While these samples are representative of the content of Science.gov,

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of Science.gov

to obtain the most current and comprehensive results.

Last update: August 15, 2014.

1

Simulation and experiment on the thermal performance of U-vertical ground coupled heat exchanger

This paper presented both the numerical simulations and experiments on the thermal performance of U-vertical ground coupled heat exchanger (UGCHE). The variation of the ground temperature and heat balance of the system were analyzed and compared in different operation modes in the numerical simulation. Experiments on the operation performance of the ground-coupled heat pump (GCHP) with the UGCHE were carried

Xinguo Li; Zhihao Chen; Jun Zhao

2006-01-01

2

Cooperative heat transfer and ground coupled storage system

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.

Metz, Philip D. (Rocky Point, NY)

1982-01-01

3

A refined computer program for the transient simulation of ground coupled heat pump systems

NASA Astrophysics Data System (ADS)

The use of the earth as a heat source/sink or storage medium for various heat pump based space conditioning systems were investigated. A computer program ground coupled system (GROCS) was developed to model the behavior of ground coupling devices. The GROCS was integrated with TRNSYS, the solar system simulation program, to permit the simulation of complete ground coupled heat pump systems. Experimental results were compared to GROCS simulation results for model validation. It is found that the model has considerable validity. A refined version of the GROCS-TRNSYS program developed to model vertical or horizontal earth coil systems, which considers system cycling is described. The design of the program and its interaction with TRNSYS are discussed.

Andrews, J. W.; Metz, P. D.; Saunders, J. H.

1983-04-01

4

Model for Ground-Coupled Heat and Moisture Transfer from Buildings

An important factor in soil heat transfer that is often over looked is the effect of moisture, which can vary the effective thermal conductivity by a factor of ten. The objective of this research was to investigate the ground-coupled heat and moisture transfer from buildings, and to develop results and tools to improve energy simulation of ground-coupled heat transfer.

Deru, M.

2003-06-01

5

Whole-Building Energy Simulation with a Three-Dimensional Ground-Coupled Heat Transfer Model.

National Technical Information Service (NTIS)

A three-dimensional, finite-element, heat-transfer computer program was developed to study ground-coupled heat transfer from buildings. It was used in conjunction with the SUNREL whole-building energy simulation program to analyze ground-coupled heat tran...

M. Deru R. Judkoff J. Neymark

2002-01-01

6

Ground coupled solar heat pump research program in the United States

The ground coupling research program funded by the Systems Development Division of the Office of Solar Applications of the US Department of Energy studies the use of the earth as a heat source/sink or storage element for solar heat pump space conditioning systems. The goal of this research program is to determine the feasibility of ground coupling, and if feasibility is confirmed, to create handbooks which facilitate widespread application of ground coupling. The research program is outlined and the research projects currently in progress and how they fit into the program are described. Progress toward the program goal is evaluated.

Metz, P D

1980-01-01

7

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

ERIC Educational Resources Information Center

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.…

Younger, Paul L.

2008-01-01

8

Analysis and field evaluation of an advanced ground-coupled heat pump system.

National Technical Information Service (NTIS)

This paper addresses the performance of a ground-coupled heat pump (GCHP) system with a water-source heat pump (WSHP) package designed expressly for such systems for a northern climate. The research objective was to minimize the life-cycle cost (LCC) of a...

V. D. Baxter M. A. Catan H. M. Hughes P. J. Hughes R. A. O'Neil

1986-01-01

9

This study presents a new approach to compute the heat transfer of ground-coupled envelope quickly and correctly which is suitable for implementation into building thermal simulation software. The heat transfer process is decomposed into three processes which are controlled by ground-coupled envelope surface temperature, outdoor ground surface temperature and the temperature difference of ground-coupled envelope surfaces. The three processes are

Xiaona Xie; Yi Jiang; Jianjun Xia

2008-01-01

10

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

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. 12 refs., 11 figs., 1 tab.

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

1991-09-01

11

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

NASA Astrophysics Data System (ADS)

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.

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

1991-09-01

12

Ground-coupled heat pump research at the University of Tennessee Washington, D.C., 10 Dec. 1984

NASA Astrophysics Data System (ADS)

The seasonal performance of a horizontal-coil ground-coupled heat pump system in both the heating and cooling mode was evaluated to determine its potential for use in the Knoxville, TN area. The effects of the significant parameters on performance were determined with the required data to develop an optimized system. The ground-coupled heat pump system was installed in TECH House I. The following conclusions are presented: (1) the data indicate that the ground coil heat exchanger is undersized for summer operation, operation during the winter season was acceptable with an overall seasonal performance factor of 2.6 which is higher than a typical air-air heat pump; (2) an undersized ground coil in a ground-coupled heat pump system will produce a significant performance penalty; (3) backfilling with clay must be carefully done to avoid having air pockets in the ground due to the tendency of clay to agglomerate; (4) backfilling with sand around the ground coil produced improved performance of the system during the initial summer of operation; (5) during winter operation, no electric resistance backup heating is required; (6) a ground-coupled heat pump in this area of the country must be sized based on the cooling peak which will normally result in an overdesign for the winter season, such as overdesign maybe, desirable because of reduced need for backup resistance heat.

Johnson, W. S.; McGraw, B. A.; Baugh, R. N.; Griffith, W. A.

13

Vertical eddy heat fluxes from model simulations

NASA Technical Reports Server (NTRS)

Vertical eddy fluxes of heat are calculated from simulations with a variety of climate models, ranging from three-dimensional GCMs to a one-dimensional radiative-convective model. The models' total eddy flux in the lower troposphere is found to agree well with Hantel's analysis from observations, but in the mid and upper troposphere the models' values are systematically 30 percent to 50 percent smaller than Hantel's. The models nevertheless give very good results for the global temperature profile, and the reason for the discrepancy is unclear. The model results show that the manner in which the vertical eddy flux is carried is very sensitive to the parameterization of moist convection. When a moist adiabatic adjustment scheme with a critical value for the relative humidity of 100 percent is used, the vertical transports by large-scale eddies and small-scale convection on a global basis are equal: but when a penetrative convection scheme is used, the large-scale flux on a global basis is only about one-fifth to one-fourth the small-scale flux. Comparison of the model results with observations indicates that the results with the latter scheme are more realistic. However, even in this case, in mid and high latitudes the large and small-scale vertical eddy fluxes of heat are comparable in magnitude above the planetary boundary layer.

Stone, Peter H.; Yao, Mao-Sung

1991-01-01

14

Characteristics Of Vertical Mantle Heat Exchangers For Solar Water Heaters

The flow structure in vertical mantle heat exchangers was investigated using a full-scale tank designed to facilitate flow visualisation. The flow structure and velocities in the mantle were measured using a particle Image Velocimetry (PIV) system. A CFD simulation model of vertical mantle heat exchangers was also developed for detailed evaluation of the heat flux distribution over the mantle surface.

