part of the stress tensor

  13. A study of free convection induced by a vertical wavy surface with heat flux in a porous enclosure

    SciTech Connect

    Kumar, B.V.R.

    2000-04-01

    Study of natural convection in porous enclosures is of great importance in several scientific and engineering applications such as nuclear waste management, transpiration cooling, building thermal insulators, geothermal power plants, grain storage, and so on. Here, free convection induced by a vertical wavy surface with uniform heat flux in a porous enclosure has been analyzed numerically using the finite element method (FEM). The flow and the convection process in the cavity is found to be sensitive to the flow parameter Rayleigh number (Ra), and geometrical parameters like wave amplitude (a), wave phase ({phi}), and number of waves (N) in the vertical dimension of the cavity. The study reveals that small sinusoidal drifts from the smoothness of a vertical wall with a phase angle of 60{degree} and high frequency enhances the free convection from a vertical wall with uniform heat flux.

  14. Numerical simulation of supercritical heat transfer under severe axial density gradient in a narrow vertical tube

    SciTech Connect

    Bae, Y. Y.; Hong, S. D.; Kim, Y. W. [Korea Atomic Energy Research Inst., 1045 Daedeokdaero, Daejeon (Korea, Republic of)

    2012-07-01

    A number of computational works have been performed so far for the simulation of heat transfer in a supercritical fluid. The simulations, however, faced a lot of difficulties when heat transfer deteriorates due either to buoyancy or by acceleration. When the bulk temperature approaches the pseudo-critical temperature the fluid experiences a severe axial density gradient on top of a severe radial one. Earlier numerical calculations showed, without exception, unrealistic over-predictions, as soon as the bulk temperature exceeded the pseudo-critical temperature. The over-predictions might have been resulted from an inapplicability of widely-used turbulence models. One of the major causes for the difficulties may probably be an assumption of a constant turbulent Prandtl number. Recent research, both numerical and experimental, indicates that the turbulent Prandtl number is never a constant when the gradient of physical properties is significant. This paper describes the applicability of a variable turbulent Prandtl number to the numerical simulation of heat transfer in supercritical fluids flowing in narrow vertical tubes. (authors)

  15. Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing Vertically Downward in a Small Diameter Tube

    NASA Astrophysics Data System (ADS)

    Miyata, Kazushi; Mori, Hideo; Ohishi, Katsumi; Tanaka, Hirokazu

    Experiments were performed on boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically downward in a copper smooth tube of 1.0 mm inside diameter for the development of a high-performance heat exchanger using small diameter tubes for air conditioning systems. Local heat transfer coefficients were measured in a range of mass fluxes from 30 to 200 kg/(m2•s), heat fluxes from 1 to 16 kW/m2 and quality from 0.1 to over 1 at evaporation temperature of 10°C. Pressure drops were measured and flow patterns were observed at mass fluxes from 30 to 200 kg/(m2•s) and quality from 0.1 to 0.9. The characteristics of frictional pressure drop, heat transfer coefficient and dryout qualities were clarified by comparing the measurements with the data for the vertically upward flow previously obtained.

  16. Radiative heat transfer to hydromagnetic flow of a slightly rarefied binary gas in a vertical channel

    NASA Astrophysics Data System (ADS)

    Bestman, A. R.; Alabraba, M. A.; Ogulu, A.

    1992-03-01

    The paper considers the fully-developed slip flow in a vertical channel with radiative heat transfer and mass transfer in the presence of an externally applied magnetic field. The problem is modeled by the compressible Navier-Stokes equations, so that the gas is only slightly rarefied. Invoking the exact integral equation for radiation, the problem is reduced to a set of ordinary integro-differential equations. By realistic assumptions, the set is linearized and the temperature is reduced to a mixed Fredholm-Volterra integral equation which is solved by standard iterative procedure. Thereafter the concentration equation is solved by the WKB approximation while the velocity is obtained by the finite difference scheme. These solutions are discussed qualitatively.

  17. Exact Solution Of MHD Mixed Convection Periodic Flow In A Rotating Vertical Channel With Heat Radiation

    NASA Astrophysics Data System (ADS)

    Singh, K. D.

    2013-08-01

    Magnetohydrodynamic (MHD) mixed convection flow of a viscous, incompressible and electrically conducting fluid in a vertical channel is analyzed analytically. A magnetic field of uniform strength is applied perpendicular to the planes of the channel walls. The fluid is acted upon by a periodic variation of the pressure gradient in the vertically upward direction. The temperature of one of the plates is non-uniform and the temperature difference of the walls of the channel is high enough to induce heat transfer due to radiation. The fluid and the channel rotate in unison with an angular velocity about the axis normal to the plates of the channel. An exact analytical solution of the problem is obtained. Two cases of small and large rotation have been considered to assess the effects of different parameters involved in the flow problem. The velocity field, the amplitude and the phase angle of the shear stress are shown graphically and discussed in detail. During analysis it is found that the flow problem studied by Makinde and Mhone (2005) is incorrect physically and mathematically

  18. Sensitivity of shortwave radiative flux density, forcing, and heating rates to the aerosol vertical profile

    SciTech Connect

    Guan, Hong; Schmid, Beat; Bucholtz, Anthony; Bergstrom, Robert

    2010-03-31

    The effect of the aerosol vertical distribution on the solar radiation profiles, for idealized and measured profiles of optical properties (extinction and single-scattering albedo (SSA)) during the May 2003 Atmospheric Radiation Measurement (ARM) Aerosol Intensive Observation Period (AIOP), has been investigated using the Rapid Radiative Transfer Model Shortwave (RRTM_SW) code. Calculated profiles of down-welling and up-welling solar fluxes during the AIOP have been compared with the data measured by up- and down-looking solar broadband radiometers aboard a profiling research aircraft. The measured profiles of aerosol extinction, SSA, and water vapor obtained from the same aircraft that carried the radiometers served as the inputs for the model calculations. It is noteworthy that for this study, the uplooking radiometers were mounted on a stabilized platform that kept the radiometers parallel with respect to the earth’s horizontal plane. The results indicate that the shape of the aerosol extinction profiles has very little impact on direct radiative forcings at the top of atmosphere and surface in a cloud-free sky. However, as long as the aerosol is not purely scattering, the shape of the extinction profiles is important for forcing profiles. Identical extinction profiles with different absorption profiles drastically influence the forcing and heating rate profiles. Using aircraft data from 19 AIOP profiles over the Southern Great Plains (SGP), we are able to achieve broadband down-welling solar flux closure within 0.8% (bias difference) or 1.8% (rms difference), well within the expected measurement uncertainty of 1 to 3%. The poorer agreement in up-welling flux (bias -3.7%, rms 10%) is attributed to the use of inaccurate surface albedo data. The sensitivity tests reveal the important role accurate, vertically resolved aerosol extinction data plays in tightening flux closure. This study also suggests that in the presence of a strongly absorbing substance, aircraft flux measurements from a stabilized platform have the potential to determine heating rate profiles. These measurement-based heating rate profiles provide useful data for heating rate closure studies and indirect estimates of single scattering albedo assumed in radiative transfer calculations.

  19. Investigation on the heat transfer characteristics during flow boiling of liquefied natural gas in a vertical micro-fin tube

    NASA Astrophysics Data System (ADS)

    Xu, Bin; Shi, Yumei; Chen, Dongsheng

    2014-03-01

    This paper presents an experimental investigation on the heat transfer characteristics of liquefied natural gas flow boiling in a vertical micro-fin tube. The effect of heat flux, mass flux and inlet pressure on the flow boiling heat transfer coefficients was analyzed. The Kim, Koyama, and two kinds of Wellsandt correlations with different Ftp coefficients were used to predict the flow boiling heat transfer coefficients. The predicted results showed that the Koyama correlation was the most accurate over the range of experimental conditions.

  20. Vertical Profiles of Latent Heating in TRMM: Validation and Assimilation in the GEOS Data Assimilation System. [Year 2001 Project Report

    NASA Technical Reports Server (NTRS)

    Zhang, Ming-Hua

    2001-01-01

    I have derived the vertical profiles of apparent heating Q and Q2 by using 3-hourly balloon sounding data from the ARM SGP sounding array for three IOPs in 2000. These IOPs cover the periods from 3/1 to 3/22, from 9/25 to 10/8, and from 11/27 to 12/22. These heating profiles will be collocated with the TRMM heating profiles for validation studies once the TRMM profiles become available to the investigators. I have also produced the objective analyses of Q1, Q2 and forcing fields for the international GCSS Case 3 Intercomparison project. The GSFC CRM participated in study, based on which TRMM heating profiles are derived. I have also studied to assimilate the vertical heating profile by constraining the cloud-base mass flux in the cumulus convection scheme using the CCM3. I first derive the vertical heating profile for each convective plume of unit cloud-base mass flux. The observed heating profile form ARM is then de-convoluted to derive the cloud base mass fluxes of all individual plumes. These fluxes are compared with those derived from the quasi-equilibrium hypothesis. They are shown to improve many other aspects of the model behavior.

  1. Vertical ocean heat fluxes beneath Linear Kinematic Features: a potential mechanism for rapid sea-ice decline in the Arctic

    NASA Astrophysics Data System (ADS)

    Slavin, A.; Tremblay, B.; Straub, D.

    2013-12-01

    The Cold Halocline Layer is known to provide a strong barrier to vertical exchange in the surface Arctic ocean. We show modelling evidence, supported by observations, for strong Ekman pumping velocities beneath active leads, where discontinuity in the sea-ice drifts and the surface ice-ocean stresses momentum transfer are present. On Figure 1 shown an example of the lead opening. The anomalous vertical velocities beneath the leads extend hundreds of meters below the surface, well into the Atlantic Layer, and bring up large amount of ocean heat (of the order of hundred's of W/m2) into the mixed layer (see Figure 2 - cross section of the lead from Figure 1). We use a high resolution (4 km) general circulation model with a good representation of the CHL and NSTM (the MITgcm). Results show vertical ocean heat fluxes in winter of approximately 3 W/m2 when averaged over the ice-covered Arctic ocean which is equivalent to 15 cm sea-ice melt during a year. We suggest that this process is important in controlling the Arctic sea-ice mass balance and a potentially important player in the recent sea-ice decline - one that is not represented in lower-resolution global climate models. In a future climate with thinner and more mobile pack ice, this contribution from the ocean will only amplify. a) - Sea-ice shear strain rate, day-1 b) - vertical advective ocean heat flux, W/m2 at 40 m depth, c) - sea-ice stress curl, s-1 and d) - sea-ice divergence, s-1. Vertical section across the sea-ice lead of vertical velocity in m/day (a), temperature in oC (b) and vertical advective ocean heat flux in W/m2 (c).

  2. Buoyancy-driven flows of a radiatively participating fluid in a vertical cylinder heated from below

    NASA Technical Reports Server (NTRS)

    Salinger, A. G.; Brandon, S.; Aris, R.; Derby, J. J.

    1993-01-01

    The effect of radiative energy transport on the onset and evolution of natural convective flows is studied in a Rayleigh-Benard system. Steady, axisymmetric flows of a radiatively participating fluid contained in a rigid-walled, vertical cylinder which is heated on the base, cooled on top, and insulated on the side wall are calculated by using the Galerkin FEM. Bifurcation analysis techniques are used to investigate the changes in the flow structure due to internal radiation. The results of this two-parameter study - where the Rayleigh number, Ra and optical thickness, tau, are varied - apply to fluids ranging from opaque to nearly transparent with respect to IR radiation. For any nonopaque fluid, internal radiation eliminates the static state that without radiation, exists for all values of the Rayleigh number. This heat transfer mechanism also destroys a symmetry of the system that relates clockwise and counterclockwise flows. The connectivity between characteristic flow families and the range of Ra where families are stable are found to depend greatly on tau. Results demonstrate the inadequacy of characterizing the behavior of this system using simple notions of radiative transfer in optically thick or thin media; the nonlinear interaction of radiation and flow are far more complicated than these asymptotic limits would imply.

  3. The impact of latent heat release on synoptic-scale vertical motions and the development of an extratropical cyclone system

    NASA Technical Reports Server (NTRS)

    Smith, P. J.; Dare, P. M.; Lin, S.-J.

    1984-01-01

    This study investigates the influence of stable and convective latent heat release on synoptic-scale vertical motions and the corresponding evolution of an extratropical cyclone during a 48 h period of strong development. The cyclone's early evolution was dominated by dry dynamical processes. By midway through the period, however, forcing by latent heat release accounted for over 50 percent of the upward vertical motions, with the convective component dominating. The cyclone's development was most intense during the second 24 h, despite a decrease in latent heat release. During the latter period, the reduced direct latent heat influence may have been augmented by an indirect influence, in which pre-existing dry dynamical forcing was enhanced by diabatic intensification of vorticity and thermal gradients.

  4. Velocity and temperature distribution of air in the boundary layer of a vertical plate for free-convective heat transfer

    E-print Network

    Jullienne, Jean Maxime Jose

    1962-01-01

    VELOCITY AND TEMPERATURE DISTRIBUTION OF AIR IN THE BOUNDARY LAYER OF A VERTICAL PLATE FOR FREE-CONVECTIVE HEAT TRANSFER A Thesis By JEAN MAXIME JOSE JULLIENNE Submitted to . the . Graduate School of the Agricultural. and Mechanical. College...-CONVECTIVE, HEAT TRANSFER A Thesis By JEAN MAXIME JOSE . JULLIENE Approved as to style . and content by: 1tt e ea o Department or tu eat . visor Angnsty 1962 ACKNOWLEDGMENTS This investigation, . designated as a part of Project 0915, was. made possible...

  5. Soret and Dufour effects on natural convection heat and mass transfer from a vertical cone in a porous medium

    Microsoft Academic Search

    Ching-Yang Cheng

    2009-01-01

    This work studies the Soret and Dufour effects on the boundary layer flow due to natural convection heat and mass transfer over a downward-pointing vertical cone in a porous medium saturated with Newtonian fluids with constant wall temperature and concentration. A similarity analysis is performed, and the obtained similar equations are solved by cubic spline collocation method. The effects of

  6. Open-cycle absorption solar cooling: Natural convection heat and mass transfer from falling films in vertical channels. Final report

    Microsoft Academic Search

    G. A. Buck; B. D. Wood

    1992-01-01

    In the design of solar collector\\/regenerators for use in open cycle absorption refrigeration (OCAR) units, the problem of predicting evaporation mtes and solution temperatures is of paramount importance in determining overall cycle performance. The governing equations for natural convection flow in a vertical channel bounded by a heated falling film (simulating a glazed collector\\/regenerator) were solved using several different finite

  7. Open-cycle absorption solar cooling: Natural convection heat and mass transfer from falling films in vertical channels

    Microsoft Academic Search

    G. A. Buck; B. D. Wood

    1992-01-01

    In the design of solar collector\\/regenerators for use in open cycle absorption refrigeration (OCAR) units, the problem of predicting evaporation rates and solution temperatures is of paramount importance in determining overall cycle performance. The governing equations for natural convection flow in a vertical channel bounded by a heated falling film (simulating a glazed collector\\/regenerator) were solved using several different finite

  8. Finite difference analysis of radiative free convection flow past an impulsively started vertical plate with variable heat and mass flux

    Microsoft Academic Search

    V. R. Prasad; N. Bhaskar Reddy; R. Muthucumaraswamy; B. Vasu

    A numerical solution of the unsteady radiative free convection flow of an incompressible viscous fluid past an impulsively started vertical plate with variable heat and mass flux is presented here. This type of problem finds application in many technological and engineering fields such as rocket propulsion systems, spacecraft re- entry aerothermodynamics, cosmical flight aerodynamics, plasma physics, glass production and furnace

  9. Non-Darcy natural convection heat and mass transfer along a vertical permeable cylinder embedded in a porous medium

    Microsoft Academic Search

    M. A. Hossain; Kambiz Vafai; Khalil M. N. Khanafer

    1999-01-01

    Combined heat and mass transfer in non-Darcy natural convection flow along a permeable vertical cylinder embedded in a saturated porous medium is studied. The boundary layer analysis is formulated in terms of the combined thermal and solutal buoyancy effect. The flow field characteristics are analyzed using the implicit finite difference method as well as the local nonsimilarity method. The effect

  10. Experimental study of unsteady thermal characteristics and rotation induced stabilization of air convection in a bottom heated rotating vertical cylinder

    Microsoft Academic Search

    Y. T. Ker; Y. H. Li; T. F. Lin

    1998-01-01

    Flow stabilization by cavity rotation in convection of air (Pr = 0.7) in a vertical circular cylinder heated from below is studied experimentally. The cylinder is rotated at a constant speed about its own axis. In the experiment the time variations of the air temperature at selected locations in the cylinder are measured. Results are obtained for a cylinder with

  11. A general correlation for saturated two-phase flow boiling heat transfer inside horizontal and vertical tubes

    Microsoft Academic Search

    S. G. Kandlikar

    1990-01-01

    A simple correlation was developed earlier by Kandlikar (1983) for predicting saturated flow boiling heat transfer coefficients inside horizontal and vertical tubes. It was based on a model utilizing the contributions due to nucleate boiling and convective mechanisms. It incorporated a fluid-dependent parameter F{sub fl} in the nucleate boiling term. The predictive ability of the correlation for different refrigerants was

  12. Numerical modeling of a 2 K J-T heat exchanger used in Fermilab Vertical Test Stand VTS-1

    NASA Astrophysics Data System (ADS)

    Gupta, Prabhat Kumar; Rabehl, Roger

    2014-07-01

    Fermilab Vertical Test Stand-1 (VTS-1) has been in operation since 2007 for testing superconducting radio frequency (SCRF) cavities at 2 K. This test stand includes a heat exchanger consisting of a single layer; helically wound finned tube, upstream of the J-T valve. A finite difference thermal model has been developed in Engineering Equation Solver (EES) to study the thermal performance of this heat exchanger during refilling of the test stand. The model can predict heat exchanger performance under various other operating conditions and is therefore useful as a design tool for similar heat exchangers in other facilities. The present paper discusses the different operational modes of this heat exchanger and its thermal characteristics under these operational modes. Results of this model have been compared with experimental data gathered from the VTS-1 heat exchanger, and they are in good agreement with the present model.

  13. Modeling of Heat Transfer in Geothermal Heat Exchangers

    E-print Network

    Cui, P.; Man, Y.; Fang, Z.

    2006-01-01

    Ground-coupled heat pump (GCHP) systems have been gaining increasing popularity for space conditioning in residential and commercial buildings. The geothermal heat exchanger (GHE) is devised for extraction or injection of thermal energy from...

  14. Numerical investigation of natural convection in a rectangular enclosure due to partial heating and cooling at vertical walls

    NASA Astrophysics Data System (ADS)

    Alam, Pravez; Kumar, Ashok; Kapoor, S.; Ansari, S. R.

    2012-06-01

    A comprehensive numerical investigation on the natural convection in a rectangular enclosure is presented. The flow is induced due to the constant partial heating at lower half of the left vertical wall and partial cooling at upper half of the right vertical wall along with rest walls are adiabatic. In this investigation the Special attention is given to understand the effect of aspect ratio and heat source intensity i.e. Rayleigh number, Ra, on the fluid flow configuration as well as on the local and average heat transfer rates. The range of Rayleigh (Ra) and aspect ratio ( A) is taken [10 3, 10 6] and [0.5, 4] respectively. The results are presented in terms of stream function ( ?), temperature ( ?) and heat transfer rates (local Nusselt numbers NuL, and average Nusselt numbers Nu). The numerical experiments show that increasing of Ra implies the enhancement of thermal buoyancy force, which in turn increases the thermal convection in the cavity. As a result, the local as well as average heat transfer rate is expected to increase. The local transfer rate ( NuL) is increases in the small region near the left vertical wall of the left wall of the cavity and after that it is decreases in the middle portion of heated region. And, it start to increase near to the middle point of left wall. It is also observed that the local heat transfer is increases as increases the aspect ratio. The average heat transfer rate (Nu) is increases as the aspect ratio A increases from 0.5 to 1 and beyond that it is decreases smoothly. It is also found that the heat transfer rate attains its maximum value at aspect ratio one.

  15. Unsteady Heat and Mass Transfer MHD Flow of a Chemically Reacting Fluid Past an Impulsively Started Vertical Plate with Radiation

    NASA Astrophysics Data System (ADS)

    Reddy, M. Gnaneswara

    2014-09-01

    The object of this study is to investigate thermal radiation in an unsteady fl ow of a viscous incompressible chemically reacting hydromagnetic fluid past an impulsively started vertical plate with heat and mass transfer. The fluid is a gray, absorbing-emitting, and nonscattering medium, and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing equations are solved using an implicit finite difference scheme of the Crank-Nicolson type. Numerical results for the transient velocity, temperature, concentration, local as well as average skin frictions, and the rate of heat and mass transfer are shown graphically.

  16. An investigation of heat exchange of liquid metal during flow in a vertical tube with non-uniform heating in the transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Mel'nikov, I. A.; Razuvanov, N. G.; Sviridov, V. G.; Sviridov, E. V.; Shestakov, A. A.

    2013-05-01

    The results of experimental investigations of heat exchange during the downflow of liquid metal in a vertical tube with non-uniform heating in the transverse magnetic field are presented. The experiment was more realistic in terms of conditions of the blanket of a fusion reactor of the tokamak type. Profiles of the average temperature, distribution of local and mean heat transfer coefficients (Nusselt numbers), and the intensities and spectra of temperature pulsations have been measured. On certain combinations of operating parameters in the strong magnetic field low-frequency temperature pulsations with abnormal intensity were found.

  17. Unsteady convection flow and heat transfer over a vertical stretching surface.

    PubMed

    Cai, Wenli; Su, Ning; Liu, Xiangdong

    2014-01-01

    This paper investigates the effect of thermal radiation on unsteady convection flow and heat transfer over a vertical permeable stretching surface in porous medium, where the effects of temperature dependent viscosity and thermal conductivity are also considered. By using a similarity transformation, the governing time-dependent boundary layer equations for momentum and thermal energy are first transformed into coupled, non-linear ordinary differential equations with variable coefficients. Numerical solutions to these equations subject to appropriate boundary conditions are obtained by the numerical shooting technique with fourth-fifth order Runge-Kutta scheme. Numerical results show that as viscosity variation parameter increases both the absolute value of the surface friction coefficient and the absolute value of the surface temperature gradient increase whereas the temperature decreases slightly. With the increase of viscosity variation parameter, the velocity decreases near the sheet surface but increases far away from the surface of the sheet in the boundary layer. The increase in permeability parameter leads to the decrease in both the temperature and the absolute value of the surface friction coefficient, and the increase in both the velocity and the absolute value of the surface temperature gradient. PMID:25264737

  18. Multiple buoyancy driven flows in a vertical cylinder heated from below

    NASA Technical Reports Server (NTRS)

    Yamaguchi, Y.; Chang, C. J.; Brown, R. A.

    1983-01-01

    The structure of axisymmetric buoyancy-driven convection in a vertical cylinder heated from below is probed by finite element solution of the Boussinesq equations coupled with computed-implemented perturbation techniques for detecting and tracking multiple flows and for determining flow stability. Results are reported for fluids with Prandtl number of one and for cylinders with aspect ratio (Lambda) (defined as the height to radius of the cylinder) between 0.5 and 2.25. Extensive calculations of the neutral stability curve for the static solution and of the nonlinear motions along the bifurcating flow families show a continuous evolution of the primary cellular motion from a single toroidal cell to two and three cells nested radially in the cylinder, instead of the sharp transitions found for a cylinder with shear-free sidewalls. The smooth transitions in flow structure with Rayleigh number and lambda are explained by nonlinear connectivity between the first two bifurcating flow families formed either by a secondary bifurcation point for Lambda or = Lambda * approximately 0.80 or by a limit point for Lambda Lambda *. The transition between these two modes may be described by the theory of multiple limit point bifurcation.

  19. Rayleigh-Benard Convection in a Vertical Cylinder Heated from Below with a Nonuniform Temperature

    NASA Astrophysics Data System (ADS)

    Luo, Gang; Vanka, Pratap

    2001-11-01

    Rayleigh-Benard convection in a vertical cylinder heated from below with a uniform bottom wall temperature has been studied extensively. At low aspect ratios, the flow starts as an axisymmetric pattern and gradually becomes non-axisymmetric when the Rayleigh number is increased. For aspect ratios around and greater than unity, the first stable flow pattern is a non-axisymmetric mode at all Rayleigh numbers beyond the first critical value. Almost all of the studies of natural convection flow in a cylinder have been concerned with a uniform bottom wall temperature. Even with this simple boundary condition, the flow is very complex, with a number of bifurcations in the Rayleigh number aspect ratio space. However, no previous studies have investigated what would happen if the bottom wall has a radially nonuniform temperature distribution. In this work, we have numerically studied the transitions in natural convection in a cylinder where the bottom wall has a parabolic temperature distribution and the side walls are perfectly conducting. The flow fields at two different nonuniformity factors and several Rayleigh numbers have been computed with a finite volume method.

  20. Unsteady Convection Flow and Heat Transfer over a Vertical Stretching Surface

    PubMed Central

    Cai, Wenli; Su, Ning; Liu, Xiangdong

    2014-01-01

    This paper investigates the effect of thermal radiation on unsteady convection flow and heat transfer over a vertical permeable stretching surface in porous medium, where the effects of temperature dependent viscosity and thermal conductivity are also considered. By using a similarity transformation, the governing time-dependent boundary layer equations for momentum and thermal energy are first transformed into coupled, non-linear ordinary differential equations with variable coefficients. Numerical solutions to these equations subject to appropriate boundary conditions are obtained by the numerical shooting technique with fourth-fifth order Runge-Kutta scheme. Numerical results show that as viscosity variation parameter increases both the absolute value of the surface friction coefficient and the absolute value of the surface temperature gradient increase whereas the temperature decreases slightly. With the increase of viscosity variation parameter, the velocity decreases near the sheet surface but increases far away from the surface of the sheet in the boundary layer. The increase in permeability parameter leads to the decrease in both the temperature and the absolute value of the surface friction coefficient, and the increase in both the velocity and the absolute value of the surface temperature gradient. PMID:25264737

  1. Natural convection heat transfer and fluid dynamics for a pair of vertically aligned isothermal horizontal cylinders

    Microsoft Academic Search

    Tim Persoons; Ian M. O’Gorman; David B. Donoghue; Gerry Byrne; Darina B. Murray

    2011-01-01

    This paper discusses the close interaction between local fluid dynamics and natural convection heat transfer from a pair of isothermally heated horizontal cylinders submerged in water. The presence of a second heated cylinder induces heat transfer enhancements of up to 10%, and strong fluctuations in local heat transfer rate. Therefore specific attention is focused on how the local heat transfer

  2. Experimental investigation of convection heat transfer of CO{sub 2} at supercritical pressures in a vertical circular tube

    SciTech Connect

    Li, Zhi-Hui; Jiang, Pei-Xue; Zhao, Chen-Ru; Zhang, Yu. [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China)

    2010-11-15

    The convection heat transfer characteristics of supercritical CO{sub 2} in a vertical circular tube of 2 mm inner diameter were investigated experimentally for pressures ranging from 78 to 95 bar, inlet temperatures from 25 to 40 C, and inlet Reynolds numbers from 3800 to 20,000. The effects of the heat flux, thermo-physical properties, buoyancy and thermal acceleration on the convection heat transfer were analyzed. The experimental results show that for high inlet Reynolds numbers (e.g. Re = 9000) and high heat fluxes, a significant local deterioration and recovery of the heat transfer was found for upward flows but not for downward flows. Comparison of the experimental data for inlet Reynolds numbers from 3800 to 20,000 with some well-known empirical correlations showed large differences especially when the heat transfer deteriorates and then recovers when the effect of buoyancy is significant. The experimental data was used to develop modified local turbulent Nusselt number correlations for supercritical CO{sub 2} flowing in vertical small circular tubes. (author)

  3. Parametric studies and correlations for combined conduction-mixed convection-radiation from a non-identically and discretely heated vertical plate

    Microsoft Academic Search

    G. Ganesh Kumar; C. Gururaja Rao

    2011-01-01

    The present paper reports the parametric studies and correlations for the problem of combined conduction-mixed convection-radiation from a non-identically and discretely heated vertical plate. Three discrete heat sources of non-identical heights but with identical volumetric rate of heat generation are assumed to be flush-mounted in a thin vertical plate. The longest and the shortest heaters are provided at the leading

  4. Forced convection heat transfer from a wire inserted into a vertically-mounted pipe to liquid hydrogen flowing upward

    NASA Astrophysics Data System (ADS)

    Tatsumoto, H.; Shirai, Y.; Shiotsu, M.; Naruo, Y.; Kobayashi, H.; Inatani, Y.

    2014-12-01

    Forced convection heat transfer from a PtCo wire with a length of 120 mm and a diameter of 1.2 mm that was inserted into a vertically-mounted pipe with a diameter of 8.0 mm to liquid hydrogen flowing upward was measured with a quasi-steady increase of a heat generation rate for wide ranges of flow rate under saturated conditions. The pressures were varied from 0.4 MPa to 1.1 MPa. The non-boiling heat transfer characteristic agrees with that predicted by Dittus-Boelter correlation. The critical heat fluxes are higher for higher flow rates and lower pressures. Effect of Weber number on the CHF was clarified and a CHF correlation that can describe the experimental data is derived based on our correlation for a pipe.

  5. Numerical modeling of a 2K J-T heat exchanger used in Fermilab Vertical Test Stand VTS-1

    SciTech Connect

    Gupta, Prabhat Kumar [Raja Ramanna Centre for Advanced Technology (RRCAT), Indore (MP), India; Rabehl, Roger [FNAL

    2014-07-01

    Fermilab Vertical Test Stand-1 (VTS-1) is in operation since 2007 for testing the superconducting RF cavities at 2 K. This test stand has single layer coiled finned tubes heat exchanger before J-T valve. A finite difference based thermal model has been developed in Engineering Equation Solver (EES) to study its thermal performance during filling and refilling to maintain the constant liquid level of test stand. The model is also useful to predict its performance under other various operating conditions and will be useful to design the similar kind of heat exchanger for future needs. Present paper discusses the different operational modes of this heat exchanger and its thermal characteristics under these operational modes. Results of this model have also been compared with the experimental data gathered from the VTS-1 heat exchanger and they are in good agreement with the present model.

  6. High Rayleigh number convection in rectangular enclosures with differentially heated vertical walls and aspect ratios between zero and unity

    NASA Technical Reports Server (NTRS)

    Kassemi, Siavash A.

    1988-01-01

    High Rayleigh number convection in a rectangular cavity with insulated horizontal surfaces and differentially heated vertical walls was analyzed for an arbitrary aspect ratio smaller than or equal to unity. Unlike previous analytical studies, a systematic method of solution based on linearization technique and analytical iteration procedure was developed to obtain approximate closed-form solutions for a wide range of aspect ratios. The predicted velocity and temperature fields are shown to be in excellent agreement with available experimental and numerical data.

  7. Numerical simulation of laminar natural convection in a laterally heated vertical cylindrical enclosure: application to crystal growth

    Microsoft Academic Search

    Subhransu Roy; Abhra Roy; R. C. Arora

    2006-01-01

    Laminar natural convection has been studied in a laterally heated vertical cylindrical enclosure with a free insulated surface\\u000a and a centrally located constant temperature wall at the top. These conditions are a simplification of the conditions existing\\u000a in a Czochralski crystal pulling system. The laminar, axisymmetric flow of a Newtonian, constant physical properties fluid\\u000a under Boussinesq’s approximation has been considered.

  8. Effects of mass transfer on flow past an impulsively started infinite vertical plate with constant heat flux and chemical reaction

    Microsoft Academic Search

    U. N. Das; R. Deka; V. M. Soundalgekar

    1994-01-01

    An exact solution to the flow due to impulsive motion of an infinite vertical plate in its own plane in the presence of i)\\u000a species concentration ii) constant heat flux at the plate iii) chemical reaction of first order, has been derived by the Laplace-transform\\u000a technique. Velocity and concentration profiles are shown on graphs. It is observed that due to

  9. Unsteady free convection flow near an infinite vertical plate with prescribed surface heat flux and skin friction

    NASA Astrophysics Data System (ADS)

    Sohail, A.; Samiulhaq; Vieru, D.

    2014-02-01

    The unsteady free convection flow of an incompressible viscous fluid over an infinite vertical plate, under prescribed forms of the surface shear and heat flux, is numerically studied. The governing partial differential equations are transformed in a non-dimensional system of nonlinear ordinary differential equations, whose solutions are obtained by means of the Bulirsch-Stoer method. The influence of pertinent parameters on the dimensionless velocity and temperature fields is graphically underlined. The friction parameter ? and the heat flux coefficient q have a meaningful influence especially on the velocity.

  10. MHD free convective boundary layer flow of a nanofluid past a flat vertical plate with Newtonian heating boundary condition.

    PubMed

    Uddin, Mohammed J; Khan, Waqar A; Ismail, Ahmed I

    2012-01-01

    Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement. PMID:23166688

  11. MHD Free Convective Boundary Layer Flow of a Nanofluid past a Flat Vertical Plate with Newtonian Heating Boundary Condition

    PubMed Central

    Uddin, Mohammed J.; Khan, Waqar A.; Ismail, Ahmed I.

    2012-01-01

    Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement. PMID:23166688

  12. Explicit formulas for laminar natural convection heat transfer along vertical cylinders with power-law wall temperature distribution

    NASA Astrophysics Data System (ADS)

    Muñoz-Cobo, José; Corberán, José; Chiva, Sergio

    2002-06-01

    Natural convection heat transfer coefficients for vertical cylinders with variable surface temperature distribution must be found by complex numerical integration of the corresponding system of governing differential equations. Its evaluation for practical heat transfer calculations is always based on more or less complex correlations fitted to numerical or experimental results. This paper presents alternative approximate formulas for the calculation of the local Nusselt number and heat transfer coefficient and for laminar natural convection around vertical cylinders with power-law wall temperature distribution. These formulae have been derived from the integration of the energy and momentum equations, following the integral method and assuming some simplifying hypothesis, and then, finally fitted to numerical results in order to improve their accuracy. The formula obtained, with only two fitted coefficients, is able to predict the corresponding Nusselt number with a maximum error of 7% over a very wide range of Prandtl numbers (0.1-100) and curvatures, from slender vertical cylinders and needles to the flat plate case, and for the power-law exponents of practical interest.

  13. A complete conjugate conduction convection and radiation problem for a heated block in a vertical differentially heated square enclosure

    Microsoft Academic Search

    Y. Liu; N. Phan-Thien

    1999-01-01

    The complete conjugate heat conduction, convection and radiation problem for a heated block in a differentially heated square\\u000a enclosure is solved by an operator-splitting pseudo-time-stepping finite element method. The main feature of the solution\\u000a procedure is that the multi-phases are treated as a single computational domain with unknown interfacial boundary conditions.\\u000a The temperature distribution in the heated block and in

  14. Experimental investigation of free-convection heat transfer in vertical tube at large Grashof numbers / E. R. G. Eckert, A. J. Diaguila

    NASA Technical Reports Server (NTRS)

    Eckert, E R G; Diaguila, A J

    1952-01-01

    Local free-convection heat-transfer coefficients and temperature fields in the turbulent flow range were obtained within a vertical, stationary tube closed at the boom, heated along its walls, and having a length-to-diameter ratio of 5. Convective heat-transfer coefficients were correlated by the general relations for free-convection heat transfer. These coefficients, converted to dimensionless Nusselt numbers were 35 percent below known relations for vertical flat plates. Air temperature measurements within the tube indicated a thin boundary layer along the heated wall surface and unstable conditions in the air flow.

  15. Retrieved Vertical Profiles of Latent Heat Release Using TRMM Rainfall Products

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Lang, S.; Olson, W. S.; Meneghini, R.; Yang, S.; Simpson, J.; Kummerow, C.; Smith, E.

    2000-01-01

    This paper represents the first attempt to use TRMM rainfall information to estimate the four dimensional latent heating structure over the global tropics for February 1998. The mean latent heating profiles over six oceanic regions (TOGA COARE IFA, Central Pacific, S. Pacific Convergence Zone, East Pacific, Indian Ocean and Atlantic Ocean) and three continental regions (S. America, Central Africa and Australia) are estimated and studied. The heating profiles obtained from the results of diagnostic budget studies over a broad range of geographic locations are used to provide comparisons and indirect validation for the heating algorithm estimated heating profiles. Three different latent heating algorithms, the Goddard Convective-Stratiform (CSH) heating, the Goddard Profiling (GPROF) heating, and the Hydrometeor heating (HH) are used and their results are intercompared. The horizontal distribution or patterns of latent heat release from the three different heating retrieval methods are quite similar. They all can identify the areas of major convective activity (i.e., a well defined ITCZ in the Pacific, a distinct SPCZ) in the global tropics. The magnitude of their estimated latent heating release is also not in bad agreement with each other and with those determined from diagnostic budget studies. However, the major difference among these three heating retrieval algorithms is the altitude of the maximum heating level. The CSH algorithm estimated heating profiles only show one maximum heating level, and the level varies between convective activity from various geographic locations. These features are in good agreement with diagnostic budget studies. By contrast, two maximum heating levels were found using the GPROF heating and HH algorithms. The latent heating profiles estimated from all three methods can not show cooling between active convective events. We also examined the impact of different TMI (Multi-channel Passive Microwave Sensor) and PR (Precipitation Radar) rainfall information on latent heating structures.

  16. Augmentation of condensation heat transfer with electrohydrodynamics on vertical enhanced tubes

    E-print Network

    Motte, Edouard

    1994-01-01

    transfer. [Carey, 1992] Fig. 2. 2 Schematic representation of wires used to enhance film condensation on vertical tubes. [Carey, 1992] Fig. 3. 1 Experimental apparatus Fig. 3. 2 Thermocouple bead soldered on the tube wall surface Fig. 4. 1 Electrode...

  17. Measuring the electrical properties of soil using a calibrated ground-coupled GPR system

    USGS Publications Warehouse

    Oden, C.P.; Olhoeft, G.R.; Wright, D.L.; Powers, M.H.

