Mercury Exchange at the Air-Water-Soil Interface: An Overview of Methods

Directory of Open Access Journals (Sweden)

Fengman Fang

2002-01-01

Full Text Available An attempt is made to assess the present knowledge about the methods of determining mercury (Hg exchange at the air-water-soil interface during the past 20 years. Methods determining processes of wet and dry removal/deposition of atmospheric Hg to aquatic and terrestrial ecosystems, as well as methods determining Hg emission fluxes to the atmosphere from natural surfaces (soil and water are discussed. On the basis of the impressive advances that have been made in the areas relating to Hg exchange among air-soil-water interfaces, we analyzed existing problems and shortcomings in our current knowledge. In addition, some important fields worth further research are discussed and proposed.

Global changes and the air-sea exchange of chemicals

International Nuclear Information System (INIS)

1991-01-01

Present and potential future changes to the global environment have important implications for marine pollution and for the air-sea exchange of both anthropogenic and natural substances. This report addresses three issues related to the potential impact of global change on the air-sea exchange of chemicals: Global change and the air-sea transfer of the nutrients nitrogen and iron. Global change and the air-sea exchange of gases. Oceanic responses to radiative and oxidative changes in the atmosphere. The deposition of atmospheric anthropogenic nitrogen has probably increased biological productivity in coastal regions along many continental margins. Atmospheric deposition of new nitrogen may also have increased productivity somewhat in mid-ocean regions. The projected future increases of nitrogen oxide emissions from Asia, Africa and South America will provide significant increases in the rate of deposition of oxidized nitrogen to the central North Pacific, the equatorial Atlantic, and the equatorial and central South Indian Oceans. Atmospheric iron may be an important nutrient in certain open regions. Future changes will likely occur if there are changing patterns of aridity and wind speed as a result of climate change. The most important future effects on surface ocean p CO2 will likely be caused by changes in ocean circulation. The pH of the ocean would decrease by ∼0.3 units for a doubling of p CO2 , reducing the capacity of the ocean to take up CO 2 . There is increasing evidence that dimethyl sulfide from the ocean is a source of cloud condensation nuclei and thus a factor controlling cloud albedo. By 2060 in the southern hemisphere reduction in total column stratospheric ozone from recent levels could reach 2 to 5% in the tropics, 10% at mid latitudes, and over 20% at 60 deg C. S. In this same time frame increases in ground-level effective UV-B radiation could reach 5%, 26% and 66%, at low, mid, and high latitudes in the southern hemisphere. Changes in

Tracers of air-sea gas exchange

International Nuclear Information System (INIS)

Liss, P.S.

1988-01-01

The flux of gas across the air-sea interface is determined by the product of the interfacial concentration difference driving the exchange and a rate constant, often termed the transfer velocity. The concentration-difference term is generally obtained by direct measurement, whereas more indirect approaches are required to estimate the transfer velocity and its variation as a function of controlling parameters such as wind and sea state. Radioactive tracers have proved particularly useful in the estimation of air-sea transfer velocities and, recently, stable purposeful tracers have also started to be used. In this paper the use of the following tracers to determine transfer velocities at the sea surface is discussed: natural and bomb-produced 14 C, dissolved oxygen, 222 Rn and sulphur hexafluoride. Other topics covered include the relation between transfer velocity and wind speed as deduced from tracer and wind-tunnel studies, and the discrepancy between transfer velocities determined by using tracers and from eddy correlation measurements in the atmosphere. (author)

Air-sea heat exchange, an element of the water cycle

Science.gov (United States)

Chahine, M. T.

1984-01-01

The distribution and variation of water vapor, clouds and precipitation are examined. Principal driving forces for these distributions are energy exchange and evaporation at the air-sea interface, which are also important elements of air-sea interaction studies. The overall aim of air-sea interaction studies is to quantitatively determine mass, momentum and energy fluxes, with the goal of understanding the mechanisms controlling them. The results of general circulation simulations indicate that the atmosphere in mid-latitudes responds to changes in the oceanic surface conditions in the tropics. This correlation reflects the strong interaction between tropical and mid-latitude conditions caused by the transport of heat and momentum from the tropics. Studies of air-sea exchanges involve a large number of physica, chemical and dynamical processes including heat flux, radiation, sea-surface temperature, precipitation, winds and ocean currents. The fluxes of latent heat are studied and the potential use of satellite data in determining them evaluated. Alternative ways of inferring heat fluxes will be considered.

Statistics of surface divergence and their relation to air-water gas transfer velocity

Science.gov (United States)

Asher, William E.; Liang, Hanzhuang; Zappa, Christopher J.; Loewen, Mark R.; Mukto, Moniz A.; Litchendorf, Trina M.; Jessup, Andrew T.

2012-05-01

Air-sea gas fluxes are generally defined in terms of the air/water concentration difference of the gas and the gas transfer velocity,kL. Because it is difficult to measure kLin the ocean, it is often parameterized using more easily measured physical properties. Surface divergence theory suggests that infrared (IR) images of the water surface, which contain information concerning the movement of water very near the air-water interface, might be used to estimatekL. Therefore, a series of experiments testing whether IR imagery could provide a convenient means for estimating the surface divergence applicable to air-sea exchange were conducted in a synthetic jet array tank embedded in a wind tunnel. Gas transfer velocities were measured as a function of wind stress and mechanically generated turbulence; laser-induced fluorescence was used to measure the concentration of carbon dioxide in the top 300 μm of the water surface; IR imagery was used to measure the spatial and temporal distribution of the aqueous skin temperature; and particle image velocimetry was used to measure turbulence at a depth of 1 cm below the air-water interface. It is shown that an estimate of the surface divergence for both wind-shear driven turbulence and mechanically generated turbulence can be derived from the surface skin temperature. The estimates derived from the IR images are compared to velocity field divergences measured by the PIV and to independent estimates of the divergence made using the laser-induced fluorescence data. Divergence is shown to scale withkLvalues measured using gaseous tracers as predicted by conceptual models for both wind-driven and mechanically generated turbulence.

Continuous measurement of air-water gas exchange by underwater eddy covariance

Science.gov (United States)

Berg, Peter; Pace, Michael L.

2017-12-01

Exchange of gases, such as O2, CO2, and CH4, over the air-water interface is an important component in aquatic ecosystem studies, but exchange rates are typically measured or estimated with substantial uncertainties. This diminishes the precision of common ecosystem assessments associated with gas exchanges such as primary production, respiration, and greenhouse gas emission. Here, we used the aquatic eddy covariance technique - originally developed for benthic O2 flux measurements - right below the air-water interface (˜ 4 cm) to determine gas exchange rates and coefficients. Using an acoustic Doppler velocimeter and a fast-responding dual O2-temperature sensor mounted on a floating platform the 3-D water velocity, O2 concentration, and temperature were measured at high-speed (64 Hz). By combining these data, concurrent vertical fluxes of O2 and heat across the air-water interface were derived, and gas exchange coefficients were calculated from the former. Proof-of-concept deployments at different river sites gave standard gas exchange coefficients (k600) in the range of published values. A 40 h long deployment revealed a distinct diurnal pattern in air-water exchange of O2 that was controlled largely by physical processes (e.g., diurnal variations in air temperature and associated air-water heat fluxes) and not by biological activity (primary production and respiration). This physical control of gas exchange can be prevalent in lotic systems and adds uncertainty to assessments of biological activity that are based on measured water column O2 concentration changes. For example, in the 40 h deployment, there was near-constant river flow and insignificant winds - two main drivers of lotic gas exchange - but we found gas exchange coefficients that varied by several fold. This was presumably caused by the formation and erosion of vertical temperature-density gradients in the surface water driven by the heat flux into or out of the river that affected the turbulent

CONVECTIVE HEAT EXCHANGE ON THE LATERAL SURFACE OF A RELATIVELY LONG CYCLONE CHAMBER

Directory of Open Access Journals (Sweden)

E. N. Saburov

2016-01-01

Full Text Available The high-turbulent swirling flows of heat carrier that are created by a cyclone chamber are used in industry. They make it possible to intensify processes of heat and mass exchange. The results of an experimental study of convective heat transfer on the lateral surface of the active volume of a relatively long cyclone chamber considerably exceeding the length of the chambers that were used in previously performed studies are presented and analyzed in the article. Air supply in the swirler of the chamber was performed tangentially from diametrically opposite sides of the two input channels. The gas outlet was implemented from the opposite end. The heat transfer by convection to the swirling air flow was studied by the method of changing the state of aggregation of a heating agent – condensation of slightly superheated steam. Collecting condensate from the working section was made through a water seal for maintaining a constant pressure calorimeter. The amount of heat transferred during experiment was determined by weight of the collected condensate. The specific features of influence of geometrical characteristics of cyclone chamber on intensity of heat exchange are considered. In the experiments we varied the relative diameter of the outlet port of the chamber dвых and the relative area of the input channels fвх. Segmental construction of the chamber made it possible to move a calorimeter on its length. The local heat transfer coefficient was determined for various values of the dimensionless longitudinal coordinate z coinciding with the axis of the chamber, and counted from the back end of the swirler. The estimated equations of heat transfer obtained during the research are presented and recommended for use in practice of engineering. The considered problem is of an interest from the point of view of further research of aerodynamics and of convective heat transfer in a highly swirling flow cyclone devices, in order to improve the

Heat Recovery Ventilation for Housing: Air-to-Air Heat Exchangers.

Science.gov (United States)

Corbett, Robert J.; Miller, Barbara

The air-to-air heat exchanger (a fan powered ventilation device that recovers heat from stale outgoing air) is explained in this six-part publication. Topic areas addressed are: (1) the nature of air-to-air heat exchangers and how they work; (2) choosing and sizing the system; (3) installation, control, and maintenance of the system; (4) heat…

Air-side performance evaluation of three types of heat exchangers in dry, wet and periodic frosting conditions

Energy Technology Data Exchange (ETDEWEB)

Zhang, Ping [Zhejiang Vocational College of Commerce, Hangzhou, Binwen Road 470 (China); Department of Mechanical Science and Engineering University of Illinois at Urbana-Champaign 1206 West Green Street, Urbana, IL 61801 (United States); Hrnjak, P.S. [Department of Mechanical Science and Engineering University of Illinois at Urbana-Champaign 1206 West Green Street, Urbana, IL 61801 (United States)

2009-08-15

The performances of three types of heat exchangers that use the louver fin geometry: (1) parallel flow parallel fin with extruded flat tubes heat exchanger (PF{sup 2}), (2) parallel flow serpentine fin with extruded flat tubes heat exchanger (PFSF) and (3) round tube wave plate fin heat exchanger (RTPF) have been experimentally studied under dry, wet and frost conditions and results are presented. The parameters quantified include air-side pressure drop, water retention on the surface of the heat exchanger, capacity and overall heat transfer coefficient for air face velocity 0.9, 2 and 3 m/s, air humidity 70% and 80% and different orientations. The performances of three types of heat exchanger are compared and the results obtained are presented. The condensate drainage behavior of the air-side surface of these three heat exchanger types was studied using both the dip testing method and wind tunnel experiment. (author)

Tritiated water vapor in the surface air at Tokyo

International Nuclear Information System (INIS)

Inoue, Hisayuki; Katsuragi, Yukio; Shigehara, Koji

1984-01-01

Tritium concentration in water vapor in the air near the surface and in the precipitation at Tokyo was measured during the period from 9 August to 20 November in 1974. From August to the middle of October, tritium mixing ratios in the surface air had relatively higher values except those in air masses which were associated with a typhoon. The mixing ratios of tritium in the air decreased abruptly at the middle of October, which indicates the decrease of tritium influx from aloft. These data exhibit the salient feature that variations in tritium concentration in TR are linear to the reciprocal of the content of water vapor during each period. Tritium concentrations in vapor and rain water collected simultaneously show nearly equal values. One of the reasons for the good correlation of tritium concentration between falling drops and ambient air is considered to be the result of the rapid isotopic exchange. (author)

Influence of the convective surface transfer coefficients on the Heat, Air, and Moisture (HAM) building performance

DEFF Research Database (Denmark)

Steskens, Paul Wilhelmus Maria Hermanus; Janssen, Hans; Rode, Carsten

2009-01-01

Current models to predict heat, air and moisture (HAM) conditions in buildings assume constant boundary conditions for the temperature and relative humidity of the neighbouring air and for the surface heat and moisture transfer coefficients. These assumptions may introduce errors in the predicted...... influence on the predicted hygrothermal conditions at the surface of a building component and on the heat and vapour exchange with the indoor environment....

Radiative heat exchange between surfaces

International Nuclear Information System (INIS)

Yener, Y.; Yuncu, H.

1987-01-01

The geometrical features of radiative heat exchange between surfaces are discussed first by developing various radiation shape factor relations. The governing equations for enclosures with diffusely emitting and diffusely reflecting surfaces, as well as the equations for enclosures with gray surfaces having specular component of reflectivity are introduced next. Finally, a simplified model for enclosures with isothermal surfaces under the assumption of uniform radiosity over the surfaces is discussed, and various working relations for different conditions are presented

Plate heat exchangers in air conditioning applications. Development of air-coolers, air-heaters and air-conditioning units with low pressure loss. Plattenwaermetauscher in raumlufttechnischen Anlagen. Entwicklung stroemungsoptimierter Luftkuehler, Lufterhitzer und Klimageraete

Energy Technology Data Exchange (ETDEWEB)

Bach, H; Diemer, R; Eisenmann, G; Goettling, D; Madjidi, M

1989-08-01

To prepare the development of a water to air plate heat exchanger the state of the art, i.e. the technological knowhow and the design basis are given. The concept and ideas are presented which lead to a slightly wavy plate. Furthermore an exemplary design of a plate heat exchanger and an air-conditioning unit is described and finally the application of plate heat exchangers as direct evaporators and the potential icing problems are investigated. Comparing measured and calculated data shows that the performance of plates with plane surfaces can be predicted fairly well by the presented design methods. The performance of plates with strongly wavy surface however has to be measured. Optimization calculations yield to an air gap of slightly over 4 mm. Comparison with an air-conditioning unit demonstrates that the strongest advantage is for the air cooler (one third of the pressure loss) that a new concept of an air-conditioning unit has lower losses in the fan unit and that it does not need an eliminator. This results in half the volume for the new unit, in a pressure drop of 88%, fan power of 90% and fan revolutions of 50%. (orig./GL).

Air-surface exchange measurements of gaseous elemental mercury over naturally enriched and background terrestrial landscapes in Australia

Directory of Open Access Journals (Sweden)

G. C. Edwards

2013-05-01

Full Text Available This paper presents the first gaseous elemental mercury (GEM air-surface exchange measurements obtained over naturally enriched and background (−1 Hg terrestrial landscapes in Australia. Two pilot field studies were carried out during the Australian autumn and winter periods at a copper-gold-cobalt-arsenic-mercury mineral field near Pulganbar, NSW. GEM fluxes using a dynamic flux chamber approach were measured, along with controlling environmental parameters over three naturally enriched and three background substrates. The enriched sites results showed net emission to the atmosphere and a strong correlation between flux and substrate Hg concentration, with average fluxes ranging from 14 ± 1 ng m−2 h−1 to 113 ± 6 ng m−2 h−1. Measurements at background sites showed both emission and deposition. The average Hg flux from all background sites showed an overall net emission of 0.36 ± 0.06 ng m−2 h−1. Fluxes show strong relationships with temperature, radiation, and substrate parameters. A compensation point of 2.48, representative of bare soils was determined. For periods of deposition, dry deposition velocities ranged from 0.00025 cm s−1 to 0.0083 cm s−1 with an average of 0.0041 ± 0.00018 cm s−1, representing bare soil, nighttime conditions. Comparison of the Australian data to North American data suggests the need for Australian-specific mercury air-surface exchange data representative of Australia's unique climatic conditions, vegetation types, land use patterns and soils.

Aqueous turbulence structure immediately adjacent to the air - water interface and interfacial gas exchange

Science.gov (United States)

Wang, Binbin

. Comparison between the turbulence structures measured during the wind wave initiation period and those obtained during the growing period was presented. Significant wave effects on near surface turbulence were found. A universal scaling law was proposed to parameterize turbulent dissipation rate immediately below the air-water interface with friction velocity, significant wave height and wave age. Finally, the gas transfer velocity was measured with a floating chamber (FC) system, along with simultaneously FPIV measurements. Turbulent dissipation rate both at the interface and at a short distance away from the interface (~ 10 cm) were analyzed and used to examine the small scale eddy model. The model coefficient was found to be dependent on the level of turbulence, instead of being a constant. An empirical relationship between the model coefficient and turbulent dissipation rate was provided, which improved the accuracy of the gas transfer velocity estimation by more than 100% for data acquired. Other data from the literature also supported this empirical relation. Furthermore, the relationship between model coefficient and turbulent Reynolds number was also investigated. In addition to physical control of gas exchange, the disturbance on near surface hydrodynamics by the FC was also discussed. Turbulent dissipation rates are enhanced at the short distance away from the interface, while the surface dissipation rates do not change significantly.

An experimental study of the air-side particulate fouling in finned-tube heat exchangers of air conditioners through accelerated tests

International Nuclear Information System (INIS)

Ahn, Young Chull; Cho, Jae Min; Lee, Jae Keun; Lee, Hyun Uk; Ahn, Seung Phyo; Youn, Deok Hyun; Kang, Tae Wook; Ock, Ju Jo

2003-01-01

The air-side particulate fouling in the heat exchangers of HVAC applications degrades the performance of cooling capacity, pressure drop across a heat exchanger, and indoor air quality. Indoor and outdoor air contaminants foul heat exchangers. The purpose of this study is to investigate the fouling characteristics trough accelerated tests. The fouling characteristics are analyzed as functions of a dust concentration (1.28 and 3.84 g/m 3 ), a face velocity (0.5, 1.0, and 1.5 m/s), and a surface condition. The cooling capacity in the slitted finned-tube heat exchangers at the face velocity of 1 m/s decreases about 2% and the pressure drop increases up to 57%. The rate of build-up of fouling is observed to be 3 times slower for this three-fold reduction of dust concentration whilst still approaching the same asymptotic level

Spatiotemporally resolved air exchange rate as a modifier of acute air pollution-related morbidity in Atlanta.

Science.gov (United States)

Sarnat, Jeremy A; Sarnat, Stefanie Ebelt; Flanders, W Dana; Chang, Howard H; Mulholland, James; Baxter, Lisa; Isakov, Vlad; Özkaynak, Halûk

2013-01-01

Epidemiological studies frequently use central site concentrations as surrogates of exposure to air pollutants. Variability in air pollutant infiltration due to differential air exchange rates (AERs) is potentially a major factor affecting the relationship between central site concentrations and actual exposure, and may thus influence observed health risk estimates. In this analysis, we examined AER as an effect modifier of associations between several urban air pollutants and corresponding emergency department (ED) visits for asthma and wheeze during a 4-year study period (January 1999-December 2002) for a 186 ZIP code area in metro Atlanta. We found positive associations for the interaction between AER and pollution on asthma ED visits for both carbon monoxide (CO) and nitrogen oxides (NO(x)), indicating significant or near-significant effect modification by AER on the pollutant risk-ratio estimates. In contrast, the interaction term between particulate matter (PM)(2.5) and AER on asthma ED visits was negative and significant. However, alternative distributional tertile analyses showed PM(2.5) and AER epidemiological model results to be similar to those found for NOx and CO (namely, increasing risk ratios (RRs) with increasing AERs when ambient PM(2.5) concentrations were below the highest tertile of their distribution). Despite the fact that ozone (O(3)) was a strong independent predictor of asthma ED visits in our main analysis, we found no O(3)-AER effect modification. To our knowledge, our findings for CO, NOx, and PM(2.5) are the first to provide an indication of short-term (i.e., daily) effect modification of multiple air pollution-related risk associations with daily changes in AER. Although limited to one outcome category in a single large urban locale, the findings suggest that the use of relatively simple and easy-to-derive AER surrogates may reflect intraurban differences in short-term exposures to pollutants of ambient origin.

A coupled surface/subsurface flow model accounting for air entrapment and air pressure counterflow

DEFF Research Database (Denmark)

Delfs, Jens Olaf; Wang, Wenqing; Kalbacher, Thomas

2013-01-01

wave) shallow flow and two-phase flow in a porous medium. The simultaneous mass transfer between the soil, overland, and atmosphere compartments is achieved by upgrading a fully established leakance concept for overland-soil liquid exchange to an air exchange flux between soil and atmosphere. In a new...... algorithm, leakances operate as a valve for gas pressure in a liquid-covered porous medium facilitating the simulation of air out-break events through the land surface. General criteria are stated to guarantee stability in a sequential iterative coupling algorithm and, in addition, for leakances to control...

Surface area of antimony oxide by isotope exchange and other methods

Energy Technology Data Exchange (ETDEWEB)

Rao, Y.K.; Acharya, B.V.; Rangamannar, B.

1985-06-17

Specific surface areas of antimony oxide samples, one commercial, the other prepared from antimony trichloride were measured by heterogeneous isotope exchange, gas adsorption, air permeability and microscopic methods. Specific surface areas obtained by these four methods for the two samples were compared and the observed differences are explained.

Air and Ground Surface Temperature Relations in a Mountainous Basin, Wolf Creek, Yukon Territory

Science.gov (United States)

Roadhouse, Emily A.

The links between climate and permafrost are well known, but the precise nature of the relationship between air and ground temperatures remains poorly understood, particularly in complex mountain environments. Although previous studies indicate that elevation and potential incoming solar radiation (PISR) are the two leading factors contributing to the existence of permafrost at a given location, additional factors may also contribute significantly to the existence of mountain permafrost, including vegetation cover, snow accumulation and the degree to which individual mountain landscapes are prone to air temperature inversions. Current mountain permafrost models consider only elevation and aspect, and have not been able to deal with inversion effects in a systematic fashion. This thesis explores the relationship between air and ground surface temperatures and the presence of surface-based inversions at 27 sites within the Wolf Creek basin and surrounding area between 2001 and 2006, as a first step in developing an improved permafrost distribution TTOP model. The TTOP model describes the relationship between the mean annual air temperature and the temperature at the top of permafrost in terms of the surface and thermal offsets (Smith and Riseborough, 2002). Key components of this model are n-factors which relate air and ground climate by establishing the ratio between air and surface freezing (winter) and thawing (summer) degree-days, thus summarizing the surface energy balance on a seasonal basis. Here we examine (1) surface offsets and (2) freezing and thawing n-factor variability at a number of sites through altitudinal treeline in the southern Yukon. Thawing n-factors (nt) measured at individual sites remained relatively constant from one year to the next and may be related to land cover. During the winter, the insulating effect of a thick snow cover results in higher surface temperatures, while thin snow cover results in low surface temperatures more closely

Experimental evaluation of sodium to air heat exchanger performance

International Nuclear Information System (INIS)

Vinod, V.; Pathak, S.P.; Paunikar, V.D.; Suresh Kumar, V.A.; Noushad, I.B.; Rajan, K.K.

2013-01-01

Highlights: ► Sodium to air heat exchangers are used to remove the decay heat produced in fast breeder reactor after shutdown. ► Finned tube sodium to air heat exchanger with sodium on tube side was tested for its heat transfer performance. ► A one dimensional computer code was validated by the experimental data obtained. ► Non uniform sodium and air flow distribution was present in the heat exchanger. - Abstract: Sodium to air heat exchangers (AHXs) is used in Prototype Fast Breeder Reactor (PFBR) circuits to reject the decay heat produced by the radioactive decay of the fission products after reactor shutdown, to the atmospheric air. The heat removal through sodium to air heat exchanger maintains the temperature of reactor components in the pool within safe limits in case of non availability of normal heat transport path. The performance of sodium to air heat exchanger is very critical to ensure high reliability of the decay heat removal systems in sodium cooled fast breeder reactors. Hence experimental evaluation of the adequacy of the heat transfer capability gives confidence to the designers. A finned tube cross flow sodium to air heat exchanger of 2 MW heat transfer capacity with sodium on tube side and air on shell side was tested in the Steam Generator Test Facility at Indira Gandhi Center for Atomic Research, India. Heat transfer experiments were carried out with forced circulation of sodium and air, which confirmed the adequacy of heat removal capacity of the heat exchanger. The testing showed that 2.34 MW of heat power is transferred from sodium to air at nominal flow and temperature conditions. A one dimensional computer code developed for design and analysis of the sodium to air heat exchanger was validated by the experimental data obtained. An equivalent Nusselt number, Nu eq is derived by approximating that the resistance of heat transfer from sodium to air is contributed only by the film resistance of air. The variation of Nu eq with respect

On factors influencing air-water gas exchange in emergent wetlands

Science.gov (United States)

Ho, David T.; Engel, Victor C.; Ferron, Sara; Hickman, Benjamin; Choi, Jay; Harvey, Judson W.

2018-01-01

Knowledge of gas exchange in wetlands is important in order to determine fluxes of climatically and biogeochemically important trace gases and to conduct mass balances for metabolism studies. Very few studies have been conducted to quantify gas transfer velocities in wetlands, and many wind speed/gas exchange parameterizations used in oceanographic or limnological settings are inappropriate under conditions found in wetlands. Here six measurements of gas transfer velocities are made with SF6 tracer release experiments in three different years in the Everglades, a subtropical peatland with surface water flowing through emergent vegetation. The experiments were conducted under different flow conditions and with different amounts of emergent vegetation to determine the influence of wind, rain, water flow, waterside thermal convection, and vegetation on air-water gas exchange in wetlands. Measured gas transfer velocities under the different conditions ranged from 1.1 cm h−1 during baseline conditions to 3.2 cm h−1 when rain and water flow rates were high. Commonly used wind speed/gas exchange relationships would overestimate the gas transfer velocity by a factor of 1.2 to 6.8. Gas exchange due to thermal convection was relatively constant and accounted for 14 to 51% of the total measured gas exchange. Differences in rain and water flow among the different years were responsible for the variability in gas exchange, with flow accounting for 37 to 77% of the gas exchange, and rain responsible for up to 40%.

Global changes and the air-sea exchange of chemicals. Reports and studies. No. 48

Energy Technology Data Exchange (ETDEWEB)

GESAMP-IMO/FAO/UNESCO/WMO/WHO/IAEA/UN/UNEP Joint Group of Experts on the Scientific Aspects of Marine Pollution

1992-12-31

Present and future changes to global environment have implications for marine pollution and for air-sea exchange of both anthropogenic and natural substances. This report addresses 3 issues related to potential impact of global change on air-sea exchange of chemicals: Global change and air-sea transfer of nutrients nitrogen and iron. Global change and air-sea exchange of gases. Oceanic responses to radiative and oxidative changes in atmosphere. Deposition of atmospheric anthropogenic nitrogen has probably increased bio- productivity in coastal regions along continental margins. Atmospheric deposition of new nitrogen may also have increased productivity somewhat in mid-ocean regions. Projected future increases of N oxide emissions from Asia, Africa and South America will increase the rate of deposition of oxidized nitrogen to central North Pacific, equatorial Atlantic, and equatorial and central South Indian Oceans. Atmospheric iron may be an important nutrient in certain open regions. Future changes will likely occur from changed aridity and wind speed as a result of climate change. The most important future effects on surface ocean p{sub CO2} will likely be caused by changes in ocean circulation. The pH of ocean would decrease by {approx}0.3 units for a doubling of p{sub CO2}, reducing the capacity of the ocean to take up CO{sub 2}. There is evidence that dimethyl sulfide from ocean is a source of cloud condensation nuclei and thus a factor controlling cloud albedo. By 2060 in the southern hemisphere reduction in total column stratospheric ozone from recent levels could reach 2 to 5% in the tropics, 10% at mid latitudes, and over 20% at 60 deg C. S. Increases in ground-level effective UV-B radiation could also reach 5%, 26% and 66%, at low, mid, and high latitudes in southern hemisphere. Changes in photochemical processes in the surface waters of the ocean could also happen.

Experimental study of heat transfer and pressure drop characteristics of air/water and air-steam/water heat exchange in a polymer compact heat exchanger

NARCIS (Netherlands)

Cheng, L.; Geld, van der C.W.M.

2005-01-01

Experiments of heat transfer and pressure drop in a polymer compact heat exchanger made of PolyVinyliDene-Fluoride were conducted under various conditions for air/water heat exchange and air-steam/water heat exchange, respectively. The overall heat transfer coefficients of air-steam/water heat

Application of ground-to-air heat exchanger for preheating of supply air

Science.gov (United States)

Sorokins, Juris; Borodinecs, Anatolijs; Zemitis, Jurgis

2017-10-01

This study focuses on assessing the contribution of the passive ground-coupled air heat exchanger system to decreasing the energy consumption of air conditioning and ventilation systems for office buildings in the Latvian climate conditions. The theoretical part of the thesis deals with methods of office building ventilation, supply air preheating and heat recovery as well as particularities of using ground-coupled air heat exchangers, their design parameters and their joint impact on the thermal performance. The engineering project part includes a ventilation system for an office building with an integrated ground-coupled air heat exchanger. By simulating energy consumption of the ventilation system for a duration of one year, the thesis analyzes the contribution of the heat exchanger to the overall energy consumption, which totals 9.53 MWh and 4.02 MWh a year, according to the desired parameters of the indoor climate. The possible alternative heat recovery solutions are investigated to reach by European Regional Development Fund project Nr.1.1.1.1/16/A/048 “NEARLY ZERO ENERGY SOLUTIONS FOR UNCLASSIFIED BUILDINGS”.

Anti-freezing of air-cooled heat exchanger by switching off sectors

International Nuclear Information System (INIS)

Wang, Weijia; Kong, Yanqiang; Huang, Xianwei; Yang, Lijun; Du, Xiaoze; Yang, Yongping

2017-01-01

Highlights: • The anti-freezing of air-cooled heat exchanger by switching off sectors is studied. • The water side heat loads of various sectors are compared for different cases. • Anti-freezing turbine back pressure is proposed and obtained for various cases. • As wind speed increases, the energy efficiency can be clearly improved by sector off. • By switching frontal sector off, anti-freezing operation is most energy efficient. - Abstract: With the air side huge heat transfer surface, the air-cooled heat exchanger will take a serious freezing risk in cold winter. Therefore, it is of benefit to the safe operation of natural draft dry cooling system to propose the anti-freezing measures. In this work, the flow and heat transfer models of the cooling air coupling with the circulating water, are developed and numerically simulated for the anti-freezing by switching various sectors off. The local thermo-flow fields of cooling air are presented, and the water side heat loads of various sectors are compared for various cases. The anti-freezing turbine back pressure is proposed and obtained for the energy efficiency analysis. The results show that the sector switching off approach can effectively prevent the air-cooled heat exchanger from freezing and improve the energy efficiency of the cooling system, especially at high wind speeds. Moreover, with the frontal sector switching off, the most energy efficient anti-freezing operation of natural draft dry cooling system can be achieved.

Thermal-economic optimization of an air-cooled heat exchanger unit

International Nuclear Information System (INIS)

Alinia Kashani, Amir Hesam; Maddahi, Alireza; Hajabdollahi, Hassan

2013-01-01

Thermodynamic modeling and optimal design of an air-cooled heat exchanger (ACHE) unit are developed in this study. For this purpose, ε–NTU method and mathematical relations are applied to estimate the fluids outlet temperatures and pressure drops in tube and air sides. The main goal of this study is minimizing of two conflicting objective functions namely the temperature approach and the minimum total annual cost, simultaneously. For this purpose, fast and elitist non-dominated sorting genetic-algorithm (NSGA-II) is applied to minimize the objective functions by considering ten design parameters. In addition, a set of typical constraints, governing on the ACHE unit design, is subjected to obtain more practical optimum design points. Furthermore, sensitivity analysis of change in the objective functions, when the optimum design parameters vary, is conducted and the degree of each parameter on conflicting objective functions has been investigated. Finally, a selection procedure of the best optimum point is introduced and final optimum design point is determined. -- Highlights: ► Multi-objective optimization of air-cooled heat exchanger. ► Considering ten new design parameters in this type of heat exchanger. ► A detailed cost function is used to estimate the heat exchanger investment cost. ► Presenting a mathematical relation for optimum total cost vs. temperature approach. ► The sensitivity analysis of parameters in the optimum situation

Global Validation of MODIS Atmospheric Profile-Derived Near-Surface Air Temperature and Dew Point Estimates

Science.gov (United States)

Famiglietti, C.; Fisher, J.; Halverson, G. H.

2017-12-01

This study validates a method of remote sensing near-surface meteorology that vertically interpolates MODIS atmospheric profiles to surface pressure level. The extraction of air temperature and dew point observations at a two-meter reference height from 2001 to 2014 yields global moderate- to fine-resolution near-surface temperature distributions that are compared to geographically and temporally corresponding measurements from 114 ground meteorological stations distributed worldwide. This analysis is the first robust, large-scale validation of the MODIS-derived near-surface air temperature and dew point estimates, both of which serve as key inputs in models of energy, water, and carbon exchange between the land surface and the atmosphere. Results show strong linear correlations between remotely sensed and in-situ near-surface air temperature measurements (R2 = 0.89), as well as between dew point observations (R2 = 0.77). Performance is relatively uniform across climate zones. The extension of mean climate-wise percent errors to the entire remote sensing dataset allows for the determination of MODIS air temperature and dew point uncertainties on a global scale.

Global observations and modeling of atmosphere-surface exchange of elemental mercury: a critical review

Science.gov (United States)

Zhu, Wei; Lin, Che-Jen; Wang, Xun; Sommar, Jonas; Fu, Xuewu; Feng, Xinbin

2016-04-01

Reliable quantification of air-surface fluxes of elemental Hg vapor (Hg0) is crucial for understanding mercury (Hg) global biogeochemical cycles. There have been extensive measurements and modeling efforts devoted to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc.) in the past three decades. However, large uncertainties remain due to the complexity of Hg0 bidirectional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a critical review on the state of science in the atmosphere-surface exchange of Hg0. Specifically, the advancement of flux quantification techniques, mechanisms in driving the air-surface Hg exchange and modeling efforts are presented. Due to the semi-volatile nature of Hg0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence and the presence of reactants (e.g., O3, radicals, etc.). However, the effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling. We compile an up-to-date global observational flux database and discuss the implication of flux data on the global Hg budget. Mean Hg0 fluxes obtained by micrometeorological measurements do not appear to be significantly greater than the fluxes measured by dynamic flux chamber methods over unpolluted surfaces (p = 0.16, one-tailed, Mann-Whitney U test). The spatiotemporal coverage of existing Hg0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia). The magnitude of the evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg0 flux observations in East

20 Years of Air-Water Gas Exchange Observations for Pesticides in the Western Arctic Ocean.

Science.gov (United States)

Jantunen, Liisa M; Wong, Fiona; Gawor, Anya; Kylin, Henrik; Helm, Paul A; Stern, Gary A; Strachan, William M J; Burniston, Deborah A; Bidleman, Terry F

2015-12-01

The Arctic has been contaminated by legacy organochlorine pesticides (OCPs) and currently used pesticides (CUPs) through atmospheric transport and oceanic currents. Here we report the time trends and air-water exchange of OCPs and CUPs from research expeditions conducted between 1993 and 2013. Compounds determined in both air and water were trans- and cis-chlordanes (TC, CC), trans- and cis-nonachlors (TN, CN), heptachlor exo-epoxide (HEPX), dieldrin (DIEL), chlorobornanes (ΣCHBs and toxaphene), dacthal (DAC), endosulfans and metabolite endosulfan sulfate (ENDO-I, ENDO-II, and ENDO SUL), chlorothalonil (CHT), chlorpyrifos (CPF), and trifluralin (TFN). Pentachloronitrobenzene (PCNB and quintozene) and its soil metabolite pentachlorothianisole (PCTA) were also found in air. Concentrations of most OCPs declined in surface water, whereas some CUPs increased (ENDO-I, CHT, and TFN) or showed no significant change (CPF and DAC), and most compounds declined in air. Chlordane compound fractions TC/(TC + CC) and TC/(TC + CC + TN) decreased in water and air, while CC/(TC + CC + TN) increased. TN/(TC + CC + TN) also increased in air and slightly, but not significantly, in water. These changes suggest selective removal of more labile TC and/or a shift in chlordane sources. Water-air fugacity ratios indicated net volatilization (FR > 1.0) or near equilibrium (FR not significantly different from 1.0) for most OCPs but net deposition (FR exchange direction of other CUPs varied. Understanding the processes and current state of air-surface exchange helps to interpret environmental exposure and evaluate the effectiveness of international protocols and provides insights for the environmental fate of new and emerging chemicals.

Relationship between indoor radon concentrations and air exchange rate

International Nuclear Information System (INIS)

Wang Jingshu; Liu Yuyu; Yao Xiaohua; Meng Jianfeng; Zhang Yongyi; Wang Xiaohe; Yu Xiufen.

1995-01-01

The indoor concentration of radon and the air exchange rate were simultaneously measured in four empty rooms, made of brick and cement, which were located in different floors of dwelling houses in Taiyuan, Shanxi, China. SF 6 tracer gas decay method was used to measure the air exchange rate. Indoor radon was collected with the dimembrane method. When the ventilation rate increased, the concentration of radon dropped rapidly. Regression analysis indicated that the indoor concentration of radon was equal to the outdoor level of radon when the air exchange rate was greater than 3-4. SF 6 decay method was an effective and convenient method for measuring the air exchange rate. There was no marked difference in measurements obtained in different locations of a room. (N.K.)

Dry/wet performance of a plate-fin air-cooled heat exchanger with continuous corrugated fins

International Nuclear Information System (INIS)

Hauser, S.G.; Kreid, D.K.; Johnson, B.M.

1981-01-01

The performance and operating characteristics of a plate-fin heat exchanger in dry/wet or deluge operations was experimentally determined. Development of the deluge heat/mass transfer model continued. The experiments were conducted in a specially-designed wind tunnel at the PNL. Air that was first heated and humidified to specified conditions was circulated at a controlled rate through a 2 ft x 6 ft heat exchanger module. The heat exchanger used in the tests was a wavy surface, plate fin on tube configuration. Hot water was circulated through the tubes at high flow rates to maintain an essentially isothermal condition on the tube side. Deionized water sprayed on the top of the vertically oriented plate fins was collected at the bottom of the core and recirculated. Instrumentation was provided for measurement of flow rates and thermodynamic conditions in the air, in the core circulation water, and in the deluge water. Measurements of the air side pressure drop and heat rejection rate were made as a function of air flow rate, air inlet temperature and humidity, deluge water flow rate, and the core inclination from the vertical. An overall heat transfer coefficient and an effective deluge film convective coefficient was determined. The deluge model, for predicting heat transfer from a wet finned heat exchanger was further developed and refined, and a major extension of the model was formulated that permits simultaneous calculation of both the heat transfer and evaporation rates from the wetted surface. The experiments showed an increase in the heat rejection rate due to wetting, accompanied by a proportional increase in the air side pressure drop. For operation at the same air side pressure drop, the enhancement ratio Q/sub w//Q/sub d/ varied between 2 and 5 for the conditions tested. Thus, the potential enhancement of heat transfer due to wetting can be substantial

Impact of ambient air temperature and heat load variation on the performance of air-cooled heat exchangers in propane cycles in LNG plants – Analytical approach

International Nuclear Information System (INIS)

Fahmy, M.F.M.; Nabih, H.I.

2016-01-01

Highlights: • An analytical method regulated the air flow rate in an air-cooled heat exchanger. • Performance of an ACHE in a propane cycle in an LNG plant was evaluated. • Summer inlet air temperature had higher impact on ACHE air flow rate requirement. - Abstract: An analytical method is presented to evaluate the air flow rate required in an air-cooled heat exchanger used in a propane pre-cooling cycle operating in an LNG (liquefied natural gas) plant. With variable ambient air inlet temperature, the air flow rate is to be increased or decreased so as to assure and maintain good performance of the operating air-cooled heat exchanger at the designed parameters and specifications. This analytical approach accounts for the variations in both heat load and ambient air inlet temperature. The ambient air inlet temperature is modeled analytically by simplified periodic relations. Thus, a complete analytical method is described so as to manage the problem of determining and accordingly regulate, either manually or automatically, the flow rate of air across the finned tubes of the air-cooled heat exchanger and thus, controls the process fluid outlet temperature required for the air-cooled heat exchangers for both cases of constant and varying heat loads and ambient air inlet temperatures. Numerical results are obtained showing the performance of the air-cooled heat exchanger of a propane cycle which cools both NG (natural gas) and MR (mixed refrigerant) streams in the LNG plant located at Damietta, Egypt. The inlet air temperature variation in the summer time has a considerable effect on the required air mass flow rate, while its influence becomes relatively less pronounced in winter.

Quasi-steady-state model of a counter flow air-to-air heat exchanger with phase change

DEFF Research Database (Denmark)

Rose, Jørgen; Nielsen, Toke Rammer; Kragh, Jesper

2008-01-01

-exchanger. Developing highly efficient heat-exchangers and strategies to avoid/remove frost formation implies the use of detailed models to predict and evaluate different heat-exchanger designs and strategies. This paper presents a quasi-steady-state model of a counter-flow air-to-air heat-exchanger that takes...

Safety technology for air-cooled heat exchangers

International Nuclear Information System (INIS)

Kawai, Masafumi; Miyamoto, Hitoshi

2011-01-01

The air-cooled heat exchanger is a device that enables a large amount of heat exchange (cooling) by utilizing the atmosphere as a stable and infinite heat sink. It is widely used in general industrial plants, and nowadays it is also utilized in nuclear facilities. This type of exchanger is advantageous in that it can be constructed in any location without having to be near the sea or rivers. It can be operated safely if a natural disaster, such as a tsunami or flood, occurs, thus contributing to the safety of the mother facility. IHI's air-cooled heat exchangers are designed to ensure safe operation and withstand a large earthquake or severe atmospheric conditions. This report describes the technologies used to establish these safety features and their performance. (author)

Relationships between Hg Air-surface exchange, Soil Moisture and Precipitation at a Background Vegetated Site in South-Eastern Australia.

Science.gov (United States)

Macsween, K.; Edwards, G. C.

2017-12-01

Despite many decades of research, the controlling mechanisms of mercury (Hg) air-surface exhange are still poorly understood. Particularly in Australian ecosystems where there are few anthropogenic inputs. A clear understanding of these mechanisms is vital for accurate representation in the global Hg models, particularly regarding re-emission. Water is known to have a considerable influence on Hg exchange within a terrestrial ecosystem. Precipitation has been found to cause spikes is Hg emissions during the initial stages of rain event. While, Soil moisture content is known to enhance fluxes between 15 and 30% Volumetric soil water (VSW), above which fluxes become suppressed. Few field experiments exist to verify these dominantly laboratory or controlled experiments. Here we present work looking at Hg fluxes over an 8-month period at a vegetated background site. The aim of this study is to identify how changes to precipitation intensity and duration, coupled with variable soil moisture content may influence Hg flux across seasons. As well as the influence of other meteorological variables. Experimentation was undertaken using aerodynamic gradient micrometeorological flux method, avoiding disruption to the surface, soil moisture probes and rain gauge measurements to monitor alterations to substrate conditions. Meteorological and air chemistry variables were also measured concurrently throughout the duration of the study. During the study period, South-Eastern Australia experienced several intense east coast low storm systems during the Autumn and Spring months and an unusually dry winter. VSW rarely reached above 30% even following the intense rainfall experienced during the east coast lows. The generally dry conditions throughout winter resulted in an initial spike in Hg emissions when rainfall occurred. Fluxes decreased shortly after the rain began but remained slightly elevated. Given the reduced net radiation and cooler temperatures experienced during the winter

A passive air sampler for characterizing the vertical concentration profile of gaseous phase polycyclic aromatic hydrocarbons in near soil surface air.

Science.gov (United States)

Zhang, Yuzhong; Deng, Shuxing; Liu, Yanan; Shen, Guofeng; Li, Xiqing; Cao, Jun; Wang, Xilong; Reid, Brian; Tao, Shu

2011-03-01

Air-soil exchange is an important process governing the fate of polycyclic aromatic hydrocarbons (PAHs). A novel passive air sampler was designed and tested for measuring the vertical concentration profile of 4 low molecular weight PAHs in gaseous phase (PAH(LMW4)) in near soil surface air. Air at various heights from 5 to 520 mm above the ground was sampled by polyurethane foam disks held in down-faced cartridges. The samplers were tested at three sites: A: an extremely contaminated site, B: a site near A, and C: a background site on a university campus. Vertical concentration gradients were revealed for PAH(LMW4) within a thin layer close to soil surface at the three sites. PAH concentrations either decreased (Site A) or increased (Sites B and C) with height, suggesting either deposition to or evaporation from soils. The sampler is a useful tool for investigating air-soil exchange of gaseous phase semi-volatile organic chemicals. Copyright © 2010 Elsevier Ltd. All rights reserved.

An experimental investigation on air-side performances of finned tube heat exchangers for indirect air-cooling tower

Directory of Open Access Journals (Sweden)

Du Xueping

2014-01-01

Full Text Available A tremendous quantity of water can be saved if the air cooling system is used, comparing with the ordinary water-cooling technology. In this study, two kinds of finned tube heat exchangers in an indirect air-cooling tower are experimentally studied, which are a plain finned oval-tube heat exchanger and a wavy-finned flat-tube heat exchanger in a cross flow of air. Four different air inlet angles (90°, 60 °, 45°, and 30° are tested separately to obtain the heat transfer and resistance performance. Then the air-side experimental correlations of the Nusselt number and friction factor are acquired. The comprehensive heat transfer performances for two finned tube heat exchangers under four air inlet angles are compared. For the plain finned oval-tube heat exchanger, the vertical angle (90° has the worst performance while 45° and 30° has the best performance at small ReDc and at large ReDc, respectively. For the wavy-finned flat-tube heat exchanger, the worst performance occurred at 60°, while the best performance occurred at 45° and 90° at small ReDc and at large ReDc, respectively. From the comparative results, it can be found that the air inlet angle has completely different effects on the comprehensive heat transfer performance for the heat exchangers with different structures.

Technology Candidates for Air-to-Air and Air-to-Ground Data Exchange

Science.gov (United States)

Haynes, Brian D.

2015-01-01

Technology Candidates for Air-to-Air and Air-to-Ground Data Exchange is a two-year research effort to visualize the U. S. aviation industry at a point 50 years in the future, and to define potential communication solutions to meet those future data exchange needs. The research team, led by XCELAR, was tasked with identifying future National Airspace System (NAS) scenarios, determining requirements and functions (including gaps), investigating technical and business issues for air, ground, & air-to-ground interactions, and reporting on the results. The project was conducted under technical direction from NASA and in collaboration with XCELAR's partner, National Institute of Aerospace, and NASA technical representatives. Parallel efforts were initiated to define the information exchange functional needs of the future NAS, and specific communication link technologies to potentially serve those needs. Those efforts converged with the mapping of each identified future NAS function to potential enabling communication solutions; those solutions were then compared with, and ranked relative to, each other on a technical basis in a structured analysis process. The technical solutions emerging from that process were then assessed from a business case perspective to determine their viability from a real-world adoption and deployment standpoint. The results of that analysis produced a proposed set of future solutions and most promising candidate technologies. Gap analyses were conducted at two points in the process, the first examining technical factors, and the second as part of the business case analysis. In each case, no gaps or unmet needs were identified in applying the solutions evaluated to the requirements identified. The future communication solutions identified in the research comprise both specific link technologies and two enabling technologies that apply to most or all specific links. As a result, the research resulted in a new analysis approach, viewing the

A review of air exchange rate models for air pollution exposure assessments.

Science.gov (United States)

Breen, Michael S; Schultz, Bradley D; Sohn, Michael D; Long, Thomas; Langstaff, John; Williams, Ronald; Isaacs, Kristin; Meng, Qing Yu; Stallings, Casson; Smith, Luther

2014-11-01

A critical aspect of air pollution exposure assessments is estimation of the air exchange rate (AER) for various buildings where people spend their time. The AER, which is the rate of exchange of indoor air with outdoor air, is an important determinant for entry of outdoor air pollutants and for removal of indoor-emitted air pollutants. This paper presents an overview and critical analysis of the scientific literature on empirical and physically based AER models for residential and commercial buildings; the models highlighted here are feasible for exposure assessments as extensive inputs are not required. Models are included for the three types of airflows that can occur across building envelopes: leakage, natural ventilation, and mechanical ventilation. Guidance is provided to select the preferable AER model based on available data, desired temporal resolution, types of airflows, and types of buildings included in the exposure assessment. For exposure assessments with some limited building leakage or AER measurements, strategies are described to reduce AER model uncertainty. This review will facilitate the selection of AER models in support of air pollution exposure assessments.

The new exchangers in refrigeration and air, conditioning applications

Energy Technology Data Exchange (ETDEWEB)

Marvillet, Ch [CEA, 38 - Grenoble (France). GRETh

1998-12-31

The investigation carried out by the `heat exchangers` network has revealed a number of points which should be noted here at the beginning of this presentation. It has been observed that most of today`s products (fin and tube heat exchangers) are designed along traditional lines. However despite this `conservatism`, a lot of attention is found on the technical and innovative techniques used in other areas of the world (particularly in Japan). Moreover, some of these innovative techniques (micro fin tubes, louvered fins) tend to be more frequently applied than others, and their gradual introduction into products which are `made in the EEC` is to be expected. The purpose of this paper is to respond, at least partially, to the interest shown by the industries contacted. during this investigation in these new techniques. In the first chapter, an overview of the information available today on high performance thermal heat exchange surfaces will be given. Micro-fin tubes and louvered fins will be the two surfaces considered in the first part of this document. According to this investigation, the fin and tube heat exchanger remains the only product available today for evaporating and condensing refrigerant applications using air as the fluid to be treated. Other technological solutions exist, however; brazed fin and plate heat exchangers commonly used in applications where compactness is an essential quality will be examined in the second part of this document. Moreover, the use of fluids which will replace CFCS in the years to come, and the possible comeback of ammonia will certainly have consequences on the design of evaporators and condensers. In the third part of this document the effects of these changes on fin and tube heat exchangers will be evaluated, and the first published results of the use of substitution fluids will be discussed. (author) 16 refs.

The new exchangers in refrigeration and air, conditioning applications

Energy Technology Data Exchange (ETDEWEB)

Marvillet, Ch. [CEA, 38 - Grenoble (France). GRETh

1997-12-31

The investigation carried out by the `heat exchangers` network has revealed a number of points which should be noted here at the beginning of this presentation. It has been observed that most of today`s products (fin and tube heat exchangers) are designed along traditional lines. However despite this `conservatism`, a lot of attention is found on the technical and innovative techniques used in other areas of the world (particularly in Japan). Moreover, some of these innovative techniques (micro fin tubes, louvered fins) tend to be more frequently applied than others, and their gradual introduction into products which are `made in the EEC` is to be expected. The purpose of this paper is to respond, at least partially, to the interest shown by the industries contacted. during this investigation in these new techniques. In the first chapter, an overview of the information available today on high performance thermal heat exchange surfaces will be given. Micro-fin tubes and louvered fins will be the two surfaces considered in the first part of this document. According to this investigation, the fin and tube heat exchanger remains the only product available today for evaporating and condensing refrigerant applications using air as the fluid to be treated. Other technological solutions exist, however; brazed fin and plate heat exchangers commonly used in applications where compactness is an essential quality will be examined in the second part of this document. Moreover, the use of fluids which will replace CFCS in the years to come, and the possible comeback of ammonia will certainly have consequences on the design of evaporators and condensers. In the third part of this document the effects of these changes on fin and tube heat exchangers will be evaluated, and the first published results of the use of substitution fluids will be discussed. (author) 16 refs.