L. J. Shah; G. L. Morrison; M. Behnia

1999-01-01

15

Vertical Eddy Flux of Heat in the Atmosphere

The thermodynamics of open systems is developed for a special atmospheric system in order to obtain a precise definition of the vertical eddy flux of heat. The upward eddy flux of heat per unit area is Vzh, where is density, Vz is a specially defined fluctuation of the vertical component of velocity, and h is specific enthalpy.In terms of the

R. B. Montgomery

1948-01-01

16

A cost effective vertical air\\/water solar heating collector

A description is presented of a vertical air\\/water collector which combines high efficiency with low cost. The low-cost characteristics of the total system are obtained by utilizing an air system for heat collection along with a water system for heat storage. The heat exchanger is in the top of the collector. It is protected from freezing, and is available to

T. H. Markowitz; R. L. Hummel

1978-01-01

17

Calculation of vertical temperature gradients in heated rooms.

National Technical Information Service (NTIS)

This paper deals with a simple model which predicts the vertical temperature gradient in a heated room. The gradient is calculated from a dimensionless temperature profile which is determined by two room air temperatures only, the mean temperature in the ...

H. Overby M. Steen-Thoede

1990-01-01

18

The vertical structure of ocean heat transport

NASA Astrophysics Data System (ADS)

One of the most important contributions the ocean makes to Earth's climate is through its poleward heat transport: about 1.5 PW or more than 30% of that accomplished by the ocean-atmosphere system (Trenberth and Caron, 2001). Recently, concern has arisen over whether global warming could affect this heat transport (Watson et al., 2001), for example, reducing high latitude convection and triggering a collapse of the deep overturning circulation (Rahmstorf, 1995). While the consequences of abrupt changes in oceanic circulation should be of concern, we argue that the attention devoted to deep circulations is disproportionate to their role in heat transport. For this purpose, we introduce a heat function which identifies the contribution to the heat transport by different components of the oceanic circulation. A new view of the ocean emerges in which a shallow surface intensified circulation dominates the poleward heat transport.

Boccaletti, G.; Ferrari, R.; Adcroft, A.; Ferreira, D.; Marshall, J.

2005-05-01

19

New solutions for the short-time analysis of geothermal vertical boreholes

Many models, either numerical or analytical, have been proposed to analyse the thermal response of vertical heat exchangers that are used in ground coupled heat pump systems (GCHP). In both approaches, most of the models are valid after few hours of operation since they neglect the heat capacity of the borehole. This is valid for design purposes, where the time

Louis Lamarche; Benoit Beauchamp

2007-01-01

20

Supercritical-water heat transfer in a vertical bare tube

This paper presents selected results on heat transfer to supercritical water flowing upward in a 4-m-long vertical bare tube. Supercritical-water heat-transfer data were obtained at pressures of about 24MPa, mass fluxes of 200–1500kg\\/m2s, heat fluxes up to 884kW\\/m2 and inlet temperatures from 320 to 350°C for several combinations of wall and bulk-fluid temperatures that were below, at or above the

Sarah Mokry; Igor Pioro; Pavel Kirillov; Yevgeniy Gospodinov

2010-01-01

21

Boiling heat transfer enhancement in subsurface horizontal and vertical tunnels

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)

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

22

Pr<1 intrusion flow induced by a vertical heated wall.

A horizontal flow induced by a vertical heated wall with a low Prandtl number (e.g., Pr<1 for air and liquid metals) is common in nature and industry. In this paper, a Pr<1 intrusion flow induced by a vertical heated boundary of an open sided cavity (that is, a cavity with one heated wall and open at the other end) is investigated by a scaling analysis and direct numerical simulations. The scaling analysis of the intrusion flow reveals that there are four possible flow regimes dependent on the Rayleigh and Prandtl numbers. In a typical case, the intrusion flow could travel under different dynamical and thermal processes such as unsteady (or steady) conduction-viscous, conduction-inertial, and convection-inertial dominance. Proper scaling relations have been presented to quantify these flows under different flow regimes. Furthermore, corresponding numerical simulations have verified the scaling results. PMID:20866916

Xu, Feng; Patterson, John C; Lei, Chengwang

2010-08-01

23

Bound on vertical heat transport at large Prandtl number

NASA Astrophysics Data System (ADS)

We prove a new upper bound on the vertical heat transport in Rayleigh-Bénard convection of the form c Ra( under the assumption that the ratio of Prandtl number over Rayleigh number satisfies {Pr}/{Ra}?c0 where the non-dimensional constant c0 depends on the aspect ratio of the domain only. This new rigorous bound agrees with the (optimal) Ra bound (modulo logarithmic correction) on vertical heat transport for the infinite Prandtl number model for convection due to Constantin and Doering [P. Constantin, C.R. Doering, Infinite Prandtl number convection, J. Stat. Phys. 94 (1) (1999) 159-172] and Doering, Otto and Reznikoff [C.R. Doering, F. Otto, M.G. Reznikoff, Bounds on vertical heat transport for infinite Prandtl number Rayleigh-Bénard convection, J. Fluid Mech. 560 (2006) 229-241]. It also improves a uniform (in Prandtl number) Ra bound for the Nusselt number [P. Constantin, C.R. Doering, Heat transfer in convective turbulence, Nonlinearity 9 (1996) 1049-1060] in the case of large Prandtl number.

Wang, Xiaoming

2008-05-01

24

Retrieving Latent Heat Vertical Structure Using Precipitation and Cloud Profiles

NASA Astrophysics Data System (ADS)

The latent heat (LH) released from tropical precipitation plays a critical role in driving regional and global atmosphere circulation. However, the vertical distribution of LH is one of most difficult parameters to be measured and has a large uncertainty in both residual diagnostic products and satellite retrievals. Most of current satellite LH products use limited observational information of precipitation and cloud profiles and highly depend on cloud resolving model (CRM) simulations. Our novel approach, distinguishing from existing schemes, is directly using observable precipitation and cloud profiles in combination with phase change partition parameterization of various kinds from the CRM simulations to produce the latent heating profiles. This hybrid latent heat algorithm separately deals with the condensation-evaporation heating (LHc_e), the deposition-sublimation heating (LHd_s) and the freezing-melting heating (LHf_m) for convective rain, stratiform rain, and shallow warm rain. Each component is based on physical processes, such as nucleation and auto conversion, by combining observable precipitation and cloud profiles. Although the proposed algorithm utilizes microphysical parameterizations from a specific CRM, the general LH vertical structure is primarily determined by the precipitation and cloud profiles observable from cloud and precipitation radars available at ground sites or from satellite platforms, and less sensitive to the specific CRM. The self consistency tests of this algorithm show good agreements with the CRM simulated LH at different spatial and temporal scales, even at simultaneous and pixel level. The applications of this algorithm are expected to provide new information for understanding the heating budget in the atmosphere and its impacts on the atmosphere circulations at various spatial and temporal scales.

Li, R.; Min, Q.; Wu, X.