    2008-01-01

    Traditional methods for estimating vadose zone soil properties using ground penetrating radar (GPR) include measuring travel time, fitting diffraction hyperbolae, and other methods exploiting geometry. Additional processing techniques for estimating soil properties are possible with properly calibrated GPR systems. Such calibration using ground-coupled antennas must account for the effects of the shallow soil on the antenna's response, because changing soil properties result in a changing antenna response. A prototype GPR system using ground-coupled antennas was calibrated using laboratory measurements and numerical simulations of the GPR components. Two methods for estimating subsurface properties that utilize the calibrated response were developed. First, a new nonlinear inversion algorithm to estimate shallow soil properties under ground-coupled antennas was evaluated. Tests with synthetic data showed that the inversion algorithm is well behaved across the allowed range of soil properties. A preliminary field test gave encouraging results, with estimated soil property uncertainties (????) of ??1.9 and ??4.4 mS/m for the relative dielectric permittivity and the electrical conductivity, respectively. Next, a deconvolution method for estimating the properties of subsurface reflectors with known shapes (e.g., pipes or planar interfaces) was developed. This method uses scattering matrices to account for the response of subsurface reflectors. The deconvolution method was evaluated for use with noisy data using synthetic data. Results indicate that the deconvolution method requires reflected waves with a signal/noise ratio of about 10:1 or greater. When applied to field data with a signal/noise ratio of 2:1, the method was able to estimate the reflection coefficient and relative permittivity, but the large uncertainty in this estimate precluded inversion for conductivity. ?? Soil Science Society of America.

  18. Numerical simulation of laminar natural convection in a laterally heated vertical cylindrical enclosure: application to crystal growth

    NASA Astrophysics Data System (ADS)

    Roy, Subhransu; Roy, Abhra; Arora, R. C.

    2006-01-01

    Laminar natural convection has been studied in a laterally heated vertical cylindrical enclosure with a free insulated surface and a centrally located constant temperature wall at the top. These conditions are a simplification of the conditions existing in a Czochralski crystal pulling system. The laminar, axisymmetric flow of a Newtonian, constant physical properties fluid under Boussinesq’s approximation has been considered. Governing equations in primitive variable form are solved numerically by control volume method. SIMPLE algorithm due to Patankar has been used for the numerical simulation. The effects of the constant wall heat flux boundary condition at the side wall have been investigated whereas the bottom wall is considered to be insulated. Streamlines and isotherms are presented for various Rayleigh numbers and Prandtl numbers. Heat flux vectors through the melt are plotted for selected cases. The axial velocity and temperature variations at different horizontal sections of the crucible have been presented graphically to explain the transport processes inside the crucible. It has been observed that in case of low Pr and high Ra, flow separation occurs at the vertical wall of the crucible which leads to an oscillatory flow as Ra increases. The investigation has been extended to the oscillatory regime of flow in the zone of supercritical Rayleigh numbers and some unsteady results are also presented. Finally a heat transfer correlation has been developed for steady-state case.

  19. The vertical structure of diabatic heating associated with the Madden-Julian oscillation simulated by the Goddard Laboratory for Atmospheres climate model

    NASA Technical Reports Server (NTRS)

    Chen, Tsing-Chang; Yen, Ming-Cheng; Pfaendtner, James; Sud, Y. C.

    1993-01-01

    The diabatic heating structure of the nine-layer Goddard Laboratory for Atmospheres model of the Madden-Julian oscillation (MJO) is illustrated with composite charts made for those times when this low-frequency mode reaches its maximum and minimum amplitudes. These composite charts compare the vertically integrated diabatic heating with potential functions, the vertical distribution of diabatic heating with the east-west mass flux function in the tropics, and the vertical profiles of diabatic heating at the centers of maximum and minimum MJO amplitude. Three interesting features of the model MJO's diabatic heating are revealed: (1) the maximum heating rate of this low-frequency mode is located over the Asian monsoon region and its amplitude is about a half of the maximum value of the seasonal mean heating rate in this region, (2) the vertical diabatic heating rate profile has a maximum at 500 mbar and resembles the seasonal mean total heating profile, and (3) the total diabatic heating is for the most part composed of the latent heat released by cumulus convection.

  20. Diurnal and vertical variability of the sensible heat and carbon dioxide budgets in the atmospheric surface layer

    USGS Publications Warehouse

    Casso-Torralba, P.; de Arellano, J. V. -G.; Bosveld, F.; Soler, M.R.; Vermeulen, A.; Werner, C.; Moors, E.

    2008-01-01

    The diurnal and vertical variability of heat and carbon dioxide (CO2) in the atmospheric surface layer are studied by analyzing measurements from a 213 in tower in Cabauw (Netherlands). Observations of thermodynamic variables and CO2 mixing ratio as well as vertical profiles of the turbulent fluxes are used to retrieve the contribution of the budget terms in the scalar conservation equation. On the basis of the daytime evolution of turbulent fluxes, we calculate the budget terms by assuming that turbulent fluxes follow a linear profile with height. This assumption is carefully tested and the deviation ftom linearity is quantified. The budget calculation allows us to assess the importance of advection of heat and CO2 during day hours for three selected days. It is found that, under nonadvective conditions, the diurnal variability of temperature and CO2 is well reproduced from the flux divergence measurements. Consequently, the vertical transport due to the turbulent flux plays a major role in the daytime evolution of both scalars and the advection is a relatively small contribution. During the analyzed days with a strong contribution of advection of either heat or carbon dioxide, the flux divergence is still an important contribution to the budget. For heat, the quantification of the advection contribution is in close agreement with results from a numerical model. For carbon dioxide, we qualitatively corroborate the results with a Lagrangian transport model. Our estimation of advection is compared with, traditional estimations based on the Net Ecosystem-atmosphere Exchange (NEE). Copyright 2008 by the American Geophysical Union.

  1. Seismic-geodynamic constraints on three-dimensional structure, vertical flow, and heat transfer in the mantle

    USGS Publications Warehouse

    Forte, A.M.; Woodward, R.L.

    1997-01-01

    Joint inversions of seismic and geodynamic data are carried out in which we simultaneously constrain global-scale seismic heterogeneity in the mantle as well as the amplitude of vertical mantle flow across the 670 km seismic discontinuity. These inversions reveal the existence of a family of three-dimensional (3-D) mantle models that satisfy the data while at the same time yielding predictions of layered mantle flow. The new 3-D mantle models we obtain demonstrate that the buoyancy forces due to the undulations of the 670 km phase-change boundary strongly inhibit the vertical flow between the upper and lower mantle. The strong stabilizing effect of the 670 km topography also has an important impact on the predicted dynamic topography of the Earth's solid surface and on the surface gravity anomalies. The new 3-D models that predict strongly or partially layered mantle flow provide essentially identical fits to the global seismic data as previous models that have, until now, predicted only whole-mantle flow. The convective vertical transport of heat across the mantle predicted on the basis of the new 3-D models shows that the heat flow is a minimum at 1000 km depth. This suggests the presence at this depth of a globally defined horizon across which the pattern of lateral heterogeneity changes rapidly. Copyright 1997 by the American Geophysical Union.

  2. Equipment for the emplacement of heat-producing waste in long horizontal boreholes. [Horizontal vs vertical emplacement

    SciTech Connect

    Young, K.D.; Scully, L.W.; Fisk, A.; deBakker, P.; Friant, J.; Anderson, A.

    1983-01-01

    Emplacement of heat-producing waste in long horizontal holes may offer several technical and economic advantages over shallow vertical hole emplacement. Less of the host rock suffers damage as a result of drift construction; the heat from the waste can be isolated from the access drifts for long periods of time; and the amount of rock which must be excavated is much less than in traditional disposal scenarios. One of the major reasons that has been used to reject the long hole concept in the past and adhere to the shallow vertical hole concept is the equipment required to drill the holes and to emplace and retrieve the waste. Such equipment does not currently exist. It clearly is more difficult to drill a 600 to 1000 foot horizontal hole, possibly 3 to 4 feet in diameter, and place a canister of waste at the end of it than to drill a 30 foot vertical hole and lower the waste to the bottom. A liner, for emplacement hole stabilization, appears to be feasible by adapting existing technology for concrete slip forming or jacking in a steel liner. The conceptual design of the equipment to drill long horizontal holes, emplace waste and retrieve waste will be discussed. Various options in concept will be presented as well as their advantages and disadvantages. The operating scenario of the selected concept will be described as well as solutions to potential problems encountered.

  3. LDA measurements and numerical simulation of the induced flow through a rectangular chamber containing a vertical cylindrical heat source

    NASA Astrophysics Data System (ADS)

    Baskaya, S.; Gilchrist, A.; Fraser, Simon M.

    1993-08-01

    Experimental (LDA) and computational (CFD) investigations of steady, laminar natural convection in a horizontally vented chamber containing a vertical heated cylinder at the center are reported. The heated cylinder was located on the lower adiabatic wall of the chamber and was 2/3 the height of the chamber. The cylinder surfaces were maintained at a constant temperature. The chamber inlet and outlet were located at the bottom and top of facing vertical walls, respectively. In this study, experiments were conducted using laser-Doppler anemometry (LDA) with a two-component Ar-Ion laser connected to two burst spectrum analyzers (BSA). Velocity profiles (of both vertical and horizontal velocity components) were measured at the inlet, outlet and at other locations inside the chamber. For the numerical simulation (3-D, steady-state, laminar) the governing equations were solved using the computational fluid dynamics code PHOENICS. Comparison of the experimental data with computational results showed satisfactory agreement and the importance that LDA measurements have in verifying CFD simulations.

  4. Ocean Turbulence. Paper 2; One-Point Closure Model Momentum, Heat and Salt Vertical Diffusivities in the Presence of Shear

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Howard, A.; Cheng, Y.; Dubovikov, M. S.

    1999-01-01

    We develop and test a 1-point closure turbulence model with the following features: 1) we include the salinity field and derive the expression for the vertical turbulent diffusivities of momentum K(sub m) , heat K(sub h) and salt K(sub s) as a function of two stability parameters: the Richardson number R(sub i) (stratification vs. shear) and the Turner number R(sub rho) (salinity gradient vs. temperature gradient). 2) to describe turbulent mixing below the mixed layer (ML), all previous models have adopted three adjustable "background diffusivities" for momentum, heat and salt. We propose a model that avoids such adjustable diffusivities. We assume that below the ML, the three diffusivities have the same functional dependence on R( sub i) and R(sub rho) as derived from the turbulence model. However, in order to compute R(sub i) below the ML, we use data of vertical shear due to wave-breaking.measured by Gargett et al. The procedure frees the model from adjustable background diffusivities and indeed we employ the same model throughout the entire vertical extent of the ocean. 3) in the local model, the turbulent diffusivities K(sub m,h,s) are given as analytical functions of R(sub i) and R(sub rho). 5) the model is used in an O-GCM and several results are presented to exhibit the effect of double diffusion processes. 6) the code is available upon request.

  5. Evaporation heat transfer and friction characteristics of R-134a flowing downward in a vertical corrugated tube

    SciTech Connect

    Aroonrat, Kanit; Wongwises, Somchai [Fluid Mechanics, Thermal Engineering and Multiphase Flow Research Lab. (FUTURE), Department of Mechanical Engineering, King Mongkut's University of Technology Thonburi, Bangmod, Bangkok 10140 (Thailand)

    2011-01-15

    Differently from most previous studies, the heat transfer and friction characteristics of the pure refrigerant HFC-134a during evaporation inside a vertical corrugated tube are experimentally investigated. The double tube test sections are 0.5 m long with refrigerant flowing in the inner tube and heating water flowing in the annulus. The inner tubes are one smooth tube and two corrugated tubes, which are constructed from smooth copper tube of 8.7 mm inner diameter. The test runs are performed at evaporating temperatures of 10, 15, and 20 C, heat fluxes of 20, 25, and 30 kW/m{sup 2}, and mass fluxes of 200, 300, and 400 kg/m{sup 2} s. The quality of the refrigerant in the test section is calculated using the temperature and pressure obtained from the experiment. The pressure drop across the test section is measured directly by a differential pressure transducer. The effects of heat flux, mass flux, and evaporation temperature on the heat transfer coefficient and two-phase friction factor are also discussed. It is found that the percentage increases of the heat transfer coefficient and the two-phase friction factor of the corrugated tubes compared with those of the smooth tube are approximately 0-10% and 70-140%, respectively. (author)

  6. Modeling Vertical Structure and Heat Transport within the Oceans of Ice-covered Worlds (Invited)

    Microsoft Academic Search

    J. C. Goodman

    2010-01-01

    Indirect observational evidence provides a strong case for liquid oceans beneath the icy crust of Europa and several other frozen moons in the outer solar system. However, little is known about the fluid circulation within these exotic oceans. As a first step toward understanding circulations driven by buoyancy (rather than mechanical forcing from tides), one must understand the typical vertical

  7. Natural Convection Heat and Mass Transfer from Falling Films in Vertical Channels

    Microsoft Academic Search

    Gregory Allen Buck

    1990-01-01

    In the design of solar collector\\/regenerators for use in open cycle absorption refrigeration (OCAR) units, the problem of predicting evaporation rates and solution temperatures is of paramount importance in determining overall cycle performance. This transport of heat and mass is dominated by natural convection with buoyant forces primarily generated as a result of film heating by the solar flux, but

  8. Mixed convection heat transfer past in-line cylinders in a vertical duct

    SciTech Connect

    Gowda, Y.T.K.; Narayana, P.A.A.; Seetharamu, K.N. [Indian Inst. of Tech., Madras (India)

    1997-04-01

    Heat transfer and fluid flow over a row of in-line cylinders placed between two parallel plates are studied numerically. Solutions of governing equations have been obtained using Euler`s explicit algorithm. Numerical results have been obtained for duct wall spacings S/D = 1.5, 2.0, and 2.5; Re = 50 and 100; and Pr = 0.7. The effect of Richardson number on the flow and heat transfer has been investigated in the range of Ri = {minus}5.0 to +5.0. Streamlines, temperature contours, local and average Nusselt numbers, pressure, and shear stress distribution around the cylinders are presented. There are considerable effects of buoyancy and the blockage on flow and heat transfer over the cylinders. The problem of mixed convection heat transfer from isothermal horizontal cylinders has received considerable attention in view of practical applications in heat exchangers, and solar extraction systems.

  9. Stability of a vertical liquid film with consideration of the marangoni effect and heat exchange with the environment

    NASA Astrophysics Data System (ADS)

    Burmistrova, O. A.

    2014-05-01

    The stability of a free vertical liquid film under the combined action of gravity and thermocapillary forces has been studied. An exact solution of the Navier-Stokes and thermal conductivity equations is obtained for the case of plane steady flow with constant film thickness. It is shown that if the free surfaces of the film are perfectly heat insulated, the liquid flow rate through the cross section of the layer is zero. It is found that to close the model with consideration of the heat exchange with the environment, it is necessary to specify the liquid flow rate and the derivative of the temperature with respect to the longitudinal coordinate or the flow rate and the film thickness. The stability of the solution with constant film thickness at small wave numbers is studied. A solution of the spectral problem for perturbations in the form of damped oscillations is obtained.

  10. Chaotic dynamics of a convection roll in a highly confined, vertical, differentially heated fluid layer

    NASA Astrophysics Data System (ADS)

    Gao, Zhenlan; Podvin, Berengere; Sergent, Anne; Xin, Shihe

    2015-01-01

    Direct numerical simulation is used to study the air flow between two vertical plates maintained at different temperatures. The periodic dimensions of the plates are small so as to accommodate only one flow structure, which consists of a convection roll with oblique vorticity braids. At lower Rayleigh numbers, the roll and the braids grow and shrink alternatively following a cyclical process. As the Rayleigh number is increased, the flow becomes temporally chaotic through a period-doubling cascade. Windows corresponding to multiperiodic regimes and interior crises are observed. As the Rayleigh number is further increased, the structure intermittently switches between two vertical positions, which is seen to correspond to an "attractor-merging" crisis. The chaotic flow dynamics are characterized and the corresponding physical mechanisms are identified. We show that some of the flow key features, such as the chaotic oscillation and intermittency, can be captured by a low-order model.

  11. MHD Boundary Layer Slip Flow and Heat Transfer of Nanofluid Past a Vertical Stretching Sheet with Non-Uniform Heat Generation/Absorption

    NASA Astrophysics Data System (ADS)

    Das, S.; Jana, R. N.; Makinde, O. D.

    2014-08-01

    An investigation of the magnetohydrodynamics (MHD) boundary layer slip flow over a vertical stretching sheet in nanofluid with non-uniform heat generation/absorbtion in the presence of a uniform transverse magnetic field has been carried out. The governing non-linear partial differential equations are transformed into a system of coupled non-linear ordinary differential equations using similarity transformations and then solved numerically using the Runge-Kutta fourth order method with shooting technique. Numerical results are obtained for the fluid velocity, temperature as well as the shear stress and the rate of heat transfer at the surface of the sheet. The results show that there are significant effects of various pertinent parameters on velocity and temperature profiles.

  12. Influence of wick properties in a vertical LHP on remove waste heat from electronic equipment

    SciTech Connect

    Smitka, Martin, E-mail: martin.smitka@fstroj.uniza.sk, E-mail: patrik.nemec@fstroj.uniza.sk, E-mail: milan.malcho@fstroj.uniza.sk; Nemec, Patrik, E-mail: martin.smitka@fstroj.uniza.sk, E-mail: patrik.nemec@fstroj.uniza.sk, E-mail: milan.malcho@fstroj.uniza.sk; Malcho, Milan, E-mail: martin.smitka@fstroj.uniza.sk, E-mail: patrik.nemec@fstroj.uniza.sk, E-mail: milan.malcho@fstroj.uniza.sk [University of Žilina, Faculty of Mechanical Engineering, Department of Power Engeneering, Univerzitna 1, 010 26 Žilina (Slovakia)

    2014-08-06

    The loop heat pipe is a vapour-liquid phase-change device that transfers heat from evaporator to condenser. One of the most important parts of the LHP is the porous wick structure. The wick structure provides capillary force to circulate the working fluid. To achieve good thermal performance of LHP, capillary wicks with high permeability and porosity and fine pore radius are expected. The aim of this work is to develop porous wick of sintered nickel powder with different grain sizes. These porous wicks were used in LHP and there were performed a series of measurements to remove waste heat from the insulated gate bipolar transistor (IGBT)

  13. BUOYANCY-AIDED MIXED CONVECTION WITH CONDUCTION AND SURFACE RADIATION FROM A VERTICAL ELECTRONIC BOARD WITH A TRAVERSABLE DISCRETE HEAT SOURCE

    Microsoft Academic Search

    C. Gururaja Rao

    2004-01-01

    This article presents the results of a comprehensive fundamental numerical study of the problem of buoyancy-aided mixed convection with conduction and surface radiation from a vertical electronic board provided with a traversable, flush-mounted, discrete heat source. Air, a radiatively transparent medium, is considered to be the cooling agent. The governing equations in primitive variables for fluid flow and heat transfer

  14. The flow structure under mixed convection in a uniformly heated vertical pipe

    E-print Network

    Lee, Jeongik

    2005-01-01

    For decay heat removal systems in the conceptual Gas-cooled Fast Reactor (GFR) currently under development, passive emergency cooling using natural circulation of a gas at an elevated pressure is being considered. Since ...

  15. Geometry effects on conjugate natural convection heat transfer in vertical eccentric annuli

    Microsoft Academic Search

    Maged A. I. El-Shaarawi; Esmail M. A. Mokheimer; Ahmad Jamal

    2007-01-01

    Purpose – To explore the effect of the annulus geometrical parameters on the induced flow rate and the heat transfer under the conjugate (combined conduction and free convection) thermal boundary conditions with one cylinder heated isothermally while the other cylinder is kept at the inlet fluid temperature. Design\\/methodology\\/approach – A finite-difference algorithm has been developed to solve the bipolar boundary-layer

  16. Interaction of surface radiation with conjugate mixed convection from a vertical channel with multiple discrete heat sources

    NASA Astrophysics Data System (ADS)

    Londhe, Shrikant D.; Gururaja Rao, C.

    2014-09-01

    Important results of a numerical study performed on combined conduction-mixed convection-surface radiation from a vertical channel equipped with three identical flush-mounted discrete heat sources in its left wall are provided here. The channel has walls of identical height with the spacing varied by varying its aspect ratio (AR). The cooling medium is air that is considered to be radiatively transparent. The heat generated in the channel gets conducted along its walls before getting dissipated by mixed convection and radiation. The governing equations for fluid flow and heat transfer are considered without boundary layer approximations and are transformed into vorticity-stream function form and are later normalized. The resulting equations are solved, along with relevant boundary conditions, making use of the finite volume method. The computer code written for the purpose is validated both for fluid flow and heat transfer results with those available in the literature. Detailed parametric studies have been performed and the effects of modified Richardson number, surface emissivity, thermal conductivity and AR on various pertinent results have been looked into. The significance of radiation in various regimes of mixed convection has been elucidated. The relative contributions of mixed convection and radiation in carrying the mandated cooling load have been thoroughly explored.

  17. MHD Forced Convective Laminar Boundary Layer Flow from a Convectively Heated Moving Vertical Plate with Radiation and Transpiration Effect

    PubMed Central

    Uddin, Md. Jashim; Khan, Waqar A.; Ismail, A. I. Md.

    2013-01-01

    A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to whilst the magnetic field and mass transfer velocity are taken to be proportional to where is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

  18. MHD forced convective laminar boundary layer flow from a convectively heated moving vertical plate with radiation and transpiration effect.

    PubMed

    Uddin, Md Jashim; Khan, Waqar A; Ismail, A I Md

    2013-01-01

    A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to x(m) whilst the magnetic field and mass transfer velocity are taken to be proportional to x((m-1)/2) where x is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

  19. A susceptor with a ?-shaped slot in a vertical MOCVD reactor by induction heating

    NASA Astrophysics Data System (ADS)

    Zhiming, Li; Hailing, Li; Xiaobing, Gan; Haiying, Jiang; Jinping, Li; Xiaoqian, Fu; Yanbin, Han; Yingjie, Xia; Jianqin, Yin; Yimei, Huang; Shigang, Hu

    2014-09-01

    By using the numerical simulation for the temperature field in the metal organic vapor deposition (MOCVD) reactor by induction heating, it is found that the temperature distribution in the conventional cylinder-shaped susceptor is nonuniform due to the skin effect of the induced current, which makes the temperature distribution of the wafer nonuniform. Therefore, a novel susceptor with a ?-shaped slot is proposed. This slot changes the mode and the rate of the heat transfer in the susceptor, which improves the uniformity of the temperature distribution in the wafer. By using the finite element method (FEM), the susceptor with this structure for heating a wafer of four inches in diameter is optimized. It is observed that the optimized susceptor with the ?-shaped slot makes the uniformity of the temperature distribution in the wafer improve by more than 85%, and a good uniformity of temperature distributions is kept under different wafer temperatures, which may be beneficial to the film growth.

  20. Influence of Test Tube Material on Subcooled Flow Boiling Critical Heat Flux in Short Vertical Tube

    Microsoft Academic Search

    Koichi Hata; Masahiro Shiotsu; Nobuaki Noda

    2007-01-01

    The steady state subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3 m\\/s), the inlet subcoolings (DeltaTsub,in=48.6 to 154.7 K), the inlet pressure (Pin=735.2 to 969.0 kPa) and the increasing heat input (Q0 exp(t\\/tau), tau=10, 20 and 33.3 s) are systematically measured with the experimental water loop. The 304 Stainless Steel (SUS304) test tube of

  1. Effects of heat and mass transfer in flow along a vertical stretching cylinder with slip conditions

    NASA Astrophysics Data System (ADS)

    Hayat, T.; Qayyum, A.; Alsaedi, A.

    2014-04-01

    This article explores the magnetohydrodynamic (MHD) axisymmetric flow by a stretching cylinder with slip conditions. Simultaneous effects of heat and mass transfer are considered. The relevant equations are computed. Impact of various parameters on the velocity, temperature, concentration, skin friction, Nusselt number and Sherwood number is discussed.

  2. Nonsimilar hydromagnetic simultaneous heat and mass transfer by mixed convection from a vertical plate embedded in a uniform porous medium

    SciTech Connect

    Chamkha, A.J.; Khaled, A.R.A. [Kuwait Univ., Safat (Kuwait). Dept. of Mechanical and Industrial Engineering

    1999-08-27

    Simultaneous heat and mass transfer from different geometries embedded in porous media has many engineering and geophysical applications, such as migration of water in geothermal reservoirs, underground spreading of chemical wastes and other pollutants, thermal insulation, enhanced oil recovery, packed-bed catalytic reactors, cooling of nuclear reactors, grain storage, and evaporative cooling and solidification. This work considers steady, laminar, hydromagnetic simultaneous heat and mass transfer by mixed convection flow over a permeable vertical plate immersed in a uniform porous medium for the cases of power law variations of both the wall temperature and concentration and the wall heat flux and mass flux. Appropriate transformations are employed to transform the governing differential equations to a nonsimilar form. The transformed equations are solved numerically by an accurate, implicit, iterative, finite difference method. The obtained results are validated by favorable comparisons with previously published work on special cases of the problem. A parametric study illustrating the influence of all involved parameters on the local Nusselt and Sherwood numbers is conducted. The results of this parametric study are shown graphically, and the physical aspects of the problem are discussed.

  3. Effects of nanoparticle migration on hydromagnetic mixed convection of alumina/water nanofluid in vertical channels with asymmetric heating

    NASA Astrophysics Data System (ADS)

    Malvandi, A.; Ganji, D. D.

    2015-02-01

    The effects of nanoparticle migration on mixed convection of alumina/water nanofluid inside a vertical channel in the presence of a uniform magnetic field have been investigated theoretically. Walls are subjected to different heat fluxes; q lw ' ' for the left wall and q rw ' ' for the right wall, and nanoparticles are assumed to have a slip velocity relative to the base fluid induced by the Brownian motion and thermophoresis. Considering hydrodynamically and thermally fully developed flow, the governing equations including continuity, momentum, and energy equations have been reduced to two-point ordinary boundary value differential equations and they have been solved numerically. It is shown that nanoparticles eject themselves from the heated walls, construct a depleted region, and accumulate in the core region, but they are more likely to accumulate toward the wall with the lower heat flux. In addition, inclusion of nanoparticles in the presence of a magnetic field has a negative effect on the performance.

  4. Influence of Test Tube Material on Subcooled Flow Boiling Critical Heat Flux in Short Vertical Tube

    SciTech Connect

    Koichi Hata [Institute of Advanced Energy, Kyoto Univ., Gokasho, Uji, Kyoto 611-0011 (Japan); Masahiro Shiotsu [Dept. of Energy Science and Technology, Kyoto University, Kyoto University, Kyoto 606-8501 (Japan); Nobuaki Noda [National Institute for Fusion Science, 322-6, Oroshi-cho, Toki, GIFU, 509-5292 (Japan)

    2006-07-01

    The steady state subcooled flow boiling critical heat flux (CHF) for the flow velocities (u = 4.0 to 13.3 m/s), the inlet subcooling ({delta}T{sub sub,in} = 48.6 to 154.7 K), the inlet pressure (P{sub in} = 735.2 to 969.0 kPa) and the increasing heat input (Q{sub 0} exp(t/t), t = 10, 20 and 33.3 s) are systematically measured with the experimental water loop. The 304 Stainless Steel (SUS304) test tubes of inner diameters (d = 6 mm), heated lengths (L = 66 mm) and L/d = 11 with the inner surface of rough finished (Surface roughness, R{sub a} = 3.18 {mu}m), the Cupro Nickel (Cu-Ni 30%) test tubes of d = 6 mm, L = 60 mm and L/d = 10 with R{sub a} = 0.18 {mu}m and the Platinum (Pt) test tubes of d = 3 and 6 mm, L = 66.5 and 69.6 mm, and L/d 22.2 and 11.6 respectively with R{sub a} = 0.45 {mu}m are used in this work. The CHF data for the SUS304, Cu-Ni 30% and Pt test tubes were compared with SUS304 ones for the wide ranges of d and L/d previously obtained and the values calculated by the authors' published steady state CHF correlations against outlet and inlet subcooling. The influence of the test tube material on CHF is investigated into details and the dominant mechanism of subcooled flow boiling critical heat flux is discussed. (authors)

  5. Influence of Test Tube Material on Subcooled Flow Boiling Critical Heat Flux in Short Vertical Tube

    NASA Astrophysics Data System (ADS)

    Hata, Koichi; Shiotsu, Masahiro; Noda, Nobuaki

    The steady state subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3 m/s), the inlet subcoolings (?Tsub,in=48.6 to 154.7 K), the inlet pressure (Pin=735.2 to 969.0 kPa) and the increasing heat input (Q0 exp(t/?), ?=10, 20 and 33.3 s) are systematically measured with the experimental water loop. The 304 Stainless Steel (SUS304) test tube of inner diameter (d=6 mm), heated length (L=66 mm) and L/d=11 with the inner surface of rough finished (Surface roughness, Ra=3.18 ?m), the Cupro Nickel (Cu-Ni 30%) test tube of d=6 mm, L=60 mm and L/d=10 with Ra=0.18 ?m and the Platinum (Pt) test tubes of d=3 and 6 mm, L=66.5 and 69.6 mm, and L/d=22.2 and 11.6 respectively with Ra=0.45 ?m are used in this work. The CHF data for the SUS304, Cu-Ni 30% and Pt test tubes were compared with SUS304 ones for the wide ranges of d and L/d previously obtained and the values calculated by the authors' published steady state CHF correlations against outlet and inlet subcoolings. The influence of the test tube material on CHF is investigated into details and the dominant mechanism of subcooled flow boiling critical heat flux is discussed.

  6. Plasma heating effects on divertor flow vertical asymmetries in the Uragan-3M torsatron

    Microsoft Academic Search

    V. V. Chechkin; L. I. Grigor'eva; E. L. Sorokovoy; M. S. Smirnova; A. S. Slavnyj; E. D. Volkov; N. I. Nazarov; S. A. Tsybenko; A. V. Lozin; A. P. Litvinov; V. G. Konovalov; V. N. Bondarenko; A. N. Shapoval; A. Ye. Kulaga; Yu. K. Mironov; T. Mizuuchi; S. Masuzaki; K. Yamazaki

    2003-01-01

    In the l = 3\\/m = 9 Uragan-3M (U-3M) torsatron (R0 = 1 m, abar; ap 12 m, Bphgr = 0.7 T, igr(abar)\\/2pgr ap 0.4), an open helical divertor has been realized. Recently, under RF plasma production and heating conditions, a strong up-down asymmetry of diverted plasma flow has been observed as a result of measurements of distributions of this

  7. Effects of slip and heat transfer on a peristaltic flow of a Carreau fluid in a vertical asymmetric channel

    NASA Astrophysics Data System (ADS)

    Akram, S.

    2014-12-01

    In the present paper the results of numerical modeling of peristaltic flow of a Carreau fluid in a vertical asymmetric channel are presented. The effects of slip and heat transfer have been analyzed. Using the approximation of long wavelength, low Reynolds number and with the suitable dimensionless variables, the reduced equations have been solved analytically by regular perturbation method. The expressions for velocity, stream function, temperature, pressure gradient and pressure rise have been computed which strongly depend on the physical parameters of the Carreau fluid. With the help of analytical results the expression for pressure rise has been computed using numerical integration scheme. To reveal the tendency of the solutions, typical results for velocity, temperature, stream function, pressure gradient and pressure rise are presented for different values of controlling parameters.

  8. Study of dynamic structure and heat and mass transfer of a vertical ceramic tiles dryer using CFD simulations

    NASA Astrophysics Data System (ADS)

    Kriaa, Wassim; Bejaoui, Salma; Mhiri, Hatem; Le Palec, Georges; Bournot, Philippe

    2014-02-01

    In this study, we developed a two-dimensional Computational Fluid Dynamics (CFD) model to simulate dynamic structure and heat and mass transfer of a vertical ceramic tiles dryer (EVA 702). The carrier's motion imposed the choice of a dynamic mesh based on two methods: "spring based smoothing" and "local remeshing". The dryer airflow is considered as turbulent ( Re = 1.09 × 105 at the dryer inlet), therefore the Re-Normalization Group model with Enhanced Wall Treatment was used as a turbulence model. The resolution of the governing equation was performed with Fluent 6.3 whose capacities do not allow the direct resolution of drying problems. Thus, a user defined scalar equation was inserted in the CFD code to model moisture content diffusion into tiles. User-defined functions were implemented to define carriers' motion, thermo-physical properties… etc. We adopted also a "two-step" simulation method: in the first step, we follow the heat transfer coefficient evolution (Hc). In the second step, we determine the mass transfer coefficient (Hm) and the features fields of drying air and ceramic tiles. The found results in mixed convection mode (Fr = 5.39 at the dryer inlet) were used to describe dynamic and thermal fields of airflow and heat and mass transfer close to the ceramic tiles. The response of ceramic tiles to heat and mass transfer was studied based on Biot numbers. The evolutions of averages temperature and moisture content of ceramic tiles were analyzed. Lastly, comparison between experimental and numerical results showed a good agreement.

  9. A Vertical Resonance Heating Model for X- or Peanut-Shaped Galactic Bulges

    E-print Network

    Quillen, Alice C; Sharma, Sanjib; Di Matteo, Paola

    2013-01-01

    We explore a second order Hamiltonian vertical resonance model for X-shaped galactic bulges. We examine N-body simulations and find that due to the bar slowing down and disk thickening during bar buckling, the resonance and associated peanut-shape moves outward. The peanut-shape is consistent with the location of the resonance, independent of whether the bar buckled or not. We estimate the resonance width from the potential m=4 Fourier component and find that the resonance is narrow, affecting orbits in angular momentum over a range dL/L ~ 0.05. As the resonance moves outward, stars originally in the mid plane are forced out of the mid plane and into orbits just within the resonance separatrix. The height of these orbits, estimated from the Hamiltonian model, is consistent with the peanut-shape height. The X-shape is comprised of stars in these orbits as they are the only ones that would support the peanut-shape in the drifting system. The resonance condition in the Milky Way bulge relates the mid-plane mass ...

  10. Ocean Turbulence. Paper 3; Two-Point Closure Model Momentum, Heat and Salt Vertical Diffusivities in the Presence of Shear

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Dubovikov, M. S.; Howard, A.; Cheng, Y.

    1999-01-01

    In papers 1 and 2 we have presented the results of the most updated 1-point closure model for the turbulent vertical diffusivities of momentum, heat and salt, K(sub m,h,s). In this paper, we derive the analytic expressions for K(sub m,h,s) using a new 2-point closure model that has recently been developed and successfully tested against some approx. 80 turbulence statistics for different flows. The new model has no free parameters. The expressions for K(sub m, h. s) are analytical functions of two stability parameters: the Turner number R(sub rho) (salinity gradient/temperature gradient) and the Richardson number R(sub i) (temperature gradient/shear). The turbulent kinetic energy K and its rate of dissipation may be taken local or non-local (K-epsilon model). Contrary to all previous models that to describe turbulent mixing below the mixed layer (ML) have adopted three adjustable "background diffusivities" for momentum. heat and salt, we propose a model that avoids such adjustable diffusivities. We assume that below the ML, K(sub m,h,s) have the same functional dependence on R(sub i) and R(sub rho) derived from the turbulence model. However, in order to compute R(sub i) below the ML, we use data of vertical shear due to wave-breaking measured by Gargett et al. (1981). The procedure frees the model from adjustable background diffusivities and indeed we use the same model throughout the entire vertical extent of the ocean. Using the new K(sub m,h, s), we run an O-GCM and present a variety of results that we compare with Levitus and the KPP model. Since the traditional 1-point (used in papers 1 and 2) and the new 2-point closure models used here represent different modeling philosophies and procedures, testing them in an O-GCM is indispensable. The basic motivation is to show that the new 2-point closure model gives results that are overall superior to the 1-point closure in spite of the fact that the latter rely on several adjustable parameters while the new 2-point closure has none. After the extensive comparisons presented in papers 1 and 2, we conclude that the new model presented here is overall superior for it not only is parameter free but also 2 because is part of a more general turbulence model that has been previously successfully tested on a wide variety of other types of turbulent flows.

  11. Detecting hidden volcanic explosions from Mt. Cleveland Volcano, Alaska with infrasound and ground-couples airwaves

    USGS Publications Warehouse

    De Angelis, Slivio; Fee, David; Haney, Matthew; Schneider, David

    2012-01-01

    In Alaska, where many active volcanoes exist without ground-based instrumentation, the use of techniques suitable for distant monitoring is pivotal. In this study we report regional-scale seismic and infrasound observations of volcanic activity at Mt. Cleveland between December 2011 and August 2012. During this period, twenty explosions were detected by infrasound sensors as far away as 1827 km from the active vent, and ground-coupled acoustic waves were recorded at seismic stations across the Aleutian Arc. Several events resulting from the explosive disruption of small lava domes within the summit crater were confirmed by analysis of satellite remote sensing data. However, many explosions eluded initial, automated, analyses of satellite data due to poor weather conditions. Infrasound and seismic monitoring provided effective means for detecting these hidden events. We present results from the implementation of automatic infrasound and seismo-acoustic eruption detection algorithms, and review the challenges of real-time volcano monitoring operations in remote regions. We also model acoustic propagation in the Northern Pacific, showing how tropospheric ducting effects allow infrasound to travel long distances across the Aleutian Arc. The successful results of our investigation provide motivation for expanded efforts in infrasound monitoring across the Aleutians and contributes to our knowledge of the number and style of vulcanian eruptions at Mt. Cleveland.

  12. Particle image velocimetry measurements for opposing flow in a vertical channel with a differential and asymmetric heating condition

    SciTech Connect

    Martinez-Suastegui, L. [Graduate Student, Facultad de Ingenieria, Universidad Nacional Autonoma de Mexico, C.U., Mexico 04510 D.F. (Mexico); Trevino, C. [Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, C.U., Mexico 04510 D.F. (Mexico)

    2007-10-15

    Particle image velocimetry (PIV) measurements were carried out in an experimental investigation of laminar mixed convection in a vertical duct with a square cross-section. The main downward water-flow is driven by gravity while a portion of a lateral side is heated, and buoyancy forces produce non-stationary vortex structures close to the heated region. Various ranges of the Grashof number, Gr are studied in combination with the Reynolds number, Re varying from 300 to 700. The values of the generalized buoyancy parameter or Richardson number, Ri = Gr/Re{sup 2} parallel to the Grashof number are included in the results. The influence of these nondimensional parameters and how they affect the fluid flow structure and vortex sizes and locations are reported. The flow patterns are nonsymmetric, periodic, and exhibit increasing complexity and frequency for increasing buoyancy. For the averaged values of the resulting vortex dimensions, it was found that a better and more congruent representation occurs when employing the Grashof and Reynolds numbers as independent parameters. (author)

  13. Estimation of lacustrine groundwater discharge using heat as a tracer and vertical hydraulic gradients - a comparison

    NASA Astrophysics Data System (ADS)

    Rudnick, S.; Lewandowski, J.; Nützmann, G.