Current issues and uncertainties in the measurement and modelling of air-vegetation exchange and within-plant processing of POPs

International Nuclear Information System (INIS)

Barber, Jonathan L.; Thomas, Gareth O.; Kerstiens, Gerhard; Jones, Kevin

2004-01-01

Air-vegetation exchange of POPs is an important process controlling the entry of POPs into terrestrial food chains, and may also have a significant effect on the global movement of these compounds. Many factors affect the air-vegetation transfer including: the physicochemical properties of the compounds of interest; environmental factors such as temperature, wind speed, humidity and light conditions; and plant characteristics such as functional type, leaf surface area, cuticular structure, and leaf longevity. The purpose of this review is to quantify the effects these differences might have on air/plant exchange of POPs, and to point out the major gaps in the knowledge of this subject that require further research. Uptake mechanisms are complicated, with the role of each factor in controlling partitioning, fate and behaviour process still not fully understood. Consequently, current models of air-vegetation exchange do not incorporate variability in these factors, with the exception of temperature. These models instead rely on using average values for a number of environmental factors (e.g. plant lipid content, surface area), ignoring the large variations in these values. The available models suggest that boundary layer conductance is of key importance in the uptake of POPs, although large uncertainties in the cuticular pathway prevents confirmation of this with any degree of certainty, and experimental data seems to show plant-side resistance to be important. Models are usually based on the assumption that POP uptake occurs through the lipophilic cuticle which covers aerial surfaces of plants. However, some authors have recently attached greater importance to the stomatal route of entry into the leaf for gas phase compounds. There is a need for greater mechanistic understanding of air-plant exchange and the 'scaling' of factors affecting it. The review also suggests a number of key variables that researchers should measure in their experiments to allow comparisons

Tritium isotopic exchange in air detritiation dryers

International Nuclear Information System (INIS)

Everatt, A.E.; Johnson, R.E.; Senohrabek, J.A.; Shultz, C.M.

1989-02-01

Isotopic exchange between tritiated and non-tritiated water species in a molecular sieve bed has been demonstrated. At high humidities (+6 degrees Celsius dew point) the rate of tritium isotopic exchange in a 2.4 L molecular sieve bed has been demonstrated to be at least 50% of published exchange rates. In an industrial-sized air detritiation dryer, utilizing the pretreatment technique of H 2 O steam washing to elute the residual tritium, a DF of 12 600 has been demonstrated when operating at an inlet vapor tritium concentration of 14 Ci/kg and at inlet and outlet dew points of 4.8 and -54 degrees Celsius, respectively. In the NPD dryer bed studied, which was not optimally designed for full benefit from isotopic exchange, at least one order of magnitude in additional detritiation is attributed to isotopic exchange in the unsaturated zone. The technique of eluting the residual tritium from an industrial sized bed by H 2 O washing at high temperature, high humidity and low bed loading has been demonstrated to be a fast and effective way of removing tritium from a molecular sieve bed during regeneration. The isotopic exchange model accurately predicted the exchange between tritiated and non-tritiated water species in a molecular sieve bed where there is no net adsorption or desorption. The model's prediction of the tritium breakthrough trend observed in the NPD tests was poor; however, a forced fit can be achieved if the exchange rates in the MTZ and the unsaturated zone are manipulated. More experiments are needed to determine the relative rates of tritium exchange in the saturated, mass transfer, and unsaturated zones of a dryer bed

A passive air sampler for characterizing the vertical concentration profile of gaseous phase polycyclic aromatic hydrocarbons in near soil surface air

International Nuclear Information System (INIS)

Zhang Yuzhong; Deng Shuxing; Liu Yanan; Shen Guofeng; Li Xiqing; Cao Jun; Wang Xilong; Reid, Brian; Tao Shu

2011-01-01

Air-soil exchange is an important process governing the fate of polycyclic aromatic hydrocarbons (PAHs). A novel passive air sampler was designed and tested for measuring the vertical concentration profile of 4 low molecular weight PAHs in gaseous phase (PAH LMW4 ) in near soil surface air. Air at various heights from 5 to 520 mm above the ground was sampled by polyurethane foam disks held in down-faced cartridges. The samplers were tested at three sites: A: an extremely contaminated site, B: a site near A, and C: a background site on a university campus. Vertical concentration gradients were revealed for PAH LMW4 within a thin layer close to soil surface at the three sites. PAH concentrations either decreased (Site A) or increased (Sites B and C) with height, suggesting either deposition to or evaporation from soils. The sampler is a useful tool for investigating air-soil exchange of gaseous phase semi-volatile organic chemicals. - Research highlights: → Design, field test and calibration of the novel passive air sampler, PAS-V-I. → Vertical concentration gradients of PAH LMW4 within a thin layer close to soil. → Comparison of results between PAS-V-I measurement and fugacity approach. → Potential application of PAS-V-I and further modifications. - A novel passive sampling device was developed and tested for measuring vertical concentration profile of gaseous phase polycyclic aromatic hydrocarbons in near soil surface air.

Using a passive air sampler to monitor air-soil exchange of organochlorine pesticides in the pasture of the central Tibetan Plateau.

Science.gov (United States)

Wang, Chuanfei; Wang, Xiaoping; Ren, Jiao; Gong, Ping; Yao, Tandong

2017-02-15

Air-soil exchange is a key process controlling the fate of persistent organic pollutants (POPs). However, the "sink effect" of soil for POPs in Tibetan pasture has not been clear. In NamCo, in the central Tibetan Plateau (TP) where the land is covered by grass, a modified passive air sampler (PAS) (thickness: 2cm) was tested. Using the PAS, the atmospheric gaseous phase organochlorine pesticides (OCPs) at 11 heights from close-to-surface (2cm) to 200cm above ground, in summer and in winter, were measured. Concentrations of OCPs in summer were higher than those in winter. Both in summer and winter, atmospheric concentrations of OCPs decreased with decreasing height from 200 to 2cm, indicating that OCPs were being deposited from air to soil. Air deposition of OCPs was possibly driven by wind speed. Furthermore, based on air OCPs at 0-3cm near the surface, the interface exchange of OCPs between air and soil was studied by the fugacity method. The results showed that pastural soil in the TP was a "sink" of OCPs even in summer. The mean deposition fluxes of α-HCH, γ-HCH and o,p'-DDT were 0.72, 0.24 and 0.54pg/h/m 2 , respectively, and it was estimated that the level of these pollutants in the soil will double every 24, 66 and 206years, respectively. This study will contribute to the further understanding of global cycling of POPs in different land covers. Copyright © 2016 Elsevier B.V. All rights reserved.

Eddy covariance measurement of the spatial heterogeneity of surface energy exchanges over Heron Reef, Great Barrier Reef, Australia

Science.gov (United States)

MacKellar, M.; McGowan, H. A.; Phinn, S. R.

2011-12-01

Coral reefs cover 2.8 to 6.0 x 105 km2 of the Earth's surface and are warm, shallow regions that are believed to contribute enhanced sensible and latent heat to the atmosphere, relative to the surrounding ocean. To predict the impact of climate variability on coral reefs and their weather and climate including cloud, winds, rainfall patterns and cyclone genesis, accurate parameterisation of air-sea energy exchanges over coral reefs is essential. This is also important for the parameterisation and validation of regional to global scale forecast models to improve prediction of tropical and sub-tropical marine and coastal weather. Eddy covariance measurements of air-sea fluxes over coral reefs are rare due to the complexities of installing instrumentation over shallow, tidal water. Consequently, measurements of radiation and turbulent flux data for coral reefs have been captured remotely (satellite data) or via single measurement sites downwind of coral reefs (e.g. terrestrial or shipboard instrumentation). The resolution of such measurements and those that have been made at single locations on reefs may not capture the spatial heterogeneity of surface-atmosphere energy exchanges due to the different geomorphic and biological zones on coral reefs. Accordingly, the heterogeneity of coral reefs with regard to substrate, benthic communities and hydrodynamic processes are not considered in the characterization of the surface radiation energy flux transfers across the water-atmosphere interface. In this paper we present a unique dataset of concurrent in situ eddy covariance measurements made on instrumented pontoons of the surface energy balance over different geomorphic zones of a coral reef (shallow reef flat, shallow and deep lagoons). Significant differences in radiation transfers and air-sea turbulent flux exchanges over the reef were highlighted, with higher Bowen ratios over the shallow reef flat. Increasing wind speed was shown to increase flux divergence between

Heat pipe heat exchanger for heat recovery in air conditioning

Energy Technology Data Exchange (ETDEWEB)

Abd El-Baky, Mostafa A.; Mohamed, Mousa M. [Mechanical Power Engineering Department, Faculty of Engineering, Minufiya University, Shebin El-Kom (Egypt)

2007-03-15

The heat pipe heat exchangers are used in heat recovery applications to cool the incoming fresh air in air conditioning applications. Two streams of fresh and return air have been connected with heat pipe heat exchanger to investigate the thermal performance and effectiveness of heat recovery system. Ratios of mass flow rate between return and fresh air of 1, 1.5 and 2.3 have been adapted to validate the heat transfer and the temperature change of fresh air. Fresh air inlet temperature of 32-40{sup o}C has been controlled, while the inlet return air temperature is kept constant at about 26{sup o}C. The results showed that the temperature changes of fresh and return air are increased with the increase of inlet temperature of fresh air. The effectiveness and heat transfer for both evaporator and condenser sections are also increased to about 48%, when the inlet fresh air temperature is increased to 40{sup o}C. The effect of mass flow rate ratio on effectiveness is positive for evaporator side and negative for condenser side. The enthalpy ratio between the heat recovery and conventional air mixing is increased to about 85% with increasing fresh air inlet temperature. The optimum effectiveness of heat pipe heat exchanger is estimated and compared with the present experimental data. The results showed that the effectiveness is close to the optimum effectiveness at fresh air inlet temperature near the fluid operating temperature of heat pipes. (author)

Air-cleaning apparatus

International Nuclear Information System (INIS)

Howard, A.G.

1981-01-01

An air-cleaning, heat-exchange apparatus includes a main housing portion connected by means of an air inlet fan to the kitchen exhaust stack of a restaurant. The apparatus includes a plurality of heat exchangers through which a heat-absorptive fluid is circulated, simultaneously, by means of a suitable fluid pump. These heat exchangers absorb heat from the hot exhaust gas, out of the exhaust stack of the restaurant, which flows over and through these heat exchangers and transfers this heat to the circulating fluid which communicates with remote heat exchangers. These remote heat exchangers further transfer this heat to a stream of air, such as that from a cold-air return duct for supplementing the conventional heating system of the restaurant. Due to the fact that such hot exhaust gas is heavily grease laden , grease will be deposited on virtually all internal surfaces of the apparatus which this exhaust gas contacts. Consequently, means are provided for spraying these contacted internal surfaces , as well as the hot exhaust gas itself, with a detergent solution in which the grease is soluble, thereby removing grease buildup from these internal surfaces

Air breathing and aquatic gas exchange during hypoxia in armoured catfish.

Science.gov (United States)

Scott, Graham R; Matey, Victoria; Mendoza, Julie-Anne; Gilmour, Kathleen M; Perry, Steve F; Almeida-Val, Vera M F; Val, Adalberto L

2017-01-01

Air breathing in fish is commonly believed to have arisen as an adaptation to aquatic hypoxia. The effectiveness of air breathing for tissue O 2 supply depends on the ability to avoid O 2 loss as oxygenated blood from the air-breathing organ passes through the gills. Here, we evaluated whether the armoured catfish (Hypostomus aff. pyreneusi)-a facultative air breather-can avoid branchial O 2 loss while air breathing in aquatic hypoxia, and we measured various other respiratory and metabolic traits important for O 2 supply and utilization. Fish were instrumented with opercular catheters to measure the O 2 tension (PO 2 ) of expired water, and air breathing and aquatic respiration were measured during progressive stepwise hypoxia in the water. Armoured catfish exhibited relatively low rates of O 2 consumption and gill ventilation, and gill ventilation increased in hypoxia due primarily to increases in ventilatory stroke volume. Armoured catfish began air breathing at a water PO 2 of 2.5 kPa, and both air-breathing frequency and hypoxia tolerance (as reflected by PO 2 at loss of equilibrium, LOE) was greater in individuals with a larger body mass. Branchial O 2 loss, as reflected by higher PO 2 in expired than in inspired water, was observed in a minority (4/11) of individuals as water PO 2 approached that at LOE. Armoured catfish also exhibited a gill morphology characterized by short filaments bearing short fused lamellae, large interlamellar cell masses, low surface area, and a thick epithelium that increased water-to-blood diffusion distance. Armoured catfish had a relatively low blood-O 2 binding affinity when sampled in normoxia (P 50 of 3.1 kPa at pH 7.4), but were able to rapidly increase binding affinity during progressive hypoxia exposure (to a P 50 of 1.8 kPa). Armoured catfish also had low activities of several metabolic enzymes in white muscle, liver, and brain. Therefore, low rates of metabolism and gill ventilation, and a reduction in branchial gas-exchange

Sea ice contribution to the air-sea CO(2) exchange in the Arctic and Southern Oceans

DEFF Research Database (Denmark)

Rysgaard...[], Søren; Bendtsen, Jørgen; Delille, B.

2011-01-01

Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO(2) and the subsequent effect on air-sea CO(2) exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air......-sea CO(2) exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO(2) uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO(2) uptake in ice-free polar seas. This sea......-sea CO(2) exchange during winter, and (3) release of CO(2)-depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO(2) drawdown during primary production in sea ice and surface oceanic waters....

Microbes at Surface-Air Interfaces: The Metabolic Harnessing of Relative Humidity, Surface Hygroscopicity, and Oligotrophy for Resilience

Science.gov (United States)

Stone, Wendy; Kroukamp, Otini; Korber, Darren R.; McKelvie, Jennifer; Wolfaardt, Gideon M.

2016-01-01

The human environment is predominantly not aqueous, and microbes are ubiquitous at the surface-air interfaces with which we interact. Yet microbial studies at surface-air interfaces are largely survival-oriented, whilst microbial metabolism has overwhelmingly been investigated from the perspective of liquid saturation. This study explored microbial survival and metabolism under desiccation, particularly the influence of relative humidity (RH), surface hygroscopicity, and nutrient availability on the interchange between these two phenomena. The combination of a hygroscopic matrix (i.e., clay or 4,000 MW polyethylene glycol) and high RH resulted in persistent measurable microbial metabolism during desiccation. In contrast, no microbial metabolism was detected at (a) hygroscopic interfaces at low RH, and (b) less hygroscopic interfaces (i.e., sand and plastic/glass) at high or low RH. Cell survival was conversely inhibited at high RH and promoted at low RH, irrespective of surface hygroscopicity. Based on this demonstration of metabolic persistence and survival inhibition at high RH, it was proposed that biofilm metabolic rates might inversely influence whole-biofilm resilience, with ‘resilience’ defined in this study as a biofilm’s capacity to recover from desiccation. The concept of whole-biofilm resilience being promoted by oligotrophy was supported in desiccation-tolerant Arthrobacter spp. biofilms, but not in desiccation-sensitive Pseudomonas aeruginosa biofilms. The ability of microbes to interact with surfaces to harness water vapor during desiccation was demonstrated, and potentially to harness oligotrophy (the most ubiquitous natural condition facing microbes) for adaptation to desiccation. PMID:27746774

Numerical study of a PCM-air heat exchanger's thermal performance

Science.gov (United States)

Herbinger, F.; Bhouri, M.; Groulx, D.

2016-09-01

In this paper, the use of PCMs in HVAC applications is investigated by studying numerically the thermal performance of a PCM-air heat exchanger. The PCM used in this study is dodecanoic acid. A symmetric 3D model, incorporating conductive and convective heat transfer (air only) as well as laminar flow, was created in COMSOL Multiphysics 5.0. Simulations examined the dependence of the heat transfer rate on the temperature and velocity of the incoming air as well as the size of the channels in the heat exchanger. Results indicated that small channels size lead to a higher heat transfer rates. A similar trend was also obtained for high incoming air temperature, whereas the heat transfer rate was less sensitive to the incoming air velocity.

Radiation exchange factors between specular inner surfaces of a rectangular enclosure such as transplant production unit

International Nuclear Information System (INIS)

Abdel-Ghany, Ahmed M.; Kozai, Toyoki

2006-01-01

General mathematical relations are presented for the specular exchange factors, F S , of diffuse radiation exchange between the inner surfaces of a rectangular enclosure. Three of these surfaces are specular reflectors, diffuse emitters and the fourth surface is a diffuse reflector, diffuse emitter. This enclosure can be used as a transplant production unit with artificial lighting for electric energy saving purposes. An image system and the crossed string method are used to derive these relations. The resulting expressions are conceptually simple and similar to the commonly known expressions of the exchange factors between diffuse surfaces, F. The accuracy of the presented F S relations was examined for different numbers of multiple reflections, N, on the specular surfaces and for different aspect ratios (ratio of the width, w to the height, h). The results proved that the relations are accurate and strongly satisfy the well-known relation of the radiation exchange between enclosure surfaces and satisfy the reciprocity relation. For any aspect ratio, considering N of 150 between highly reflective surfaces (ρ = 0.99) is sufficient to estimate the F S factors without any possible error. Using specular reflecting surfaces in such cases significantly reduces the electric energy consumption used for lighting

Seasonal air-water exchange fluxes of polychlorinated biphenyls in the Hudson River Estuary

International Nuclear Information System (INIS)

Yan Shu; Rodenburg, Lisa A.; Dachs, Jordi; Eisenreich, Steven J.

2008-01-01

Polychlorinated biphenyls (PCBs) were measured in the air and water over the Hudson River Estuary during six intensive field campaigns from December 1999 to April 2001. Over-water gas-phase ΣPCB concentrations averaged 1100 pg/m 3 and varied with temperature. Dissolved-phase ΣPCB concentrations averaged 1100 pg/L and displayed no seasonal trend. Uncertainty analysis of the results suggests that PCBs with 5 or fewer chlorines exhibited net volatilization. The direction of net air/water exchange could not be determined for PCBs with 6 or more chlorines. Instantaneous net fluxes of ΣPCBs ranged from +0.2 to +630 ng m -2 d -1 . Annual fluxes of ΣPCBs were predicted from modeled gas-phase concentrations, measured dissolved-phase concentrations, daily surface water temperatures and wind speeds. The net volatilization flux was +62 μg m -2 yr -1 , corresponding to an annual loss of +28 kg/yr of ΣPCBs from the Hudson River Estuary for the year of 2000. - Investigation of the air-water exchange of PCBs in the Hudson River Estuary suggests that PCBs with 5 or fewer chlorines undergo net volatilization

Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

Directory of Open Access Journals (Sweden)

Nicola H. Perry

2016-10-01

Full Text Available Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic, and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER, Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance.

PHYSICAL EXCHANGES AT THE AIR-SEA INTERFACE UK-SOLAS Field Measurements

NARCIS (Netherlands)

Brooks, Ian M.; Yelland, Margaret J.; Upstill-Goddard, Robert C.; Nightingale, Philip D.; Archer, Steve; d'Asaro, Ericic; Beale, Rachael; Beatty, Cory; Blomquist, Byron; Bloom, A. Anthony; Brooks, Barbara J.; Cluderay, John; Coles, David; Dacey, John; DeGrandpre, Michael; Dixon, Jo; Drennan, William M.; Gabriele, Joseph; Goldson, Laura; Hardman-Mountford, Nick; Hill, Martin K.; Horn, Matt; Hsueh, Ping-Chang; Huebert, Barry; de Leeuw, Gerrit; Leighton, Timothy G.; Liddicoat, Malcolm; Lingard, Justin J. N.; McNeil, Craig; McQuaid, James B.; Moat, Ben I.; Moore, Gerald; Neill, Craig; Norris, Sarah J.; O'Doherty, Simon; Pascal, Robin W.; Prytherch, John; Rebozo, Mike; Sahlee, Erik; Salter, Matt; Schuster, Ute; Skjelvan, Ingunn; Slagter, Hans; Smith, Michael H.; Smith, Paul D.; Srokosz, Meric; Stephens, John A.; Taylor, Peter K.; Telszewski, Maciej; Walsh, Roisin; Ward, Brian; Woolf, David K.; Young, Dickon; Zemmelink, Henk

As part of the U. K. contribution to the international Surface Ocean-Lower Atmosphere Study, a series of three related projects-DOGEE, SEASAW, and HiWASE-undertook experimental studies of the processes controlling the physical exchange of gases and sea spray aerosol at the sea surface. The studies

Organochlorine pesticides in surface soils from obsolete pesticide dumping ground in Hyderabad City, Pakistan: contamination levels and their potential for air-soil exchange.

Science.gov (United States)

Alamdar, Ambreen; Syed, Jabir Hussain; Malik, Riffat Naseem; Katsoyiannis, Athanasios; Liu, Junwen; Li, Jun; Zhang, Gan; Jones, Kevin C

2014-02-01

This study was conducted to examine organochlorine pesticides (OCPs) contamination levels in the surface soil and air samples together with air-soil exchange fluxes at an obsolete pesticide dumping ground and the associated areas from Hyderabad City, Pakistan. Among all the sampling sites, concentrations of OCPs in the soil and air samples were found highest in obsolete pesticide dumping ground, whereas dominant contaminants were dichlorodiphenyltrichloroethane (DDTs) (soil: 77-212,200 ng g(-1); air: 90,700 pg m(-3)) and hexachlorocyclohexane (HCHs) (soil: 43-4,090 ng g(-1); air: 97,400 pg m(-3)) followed by chlordane, heptachlor and hexachlorobenzene (HCB). OCPs diagnostic indicative ratios reflect historical use as well as fresh input in the study area. Moreover, the air and soil fugacity ratios (0.9-1.0) at the dumping ground reflecting a tendency towards net volatilization of OCPs, while at the other sampling sites, the fugacity ratios indicate in some cases deposition and in other cases volatilization. Elevated concentrations of DDTs and HCHs at pesticide dumping ground and its surroundings pose potential exposure risk to biological organisms, to the safety of agricultural products and to the human health. Our study thus emphasizes the need of spatio-temporal monitoring of OCPs at local and regional scale to assess and remediate the future adverse implications. © 2013.

Heat exchanger design for hot air ericsson-brayton piston engine

Directory of Open Access Journals (Sweden)

Ďurčanský P.

2014-03-01

Full Text Available One of the solutions without negative consequences for the increasing energy consumption in the world may be use of alternative energy sources in micro-cogeneration. Currently it is looking for different solutions and there are many possible ways. Cogeneration is known for long time and is widely used. But the installations are often large and the installed output is more suitable for cities or industry companies. When we will speak about decentralization, the small machines have to be used. The article deals with the principle of hot-air engines, their use in combined heat and electricity production from biomass and with heat exchangers as primary energy transforming element. In the article is hot air engine presented as a heat engine that allows the conversion of heat into mechanical energy while heat supply can be external. In the contribution are compared cycles of hot-air engine. Then are compared suitable heat exchangers for use with hot air Ericsson-Brayton engine. In the final part is proposal of heat exchanger for use in closed Ericsson-Brayton cycle.

Heat exchanger design for hot air ericsson-brayton piston engine

Science.gov (United States)

Ďurčanský, P.; Lenhard, R.; Jandačka, J.

2014-03-01

One of the solutions without negative consequences for the increasing energy consumption in the world may be use of alternative energy sources in micro-cogeneration. Currently it is looking for different solutions and there are many possible ways. Cogeneration is known for long time and is widely used. But the installations are often large and the installed output is more suitable for cities or industry companies. When we will speak about decentralization, the small machines have to be used. The article deals with the principle of hot-air engines, their use in combined heat and electricity production from biomass and with heat exchangers as primary energy transforming element. In the article is hot air engine presented as a heat engine that allows the conversion of heat into mechanical energy while heat supply can be external. In the contribution are compared cycles of hot-air engine. Then are compared suitable heat exchangers for use with hot air Ericsson-Brayton engine. In the final part is proposal of heat exchanger for use in closed Ericsson-Brayton cycle.

Air-sea Exchange of Polycyclic Aromatic Hydrocarbons (PAHs), Polychlorinated Biphenyls (PCBs), Organochlorine Pesticides (OCPs) and Polybrominated Diphenyl Ethers (PBDEs) in the Mediterranean Sea

Science.gov (United States)

Lammel, G. P.; Heil, A.; Kukucka, P.; Meixner, F. X.; Mulder, M. D.; Prybilova, P.; Prokes, R.; Rusina, T. S.; Song, G. Z.; Vrana, B.

2015-12-01

The marine atmospheric environment is a receptor for persistent organic pollutants (POPs) which are advected from sources on land, primary, such as biomass burning by-products (PAHs, dioxins), and secondary, such as volatilization from contaminated soils (PCBs, pesticides). Primary sources do not exist in the marine environment, except for PAHs (ship engines) but following previous atmospheric deposition, the sea surface may turn to a secondary source by reversal of diffusive air-sea mass exchange. No monitoring is in place. We studied the vertical fluxes of a wide range of primary and secondary emitted POPs based on measurements in air and surface seawater at a remote coastal site in the eastern Mediterranean (2012). To this end, silicon rubbers were used as passive water samplers, vertical concentration gradients were determined in air and fluxes were quantified based on Eddy covariance. Diffusive air-sea exchange fluxes of hexachlorocyclohexanes (HCHs) and semivolatile PAHs were found close to phase equilibrium, except one PAH, retene, a wood burning tracer, was found seasonally net-volatilisational. Some PCBs, p,p'-DDE, penta- and hexachlorobenzene (PeCB, HCB) were mostly net-depositional, while PBDEs were net-volatilizational. Fluxes determined at a a remote coastal site ranged -33 - +2.4 µg m-2 d-1 for PAHs and -4.0 - +0.3 µg m-2 d-1for halogenated compounds ( 0 means net-volatilization). It is concluded that nowadays in open seas more pollutants are undergoing reversal of the direction of air-sea exchange. Recgional fire activity records in combination with box model simulations suggest that deposition of retene during summer is followed by a reversal of air-sea exchange. The seawater surface as secondary source of pollution should be assessed based on flux measurements across seasons and over longer time periods.

Helium-air exchange flows through partitioned opening and two-opening

International Nuclear Information System (INIS)

Kang, T. I.

1997-01-01

This paper describes experimental investigations of helium-air exchange flows through partitioned opening and two-opening. Such exchange flows may occur following rupture accident of stand pipe in high temperature engineering test reactor. A test vessel with the two types of small opening on top of test cylinder is used for experiments. An estimation method of mass increment is developed to measure the exchange flow rate. Upward flow of the helium and downward flow of the air in partitioned opening system interact out of entrance and exit of the opening. Therefore, an experiment with two-opening system is made to investigate effect of the fluids interaction of partitioned opening system. As a result of comparison of the exchange flow rates between two types of the opening system, it is demonstrated that the exchange flow rate of the two-opening system is larger than that of the partitioned opening system because of absence of the effect of fluids interaction. (author)

Influence of source type and air exchange on variations of indoor radon concentration

International Nuclear Information System (INIS)

Arvela, H.; Winqvist, K.

1986-04-01

The model relates radon concentration to source strength and its variations, air exchange rate and meteorological factors. Two types of sources have been studied. The pressure difference dependent source is made up of radon transported with soil pore air and driven by pressure difference due to the stack effect. The constant source is made up of radon transported by diffusion from building materials or from soil. The air exchange rate depends exponentially on indoor-outdoor temperature difference and linearly on wind speed. These two inputs have been summed in quadrature. In a house with a constant source radon concentration decreases when the air exchange rate increases due to the increasing temperature difference, whereas the pressure difference dependent source causes an increasing concentration. This is due to the fact that the effect of the source strength increase is stronger than the decreasing effect of air exchange on concentration. The winter-summer concentration ratio depends on the combination of the two types of source. A pure pressure dependent source leads to the winter-summer ratio of 2-3.5 (winter -5 deg C, summer +15 deg C, wind speed 3 m/s). A strong contribution of a constant source is needed to cause a summer concentration higher than the winter concentration. The model is in agreement with the winter-summer concentration ratios measured. This ratio increases with the increasing winter concentration. The measured ratio was near 1.0 for houses with winter concentration of 200 Bq m''3 or less and near 2.0 with concentration of 1000 Bq m''3. In a house with a constant source, the diurnal maximum occurs in the afternoon, while in houses with a pressure difference dependent source the time of maximum is early in the morning

Experimental investigation of thermal conductivity coefficient and heat exchange between fluidized bed and inclined exchange surface

Directory of Open Access Journals (Sweden)

B. Stojanovic

2009-06-01

Full Text Available The paper presents experimental research of thermal conductivity coefficients of the siliceous sand bed fluidized by air and an experimental investigation of the particle size influence on the heat transfer coefficient between fluidized bed and inclined exchange surfaces. The measurements were performed for the specific fluidization velocity and sand particle diameters d p=0.3, 0.5, 0.9 mm. The industrial use of fluidized beds has been increasing rapidly in the past 20 years owing to their useful characteristics. One of the outstanding characteristics of a fluidized bed is that it tends to maintain a uniform temperature even with nonuniform heat release. On the basis of experimental research, the influence of the process's operational parameters on the obtained values of the bed's thermal conductivity has been analyzed. The results show direct dependence of thermal conductivity on the intensity of mixing, the degree of fluidization, and the size of particles. In the axial direction, the coefficients that have been treated have values a whole order higher than in the radial direction. Comparison of experimental research results with experimental results of other authors shows good agreement and the same tendency of thermal conductivity change. It is well known in the literature that the value of the heat transfer coefficient is the highest in the horizontal and the smallest in the vertical position of the heat exchange surface. Variation of heat transfer, depending on inclination angle is not examined in detail. The difference between the values of the relative heat transfer coefficient between vertical and horizontal heater position for all particle sizes reduces by approximately 15% with the increase of fluidization rate.

Atmospheric deposition and air-sea gas exchange fluxes of DDT and HCH in the Yangtze River Estuary, East China Sea

Science.gov (United States)

Li, Zhongxia; Lin, Tian; Li, Yuanyuan; Jiang, Yuqing; Guo, Zhigang

2017-07-01

The Yangtze River Estuary (YRE) is strongly influenced by the Yangtze River and lies on the pathway of the East Asian Monsoon. This study examined atmospheric deposition and air-sea gas exchange fluxes of dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) to determine whether the YRE is a sink or source of selected pesticides at the air-water interface under the influences of river input and atmospheric transport. The air-sea gas exchange of DDT was characterized by net volatilization with a marked difference in its fluxes between summer (140 ng/m2/d) and the other three seasons (12 ng/m2/d), possibly due to the high surface seawater temperatures and larger riverine input in summer. However, there was no obvious seasonal variation in the atmospheric HCH deposition, and the air-sea gas exchange reached equilibrium because of low HCH levels in the air and seawater after the long-term banning of HCH and the degradation. The gas exchange flux of HCH was comparable to the dry and wet deposition fluxes at the air-water interface. This suggests that the influences from the Yangtze River input and East Asian continental outflow on the fate of HCH in the YRE were limited. The gas exchange flux of DDT was about fivefold higher than the total dry and wet deposition fluxes. DDT residues in agricultural soil transported by enhanced riverine runoff were responsible for sustaining such a high net volatilization in summer. Moreover, our results indicated that there were fresh sources of DDT from the local environment to sustain net volatilization throughout the year.

Groundwater–Surface Water Exchange

DEFF Research Database (Denmark)

Karan, Sachin

The exchange of groundwater-surface water has been invetigated in the western part of Denmark. Holtum AA provides the framework for all the performed investigations. Several methods are used, primarily eld based measurements ombined with numerical models to achieve insight to the governing...... processes of interaction between groundwater and surface water. By using heat as a tracer it has been possible to use temperature directly as calibrationtargets in a groundwater and heat transport model. Thus, it is possible to use heat investigate the change in groundwater discharge in dynamic conditions...... by using simple temperature devices along a stream to delineate the areas of interest in regard to GW{SW exchange. Thus, at several locations in a stream a temperature data logger was placed in the water column and right at the streambed-water interface. By looking at the correlation of streambed...

A three-dimensional numerical study and comparison between the air side model and the air/water side model of a plain fin-and-tube heat exchanger

International Nuclear Information System (INIS)

Borrajo-Pelaez, R.; Ortega-Casanova, J.; Cejudo-Lopez, J.M.

2010-01-01

CFD is becoming an important heat exchanger research technique. It constitutes an inexpensive prediction method, avoiding the need of testing numerous prototypes. Current work in this field is mostly based on air flow models assuming constant temperature of fin-and-tube surface. The purpose of this paper is to present an enhanced model, whose innovation lies in considering additionally the water flow in the tubes and the conduction heat transfer through the fin and tubes, to demonstrate that the neglect of these two phenomena causes a simulation result accuracy reduction. 3-D Numerical simulations were accomplished to compare both an air side and an air/water side model. The influence of Reynolds number, fin pitch, tube diameter, fin length and fin thickness was studied. The exchanger performance was evaluated through two non-dimensional parameters: the air side Nusselt number and a friction factor. It was found that the influence of the five parameters over the mechanical and thermal efficiencies can be well reported using these non-dimensional coefficients. The results from the improved model showed more real temperature contours, with regard to those of the simplified model. Therefore, a higher accuracy of the heat transfer was achieved, yielding better predictions on the exchanger performance.

Corresponding Relation between Warm Season Precipitation Extremes and Surface Air Temperature in South China

Institute of Scientific and Technical Information of China (English)

SUN; Wei; LI; Jian; YU; Ru-Cong

2013-01-01

Hourly data of 42 rain gauges over South China during 1966–2005 were used to analyze the corresponding relation between precipitation extremes and surface air temperature in the warm season(May to October).The results show that below 25℃,both daily and hourly precipitation extremes in South China increase with rising temperature.More extreme events transit to the two-time Clausius-Clapeyron(CC)relationship at lower temperatures.Daily as well as hourly precipitation extremes have a decreasing tendency nearly above 25℃,among which the decrease of hourly extremes is much more significant.In order to investigate the efects of rainfall durations,hourly precipitation extremes are presented by short duration and long duration precipitation,respectively.Results show that the dramatic decrease of hourly rainfall intensities above 25℃ is mainly caused by short duration precipitation,and long duration precipitation extremes rarely occur in South China when surface air temperature surpasses 28℃.

Distribution and air-sea exchange of current-use pesticides (CUPs) from East Asia to the high Arctic Ocean.

Science.gov (United States)

Zhong, Guangcai; Xie, Zhiyong; Cai, Minghong; Möller, Axel; Sturm, Renate; Tang, Jianhui; Zhang, Gan; He, Jianfeng; Ebinghaus, Ralf

2012-01-03

Surface seawater and marine boundary layer air samples were collected on the ice-breaker R/V Xuelong (Snow Dragon) from the East China Sea to the high Arctic (33.23-84.5° N) in July to September 2010 and have been analyzed for six current-use pesticides (CUPs): trifluralin, endosulfan, chlorothalonil, chlorpyrifos, dacthal, and dicofol. In all oceanic air samples, the six CUPs were detected, showing highest level (>100 pg/m(3)) in the Sea of Japan. Gaseous CUPs basically decreased from East Asia (between 36.6 and 45.1° N) toward Bering and Chukchi Seas. The dissolved CUPs in ocean water ranged widely from air. Trifluralin in seawater was relatively high in the Sea of Japan (35.2° N) and evenly distributed between 36.9 and 72.5° N, but it remained below the detection limit at the highest northern latitudes in Chukchi Sea. In contrast with other CUPs, concentrations of chlorothalonil and dacthal were more abundant in Chukchi Sea and in East Asia. The air-sea gas exchange of CUPs was generally dominated by net deposition. Latitudinal trends of fugacity ratios of α-endosulfan, chlorothalonil, and dacthal showed stronger deposition of these compounds in East Asia than in Chukchi Sea, while trifluralin showed stronger deposition in Chukchi Sea (-455 ± 245 pg/m(2)/day) than in the North Pacific (-241 ± 158 pg/m(2)/day). Air-sea gas exchange of chlorpyrifos varied from net volatilizaiton in East Asia (<40° N) to equilibrium or net deposition in the North Pacific and the Arctic.

Control and prevention of ice formation and accretion on heat exchangers for ventilation systems

DEFF Research Database (Denmark)

Rahimi, Maral; Afshari, Alireza

2015-01-01

In cold climates, the application of mechanical ventilation systems with heat recovery like are airto-air exchangers is used for reducing energy consumption for heating buildings by transferring heat exhausted air to supply air. However, increase efficiency of heat exchanger results in lower...... exhaust air temperatures and Ice formation on heat exchanger fins, which can cause problem and is not favourable. Therefore, prevention and control of ice formation on heat exchangers is necessary. The existing methods are divided into two different methods: active and passive ice control methods....... The active methods are e.g. bypass, recirculation, preheating. The passive methods relate to the surface characteristics of the heat exchanger fins as they have effect on ice formation in initial phase. All these methods have varying levels of success, cost, and effectiveness, which are depending on the heat...

Performance study of desiccant coated heat exchanger air conditioning system in winter

International Nuclear Information System (INIS)

Ge, T.S.; Dai, Y.J.; Wang, R.Z.

2016-01-01

Highlights: • Performance of desiccant coated heat exchanger AC system is predicted. • Effects of main operation parameters and climatic conditions are discussed. • Regeneration temperature of 30 °C is recommended under simulation condition. • Higher ambient humidity ratio results in increased humidity ratio of supply air. • Temperature of ambient air has neglectable effect on supply air. - Abstract: Conventional air source heat pump system faces several challenges when adopted in winter season. Solid desiccant air conditioning system can provide humidification and heating power simultaneously and can be driven by low grade thermal energy; it provides a good alternative for air source heat pump systems. However, conventional solid desiccant air conditioning system adopts desiccant wheel with high cost as core component, which hinders the development of such system. Recently, desiccant coated heat exchanger (DCHE) with low initial cost and high efficiency was developed and this paper aims to investigate performance of DCHE air conditioning system adopted in Shanghai winter season. Performance of the system is predicted by a developed mathematical model where supply air states, mass of humidification and coefficient of performance (COP) are adopted as performance indices to evaluate the feasibility and energy utilization ratio of the system. Effects of regeneration water temperature on system performance are analyzed. It is found that under the simulation condition, relatively low regeneration temperature (such as 20 °C) cannot meet the designed standard and relatively high regeneration temperature (such as 40 °C) provides too much extra heating power, thus moderate regeneration temperature around 30 °C is recommended. Meanwhile, switch time is a crucial operation parameter for the system to obtain satisfied supply air, switch time from 40 s to 80 s and from 70 s to 240 s are recommended for transient and average supply air states, respectively. Both

Impacts of Changes of Indoor Air Pressure and Air Exchange Rate in Vapor Intrusion Scenarios.

Science.gov (United States)

Shen, Rui; Suuberg, Eric M

2016-02-01

There has, in recent years, been increasing interest in understanding the transport processes of relevance in vapor intrusion of volatile organic compounds (VOCs) into buildings on contaminated sites. These studies have included fate and transport modeling. Most such models have simplified the prediction of indoor air contaminant vapor concentrations by employing a steady state assumption, which often results in difficulties in reconciling these results with field measurements. This paper focuses on two major factors that may be subject to significant transients in vapor intrusion situations, including the indoor air pressure and the air exchange rate in the subject building. A three-dimensional finite element model was employed with consideration of daily and seasonal variations in these factors. From the results, the variations of indoor air pressure and air exchange rate are seen to contribute to significant variations in indoor air contaminant vapor concentrations. Depending upon the assumptions regarding the variations in these parameters, the results are only sometimes consistent with the reports of several orders of magnitude in indoor air concentration variations from field studies. The results point to the need to examine more carefully the interplay of these factors in order to quantitatively understand the variations in potential indoor air exposures.

The air-sea exchange of mercury in the low latitude Pacific and Atlantic Oceans

Science.gov (United States)

Mason, Robert P.; Hammerschmidt, Chad R.; Lamborg, Carl H.; Bowman, Katlin L.; Swarr, Gretchen J.; Shelley, Rachel U.

2017-04-01

Air-sea exchange is an important component of the global mercury (Hg) cycle as it mediates the rate of increase in ocean Hg, and therefore the rate of change in levels of methylmercury (MeHg), the most toxic and bioaccumulative form of Hg in seafood and the driver of human health concerns. Gas evasion of elemental Hg (Hg0) from the ocean is an important sink for ocean Hg with previous studies suggesting that evasion is not uniform across ocean basins. To understand further the factors controlling Hg0 evasion, and its relationship to atmospheric Hg deposition, we made measurements of dissolved Hg0 (DHg0) in surface waters, along with measurements of Hg in precipitation and on aerosols, and Hg0 in marine air, during two GEOTRACES cruises; GP16 in the equatorial South Pacific and GA03 in the North Atlantic. We contrast the concentrations and estimated evasion fluxes of Hg0 during these cruises, and the factors influencing this exchange. Concentrations of DHg0 and fluxes were lower during the GP16 cruise than during the GA03 cruise, and likely reflect the lower atmospheric deposition in the South Pacific. An examination of Hg/Al ratios for aerosols from the cruises suggests that they were anthropogenically-enriched relative to crustal material, although to a lesser degree for the South Pacific than the aerosols over the North Atlantic. Both regions appear to be net sources of Hg0 to the atmosphere (evasion>deposition) and the reasons for this are discussed. Overall, the studies reported here provide further clarification on the factors controlling evasion of Hg0 from the ocean surface, and the role of anthropogenic inputs in influencing ocean Hg concentrations.

Dynamic model of counter flow air to air heat exchanger for comfort ventilation with condensation and frost formation

DEFF Research Database (Denmark)

Nielsen, Toke Rammer; Rose, Jørgen; Kragh, Jesper

2009-01-01

must be calculated under conditions with condensation and freezing. This article presents a dynamic model of a counter flow air to air heat exchanger taking into account condensation and freezing and melting of ice. The model is implemented in Simulink and results are compared to measurements......In cold climates heat recovery in the ventilation system is essential to reduce heating energy demand. Condensation and freezing occur often in efficient heat exchangers used in cold climates. To develop efficient heat exchangers and defrosting strategies for cold climates, heat and mass transfer...

Time lag between the tropopause height and the levels of 7Be concentration in near surface air

Science.gov (United States)

Ioannidou, A.; Vasileiadis, A.; Melas, D.

2012-04-01

The concentration of 7Be at near surface air has been determined over 2009, a year of a deep solar minimum, in the region of Thessaloniki, Greece at 40°62' N, 22°95'E. In geomagnetic latitudes over 40° N, the elevation of the tropopause during the warm summer months and the vertical exchange of air masses within the troposphere cause greater mixture of the air masses resulting in higher concentration levels for 7Be in surface air. The positive correlation between the monthly activity concentration of 7Be and the tropopause height (0.94, p rate of vertical transport within the troposphere, especially during warmer summer months, has as a result the descent to surface of air masses enriched in 7Be. However, the 7Be concentration levels in near surface air are not expected to respond immediately to the change of elevation of the tropopause. It was found that there's a time lag of ~ 3 days between the change in the daily surface concentrations of 7Be the change in the elevation of the tropopause.

Air-soil exchange of organochlorine pesticides in a sealed chamber.

Science.gov (United States)

Yang, Bing; Han, Baolu; Xue, Nandong; Zhou, Lingli; Li, Fasheng

2015-01-01

So far little is known about air-soil exchange under any sealed circumstances (e.g., in plastic and glass sheds), which however has huge implications for the soil-air-plant pathways of persistent organic pollutants including organochlorine pesticides (OCPs). A newly designed passive air sampler was tested in a sealed chamber for measuring the vertical concentration profiles of gaseous phase OCPs (hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs)). Air was sampled at 5, 15, and 30 cm above ground level every 10th day during a 60-day period by deploying polyurethane foam cylinders housed in acrylonitrile butadiene styrene-covered cartridges. Concentrations and compositions of OCPs along the vertical sections indicated a clear relationship with proximity to the mixture of HCHs and DDTs which escapes from the soils. In addition, significant positive correlations were found between air temperatures and concentrations of HCHs and DDTs. These results indicated revolatilization and re-deposition being at or close to dynamic pseudo-equilibrium with the overlying air. The sampler used for addressing air-soil exchange of persistent organic pollutants in any sealed conditions is discussed. Copyright © 2014. Published by Elsevier B.V.

Investigation and optimization of the depth of flue gas heat recovery in surface heat exchangers

Science.gov (United States)

Bespalov, V. V.; Bespalov, V. I.; Melnikov, D. V.

2017-09-01

Economic issues associated with designing deep flue gas heat recovery units for natural gas-fired boilers are examined. The governing parameter affecting the performance and cost of surface-type condensing heat recovery heat exchangers is the heat transfer surface area. When firing natural gas, the heat recovery depth depends on the flue gas temperature at the condenser outlet and determines the amount of condensed water vapor. The effect of the outlet flue gas temperature in a heat recovery heat exchanger on the additionally recovered heat power is studied. A correlation has been derived enabling one to determine the best heat recovery depth (or the final cooling temperature) maximizing the anticipated reduced annual profit of a power enterprise from implementation of energy-saving measures. Results of optimization are presented for a surface-type condensing gas-air plate heat recovery heat exchanger for the climatic conditions and the economic situation in Tomsk. The predictions demonstrate that it is economically feasible to design similar heat recovery heat exchangers for a flue gas outlet temperature of 10°C. In this case, the payback period for the investment in the heat recovery heat exchanger will be 1.5 years. The effect of various factors on the optimal outlet flue gas temperature was analyzed. Most climatic, economical, or technological factors have a minor effect on the best outlet temperature, which remains between 5 and 20°C when varying the affecting factors. The derived correlation enables us to preliminary estimate the outlet (final) flue gas temperature that should be used in designing the heat transfer surface of a heat recovery heat exchanger for a gas-fired boiler as applied to the specific climatic conditions.

The condensation of steam on the external surfaces of the shells of HIFAR heavy water heat exchangers during a loss-of-coolant accident

International Nuclear Information System (INIS)

Chapman, A.G.

1987-03-01

A study of steam condensation rates on the HIFAR heavy water heat exchangers was undertaken to predict thermohydraulic conditions in the HIFAR containment during a postulated loss-of-coolant accident (LOCA). The process of surface condensation from a mixture of air and steam, and methods for calculating the rate of condensation, are briefly reviewed. Suitable experimental data are used to estimate coefficients of condensation heat transfer to cool surfaces in a reactor containment during a LOCA. The relevance of the available data to a LOCA in the HIFAR materials testing reactor is examined, and two sets of data are compared. The differences between air/H 2 O and air/D 2 O mixtures are discussed. Formulae are derived for the estimation of the coefficient of heat transfer from the heat exchanger shells to the cooling water, and a method of calculating the rate of condensation per unit area of surface is developed

Impulse exchange at the surface of the ocean and the fractal dimension of drifter trajectories

Directory of Open Access Journals (Sweden)

D. M. Summers

2002-01-01

Full Text Available An impulse-based model is developed to represent a coupling between turbulent flow in the atmosphere and turbulent flow in the ocean. In particular, it is argued that the atmosphere flowing horizontally over the ocean surface generates a velocity fluctuation field in the latter's near-surface flow. The mechanism for this can be understood kinematically in terms of an exchange of tangentially-oriented fluid impulse at the air-sea interface. We represent this exchange numerically through the creation of Lagrangian elements of impulse density. An indication of the efficacy of such a model would lie in its ability to predict the observed fractal dimension of lateral trajectories of submerged floats set adrift in the ocean. To this end, we examine the geometry of lateral tracer-paths determined from the present model.

Study on the optium operation of the solar assisted air-source heat pump system. Part 5. ; Fundamental performance of a SOL-AIR PANEL effected by environmental condition that can be controlled artifically. SOL-AIR heat pump system no saiteki untenho ni kansuru kenkyu. 5. ; Jinko kankyo joken hendo ni uoru shuhonetsu panel no kiso tokusei

Energy Technology Data Exchange (ETDEWEB)

Nakajima, Y; Ohashi, K; Kasuya, A [Kogauin Univ., Tokyo (Japan); Shiraishi, K; Hino, T [Kajima Institute of Construction Technology, Tokyo (Japan)

1990-12-06

This paper follows the privious paper which reports about the experimental system of the solar air panel and the experimental conditions in the artificial environmental room. In this paper the basic performance of heat exchange of a solar panel related to the difference of the artificial enviromental conditions such as the wind speed, the wind direction, the radiation, and the dry or wet surface of the solar air panel, and the results of its analysis are presented. As a result of the experiment, the following were determined: wind direction affects the heat exchange characteristics of the solar air panel; the slits lead to improved heat conduction on both sides of the panel; and when the flat surface of the panel is wet the amount of all the heat exchange increases, due to increased air circulation and evaporation. It is possible to estimate the total quantity of heat exchange, and to determine the fundamental performance of a solar air panel. 7 refs., 10 figs.

Short-term Rn-222 concentration changes in underground spaces with limited air exchange

Science.gov (United States)

Fijałkowska-Lichwa, Lidia; Przylibski, Tadeusz A.