2011-12-01

25

Mixed Convective Boiling Heat Transfer in a Vertical Capillary Structure Heated Asymmetrically

Mixed convective boiling heat transfer in a vertically oriented capillary porous structure with asymmetric heating of opposing walls is numerically investigated using a multiphase mixture model. Liquid saturation distributions, isotherms, as well as liquid and vapor velocity fields subjected to both superimposed aiding and opposing flows are analyzed and presented. The liquid velocity distributions for both aiding and opposing flows

T. S. Zhao; Q. Liao

1999-01-01

26

Flow regimes and heat transfer in vertical narrow annuli

In shell side boiling heat exchangers narrow crevices that are formed between the tubes and the tube support structure provide areas for local thermal-hydraulic conditions which differ significantly from bulk fluid conditions. Understanding of the processes of boiling and dryout in flow restricted crevices can help in designing of tube support geometries to minimize the likelihood of tube support plate and tube corrosion observed in commercial power plant steam generators. This paper describes a one dimensional thermal-hydraulic model of a vertical crevice between a tube and a support plate with cylindrical holes. The annulus formed by the support plate hole and an eccentrically located tube has been represented by vertical strips. The formation, growth and collapse of a steam bubble in each strip has been determined. Based on the bubble history, and flow regimes characterized by ``isolated`` bubbles, ``coalesced`` bubbles and liquid deficient regions have been defined.

Ulke, A.; Goldberg, I.

1993-11-01

27

Experiments were done using subcooled Freon-113 sprayed vertically downward. Local and average heat transfers were investigated fro Freon-113 sprays with 40 C subcooling, droplet sizes 200-1250{mu}m, and droplet breakup velocities 5-29 m/s. Full-cone type nozzles were used to generate the spray. Test assemblies consisted of 1 to 6 7.62 cm vertical constant heat flux surfaces parallel with each other and aligned horizontally. Distance between heated surfaces was varied from 6.35 to 76.2 mm. Steady state heat fluxes as high as 13 W/cm{sup 2} were achieved. Dependence on the surface distance from axial centerline of the spray was found. For surfaces sufficiently removed from centerline, local and average heat transfers were identical and correlated by a power relation of the form seen for normal-impact sprays which involves the Weber number, a nondimensionalized temperature difference, and a mass flux parameter. For surfaces closer to centerline, the local heat transfer depended on vertical location on the surface while the average heat transfer was described by a semi-log correlation involving the same parameters. The heat transfer was independent of the distance (gap) between the heated surfaces for the gaps investigated.

Kendall, C.M. [Lawrence Livermore National Lab., CA (United States); Holman, J.P. [Southern Methodist Univ., Dallas, TX (United States). Dept. of Mechanical Engineering

1996-06-06

28

Vertical Variation In Heat Flow Density: Palaeoclimate After All?

NASA Astrophysics Data System (ADS)

Vertical variation in heat flow density (HFD) in the upper crust is one of the Sbig' ´ problems in geothermics. Several factors have been proposed to produce the variation, such as convective heat transfer by migration of fluids, palaeoclimatic conductive dis- turbances, endo/exothermic mineral reactions, or thermal conductivity contrasts. We present evidence indicating that palaeoclimatic surface temperature variations are the major factor behind the vertical variation in stable continental areas. We report an analysis of heat flow density (HFD) in the Fennoscandian Shield (FS) and East Euro- pean Platform (EEP) where HFD shows a systematic variation with depth. The HFD data (1352 values) averaged in 25 m depth intervals and in 1 degree times 2 degrees latitude-longitude areas increase from about 35-40 mW m-2 in the first 500 m to about 45 mW m-2 at 1000 m, reaching finally about 50 mW m-2 between 1000-3000 m and deeper. We attribute this variation to long-term climatic changes in ground sur- face temperatures (GST) during the Weichselian (Late Pleistocene) glaciation and the Holocene. Monte Carlo inversion was applied for determining ground surface temper- ature histories during the past 100,000 years, and the results indicate a gradual cool- ing through the Weichselian until the Last Glacial Maximum, followed by an average warming of 8.0 s´ 4.5 degrees at about 10,000 years BP.

Kukkonen, I. T.; Joeleht, A.

29

Critical heat flux (CHF) experiments have been carried out in a wide range of pressure for an internally heated vertical annulus. The experimental conditions covered a range of pressure from 0.57 to 15.01 MPa, mass fluxes of 0 kg m?2 s?1 and from 200 to 650 kg m?2 s?1, and inlet subcoolings from 85 to 413 kJ kg?1. Most of

Se-Young Chun; Heung-June Chung; Sang-Ki Moon; Sun-Kyu Yang; Moon-Ki Chung; Thomas Schoesse; Masanori Aritomi

2001-01-01

30

Application of Ground-Coupled GPR to Pavement Evaluation.

National Technical Information Service (NTIS)

Four case studies are presented in which ground-coupled ground-penetrating radar (GPR) was used successfully to identify subsurface problems in highway projects. These include identifying the extent of a subsurface aquifer so that a drainage system can be...

T. Scullion S. Servos J. Ragsdale T. Saarenketo

1997-01-01

31

National Technical Information Service (NTIS)

Experimental results on temperature and heat flow in a set of three vertical cylinders with internal generation of heat, water submerged and in free convection are presented in this work . Temperature distribution, Nusselt number and convective coefficien...

M. L. Serrano Ramirez

1993-01-01

32

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

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

33

Natural convection heat transfer from vertical parallel plates to air

NASA Astrophysics Data System (ADS)

Two-dimensional Navier-Stokes and energy equations are numerically solved for laminar natural convection of air between vertical parallel plane plates with uniform heat flux. Calculations are carried out under the conditions of the modified Grashof number (2.3 x 10(exp 3) less than or equals to Gr(sup *) less than or equals to 8.8 x 10(exp 5)) and height to plate spacing ratio (8 less than or equals to l/h less than or equals to 30), which covers the practical range encountered with the air cooling system of electronic equipment. The numerical solutions are compared with present experimental results. The local Nusselt numbers and induced flow rates obtained numerically agree well with those measured. A correlation expression for the local Nusselt number is proposed which can predict the local plate temperature within 5 percent error. When the value of dimensionless variable Phi = ((h/x)Gr(sup *)Pr)/((h/l)Gr(sup *)Pr) is greater than approximately 10(exp 2). The existing results based on the boundary layer approximation are found to be not applicable for predicting the maximum plate temperature.

Fujii, Motoo; Gima, Satoru; Tomimura, Toshio; Zhang, Xing

1993-09-01

34

NASA Astrophysics Data System (ADS)

Observational studies have shown that an unprecedented warm anomaly has recently affected the temperature of the Atlantic Water (AW) layer lying at intermediate depth in the Arctic Ocean. Using observations from four profiling moorings, deployed in the interior of the Canada Basin between 2003 and 2011, the upward diffusive vertical heat flux from this layer is quantified. Vertical diffusivity is first estimated from a fine-scale parameterization method based on CTD and velocity profiles. Resulting diffusive vertical heat fluxes from the AW are in the range 0.1-0.2 W m-2 on average. Although large over the period considered, the variations of the AW temperature maximum yields small variations for the temperature gradient and thus the vertical diffusive heat flux. In most areas, variations in upward diffusive vertical heat flux from the AW have only a limited effect on temperature variations of the overlying layer. However, the presence of eddies might be an effective mechanism to enhance vertical heat transfer, although the small number of eddies sampled by the moorings suggest that this mechanism remains limited and intermittent in space and time. Finally, our results suggest that computing diffusive vertical heat flux with a constant vertical diffusivity of ˜2 × 10-6 m2 s-1 provides a reasonable estimate of the upward diffusive heat transfer from the AW layer, although this approximation breaks down in the presence of eddies.