    2015-03-01

    Lacustrine groundwater discharge (LGD) can play a major role in water and nutrient balances of lakes. Unfortunately, studies often neglect this input path due to methodological difficulties in the determination. In a previous study we described a method which allows the estimation of LGD and groundwater recharge using hydraulic head data and groundwater net balances based on meteorological data. The aim of this study is to compare these results with discharge rates estimated by inverse modelling of heat transport using temperature profiles measured in lake bed sediments. We were able to show a correlation between the fluxes obtained with the different methods, although the time scales of the methods differ substantially. As a consequence, we conclude that the use of hydraulic head data and meteorologically-based groundwater net balances to estimate LGD is limited to time scales similar to the calibration period.

  14. Effect of viscous dissipation on an MHD free convective flow past a semi-infinite vertical cone with a variable surface heat flux

    NASA Astrophysics Data System (ADS)

    Palani, G.; Ragavan, A. R.; Thandapani, E.

    2013-11-01

    An analysis is presented to investigate the influence of viscous dissipation on a free convection flow over a vertical cone with a variable surface heat flux under the action of a transverse magnetic field. The heat transfer characteristics of the free convection flow are investigated numerically. Numerical solutions for transformed governing equations with a variable surface heat flux are obtained. Velocity, temperature, local shear stress, and heat transfer coefficients are calculated for various values of the problem parameters and presented in the graphical form. The effects of the magnetic parameter, the dissipation number, the power-law index, the angle between the cone generatrix and the vertical line, and the Prandtl number on the flow are discussed. For validation of the present numerical results, they are compared with available experimental data and are found to agree well.

  15. Heat transfer, pressure drop and void fraction in two- phase, two-component flow in a vertical tube

    NASA Astrophysics Data System (ADS)

    Sujumnong, Manit

    1998-09-01

    There are very few data existing in two-phase, two- component flow where heat transfer, pressure drop and void fraction have all been measured under the same conditions. Such data are very valuable for two-phase heat-transfer model development and for testing existing heat-transfer models or correlations requiring frictional pressure drop (or wall shear stress) and/or void fraction. An experiment was performed which adds markedly to the available data of the type described in terms of the range of gas and liquid flow rates and liquid Prandtl number. Heat transfer and pressure drop measurements were taken in a vertical 11.68-mm i.d. tube for two-phase (gas-liquid) flows covering a wide range of conditions. Mean void fraction measurements were taken, using quick- closing valves, in a 12.7-mm i.d. tube matching very closely pressures, temperatures, gas-phase superficial velocities and liquid-phase superficial velocities to those used in the heat-transfer and pressure-drop experiments. The gas phase was air while water and two aqueous solutions of glycerine (59 and 82% by mass) were used as the liquid phase. In the two-phase experiments the liquid Prandtl number varied from 6 to 766, the superficial liquid velocity from 0.05 to 8.5 m/s, and the superficial gas velocity from 0.02 to 119 m/s. The measured two-phase heat-transfer coefficients varied by a factor of approximately 1000, the two-phase frictional pressure drop ranged from small negative values (in slug flow) to 93 kPa and the void fraction ranged from 0.01 to 0.99; the flow patterns observed included bubble, slug, churn, annular, froth, the various transitions and annular-mist. Existing heat-transfer models or correlations requiring frictional pressure drop (or wall shear stress) and/or void fraction were: tested against the present data for mean heat-transfer coefficients. It was found that the methods with more restrictions (in terms of the applicable range of void fraction, liquid Prandtl number or liquid superficial Reynolds number) give better predictions. Among the most restrictive methods, the method of Drucker et al. is recommended. A method less restrictive, but still giving good predictions, is the Liquid Acceleration Model for superficial liquid Reynolds numbers greater than 2000. For local heat-transfer coefficients, a method proposed by Vijay, where Spalding's single-phase boundary-layer theory was adapted to the two-phase case, was tested considering the flow patterns individually and various methods of calculating two-phase properties. Good predictions were obtained for the case of bubble and froth flows when liquid properties were used as the two- phase mixture properties.

  16. Critical Heat Fluxes of Subcooled Water Flow Boiling against Inlet Subcooling in Short Vertical Tube

    NASA Astrophysics Data System (ADS)

    Hata, Koichi; Komori, Hirokazu; Shiotsu, Masahiro; Noda, Nobuaki

    The critical heat fluxes (CHFs) of subcooled water flow boiling for the test tube inner diameters (d=3 and 6mm) and the heated lengths (L=67, 120 and 150mm) are systematically measured for the flow velocities (u=4.0 to 13.3m/s), the inlet subcoolings (?Tsub, in=48 to 148K), the outlet subcoolings (?Tsub, out=10.5 to 95.1K), the inlet pressure (Pin=753 to 995kPa) and the outlet pressure (Pout=720 to 887kPa). The SUS304 tubes of L=67, 120 and 150mm for d=3mm and L=150mm for d=6mm are used. The values of L/d are 22, 40 and 50 for d=3mm, and 25 for d=6mm, respectively. The CHFs, qcr, sub, for a fixed ?Tsub, out become gradually lower with an increase in the L/d in the whole experimental range. The CHF correlation against outlet subcooling, which has been previously derived for L/d lower than 16, was modified to new one containing the L/d effect based on these experimental data. Furthermore, the relation between qcr, sub and L/d for a fixed ?Tsub, in was checked. The values of qcr, sub for a fixed ?Tsub, in became exponentially lower with the increase in L/d. CHF correlation against inlet subcooling has been given based on the experimental data for L/d ranging from 4.08 to 50. The correlations against outlet and inlet subcoolings can describe not only the CHFs obtained in this work for the inner diameter of 3 and 6mm at the outlet pressure of around 800kPa but also the authors' published CHFs data (1611 points) for the wide ranges of Pin=159kPa to 1MPa, d=3 to 12mm, L=33 to 150mm and u=4.0 to 13.3m/s within 15% difference for 30K??Tsub, out?140K and 40K??Tsub, in?151K.

  17. Heat transfer and flow behaviour of aqueous suspensions of TiO 2 nanoparticles (nanofluids) flowing upward through a vertical pipe

    Microsoft Academic Search

    Yurong He; Yi Jin; Haisheng Chen; Yulong Ding; Daqiang Cang; Huilin Lu

    2007-01-01

    Stable aqueous TiO2 nanofluids with different particle (agglomerate) sizes and concentrations are formulated and measured for their static thermal conductivity and rheological behaviour. The nanofluids are then measured for their heat transfer and flow behaviour upon flowing upward through a vertical pipe in both the laminar and turbulent flow regimes. Addition of nanoparticles into the base liquid enhances the thermal

  18. Influence of a magnetic field on heat and mass transfer by natural convection from vertical surfaces in porous media considering Soret and Dufour effects

    Microsoft Academic Search

    Adrian Postelnicu

    2004-01-01

    The heat and mass transfer characteristics of natural convection about a vertical surface embedded in a saturated porous medium subjected to a magnetic field is numerically studied, by taking into account the diffusion-thermo (Dufour) and thermal-diffusion (Soret) effects. The governing partial differential equations are transformed into a set of coupled differential equations, which are solved numerically using a finite difference

  19. Characterizing fractured rock aquifers using heated Distributed Fiber-Optic Temperature Sensing to determine borehole vertical flow

    NASA Astrophysics Data System (ADS)

    Read, T. O.; Bour, O.; Selker, J. S.; Le Borgne, T.; Bense, V.; Hochreutener, R.; Lavenant, N.

    2013-12-01

    In highly heterogeneous media, fracture network connectivity and hydraulic properties can be estimated using methods such as packer- or cross-borehole pumping-tests. Typically, measurements of hydraulic head or vertical flow in such tests are made either at a single location over time, or at a series of depths by installing a number of packers or raising or lowering a probe. We show how this often encountered monitoring problem, with current solutions sacrificing either one of temporal or spatial information, can be addressed using Distributed Temperature Sensing (DTS). Here, we electrically heat the conductive cladding materials of cables deployed in boreholes to determine the vertical flow profile. We present results from heated fiber optic cables deployed in three boreholes in a fractured rock aquifer at the much studied experimental site near Ploemeur, France, allowing detailed comparisons with alternative methods (e.g. Le Borgne et al., 2007). When submerged in water and electrically heated, the cable very rapidly reaches a steady state temperature (less than 60 seconds). The steady state temperature of the heated cable, measured using the DTS method, is then a function of the velocity of the fluid in the borehole. We find that such cables are sensitive to a wide range of fluid velocities, and thus suitable for measuring both ambient and pumped flow profiles at the Ploemeur site. The cables are then used to monitor the flow profiles during all possible configurations of: ambient flow, cross-borehole- (pumping one borehole, and observing in another), and dipole-tests (pumping one borehole, re-injection in another). Such flow data acquired using DTS may then be used for tomographic flow inversions, for instance using the approach developed by Klepikova et al., (submitted). Using the heated fiber optic method, we are able to observe the flow response during such tests in high spatial detail, and are also able to capture temporal flow dynamics occurring at the start of both the pumping and recovery phase of cross-borehole- and dipole- tests. In addition, the clear advantage of this is that by deploying a single fiber optic cable in multiple boreholes at a site, the flow profiles in all boreholes can be simultaneously measured, allowing many different pumping experiments to be conducted and monitored in a time efficient manner. Klepikova M. V., Le Borgne T., Bour O., and J-R.de Dreuzy, Inverse modelling of flow tomography experiments in fractured media, submitted to Water Resources Research. Le Borgne T., Bour O., Riley M. S., Gouze P., Pezard P.A., Belghoul A., Lods G., Le Provost R., Greswell R. B., Ellis P.A., Isakov E., and B. J. Last, Comparison of alternative methodologies for identifying and characterizing preferential flow paths in heterogeneous aquifers. Journal of Hydrology 2007, 345, 134-148.

  20. Critical Heat Fluxes of Subcooled Water Flow Boiling Against Outlet Subcooling in Short Vertical Tube

    SciTech Connect

    Koichi Hata; Toshiyuki Sato; Takeya Tanimoto; Masahiro Shiotsu [Department of Energy Science and Technology, Kyoto University, Uji 611-0011 (Japan); Nobuaki Noda [National Institute for Fusion Science, Toki 509-5292 (Japan)

    2002-07-01

    The critical heat fluxes (CHFs) of subcooled water flow boiling are systematically measured for the flow velocities (u=4.0 to 13.3 m/s), the outlet sub-cooling ({delta}T{sub sub,out}=3 to 129 K) and the outlet pressure (P{sub out}=800 kPa). The SUS304 test tubes of 3, 6, 9 and 12 mm in inner-diameter, d, and 33, 66, 99 and 133 mm in length, L, respectively for L/d=11 are used. The CHFs first become lower and then become higher with the increase in subcooling. The CHFs for four different inner-diameters with L/d=11 measured here become higher with the decrease in the diameter. CHF correlation for the latter increasing regime was given in non-dimensional form against average outlet sub-cooling based on the experimental data. The correlation can describe not only the CHFs obtained in this work at the outlet pressure of 800 kPa but also the authors' published CHFs (1284 points) for the wide range of P{sub out}=159 kPa to 1 MPa, d=6, 9 and 12 mm, L=49, 99 and 149 mm, {delta}T{sub sub,out}=-4 to 130 K and u=4.0 to 13.3 m/s within 15 % difference for 50 K{delta}T{sub sub,out}130 K and within +30 to -10 % for 30 K<{delta}T{sub sub,out}<50 K. (authors)

  1. Effect of Smoke and Moisture on Vertical Heating Rate of Southeast Atlantic

    NASA Astrophysics Data System (ADS)

    Adebiyi, A.; Zuidema, P.

    2012-12-01

    Seasonal biomass burning in the southwestern Africa Savannah produces a layer of dark smoke over the southeast Atlantic Ocean(SEA) with the peak typically occurring during August and September(AS). This absorbing layer, distinctively separated from the underlying stratocumulus deck, has been shown to preserve humidity and cloud cover in the boundary layer by enhancing the buoyancy of the free-tropospheric air above the inversion layer thereby inhibiting the entrainment of dry air through the cloud top. Using the observations from St. Helena Island(15.93S/5.67W) as a representation of SEA, we binned the Integrated Global Radiosonde Archive's(IGRA) soundings for AS by the fine-mode aerosol optical depth(AOD) for smoke using the Moderate Resolution Imaging Spectroradiometer(MODIS). It was noted that higher AOD is associated with relatively positive moisture and cooler temperature anomaly below the boundary layer. We also examine the relative impact of smoke and moisture at the same location by preforming a number experiments using the Santa Barbara DISORT Atmospheric Radiative Transfer model constrained by the averaged sounding and observations from MODIS and CALIPSO satellite products for AS. It was found that for every 0.1 increase in AOD, the average heating rate within the smoke layer increases by approximately 0.83K/day, if there is an underlying cloud due to the reflection of the cloud in shortwave and 0.56K/day, if there is no underlying cloud. The result will aid regional and climate model evaluations of black carbon indirect effect for southeast Atlantic.

  2. Experimental study on boiling heat transfer and two-phase frictional pressure drop characteristics of glycol-water solution in a vertical porous surface tube

    NASA Astrophysics Data System (ADS)

    Qiao, Shouxu; Wang, Haijun; Gu, Hongfang; Luo, Yushan; Zhang, Lei; Xiong, Wei

    2013-07-01

    Although much research has been conducted on investigating the flow boiling heat transfer of low saturation temperature refrigerants, there are few experimental data and theory about the flow boiling heat transfer of high saturation temperature organic mixture which exists widely in the petrochemical industry. To investigate the characteristics of flow boiling heat transfer of high saturation temperature organic mixture, experiments of glycol-water solution flow boiling in a vertical porous surface tube and a vertical smooth tube are conducted. Test tubes are uniformly heated by electrical current with a heated length of 2,000 mm. The mass flux in the experiment ranges from 500 to 1,500t?h-1 and the heat flux on test tubes ranges from 10 to 40 kW?m-2. The flow boiling heat transfer coefficients and two-phase frictional pressure drops of the two types of tubes are obtained and compared. The results indicate that: the flow boiling heat transfer coefficient in the porous surface tube is 3.8˜5.7 times of that in smooth tube and the pressure drop of the porous surface tube is 0.99˜1.007 times of that in the smooth tube. The physical mechanisms of the enhanced heat transfer characteristics of flow boiling in the porous surface tube are analyzed. By the regression analysis of the experimental data, correlations predicting the flow boiling heat transfer coefficient and pressure drop of glycol-water solution within the error range of ±20% are established. The experimental results can be used to guide the design of heat exchange equipment using the porous surface tube as heat transfer elements under these test conditions.

  3. Subcooled boiling heat transfer in a short vertical SUS304-tube at liquid Reynolds number range 5.19 × 10 4 to 7.43 × 10 5

    Microsoft Academic Search

    Koichi Hata; Suguru Masuzaki

    2009-01-01

    The subcooled boiling heat transfer and the steady-state critical heat fluxes (CHFs) in a short vertical SUS304-tube for the flow velocities (u=17.28–40.20m\\/s), the inlet liquid temperatures (Tin=293.30–362.49K), the inlet pressures (Pin=842.90–1467.93kPa) and the exponentially increasing heat input (Q=Q0exp(t\\/?), ?=8.5s) are systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304

  4. Computation of flow and heat transfer around a vertical discrete protruding heater using an operator-splitting algorithm

    SciTech Connect

    Mishra, D.; Muralidhar, K.; Ghoshdastidar, P.S. [Indian Inst. of Tech., Kanpur (India). Dept. of Mechanical Engineering

    1995-07-01

    Steady mixed convection around a heated block placed in a vertical channel is numerically studied. The block aspect ratio is taken as 1 / 3. The following range of parameters has been considered: 200{<=}Re{<=}1,000 and Gr = 0 and 10{sup 5}. The governing equations have been solved using an operator-splitting technique. this method splits the equations into advection, diffusion, and source terms and solves each component in an implicit time-marching scheme as accurately as possible. The results obtained using this method have been compared with those obtained using the second upwind procedure for the advection terms. The overall destruction of the local flow quantities around the heater is seen to be quite similar for the two methods. However, the average Nusselt number computed using the two methods has significant differences. The operator-splitting method shows that the mixed convection Nusselt number can fall below that of the forced convection value for a certain range of parameters. A comparison of CPU times also shows the operator-splitting method to be superior to upwinding.

  5. Heat Transfer Mechanism of a Vertical Wall Inside a Two-Phase Closed Thermosiphon Evaporator and Its Estimation

    NASA Astrophysics Data System (ADS)

    O-Uchi, Masaki; Hirose, Koichi; Saito, Futami

    The inside heat transfer coefficient, overall heat transfer coefficient, and heat flow rate at the heating section of the thermosiphon were determined for each heating method. In order to observe the heat transfer mechanism in the evaporator, a thermosiphon unit made of glass was assembled and conducted separately. The results of these experiments with these two units are summarized as follows. (1) Nucleate boiling due to the internal heat transfer mechanism improves the heat transfer characteristics of the thermosiphon unit. Under the specific heating conditions with dropwise condensation, there are two types of heat transfer mechanism occur in the evaporator accompanying nucleate boiling, i. e. latent heat transfer and sensible heat transfer. (2) In the case of latent heat transfer, the inside heat transfer coefficient has an upper limit which can be used as a criterion to determine the type of internal heat transfer mechanism.

  6. Convection heat transfer of CO{sub 2} at supercritical pressures in a vertical mini tube at relatively low reynolds numbers

    SciTech Connect

    Jiang, Pei-Xue; Zhang, Yu.; Zhao, Chen-Ru; Shi, Run-Fu [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China)

    2008-09-15

    Convection heat transfer of CO{sub 2} at supercritical pressures in a 0.27 mm diameter vertical mini tube was investigated experimentally and numerically for upward and downward flows at relatively low inlet Reynolds numbers (2900 and 1900). The effects of inlet temperature, pressure, mass flow rate, heat flux, flow direction, buoyancy and flow acceleration on the convection heat transfer were investigated. For inlet Reynolds numbers less than 2.9 x 10{sup 3}, the local wall temperature varies non-linearly for both flow directions at high heat fluxes (113 kW/m{sup 2}). For the mini tube used in the current study, the buoyancy effect is normally low even when the heating is relatively strong, while the flow acceleration due to heating can strongly influence the turbulence and reduce the heat transfer for high heat fluxes. For relatively low Reynolds numbers (Re{sub in} {<=} 2.9 x 10{sup 3}) and the low heat flux (30.0 kW/m{sup 2}) the predicted values using the LB low Reynolds number correspond well with the measured data. However, for the high heat flux (113 kW/m{sup 2}), the predicted values do not correspond well with the measured data due to the influence of the flow acceleration on the turbulence. (author)

  7. Comparison of DOE-2.1E with Energyplus and TRNSYS for Ground Coupled Residential Buildings in Hot anf Humid Climates Stage 1

    E-print Network

    Andolsun, S.; Culp, C.

    2011-01-01

    ]. This energy flow includes convection to air and longwave radiation to other surfaces or sky [12]. McDowell et al. [11] presents a concise summary of the TRNSYS ground coupling models as follows. According to their descriptions, the TRNSYS ground coupling..., Fourth National IBPSA-USA Conference, New York, USA (2010). [11] T.P. McDowell, J.W. Thornton, M.J. Duffy, Comparison of a Ground-Coupling Reference Standard Model to Simplified Approaches. Eleventh International IBPSA Conference, Glasgow, Scotland...

  8. Heat flux measurement from vertical temperature profile and thermal infrared imagery in low-flux fumarolic zones

    NASA Astrophysics Data System (ADS)

    Gaudin, Damien; Finizola, Anthony; Beauducel, François; Brothelande, Elodie; Allemand, Pascal; Delacourt, Christophe; Delcher, Eric; Peltier, Aline

    2014-05-01

    Hydrothermal systems are associated to most of the dormant volcanoes. Heat is transported by steam from the hot magma body in the connected porosity and the fissures of the rock to the surface. If the flux is low enough (<500 W/m²), the steam mainly condensates in the soil close to surface, and a significant proportion of the heat is transported to the surface by conduction, producing a gradient of temperature and a thermal anomaly detectable at the surface. Detecting and monitoring these fluxes is crucial for hazard management, since it reflects the state of the magma body in depth. In order to quantify this flux two methods are considered. First, a vertical profile of temperature is measured by a series of thermocouples, and the conducted flux is estimated thanks to the Fourier law. Secondly, a more recent method uses the thermal infrared imagery to monitor the surface temperature anomaly (STA) between the studied zone and an equivalent zone not affected by the geothermal flux. The heat flux from the soil to the atmosphere is computed as the sum of (1) the radiative flux, (2) the sensible flux and (3) the residual steam flux. These two methods are complementary and have an equivalent uncertainty of approximately 20%, which would allow to track the major changes in the hydrothermal system. However, the surface and sub-surface temperatures are strongly influenced by the climate. For instance, it has been widely demonstrated that the surface temperature dramatically decreases after a rainfall. In order to estimate the reliability of the measurements, a numerical model simulating the evolution of the subsurface temperature in low flux fumarolic zone has been built. In depth, the heat can be transported either by conduction, or by the rising steam, or by condensed water. In surface, both the radiative flux and the sensible flux (convection of the atmosphere) are taken into account. This model allows to estimate the changes of temperature due to a variation of solar illumination, wind, or rainfalls. It has been successfully tested during 5 months with a permanent station built on the Ty fault on La Soufrière volcano (Guadeloupe, Lesser Antilles). Results show that the diurnal cycle has a significant influence on the temperature up to ca. 30 cm depth, hindering the use of the thermal gradient in this zone, while the STA has a negligible variation. Rain has a more dramatic influence: the surface temperature and the STA are significantly affected, even for small rains. The model shows that the drop of temperature and the affected thickness are mainly controlled by the amount of rain, while the relaxation time is primarily a function of the heat flux. These results have strong implications in the interpretation and the reliability of the temperature surveys, and could be used to correct them from the climate fluctuations.

  9. A computational solution of hydromagnetic-free convective flow past a vertical plate in a rotating heat-generating fluid with Hall and ion-slip currents

    Microsoft Academic Search

    H. Naroua

    2007-01-01

    Taking Hall and ion-slip current into account, the unsteady magnetohydrodynamic heat-generating free convective flow of a partially ionized gas past an infinite vertical plate in a rotating frame of reference is investigated theoretically. A computer program using finite elements is employed to solve the coupled non-linear differential equations for velocity and temperature fields. The effects of Hall and ion-slip currents

  10. Influence of chemical reaction on heat and mass transfer by natural convection from vertical surfaces in porous media considering Soret and Dufour effects

    Microsoft Academic Search

    Adrian Postelnicu

    2007-01-01

    The heat and mass transfer characteristics of natural convection about a vertical surface embedded in a saturated porous medium\\u000a subjected to a chemical reaction is numerically analyzed, by taking into account the diffusion-thermo (Dufour) and thermal-diffusion\\u000a (Soret) effects. The transformed governing equations are solved by a very efficient numerical method, namely, a modified version\\u000a of the Keller-box method for ordinary

  11. Numerical Investigation of Coupled Turbulent Flow, Heat Transfer, and Macroscopic Solidification in a Vertical Twin-Roll Thin-Strip Caster

    Microsoft Academic Search

    S. H. Seyedein; M. Hasan

    1997-01-01

    A vertical twin-roll continuous thin-strip casting process for stainless steel has been mathematically modeled. The model takes into account the coupled turbulent flow, heat transfer, and macroscopic solidification aspects of the process. A low-Reynolds-number K-? turbulence model was used to account for the turbulent effects. The transport equations for the wedge-shaped caster's cavity were solved using a boundary-fitted nanorthogonal coordinate

  12. Development and Application of a Ground-Coupled Heat Pump Simulation Model for Residential Code-Compliance Simulation in Texas

    E-print Network

    Do, Sung Lok

    2014-04-18

    for Horizontal GHX Models ...... 198 Figure 5-13: Hourly Solar Radiation Absorbed by the Entire Pond’s Surface .............. 199 Figure 5-14: Hourly Thermal Radiation from Water to Sky at the Entire Pond’s Surface... ............................................ 119 Table 4-6: Summary of Sensors Installed at the Solar Test Bench ................................ 125 Table 4-7: List of the STB Weather Data Used for the Pond Temperature Calculation...

  13. Nonlinear Radiation Heat Transfer Effects in the Natural Convective Boundary Layer Flow of Nanofluid Past a Vertical Plate: A Numerical Study

    PubMed Central

    Mustafa, Meraj; Mushtaq, Ammar; Hayat, Tasawar; Ahmad, Bashir

    2014-01-01

    The problem of natural convective boundary layer flow of nanofluid past a vertical plate is discussed in the presence of nonlinear radiative heat flux. The effects of magnetic field, Joule heating and viscous dissipation are also taken into consideration. The governing partial differential equations are transformed into a system of coupled nonlinear ordinary differential equations via similarity transformations and then solved numerically using the Runge–Kutta fourth-fifth order method with shooting technique. The results reveal an existence of point of inflection for the temperature distribution for sufficiently large wall to ambient temperature ratio. Temperature and thermal boundary layer thickness increase as Brownian motion and thermophoretic effects intensify. Moreover temperature increases and heat transfer from the plate decreases with an increase in the radiation parameter. PMID:25251242

  14. The effect of transpiration on coupled heat and mass transfer in mixed convection over a vertical plate embedded in a saturated porous medium

    SciTech Connect

    Yih, K.A. [Air Forces Inst. of Aeronautical Technology, Kaoshiuang (Taiwan, Province of China). Dept. of General Course] [Air Forces Inst. of Aeronautical Technology, Kaoshiuang (Taiwan, Province of China). Dept. of General Course

    1997-03-01

    Effect of transpiration velocity on the heat and mass transfer characteristics of mixed convection about a permeable vertical plate embedded in a saturated porous medium under the coupled effects of thermal and mass diffusion is numerically analyzed. The plate is maintained at a uniform temperature and species concentration with constant transpiration velocity. The transformed governing equations are solved by Keller box method. Numerical results for the local Nusselt number and local Sherwood number are presented. In general, it has been found for thermally assisted flow that the local surface heat and mass transfer rates increase owing to suction of fluid. This trend reversed for blowing of fluid. It is apparent that the Lewis number has a pronounced effect on the local Sherwood number than it does on the local Nusselt number. Increasing the Lewis number decreases (increases) the local heat (mass) transfer rate.

  15. Nonlinear radiation heat transfer effects in the natural convective boundary layer flow of nanofluid past a vertical plate: a numerical study.

    PubMed

    Mustafa, Meraj; Mushtaq, Ammar; Hayat, Tasawar; Ahmad, Bashir

    2014-01-01

    The problem of natural convective boundary layer flow of nanofluid past a vertical plate is discussed in the presence of nonlinear radiative heat flux. The effects of magnetic field, Joule heating and viscous dissipation are also taken into consideration. The governing partial differential equations are transformed into a system of coupled nonlinear ordinary differential equations via similarity transformations and then solved numerically using the Runge-Kutta fourth-fifth order method with shooting technique. The results reveal an existence of point of inflection for the temperature distribution for sufficiently large wall to ambient temperature ratio. Temperature and thermal boundary layer thickness increase as Brownian motion and thermophoretic effects intensify. Moreover temperature increases and heat transfer from the plate decreases with an increase in the radiation parameter. PMID:25251242

  16. Excellent scalability including self-heating phenomena of vertical-channel field-effect-diode type capacitor-less one transistor dynamic random access memory cell

    NASA Astrophysics Data System (ADS)

    Imamoto, Takuya; Endoh, Tetsuo

    2014-01-01

    The scalability study and the impact of the self-heating effect (SHE) on memory operation of the bulk vertical-channel field effect diode (FED) type capacitorless one transistor (1T) dynamic random access memory (DRAM) cell are investigated via device simulator for the first time. The vertical-channel FED type 1T-DRAM cell shows the excellent hold characteristics (100 ms at 358 K of ambient temperature) with large enough read current margin (1 µA/cell) even when silicon pillar diameter (D) is scaled down from 20 to 12 nm. It is also shown that by employing the vertical-channel FED type, maximum lattice temperature in the memory cell due to SHE (T_{\\text{L}}^{\\text{Max}}) can be suppressed to a negligible small value and only reach 300.6 from 300 K ambient temperature due to the low lateral electric field, while the vertical-channel bipolar junction transistor (BJT) type 1T-DRAM shows significant SHE (T_{\\text{L}}^{\\text{Max}} = 330.6 K). Moreover, this excellent thermal characteristic can be maintained even when D is scaled down from 20 to 12 nm.

  17. Downflow heat transfer in a heated ribbed vertical annulus with a cosine power profile (results from test series ECS2c)

    Microsoft Academic Search

    J. L. Anderson; K. G. Condie; T. K. Larson

    1991-01-01

    Experiments designed to investigate downflow heat transfer in a heated, ribbed annulus test section simulating one of the annular coolant channels of a Savannah River Plant production reactor Mark 22 fuel assembly have been conducted at the Idaho National Engineering Laboratory. The inner surface of the annulus was constructed of aluminum and was electrically heated to provide an axial cosine

  18. Vertical Profiles of Latent Heat Release over the Global Tropics using TRMM Rainfall Products from December 1997 to November 2002

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Lang, S.; Simpson, J.; Meneghini, R.; Halverson, J.; Johnson, R.; Adler, R.

    2003-01-01

    NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2000. Rainfall, latent heating and radar reflectivity structures between El Nino (DJF 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs west Pacific, Africa vs. S. America ) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in stratiform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. The Goddard Cumulus Ensemble Model is being used to simulate various mesoscale convective systems that developed in different geographic locations. Specifically, the model estimated rainfall, radar reflectivity and latent heating profiles will be compared to observational data collected from TRMM field campaigns over the South China Sea in 1998 (SCSMEX), Brazil in 1999 (TRMM-LBA), and the central Pacific in 1999 (KWAJEX). Sounding diagnosed heating budgets and radar reflectivity from these experiments can provide the means to validate (heating product) as well as improve the GCE model. Review of other latent heating algorithms will be discussed in the workshop.

  19. Vertical Profiles of Latent Heat Release Over the Global Tropics using TRMM Rainfall Products from December 1997 to November 2001

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Lang, S.; Simpson, J.; Meneghini, R.; Halverson, J.; Johnson, R.; Adler, R.; Starr, David (Technical Monitor)

    2002-01-01

    NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2000. Rainfall, latent heating and radar reflectivity structures between El Nino (DJF 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs west Pacific, Africa vs S. America) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in stratiform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. Additional information is included in the original extended abstract.

  20. Vertical Profiles of Latent Heat Release over the Global Tropics Using TRMM Rainfall Products from December 1997 to November 2002

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.

    2003-01-01

    NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2000. Rainfall, latent heating and radar reflectivity structures between El Nino (DJF 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs west Pacific, Africa vs S. America) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in straitform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. The Goddard Cumulus Ensemble Model is being used to simulate various mesoscale convective systems that developed in different geographic locations. Specifically, the model estimated rainfall, radar reflectivity and latent heating profiles will be compared to observational data collected from TRMM field campaigns over the South China Sea in 1998 (SCSMXX), Brazil in 1999 (TRMM- LBA), and the central Pacific in 1999 (KWAJEX). Sounding diagnosed heating budgets and radar reflectivity from these experiments can provide the means to validate (heating product) as well as improve the GCE model.

  1. Vertical Profiles of Latent Heat Release over the Global Tropics using TRMM rainfall products from December 1997 to November 2001

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Lang, S.; Simpson, J.; Meneghini, R.; Halverson, J.; Johnson, R.; Adler, R.

    2002-01-01

    NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2001. Rainfall, latent heating and radar reflectivity structures between El Nino (DE 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs. west Pacific, Africa vs. S. America) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in strtaiform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. The Goddard Cumulus Ensemble Model is being used to simulate various mesoscale convective systems that developed in different geographic locations. Specifically, the model estimated rainfall, radar reflectivity and latent heating profiles will be compared to observational data collected from TRMM field campaigns over the South China Sea in 1998 (SCSMEX), Brazil in 1999 (TRMM-LBA), and the central Pacific in 1999 (KWAJEX). Sounding diagnosed heating budgets and radar reflectivity from these experiments can provide the means to validate (heating product) as well as improve the GCE model.

  2. Vertical Profiles of Latent Heat Release Over the Global Tropics using TRMM Rainfall Products from December 1997 to November 2001

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Lang, S.; Simpson, J.; Meneghini, R.; Halverson, J.; Johnson, R.; Adler, R.; Starr, David (Technical Monitor)

    2002-01-01

    NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2000. Rainfall, latent heating and radar reflectivity structures between El Nino (DJF 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs west Pacific, Africa vs S. America) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in stratiform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. The Goddard Cumulus Ensemble Model is being used to simulate various mesoscale convective systems that developed in different geographic locations. Specifically, the model estimated rainfall, radar reflectivity and latent heating profiles will be compared to observational data collected from TRMM field campaigns over the South China Sea in 1998 (SCSMEX), Brazil in 1999 (TRMM-LBA), and the central Pacific in 1999 (KWAJEX). Sounding diagnosed heating budgets and radar reflectivity from these experiments can provide the means to validate (heating product) as well as improve the GCE model.

  3. Heat transfer modeling in the vertical tubes of the passive containment cooling system of the simplified boiling water reactor

    Microsoft Academic Search

    Luis E. Herranz; José L. Muñoz-Cobo; G. Verdú

    1997-01-01

    The long term containment cooling of GE's passive BWR design is based on a new safety system called PCCS (passive containment cooling system). Performance of this system relies on the pressure difference between the drywell and wetwell in case of an accident and on the condensation of steam moving downward inside vertical tubes fully submerged in a water pool initially

  4. Free convection about a vertical flat plate embedded in a porous medium with application to heat transfer from a dike

    Microsoft Academic Search

    Ping Cheng; W. J. Minkowycz

    1977-01-01

    An analysis is made for steady free convection about a vertical flat plate embedded in a saturated porous medium at high Rayleigh numbers. Within the framework of boundary layer approximations, similarity solutions are obtained for a class of problems where wall temperature varies as xlambda, i.e., a power function of distance from the origin where wall temperature begins to deviate

  5. Various computational conditions of oscillatory natural convection of zero Prandtl number fluid in an open boat heated and cooled from opposing vertical walls

    SciTech Connect

    Okada, Kazuto (Kyushu Univ., Kasuga (Japan). Interdisciplinary Graduate School of Engineering Science); Ozoe, Hiroyuki (Kyushu Univ., Kasuga (Japan). Inst. of Advanced Material Study)

    1993-03-01

    The finite-difference computational scheme is developed for two-dimensional oscillatory natural convection of zero Prandtl number fluid in an open boat heated and cooled from opposing vertical walls. Various computational conditions are tested, such as the initial condition, time step length, finite-difference width, and finite-difference scheme. Instantaneous contour maps and velocity vectors in oscillatory states are presented in a series of maps to represent the fluctuating characteristics of two-dimensional roll cells. The physical conditions are for a boat with aspect ratio A = 3[minus]5 at Pr = 0 and Gr = 14,000-40,000.

  6. Experimental studies on the enhanced flow boiling heat transfer and pressure drop of organic fluid with high saturation temperature in vertical porous coated tube

    NASA Astrophysics Data System (ADS)

    Yang, Dong; Shen, Zhi; Chen, Tingkuan; Zhou, Chenn Q.

    2013-07-01

    The characteristics of flow boiling heat transfer and pressure drop of organic fluid with high saturation temperature in a vertical porous coated tube are experimentally studied in this paper. The experiments are performed at evaporation pressure of 0.16-0.31MPa, mass flux of 390-790kg/m2s, and vapor quality of 0.06-0.58. The variations of heat transfer coefficient and pressure drop with vapor quality are measured and compared to the results of smooth tube. Boiling curves are generated at mass flux of 482 and 675kg/m2s. The experimental results indicate that the heat transfer coefficients of the porous tube are 1.8-3.5 times those of smooth tube, and that the frictional pressure drops of the porous tube are 1.1-2.9 times those of smooth tube. The correlations for heat transfer coefficient and frictional pressure drop are derived, in which the effect of fluid molecular weight is included. The experiments show that significant heat transfer enhancement is accompanied by a little pressure drop penalty, the application of the porous coated tube is promising in the process industries.

  7. Ground-coupled acoustic airwaves from Mount St. Helens provide constraints on the May 18, 1980 eruption

    NASA Astrophysics Data System (ADS)

    Johnson, Jeffrey B.; Malone, Stephen D.

    2007-06-01

    The May 18, 1980 Mount St. Helens eruption perturbed the atmosphere and generated atmosphere-to-ground coupled airwaves, which were recorded on at least 35 seismometers operated by the Pacific Northwest Seismograph Network (PNSN). From 102 distinct travel time picks we identify coherent airwaves crossing Washington State primarily to the north and east of the volcano. The travel time curves provide evidence for both stratospheric refractions (at 200 to 300 km from the volcano) as well as probable thermospheric refractions (at 100 to 350 km). The very few first-hand reports of audible volcano sounds within about 80 km of the volcano coincide with a general absence of ground-coupled acoustic arrivals registered within about 100 km and are attributed to upward refraction of sound waves. From the coherent refracted airwave arrivals, we identify at least four distinct sources which we infer to originate 10 s, 114 s, ˜ 180 s and 319 s after the onset of an 8:32:11 PDT landslide. The first of these sources is attributed to resultant depressurization and explosion of the cryptodome. Most of the subsequent arrivals also appear to be coincident with a source located at or near the presumed volcanic conduit, but at least one of the later arrivals suggests an epicenter displaced about 9 km to the northwest of the vent. This dislocation is compatible with the direction of the sector collapse and lateral blast. We speculate that this concussion corresponds to a northern explosion event associated with hot cryptodome entering the Toutle River Valley.