2010-05-01

Authors conducted research on radon concentration in two underground structures located in the vicinity of Kletno (Sudety Mts., SW Poland), which are accessible for visitors. One of these structures is Niedźwiedzia (Bear) Cave, and the second one is the part of former uranium mine - Fluorite Adit. Both selected underground structures are characterized by almost constant temperature, changing within the range from +5 to +7° C and also constant relative humidity, close to 100%. Both these parameters testify that air exchange with the atmosphere is very limited. Air exchange is limited particularly in Niedźwiedzia Cave, which microclimate is protected i.e. by applying of locks at the entrance and exit of tourist route. The measurements were conducted between 16.05.2008. and 15.11.2009., by the use of a new Polish equipment - SRDN-3 devices with semiconductor detector. SRDN-3 device records every hour radon concentration as well as atmospheric parameters - relative humidity and temperature. At the same time authors conducted measurements of basic parameters in the open atmosphere close to Niedźwiedzia Cave. Obtained results of atmospheric parameters measurements may be used for both underground structures; because they are located within the distance of about 1 km. Atmospheric parameters were measured by the use of automatic weather station VantagePro2. On the base of conducted research authors corroborate, that the differences of radon concentration in both underground structures reach three orders of magnitude during a year. In Niedźwiedzia Cave these values are in the range from below 88 Bq/m3 (detection limit of the SRDN-3 device) up to 12 kBq/m3. Related values in Fluorite Adit are between < 88 Bq/m3 and 35 kBq/m3. It was observed also the different course of daily radon concentration changes in both structures. Additionally, authors registered that daily course of radon concentration changes differs due to season of the year. Such changes are observed in

Sea ice contribution to the air-sea CO{sub 2} exchange in the Arctic and Southern Oceans

Energy Technology Data Exchange (ETDEWEB)

Rysgaard, Soeren (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark); Centre for Earth Observation Science, CHR Faculty of Environment Earth and Resources, Univ. of Manitoba, Winnipeg (Canada)), e-mail: rysgaard@natur.gl; Bendtsen, Joergen (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark); Centre for Ice and Climate, Niels Bohr Inst., Univ. of Copenhagen, Copenhagen O (Denmark)); Delille, Bruno (Unit' e d' Oceanographie Chimique, Interfacultary Centre for Marine Research, Universite de Liege, Liege (Belgium)); Dieckmann, Gerhard S. (Alfred Wegener Inst. for Polar and Marine Research, Bremerhaven (Germany)); Glud, Ronnie N. (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark); Scottish Association of Marine Sciences, Scotland UK, Southern Danish Univ. and NordCee, Odense M (Denmark)); Kennedy, Hilary; Papadimitriou, Stathys (School of Ocean Sciences, Bangor Univ., Menai Bridge, Anglesey, Wales (United Kingdom)); Mortensen, John (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark)); Thomas, David N. (School of Ocean Sciences, Bangor Univ., Menai Bridge, Anglesey, Wales (United Kingdom); Finnish Environment Inst. (SYKE), Marine Research Centre, Helsinki (Finland)); Tison, Jean-Louis (Glaciology Unit, Dept. of Earth and Environmental Sciences, Universite Libre de Bruxelles, Bruxelles, (Belgium))

2011-11-15

Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO{sub 2} and the subsequent effect on air-sea CO{sub 2} exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air-sea CO{sub 2} exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO{sub 2} uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO{sub 2} uptake in ice-free polar seas. This sea-ice driven CO{sub 2} uptake has not been considered so far in estimates of global oceanic CO{sub 2} uptake. Net CO{sub 2} uptake in sea-ice-covered oceans can be driven by; (1) rejection during sea-ice formation and sinking of CO{sub 2}-rich brine into intermediate and abyssal oceanic water masses, (2) blocking of air-sea CO{sub 2} exchange during winter, and (3) release of CO{sub 2}-depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO{sub 2} drawdown during primary production in sea ice and surface oceanic waters

Air Circulation and Heat Exchange under Reduced Pressures

Science.gov (United States)

Rygalov, Vadim; Wheeler, Raymond; Dixon, Mike; Hillhouse, Len; Fowler, Philip

Low pressure atmospheres were suggested for Space Greenhouses (SG) design to minimize sys-tem construction and re-supply materials, as well as system manufacturing and deployment costs. But rarified atmospheres modify heat exchange mechanisms what finally leads to alter-ations in thermal control for low pressure closed environments. Under low atmospheric pressures (e.g., lower than 25 kPa compare to 101.3 kPa for normal Earth atmosphere), convection is becoming replaced by diffusion and rate of heat exchange reduces significantly. During a period from 2001 to 2009, a series of hypobaric experiments were conducted at Space Life Sciences Lab (SLSLab) NASA's Kennedy Space Center and the Department of Space Studies, University of North Dakota. Findings from these experiments showed: -air circulation rate decreases non-linearly with lowering of total atmospheric pressure; -heat exchange slows down with pressure decrease creating risk of thermal stress (elevated leaf tem-peratures) for plants in closed environments; -low pressure-induced thermal stress could be reduced by either lowering system temperature set point or increasing forced convection rates (circulation fan power) within certain limits; Air circulation is an important constituent of controlled environments and plays crucial role in material and heat exchange. Theoretical schematics and mathematical models are developed from a series of observations. These models can be used to establish optimal control algorithms for low pressure environments, such as a space greenhouse, as well as assist in fundamental design concept developments for these or similar habitable structures.

Mercury fluxes from air/surface interfaces in paddy field and dry land

Energy Technology Data Exchange (ETDEWEB)

Zhu Jinshan [Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, No. 216, Tiansheng Street, Beibei, Chongqing 400715 (China); Wang Dingyong, E-mail: dywang@swu.edu.cn [Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, No. 216, Tiansheng Street, Beibei, Chongqing 400715 (China)] [Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400716 (China); Liu Xiao; Zhang Yutong [Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, No. 216, Tiansheng Street, Beibei, Chongqing 400715 (China)

2011-02-15

Research highlights: {yields} It was found that agricultural fields are important local atmospheric Hg sources in the region. {yields} The Hg emissions from dry cornfield were higher than those from the flooded rice paddy, higher mercury emissions in the warm season than the cold season, and during daytime than at night. {yields} Mercury evasion is strongly related to solar radiation which is important in the emission of Hg at both sites. - Abstract: In order to provide insight into the characteristics of Hg exchange in soil/water-air surface from cropland (including paddy field and dry land), Hg fluxes were measured in Chengjiang. Mercury fluxes were measured using the dynamic flux chamber method, coupled with a Lumex (registered) multifunctional Hg analyzer RA-915{sup +} (Lumex Ltd., Russia). The Hg fluxes from paddy field and dry land were alternatively measured every 30 min. Data were collected for 24-48 h once per month for 5 months. Mercury fluxes in both fields were synchronously measured under the same conditions to compare Hg emissions between paddy field and dry land over diurnal and seasonal periods and find out what factors affect Hg emission on each surface. These results indicated that air Hg concentrations at the monitoring site was double the value observed at the global background sites in Europe and North America. The Hg release fluxes were 46.5 {+-} 22.8 ng m{sup -2} h{sup -1} in the warm season, 15.5 {+-} 18.8 ng m{sup -2} h{sup -1} in the cold season for dry land, and 23.8 {+-} 15.6 ng m{sup -2} h{sup -1} in the warm season, 6.3 {+-} 11.9 ng m{sup -2} h{sup -1} in the cold season for paddy field. Solar radiation is important in the emission of Hg over both sites. Hg exchange at the soil/air and water/air interfaces showed temporal variations. The amount of Hg emission from dry land was higher than that from the paddy field, and the emission in daytime was higher than that at night. Moreover, Hg emissions from land covered by crops, was lower

Surface - atmosphere exchange of ammonia over grazed pasture

NARCIS (Netherlands)

Plantaz, M.A.H.G.

1998-01-01

This thesis deals with the exchange of ammonia between the atmosphere and grazed pasture in an area of intensive livestock breeding. The term exchange is used because gaseous ammonia can be taken up (dry deposition) as well as released (emission) by this type of surface.
Ammonia exchange

Energy exchange in thermal energy atom-surface scattering: impulsive models

International Nuclear Information System (INIS)

Barker, J.A.; Auerbach, D.J.

1979-01-01

Energy exchange in thermal energy atom surface collisions is studied using impulsive ('hard cube' and 'hard sphere') models. Both models reproduce the observed nearly linear relation between outgoing and incoming energies. In addition, the hard-sphere model accounts for the widths of the outcoming energy distributions. (Auth.)

Theoretical evaluation on the impact of heat exchanger in Advanced Adiabatic Compressed Air Energy Storage system

International Nuclear Information System (INIS)

Yang, Ke; Zhang, Yuan; Li, Xuemei; Xu, Jianzhong

2014-01-01

Highlights: • A multi-stage AA-CAES system model is established based on thermodynamic theory. • Four Cases about pressure loss and effectiveness of heat exchanger are investigated. • The impact of pressure loss on conversion of heat energy in TES is more sensitive. • The impact of heat exchanger effectiveness in charge process on system is stronger. • Pressure loss in heat exchanger affects the change trends of system efficiency. - Abstract: Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) is a large-scale energy storage system based on gas turbine technology and thermal energy storage (TES). Electrical energy can be converted into internal energy of air and heat energy in TES during the charge process, while reverse energy conversion proceeds during discharge process. The performance of AA-CAES system requires further improvement in order to increase efficiency. In this paper, a multi-stage AA-CAES system model is established, and the influence of effectiveness and pressure loss in heat exchanger on energy conversion and utilization efficiency of AA-CAES system is analyzed theoretically based on the theory of thermodynamics. Four Cases about effectiveness and pressure loss of heat exchanger are investigated and compared with each other. It is found that effectiveness and pressure loss of heat exchanger are directly related to energy conversion and utilization in AA-CAES system. System efficiency changes with the variation of heat exchanger effectiveness and the impact of pressure loss on conversion of heat energy in TES is more sensitive than that of internal energy of air. Pressure loss can cause the complexity of system efficiency change. With appropriate selection of the values of heat exchanger effectiveness for both charge and discharge processes, an AA-CAES system with a higher efficiency could be expected

Exchange of polycyclic aromatic hydrocarbons across the air-water interface in the Bohai and Yellow Seas

Science.gov (United States)

Chen, Yingjun; Lin, Tian; Tang, Jianhui; Xie, Zhiyong; Tian, Chongguo; Li, Jun; Zhang, Gan

2016-09-01

In this study, air and surface seawater samples collected from the Bohai (BS) and Yellow Seas (YS) in May 2012 were determined exchange of PAHs, especially of low-molecular-weight (LMW) PAHs (three- and four-ring PAHs) at the air-water interface. Net volatilization fluxes of LMW PAHs were 266-1454 ng/m2/d and decreased with distance from the coast, indicating that these PAHs transported from coastal runoff were potential contributors to the atmosphere in the BS and YS. Moreover, LMW PAHs were enriched in the dissolved phase compared with those in the particulate phase in the water column, possibly suggesting that the volatilized LMW PAHs were directly derived from wastewater discharge or petroleum pollution rather than released from contaminated sediments. The air-sea exchange fluxes of the three-ring PAHs were 2- to 20-fold higher than their atmospheric deposition fluxes in the BS and YS. The input to and output from the water reached equilibrium for four-ring PAHs. Differently, five- and six-ring PAHs were introduced into the marine environment primarily through dry and wet deposition, indicating that the water column was still a sink of these PAHs from the surrounding atmosphere.

Air-water oxygen exchange in a large whitewater river

Science.gov (United States)

Hall, Robert O.; Kennedy, Theodore A.; Rosi-Marshall, Emma J.

2012-01-01

Air-water gas exchange governs fluxes of gas into and out of aquatic ecosystems. Knowing this flux is necessary to calculate gas budgets (i.e., O2) to estimate whole-ecosystem metabolism and basin-scale carbon budgets. Empirical data on rates of gas exchange for streams, estuaries, and oceans are readily available. However, there are few data from large rivers and no data from whitewater rapids. We measured gas transfer velocity in the Colorado River, Grand Canyon, as decline in O2 saturation deficit, 7 times in a 28-km segment spanning 7 rapids. The O2 saturation deficit exists because of hypolimnetic discharge from Glen Canyon Dam, located 25 km upriver from Lees Ferry. Gas transfer velocity (k600) increased with slope of the immediate reach. k600 was -1 in flat reaches, while k600 for the steepest rapid ranged 3600-7700 cm h-1, an extremely high value of k600. Using the rate of gas exchange per unit length of water surface elevation (Kdrop, m-1), segment-integrated k600 varied between 74 and 101 cm h-1. Using Kdrop we scaled k600 to the remainder of the Colorado River in Grand Canyon. At the scale corresponding to the segment length where 80% of the O2 exchanged with the atmosphere (mean length = 26.1 km), k600 varied 4.5-fold between 56 and 272 cm h-1 with a mean of 113 cm h-1. Gas transfer velocity for the Colorado River was higher than those from other aquatic ecosystems because of large rapids. Our approach of scaling k600 based on Kdrop allows comparing gas transfer velocity across rivers with spatially heterogeneous morphology.

Long-range atmospheric transport of persistent organic pollutants, I: description of surface-atmosphere exchange modules and implementation in EUROS.

NARCIS (Netherlands)

Jacobs, C.M.J.; Pul, van W.A.J.

1996-01-01

Concerns a description of a model for the exchange of gaseous Persistent Organic Pollutants (POP) at land and sea surfaces and its application in the Eulerian air pollution transport model EUROS. Sample simulations of the net deposition of lindane over Europe are discussed. For non-emission areas

Preliminary Analysis on Heat Removal Capacity of Passive Air-Water Combined Cooling Heat Exchanger Using MARS

International Nuclear Information System (INIS)

Kim, Seung-Sin; Jeon, Seong-Su; Hong, Soon-Joon; Bae, Sung-Won; Kwon, Tae-Soon

2015-01-01

Current design requirement for working time of PAFS heat exchanger is about 8 hours. Thus, it is not satisfied with the required cooling capability for the long term SBO(Station Black-Out) situation that is required to over 72 hours cooling. Therefore PAFS is needed to change of design for 72 hours cooling. In order to acquirement of long terms cooling using PAFS, heat exchanger tube has to be submerged in water tank for long time. However, water in the tank is evaporated by transferred heat from heat exchanger tubes, so water level is gradually lowered as time goes on. The heat removal capacity of air cooling heat exchanger is core parameter that is used for decision of applicability on passive air-water combined cooling system using PAFS in long term cooling. In this study, the development of MARS input model and plant accident analysis are performed for the prediction of the heat removal capacity of air cooling heat exchanger. From analysis result, it is known that inflow air velocity is the decisive factor of the heat removal capacity and predicted air velocity is lower than required air velocity. But present heat transfer model and predicted air velocity have uncertainty. So, if changed design of PAFS that has over 4.6 kW heat removal capacity in each tube, this type heat exchanger can be applied to long term cooling of the nuclear power plant

Time lag between the tropopause height and the levels of 7Be concentration in near surface air

Directory of Open Access Journals (Sweden)

Melas D.

2012-04-01

Full Text Available The concentration of 7Be at near surface air has been determined over 2009, a year of a deep solar minimum, in the region of Thessaloniki, Greece at 40°62′ N, 22°95'E. In geomagnetic latitudes over 40° N, the elevation of the tropopause during the warm summer months and the vertical exchange of air masses within the troposphere cause greater mixture of the air masses resulting in higher concentration levels for 7Be in surface air. The positive correlation between the monthly activity concentration of 7Be and the tropopause height (0.94, p < 0.0001, and also between 7Be concentration and the temperature T (°C (R = 0.97, p < 0.001, confirm that the increased rate of vertical transport within the troposphere, especially during warmer summer months, has as a result the descent to surface of air masses enriched in 7Be. However, the 7Be concentration levels in near surface air are not expected to respond immediately to the change of elevation of the tropopause. It was found that there's a time lag of ~ 3 days between the change in the daily surface concentrations of 7Be the change in the elevation of the tropopause.

Experimental temperature analysis of simple & hybrid earth air tunnel heat exchanger in series connection at Bikaner Rajasthan India

Science.gov (United States)

Jakhar, O. P.; Sharma, Chandra Shekhar; Kukana, Rajendra

2018-05-01

The Earth Air Tunnel Heat Exchanger System is a passive air-conditioning system which has no side effect on earth climate and produces better cooling effect and heating effect comfortable to human body. It produces heating effect in winter and cooling effect in summer with the minimum power consumption of energy as compare to other air-conditioning devices. In this research paper Temperature Analysis was done on the two systems of Earth Air Tunnel Heat Exchanger experimentally for summer cooling purpose. Both the system was installed at Mechanical Engineering Department Government Engineering College Bikaner Rajasthan India. Experimental results concludes that the Average Air Temperature Difference was found as 11.00° C and 16.27° C for the Simple and Hybrid Earth Air Tunnel Heat Exchanger in Series Connection System respectively. The Maximum Air Temperature Difference was found as 18.10° C and 23.70° C for the Simple and Hybrid Earth Air Tunnel Heat Exchanger in Series Connection System respectively. The Minimum Air Temperature Difference was found as 5.20° C and 11.70° C for the Simple and Hybrid Earth Air Tunnel Heat Exchanger in Series Connection System respectively.

Constructal design of finned tubes used in air-cooled heat exchangers

Energy Technology Data Exchange (ETDEWEB)

Shokouhmand, Hossein; Mahjoub, Shoeib [University of Tehran, Tehran (Iran, Islamic Republic of); Salimpour, Mohammad Reza [Isfahan University of Technology, Isfahan (Iran, Islamic Republic of)

2014-06-15

The present study documents the constructal design and optimization of finned tubes used in air-cooled heat exchangers. The considered tubes are equipped with annular fins. The aim is to minimize the overall thermal resistance by morphing the geometry. The geometrical and thermo-physical parameters considered are the number of fins, ratio of fin height to tube diameter, Stanton number, ratio of fin conductivity to air conductivity, ratio of in-tube fluid conductivity to air conductivity and dimensionless pressure drop. Two constraints are applied in the optimization process: fixed overall volume of heat exchanger and fixed volume fraction of fin material. It is found that there exist optimal values for the number and the height of fins. Moreover, the optimal heat transfer has an extremum in a special volume fraction of fin material.

Constructal design of finned tubes used in air-cooled heat exchangers

International Nuclear Information System (INIS)

Shokouhmand, Hossein; Mahjoub, Shoeib; Salimpour, Mohammad Reza

2014-01-01

The present study documents the constructal design and optimization of finned tubes used in air-cooled heat exchangers. The considered tubes are equipped with annular fins. The aim is to minimize the overall thermal resistance by morphing the geometry. The geometrical and thermo-physical parameters considered are the number of fins, ratio of fin height to tube diameter, Stanton number, ratio of fin conductivity to air conductivity, ratio of in-tube fluid conductivity to air conductivity and dimensionless pressure drop. Two constraints are applied in the optimization process: fixed overall volume of heat exchanger and fixed volume fraction of fin material. It is found that there exist optimal values for the number and the height of fins. Moreover, the optimal heat transfer has an extremum in a special volume fraction of fin material.

Thermal Sizing of Heat Exchanger Tubes for Air Natural Convective Cooling System of Emergency Cooling Tank

Energy Technology Data Exchange (ETDEWEB)

Kim, Myoung Jun; Lee, Hee Joon [Kookmin Univ., Seoul (Korea, Republic of); Moon, Joo Hyung; Bae, Youngmin; Kim, Youngin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-05-15

For the long operation of secondary passive cooling system, however, water level goes down by evaporation in succession at emergency cooling tank. At the end there would be no place to dissipate heat from condensation heat exchanger. Therefore, steam cooling heat exchanger is put on the top of emergency cooling tank to maintain appropriate water level by collecting evaporating steam. Steam cooling heat exchanger is installed inside an air chimney and evaporated steam is cooled down by air natural convection. In this study, thermal sizing of steam cooling heat exchanger under air natural convection was conducted by TSCON program for the design of experimental setup as shown in Fig. 2. Thermal sizing of steam cooling heat exchanger tube under air natural convection was conducted by TSCON program for the design of experimental setup. 25 - 1' tubes which has a length 1687 mm was determined as steam cooling heat exchanger at 2 kW heat load and 100 liter water pool in emergency cooling tank (experimental limit condition). The corresponding width of two tubes is 50 mm and has 5 by 5 tube array for heat exchanger.

Thermal Sizing of Heat Exchanger Tubes for Air Natural Convective Cooling System of Emergency Cooling Tank

International Nuclear Information System (INIS)

Kim, Myoung Jun; Lee, Hee Joon; Moon, Joo Hyung; Bae, Youngmin; Kim, Youngin

2014-01-01

For the long operation of secondary passive cooling system, however, water level goes down by evaporation in succession at emergency cooling tank. At the end there would be no place to dissipate heat from condensation heat exchanger. Therefore, steam cooling heat exchanger is put on the top of emergency cooling tank to maintain appropriate water level by collecting evaporating steam. Steam cooling heat exchanger is installed inside an air chimney and evaporated steam is cooled down by air natural convection. In this study, thermal sizing of steam cooling heat exchanger under air natural convection was conducted by TSCON program for the design of experimental setup as shown in Fig. 2. Thermal sizing of steam cooling heat exchanger tube under air natural convection was conducted by TSCON program for the design of experimental setup. 25 - 1' tubes which has a length 1687 mm was determined as steam cooling heat exchanger at 2 kW heat load and 100 liter water pool in emergency cooling tank (experimental limit condition). The corresponding width of two tubes is 50 mm and has 5 by 5 tube array for heat exchanger

Probabilistic estimation of residential air exchange rates for population-based human exposure modeling

Science.gov (United States)

Residential air exchange rates (AERs) are a key determinant in the infiltration of ambient air pollution indoors. Population-based human exposure models using probabilistic approaches to estimate personal exposure to air pollutants have relied on input distributions from AER meas...

Fabrication of High-Temperature Heat Exchangers by Plasma Spraying Exterior Skins on Nickel Foams

Science.gov (United States)

Hafeez, P.; Yugeswaran, S.; Chandra, S.; Mostaghimi, J.; Coyle, T. W.

2016-06-01

Thermal-sprayed heat exchangers were tested at high temperatures (750 °C), and their performances were compared to the foam heat exchangers made by brazing Inconel sheets to their surface. Nickel foil was brazed to the exterior surface of 10-mm-thick layers of 10 and 40 PPI nickel foam. A plasma torch was used to spray an Inconel coating on the surface of the foil. A burner test rig was built to produce hot combustion gases that flowed over exposed face of the heat exchanger. Cooling air flowed through the foam heat exchanger at rates of up to 200 SLPM. Surface temperature and air inlet/exit temperature were measured. Heat transfer to air flowing through the foam was significantly higher for the thermally sprayed heat exchangers than for the brazed heat exchangers. On an average, thermally sprayed heat exchangers show 36% higher heat transfer than conventionally brazed foam heat exchangers. At low flow rates, the convective resistance is large (~4 × 10-2 m2 K/W), and the effect of thermal contact resistance is negligible. At higher flow rates, the convective resistance decreases (~2 × 10-3 m2 K/W), and the lower contact resistance of the thermally sprayed heat exchanger provides better performance than the brazed heat exchangers.

The effects of rice canopy on the air-soil exchange of polycyclic aromatic hydrocarbons and organochlorine pesticides using paired passive air samplers.

Science.gov (United States)

Wang, Yan; Wang, Shaorui; Luo, Chunling; Li, Jun; Ming, Lili; Zhang, Gan; Li, Xiangdong

2015-05-01

The rice canopy in paddy fields can influence the air-soil exchange of organic chemicals. We used paired passive air samplers to assess the exchange of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in a paddy field, South China. Levels of OCPs and light PAHs were generally higher under the canopy than above it. We found that the rice canopy can physically obstruct the evaporation of most OCPs and light PAHs, and can also act as a barrier to the gaseous deposition of p,p'-DDT and heavy PAHs. Paddy fields can behave as a secondary source of OCPs and light PAHs. The homolog patterns of these two types of chemical varied slightly between the air below and above the rice canopy, implying contributions of different sources. Paired passive air samplers can be used effectively to assess the in situ air-soil exchange of PAHs and OCPs in subtropical paddy fields. Copyright © 2015 Elsevier Ltd. All rights reserved.

Performance analyses of helical coil heat exchangers. The effect of external coil surface modification on heat exchanger effectiveness

Science.gov (United States)

Andrzejczyk, Rafał; Muszyński, Tomasz

2016-12-01

The shell and coil heat exchangers are commonly used in heating, ventilation, nuclear industry, process plant, heat recovery and air conditioning systems. This type of recuperators benefits from simple construction, the low value of pressure drops and high heat transfer. In helical coil, centrifugal force is acting on the moving fluid due to the curvature of the tube results in the development. It has been long recognized that the heat transfer in the helical tube is much better than in the straight ones because of the occurrence of secondary flow in planes normal to the main flow inside the helical structure. Helical tubes show good performance in heat transfer enhancement, while the uniform curvature of spiral structure is inconvenient in pipe installation in heat exchangers. Authors have presented their own construction of shell and tube heat exchanger with intensified heat transfer. The purpose of this article is to assess the influence of the surface modification over the performance coefficient and effectiveness. The experiments have been performed for the steady-state heat transfer. Experimental data points were gathered for both laminar and turbulent flow, both for co current- and countercurrent flow arrangement. To find optimal heat transfer intensification on the shell-side authors applied the number of transfer units analysis.

Improved Formulations for Air-Surface Exchanges Related to National Security Needs: Dry Deposition Models

Energy Technology Data Exchange (ETDEWEB)

Droppo, James G.

2006-07-01

The Department of Homeland Security and others rely on results from atmospheric dispersion models for threat evaluation, event management, and post-event analyses. The ability to simulate dry deposition rates is a crucial part of our emergency preparedness capabilities. Deposited materials pose potential hazards from radioactive shine, inhalation, and ingestion pathways. A reliable characterization of these potential exposures is critical for management and mitigation of these hazards. A review of the current status of dry deposition formulations used in these atmospheric dispersion models was conducted. The formulations for dry deposition of particulate materials from am event such as a radiological attack involving a Radiological Detonation Device (RDD) is considered. The results of this effort are applicable to current emergency preparedness capabilities such as are deployed in the Interagency Modeling and Atmospheric Assessment Center (IMAAC), other similar national/regional emergency response systems, and standalone emergency response models. The review concludes that dry deposition formulations need to consider the full range of particle sizes including: 1) the accumulation mode range (0.1 to 1 micron diameter) and its minimum in deposition velocity, 2) smaller particles (less than .01 micron diameter) deposited mainly by molecular diffusion, 3) 10 to 50 micron diameter particles deposited mainly by impaction and gravitational settling, and 4) larger particles (greater than 100 micron diameter) deposited mainly by gravitational settling. The effects of the local turbulence intensity, particle characteristics, and surface element properties must also be addressed in the formulations. Specific areas for improvements in the dry deposition formulations are 1) capability of simulating near-field dry deposition patterns, 2) capability of addressing the full range of potential particle properties, 3) incorporation of particle surface retention/rebound processes, and

Winter-regime surface heat loss from heated streams

International Nuclear Information System (INIS)

Paily, P.P.; Macagno, E.O.; Kennedy, J.F.

1974-01-01

Evaluation of the rate of surface heat exchange between the water and air is a significant factor in any study of the thermal response of heated streams to heat inputs. Existing methods to determine the amount of heat transfer across the water surface are surveyed, and the different formulas developed for determining the heat exchange components are compiled. Heat-transfer models that have been proposed in the literature are reviewed, and a new linearized model for determining the rate of surface heat exchange is proposed. Generalized relations between the major climatological factors and the coefficients of the linearized heat-loss rate are established by multiple-regression analysis. The analysis is limited to cold-period conditions, in the sense that air temperatures below the freezing point of water only are considered in developing the regression equations. A computer program, using FORTRAN, is presented which enables the computation of the coefficients appearing in the linearized heat-loss rate for all combinations of the various climatological factors

Dynamic air layer on textured superhydrophobic surfaces

KAUST Repository

Vakarelski, Ivan Uriev

2013-09-03

We provide an experimental demonstration that a novel macroscopic, dynamic continuous air layer or plastron can be sustained indefinitely on textured superhydrophobic surfaces in air-supersaturated water by a natural gas influx mechanism. This type of plastron is an intermediate state between Leidenfrost vapor layers on superheated surfaces and the equilibrium Cassie-Baxter wetting state on textured superhydrophobic surfaces. We show that such a plastron can be sustained on the surface of a centimeter-sized superhydrophobic sphere immersed in heated water and variations of its dynamic behavior with air saturation of the water can be regulated by rapid changes of the water temperature. The simple experimental setup allows for quantification of the air flux into the plastron and identification of the air transport model of the plastron growth. Both the observed growth dynamics of such plastrons and millimeter-sized air bubbles seeded on the hydrophilic surface under identical air-supersaturated solution conditions are consistent with the predictions of a well-mixed gas transport model. © 2013 American Chemical Society.

Isopleths of surface air concentration and surface air kerma rate due to a radioactive cloud released from a stack (3)

International Nuclear Information System (INIS)

Tachibana, Haruo; Kikuchi, Masamitsu; Sekita, Tsutomu; Yamaguchi, Takenori

2004-06-01

This report is a revised edition of 'Isopleths of Surface Air Concentration and Surface Air Absorbed Dose Rate due to a Radioactive Cloud Released from a Stack(II) '(JAERI-M 90-206) and based on the revised Nuclear Safety Guidelines reflected the ICRP1990 Recommendation. Characteristics of this report are the use of Air Karma Rate (Gy/h) instead of Air Absorbed Dose Rate (Gy/h), and the record of isopleths of surface air concentration and surface air karma rate on CD-ROM. These recorded data on CD-ROM can be printed out on paper and/or pasted on digital map by personal computer. (author)

Thermal characterisation of compact heat exchangers for air heating and cooling in electric vehicles

International Nuclear Information System (INIS)

Torregrosa-Jaime, B.; Corberán, J.M.; Payá, J.; Delamarche, J.L.

2017-01-01

The use of air conditioning in all-electric cars reduces their driving range by 33% in average. With the purpose of reducing the energy consumption of the vehicle and optimising the performance of the batteries, the mobile air-conditioning can be integrated with the temperature control system of the powertrain by means of a coolant loop. In such layouts, the air-to-coolant heat exchangers must operate efficiently in both air heating and cooling modes. Dynamic simulation tools comprising the entire thermal system are essential to assess its performance. In this context, fast but accurate models of the system components are required. This paper presents the thermal characterisation of a commercial compact louvered-fin flat-tube heat exchanger (heater core) for this novel application, based on an experimental campaign comprising 279 working points that reflect real air-conditioning (heating and cooling) working conditions. A general methodology to fit a single correlation of the global heat transfer coefficient for both dry and wet working conditions is explained. The semiempirical correlation developed is employed in a single-node model of the heat exchanger that requires minimal computation time. The present model predicts the heat transfer rate with an average deviation of 3.5% in the cases with dehumidification and 1.9% in the cases when the heat exchanger remains dry.

A Novel RFID Sensing System Using Enhanced Surface Wave Technology for Battery Exchange Stations

Directory of Open Access Journals (Sweden)

Yeong-Lin Lai

2014-01-01

Full Text Available This paper presents a novel radio-frequency identification (RFID sensing system using enhanced surface wave technology for battery exchange stations (BESs of electric motorcycles. Ultrahigh-frequency (UHF RFID technology is utilized to automatically track and manage battery and user information without manual operation. The system includes readers, enhanced surface wave leaky cable antennas (ESWLCAs, coupling cable lines (CCLs, and small radiation patches (SRPs. The RFID sensing system overcomes the electromagnetic interference in the metallic environment of a BES cabinet. The developed RFID sensing system can effectively increase the efficiency of BES operation and promote the development of electric vehicles which solve the problem of air pollution as well as protect the environment of the Earth.

Parametric investigation of a non-constant cross sectional area air to air heat exchanger

International Nuclear Information System (INIS)

Cárdenas, Bruno; Garvey, Seamus; Kantharaj, Bharath; Simpson, Michael

2017-01-01

Highlights: • Evaluation of complex geometry aimed at minimizing volume per unit of exergy transfer. • The use of a non-constant cross-section for the heat exchanger is proposed. • The performance gains attainable via modern manufacturing techniques are discussed. • The trade-off between overall exergy efficiency and cost is thoroughly analysed. • A quadratic proportion between volume and characteristic dimension has been found. - Abstract: The present article addresses the design, mathematical modelling and analysis of a novel highly exergy-efficient air to air heat exchanger. An intricate design based on an hexagonal mesh is proposed for the cross-sectional area of the heat exchanger with aims to explore the performance gains that can be obtained by exploiting the capabilities and benefits offered by modern fabrication techniques such as additive manufacturing. Special attention is paid to understanding the relationship or trade-off that exists between the overall exergy efficiency of the heat exchanger and its cost. The iterative algorithm used to find the geometrical parameters that yield the best performance in terms of volume of material required per unit of exergy transfer at a certain level of efficiency, as well as the assumptions and simplifications made, are comprehensively explained. It has been found through the analyses carried out performed, which are thoroughly discussed throughout the paper, that if the characteristic dimension of the heat exchanger is scaled up by a factor of n, the volume of material per kW of exergy transfer at certain exergy efficiency will increase by a factor of n squared. This is a very important observation, possibly applicable to other types of heat exchangers, that indicates that performance improves dramatically at smaller scales. The overall performance of the case study presented is satisfactory, a volume of material as low as 84.8 cm"3 for one kW of exergy transfer can be achieved with a 99% exergy

Behavior of cross flow heat exchangers during the cooling and dehumidification of air

Energy Technology Data Exchange (ETDEWEB)

Ober, C [Karlsruhe Univ. (TH) (Germany, F.R.). Inst. fuer Mess- und Regelungstechnik mit Maschinenlaboratorium

1980-09-01

The task of cross flow heat exchangers in room air engineering consists on the one hand in heating up the air and, on the other hand, in the simultaneous cooling and dehumidification. The facilities used for this purpose generally are multi-row finned pipe heat exchangers which when used for cooling contain cold water or brine as the working fluid. The use of directly evaporating freezing mixtures may not be included in this consideration. The model establishment for the dynamic and the static behavior of multi-row cross flow heat exchangers during cooling and dehumidification of air has been derived in this contribution. The representation is performed for the dynamic case in the complex, display range of the Laplace transformation. A comparison with experimental results can be done very simply by means of measurements of the frequency-responce curves in the form of Bode diagrams. The description of the static behaviour may be applied as a basis for humidity controls with more favourable energy utilization.

Investigation of heat transfer inside a PCM-air heat exchanger: a numerical parametric study

Science.gov (United States)

Herbinger, Florent; Bhouri, Maha; Groulx, Dominic

2017-07-01

In this paper, the use of PCMs for thermal storage of energy in HVAC applications was investigated by studying numerically the thermal performance of a PCM-air heat exchanger. The PCM used in this study was dodecanoic acid. A symmetric 3D model, incorporating conductive and convective heat transfer (air only) as well as laminar flow, was created in COMSOL Multiphysics 5.0. Simulations examined the dependence of the heat transfer rate on the temperature and velocity of the incoming air as well as the size of the channels in the heat exchanger. Results indicated that small channels size lead to a higher heat transfer rates. A similar trend was also obtained for high incoming air temperature, whereas the heat transfer rate was less sensitive to the incoming air velocity.

Air/sea DMS gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

Science.gov (United States)

Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

2013-05-01

Shipboard measurements of eddy covariance DMS air/sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air/sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near surface water side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air/sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

A CRITICAL ASSESSMENT OF ELEMENTAL MERCURY AIR/WATER EXCHANGE PARTNERS

Science.gov (United States)

Although evasion of elemental mercury from aquatic systems can significantly deplete net mercury accumulation resulting from atmospheric deposition, the current ability to model elemental mercury air/water exchange is limited by uncertainties in our understanding of all gaseous a...

Solar-Enhanced Air-Cooled Heat Exchangers for Geothermal Power Plants

Directory of Open Access Journals (Sweden)

Kamel Hooman

2017-10-01

Full Text Available This paper focuses on the optimization of a Solar-Enhanced Natural-Draft Dry-Cooling Tower (SENDDCT, originally designed by the Queensland Geothermal Energy Centre of Excellence (QGECE, as the air-cooled condenser of a geothermal power plant. The conventional method of heat transfer augmentation through fin-assisted area extension is compared with a metal foam-wrapped tube bundle. Both lead to heat-transfer enhancement, albeit at the expense of a higher pressure drop when compared to the bare tube bundle as our reference case. An optimal design is obtained through the use of a simplified analytical model and existing correlations by maximizing the heat transfer rate with a minimum pressure drop goal as the constraint. Sensitivity analysis was conducted to investigate the effect of sunroof diameter, as well as tube bundle layouts and tube spacing, on the overall performance of the system. Aiming to minimize the flow and thermal resistances for a SENDDCT, an optimum design is presented for an existing tower to be equipped with solar panels to afterheat the air leaving the heat exchanger bundles, which are arranged vertically around the tower skirt. Finally, correlations are proposed to predict the total pressure drop and heat transfer of the extended surfaces considered here.

Responses of Surface Ozone Air Quality to Anthropogenic Nitrogen Deposition

Science.gov (United States)

Zhang, L.; Zhao, Y.; Tai, A. P. K.; Chen, Y.; Pan, Y.

2017-12-01

Human activities have substantially increased atmospheric deposition of reactive nitrogen to the Earth's surface, inducing unintentional effects on ecosystems with complex environmental and climate consequences. One consequence remaining unexplored is how surface air quality might respond to the enhanced nitrogen deposition through surface-atmosphere exchange. We combine a chemical transport model (GEOS-Chem) and a global land model (Community Land Model) to address this issue with a focus on ozone pollution in the Northern Hemisphere. We consider three processes that are important for surface ozone and can be perturbed by addition of atmospheric deposited nitrogen: emissions of biogenic volatile organic compounds (VOCs), ozone dry deposition, and soil nitrogen oxide (NOx) emissions. We find that present-day anthropogenic nitrogen deposition (65 Tg N a-1 to the land), through enhancing plant growth (represented as increases in vegetation leaf area index (LAI) in the model), could increase surface ozone from increased biogenic VOC emissions, but could also decrease ozone due to higher ozone dry deposition velocities. Meanwhile, deposited anthropogenic nitrogen to soil enhances soil NOx emissions. The overall effect on summer mean surface ozone concentrations show general increases over the globe (up to 1.5-2.3 ppbv over the western US and South Asia), except for some regions with high anthropogenic NOx emissions (0.5-1.0 ppbv decreases over the eastern US, Western Europe, and North China). We compare the surface ozone changes with those driven by the past 20-year climate and historical land use changes. We find that the impacts from anthropogenic nitrogen deposition can be comparable to the climate and land use driven surface ozone changes at regional scales, and partly offset the surface ozone reductions due to land use changes reported in previous studies. Our study emphasizes the complexity of biosphere-atmosphere interactions, which can have important

Quantifying Hyporheic Exchanges in a Large Scale River Reach Using Coupled 3-D Surface and Subsurface Computational Fluid Dynamics Simulations.

Energy Technology Data Exchange (ETDEWEB)

Hammond, Glenn Edward; Bao, J; Huang, M; Hou, Z; Perkins, W; Harding, S; Titzler, S; Ren, H; Thorne, P; Suffield, S; Murray, C; Zachara, J

2017-03-01

Hyporheic exchange is a critical mechanism shaping hydrological and biogeochemical processes along a river corridor. Recent studies on quantifying the hyporheic exchange were mostly limited to local scales due to field inaccessibility, computational demand, and complexity of geomorphology and subsurface geology. Surface flow conditions and subsurface physical properties are well known factors on modulating the hyporheic exchange, but quantitative understanding of their impacts on the strength and direction of hyporheic exchanges at reach scales is absent. In this study, a high resolution computational fluid dynamics (CFD) model that couples surface and subsurface flow and transport is employed to simulate hyporheic exchanges in a 7-km long reach along the main-stem of the Columbia River. Assuming that the hyporheic exchange does not affect surface water flow conditions due to its negligible magnitude compared to the volume and velocity of river water, we developed a one-way coupled surface and subsurface water flow model using the commercial CFD software STAR-CCM+. The model integrates the Reynolds-averaged Navier-Stokes (RANS) equation solver with a realizable κ-ε two-layer turbulence model, a two-layer all y⁺ wall treatment, and the volume of fluid (VOF) method, and is used to simulate hyporheic exchanges by tracking the free water-air interface as well as flow in the river and the subsurface porous media. The model is validated against measurements from acoustic Doppler current profiler (ADCP) in the stream water and hyporheic fluxes derived from a set of temperature profilers installed across the riverbed. The validated model is then employed to systematically investigate how hyporheic exchanges are influenced by surface water fluid dynamics strongly regulated by upstream dam operations, as well as subsurface structures (e.g. thickness of riverbed and subsurface formation layers) and hydrogeological properties (e.g. permeability). The results

Solid oxide fuel cell power plant having a fixed contact oxidation catalyzed section of a multi-section cathode air heat exchanger

Science.gov (United States)

Saito, Kazuo; Lin, Yao

2015-02-17

The multi-section cathode air heat exchanger (102) includes at least a first heat exchanger section (104), and a fixed contact oxidation catalyzed section (126) secured adjacent each other in a stack association. Cool cathode inlet air flows through cool air channels (110) of the at least first (104) and oxidation catalyzed sections (126). Hot anode exhaust flows through hot air channels (124) of the oxidation catalyzed section (126) and is combusted therein. The combusted anode exhaust then flows through hot air channels (112) of the first section (104) of the cathode air heat exchanger (102). The cool and hot air channels (110, 112) are secured in direct heat exchange relationship with each other so that temperatures of the heat exchanger (102) do not exceed 800.degree. C. to minimize requirements for using expensive, high-temperature alloys.

Measurements of VOC/SVOC emission factors from burning incenses in an environmental test chamber: influence of temperature, relative humidity, and air exchange rate.

Science.gov (United States)

Manoukian, A; Buiron, D; Temime-Roussel, B; Wortham, H; Quivet, E

2016-04-01

This study investigates the influence of three environmental indoor parameters (i.e., temperature, relative humidity, and air exchange rate) on the emission of 13 volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) during incense burning. Experiments have been carried out using an environmental test chamber. Statistical results from a classical two-level full factorial design highlight the predominant effect of ventilation on emission factors. The higher the ventilation, the higher the emission factor. Moreover, thanks to these results, an estimation of the concentration range for the compounds under study can be calculated and allows a quick look of indoor pollution induced by incense combustion. Carcinogenic substances (i.e., benzene, benzo(a)pyrene, and formaldehyde) produced from the incense combustion would be predicted in typical living indoors conditions to reach instantaneous concentration levels close to or higher than air quality exposure threshold values.

Numerical investigation of the energy performance of a guideless irregular heat and mass exchanger with corrugated heat transfer surface for dew point cooling

International Nuclear Information System (INIS)

Xu, Peng; Ma, Xiaoli; Diallo, Thierno M.O.; Zhao, Xudong; Fancey, Kevin; Li, Deying; Chen, Hongbing

2016-01-01

The paper presents an investigation into the energy performance of a novel irregular heat and mass exchanger for dew point cooling which, compared to the existing flat-plate heat exchangers, removed the use of the channel supporting guides and implemented the corrugated heat transfer surface, thus expecting to achieve the reduced air flow resistance, increased heat transfer area, and improved energy efficiency (i.e. Coefficient of Performance (COP)) of the air cooling process. CFD simulation was carried out to determine the flow resistance (K) factors of various elements within the dry and wet channels of the exchanger, while the ‘finite-element’ based ‘Newton-iteration’ numerical simulation was undertaken to investigate its cooling capacity, cooling effectiveness and COP at various geometrical and operational conditions. Compared to the existing flat-plate heat and mass exchangers with the same geometrical dimensions and operational conditions, the new irregular exchanger could achieve 32.9%–37% higher cooling capacity, dew-point and wet-bulb effectiveness, 29.7%–33.3% higher COP, and 55.8%–56.2% lower pressure drop. While undertaking dew point air cooling, the irregular heat and mass exchanger had the optimum air velocity of 1 m/s within the flow channels and working-to-intake air ratio of 0.3, which allowed the highest cooling capacity and COP to be achieved. In terms of the exchanger dimensions, the optimum height of the channel was 5 mm while its length was in the range 1–2 m. Overall, the proposed irregular heat and mass exchanger could lead to significant enhanced energy performance compared to the existing flat-plate dew point cooling heat exchanger of the same geometrical dimensions. To achieve the same amount cooling output, the irregular heat and mass exchanger had the reduced size and cost against the flat-plate ones. - Highlights: • Numerical investigation of an irregular heat and mass exchanger was undertaken. • A �

Signatures of Air-Wave Interactions Over a Large Lake

Science.gov (United States)

Li, Qi; Bou-Zeid, Elie; Vercauteren, Nikki; Parlange, Marc

2018-01-01

The air-water exchange of momentum and scalars (temperature and water vapour) is investigated using the Lake-Atmosphere Turbulent EXchange (LATEX) dataset. The wind waves and swell are found to affect the coupling between the water surface and the air differently. The surface-stress vector aligns with the wind velocity in the presence of wind waves, but a wide range of stress-wind misalignment angles is observed during swell. The momentum transport efficiency decreases when significant stress-wind misalignment is present, suggesting a strong influence of surface wave properties on surface drag. Based on this improved understanding of the role of wave-wind misalignment, a new relative wind speed for surface-layer similarity formulations is proposed and tested using the data. The new expression yields a value of the von Kármán constant (κ ) of 0.38, compared to 0.36 when using the absolute wind speed, as well as reduced data fitting errors. Finally, the ratios of aerodynamic to scalar roughness lengths are computed and various existing models in the literature are tested using least-square fitting to the observed ratios. The tests are able to discriminate between the performance of various models; however, they also indicate that more investigations are required to understand the physics of scalar exchanges over waves.

Signatures of Air-Wave Interactions Over a Large Lake

Science.gov (United States)

Li, Qi; Bou-Zeid, Elie; Vercauteren, Nikki; Parlange, Marc

2018-06-01

The air-water exchange of momentum and scalars (temperature and water vapour) is investigated using the Lake-Atmosphere Turbulent EXchange (LATEX) dataset. The wind waves and swell are found to affect the coupling between the water surface and the air differently. The surface-stress vector aligns with the wind velocity in the presence of wind waves, but a wide range of stress-wind misalignment angles is observed during swell. The momentum transport efficiency decreases when significant stress-wind misalignment is present, suggesting a strong influence of surface wave properties on surface drag. Based on this improved understanding of the role of wave-wind misalignment, a new relative wind speed for surface-layer similarity formulations is proposed and tested using the data. The new expression yields a value of the von Kármán constant (κ ) of 0.38, compared to 0.36 when using the absolute wind speed, as well as reduced data fitting errors. Finally, the ratios of aerodynamic to scalar roughness lengths are computed and various existing models in the literature are tested using least-square fitting to the observed ratios. The tests are able to discriminate between the performance of various models; however, they also indicate that more investigations are required to understand the physics of scalar exchanges over waves.

Miniaturized Air-to-Refrigerant Heat Exchangers

Energy Technology Data Exchange (ETDEWEB)

Radermacher, Reinhard [Univ. of Maryland, College Park, MD (United States); Bacellar, Daniel [Univ. of Maryland, College Park, MD (United States); Aute, Vikrant [Univ. of Maryland, College Park, MD (United States); Huang, Zhiwei [Univ. of Maryland, College Park, MD (United States); Hwang, Yunho [Univ. of Maryland, College Park, MD (United States); Ling, Jiazhen [Univ. of Maryland, College Park, MD (United States); Muehlbauer, Jan [Univ. of Maryland, College Park, MD (United States); Tancabel, James [Univ. of Maryland, College Park, MD (United States); Abdelaziz, Omar [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Zhang, Mingkan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-05-23

Air-to-refrigerant Heat eXchangers (HX) are an essential component of Heating, Ventilation, Air-Conditioning, and Refrigeration (HVAC&R) systems, serving as the main heat transfer component. The major limiting factor to HX performance is the large airside thermal resistance. Recent literature aims at improving heat transfer performance by utilizing enhancement methods such as fins and small tube diameters; this has lead to almost exhaustive research on the microchannel HX (MCHX). The objective of this project is to develop a miniaturized air-to-refrigerant HX with at least 20% reduction in volume, material volume, and approach temperature compared to current state-of-the-art multiport flat tube designs and also be capable of production within five years. Moreover, the proposed HX’s are expected to have good water drainage and should succeed in both evaporator and condenser applications. The project leveraged Parallel-Parametrized Computational Fluid Dynamics (PPCFD) and Approximation-Assisted Optimization (AAO) techniques to perform multi-scale analysis and shape optimization with the intent of developing novel HX designs whose thermal-hydraulic performance exceeds that of state-of-the-art MCHX. Nine heat exchanger geometries were initially chosen for detailed analysis, selected from 35+ geometries which were identified in previous work at the University of Maryland, College Park. The newly developed optimization framework was exercised for three design optimization problems: (DP I) 1.0kW radiator, (DP II) 10kW radiator and (DP III) 10kW two-phase HX. DP I consisted of the design and optimization of 1.0kW air-to-water HX’s which exceeded the project requirements of 20% volume/material reduction and 20% better performance. Two prototypes for the 1.0kW HX were prototyped, tested and validated using newly-designed airside and refrigerant side test facilities. DP II, a scaled version DP I for 10kW air-to-water HX applications, also yielded optimized HX designs

Surface Modification and Surface - Subsurface Exchange Processes on Europa

Science.gov (United States)

Phillips, C. B.; Molaro, J.; Hand, K. P.

2017-12-01

The surface of Jupiter's moon Europa is modified by exogenic processes such as sputtering, gardening, radiolysis, sulfur ion implantation, and thermal processing, as well as endogenic processes including tidal shaking, mass wasting, and the effects of subsurface tectonic and perhaps cryovolcanic activity. New materials are created or deposited on the surface (radiolysis, micrometeorite impacts, sulfur ion implantation, cryovolcanic plume deposits), modified in place (thermal segregation, sintering), transported either vertically or horizontally (sputtering, gardening, mass wasting, tectonic and cryovolcanic activity), or lost from Europa completely (sputtering, plumes, larger impacts). Some of these processes vary spatially, as visible in Europa's leading-trailing hemisphere brightness asymmetry. Endogenic geologic processes also vary spatially, depending on terrain type. The surface can be classified into general landform categories that include tectonic features (ridges, bands, cracks); disrupted "chaos-type" terrain (chaos blocks, matrix, domes, pits, spots); and impact craters (simple, complex, multi-ring). The spatial distribution of these terrain types is relatively random, with some differences in apex-antiapex cratering rates and latitudinal variation in chaos vs. tectonic features. In this work, we extrapolate surface processes and rates from the top meter of the surface in conjunction with global estimates of transport and resurfacing rates. We combine near-surface modification with an estimate of surface-subsurface (and vice versa) transport rates for various geologic terrains based on an average of proposed formation mechanisms, and a spatial distribution of each landform type over Europa's surface area. Understanding the rates and mass balance for each of these processes, as well as their spatial and temporal variability, allows us to estimate surface - subsurface exchange rates over the average surface age ( 50myr) of Europa. Quantifying the timescale

Membrane heat exchanger in HVAC energy recovery systems, systems energy analysis

Energy Technology Data Exchange (ETDEWEB)

Nasif, M. [School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia); Opus International Consultants (New Zealand); AL-Waked, R. [Mechanical Engineering Department, Prince Mohammad Bin Fahd University (PMU), P.O. Box 1614, AlKhobar 31952 (Saudi Arabia); Morrison, G. [School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia); Behnia, M. [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia)

2010-10-15

The thermal performance of an enthalpy/membrane heat exchanger is experimentally investigated. The heat exchanger utilizes a 60gsm Kraft paper as the heat and moisture transfer surface for HVAC energy recovery. The heat exchanger sensible, latent and total effectiveness have been determined through temperature and moisture content measurements. The annual energy consumption of an air conditioner coupled with an enthalpy/membrane heat exchanger is also studied and compared with a conventional air conditioning cycle using in-house modified HPRate software. The heat exchanger effectiveness are used as thermal performance indicators and incorporated in the modified software. Energy analysis showed that an air conditioning system coupled with a membrane heat exchanger consumes less energy than a conventional air conditioning system in hot and humid climates where the latent load is high. It has been shown that in humid climate a saving of up to 8% in annual energy consumption can be achieved when membrane heat exchanger is used instead of a conventional HVAC system. (author)

Air-sea dimethylsulfide (DMS) gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

Science.gov (United States)

Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

2013-11-01

Shipboard measurements of eddy covariance dimethylsulfide (DMS) air-sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air-sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near-surface water-side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air-sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

Reducing the energy consumption of an earth–air heat exchanger with a PID control system

International Nuclear Information System (INIS)

Diaz-Mendez, S.E.; Patiño-Carachure, C.; Herrera-Castillo, J.A.