Lique, Camille; Guthrie, John D.; Steele, Michael; Proshutinsky, Andrey; Morison, James H.; Krishfield, Richard

2014-01-01

35

NASA Astrophysics Data System (ADS)

The influence of convective heating on movement and vertical coupling of tropical cyclones (TCs) is investigated using a hurricane model with different environmental flows. The authors identify two processes by which convective heating may affect TC motion. One is the advection of symmetric potential vorticity (PV) by heating-induced asymmetric flow. The other is the direct generation of a positive PV tendency by asymmetric heating, which acts to shift a TC to the region of maximum downward gradient of asymmetric heating. A steering level exists that is located at the level where the direct influence of asymmetric heating vanishes, normally in the lower troposphere. At that level, a TC moves with the asymmetric flow averaged within a radius of 200 km, because the influence of asymmetric flows on TC motion is weighted by the horizontal PV gradient that is primarily confined within the TC core. Although the vertical shear in the asymmetric flow (including environmental and heating-induced flows) could tilt the vortex, the influence of asymmetric heating tends to offset the vertical tilt caused by the vertical shear through a fast adjustment between the asymmetric wind and diabatic heating. Therefore, diabatic heating enhances the vertical coupling.

Wu, Liguang; Wang, Bin

2001-12-01

36

Critical heat flux prediction for saturated flow boiling of water in vertical tubes

This study presents a new analytical model for the prediction of the critical heat flux (CHF) in water saturated flow boiling in round vertical and uniformly heated pipes. The CHF is assumed to occur in annular flow when the liquid film vanishes at the exit section of the heated channel. Channel pressure drop is calculated using the Friedel correlation. Liquid

Gian Piero Celata; Kaichiro Mishima; Giuseppe Zummo

2001-01-01

37

The finite difference method in conjunction with the least-squares scheme and the experimental temperature data is proposed to predict the average natural-convection heat transfer coefficient and the fin efficiency on a vertical square fin of one-circular tube plate finned-tube heat exchangers. In the present study, the radiation and convection heat transfer coefficients are simultaneously taken into consideration. The heat transfer

Han-Taw Chen; Jui-Che Chou

2006-01-01

38

GAS-LIQUID-PHASE HEAT TRANSFER ON VERTICAL-TUBE BAFFLES IN MECHANICALLY-AGITATED VESSELS

An experimental investigation of heat transfer coefficients has been carried out in mechanically agitated air-water dispersions to and from vertical tubes acting as baffles in addition to heat exchange surface in a vertical cylindrical tank. Air was dispersed into water, which served as a two-phase fluid. Agitation was provided by a dual, 4-blade turbine impeller. A modified Reynolds number has

MAJID SALIM

1983-01-01

39

An analytical model for near-saturated pool boiling critical heat flux on vertical surfaces

Photographic studies of vertical pool boiling for near-saturated conditions were conducted in order to determine the critical heat flux (CHF) trigger mechanism. The studies revealed that, for heat fluxes near CHF, vertical pool boiling exhibits vapor behavior similar to that observed in flow boiling. At fluxes slightly below CHF, the Kelvin-Helmholtz instability creates a wavy layer at the liquid-vapor interface.

Issaim Mudawar; Alicia H. Howard; Christopher O. Gersey

1997-01-01

40

Power-law fluid flow in heated vertical ducts

NASA Astrophysics Data System (ADS)

A hydrodynamically and thermally fully developed flow in a vertical duct is investigated. It is assumed that the wall of the duct is maintained at a temperature which varies linearly with respect to the depth of the duct to model a vertical duct in the Earth. Furthermore, in order to investigate flows during the drilling of muds and the cementing process in oil wells, the fluid is assumed to be a power-law fluid and the fluid flow in concentric annuli are investigated. The conditions under which multiple solutions are obtained is studied and the effects of the Rayleigh number n, the relative thickness of the channels, and the enforced pressure gradient are investigated.

Jones, A. T.; Ingham, D. B.

1994-04-01

41

Method and apparatus for determining vertical heat flux of geothermal field

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.

Poppendiek, Heinz F. (LaJolla, CA)

1982-01-01

42

Forced and mixed convection heat and mass transfer are studied numerically for water containing metallic corrosion products\\u000a in a heated or cooled vertical tube with variable thermophysical properties at super-critical pressures. The fouling mechanisms\\u000a and fouling models are presented. The influence of variable properties at super-critical pressures on forced or mixed convection\\u000a has been analyzed. The differences between heat and

Pei-Xue Jiang; Ze-Pei Ren; Bu-Xuan Wang

1995-01-01

43

An experimental study has been made of critical heat flux (CHF) of natural convective boiling on uniformly heated inner tubes in vertical annular tubes. The experiment was performed at a pressure ofP=0.1 to 3.1 MPa for the clearance of 0.4 to 4.0 mm, the heated tube diameter of 5 to 10.6 mm, the annular tube length ofL=58 to 840 mm

Masanori Monde; Yuichiro Mitutake; Shinji Kubo

1994-01-01

44

Natural convection heat transfer from a vertical plate to supercritical helium

A vertical copper plate was used to study heat transfer by natural convection to helium at supercritical pressures. The results revealed an appreciable discrepancy between the experimental data for the mean heat transfer coefficient and the value of this coefficient, calculated from the equation for carbon dioxide and water at super-critical pressures. A modified equation, written in dimensionless numbers, which

V. I. Deev; A. K. Kondratenko; V. I. Petrovichev; V. E. Keilin; I. A. Kovalev

1978-01-01

45

NASA Astrophysics Data System (ADS)

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.

Bieli?ski, Henryk; Mikielewicz, Jaros?aw

2010-10-01

46

NASA Technical Reports Server (NTRS)

The heat flow experiment conducted during the Apollo 17 flight in the Taurus-Littrow area of the moon is discussed. The concept of the experiment is based on the direct measurement of the vertical flow of heat through the regolith. The measurement is made far enough below the surface so that the time-varying heat flow resulting from the very large diurnal variations of the surface temperature is small as compared with the flow from the interior. The equipment used for the experiment is described and illustrated. Graphs are developed to present the results of heat flow and surface temperature measurements.

Langseth, M. G., Jr.; Keihm, S. J.; Chute, J. L., Jr.

1973-01-01

47

Natural convection along slender vertical cylinders with variable surface heat flux

Heat transfer by natural convection along a vertical cylinder has been analyzed rather extensively by many investigators using different solution methods. The major restriction to most of these studies is that the solutions are valid only for cylinders with small surface curvature, that is, for cylinders whose diameters are not small. To data no analysis seems to have been presented for natural convection along slender vertical cylinders under the variable surface heat flux condition, and this has motivated the present study as a supplement to the solution of the problem with variable wall temperature.

Heckel, J.J.; Chen, T.S.; Armaly, B.F. (Univ. of Missouri, Rolla (United States))

1989-11-01

48

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

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.

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

49

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

NASA Astrophysics Data System (ADS)

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.