  8. Vertical profiles of temperature and contaminant concentration in rooms ventilated by displacement with heat loss through room envelopes.

    PubMed

    Xu, M; Yamanaka, T; Kotani, H

    2001-06-01

    The purpose of this study is to examine the effect of heat loss through walls upon the gradients of temperature and contaminant concentration in room with displacement ventilation. It is known that conduction heat loss is governed by outside temperature, heat load inside the room, supply air temperature and overall heat transfer coefficient of walls. Experiments were conducted to measure the temperature gradient and the ventilation efficiency in the room ventilated by displacement ventilation with various combinations of heat load and temperature difference between supply air and outside air. In order to simulate the change of seasons, the supply air temperature was changed instead of the outside air temperature. The effect of supply air temperature and heat generation inside the room on the temperature gradient and the concentration of tracer gas were investigated through the experiments. As a result, it turned out that the higher the heat generation rate and the lower the supply temperature, the stronger the temperature stratification and the lower the concentration in the lower zone. Additionally, ventilation heat loss turned out to be a good index for assessing the concentration in the lower zone. Temperature differences of around 3 degrees C between supply air temperature and exhaust temperature are at least needed for displacement ventilation under the conditions of the experiment presented in this paper. PMID:11394009

  9. Current status of ground source heat pumps and underground thermal energy storage in Europe

    Microsoft Academic Search

    Burkhard Sanner; Constantine Karytsas; Dimitrios Mendrinos; Ladislaus Rybach

    2003-01-01

    Geothermal Heat Pumps, or Ground Coupled Heat Pumps (GCHP), are systems combining a heat pump with a ground heat exchanger (closed loop systems), or fed by ground water from a well (open loop systems). They use the earth as a heat source when operating in heating mode, with a fluid (usually water or a water–antifreeze mixture) as the medium that

  10. Combined Effect of Buoyancy Force and Navier Slip on MHD Flow of a Nanofluid over a Convectively Heated Vertical Porous Plate

    PubMed Central

    2013-01-01

    We examine the effect of magnetic field on boundary layer flow of an incompressible electrically conducting water-based nanofluids past a convectively heated vertical porous plate with Navier slip boundary condition. A suitable similarity transformation is employed to reduce the governing partial differential equations into nonlinear ordinary differential equations, which are solved numerically by employing fourth-order Runge-Kutta with a shooting technique. Three different water-based nanofluids containing copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are taken into consideration. Graphical results are presented and discussed quantitatively with respect to the influence of pertinent parameters, such as solid volume fraction of nanoparticles (?), magnetic field parameter (Ha), buoyancy effect (Gr), Eckert number (Ec), suction/injection parameter (fw), Biot number (Bi), and slip parameter (?), on the dimensionless velocity, temperature, skin friction coefficient, and heat transfer rate. PMID:24222749

  11. On the importance of cavity-length and heat dissipation in GaN-based vertical-cavity surface-emitting lasers

    PubMed Central

    Liu, W. J.; Hu, X. L.; Ying, L. Y.; Chen, S. Q.; Zhang, J. Y.; Akiyama, H.; Cai, Z. P.; Zhang, B. P.

    2015-01-01

    Cavity-length dependence of the property of optically pumped GaN-based vertical-cavity surface-emitting lasers (VCSELs) with two dielectric distributed Bragg reflectors was investigated. The cavity lengths were well controlled by employing etching with inductively coupled plasma and chemical mechanical polishing. It was found that the lasing characteristics including threshold, slope efficiency and spontaneous emission coupling factor were substantially improved with reducing the cavity length. In comparison with the device pumped by a 400?nm pulsed laser, the lasing spectrum was featured by a red shift and simultaneous broadening with increasing the pumping energy of a 355?nm pulsed laser. Moreover, the lasing threshold was much higher when pumped by a 355?nm pulsed laser. These were explained by taking into account of the significant heating effect under 355?nm pumping. Our results demonstrate that a short cavity length and good heat-dissipation are essential to GaN-based VCSELs. PMID:25873327

  12. Combined effect of buoyancy force and Navier slip on MHD flow of a nanofluid over a convectively heated vertical porous plate.

    PubMed

    Mutuku-Njane, Winifred Nduku; Makinde, Oluwole Daniel

    2013-01-01

    We examine the effect of magnetic field on boundary layer flow of an incompressible electrically conducting water-based nanofluids past a convectively heated vertical porous plate with Navier slip boundary condition. A suitable similarity transformation is employed to reduce the governing partial differential equations into nonlinear ordinary differential equations, which are solved numerically by employing fourth-order Runge-Kutta with a shooting technique. Three different water-based nanofluids containing copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are taken into consideration. Graphical results are presented and discussed quantitatively with respect to the influence of pertinent parameters, such as solid volume fraction of nanoparticles (?), magnetic field parameter (Ha), buoyancy effect (Gr), Eckert number (Ec), suction/injection parameter (f w ), Biot number (Bi), and slip parameter ( ? ), on the dimensionless velocity, temperature, skin friction coefficient, and heat transfer rate. PMID:24222749

  13. On the importance of cavity-length and heat dissipation in GaN-based vertical-cavity surface-emitting lasers.

    PubMed

    Liu, W J; Hu, X L; Ying, L Y; Chen, S Q; Zhang, J Y; Akiyama, H; Cai, Z P; Zhang, B P

    2015-01-01

    Cavity-length dependence of the property of optically pumped GaN-based vertical-cavity surface-emitting lasers (VCSELs) with two dielectric distributed Bragg reflectors was investigated. The cavity lengths were well controlled by employing etching with inductively coupled plasma and chemical mechanical polishing. It was found that the lasing characteristics including threshold, slope efficiency and spontaneous emission coupling factor were substantially improved with reducing the cavity length. In comparison with the device pumped by a 400?nm pulsed laser, the lasing spectrum was featured by a red shift and simultaneous broadening with increasing the pumping energy of a 355?nm pulsed laser. Moreover, the lasing threshold was much higher when pumped by a 355?nm pulsed laser. These were explained by taking into account of the significant heating effect under 355?nm pumping. Our results demonstrate that a short cavity length and good heat-dissipation are essential to GaN-based VCSELs. PMID:25873327

  14. Mass transfer effects on the unsteady mhd radiative- convective flow of a micropolar fluid past a vertical porous plate with variable heat and mass fluxes

    NASA Astrophysics Data System (ADS)

    Reddy, M. Gnaneswara

    2013-03-01

    The problem of unsteady two-dimensional laminar flow of a viscous incompressible micropolar fluid past a vertical porous plate in the presence of a transverse magnetic field and thermal radiation with variable heat and mass fluxes is considered. The free stream velocity is subjected to exponentially increasing or decreasing small perturbations. A uniform magnetic field acts perpendicularly to a porous surface where a micropolar fluid is absorbed with a suction velocity varying with time. The Rosseland approximation is used to describe radiative heat transfer in the limit of optically thick fluids. The effects of the flow parameters and thermophysical properties on the velocity and temperature fields across the boundary layer are investigated. The effects of various parameters on the velocity, microrotation velocity, temperature, and concentration profiles are given graphically, and the values of the skin friction and couple stress coefficients are presented.

  15. Improving the thermal performance of coaxial borehole heat exchangers

    Microsoft Academic Search

    E. Zanchini; S. Lazzari; A. Priarone

    2010-01-01

    Borehole heat exchangers are the fundamental component of ground coupled heat pumps, which are now widely employed for energy saving in building heating and cooling. The improvement of the thermal efficiency of Coaxial Borehole Heat Exchangers (CBHEs) is pursued in this paper by investigating the effects of thermal short-circuiting and of flow rate, as well as of the constituent materials

  16. Heat and mass transfer of an unsteady MHD natural convection flow of a rotating fluid past a vertical porous flat plate in the presence of radiative heat transfer

    Microsoft Academic Search

    I. U. Mbeledogu; A. Ogulu

    2007-01-01

    Analytical closed-form solution of the unsteady hydro-magnetic natural convection heat and mass transfer flow of a rotating, incompressible, viscous Boussinesq fluid is presented in this study in the presence of radiative heat transfer and a first order chemical reaction between the fluid and the diffusing species. The Rosseland approximation for an optically thick fluid is invoked to describe the radiative

  17. Effect of pitch-to-diameter ratio on the natural convection heat transfer of two vertically aligned horizontal cylinders

    Microsoft Academic Search

    Myeong-Seon Chae; Bum-Jin Chung

    2011-01-01

    Natural convection heat transfer experiments were conducted for two parallel horizontal cylinders using various pitch-to-diameter ratios (P\\/D) from 1.02 to 9 for the Prandtl numbers between 2014 and 8334 and Rayleigh numbers between 7.3×107 and 4.5×1010. Based upon analogy concept, mass transfer rate were measured instead of heat transfer rates by measuring the limiting current of the cathodic deposition of

  18. Forced and mixed convection heat transfer to supercritical CO{sub 2} vertically flowing in a uniformly-heated circular tube

    SciTech Connect

    Bae, Yoon-Yeong; Kim, Hwan-Yeol [Korea Atomic Energy Research Institute, 1045 Daedeokdaero, Yuseong, Daejeon 305-353 (Korea); Kang, Deog-Ji [Korea Hydro and Nuclear Power Co. Ltd., 216 Kori, Jangan-eup, Gijang-gun, Busan 619-711 (Korea)

    2010-11-15

    An experiment of heat transfer to CO{sub 2}, which flows upward and downward in a circular tube with an inner diameter of 6.32 mm, was carried out with mass flux of 285-1200 kg/m{sup 2} s and heat flux of 30-170 kW/m{sup 2} at pressures of 7.75 and 8.12 MPa, respectively. The corresponding Reynolds number at the tube test section inlet ranges from 1.8 x 10{sup 4} to 3.8 x 10{sup 5}. The tube inner diameter corresponds to the equivalent hydraulic diameter of the fuel assembly sub-channel, which is being studied at KAERI. Among the tested correlations, the Bishop correlation predicted the experimental data most accurately, but only 66.9% of normal heat transfer data were predicted within {+-}30% error range. The Watts and Chou correlation, which is claimed to be valid for both the normal and deteriorated heat transfer regime, showed unsatisfactory performance. A significant decrease in Nusselt number was observed in the range of 10{sup -6}heat transfer deterioration regime. The heat transfer deteriorated when the value of the buoyancy parameter Gr{sub b}/Re{sub b}{sup 2.7} exceeded 2.0 x 10{sup -5} close to the Jackson and Hall's criterion. As soon as the heat transfer deteriorated, it entered a new regime and did not return to a normal heat transfer regime, although the value of buoyancy parameter Gr{sub b}/Re{sub b}{sup 2.7} reduced below the deterioration criterion 2.0 x 10{sup -5}. It may justify the requirement of developing separate correlations for the normal and deterioration regimes, as proposed in this paper. (author)

  19. Critical heat-flux experiments under low-flow conditions in a vertical annulus. [PWR; BWR; LMFBR

    SciTech Connect

    Mishima, K.; Ishii, M.

    1982-03-01

    An experimental study was performed on critical heat flux (CHF) at low flow conditions for low pressure steam-water upward flow in an annulus. The test section was transparent, therefore, visual observations of dryout as well as various instrumentations were made. The data indicated that a premature CHF occurred due to flow regime transition from churn-turbulent to annular flow. It is shown that the critical heat flux observed in the experiment is essentially similar to a flooding-limited burnout and the critical heat flux can be well reproduced by a nondimensional correlation derived from the previously obtained criterion for flow regime transition. The observed CHF values are much smaller than the standard high quality CHF criteria at low flow, corresponding to the annular flow film dryout. This result is very significant, because the coolability of a heater surface at low flow rates can be drastically reduced by the occurrence of this mode of CHF.

  20. Hydrodynamics and heat transfer of a water flow with supercritical parameters in a vertical assembly of fuel elements

    NASA Astrophysics Data System (ADS)

    Avramenko, A. A.; Kondrat?eva, E. A.; Kovetskaya, M. M.; Tyrinov, A. I.

    2013-07-01

    Water flow in a hexahedral seven-rod fuel assembly at supercritical pressure has been modeled. Consideration has been given to nonstationary regimes of this flow in the case of a stepwise increase in the heat flux on the fuelelement surface and of a drop in the flow rate of the coolant at entry. Numerical investigation of the processes of hydrodynamics and heat transfer was based on the RNG k-? turbulence model; equations of state of the IF-97 formulation were used. Hydrodynamic and thermal characteristics of the coolant flow in the indicated assembly have been obtained as a result of the modeling.

  1. Experimental observations of the thermal flow around a square obstruction on a vertical wall in a differentially heated cavity

    Microsoft Academic Search

    Feng Xu; John C. Patterson; Chengwang Lei

    2006-01-01

    The transient thermal boundary layer flow around a square obstruction placed at the middle of the hot wall in a differentially heated cavity is visualized using a shadowgraph technique. The results show that the thermal boundary layer flow, which is blocked by the obstruction, firstly forms an intrusion head under the obstruction (the lower intrusion head). Subsequently, the lower intrusion

  2. Transient radiative hydromagnetic free convection ?ow past an impulsively started vertical plate with uniform heat and mass ?ux

    Microsoft Academic Search

    V. Ramachandra Prasad; N. Bhaskar Reddy; R. Muthucumaraswamy

    The interaction of free convection with thermal radiation of viscous incompressible MHD unsteady ?ow past an impulsively started ver- tical plate with uniform heat and mass ?ux is analyzed. This type of problem flnds application in many technological and engineer- ing flelds such as rocket propulsion systems, space craft re-entry aerothermodynamics, cosmical ?ight aerodynamics, plasma physics, glass production and furnace

  3. Experimental investigation on heat transfer coefficient during upward flow condensation of R410A in vertical smooth tubes

    NASA Astrophysics Data System (ADS)

    Yang, Yunxiao; Jia, Li

    2015-04-01

    This paper presents an experimental investigation on condensation of R410A upward flow in vertical tubes with the same inner diameter of 8.02mm and different lengths of 300 mm, 400 mm, 500 mm and 600mm. Condensation experiments were performed at mass fluxes of 103-490 kg m-2s-1. The saturation temperatures of experimental condition were 31°C, 38°C and 48°C, alternatively. The average vapor quality in the test section is between 0.91 and 0.98. The effects of tube length, mass flux and condensation temperature on condensation were discussed. Four correlations used for the upward flow condensation were compared with the experimental data obtained from various experimental conditions. A modified correlation was proposed within a ±15% deviation range.

  4. Heat Transfer Analysis of MHD Thin Film Flow of an Unsteady Second Grade Fluid Past a Vertical Oscillating Belt

    PubMed Central

    Gul, Taza; Islam, Saeed; Shah, Rehan Ali; Khan, Ilyas; Khalid, Asma; Shafie, Sharidan

    2014-01-01

    This article aims to study the thin film layer flowing on a vertical oscillating belt. The flow is considered to satisfy the constitutive equation of unsteady second grade fluid. The governing equation for velocity and temperature fields with subjected initial and boundary conditions are solved by two analytical techniques namely Adomian Decomposition Method (ADM) and Optimal Homotopy Asymptotic Method (OHAM). The comparisons of ADM and OHAM solutions for velocity and temperature fields are shown numerically and graphically for both the lift and drainage problems. It is found that both these solutions are identical. In order to understand the physical behavior of the embedded parameters such as Stock number, frequency parameter, magnetic parameter, Brinkman number and Prandtl number, the analytical results are plotted graphically and discussed. PMID:25383797

  5. New CHF correlation scheme proposed for vertical rectangular channels heated from both sides in nuclear research reactors

    Microsoft Academic Search

    Y. Sudo; M. Kaminaga

    1993-01-01

    In this study, an investigation was carried out to identify the important parameters affecting critical heat flux (CHF) in rectangular channels, focusing on the effects of flow direction, channel inlet subcooling from 1 to 213 K, the channel outlet condition extending from subcooling of 0-74 K to quality of 0-1.0, pressure of 0.1 to 4 MPa, water mass flux of

  6. Vertical two chamber reaction furnace

    Microsoft Academic Search

    Blaugher

    1999-01-01

    A vertical two chamber reaction furnace is disclosed. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the

  7. Vertical two chamber reaction furnace

    Microsoft Academic Search

    Blaugher; Richard D

    1999-01-01

    A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber.

  8. Effect of thermal-hydrogeological and borehole heat exchanger properties on performance and impact of vertical closed-loop geothermal heat pump systems

    NASA Astrophysics Data System (ADS)

    Dehkordi, S. Emad; Schincariol, Robert A.

    2013-10-01

    Ground-source geothermal systems are drawing increasing attention and popularity due to their efficiency, sustainability and being implementable worldwide. Consequently, design software and regulatory guidelines have been developed. Interaction with the subsurface significantly affects the thermal performance, sustainability, and impacts of such systems. Reviewing the related guidelines and the design software, room for improvement is evident, especially in regards to interaction with groundwater movement. In order to accurately evaluate the thermal effect of system and hydrogeological properties on a borehole heat exchanger, a fully discretized finite-element model is used. Sensitivity of the loop outlet temperatures and heat exchange rates to hydrogeological, system and meteorological factors (i.e. groundwater flux, thermal conductivity and volumetric heat capacity of solids, porosity, thermal dispersivity, grout thermal conductivity, background and inlet temperatures) are analyzed over 6-month and 25-year operation periods. Furthermore, thermal recovery during 25 years after system decommissioning has been modeled. The thermal plume development, transport and dissipation are also assessed. This study shows the importance of subsurface thermal conductivity, groundwater flow (flux > 10-7 m/s), and background and inlet temperature on system performance and impact. It also shows the importance of groundwater flow (flux > 10-8 m/s) on thermal recovery of the ground over other factors.

  9. Infrasound and Seismic Observation of the Hayabusa Reentry: Burst Signals and Air-to-Ground Coupling Process

    NASA Astrophysics Data System (ADS)

    Ishihara, Y.; Hiramatsu, Y.; Yamamoto, M.; Furumoto, M.; Fujita, K.

    2012-12-01

    The Hayabusa, the world's first sample-return minor body explorer, reentered the Earth's atmosphere on June 13, 2010. This was the third direct reentry event from the interplanetary transfer orbit to the Earth at a velocity of over 11.2 km/s, and was the world's first case of a direct reentry of the spacecraft itself from the interplanetary transfer orbit. This was the very good and rare opportunity to study bolide class meteor phenomena by various aspects. Multi-site ground observations of the Hayabusa reentry were carried out in the Woomera Prohibited Area, Australia (Fujita et al., 2011). The observations were configured with optical imaging, spectroscopies, and shockwave detection with infrasound and seismic sensors. At three main stations (GOS2, GOS2A, and GOS2B), we installed small aperture infrasound/seismic arrays, as well as three single component seismic sub stations (GOS2B-sub1, to GOS2B-sub3) (Yamamoto et al., 2011; Ishihara et al., 2012). The infrasound and seismic sensors clearly recorded sonic-boom-type shockwaves from the Hayabusa sample return capsule (Ishihara et al., 2012). In addition, following capsule signal, lots of signals that probably correspond shockwave from disrupted fragments of spacecraft and energetic bursts of the spacecraft were also recorded (Yamamoto et al., 2011). In this study, we analyze signals generated by hypersonic motion of the disrupted fragments and energetic burst of the spacecraft. In addition, we examine the air-to-ground coupling process by comparing the waveforms computed by finite difference scheme with the actual ones. At all three arrayed main stations, after the capsule's shockwave arrival, we detect multiple shockwave signals by both infrasound and seismic sensors. For some of these signals arrive within 10 seconds after capsule's signal, we can identify one to one correspondence with optically tracked disrupted fragments of the spacecraft. Far after the capsule's signal, we also detect some arrivals of wave packets. Based on the arrival time and the slowness of the signals, we identified one of these signals as the shockwave signal that corresponds to the energetic burst of the spacecraft at altitude of 57.3 km, which was recorded by video. However, we could not identify a lot of signals as the direct arrivals of the burst and sonic-boom-type shockwave. Some of those unidentified signals were probably related the multipath phases of the burst and sonic boom shockwaves. To study the air-to-ground coupling, we compare the observed waveforms to synthetic waveforms computed by 2-D finite difference scheme. For the actual seismic data, we can find precursor wave packets slightly prior to the direct-coupled wave from the capsule at GOS2 and GOS2A station. On the other hand, GOS2B and sub stations did not recorded distinct precursor wave. According to the synthetic waveforms, apparent velocity of the incident air-pressure wave controls the existence of the precursor wave prior to the direct coupling. When the apparent velocity of the incident pressure wave is almost identical to the phase velocity of ground surface wave, the surface wave is excited efficiently as precursor wave. Namely, for GOS2B station, the elevation angle of the incident shockwave is high. Therefore, the apparent velocity of the shockwave is too fast to generate the precursor surface wave.

  10. Hydromagnetic simultaneous heat and mass transfer by mixed convection from a vertical plate embedded in a stratified porous medium with thermal dispersion effects

    NASA Astrophysics Data System (ADS)

    Chamkha, A. J.; Khaled, A.-R. A.

    The problem of steady, laminar, hydromagnetic simultaneous heat and mass transfer by mixed convection flow over a vertical plate embedded in a uniform porous medium with a stratified free stream and taking into account the presence of thermal dispersion is investigated for the case of power-law variations of both the wall temperature and concentration. Certain transformations are employed to transform the governing differential equations to a local similarity form. The transformed equations are solved numerically by an efficient implicit, iterative, finite-difference scheme. The obtained results are checked against previously published work on special cases of the problem and are found to be in excellent agreement. A parametric study illustrating the influence of the magnetic field, porous medium inertia effects, heat generation or absorption, lateral wall mass flux, concentration to thermal buoyancy ratio, and the Lewis number on the fluid velocity, temperature and concentration as well as the Nusselt and the Sherwood numbers is conducted. The results of this parametric study is shown graphically and the physical aspects of the problem are discussed.

  11. Comment on Influence of convective boundary condition on double diffusive mixed convection from a permeable vertical surface, by P.M. Patil, E. Momoniat, S. Roy, International Journal of Heat and Mass Transfer, 70 (2014) 313-321

    E-print Network

    Pantokratoras, Asterios

    2014-01-01

    In the above paper the authors treat the boundary layer flow along a stationary, vertical, permeable, flat plate within a vertical free stream. Fluid is sucked or injected through the vertical plate. The fluid species concentration at the plate is constant and different from that of the ambient fluid. It is also assumed that the plate is heated by convection from another fluid with constant temperature with a constant heat transfer coefficient. The temperature and species concentration difference between the plate and the ambient fluid creates buoyancy forces and the flow is characterized as mixed convection. The partial differential equations of the boundary layer flow (Eqs. 1-4 in their paper) are transformed and subsequently are solved numerically using an implicit finite difference scheme in combination with a quasi-linearization technique. The quasi-linearization technique is a Newton-Raphson method. The results are presented in 12 figures.

  12. Analysis of hyperbolic signatures from small discontinuities using an UWB ground-coupled radar: FDTD simulations and field experiments

    NASA Astrophysics Data System (ADS)

    Sagnard, Florence; Tebchrany, Elias; Baltazart, Vincent

    2013-04-01

    Ground penetrating radar (GPR) is a well-known non-destructive technique based on electromagnetic wave propagation that is able to detect by reflection or scattering of waves dielectric discontinuities in the underground. Our application is mainly concerned with civil engineering to perform supervision, inventory, and soil characterization. Because the air-coupled radar suffers from a significant reflection at the ground interface that reduces energy transfer of electromagnetic radiation in the sub-surface and penetration depth, we have developed an ultra-wide band (UWB) ground-coupled radar made of a pair of partially shielded compact planar bowtie slot antennas. As the antenna dimension (36*23 cm2) is close to the A4 sheet size, the maturity of the microstrip technology has allowed to design a particular geometry on the FR4 substrate (h=1.5 mm) which is able to operate at frequencies from 460 MHz to beyond 4 GHz in air. Contrary to a commercial GPR where details on antenna design are not available, it appears here possible to know and control the radiation characteristics and develop full-wave FDTD modeling that can represent field experiments for comparisons and analyses. The objective of this work is to improve, by means of a parametric study, the knowledge of physical phenomena involved in dielectric polarization when waves interact with buried discontinuities and particularly cracks, pipes, delaminations that can be distinguished by their shape, size, dielectric contrast with the surrounding medium, orientation relative to the electric field… Thus, we have first characterized by FDTD modeling and field measurements in a wet sand the radar link in two perpendicular polarizations (parallel and mirror) in the presence of a common soil (epsilon'=5.5, sigma=0.01 S/m) considering variable offsets. Afterwards, we have studied and analyzed the hyperbola signatures generated by the presence of buried canonical objects (pipes, strips) with several dielectric properties (dielectric and conductive) in a wet sand with a small lateral dimension (less than 20 mm) in both polarizations. Comparisons with FDTD simulations including the detailed structure of the antennas appear promising as they have allowed to interpret the measurements and take advantage of signal polarization to extract information associated with the discontinuities. After cluster removal using classical data processing (SVD, median value substraction…), the analytical model based on the ray theory and including the antenna size has allowed to first analyze the hyperbola responses. This study is supposed to prepare the development of data processing associated with B-scans to extract quantitative information from the electromagnetic probing of the subsurface in a very large frequency band.

  13. Oscillatory MHD Convective Flow of Second Order Fluid Through Porous Medium in a Vertical Rotating Channel in Slip-Flow Regime with Heat Radiation

    NASA Astrophysics Data System (ADS)

    Garg, B. P.; Singh, K. D.; Bansal, A. K.

    2015-02-01

    An analysis of an oscillatory magnetohydrodynamic (MHD) convective flow of a second order (viscoelastic), incompressible, and electrically conducting fluid through a porous medium bounded by two infinite vertical parallel porous plates is presented. The two porous plates with slip-flow condition and the no-slip condition are subjected respectively to a constant injection and suction velocity. The pressure gradient in the channel varies periodically with time. A magnetic field of uniform strength is applied in the direction perpendicular to the planes of the plates. The induced magnetic field is neglected due to the assumption of a small magnetic Reynolds number. The temperature of the plate with no-slip condition is non-uniform and oscillates periodically with time and the temperature difference of the two plates is assumed high enough to induce heat radiation. The entire system rotates in unison about the axis perpendicular to the planes of the plates. Adopting complex variable notations, a closed form solution of the problem is obtained. The analytical results are evaluated numerically and then presented graphically to discuss in detail the effects of different parameters of the problem. The velocity, temperature and the skin-friction in terms of its amplitude and phase angle have been shown graphically to observe the effects of the viscoelastic parameter ?, rotation parameter ?, suction parameter ? , Grashof number Gr, Hartmann number M, the pressure A, Prandtl number Pr, radiation parameter N and the frequency of oscillation ? .

  14. Steady MHD free convection heat and mass transfer flow about a vertical porous surface with thermal diffusion and induced magnetic field

    NASA Astrophysics Data System (ADS)

    Touhid Hossain, M. M.; Afruz-Zaman, Md.; Rahman, Fouzia; Hossain, M. Arif

    2013-09-01

    In this study the thermal diffusion effect on the steady laminar free convection flow and heat transfer of viscous incompressible MHD electrically conducting fluid above a vertical porous surface is considered under the influence of an induced magnetic field. The governing non-dimensional equations relevant to the problem, containing the partial differential equations, are transformed by usual similarity transformations into a system of coupled non-linear ordinary differential equations and will be solved analytically by using the perturbation technique. On introducing the non-dimensional concept and applying Boussinesq's approximation, the solutions for velocity field, temperature distribution and induced magnetic field to the second order approximations are obtained for large suction with different selected values of the established dimensionless parameters. The influences of these various establish parameters on the velocity and temperature fields and on the induced magnetic fields are exhibited under certain assumptions and are studied graphically in the present analysis. It is observed that the effects of thermal-diffusion and large suction have great importance on the velocity, temperature and induced magnetic fields and mass concentration for several fluids considered, so that their effects should be taken into account with other useful parameters associated. It is also found that the dimensionless Prandtl number, Grashof number, Modified Grashof number and magnetic parameter have an appreciable influence on the concerned independent variables.

  15. Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997

    SciTech Connect

    Allan, M.L.

    1997-11-01

    Grout is used to seal the annulus between the borehole and heat exchanger loops in vertical geothermal (ground coupled, ground source, GeoExchange) heat pump systems. The grout provides a heat transfer medium between the heat exchanger and surrounding formation, controls groundwater movement and prevents contamination of water supply. Enhanced heat pump coefficient of performance (COP) and reduced up-front loop installation costs can be achieved through optimization of the grout thermal conductivity. The objective of the work reported was to characterize thermal conductivity and other pertinent properties of conventional and filled cementitious grouts. Cost analysis and calculations of the reduction in heat exchanger length that could be achieved with such grouts were performed by the University of Alabama. Two strategies to enhance the thermal conductivity of cementitious grouts were used simultaneously. The first of these was to incorporate high thermal conductivity filler in the grout formulations. Based on previous tests (Allan and Kavanaugh, in preparation), silica sand was selected as a suitable filler. The second strategy was to reduce the water content of the grout mix. By lowering the water/cement ratio, the porosity of the hardened grout is decreased. This results in higher thermal conductivity. Lowering the water/cement ratio also improves such properties as permeability, strength, and durability. The addition of a liquid superplasticizer (high range water reducer) to the grout mixes enabled reduction of water/cement ratio while retaining pumpability. Superplasticizers are commonly used in the concrete and grouting industry to improve rheological properties.

  16. Analysis of solar aided heat pump systems with seasonal thermal energy storage in surface tanks

    Microsoft Academic Search

    R. Yumruta?; M. Ünsal

    2000-01-01

    Annual periodic performance of a solar assisted ground-coupled heat pump space heating system with seasonal energy storage in a hemispherical surface tank is investigated using analytical and computational methods. The system investigated employs solar energy collection and dumping into a seasonal surface tank throughout the whole year with extraction of thermal energy from the tank for space heating during the

  17. Numerical investigation of coupled turbulent flow, heat transfer, and macroscopic solidification in a vertical twin-roll thin-strip caster

    SciTech Connect

    Seyedein, S.H.; Hasan, M. [McGill Univ., Montreal, Quebec (Canada). Dept. of Mining and Metallurgical Engineering

    1997-08-29

    A vertical twin-roll continuous thin-strip casting process for stainless steel has been mathematically modeled. The model takes into account the coupled turbulent flow, heat transfer, and macroscopic solidification aspects of the process. A low-Reynolds-number {kappa}-{var_epsilon} turbulence model was used to account for the turbulent effects. The transport equations for the wedge-shaped caster`s cavity were solved using a boundary-fitted nonorthogonal coordinate system. A control-volume-based, iterative finite difference scheme on a staggered grid was used to solve the discretized transformed equations. The SIMPLE algorithm was employed to resolve the velocity-pressure coupling in the momentum equations. The parameters examined in this study include the Darcy coefficient and turbulent damping factor for the mushy region, the roll gap, and the inlet nozzle width. The effects of these process parameters on the turbulent flow and temperature fields, the turbulent eddy viscosity distributions, and the extents of the mushy and solidified regions were ascertained. A change of the Darcy coefficient above 800 did not show any significant effect on the results. The three types of liquid-fraction-dependent turbulent damping factor used for modeling the mushy region did not show a measurable effect on the solidified shell thickness but showed a noticeable influence on the velocity and temperature distributions in both liquid and mushy regions. For a fixed width of the nozzle, an increase in the roll gap increased the penetration depth of the plunging inlet jet but decreased the extent of the mushy region. The solidified shell profile was insensitive to the change of the roll gap. For a fixed roll gap, an increase in the width of the nozzle decreased the penetration depth of the nozzle but increased the extent of the mushy region, while the solidified shell thickness remained practically unaffected.

  18. Diagnosis of the Course Vertical Profile of Radiative Heating with CERES Surface and Atmosphere Radiation Budget (SARB) for Terra and Aqua

    NASA Astrophysics Data System (ADS)

    Charlock, T. P.; Rose, F. G.; Rutan, D. A.

    2007-12-01

    The vertical profiles of SW and LW fluxes (surface, 500 hPa, 200 hPa, 70 hPa, and TOA) have been computed over the globe with the Langley Fu-Liou (FL) code and inputs for clouds from MODIS (Minnis et al.), aerosols from the MODIS-Atmosphere Team and the NCAR Model for Atmospheric Transport and Chemistry (MATCH), temperature and humidity from GEOS-4, and ozone from SMOBA (mostly SBUV). Surface spectral albedo for the ice-free ocean was based on Jin et al.; clear-sky broadband CERES SW observations and a look-up table to FL were used to develop surface albedo elsewhere. Tuned (i.e., based on adjustments to cloud properties) and untuned fluxes were compared with CERES at TOA for every footprint. Systematic validation with independent broadband SW and LW measurements at 60 sites worldwide has been a severe teacher on disparate accounts: RMS discrepancies of calculations with observations show that computed instantaneous diabatic profiles with clouds have limited meaning. For clear footprints over land, time-mean computed and observed surface insolations often agree, but this is partly due to offsetting errors in the code and aerosol inputs (MFRSR and Cimel photometers show MODIS Collection 4 land optical depths are too high). CERES broadband SW TOA observations appear to be low by 2-3 percent. Matched surface and TOA validation indicates, however, the LW profiles merit attention on the monthly scale: the interannual variability of surface LW downwelling compares astoundingly well with collocated ARM measurements of E13 and C01 (RMS of retrieval and measurement less than RMS of measurements). On both the interannual (deviation of an individual month from the calendar monthly mean) and synoptic (snapshot deviation from the mean of the individual month) scales, layer radiative heating correlates with layer water vapor more strongly than with layer temperature; and coherence in the upper troposphere exceeds that in the lower troposphere. Clouds introduce noise and reduce the correlation of layer radiative heating with water vapor, but all-sky regressions can have more slope than do clear-sky regressions, so total radiative divergence explained by fluctuations of water vapor increases in a cloudy sky. We will summarize such profile results from sites where matched TOA and surface validation give sufficient confidence.

  19. The Maximum Drop-Height of a Droplet in a Vertical Countercurrent Water-Air Heat and Moisture Exchange Tower Attached to a Main Fan Diffuser in a Coal Mine

    NASA Astrophysics Data System (ADS)

    Chen, S.; Cui, H.; Wang, H.; Zhao, J.

    2014-10-01

    A vertical countercurrent water-air heat and moisture exchange tower attached to a main fan diffuser is designed. To reduce water loss blown away by the airflow from the exchange tower, the forces acting on droplets are analysed. Droplet motion may be classified under four conditions: (1) downward initial acceleration; (2) upward initial acceleration; (3) droplet blown away by airflow; (4) droplet suspension. With droplet break-up neglected, a general equation for the maximum droplet drop-height is presented and numerical calculations are performed. Equations for the maximum drop-height under Conditions 3 and 4 are deduced, and the equation for Condition 3 is applied to an engineering case study. The effect of air velocity on the maximum drop-height is more significant than that of other factors. The conclusions provide a novel approach to optimizing the design of vertical countercurrent water-air heat and moisture exchange towers attached to main fan diffusers.

  20. THE VERTICAL

    NASA Technical Reports Server (NTRS)

    Albert, Stephen L.; Spencer, Jeffrey B.

    1994-01-01

    'THE VERTICAL' computer keyboard is designed to address critical factors which contribute to Repetitive Motion Injuries (RMI) (including Carpal Tunnel Syndrome) in association with computer keyboard usage. This keyboard splits the standard QWERTY design into two halves and positions each half 90 degrees from the desk. In order to access a computer correctly. 'THE VERTICAL' requires users to position their bodies in optimal alignment with the keyboard. The orthopaedically neutral forearm position (with hands palms-in and thumbs-up) reduces nerve compression in the forearm. The vertically arranged keypad halves ameliorate onset occurrence of keyboard-associated RMI. By utilizing visually-reference mirrored mylar surfaces adjustable to the user's eye, the user is able to readily reference any key indicia (reversed) just as they would on a conventional keyboard. Transverse adjustability substantially reduces cumulative musculoskeletal discomfort in the shoulders. 'THE VERTICAL' eliminates the need for an exterior mouse by offering a convenient finger-accessible curser control while the hands remain in the vertically neutral position. The potential commercial application for 'THE VERTICAL' is enormous since the product can effect every person who uses a computer anywhere in the world. Employers and their insurance carriers are spending hundreds of millions of dollars per year as a result of RMI. This keyboard will reduce the risk.

  1. Field and Laboratory Study of a Ground-Coupled Water Source Heat Pump with an Integral Enthalpy Exchange System for Classrooms

    E-print Network

    Domitrovic, R.; Hayzen, G. J.; Johnson, W. S.; Chen, F. C.

    2002-01-01

    School classroom space-conditioning equipment in hot and humid climates is often excessively burdened by the requirement to dehumidify incoming air to maintain proper thermal comfort and air quality. To that end, application of new or modified...

  2. Vertical Farm

    NSDL National Science Digital Library

    With the continued growth of the human population of the Earth, there is increasing concern with the planet's ability to provide sustenance for all of its inhabitants. This compelling website by Dickson Despommier and his colleagues at Columbia University provides a worthy alternative to other forms of agriculture: the vertical farm. As Dr. Despommier notes on the site, "..they offer the promise of urban renewal, sustainable production of a safe and varied food supply (year-round crop production), and the eventual repair of ecosystems that have been sacrificed for horizontal farming." The site offers a great deal of information about these vertical farms, a detailed essay on the importance of such farms, a number of potential designs, and a discussion forum. Finally, there are a number of plans that indicate how this type of farm might be effectively created and sustained.