2014-01-01

Highlights: • The application of control actions to green technologies has been simulated. • Energy consumption of green technologies can be reduced even more. • The efficiency of green technologies can be raised. • Environmental concerns can be diminished. • The sustainability of the planet can be increased. - Abstract: Reducing environmental emissions is one of the challenges that human being has to overcome. It can only be reached with a proper energetic efficiency and management of the processes that exist in the society nowadays. Several academic works have mentioned that raising the efficiency of a process it also increases sustainability and in turn decreases the environmental impact. One process that requires much attention is the cooling and heating of buildings; this process contributes to the major part of the electric bill, in particular, if a conventional and old air conditioning is used as commonly occurs in many countries. In recent years there have been developed new alternatives that are used in few countries, such as the earth–air heat exchanger, where air is passed through a heat exchanger buried a few meters below the ground. The heat exchanger takes advantage of the well-known difference between the temperature of the surrounding air and the temperature of the ground for cooling or heating the air that is subsequently injected into the buildings. This process requires less energy, then in the present work is thought that a PID (Proportional, Integral and Derivative) controller can be applied to an earth–air heat exchanger to reduce even more the energy consumption. Therefore, a simulation of a thermodynamic model of an earth–air heat exchanger was done and used along with a PID controller, to estimate savings in energy consumption. The results show that the energy consumption can be reduced up to 87% with the PID control, hence the efficiency of the process is increased as well as the sustainability of the planet and thus the

Micrometeorological measurement of hexachlorobenzene and polychlorinated biphenyl compound air-water gas exchange in Lake Superior and comparison to model predictions

Directory of Open Access Journals (Sweden)

M. D. Rowe

2012-05-01

Full Text Available Air-water exchange fluxes of persistent, bioaccumulative and toxic (PBT substances are frequently estimated using the Whitman two-film (W2F method, but micrometeorological flux measurements of these compounds over water are rarely attempted. We measured air-water exchange fluxes of hexachlorobenzene (HCB and polychlorinated biphenyls (PCBs on 14 July 2006 in Lake Superior using the modified Bowen ratio (MBR method. Measured fluxes were compared to estimates using the W2F method, and to estimates from an Internal Boundary Layer Transport and Exchange (IBLTE model that implements the NOAA COARE bulk flux algorithm and gas transfer model. We reveal an inaccuracy in the estimate of water vapor transfer velocity that is commonly used with the W2F method for PBT flux estimation, and demonstrate the effect of use of an improved estimation method. Flux measurements were conducted at three stations with increasing fetch in offshore flow (15, 30, and 60 km in southeastern Lake Superior. This sampling strategy enabled comparison of measured and predicted flux, as well as modification in near-surface atmospheric concentration with fetch, using the IBLTE model. Fluxes estimated using the W2F model were compared to fluxes measured by MBR. In five of seven cases in which the MBR flux was significantly greater than zero, concentration increased with fetch at 1-m height, which is qualitatively consistent with the measured volatilization flux. As far as we are aware, these are the first reported ship-based micrometeorological air-water exchange flux measurements of PCBs.

The boundary condition for vertical velocity and its interdependence with surface gas exchange

Science.gov (United States)

Kowalski, Andrew S.

2017-07-01

The law of conservation of linear momentum is applied to surface gas exchanges, employing scale analysis to diagnose the vertical velocity (w) in the boundary layer. Net upward momentum in the surface layer is forced by evaporation (E) and defines non-zero vertical motion, with a magnitude defined by the ratio of E to the air density, as w = E/ρ. This is true even right down at the surface where the boundary condition is w|0 = E/ρ|0 (where w|0 and ρ|0 represent the vertical velocity and density of air at the surface). This Stefan flow velocity implies upward transport of a non-diffusive nature that is a general feature of the troposphere but is of particular importance at the surface, where it assists molecular diffusion with upward gas migration (of H2O, for example) but opposes that of downward-diffusing species like CO2 during daytime. The definition of flux-gradient relationships (eddy diffusivities) requires rectification to exclude non-diffusive transport, which does not depend on scalar gradients. At the microscopic scale, the role of non-diffusive transport in the process of evaporation from inside a narrow tube - with vapour transport into an overlying, horizontal airstream - was described long ago in classical mechanics and is routinely accounted for by chemical engineers, but has been neglected by scientists studying stomatal conductance. Correctly accounting for non-diffusive transport through stomata, which can appreciably reduce net CO2 transport and marginally boost that of water vapour, should improve characterisations of ecosystem and plant functioning.

PCM-air heat exchangers for free-cooling applications in buildings: Experimental results of two real-scale prototypes

International Nuclear Information System (INIS)

Lazaro, Ana; Dolado, Pablo; Marin, Jose M.; Zalba, Belen

2009-01-01

Latent heat storage using phase change materials (PCM) can be used for free-cooling. In this application low air temperature is used to solidify the PCM during the night and then during the next day, the inside air of a building can be cooled down by exchanging heat with PCM. Short times for charging and discharging the PCM are required. PCM have in general low thermal conductivity, therefore the heat exchanger design is very important to fulfil free-cooling requirements. This paper presents an experimental setup for testing PCM-air real-scale heat exchangers and the results for two real-scale prototypes. Results show that a heat exchanger using a PCM with lower thermal conductivity and lower total stored energy, but adequately designed, has higher cooling power and can be applied for free-cooling

Heat exchanger operation in the externally heated air valve engine with separated settling chambers

International Nuclear Information System (INIS)

Kazimierski, Zbyszko; Wojewoda, Jerzy

2014-01-01

The crucial role in the externally heated air valve engine is played by its heat exchangers which work in a closed cycle. These are: a heater and a cooler and they are subject to a numerical analysis in the paper. Both of them are equipped with fixed volumes that are separate settling chambers causing that heat exchangers behave as almost stationary recuperators and analysis of the stationary behaviour is the main goal of the paper. Power and efficiency of the engine must be not lower than their averaged values for the same engine working in unsteady conditions. The results of calculations confirm such a statement. The pressure drop in the exchanger is another natural phenomenon presented. It has been overcome by use of additional blowers and the use of them is an additional focus of the presented analysis. A separation of settling chambers and additional blowers is a novelty in the paper. There is also a pre-heater applied in the engine which does not differ from well-known heat exchangers met in energy generation devices. The main objective of the paper is to find the behaviour of the engine model under stationary conditions of the heat exchangers and compare it with the non-stationary ones. - Highlights: • Externally heated air engine combined with forced working gas flow (supercharging). • Separate settling chambers allow for achieving stable and constant heat exchange parameters. • Pressure drop in heat exchangers overcome by additional blowers. • Reciprocating piston air engine, cam governing system, standard lubrication for externally heated engine. • Different fuels: oil, coal, gas, biomass also solar or nuclear energy

Respiratory Mechanics and Gas Exchange: The Effect of Surfactants

Science.gov (United States)

Jbaily, Abdulrahman; Szeri, Andrew J.

2017-11-01

The purpose of the lung is to exchange gases, primarily oxygen and carbon dioxide, between the atmosphere and the circulatory system. To enable this exchange, the airways in the lungs terminate in some 300 million alveoli that provide adequate surface area for transport. During breathing, work must be done to stretch various tissues to accommodate a greater volume of gas. Considerable work must also be done to expand the liquid lining (hypophase) that coats the interior surfaces of the alveoli. This is enabled by a surface active lipo-protein complex, known as pulmonary surfactant, that modifies the surface tension at the hypophase-air interface. Surfactants also serve as physical barriers that modify the rate of gas transfer across interfaces. We develop a mathematical model to study the action of pulmonary surfactant and its determinative contributions to breathing. The model is used to explore the influence of surfactants on alveolar mechanics and on gas exchange: it relates the work of respiration at the level of the alveolus to the gas exchange rate through the changing influence of pulmonary surfactant over the breathing cycle. This work is motivated by a need to develop improved surfactant replacement therapies to treat serious medical conditions.

Thermal performance of a spirally coiled finned tube heat exchanger under wet-surface conditions

International Nuclear Information System (INIS)

Wongwises, Somchai; Naphon, Paisarn

2006-01-01

This paper is a continuation of the author's previous work on spiral coil heat exchangers. In the present study, the heat transfer characteristics and the performance of a spirally coiled finned tube heat exchanger under wet-surface conditions are theoretically and experimentally investigated. The test section is a spiral-coil heat exchanger which consists of a steel shell and a spirally coiled tube unit. The spiral-coil unit consists of six layers of concentric spirally coiled finned tubes. Each tube is fabricated by bending a 9.6 mm diameter straight copper tube into a spiral-coil of four turns. The innermost and outermost diameters of each spiral-coil are 145.0 and 350.4 mm, respectively. Aluminium crimped spiral fins with thickness of 0.6 mm and outer diameter of 28.4 mm are placed around the tube. The edge of fin at the inner diameter is corrugated. Air and water are used as working fluids in shell side and tube side, respectively. The experiments are done under dehumidifying conditions. A mathematical model based on the conservation of mass and energy is developed to simulate the flow and heat transfer characteristics of working fluids flowing through the heat exchanger. The results obtained from the present model show reasonable agreement with the experimental data

Numerical Analysis of Flow Distribution in a Sodium Chamber of a Finned-tube Sodium-to-Air Heat Exchanger

Energy Technology Data Exchange (ETDEWEB)

Jo, Youngchul; Son, Seokkwon; Kim, Hyungmo; Eoh, Jaehyuk; Jeong, Jiyoung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

DHR systems consist of two diverse heat removal loops such as passive and active DHR systems, and the heat load imposed on the primary sodium pool is safely rejected into the environment through different kinds of sodium-to-air heat exchangers, e.g. M-shape and helical-coil type air-coolers. The former is called as an FHX(Forced-draft sodium-to-air Heat Exchanger) and the latter is simply called as an AHX(natural-draft sodium-to-Air Heat Exchanger). In a general sodium-to-air heat exchanger design, convection resistance in a shell-side air flow path becomes dominant factor affecting the mechanism of conjugate heat transfer from the sodium flow inside the tube to the air path across the sodium tube wall. Hence verification of the flow and heat transfer characteristics is one of the most important tasks to demonstrate decay heat removal performance. To confirm a kind of ultimate heat sink heat exchanger, a medium-scale Sodium thermal-hydraulic Experiment Loop for Finned-tube sodium-to-Air Heat exchanger (here after called the SELFA) has been designed and is recently being constructed at KAERI site. The introduction of the flow baffle inside the upper sodium chamber of the model FHX unit in the SELFA facility is briefly proposed and discussed as well. The present study aims at introducing a flow baffle design inside the upper sodium chamber to make more equalized flowrates flowing into each heat transfer tube of the model FHX unit. In the cases without the flow baffle geometry, it was observed lager discrepancies in flowrates at the heat transfer tubes. However it was also found that those kinds of discrepancies could be definitely decreased at around 1/10 by employing a flow baffle.

Air-Sea Momentum and Enthalpy Exchange in Coupled Atmosphere-Wave-Ocean Modeling of Tropical Cyclones

Science.gov (United States)

Curcic, M.; Chen, S. S.

2016-02-01

The atmosphere and ocean are coupled through momentum, enthalpy, and mass fluxes. Accurate representation of these fluxes in a wide range of weather and climate conditions is one of major challenges in prediction models. Their current parameterizations are based on sparse observations in low-to-moderate winds and are not suited for high wind conditions such as tropical cyclones (TCs) and winter storms. In this study, we use the Unified Wave INterface - Coupled Model (UWIN-CM), a high resolution, fully-coupled atmosphere-wave-ocean model, to better understand the role of ocean surface waves in mediating air-sea momentum and enthalpy exchange in TCs. In particular, we focus on the explicit treatment of wave growth and dissipation for calculating atmospheric and oceanic stress, and its role in upper ocean mixing and surface cooling in the wake of the storm. Wind-wave misalignment and local wave disequilibrium result in difference between atmospheric and oceanic stress being largest on the left side of the storm. We find that explicit wave calculation in the coupled model reduces momentum transfer into the ocean by more than 10% on average, resulting in reduced cooling in TC's wake and subsequent weakening of the storm. We also investigate the impacts of sea surface temperature and upper ocean parameterization on air-sea enthalpy fluxes in the fully coupled model. High-resolution UWIN-CM simulations of TCs with various intensities and structure are conducted in this study to better understand the complex TC-ocean interaction and improve the representation of air-sea coupling processes in coupled prediction models.

Effect of Air Cleaning Technologies in Conjunction With the Use of Rotary Heat Exchangers in Residential Buildings

DEFF Research Database (Denmark)

Afshari, Alireza; Bergsøe, Niels Christian; Ekberg, Lars

2013-01-01

This study is part of a research project concerning the possibilities of applying efficient air cleaning technologies using rotary heat exchanger in residential buildings. The purpose of this project was to identify and adapt new air-cleaning technologies for implementation in HVAC systems...... with rotary air-to-air heat exchangers. For this purpose, a mechanical filter with low pressure drop and a 4 cm thick activated carbon filter were selected for testing in a laboratory environment. The measurements included testing of the filters, separately and combined, in a ductwork to study the efficiency...

Study of heat transfer and pressure drop characteristics of air heat exchanger using PCM for free cooling applications

Directory of Open Access Journals (Sweden)

Kalaiselvam Sivakumar

2016-01-01

Full Text Available Free cooling is the process of storing the cool energy available in the night ambient air and using it during the day. The heat exchanger used in this work is a modular type which is similar to the shell and tube heat exchanger. The shell side is filled with Phase Change Materials (PCM and air flow is through the tubes in the module. The modules of the heat exchanger are arranged one over other with air spacers in between each module. The air space provided in between the module in-creases the retention time of the air for better heat transfer. Transient Computational Fluid Dynamics modeling is carried out for single air passage in a modular heat exchanger. It shows that the PCM phase transition time in the module in which different shape of fins is adopted. The module with rectangular fins has 17.2 % reduction in solidification compared with the plain module. Then steady state numerical analysis is accomplished to the whole module having the fin of high heat transfer, so that pressure drop, flow and thermal characteristics across the module and the air spacers are deter-mined for various air inlet velocities of 0.4 to 1.6 m/s. To validate the computational results, experiments are carried out and the agreement was found to be good.

Oxygen exchange at gas/oxide interfaces: how the apparent activation energy of the surface exchange coefficient depends on the kinetic regime.

Science.gov (United States)

Fielitz, Peter; Borchardt, Günter

2016-08-10

In the dedicated literature the oxygen surface exchange coefficient KO and the equilibrium oxygen exchange rate [Fraktur R] are considered to be directly proportional to each other regardless of the experimental circumstances. Recent experimental observations, however, contradict the consequences of this assumption. Most surprising is the finding that the apparent activation energy of KO depends dramatically on the kinetic regime in which it has been determined, i.e. surface exchange controlled vs. mixed or diffusion controlled. This work demonstrates how the diffusion boundary condition at the gas/solid interface inevitably entails a correlation between the oxygen surface exchange coefficient KO and the oxygen self-diffusion coefficient DO in the bulk ("on top" of the correlation between KO and [Fraktur R] for the pure surface exchange regime). The model can thus quantitatively explain the range of apparent activation energies measured in the different regimes: in the surface exchange regime the apparent activation energy only contains the contribution of the equilibrium exchange rate, whereas in the mixed or in the diffusion controlled regime the contribution of the oxygen self-diffusivity has also to be taken into account, which may yield significantly higher apparent activation energies and simultaneously quantifies the correlation KO ∝ DO(1/2) observed for a large number of oxides in the mixed or diffusion controlled regime, respectively.

[Summer Greenhouse Gases Exchange Flux Across Water-air Interface in Three Water Reservoirs Located in Different Geologic Setting in Guangxi, China].

Science.gov (United States)

Li, Jian-hong; Pu, Jun-bing; Sun, Ping-an; Yuan, Dao-xian; Liu, Wen; Zhang, Tao; Mo, Xue

2015-11-01

Due to special hydrogeochemical characteristics of calcium-rich, alkaline and DIC-rich ( dissolved inorganic carbon) environment controlled by the weathering products from carbonate rock, the exchange characteristics, processes and controlling factors of greenhouse gas (CO2 and CH4) across water-air interface in karst water reservoir show obvious differences from those of non-karst water reservoir. Three water reservoirs (Dalongdong reservoir-karst reservoir, Wulixia reservoir--semi karst reservoir, Si'anjiang reservoir-non-karst reservoir) located in different geologic setting in Guangxi Zhuang Autonomous Region, China were chosen to reveal characteristics and controlling factors of greenhouse gas exchange flux across water-air interface. Two common approaches, floating chamber (FC) and thin boundary layer models (TBL), were employed to research and contrast greenhouse gas exchange flux across water-air interface from three reservoirs. The results showed that: (1) surface-layer water in reservoir area and discharging water under dam in Dalongdong water reservoir were the source of atmospheric CO2 and CH4. Surface-layer water in reservoir area in Wulixia water reservoir was the sink of atmospheric CO2 and the source of atmospheric CH4, while discharging water under dam was the source of atmospheric CO2 and CH4. Surface-layer water in Si'anjiang water reservoir was the sink of atmospheric CO2 and source of atmospheric CH4. (2) CO2 and CH4 effluxes in discharging water under dam were much more than those in surface-layer water in reservoir area regardless of karst reservoir or non karst reservoir. Accordingly, more attention should be paid to the CO2 and CH4 emission from discharging water under dam. (3) In the absence of submerged soil organic matters and plants, the difference of CH4 effluxes between karst groundwater-fed reservoir ( Dalongdong water reservoir) and non-karst area ( Wulixia water reservoir and Si'anjiang water reservoir) was less. However, CO2

Surface Flux Modeling for Air Quality Applications

Directory of Open Access Journals (Sweden)

Limei Ran

2011-08-01

Full Text Available For many gasses and aerosols, dry deposition is an important sink of atmospheric mass. Dry deposition fluxes are also important sources of pollutants to terrestrial and aquatic ecosystems. The surface fluxes of some gases, such as ammonia, mercury, and certain volatile organic compounds, can be upward into the air as well as downward to the surface and therefore should be modeled as bi-directional fluxes. Model parameterizations of dry deposition in air quality models have been represented by simple electrical resistance analogs for almost 30 years. Uncertainties in surface flux modeling in global to mesoscale models are being slowly reduced as more field measurements provide constraints on parameterizations. However, at the same time, more chemical species are being added to surface flux models as air quality models are expanded to include more complex chemistry and are being applied to a wider array of environmental issues. Since surface flux measurements of many of these chemicals are still lacking, resistances are usually parameterized using simple scaling by water or lipid solubility and reactivity. Advances in recent years have included bi-directional flux algorithms that require a shift from pre-computation of deposition velocities to fully integrated surface flux calculations within air quality models. Improved modeling of the stomatal component of chemical surface fluxes has resulted from improved evapotranspiration modeling in land surface models and closer integration between meteorology and air quality models. Satellite-derived land use characterization and vegetation products and indices are improving model representation of spatial and temporal variations in surface flux processes. This review describes the current state of chemical dry deposition modeling, recent progress in bi-directional flux modeling, synergistic model development research with field measurements, and coupling with meteorological land surface models.

The importance of determining the air exchange rate in flats and buildings for calculations of the averted indoor inhalation doses arising from contaminated outdoor air

International Nuclear Information System (INIS)

Jilek, Karel; Thomas, J.; Bulanek, B.; Lenk, J.; Marikova, S.

2015-01-01

The indoor-outdoor air exchange rate is an important parameter when refining estimates of the averted inhaled doses to population in houses and buildings after an emergency event resulting in contamination of outdoor air with a radioactive material. The air exchange rates measured in 70 occupied houses and in 20 unoccupied houses using N 2 O as the tracer gas are presented, and the results of modelling the averted doses in the residential buildings for both gaseous and aerosol outdoor contaminants are demonstrated. (orig.)

Estimation of bias with the single-zone assumption in measurement of residential air exchange using the perfluorocarbon tracer gas method.

Science.gov (United States)

Van Ryswyk, K; Wallace, L; Fugler, D; MacNeill, M; Héroux, M È; Gibson, M D; Guernsey, J R; Kindzierski, W; Wheeler, A J

2015-12-01

Residential air exchange rates (AERs) are vital in understanding the temporal and spatial drivers of indoor air quality (IAQ). Several methods to quantify AERs have been used in IAQ research, often with the assumption that the home is a single, well-mixed air zone. Since 2005, Health Canada has conducted IAQ studies across Canada in which AERs were measured using the perfluorocarbon tracer (PFT) gas method. Emitters and detectors of a single PFT gas were placed on the main floor to estimate a single-zone AER (AER(1z)). In three of these studies, a second set of emitters and detectors were deployed in the basement or second floor in approximately 10% of homes for a two-zone AER estimate (AER(2z)). In total, 287 daily pairs of AER(2z) and AER(1z) estimates were made from 35 homes across three cities. In 87% of the cases, AER(2z) was higher than AER(1z). Overall, the AER(1z) estimates underestimated AER(2z) by approximately 16% (IQR: 5-32%). This underestimate occurred in all cities and seasons and varied in magnitude seasonally, between homes, and daily, indicating that when measuring residential air exchange using a single PFT gas, the assumption of a single well-mixed air zone very likely results in an under prediction of the AER. The results of this study suggest that the long-standing assumption that a home represents a single well-mixed air zone may result in a substantial negative bias in air exchange estimates. Indoor air quality professionals should take this finding into consideration when developing study designs or making decisions related to the recommendation and installation of residential ventilation systems. © 2014 Her Majesty the Queen in Right of Canada. Indoor Air published by John Wiley & Sons Ltd Reproduced with the permission of the Minister of Health Canada.

The influence of surface treatment on mass transfer between air and building material

DEFF Research Database (Denmark)

Kwiatkowski, Jerzy; Rode, Carsten; Hansen, Kurt Kielsgaard

2008-01-01

for the experiments: gypsum board and calcium silicate. The wallpaper and paint were used as finishing materials. Impact of the following parameters for changes of RH was studied: coating, temperature and air movement. The measurements showed that acryl paint (diffusion open) can significantly decrease mass uptake......The processes of mass transfer between air and building structure and in the material influence not only the conditions within the material but also inside the connected air spaces. The material which absorbs and desorbs water vapour can be used to moderate the amplitude of indoor relative humidity...... and therefore to participate in the improvement of the indoor air quality and energy saving. Many parameters influence water vapour exchange between indoor air and building material. The aim of this work is to present the change of mass transfer under different climatic and material conditions. The measurements...

The boundary condition for vertical velocity and its interdependence with surface gas exchange

Directory of Open Access Journals (Sweden)

A. S. Kowalski

2017-07-01

Full Text Available The law of conservation of linear momentum is applied to surface gas exchanges, employing scale analysis to diagnose the vertical velocity (w in the boundary layer. Net upward momentum in the surface layer is forced by evaporation (E and defines non-zero vertical motion, with a magnitude defined by the ratio of E to the air density, as w = E/ρ. This is true even right down at the surface where the boundary condition is w|0 = E/ρ|0 (where w|0 and ρ|0 represent the vertical velocity and density of air at the surface. This Stefan flow velocity implies upward transport of a non-diffusive nature that is a general feature of the troposphere but is of particular importance at the surface, where it assists molecular diffusion with upward gas migration (of H2O, for example but opposes that of downward-diffusing species like CO2 during daytime. The definition of flux–gradient relationships (eddy diffusivities requires rectification to exclude non-diffusive transport, which does not depend on scalar gradients. At the microscopic scale, the role of non-diffusive transport in the process of evaporation from inside a narrow tube – with vapour transport into an overlying, horizontal airstream – was described long ago in classical mechanics and is routinely accounted for by chemical engineers, but has been neglected by scientists studying stomatal conductance. Correctly accounting for non-diffusive transport through stomata, which can appreciably reduce net CO2 transport and marginally boost that of water vapour, should improve characterisations of ecosystem and plant functioning.

Effect of geometric factors on performance of a sodium to air heat exchanger in a fast breeder reactor

International Nuclear Information System (INIS)

Kannan, K.; Vinod, V.; Padmakumar, G.; Rudramoorthy, R.; Rajan, K.K.

2015-01-01

Highlights: • A heat exchanger analysis (HE) before scale up reduces excess heat transfer area. • Representative Elementary Volume analysis of a HE speeds up the solution. • The error in air temperature rise prediction by numerical across HE is within 5%. • When both pitches are reduced, the maximum increase in heat flux is experienced. • The experience has resulted in better design of next level heat exchangers. - Abstract: Prototype fast breeder reactor (PFBR) has a safety grade decay heat removal system whose performance depends on the effective functioning of natural convection heat exchangers called sodium to air heat exchangers. The development of Representative Elementary Volume (REV) model for the sodium to air heat exchanger is necessary to envisage its design and to study the effect of various factors for continuous improvement in design. With a Representative Elementary Volume, the hydrodynamic and heat transfer characteristics of the heat exchanger was studied and the results agree well with experimental data. The effect of longitudinal pitch and transverse pitch on the heat exchanger performance has been studied and an improvement of 22% in heat transfer is predicted

Enthalpy analysis and Heat Exchanger Sizing of an Air-cooled Proton Exchange Membrane Fuel Cell System

DEFF Research Database (Denmark)

Gao, Xin; Berning, Torsten; Kær, Søren Knudsen

below -20 °C in the winter which make liquid-cooled fuel cells impossible. In such cases, air-cooled fuel cell systems are deployed where the air that is fed to the fuel cell serves both as reactant supplier and coolant to remove the waste heat that is generated during fuel cell operation. In some cases...... in order to optimize the operating conditions and the performance of such a system. The adjustable parameters include the fan speed that determines the amount of air that is brought into the system, and the size and rotating speed of the rotating enthalpy wheel. In addition, computational fluid dynamics...... or an ordinary heat exchanger can fulfill the heat recovery demand. Despite the fact that the air enters the stack at a cold temperature, even the forefront of the stack is at a much elevated and desired stack temperature with the help of supplying an acceptable amount of power to an electric stack heater. So...

A new model for predicting performance of fin-and-tube heat exchanger under frost condition

International Nuclear Information System (INIS)

Cui, J.; Li, W.Z.; Liu, Y.; Zhao, Y.S.

2011-01-01

Accurate prediction of frost characteristics has crucial influence on designing effective heat exchangers. In this paper, a new CFD (Computational Fluid Dynamics) model has been proposed to predict the frost behaviour. The initial period of frost formation can be predicted and the influence of surface structure can be considered. The numerical simulations have been carried out to investigate the performance of fin-and-tube heat exchanger under frost condition. The results have been validated by comparison of simulations with the data computed by empirical formulas. The transient local frost formation has been obtained. The average frost thickness, heat exchanger coefficient and pressure drop on air side has been analysed as well. In addition, the influence factors have also been discussed, such as fin pitch, relative humidity, air flow rate and evaporating temperature of refrigerant.

Assessing Near-surface Heat, Water Vapor and Carbon Dioxide Exchange Over a Coastal Salt-marsh

Science.gov (United States)

Bogoev, I.; O'Halloran, T. L.; LeMoine, J.

2017-12-01

Coastal ecosystems play an important role in mitigating the effects of climate change by storing significant quantities of carbon. A growing number of studies suggest that vegetated estuarine habitats, specifically salt marshes, have high long-term rates of carbon sequestration, perhaps even higher than mature tropical and temperate forests. Large amounts of carbon, accumulated over thousands of years, are stored in the plant materials and sediment. Improved understanding of the factors that control energy and carbon exchange is needed to better guide restoration and conservation management practices. To that end, we recently established an observation system to study marsh-atmosphere interactions within the North Inlet-Winyah Bay National Estuarine Research Reserve. Near-surface fluxes of heat, water vapor (H2O) and carbon dioxide (CO2) were measured by an eddy-covariance system consisting of an aerodynamic open-path H2O / CO2 gas analyzer with a spatially integrated 3D sonic anemometer/thermometer (IRGASON). The IRGASON instrument provides co-located and highly synchronized, fast response H2O, CO2 and air- temperature measurements, which eliminates the need for spectral corrections associated with the separation between the sonic anemometer and the gas analyzer. This facilitates calculating the instantaneous CO2 molar mixing ratio relative to dry air. Fluxes computed from CO2 and H2O mixing ratios, which are conserved quantities, do not require post-processing corrections for air-density changes associated with temperature and water vapor fluctuations. These corrections are particularly important for CO2, because they could be even larger than the measured flux. Here we present the normalized frequency spectra of air temperature, water vapor and CO2, as well as their co-spectra with the co-located vertical wind. We also show mean daily cycles of sensible, latent and CO2 fluxes and analyze correlations with air/water temperature, wind speed and light availability.

Biphilic Surfaces for Enhanced Water Collection from Humid Air

Science.gov (United States)

Benkoski, Jason; Gerasopoulos, Konstantinos; Luedeman, William

Surface wettability plays an important role in water recovery, distillation, dehumidification, and heat transfer. The efficiency of each process depends on the rate of droplet nucleation, droplet growth, and mass transfer. Unfortunately, hydrophilic surfaces are good at nucleation but poor at shedding. Hydrophobic surfaces are the reverse. Many plants and animals overcome this tradeoff through biphilic surfaces with patterned wettability. For example, the Stenocara beetle uses hydrophilic patches on a superhydrophobic background to collect fog from air. Cribellate spiders similarly collect fog on their webs through periodic spindle-knot structures. In this study, we investigate the effects of wettability patterns on the rate of water collection from humid air. The steady state rate of water collection per unit area is measured as a function of undercooling, angle of inclination, water contact angle, hydrophilic patch size, patch spacing, area fraction, and patch height relative to the hydrophobic background. We then model each pattern by comparing the potential and kinetic energy of a droplet as it rolls downwards at a fixed angle. The results indicate that the design rules for collecting fog differ from those for condensation from humid air. The authors gratefully acknowledge the Office of Naval Research for financial support through Grant Number N00014-15-1-2107.

Numerical investigation on various heat exchanger performances to determine an optimum configuration for charge air cooler, oil and water radiators in F1 sidepods

International Nuclear Information System (INIS)

Salmon, Pierre; Könözsy, László; Temple, Clive; Grove, Stuart

2017-01-01

Highlights: • Three-dimensional CFD transitional flow simulations in formula one car sidepods. • Determination of an optimum heat exchanger configuration placed in the sidepods. • Prediction of heat transfer and pressure drop to mass flow rate correlation curves. • Performance of heat exchanger configurations for non-isothermal transitional flows. • Overcome the difficulties of macroscopic heat exchanger and porous media methods. - Abstract: The present work focuses on a three-dimensional CFD approach to predict the performance of various heat exchangers in conjunction with non-isothermal transitional flows for motorsport applications. The objective of this study is to determine the heat transfer, pressure drop and inhomogeneous flow behaviour for distinct heat exchangers to identify an optimum configuration for the charge air cooler, water and oil radiators placed in the sidepods of a formula one (F1) car. Therefore, a comprehensive analysis of various heat exchanger configurations has been carried out in this work. In order to assess the reliability of the obtained results, a mesh sensitivity study along with additional parametric investigations have been performed to provide numerical parameters predicting accurately (a) the heat transfer rate at the fluid-solid interface and (b) the sporadic separation. As a result of the performed validation procedure in this study, the aerodynamic- and thermal boundary layer development along with the convective characteristics of the air flow have been captured accurately near to the heated surface. The characterization of a heat exchanger core and a core configuration in a closed domain is also possible with this procedure. The presented three-dimensional CFD approach could overcome the difficulties of macroscopic heat exchanger and porous media methods for F1 applications, because it can be used to predict the heat transfer and pressure drop related to the mass flow rate correlation curves. The contribution of

A top-down approach of surface carbonyl sulfide exchange by a Mediterranean oak forest ecosystem in southern France

Science.gov (United States)

Belviso, Sauveur; Reiter, Ilja Marco; Loubet, Benjamin; Gros, Valérie; Lathière, Juliette; Montagne, David; Delmotte, Marc; Ramonet, Michel; Kalogridis, Cerise; Lebegue, Benjamin; Bonnaire, Nicolas; Kazan, Victor; Gauquelin, Thierry; Fernandez, Catherine; Genty, Bernard

2016-12-01

The role that soil, foliage, and atmospheric dynamics have on surface carbonyl sulfide (OCS) exchange in a Mediterranean forest ecosystem in southern France (the Oak Observatory at the Observatoire de Haute Provence, O3HP) was investigated in June of 2012 and 2013 with essentially a top-down approach. Atmospheric data suggest that the site is appropriate for estimating gross primary production (GPP) directly from eddy covariance measurements of OCS fluxes, but it is less adequate for scaling net ecosystem exchange (NEE) to GPP from observations of vertical gradients of OCS relative to CO2 during the daytime. Firstly, OCS and carbon dioxide (CO2) diurnal variations and vertical gradients show no net exchange of OCS at night when the carbon fluxes are dominated by ecosystem respiration. This contrasts with other oak woodland ecosystems of a Mediterranean climate, where nocturnal uptake of OCS by soil and/or vegetation has been observed. Since temperature, water, and organic carbon content of soil at the O3HP should favor the uptake of OCS, the lack of nocturnal net uptake would indicate that its gross consumption in soil is compensated for by emission processes that remain to be characterized. Secondly, the uptake of OCS during the photosynthetic period was characterized in two different ways. We measured ozone (O3) deposition velocities and estimated the partitioning of O3 deposition between stomatal and non-stomatal pathways before the start of a joint survey of OCS and O3 surface concentrations. We observed an increasing trend in the relative importance of the stomatal pathway during the morning hours and synchronous steep drops of mixing ratios of OCS (amplitude in the range of 60-100 ppt) and O3 (amplitude in the range of 15-30 ppb) after sunrise and before the break up of the nocturnal boundary layer. The uptake of OCS by plants was also characterized from vertical profiles. However, the time window for calculation of the ecosystem relative uptake (ERU) of OCS

Probabilistic estimation of residential air exchange rates for ...

Science.gov (United States)

Residential air exchange rates (AERs) are a key determinant in the infiltration of ambient air pollution indoors. Population-based human exposure models using probabilistic approaches to estimate personal exposure to air pollutants have relied on input distributions from AER measurements. An algorithm for probabilistically estimating AER was developed based on the Lawrence Berkley National Laboratory Infiltration model utilizing housing characteristics and meteorological data with adjustment for window opening behavior. The algorithm was evaluated by comparing modeled and measured AERs in four US cities (Los Angeles, CA; Detroit, MI; Elizabeth, NJ; and Houston, TX) inputting study-specific data. The impact on the modeled AER of using publically available housing data representative of the region for each city was also assessed. Finally, modeled AER based on region-specific inputs was compared with those estimated using literature-based distributions. While modeled AERs were similar in magnitude to the measured AER they were consistently lower for all cities except Houston. AERs estimated using region-specific inputs were lower than those using study-specific inputs due to differences in window opening probabilities. The algorithm produced more spatially and temporally variable AERs compared with literature-based distributions reflecting within- and between-city differences, helping reduce error in estimates of air pollutant exposure. Published in the Journal of

[Characteristics of mercury exchange flux between soil and atmosphere under the snow retention and snow melting control].

Science.gov (United States)

Zhang, Gang; Wang, Ning; Ai, Jian-Chao; Zhang, Lei; Yang, Jing; Liu, Zi-Qi

2013-02-01

Jiapigou gold mine, located in the upper Songhua River, was once the largest mine in China due to gold output, where gold extraction with algamation was widely applied to extract gold resulting in severe mercury pollution to ambient environmental medium. In order to study the characteristics of mercury exchange flux between soil (snow) and atmosphere under the snow retention and snow melting control, sampling sites were selected in equal distances along the slope which is situated in the typical hill-valley terrain unit. Mercury exchange flux between soil (snow) and atmosphere was determined with the method of dynamic flux chamber and in all sampling sites the atmosphere concentration from 0 to 150 cm near to the earth in the vertical direction was measured. Furthermore, the impact factors including synchronous meteorology, the surface characteristics under the snow retention and snow melting control and the mercury concentration in vertical direction were also investigated. The results are as follows: During the period of snow retention and melting the air mercury tends to gather towards valley bottom along the slope and an obvious deposit tendency process was found from air to the earth's surface under the control of thermal inversion due to the underlying surface of cold source (snow surface). However, during the period of snow melting, mercury exchange flux between the soil and atmosphere on the surface of the earth with the snow being melted demonstrates alternative deposit and release processes. As for the earth with snow covered, the deposit level of mercury exchange flux between soil and atmosphere is lower than that during the period of snow retention. The relationship between mercury exchange flux and impact factors shows that in snow retention there is a remarkable negative linear correlation between mercury exchange flux and air mercury concentration as well as between the former and the air temperature. In addition, in snow melting mercury exchange

The marketing-finance interface: A relational exchange perspective

NARCIS (Netherlands)

Ruyter, de J.C.; Wetzels, M.G.M.

2000-01-01

In marketing theory and practice the concept of relational exchanges has gained wide popularity particularly with regards to external exchange parties, such as consumers and marketing channel intermediaries. However, the concept of relational exchange could also be applied to marketing interfaces

Air-sea exchange over Black Sea estimated from high resolution regional climate simulations

Science.gov (United States)

Velea, Liliana; Bojariu, Roxana; Cica, Roxana

2013-04-01

Black Sea is an important influencing factor for the climate of bordering countries, showing cyclogenetic activity (Trigo et al, 1999) and influencing Mediterranean cyclones passing over. As for other seas, standard observations of the atmosphere are limited in time and space and available observation-based estimations of air-sea exchange terms present quite large ranges of uncertainty. The reanalysis datasets (e.g. ERA produced by ECMWF) provide promising validation estimates of climatic characteristics against the ones in available climatic data (Schrum et al, 2001), while cannot reproduce some local features due to relatively coarse horizontal resolution. Detailed and realistic information on smaller-scale processes are foreseen to be provided by regional climate models, due to continuous improvements of physical parameterizations and numerical solutions and thus affording simulations at high spatial resolution. The aim of the study is to assess the potential of three regional climate models in reproducing known climatological characteristics of air-sea exchange over Black Sea, as well as to explore the added value of the model compared to the input (reanalysis) data. We employ results of long-term (1961-2000) simulations performed within ENSEMBLE project (http://ensemblesrt3.dmi.dk/) using models ETHZ-CLM, CNRM-ALADIN, METO-HadCM, for which the integration domain covers the whole area of interest. The analysis is performed for the entire basin for several variables entering the heat and water budget terms and available as direct output from the models, at seasonal and annual scale. A comparison with independent data (ERA-INTERIM) and findings from other studies (e.g. Schrum et al, 2001) is also presented. References: Schrum, C., Staneva, J., Stanev, E. and Ozsoy, E., 2001: Air-sea exchange in the Black Sea estimated from atmospheric analysis for the period 1979-1993, J. Marine Systems, 31, 3-19 Trigo, I. F., T. D. Davies, and G. R. Bigg (1999): Objective

Design Evaluation of Thermal-hydraulic Test Facility for a Finned-tube Sodium-to-Air Heat Exchanger

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyungmo; Kim, Byeong-Yeon; Ko, Yung Joo; Cho, Youngil; Kim, Jong-Man; Son, Seok-Kwon; Jo, Youngchul; Kang, Byeong Su; Jung, Minhwan; Eoh, Jaehyuk; Lee, Hyeong-Yeon; Jeong, Ji-Young [KAERI, Daejeon (Korea, Republic of)

2016-05-15

This paper introduces the recent progress of overall design phase for the SELFA facility and deals with basic thermal-hydraulic design parameters and its design validation as well. For more reliable design of the safety-grade decay heat removal system (DHRS) in PGSFR (Prototype Gen-IV Sodium-cooled Fast Reactor), two kinds of sodium-to-air heat exchangers have been employed in the system as an ultimate heat sink. One is a natural draft sodium-to-air heat exchanger (AHX) with helically-coiled sodium tubes, and the other is a forced draft sodium-to-air heat exchanger (FHX) with finned tubes with a straight-type arranged. Since the FHX is normally operated in an active mode with a forced air draft conditions, its performance should be verified for any anticipated operating conditions. To validate the test section design, evaluations of both thermal-hydraulic and mechanical design have been carried out, and some new concepts or devices were newly employed to replicate the prototypic conditions as closely as possible.

Indoor Levels of Formaldehyde and Other Pollutants and Relationship to Air Exchange Rates and Human Activities

Science.gov (United States)

Huangfu, Y.; O'Keeffe, P.; Kirk, M.; Walden, V. P.; Lamb, B. K.; Jobson, B. T.

2017-12-01

This paper reports results on an indoor air quality study conducted on six homes in summer and winter, contrasting indoor and outdoor concentrations of O3, CO, CO2, NOx, PM2.5, and selected volatile organic hydrocarbons measured by PTR-MS. Data were collected as 1 minute averages. Air exchange rates of the homes were determined by CO2 tracer release. Smart home sensors, recording human activity level in various places in the home, and window and doors openings, were utilized to better understand the link between human activity and indoor air pollution. From our study, averaged air exchange rates of the homes ranged from 0.2 to 1.2 hour-1 and were greatly affected by the ventilation system type and window and door openings. In general, a negative correlation between air exchange rate and indoor VOCs levels was observed, with large variation of pollutant levels between the homes. For most of the VOCs measured in the house, including formaldehyde and acetaldehyde, summer levels were much higher than winter levels. In some homes formaldehyde levels displayed a time of day variation that was linked to changes in indoor temperature. During a wildfire period in the summer of 2015, outdoor levels of PM2.5, formaldehyde, and benzene dramatically increased, significantly impacting indoor levels due to infiltration. Human activities, such as cooking, can significantly change the levels of most of the compounds measured in the house and the levels can be significantly elevated for short periods of time, with peak levels can be several orders higher compared with typical levels. The data suggest that an outcome of state energy codes that require new homes to be energy efficient, and as a consequence built with lower air exchange rates, will be unacceptable levels of air toxics, notably formaldehyde.

Atmospheric concentrations and air-soil gas exchange of polycyclic aromatic hydrocarbons (PAHs) in remote, rural village and urban areas of Beijing-Tianjin region, North China.

Science.gov (United States)

Wang, Wentao; Simonich, Staci; Giri, Basant; Chang, Ying; Zhang, Yuguang; Jia, Yuling; Tao, Shu; Wang, Rong; Wang, Bin; Li, Wei; Cao, Jun; Lu, Xiaoxia

2011-07-01

Forty passive air samplers were deployed to study the occurrence of gas and particulate phase PAHs in remote, rural village and urban areas of Beijing-Tianjin region, North China for four seasons (spring, summer, fall and winter) from 2007 to 2008. The influence of emissions on the spatial distribution pattern of air PAH concentrations was addressed. In addition, the air-soil gas exchange of PAHs was studied using fugacity calculations. The median gaseous and particulate phase PAH concentrations were 222 ng/m³ and 114 ng/m³, respectively, with a median total PAH concentration of 349 ng/m³. Higher PAH concentrations were measured in winter than in other seasons. Air PAH concentrations measured at the rural villages and urban sites in the northern mountain region were significantly lower than those measured at sites in the southern plain during all seasons. However, there was no significant difference in PAH concentrations between the rural villages and urban sites in the northern and southern areas. This urban-rural PAH distribution pattern was related to the location of PAH emission sources and the population distribution. The location of PAH emission sources explained 56%-77% of the spatial variation in ambient air PAH concentrations. The annual median air-soil gas exchange flux of PAHs was 42.2 ng/m²/day from soil to air. Among the 15 PAHs measured, acenaphthylene (ACY) and acenaphthene (ACE) contributed to more than half of the total exchange flux. Furthermore, the air-soil gas exchange fluxes of PAHs at the urban sites were higher than those at the remote and rural sites. In summer, more gaseous PAHs volatilized from soil to air because of higher temperatures and increased rainfall. However, in winter, more gaseous PAHs deposited from air to soil due to higher PAH emissions and lower temperatures. The soil TOC concentration had no significant influence on the air-soil gas exchange of PAHs. Copyright © 2011 Elsevier B.V. All rights reserved.

Air-side performance of a parallel-flow parallel-fin (PF{sup 2}) heat exchanger in sequential frosting

Energy Technology Data Exchange (ETDEWEB)

Zhang, Ping [Zhejiang Vocational College of Commerce, Hangzhou, Binwen Road 470 (China); Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, IL 61801 (United States); Hrnjak, P.S. [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, IL 61801 (United States)

2010-09-15

The thermal-hydraulic performance in periodic frosting conditions is experimentally studied for the parallel-flow parallel-fin heat exchanger, henceforth referred to as a PF{sup 2} heat exchanger, a new style of heat exchanger that uses louvered bent fins on flat tubes to enhance water drainage when the flat tubes are horizontal. Typically, it takes a few frosting/defrosting cycles to come to repeatable conditions. The criterion for the initiation of defrost and a sufficiently long defrost period are determined for the test PF{sup 2} heat exchanger and test condition. The effects of blower operation on the pressure drop, frost accumulation, water retention, and capacity in time are compared under the conditions of 15 sequential frosting cycles. Pressure drop across the heat exchanger and overall heat transfer coefficient are quantified under frost conditions as functions of the air humidity and air face velocity. The performances of two types of flat-tube heat exchangers, PF{sup 2} heat exchanger and conventional parallel-flow serpentine-fin (PFSF) heat exchanger, are compared and the results obtained are presented. (author)

Plutonium isotopes in the surface air in Japan

International Nuclear Information System (INIS)

Hirose, K.; Sugimura, Y.

1990-01-01

Plutonium isotope concentrations in the surface air at Tsukuba, Japan are reported during the period from 1981 to the end of 1986. The 239,240 Pu concentration in the surface air, which showed a marked seasonal variation with a spring maximum and fall minimum, decreased until the end of 1985 according to the stratospheric residence time of 1.15 years. In May 1986, elevated 239,240 Pu concentrations with high 238 Pu/ 239,240 Pu activity ratios were observed. The serial trend of plutonium concentration in the surface air is similar to the concentrations of the Chernobyl-released radionuclides. These findings suggest that a significant part of the plutonium in the surface air in May 1986 was due to the Chernobyl fallout. (author) 15 refs.; 2 figs.; 3 tabs

Thermal-hydraulic performance of the finned surface of a compact heat exchanger

International Nuclear Information System (INIS)

Errasti Cabrera, Michel

2015-01-01

In this work the thermal-hydraulic behavior of the finned surface of a compact heat exchanger is obtained in tube-fin configuration corrugated (wavy). Through numerical simulation are determined average values ​​of intensification of heat transfer and pressure loss in the inter-channel finned. The objective is to characterize the surface to use as a reference, to make comparisons with other heat exchange surfaces enhanced using traditional techniques combined with more current, such as vortex generators. The study is conducted in laminar flow, with Reynolds numbers below 1000. In the working model compact exchanger tubes and corrugated fins (wavy) heat is described, and the results of the coefficient of overall heat transfer and the pressure drop are explained from the local characteristics of the velocity field and temperature inside the heat exchanger. (Full text)

Histological examination of spruce needles from a long-term gas exchange experiment in pure and polluted air in the field

International Nuclear Information System (INIS)

Maier-Maercker, U.; Koch, W.

1992-01-01

At the end of a 4-year period of gas exchange measurements in a natural stand in the Lower Bavarian Forest, needles of an adult spruce [Picea abies (L.) Karst.] were harvested from two chambers, one with pure air and the other with ambient air. The needles were examined as to their histological properties in the stomatal apparatus and in the bundle sheath. In needles from the polluted air UV absorbance at 280 nm was decreased in the walls of the stomatal apparatus. Simultaneously, the deposition of compounds with an absorption maximum at 310 nm increased within the encrusted plate-like thickenings of the subsidiary cells. The contents of the lumina of hypodermal cells and of the bundle sheath exhibited a greater degree of autofluorescence in ambient-air material than in pure-air leaf organs. Differences between needles exposed to pure and polluted air are gradual. The “damaged” condition is rare in pure air, common in polluted air. The needles from outside the chambers occupied an intermediate position between pure-air and ambient-air needles. This fact is traced to an unnaturally high pollutant load in the liquid phase of the needle surfaces within the ambient-air chamber because in order to compensate pollutant losses within the system, SO 2 and O 3 were added even during periods of irrigation. The reduction of absorption capacity at 280 nm in the walls of the stomatal apparatus is attributed to destruction of lignin due to the high reactivity of the pollutants in the liquid phase on the damp needle surface. The importance of delignification with regard to hydroregulation is discussed

Air-water Gas Exchange Rates on a Large Impounded River Measured Using Floating Domes (Poster)

Science.gov (United States)

Mass balance models of dissolved gases in rivers typically serve as the basis for whole-system estimates of greenhouse gas emission rates. An important component of these models is the exchange of dissolved gases between air and water. Controls on gas exchange rates (K) have be...

Corrosion protected reversing heat exchanger

International Nuclear Information System (INIS)

Zawierucha, R.

1984-01-01

A reversing heat exchanger of the plate and fin type having multiple aluminum parting sheets in a stacked arrangement with corrugated fins separating the sheets to form multiple flow paths, means for closing the ends of the sheets, an input manifold arrangement of headers for the warm end of of the exchanger and an output manifold arrangement for the cold end of the exchanger with the input air feed stream header and the waste gas exhaust header having an alloy of zinc and aluminum coated on the inside surface for providing corrosion protection to the stack

Numerical analysis of the efficiency of earth to air heat exchange systems in cold and hot-arid climates

International Nuclear Information System (INIS)

Fazlikhani, Faezeh; Goudarzi, Hossein; Solgi, Ebrahim

2017-01-01

Highlights: • A numerical model is developed to evaluate performance of earth to air heat exchanger. • The cooling/heating potential of earth to air heat exchanger is investigated in hot-dry and cold climates. • The more performance of earth to air heat exchanger in hot-dry climates compared to cold climates. • The high efficiency of earth to air heat exchanger for pre-heating in both hot-dry and cold climates. - Abstract: In order to examine and compare the efficiency of earth to air heat exchanger (EAHE) systems in hot-arid (Yazd) and cold (Hamadan) climates in Iran a steady state model was developed to evaluate the impact of various parameters including inlet air temperatures, pipe lengths and ground temperatures on the cooling and heating potential of EAHEs in both climates. The results demonstrated the ability of the system to not only improve the average temperature and decrease the temperature fluctuation of the outlet air temperature of EAHE, but also to trigger considerable energy saving. It was found that in both climates, the system is highly utilized for pre-heating, and its usage is unfeasible in certain periods throughout the year. In winter, EAHEs have the potential of increasing the air temperature in the range of 0.2–11.2 °C and 0.1–17.2 °C for Yazd and Hamadan, respectively. However, in summer, the system decreases the air temperature for the aforementioned cities in the range of 1.3–11.4 °C and 5.7–11.1 °C, respectively. The system ascertains to be more efficient in the hot-arid climate of Yazd, where it can be used on 294 days of the year, leading to 50.1–63.6% energy saving, when compared to the cold climate of Hamadan, where it can be used on 225 days of the year resulting in a reduction of energy consumption by 24.5–47.9%.

Novel exchange mechanisms in the surface diffusion of oxides

International Nuclear Information System (INIS)

Harris, Duncan J; Lavrentiev, Mikhail Yu; Harding, John H; Allan, Neil L; Purton, John A

2004-01-01

We use temperature-accelerated dynamics to show the importance of exchange mechanisms in surface diffusion and growth of simple oxides. Such mechanisms can dominate transport processes both on terraces and steps for both homoepitaxial and heteroepitaxial growth. We suggest that the mixing inevitable when an exchange mechanism is present must be considered when attempts are made to grow sharp interfaces in oxide nanostructures. (letter to the editor)

Exchange energy of inhomogenous electron gas near a metal surface

International Nuclear Information System (INIS)

Miglio, L.; Tosi, M.P.; March, N.H.

1980-12-01

Using the first-order density matrix of an infinite-barrier model of a metal surface, the exchange energy density can be evaluated exactly as a function of distance z from the barrier. This result is compared with the local approximation -3/4e 2 (3/π)sup(1/3) rhosup(4/3)(z) where rho is the electron density in the model. The local approximation is demonstrated to be quantitatively accurate at all z. The integrated surface exchange energy is given to within 3% by the local theory. (author)

Fluidized bed heat exchanger utilizing angularly extending heat exchange tubes

Science.gov (United States)

Talmud, Fred M.; Garcia-Mallol, Juan-Antonio

1980-01-01

A fluidized bed heat exchanger in which air is passed through a bed of particulate material containing fuel disposed in a housing. A steam/water natural circulation system is provided and includes a steam drum disposed adjacent the fluidized bed and a series of tubes connected at one end to the steam drum. A portion of the tubes are connected to a water drum and in the path of the air and the gaseous products of combustion exiting from the bed. Another portion of the tubes pass through the bed and extend at an angle to the upper surface of the bed.