Tandian, Nathanael P.; Umar, Efrizon; Hardianto, Toto; Febriyanto, Catur

2012-06-01

50

Study on falling film generation heat transfer of lithium bromide solution in vertical tubes

Falling film generation process in lithium bromide absorption refrigeration generation system is researched in this paper.\\u000a To describe the coupled heat and mass transfer of laminar falling film in vertical generation tube, a mathematical model is\\u000a developed, in which the effect of mass transfer on heat transfer is carefully evaluated. Moreover, an equation related Re\\u000a number with solution volume flow

Chengming Shi; Canjun Xu; Huili Hu; Yang Ying

2009-01-01

51

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

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

Chin-Hsiang Cheng; Chun-Jen Weng

1993-01-01

52

Laminar natural convection heat and mass transfer in vertical rectangular ducts

The present work investigates numerically the laminar natural convection heat and mass transfer in open vertical rectangular ducts with uniform wall temperature\\/uniform wall concentration (UWT\\/UWC) or uniform heat flux\\/uniform mass flux (UHF\\/UMF) boundary conditions. The vorticity–velocity formulation is applied to solve for the coupled momentum, energy and concentration equations. Results of dimensionless induced volume rate Q, average Nusselt number Nu

Kuan-Tzong Lee

1999-01-01

53

Heat transfer enhancement by the chimney effect in a vertical isoflux channel

The ease of thermal control by means of air natural convection stimulates the investigation of configurations with the aim at improving the thermal performance. The effect of adding adiabatic extensions downstream of a vertical isoflux symmetrically heated channel has been experimentally analyzed. Optimal configurations have been identified through the measured wall temperature profiles, with reference to the extension and expansion

A Auletta; O Manca; B Morrone; V Naso

2001-01-01

54

Local Heat Transfer During Condensation with Forced Convection in a Vertical Tube.

National Technical Information Service (NTIS)

The local heat transfer coefficients during the condensation of pure substances in a vertical tube has been measured by varying separately the mass flux density of the vapor and the trickling quantity. The substances used in the experiments are water and ...

F. Blangetti

1979-01-01

55

Three-dimensional computation of heat transfer from flames between vertical parallel walls

The heat transfer from turbulent diffusion flames between vertical walls has been computed for different wall and burner configurations. The buoyancy-modified k ? ? model was used to study the turbulent characteristics of the flow. The flamelet concept, coupled to a prescribed probability density function, was employed to model the nonpremixed combustion process. With the nucleation, surface growth, coagulation, and

Zhenghua Yan; Göran Holmstedt

1999-01-01

56

Non-linear dynamics and pattern formation in a vertical fluid layer heated from the side

We study both experimentally and numerically the convective flow in a tall vertical slot with differently heated walls. The flow is investigated for the fluid with the Prandtl number Pr=26, which is large enough to ensure the traveling waves as primary instability and small enough to prevent boundary layer convection. The flow evolution is determined on the base of the

Dmitry A Bratsun; Alexej V Zyuzgin; Gennady F Putin

2003-01-01

57

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

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

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

1999-01-01

58

Empirical Models of the Eddy Heat Flux and Vertical Shear on Short Time Scales

The relationship between the eddy heat flux and vertical shear in the extratropical atmosphere is studied by developing various linear stochastic models fitted to the observed January and July Northern Hemispheric data. Models are univariate or bivariate, continuous or discrete. An objective procedure selects the second-order bivariate model as most appropriate in midlatitudes. The first-order continuous bivariate model indicates that

Steven J. Ghan

1984-01-01

59

Prediction of the critical heat flux in annular regime in various vertical channels

The axial variation of film flow rate in annular regime was analyzed to predict the critical heat flux in water saturated flow boiling in various vertical channels. In the analyses, several quantities including the deposition and entrainment rates of droplets were evaluated with the correlations that were based on the separate experimental data of film flow rate and droplet flow

Tomio Okawa; Akio Kotani; Isao Kataoka; Masanori Naitoh

2004-01-01

60

An experimental study of the conditions for the onset of thermally induced oscillations and their influence on heat transfer in an ascending flow of supercritical helium in a heated vertical tube is reported.

V. A. Bogachev; V. M. Eroshenko; E. V. Kuznetsov

1986-01-01

61

Buoyancy effects on the laminar boundary layer heat transfer along vertically moving cylinders

NASA Astrophysics Data System (ADS)

The local similarity method (Lloyd, Sparrow, 1970) is used to study the effects of buoyancy force on the laminar boundary layer heat transfer along vertically moving cylinders. Cases of prescribed surface temperature and wall heat flux in power of streamwise distance are analyzed. Local similarity solutions are obtained to show the effects of the transverse curvature of the cylinder surface and buoyancy parameters on the surface friction and heat transfer rate. It is known, however, that the local non-similarity method (Sparrow, Quack, Boerner, 1970) and the finite difference method (Mucoglu, Chen, 1979) would give more accurate results.

Lin, H.-T.; Shih, Y.-P.

1981-01-01

62

NASA Technical Reports Server (NTRS)

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.

Brandon, S.; Derby, J. J.

1992-01-01

63

Mixed Convection Heat Transfer in Micropolar Nanofluid over a Vertical Slender Cylinder

NASA Astrophysics Data System (ADS)

Analysis is carried for the problem of boundary layer steady flow and heat transfer of a micropolar fluid containing nanoparticles over a vertical cylinder. The governing partial differential equations of linear momentum, angular momentum, heat transfer and nano concentration are reduced to nonlinear coupled ordinary differential equations by applying the boundary layer approximations and a suitable similarity transformation. These nonlinear coupled ordinary differential equations, subject to the appropriate boundary conditions, are then solved by using the homotopy analysis method. The effects of the physical parameters on the flow, heat transfer and nanoparticle concentration characteristics of the model are presented through graphs and the salient features are discussed.

Abdul, Rehman; Nadeem, S.

2012-12-01

64

Prediction of two-phase flow and heat transfer in vertical pipes

NASA Astrophysics Data System (ADS)

A prediction procedure for gas-solid flows in vertical pipes with and without heat transfer is presented. Separate conservation equations are formulated for each phase and the interaction between the phases is accounted for by including interfacial drag and energy exchange terms in the corresponding equations. A 'two-phase two-equation model' of turbulence is used. The logarithmic wall function for single phase is modified for two-phase flow, in order to account for heat and momentum transfer to each phase at the wall. Good agreement is obtained between predictions and experimental data for flow and heat transfer in vertical pipes for particle sizes 30,100 and 800 microns.

Abou-Ellail, M. M. M.; Abou-Arab, T. W.