  3. Perturbation analysis of unsteady magnetohydrodynamic convective heat and mass transfer in a boundary layer slip flow past a vertical permeable plate with thermal radiation and chemical reaction

    Microsoft Academic Search

    Dulal Pal; Babulal Talukdar

    2010-01-01

    An analytical study for the problem of unsteady mixed convection with thermal radiation and first-order chemical reaction on magnetohydrodynamics boundary layer flow of viscous, electrically conducting fluid past a vertical permeable plate has been presented. Slip boundary condition is applied at the porous interface. The classical model is used for studying the effect of radiation for optically thin media. The

  4. Downflow dryout in a heated ribbed vertical annulus with a cosine power profile (Results from test series ECS2, WSR, and ECS2cE)

    Microsoft Academic Search

    T. K. Larson; J. L. Anderson; K. G. Condie

    1990-01-01

    Experiments designed to investigate surface dryout in a heated, ribbed annulus test section simulating one of the annular coolant channels of a Savannah River Plant production reactor Mark 22 fuel assembly have been conducted at the Idaho National Engineering Laboratory. The inner surface of the annulus was constructed of aluminum and was electrically heated to provide an axial cosine power

  5. Vertical Profiles of Latent Heat Release and Their Retrieval for TOGA COARE Convective Systems Using a Cloud Resolving Model, SSM/I, and Ship-borne Radar Data

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Lang, S.; Simpson, J.; Olson, W. S.; Johnson, D.; Ferrier, B.; Kummerow, C.; Adler, R.

    1999-01-01

    Latent heating profiles associated with three (TOGA COARE) Tropical Ocean and Global Atmosphere Coupled Ocean Atmosphere Response Experiment active convective episodes (December 10-17 1992; December 19-27 1992; and February 9-13 1993) are examined using the Goddard Cumulus Ensemble (GCE) Model and retrieved by using the Goddard Convective and Stratiform Heating (CSH) algorithm . The following sources of rainfall information are input into the CSH algorithm: Special Sensor Microwave Imager (SSM/1), Radar and the GCE model. Diagnostically determined latent heating profiles calculated using 6 hourly soundings are used for validation. The GCE model simulated rainfall and latent heating profiles are in excellent agreement with those estimated by soundings. In addition, the typical convective and stratiform heating structures (or shapes) are well captured by the GCE model. Radar measured rainfall is smaller than that both estimated by the GCE model and SSM/I in all three different COARE IFA periods. SSM/I derived rainfall is more than the GCE model simulated for the December 19-27 and February 9-13 periods, but is in excellent agreement with the GCE model for the December 10-17 period. The GCE model estimated stratiform amount is about 50% for December 19-27, 42% for December 11-17 and 56% for the February 9-13 case. These results are consistent with large-scale analyses. The accurate estimates of stratiform amount is needed for good latent heating retrieval. A higher (lower) percentage of stratiform rain can imply a maximum heating rate at a higher (lower) altitude. The GCE model always simulates more stratiform rain (10 to 20%) than the radar for all three convective episodes. SSM/I derived stratiform amount is about 37% for December 19-27, 48% for December 11-17 and 41% for the February 9-13 case. Temporal variability of CSH algorithm retrieved latent heating profiles using either GCE model simulated or radar estimated rainfall and stratiform amount is in good agreement with that diagnostically determined for all three periods. However, less rainfall and a smaller stratiform percentage estimated by radar resulted in a weaker (underestimated) latent heating profile and a lower maximum latent heating level compared to those determined diagnostically. Rainfall information from SSM/I can not retrieve individual convective events due to poor temporal sampling. Nevertheless, this study suggests that a good 4r, rainfall retrieval from SSM/I for a convective event always leads to a good latent heating retrieval. Sensitivity testing has been performed and the results indicate that the SSM/I derived time averaged stratiform amount may be underestimated for December 19-27. Time averaged heating profiles derived from SSM/I, however, are not in bad agreement with those derived by soundings for the December 10-17 convective period. The heating retrievals may be more accurate for longer time scales provided there is no bias in the sampling.

  6. Rate of heat recovery from a hot-water store: Influence of the aspect ratio of a vertical-axis open-ended cylinder beneath a submerged heat-exchanger

    Microsoft Academic Search

    R. Mote; S. D. Probert; D. Nevrala

    1992-01-01

    A coiled finned-pipe heat-exchanger was employed to extract heat rapidly, from a 90-litre hot-water charged tank; the water being initially at a temperature of approximately 80°C. Free-convective buoyancy movements of the water around the outside of this coiled pipe (immersed in the store) occur as a result of initially-cold water (at 20°C) being forced internally through the heat-exchanger's pipe. The

  7. 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.

  8. A controlled experiment to investigate the correlation between early-time signal attributes of ground-coupled radar and soil dielectric properties

    NASA Astrophysics Data System (ADS)

    Pettinelli, Elena; Di Matteo, Andrea; Beaubien, Stanley Eugene; Mattei, Elisabetta; Lauro, Sebastian Emanuel; Galli, Alessandro; Vannaroni, Giuliano

    2014-02-01

    Ground-coupled radar has been used in the literature to estimate shallow subsoil permittivity using ground-wave velocity measurements. It has also been shown that the electromagnetic (EM) properties of the soil significantly affect antenna performance, modifying in particular the amplitude, shape, and duration of the 'early-time' Ground Penetrating Radar (GPR) signals. To quantitatively evaluate these effects we built a test site consisting of a 4 × 7 × 1.2 m volume filled primarily with sand; this volume is hydraulically isolated from the surroundings and contains buried pipes in which water can be introduced or removed to control the level of the water table. On a regular grid of 28 points we measured the soil dielectric properties at depth intervals of 0-10 and 0-20 cm using Time Domain Reflectometry (TDR) probes, and collected GPR data using both 250 and 500 MHz bistatic antennas. The measurements were performed with the water table at different depths to systematically change the shallow-soil dielectric properties. Relative permittivity and conductivity values were calculated from the TDR data, and the average envelopes of the first half cycle of the early-time GPR signals were computed. Data analysis shows a high degree of linear correlation (r ? 0.8) between the early-time signal attributes for both antenna frequencies and the EM properties obtained using both TDR probe lengths. The highest correlation (r = 0.9) was found between the 500 MHz data and the permittivity measured along the 0-20 cm depth interval; this relationship is explained in terms of ground wave penetration. The results of our investigation confirm previous field observations and are in full agreement with theoretical predictions and related numerical simulations, highlighting the potential for alternative convenient approaches to predict EM properties of the shallow subsoil.

  9. Year round experimental study on a constant temperature and humidity air-conditioning system driven by ground source heat pump

    Microsoft Academic Search

    X. Yu; R. Z. Wang; X. Q. Zhai

    2011-01-01

    Numerous studies about the ground source heat pump building heating and cooling systems have been constructed in office building, hotel, residential building and school et al. However, few researches about the constant temperature and humidity air-conditioning system driven by ground-coupled heat pumps were carried out. In this paper, a constant temperature and humidity air-conditioning system driven by ground source heat pump

  10. Hybrid Heat Pumps Using Selective Water Sorbents (SWS)

    SciTech Connect

    Ally, M. R.

    2006-11-30

    The development of the ground-coupled and air-coupled Heating Ventilation and Air-Conditioning (HVAC) system is essential in meeting the goals of Zero Energy Houses (ZEH), a viable concept vigorously pursued under DOE sponsorship. ORNL has a large Habitat for Humanity complex in Lenoir City where modem buildings technology is incorporated on a continual basis. This house of the future is planned for lower and middle income families in the 21st century. The work undertaken in this CRADA is an integral part of meeting DOE's objectives in the Building America program. SWS technology is a prime candidate for reducing the footprint, cost and improve the performance of ground-coupled heat pumps. The efficacy of this technique to exchange energy with the ground is a topic of immense interest to DOE, builders and HVAC equipment manufacturers. If successful, the SWS concept will become part of a packaged ZEH kit for affordable and high-end houses. Lennox Industries entered into a CRADA with Oak Ridge National Laboratory in November 2004. Lennox, Inc. agreed to explore ways of using Selective Water Sorbent materials to boost the efficiency of air-coupled heat pumps whereas ORNL concentrated on ground-coupled applications. Lennox supplied ORNL with heat exchangers and heat pump equipment for use at ORNL's Habitat for Humanity site in Lenoir City, Tennessee. Lennox is focused upon air-coupled applications of SWS materials at the Product Development and Research Center in Carrollton, TX.

  11. Recent refinements and increased capabilities in balloon vertical performance analysis

    Microsoft Academic Search

    G. R. Conrad

    1993-01-01

    A balloon vertical performance analysis model named THERMTRAJ (THERMal TRAJectory) was developed in the late '70's. This model combines the vertical equation of motion with heat balance equations to predict the balloon altitude, vertical rate, skin and gas temperatures versus time. THERMTRAJ provided significant improvement in performance analysis capabilities, but suffers from inadequacies, e.g., 1) assumed spherical shape, with maximum

  12. Natural Convection of Liquid Metals in Vertical Cavities

    E-print Network

    Beckermann, Christoph

    Natural Convection of Liquid Metals in Vertical Cavities F. Wolff Research Assistant C. Beckermann- vection heat transfer and fluid flow in vertical cavities filled with liquid metals. Experiments vertical walls show a variation reflecting the complicated flow patterns. The need for highly accurate

  13. Optimizing three-frequency Na, Fe, and He lidars for measurements of wind, temperature, and species density and the vertical fluxes of heat and constituents.

    PubMed

    Gardner, Chester S; Vargas, Fabio A

    2014-07-01

    The measurement accuracies of three-frequency resonance fluorescence Doppler lidars are limited by photon noise and uncertainties in the laser frequency and line width. We analyze the performance of Na, Fe, and He lidars using a new technique, which incorporates precise information about the absorption spectrum of the species and the pulse spectrum of the lasers. We derive the measurement errors associated with photon noise, laser frequency errors, and laser line width errors. Optimizing the lidar design, based upon the measurement requirements, can improve system performance by reducing the required integration times, enabling measurements to be made in less time or at higher altitudes where the densities and signal levels are smaller. The optimum frequency shift for observing heat and constituent transport velocities is 689 MHz (580 MHz) at night (day) for Na lidars and 774 MHz (597 MHz) for Fe lidars. The optimum frequency shift for observing winds, temperature, and He densities is 3.66 GHz (3.16 GHz) at night (day) for He lidars. PMID:25089967

  14. Steady response to heating: Gaussian heat source

    E-print Network

    Frierson, Dargan

    #12;Equatorial Waves Alternative theory for wave speed: ¡ Higher vertical mode structure causes phaseGill Model Steady response to heating: Gaussian heat source in center of domain. Boundary: Heating applied in region A. Only subsidence contours are drawn (there is upward motion elsewhere). From

  15. Vertical constituent transport in the mesosphere

    NASA Technical Reports Server (NTRS)

    Strobel, Darrell F.; Summers, Michael E.; Bevilacqua, Richard M.; Deland, Matthew T.; Allen, Mark

    1987-01-01

    Ground-based microwave spectroscopy measurements of mesospheric CO and H2O vertical mixing ratio profiles are used to infer vertical mixing rates in the upper mesosphere. The CO and H2O data consistently imply vertical eddy diffusion coefficients in the 70- to 85-km region of 100,000-200,000 sq cm/s during spring through summer at midlatidues. Although chemical acceleration of vertical transport is substantial for O and O3, below the mesopause, the divergences of their associated fluxes are modest, with at most a factor of 2 effect on the concentrations of O and O3 for measured variability in gravity wave activity. Comparison of Solar Mesosphere Explorer (SME) O3 data with model results reinforces the conclusions of slow vertical mixing in the upper mesosphere as a consequence of the reduced HO(x) catalytic loss of odd oxygen. The changes in chemical rate constants recommended by Rusch and Eckman (1985), in conjunction with slow vertical mixing, yield good agreement with SME O3 data. The slow vertical mixing deduced in this study is consistent with upper limits obtained from studies of the mesospheric heat budget and could be construed as evidence for an advectively controlled mesosphere. A comparison of the vertical eddy diffusion coefficients for momentum stresses, constituent transport, and heat transport suggests that the eddy Prandtl number must be of order 10.

  16. Solr assisted heat pump research and development program in the United States

    SciTech Connect

    Andrews, J W

    1980-01-01

    A review of the historical progress and current status of the solar assisted heat pump research and development, supported by the United States Department of Energy, is presented. Much of this work has had as its focus the need for a better source of auxiliary or backup heat than the electric resistance which has generally been assumed in computer simulations of these systems. The two leading candidates are the use of the ground as an alternate heat source/sink or storage element (ground coupling) and the use of fossil fuel burned on site (the bivalent system). The United States program has emphasized ground coupling. Much of the analytical work and heat pump development is applicable to bivalent systems, and some results of this work are discussed. Project descriptions and technical accomplishments for the currently active projects are presented.

  17. Field observations and numerical models of GPR response from vertical pavement cracks

    NASA Astrophysics Data System (ADS)

    Diamanti, Nectaria; Redman, David

    2012-06-01

    High resolution ground-coupled GPR is useful for determining thickness, deterioration, jointing and cracks in pavements. Although only millimetres in width, vertical cracks can present a significant target in reflection profiles. On composite pavements, consisting of asphalt over concrete, we have observed responses at locations above joints in the underlying concrete that we attribute to cracks within the asphalt layer. On some asphalt pavement, we observed significantly stronger diffraction and waveguide effects responses at a 250 MHz centre frequency rather than at 1000 MHz, despite the small crack apertures. Using numerical modelling we show the importance of crack filling material, crack aperture, crack height, asphalt conductivity and the GPR centre frequency on the observed response. Our observations and models clearly show the potential of GPR to detect and characterise vertical cracks. We recommend a multi-frequency approach to GPR surveys of pavement: high frequency for crack characterisation and lower frequency for crack detection.

  18. Vertical Map Storage.

    ERIC Educational Resources Information Center

    Perry, Joanne M.

    1982-01-01

    Discusses the superiority of vertical filing of maps in compressor-style vertical units over horizontal filing in drawers, emphasizing such factors as physical protection of the collection, ease of filing and retrieval, and efficient use of space. Disadvantages of vertical filing are also reviewed. (Author/JL)

  19. Vertical bounce of two vertically aligned balls

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2007-11-01

    When a tennis ball rests on top of a basketball and both drop to the floor together, the tennis ball is projected vertically at high speed. A mass-spring model of the impact, as well as air track data, suggest that the tennis ball should be projected at relatively low speed. Measurements of the forces on each ball and the bounce of vertically aligned superballs are used to resolve the discrepancy.

  20. Vertical axis wind turbines

    DOEpatents

    Krivcov, Vladimir (Miass, RU); Krivospitski, Vladimir (Miass, RU); Maksimov, Vasili (Miass, RU); Halstead, Richard (Rohnert Park, CA); Grahov, Jurij (Miass, RU)

    2011-03-08

    A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.

  1. Simulation of the effect of methane bubble plumes on vertical mixing in Mono Lake

    Microsoft Academic Search

    José R. Romero; John C. Patterson; John M. Melack

    1996-01-01

    A one-dimensional vertical mixing model modified for application to hypersaline Mono Lake reproduced mixed layer dynamics well but hypolimnetic heating was underestimated. One possible source of increased hypolimnetic heating is vertical mixing caused by bubble plumes of methane rising from the sediments. Estimates of vertical mixing from methane seepage in Mono Lake were made with the inclusion of a bubble

  2. Offset vertical radar profiling

    USGS Publications Warehouse

    Witten, A.; Lane, J.

    2003-01-01

    Diffraction tomography imaging was applied to VRP data acquired by vertically moving a receiving antenna in a number of wells. This procedure simulated a vertical downhole receiver array. Similarly, a transmitting antenna was sequentially moved along a series of radial lines extending outward from the receiver wells. This provided a sequence of multistatic data sets and, from each data set, a two-dimensional vertical cross-sectional image of spatial variations in wave speed was reconstructed.

  3. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D. (Evergreen, CO)

    1999-03-16

    A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.

  4. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1999-03-16

    A vertical two chamber reaction furnace is disclosed. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

  5. Soret Instability in a Vertical Brinkman Porous Enclosure

    Microsoft Academic Search

    F. Joly; P. Vasseur; G. Labrosse

    2001-01-01

    This paper presents ananalytical and numerical study of theinèuence of theSoret effect on the onset of convection in a vertical porous layer subject to uniform heat èuxes along the vertical walls. In the formulation of the problem use is made of the Brinkman-extended Darcy model, which is relevant to sparsely packed porous media. The analysis deals with the particular situation

  6. Soret-driven thermosolutal convection in a vertical enclosure

    Microsoft Academic Search

    F. Joly; P. Vasseur; G. Labrosse

    2000-01-01

    The purpose of this paper is to investigate the influence of the Soret effect on natural convection in a vertical cavity filled with a binary liquid. The two vertical walls of the cavity are subject to constant fluxes of heat while the two horizontal ones are adiabatic. The analysis deals with the particular situation where the buoyancy forces induced by

  7. Geothermal direct-heat utilization assistance. Quarterly project progress report, October--December 1993

    SciTech Connect

    Not Available

    1993-12-31

    This report consists of brief summaries of the activities of the Geo-Heat Center during the report period. Technical assistance was given to requests from 20 states in the following applications: space and district heating; geothermal heat pumps; greenhouses; aquaculture; industrial plants; electric power; resource/well; equipment; and resort/spa. Research and development activities progressed on (1) compilation of data on low-temperature resources and (2) evaluation of groundwater vs. ground-coupled heat pumps. Also summarized are technology transfer activities and geothermal progress monitoring activities.

  8. Methods of testing parameterizations: Vertical ocean mixing

    NASA Technical Reports Server (NTRS)

    Tziperman, Eli

    1992-01-01

    The ocean's velocity field is characterized by an exceptional variety of scales. While the small-scale oceanic turbulence responsible for the vertical mixing in the ocean is of scales a few centimeters and smaller, the oceanic general circulation is characterized by horizontal scales of thousands of kilometers. In oceanic general circulation models that are typically run today, the vertical structure of the ocean is represented by a few tens of discrete grid points. Such models cannot explicitly model the small-scale mixing processes, and must, therefore, find ways to parameterize them in terms of the larger-scale fields. Finding a parameterization that is both reliable and plausible to use in ocean models is not a simple task. Vertical mixing in the ocean is the combined result of many complex processes, and, in fact, mixing is one of the less known and less understood aspects of the oceanic circulation. In present models of the oceanic circulation, the many complex processes responsible for vertical mixing are often parameterized in an oversimplified manner. Yet, finding an adequate parameterization of vertical ocean mixing is crucial to the successful application of ocean models to climate studies. The results of general circulation models for quantities that are of particular interest to climate studies, such as the meridional heat flux carried by the ocean, are quite sensitive to the strength of the vertical mixing. We try to examine the difficulties in choosing an appropriate vertical mixing parameterization, and the methods that are available for validating different parameterizations by comparing model results to oceanographic data. First, some of the physical processes responsible for vertically mixing the ocean are briefly mentioned, and some possible approaches to the parameterization of these processes in oceanographic general circulation models are described in the following section. We then discuss the role of the vertical mixing in the physics of the large-scale ocean circulation, and examine methods of validating mixing parameterizations using large-scale ocean models.

  9. Vertical diffusivity of the Western Arctic Ocean halocline

    NASA Astrophysics Data System (ADS)

    Shaw, William J.; Stanton, Timothy P.

    2014-08-01

    A nearly year-long series of upper ocean temperature, conductivity, and temperature microstructure profiles were collected from an ice camp drifting in the Beaufort Gyre as part of the 1997-1998 Surface Heat Budget of the Arctic Experiment (SHEBA). Geographically, the record includes portions over the deep Canada Basin and the steep bathymetry of the Chukchi Borderlands region. Hydrographically, the record includes "cool," Pacific-origin haloclines, which contain a variety of subsurface temperature maxima, and cold haloclines typical of the Eurasian Basins. We present estimates of the vertical turbulent diffusivity derived from the dissipation rate of thermal variance and calculations of the associated vertical heat fluxes. We find that vertical diffusion proceeds at molecular rates in the deep basins and away from topographic features. While still relatively small, diffusivity is enhanced by 1 order of magnitude near and above the Chukchi Borderlands. The enhanced diffusivity is correlated to an increase in water column strain variance above the Borderlands, providing a linkage between bathymetry, internal wave activity and turbulence. The Chukchi Borderlands play a significant role in heat transport in the Western Arctic. They are a pathway for horizontal heat transport and a hot spot for vertical heat transport. Vertical fluxes make a substantial contribution to the energy balance of the sea ice cover in this region. Heat fluxes between the halocline and underlying Atlantic Water are shown to be small and lacking vertical connection near surface waters.

  10. Natural convection heat transfer in liquid metals

    Microsoft Academic Search

    J. R. Welty

    1973-01-01

    Research progress for the reporting period is reported on: (1) natural convection studies in mercury confined between two vertical heated pipes, and (2) natural convection heat transfer studies in mercury adjacent to a vertical cylinder with constant heat flux. A bibliography of publications developed on the project for prior years is presented.

  11. Heat transfer system

    DOEpatents

    Not Available

    1980-03-07

    A heat transfer system for a nuclear reactor is described. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.

  12. Heat transfer system

    DOEpatents

    McGuire, Joseph C. (Richland, WA)

    1982-01-01

    A heat transfer system for a nuclear reactor. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.

  13. Vertical Line Test

    NSDL National Science Digital Library

    2011-05-24

    In this activity, students try to connect given points on a graph in a way that they will pass the vertical line test. If the points can't be made to pass the vertical line test, the student must adjust the points so they will pass the test. This activity allows students to explore the vertical line test for functions. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

  14. Micromachined electrostatic vertical actuator

    DOEpatents

    Lee, Abraham P. (Walnut Creek, CA); Sommargren, Gary E. (Santa Cruz, CA); McConaghy, Charles F. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

    1999-10-19

    A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

  15. ACCVD Growth of Vertically Aligned Single-Walled Carbon Nanotubes on a Quartz Substrate

    E-print Network

    Maruyama, Shigeo

    ACCVD Growth of Vertically Aligned Single-Walled Carbon Nanotubes on a Quartz Substrate Shigeo: maruyama@photon.t.u-tokyo.ac.jp Vertically aligned single-walled carbon nanotubes (SWNTs) up to 5 microns of CVD growth of vertically aligned SWNTs [2], hydrogen gas was supplied only during the heating-up stage

  16. Enhancement of heat transfer

    NASA Astrophysics Data System (ADS)

    Nakayama, W.

    Recent publications on enhancement of heat transfer are reviewed, emphasizing the effects of roughness elements, fins, and porous surfaces. Enhancement of forced convective heat transfer on roughened surfaces, performance evaluation of enhanced surfaces, viscous flows in cooled tubes and tubes with swirlers, and active methods of enhancement are addressed. Aspects of pool boiling heat transfer are considered, including nucleate boiling heat transfer on rough surfaces and porous surfaces, and maximum and minimum heat fluxes. Evaporative heat transfer is discussed for thin-film evaporation on structured surfaces and liquid spray cooling of a heated surface. Condensation heat transfer on external surfaces is covered, including filmwise condensation on vertical finned and fluted surfaces and on horizontal tubes. In-tube boiling and condensation are treated, discussing their enhancement by fins and inserts, as well as critical heat flux in coiled, rifled, and corrugated tubes.

  17. Thermal Impacts of Vertical Greenery Systems

    NASA Astrophysics Data System (ADS)

    Safikhani, Tabassom; Abdullah, Aminatuzuhariah Megat; Ossen, Dilshan Remaz; Baharvand, Mohammad

    2014-12-01

    - Using vertical greenery systems to reduce heat transmission is becoming more common in modern architecture. Vertical greenery systems are divided into two main categories; green facades and living walls. This study aims to examine the thermal performance of vertical greenery systems in hot and humid climates. An experimental procedure was used to measure indoor temperature and humidity. These parameters were also measured for the gap between the vertical greenery systems and wall surfaces. Three boxes were used as small-scale rooms. Two boxes were provided with either a living wall or a green facade and one box did not have any greenery (benchmark). Blue Trumpet Vine was used in the vertical greenery systems. The data were recorded over the course of three sunny days in April 2013. An analyses of the results showed that the living wall and green facade reduced indoor temperature up to 4.0 °C and 3.0 °C, respectively. The living wall and green facade also reduced cavity temperatures by 8.0 °C and 6.5 °C, respectively.

  18. Vertical Propagation of Lakewide Internal Waves

    NASA Astrophysics Data System (ADS)

    Henderson, Stephen; Harrison, John; Deemer, Bridget

    2013-04-01

    Internal seiches dominate flows in the interior of many lakes. Seiche dissipation generates turbulence, which is responsible for mixing heat, sediments, chemicals, organisms, and pollutants. We present observations of a new type of seiche-like internal wave propagating vertically in a small lake (main basin 3000m by 400m by 18m). Velocity and temperature profiles indicate that the observed waves, like seiches, had horizontal wavelengths exceeding the metalimnion length. However, the vertical propagation of the observed waves contrasts with the vertically-standing behavior of non-dissipative seiches. The observed propagation was predicted by a simple model for dissipation in the bottom boundary layer. The model and data indicate that the waves had small vertical group velocity, leading to a slow supply of energy to the lakebed, which could easily be dissipated rather than being reflected. Similar slow vertical propagation and boundary layer absorption is predicted in other short, deep lakes with strong near-bed stratification. The absence of upward-propagating energy precludes seiche resonance, limits focusing of waves toward attractors, and suggests that hypolimnion dissipation was limited by the supply of downward-propagating energy.

  19. Aiding Vertical Guidance Understanding

    NASA Technical Reports Server (NTRS)

    Feary, Michael; McCrobie, Daniel; Alkin, Martin; Sherry, Lance; Polson, Peter; Palmer, Everett; McQuinn, Noreen

    1998-01-01

    A two-part study was conducted to evaluate modern flight deck automation and interfaces. In the first part, a survey was performed to validate the existence of automation surprises with current pilots. Results indicated that pilots were often surprised by the behavior of the automation. There were several surprises that were reported more frequently than others. An experimental study was then performed to evaluate (1) the reduction of automation surprises through training specifically for the vertical guidance logic, and (2) a new display that describes the flight guidance in terms of aircraft behaviors instead of control modes. The study was performed in a simulator that was used to run a complete flight with actual airline pilots. Three groups were used to evaluate the guidance display and training. In the training, condition, participants went through a training program for vertical guidance before flying the simulation. In the display condition, participants ran through the same training program and then flew the experimental scenario with the new Guidance-Flight Mode Annunciator (G-FMA). Results showed improved pilot performance when given training specifically for the vertical guidance logic and greater improvements when given the training and the new G-FMA. Using actual behavior of the avionics to design pilot training and FMA is feasible, and when the automated vertical guidance mode of the Flight Management System is engaged, the display of the guidance mode and targets yields improved pilot performance.

  20. Vertical Integration and Communication

    Microsoft Academic Search

    Kenneth J. Arrow

    1975-01-01

    Among the many possible motives for vertical integration, the one emphasized here is uncertainty in the supply of the upstream good and the consequent need for information by downstream firms. The basic conclusion is that, even when the initial conditions are of the type usually thought of as competitive, the upshot will be a tendency to imperfect competition.

  1. Coupling of wall conduction with natural convection from heated cylinders in a rectangular enclosure

    Microsoft Academic Search

    Marcel Lacroix; Antoine Joyeux

    1996-01-01

    A numerical study has been conducted for natural convection heat transfer for air from two vertically separated horizontal heated cylinders confined to a rectangular enclosure having vertical walls of finite conductances and horizontal walls at the heat sink temperature. The interaction between convection in the fluid filled cavity and conduction in the vertical walls is investigated. Results have been obtained

  2. Vertical Motion Simulator

    NSDL National Science Digital Library

    The Vertical Motion Simulator (VMS), at the NASA Ames Research Center, is an advanced flight simulation facility. This Web site provides thorough descriptions of all of the VMS systems. The VMS is a full immersion environment, complete with customizable cockpit, controls, and instrumentation to give the appearance of any aerospace vehicle. One of its most intriguing characteristics is "out-the-window graphics." This allows the pilot to see computer generated imagery of real locations, so virtually everything is identical to the actual flying experience. Even aircraft that are still in the design stage can be simulated on the VMS.

  3. Vertical solar louver project

    NASA Astrophysics Data System (ADS)

    Bier, C. J.

    1984-09-01

    The thermal network analysis computer program MICROPAS was used to analyze Vertical Solar Louvers and other reference solar designs in eight selected climates. The results have been used to generate a set of correlation coefficients for use in performance predictions by the Solar Load Ratio method. At low mass VSL were shown to be superior to ordinary direct gain and equal to the trombe wall systems in energy savings. The energy savings advantage of VSL over direct gain disappears in comparable systems of high mass. Identical solar water tanks of oval cross section were compared in the water wall and VSL configurations.

  4. 'Endurance' Untouched (vertical)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This navigation camera mosaic, created from images taken by NASA's Mars Exploration Rover Opportunity on sols 115 and 116 (May 21 and 22, 2004) provides a dramatic view of 'Endurance Crater.' The rover engineering team carefully plotted the safest path into the football field-sized crater, eventually easing the rover down the slopes around sol 130 (June 12, 2004). To the upper left of the crater sits the rover's protective heatshield, which sheltered Opportunity as it passed through the martian atmosphere. The 360-degree view is presented in a vertical projection, with geometric and radiometric seam correction.

  5. Heat-pipe Earth.

    PubMed

    Moore, William B; Webb, A Alexander G

    2013-09-26

    The heat transport and lithospheric dynamics of early Earth are currently explained by plate tectonic and vertical tectonic models, but these do not offer a global synthesis consistent with the geologic record. Here we use numerical simulations and comparison with the geologic record to explore a heat-pipe model in which volcanism dominates surface heat transport. These simulations indicate that a cold and thick lithosphere developed as a result of frequent volcanic eruptions that advected surface materials downwards. Declining heat sources over time led to an abrupt transition to plate tectonics. Consistent with model predictions, the geologic record shows rapid volcanic resurfacing, contractional deformation, a low geothermal gradient across the bulk of the lithosphere and a rapid decrease in heat-pipe volcanism after initiation of plate tectonics. The heat-pipe Earth model therefore offers a coherent geodynamic framework in which to explore the evolution of our planet before the onset of plate tectonics. PMID:24067709

  6. Measurement of ultralow vertical emittance using a calibrated vertical undulator

    NASA Astrophysics Data System (ADS)

    Wootton, K. P.; Boland, M. J.; Rassool, R. P.

    2014-11-01

    Very few experimental techniques are useful for the direct observation of ultralow vertical emittance in electron storage rings. In this work, quantitative measurements of ultralow (pm rad) electron beam vertical emittance using a vertical undulator are presented. An undulator radiation model was developed using the measured magnetic field of the APPLE-II type undulator. Using calibrated experimental apparatus, a geometric vertical emittance of ?y=0.9 ±0.3 pm rad has been observed. These measurements could also inform modeling of the angular distribution of undulator radiation at high harmonics, for proposed diffraction-limited storage ring light sources.

  7. Observation of Picometer Vertical Emittance with a Vertical Undulator

    NASA Astrophysics Data System (ADS)

    Wootton, K. P.; Boland, M. J.; Dowd, R.; Tan, Y.-R. E.; Cowie, B. C. C.; Papaphilippou, Y.; Taylor, G. N.; Rassool, R. P.

    2012-11-01

    Using a vertical undulator, picometer vertical electron beam emittances have been observed at the Australian Synchrotron storage ring. An APPLE-II type undulator was phased to produce a horizontal magnetic field, which creates a synchrotron radiation field that is very sensitive to the vertical electron beam emittance. The measured ratios of undulator spectral peak heights are evaluated by fitting to simulations of the apparatus. With this apparatus immediately available at most existing electron and positron storage rings, we find this to be an appropriate and novel vertical emittance diagnostic.

  8. Vertical counterflow evaporative cooler

    DOEpatents

    Bourne, Richard C.; Lee, Brian Eric; Callaway, Duncan

    2005-01-25

    An evaporative heat exchanger having parallel plates that define alternating dry and wet passages. A water reservoir is located below the plates and is connected to a water distribution system. Water from the water distribution system flows through the wet passages and wets the surfaces of the plates that form the wet passages. Air flows through the dry passages, mixes with air below the plates, and flows into the wet passages before exiting through the top of the wet passages.

  9. Natural convection in a long vertical cylinder under gravity modulation

    Microsoft Academic Search

    M. Wadih; B. Roux

    1988-01-01

    The onset of convection in differentially heated cylinders under gravity modulation is examined, with special consideration given to the case of a vertical cylinder of infinite length, when a negative temperature gradient is maintained in the upward direction. The effect of modulation on the stability limits given by linear theory in the standard steady case is analyzed. A method based

  10. A parametric model of vertical eddy fluxes in the atmosphere

    Microsoft Academic Search

    Jean-François Louis

    1979-01-01

    A scheme for the representation of the vertical eddy fluxes of heat, momentum and water vapour in a forecast model is presented. An important feature of the scheme is the dependence of the diffusion coefficients on the static stability of the atmosphere. Two tests are presented, using the scheme in a one-dimensional model: the simulation of the diurnal cycle, and

  11. 4. VIEW OF VERTICAL BORING MACHINE. (Bullard) Vertical turning lathe ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. VIEW OF VERTICAL BORING MACHINE. (Bullard) Vertical turning lathe (VTL). Machining the fixture for GE Turboshroud. G.S. O'Brien, operator. - Juniata Shops, Machine Shop No. 1, East of Fourth Avenue at Third Street, Altoona, Blair County, PA

  12. DISTANCES BETWEEN PAIRS OF VERTICES AND VERTICAL PROFILE IN CONDITIONED

    E-print Network

    Janson, Svante

    DISTANCES BETWEEN PAIRS OF VERTICES AND VERTICAL PROFILE IN CONDITIONED GALTON­WATSON TREES LUC DEVROYE AND SVANTE JANSON Abstract. We consider a conditioned Galton­Watson tree and prove an estimate of a randomly labelled conditioned Galton­Watson tree converges in distribution, after suitable normalization

  13. DISTANCES BETWEEN PAIRS OF VERTICES AND VERTICAL PROFILE IN CONDITIONED

    E-print Network

    Janson, Svante

    DISTANCES BETWEEN PAIRS OF VERTICES AND VERTICAL PROFILE IN CONDITIONED GALTON--WATSON TREES LUC DEVROYE AND SVANTE JANSON Abstract. We consider a conditioned Galton--Watson tree and prove an estimate of a randomly labelled conditioned Galton--Watson tree converges in distribution, after suitable normalization

  14. A new contribution to the finite line-source model for geothermal boreholes

    Microsoft Academic Search

    Louis Lamarche; Benoit Beauchamp

    2007-01-01

    Heat transfer around vertical ground heat exchangers is a common problem for the design and simulation of ground-coupled heat pump (GCHP) systems. Most models are based on step response of the heat transfer rate, and the superposition principle allows the final solution to be in the form of the convolution of these contributions. The step response is thus a very

  15. Geothermal Heat Transfer

    SciTech Connect

    Basmajian, V.V.

    1986-01-28

    This patent describes a heat transfer apparatus which consists of: heat exchanging means for orientation in the earth below ground substantially vertically, having a hollow conduit of length from top to bottom much greater than the span across the hollow conduit orthogonal to its length with a top, bottom and an intermediate portion contiguous and communicating with the top and bottom portions for allowing thermally conductive fluid to flow freely between the top, intermediate and bottom portions for immersion in thermally conductive fluid in the region around the heat exchanging means for increasing the heat flow between the latter and earth when inserted into a substantially vertical borehole in the earth with the top portion above the bottom portion. The heat exchanger consists of heat exchanging conduit means in the intermediate portion for carrying refrigerant. The heat exchanging conduit consisting of tubes of thermally conductive material for carrying the refrigerant and extending along the length of the hollow conduit for a tube length that is less than the length of the hollow conduit. The hollow conduit is formed with port means between the top and the plurality of tubes for allowing the thermally conductive fluid to pass in a flow path embracing the tubes, the bottom portion, an outer channel around the hollow conduit and the port means.

  16. Heat pipe array heat exchanger

    DOEpatents

    Reimann, Robert C. (Lafayette, NY)

    1987-08-25

    A heat pipe arrangement for exchanging heat between two different temperature fluids. The heat pipe arrangement is in a ounterflow relationship to increase the efficiency of the coupling of the heat from a heat source to a heat sink.

  17. Vertically reciprocating auger

    NASA Technical Reports Server (NTRS)

    Etheridge, Mark; Morgan, Scott; Fain, Robert; Pearson, Jonathan; Weldi, Kevin; Woodrough, Stephen B., Jr.

    1988-01-01

    The mathematical model and test results developed for the Vertically Reciprocating Auger (VRA) are summarized. The VRA is a device capable of transporting cuttings that result from below surface drilling. It was developed chiefly for the lunar surface, where conventional fluid flushing while drilling would not be practical. The VRA uses only reciprocating motion and transports material through reflections with the surface above. Particles are reflected forward and land ahead of radially placed fences, which prevent the particles from rolling back down the auger. Three input wave forms are considered to drive the auger. A modified sawtooth wave form was chosen for testing, over a modified square wave or sine wave, due to its simplicity and effectiveness. The three-dimensional mathematical model predicted a sand throughput rate of 0.2667 pounds/stroke, while the actual test setup transported 0.075 pounds/stroke. Based on this result, a correction factor of 0.281 is suggested for a modified sawtooth input.

  18. Measuring Growth with Vertical Scales

    ERIC Educational Resources Information Center

    Briggs, Derek C.

    2013-01-01

    A vertical score scale is needed to measure growth across multiple tests in terms of absolute changes in magnitude. Since the warrant for subsequent growth interpretations depends upon the assumption that the scale has interval properties, the validation of a vertical scale would seem to require methods for distinguishing interval scales from…

  19. Functions and Vertical Line Test

    NSDL National Science Digital Library

    2011-01-17

    This lesson is designed to introduce students to the vertical line test for functions as well as practice plotting points and drawing simple functions. The lesson provides links to discussions and activities related to the vertical line test and functions as well as suggested ways to integrate them into the lesson.