Fabrication of a superhydrophobic surface with fungus-cleaning properties on brazed aluminum for industrial application in heat exchangers

Science.gov (United States)

Lee, Jeong-Won; Hwang, Woonbong

2018-06-01

Extensive research has been carried out concerning the application of superhydrophobic coating in heat exchangers, but little is known about the application of this technique to brazed aluminum heat exchangers (BAHEs). In this work, we describe a new superhydrophobic coating method, which is suitable for BAHE use on an industrial scale. We first render the BAHE superhydrophobic by fabricating micro/nanostructures using solution dipping followed by fluorination. After the complete removal of the silicon residue, we verify using surface analysis that the BAHE surface is perfectly superhydrophobic. We also studied the fungus-cleaning properties of the superhydrophobic surface by growing fungus for 4 weeks in a moist environment on BAHE fins with and without superhydrophobic coating. We observed that, whereas the fungus grown on the untreated fins is extremely difficult to remove, the fungus on the fins with the superhydrophobic coating can be removed easily with only a modest amount of water. We also found that the coated BAHE fins exhibit excellent resistance to moisture. The superhydrophobic coating method that we propose is therefore expected to have a major impact in the heating, ventilating and air conditioning industry market.

Modeling the airside dynamic behavior of a heat exchanger under frosting conditions

International Nuclear Information System (INIS)

Gao, Tieyu; Gong, Jianying

2011-01-01

A general distributed model with a non-steady-state heat exchanger model coupled with a frost model was developed to study the dynamic behavior of an airside heat exchanger in an air-to-water heat pump heater/chiller unit. The effects of water vapor diffusion and uneven fin temperature distribution were considered. The model was found to agree well with reported experimental results. Compared with the routine model, the present model has higher precision of frost layer thickness especially on the fin surface. Results include the propagation of frost formation along the tube and its effect on the dynamic characteristics of refrigerant, air, and tube sides. According to the results, the temperature difference between air and tube surface temperature was proposed to be the main driving force of frosting. Tube surface temperature is the most important factor affecting frosting when there is little variation in air humidity. Frost at the fin base was found to be thicker than that at the fin tip due to the fact that the frost layer grows faster with lower tube surface temperature

Methane flux across the air-water interface - Air velocity effects

Science.gov (United States)

Sebacher, D. I.; Harriss, R. C.; Bartlett, K. B.

1983-01-01

Methane loss to the atmosphere from flooded wetlands is influenced by the degree of supersaturation and wind stress at the water surface. Measurements in freshwater ponds in the St. Marks Wildlife Refuge, Florida, demonstrated that for the combined variability of CH4 concentrations in surface water and air velocity over the water surface, CH4 flux varied from 0.01 to 1.22 g/sq m/day. The liquid exchange coefficient for a two-layer model of the gas-liquid interface was calculated as 1.7 cm/h for CH4 at air velocity of zero and as 1.1 + 1.2 v to the 1.96th power cm/h for air velocities from 1.4 to 3.5 m/s and water temperatures of 20 C.

Exchange of deuterium with hydrogen of zeolite catalyst surface

International Nuclear Information System (INIS)

Minachev, Kh.M.; Dmitriev, R.V.; Penchev, V.; Kanazirev, V.; Minchev, Kh.; Kasimov, Ch.K.; Bylgarska Akademiya na Naukite, Sofia. Inst. za Obshta i Organichna Khimiya; AN Azerbajdzhanskoj SSR, Baku. Inst. Neftekhimicheskikh Protsessov)

1981-01-01

Isotope heteromolecular exchange of hydrogen on the reduced nickel-containing zeolites takes places at the temperatures above 100 deg and it is controlled by activated hydrogen transfer from metal particles on the substrate surface. High-temperature redox treatment of nickel-containing zeolites results in the formation of large nickel crystallites on zeolite external faces. The rest part of nickel remains in zeolite pores and conditions a high promoting effect in the exchange reaction. Catalytic activity of reduced zeolites NiCaNaY in toluene disproportionation increases considerably only in the cases when nickel is introduced into zeolite by means of ion exchange. Close spatial location of nickel particles and OH groups promotes the procedure of both isotope exchange and disproportionation of toluene [ru

A continuous-flow denuder for the measurement of ambient concentrations and surface-exchange fluxes of ammonia

Science.gov (United States)

Wyers, G. P.; Otjes, R. P.; Slanina, J.

A new diffusion denuder is described for the continuous measurement of atmospheric ammonia. Ammonia is collected in an absorption solution in a rotating denuder, separated from interfering compounds by diffusion through a semi-permeable membrane and detected by conductometry. The method is free from interferences by other atmospheric gases, with the exception of volatile amines. The detection limit is 6 ng m -3 for a 30-min integration time. This compact instrument is fully automated and suited for routine deployment in field studies. The precision is sufficiently high for micrometeorological studies of air-surface exchange of ammonia.

Safety-related control air systems

International Nuclear Information System (INIS)

Anon.

1977-01-01

This Standard applies to those portions of the control air system that furnish air required to support, control, or operate systems or portions of systems that are safety related in nuclear power plants. This Standard relates only to the air supply system(s) for safety-related air operated devices and does not apply to the safety-related air operated device or to air operated actuators for such devices. The objectives of this Standard are to provide (1) minimum system design requirements for equipment, piping, instruments, controls, and wiring that constitute the air supply system; and (2) the system and component testing and maintenance requirements

Group IV nanocrystals with ion-exchangeable surface ligands and methods of making the same

Science.gov (United States)

Wheeler, Lance M.; Nichols, Asa W.; Chernomordik, Boris D.; Anderson, Nicholas C.; Beard, Matthew C.; Neale, Nathan R.

2018-01-09

Methods are described that include reacting a starting nanocrystal that includes a starting nanocrystal core and a covalently bound surface species to create an ion-exchangeable (IE) nanocrystal that includes a surface charge and a first ion-exchangeable (IE) surface ligand ionically bound to the surface charge, where the starting nanocrystal core includes a group IV element.

Air-sea exchange of gaseous mercury in the tropical coast (Luhuitou fringing reef) of the South China Sea, the Hainan Island, China.

Science.gov (United States)

Ci, Zhijia; Zhang, Xiaoshan; Wang, Zhangwei

2016-06-01

The air-sea exchange of gaseous mercury (mainly Hg(0)) in the tropical ocean is an important part of the global Hg biogeochemical cycle, but the related investigations are limited. In this study, we simultaneously measured Hg(0) concentrations in surface waters and overlaying air in the tropical coast (Luhuitou fringing reef) of the South China Sea (SCS), Hainan Island, China, for 13 days on January-February 2015. The purpose of this study was to explore the temporal variation of Hg(0) concentrations in air and surface waters, estimate the air-sea Hg(0) flux, and reveal their influencing factors in the tropical coastal environment. The mean concentrations (±SD) of Hg(0) in air and total Hg (THg) in waters were 2.34 ± 0.26 ng m(-3) and 1.40 ± 0.48 ng L(-1), respectively. Both Hg(0) concentrations in waters (53.7 ± 18.8 pg L(-1)) and Hg(0)/THg ratios (3.8 %) in this study were significantly higher than those of the open water of the SCS in winter. Hg(0) in waters usually exhibited a clear diurnal variation with increased concentrations in daytime and decreased concentrations in nighttime, especially in cloudless days with low wind speed. Linear regression analysis suggested that Hg(0) concentrations in waters were positively and significantly correlated to the photosynthetically active radiation (PAR) (R (2) = 0.42, p sea Hg(0) fluxes were estimated to be 1.73 ± 1.25 ng m(-2) h(-1) with a large range between 0.01 and 6.06 ng m(-2) h(-1). The high variation of Hg(0) fluxes was mainly attributed to the greatly temporal variation of wind speed.

Air-sea gas exchange of HCHs and PCBs and enantiomers of α-HCH in the Kattegat Sea region

International Nuclear Information System (INIS)

Sundqvist, Kristina L.; Wingfors, Haakan; Brorstoem-Lunden, Eva; Wiberg, Karin

2004-01-01

Concentrations and air-water gas exchange of polychlorinated biphenyls (PCBs) and hexachlorocyclohexanes (HCHs) were determined in nine paired air and water samples. The samples were collected monthly in the Kattegat Sea between December 1998 and November 1999. Average fugacity and flux values indicated that PCBs were oversaturated in the water, while HCHs were net deposited. Variations were large over the year, especially during spring and summer. Air parcel back trajectories suggested that air concentrations over the Kattegat Sea are largely dependent of air mass origin. Seasonal trends were detected for airborne HCHs and for PCBs in water. The air and water enantiomeric compositions of α-HCH indicated that a larger portion of α-HCH in air originated from the underlying water during summer than during winter. - Air-water exchange of PCBs and HCHs is studied in the Kattegat Sea and shows to vary seasonally

A review on the thermal hydraulic characteristics of the air-cooled

Indian Academy of Sciences (India)

In this paper, a review is presented on the experimental investigations and the numerical simulations performed to analyze the thermal-hydraulic performance of the air-cooled heat exchangers. The air-cooled heat exchangers mostly consist of the finned-tube bundles. The primary role of the extended surfaces (fins) is to ...

Numerical calibration and experimental validation of a PCM-Air heat exchanger model

International Nuclear Information System (INIS)

Stathopoulos, N.; El Mankibi, M.; Santamouris, Mattheos

2017-01-01

Highlights: • Development of a PCM-Air heat exchanger experimental unit and its numerical model. • Differential Scanning Calorimetry for PCM properties. • Ineptitude of DSC obtained heat capacity curves. • Creation of adequate heat capacity curves depending on heat transfer rates. • Confrontation of numerical and experimental results and validation of the model. - Abstract: Ambitious goals have been set at international, European and French level for energy consumption and greenhouse gas emissions decrease of the building sector. Achieving them requires renewable energy integration, a technology that presents however an important drawback: intermittent energy production. In response, thermal energy storage (TES) technology applications have been developed in order to correlate energy production and consumption of the building. Phase Change Materials (PCMs) have been widely used in TES applications as they offer a high storage density and adequate phase change temperature range. It is important to accurately know the thermophysical properties of the PCM, both for experimental (system design) and numerical (correct prediction) purposes. In this paper, the fabrication of a PCM – Air experimental prototype is presented at first, along with the development of a numerical model simulating the downstream temperature evolution of the heat exchanger. Particular focus is given to the calibration method and the validation of the model using experimental characterization results. Differential scanning calorimetry (DSC) is used to define the thermal properties of the PCM. Initial numerical results are underestimated compared to experimental ones. Various factors were investigated, pointing to the ineptitude of the heat capacity parameter, as DSC results depend on heating/cooling rates. Adequate heat capacity curves were empirically determined, depending on heat transfer rates and based on DSC results and experimental observations. The results of the proposed model

Fundamental structural aspects and features in the bioengineering of the gas exchangers: comparative perspectives.

Science.gov (United States)

Maina, J N

2002-01-01

the ubiquitous method of transfer of O2 across biological tissues. Gills, evaginated gas exchangers, were the primordial respiratory organs that evolved for water breathing, whereas lungs (invaginated gas exchangers) developed for terrestrial (air) breathing. Transitional (= bimodal = amphibious) breathing has evolved in animals with specialized organs that extract O2 from both water and air. Lungs are tidally (= bidirectionally) ventilated, while gills are unidirectionally ventilated, a feature that allows the highly efficient counter-current disposition between blood and water. Since animals occupy inconstant environmental milieus and their metabolic states vary, gas exchangers are designed to operate optimally across a spectrum of conditions that range from resting to exercise and even under hypoxia. Inbuilt structural and functional flexibility provides the requisite safety factors that allow adjustments to modest pressures. The fundamental structural features that determine the respiratory function of a gas exchanger are respiratory surface area, thickness of the blood-water/gas (tissue) barrier and volume of the pulmonary capillary blood. The diffusing capacity of a gas exchanger correlates directly with the surface area and inversely with the thickness of the blood-water/gas (tissue) barrier. An extensive surface area is generated in gills by extensive stratification of the gas exchanger and in lungs by profuse internal subdivision. Compartmentalization yields small terminal gas exchange compartments that compel greater commitment of energy to ventilate. The surfactant, a phospholipid lining, reduces the forces of surface tension at the air-water interface. This attenuates the propensity of physical collapse of the minute gas exchange units and minimizes the cost of ventilation. The surfactant characterizes all the gas exchangers derived from the piscine air bladder. In the lower air-breathing vertebrates, such as the lungfishes (Dipnoi), amphibians and certain

Surfactant control of air-sea gas exchange from North Sea coastal waters and the Atlantic Meridional Transect

Science.gov (United States)

Pereira, R.

2016-02-01

Suppression of gas transfer velocity (kw) by surfactants are well established, both in laboratory wind flumes and purposeful oceanic releases. However, the effects on kw of time and space varying concentrations of natural surfactant are inadequately studied. We have developed an automated gas exchange tank for simultaneous high precision measurement of kw in unmodified seawater samples. Here we present data from two studies along a coastal North Sea transect during 2012-2013 and the Atlantic Meridional Transect (AMT) 24 from September to November 2014. Measurements of surfactant activity (SA), CDOM absorbance and chlorophyll-a have enabled us to characterize the effects of variable amounts of natural surfactant on kw. North Sea coastal waters range in k660 (kw normalized to the value for CO2 in freshwater at 20oC) was 6.8-24.5 cm hr-1 (n=20), with the ranges of SA, total CDOM absorbance (200-450 nm) and chlorophyll-a measured in the surface microlayer (SML) of our seawater samples were 0.08-0.38 mg l-1 T-X-100, 0.13-4.7 and 0.09-1.54 µg l-1, respectively. The AMT k660 ranged from 7.0-23.9 cm hr-1 (n=22), with SA measured in the SML and subsurface water (SSW) of our seawater samples ranging from 0.15-1.08 mg l-1 T-X-100 and 0.07-0.43 mg l-1 T-X-100, respectively. Importantly, we found 12-45% (North Sea) and 1-43% (AMT) k660 suppression relative to Milli-Q water that relate to seasonal and spatial differences in SA. The North Sea demonstrated notable seasonal influences on k660 suppression that were related to CDOM absorbance and chlorophyll-a. The degree of k660 suppression was highest in summer consistent with k660 control by natural surfactant. The degree of k660 suppression decreased with distance offshore in the North Sea and displayed a strong relationship with SA (r2 = 0.51-0.64, p = 0.02, n = 20). The AMT demonstrated notable differences in k660 suppression between hemispheres and across the Longhurst Provinces but the overall relationship between k660

Heat exchanger for cooling a liquid metal with air, including panels of identical tubes

International Nuclear Information System (INIS)

Malaval, C.

1985-01-01

The heat exchanger includes panels of identical tubes, each one comprising two horizontal collectors situated at the vertical of each other and a group of vertical tubes for cooling arranged in a horizontal parallelepiped casing opened on two of its opposite sides. The air flows from the inlet to the outlet face of the casing. The panels of tubes are arranged side by side so that their outlet faces form a prismatic surface of which the height is vertical and the inner space communicates with a vertical axis chimney. Each one of the panels is hanging from a fixed structure by means of articulated fasteners, by means of its upper collector only. The invention applies, more particularly, for cooling the primary sodium of fast neutron reactors after they are stopped [fr

Air plasma processing of poly(methyl methacrylate) micro-beads: Surface characterisations

International Nuclear Information System (INIS)

Liu Chaozong; Cui Naiyi; Osbeck, Susan; Liang He

2012-01-01

Highlights: ► PMMA micro-beads were processed using a rotary air plasma reactor. ► Surface chemistry and surface texture of PMMA micro-beads were characterised. ► Surface wettability was evaluated using “floating” water contact angle method. ► Surface oxidation and texture changes induced by air plasma attributed to the improvement of surface wettability. - Abstract: This paper reports the surface processing of poly(methyl methacrylate) (PMMA) micro-beads by using a rotary air plasma reactor, and its effects on surface properties. The surface properties, including surface wettability, surface chemistry and textures of the PMMA beads, were characterised. It was observed that the air plasma processing can improve the surface wettability of the PMMA microbeads significantly. A 15 min plasma processing can reduce the surface water contact angle of PMMA beads to about 50° from its original value of 80.3°. This was accompanied by about 8% increase in surface oxygen concentration as confirmed by XPS analysis. The optical profilometry examination revealed the air plasma processing resulted in a rougher surface that has a “delicate” surface texture. It is concluded that the surface chemistry and texture, induced by air plasma processing, co-contributed to the surface wettability improvement of PMMA micro-beads.

Global evaluation of ammonia bidirectional exchange and livestock diurnal variation schemes

Science.gov (United States)

Bidirectional air–surface exchange of ammonia (NH3) has been neglected in many air quality models. In this study, we implement the bidirectional exchange of NH3 in the GEOS-Chem global chemical transport model. We also introduce an updated diurnal variability scheme for NH3...

Air-sea interactions during strong winter extratropical storms

Science.gov (United States)

Nelson, Jill; He, Ruoying; Warner, John C.; Bane, John

2014-01-01

A high-resolution, regional coupled atmosphere–ocean model is used to investigate strong air–sea interactions during a rapidly developing extratropical cyclone (ETC) off the east coast of the USA. In this two-way coupled system, surface momentum and heat fluxes derived from the Weather Research and Forecasting model and sea surface temperature (SST) from the Regional Ocean Modeling System are exchanged via the Model Coupling Toolkit. Comparisons are made between the modeled and observed wind velocity, sea level pressure, 10 m air temperature, and sea surface temperature time series, as well as a comparison between the model and one glider transect. Vertical profiles of modeled air temperature and winds in the marine atmospheric boundary layer and temperature variations in the upper ocean during a 3-day storm period are examined at various cross-shelf transects along the eastern seaboard. It is found that the air–sea interactions near the Gulf Stream are important for generating and sustaining the ETC. In particular, locally enhanced winds over a warm sea (relative to the land temperature) induce large surface heat fluxes which cool the upper ocean by up to 2 °C, mainly during the cold air outbreak period after the storm passage. Detailed heat budget analyses show the ocean-to-atmosphere heat flux dominates the upper ocean heat content variations. Results clearly show that dynamic air–sea interactions affecting momentum and buoyancy flux exchanges in ETCs need to be resolved accurately in a coupled atmosphere–ocean modeling framework.

Studies on the air distribution and thermal performance of the air circulation wall. Part 4. Study on the thermal emissivity of the air circulation layer`s surfaces; Gaidannetsu tsuki koho ni okeru tsuki sonai no netsu tsuki tokusei ni kansuru kenkyu. 4. Tsuki sonai hyomen no hosha tokusei ni kansuru kosatsu

Energy Technology Data Exchange (ETDEWEB)

Kamimori, K; Sakai, K; Ishihara, O [Kumamoto University, Kumamoto (Japan)

1996-10-27

The thermal and air distribution characteristics of the air circulation wall in a heat-insulated system were grasped using an experimental model. In this paper, the difference in the heat exchange between the wall and air was confirmed based on the radiation on the circulation layer`s surface. In this system, thin air circulation layers with ventilating holes at the top and bottom are attached to the south and north outer walls of a wooden building. This system is a kind of passive solar house that achieves the insolation screening effect and the temperature rising effect based on solar collection. The heat flow in a circulation layer is eliminated by the natural convection heat transfer on the outer wall. The heat flow passing through insulating materials is the heat transfer by radiation. The heat flow based on the in-layer natural convection is increasingly eliminated by the decrease in temperature on the air circulation layer`s surface. The decrease in room surface temperature using aluminum foil and the reflective heat-insulated effect showed that the heat passing through the wall surface decreases as the convection heat transfer in an air circulation layer increases. 6 refs., 20 figs., 3 tabs.

Laser Processed Condensing Heat Exchanger Technology Development

Science.gov (United States)

Hansen, Scott; Wright, Sarah; Wallace, Sarah; Hamilton, Tanner; Dennis, Alexander; Zuhlke, Craig; Roth, Nick; Sanders, John

2017-01-01

The reliance on non-permanent coatings in Condensing Heat Exchanger (CHX) designs is a significant technical issue to be solved before long-duration spaceflight can occur. Therefore, high reliability CHXs have been identified by the Evolvable Mars Campaign (EMC) as critical technologies needed to move beyond low earth orbit. The Laser Processed Condensing Heat Exchanger project aims to solve these problems through the use of femtosecond laser processed surfaces, which have unique wetting properties and potentially exhibit anti-microbial growth properties. These surfaces were investigated to identify if they would be suitable candidates for a replacement CHX surface. Among the areas researched in this project include microbial growth testing, siloxane flow testing in which laser processed surfaces were exposed to siloxanes in an air stream, and manufacturability.

Air-Seawater Exchange of Organochlorine Pesticides along the Sediment Plume of a Large Contaminated River.

Science.gov (United States)

Lin, Tian; Guo, Zhigang; Li, Yuanyuan; Nizzetto, Luca; Ma, Chuanliang; Chen, Yingjun

2015-05-05

Gaseous exchange fluxes of organochlorine pesticides (OCPs) across the air-water interface of the coastal East China Sea were determined in order to assess whether the contaminated plume of the Yangtze River could be an important regional source of OCPs to the atmosphere. Hexachlorocyclohexanes (HCHs), chlordane compounds (CHLs), and dichlorodiphenyltrichloroethanes (DDTs) were the most frequently detected OCPs in air and water. Air-water exchange was mainly characterized by net volatilization for all measured OCPs. The net gaseous exchange flux ranged 10-240 ng/(m2·day) for γ-HCH, 60-370 ng/(m2·day) for trans-CHL, 97-410 ng/(m2·day) for cis-CHL, and ∼0 (e.g., equilibrium) to 490 ng/(m2·day) for p,p'-DDE. We found that the plume of the large contaminated river can serve as a significant regional secondary atmospheric source of legacy contaminants released in the catchment. In particular, the sediment plume represented the relevant source of DDT compounds (especially p,p'-DDE) sustaining net degassing when clean air masses from the open ocean reached the plume area. In contrast, a mass balance showed that, for HCHs, contaminated river discharge (water and sediment) plumes were capable of sustaining volatilization throughout the year. These results demonstrate the inconsistencies in the fate of HCHs and DDTs in this large estuarine system with declining primary sources.

Use of a numerical simulation approach to improve the estimation of air-water exchange fluxes of polycyclic aromatic hydrocarbons in a coastal zone.

Science.gov (United States)

Lai, I-Chien; Lee, Chon-Lin; Ko, Fung-Chi; Lin, Ju-Chieh; Huang, Hu-Ching; Shiu, Ruei-Feng

2017-07-15

The air-water exchange is important for determining the transport, fate, and chemical loading of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere and in aquatic systems. Investigations of PAH air-water exchange are mostly based on observational data obtained using complicated field sampling processes. This study proposes a new approach to improve the estimation of long-term PAH air-water exchange fluxes by using a multivariate regression model to simulate hourly gaseous PAH concentrations. Model performance analysis and the benefits from this approach indicate its effectiveness at improving the flux estimations and at decreasing the field sampling difficulty. The proposed GIS mapping approach is useful for box model establishment and is tested for visualization of the spatiotemporal variations of air-water exchange fluxes in a coastal zone. The air-water exchange fluxes illustrated by contour maps suggest that the atmospheric PAHs might have greater impacts on offshore sites than on the coastal area in this study. Copyright © 2017 Elsevier Ltd. All rights reserved.

Heat Transfer in Metal Foam Heat Exchangers at High Temperature

Science.gov (United States)

Hafeez, Pakeeza

Heat transfer though open-cell metal foam is experimentally studied for heat exchanger and heat shield applications at high temperatures (˜750°C). Nickel foam sheets with pore densities of 10 and 40 pores per linear inch (PPI), have been used to make the heat exchangers and heat shields by using thermal spray coating to deposit an Inconel skin on a foam core. Heat transfer measurements were performed on a test rig capable of generating hot gas up to 1000°C. The heat exchangers were tested by exposing their outer surface to combustion gases at a temperature of 550°C and 750°C while being cooled by air flowing through them at room temperature at velocities up to 5 m/s. The temperature rise of the air, the surface temperature of the heat exchangers and the air temperature inside the heat exchanger were measured. The volumetric heat transfer coefficient and Nusselt number were calculated for different velocities. The heat transfer performance of the 40PPI sample brazed with the foil is found to be the most efficient. Pressure drop measurements were also performed for 10 and 40PPI metal foam. Thermographic measurements were done on 40PPI foam heat exchangers using a high temperature infrared camera. A high power electric heater was used to produce hot air at 300°C that passed over the foam heat exchanger while the cooling air was blown through it. Heat shields were made by depositing porous skins on metal foam and it was observed that a small amount of coolant leaking through the pores notably reduces the heat transfer from the hot gases. An analytical model was developed based assuming local thermal non-equilibrium that accounts for the temperature difference between solid and fluid phase. The experimental results are found to be in good agreement with the predicted values of the model.

Validation of AIRS V6 Surface Temperature over Greenland with GCN and NOAA Stations

Science.gov (United States)

Lee, Jae N.; Hearty, Thomas; Cullather, Richard; Nowicki, Sophie; Susskind, Joel

2016-01-01

This work compares the temporal and spatial characteristics of the AIRSAMSU (Atmospheric Infrared Sounder Advanced Microwave Sounding Unit A) Version 6 and MODIS (Moderate resolution Imaging Spectroradiometer) Collection 5 derived surface temperatures over Greenland. To estimate uncertainties in space-based surface temperature measurements, we re-projected the MODIS Ice Surface Temperature (IST) to 0.5 by 0.5 degree spatial resolution. We also re-gridded AIRS Skin Temperature (Ts) into the same grid but classified with different cloud conditions and surface types. These co-located data sets make intercomparison between the two instruments relatively straightforward. Using this approach, the spatial comparison between the monthly mean AIRS Ts and MODIS IST is in good agreement with RMS 2K for May 2012. This approach also allows the detection of any long-term calibration drift and the careful examination of calibration consistency in the MODIS and AIRS temperature data record. The temporal correlations between temperature data are also compared with those from in-situ measurements from GC-Net (GCN) and NOAA stations. The coherent time series of surface temperature evident in the correlation between AIRS Ts and GCN temperatures suggest that at monthly time scales both observations capture the same climate signal over Greenland. It is also suggested that AIRS surface air temperature (Ta) can be used to estimate the boundary layer inversion.

Impact of chemical lateral boundary conditions in a regional air quality forecast model on surface ozone predictions during stratospheric intrusions

Science.gov (United States)

Pendlebury, Diane; Gravel, Sylvie; Moran, Michael D.; Lupu, Alexandru

2018-02-01

A regional air quality forecast model, GEM-MACH, is used to examine the conditions under which a limited-area air quality model can accurately forecast near-surface ozone concentrations during stratospheric intrusions. Periods in 2010 and 2014 with known stratospheric intrusions over North America were modelled using four different ozone lateral boundary conditions obtained from a seasonal climatology, a dynamically-interpolated monthly climatology, global air quality forecasts, and global air quality reanalyses. It is shown that the mean bias and correlation in surface ozone over the course of a season can be improved by using time-varying ozone lateral boundary conditions, particularly through the correct assignment of stratospheric vs. tropospheric ozone along the western lateral boundary (for North America). Part of the improvement in surface ozone forecasts results from improvements in the characterization of near-surface ozone along the lateral boundaries that then directly impact surface locations near the boundaries. However, there is an additional benefit from the correct characterization of the location of the tropopause along the western lateral boundary such that the model can correctly simulate stratospheric intrusions and their associated exchange of ozone from stratosphere to troposphere. Over a three-month period in spring 2010, the mean bias was seen to improve by as much as 5 ppbv and the correlation by 0.1 depending on location, and on the form of the chemical lateral boundary condition.

Dataset for Probabilistic estimation of residential air exchange rates for population-based exposure modeling

Data.gov (United States)

U.S. Environmental Protection Agency — This dataset provides the city-specific air exchange rate measurements, modeled, literature-based as well as housing characteristics. This dataset is associated with...

Effect of wind waves on air-sea gas exchange: proposal of an overall CO2 transfer velocity formula as a function of breaking-wave parameter

International Nuclear Information System (INIS)

Zhao, D.; Suzuki, Y.; Komori, S.

2003-01-01

A new formula for gas transfer velocity as a function of the breaking-wave parameter is proposed based on correlating gas transfer with whitecap coverage. The new formula for gas transfer across an air-sea interface depends not only on wind speed but also on wind-wave state. At the same wind speed, a higher gas transfer velocity will be obtained for a more developed wind-sea, which is represented by a smaller spectral peak frequency of wind waves. We suggest that the large uncertainties in the traditional relationship of gas transfer velocity with wind speed be ascribed to the neglect of the effect of wind waves. The breaking-wave parameter can be regarded as a Reynolds number that characterizes the intensity of turbulence associated with wind waves in the downward-bursting boundary layer (DBBL). DBBL provides an effective way to exchange gas across the air-sea interface, which might be related to the surface renewal

Collecting performance of an evacuated tubular solar high-temperature air heater with concentric tube heat exchanger

International Nuclear Information System (INIS)

Wang, Ping-Yang; Li, Shuang-Fei; Liu, Zhen-Hua

2015-01-01

Highlights: • A novel evacuated tube solar high temperature air heater is designed. • The solar air heater system consists of 30 linked collecting units. • Every unit consisted of a evacuated tube, a simplified CPC and concentric tube. • The flow air is heated over temperature of 200 °C. - Abstract: A set of evacuated tube solar high temperature air heaters with simplified CPC (compound parabolic concentrator) and concentric tube heat exchanger is designed to provide flow air with a temperature of 150–230 °C for industrial production. The solar air heater system consists of 30 linked collecting units. Each unit includes a simplified CPC and an all-glass evacuated tube absorber with a concentric copper tube heat exchanger installed inside. A stainless steel mesh layer with high thermal conductivity is filled between the evacuated tube and the concentric copper tube. Air passes through each collecting unit, and its temperature increases progressively. An experimental investigation of the thermal performance of the air heater is performed, and the experimental results demonstrate the presented high-temperature solar air heater has excellent collecting performance and large output power, even in the winter. The measured thermal efficiency corresponding to the air temperature of 70 °C reaches 0.52. With the increase of air temperature, thermal efficiency reaches 0.35 at an air temperature of 150 °C, and 0.21 at an air temperature of 220 °C.

Preparation of Two-Layer Anion-Exchange Poly(ethersulfone Based Membrane: Effect of Surface Modification

Directory of Open Access Journals (Sweden)

Lucie Zarybnicka

2016-01-01

Full Text Available The present work deals with the surface modification of a commercial microfiltration poly(ethersulfone membrane by graft polymerization technique. Poly(styrene-co-divinylbenzene-co-4-vinylbenzylchloride surface layer was covalently attached onto the poly(ethersulfone support layer to improve the membrane electrochemical properties. Followed by amination, a two-layer anion-exchange membrane was prepared. The effect of surface layer treatment using the extraction in various solvents on membrane morphological and electrochemical characteristics was studied. The membranes were tested from the point of view of water content, ion-exchange capacity, specific resistance, permselectivity, FT-IR spectroscopy, and SEM analysis. It was found that the two-layer anion-exchange membranes after the extraction using tetrahydrofuran or toluene exhibited smooth and porous surface layer, which resulted in improved ion-exchange capacity, electrical resistance, and permselectivity of the membranes.

Frost behavior of a fin surface with temperature variation along heat exchanger fins

International Nuclear Information System (INIS)

Kim, Jung Soo; Kim, Min Soo; Lee, Kwan Soo; Kim, Ook Joong

2007-01-01

This paper presents a mathematical model for predicting the frost behavior formed on heat exchanger fins, considering fin heat conduction under frosting condition. The model is composed of air-side, the frost layer, and fin region, and they are coupled to the frost layer. The frost behavior is more accurately predicted with fin heat conduction considered (Case A) than with a constant fin surface temperature assumed (Case B). The results indicate that the frost thickness and heat transfer rate for Case B are over-predicted in most regions of the fin, as compared to those for Case A. Also, for Case A, the maximum frost thickness varies little with the fin length variations, and the extension of the fin length over 30 mm contributes insignificantly to heat transfer

Surface defect chemistry and oxygen exchange kinetics in La2-xCaxNiO4+δ

Science.gov (United States)

Tropin, E. S.; Ananyev, M. V.; Farlenkov, A. S.; Khodimchuk, A. V.; Berenov, A. V.; Fetisov, A. V.; Eremin, V. A.; Kolchugin, A. A.

2018-06-01

Surface oxygen exchange kinetics and diffusion in La2-xCaxNiO4+δ (x = 0; 0.1; 0.3) have been studied by the isotope exchange method with gas phase equilibration in the temperature range of 600-800 °C and oxygen pressure range 0.13-2.5 kPa. Despite an enhanced electrical conductivity of La2-xCaxNiO4+δ theirs oxygen surface exchange (k*) and oxygen tracer diffusion (D*) coefficients were significantly lower in comparison with La2NiO4+δ. The rates of the elementary stages of oxygen exchange have been calculated. Upon Ca doping the change of the rate-determining stage was observed. The surface of the oxides was found to be inhomogeneous towards oxygen exchange process according to the recently developed model. The reasons of such inhomogeneity are discussed as well as Ca influence on the surface defect chemistry and oxygen surface exchange and diffusivity.

The use of helical heat exchanger for heat recovery domestic water-cooled air-conditioners

International Nuclear Information System (INIS)

Yi Xiaowen; Lee, W.L.

2009-01-01

An experimental study on the performance of a domestic water-cooled air-conditioner (WAC) using tube-in-tube helical heat exchanger for preheating of domestic hot water was carried out. The main aims are to identify the comprehensive energy performance (space cooling and hot water preheating) of the WAC and the optimum design of the helical heat exchanger taking into account the variation in tap water flow rate. A split-type WAC was set up for experimental study at different indoor and outdoor conditions. The cooling output, the amount of recovered heat, and the power consumption for different hot water flow rates were measured. The experimental results showed that the cooling coefficient of performance (COP) of the WAC improves with the inclusion of the heat recovery option by a minimum of 12.3%. This can be further improved to 20.6% by an increase in tap water flow rate. Same result was observed for the comprehensive COP of the WAC. The maximum achievable comprehensive COP was 4.92 when the tap water flow rate was set at 7.7 L/min. The overall heat transfer coefficient of the helical heat exchanger under various operating conditions were determined by Wilson plot. A mathematical model relating the over all heat transfer coefficient to the outer pipe diameter was established which provides a convenient way of optimising the design of the helical heat exchanger

The Arctic Ocean marine carbon cycle: evaluation of air-sea CO2 exchanges, ocean acidification impacts and potential feedbacks

Directory of Open Access Journals (Sweden)

N. R. Bates

2009-11-01

Full Text Available At present, although seasonal sea-ice cover mitigates atmosphere-ocean gas exchange, the Arctic Ocean takes up carbon dioxide (CO2 on the order of −66 to −199 Tg C year−1 (1012 g C, contributing 5–14% to the global balance of CO2 sinks and sources. Because of this, the Arctic Ocean has an important influence on the global carbon cycle, with the marine carbon cycle and atmosphere-ocean CO2 exchanges sensitive to Arctic Ocean and global climate change feedbacks. In the near-term, further sea-ice loss and increases in phytoplankton growth rates are expected to increase the uptake of CO2 by Arctic Ocean surface waters, although mitigated somewhat by surface warming in the Arctic. Thus, the capacity of the Arctic Ocean to uptake CO2 is expected to alter in response to environmental changes driven largely by climate. These changes are likely to continue to modify the physics, biogeochemistry, and ecology of the Arctic Ocean in ways that are not yet fully understood. In surface waters, sea-ice melt, river runoff, cooling and uptake of CO2 through air-sea gas exchange combine to decrease the calcium carbonate (CaCO3 mineral saturation states (Ω of seawater while seasonal phytoplankton primary production (PP mitigates this effect. Biological amplification of ocean acidification effects in subsurface waters, due to the remineralization of organic matter, is likely to reduce the ability of many species to produce CaCO3 shells or tests with profound implications for Arctic marine ecosystems

Performance characteristics of solar air heater with surface mounted obstacles

International Nuclear Information System (INIS)

Bekele, Adisu; Mishra, Manish; Dutta, Sushanta

2014-01-01

Highlights: • Solar air heater with delta shaped obstacles have been studied. • Obstacle angle of incidence strongly affects the thermo-hydraulic performance. • Thermal performance of obstacle mounted collectors is superior to smooth collectors. • Thermo-hydraulic performance of the present SAH is higher than those in previous studies. - Abstract: The performance of conventional solar air heaters (SAHs) can be improved by providing obstacles on the heated wall (i.e. on the absorber plate). Experiments have been performed to collect heat transfer and flow-friction data from an air heater duct with delta-shaped obstacles mounted on the absorber surface and having an aspect ratio 6:1 resembling the conditions close to the solar air heaters. This study encompassed for the range of Reynolds number (Re) from 2100 to 30,000, relative obstacle height (e/H) from 0.25 to 0.75, relative obstacle longitudinal pitch (P l /e) from 3/2 to 11/2, relative obstacle transverse pitch (P t /b) from 1 to 7/3 and the angle of incidence (α) varied from 30° to 90°. The thermo-hydraulic performance characteristics of SAH have been compared with the previous published works and the optimum range of the geometries have been explored for the better performance of such air-heaters compared to the other designs of solar air heaters

Helium-air exchange flow through an opening with a partition

International Nuclear Information System (INIS)

Kang, Tae-il; Okamoto, Koji; Madarame, Haruki; Fumizawa, Motoo.

1993-01-01

The helium-air exchange flow through a small vertical opening with a partition was experimentally investigated. The vertical partition was aligned with the center line of the small opening to evaluate the effects of the multiple openings. The dimensionless exchange flow rates, i.e., Froude numbers, were experimentally obtained with several opening ratios (H 1 /D f ), i.e., the ratio of the height to the effective diameter of the opening. In the case of low opening ratios (H 1 /D f 1 /D f ≥ 0.75), the measured Froude numbers for the multiple openings were larger than those for the single opening, because the upward and downward flows were separated by the vertical partition. Based on the balance between the pressure losses in the openings and the driving force due to density difference, the exchange flow rate was calculated, and found to agree qualitatively with the measured Froude numbers. The effect of the upward and downward flow interaction at the exit of the opening was found to play an important role in the prediction of the Froude number. (author)

Radionuclides and trace metals in surface air. Appendix C

International Nuclear Information System (INIS)

Feely, H.W.; Toonkel, L.E.; Larsen, R.J.

1981-01-01

Since January 1963, the Environmental Measurements Laboratory (EML), formerly the Health and Safety Laboratory (HASL), has been conducting the Surface Air Sampling Program. This study is a direct outgrowth of a program initiated by the US Naval Research Laboratory (NRL) in 1957 and continued through 1962. The primary objective of this program is to study the spatial and temporal distribution of specific natural and man-made radioisotopes, and of trace metals in the surface air. Other special studies of surface air contamination have been performed during the course of the program

Theme and variations: amphibious air-breathing intertidal fishes.

Science.gov (United States)

Martin, K L

2014-03-01

Over 70 species of intertidal fishes from 12 families breathe air while emerging from water. Amphibious intertidal fishes generally have no specialized air-breathing organ but rely on vascularized mucosae and cutaneous surfaces in air to exchange both oxygen and carbon dioxide. They differ from air-breathing freshwater fishes in morphology, physiology, ecology and behaviour. Air breathing and terrestrial activity are present to varying degrees in intertidal fish species, correlated with the tidal height of their habitat. The gradient of amphibious lifestyle includes passive remainers that stay in the intertidal zone as tides ebb, active emergers that deliberately leave water in response to poor aquatic conditions and highly mobile amphibious skipper fishes that may spend more time out of water than in it. Normal terrestrial activity is usually aerobic and metabolic rates in air and water are similar. Anaerobic metabolism may be employed during forced exercise or when exposed to aquatic hypoxia. Adaptations for amphibious life include reductions in gill surface area, increased reliance on the skin for respiration and ion exchange, high affinity of haemoglobin for oxygen and adjustments to ventilation and metabolism while in air. Intertidal fishes remain close to water and do not travel far terrestrially, and are unlikely to migrate or colonize new habitats at present, although in the past this may have happened. Many fish species spawn in the intertidal zone, including some that do not breathe air, as eggs and embryos that develop in the intertidal zone benefit from tidal air emergence. With air breathing, amphibious intertidal fishes survive in a variable habitat with minimal adjustments to existing structures. Closely related species in different microhabitats provide unique opportunities for comparative studies. © 2013 The Fisheries Society of the British Isles.

Influence of the adhesion force crystal/heat exchanger surface on fouling mitigation

International Nuclear Information System (INIS)

Forster, M.; Augustin, W.; Bohnet, M.

1999-01-01

The accumulation of unwanted crystalline deposits (fouling) reduces the efficiency of heat exchangers considerably. In order to decrease the cost of fouling two strategies have been developed. The first fouling mitigation strategy is based on the modification of energy-and-geometry-related characteristics of the heat transfer surface to realize an increased duration of the induction period. By means of a drop-shape-analysis measurement device the interaction at the interface crystal/heat transfer surface is determined. The deployment of the fracture energy model and the interfacial defect model relates wetting characteristics to the adhesion phenomenon. Hence, a first estimation of the optimal choice of surface material is realized. Furthermore, the influence of surface topography on interfacial interactions has been analyzed. The second fouling mitigation strategy is based on the adjustment of the hydrodynamic flow conditions using a pulsation technique. Here, single strokes of higher velocity are superimposed on the stationary flow. These strokes shift the equilibrium of forces to an improved removal process. Fouling experiments have proved that pulsation is a powerful tool to mitigate the built-up of fouling layers on heat transfer surfaces. (author)

The Effect of Rain on Air-Water Gas Exchange

Science.gov (United States)

Ho, David T.; Bliven, Larry F.; Wanninkhof, Rik; Schlosser, Peter

1997-01-01

The relationship between gas transfer velocity and rain rate was investigated at NASA's Rain-Sea Interaction Facility (RSIF) using several SF, evasion experiments. During each experiment, a water tank below the rain simulator was supersaturated with SF6, a synthetic gas, and the gas transfer velocities were calculated from the measured decrease in SF6 concentration with time. The results from experiments with IS different rain rates (7 to 10 mm/h) and 1 of 2 drop sizes (2.8 or 4.2 mm diameter) confirm a significant and systematic enhancement of air-water gas exchange by rainfall. The gas transfer velocities derived from our experiment were related to the kinetic energy flux calculated from the rain rate and drop size. The relationship obtained for mono-dropsize rain at the RSIF was extrapolated to natural rain using the kinetic energy flux of natural rain calculated from the Marshall-Palmer raindrop size distribution. Results of laboratory experiments at RSIF were compared to field observations made during a tropical rainstorm in Miami, Florida and show good agreement between laboratory and field data.

Seasonal atmospheric deposition and air-sea gas exchange of polycyclic aromatic hydrocarbons over the Yangtze River Estuary, East China Sea: Implications for source-sink processes

Science.gov (United States)

Jiang, Yuqing; Lin, Tian; Wu, Zilan; Li, Yuanyuan; Li, Zhongxia; Guo, Zhigang; Yao, Xiaohong

2018-04-01

In this work, air samples and surface seawater samples covering four seasons from March 2014 to January 2015 were collected from a background receptor site in the YRE to explore the seasonal fluxes of air-sea gas exchange and dry and wet deposition of 15 polycyclic aromatic hydrocarbons (PAHs) and their source-sink processes at the air-sea interface. The average dry and wet deposition fluxes of 15 PAHs were estimated as 879 ± 1393 ng m-2 d-1 and 755 ± 545 ng m-2 d-1, respectively. Gaseous PAH release from seawater to the atmosphere averaged 3114 ± 1999 ng m-2 d-1 in a year round. The air-sea gas exchange of PAHs was the dominant process at the air-sea interface in the YRE as the magnitude of volatilization flux of PAHs exceeded that of total dry and wet deposition. The gas PAH exchange flux was dominated by three-ring PAHs, with the highest value in summer and lowest in winter, indicating a marked seasonal variation owing to differences in Henry's law constants associated with temperature, as well as wind speed and gaseous-dissolved gradient among seasons. Based on the simplified mass balance estimation, a net 11 tons y-1 of PAHs (mainly three-ring PAHs) were volatilized from seawater to the atmosphere in a ∼20,000 km2 area in the YRE. Other than the year-round Yangtze River input and ocean ship emissions, the selective release of low-molecular-weight PAHs from bottom sediments in winter due to resuspension triggered by the East Asian winter monsoon is another potential source of PAHs. This work suggests that the source-sink processes of PAHs at the air-sea interface in the YRE play a crucial role in regional cycling of PAHs.

Tolerance Levels of Roadside Trees to Air Pollutants Based on Relative Growth Rate and Air Pollution Tolerance Index

Directory of Open Access Journals (Sweden)

SULISTIJORINI

2008-09-01

Full Text Available Motor vehicles release carbon monoxide, nitrogen dioxide, sulphur dioxide, and particulate matters to the air as pollutants. Vegetation can absorb these pollutants through gas exchange processes. The objective of this study was to examine the combination of the relative growth rate (RGR and physiological responses in determining tolerance levels of plant species to air pollutants. Physiological responses were calculated as air pollution tolerance index (APTI. Eight roadside tree species were placed at polluted (Jagorawi highway and unpolluted (Sindangbarang field area. Growth and physiological parameters of the trees were recorded, including plant height, leaf area, total ascorbate, total chlorophyll, leaf-extract pH, and relative water content. Scoring criteria for the combination of RGR and APTI method was given based on means of the two areas based on two-sample t test. Based on the total score of RGR and APTI, Lagerstroemia speciosa was categorized as a tolerant species; and Pterocarpus indicus, Delonix regia, Swietenia macrophylla were categorized as moderately tolerant species. Gmelina arborea, Cinnamomum burmanii, and Mimusops elengi were categorized as intermediate tolerant species. Lagerstroemia speciosa could be potentially used as roadside tree. The combination of RGR and APTI value was better to determinate tolerance level of plant to air pollutant than merely APTI method.

The EUSTACE project: delivering global, daily information on surface air temperature

Science.gov (United States)

Ghent, D.; Rayner, N. A.

2017-12-01

Day-to-day variations in surface air temperature affect society in many ways; however, daily surface air temperature measurements are not available everywhere. A global daily analysis cannot be achieved with measurements made in situ alone, so incorporation of satellite retrievals is needed. To achieve this, in the EUSTACE project (2015-2018, https://www.eustaceproject.eu) we have developed an understanding of the relationships between traditional (land and marine) surface air temperature measurements and retrievals of surface skin temperature from satellite measurements, i.e. Land Surface Temperature, Ice Surface Temperature, Sea Surface Temperature and Lake Surface Water Temperature. Here we discuss the science needed to produce a fully-global daily analysis (or ensemble of analyses) of surface air temperature on the centennial scale, integrating different ground-based and satellite-borne data types. Information contained in the satellite retrievals is used to create globally-complete fields in the past, using statistical models of how surface air temperature varies in a connected way from place to place. This includes developing new "Big Data" analysis methods as the data volumes involved are considerable. We will present recent progress along this road in the EUSTACE project, i.e.: • identifying inhomogeneities in daily surface air temperature measurement series from weather stations and correcting for these over Europe; • estimating surface air temperature over all surfaces of Earth from surface skin temperature retrievals; • using new statistical techniques to provide information on higher spatial and temporal scales than currently available, making optimum use of information in data-rich eras. Information will also be given on how interested users can become involved.

Photocatalytic surface reactions on indoor wall paint.

Science.gov (United States)

Salthammer, T; Fuhrmann, F

2007-09-15

The reduction of indoor air pollutants by air cleaning systems has received considerable interest, and a number of techniques are now available. So far, the method of photocatalysis was mainly applied by use of titanium dioxide (TiO2) in flow reactors under UV light of high intensity. Nowadays, indoor wall paints are equipped with modified TiO2 to work as a catalyst under indoor daylight or artificial light. In chamber experiments carried out under indoor related conditions itwas shown thatthe method works for nitrogen dioxide with air exchange and for formaldehyde without air exchange at high concentrations. In further experiments with volatile organic compounds (VOCs), a small effect was found for terpenoids with high kOH rate constants. For other VOCs and carbon monoxide there was no degradation at all or the surface acted as a reversible sink. Secondary emissions from the reaction of paint constituents were observed on exposure to light. From the results it is concluded that recipes of photocatalytic wall paints need to be optimized for better efficiency under indoor conditions.

Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden-Popper phases?

Science.gov (United States)

Tomkiewicz, Alex C; Tamimi, Mazin A; Huq, Ashfia; McIntosh, Steven

2015-01-01

The possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of three Ruddlesden-Popper phases, general form A(n-1)A(2)'B(n)O(3n+1), A(n-1)A(2)'B(n)X(3n+1); LaSrCo(0.5)Fe(0.5)O(4-δ) (n = 1), La(0.3)Sr(2.7)CoFeO(7-δ) (n = 2) and LaSr3Co(1.5)Fe(1.5)O(10-δ) (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. This is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. We conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.

The potential role of sea spray droplets in facilitating air-sea gas transfer

Science.gov (United States)

Andreas, E. L.; Vlahos, P.; Monahan, E. C.

2016-05-01

For over 30 years, air-sea interaction specialists have been evaluating and parameterizing the role of whitecap bubbles in air-sea gas exchange. To our knowledge, no one, however, has studied the mirror image process of whether sea spray droplets can facilitate air-sea gas exchange. We are therefore using theory, data analysis, and numerical modeling to quantify the role of spray on air-sea gas transfer. In this, our first formal work on this subject, we seek the rate-limiting step in spray-mediated gas transfer by evaluating the three time scales that govern the exchange: τ air , which quantifies the rate of transfer between the atmospheric gas reservoir and the surface of the droplet; τ int , which quantifies the exchange rate across the air-droplet interface; and τ aq , which quantifies gas mixing within the aqueous solution droplet.

Gaseous and Freely-Dissolved PCBs in the Lower Great Lakes Based on Passive Sampling: Spatial Trends and Air-Water Exchange.

Science.gov (United States)

Liu, Ying; Wang, Siyao; McDonough, Carrie A; Khairy, Mohammed; Muir, Derek C G; Helm, Paul A; Lohmann, Rainer

2016-05-17

Polyethylene passive sampling was performed to quantify gaseous and freely dissolved polychlorinated biphenyls (PCBs) in the air and water of Lakes Erie and Ontario during 2011-2012. In view of differing physical characteristics and the impacts of historical contamination by PCBs within these lakes, spatial variation of PCB concentrations and air-water exchange across these lakes may be expected. Both lakes displayed statistically similar aqueous and atmospheric PCB concentrations. Total aqueous concentrations of 29 PCBs ranged from 1.5 pg L(-1) in the open lake of Lake Erie (site E02) in 2011 spring to 105 pg L(-1) in Niagara (site On05) in 2012 summer, while total atmospheric concentrations were 7.7-634 pg m(-3) across both lakes. A west-to-east gradient was observed for aqueous PCBs in Lake Erie. River discharge and localized influences (e.g., sediment resuspension and regional alongshore transport) likely dominated spatial trends of aqueous PCBs in both lakes. Air-water exchange fluxes of Σ7PCBs ranged from -2.4 (±1.9) ng m(-2) day(-1) (deposition) in Sheffield (site E03) to 9.0 (±3.1) ng m(-2) day(-1) (volatilization) in Niagara (site On05). Net volatilization of PCBs was the primary trend across most sites and periods. Almost half of variation in air-water exchange fluxes was attributed to the difference in aqueous concentrations of PCBs. Uncertainty analysis in fugacity ratios and mass fluxes in air-water exchange of PCBs indicated that PCBs have reached or approached equilibrium only at the eastern Lake Erie and along the Canadian shore of Lake Ontario sites, where air-water exchange fluxes dominated atmospheric concentrations.