65

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)

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

66

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

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

1984-01-01

67

Experimental investigation of the local heat transfer in a vertical gas-liquid slug unit

NASA Astrophysics Data System (ADS)

Heat transfer mechanism in two-phase flows and particularly in vertical slug flow is of high interest both for basic hydrodynamic research and for industrial applications. Two-phase slug flow is highly complicated and only a limited number of heat transfer studies have been carried out. The flow field around a single Taylor bubble propagating in a vertical pipe can be subdivided into three distinct hydrodynamic regions: the gas bubble surrounded by a thin liquid film, a highly turbulent liquid wake in the vicinity of the bubble bottom, and the far wake region. Experimental and theoretical works were presented during the last decades investigating the hydrodynamic parameters in each region. Due to the complexity and intermittent nature of slug flow the existing data on the heat transfer in slug flow is limited to a narrow range of operational conditions. To improve the understanding of the heat transfer mechanism in slug flow a new experimental setup was constructed. A part of the vertical pipe wall was replaced by a thin metal foil heated by electrical current. An IR video camera was used to determine the temporal variation of the instantaneous temperature field along the foil at two locations: at the thermal entrance region and at the upper part of the foil where thermal boundary is thicker. The video camera was synchronized with a sensor that determined the instantaneous location of the Taylor bubble. The results of the instantaneous heat transfer measurements along the liquid film and in the wake of the Taylor bubble can be correlated with the detailed velocity measurements carried out in the same facility (Shemer et al. 2007)[1]. The effect of the local hydrodynamic parameters on the heat transfer coefficient in each region is examined.

Babin, Valery; Shemer, Lev; Barnea, Dvora

2012-03-01

68

Heat transfer to water from a vertical tube bundle under natural-circulation conditions. [PWR; BWR

The natural circulation heat transfer data for longitudinal flow of water outside a vertical rod bundle are needed for developing correlations which can be used in best estimate computer codes to model thermal-hydraulic behavior of nuclear reactor cores under accident or shutdown conditions. The heat transfer coefficient between the fuel rod surface and the coolant is the key parameter required to predict the fuel temperature. Because of the absence of the required heat transfer coefficient data base under natural circulation conditions, experiments have been performed in a natural circulation loop. A seven-tube bundle having a pitch-to-diameter ratio of 1.25 was used as a test heat exchanger. A circulating flow was established in the loop, because of buoyancy differences between its two vertical legs. Steady-state and transient heat transfer measurements have been made over as wide a range of thermal conditions as possible with the system. Steady state heat transfer data were correlated in terms of relevant dimensionless parameters. Empirical correlations for the average Nusselt number, in terms of Reynolds number, Rayleigh number and the ratio of Grashof to Reynolds number are given.

Gruszczynski, M.J.; Viskanta, R.

1983-01-01

69

NASA Astrophysics Data System (ADS)

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.

Kim, Jeong-Hun; Arima, Hirofumi; Ikegami, Yasuyuki

70

General analysis of steady laminar mixed convection heat transfer on vertical slender cylinders

A general analysis has been developed to study fluid flow and heat transfer characteristics for steady laminar mixed convection on vertical slender cylinders covering the entire range from pure forced to pure natural convection. Two uniquely transformed sets of axisymmetric boundary-layer equations for the constant wall heat flux case and the isothermal surface case are solved using a two-point finite difference method with Newton linearization. Of interest are the effects of the new mixed convection parameter, the cylinder heating/cooling mode, the transverse curvature parameter, and the Prandtl number on the velocity/temeprature profiles and on the local skin friction parameter and the heat transfer parameter. The results of the validated computer simulation model are as follows. Depending upon the magnitude and direction of the buoyancy force, i.e., the value of the mixed convection parameter and the heating or cooling mode applied, natural convection can have a significant effect on the thermal flow field around vertical cylinders. Specifically, strong variations of the local skin friction parameter and reversing trends in the heat transfer parameter are produced as the buoyancy force becomes stronger in aiding flow. The skin friction parameter increases with higher curvature parameters and Prandtl numbers. Similarly, the modified Nusselt number is larger for higher transverse curvature parameters; however, this parameter may reverse the impact of the Prandtl number on the Nusselt number for predominantly forced convection.

Wang, T.Y.; Kleinstreuer, C. (North Carolina State Univ., Raleigh (United States))

1989-05-01

71

Remote sensing of vertical velocity variance and surface heat flux in a convective boundary layer

The vertical velocity variance in the convective atmospheric boundary layer is estimated from measurements made with a 915-MHz boundary layer wind-profiling radar. The vertical velocity variance estimates are used to infer the surface virtual heat flux through a relationship with the convective velocity scale w{sub *}. The flux estimates are compared with in situ surface flux measurements and estimates extrapolated to the surface from direct eddy correlation measurements made with a profiler and radio acoustic sounding system. The measurements were made during the Rural Oxidants in the Southern Environment II Experiment in June 1992. The experiment area is primarily pine forest, and the dominant weather conditions were hot with light winds. The profiler variance measurements are compatible with theory and earlier observations. Both remote radar methods of estimating surface virtual heat flux agree with in situ measurements to within the sampling uncertainty. 28 ref., 6 figs.

Angevine, W.M. [Univ. of Colorado, Boulder, CO (United States)] [Univ. of Colorado, Boulder, CO (United States); Doviak, R.J. [National Severe Storms Lab., Norman, OK (United States)] [National Severe Storms Lab., Norman, OK (United States); Sorbjan, Z. [Univ. of Oklahoma, Norman, OK (United States)] [Univ. of Oklahoma, Norman, OK (United States)

1994-08-01

72

Slide dampers for a vertical type of apparatus for continuously heat-treating solid waste

This patent describes a slide damper system used for a vertical type of furnace for continuously heat-treating non-particulate matter to recover the resulting combustive gases and\\/or liquids, comprising a gas sealing slide damper disposed in the upper portion of the furnace for sealing the interior of the furnace from the open air; at least two V-shaped slide damper means having

K. Michimae; A. Amamiya; H. Akimoto

1988-01-01

73

Steady gas hydrate growth along vertical heat transfer tube without stirring

The hydration characteristics of a quiescent reactor with inner-placed vertical heat transfer tube were researched, the reaction materials were 300ppm sodium dodecyl sulfate water solution and R141b. The growth morphology were described through the photos taken during the growth\\/decomposition processes. The temperatures of two points inside the reactor were also recorded and analyzed. The mass transfer mechanism was explained by

Yingming Xie; Kaihua Guo; Deqing Liang; Shuanshi Fan; Jianming Gu

2005-01-01

74

An experimental study has been carried out for the critical heat flux (CHF) during the natural convective boiling of R-113 at various pressures in a vertical channel. The pressure ranges from 1 to 3 bar and the channel gap-size from 0.3 mm to 2.5 mm as its height is kept constant. Data for pool boiling are also obtained. At all

J. Bonjour; M. Lallemand

1997-01-01

75

Nondimensional analysis of boiling dry a vertical channel with a uniform heat flux

A thermal-hydraulic model has been developed for describing the phenomenon of hydrodynamically-controlled dryout, or the boil-off phenomenon, in a vertical channel with a spatially-averaged or uniform heat flux. The use of the drift flux correlation for the void fraction profile, along with mass and energy balances for the system, leads to a dimensionless closed-form solution for the predictions of two-phase

K. H. Sun; R. B. Duffey; C. Lin

1981-01-01

76

Development of an Algorithm to Predict Vertical Heat Transfer Through Ceiling\\/Floor Conduction

This paper describes a new algorithm of the Consolidated Fire Growth and Smoke Transport (CFAST) fire model and compares the results with data from real-scale fire tests conducted aboard the ex-USS Shadwell, the U.S. Navy's Research and Development Damage Control Platform. The new phenomenon modeled in this work is the conduction of heat in the vertical direction. The Shadwell tests

J. L. Bailey; W. W. Jones; P. A. Tatem; G. P. Forney

1998-01-01

77

An approach to heat and mass transfer analysis during film condensation inside a vertical tube

An Investigation was conducted to determine the effects of non-condensing gas on vapor condensation. Experiments were carried out during condensation of a mixture of water vapor/non-condensing gas along the inner surface of a vertical tube. Air was used as non-condensing gas and the various profiles of the water vapor/non-condensing gas mixture were employed. A theoretical analysis to predict the heat and mass transfer is presented. The amount of the condensed water obtained by the experiments was found to be close to the theoretical results. The obtained heat and mass transfer results were in good agreement with earlier published results.