  20. Latitude and longitude vertical disparity

    PubMed Central

    Read, Jenny C. A.; Phillipson, Graeme P.; Glennerster, Andrew

    2010-01-01

    The literature on vertical disparity is complicated by the fact that several different definitions of the term “vertical disparity” are in common use, often without a clear statement about which is intended or a widespread appreciation of the properties of the different definitions. Here, we examine two definitions of retinal vertical disparity: elevation-latitude and elevation-longitude disparity. Near the fixation point, these definitions become equivalent, but in general, they have quite different dependences on object distance and binocular eye posture, which have not previously been spelt out. We present analytical approximations for each type of vertical disparity, valid for more general conditions than previous derivations in the literature: we do not restrict ourselves to objects near the fixation point or near the plane of regard, and we allow for non-zero torsion, cyclovergence and vertical misalignments of the eyes. We use these expressions to derive estimates of the latitude and longitude vertical disparity expected at each point in the visual field, averaged over all natural viewing. Finally, we present analytical expressions showing how binocular eye position – gaze direction, convergence, torsion, cyclovergence, and vertical misalignment – can be derived from the vertical disparity field and its derivatives at the fovea. PMID:20055544

  1. Fast vertical mining using diffsets

    Microsoft Academic Search

    Mohammed Javeed Zaki; Karam Gouda

    2003-01-01

    A number of vertical mining algorithms have been proposed recently for association mining, which have shown to be very effective and usually outperform horizontal approaches. The main advantage of the vertical format is support for fast frequency counting via intersection operations on transaction ids (tids) and automatic pruning of irrelevant data. The main problem with these approaches is when intermediate

  2. Vertical Mergers and Market Foreclosure

    Microsoft Academic Search

    Michael A Salinger

    1988-01-01

    The model in this paper illustrates three effects of vertical mergers when both stages are oligopolistic and vertically integrated and unintegrated producers coexist. First, the merging firm increases its final good output. Second, the resulting backward shift in the residual demand curve facing unintegrated final good producers lowers their demand for the intermediate good. Third, the merged firm withdraws from

  3. Transition from film boiling to nucleate boiling in forced convection vertical flow

    E-print Network

    Iloeje, Onwuamaeze C.

    1972-01-01

    The mechanism of collapse of forced cnnvection annular vertical flow film boiling, with liquid core, is investigated using liquid nitrogen at low pressures. The report includes the effect of heat flux from the buss bar. ...

  4. A Simple Model of Climatological Rainfall and Vertical Motion Patterns over the Tropical Oceans

    E-print Network

    Back, Larissa E.

    A simple model is developed that predicts climatological rainfall, vertical motion, and diabatic heating profiles over the tropical oceans given the sea surface temperature (SST), using statistical relationships deduced ...

  5. Localised convection cells in the presence of a vertical magnetic field

    E-print Network

    Localised convection cells in the presence of a vertical magnetic field J. H. P. Dawes Department October 27, 2005 Abstract Thermal convection in a horizontal fluid layer heated uniformly from below usually produces an array of convection cells of roughly equal amplitudes. In the presence of a vertical

  6. Dynamics of vertical mixing in a shallow lake with submersed macrophytes

    Microsoft Academic Search

    William R. Herb; Heinz G. Stefan

    2005-01-01

    A model for vertical turbulent diffusion and stratification in a shallow lake with submersed macrophytes is formulated on the basis of a one-dimensional equation for production, transport, and dissipation of turbulent kinetic energy, coupled with a vertical heat transfer equation. Numerical solutions of the coupled equations allow simulation of the hourly variation of water temperature profiles in a shallow lake

  7. Numerical simulation of water evaporation inside vertical circular tubes

    NASA Astrophysics Data System (ADS)

    Oc?o?, Pawe?; Nowak, Marzena; Majewski, Karol

    2013-10-01

    In this paper the results of simplified numerical analysis of water evaporation in vertical circular tubes are presented. The heat transfer in fluid domain (water or wet steam) and solid domain (tube wall) is analyzed. For the fluid domain the temperature field is calculated solving energy equation using the Control Volume Method and for the solid domain using the Finite Element Method. The heat transfer between fluid and solid domains is conjugated using the value of heat transfer coefficient from evaporating liquid to the tube wall. It is determined using the analytical Steiner-Taborek correlation. The pressure changes in fluid are computed using Friedel model.

  8. A vertical microfluidic probe.

    PubMed

    Kaigala, G V; Lovchik, R D; Drechsler, U; Delamarche, E

    2011-05-01

    Performing localized chemical events on surfaces is critical for numerous applications. We earlier invented the microfluidic probe (MFP), which circumvented the need to process samples in closed microchannels by hydrodynamically confining liquids that performed chemistries on surfaces (Juncker et al. Nat. Mater. 2005, 4, 622-628). Here we present a new and versatile probe, the vertical MFP (vMFP), which operates in the scanning mode while overcoming earlier challenges that limited the practical implementation of the MFP technology. The key component of the vMFP is the head, a microfluidic device (?1 cm(2) in area) consisting of glass and Si and having microfluidic features fabricated in-plane in the Si layer. The base configuration of the head has two micrometer-size channels that inject/aspirate liquids and terminate at the apex which is ?1 mm(2). In scanning mode, the head is oriented vertically with the apex parallel to the surface with typical spacing of 1-30 ?m. Such length scales and using flow rates from nanoliters/second to microliters/second allow chemical events to be performed on surfaces with tens of picoliter quantities of reagents. Before scanning, the head is clipped on a holder for leak-free, low dead volume interface assembly, providing a simple world-to-chip interface. Surfaces are scanned by mounting the holder on a computer-controlled stage having ?0.1 ?m resolution in positioning. We present detailed steps to fabricate vMFP heads having channels with dimensions from 1 ?m × 1 ?m to 50 ?m × 50 ?m for liquid localization over areas of 10-10,000 ?m(2). Additionally, advanced design strategies are described to achieve high yield in fabrication and to support a broad range of applications. These include particulate filters, redundant aperture architectures, inclined flow-paths that service apertures, and multiple channels to enable symmetric flow confinement. We also present a method to characterize flow confinement and estimate the distance between the head and the surface by monitoring the evolution of a solution of fluorescently labeled antibody on an activated glass surface. This flow characterization reveals regimes of operation suitable for different surface topographies. We further integrate the dispensing of immersion liquid to the vMFP head for processing surfaces for extended periods of time (?60 min). The versatility of the vMFP is exemplified by patterning fluorescently labeled proteins, inactivation of cells using sodium hypochlorite, and staining living NIH fibroblasts with Cellomics. These applications are enabled by the compact design of the head, which provides easy access to the surface, simplifies alignment, and enables processing surfaces having dimensions from the micrometer to the centimeter scale and with large topographical variations. We therefore believe that ease-of-operation, reconfigurability, and conservative use of chemicals by the vMFP will lead to its widespread use by microtechnologists and the chemical and biomedical communities. PMID:21476506

  9. Vertical axis wind turbine airfoil

    DOEpatents

    Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich

    2012-12-18

    A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.

  10. Horizontal Inequity and Vertical Redistribution

    Microsoft Academic Search

    Peter J. Lambert; Xavier Ramos

    1997-01-01

    Inequality of post-tax income among pre-tax equals is evaluated andaggregated to form a global index of horizontal inequity in the income tax.The vertical action of the tax is captured by its inequality effect on averagebetween groups of pre-tax equals. Putting the two together, horizontalinequity measures loss of vertical performance. The identification problem,which has previously been thought insuperable, is addressed by

  11. Thermal stratification in intermittently heated heavyweight buildings (Churches)

    Microsoft Academic Search

    C. R. Bemrose; I. E. Smith

    1992-01-01

    Vertical temperature gradients have been monitored hourly during the winter heating period in two mediaeval churches with typical usage once or twice per week. Little stratification was found except during periods of solar gain, and temperature inversion often occurred because of heat loss through uninsulated roofs. Correlations between vertical temperature gradient and ambient temperature have shown the effect of roof

  12. Heat transfer of high thermal energy storage with heat exchanger for solar trough power plant

    Microsoft Academic Search

    Sarayooth Vaivudh; Wattanapong Rakwichian; Sirinuch Chindaruksa

    2008-01-01

    High temperature thermal energy storage was studied by a lab-scale cylindrical storage tank experiment. A heat exchanger of thermal energy storage is used for separating two fluids, storage medium, and heat transfer fluid (HTF). There are two types of pipe in the heat exchanger, a vertical straight pipe and a helical coiled pipe. The experimental results were validated with the

  13. Vertical Slot Convection: A linear study

    SciTech Connect

    McAllister, A. (Tokyo Univ. (Japan)); Steinolfson, R. (Southwest Research Inst., San Antonio, TX (United States)); Tajima, T. (Texas Univ., Austin, TX (United States). Inst. for Fusion Studies)

    1992-11-01

    The linear stability properties of fluid convection in a vertical slot were studied. We use a Fourier-Chebychev decomposition was used to set up the linear eigenvalue problems for the Vertical Slot Convection and Benard problems. The eigenvalues, neutral stability curves, and critical point values of the Grashof number, G, and the wavenumber were determined. Plots of the real and imaginary parts of the eigenvalues as functions of G and [alpha] are given for a wide range of the Prandtl number, Pr, and special note is made of the complex mode that becomes linearly unstable above Pr [approximately] 12.5. A discussion comparing different special cases facilitates the physical understanding of the VSC equations, especially the interaction of the shear-flow and buoyancy induced physics. Making use of the real and imaginary eigenvalues and the phase properties of the eigenmodes, the eigenmodes were characterized. One finds that the mode structure becomes progressively simpler with increasing Pr, with the greatest complexity in the mid ranges where the terms in the heat equation are of roughly the same size.

  14. Vertical Slot Convection: A linear study

    SciTech Connect

    McAllister, A. [Tokyo Univ. (Japan); Steinolfson, R. [Southwest Research Inst., San Antonio, TX (United States); Tajima, T. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies

    1992-11-01

    The linear stability properties of fluid convection in a vertical slot were studied. We use a Fourier-Chebychev decomposition was used to set up the linear eigenvalue problems for the Vertical Slot Convection and Benard problems. The eigenvalues, neutral stability curves, and critical point values of the Grashof number, G, and the wavenumber were determined. Plots of the real and imaginary parts of the eigenvalues as functions of G and {alpha} are given for a wide range of the Prandtl number, Pr, and special note is made of the complex mode that becomes linearly unstable above Pr {approximately} 12.5. A discussion comparing different special cases facilitates the physical understanding of the VSC equations, especially the interaction of the shear-flow and buoyancy induced physics. Making use of the real and imaginary eigenvalues and the phase properties of the eigenmodes, the eigenmodes were characterized. One finds that the mode structure becomes progressively simpler with increasing Pr, with the greatest complexity in the mid ranges where the terms in the heat equation are of roughly the same size.

  15. Convective flows in enclosures with vertical temperature or concentration gradients

    NASA Technical Reports Server (NTRS)

    Wang, L. W.; Chai, A. T.; Sun, D. J.

    1989-01-01

    The transport process in the fluid phase during the growth of a crystal has a profound influence on the structure and quality of the solid phase. In vertical growth techniques the fluid phase is often subjected to vertical temperature and concentration gradients. The main objective is to obtain more experimental data on convective flows in enclosures with vertical temperature or concentration gradients. Among actual crystal systems the parameters vary widely. The parametric ranges studied for mass transfer are mainly dictated by the electrochemical system employed to impose concentration gradients. Temperature or concentration difference are maintained between two horizontal end walls. The other walls are kept insulated. Experimental measurements and observations were made of the heat transfer or mass transfer, flow patterns, and the mean and fluctuating temperature distribution. The method used to visualize the flow pattern in the thermal cases is an electrochemical pH-indicator method. Laser shadowgraphs are employed to visualize flow patterns in the solutal cases.

  16. Convective flows in enclosures with vertical temperature or concentration gradients

    NASA Technical Reports Server (NTRS)

    Wang, L. W.; Chai, A. T.; Sun, D. J.

    1988-01-01

    The transport process in the fluid phase during the growth of a crystal has a profound influence on the structure and quality of the solid phase. In vertical growth techniques the fluid phase is often subjected to vertical temperature and concentration gradients. The main objective is to obtain more experimental data on convective flows in enclosures with vertical temperature or concentration gradients. Among actual crystal systems the parameters vary widely. The parametric ranges studied for mass transfer are mainly dictated by the electrochemical system employed to impose concentration gradients. Temperature or concentration difference are maintained between two horizontal end walls. The other walls are kept insulated. Experimental measurements and observations were made of the heat transfer or mass transfer, flow patterns, and the mean and fluctuating temperature distribution. The method used to visualize the flow pattern in the thermal cases is an electrochemical pH-indicator method. Laser shadowgraphs are employed to visualize flow patterns in the solutal cases.

  17. Conduction-radiation effects on periodic magnetohydrodynamic natural convection boundary layer flow along a vertical surface

    Microsoft Academic Search

    Sadia Siddiqa; M. A. Hossain; Rama Subba Reddy Gorla

    The problem of magnetohydrodynamic natural convection periodic boundary layer flow of an electrically conducting and optically dense gray viscous fluid along a heated vertical plate is analyzed. Here, magnetic field is considered in the transverse direction and taken as a sinusoidal function of x¯. In the analysis radiative heat flux is examined by assuming optically thick radiation limit. Attempt is

  18. Vertical saccades in dyslexic children.

    PubMed

    Tiadi, Aimé; Seassau, Magali; Bui-Quoc, Emmanuel; Gerard, Christophe-Loïc; Bucci, Maria Pia

    2014-11-01

    Vertical saccades have never been studied in dyslexic children. We examined vertical visually guided saccades in fifty-six dyslexic children (mean age: 10.5±2.56 years old) and fifty-six age matched non dyslexic children (mean age: 10.3±1.74 years old). Binocular eye movements were recorded using an infrared video-oculography system (mobileEBT®, e(ye)BRAIN). Dyslexic children showed significantly longer latency than the non dyslexic group, also the occurrence of anticipatory and express saccades was more important in dyslexic than in non dyslexic children. The gain and the mean velocity values were significantly smaller in dyslexic than in non dyslexic children. Finally, the up-down asymmetry reported in normal population for the gain and the velocity of vertical saccades was observed in dyslexic children and interestingly, dyslexic children also reported an up-down asymmetry for the mean latency. Taken together all these findings suggested impairment in cortical areas responsible of vertical saccades performance and also at peripheral level of the extra-ocular oblique muscles; moreover, a visuo-attentionnal bias could explain the up-down asymmetry reported for the vertical saccade triggering. PMID:25151607

  19. Natural convection between a vertical cylinder and a surrounding array

    SciTech Connect

    McEligot, D.M.; O`Brien, J.E.; Stoots, C.M.; Larson, T.K.; Christenson, W.A.; Mecham, D.C.; Lussie, W.G.

    1992-09-01

    The generic situation considered is natural convection between a single heated, vertical cylinder and a surrounding array of cooler vertical cylinders in a triangular pattern. The ratio of the test section temperature to the cooling tube temperature was varied up to 2.6 by adjusting the electrical power. The Rayleigh number, based on test section diameter and air properties evaluated at cooling tube temperature, ranged from 2.9 x 10{sup 4} to 4.6 x 10{sup 5}. Results indicate that the convective heat transfer data could be approximated as Nu{sub D} (T{sub ts}/T{sub ct}){sup 0.14} = 0.156 Ra{sub D}{sup 1/3} in the apparent turbulent region for Ra{sub L} > 1.2 x 10{sup 11.}

  20. Natural convection between a vertical cylinder and a surrounding array

    SciTech Connect

    McEligot, D.M.; O'Brien, J.E.; Stoots, C.M.; Larson, T.K.; Christenson, W.A.; Mecham, D.C.; Lussie, W.G.

    1992-01-01

    The generic situation considered is natural convection between a single heated, vertical cylinder and a surrounding array of cooler vertical cylinders in a triangular pattern. The ratio of the test section temperature to the cooling tube temperature was varied up to 2.6 by adjusting the electrical power. The Rayleigh number, based on test section diameter and air properties evaluated at cooling tube temperature, ranged from 2.9 x 10{sup 4} to 4.6 x 10{sup 5}. Results indicate that the convective heat transfer data could be approximated as Nu{sub D} (T{sub ts}/T{sub ct}){sup 0.14} = 0.156 Ra{sub D}{sup 1/3} in the apparent turbulent region for Ra{sub L} > 1.2 x 10{sup 11.}

  1. Vertical and Interfacial Transport in Wetlands (Invited)

    NASA Astrophysics Data System (ADS)

    Variano, E. A.

    2010-12-01

    The objective of this work is to understand the fluxes connecting the water column, substrate, and atmosphere in wetland environments. To do this, analytical, numerical, and laboratory models have been used to quantify the hydrodynamic contributions to vertical fluxes. A key question is whether the hydrodynamic transport can be modeled as a diffusivity, and, if so, what the vertical structure of this diffusivity is. This question will be addressed in a number of flow types and for a number of fluxes. The fluxes of interest are heat, sediment, dissolved gases (such as methane and oxygen) and other dissolved solutes (such as nutrients and pollutants). The flows of interest include: unidirectional current, reversing flow (under waves, seiches, and tides), wind-sheared surface flows, and thermal convection. Rain and bioturbation can be important, but are not considered in the modeling work discussed herein. Specifically, we will present results on gas transport at wind-sheared free surface, sediment transport in unidirectional flow, and heat transfer in an oscillating flow cause by a seiche. All three of these will be used to consider the question of appropriate analytical models for vertical transport. The analytic models considered here are all 1D models that assume homogeneity in the horizontal plane. The numerical models use finite element methods and resolve the flow around individual vegetation stems in an idealized geometry. Laboratory models discussed herein also use an idealized geometry. Vegetation is represented by an array of cylinders, whose geometry is modeled after Scirpus spp. wetlands in Northern California. The laboratory model is constructed in a way that allows optical access to the flow, even in dense vegetation and far from boundaries. This is accomplished by using fluoropolymer plastics to construct vegetation models. The optical access allows us to employ particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) to measure the velocity and scalar fields, respectively. To study sediment transport, an additional step is needed. Idealized sediment grains are manufactured, again using fluoropolymers. This allows the sediment and fluid phase to be resolved simultaneously, and the velocities of each to be determined independently of the other. The use of fluoropolymers means that the laboratory imaging techniques do not suffer from blockage during laser light delivery or during image capture by digital cameras. Cameras are paired and run in stereoscopic mode to allow three-dimensional velocities to be determined. This is important given the 3D nature of flow through vegetation. Current results from ongoing laboratory, field, and modeling efforts will be discussed, as well as the upcoming steps.

  2. Free convection over a vertical porous plate with transpiration

    NASA Technical Reports Server (NTRS)

    Parikh, P. G.; Moffat, R. J.; Kays, W. M.; Bershader, D.

    1974-01-01

    The problem of free convection over an isothermal vertical porous plate with transpiration is studied both numerically and experimentally. Numerical solutions to the variable-property transpired free-convection boundary layer equations have been obtained using the finite difference procedure of Patankar and Spalding (1967). The effects of uniform transpiration on heat transfer and on temperature and velocity profiles are predicted. Interferometrically measured nondimensional temperature profiles for the uniform wall temperature and transpiration case agreed closely with these numerical predictions.

  3. Vertical feed stick wood fuel burning furnace system

    DOEpatents

    Hill, Richard C. (Orono, ME)

    1982-01-01

    A stove or furnace for efficient combustion of wood fuel includes a vertical feed combustion chamber (15) for receiving and supporting wood fuel in a vertical attitude or stack. A major upper portion of the combustion chamber column comprises a water jacket (14) for coupling to a source of water or heat transfer fluid for convection circulation of the fluid. The locus (31) of wood fuel combustion is thereby confined to the refractory base of the combustion chamber. A flue gas propagation delay channel (34) extending laterally from the base of the chamber affords delayed travel time in a high temperature refractory environment sufficient to assure substantially complete combustion of the gaseous products of wood burning with forced air prior to extraction of heat in heat exchanger (16). Induced draft draws the fuel gas and air mixture laterally through the combustion chamber and refractory high temperature zone to the heat exchanger and flue. Also included are active sources of forced air and induced draft, multiple circuit couplings for the recovered heat, and construction features in the refractory material substructure and metal component superstructure.

  4. Measurements of vertical bar Vcb vertical bar and vertical bar Vub vertical bar at BaBar

    SciTech Connect

    Rotondo, M. [Dipartimento di Fisica Galileo Galilei, Via Marzolo 8, Padova 35131 (Italy)

    2005-10-12

    We report results from the BABAR Collaboration on the semileptonic B decays, highlighting the measurements of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix elements Vub and Vcb. We describe the techniques used to obtain the matrix element |Vcb| using the measurement of the inclusive B {yields} Xclv process and a large sample of exclusive B {yields} D*lv decays. The vertical bar Vub vertical bar matrix elements has been measured studying different kinematic variables of the B {yields} Xulv process, and also with the exclusive reconstruction of B {yields} {pi}({rho})lv decays.

  5. Vertical motion simulator familiarization guide

    NASA Technical Reports Server (NTRS)

    Danek, George L.

    1993-01-01

    The Vertical Motion Simulator Familiarization Guide provides a synoptic description of the Vertical Motion Simulator (VMS) and descriptions of the various simulation components and systems. The intended audience is the community of scientists and engineers who employ the VMS for research and development. The concept of a research simulator system is introduced and the building block nature of the VMS is emphasized. Individual sections describe all the hardware elements in terms of general properties and capabilities. Also included are an example of a typical VMS simulation which graphically illustrates the composition of the system and shows the signal flow among the elements and a glossary of specialized terms, abbreviations, and acronyms.

  6. Convection in vertical Bridgman configurations

    NASA Technical Reports Server (NTRS)

    Narayanan, Ranga

    1991-01-01

    We are interested in tracing the convective profiles of vertical Bridgman growth in two configurations, the pure Rayleigh convective mode and the combined Rayleigh-Marangoni mode. In order to do so, we conducted a numerical investigation that involved a finite volume calculation. The governing equations were integrated about a cell volume, using the Gauss Theorem and the volume variables like temperature and velocity were related to the surface variables. In order to solve for the pressure field, we employed the continuity equation and the residuals resulted in a Poisson equation. Results and comments for the Rayleigh and Marangoni problems in a vertical cylinder or Bridgman configuration are given.

  7. Fast reactor power plant design having heat pipe heat exchanger

    DOEpatents

    Huebotter, P.R.; McLennan, G.A.

    1984-08-30

    The invention relates to a pool-type fission reactor power plant design having a reactor vessel containing a primary coolant (such as liquid sodium), and a steam expansion device powered by a pressurized water/steam coolant system. Heat pipe means are disposed between the primary and water coolants to complete the heat transfer therebetween. The heat pipes are vertically oriented, penetrating the reactor deck and being directly submerged in the primary coolant. A U-tube or line passes through each heat pipe, extended over most of the length of the heat pipe and having its walls spaced from but closely proximate to and generally facing the surrounding walls of the heat pipe. The water/steam coolant loop includes each U-tube and the steam expansion device. A heat transfer medium (such as mercury) fills each of the heat pipes. The thermal energy from the primary coolant is transferred to the water coolant by isothermal evaporation-condensation of the heat transfer medium between the heat pipe and U-tube walls, the heat transfer medium moving within the heat pipe primarily transversely between these walls.

  8. Fast reactor power plant design having heat pipe heat exchanger

    DOEpatents

    Huebotter, Paul R. (Western Springs, IL); McLennan, George A. (Downers Grove, IL)

    1985-01-01

    The invention relates to a pool-type fission reactor power plant design having a reactor vessel containing a primary coolant (such as liquid sodium), and a steam expansion device powered by a pressurized water/steam coolant system. Heat pipe means are disposed between the primary and water coolants to complete the heat transfer therebetween. The heat pipes are vertically oriented, penetrating the reactor deck and being directly submerged in the primary coolant. A U-tube or line passes through each heat pipe, extended over most of the length of the heat pipe and having its walls spaced from but closely proximate to and generally facing the surrounding walls of the heat pipe. The water/steam coolant loop includes each U-tube and the steam expansion device. A heat transfer medium (such as mercury) fills each of the heat pipes. The thermal energy from the primary coolant is transferred to the water coolant by isothermal evaporation-condensation of the heat transfer medium between the heat pipe and U-tube walls, the heat transfer medium moving within the heat pipe primarily transversely between these walls.

  9. Recent Progress with Vertical Transistors

    Microsoft Academic Search

    Lothar Risch; Thomas Aeugle; Wolfgang Rosner

    1997-01-01

    Vertical MOS transistors are a promising approach for channel lengths in the range of 100 to 25nm without the need for extreme fine line lithography. These devices provide high satura­ tion currents due to the short channel length and small lateral size due to the 3D-geometry. The channel is defined by epitaxy which can be grown with very good layer

  10. Quantum well vertical cavity laser

    SciTech Connect

    Huang, R.F.; Jewell, J.L.; McCall, S.L. Jr.; Tai, K.

    1991-03-12

    This patent describes an apparatus which comprises: quantum well laser vertical cavity structure for lasing in a direction non-parallel to the major dimensions of a quantum well, such laser consisting essentially of an active element containing one or two quantum wells and a cavity dependent upon reflectance as between two distributed feedback mirrors.

  11. Equilibrium structures in vertical oligopoly

    Microsoft Academic Search

    Masahiro Abiru; Babu Nahata; Subhashis Raychaudhuri; Michael Waterson

    1998-01-01

    The central purpose of this paper is to examine vertical integration as an equilibrium phenomenon. We model it as integration between Cournot oligopolists in both the upstream and the downstream stages. We consider the issue of private profitability versus collective profitability and show that under several situations the equilibrium outcomes may result in a Prisoner's dilemma. The analysis is extended

  12. Graphene vertical hot-electron terahertz detectors

    SciTech Connect

    Ryzhii, V., E-mail: v-ryzhii@riec.tohoku.ac.jp [Research Institute for Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Center for Photonics and Infrared Engineering, Bauman Moscow State Technical University and Institute of Ultra High Frequency Semiconductor Electronics, Russian Academy of Sciences, Moscow 111005 (Russian Federation); Satou, A.; Otsuji, T. [Research Institute for Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Ryzhii, M. [Department of Computer Science and Engineering, University of Aizu, Aizu-Wakamatsu 965-8580 (Japan); Mitin, V. [Department of Electrical Engineering, University at Buffalo, Buffalo, New York 1460-1920 (United States); Shur, M. S. [Departments of Electrical, Electronics, and Systems Engineering and Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2014-09-21

    We propose and analyze the concept of the vertical hot-electron terahertz (THz) graphene-layer detectors (GLDs) based on the double-GL and multiple-GL structures with the barrier layers made of materials with a moderate conduction band off-set (such as tungsten disulfide and related materials). The operation of these detectors is enabled by the thermionic emissions from the GLs enhanced by the electrons heated by incoming THz radiation. Hence, these detectors are the hot-electron bolometric detectors. The electron heating is primarily associated with the intraband absorption (the Drude absorption). In the frame of the developed model, we calculate the responsivity and detectivity as functions of the photon energy, GL doping, and the applied voltage for the GLDs with different number of GLs. The detectors based on the cascade multiple-GL structures can exhibit a substantial photoelectric gain resulting in the elevated responsivity and detectivity. The advantages of the THz detectors under consideration are associated with their high sensitivity to the normal incident radiation and efficient operation at room temperature at the low end of the THz frequency range. Such GLDs with a metal grating, supporting the excitation of plasma oscillations in the GL-structures by the incident THz radiation, can exhibit a strong resonant response at the frequencies of several THz (in the range, where the operation of the conventional detectors based on A{sub 3}B{sub 5} materials, in particular, THz quantum-well detectors, is hindered due to a strong optical phonon radiation absorption in such materials). We also evaluate the characteristics of GLDs in the mid- and far-infrared ranges where the electron heating is due to the interband absorption in GLs.

  13. Graphene vertical hot-electron terahertz detectors

    NASA Astrophysics Data System (ADS)

    Ryzhii, V.; Satou, A.; Otsuji, T.; Ryzhii, M.; Mitin, V.; Shur, M. S.

    2014-09-01

    We propose and analyze the concept of the vertical hot-electron terahertz (THz) graphene-layer detectors (GLDs) based on the double-GL and multiple-GL structures with the barrier layers made of materials with a moderate conduction band off-set (such as tungsten disulfide and related materials). The operation of these detectors is enabled by the thermionic emissions from the GLs enhanced by the electrons heated by incoming THz radiation. Hence, these detectors are the hot-electron bolometric detectors. The electron heating is primarily associated with the intraband absorption (the Drude absorption). In the frame of the developed model, we calculate the responsivity and detectivity as functions of the photon energy, GL doping, and the applied voltage for the GLDs with different number of GLs. The detectors based on the cascade multiple-GL structures can exhibit a substantial photoelectric gain resulting in the elevated responsivity and detectivity. The advantages of the THz detectors under consideration are associated with their high sensitivity to the normal incident radiation and efficient operation at room temperature at the low end of the THz frequency range. Such GLDs with a metal grating, supporting the excitation of plasma oscillations in the GL-structures by the incident THz radiation, can exhibit a strong resonant response at the frequencies of several THz (in the range, where the operation of the conventional detectors based on A3B5 materials, in particular, THz quantum-well detectors, is hindered due to a strong optical phonon radiation absorption in such materials). We also evaluate the characteristics of GLDs in the mid- and far-infrared ranges where the electron heating is due to the interband absorption in GLs.

  14. Heat pumps

    NASA Astrophysics Data System (ADS)

    Gilli, P. V.

    1982-11-01

    Heat pumps for residential/commercial space heating and hot tap water make use of free energy of direct or indirect solar heat and save from about 40 to about 70 percent of energy if compared to a conventional heating system with the same energy basis. In addition, the electrically driven compressor heat pump is able to substitute between 40% (bivalent alternative operation) to 100% (monovalent operation) of the fuel oil of an oilfired heating furnace. For average Central European conditions, solar space heating systems with high solar coverage factor show the following sequence of increasing cost effectiveness: pure solar systems (without heat pumps); heat pump assisted solar systems; solar assisted heat pump systems; subsoil/water heat pumps; air/water heat pumps; air/air heat pumps.

  15. Film boiling on the inside of vertical tubes with upward flow of the fluid at low qualities

    E-print Network

    Dougall, R. S.

    1963-01-01

    Flow regimes, local heat transfer coefficients, and temperature distributions along the wall have been studied for film boiling inside a vertical tube with upward flow of a saturated liquid. The area of interest has been ...

  16. Capturing vertical profiles of aerosols and black carbon over the Indian Ocean using autonomous unmanned aerial vehicles

    Microsoft Academic Search

    C. E. Corrigan; G. C. Roberts; M. V. Ramana; D. Kim; V. Ramanathan

    2007-01-01

    Measurements of the vertical distribution of aerosol properties provide essential information for generating more accurate model estimates of radiative forcing and atmospheric heating rates compared with employing remotely sensed column averaged properties. A month long campaign over the Indian Ocean during March 2006 investigated the interaction of aerosol, clouds, and radiative effects. Routine vertical profiles of aerosol and water vapor

  17. Capturing vertical profiles of aerosols and black carbon over the Indian Ocean using autonomous unmanned aerial vehicles

    Microsoft Academic Search

    C. E. Corrigan; G. C. Roberts; M. V. Ramana; D. Kim; V. Ramanathan

    2008-01-01

    Measurements of the vertical distribution of aerosol properties provide essential information for generating more accurate model estimates of radiative forcing and atmospheric heating rates compared with employing remotely sensed column averaged properties. A month long campaign over the Indian Ocean during March 2006 investigated the interaction of aerosol, clouds, and radiative effects. Routine vertical profiles of aerosol and water vapor

  18. High-Rayleigh-Number Convection in a Vertical Channel M. Gibert,* H. Pabiou, F. Chilla`, and B. Castaing

    E-print Network

    Boyer, Edmond

    High-Rayleigh-Number Convection in a Vertical Channel M. Gibert,* H. Pabiou, F. Chilla`, and B between convective heat flux and temperature gradient in a vertical channel filled with water, the average of the temperature gradient. Consequently, inertial processes should control the convection, with poor influence

  19. Vertical leakage and vertically averaged vertical conductance for Karst Lakes in Florida

    Microsoft Academic Search

    L. H. Motz

    1998-01-01

    In the karst lake district in peninsular Florida in the southeastern United States, as many as 70% of the lakes lack surface outlets, and groundwater outflow is an important part of the water budgets of these lakes. For 11 karst lakes in the Central Lake District, vertical leakage from the lakes to the upper Floridan aquifer averages 0.12 to 4.27

  20. An Experimental Study of Upward and Downward Flow of Supercritical Carbon Dioxide in a Straight Pipe Heat Exchanger with Constant Wall Heat Flux

    E-print Network

    Umrigar, Eric Dara

    2014-05-01

    An experimental analysis was conducted on a single circular tube heat exchanger using supercritical carbon dioxide as the working fluid. The heat exchanger was operated in two different orientations: vertically upward and downward. The experimental...

  1. Vertically Integrated Circuits at Fermilab

    SciTech Connect

    Deptuch, Grzegorz; Demarteau, Marcel; Hoff, James; Lipton, Ronald; Shenai, Alpana; Trimpl, Marcel; Yarema, Raymond; Zimmerman, Tom; /Fermilab

    2009-01-01

    The exploration of the vertically integrated circuits, also commonly known as 3D-IC technology, for applications in radiation detection started at Fermilab in 2006. This paper examines the opportunities that vertical integration offers by looking at various 3D designs that have been completed by Fermilab. The emphasis is on opportunities that are presented by through silicon vias (TSV), wafer and circuit thinning and finally fusion bonding techniques to replace conventional bump bonding. Early work by Fermilab has led to an international consortium for the development of 3D-IC circuits for High Energy Physics. The consortium has submitted over 25 different designs for the Fermilab organized MPW run organized for the first time.

  2. Global Vertical Rates from VLBl

    NASA Technical Reports Server (NTRS)

    Ma, Chopo; MacMillan, D.; Petrov, L.

    2003-01-01

    The analysis of global VLBI observations provides vertical rates for 50 sites with formal errors less than 2 mm/yr and median formal error of 0.4 mm/yr. These sites are largely in Europe and North America with a few others in east Asia, Australia, South America and South Africa. The time interval of observations is up to 20 years. The error of the velocity reference frame is less than 0.5 mm/yr, but results from several sites with observations from more than one antenna suggest that the estimated vertical rates may have temporal variations or non-geophysical components. Comparisons with GPS rates and corresponding site position time series will be discussed.

  3. Kinematic Fitting of Detached Vertices

    SciTech Connect

    Paul Mattione

    2007-05-01

    The eg3 experiment at the Jefferson Lab CLAS detector aims to determine the existence of the $\\Xi_{5}$ pentaquarks and investigate the excited $\\Xi$ states. Specifically, the exotic $\\Xi_{5}^{--}$ pentaquark will be sought by first reconstructing the $\\Xi^{-}$ particle through its weak decays, $\\Xi^{-}\\to\\pi^{-}\\Lambda$ and $\\Lambda\\to\\pi^{-}$. A kinematic fitting routine was developed to reconstruct the detached vertices of these decays, where confidence level cuts on the fits are used to remove background events. Prior to fitting these decays, the exclusive reaction $\\gamma D\\rightarrow pp\\pi^{-}$ was studied in order to correct the track measurements and covariance matrices of the charged particles. The $\\Lambda\\rightarrow p\\pi^{-}$ and $\\Xi^{-}\\to\\pi^{-}\\Lambda$ decays were then investigated to demonstrate that the kinematic fitting routine reconstructs the decaying particles and their detached vertices correctly.

  4. Buoyancy-induced two-dimensional vertical flows in a thermally stratified environment

    Microsoft Academic Search

    Y. Jaluria; K. Himasekhar

    1983-01-01

    A numerical study of the vertical two-dimensional natural convection flow over a heated vertical surface and that in a thermal plume, the ambient medium being stably stratified due to a temperature increase with height is carried out. Employing finite difference techniques, these buoyancy-induced flows are studied at various stratification levels, ambient temperature distributions and at two Prandtl numbers, 6.7 and

  5. An experimental investigation of bubble growth and detachment in vertical upflow and downflow boiling

    Microsoft Academic Search

    G. E. Thorncroft; J. F. Klausner; R. Mei

    1998-01-01

    A visual study of vapor bubble growth and departure in vertical upflow and downflow forced convection boiling is presented. A vertical flow boiling facility was constructed with a transparent, electrically-heated test section in which the ebullition process could be observed. High-speed digital images of flow boiling phenomena were obtained, which were used to measure bubble growth, departure diameters, and lift-off

  6. NASA-Ames vertical gun

    NASA Technical Reports Server (NTRS)

    Schultz, P. H.

    1984-01-01

    A national facility, the NASA-Ames vertical gun range (AVGR) has an excellent reputation for revealing fundamental aspects of impact cratering that provide important constraints for planetary processes. The current logistics in accessing the AVGR, some of the past and ongoing experimental programs and their relevance, and the future role of this facility in planetary studies are reviewed. Publications resulting from experiments with the gun (1979 to 1984) are listed as well as the researchers and subjects studied.

  7. Vertical Structure of the Atmosphere

    NSDL National Science Digital Library

    Earth is surrounded by a protective atmosphere, composed of nitrogen, oxygen, and argon, and trace amounts of other gases, that protects Earth's surface from damaging solar radiation and plays a major role in water and energy transport. This interactive feature shows the vertical structure of the atmosphere. Viewers can see the regions of the atmosphere, some of the objects (natural and man-made) found at various altitudes, as well as the variations in air temperature and pressure with altitude.

  8. Vertical integration, collusion, and tariffs

    Microsoft Academic Search

    Pedro Mendi; Rafael Moner-Colonques; José J. Sempere-Monerris

    2011-01-01

    This article presents a link between tariff rates and industry structure in a dynamic setting. We examine the role of tariffs\\u000a on final-goods in a firm’s decision to integrate and collude in the presence of competitive imports. It is shown that, under\\u000a some conditions, the upstream firm has an incentive to engage in vertical integration to introduce profitably a wholesale

  9. Vertical Height of the Atmosphere

    NSDL National Science Digital Library

    2012-08-03

    This is a lesson about the vertical dimension of the atmosphere and includes four activities. Activity 1 Introduces concepts related to distance, including length and height and units of measurement. Students are asked to make comparisons of distances. In activity 2, students learn about the vertical profile of the atmosphere. They work with a graph and plot the heights of objects and the layers of the atmosphere: troposphere, stratosphere, mesosphere, thermosphere, and exosphere. In activity 3, students learn about other forms of visual displays using satellite imagery. They compare images of the same weather feature, a hurricane, using two different images from MODIS and CALIPSO. One image is looking down on the hurricane from space, the other looks through the hurricane to display a profile of the hurricane. Activity 4 reinforces the concept of the vertical nature of the atmosphere. Students will take a CALIPSO satellite image that shows a profile of the atmosphere and use this information to plot mountains and clouds on their own graph of the atmosphere. The recommended order for the activities is to complete the first two activities on day one, and the second two activities on day two. Each day will require approximately 1 to 1.5 hours.