MARS Simulation of Air Cooling Heat Exchanger Connected with PAFS

Energy Technology Data Exchange (ETDEWEB)

Jeon, Seong-Su; Hong, Soon-Joon [FNC Technology Co., Yongin (Korea, Republic of); Bae, Sung-Won; Kwon, Tae-Soon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

Current working time of PAFS cannot meet the required 72 hours cooling capability for the long term Station Black-Out (SBO) situation. Therefore, it is required to improve the design of PAFS for the long term cooling. In order to ensure the long term cooling of PAFS, the heat exchanger tube should be submerged in the water of the PAFS pool. It can be achieved by condensing the steam vented from the PAFS pool. The Air Cooling Heat Exchanger (ACHX) is installed above the PAFS pool. It is expected that the ACHX condenses the steam vented from the PAFS pool and delays the depletion time of the water in the PCCT. Therefore, this paper introduces the MARS-KS1.4 modeling of the ACHX and the performance analysis results on the PAFS connected with the ACHX. For the long term cooling with PAFS, KAERI proposed a new passive air-water combined cooling system. In this study, the modeling of the ACHX and the performance analysis on the PAFS connected with the ACHX were carried out with MARS. MARS predicted the behavior of main thermal-hydraulic variables of ACHX reasonably. Then, it was found that the long term cooling of PAFS could be achieved by the installation of the ACHX in which the tube length is 6 m and the number of tubes is 8000.

Instrumentation and Control Systems for Sodium thermal hydraulic Experiment Loop for Finned-tube sodium-to-Air heat exchanger (SELFA)

Energy Technology Data Exchange (ETDEWEB)

Kim, Byeong Yeon; Kim, Hyung Mo; Cho, Youn Gil; Kim, Jong Man; Ko, Yung Joo; Kang, Byeong Su; Jung, Min Hwan; Jeong, Ji Young [KAERI, Daejeon (Korea, Republic of)

2016-05-15

A forced-draft sodium-to-air heat exchanger (FHX) is a part of decay heat removal system (DHRS) in Prototype Gen-IV Sodium-cooled fast reactor (PGSFR), which is being developed at Korea Atomic Energy Research Institute (KAERI). Sodium thermal hydraulic Experiment Loop for Finned-tube sodium-to-Air heat exchanger (SELFA) is a test facility for verification and validation of the design code for a forced-draft sodium-to-air heat exchanger (FHX). In this paper, we have provided design and fabrication features for the instrumentation and control systems of SELFA. In general, the instrumentation systems and control systems are coupled for measurement and control of process variables. Instrumentation systems have been designed for investigating thermal-hydraulic characteristics of FHX and control systems have been designed to control the main components (e.g. electromagnetic pumps, heaters, valves etc.) required for test in SELFA. In this paper, we have provided configurations of instrumentation and control systems for Sodium thermal hydraulic Experiment Loop for Finned-tube sodium-to-Air heat exchanger (SELFA). The instrumentation and control systems of SELFA have been implemented based on the expected operation ranges and lesson learned from operational experience of 'Sodium integral effect test loop for safety simulation and assessment-1' (STELLA-1)

Observations and Modeling of Turbulent Air-Sea Coupling in Coastal and Strongly Forced Condition

Science.gov (United States)

Ortiz-Suslow, David G.

The turbulent fluxes of momentum, mass, and energy across the ocean-atmosphere boundary are fundamental to our understanding of a myriad of geophysical processes, such as wind-wave generation, oceanic circulation, and air-sea gas transfer. In order to better understand these fluxes, empirical relationships were developed to quantify the interfacial exchange rates in terms of easily observed parameters (e.g., wind speed). However, mounting evidence suggests that these empirical formulae are only valid over the relatively narrow parametric space, i.e. open ocean conditions in light to moderate winds. Several near-surface processes have been observed to cause significant variance in the air-sea fluxes not predicted by the conventional functions, such as a heterogeneous surfaces, swell waves, and wave breaking. Further study is needed to fully characterize how these types of processes can modulate the interfacial exchange; in order to achieve this, a broad investigation into air-sea coupling was undertaken. The primary focus of this work was to use a combination of field and laboratory observations and numerical modeling, in regimes where conventional theories would be expected to breakdown, namely: the nearshore and in very high winds. These seemingly disparate environments represent the marine atmospheric boundary layer at its physical limit. In the nearshore, the convergence of land, air, and sea in a depth-limited domain marks the transition from a marine to a terrestrial boundary layer. Under extreme winds, the physical nature of the boundary layer remains unknown as an intermediate substrate layer, sea spray, develops between the atmosphere and ocean surface. At these ends of the MABL physical spectrum, direct measurements of the near-surface processes were made and directly related to local sources of variance. Our results suggest that the conventional treatment of air-sea fluxes in terms of empirical relationships developed from a relatively narrow set of

Performance Analysis of Window Type Air Conditioning with Addition of Heat Exchanger Equipment

Directory of Open Access Journals (Sweden)

I Ketut Gede Wirawan

2012-11-01

Full Text Available One manner to be used to increase refregration effect is by flowing hot refrigerant out from condensor, it is then touched with the refrigerant out from evaporator on a heat exchanger of counterflow type. Experiment was done by taking samples of pressure at suction (p1 and discharge (p2 of compressor and box temperature (Tr1, Tr2, Tr3, Tr4. By knowing of pressure at suction (p1, the enthalpy into compressor is known. By assuming the process is isentropic (compressor, isobar (condenser and evaporator, and isenthalpy (expansion valve, the enthalpy into condensor, expansion valve and evaporator were known. In 60 minutes, compression work of air conditioning with heat exchanger is 31,588 kJ/kg, and without heat exchanger is 33,796 kJ/kg. Effect refrigeration average with modification is 155,55 kJ/kg and without modification was 153,40 kJ/kg so that coefficient of performance with modification more than without modification. Air conditioning with modification had initial refrigration rate was 67,193 J/s and 0,043 J/s at the end minute, meanwhile, refrigeration without modification had cooling rate at start 66,538 J/s and 0,935 J/s at the end.

Experimental investigation of air side heat transfer and fluid flow performances of multi-port serpentine cross-flow mesochannel heat exchanger

International Nuclear Information System (INIS)

Siddiqui, Faisal A.; Dasgupta, Engr Sarbadaman; Fartaj, Amir

2012-01-01

Highlights: ► Air side heat transfer and flow characteristics of mesochannel cross-flow heat exchanger are studied experimentally. ► Hot ethylene glycol–water mixture (50:50) at constant mass flow rate is used against varying air flow. ► Air side heat transfer and fluid flow key parameters such as Nusselt number, Colburn factor, friction factor are obtained. ► General correlations are proposed for air side heat transfer and fluid flow parameters. - Abstract: Air side force convective heat transfer and flow characteristics of cross-flow mesochannel heat exchanger are investigated experimentally. A series of experiments representing 36 different operating conditions have been conducted on a finned mesochannel heat exchanger through the fully automated dynamic single-phase experimental facility which is capable of handling a wide variety of working fluids in air-to-liquid cross-flow orientation. The mesochannel heat exchanger is made of 15 aluminum slabs with arrays of wavy fins between slabs; 68 one millimeter circular diameter port located at each slab, and the air side frontal area of 304-mm × 304-mm. The ethylene glycol–water mixture as the working fluid in the liquid side was forced to flow through mesochannels maintaining constant inlet temperature and flow rate at 74 °C and 0.0345 kg/s respectively whereas the inlet flowing air into the arrays of wavy fins was changed at four different temperature levels from 28 °C to 43 °C. Frontal air velocity was altered in nine steps from 3 m/s to 11 m/s at each temperature level corresponding range of Reynolds number 752 a a ) and Colburn factor (j a ) were found higher in comparison with other studies.

AirSWOT Measurements of Water Surface Elevations and Hydraulic Gradients over the Yukon Flats, Alaska

Science.gov (United States)

Pitcher, L. H.; Pavelsky, T.; Smith, L. C.; Moller, D.; Altenau, E. H.; Lion, C.; Bertram, M.; Cooley, S. W.

2017-12-01

AirSWOT is an airborne, Ka-band synthetic aperture radar interferometer (InSAR) intended to quantify surface water fluxes by mapping water surface elevations (WSE). AirSWOT will also serve as a calibration/validation tool for the Surface Water and Ocean Topography (SWOT) satellite mission (scheduled for launch in 2021). The hydrology objectives for AirSWOT and SWOT are to measure WSE with accuracies sufficient to estimate hydrologic fluxes in lakes, wetlands and rivers. However, current understanding of the performance of these related though not identical instruments when applied to complex river-lake-wetland fluvial environments remains predominantly theoretical. We present AirSWOT data acquired 15-June-2015 over the Yukon Flats, Alaska, USA, together with in situ field surveys, to assess the accuracy of AirSWOT WSE measurements in lakes and rivers. We use these data to demonstrate that AirSWOT can be used to estimate large-scale hydraulic gradients across wetland complexes. Finally, we present key lessons learned from this AirSWOT analysis for consideration in future campaigns, including: maximizing swath overlap for spatial averaging to minimize uncertainty as well as orienting flight paths parallel to river flow directions to reduce along track aircraft drift for neighboring flight paths. We conclude that spatially dense AirSWOT measurements of river and lake WSEs can improve geospatial understanding of surface water hydrology and fluvial processes.

Correlation between δ18O in precipitation and surface air temperature on different time-scale in China

International Nuclear Information System (INIS)

Zhang Lin; Chen Zongyu; Nie Zhenlong; Liu Fuliang; Jia Yankun; Zhang Xiangyang

2008-01-01

The relation between isotopic compositions of precipitation and surface air temperature provides a unique tool for paleoclimate studies, among which the relation between long term changes in δ 18 O of precipitation and surface air temperature at different stations or in a given location seems to be the most appropriate to paleoclimatic reconstructions. Analysis was conducted on monthly and annual mean δ 18 O content of precipitation and surface air temperature at spatial and fixed locations by using the data of China (1985-2002) in Global Network of Isotopes in Precipitation (GNIP) Database. This study shows that there is a positive correlation between δ 18 O of precipitation and surface air temperature for stations located in north of 34 degree-36 degree N latitudes. The seasonal δ 18 O-temperature gradient derived from the monthly data of 12 stations in northern China is about 0.034% degree C -1 . The δ 18 O-temperature gradient, however, derived from the long term annual mean data of 13 stations, is about 0.052% degree C -1 , which is substantially larger than the seasonal gradient. (authors)

The Contaminant Distribution in a Ventilated Room with Different Air Terminal Devices

DEFF Research Database (Denmark)

Heiselberg, Per; Nielsen, Peter V.

The room ventilation is investigated for three different air terminal devices under isothermal conditions. Velocity distribution in the occupied zone is measured for each air terminal device at different air exchange rates. The maximum air exchange rate is determined on the base of both the throw...... of the jets and the comfort requirements applied to measured air velocities in the occupied zone. Normalized concentration distribution in the test room is determined along a vertical line through the middle of the room as a function of the air exchange rate and the density of the tracer gas. The relative...... ventilation efficiency, , based on the room average concentration is also determined as a function of the air exchange rate and the density of the tracer gas. The influence from the position of the return opening on the relative ventilation efficiency is found for one air terminal device....

Heat transfer and pressure drop amidst frost layer presence for the full geometry of fin-tube heat exchanger

International Nuclear Information System (INIS)

Kim, Sung Jool; Choi, Ho Jin; Ha, Man Yeong; Kim, Seok Ro; Bang, Seon Wook

2010-01-01

The present study numerically solves the flow and thermal fields in the full geometry of heat exchanger modeling with frost layer presence on the heat exchanger surface. The effects of air inlet velocity, air inlet temperature, frost layer thickness, fin pitch, fin thickness, and heat exchanger shape on the thermo-hydraulic performance of a fin-tube heat exchanger are investigated. Heat transfer rate rises with increasing air inlet velocity and temperature, and decreasing frost layer thickness and fin pitch. Pressure drop rises with increasing air inlet velocity and frost layer thickness, and decreasing fin pitch. The effect of fin thickness on heat transfer and pressure drop is negligible. Based on the present results, we derived the correlations, which express pressure drop and temperature difference between air inlet and outlet as a function of air inlet velocity and temperature, as well as frost layer thickness

Compact modeling of a telecom back-up unit powered by air-cooled proton exchange membrane fuel cell

DEFF Research Database (Denmark)

Gao, Xin; Kær, Søren Knudsen

2018-01-01

Applications of proton exchange membrane fuel cells (PEMFC’s) are expanding in portable, automotive and stationary markets. One promising application is the back-up power for telecommunication applications in remote areas where usually air-cooled PMEFC’s are used. An air-cooled PEMFC system is much...

Field Observations of Coastal Air-Sea Interaction

Science.gov (United States)

Ortiz-Suslow, D. G.; Haus, B. K.; Williams, N. J.; Graber, H. C.

2016-12-01

In the nearshore zone wind, waves, and currents generated from different forcing mechanisms converge in shallow water. This can profoundly affect the physical nature of the ocean surface, which can significantly modulate the exchange of momentum, heat, and mass across the air-sea interface. For decades, the focus of air-sea interaction research has been on the open ocean while the shallow water regime has been relatively under-explored. This bears implications for efforts to understand and model various coastal processes, such as mixing, surface transport, and air-sea gas flux. The results from a recent study conducted at the New River Inlet in North Carolina showed that directly measured air-sea flux parameters, such as the atmospheric drag coefficient, are strong functions of space as well as the ambient conditions (i.e. wind speed and direction). The drag is typically used to parameterize the wind stress magnitude. It is generally assumed that the wind direction is the direction of the atmospheric forcing (i.e. wind stress), however significant wind stress steering off of the azimuthal wind direction was observed and was found to be related to the horizontal surface current shear. The authors have just returned from a field campaign carried out within Monterey Bay in California. Surface observations made from two research vessels were complimented by an array of beach and inland flux stations, high-resolution wind forecasts, and satellite image acquisitions. This is a rich data set and several case studies will be analyzed to highlight the importance of various processes for understanding the air-sea fluxes. Preliminary findings show that interactions between the local wind-sea and the shoaling, incident swell can have a profound effect on the wind stress magnitude. The Monterey Bay coastline contains a variety of topographical features and the importance of land-air-sea interactions will also be investigated.

Air/ground heat exchanger (GHE): Modelling, design, performance; Luft-/Erdwaermetauscher EWT: Modellierung, Auslegung und Betriebserfahrungen

Energy Technology Data Exchange (ETDEWEB)

Gerber, A. [Fraunhofer-Inst. fuer Solare Energiesysteme, Freiburg (Germany); Pfafferott, J. [Energieversorgung Spree-Schwarze Elster AG (ESSAG), Cottbus (Germany); Dibowski, G. [Deutsches Zentrum fuer Luft- und Raumfahrt e.V. (DLR), Koeln (Germany). Abt. Sonnenofen

1998-02-01

Air/Ground Heat Exchanger (GHE) utilize soil for seasonal heat storage and are used for air preheating or -cooling. Design and layout require suitable tools which adequately describe the complex heat temperature mechanisms in soils. Since heat densities in soil and heat exchange coefficients between air and GHE are both low, a detailed characterization of the soil and a precise modeling of the heat exchange processes within the GHE are needed. Tools for the design and yield prediction of GHE are presented by way of examples. Results are compared with measured data and both opportunities and limitations of GHEs are discussed using calculated and actual data. (orig.) [Deutsch] Luft-/Erdwaermetauscher EWT nutzen das Erdreich als saisonalen Energiespeicher, sie werden beispielsweise zur Zuluft-Vorerwaermung oder -kuehlung eingesetzt. Die Planung und Auslegung von Luft-/Erdwaermetauschern erfordert geeignete Hilfsmittel, um das komplizierte Temperaturfeld im Erdreich mit ausreichender Genauigkeit abbilden zu koennen. Da die Waermestromdichten im Erdreich und der Waermeuebergang zwischen der Luft im Luft-/Erdwaermetauscher und dem umgebenden Erdreich gering sind, ist sowohl eine detaillierte Abbildung des Erdreichs als auch die Modellierung des Waermeuebergangs im Luft-/Erdwaermetauscher erforderlich. Verfahren zur Auslegung und Ertragsvorhersage von Luft-/Erdwaermetauschern werden vorgestellt und deren Anwendung demonstriert. Die Ergebnisse werden mit Betriebserfahrungen von realisierten Luft-/Erdwrmetauschern verglichen. Moeglichkeiten und Grenzen von Luft-/Erdwaermetauschern werden anhand von Praxis und Simulationsrechnungen diskutiert. (orig.)

Study on flow rate measurement and visualization of helium-air exchange flow through a small opening

International Nuclear Information System (INIS)

Fumizawa, Motoo

1992-01-01

This paper deals with an experimental investigation on buoyancy-driven exchange flows through horizontal and inclined openings. The method of the mass increment was developed to measure the flow rate in helium-air system and a displacement fringe technique was adopted in Mach-Zehnder interferometer to visualize the flow. As the result, the followings were obtained: Flow visualization results indicate that the upward and downward plumes of helium and air break through the opening intermittently, and they swing in the lateral direction through the horizontal opening. It is clearly visualized that the exchange flows through the inclined openings take place smoothly and stably in the separated passages. The inclination angle for the maximum Froude number decreases with increasing length-to-diameter ratio in the helium-air system, on the contrary to Mercer's experimental results in the water-brine system indicating that the angle remains almost constant. (author)

Experimental investigation of water sprayed finned heat exchanger tube bundles

International Nuclear Information System (INIS)

Sommer, A.

1987-07-01

Experimental investigations have been made to study the performance of two finned tube-bundle heat exchangers (FORGO type) when wetted by water sprays. The heat exchangers are designed to cool water in a dry cooling tower. The test-elements had a frontal area of 1 m 2 . The water sprays were created by 20 nozzles, 200 mm in front of the heat exchangers. Air velocities at the inlet of the coolers were in the range 0,8 m/s to 12 m/s and initial temperature differences ITD reached 45 degrees C. The test facility was designed to determine the combined latent and sensible heat fluxes in the wetted heat exchanger, the airside pressure drop and the air humidity and temperature at the exchanger inlet and outlet, and to measure the weight of the water wetting the cooler's surface. The sprayed test elements were investigated in different positions, but most of the experiments were carried out in the position with the fins horizontal

Polychlorinated naphthalenes (PCNs) in the surface soils of the Pearl River Delta, South China: Distribution, sources, and air-soil exchange

International Nuclear Information System (INIS)

Wang Yan; Cheng Zhineng; Li Jun; Luo Chunling; Xu Yue; Li Qilu; Liu Xiang; Zhang Gan

2012-01-01

Polychlorinated naphthalenes (PCNs) are now under review by the Stockholm Convention as a candidate for POPs for their persistence, toxicity, bioaccumulation, and long-range atmospheric transport. Data regarding PCN levels and their environmental fate are sparse in China. The PCN concentration and distribution in soils of the Pearl River Delta were reported, and the average total concentration was 59.9 ± 86.7 pg/g. Tri-CNs was the dominant homologue group, and CN 24 was the most abundant congener. A gradient of PCN levels between more and less developed areas was observed. Based on fugacity fraction results, CN 51 is proposed as a possible source marker for specific combustion emissions. Air-soil exchange of PCNs was estimated by calculating the soil and air fugacity. Fugacity fraction values indicated that tri- to penta-CNs were closer to equilibrium in winter and toward net volatilization in summer, while hexa-CNs experienced net air-to-soil transfer in both seasons. Highlights: ► A gradient of PCN levels between highly and less developed areas was observed. ► CN 51 may be a new specific source indicator compared to other congeners. ► Soil acts as a secondary source in summer and a recipient in winter for PCNs in PRD. ► Low-chlorinated PCNs released from the PRD may transport to North China. - As a potential source during the hot period, low-chlorinated PCNs released from contaminated soils may transport to nearby regions.

EML Surface Air Sampling Program, 1990--1993 data

International Nuclear Information System (INIS)

Larsen, R.J.; Sanderson, C.G.; Kada, J.

1995-11-01

Measurements of the concentrations of specific atmospheric radionuclides in air filter samples collected for the Environmental Measurements Laboratory's Surface Air Sampling Program (SASP) during 1990--1993, with the exception of April 1993, indicate that anthropogenic radionuclides, in both hemispheres, were at or below the lower limits of detection for the sampling and analytical techniques that were used to collect and measure them. The occasional detection of 137 Cs in some air filter samples may have resulted from resuspension of previously deposited debris. Following the April 6, 1993 accident and release of radionuclides into the atmosphere at a reprocessing plant in the Tomsk-7 military nuclear complex located 16 km north of the Siberian city of Tomsk, Russia, weekly air filter samples from Barrow, Alaska; Thule, Greenland and Moosonee, Canada were selected for special analyses. The naturally occurring radioisotopes that the authors measure, 7 Be and 210 Pb, continue to be detected in most air filter samples. Variations in the annual mean concentrations of 7 Be at many of the sites appear to result primarily from changes in the atmospheric production rate of this cosmogenic radionuclide. Short-term variations in the concentrations of 7 Be and 210 Pb continued to be observed at many sites at which weekly air filter samples were analyzed. The monthly gross gamma-ray activity and the monthly mean surface air concentrations of 7 Be, 95 Zr, 137 Cs, 144 Ce, and 210 Pb measured at sampling sites in SASP during 1990--1993 are presented. The weekly mean surface air concentrations of 7 Be, 95 Zr, 137 Cs, 144 Ce, and 210 Pb for samples collected during 1990--1993 are given for 17 sites

Fluxes and exchange rates of radon and oxygen across an air-sea interface

International Nuclear Information System (INIS)

Duenas, C.; Fernandez, M.C.; La Torre, M. de

1986-01-01

The flux of 222 Rn and O 2 from shallow water off the Bay of Malaga has been measured. The mean value of flux of 222 Rn is evaluated to be 74 atoms/m 2 · s. The Bay is a weak source of oxygen to the atmosphere, where the net production of oxygen is found to be 1.82 mol/m 2 · y. Moreover, the gas exchange rates of 222 Rn and O 2 across the air-sea interface has been determined by the radon method. The gas exchange rates and the wind speed have been estimated. (author)

Skating on a Film of Air: Drops Impacting on a Surface

Science.gov (United States)

Kolinski, John M.; Rubinstein, Shmuel M.; Mandre, Shreyas; Brenner, Michael P.; Weitz, David A.; Mahadevan, L.

2012-02-01

The commonly accepted description of drops impacting on a surface typically ignores the essential role of the air that is trapped between the impacting drop and the surface. Here we describe a new imaging modality that is sensitive to the behavior right at the surface. We show that a very thin film of air, only a few tens of nanometers thick, remains trapped between the falling drop and the surface as the drop spreads. The thin film of air serves to lubricate the drop enabling the fluid to skate on the air film laterally outward at surprisingly high velocities, consistent with theoretical predictions. Eventually this thin film of air breaks down as the fluid wets the surface via a spinodal-like mechanism. Our results show that the dynamics of impacting drops are much more complex than previously thought, with a rich array of unexpected phenomena that require rethinking classic paradigms.

Uncertainty quantification of surface-water/groundwater exchange estimates in large wetland systems using Python

Science.gov (United States)

Hughes, J. D.; Metz, P. A.

2014-12-01

Most watershed studies include observation-based water budget analyses to develop first-order estimates of significant flow terms. Surface-water/groundwater (SWGW) exchange is typically assumed to be equal to the residual of the sum of inflows and outflows in a watershed. These estimates of SWGW exchange, however, are highly uncertain as a result of the propagation of uncertainty inherent in the calculation or processing of the other terms of the water budget, such as stage-area-volume relations, and uncertainties associated with land-cover based evapotranspiration (ET) rate estimates. Furthermore, the uncertainty of estimated SWGW exchanges can be magnified in large wetland systems that transition from dry to wet during wet periods. Although it is well understood that observation-based estimates of SWGW exchange are uncertain it is uncommon for the uncertainty of these estimates to be directly quantified. High-level programming languages like Python can greatly reduce the effort required to (1) quantify the uncertainty of estimated SWGW exchange in large wetland systems and (2) evaluate how different approaches for partitioning land-cover data in a watershed may affect the water-budget uncertainty. We have used Python with the Numpy, Scipy.stats, and pyDOE packages to implement an unconstrained Monte Carlo approach with Latin Hypercube sampling to quantify the uncertainty of monthly estimates of SWGW exchange in the Floral City watershed of the Tsala Apopka wetland system in west-central Florida, USA. Possible sources of uncertainty in the water budget analysis include rainfall, ET, canal discharge, and land/bathymetric surface elevations. Each of these input variables was assigned a probability distribution based on observation error or spanning the range of probable values. The Monte Carlo integration process exposes the uncertainties in land-cover based ET rate estimates as the dominant contributor to the uncertainty in SWGW exchange estimates. We will discuss

Microbial communities related to volatile organic compound emission in automobile air conditioning units.

Science.gov (United States)

Diekmann, Nina; Burghartz, Melanie; Remus, Lars; Kaufholz, Anna-Lena; Nawrath, Thorben; Rohde, Manfred; Schulz, Stefan; Roselius, Louisa; Schaper, Jörg; Mamber, Oliver; Jahn, Dieter; Jahn, Martina

2013-10-01

During operation of mobile air conditioning (MAC) systems in automobiles, malodours can occur. We studied the microbial communities found on contaminated heat exchanger fins of 45 evaporators from car MAC systems which were operated in seven different regions of the world and identified corresponding volatile organic compounds. Collected biofilms were examined by scanning electron microscopy and fluorescent in situ hybridization. The detected bacteria were loosely attached to the metal surface. Further analyses of the bacteria using PCR-based single-strand conformation polymorphism and sequencing of isolated 16S rRNA gene fragments identified highly divergent microbial communities with multiple members of the Alphaproteobacteriales, Methylobacteria were the prevalent bacteria. In addition, Sphingomonadales, Burkholderiales, Bacillales, Alcanivorax spp. and Stenotrophomonas spp. were found among many others depending on the location the evaporators were operated. Interestingly, typical pathogenic bacteria related to air conditioning systems including Legionella spp. were not found. In order to determine the nature of the chemical compounds produced by the bacteria, the volatile organic compounds were examined by closed loop stripping analysis and identified by combined gas chromatography/mass spectrometry. Sulphur compounds, i.e. di-, tri- and multiple sulphides, acetylthiazole, aromatic compounds and diverse substituted pyrazines were detected. Mathematical clustering of the determined microbial community structures against their origin identified a European/American/Arabic cluster versus two mainly tropical Asian clusters. Interestingly, clustering of the determined volatiles against the origin of the corresponding MAC revealed a highly similar pattern. A close relationship of microbial community structure and resulting malodours to the climate and air quality at the location of MAC operation was concluded.

Condensation heat transfer coefficient of air-cooled condensing heat exchanger of emergency cooldown tank in long-term passive cooling system

International Nuclear Information System (INIS)

Huh, Seon Jeong; Lee, Hee Joon; Moon, Joo Hyung; Bae, Youngmin; Kim, Young In

2017-01-01

For the design purpose of air-cooled condensing heat exchanger of emergency cooldown tank, average condensation heat transfer coefficient inside a circular tube was reduced by a thermal sizing program using the experimental data of Kim et al. It was compared to the existing condensation heat transfer correlations. Moreover, a sensitivity analysis of both inside condensation and outside air natural convection correlations was performed. Although condensation heat transfer did not play a great role to design over 10 3 W/m 2 /K, the improved Shah's correlation gives the best prediction for the design. Consequently, air natural convection coefficient significantly affects the design of air-cooled condensing heat exchanger. (author)

Scaling properties of fracture surfaces on glass strengthened by ionic exchange

International Nuclear Information System (INIS)

Garza-Mendez, F.J.; Hinojosa-Rivera, M.; Gomez, I.; Sanchez, E.M.

2007-01-01

In this work the results of the statistical topometric analysis of fracture surfaces of soda-lime-silica glass with and without ionic exchange treatment are reported. In this case, the mechanism of substitution is K + -Na + . atomic force microscopy (AFM) was employed to record the topometric data from the fracture surface. The roughness exponent (ζ) and the correlation length (ξ) were calculated by the variable bandwidth method. The analysis for both glasses (subjected and non-subjected to ionic exchange) for ζ shows a value ∼0.8, this value agrees well with that reported in the literature for rapid crack propagation in a variety of materials. The correlation length shows different values for each condition. These results, along with those of microhardness indentations suggest that the self-affine correlation length is influenced by the complex interactions of the stress field of microcracks with that resulting from the collective behavior of the point defects introduced by the strengthening mechanism of ionic exchange

Concentrations, Trends, and Air-Water Exchange of PAHs and PBDEs Derived from Passive Samplers in Lake Superior in 2011.

Science.gov (United States)

Ruge, Zoe; Muir, Derek; Helm, Paul; Lohmann, Rainer

2015-12-01

Polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenylethers (PBDEs) are both currently released into the environment from anthropogenic activity. Both are hence primarily associated with populated or industrial areas, although wildfires can be an important source of PAHs, as well. Polyethylene passive samplers (PEs) were simultaneously deployed in surface water and near surface atmosphere to determine spatial trends and air-water gaseous exchange of 21 PAHs and 11 PBDEs at 19 sites across Lake Superior in 2011. Surface water and atmospheric PAH concentrations were greatest at urban sites (up to 65 ng L(-1) and 140 ng m(-3), respectively, averaged from June to October). Near populated regions, PAHs displayed net air-to-water deposition, but were near equilibrium off-shore. Retene, probably depositing following major wildfires in the region, dominated dissolved PAH concentrations at most Lake Superior sites. Atmospheric and dissolved PBDEs were greatest near urban and populated sites (up to 6.8 pg L(-1) and 15 pg m(-3), respectively, averaged from June to October), dominated by BDE-47. At most coastal sites, there was net gaseous deposition of BDE-47, with less brominated congeners contributing to Sault Ste. Marie and eastern open lake fluxes. Conversely, the central open lake and Eagle Harbor sites generally displayed volatilization of PBDEs into the atmosphere, mainly BDE-47.

Focus State Roadway Departure Safety Plans and High Friction Surface Treatments Peer Exchange : an RPSCB Peer Exchange

Science.gov (United States)

2014-08-01

This report summarizes the Focus State Roadway Departure Safety Plans and High Friction Surface Treatments Peer Exchange, held in Birmingham, Alabama, sponsored by the Federal Highway Administration (FHWA) Office of Safetys Roadway Safety Professi...

Global surface temperature in relation to northeast monsoon rainfall ...

Indian Academy of Sciences (India)

is observed that the meridional gradient in surface air temperature anomalies between Europe and ... Surface air tempera- ture is one of the factors that influence monsoon variability. The distribution of surface air temper- ature over land and sea determines the locations ..... Asia, north Indian Ocean, northeast Russia and.

Impact of Bay-Breeze Circulations on Surface Air Quality and Boundary Layer Export

Science.gov (United States)

Loughner, Christopher P.; Tzortziou, Maria; Follette-Cook, Melanie; Pickering, Kenneth E.; Goldberg, Daniel; Satam, Chinmay; Weinheimer, Andrew; Crawford, James H.; Knapp, David J.; Montzka, Denise D.;

Radiation control report on intermediate heat exchanger replacement and related works

International Nuclear Information System (INIS)

Kanou, Y.; Yamanaka, T.; Sasajima, T.; Hoshiba, H.; Emori, S.; Shindou, K.

2002-03-01

The 13th periodical inspection of the experimental fast reactor JOYO is being made from Jun. 2000 to Jan. 2003. While this inspection, from the end of Oct. 2000 to Nov. 2001, the MK-III modification work on heat transport system was made in lower region of the reactor containment vessel in the reactor facility (under floor area). In the MK-III modification work, the works important to radiation control were the replacement of intermediate heat exchangers (IHXs) and fixtures, and the picking out of the surveillance material from primary heat transport piping carried out in the maintenance building. Because the working areas of these works were executed in small space around the complicated primary heat transport piping, workability was bad and dose rate from the corrosion products (CP) in piping or fixtures was high. In such condition, radiation control was performed mainly concerned about external exposure. The planted total external exposure of the IHX replacement and related works was 7135 man-mSv (target of total dose control: less than 5708 man-mSv, 80% of the plan), derived from special radiation work plants for segmental works, concerned about work procedure, number of workers, period of work, dose rate of working area and surface dose rate of equipments. The special radiation control organization was established for such long and large-scale work. The spatial organization held detailed discussion about radiation control of this work with the execution section and contractors appropriately, performance careful external/internal exposure control and surface contamination control and made efforts to reduce te external exposure thoroughly. As a result of these action, the total external exposure was 2386 man·mSv (≅33% of the plan, ≅42% of the target) and the maximum individual exposure were 24.7 mSv for staffs and 21.7mSv for contractors. The dose rate, surface contamination and air contamination while the works were kept under the control level with the

Dry deposition and soil-air gas exchange of polychlorinated biphenyls (PCBs) in an industrial area.

Science.gov (United States)

Bozlaker, Ayse; Odabasi, Mustafa; Muezzinoglu, Aysen

2008-12-01

Ambient air and dry deposition, and soil samples were collected at the Aliaga industrial site in Izmir, Turkey. Atmospheric total (particle+gas) Sigma(41)-PCB concentrations were higher in summer (3370+/-1617 pg m(-3), average+SD) than in winter (1164+/-618 pg m(-3)), probably due to increased volatilization with temperature. Average particulate Sigma(41)-PCBs dry deposition fluxes were 349+/-183 and 469+/-328 ng m(-2) day(-1) in summer and winter, respectively. Overall average particulate deposition velocity was 5.5+/-3.5 cm s(-1). The spatial distribution of Sigma(41)-PCB soil concentrations (n=48) showed that the iron-steel plants, ship dismantling facilities, refinery and petrochemicals complex are the major sources in the area. Calculated air-soil exchange fluxes indicated that the contaminated soil is a secondary source to the atmosphere for lighter PCBs and as a sink for heavier ones. Comparable magnitude of gas exchange and dry particle deposition fluxes indicated that both mechanisms are equally important for PCB movement between air and soil in Aliaga.

Investigation of the influence of atmospheric stability and turbulence on land-atmosphere exchange

Science.gov (United States)

Osibanjo, O.; Holmes, H.

2015-12-01

Surface energy fluxes are exchanged between the surface of the earth and the atmosphere and impact weather, climate, and air quality. The radiation from the sun triggers the surface-atmosphere interaction during the day as heat is transmitted to the surface and the surface heats the air directly above generating wind (i.e., thermal turbulence) that transports heat, moisture, and momentum in the atmospheric boundary layer (ABL). This process is impacted by greenhouse gasses (i.e., water vapor, carbon dioxide and other trace gases) that absorb heat emitted by the earth's surface. The concentrations of atmospheric greenhouse gasses are increasing leading to changes in ABL dynamics as a result of the changing surface energy balance. The ABL processes are important to characterize because they are difficult to parameterize in global and regional scale atmospheric models. Empirical data can be collected using eddy covariance micrometeorological methods to measure turbulent fluxes (e.g., sensible heat, moisture, and CO2) and quantify the exchange between the surface and the atmosphere. The objective of this work is to calculate surface fluxes using observational data collected during one week in September 2014 from a monitoring site in Echo, Oregon. The site is located in the Columbia Basin with rolling terrain, irrigated farmland, and over 100 wind turbines. The 10m tower was placed in a small valley depression to isolate nighttime cold air pools. This work will present observations of momentum, sensible heat, moisture, and carbon dioxide fluxes from data collected at a sampling frequency of 10Hz at four heights. Atmospheric stability is determined using Monin-Obukov length and flux Richardson number, and the impact of stability on surface-atmosphere exchange is investigated. This work will provide a better understanding of surface fluxes and mixing, particularly during stable ABL periods, and the results can be used to compare with numerical models.

De novo transcriptome analysis of pneumatophores (modified roots in the true mangrove species Avicennia marina and identification of the genes related to root gas exchange

Directory of Open Access Journals (Sweden)

Purushothaman Natarajan

2017-10-01

Full Text Available Mangroves plants which grow in estuaries naturally tolerate extreme conditions of high salinity (90 ppt and high light intensity. Avicennia marina is a true mangrove tree species with physiological adaptations like modified root system (pneumatophores and salt excretion glands in leaves as its one of the unique features to consider. The pneumatophores are a special type of roots with negative geotropism that project above the water surface or the level of flooded soils [1]. In contact with air these roots develop lenticels, which improve gas exchange between roots and environment [2]. In swamps and wetlands the presence of pneumatophores facilitates oxygen diffusion through the tissues, maintaining levels adequate for cellular respiration [3]. Objective of this study was to perform the whole transcriptome analysis of pneumatophore tissue of A. marina by Illumina sequencing and to identify putative genes involved in process of root gas exchange. We generated 19.73 million of paired-end reads and assembled into 86,856 unigenes with an average length of 772 bp. Further, annotation, tissue specific gene expression and genes related to root gas exchange will be presented.

EML Surface Air Sampling Program, 1990--1993 data

Energy Technology Data Exchange (ETDEWEB)

Larsen, R.J.; Sanderson, C.G.; Kada, J.

1995-11-01

Measurements of the concentrations of specific atmospheric radionuclides in air filter samples collected for the Environmental Measurements Laboratory`s Surface Air Sampling Program (SASP) during 1990--1993, with the exception of April 1993, indicate that anthropogenic radionuclides, in both hemispheres, were at or below the lower limits of detection for the sampling and analytical techniques that were used to collect and measure them. The occasional detection of {sup 137}Cs in some air filter samples may have resulted from resuspension of previously deposited debris. Following the April 6, 1993 accident and release of radionuclides into the atmosphere at a reprocessing plant in the Tomsk-7 military nuclear complex located 16 km north of the Siberian city of Tomsk, Russia, weekly air filter samples from Barrow, Alaska; Thule, Greenland and Moosonee, Canada were selected for special analyses. The naturally occurring radioisotopes that the authors measure, {sup 7}Be and {sup 210}Pb, continue to be detected in most air filter samples. Variations in the annual mean concentrations of {sup 7}Be at many of the sites appear to result primarily from changes in the atmospheric production rate of this cosmogenic radionuclide. Short-term variations in the concentrations of {sup 7}Be and {sup 210}Pb continued to be observed at many sites at which weekly air filter samples were analyzed. The monthly gross gamma-ray activity and the monthly mean surface air concentrations of {sup 7}Be, {sup 95}Zr, {sup 137}Cs, {sup 144}Ce, and {sup 210}Pb measured at sampling sites in SASP during 1990--1993 are presented. The weekly mean surface air concentrations of {sup 7}Be, {sup 95}Zr, {sup 137}Cs, {sup 144}Ce, and {sup 210}Pb for samples collected during 1990--1993 are given for 17 sites.

Magnon dispersion relation and exchange interactions in MnF2

DEFF Research Database (Denmark)

Nikotin, O.; Lindgård, Per-Anker; Dietrich, O. W.

1969-01-01

The magnon dispersion relation for MnF2 at 4·2 °K has been measured by means of the triple-axis neutron scattering technique along the symmetry lines in the (010) plane of the Brillouin zone. Using an exact dipole model, the three nearest-neighbour exchange constants were found to be J1 = 0·028 ± 0......·001 mev, J2 = -0·152 ± 0·001 mev and J3 = -0·004 ± 0·001 mev. The second moment was also calculated with this model. The density of magnon states was evaluated by applying a six-parameter simulation of the dispersion surface. The critical points in the density of states agree well with those obtained...... by optical double-magnon experiments, whereas the detailed shape of the density of states differs significantly, indicating that the effect of magnon-magnon interactions rather than that of distant-neighbour exchange is of primary importance in the optical measurements....

Experimental study on heat transfer performance of fin-tube exchanger and PSHE for waste heat recovery

Science.gov (United States)

Chen, Ting; Bae, Kyung Jin; Kwon, Oh Kyung

2018-02-01

In this paper, heat transfer characteristics of fin-tube heat exchanger and primary surface heat exchanger (PSHE) used in waste heat recovery were investigated experimentally. The flow in the fin-tube heat exchanger is cross flow and in PSHE counter flow. The variations of friction factor and Colburn j factor with air mass flow rate, and Nu number with Re number are presented. Various comparison methods are used to evaluate heat transfer performance, and the results show that the heat transfer rate of the PSHE is on average 17.3% larger than that of fin-tube heat exchanger when air mass flow rate is ranging from 1.24 to 3.45 kg/min. However, the PSHE causes higher pressure drop, and the fin-tube heat exchanger has a wider application range which leads to a 31.7% higher value of maximum heat transfer rate compared to that of the PSHE. Besides, under the same fan power per unit frontal surface, a higher heat transfer rate value is given in the fin-tube heat exchanger.

Heat Exchange with Air and Temperature Profile of a Moving Oversize Tire

Science.gov (United States)

Grinchuk, P. S.; Fisenko, S. P.

2016-11-01

A one-dimensional mathematical model of heat transfer in a tire with account for the deformation energy dissipation and heat exchange of a moving tire with air has been developed. The mean temperature profiles are calculated and transition to a stationary thermal regime is considered. The influence of the rate of energy dissipation and of effective thermal conductivity of rubber on the temperature field is investigated quantitatively.

Cycle performance of alternative refrigerants for domestic air-conditioning system based on a small finned tube heat exchanger

International Nuclear Information System (INIS)

Cheng, Song; Wang, Shuangfeng; Liu, Zhongmin

2014-01-01

In order to find alternative refrigerants which exhibit both favorable cycle performance and environmental friendliness, R32 and R290 were utilized to contrast to R22 and R410A as substitutes in the present study. The experiments were conducted with a 5 mm finned tube heat exchanger based on the enthalpy method in a small split household air conditioner. The results showed that in nominal cooling conditions, the COP R of R32 and R290 were 26.8% and 20.4% higher than R22, 7.3% and 2.1% higher than R410A. And in nominal heating conditions, the COP HR of R32 and R290 were both 11.0% higher than R22, 5.3% higher than R410A. The systems with R290 and R32 have similar capacities to that with R22 and R410A in heating mode, but a relatively huge difference of capacities in cooling mode. In consideration of charge amount, R290 could be considered as the most superior alternative refrigerant in air conditioners with the small finned tube heat exchanger. - Highlights: •Comparisons are made in the air conditioner system based on 5 mm tube fin heat exchanger. •The R22 system has a similar performance to others in heating mode while a huge difference in cooling mode. •The optimal charge of R290 is reduced with nearly no decline in the capacity and COP. •SLHX is attached to the system of R290 and successfully promote safety and capacity. •Heat loads are taken into account to evaluate the advantages and disadvantages of R290 and R32

Measurement of air exchange rates in different indoor environments using continuous CO2 sensors

Institute of Scientific and Technical Information of China (English)

Yan YOU; Can Niu; Jian Zhou; Yating Liu; Zhipeng Bai; Jiefeng Zhang; Fei He; Nan Zhang

2012-01-01

A new air exchange rate (AER) monitoring method using continuous CO2 sensors was developed and validated through both laboratory experiments and field studies.Controlled laboratory simulation tests were conducted in a 1-m3 environmental chamber at different AERs (0.1-10.0 hr-1).AERs were determined using the decay method based on box model assumptions.Field tests were conducted in classrooms,dormitories,meeting rooms and apartments during 2-5 weekdays using CO2 sensors coupled with data loggers.Indoor temperature,relative humidity (RH),and CO2 concentrations were continuously monitored while outdoor parameters combined with on-site climate conditions were recorded.Statistical results indicated that good laboratory performance was achieved:duplicate precision was within 10％,and the measured AERs were 90％-120％ of the real AERs.Average AERs were 1.22,1.37,1.10,1.91 and 0.73 hr-1 in dormitories,air-conditioned classrooms,classrooms with an air circulation cooling system,reading rooms,and meeting rooms,respectively.In an elderly particulate matter exposure study,all the homes had AER values ranging from 0.29 to 3.46 hr-1 in fall,and 0.12 to 1.39 hr-1 in winter with a median AER of 1.15.

Measurement of air exchange rates in different indoor environments using continuous CO2 sensors.

Science.gov (United States)

You, Yan; Niu, Can; Zhou, Jian; Liu, Yating; Bai, Zhipeng; Zhang, Jiefeng; He, Fei; Zhang, Nan

2012-01-01

A new air exchange rate (AER) monitoring method using continuous CO2 sensors was developed and validated through both laboratory experiments and field studies. Controlled laboratory simulation tests were conducted in a 1-m3 environmental chamber at different AERs (0.1-10.0 hr(-1)). AERs were determined using the decay method based on box model assumptions. Field tests were conducted in classrooms, dormitories, meeting rooms and apartments during 2-5 weekdays using CO2 sensors coupled with data loggers. Indoor temperature, relative humidity (RH), and CO2 concentrations were continuously monitored while outdoor parameters combined with on-site climate conditions were recorded. Statistical results indicated that good laboratory performance was achieved: duplicate precision was within 10%, and the measured AERs were 90%-120% of the real AERs. Average AERs were 1.22, 1.37, 1.10, 1.91 and 0.73 hr(-1) in dormitories, air-conditioned classrooms, classrooms with an air circulation cooling system, reading rooms, and meeting rooms, respectively. In an elderly particulate matter exposure study, all the homes had AER values ranging from 0.29 to 3.46 hr(-1) in fall, and 0.12 to 1.39 hr(-1) in winter with a median AER of 1.15.

COMPUTER PROGRAM FOR CALCULATION MICROCHANNEL HEAT EXCHANGERS FOR AIR CONDITIONING SYSTEMS

Directory of Open Access Journals (Sweden)

Olga V. Olshevska

2016-08-01

Full Text Available Creating a computer program to calculate microchannel air condensers to reduce design time and carrying out variant calculations. Software packages for thermophysical properties of the working substance and the coolant, the correlation equation for calculating heat transfer, aerodynamics and hydrodynamics, the thermodynamic equations for the irreversible losses and their minimization in the heat exchanger were used in the process of creating. Borland Delphi 7 is used for creating software package.

Air-water gas exchange and CO2 flux in a mangrove-dominated estuary

Science.gov (United States)

Ho, David T.; Ferrón, Sara; Engel, Victor C.; Larsen, Laurel G.; Barr, Jordan G.

2014-01-01

Mangrove forests are highly productive ecosystems, but the fate of mangrove-derived carbon remains uncertain. Part of that uncertainty stems from the fact that gas transfer velocities in mangrove-surrounded waters are not well determined, leading to uncertainty in air-water CO2 fluxes. Two SF6 tracer release experiments were conducted to determine gas transfer velocities (k(600) = 8.3 ± 0.4 and 8.1 ± 0.6 cm h−1), along with simultaneous measurements of pCO2 to determine the air-water CO2 fluxes from Shark River, Florida (232.11 ± 23.69 and 171.13 ± 20.28 mmol C m−2 d−1), an estuary within the largest contiguous mangrove forest in North America. The gas transfer velocity results are consistent with turbulent kinetic energy dissipation measurements, indicating a higher rate of turbulence and gas exchange than predicted by commonly used wind speed/gas exchange parameterizations. The results have important implications for carbon fluxes in mangrove ecosystems.

Conceptual Design of a Condensing Heat Exchanger for Space Systems Using Porous Media

Science.gov (United States)

Hasan, Mohammad M.; Khan, Lutful I.; Nayagam, Vedha; Balasubramaniam, Ramaswamy

2006-01-01

Condensing heat exchangers are used in many space applications in the thermal and humidity control systems. In the International Space Station (ISS), humidity control is achieved by using a water cooled fin surface over which the moist air condenses, followed by "slurper bars" that take in both the condensate and air into a rotary separator and separates the water from air. The use of a cooled porous substrate as the condensing surface provides and attractive alternative that combines both heat removal as well as liquid/gas separation into a single unit. By selecting the pore sizes of the porous substrate a gravity independent operation may also be possible with this concept. Condensation of vapor into and on the porous surface from the flowing air and the removal of condensate from the porous substrate are the critical processes involved in the proposed concept. This paper describes some preliminary results of the proposed condensate withdrawal process and discusses the on-going design and development work of a porous media based condensing heat exchanger at the NASA Glenn Research Center in collaboration with NASA Johnson Space Center.

Towards constraining the stratosphere-troposphere exchange of radiocarbon: strategies of stratospheric 14CO2 measurements using AirCore

Science.gov (United States)

Chen, Huilin; Paul, Dipayan; Meijer, Harro; Miller, John; Kivi, Rigel; Krol, Maarten

2016-04-01

Radiocarbon (14C) plays an important role in the carbon cycle studies to understand both natural and anthropogenic carbon fluxes, but also in atmospheric chemistry to constrain hydroxyl radical (OH) concentrations in the atmosphere. Apart from the enormous 14C emissions from nuclear bomb testing in the 1950s and 1960s, radiocarbon is primarily produced in the stratosphere due to the cosmogenic production. To this end, better understanding the stratospheric radiocarbon source is very useful to advance the use of radiocarbon for these applications. However, stratospheric 14C observations have been very limited so that there are large uncertainties on the magnitude and the location of the 14C production as well as the transport of radiocarbon from the stratosphere to the troposphere. Recently we have successfully made stratospheric 14C measurements using AirCore samples from Sodankylä, Northern Finland. AirCore is an innovative atmospheric sampling system, which passively collects atmospheric air samples into a long piece of coiled stainless steel tubing during the descent of a balloon flight. Due to the relatively low cost of the consumables, there is a potential to make such AirCore profiling in other parts of the world on a regular basis. In this study, we simulate the 14C in the atmosphere and assess the stratosphere-troposphere exchange of radiocarbon using the TM5 model. The Sodankylä radiocarbon measurements will be used to verify the performance of the model at high latitude. Besides this, we will also evaluate the influence of different cosmogenic 14C production scenarios and the uncertainties in the OH field on the seasonal cycles of radiocarbon and on the stratosphere-troposphere exchange, and based on the results design a strategy to set up a 14C measurement program using AirCore.

Characteristics of floc formation of anion and cation exchange resin in precoat filter using powdered ion exchange resin

International Nuclear Information System (INIS)

Adachi, Tetsurou; Sawa, Toshio; Shindoh, Toshikazu.

1989-01-01

The filtration performance of mixed filter aid consisting of powdered anion and cation exchange resins used in the precoat filter is closely related to the characteristics of floc formation. The physical, chemical and electrochemical properties of powdered ion exchange resin were measured and the factors related to floc formation of anion and cation exchange resin were investigated by measuring the specific settle volume of resin floc as an evaluating index. It was found that these factors were mixing ratio, nature of resins and particle size of resins. In addition, it was assumed on the bases of these results that the amount of resin floc was related to sum of the surface electric charges of both resins. The filling ratio of resin floc was related to their product by multiplication and an experimental expression was obtained. The specific settle volume of resin floc could then be simulated by particle size, surface area, ion exchange capacity and degree of ionization of the powdered ion exchange resin. (author)

Characteristics of floc formation of anion and cation exchange resin in precoat filter using powdered ion exchange resin

Energy Technology Data Exchange (ETDEWEB)

Adachi, Tetsurou (Nitto Denko Corp., Ibaraki, Osaka (Japan)); Sawa, Toshio; Shindoh, Toshikazu

1989-09-01

The filtration performance of mixed filter aid consisting of powdered anion and cation exchange resins used in the precoat filter is closely related to the characteristics of floc formation. The physical, chemical and electrochemical properties of powdered ion exchange resin were measured and the factors related to floc formation of anion and cation exchange resin were investigated by measuring the specific settle volume of resin floc as an evaluating index. It was found that these factors were mixing ratio, nature of resins and particle size of resins. In addition, it was assumed on the bases of these results that the amount of resin floc was related to sum of the surface electric charges of both resins. The filling ratio of resin floc was related to their product by multiplication and an experimental expression was obtained. The specific settle volume of resin floc could then be simulated by particle size, surface area, ion exchange capacity and degree of ionization of the powdered ion exchange resin. (author).