Kotcioglu, I.; Gullapoglu, S. (Ataturk Univ., Erzurum (Turkey)); Uyarel, A.Y. (Gazi Univ., Ankara (Turkey)); Kaygusuz, K. (Karadeniz Technical Univ., Trabzon (Turkey)); Dincer, I. (TUBITAK-Marmara Research Center, Kocaeli (Turkey))

1993-03-01

78

Radiative-convective heat transfer to solid spherical particles in a vertical channel flow

NASA Astrophysics Data System (ADS)

A numerical study has been conducted pertaining to the problem of radiative convective heat transfer to solid spherical particles in a vertical channel flow. The gas phase is treated within the context of an Eulerian (continuum) formulation. For the particulate phase, a Lagrangian approach has been employed that includes two-way coupling of momentum and heat transfer between phases. The gas flow is in laminar regime and the particle Reynolds number based on the particle radius and skip velocity between phases is of order one. The particulate phase is dilute enough that direct particle, particle interactions are negligible but particle volume fraction effects are retained in the transport equations for the gas phase. The particle and channel wall surfaces are taken as diffusely emitting and reflecting. For the particulate phase, radiative heat transfer is directly coupled with convective heat transfer through the energy conservation equation and for the walls, through the thermal boundary condition.

Lee, J. S.

1985-12-01

79

Augmentation of heat transfer in a bubble agitated vertical rectangular channel

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

80

NASA Astrophysics Data System (ADS)

It is well known that the main direct effect of aerosols is the cooling of the surface and warming of the atmosphere, which impact atmospheric dynamics via the weakening of convection and the inhibition of cloud forming. In order to be able to fully understand and parameterize this throughout the atmosphere, a detailed vertical profile of the aerosol induced surface cooling and atmospheric heating is required. To get a vertical profile like this, detailed vertically resolved data on aerosol optical properties are required. Such data have now become available from CALIOP lidar onboard CALIPSO satellite. Its near-nadir viewing geometry allows for viewing curtains of the atmosphere, thereby defining with sufficient accuracy the vertical position of aerosols and clouds. In this study, CALIOP Level 2-Version 3 Layer and Profile data for the Mediterranean region from January 2007 to December 2011 have been used. The Mediterranean region was chosen, as it is an area with a mixture of aerosol types, both natural and anthropogenic, where aerosol radiative effects take large values. Furthermore, it is in the proximity of Sahara desert dust, making the area one with large aerosol load. The original CALIOP data have been regridded at a 1°x1° latitude-longitude resolution and at 160 vertical layers. The use of both Layer and Profile data has enabled the derivation of useful 'climatological' products, like spatial properties of aerosol layers, as well as optical properties of them. A comparison with the recently distributed (December 2011) CALIOP Level 3 data, as well as with other satellite data, is presented. Initial results, in agreement with previous studies, reveal that CALIOP aerosol optical depth (AOD) is biased low by around 20%, when compared to other satellite products, such as MODIS. The regridded data are subsequently used in a spectral radiative transfer model and the vertical profile of direct radiative effect is computed. From that, a vertical heating rate profile due to aerosols is derived for each model grid. The geographical and seasonal variability of these rates are investigated, in relation with the corresponding variability of aerosol optical properties. According to preliminary results, the determination of the cooling/heating rate above the surface and within the atmosphere is not affected by the aforementioned bias of CALIOP AOD. The findings of this study are expected to be particularly useful to future studies that deal with the modelling of the aerosol direct, indirect and semi-direct effects (e.g.. Monitoring Atmospheric Composition and Climate II) while the aerosol induced modification of atmospheric lapse rates will be the basis for further studies of aerosol effects on atmospheric dynamics.

Pappas, Vasileios; Hatzianastassiou, Nikos; Matsoukas, Christos; Vardavas, Ilias

2013-04-01

81

Modeling vertical exchange of heat, salt, and other dissolved substances in the Cariaco Basin

NASA Astrophysics Data System (ADS)

A simple 1.5-dimensional model of vertical exchange for heat, salt, and other dissolved substances has been developed for the Cariaco Basin. The model parameters are derived based on the temperature and salinity data collected monthly at a deepwater station in the eastern part of the basin from 1995 through 2007 during the CARIACO time series program. The model describes the processes of turbulent (eddy) diffusion, which includes the integrated effect of diffusive exchange mechanisms acting in the basin, and of vertical advection, which arises following injection of dense water into deep layers following an inflow from the Caribbean Sea. The model takes into account the changes in the horizontal cross-section area of the basin with respect to depth. Temporal variability is an important feature of the hydrography of the Cariaco Basin. To assess profiles of the vertical eddy diffusion coefficient and vertical advection velocity, we examined a time series of CTD profiles (potential temperature and salinity). Two distinct time intervals were identified as the result of this examination. During the first period, the thermohaline structure of the basin was apparently influenced by one or more inflows. The second period, in contrast, showed little or no influence of an inflow. The data from the second period, where no inflows were observed, were incorporated into corresponding transfer equations to assess the profile of the vertical eddy diffusion coefficient, k(z). Then, the result of this assessment was used with the data from the first period to estimate the profile of the vertical advection velocity, W(z), for a time when the effects of an inflow were evident. For that case, the transfer equations include the terms describing the effect of the inflow. Analysis of the vertical profile of the turbulent diffusion coefficient suggests that, in the upper stratified part of the water column, the diffusion mechanism is mostly associated with transient mixing events, which occur due to shear instability in the field of low frequency internal waves. We speculate that below 400 m bottom friction over the sloping bottom and geothermal heat flux play the decisive role in the vertical exchange. Analysis of the W(z) profiles reveals two layers dominated by the entrainment of the ambient fluid into the down flow of dense water from the Caribbean Sea, and two layers where this down flow breaks down through the formation of isopycnal intrusions.

Samodurov, A. S.; Scranton, M. I.; Astor, Y.; Ivanov, L. I.; Chukharev, A. M.; Belokopytov, V. N.; Globina, L. V.