  10. Turbulent natural and mixed convection along a vertical plate

    SciTech Connect

    Abu-Mulaweh, H.I.; Armaly, B.F.; Chen, T.S.; Zhao, J.Z.

    1997-07-01

    Measurements of turbulent boundary-layer air flow in natural and mixed convection adjacent to an isothermal vertical flat plate are reported. Laser-Doppler velocimeter and cold wire anemometer were used, respectively, to measure simultaneously the mean turbulent velocity and temperature distributions were measured for a temperature difference, {Delta}T, of 30 C between the heated wall and the free stream air at a fixed location x = 3 m (with a corresponding Grashof number Gr{sub x} = 8.55 x 10{sup 10}), and for a range of free stream velocities 0 m/s {le} U{sub {infinity} } {le} 0.41 m/s. The effect of small free stream velocity on the turbulent natural convection is examined. These results reveal that the introduction of small free stream velocity on turbulent natural convection flow suppresses turbulence and decreases the heat transfer rate from the heated wall.

  11. Vertical silicon nanowire arrays for gas sensing

    E-print Network

    Zhao, Hangbo

    2014-01-01

    The goal of this research was to fabricate and characterize vertically aligned silicon nanowire gas sensors. Silicon nanowires are very attractive for gas sensing applications and vertically aligned silicon nanowires are ...

  12. Vertical Integration and Technology: Theory and Evidence

    E-print Network

    Acemoglu, Daron

    We study the determinants of vertical integration. We first derive a number of predictions regarding the relationship between technology intensity and vertical integration from a simple incomplete contracts model. Then, ...

  13. Vertical feed stick wood fuel burning furnace system

    DOEpatents

    Hill, Richard C. (Orono, ME)

    1984-01-01

    A new and improved stove or furnace for efficient combustion of wood fuel including a vertical feed combustion chamber for receiving and supporting wood fuel in a vertical attitude or stack, a major upper portion of the combustion chamber column comprising a water jacket for coupling to a source of water or heat transfer fluid and for convection circulation of the fluid for confining the locus of wood fuel combustion to the bottom of the vertical gravity feed combustion chamber. A flue gas propagation delay channel extending from the laterally directed draft outlet affords delayed travel time in a high temperature environment to assure substantially complete combustion of the gaseous products of wood burning with forced air as an actively induced draft draws the fuel gas and air mixture laterally through the combustion and high temperature zone. Active sources of forced air and induced draft are included, multiple use and circuit couplings for the recovered heat, and construction features in the refractory material substructure and metal component superstructure.

  14. Carbothermic reduction with parallel heat sources

    DOEpatents

    Troup, Robert L. (Murrysville, PA); Stevenson, David T. (Washington Township, Washington County, PA)

    1984-12-04

    Disclosed are apparatus and method of carbothermic direct reduction for producing an aluminum alloy from a raw material mix including aluminum oxide, silicon oxide, and carbon wherein parallel heat sources are provided by a combustion heat source and by an electrical heat source at essentially the same position in the reactor, e.g., such as at the same horizontal level in the path of a gravity-fed moving bed in a vertical reactor. The present invention includes providing at least 79% of the heat energy required in the process by the electrical heat source.

  15. Vertical constituent transport in the mesosphere

    Microsoft Academic Search

    Darrell F. Strobel; Michael E. Summers; Richard M. Bevilacqua; Matthew T. Deland; Mark Allen

    1987-01-01

    Ground-based microwave spectroscopy measurements of mesospheric CO and H2O vertical mixing ratio profiles are used to infer vertical mixing rates in the upper mesosphere. The CO and H2O data consistently imply vertical eddy diffusion coefficients in the 70- to 85-km region of 100,000-200,000 sq cm\\/s during spring through summer at midlatidues. Although chemical acceleration of vertical transport is substantial for

  16. The Commonwealth Building: Groundbreaking history with a groundwater heat pump

    SciTech Connect

    Hatten, M.J.; Morrison, W.B.

    1995-07-01

    In 1946, following a wartime moratorium on the construction of commercial buildings, a savings and loan in Portland, Oregon, was granted the first permit to build a new commercial office building. The Equitable Building -- known today as the Commonwealth Building -- was subsequently designed and constructed, incorporating many other ``firsts`` in the architectural, mechanical, and electrical design of commercial buildings. For example, the groundwater heat pump plant, designed by J. Donald Kroeker, has become known as the first major commercial installation of a central ground-coupled heat pump in the US. In addition to being the first large commercial groundwater source heat pump installation, the Commonwealth Building was the first building designed in an architectural style that was to become the standard for many decades. The architect, Pietro Belluschi, was a nationally recognized Portland architect. The building has become something of a legend in its use of innovative building systems technology. Throughout the intervening years, the Commonwealth Building has received credit as: (1) The first building to use a central heat pump system, coupled to the earth, in the form of well water, for both heating and cooling. (2) The first building in the United States to be constructed with fixed double-paned glazing. (3) The first building to recover heat from toilet exhaust for use in pre-heating fresh air. (4) The first building to use an exterior building system composed of aluminum sheathing. (5) The first building to make significant use of cold cathode fluorescent lighting for flexibility in tenant space layout. Within the building engineering community, the central, well-coupled heat pump system in the Commonwealth Building has received the greatest acclaim. The building was recognized by the ASME as a National Historical Mechanical Engineering Landmark in 1980. The central heat pump plant has many unique features and an intriguing operational history.

  17. Intensification of heat transfer in flash film evaporators

    Microsoft Academic Search

    L. P. Pertsev; P. E. Novikov; E. P. Novikov; P. A. Kapustenko

    1992-01-01

    The horizontal arrangement of the panels in the evaporator was selected after analysis of the process of heat transfer in different sections of the heat-exchange elements of known panel-type vertical gravity film evaporators, which showed a low local heat transfer in the first upper section of the panel (because of the instability of the film flow of the solution being

  18. Pribnow, Kinoshita & Stein -1 -ODP Heat Flow Report Daniel Pribnow

    E-print Network

    associated with fluid flow and gas hydrate formation. To calculate heat flow, temperatures with depth-situ conditions. Heat flow values, calculated using the Bullard method, range from 5 mW m-2 to 13 W m-2 . Tem is essentially vertical and conductive, then heat flow can be calculated using Fourier's Law. In this case

  19. How vertical disparities assist judgements of distance

    Microsoft Academic Search

    Eli Brenner; Jeroen B. J. Smeets; Michael S. Landy

    2001-01-01

    The ratio of the vertical sizes of corresponding features in the two eyes' retinal images depends both on the associated object's distance and on its horizontal direction relative to the head (eccentricity). It is known that manipulations of vertical size ratio can affect perceived distance, size, depth and shape. We examined how observers use the vertical size ratio to determine

  20. Vertical Lift - Not Just For Terrestrial Flight

    NASA Technical Reports Server (NTRS)

    Young, Larry A

    2000-01-01

    Autonomous vertical lift vehicles hold considerable potential for supporting planetary science and exploration missions. This paper discusses several technical aspects of vertical lift planetary aerial vehicles in general, and specifically addresses technical challenges and work to date examining notional vertical lift vehicles for Mars, Titan, and Venus exploration.

  1. Modernizing Vertical Datums in the United States

    Microsoft Academic Search

    D. B. Zilkoski; D. A. Smith

    2006-01-01

    The National Geodetic Survey (NGS) defines and maintains the National Spatial Reference System (NSRS). Additionally, NGS has a definitive role in providing direct access to the NSRS. An important aspect of the NSRS is the vertical datum, to which geodetic control of elevations is referred. The current official vertical datum for the United States is the North American Vertical Datum

  2. Vertically aligned nanostructure scanning probe microscope tips

    DOEpatents

    Guillorn, Michael A.; Ilic, Bojan; Melechko, Anatoli V.; Merkulov, Vladimir I.; Lowndes, Douglas H.; Simpson, Michael L.

    2006-12-19

    Methods and apparatus are described for cantilever structures that include a vertically aligned nanostructure, especially vertically aligned carbon nanofiber scanning probe microscope tips. An apparatus includes a cantilever structure including a substrate including a cantilever body, that optionally includes a doped layer, and a vertically aligned nanostructure coupled to the cantilever body.

  3. Vertical Contracts and Mandatory Universal Distribution

    E-print Network

    Kammen, Daniel M.

    Vertical Contracts and Mandatory Universal Distribution Larry S. Karp Jeffrey M. Perloff July 2012 consumer welfare. Keywords: vertical restrictions, mandatory universal distribution, new product oligopoly or hurts consumers and society. We assume that there is a vertical industry structure, with two types

  4. Vertical nanopillars for highly localized fluorescence imaging

    E-print Network

    Cui, Yi

    Vertical nanopillars for highly localized fluorescence imaging Chong Xiea,1 , Lindsey Hansonb,1 of observation volume is required. Here, we demonstrate the use of vertically aligned silicon dioxide nanopillars along its vertical surface. This effect creates highly confined illumination volume that selectively

  5. Vertical partitioning algorithms for database design

    Microsoft Academic Search

    Shamkant B. Navathe; Stefano Ceri; Gio Wiederhold; Jinglie Dou

    1984-01-01

    This paper addresses the vertical partitioning of a set of logical records or a relation into fragments. The rationale behind vertical partitioning is to produce fragments, groups of attribute columns, that “closely match” the requirements of transactions.Vertical partitioning is applied in three contexts: a database stored on devices of a single type, a database stored in different memory levels, and

  6. Vertical leakage and vertically averaged vertical conductance for karst lakes in Florida

    Microsoft Academic Search

    L. H. Motz

    1998-01-01

    In the karst lake district in peninsular Florida in the southeastern United States, as many as 70% of the lakes lack surface outlets, and groundwater outflow is an important part of the water budgets of these lakes. For 11 karst lakes in the Central Lake District, vertical leakage from the lakes to the upper Floridan aquifer averages 0.12 to 4.27myr-1.

  7. Heat waves

    Microsoft Academic Search

    D. D. Joseph; Luigi Preziosi

    1989-01-01

    The concept of transmission of heat by waves is reviewed and interpreted. The notion of an effective thermal conductivity, an effective heat capacity, and relaxation functions for heat and energy is introduced along lines used recently to describe the elastic response of viscous liquids. An annotated bibliography of the literature on heat waves, from the beginning until now, gives a

  8. Flow reversals in a vertical channel

    NASA Astrophysics Data System (ADS)

    Tisserand, J.-C.; Creyssels, M.; Gibert, M.; Castaing, B.; Chilla, F.

    Convection is one of the most relevant heat transport mechanism and we can find it in many situations as for example geophysics or astrophysics. We study it in a vertical channel which links two chambers, the cold one at the upper end and the hot one at the lower end. In the channel, the flow is either globally ascending in the right part, and descending in the left one, or the opposite. Thus, we can see flow reversals and they can be characterized by a time ?. It is worth noticing that reversals can be found in other situations such as for example with earth magnetic field or in the recent magnetic turbulent dynamo experiment [1]. Here, we study the variation of ? with the difference of temperature ?T between the hot plate and the cold plate. For the experiments, the cell, filled with water, is constituted of a Rayleigh-Benard'fs cell with two horizontal plates : the upper is cold and the bottom one is hot. The section of the cell is 40 × 10 cm2 and its height is 40 cm. The thickness of the walls, made with PMMA, is 2 cm. Furthermore, two honeycomb structures allow to prevent convection from appearing in about 50% of the cell and, as we can see on Fig. 1, between these structures, the channel, which is the zone of interest, has a cross section of 10 × cm2 and its height is 20 cm. Besides, the temperature of the upper plate is regulated by water bath and thanks to resistors, Joule effect heats the bottom plate.

  9. Exergoeconomic analysis of a solar assisted ground-source heat pump greenhouse heating system

    Microsoft Academic Search

    Onder Ozgener; Arif Hepbasli

    2005-01-01

    EXCEM analysis may prove useful to investigators in engineering and other disciplines due to the methodology are being based on the quantities exergy, cost, energy and mass. The main objective of the present study is to investigate between capital costs and thermodynamic losses for devices in solar assisted ground-source heat pump greenhouse heating system (SAGSHPGHS) with a 50 m vertical

  10. Natural Convection Heat Transfer around Heated Cylinders Inside a Cavity with Conducting Walls

    Microsoft Academic Search

    Marcel Lacroix; Antoine Joyeux

    1995-01-01

    A numerical study has been conducted for natural convection heat transfer for air around two vertically separated horizontal heated cylinders placed inside a rectangular enclosure having finite wall conductances. The interaction between convection in the fluid-filled cavity and conduction in the walls surrounding the cavity is investigated. Results have been obtained for Rayleigh numbers Ra between 10 and 10, dimensionless

  11. Ohmic Heating in Rising Phase of Confining Field in Heliotron DR

    Microsoft Academic Search

    Shigeyuki Morimoto; Sakuji Kobayashi; Atsuo Iiyoshi; Koji Uo

    1986-01-01

    Ohmic heating which uses helical-vertical windings as a transformer was examined in Heliotron DR. This is a possible method for providing a high-density target plasma for further heating in Heliotron\\/Torsatron systems.

  12. Recent refinements and increased capabilities in balloon vertical performance analysis

    NASA Technical Reports Server (NTRS)

    Conrad, G. R.

    1993-01-01

    The NASA Thermal Trajectory analysis model for predicting the vertical performance of balloons is described in terms of two critical refinements and recent results. The model employs heat-balance equations and a vertical equation of motion, and revised methods are employed to predict maximum balloon volume, balloon shape, and the continuous computation of gas loss. Also incorporated are modeling techniques for assessing the solar radiation input that can affect the load tapes, and autoballast control algorithms are employed. The model permits the evaluation of the presence of cap layers as well as the effects of small leaks and programmed venting. The revised model is shown to give good predictions of balloon performance during flight in terms of altitude changes, descent rates, gas-mass flow, and leak potential. The model is found to be more versatile due to autoballasting and leak analysis, and good prediction are possible for the float phase and descent of current balloon shapes.

  13. Neighbourly polytopes with few vertices

    SciTech Connect

    Devyatov, Rostislav A [M. V. Lomonosov Moscow State University, Faculty of Mechanics and Mathematics, Moscow (Russian Federation)

    2011-10-31

    A family of neighbourly polytopes in R{sup 2d} with N=2d+4 vertices is constructed. All polytopes in the family have a planar Gale diagram of a special type, namely, with exactly d+3 black points in convex position. These Gale diagrams are parametrized by 3-trees (trees with a certain additional structure). For all polytopes in the family, the number of faces of dimension m containing a given vertex A depends only on d and m. Bibliography: 7 titles.

  14. Vertical-Bloch-Line Memory

    NASA Technical Reports Server (NTRS)

    Katti, Romney R.; Wu, Jiin-Chuan; Stadler, Henry L.

    1993-01-01

    Vertical-Bloch-line memory is developmental very-large-scale integrated-circuit block-access magnetic memory. Stores data in form of localized pairs of twists (VBL pairs) in magnetic field at edge of ferromagnetic domain in each stripe. Presence or absence of VBL pair at bit position denotes one or zero, respectively. Offers advantages of resistance to ionizing radiation, potential areal storage density approximately less than 1 Gb/cm squared, data rates approximately less than 1 Gb/s, and average access times of order of milliseconds. Furthermore, mass, volume, and demand for power less than other magnetic and electronic memories.

  15. ATLAS LTCS Vertically Challenged System Lessons Learned

    NASA Technical Reports Server (NTRS)

    Patel, Deepak; Garrison, Matt; Ku, Jentung

    2014-01-01

    Re-planning of LTCS TVAC testing and supporting RTA (Receiver Telescope Assembly) Test Plan and Procedure document preparation. The Laser Thermal Control System (LTCS) is designed to maintain the lasers onboard Advanced Topographic Laser Altimeter System (ATLAS) at their operational temperatures. In order to verify the functionality of the LTCS, a thermal balance test of the thermal hardware was performed. During the first cold start of the LTCS, the Loop Heat Pipe (LHP) was unable to control the laser mass simulators temperature. The control heaters were fully on and the loop temperature remained well below the desired setpoint. Thermal analysis of the loop did not show these results. This unpredicted behavior of the LTCS was brought up to a panel of LHP experts. Based on the testing and a review of all the data, there were multiple diagnostic performed in order to narrow down the cause. The prevailing theory is that gravity is causing oscillating flow within the loop, which artificially increased the control power needs. This resulted in a replan of the LTCS test flow and the addition of a GSE heater to allow vertical operation.

  16. Laser tracking for vertical control

    NASA Technical Reports Server (NTRS)

    Dunn, Peter; Torrence, Mark; Pavlis, Erricos; Kolenkiewicz, Ron; Smith, David

    1993-01-01

    The Global Laser Tracking Network has provided LAGEOS ranging data of high accuracy since the first MERIT campaign in late 1983 and we can now resolve centimeter-level three dimensional positions of participating observatories at monthly intervals. In this analysis, the station height estimates have been considered separately from the horizontal components, and can be determined by the strongest stations with a formal standard error of 2 mm using eight years of continuous observations. The rate of change in the vertical can be resolved to a few mm/year, which is at the expected level of several geophysical effects. In comparing the behavior of the stations to that predicted by recent models of post-glacial rebound, we find no correlation in this very small effect. Particular attention must be applied to data and survey quality control when measuring the vertical component, and the survey observations are critical components of the geodynamic results. Seasonal patterns are observed in the heights of most stations, and the possibility of secular motion at the level of several millimeters per year cannot be excluded. Any such motion must be considered in the interpretation of horizontal inter-site measurements, and can help to identify mechanisms which can cause variations which occur linearly with time, seasonally, or abruptly.

  17. Experimental study of two-phase water flow in vertical thin rectangular channels

    NASA Astrophysics Data System (ADS)

    Wright, Christopher T.; O'Brien, James E.; Anderson, Elgin A.

    2001-11-01

    An experimental heat transfer study of two-phase water flow in vertical thin rectangular channels with side vents is conducted. A multiple, heated channel configuration with up- and down-flow conditions is investigated. Parallel heated and unheated flow channels test the effects of cross flow on the onset of nucleate boiling (ONB) and critical heat flux (CHF). The test apparatus provides pressure and substrate temperature data and visual data of the boiling regimes and side-vent flow patterns. The objectives are to determine the two-phase, heat and mass transfer characteristics between adjacent channels as permitted by side-vent cross flow. These data will help develop ONB and CHF correlations for flow geometries typical of plate-type nuclear reactors and heat exchangers. Fundamentally, the data shows how the geometry, flow conditions, and channel configurations affect the heat transfer characteristics of interior channel flows, essential in understanding the ONB and CHF phenomena.

  18. Heating Structures Derived from Satellite

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Adler, R.; Haddad, Z.; Hou, A.; Kakar, R.; Krishnamurti, T. N.; Kummerow, C.; Lang, S.; Meneghini, R.; Olson, W.

    2004-01-01

    Rainfall is a key link in the hydrologic cycle and is a primary heat source for the atmosphere. The vertical distribution of latent-heat release, which is accompanied by rainfall, modulates the large-scale circulations of the tropics and in turn can impact midlatitude weather. This latent heat release is a consequence of phase changes between vapor, liquid, and solid water. The Tropical Rainfall Measuring Mission (TRMM), a joint U.S./Japan space project, was launched in November 1997. It provides an accurate measurement of rainfall over the global tropics which can be used to estimate the four-dimensional structure of latent heating over the global tropics. The distributions of rainfall and inferred heating can be used to advance our understanding of the global energy and water cycle. This paper describes several different algorithms for estimating latent heating using TRMM observations. The strengths and weaknesses of each algorithm as well as the heating products are also discussed. The validation of heating products will be exhibited. Finally, the application of this heating information to global circulation and climate models is presented.

  19. Meridional heat transport at the onset of winter stratospheric warming

    NASA Technical Reports Server (NTRS)

    Conte, M.

    1981-01-01

    A continuous vertical flow of energy toward high altitude was verified. This process produced a dynamic instability of the stratospheric polar vortex. A meridional heat transport ws primed toward the north, which generated a warming trend.

  20. Benchmark of CFD Simulations Using Temperatures Measured Within an Enclosed Array of Heater Rods Oriented Vertically and Horizontally

    Microsoft Academic Search

    Narayana Rao Chalasani

    2010-01-01

    Experiments and computational fluid dynamics\\/radiation heat transfer simulations of an 8x8 array of heated rods within an aluminum enclosure are performed. This configuration represents a region inside the channel of a spent boiling water reactor (BWR) fuel assembly between two consecutive spacer plates. The heater rods can be oriented horizontally or vertically to represent transport or storage conditions, respectively. The

  1. Heat exchanger for geothermal heating and cooling systems

    SciTech Connect

    Rawlings, J.P.; Partin, J.R.

    1986-03-11

    This patent describes an apparatus for achieving heat exchange between a liquid medium and the earth in a vertical borehole in the earth. This apparatus consists of: a casing adapted to be positioned in a vertical borehole in the earth, the exterior surface of the casing being in thermal contact with the earth; a cap closing the casing lower end; a dip tube of external diameter smaller than the interior diameter of the casing, the dip tube being positioned within the casing providing an annular area between the interior of the casing and the exterior of the dip tube, the bottom end of the dip tube being open and spaced above the cap; a top manifold providing a first part connected to the upper end of the casing, a second part connected to the upper end of the dip tube, the second part having a vertical vent hole therein, a third part providing means to connect an outlet conduit, and a fourth part providing means to connect a supply conduit, the first and third parts and the second and fourth parts respectively communicating with each other within the manifold. The fluid exchanges heat with the earth as it flows in the casing. The manifold provides the connection to the casing, dip tube, output conduit and supply conduit in a common vertical plane; and means to close the hole to prevent the passage of fluid therethrough.

  2. Entirely passive heat pipe apparatus capable of operating against gravity

    DOEpatents

    Koenig, Daniel R. (Santa Fe, NM)

    1982-01-01

    The disclosure is directed to an entirely passive heat pipe apparatus capable of operating against gravity for vertical distances in the order of 3 to 7 meters and more. A return conduit into which an inert gas is introduced is used to lower the specific density of the working fluid so that it may be returned a greater vertical distance from condenser to evaporator.

  3. Simplified numerical study of evaporation processes inside vertical tubes

    NASA Astrophysics Data System (ADS)

    Oc?o?, Pawe?; Nowak, Marzena; ?opata, Stanis?aw

    2014-04-01

    The paper presents a simplified numerical model of evaporation processes inside vertical tubes. In this model only the temperature fields in the fluid domain (the liquid or two-phase mixture) and solid domain (a tube wall) are determined. Therefore its performance and efficiency is high. The analytical formulas, which allow calculating the pressure drop and the distribution of heat transfer coefficient along the tube length, are used in this model. The energy equation for the fluid domain is solved with the Control Volume Method and for the solid domain with the Finite Element Method in order to determine the temperature field for the fluid and solid domains.

  4. A Vertical Diffusion Scheme to estimate the atmospheric rectifier effect

    NASA Astrophysics Data System (ADS)

    Chen, Baozhang; Chen, Jing M.; Liu, Jane; Chan, Douglas; Higuchi, Kaz; Shashkov, Alexander

    2004-02-01

    The magnitude and spatial distribution of the carbon sink in the extratropical Northern Hemisphere remain uncertain in spite of much progress made in recent decades. Vertical CO2 diffusion in the planetary boundary layer (PBL) is an integral part of atmospheric CO2 transport and is important in understanding the global CO2 distribution pattern, in particular, the rectifier effect on the distribution [Keeling et al., 1989; Denning et al., 1995]. Attempts to constrain carbon fluxes using surface measurements and inversion models are limited by large uncertainties in this effect governed by different processes. In this study, we developed a Vertical Diffusion Scheme (VDS) to investigate the vertical CO2 transport in the PBL and to evaluate CO2 vertical rectification. The VDS was driven by the net ecosystem carbon flux and the surface sensible heat flux, simulated using the Boreal Ecosystem Productivity Simulator (BEPS) and a land surface scheme. The VDS model was validated against half-hourly CO2 concentration measurements at 20 m and 40 m heights above a boreal forest, at Fraserdale (49°52'29.9''N, 81°34'12.3''W), Ontario, Canada. The amplitude and phase of the diurnal/seasonal cycles of simulated CO2 concentration during the growing season agreed closely with the measurements (linear correlation coefficient (R) equals 0.81). Simulated vertical and temporal distribution patterns of CO2 concentration were comparable to those measured at the North Carolina tower. The rectifier effect, in terms of an annual-mean vertical gradient of CO2 concentration in the atmosphere that decreases from the surface to the top of PBL, was found at Fraserdale to be about 3.56 ppmv. Positive covariance between the seasonal cycles of plant growth and PBL vertical diffusion was responsible for about 75% of the effect, and the rest was caused by covariance between their diurnal cycles. The rectifier effect exhibited strong seasonal variations, and the contribution from the diurnal cycle was mostly confined to the surface layer (less than 300 m).

  5. Critical heat flux in a locally heated liquid film driven by gas flow in a minichannel

    NASA Astrophysics Data System (ADS)

    Zaitsev, D. V.; Rodionov, D. A.; Kabov, O. A.

    2009-07-01

    The rupture of a liquid film driven by friction with a gas flow in a horizontal minichannel and the heat-exchange crisis in this film locally heated by a 1 × 1 cm source in the channel wall has been experimentally studied. A heat flux of 250 W/cm2 is achieved, which is greater by an order of magnitude than the limiting heat flux for a vertically falling liquid film with the same Reynolds number (Re l = 21). These experiments confirmed good prospects for using gas-flow-driven liquid films in cooling systems of devices with intense local heat evolution.

  6. Turbulence Spectra above a Vegetated Surface under Conditions of Sensible Heat Advection

    Microsoft Academic Search

    Raymond P. Motha; Shashi B. Verma; Norman J. Rosenberg

    1979-01-01

    Spectra of vertical and horizontal velocity, air temperature and humidity fluctuations were analyzed from measurements made over a well-watered alfalfa crop under conditions of sensible heat advection. Vertical velocity and air temperature spectra as well as cospectra of momentum, sensible heat and water vapor were found to be dependent on atmospheric thermal stratification. These spectra and cospectra were shifted toward

  7. Vertical combustor for refuse combustion

    SciTech Connect

    Chung, P.M.

    1981-06-01

    A vertical combustor for refuse-particle combustion was analyzed for waste-to-energy recovery. A one-dimensional model was constructed that consisted of fuel particles, inert solid particles, and the gaseous mixture. The gaseous mixture was divided further into six chemical species that are involved in combustion at temperatures below about 2000/sup 0/F. It was concluded that such combustors may be viable in the United States since US refuse contains large amounts of volatile matter. Combustion of the relatively small char, however, may not be cost-effective in the present combustor where the fuel residence time is on the order of 2 s for a combustor height of 20 to 30 ft. A computer solution was designed to optimize a given combustor system. A simplified version of the solution was programmed for a TI-59 programmable hand calculator for field use.

  8. Surface tension profiles in vertical soap films

    E-print Network

    N. Adami; H. Caps

    2013-10-01

    Surface tension profiles in vertical soap films are experimentally investigated. Measurements are performed introducing deformable elastic objets in the films. The shape adopted by those objects set in the film can be related to the surface tension value at a given vertical position by numerical solving of adapted elasticity equations. We show that the observed dependency of the surface tension versus the vertical position in the soap film can be reproduced by simple modeling taking into account film thickness measurements.

  9. Surface tension profiles in vertical soap films

    E-print Network

    Adami, N

    2013-01-01

    Surface tension profiles in vertical soap films are experimentally investigated. Measurements are performed introducing deformable elastic objets in the films. The shape adopted by those objects set in the film can be related to the surface tension value at a given vertical position by numerical solving of adapted elasticity equations. We show that the observed dependency of the surface tension versus the vertical position in the soap film can be reproduced by simple modeling taking into account film thickness measurements.

  10. Horizontal and Vertical R&D Cooperation

    Microsoft Academic Search

    Joachim Inkmann

    2000-01-01

    This paper introduces a second, vertically related industry into the usual one-industry oligopoly framework of cooperative R&D investment between firms operating on the same product market. R&D efforts are affected by intra- and inter-industry R&D spillovers. Horizontal and vertical R&D cooperation scenarios are compared to R&D competition. It turns out that vertical R&D cooperation is usually the only stable equilibrium

  11. Monitoring soil water content by vertical temperature variations.

    PubMed

    Bechkit, Mohamed Amine; Flageul, Sébastien; Guerin, Roger; Tabbagh, Alain

    2014-01-01

    The availability of high sensitivity temperature sensors (0.001 K sensitivity platinum resistors), which can be positioned at intervals of a few centimeters along a vertical profile in the unsaturated zone, allows short-term in situ determinations-one day or even less-of the thermal diffusivity. The development of high data storage capabilities also makes this possible over long periods and the relative variations in thermal diffusivity allow the monitoring of the variations in water content. The processing of temperature measurements recorded at different depths is achieved by solving the heat equation, using the finite elements method, with both conductive and convective heat transfers. A first set of measurements has allowed this approach to be validated. Water content variations derived from thermal diffusivity values are in excellent agreement with TDR measurements carried out on the experimental site at Boissy-le-Châtel (Seine et Marne, France). PMID:23834312

  12. Natural convection of ferrofluids in partially heated square enclosures

    NASA Astrophysics Data System (ADS)

    Selimefendigil, Fatih; Öztop, Hakan F.; Al-Salem, Khaled

    2014-12-01

    In this study, natural convection of ferrofluid in a partially heated square cavity is numerically investigated. The heater is located to the left vertical wall and the right vertical wall is kept at constant temperature lower than that of the heater. Other walls of the square enclosure are assumed to be adiabatic. Finite element method is utilized to solve the governing equations. The influence of the Rayleigh number (104?Ra?5×105), heater location (0.25H?yh?0.75H), strength of the magnetic dipole (0???2), horizontal and vertical location of the magnetic dipole (-2H?a?-0.5H, 0.2H?b?0.8H) on the fluid flow and heat transfer characteristics are investigated. It is observed that different velocity components within the square cavity are sensitive to the magnetic dipole source strength and its position. The length and size of the recirculation zones adjacent to the heater can be controlled with magnetic dipole strength. Averaged heat transfer increases with decreasing values of horizontal position of the magnetic dipole source. Averaged heat transfer value increases from middle towards both ends of the vertical wall when the vertical location of the dipole source is varied. When the heater location is changed, a symmetrical behavior in the averaged heat transfer plot is observed and the minimum value of the averaged heat transfer is attained when the heater is located at the mid of vertical wall.

  13. A Study of Heat Transfer for Two Layered Composite Inclined Plate Crotch Absorbers

    E-print Network

    Kemner, Ken

    1S-143 M. Choi Nov., 1989 A Study of Heat Transfer for Two Layered Composite Inclined Plate Crotch used in CESR. They analyzed the heat transfer problem numerically for the case of a vertically located to the inclined photon beam penetration heating. An analytical solution for heat transfer is obtained for a full

  14. Energy, Exergy and Uncertainty Analyses of the Thermal Response Test for a Ground Heat Exchanger

    E-print Network

    Al-Shayea, Naser Abdul-Rahman

    1 Energy, Exergy and Uncertainty Analyses of the Thermal Response Test for a Ground Heat Exchanger response test of a ground heat exchanger. In this study, a vertical U-shaped ground heat exchanger with 80 of the ground heat exchanger. The thermal response test was carried out four times at different thermal loads

  15. Local effects of horizontal and vertical sound fields on natural convection from a horizontal cylinder

    Microsoft Academic Search

    P. D. Richardson

    1969-01-01

    Experiments were made with a heated horizontal circular cylinder subjected to transverse horizontal and vertical standing sound fields, and supported at a velocity antinode. Shadowgraphs of the air around the cylinder are presented for sound fields having frequencies of about 710 and 1470 Hz, with closely-spaced intervals of intensity. The observations confirm the local changes in boundary layer thickness and

  16. Heat Pipes

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Phoenix Refrigeration Systems, Inc.'s heat pipe addition to the Phoenix 2000, a supermarket rooftop refrigeration/air conditioning system, resulted from the company's participation in a field test of heat pipes. Originally developed by NASA to control temperatures in space electronic systems, the heat pipe is a simple, effective, heat transfer system. It has been used successfully in candy storage facilities where it has provided significant energy savings. Additional data is expected to fully quantify the impact of the heat pipes on supermarket air conditioning systems.

  17. Heat Pipes

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Heat Pipes were originally developed by NASA and the Los Alamos Scientific Laboratory during the 1960s to dissipate excessive heat build- up in critical areas of spacecraft and maintain even temperatures of satellites. Heat pipes are tubular devices where a working fluid alternately evaporates and condenses, transferring heat from one region of the tube to another. KONA Corporation refined and applied the same technology to solve complex heating requirements of hot runner systems in injection molds. KONA Hot Runner Systems are used throughout the plastics industry for products ranging in size from tiny medical devices to large single cavity automobile bumpers and instrument panels.

  18. Performance analysis of a solar-assisted ground-source heat pump system for greenhouse heating: an experimental study

    Microsoft Academic Search

    Onder Ozgener; Arif Hepbasli

    2005-01-01

    This study investigates the performance characteristics of a solar-assisted ground-source (geothermal) heat pump system (SAGSHPS) for greenhouse heating with a 50m vertical 32mm nominal diameter U-bend ground heat-exchanger. This system was designed and installed in the Solar Energy Institute, Ege University, Izmir (568 degree days cooling, base: 22°C, 1226 degree days heating, base: 18°C), Turkey. Based upon the measurements made

  19. Preliminary analysis of heat pipe heat exchangers for heat recovery

    Microsoft Academic Search

    J. O. Amode; K. T. Feldman

    1975-01-01

    A preliminary analysis of fin tube heat pipe heat exchangers for air-to-air heat recovery was conducted. The analysis uses conventional heat exchanger design techniques and a new heat pipe design technique which includes probabilistic design of artery wick heat pipes. The heat transfer capability of the heat pipes may be matched with that of the finned tubes in order to

  20. Vertical Diffusivities of Active and Passive Tracers

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Cheng, Y.; Howard, A. M.

    2010-01-01

    The climate models that include a carbon-cycle need the vertical diffusivity of a passive tracer. Since an expression for the latter is not available, it has been common practice to identify it with that of salt. The identification is questionable since T, S are active, not passive tracers. We present the first derivation of the diffusivity of a passive tracer in terms of Ri (Richardson number) and Rq (density ratio, ratio of salinity over temperature z-gradients). The following results have emerged: (a) The passive tracer diffusivity is an algebraic function of Ri, Rq. (b) In doubly stable regimes (DS, partial derivative of T with respect to z > 0, partial derivative of S with respect to z < 0), the passive scalar diffusivity is nearly the same as that of salt/heat for any values of Rq < 0 and Ri > 0. (c) In DC regimes (diffusive convection, partial derivative of T with respect to z < 0, partial derivative of S with respect to z < 0, Rq > 1), the passive scalar diffusivity is larger than that of salt. At Ri = O(1), it can be more than twice as large. (d) In SF regimes (salt fingers, partial derivative of T with respect to z > 0, partial derivative of S with respect to z > 0, Rq < 1), the passive scalar diffusivity is smaller than that of salt. At Ri = O(1), it can be less than half of it. (e) The passive tracer diffusivity predicted at the location of NATRE (North Atlantic Tracer Release Experiment) is discussed. (f) Perhaps the most relevant conclusion is that the common identification of the tracer diffusivity with that of salt is valid only in DS regimes. In the Southern Ocean, where there is the largest CO2 absorption, the dominant regime is diffusive convection discussed in (c) above.

  1. Numerical study of the heat transfer of two fluid flow in partially heated enclosure

    NASA Astrophysics Data System (ADS)

    Ben-Cheikh, Nader; Ouertatani, Nasreddine; Ben-Beya, Brahim; Lili, Taieb; Campo, Antonio

    2011-07-01

    This investigation addresses a systematic numerical method based on the finite volume method and a full multigrid technique to study three-dimensional flow structures and heat transfer rates in partially heated 3D enclosures. The heating occurs with a central heated strip on a large vertical wall and the opposite vertical wall is cooled to a uniform low temperature. The remaining surfaces are thermally insulated. Two different fluids: one air ( Pr = 0.7) and the other water ( Pr = 6.8) are employed encompassing descriptive Rayleigh numbers Ra bounded by 103 and 107. Typical sets of streamlines and isotherms are presented to analyze the intricate circulatory flow patterns set up by the buoyancy force of the fluids. Monomial correlations are presented for the quantification of the total heat transfer in harmony with the prevalent Rayleigh numbers for the two dissimilar working fluids.

  2. Similitude modeling of natural convection heat transfer through an aperture in passive solar heated buildings

    NASA Astrophysics Data System (ADS)

    Weber, D. D.

    1980-06-01

    An experimental study of natural convection heat transfer through a doorway in a two room passive solar heated building is described. Similitude modeling was the method used to measure natural convection heat transfer coefficients (h/sub NC/) in a model geometrically scaled down by a factor of 5. Freon gas was used as the working fluid to obtain dynamic similarity within the model. A temperature difference was maintained between the two rooms by a heated vertical wall which simulated a Trombe wall in one room, and by a cooled vertical wall which simulated a thermal storage wall in the other room. Heat transfer through the doorway was measured as a function of a characteristic temperature differential and the geometry of the doorway.

  3. Influence of transducer-ground coupling on vibration measurements

    Microsoft Academic Search

    G. R. Adhikari; A. I. Theresraj; R. N. Gupta

    2005-01-01

    Various methods of transducer mounting provide varying degrees of coupling between the transducer and the measurement surface. The influence of four of these methods on vibration measurements was studied. For this purpose, the first transducer was placed freely on a horizontal surface, the second one was ‘sandbagged’, the third one was ‘spiked’ and the fourth one was completely buried in

  4. 6, 45106, 2006 Vertical profiles of

    E-print Network

    Paris-Sud XI, Université de

    to complex vertical profiles of various reactive trace gases and makes noc- turnal chemistry altitudeACPD 6, 45­106, 2006 Vertical profiles of the nocturnal chemistry of NOx and O3 S. Wang et al.atmos-chem-phys.org/acpd/6/45/ SRef-ID: 1680-7375/acpd/2006-6-45 European Geosciences Union Atmospheric Chemistry and Physics

  5. Vertical Integration, Monopoly, and the First Amendment.

    ERIC Educational Resources Information Center

    Brennan, Timothy J.