Gas exchange rates across the sediment-water andd air-water interfaces in south San Francisco Bay

International Nuclear Information System (INIS)

Hartman, B.; Hammond, D.E.

1984-01-01

Radon 222 concentrations in the water and sedimentary columns and radon exchange rates across the sediment-water and air-water interfaces have been measured in a section of south San Francisco Bay. Two independent methods have been used to determine sediment-water exchange rates, and the annual averages of these methods agree within the uncertainity of the determinations, about 20%. The annual average of bethic fluxes from shoal areas is nearly a factor of 2 greater than fluxes from the channel areas. Fluxes from the shoal and channel areas exceed those expected from simple molecular diffusion by factors of 4 and 2, respectively, apparently due to macrofaunal irrigation. Values of the gas transfer coefficient for radon exchange across the air-water inteface were determined by constructing a radon mass balance for the water column and by direct measurement using floating chambers. The chamber method appears to yield results which are too high. Transfer coefficients computed using the mass balance method range from 0.4 m/day to 1.8 m/day, with a 6-year average of 1.0 m/day. Gas exchange is linearly dependent upon wind speed over a wind speed range of 3.2--6.4 m/s, but shows no dependence upon current velocity. Gas transfer coefficients predicted from an empirical relationship between gas exchange rates and wind speed observed in lakes and the oceans are within 30% of the coefficients determined from the radon mass balance and are considerably more accurate than coefficients predicted from theoretical gas exchange models

Gas exchange rates across the sediment-water and air-water interfaces in south San Francisco Bay

Science.gov (United States)

Hartman, Blayne; Hammond, Douglas E.

1984-01-01

Radon 222 concentrations in the water and sedimentary columns and radon exchange rates across the sediment-water and air-water interfaces have been measured in a section of south San Francisco Bay. Two independent methods have been used to determine sediment-water exchange rates, and the annual averages of these methods agree within the uncertainty of the determinations, about 20%. The annual average of benthic fluxes from shoal areas is nearly a factor of 2 greater than fluxes from the channel areas. Fluxes from the shoal and channel areas exceed those expected from simple molecular diffusion by factors of 4 and 2, respectively, apparently due to macrofaunal irrigation. Values of the gas transfer coefficient for radon exchange across the air-water interface were determined by constructing a radon mass balance for the water column and by direct measurement using floating chambers. The chamber method appears to yield results which are too high. Transfer coefficients computed using the mass balance method range from 0.4 m/day to 1.8 m/day, with a 6-year average of 1.0 m/day. Gas exchange is linearly dependent upon wind speed over a wind speed range of 3.2–6.4 m/s, but shows no dependence upon current velocity. Gas transfer coefficients predicted from an empirical relationship between gas exchange rates and wind speed observed in lakes and the oceans are within 30% of the coefficients determined from the radon mass balance and are considerably more accurate than coefficients predicted from theoretical gas exchange models.

New insights into proton surface mobility processes in PEMFC catalysts using isotopic exchange methods.

Science.gov (United States)

Ferreira-Aparicio, Paloma

2009-09-01

The surface chemistry and the adsorption/desorption/exchange behavior of a proton-exchange membrane fuel cell catalyst are analyzed as a case study for the development of tailor-made support materials of enhanced performance and stability. By using H2, D2, and CO as probe molecules, the relevance of some surface functional groups of the catalyst support on several diffusion processes taking place during the adsorption is shown. Sulfonic groups associated with the vulcanized carbon black surface have been detected by means of spectroscopic techniques (X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy) and by analysis of the desorbed products during temperature-programmed desorption tests by mass spectrometry. Such hydrophilic species have been observed to favor proton surface mobility and exchange with Pt-adsorbed deuterium even in the presence of adsorbed CO. This behavior is relevant both for the proper characterization of these kinds of catalysts using adsorption probes and for the design of new surface-modified carbon supports, enabling alternative proton-transfer pathways throughout the catalytic layers toward the membrane.

Concentration of 7Be in surface air at Suva, Fiji

International Nuclear Information System (INIS)

Garimella, S.; Koshy, K.

1998-01-01

A high-volume air sampler and a high-resolution gamma-ray spectrometer have been in use since August 1997 at the University of the South Pacific to measure the activity of 7 Be in surface air at Suva, the capital city of Fiji. Preliminary measurements during August - November 1997 indicate that the average concentration of 7 Be in surface air is approximately 4.0 mBq m -3 . Further measurements are in progress

Measuring air layer volumes retained by submerged floating-ferns Salvinia and biomimetic superhydrophobic surfaces

Directory of Open Access Journals (Sweden)

Matthias J. Mayser

2014-06-01

Full Text Available Some plants and animals feature superhydrophobic surfaces capable of retaining a layer of air when submerged under water. Long-term air retaining surfaces (Salvinia-effect are of high interest for biomimetic applications like drag reduction in ship coatings of up to 30%. Here we present a novel method for measuring air volumes and air loss under water. We recorded the buoyancy force of the air layer on leaf surfaces of four different Salvinia species and on one biomimetic surface using a highly sensitive custom made strain gauge force transducer setup. The volume of air held by a surface was quantified by comparing the buoyancy force of the specimen with and then without an air layer. Air volumes retained by the Salvinia-surfaces ranged between 0.15 and 1 L/m2 depending on differences in surface architecture. We verified the precision of the method by comparing the measured air volumes with theoretical volume calculations and could find a good agreement between both values. In this context we present techniques to calculate air volumes on surfaces with complex microstructures. The introduced method also allows to measure decrease or increase of air layers with high accuracy in real-time to understand dynamic processes.

Parametric simulation and experimental analysis of earth air heat exchanger with solar air heating duct

Directory of Open Access Journals (Sweden)

Sanjeev Jakhar

2016-06-01

Full Text Available Earth air heat exchanger (EAHE systems are insufficient to meet the thermal comfort requirements in winter conditions. The low heating potential of such systems can be improved by integrating the system with solar air heating duct (SAHD. The aim of this paper is to present a model to estimate the heating potential for EAHE system with and without SAHD. The model is generated using TRNSYS 17 simulation tool and validated against experimental investigation on an experimental set-up in Ajmer, India. The experiment was done during the winter season, where the system was evaluated for different inlet flow velocities, length and depth of buried pipe. From the experimentation, it was observed that the depth of 3.7 m is sufficient for pipe burial and the 34 m length of pipe is sufficient to get optimum EAHE outlet temperature. It is also observed that increase in flow velocity results in drop in EAHE outlet temperature, while room temperature is found to increase for higher velocities (5 m/s. The COP of the system also increased up to 6.304 when assisted with solar air heating duct. The results obtained from the experiment data are in good agreement with simulated results within the variation of up to 7.9%.

Polycyclic aromatic hydrocarbons in surface soil across the Tibetan Plateau: Spatial distribution, source and air–soil exchange

International Nuclear Information System (INIS)

Wang, Chuanfei; Wang, Xiaoping; Gong, Ping; Yao, Tandong

2014-01-01

There are limited data on polycyclic aromatic hydrocarbons (PAHs) in both the atmosphere and soil of the Tibetan Plateau (TP). Concentrations of PAHs were therefore measured in 13 XAD resin-based passive air samplers and 41 surface (0–5 cm) soil samples across the TP. The average concentration of atmospheric PAHs was 5.55 ng/m 3 , which was lower than that reported for other background areas, but higher than the Arctic. Concentrations in the soils fell in a wide range from 5.54 to 389 ng/g, with an average of 59.9 ng/g. Elevation was found to play an important role in determining the spatial distribution of soil PAHs. The air–soil exchange state showed that the soils of the TP will likely remain as a sink for high molecular weight PAHs, but may become a potential “secondary source” for low molecular weight PAHs. Highlights: • The levels of PAHs in air and soil of the Tibetan Plateau were relatively lower than other background region of world. • The soil PAHs concentration decreased with the increase of elevation. • The Tibetan Plateau will likely remain as a sink for high molecular weight PAHs. • The Tibetan Plateau may become a potential “secondary source” for low molecular weight PAHs. -- The Tibetan soil will likely remain as a sink for high molecular weight PAHs, but may become a potential “secondary source” for low molecular weight PAHs

Air-sea exchange fluxes of synthetic polycyclic musks in the North Sea and the Arctic.

Science.gov (United States)

Xie, Zhiyong; Ebinghaus, Ralf; Temme, Christian; Heemken, Olaf; Ruck, Wolfgang

2007-08-15

Synthetic polycyclic musk fragrances Galaxolide (HHCB) and Tonalide (AHTN) were measured simultaneously in air and seawater in the Arctic and the North Sea and in the rural air of northern Germany. Median concentrations of gas-phase HHCB and AHTN were 4 and 18 pg m(-3) in the Arctic, 28 and 18 pg m(-3) in the North Sea, and 71 and 21 pg m(-3) in northern Germany, respectively. Various ratios of HHCB/AHTN implied that HHCB is quickly removed by atmospheric degradation, while AHTN is relatively persistent in the atmosphere. Dissolved concentrations ranged from 12 to 2030 pg L(-1) for HHCB and from below the method detection limit (3 pg L(-1)) to 965 pg L(-1) for AHTN with median values of 59 and 23 pg L(-1), respectively. The medians of volatilization fluxes for HHCB and AHTN were 27.2 and 14.2 ng m(-2) day(-1) and the depositional fluxes were 5.9 and 3.3 ng m(-2) day(-1), respectively, indicating water-to-air volatilization is a significant process to eliminate HHCB and AHTN from the North Sea. In the Arctic, deposition fluxes dominated the air-sea gas exchange of HHCB and AHTN, suggesting atmospheric input controls the levels of HHCB and AHTN in the polar region.

Experimental investigation and CFD simulation of multi-pipe earth-to-air heat exchangers (EAHEs) flow performance

Science.gov (United States)

Amanowicz, Łukasz; Wojtkowiak, Janusz

2017-11-01

In this paper the experimentally obtained flow characteristics of multi-pipe earth-to-air heat exchangers (EAHEs) were used to validate the EAHE flow performance numerical model prepared by means of CFD software Ansys Fluent. The cut-cell meshing and the k-ɛ realizable turbulence model with default coefficients values and enhanced wall treatment was used. The total pressure losses and airflow in each pipe of multi-pipe exchangers was investigated both experimentally and numerically. The results show that airflow in each pipe of multi-pipe EAHE structures is not equal. The validated numerical model can be used for a proper designing of multi-pipe EAHEs from the flow characteristics point of view. The influence of EAHEs geometrical parameters on the total pressure losses and airflow division between the exchanger pipes can be also analysed. Usage of CFD for designing the EAHEs can be helpful for HVAC engineers (Heating Ventilation and Air Conditioning) for optimizing the geometrical structure of multi-pipe EAHEs in order to save the energy and decrease operational costs of low-energy buildings.

Safety-related control air systems - approved 1977

International Nuclear Information System (INIS)

Anon.

1978-01-01

This standard applies to those portions of the control air system that furnish air required to support, control, or operate systems or portions of systems that are safety related in nuclear power plants. This standard relates only to the air supply system(s) for safety-related air operated devices and does not apply to the safety-related air operated device or to air operated actuators for such devices. The objectives of this standard are to provide (1) minimum system design requirements for equipment, piping, instruments, controls, and wiring that constitute the air supply system; and (2) the system and component testing and maintenance requirements

Concentration of 7Be in surface air at Suva, Fiji

International Nuclear Information System (INIS)

Garimella, S.; Koshy, K.

1998-01-01

A high-volume air sampler and a high-resolution gamma-ray spectrometer have been in use since August 1997 at the University of the South Pacific to measure the activity of 7 Be in surface air at Suva, the capital city of Fiji. Preliminary measurements during August-November 1997 indicate that the average concentration of 7 Be in surface air is approximately 4.0 mBq m -3 . Further measurements are in progress. (author). 4 refs., 1 fig

Air and surface contamination patterns of meticillin-resistant Staphylococcus aureus on eight acute hospital wards.

Science.gov (United States)

Creamer, E; Shore, A C; Deasy, E C; Galvin, S; Dolan, A; Walley, N; McHugh, S; Fitzgerald-Hughes, D; Sullivan, D J; Cunney, R; Coleman, D C; Humphreys, H

2014-03-01

Meticillin-resistant Staphylococcus aureus (MRSA) can be recovered from hospital air and from environmental surfaces. This poses a potential risk of transmission to patients. To investigate associations between MRSA isolates recovered from air and environmental surfaces with those from patients when undertaking extensive patient and environmental sampling. This was a prospective observational study of patients and their environment in eight wards of a 700-bed tertiary care hospital during 2010 and 2011. Sampling of patients, air and surfaces was carried out on all ward bays, with more extended environmental sampling in ward high-dependency bays and at particular times of the day. The genetic relatedness of isolates was determined by DNA microarray profiling and spa typing. MRSA was recovered from 30/706 (4.3%) patients and from 19/132 (14.4%) air samples. On 9/132 (6.8%) occasions both patient and air samples yielded MRSA. In 32 high-dependency bays, MRSA was recovered from 12/161 (7.4%) patients, 8/32 (25%) air samples, and 21/644 (3.3%) environmental surface samples. On 10/132 (7.6%) occasions, MRSA was isolated from air in the absence of MRSA-positive patients. Patient demographic data combined with spa typing and DNA microarray profiling revealed four likely transmission clusters, where patient and environmental isolates were deemed to be very closely related. Air sampling yielded MRSA on frequent occasions, especially in high-dependency bays. Environmental and air sampling combined with patient demographic data, spa typing and DNA microarray profiling indicated the presence of clusters that were not otherwise apparent. Copyright © 2014 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

Large scale experiments with a 5 MW sodium/air heat exchanger for decay heat removal

International Nuclear Information System (INIS)

Stehle, H.; Damm, G.; Jansing, W.

1994-01-01

Sodium experiments in the large scale test facility ILONA were performed to demonstrate proper operation of a passive decay heat removal system for LMFBRs based on pure natural convection flow. Temperature and flow distributions on the sodium and the air side of a 5 MW sodium/air heat exchanger in a natural draught stack were measured during steady state and transient operation in good agreement with calculations using a two dimensional computer code ATTICA/DIANA. (orig.)

High temperature collecting performance of a new all-glass evacuated tubular solar air heater with U-shaped tube heat exchanger

International Nuclear Information System (INIS)

Wang, Pin-Yang; Guan, Hong-Yang; Liu, Zhen-Hua; Wang, Guo-San; Zhao, Feng; Xiao, Hong-Sheng

2014-01-01

Highlights: • A novel solar air heater with simplified CPC and U-type heat exchanger is designed and tested. • The system is made up of 10 linked collecting panels. • Simplified CPC has a much lower cost at the expense of slight efficiency loss. • The air heater can propose the heated air exceeding 200 °C with great air flow rate. - Abstract: Experiment and simulation are conducted on a new-type all-glass evacuated tubular solar air heater with simplified compound parabolic concentrator (CPC). The system is made up of 10 linked collecting panels and each panel includes a simplified CPC and an all-glass evacuated tube with a U-shaped copper tube heat exchanger installed inside. Air is gradually heated when passing through each U-shaped copper tube. The heat transfer model of the solar air heater is established and the outlet air temperature, the heat power and heat efficiency are calculated. Calculated and experimental results show that the present experimental system can provide the heated air exceeding 200 °C. The whole system has an outstanding high-temperature collecting performance and the present heat transfer model can meet the general requirements of engineering calculations

High surface area carbon for bifunctional air electrodes applied in zinc-air batteries

Energy Technology Data Exchange (ETDEWEB)

Arai, H [on leave from NTT Laboratories (Japan); Mueller, S; Haas, O [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1999-08-01

Bifunctional air electrodes with high surface area carbon substrates showed low reduction overpotential, thus are promising for enhancing the energy efficiency and power capability of zinc-air batteries. The improved performance is attributed to lower overpotential due to diffusion of the reaction intermediate, namely the peroxide ion. (author) 1 fig., 2 refs.

Air-water exchange of anthropogenic and natural organohalogens on International Polar Year (IPY) expeditions in the Canadian Arctic.

Science.gov (United States)

Wong, Fiona; Jantunen, Liisa M; Pućko, Monika; Papakyriakou, Tim; Staebler, Ralf M; Stern, Gary A; Bidleman, Terry F

2011-02-01

Shipboard measurements of organohalogen compounds in air and surface seawater were conducted in the Canadian Arctic in 2007-2008. Study areas included the Labrador Sea, Hudson Bay, and the southern Beaufort Sea. High volume air samples were collected at deck level (6 m), while low volume samples were taken at 1 and 15 m above the water or ice surface. Water samples were taken within 7 m. Water concentration ranges (pg L(-1)) were as follows: α-hexachlorocyclohexane (α-HCH) 465-1013, γ-HCH 150-254, hexachlorobenzene (HCB) 4.0-6.4, 2,4-dibromoanisole (DBA) 8.5-38, and 2,4,6-tribromoanisole (TBA) 4.7-163. Air concentration ranges (pg m(-3)) were as follows: α-HCH 7.5-48, γ-HCH 2.1-7.7, HCB 48-71, DBA 4.8-25, and TBA 6.4 - 39. Fugacity gradients predicted net deposition of HCB in all areas, while exchange directions varied for the other chemicals by season and locations. Net evasion of α-HCH from Hudson Bay and the Beaufort Sea during open water conditions was shown by air concentrations that averaged 14% higher at 1 m than 15 m. No significant difference between the two heights was found over ice cover. The α-HCH in air over the Beaufort Sea was racemic in winter (mean enantiomer fraction, EF = 0.504 ± 0.008) and nonracemic in late spring-early summer (mean EF = 0.476 ± 0.010). This decrease in EF was accompanied by a rise in air concentrations due to volatilization of nonracemic α-HCH from surface water (EF = 0.457 ± 0.019). Fluxes of chemicals during the southern Beaufort Sea open water season (i.e., Leg 9) were estimated using the Whitman two-film model, where volatilization fluxes are positive and deposition fluxes are negative. The means ± SD (and ranges) of net fluxes (ng m(-2) d(-1)) were as follows: α-HCH 6.8 ± 3.2 (2.7-13), γ-HCH 0.76 ± 0.40 (0.26-1.4), HCB -9.6 ± 2.7 (-6.1 to -15), DBA 1.2 ± 0.69 (0.04-2.0), and TBA 0.46 ± 1.1 ng m(-2) d(-1) (-1.6 to 2.0).

Characteristics of resin floc dispersion of anion and cation exchange resin in precoat filter using powdered ion exchange resin

Energy Technology Data Exchange (ETDEWEB)

Adachi, Tetsurou (Nitto Denko Corp., Ibaraki, Osaka (Japan)); Sawa, Toshio; Shindoh, Toshikazu

1989-09-01

The filtration performance of mixed filter aid consisting of powdered anion and cation exchange resins used in the precoat filter is closely related to the characteristics of resin floc dispersion. The factors related to resin floc dispersion of anion and cation exchange resin were investigated by measuring the specific settle volume of resin floc as an evaluating index in addition to the measurement of physical, chemical and electrochemical properties of powdered ion exchange resin. The effect of adsorption of iron oxide and polymer electrolyte and of ion exchange were determined. In addition, considered floc dispersion with adsorbing iron oxide, it was assumed that the amount and filling ratio of resin floc were related to summation and multiplication of surface electric charge respectively. An experimental expression was obtained for simulation of the change of specific settle volume of resin floc by particle size, surface area, ion exchange capacity and degree of ionization of the powdered ion exchange resin. (author).

Characteristics of resin floc dispersion of anion and cation exchange resin in precoat filter using powdered ion exchange resin

International Nuclear Information System (INIS)

Adachi, Tetsurou; Sawa, Toshio; Shindoh, Toshikazu.

1989-01-01

The filtration performance of mixed filter aid consisting of powdered anion and cation exchange resins used in the precoat filter is closely related to the characteristics of resin floc dispersion. The factors related to resin floc dispersion of anion and cation exchange resin were investigated by measuring the specific settle volume of resin floc as an evaluating index in addition to the measurement of physical, chemical and electrochemical properties of powdered ion exchange resin. The effect of adsorption of iron oxide and polymer electrolyte and of ion exchange were determined. In addition, considered floc dispersion with adsorbing iron oxide, it was assumed that the amount and filling ratio of resin floc were related to summation and multiplication of surface electric charge respectively. An experimental expression was obtained for simulation of the change of specific settle volume of resin floc by particle size, surface area, ion exchange capacity and degree of ionization of the powdered ion exchange resin. (author)

Simulation and analysis on thermodynamic performance of surface water source heat pump system

Institute of Scientific and Technical Information of China (English)

Nan Lv; Qing Zhang; Zhenqian Chen; Dongsheng Wu

2017-01-01

This work established a thermodynamic performance model of a heat pump system containing a heat pump unit model, an air conditioning cooling and heating load calculation model, a heat exchanger model and a water pump performance model based on mass and energy balances. The thermodynamic performance of a surface water source heat pump air conditioning system was simulated and verified by comparing the simulation results to an actual engineering project. In addition, the effects of the surface water temperature, heat exchanger structure and surface water pipeline transportation system on the thermodynamic performance of the heat pump air conditioning system were analyzed. Under the simulated conditions in this paper with a cooling load of 3400 kW, the results showed that a 1 ℃ decrease in the surface water temperature leads to a 2.3 percent increase in the coefficient of performance; furthermore, an additional 100 m of length for the closed-loop surface water heat exchanger tube leads to a 0.08 percent increase in the coefficient of performance. To decrease the system energy consumption, the optimal working point should be specified according to the surface water transportation length.

Implied and Local Volatility Surfaces for South African Index and Foreign Exchange Options

Directory of Open Access Journals (Sweden)

Antonie Kotzé

2015-01-01

Full Text Available Certain exotic options cannot be valued using closed-form solutions or even by numerical methods assuming constant volatility. Many exotics are priced in a local volatility framework. Pricing under local volatility has become a field of extensive research in finance, and various models are proposed in order to overcome the shortcomings of the Black-Scholes model that assumes a constant volatility. The Johannesburg Stock Exchange (JSE lists exotic options on its Can-Do platform. Most exotic options listed on the JSE’s derivative exchanges are valued by local volatility models. These models needs a local volatility surface. Dupire derived a mapping from implied volatilities to local volatilities. The JSE uses this mapping in generating the relevant local volatility surfaces and further uses Monte Carlo and Finite Difference methods when pricing exotic options. In this document we discuss various practical issues that influence the successful construction of implied and local volatility surfaces such that pricing engines can be implemented successfully. We focus on arbitrage-free conditions and the choice of calibrating functionals. We illustrate our methodologies by studying the implied and local volatility surfaces of South African equity index and foreign exchange options.

Oceanic whitecaps: Sea surface features detectable via satellite that ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

experiments that the air-sea gas transfer coefficient for each of a wide range of gases, including carbon dioxide and .... generators with which the basin was equipped, the .... whitecaps in air-sea gas exchange; Gas Transfer at Water. Surfaces ...

Quantification of air plasma chemistry for surface disinfection

International Nuclear Information System (INIS)

Pavlovich, Matthew J; Clark, Douglas S; Graves, David B

2014-01-01

Atmospheric-pressure air plasmas, created by a variety of discharges, are promising sources of reactive species for the emerging field of plasma biotechnology because of their convenience and ability to operate at ambient conditions. One biological application of ambient-air plasma is microbial disinfection, and the ability of air plasmas to decontaminate both solid surfaces and liquid volumes has been thoroughly established in the literature. However, the mechanism of disinfection and which reactive species most strongly correlate with antimicrobial effects are still not well understood. We describe quantitative gas-phase measurements of plasma chemistry via infrared spectroscopy in confined volumes, focusing on air plasma generated via surface micro-discharge (SMD). Previously, it has been shown that gaseous chemistry is highly sensitive to operating conditions, and the measurements we describe here extend those findings. We quantify the gaseous concentrations of ozone (O 3 ) and nitrogen oxides (NO and NO 2 , or NO x ) throughout the established ‘regimes’ for SMD air plasma chemistry: the low-power, ozone-dominated mode; the high-power, nitrogen oxides-dominated mode; and the intermediate, unstable transition region. The results presented here are in good agreement with previously published experimental studies of aqueous chemistry and parameterized models of gaseous chemistry. The principal finding of the present study is the correlation of bacterial inactivation on dry surfaces with gaseous chemistry across these time and power regimes. Bacterial decontamination is most effective in ‘NO x mode’ and less effective in ‘ozone mode’, with the weakest antibacterial effects in the transition region. Our results underscore the dynamic nature of air plasma chemistry and the importance of careful chemical characterization of plasma devices intended for biological applications. (paper)

Quantification of air plasma chemistry for surface disinfection

Science.gov (United States)

Pavlovich, Matthew J.; Clark, Douglas S.; Graves, David B.

2014-12-01

Atmospheric-pressure air plasmas, created by a variety of discharges, are promising sources of reactive species for the emerging field of plasma biotechnology because of their convenience and ability to operate at ambient conditions. One biological application of ambient-air plasma is microbial disinfection, and the ability of air plasmas to decontaminate both solid surfaces and liquid volumes has been thoroughly established in the literature. However, the mechanism of disinfection and which reactive species most strongly correlate with antimicrobial effects are still not well understood. We describe quantitative gas-phase measurements of plasma chemistry via infrared spectroscopy in confined volumes, focusing on air plasma generated via surface micro-discharge (SMD). Previously, it has been shown that gaseous chemistry is highly sensitive to operating conditions, and the measurements we describe here extend those findings. We quantify the gaseous concentrations of ozone (O3) and nitrogen oxides (NO and NO2, or NOx) throughout the established ‘regimes’ for SMD air plasma chemistry: the low-power, ozone-dominated mode; the high-power, nitrogen oxides-dominated mode; and the intermediate, unstable transition region. The results presented here are in good agreement with previously published experimental studies of aqueous chemistry and parameterized models of gaseous chemistry. The principal finding of the present study is the correlation of bacterial inactivation on dry surfaces with gaseous chemistry across these time and power regimes. Bacterial decontamination is most effective in ‘NOx mode’ and less effective in ‘ozone mode’, with the weakest antibacterial effects in the transition region. Our results underscore the dynamic nature of air plasma chemistry and the importance of careful chemical characterization of plasma devices intended for biological applications.

Method of burning ion-exchange resin contaminated with radioactivity

International Nuclear Information System (INIS)

Suzuki, Shigenori.

1986-01-01

Purpose: To process spent ion exchange resins to reduce their volume, without increasing the load on a off-gas system and in a stable state and at the same time not leaving any uncombusted portions. Method: The water slurries of the ion exchange resins contaminated with radioactive materials is dehydrated or dry combusted to reduce the water content. A binder is then added to solidify the ion exchange resin. The solidified ion exchange resins are then combusted in a furnace. This prevents the ion exchange resin from being dispersed by air and combustion gases. Furthermore, the solidified ion exchange resins in the form of small pellets burn from the surface inwards. Moreover the binder is carbonized by the combustion heat and promotes combustion to convert the ion exchange resins into a solid mass, making sure that no uncombusted portion is left. (Takahashi, M.)

A Technical Basis for Employing Facility Ventilation Air Exchange Rates in the Decision to Downpost

CERN Document Server

Mantooth, D S

2001-01-01

Utilizing the ventilation exchange rate as a basis for the decision to downpost a location within a facility from an airborne radiation area (ARA) based on initial air count(DAC). Not used in the case of a confirmed or suspected contamination release.

Experimental Study of the Variation Dynamic’s for Air Heat Exchanger

Directory of Open Access Journals (Sweden)

Maryia Marozava

2017-07-01

Full Text Available The development of management systems is assigned one of the leading roles. When solving the problems of regulating the technological parameters, various problems arise. One of such problems is the adjustment of control loops. For some control objects, one-time adjustment of the controller parameters can be made, and then it is periodically refined as necessary. In other objects, the changes occur very quickly, but in a certain range. In the latter case, you should first estimate the range of changes. Then find universal robust settings that will ensure the stability and quality of the stabilization system. Some of such objects are air heat exchangers. The article presents the results of the determination of the heat exchanger dynamics. The limits of the variation of the parameters of the dynamic models are determined. There is a significant nonlinearity in the transfer function of the control channel.

The contribution to surface dose form air scatter in mega voltage photon beams

International Nuclear Information System (INIS)

Carolan, M.G.; Butson, M.; Metcalfe, P.

1996-01-01

. MCNP simulations were performed for these geometries with and without air in the region above the phantom. Simulations were also performed for the 10 x 10 cm field with various thicknesses of air immediately above the phantom. The aim here is to investigate what the relative contributions to surface dose are from different regions in the air layer. Air slices 1, 5, 10 and 20 cm thick were used as well as a simulation with the full 100 cm source - surface volume filled with air. To validate the Monte Carlo calculations we compared predicted doses at depth with dose measurements using an ion chamber and found good agreement. Dose measurements using an Attix ionisation chamber in the build up region were also in agreement with the Monte Carlo predicted doses in this region when a full column of air was included in the model. Without air included in the model the predicted surface dose was ∼ 9.5% of D max . With an air layer of 20 cm immediately above the phantom the surface dose was ∼ 13% of D max . This increased to 14.5% when the full 100 cm of air was included. All of these results take into account scatter and buildup in air only. Any experimental measurements may be expected to yield slightly higher surface doses due to scatter contribution from collimators etc in the linac head. Experimental validation of this predicted result is planned using a thin walled helium volume above the phantom surface

Land Surface Process and Air Quality Research and Applications at MSFC

Science.gov (United States)

Quattrochi, Dale; Khan, Maudood

2007-01-01

This viewgraph presentation provides an overview of land surface process and air quality research at MSFC including atmospheric modeling and ongoing research whose objective is to undertake a comprehensive spatiotemporal analysis of the effects of accurate land surface characterization on atmospheric modeling results, and public health applications. Land use maps as well as 10 meter air temperature, surface wind, PBL mean difference heights, NOx, ozone, and O3+NO2 plots as well as spatial growth model outputs are included. Emissions and general air quality modeling are also discussed.

Relating saturation capacity to charge density in strong cation exchangers.

Science.gov (United States)

Steinebach, Fabian; Coquebert de Neuville, Bertrand; Morbidelli, Massimo

2017-07-21

In this work the relation between physical and chemical resin characteristics and the total amount of adsorbed protein (saturation capacity) for ion-exchange resins is discussed. Eleven different packing materials with a sulfo-functionalization and one multimodal resin were analyzed in terms of their porosity, pore size distribution, ligand density and binding capacity. By specifying the ligand density and binding capacity by the total and accessible surface area, two different groups of resins were identified: Below a ligand density of approx. 2.5μmol/m 2 area the ligand density controls the saturation capacity, while above this limit the accessible surface area becomes the limiting factor. This results in a maximum protein uptake of around 2.5mg/m 2 of accessible surface area. The obtained results allow estimating the saturation capacity from independent resin characteristics like the saturation capacity mainly depends on "library data" such as the accessible and total surface area and the charge density. Hence these results give an insight into the fundamentals of protein adsorption and help to find suitable resins, thus limiting the experimental effort in early process development stages. Copyright © 2017 Elsevier B.V. All rights reserved.

Swimming in air-breathing fishes.

Science.gov (United States)

Lefevre, S; Domenici, P; McKenzie, D J

2014-03-01

Fishes with bimodal respiration differ in the extent of their reliance on air breathing to support aerobic metabolism, which is reflected in their lifestyles and ecologies. Many freshwater species undertake seasonal and reproductive migrations that presumably involve sustained aerobic exercise. In the six species studied to date, aerobic exercise in swim flumes stimulated air-breathing behaviour, and there is evidence that surfacing frequency and oxygen uptake from air show an exponential increase with increasing swimming speed. In some species, this was associated with an increase in the proportion of aerobic metabolism met by aerial respiration, while in others the proportion remained relatively constant. The ecological significance of anaerobic swimming activities, such as sprinting and fast-start manoeuvres during predator-prey interactions, has been little studied in air-breathing fishes. Some species practise air breathing during recovery itself, while others prefer to increase aquatic respiration, possibly to promote branchial ion exchange to restore acid-base balance, and to remain quiescent and avoid being visible to predators. Overall, the diversity of air-breathing fishes is reflected in their swimming physiology as well, and further research is needed to increase the understanding of the differences and the mechanisms through which air breathing is controlled and used during exercise. © 2014 The Fisheries Society of the British Isles.

Global observations and modeling of atmosphere–surface exchange of elemental mercury: a critical review

Directory of Open Access Journals (Sweden)

W. Zhu

2016-04-01

Full Text Available Reliable quantification of air–surface fluxes of elemental Hg vapor (Hg0 is crucial for understanding mercury (Hg global biogeochemical cycles. There have been extensive measurements and modeling efforts devoted to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc. in the past three decades. However, large uncertainties remain due to the complexity of Hg0 bidirectional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a critical review on the state of science in the atmosphere–surface exchange of Hg0. Specifically, the advancement of flux quantification techniques, mechanisms in driving the air–surface Hg exchange and modeling efforts are presented. Due to the semi-volatile nature of Hg0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence and the presence of reactants (e.g., O3, radicals, etc.. However, the effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling. We compile an up-to-date global observational flux database and discuss the implication of flux data on the global Hg budget. Mean Hg0 fluxes obtained by micrometeorological measurements do not appear to be significantly greater than the fluxes measured by dynamic flux chamber methods over unpolluted surfaces (p = 0.16, one-tailed, Mann–Whitney U test. The spatiotemporal coverage of existing Hg0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia. The magnitude of the evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg0

Gas exchange across the air - water interface determined with man-made and natural tracers

International Nuclear Information System (INIS)

Wanninkhof, R.H.

1986-01-01

Gas exchange coefficients were determined on Rockland Lake, NY; Crowley Lake, CA; and Mono Lake, CA which have surface areas of 1 km 2 , 20 km 2 , and 190 km 2 , respectively, by injecting a small amount of man made tracer gas, sulfur hexafluoride (SF 6 ) into the lake and measuring the rate of concentration decrease in the water column with time. The dependency of gas exchange on wind speed is similar for the three lakes indicating that wind fetch is not a critical parameter for the gas exchange coefficient for lakes with sizes greater than 1 km 2 . Little gas exchange occurs for wind speeds less than 2.5 m/s and gas exchange increases linearly with wind speed from 2.5 to 6 m/s. The relationship of gas exchange and wind speed for the lakes agrees well with a compilation of earlier single wind speed - exchange coefficient measurements on lakes and oceans but they are lower than most results obtained in wind tunnels

Thickened boundary layer theory for air film drag reduction on a van body surface

Science.gov (United States)

Xie, Xiaopeng; Cao, Lifeng; Huang, Heng

2018-05-01

To elucidate drag reduction mechanism on a van body surface under air film condition, a thickened boundary layer theory was proposed and a frictional resistance calculation model of the van body surface was established. The frictional resistance on the van body surface was calculated with different parameters of air film thickness. In addition, the frictional resistance of the van body surface under the air film condition was analyzed by computational fluid dynamics (CFD) simulation and different air film states that influenced the friction resistance on the van body surface were discussed. As supported by the CFD simulation results, the thickened boundary layer theory may provide reference for practical application of air film drag reduction on a van body surface.

Effects of platinum stagnation surface on the lean extinction limits of premixed methane/air flames at moderate surface temperatures

Energy Technology Data Exchange (ETDEWEB)

Wiswall, J.T.; Li, J.; Wooldridge, M.S.; Im, H.G. [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI (United States)

2011-01-15

A stagnation flow reactor was used to study the effects of platinum on the lean flammability limits of atmospheric pressure premixed methane/air flames at moderate stagnation surface temperatures. Experimental and computational methods were used to quantify the equivalence ratio at the lean extinction limit ({phi}{sub ext}) and the corresponding stagnation surface temperature (T{sub s}). A range of flow rates (57-90 cm/s) and corresponding strain rates were considered. The results indicate that the gas-phase methane/air flames are sufficiently strong relative to the heterogeneous chemistry for T{sub s} conditions less than 750 K that the platinum does not affect {phi}{sub ext}. The computational results are in good agreement with the experimentally observed trends and further indicate that higher reactant flow rates (>139 cm/s) and levels of dilution (>{proportional_to}10% N{sub 2}) are required to weaken the gas-phase flame sufficiently for surface reaction to play a positive role on extending the lean flammability limits. (author)

Air-sea exchange of CO2 in the Gulf of Kutch, northern Arabian Sea based on bomb-carbon in corals and tree rings

International Nuclear Information System (INIS)

Chakraborty, S.; Ramesh, R.; Krishnaswami, S.

1994-01-01

Radiocarbon analyses were carried out in the annual bands of a 40 year old coral collected from the Gulf of Kutch (22.6degN, 70degE) in the northern Arabian Sea and in the annual rings of a teak tree from Thane (19deg14'N, 73deg24'E) near Bombay. These measurements were made in order to obtain the rates of air-sea exchange of CO 2 and the advective mixing of water in the Gulf of Kutch. The Δ 14 C peak in the Thane tree occurs in the year 1964, with a value of ∼630 part per thousand, significantly lower than that of the mean atmospheric Δ 14 C of the northern hemisphere (∼1000 part per thousand). The radiocarbon time series of the coral was modelled considering the supply of carbon and radiocarbon to the gulf through air-sea exchange and advective water transport from the open Arabian Sea. A reasonable fit for the coral data was obtained with an air-sea CO 2 exchange rate of 11-12 mol m -2 yr -1 , and an advective velocity of 28 m yr -1 between the Arabian Sea and the Gulf of Kutch; this was based on a model generated time series for radiocarbon in the Arabian Sea. The deduced velocity (∼ 28 m yr -1 ) of the advective transport of water between the Gulf and the Arabian Sea is much lower than the surface tidal current velocity in this region, but can be understood in terms of net fluxes of carbon and radiocarbon to the gulf to match the observed coral Δ 14 C time series. (author). 30 refs., 7 figs., 2 tabs

Relations between heat exchange and Rényi divergences

Science.gov (United States)

Wei, Bo-Bo

2018-04-01

In this work, we establish an exact relation which connects the heat exchange between two systems initialized in their thermodynamic equilibrium states at different temperatures and the Rényi divergences between the initial thermodynamic equilibrium state and the final nonequilibrium state of the total system. The relation tells us that the various moments of the heat statistics are determined by the Renyi divergences between the initial equilibrium state and the final nonequilibrium state of the global system. In particular the average heat exchange is quantified by the relative entropy between the initial equilibrium state and the final nonequilibrium state of the global system. The relation is applicable to both finite classical systems and finite quantum systems.

Fingerprints of surface magnetism in Cr2O3 based exchange bias heterostructures

Science.gov (United States)

He, Xi; Wang, Yi; Binek, Ch.

2009-03-01

Magnetoelectric materials experienced a recent revival as promising components of novel spintronic devices [1, 2, 3]. Since the magnetoelectric (ME) effect is relativistically small in traditional antiferromagnetic (AF) compounds like Cr2O3 (max. αzz 4ps/m) and also cross-coupling between ferroic order parameters is typically small in the modern multiferroics, it is a challenge to electrically induce sufficient magnetization required for the envisioned device applications. In exchange bias systems the bias field depends critically on the AF interface magnetization. Hence, a strong relation between the latter and the surface magnetization of the free Cr2O3 pinning layer can be expected. Our recent research indicates that there are surface magnetic phase transitions in free Cr2O3 (111) films accompanying surface structural phase transitions. Well defined AF interface magnetization is initialized through ME annealing to T=20K. Subsequently, the interface magnetization is thermally driven through phase transitions at T=120 and 210K. Their effects on the exchange bias are studied in Cr2O3 (111)/CoPt films with the help of polar Kerr and SQUID magnetometry. [1] P. Borisov et al. Phys. Rev. Lett. 94, 117203 (2005). [2] Ch. Binek, B.Doudin, J. Phys. Condens. Matter 17, L39 (2005). [3] R. Ramesh et al. 2007 Nature Materials 6 21. Financial support by NSF through Career DMR-0547887, MRSEC DMR-0820521 and the NRI.

Determinants of International Outsourcing and Performance: A Relational Exchange Perspective

Directory of Open Access Journals (Sweden)

Carl E. Dresden

2013-07-01

Full Text Available Prescriptive discussions regarding international outsourcing abound, but there are few previously proposed models of the antecedents leading to such sourcing. This empirical study utilizes the relational exchange framework proposed by Dwyer, Schurr and Oh (1987 and builds a conceptual model of the firm's use of international outsourcing within the context of relational exchange. The model concentrates on the aspects of relational exchange that are crucial antecedents to successful international outsourcing and empirically demonstrates how both economic and social factors have their influence. The resulting model demonstrates how cooperation, rather than competition, leads to successful international outsourcing.

Kinetic study of heavy metal ions removal by ion exchange in batch conical air spouted bed

Directory of Open Access Journals (Sweden)

T.M. Zewail

2015-03-01

Full Text Available Spouted bed contactor is a hybrid of fixed and fluidized bed contactors, which retains the advantages of each with good hydrodynamic conditions. The aim of the present study is to investigate the performance of a batch conical air spouted vessel for heavy metal removal by strong cation exchange resins (AMBERJET 1200 Na. The effect of various parameters such as type of heavy metal ions (Ni+2 and Pb+2, contact time, superficial air velocity and initial heavy metal ion concentration on % heavy metal ion removal has been investigated. It has been found that under optimum conditions 98% and 99% removal of Ni+2 and Pb+2 were achieved respectively. Several kinetic models were used to test the experimental data and to examine the controlling mechanism of the sorption process. The present results of Ni+2 and Pb+2 well fit pseudo second order kinetic model with a high correlation coefficient. Both film diffusion and intra-particle diffusion contribute to the ion exchange process. The present study revealed that spouted bed vessel may provide an effective alternative for conducting ion exchange reactions.

Metingen aan twee luchtwassystemen in een vleeskuikenstal met conditionering van ingaande ventilatielucht = Measurements on two air scrubbing systems on broiler houses with heat exchanger for inlet ventilation air

NARCIS (Netherlands)

Melse, R.W.; Hattum, van T.G.; Huis in 'T Veld, J.W.H.; Gerrits, F.A.

2012-01-01

The performance of two experimental air scrubber was investigated during 9 months on two broiler houses. The inlet ventilation air of the houses is led through a subsoil heat exchanger. In this report the removal efficiencies of the scrubber are reported for ammonia, odour and fine dust (PM10 and

Organochlorine pesticides in soils of Mexico and the potential for soil-air exchange

International Nuclear Information System (INIS)

Wong, Fiona; Alegria, Henry A.; Bidleman, Terry F.

2010-01-01

The spatial distribution of organochlorine pesticides (OCs) in soils and their potential for soil-air exchange was examined. The most prominent OCs were the DDTs (Geometric Mean, GM = 1.6 ng g -1 ), endosulfans (0.16 ng g -1 ), and toxaphenes (0.64 ng g -1 ). DDTs in soils of southern Mexico showed fresher signatures with higher F DDTe = p,p'-DDT/(p,p'-DDT + p,p'-DDE) and more racemic o,p'-DDT, while the signatures in the central and northern part of Mexico were more indicative of aged residues. Soil-air fugacity fractions showed that some soils are net recipients of DDTs from the atmosphere, while other soils are net sources. Toxaphene profiles in soils and air showed depletion of Parlar 39 and 42 which suggests that soil is the source to the atmosphere. Endosulfan was undergoing net deposition at most sites as it is a currently used pesticide. Other OCs showed wide variability in fugacity, suggesting a mix of net deposition and volatilization. - Chemical profiles of residues and soil-air fugacities are used to assess the potential of soil as a source of organochlorine pesticides to the air of Mexico.

The intraseasonal variability of winter semester surface air temperature in Antarctica

Directory of Open Access Journals (Sweden)

Lejiang Yu

2011-02-01

Full Text Available This study investigates systematically the intraseasonal variability of surface air temperature over Antarctica by applying empirical orthogonal function (EOF analysis to the National Centers for Environmental Prediction, US Department of Energy, Reanalysis 2 data set for the period of 1979 through 2007. The results reveal the existence of two major intraseasonal oscillations of surface temperature with periods of 26–30 days and 14 days during the Antarctic winter season in the region south of 60°S. The first EOF mode shows a nearly uniform spatial pattern in Antarctica and the Southern Ocean associated with the Antarctic Oscillation. The mode-1 intraseasonal variability of the surface temperature leads that of upper atmosphere by one day with the largest correlation at 300-hPa level geopotential heights. The intraseasonal variability of the mode-1 EOF is closely related to the variations of surface net longwave radiation the total cloud cover over Antarctica. The other major EOF modes reveal the existence of eastward propagating phases over the Southern Ocean and marginal region in Antarctica. The leading two propagating modes respond to Pacific–South American modes. Meridional winds induced by the wave train from the tropics have a direct influence on the surface air temperature over the Southern Ocean and the marginal region of the Antarctic continent.

Effect of fluoride on ion exchange, remineralization and acid resistance of surface enamel

Energy Technology Data Exchange (ETDEWEB)

Aponte-Merced, L A; Feagin, F F [Alabama Univ., Birmingham (USA)

1979-01-01

In a system of constant ion activities the rates of F/sup -/ exchange in enamel, under conditions of exchange alone and remineralization, depended on the concentration of F/sup -/ in solutions. Acid resistance of surface minerals resulted from exchange of F/sup -/ for OH/sup -/ in the enamel at pH 7.0 and 4.5. The level of 0.5 mM NaF, compared to 0.05 and 5.0 mM, caused maximum rates of isotopic exchange of /sup 45/Ca and maximum acid resistance of enamel. Similarly low levels of F/sup -/ may be feasible for use in caries prevention in the absence and presence of remineralization.

Cooperation of Horizontal Ground Heat Exchanger with the Ventilation Unit During Summer - Case Study

Science.gov (United States)

Romańska-Zapała, Anna; Furtak, Marcin; Dechnik, Mirosław

2017-10-01

and autumn), but also in individual days in the potentially most favorable periods of work exchanger (summer and winter). Inappropriate operation of the heat exchanger, will lead to a temporary increase in energy consumption for the preparation of the desired air temperature, relative to the fresh air unit which is non-pretreated. For optimal energy system operation: exchanger EAHX - air handling unit, to preserve the most favourable parameters of inlet air to handling unit, there is a need to dynamically adjust the source of fresh air, depending on changing external conditions and the required outlet temperature of central unit (temperature of air forced to the rooms).

PCB in soils and estimated soil-air exchange fluxes of selected PCB congeners in the south of Sweden

International Nuclear Information System (INIS)

Backe, Cecilia; Cousins, Ian T.; Larsson, Per

2004-01-01

PCB concentrations were studied in different soils to determine the spatial variation over a region of approximately 11 000 km 2 . PCB congener pattern was used to illustrate the spatial differences, as shown by principal component analysis (PCA). The relationship to different soil parameters was studied. PCB concentrations in soil showed a large variation between sampling-areas with median concentrations ranging between 2.3 and 332 ng g -1 (dw). Highest concentrations were found at two sites with sandy soils, one with extremely high organic carbon content. Both sites were located on the west coast of southern Sweden. Soils with similar soil textures (i.e. sandy silt moraine) did not show any significant differences in PCB concentrations. PCB congener composition was shown to differ between sites, with congener patterns almost site-specific. PCB in air and precipitation was measured and the transfer of chemicals between the soil and air compartments was estimated. Soil-air fugacity quotient calculations showed that the PCBs in the soil consistently had a higher fugacity than the PCBs in the air, with a median quotient value of 2.7. The gaseous fluxes between soil and air were estimated using standard modelling equations and a net soil-air flux estimated by subtracting bulk deposition from gaseous soil-air fluxes. It was shown that inclusion of vertical sorbed phase transport of PCBs in the soil had a large effect on the direction of the net soil-air exchange fluxes. - Soil-air exchange of PCBs is investigated and modelled across Sweden

Analysis of heterogeneous oxygen exchange and fuel oxidation on the catalytic surface of perovskite membranes

KAUST Repository

Hong, Jongsup

2013-10-01

The catalytic kinetics of oxygen surface exchange and fuel oxidation for a perovskite membrane is investigated in terms of the thermodynamic state in the immediate vicinity of or on the membrane surface. Perovskite membranes have been shown to exhibit both oxygen perm-selectivity and catalytic activity for hydrocarbon conversion. A fundamental description of their catalytic surface reactions is needed. In this study, we infer the kinetic parameters for heterogeneous oxygen surface exchange and catalytic fuel conversion reactions, based on permeation rate measurements and a spatially resolved physical model that incorporates detailed chemical kinetics and transport in the gas-phase. The conservation equations for surface and bulk species are coupled with those of the gas-phase species through the species production rates from surface reactions. It is shown that oxygen surface exchange is limited by dissociative/associative adsorption/desorption of oxygen molecules onto/from the membrane surface. On the sweep side, while the catalytic conversion of methane to methyl radical governs the overall surface reactions at high temperature, carbon monoxide oxidation on the membrane surface is dominant at low temperature. Given the sweep side conditions considered in ITM reactor experiments, gas-phase reactions also play an important role, indicating the significance of investigating both homogeneous and heterogeneous chemistry and their coupling when examining the results. We show that the local thermodynamic state at the membrane surface should be considered when constructing and examining models of oxygen permeation and heterogeneous chemistry. © 2013 Elsevier B.V.

Analysis of heterogeneous oxygen exchange and fuel oxidation on the catalytic surface of perovskite membranes

KAUST Repository

Hong, Jongsup; Kirchen, Patrick; Ghoniem, Ahmed F.

2013-01-01

The catalytic kinetics of oxygen surface exchange and fuel oxidation for a perovskite membrane is investigated in terms of the thermodynamic state in the immediate vicinity of or on the membrane surface. Perovskite membranes have been shown to exhibit both oxygen perm-selectivity and catalytic activity for hydrocarbon conversion. A fundamental description of their catalytic surface reactions is needed. In this study, we infer the kinetic parameters for heterogeneous oxygen surface exchange and catalytic fuel conversion reactions, based on permeation rate measurements and a spatially resolved physical model that incorporates detailed chemical kinetics and transport in the gas-phase. The conservation equations for surface and bulk species are coupled with those of the gas-phase species through the species production rates from surface reactions. It is shown that oxygen surface exchange is limited by dissociative/associative adsorption/desorption of oxygen molecules onto/from the membrane surface. On the sweep side, while the catalytic conversion of methane to methyl radical governs the overall surface reactions at high temperature, carbon monoxide oxidation on the membrane surface is dominant at low temperature. Given the sweep side conditions considered in ITM reactor experiments, gas-phase reactions also play an important role, indicating the significance of investigating both homogeneous and heterogeneous chemistry and their coupling when examining the results. We show that the local thermodynamic state at the membrane surface should be considered when constructing and examining models of oxygen permeation and heterogeneous chemistry. © 2013 Elsevier B.V.

Impact of indoor surface material on perceived air quality.

Science.gov (United States)

Senitkova, I

2014-03-01

The material combination impact on perceived indoor air quality for various surface interior materials is presented in this paper. The chemical analysis and sensory assessments identifies health adverse of indoor air pollutants (TVOCs). In this study, emissions and odors from different common indoor surface materials were investigated in glass test chamber under standardized conditions. Chemical measurements (TVOC concentration) and sensory assessments (odor intensity, air acceptability) were done after building materials exposure to standardized conditions. The results of the chemical and sensory assessment of individual materials and their combinations are compared and discussed within the paper. The using possibility of individual material surface sorption ability was investigated. The knowledge of targeted sorption effects can be used in the interior design phase. The results demonstrate the various sorption abilities of various indoor materials as well as the various sorption abilities of the same indoor material in various combinations. Copyright © 2013 Elsevier B.V. All rights reserved.