2013-01-01

82

Effect of vertical heat transfer on thermocapillary convection in an open shallow rectangular cavity

NASA Astrophysics Data System (ADS)

In order to understand the effect of the vertical heat transfer on thermocapillary convection characteristics in a differentially heated open shallow rectangular cavity, a series of two- and three-dimensional numerical simulations were carried out by means of the finite volume method. The cavity was filled with the 1cSt silicone oil (Prandtl number Pr = 13.9) and the aspect ratio ranged from 12 to 30. Results show that thermocapillary convection is stable at a small Marangoni number. With the increase of the heat flux on the bottom surface, thermocapillary convection transits to the asymmetrical bi-cellular pattern with the opposite rotation direction. The roll near the hot wall shrinks as the Marangoni number increases. At a large Marangoni number, numerical simulations predict two types of the oscillatory thermocapillary flow. One is the hydrothermal wave, which is dominant only in a thin cavity. The other appears in a deeper cavity and is characterized by oscillating multi-cellular flow. The critical Marangoni number for the onset of the oscillatory flow increases first and then decreases with the increase of the vertical heat flux. The three-dimensional numerical simulation can predict the propagating direction of the hydrothermal wave. The velocity and temperature fields obtained by three-dimensional simulation in the meridian plane are very close to those obtained by two-dimensional simulation.

Li, You-Rong; Zhang, Hong-Ru; Wu, Chun-Mei; Xu, Jin-Liang

2012-02-01

83

Vibration Characteristics of a Vertical Round Tube According to Heat Transfer Regimes

This paper presents the results of an experimental work on the effects of boiling heat transfer regimes on the flow-induced vibration (FIV). The experiment has been performed using an electrically heated vertical round tube through which water flows at atmospheric pressure. Vibration characteristics of the heated tube are changed significantly by heat transfer regimes and flow patterns. For single-phase liquid convection, the rod vibrations are negligible. However, on the beginning of subcooled nucleate boiling at tube exit, vibration level becomes very large. As bubble departure occurs at the nucleation site of heated surface, the vibration decreases to saturated boiling region where thermal equilibrium quality becomes 0.0 at tube exit. In saturated boiling region, vibration amplitude increases with exit quality up to a certain maximum value due to the reinforced turbulence then decreases. At liquid film dryout condition, vibration could be regarded as negligible, however, these results cannot be extended to DNB-type CHF mechanism. Frequency analysis results of vibration signals suggested that excitation sources be different with heat transfer regimes. This study would contribute to improve the understanding of the relationship between boiling heat transfer and FIV. (authors)

Yong Ho Lee; Soon Heung Chang [Korea Advanced Institute of Science and Technology, 373-1, Guseung-dong, Yuseong-ku, Daejeon, 305-701 (Korea, Republic of); Won-Pil Baek [Korea Atomic Energy Research Institute, 150, Dukjin-Dong, Yusong-Gu, Taejon 305-353 (Korea, Republic of)

2002-07-01

84

NASA Astrophysics Data System (ADS)

The anomalous global atmospheric circulation associated with the Madden-Julian oscillation (MJO) is examined using composite vertical anomalous diabatic heating structures based on Tropical Rainfall Measuring Mission (TRMM) estimates and reanalysis datasets and integrating a primitive equations model. Variations in the dynamical response from the observational and reanalysis products are investigated in relation to the detailed structure of the vertical structure of heating of the MJO, with specific focus of the role of the westward tilting with altitude in the heating, clearly evident in three reanalysis heating structures but is less well pronounced in the TRMM heating structures. It was found that the atmospheric response to the reanalysis heatings were far more consistent compared to the responses from the TRMM heating estimates. Examination of the moisture flux during the main active phase of the MJO revealed a surplus in moisture convergence ahead of the anomalous heating from each of the reanalysis integrations, which was found to be directly attributed to the vertical tilt in heating structure. In contrast, the response to the TRMM heatings showed no phase shift in moisture convergence in relation to the convective heating and was understood to be a consequence of the weaker representation of vertical tilting in heating structure. It was suggested that the westward tilt in heating could therefore play an important role in promoting convection east of the main heating region. The dynamical response to composite vertical diabatic heating structures associated with the MJO from simulations with Unified Model (UM) HadGEM3 with standard and enhanced (x1.5) entrainment rates are also examined to investigate the relationship between the dynamical response to the heating profile and quality of MJO simulations.

Taylor, J.; Woolnough, S.; Inness, P.

2013-12-01

85

An energetic and exergetic modeling of a solar-assisted vertical ground-source heat pump (GSHP) greenhouse heating system (SAGSHPGHS) for system analysis and performance assessment is presented in this study. Energy (heating coefficient of performance ‘COP’) and exergy efficiencies at various reference and entering water temperatures are also determined. The actual thermal data collected are utilized for the model calculations at different

Onder Ozgener; Arif Hepbasli

2007-01-01

86

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

The subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3m\\/s), the inlet subcoolings (DeltaTsub, 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\\/tau), tau=38.1ms to 8.3s) are systematically measured by the experimental water loop installed the pressurizer. The SUS304 tube of test

Koichi Hata; Masahiro Shiotsu; Nobuaki Noda

2006-01-01

87

National Technical Information Service (NTIS)

The results of five practical vertical ground heat exchanger sizing programs are compared against a detailed simulation model that has been calibrated to monitored data taken from one military family housing unit at Fort Polk, Louisiana. The assertion tha...

J. W. Thornton T. P. McDowell P. J. Hughes

1997-01-01

88

Buoyant instabilities in downward flow in a symmetrically heated vertical channel

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.

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

1996-07-01

89

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

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.

2013-01-01

90

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

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

Uddin, Ziya; Harmand, Souad

2013-01-01

91

Two-phase distribution in the vertical flow line of a domestic wet central heating system

NASA Astrophysics Data System (ADS)

The theoretical and experimental aspects of bubble distribution in bubbly two-phase flow are reviewed in the context of the micro bubbles present in a domestic gas fired wet central heating system. The latter systems are mostly operated through the circulation of heated standard tap water through a closed loop circuit which often results in water supersaturated with dissolved air. This leads to micro bubble nucleation at the primary heat exchanger wall, followed by detachment along the flow. Consequently, a bubbly two-phase flow characterises the flow line of such systems. The two-phase distribution across the vertical and horizontal pipes was measured through a consideration of the volumetric void fraction, quantified through photographic techniques. The bubble distribution in the vertical pipe in down flow conditions was measured to be quasi homogenous across the pipe section with a negligible reduction in the void fraction at close proximity to the pipe wall. Such a reduction was more evident at lower bulk fluid velocities.

Fsadni, A.-M.; Ge, Y. T.

2013-04-01

92

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

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.

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

1991-10-01

93

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

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.

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

94

Vertical single-wall carbon nanotube forests as plasmonic heat pipes.

High thermal conductivity of carbon nanotubes (NTs) is attractive for the heat removal applications. However, the problem of efficient thermal coupling to the heater/cooler still needs to be resolved. We study near-field electromagnetic tunneling as a mechanism of heat transfer across the interface. We report interface thermal (Kapitza) conductance between a low-density vertical metallic single-wall NT forest and a quartz substrate on the order of 50 MW/Km(2) and explain it by strong electromagnetic interaction and near-field entanglement between the surface phonon-polaritons in the polar dielectric and the NT plasmons. We predict that the thickness of the NT film can be tweaked to the resonance wavelength of these entangled modes for performance optimization of nanocarbon thermal interconnects. PMID:22480248

Nemilentsau, Andrei M; Rotkin, Slava V

2012-05-22

95

NASA Astrophysics Data System (ADS)