    This paper addresses the relationship between the First Amendment, monopoly of transmission media, and vertical integration of transmission and content provision. A survey of some of the incentives a profit-maximizing transmission monopolist may have with respect to content is followed by a discussion of how vertical integration affects those…

  6. Sewing string tree vertices with ghosts

    E-print Network

    L. Sandoval Jr

    2001-04-17

    It is shown how to sew string vertices with ghosts at tree level in order to produce new tree vertices using the Group Theoretic approach to String Theory. It is then verified the BRST invariance of the sewn vertex and shown that it has the correct ghost number.

  7. Downstream Competition, Foreclosure, and Vertical Integration

    E-print Network

    Paris-Sud XI, Université de

    Downstream Competition, Foreclosure, and Vertical Integration Gilles Chemla ¤ July 8, 2002 and Management Strategy 12, 2 (2003) 261-289." #12;Downstream Competition, Forclosure, and Vertical Integration Abstract This paper analyzes the impact of competition among downstream ¯rms on an upstream ¯rm's payo

  8. A Vertically Resolved Planetary Boundary Layer

    NASA Technical Reports Server (NTRS)

    Helfand, H. M.

    1984-01-01

    Increase of the vertical resolution of the GLAS Fourth Order General Circulation Model (GCM) near the Earth's surface and installation of a new package of parameterization schemes for subgrid-scale physical processes were sought so that the GLAS Model GCM will predict the resolved vertical structure of the planetary boundary layer (PBL) for all grid points.

  9. The green building envelope: vertical greening

    Microsoft Academic Search

    M. Ottelé

    2011-01-01

    Planting on roofs and façades is one of the most innovative and fastest developing fields of green technologies with respect to the built environment and horticulture. This thesis is focused on vertical greening of structures and to the multi-scale benefits of vegetation. Vertical green can improve the environment in urban areas and is becoming a key design consideration in modern

  10. Lunar and Vertical Distribution of Myctophidae

    Microsoft Academic Search

    S. Tsarin

    2002-01-01

    The Myctophidae are the most numerous of the mesopelagic fishes in all oceans. Daily vertical migrations which connected with nutrition and energy exchange, are charac- teristic feature of the myctophids behavior. Myctophidae in main during the nighttime basic feed. There are two ecological groups of Myctophidae on the type of vertical migrations. (Some scientists select the third intermediate group). Superficial

  11. Vertical shaft V-type engine

    Microsoft Academic Search

    T. Fujikawa; M. Hirata; S. Tamba

    1987-01-01

    A vertical crankshaft V-type engine is described which consists of a vertical crankshaft having an upper end, a pair of cylinders arranged horizontally forming a V with respect to each other, and each having a cylinder head; a carburetor operatively connected to the cylinders and mounted in the V defined by the cylinders. An air cleaner is operatively connected to

  12. Vertical-Cavity Surface-Emitting Lasers

    NASA Astrophysics Data System (ADS)

    Wilmsen, Carl W.; Temkin, Henryk; Coldren, Larry A.

    2002-01-01

    1. Introduction to VCSELs L. A. Coldren, C. W. Wilmsen and H. Temkin; 2. Fundamental issues in VCSEL design L. A. Coldren and Eric R. Hegblom; 3. Enhancement of spontaneous emission in microcavities E. F. Schubert and N. E. J. Hunt; 4. Epitaxy of vertical-cavity lasers R. P. Schneider Jr and Y. H. Young; 5. Fabrication and performance of vertical-cavity surface-emitting lasers Kent D. Choquette and Kent Geib; 6. Polarization related properties of vertical cavity lasers Dmitri Kuksenkov and Henryk Temkin; 7. Visible light emitting vertical cavity lasers Robert L. Thornton; 8. Long-wavelength vertical-cavity lasers Dubrakovo I. Babic, Joachim Piprek and John E. Bowers; 9. Overview of VCSEL applications Richard C. Williamson; 10. Optical interconnection applications and required characteristics Kenichi Kasahara; 11. VCSEL-based fiber-optic data communications Kenneth Hahn and Kirk Giboney; 12. VCSEL-based smart pixels for free space optoelectronic processing C. W. Wilmsen.

  13. Origami Multistabilty: From Single Vertices to Metasheets

    E-print Network

    Scott Waitukaitis; Rémi Menaut; Bryan Gin-ge Chen; Martin van Hecke

    2014-09-09

    We explore the surprisingly rich energy landscape of origami-like folding planar structures. We show that the configuration space of rigid-paneled degree-4 vertices, the simplest building blocks of such systems, consists of at least two distinct branches meeting at the flat state. This suggests that generic vertices are at least bistable, but we find that the nonlinear nature of these branches allows for vertices with as many as five distinct stable states. In vertices with collinear folds and/or symmetry, more branches emerge leading to up to six stable states. Finally, we introduce a procedure to tile arbitrary 4-vertices while preserving their stable states, thus allowing the design and creation of multistable origami metasheets.

  14. Vertical propagation of lakewide internal waves

    NASA Astrophysics Data System (ADS)

    Henderson, Stephen M.; Deemer, Bridget R.

    2012-03-01

    Internal waves with diurnal period dominated velocities measured by an Acoustic Doppler Profiler (ADP) in a small lake (main basin 3000 m by 400 m by 18 m). ADP profiles and an along-lake temperature section indicate that the observed waves, like seiches, had horizontal wavelengths exceeding the metalimnion length. However, unlike non-dissipative seiches, the observed waves propagated vertically, carrying energy to the lakebed where waves were absorbed, rather than being strongly reflected. This absorption is predicted by a standard parameterization of boundary layer dissipation. The absence of upward-propagating energy precludes seiche resonance, limits focusing of waves toward attractors, and suggests that hypolimnion dissipation was limited by the supply of downward-propagating energy. Vertical wavelengths were less than the lake depth. Simplified calculations suggest that vertically-propagating waves, as opposed to vertically standing seiches, are most likely where vertical wavelengths are short, near-bed stratification is strong, and lakes are short and deep.

  15. Heat collector

    SciTech Connect

    Nameda, N.; Nakamoto, Y.; Sekiya, H.; Surisawa, Y.

    1985-03-19

    A heat collector for a solar heat utilization system comprises a heat collecting pipe and a reflecting plate for focusing solar light on the pipe. This pipe has a first tubular portion for receiving solar light collected by the reflecting plate, and a second tubular portion for receiving direct solar light. The second portion has thermal expansion coefficient larger by a predetermined amount than that of the first portion, and thermally expands at the same rate as the first portion.

  16. Heat Transfer

    NSDL National Science Digital Library

    2014-09-18

    Students explore heat transfer and energy efficiency using the context of energy efficient houses. They gain a solid understanding of the three types of heat transfer: radiation, convection and conduction, which are explained in detail and related to the real world. They learn about the many ways solar energy is used as a renewable energy source to reduce the emission of greenhouse gasses and operating costs. Students also explore ways in which a device can capitalize on the methods of heat transfer to produce a beneficial result. They are given the tools to calculate the heat transferred between a system and its surroundings.

  17. Advanced Si solid phase crystallization for vertical channel in vertical NANDs

    NASA Astrophysics Data System (ADS)

    Lee, Sangsoo; Son, Yong-Hoon; Hwang, Kihyun; Shin, Yoo Gyun; Yoon, Euijoon

    2014-07-01

    The advanced solid phase crystallization (SPC) method using the SiGe/Si bi-layer structure is proposed to obtain high-mobility poly-Si thin-film transistors in next generation vertical NAND (VNAND) devices. During the SPC process, the top SiGe thin film acts as a selective nucleation layer to induce surface nucleation and equiaxial microstructure. Subsequently, this SiGe thin film microstructure is propagated to the underlying Si thin film by epitaxy-like growth. The initial nucleation at the SiGe surface was clearly observed by in situ transmission electron microscopy (TEM) when heating up to 600 °C. The equiaxial microstructures of both SiGe nucleation and Si channel layers were shown in the crystallized bi-layer plan-view TEM measurements. Based on these experimental results, the large-grained and less-defective Si microstructure is expected to form near the channel region of each VNAND cell transistor, which may improve the electrical characteristics.

  18. Advanced Si solid phase crystallization for vertical channel in vertical NANDs

    SciTech Connect

    Lee, Sangsoo [Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-742 (Korea, Republic of); Son, Yong-Hoon [Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-742 (Korea, Republic of); Semiconductor R and D Center, Samsung Electronics Co., Ltd., Hwasung 445-701 (Korea, Republic of); Hwang, Kihyun; Shin, Yoo Gyun [Semiconductor R and D Center, Samsung Electronics Co., Ltd., Hwasung 445-701 (Korea, Republic of); Yoon, Euijoon, E-mail: eyoon@snu.ac.kr [Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-742 (Korea, Republic of); Energy Semiconductor Research Center, Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of)

    2014-07-01

    The advanced solid phase crystallization (SPC) method using the SiGe/Si bi-layer structure is proposed to obtain high-mobility poly-Si thin-film transistors in next generation vertical NAND (VNAND) devices. During the SPC process, the top SiGe thin film acts as a selective nucleation layer to induce surface nucleation and equiaxial microstructure. Subsequently, this SiGe thin film microstructure is propagated to the underlying Si thin film by epitaxy-like growth. The initial nucleation at the SiGe surface was clearly observed by in situ transmission electron microscopy (TEM) when heating up to 600?°C. The equiaxial microstructures of both SiGe nucleation and Si channel layers were shown in the crystallized bi-layer plan-view TEM measurements. Based on these experimental results, the large-grained and less-defective Si microstructure is expected to form near the channel region of each VNAND cell transistor, which may improve the electrical characteristics.

  19. Decay HeatDecay Heat NCF structure decay heat is

    E-print Network

    Be instead of Pb in re-circulating blanket enhances TBR by ~6% and nuclear heating by ~10% Activity and decay in re-circulating blanket enhances TBR by ~6% and nuclear heating by ~10% Activity and decay heatDecay HeatDecay Heat NCF structure decay heat is much larger than Flibe decay heat for t > 1 minute

  20. Plasma current ramp-up assisted by outer vertical field coils in a high aspect ratio tokamak

    Microsoft Academic Search

    Osamu Mitarai; Ryuji Yoshino; Kenkichi Ushigusa

    2002-01-01

    Plasma current ramp-up assisted by outer vertical field coils with non-inductively driven current is studied during the ignition access phase in a high aspect ratio tokamak such as ITER-FEAT class tokamak reactor. In a tokamak without the Ohmic transformer, the pl1asma current ramp-up to 8 MA could be achieved by the vertical field with the heating\\/current drive power of 100

  1. A vertically integrated treatment of ice stream and ice shelf thermodynamics

    NASA Astrophysics Data System (ADS)

    Sergienko, O. V.

    2014-04-01

    The extremely small vertical shear in ice stream and ice shelf flow simplifies the equations, which govern their thermodynamic evolution. Complemented by the widely used shallow shelf approximation used to simplify the ice flow momentum balance, a vertically integrated formulation of heat transfer presented here reduces the dimensionality of the thermodynamic problem from three to two (plan view) dimensions and thus significantly reduces the computational cost of treating ice stream and ice shelf thermodynamics in models. For realistic conditions, errors in ice stiffness parameter, ice thickness, and speed caused by the vertically integrated treatment of heat transfer are less than 5% of magnitudes of these values compared to the standard three-dimensional thermomechanical computations. In addition, for the specific case of ice shelves with strong bottom melting, the governing equation describing evolution of the vertically integrated ice stiffness parameter is derived, which further reduces computational cost. The presented error analysis and formulations of ice stream and ice shelf thermodynamics in terms of the vertically integrated temperature allow the thermodynamic effects on ice deformation to be easily incorporated into studies that traditionally disregard them.

  2. Heat Problems.

    ERIC Educational Resources Information Center

    Connors, G. Patrick

    Heat problems and heat cramps related to jogging can be caused by fluid imbalances, medications, dietary insufficiency, vomiting or diarrhea, among other factors. If the condition keeps reoccurring, the advice of a physician should be sought. Some preventive measures that can be taken include: (1) running during the cooler hours of the day; (2)…

  3. Heat stroke.

    PubMed

    Leon, Lisa R; Bouchama, Abderrezak

    2015-03-01

    Heat stroke is a life-threatening condition clinically diagnosed as a severe elevation in body temperature with central nervous system dysfunction that often includes combativeness, delirium, seizures, and coma. Classic heat stroke primarily occurs in immunocompromised individuals during annual heat waves. Exertional heat stroke is observed in young fit individuals performing strenuous physical activity in hot or temperature environments. Long-term consequences of heat stroke are thought to be due to a systemic inflammatory response syndrome. This article provides a comprehensive review of recent advances in the identification of risk factors that predispose to heat stroke, the role of endotoxin and cytokines in mediation of multi-organ damage, the incidence of hypothermia and fever during heat stroke recovery, clinical biomarkers of organ damage severity, and protective cooling strategies. Risk factors include environmental factors, medications, drug use, compromised health status, and genetic conditions. The role of endotoxin and cytokines is discussed in the framework of research conducted over 30 years ago that requires reassessment to more clearly identify the role of these factors in the systemic inflammatory response syndrome. We challenge the notion that hypothalamic damage is responsible for thermoregulatory disturbances during heat stroke recovery and highlight recent advances in our understanding of the regulated nature of these responses. The need for more sensitive clinical biomarkers of organ damage is examined. Conventional and emerging cooling methods are discussed with reference to protection against peripheral organ damage and selective brain cooling. © 2015 American Physiological Society. Compr Physiol 5: 611-647, 2015. PMID:25880507

  4. Design and analysis of a 5-MW vertical-fluted-tube condenser for geothermal applications

    SciTech Connect

    Llewellyn, G.H.

    1982-03-01

    The design and analysis of an industtial-sized vertical-fluted-tube condenser. The condenser is used to condense superheated isobutane vapor discharged from a power turbine in a geothermal test facility operated for the US Department of Energy. The 5-MW condenser has 1150 coolant tubes in a four-pass configuration with a total heat transfer area of 725 m/sup 2/ (7800 ft/sup 2/). The unit is being tested at the Geothermal Components Test Facility in the Imperial Valley of East Mesa, California. The condenser design is based on previous experimental research work done at the Oak Ridge National Laboratory on condensing refrigerants on a wide variety of single vertical tubes. Condensing film coefficients obtained on the high-performance vertical fluted tubes in condensing refrigerants are as much as seven times greater than those obtained with vertical smooth tubes that have the same diameter and length. The overall heat transfer performance expected from the fluted tube condenser is four to five times the heat transfer obtained from the identical units employing smooth tubes. Fluted tube condensers also have other direct applications in the Ocean Thermal Energy Conversion (OTEC) program in condensing ammonia, in the petroleum industry in condensing light hydrocarbons, and in the air conditioning and refrigeration industry in condensing fluorocarbon vapors.

  5. Heating and Large Scale Dynamics of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Schnack, Dalton D.

    2000-01-01

    The effort was concentrated in the areas: coronal heating mechanism, unstructured adaptive grid algorithms, numerical modeling of magnetic reconnection in the MRX experiment: effect of toroidal magnetic field and finite pressure, effect of OHMIC heating and vertical magnetic field, effect of dynamic MESH adaption.

  6. Surface tension profiles in vertical soap films

    NASA Astrophysics Data System (ADS)

    Adami, N.; Caps, H.

    2015-01-01

    Surface tension profiles in vertical soap films are experimentally investigated. Measurements are performed by introducing deformable elastic objets in the films. The shape adopted by those objects once set in the film is related to the surface tension value at a given vertical position by numerically solving the adapted elasticity equations. We show that the observed dependency of the surface tension versus the vertical position is predicted by simple modeling that takes into account the mechanical equilibrium of the films coupled to previous thickness measurements.

  7. Surface tension profiles in vertical soap films.

    PubMed

    Adami, N; Caps, H

    2015-01-01

    Surface tension profiles in vertical soap films are experimentally investigated. Measurements are performed by introducing deformable elastic objets in the films. The shape adopted by those objects once set in the film is related to the surface tension value at a given vertical position by numerically solving the adapted elasticity equations. We show that the observed dependency of the surface tension versus the vertical position is predicted by simple modeling that takes into account the mechanical equilibrium of the films coupled to previous thickness measurements. PMID:25679708

  8. Effect of electron thermal motion on plasma heating in a magnetized inductively coupled plasma

    SciTech Connect

    Aman-ur-Rehman; Pu Yikang [Department of Engineering Physics, Tsinghua University, 100084 Beijing, China and Pakistan Institute of Engineering and Applied Sciences, P.O. Nilore Islamabad (Pakistan); Department of Engineering Physics, Tsinghua University, 100084 Beijing (China)

    2007-06-15

    Power absorbed inside the magnetized inductively coupled plasma (MICP) is calculated using three different warm MICP models and is then compared with the result of the cold MICP model. The comparison shows that in the propagating region ({omega}< vertical bar {omega}{sub e} vertical bar), under the cavity resonance conditions, warm plasma heating S{sub warm} is significantly less than the cold plasma heating S{sub cold}, unless the distance traveled by the electrons due to their thermal motion, during the effective wave period, becomes significantly less than the wavelength of the cavity wave. Furthermore, in the propagating region, when {omega}{approx_equal} vertical bar {omega}{sub e} vertical bar, there appears a valley on the plot of {eta}({omega})=S{sub warm}/S{sub cold} versus {omega} showing the negative effect of electron thermal motion on plasma heating. This valley widens and gets smoother with an increase in the plasma length. In the nonpropagating region ({omega}> vertical bar {omega}{sub e} vertical bar), the maximum value of {eta}({omega}) exists when {omega}- vertical bar {omega}{sub e} vertical bar {approx_equal}v{sub th}/{delta}, showing that, in the presence of the external magnetic field, the thermal motion of the electrons leads to a Doppler shift of the frequencies, at which collisionless heating is the dominant mode of electron heating. Furthermore, in the nonpropagating region, when {omega}{approx_equal} vertical bar {omega}{sub e} vertical bar, the skin depth of the right circularly polarized electric field decreases with magnetic field. This decrease in the skin depth results in an increase of collisionless heating under the Doppler-shifted wave particle resonant condition of {omega}- vertical bar {omega}{sub e} vertical bar {approx_equal}v{sub th}/{delta}. It is also observed that, for large plasma length, the results of all the three warm MICP models are consistent with each other.

  9. GROUND WATER PROTECTION ISSUES WITH GEOTHERMAL HEAT PUMPS

    SciTech Connect

    ALLAN,M.L.; PHILIPPACOPOULOS,A.J.

    1999-10-01

    Closed loop vertical boreholes used with geothermal heat pumps are grouted to facilitate heat transfer and prevent ground water contamination. The grout must exhibit suitable thermal conductivity as well as adequate hydraulic sealing characteristics. Permeability and infiltration tests were performed to assess the ability of cementitious grout to control vertical seepage in boreholes. It was determined that a superplasticized cement-sand grout is a more effective borehole sealant than neat cement over a range of likely operational temperatures. The feasibility of using non-destructive methods to verify bonding in heat exchangers is reviewed.

  10. A Newly Developed Long-Stroke Vertical Nano-Motion Platform with Gravity Compensator

    NASA Astrophysics Data System (ADS)

    Takahashi, Motohiro; Yoshioka, Hayato; Shinno, Hidenori

    Demands for three-dimensional nano-positioning are increasing in a wide range of industries. In order to meet such demands, it is necessary to realize a stable long-stroke vertical nano-motion. In long-stroke vertical motion control, the minimization of gravity load is one of the most important issues. In addition, it is important to minimize error factor from nonlinear phenomenon such as friction, vibration and heat transfer. In general, however, it is difficult to support gravity load of the moving part and to ensure that the vertical motion platform is free from such error factors which may occur during its nano-positioning. In this study, therefore, a novel vertical motion platform with a noncontact counterbalancing mechanism is developed for achieving long-stroke vertical nano-motion. The developed platform is characterized by a noncontact drive with a voice coil motor, by levitation with aerostatic guideways, by a counterbalance with noncontact vacuum cylinders, by an overall structure made of ceramics and by a symmetrical structural configuration. The positioning performance of the developed platform is evaluated through a series of vertical positioning experiments. The experimental results demonstrate that the developed platform has a superior positioning performance.

  11. On the vertical thermal structure of Io's atmosphere

    NASA Technical Reports Server (NTRS)

    Strobel, Darrell F.; Zhu, Xun; Summers, Michael F.

    1994-01-01

    A radiative-thermal conduction model for the vertical thermal structure of Io's atmosphere is developed with solar heating by SO2 absorption in UV and near-IR bands and non-local thermodynamic equilibrium (LTE) cooling by SO2 nu(sub 1), nu(sub 2), nu(sub 3), vibrational bands and rotational lines. The model predicts the existence of a mesopause in Io's atmosphere when the surface pressure exceeds approximately 10 nbar. The radiative time constant for establishing a mesosphere/mesopause on Io is only approximately 20 min, whereas the thermospheric radiative time constant is about 1 hr. These time constants are significantly shorter than the diurnal time scale and competitive with dynamic time scales. In the thermosphere when solar UV heating dominates, the asymptotic thermospheric temperature is approximately 270 K, only 140 K greater than the surface temperature because at high altiudes non-LTE cooling by SO2 rotation lines exceeds cooling in the nu(sub 2) virbrational band. Solar-heating-only modles are incapable of generating warm enough atmospheres to satisfy the observational inferences from UV and especially millimeter-wave meausrements. Joule heating driven by the penetration of Jupiter's corotational electric field into Io's conducting ionosphere is demonstrated to be the dominant heating mechanism in the subnanobar regions of Io's atmosphere with tempertures ranging from 150 to 1000 K as a function of decreasing pressure from 1 to 0.1 nbar, The asymoptotic thermospheric temperature can attain a value as high as 1800 K.

  12. Subsurface imaging with reverse vertical seismic profiles

    E-print Network

    Krasovec, Mary L. (Mary Lee), 1972-

    2001-01-01

    This thesis presents imaging results from a 3D reverse vertical seismic profile (RVSP) dataset measured at a hydrocarbon bearing pinnacle reef in northern Michigan. The study presented many challenges in seismic data ...

  13. 23. INCLINED END POST / VERTICAL / DIAGONAL / PORTAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. INCLINED END POST / VERTICAL / DIAGONAL / PORTAL BRACING DETAIL. VIEW TO SOUTHEAST. - Abraham Lincoln Memorial Bridge, Spanning Missouri River on Highway 30 between Nebraska & Iowa, Blair, Washington County, NE

  14. 30. BEARING SHOE / VERTICAL / DIAGONAL / UPPER AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    30. BEARING SHOE / VERTICAL / DIAGONAL / UPPER AND LOWER CHORD DETAIL OF DECK TRUSS. VIEW TO NORTHEAST. - Abraham Lincoln Memorial Bridge, Spanning Missouri River on Highway 30 between Nebraska & Iowa, Blair, Washington County, NE

  15. Continuous Growth of Vertically Aligned Carbon Nanotubes

    E-print Network

    Guzman de Villoria, R.

    Vertically aligned carbon nanotubes (VACNTs), sometimes called forests or carpets, are a promising material due to their unique physical and scale-dependent physical properties [1-3]. Continuous production of VACNTs is ...

  16. Vertical Axis Wind Turbine Foundation parameter study

    SciTech Connect

    Lodde, P.F.

    1980-07-01

    The dynamic failure criterion governing the dimensions of prototype Vertical Axis Wind Turbine Foundations is treated as a variable parameter. The resulting change in foundation dimensions and costs is examined.

  17. Vertical Glider Robots for Subsea Equipment Delivery

    E-print Network

    Reed, Brooks L.

    2011-01-01

    We have developed an underwater vehicle that offers significant performance improvements over existing sub sea elevators. Our Vertical Glider Robot falls under its own weight to a precise location on the seafloor, employing ...

  18. 47 CFR 73.160 - Vertical plane radiation characteristics, f(?).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 false Vertical plane radiation characteristics, f(θ...Broadcast Stations § 73.160 Vertical plane radiation characteristics, f(?). (a) The vertical plane radiation characteristics show the...

  19. 47 CFR 73.160 - Vertical plane radiation characteristics, f(?).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Vertical plane radiation characteristics, f(θ...Broadcast Stations § 73.160 Vertical plane radiation characteristics, f(?). (a) The vertical plane radiation characteristics show the...

  20. 47 CFR 73.160 - Vertical plane radiation characteristics, f(?).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Vertical plane radiation characteristics, f(θ...Broadcast Stations § 73.160 Vertical plane radiation characteristics, f(?). (a) The vertical plane radiation characteristics show the...

  1. 47 CFR 73.160 - Vertical plane radiation characteristics, f(?).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Vertical plane radiation characteristics, f(θ...Broadcast Stations § 73.160 Vertical plane radiation characteristics, f(?). (a) The vertical plane radiation characteristics show the...

  2. 47 CFR 73.160 - Vertical plane radiation characteristics, f(?).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Vertical plane radiation characteristics, f(θ...Broadcast Stations § 73.160 Vertical plane radiation characteristics, f(?). (a) The vertical plane radiation characteristics show the...

  3. Heat collector

    DOEpatents

    Merrigan, M.A.

    1981-06-29

    A heat collector and method suitable for efficiently and cheaply collecting solar and other thermal energy are provided. The collector employs a heat pipe in a gravity-assist mode and is not evacuated. The collector has many advantages, some of which include ease of assembly, reduced structural stresses on the heat pipe enclosure, and a low total materials cost requirement. Natural convective forces drive the collector, which after startup operates entirely passively due in part to differences in molecular weights of gaseous components within the collector.

  4. Heat collector

    DOEpatents

    Merrigan, Michael A. (Santa Cruz, NM)

    1984-01-01

    A heat collector and method suitable for efficiently and cheaply collecting solar and other thermal energy are provided. The collector employs a heat pipe in a gravity-assist mode and is not evacuated. The collector has many advantages, some of which include ease of assembly, reduced structural stresses on the heat pipe enclosure, and a low total materials cost requirement. Natural convective forces drive the collector, which after startup operates entirely passively due in part to differences in molecular weights of gaseous components within the collector.

  5. Nanofluid impingement jet heat transfer

    PubMed Central

    2012-01-01

    Experimental investigation to study the heat transfer between a vertical round alumina-water nanofluid jet and a horizontal circular round surface is carried out. Different jet flow rates, jet nozzle diameters, various circular disk diameters and three nanoparticles concentrations (0, 6.6 and 10%, respectively) are used. The experimental results indicate that using nanofluid as a heat transfer carrier can enhance the heat transfer process. For the same Reynolds number, the experimental data show an increase in the Nusselt numbers as the nanoparticle concentration increases. Size of heating disk diameters shows reverse effect on heat transfer. It is also found that presenting the data in terms of Reynolds number at impingement jet diameter can take into account on both effects of jet heights and nozzle diameter. Presenting the data in terms of Peclet numbers, at fixed impingement nozzle diameter, makes the data less sensitive to the percentage change of the nanoparticle concentrations. Finally, general heat transfer correlation is obtained verses Peclet numbers using nanoparticle concentrations and the nozzle diameter ratio as parameters. PMID:22340669

  6. Edge disjoint cycles through specified vertices

    Microsoft Academic Search

    Luis A. Goddyn; Ladislav Stacho

    2005-01-01

    We give a sufficient condition for a simple graphG to have k pairwise edge-disjoint cycles, each of which contains a prescribed set W of vertices. The condition is that the induced subgraph G(W) be 2k-connected, and that for any two vertices at distance two in G(W), at least one of the two has degree at least |V (G)|\\/2 + 2(k

  7. Property price gradients: the vertical dimension

    Microsoft Academic Search

    S. K. Wong; K. W. Chau; Y. Yau; A. K. C. Cheung

    2011-01-01

    This is an empirical study on the pricing of two vertical property attributes: floor level and building height. Floor level\\u000a is the vertical location of a unit in a multi-storey building; the extra price paid for a higher floor level is labelled a\\u000a floor-level premium. Previous hedonic price studies unequivocally showed that the floor-level premium is positive, but they\\u000a were

  8. Rate limits in silicon sheet growth - The connections between vertical and horizontal methods

    NASA Technical Reports Server (NTRS)

    Thomas, Paul D.; Brown, Robert A.

    1987-01-01

    Meniscus-defined techniques for the growth of thin silicon sheets fall into two categories: vertical and horizontal growth. The interactions of the temperature field and the crystal shape are analyzed for both methods using two-dimensional finite-element models which include heat transfer and capillarity. Heat transfer in vertical growth systems is dominated by conduction in the melt and the crystal, with almost flat melt/crystal interfaces that are perpendicular to the direction of growth. The high axial temperature gradients characteristic of vertical growth lead to high thermal stresses. The maximum growth rate is also limited by capillarity which can restrict the conduction of heat from the melt into the crystal. In horizontal growth the melt/crystal interface stretches across the surface of the melt pool many times the crystal thickness, and low growth rates are achievable with careful temperature control. With a moderate axial temperature gradient in the sheet a substantial portion of the latent heat conducts along the sheet and the surface of the melt pool becomes supercooled, leading to dendritic growth. The thermal supercooling is surpressed by lowering the axial gradient in the crystal; this configuration is the most desirable for the growth of high quality crystals. An expression derived from scaling analysis relating the growth rate and the crucible temperature is shown to be reliable for horizontal growth.

  9. Effect of vertical motion on current meters

    USGS Publications Warehouse

    Kallio, Nicholas A.

    1966-01-01

    The effect of vertical motion on the performance of current meters at various stream velocities was evaluated to determine whether accurate discharge measurements can be made from a bobbing boat. Three types of current meters--Ott, Price, and vane types--were tested under conditions simulating a bobbing boat. A known frequency and amplitude of vertical motion were imparted to the current meter, and the related effect on the measured stream velocity was determined. One test of the Price meter was made under actual conditions, using a boat and standard measuring gear. The results of the test under actual conditions verified those obtained by simulating the vertical movements of a boat. The tests show that for stream velocities below 2.5 feet per second the accuracy of all three meters is significantly affected when the meters are subjected to certain conditions of vertical motion that can occur during actual field operations. Both the rate of vertical motion and the frequency of vertical oscillation affect the registration of the meter. The results of these tests, presented in the form of graphs and tables, can be used as a guide to determine whether wind and stream flow are within an acceptable range for a reliable discharge measurement from a boat.

  10. Corrosive resistant heat exchanger

    DOEpatents

    Richlen, Scott L. (Annandale, VA)

    1989-01-01

    A corrosive and errosive resistant heat exchanger which recovers heat from a contaminated heat stream. The heat exchanger utilizes a boundary layer of innocuous gas, which is continuously replenished, to protect the heat exchanger surface from the hot contaminated gas. The innocuous gas is conveyed through ducts or perforations in the heat exchanger wall. Heat from the heat stream is transferred by radiation to the heat exchanger wall. Heat is removed from the outer heat exchanger wall by a heat recovery medium.

  11. WHICH HYDRAULIC MODEL TO USE IN VERTICAL FLOW CONSTRUCTED WETLANDS?

    E-print Network

    Paris-Sud XI, Université de

    WHICH HYDRAULIC MODEL TO USE IN VERTICAL FLOW CONSTRUCTED WETLANDS? Ania Morvannoua , Nicolas-equilibrium model, preferential flow path, vertical flow constructed wetlands INTRODUCTION Constructed wetlands (CWs

  12. Competitive co-existence of vertically and horizontally transmitted parasites

    E-print Network

    Lively, Curt

    of vertically transmitted bacteria within the female reproductive organs of many arthropods, especially blood by systemic fungal endophytes that are vertically transmitted through seeds (Schardl, 1996). Theory suggests

  13. Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross Bracing Detail, Vertical Cross Bracing-End Detail - Cumberland Covered Bridge, Spanning Mississinewa River, Matthews, Grant County, IN

  14. Heating and cooling system

    Microsoft Academic Search

    1976-01-01

    An environment heating and cooling system is described which consists of a solar collector, heat storage ground well, cold storage ground well, and a heat exchange apparatus. Water from a cold storage ground well is heated in the heat exchange apparatus by solar heating fluid heated in a solar collector. The heated water is stored in a heat storage ground

  15. Natural convection heat transfer from sinusoidal wavy surfaces

    Microsoft Academic Search

    S. H. Bhavnani; A. E. Bergles

    1991-01-01

    This paper presents the results of an experimental study of the natural convection heat transfer characteristics of sinusoidal wavy surfaces on vertical plates maintained at a constant temperature. Local heat transfer coefficients were obtained with a Mach-Zehnder interferometer. The heat transfer from the wavy surfaces, compared to a plane plate of equal projected area, increased with increasing amplitude-to-wavelength ratio. The

  16. Vertical transport of surface fire emissions observed from space

    NASA Astrophysics Data System (ADS)

    Gonzi, Siegfried; Palmer, Paul I.

    2010-01-01

    We use optimal estimation to infer the vertical distribution of surface emissions lofted from boreal and tropical biomass burning during June-October (JJASO) 2006. We use satellite observations of CO, a tracer of incomplete combustion, at thermal infrared and microwave wavelengths from Aura Tropospheric Emission Spectrometer (TES) and Microwave Limb Sounder (MLS), respectively. TES and MLS together typically provide two to three pieces of information. We use a maximum a posteriori (MAP) methodology to estimate emitted CO mass in five vertical regions spanning the troposphere and lower stratosphere, equivalent to estimating surface emissions. Correlations between neighboring vertical regions, due to vigorous mixing induced by surface heating, reduce the inversion to the information content provided by the data. We use a total of 1785 TES profile measurements, of which 672 are colocated with MLS. We define an injection height based on MAP statistics. We find that 10%-20% of boreal and tropical fire emissions, depending on the region, reach the free and upper troposphere during JJASO 2006. Our injection height estimates during two key pyroconvective events, Siberia (July) and Indonesia (October), qualitatively agree with measurements of aerosol index and attenuated backscatter from Aura Ozone Monitoring Instrument (OMI) and CALIPSO, respectively. Surface emissions inferred from our mass estimates agree with the Global Fire Emission Database biomass burning emission inventory to within ±10%. The small percentage of emissions injected above the boundary layer result in disproportionate changes in CO concentrations of more than 2-25 ppb and 15-160 ppb over boreal and tropical regions, respectively.

  17. Triaxial thermopile array geo-heat-flow sensor

    DOEpatents

    Carrigan, Charles R. (Tracy, CA); Hardee, Harry C. (Albuquerque, NM); Reynolds, Gerald D. (Tijeras, NM); Steinfort, Terry D. (Tijeras, NM)

    1992-01-01

    A triaxial thermopile array geothermal heat flow sensor is designed to measure heat flow in three dimensions in a reconstituted or unperturbed subsurface regime. Heat flow can be measured in conductive or permeable convective media. The sensor may be encased in protective pvc tubing and includes a plurality of thermistors and an array of heat flow transducers arranged in a vertical string. The transducers produce voltage proportional to heat flux along the subsurface regime and permit direct measurement of heat flow in the subsurface regime. The presence of the thermistor array permits a comparison to be made between the heat flow estimates obtained from the transducers and heat flow calculated using temperature differences and Fourier's Law. The device is extremely sensitive with an accuracy of less than 0.1 Heat Flow Units (HFU) and may be used for long term readings.

  18. Incipient buoyant thermal convection in a vertical cylindrical annulus

    SciTech Connect

    Littlefield, D.L. (US Army Ballistic Research Lab., Aberdeen Proving Ground, MD (USA)); Desai, P.V. (Georgia Inst. of Tech., Atlanta (USA))

    1990-11-01

    The incipient buoyant thermal convection in a vertical cylindrical annulus when heated from below is examined. The ends are assumed to be free, and the sidewalls perfectly conducting. The temperature needed to initiate fluid motion is expressed nondimensionally in terms of the Rayleigh number. The analytical conflict that arises for annuli of infinite aspects ratios due to insufficient independent boundary conditions is resolved. Calculations for the critical Rayleigh numbers are presented for a variety of geometries, and the corresponding velocity and temperature perturbations are also shown. The number of cells increases as the aspect and radius ratio decrease with a strong bias towards the development of azimuthally varying cells. These changes in cellular behavior are expected based on physical justifications and comparisons with previous studies.

  19. Estimates of the seasonal mean vertical velocity fields of the extratropical Northern Hemisphere

    NASA Technical Reports Server (NTRS)

    White, G. H.

    1983-01-01

    Indirect methods are employed to estimate the wintertime and summertime mean vertical velocity fields of the extratropical Northern Hemisphere and intercomparisons are made, together with comparisons with mean seasonal patterns of cloudiness and precipitation. Twice-daily NMC operational analyses produced general circulation statistics for 11 winters and 12 summers, permitting calculation of the seasonal NMC averages for 6 hr forecasts, solution of the omega equation, integration of continuity equation downward from 100 mb, and solution of the thermodynamic energy equation in the absence of diabatic heating. The methods all yielded similar vertical velocity patterns; however, the magnitude of the vertical velocities could not be calculated with great accuracy. Orography was concluded to have less of an effect in summer than in winter, when winds are stronger.

  20. Vertical mixing due to double diffusion in the tropical western Pacific

    NASA Astrophysics Data System (ADS)

    Lee, Chorong; Chang, Kyung-Il; Lee, Jae Hak; Richards, Kelvin J.

    2014-11-01

    This study calculates the vertical diffusivity and the fluxes of heat, salt, and buoyancy due to turbulence and double diffusion based on a 14 day time series of observations of the dissipation rates of turbulent kinetic energy and thermal variance at 0°N, 156°E from 25 October to 18 November 2012. Salt fingering dominates shear-driven turbulence below 100 m. The estimated flux and associated vertical diffusivity due to double diffusion are approximately 1 order of magnitude higher for temperature and density and 2 orders of magnitude higher for salinity compared to values calculated from a turbulence model. Under weak turbulence conditions, the turbulence model significantly underestimates the magnitude of the vertical buoyancy flux with the flux having the wrong sign. Under these conditions, fluxes induced by double-diffusive mixing need to be considered.