GROUNDWATER-SURFACE WATER EXCHANGE AND IMPLICATIONS FOR LARGE RIVER RESTORATION

Science.gov (United States)

Movement of river water into and out of high-porosity alluvial deposits can have an important influence on surface water quality and aquatic habitat. In our study of a 60-km reach of the Willamette River in Oregon, USA, we: 1) used tracers to estimate the rate of exchange betw...

Porphyromonas gingivalis Uses Specific Domain Rearrangements and Allelic Exchange to Generate Diversity in Surface Virulence Factors.

Science.gov (United States)

Dashper, Stuart G; Mitchell, Helen L; Seers, Christine A; Gladman, Simon L; Seemann, Torsten; Bulach, Dieter M; Chandry, P Scott; Cross, Keith J; Cleal, Steven M; Reynolds, Eric C

2017-01-01

Porphyromonas gingivalis is a keystone pathogen of chronic periodontitis. The virulence of P. gingivalis is reported to be strain related and there are currently a number of strain typing schemes based on variation in capsular polysaccharide, the major and minor fimbriae and adhesin domains of Lys-gingipain (Kgp), amongst other surface proteins. P. gingivalis can exchange chromosomal DNA between strains by natural competence and conjugation. The aim of this study was to determine the genetic variability of P. gingivalis strains sourced from international locations over a 25-year period and to determine if variability in surface virulence factors has a phylogenetic basis. Whole genome sequencing was performed on 13 strains and comparison made to 10 previously sequenced strains. A single nucleotide polymorphism-based phylogenetic analysis demonstrated a shallow tri-lobed phylogeny. There was a high level of reticulation in the phylogenetic network, demonstrating extensive horizontal gene transfer between the strains. Two highly conserved variants of the catalytic domain of the major virulence factor the Kgp proteinase (Kgp cat I and Kgp cat II) were found. There were three variants of the fourth Kgp C-terminal cleaved adhesin domain. Specific variants of the cell surface proteins FimA, FimCDE, MfaI, RagAB, Tpr, and PrtT were also identified. The occurrence of all these variants in the P. gingivalis strains formed a mosaic that was not related to the SNP-based phylogeny. In conclusion P. gingivalis uses domain rearrangements and genetic exchange to generate diversity in specific surface virulence factors.

Surface treatment to reduce icing; Oberflaechenbehandlung zur Vereisungsverringerung

Energy Technology Data Exchange (ETDEWEB)

Hoffmann, P.; Kulik, G.; Zehnder, M.

2003-07-01

This final report for the Swiss Federal Office of Energy (SFOE) presents the results of work done at the Swiss Federal Institute of Technology in Lausanne, Switzerland, on reducing ice formation on the evaporators of air-water heat-pumps and speeding-up the defrosting cycle by making their surfaces hydrophobic. The authors report that highest water repellence was achieved by high surface roughness and application of a strongly hydrophobic per fluorosilane coating. The results of tests carried out with uncoated and differently coated sample heat exchangers are presented. Three geometrically identical miniaturised heat exchangers were used that differed in roughness and surface wettability. Surprisingly, the rough and strongly repellent heat-exchanger showed worse defrosting behaviour than the uncoated heat-exchanger. The flat and hydrophobic-coated heat-exchanger showed the best performance. The amount of frost formed was 25% less and defrosting time was much shorter.

Advanced Architectures and Relatives of Air Electrodes in Zn–Air Batteries

Science.gov (United States)

Pan, Jing; Xu, Yang Yang; Yang, Huan; Dong, Zehua; Liu, Hongfang

2018-01-01

Abstract Zn–air batteries are becoming the promising power sources for portable and wearable electronic devices and hybrid/electric vehicles because of their high specific energy density and the low cost for next‐generation green and sustainable energy technologies. An air electrode integrated with an oxygen electrocatalyst is the most important component and inevitably determines the performance and cost of a Zn–air battery. This article presents exciting advances and challenges related to air electrodes and their relatives. After a brief introduction of the Zn–air battery, the architectures and oxygen electrocatalysts of air electrodes and relevant electrolytes are highlighted in primary and rechargeable types with different configurations, respectively. Moreover, the individual components and major issues of flexible Zn–air batteries are also highlighted, along with the strategies to enhance the battery performance. Finally, a perspective for design, preparation, and assembly of air electrodes is proposed for the future innovations of Zn–air batteries with high performance. PMID:29721418

Influence of atmospheric rainfall to γ radiation Kerma rate in surface air

International Nuclear Information System (INIS)

Xu Zhe; Wan Jun; Yu Rongsheng

2009-01-01

Objective: To investigate the influence rule of the atmospheric Rainfall to the γ radiation Kerma rate in surface air in order to revise the result of its measurement during rainfall. Methods: The influence factors of rainfall to the measurement of the γ radiation Kerma rate in air were analyzed and then the differential equation of the correlation factors was established theoretically, and by resolving the equation, the mathematical model Was obtained. The model was discussed through several practical examples. Results: The mathematical model was coincided with the tendency of curve about the measured data on the influence rule of rainfall to the γ radiation Kerma rate in surface air. Conclusion: By using the theoretical formula in this article which is established to explain the relationship between the rainfall and the γ radiation Kerma rate in surface air, the influence of rainfall to the γ radiation Kerma rate in surface air could be correctly revised. (authors)

Clean Air Markets - Monitoring Surface Water Chemistry

Science.gov (United States)

Learn about how EPA uses Long Term Monitoring (LTM) and Temporily Integrated Monitoring of Ecosystems (TIME) to track the effect of the Clean Air Act Amendments on acidity of surface waters in the eastern U.S.

Manganese concentrations in the air of the Montreal (Canada) subway in relation to surface automobile traffic density

Energy Technology Data Exchange (ETDEWEB)

Boudia, Nacera; Gareau, Lise; Zayed, Joseph [GRIS Interdisciplinary Health Research Group, University of Montreal (Canada); Halley, Renee [Transport Montreal Society (Canada); Kennedy, Greg [Department of Engineering Physics, Ecole Polytechnique de Montreal, Montreal (Canada); Lambert, Jean [Department of Social and Preventive Medicine, Faculty of Medicine, University of Montreal (Canada)

2006-07-31

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic derivative of manganese (Mn), used since 1976 in Canadian gasoline as an octane enhancer. Its combustion leads to the emission of Mn particles. Several studies carried out by our research group have established a correlation between atmospheric Mn concentrations and automobile traffic density, suggesting that MMT in gasoline could play a significant role. This study aims to measure Mn concentrations in the air of the underground subway in Montreal (Canada) and to examine the relation with nearby surface automobile traffic density and, by extension, with the use of MMT in gasoline. Three subway stations were chosen for their location in different microenvironments with different traffic densities. Respirable (MnR<5 {mu}m) and total Mn (MnT) were sampled over two weeks, 5 days/week, 12 h/day. For the station located in the lower traffic density area, relatively low levels of MnR and MnT were found, with averages of 0.018 and 0.032 {mu}g/m{sup 3}, respectively. These concentrations are within the range of the background levels in Montreal. For the other two stations, the average concentrations of MnR were twice as high and exceeded the US EPA reference concentration of 0.05 {mu}g/m{sup 3}. Although there may be several sources of Mn from different components of the subway structure and vehicles, no correlation was found between subway traffic and atmospheric Mn in the subway. Since the air in the underground subway is pumped directly from outside without filtration, our findings strongly suggest that the combustion of MMT in automobiles is an important factor. (author)

Air-water gas exchange of chlorinated pesticides in four lakes spanning a 1,205 meter elevation range in the Canadian Rocky Mountains.

Science.gov (United States)

Wilkinson, Andrew C; Kimpe, Lynda E; Blais, Jules M

2005-01-01

Concentrations of selected persistent organic pollutants (POPs) in air and water were measured from four lakes that transect the Canadian Rocky Mountains. These data were used in combination with wind velocity and temperature-adjusted Henry's law constants to estimate the direction and magnitude of chemical exchange across the air-water interface of these lakes. Bow Lake (1,975 m above sea level [masl]) was studied during the summers of 1998 through 2000; Donald (770 masl) was studied during the summer of 1999; Dixon Dam Lake (946 masl) and Kananaskis Lake (1,667 masl) were studied during the summer of 2000. Hexachlorobenzene (HCB) and dieldrin volatilized from Bow Lake in spring and summer of 1998 to 2000 at a rate of 0.92 +/-1.1 and 0.55+/-0.37 ng m(-2) d(-1), respectively. The alpha-endosulfan deposited to Bow Lake at a rate of 3.4+/-2.2 ng m(-2) d(-1). Direction of gas exchange for gamma-hexachlorocyclohexane (gamma-HCH) changed from net deposition in 1998 to net volatilization in 1999, partly because of a surge in y-HCH concentrations in the water at Bow Lake in 1999. Average gamma-HCH concentrations in air declined steadily over the three-year period, from 0.021 ng m(-3) in 1998, to 0.0023 ng m(-3) in 2000, and to volatilization in 1999 and 2000. Neither the concentrations of organochlorine compounds (OCs) in air and water, nor the direction and rate of air-water gas exchange correlate with temperature or elevation. In general, losses of pesticides by outflow were greater than the amount exchanged across the air-water interface in these lakes.

Improvements in and relating to ion-exchange

International Nuclear Information System (INIS)

Heal, H.G.

1975-01-01

It has been found that the relatively expensive ion exchange materials normally used can be extensively replaced by relatively inexpensive material comprised of long-weathered basalt. This has been found to effect rapid and efficient ion exchange with a capacity comparable with, and in some cases greater than, the usual artificial materials. The basalt should contain at least 50% by weight of particles of size below 3cm mesh. Olivine basalt has proved particularly effective. Examples given include removal of Cu and Co, application to water softening, and to the removal of 137 Cs from milk. Other applications mentioned include removal of Ca, 90 Sr, Pb, Zn, Hg, Ni, and Cr, extraction of metal ions from seawater, purification of industrial effluents, etc. (U.K.)

Characterization of the exchange of PBDEs in a subtropical paddy field of China: A significant inputs of PBDEs via air–foliage exchange

International Nuclear Information System (INIS)

Wang, Yan; Wang, Shaorui; Xu, Yue; Luo, Chunling; Li, Jun; Zhang, Gan

2015-01-01

Rice and the distinctive cultivation practices employed in rice growth can significantly influence the environmental fate of polybrominated diphenyl ethers (PBDEs) in a paddy field. We studied variations in PBDE concentrations in multiple compartments of a paddy field in the suburban area of Guangzhou, South China, including air, soil, water, and rice tissues. The input/output fluxes of air–surface and air–foliage exchange, atmospheric deposition and water input during different rice growth stages were measured simultaneously. Air–foliage and air–water diffusion exchanges were the key processes controlling inputs and outputs of PBDEs in paddy fields, respectively, whereas atmospheric deposition dominated inputs of higher brominated PBDEs. The high input of PBDEs via air–foliage exchange suggested that vegetation can significantly increase the air-to-field transport of PBDEs in ecosystems. The annual input of PBDEs in all paddy fields in Guangdong Province was estimated to be 22.1 kg. - Highlights: • PBDE concentrations in multiple compartments of a suburban paddy field were measured. • Air–water exchange was the key process controlling PBDE output in paddy fields. • Air–foliage exchange dominated the inputs of PBDEs in paddy fields. • Annual PBDE input in paddy fields in Guangdong Province was calculated to be 22 kg. - Air–foliage exchange is the most dominant inputs of PBDEs in the subtropical paddy fields

Exchangeable cations-mediated photodegradation of polycyclic aromatic hydrocarbons (PAHs) on smectite surface under visible light

Energy Technology Data Exchange (ETDEWEB)

Jia, Hanzhong, E-mail: jiahz@ms.xjb.ac.cn [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Li, Li [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Chen, Hongxia; Zhao, Yue [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); School of Geology and Mining Engineering, Xinjiang University, Urumqi 830046 (China); Li, Xiyou [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Wang, Chuanyi, E-mail: cywang@ms.xjb.ac.cn [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China)

2015-04-28

Graphical abstract: Roles of exchangeable cations in PAHs photodegradation on clay surafces under visible light. - Highlights: • Photolysis rate are strongly dependent on the type of cations on clay surface. • The strength of “cation–π” interactions governs the photodegradation rate of PAHs. • Several exchangeable cations could cause a shift in the absorption spectrum of PAHs. • Exchangeable cations influence the type and amount of reactive intermediates. - Abstract: Clay minerals saturated with different exchangeable cations are expected to play various roles in photodegradation of polycyclic aromatic hydrocarbons (PAHs) via direct and/or indirect pathways on clay surfaces. In the present study, anthracene and phenanthrene were selected as molecule probes to investigate the roles of exchangeable cations on their photodegradation under visible light irradiation. For five types of cation-modified smectite clays, the photodegradation rate of anthracene and phenanthrene follows the order: Fe{sup 3+} > Al{sup 3+} > Cu{sup 2+} >> Ca{sup 2+} > K{sup +} > Na{sup +}, which is consistent with the binding energy of cation–π interactions between PAHs and exchangeable cations. The result suggests that PAHs photolysis rate depends on cation–π interactions on clay surfaces. Meanwhile, the deposition of anthracene at the Na{sup +}-smectite and K{sup +}-smectite surface favors solar light absorption, resulting in enhanced direct photodecomposition of PAHs. On the other hand, smectite clays saturated with Fe{sup 3+}, Al{sup 3+}, and Cu{sup 2+} are highly photoreactive and can act as potential catalysts giving rise to oxidative radicals such as O{sub 2}{sup −}· , which initiate the transformation of PAHs. The present work provides valuable insights into understanding the transformation and fate of PAHs in the natural soil environment and sheds light on the development of technologies for contaminated land remediation.

Exchangeable cations-mediated photodegradation of polycyclic aromatic hydrocarbons (PAHs) on smectite surface under visible light

International Nuclear Information System (INIS)

Jia, Hanzhong; Li, Li; Chen, Hongxia; Zhao, Yue; Li, Xiyou; Wang, Chuanyi

2015-01-01

Graphical abstract: Roles of exchangeable cations in PAHs photodegradation on clay surafces under visible light. - Highlights: • Photolysis rate are strongly dependent on the type of cations on clay surface. • The strength of “cation–π” interactions governs the photodegradation rate of PAHs. • Several exchangeable cations could cause a shift in the absorption spectrum of PAHs. • Exchangeable cations influence the type and amount of reactive intermediates. - Abstract: Clay minerals saturated with different exchangeable cations are expected to play various roles in photodegradation of polycyclic aromatic hydrocarbons (PAHs) via direct and/or indirect pathways on clay surfaces. In the present study, anthracene and phenanthrene were selected as molecule probes to investigate the roles of exchangeable cations on their photodegradation under visible light irradiation. For five types of cation-modified smectite clays, the photodegradation rate of anthracene and phenanthrene follows the order: Fe 3+ > Al 3+ > Cu 2+ >> Ca 2+ > K + > Na + , which is consistent with the binding energy of cation–π interactions between PAHs and exchangeable cations. The result suggests that PAHs photolysis rate depends on cation–π interactions on clay surfaces. Meanwhile, the deposition of anthracene at the Na + -smectite and K + -smectite surface favors solar light absorption, resulting in enhanced direct photodecomposition of PAHs. On the other hand, smectite clays saturated with Fe 3+ , Al 3+ , and Cu 2+ are highly photoreactive and can act as potential catalysts giving rise to oxidative radicals such as O 2 − · , which initiate the transformation of PAHs. The present work provides valuable insights into understanding the transformation and fate of PAHs in the natural soil environment and sheds light on the development of technologies for contaminated land remediation

Experiments probing the influence of air exchange rates on secondary organic aerosols derived from indoor chemistry

DEFF Research Database (Denmark)

Weschler, Charles J.; Shields, H.C.

2003-01-01

Reactions between ozone and terpenes have been shown to increase the concentrations of submicron particles in indoor settings. The present study was designed to examine the influence of air exchange rates on the concentrations of these secondary organic aerosols as well as on the evolution...

Effect of air gap on uniformity of large-scale surface-wave plasma

International Nuclear Information System (INIS)

Lan Chaohui; Hu Xiwei; Jiang Zhonghe; Liu Minghai

2009-01-01

The effect of air gap on the uniformity of large-scale surface-wave plasma (SWP) in a rectangular chamber device is studied by using three-dimensional numerical analyses based on the finite difference time-domain (FDTD) approximation to Maxwell's equations and plasma fluid model. The spatial distributions of surface wave excited by slot-antenna array and the plasma parameters such as electron density and temperature are presented. For different air gap thicknesses, the results show that the existence of air gap would severely weaken the excitations of the surface wave and thereby the SWP. Thus the air gap should be eliminated completely in the design of the SWP source, which is opposite to the former research results. (authors)

Energy use, air infiltration, and indoor air quality in well-insulated residences

International Nuclear Information System (INIS)

Koontz, M.D.; Nagda, N.L.

1989-01-01

This paper reports two unoccupied bilevel houses of identical design and construction studied to determine the relationships among air exchange, energy consumption, and indoor air quality. The experimental house was retrofitted to increase building tightness and was equipped with an air-to-air heat exchanger; the control house was kept in its initial state of construction. Infiltration, energy, indoor air quality, and environmental parameters were monitored in both houses before and after the retrofit. It was found that the retrofit decreased air infiltration rates by nearly 25 percent, heating energy savings of 12 to 20 percent were achieved through the retrofit, and among the pollutants monitored, only radon and radon progeny increased in proportion to the reduced infiltration. Similarly, when the heat exchanger was operated, radon and radon progeny were the only pollutants reduced in proportion to the added air exchange

Spin-wave resonance frequency in ferromagnetic thin film with interlayer exchange coupling and surface anisotropy

Science.gov (United States)

Zhang, Shuhui; Rong, Jianhong; Wang, Huan; Wang, Dong; Zhang, Lei

2018-01-01

We have investigated the dependence of spin-wave resonance(SWR) frequency on the surface anisotropy, the interlayer exchange coupling, the ferromagnetic layer thickness, the mode number and the external magnetic field in a ferromagnetic superlattice film by means of the linear spin-wave approximation and Green's function technique. The SWR frequency of the ferromagnetic thin film is shifted to higher values corresponding to those of above factors, respectively. It is found that the linear behavior of SWR frequency curves of all modes in the system is observed as the external magnetic field is increasing, however, SWR frequency curves are nonlinear with the lower and the higher modes for different surface anisotropy and interlayer exchange coupling in the system. In addition, the SWR frequency of the lowest (highest) mode is shifted to higher (lower) values when the film thickness is thinner. The interlayer exchange coupling is more important for the energetically higher modes than for the energetically lower modes. The surface anisotropy has a little effect on the SWR frequency of the highest mode, when the surface anisotropy field is further increased.

The fractal geometry of nutrient exchange surfaces does not provide an explanation for 3/4-power metabolic scaling

Directory of Open Access Journals (Sweden)

Painter Page R

2005-08-01

Full Text Available Abstract Background A prominent theoretical explanation for 3/4-power allometric scaling of metabolism proposes that the nutrient exchange surface of capillaries has properties of a space-filling fractal. The theory assumes that nutrient exchange surface area has a fractal dimension equal to or greater than 2 and less than or equal to 3 and that the volume filled by the exchange surface area has a fractal dimension equal to or greater than 3 and less than or equal to 4. Results It is shown that contradicting predictions can be derived from the assumptions of the model. When errors in the model are corrected, it is shown to predict that metabolic rate is proportional to body mass (proportional scaling. Conclusion The presence of space-filling fractal nutrient exchange surfaces does not provide a satisfactory explanation for 3/4-power metabolic rate scaling.

Air exchanges and indoor carbon dioxide concentration in Australian pig buildings: Effect of housing and management factors

DEFF Research Database (Denmark)

Banhazi, T. M.; Stott, P.; Rutley, D.

2011-01-01

There has been a growing interest in improving air quality within livestock buildings. However, the influence of housing and management factors on air exchange rates and indoor gas concentrations is not well understood. The aim of this study was to determine the effects of housing and management...... production, although these buildings may not always provide an optimal environment for pig production. (C) 2011 IAgrE. Published by Elsevier Ltd. All rights reserved....

Effect of surface etching on condensing heat transfer

Energy Technology Data Exchange (ETDEWEB)

Seok, Sung Chul; Park, Jae Won; Jung, Jiyeon; Choi, Chonggun; Choi, Gyu Hong; Hwang, Seung Sik; Chung, Tae Yong; Shin, Donghoon [Kookmin University, Seoul (Korea, Republic of); Kim, Jin Jun [Hoseo University, Asan (Korea, Republic of)

2016-02-15

This study conducted experiments on humid air condensation during heat transfer in an air preheating exchanger attached to a home condensing boiler to improve thermal efficiency. An etchant composed of sulfuric acid and sodium nitrate was used to create roughness on the heat exchanger surface made from STS430J1L. A counter flow heat exchanger was fabricated to test the performance of heat transfer. Results showed that the overall heat transfer coefficients of all specimens treated with etchant improved with respect to the original specimens (not treated with etchant), and the overall heat transfer coefficient of the 60 s etching specimen increased by up to 15%. However, the increasing rate of the heat transfer coefficient was disproportional to the etching time. When the etching time specifically increased above 60 s, the heat transfer coefficient decreased. This effect was assumed to be caused by surface characteristics such as contact angle. Furthermore, a smaller contact angle or higher hydrophilicity leads to higher heat transfer coefficient.

First-order exchange coefficient coupling for simulating surface water-groundwater interactions: Parameter sensitivity and consistency with a physics-based approach

Science.gov (United States)

Ebel, B.A.; Mirus, B.B.; Heppner, C.S.; VanderKwaak, J.E.; Loague, K.

2009-01-01

Distributed hydrologic models capable of simulating fully-coupled surface water and groundwater flow are increasingly used to examine problems in the hydrologic sciences. Several techniques are currently available to couple the surface and subsurface; the two most frequently employed approaches are first-order exchange coefficients (a.k.a., the surface conductance method) and enforced continuity of pressure and flux at the surface-subsurface boundary condition. The effort reported here examines the parameter sensitivity of simulated hydrologic response for the first-order exchange coefficients at a well-characterized field site using the fully coupled Integrated Hydrology Model (InHM). This investigation demonstrates that the first-order exchange coefficients can be selected such that the simulated hydrologic response is insensitive to the parameter choice, while simulation time is considerably reduced. Alternatively, the ability to choose a first-order exchange coefficient that intentionally decouples the surface and subsurface facilitates concept-development simulations to examine real-world situations where the surface-subsurface exchange is impaired. While the parameters comprising the first-order exchange coefficient cannot be directly estimated or measured, the insensitivity of the simulated flow system to these parameters (when chosen appropriately) combined with the ability to mimic actual physical processes suggests that the first-order exchange coefficient approach can be consistent with a physics-based framework. Copyright ?? 2009 John Wiley & Sons, Ltd.

Water relations and gas exchange of fan bryophytes and their adaptations to microhabitats in an Asian subtropical montane cloud forest.

Science.gov (United States)

Song, Liang; Zhang, Yong-Jiang; Chen, Xi; Li, Su; Lu, Hua-Zheng; Wu, Chuan-Sheng; Tan, Zheng-Hong; Liu, Wen-Yao; Shi, Xian-Meng

2015-07-01

Fan life forms are bryophytes with shoots rising from vertical substratum that branch repeatedly in the horizontal plane to form flattened photosynthetic surfaces, which are well suited for intercepting water from moving air. However, detailed water relations, gas exchange characteristics of fan bryophytes and their adaptations to particular microhabitats remain poorly understood. In this study, we measured and analyzed microclimatic data, as well as water release curves, pressure-volume relationships and photosynthetic water and light response curves for three common fan bryophytes in an Asian subtropical montane cloud forest (SMCF). Results demonstrate high relative humidity but low light levels and temperatures in the understory, and a strong effect of fog on water availability for bryophytes in the SMCF. The facts that fan bryophytes in dry air lose most of their free water within 1 h, and a strong dependence of net photosynthesis rates on water content, imply that the transition from a hydrated, photosynthetically active state to a dry, inactive state is rapid. In addition, fan bryophytes developed relatively high cell wall elasticity and the osmoregulatory capacity to tolerate desiccation. These fan bryophytes had low light saturation and compensation point of photosynthesis, indicating shade tolerance. It is likely that fan bryophytes can flourish on tree trunks in the SMCF because of substantial annual precipitation, average relative humidity, and frequent and persistent fog, which can provide continual water sources for them to intercept. Nevertheless, the low water retention capacity and strong dependence of net photosynthesis on water content of fan bryophytes indicate a high risk of unbalanced carbon budget if the frequency and severity of drought increase in the future as predicted.

Measurement and modeling of diel variability of polybrominated diphenyl ethers and chlordanes in air.

Science.gov (United States)

Moeckel, Claudia; Macleod, Matthew; Hungerbühler, Konrad; Jones, Kevin C

2008-05-01

Short-term variability of concentrations of polybrominated diphenyl ethers (PBDEs) and chlordanes in air at a semirural site in England over a 5 day period is reported. Four-hour air samples were collected during a period dominated by a high pressure system that produced stable diel (24-h) patterns of meteorological conditions such as temperature and atmospheric boundary layer height. PBDE and chlordane concentrations showed clear diel variability with concentrations in the afternoon and evening being 1.9 - 2.7 times higher than in the early morning. The measurements are interpreted using a multimedia mass balance model parametrized with forcing functions representing local temperature, atmospheric boundary layer height, wind speed and hydroxyl radical concentrations. Model results indicate that reversible, temperature-controlled air-surface exchange is the primary driver of the diel concentration pattern observed for chlordanes and PBDE 28. For higher brominated PBDE congeners (47, 99 and 100), the effect of variable atmospheric mixing height in combination with irreversible deposition on aerosol particles is dominant and explains the diel patterns almost entirely. Higher concentrations of chlordanes and PBDEs in air observed at the end of the study period could be related to likely source areas using back trajectory analysis. This is the first study to clearly document diel variability in concentrations of PBDEs in air over a period of several days. Our model analysis indicates that high daytime and low nighttime concentrations of semivolatile organic chemicals can arise from different underlying driving processes, and are not necessarily evidence of reversible air-surface exchange on a 24-h time scale.

Air-sea exchanges of materials in the Indian Ocean: Concerns and strategies

Digital Repository Service at National Institute of Oceanography (India)

DileepKumar, M.

biological production is entirely due to leakage of agricultural effluents into coastal waters, as the present knowledge on the seasonal variability of nutrients and biological production in waters along the Indian coast is still limited. If this theory... to gaseous CO2 with minor reduction in pH. The gaseous CO2 in seawater determines the extent of air-sea exchange. But small changes in temperature or pH can modify gaseous CO2 content in seawater. Thus shifts in physico- chemical and biological regimes...

Organochlorine pesticides in soils of Mexico and the potential for soil-air exchange

Energy Technology Data Exchange (ETDEWEB)

Wong, Fiona [Centre for Atmospheric Research Experiments, Science and Technology Branch, Environment Canada, 6248 Eighth Line, Egbert, Ontario L01 1N0 (Canada); Department of Chemistry, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4 (Canada); Alegria, Henry A. [Department of Environmental Science, Policy and Geography, University of South Florida St. Petersburg, 140 7th Ave. S., St. Petersburg, FL 33701 (United States); Bidleman, Terry F., E-mail: terry.bidleman@ec.gc.c [Centre for Atmospheric Research Experiments, Science and Technology Branch, Environment Canada, 6248 Eighth Line, Egbert, Ontario L01 1N0 (Canada)

2010-03-15

The spatial distribution of organochlorine pesticides (OCs) in soils and their potential for soil-air exchange was examined. The most prominent OCs were the DDTs (Geometric Mean, GM = 1.6 ng g{sup -1}), endosulfans (0.16 ng g{sup -1}), and toxaphenes (0.64 ng g{sup -1}). DDTs in soils of southern Mexico showed fresher signatures with higher F{sub DDTe} = p,p'-DDT/(p,p'-DDT + p,p'-DDE) and more racemic o,p'-DDT, while the signatures in the central and northern part of Mexico were more indicative of aged residues. Soil-air fugacity fractions showed that some soils are net recipients of DDTs from the atmosphere, while other soils are net sources. Toxaphene profiles in soils and air showed depletion of Parlar 39 and 42 which suggests that soil is the source to the atmosphere. Endosulfan was undergoing net deposition at most sites as it is a currently used pesticide. Other OCs showed wide variability in fugacity, suggesting a mix of net deposition and volatilization. - Chemical profiles of residues and soil-air fugacities are used to assess the potential of soil as a source of organochlorine pesticides to the air of Mexico.

Seasonal atmospheric deposition and air-sea gaseous exchange of polycyclic aromatic hydrocarbons over the Yangtze River Estuary, East China Sea: Implication for the source-sink processes

Science.gov (United States)

Jiang, Y.; Guo, Z.

2017-12-01

As the home of the largest port in the world, the Yangtze River Estuary (YRE) in the East China Sea (ECS) is adjacent to the largest economic zone in China with more than 10% of Chinese population and provides one-fifth of national GDP. The YRE is under the path of contaminated East Asian continental outflow. These make the YRE unique for the pollutant biogeochemical cycling in the world. In this work, 94 pairs of air samples and 20 surface seawater samples covering four seasons were collected from a remote receptor site in the YRE from March 2014 to January 2015, in order to explore the seasonal fluxes of air-sea gaseous exchange and atmospheric dry and wet deposition of 15 polycyclic aromatic hydrocarbons (PAHs) and their source-sink processes at the air-sea interface. The average dry and wet deposition fluxes of 15 PAHs were estimated as 879 ± 1393 ng m-2 d-1 and 755 ± 545 ng m-2 d-1, respectively. The gaseous PAHs were released from seawater to atmosphere during the whole year with an average of 3039 ± 2030 ng m-2 d-1. The gaseous exchange of PAHs was referred as the dominant process at the air-sea interface in the YRE as the magnitude of volatilization flux of PAHs exceeded that of the total dry and wet deposition. The gaseous PAH exchange flux was dominated by 3-ring PAHs, with the highest value in summer while lowest in winter, depicting a strong seasonal variation due to temperature, wind speed and air-sea concentration gradient difference among seasons. Based on the simplified mass balance estimation, net 9.6 tons/y of PAHs was volatilized from seawater to atmosphere with an area of approximately 20000 km2 in the YRE. Apart from Yangtze River input and ocean ship emissions in the entire year, the selective release of low molecular weight PAHs from sediments in winter due to re-suspension triggered by the East Asian winter monsoon could be another possible source for dissolved PAHs. This work suggests that the source-sink processes of PAHs at air

Experiments probing the influence of air exchange rates on secondary organic aerosols derived from indoor chemistry

DEFF Research Database (Denmark)

Weschler, Charles J.; Shields, H.C.

2003-01-01

Reactions between ozone and terpenes have been shown to increase the concentrations of submicron particles in indoor settings. The present study was designed to examine the influence of air exchange rates on the concentrations of these secondary organic aerosols as well as on the evolution of the...

Enolate Stabilization by Anion-π Interactions: Deuterium Exchange in Malonate Dilactones on π-Acidic Surfaces.

Science.gov (United States)

Miros, François N; Zhao, Yingjie; Sargsyan, Gevorg; Pupier, Marion; Besnard, Céline; Beuchat, César; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

2016-02-18

Of central importance in chemistry and biology, enolate chemistry is an attractive topic to elaborate on possible contributions of anion-π interactions to catalysis. To demonstrate the existence of such contributions, experimental evidence for the stabilization of not only anions but also anionic intermediates and transition states on π-acidic aromatic surfaces is decisive. To tackle this challenge for enolate chemistry with maximal precision and minimal uncertainty, malonate dilactones are covalently positioned on the π-acidic surface of naphthalenediimides (NDIs). Their presence is directly visible in the upfield shifts of the α-protons in the (1) H NMR spectra. The reactivity of these protons on π-acidic surfaces is measured by hydrogen-deuterium (H-D) exchange for 11 different examples, excluding controls. The velocity of H-D exchange increases with π acidity (NDI core substituents: SO2 R>SOR>H>OR>OR/NR2 >SR>NR2 ). The H-D exchange kinetics vary with the structure of the enolate (malonates>methylmalonates, dilactones>dithiolactones). Moreover, they depend on the distance to the π surface (bridge length: 11-13 atoms). Most importantly, H-D exchange depends strongly on the chirality of the π surface (chiral sulfoxides as core substituents; the crystal structure of the enantiopure (R,R,P)-macrocycle is reported). For maximal π acidity, transition-state stabilizations up to -18.8 kJ mol(-1) are obtained for H-D exchange. The Brønsted acidity of the enols increases strongly with π acidity of the aromatic surface, the lowest measured pKa =10.9 calculates to a ΔpKa =-5.5. Corresponding to the deprotonation of arginine residues in neutral water, considered as "impossible" in biology, the found enolate-π interactions are very important. The strong dependence of enolate stabilization on the unprecedented seven-component π-acidity gradient over almost 1 eV demonstrates quantitatively that such important anion-π activities can be expected only from

Processes of ammonia air–surface exchange in a fertilized Zea mays canopy

Directory of Open Access Journals (Sweden)

E. Nemitz

2013-02-01

Full Text Available Recent incorporation of coupled soil biogeochemical and bi-directional NH3 air–surface exchange algorithms into regional air quality models holds promise for further reducing uncertainty in estimates of NH3 emissions from fertilized soils. While this represents a significant advancement over previous approaches, the evaluation and improvement of such modeling systems for fertilized crops requires process-level field measurements over extended periods of time that capture the range of soil, vegetation, and atmospheric conditions that drive short-term (i.e., post-fertilization and total growing season NH3 fluxes. This study examines the processes of NH3 air–surface exchange in a fertilized corn (Zea mays canopy over the majority of a growing season to characterize soil emissions after fertilization and investigate soil–canopy interactions. Micrometeorological flux measurements above the canopy, measurements of soil, leaf apoplast and dew/guttation chemistry, and a combination of in-canopy measurements, inverse source/sink, and resistance modeling were employed. Over a period of approximately 10 weeks following fertilization, daily mean and median net canopy-scale fluxes yielded cumulative total N losses of 8.4% and 6.1%, respectively, of the 134 kg N ha−1 surface applied to the soil as urea ammonium nitrate (UAN. During the first month after fertilization, daily mean emission fluxes were positively correlated with soil temperature and soil volumetric water. Diurnally, maximum hourly average fluxes of ≈ 700 ng N m−2 s−1 occurred near mid-day, coincident with the daily maximum in friction velocity. Net emission was still observed 5 to 10 weeks after fertilization, although mid-day peak fluxes had declined to ≈ 125 ng N m−2 s−1. A key finding of the surface chemistry measurements was the observation of high pH (7.0–8.5 in leaf dew/guttation, which reduced the ability of the canopy to recapture soil emissions during wet periods

Modeled Trends in Impacts of Landing and Takeoff Aircraft Emissions on Surface Air-Quality in U.S for 2005, 2010 and 2018

Science.gov (United States)

Vennam, L. P.

2014-12-01

Understanding the present-day impacts of aircraft emissions on surface air quality is essential to plan potential mitigation policies for future growth. Stringent regulation on mobile source-related emissions in the recent past coupled with anticipated rise in the growth in aviation activity can increase the relative impacts of aviation-attributable surface air quality if adequate measures for reducing aviation emissions are not implemented. Though aircraft emissions during in-flight mode (at upper altitudes) contribute a significant (70 - 80%) proportion of the total aviation emissions, landing and takeoff (LTO) related emissions can have immediate impact on surface air quality, as most of the large airports are located in urban areas, specifically those that are designated in nonattainment for O3 and/or PM2.5. In this study, we modeled impacts of aircraft emissions during LTO cycles on surface air quality using the latest version of the CMAQ model for two contemporary years (2005, 2010) and one future year (2018). For this regional scale modeling study, we used highly resolved aircraft emissions from the FAA's Aviation Environmental Design Tool (AEDT), meteorology from NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA) downscaled with the WRF model, dynamically varying chemical boundary conditions from the CAM-Chem global model (which also used the same AEDT emissions but at the global scale), and spatio-temporally resolved lightning NOx emissions estimated using National Lightning Detection Network (NLDN) flash density data. We evaluated our model results with air quality observations from surface-based networks and in-situ aircraft observation data for the contemporary years. We will present results from model evaluation using this enhanced modeling system, as well as the trajectories in aviation- related air quality (focusing on O3, NO2 and PM2.5) for the three modeling years considered in this study. These findings will help plan

Polycyclic aromatic hydrocarbon (PAH) deposition to and exchange at the air-water interface of Luhu, an urban lake in Guangzhou, China

International Nuclear Information System (INIS)

Li Jun; Cheng Hairong; Zhang Gan; Qi Shihua; Li Xiangdong

2009-01-01

Urban lakes are vulnerable to the accumulation of semivolatile organic compounds, such as PAHs from wet and dry atmospheric deposition. Little was reported on the seasonal patterns of atmospheric deposition of PAHs under Asian monsoon climate. Bulk (dry + wet) particle deposition, air-water diffusion exchange, and vapour wet deposition of PAHs in a small urban lake in Guangzhou were estimated based on a year-round monitoring. The total PAH particle deposition fluxes observed were 0.44-3.46 μg m -2 day -1 . The mean air-water diffusive exchange flux was 20.7 μg m -2 day -1 . The vapour deposition fluxes of PAHs ranged 0.15-8.26 μg m -2 day -1 . Remarkable seasonal variations of particulate PAH deposition, air-water exchange fluxes and vapour wet deposition were influenced by seasonal changes in meteorological parameters. The deposition fluxes were predominantly controlled by the precipitation intensity in wet season whereas by atmospheric concentration in dry season. - The PAH deposition fluxes were predominantly controlled by the precipitation intensity in wet season whereas by atmospheric concentration in dry season

Critical evaluation of a new passive exchange-meter for assessing multimedia fate of persistent organic pollutants at the air-soil interface

International Nuclear Information System (INIS)

Liu, Xiang; Ming, Li-Li; Nizzetto, Luca; Borgå, Katrine; Larssen, Thorjørn; Zheng, Qian; Li, Jun; Zhang, Gan

2013-01-01

A new passive exchange meter (PEM) to measure inter-compartment fluxes of persistent organic pollutants (POPs) at the interface between soil and the atmosphere is described. The PEM uses labeled reference compounds (RC) added in-situ to vegetation litter deployed in open cylinders designed to trap the vertical downward export of the RCs while allowing free exchange of POPs between litter and air. Fluxes of native compounds (bulk deposition, volatilization and downward export) are quantitatively tracked. One scope of the PEM is to investigate the influence of biogeochemical controls on contaminant re-mobilization. The PEM performance was tested in a subtropical forest by comparing measurements under dense canopy and in a canopy gap; conditions in which deposition and turn-over of organic matter (OM) occur at different rates. Significant differences in fate processes were successfully detected. Surprisingly, mobilization by leaching of more hydrophobic compounds was higher under canopy, possibly as a result of canopy mediated enhancement of OM degradation. -- Highlights: •A new tool for measuring multimedia exchange fluxes of POPs is described. •Deposition, volatilization and leaching, to and from soil surface are targeted. •Precision was sufficient to resolve fluxes differing by less than a factor of 2–5. •Gaps in forest canopy enhanced volatilization of POPs. •Higher leaching of heavier POPs from the litter in the understory is associated to rapid organic matter degradation. -- Time integrated multimedia exchange of POPs in vegetation litter is resolved under dynamic conditions of OM ageing

Symmetric scaling properties in global surface air temperature anomalies

Science.gov (United States)

Varotsos, Costas A.; Efstathiou, Maria N.

2015-08-01

We have recently suggested "long-term memory" or internal long-range correlation within the time-series of land-surface air temperature (LSAT) anomalies in both hemispheres. For example, an increasing trend in the LSAT anomalies is followed by another one at a different time in a power-law fashion. However, our previous research was mainly focused on the overall long-term persistence, while in the present study, the upward and downward scaling dynamics of the LSAT anomalies are analysed, separately. Our results show that no significant fluctuation differences were found between the increments and decrements in LSAT anomalies, over the whole Earth and over each hemisphere, individually. On the contrary, the combination of land-surface air and sea-surface water temperature anomalies seemed to cause a departure from symmetry and the increments in the land and sea surface temperature anomalies appear to be more persistent than the decrements.

Carbapenem-Resistant Acinetobacter baumannii: Concomitant Contamination of Air and Environmental Surfaces.

Science.gov (United States)

Shimose, Luis A; Masuda, Eriko; Sfeir, Maroun; Berbel Caban, Ana; Bueno, Maria X; dePascale, Dennise; Spychala, Caressa N; Cleary, Timothy; Namias, Nicholas; Kett, Daniel H; Doi, Yohei; Munoz-Price, L Silvia

2016-07-01

OBJECTIVE To concomitantly determine the differential degrees of air and environmental contamination by Acinetobacter baumannii based on anatomic source of colonization and type of ICU layout (single-occupancy vs open layout). DESIGN Longitudinal prospective surveillance study of air and environmental surfaces in patient rooms. SETTING A 1,500-bed public teaching hospital in Miami, Florida. PATIENTS Consecutive A. baumannii-colonized patients admitted to our ICUs between October 2013 and February 2014. METHODS Air and environmental surfaces of the rooms of A. baumannii-colonized patients were sampled daily for up to 10 days. Pulsed-field gel electrophoresis (PFGE) was used to type and match the matching air, environmental, and clinical A. baumannii isolates. RESULTS A total of 25 A. baumannii-colonized patients were identified during the study period; 17 were colonized in the respiratory tract and 8 were colonized in the rectum. In rooms with rectally colonized patients, 38.3% of air samples were positive for A. baumannii; in rooms of patients with respiratory colonization, 13.1% of air samples were positive (P=.0001). In rooms with rectally colonized patients, 15.5% of environmental samples were positive for A. baumannii; in rooms of patients with respiratory colonization, 9.5% of environmental samples were positive (P=.02). The rates of air contamination in the open-layout and single-occupancy ICUs were 17.9% and 21.8%, respectively (P=.5). Environmental surfaces were positive in 9.5% of instances in open-layout ICUs versus 13.4% in single-occupancy ICUs (P=.09). CONCLUSIONS Air and environmental surface contaminations were significantly greater among rectally colonized patients; however, ICU layout did not influence the rate of contamination. Infect Control Hosp Epidemiol 2016;37:777-781.

Solution Exchange Lithography: A Versatile Tool for Sequential Surface Engineering

Science.gov (United States)

Pester, Christian; Mattson, Kaila; Bothman, David; Klinger, Daniel; Lee, Kenneth; Discekici, Emre; Narupai, Benjaporn; Hawker, Craig

The covalent attachment of polymers has emerged as a viable strategy for the preparation of multi-functional surfaces. Patterned, surface-grafted polymer brushes provide spatial control over wetting, mechanical, biological or electronic properties, and allow fabrication of `intelligent' substrates which selectively adapt to their environment. However, the route towards patterned polymer brush surfaces often remains challenging, creating a demand for more efficient and less complicated fabrication strategies. We describe the design and application of a novel experimental setup to combine light-mediated and flow chemistry for the fabrication of hierarchical surface-grafted polymer brushes. Using light-mediated, surface initiated controlled radical polymerization and post-functionalization via well-established, and highly efficient chemistries, polymer brush films of previously unimaginable complexity are now shown to be accessible. This methodology allows full flexibility to exchange both lithographic photomasks and chemical environments in-situ, readily affording multidimensional thin film architectures, all from uniformly functionalized substrates.

Relation between 222Rn concentration in outdoor air and lower atmosphere

International Nuclear Information System (INIS)

Kataoka, Toshio; Mori, Tadashige; Yunoki, Eiji; Michihiro, Kenshuh; Sugiyama, Hirokazu; Shimizu, Mitsuo; Tsukamoto, Osamu; Sahashi, Ken.

1991-01-01

Using the height of the surface-based inversion layer obtained by the acoustic sounder returns and the variation of the 222 Rn concentration in the outdoor air during the presence of the surface-based inversion layer, the exhalation rate of 222 Rn is estimated to be 0.020 Bq·m -2 ·s -1 , which is observed elsewhere on land. Furthermore, the exposure rate at 1 m above the air-ground interface due to the short-lived 222 Rn daughters in the outdoor air during the presence of the surface-based inversion layer can be estimated using the height of the surface-based inversion layer and the 222 Rn concentrations in the outdoor air at the ground level before and after the onset of the surface-based inversion layer. From these treatment, it is clearly demonstrated that the monostatic acoustic sounder is useful as a supplementary method for a weather survey which forms a part of monitoring around the nuclear facilities. (author)

Atmosphere-surface interactions over polar oceans and heterogeneous surfaces

Energy Technology Data Exchange (ETDEWEB)

Vihma, T.

1995-12-31

Processes of interaction between the atmospheric boundary layer and the planetary surface have been studied with special emphasis on polar ocean surfaces: the open ocean, leads, polynyas and sea ice. The local exchange of momentum, heat and moisture has been studied experimentally both in the Weddell Sea and in the Greenland Sea. Exchange processes over heterogeneous surfaces are addressed by modelling studies. Over a homogeneous surface, the local turbulent fluxes can be reasonably well estimated using an iterative flux-profile scheme based on the Monin-Obukhov similarity theory. In the Greenland Sea, the near-surface air temperature and the generally small turbulent fluxes over the open ocean were affected by the sea surface temperature fronts. Over the sea ice cover in the Weddell Sea, the turbulent sensible heat flux was generally downwards, and together with an upward oceanic heat flux through the ice it compensated the heat loss from the surface via long-wave radiation. The wind dominated on time scales of days, while the current became important on longer time scales. The drift dynamics showed apparent spatial differences between the eastern and western regions, as well as between the Antarctic Circumpolar Current and the rest of the Weddell Sea. Inertial motion was present in regions of low ice concentration. The surface heterogeneity, arising e.g. from roughness or temperature distribution, poses a problem for the parameterization of surface exchange processes in large-scale models. In the case of neutral flow over a heterogeneous terrain, an effective roughness length can be used to parameterize the roughness effects

Atmosphere-surface interactions over polar oceans and heterogeneous surfaces

Energy Technology Data Exchange (ETDEWEB)

Vihma, T

1996-12-31

Processes of interaction between the atmospheric boundary layer and the planetary surface have been studied with special emphasis on polar ocean surfaces: the open ocean, leads, polynyas and sea ice. The local exchange of momentum, heat and moisture has been studied experimentally both in the Weddell Sea and in the Greenland Sea. Exchange processes over heterogeneous surfaces are addressed by modelling studies. Over a homogeneous surface, the local turbulent fluxes can be reasonably well estimated using an iterative flux-profile scheme based on the Monin-Obukhov similarity theory. In the Greenland Sea, the near-surface air temperature and the generally small turbulent fluxes over the open ocean were affected by the sea surface temperature fronts. Over the sea ice cover in the Weddell Sea, the turbulent sensible heat flux was generally downwards, and together with an upward oceanic heat flux through the ice it compensated the heat loss from the surface via long-wave radiation. The wind dominated on time scales of days, while the current became important on longer time scales. The drift dynamics showed apparent spatial differences between the eastern and western regions, as well as between the Antarctic Circumpolar Current and the rest of the Weddell Sea. Inertial motion was present in regions of low ice concentration. The surface heterogeneity, arising e.g. from roughness or temperature distribution, poses a problem for the parameterization of surface exchange processes in large-scale models. In the case of neutral flow over a heterogeneous terrain, an effective roughness length can be used to parameterize the roughness effects

Functionalization of Cadmium Selenide Quantum Dots with Poly(ethylene glycol): Ligand Exchange, Surface Coverage, and Dispersion Stability.

Science.gov (United States)

Wenger, Whitney Nowak; Bates, Frank S; Aydil, Eray S

2017-08-22

Semiconductor quantum dots synthesized using rapid mixing of precursors by injection into a hot solution of solvents and surfactants have surface ligands that sterically stabilize the dispersions in nonpolar solvents. Often, these ligands are exchanged to disperse the quantum dots in polar solvents, but quantitative studies of quantum dot surfaces before and after ligand exchange are scarce. We studied exchanging trioctylphosphine (TOP) and trioctylphosphine oxide (TOPO) ligands on as-synthesized CdSe quantum dots dispersed in hexane with a 2000 g/mol thiolated poly(ethylene glycol) (PEG) polymer. Using infrared spectroscopy we quantify the absolute surface concentration of TOP/TOPO and PEG ligands per unit area before and after ligand exchange. While 50-85% of the TOP/TOPO ligands are removed upon ligand exchange, only a few are replaced with PEG. Surprisingly, the remaining TOP/TOPO ligands outnumber the PEG ligands, but these few PEG ligands are sufficient to disperse the quantum dots in polar solvents such as chloroform, tetrahydrofuran, and water. Moreover, as-synthesized quantum dots once easily dispersed in hexane are no longer dispersible in nonpolar solvents after ligand exchange. A subtle coverage-dependent balance between attractive PEG-solvent interactions and repulsive TOP/TOPO-solvent interactions determines the dispersion stability.

Recovering heat from waste air from stables

Energy Technology Data Exchange (ETDEWEB)

1983-01-01

A milk cow gives off 35.7 kW h/d via its body, excreta and urine. 68.4% of this is body heat. Part of this waste heat escapes with the waste air from the cowsheds. The heat can be recovered from the waste air by an air/air heat exchanger. The air is collected and taken to a heat exchanger. In the heat exchanger, fresh air is heated by the waste air, and is distributed over the cowshed by a system of ducts. The heated waste air escapes through a central chimney at the end of the heat exchanger. It is sensible to fit the heat exchanger above the cowshed roof, if there is sufficient space available and the chimney should run upwards from the cowshed. A double heat exchanger makes it possible to allocate each half of the cowshed to half of the heat exchanger.

Dry coolers and air-condensing units (Review)

Science.gov (United States)

Milman, O. O.; Anan'ev, P. A.

2016-03-01

The analysis of factors affecting the growth of shortage of freshwater is performed. The state and dynamics of the global market of dry coolers used at electric power plants are investigated. Substantial increase in number and maximum capacity of air-cooled condensers, which have been put into operation in the world in recent years, are noted. The key reasons facilitating the choice of developers of the dry coolers, in particular the independence of the location of thermal power plant from water sources, are enumerated. The main steam turbine heat removal schemes using air cooling are considered, their comparison of thermal efficiency is assessed, and the change of three important parameters, such as surface area of heat transfer, condensate pump flow, and pressure losses in the steam exhaust system, are estimated. It is shown that the most effective is the scheme of direct steam condensation in the heat-exchange tubes, but other schemes also have certain advantages. The air-cooling efficiency may be enhanced much more by using an air-cooling hybrid system: a combination of dry and wet cooling. The basic applied constructive solutions are shown: the arrangement of heat-exchange modules and the types of fans. The optimal mounting design of a fully shopassembled cooling system for heat-exchange modules is represented. Different types of heat-exchange tubes ribbing that take into account the operational features of cooling systems are shown. Heat transfer coefficients of the plants from different manufacturers are compared, and the main reasons for its decline are named. When using evaporative air cooling, it is possible to improve the efficiency of air-cooling units. The factors affecting the faultless performance of dry coolers (DC) and air-condensing units (ACU) and the ways of their elimination are described. A high velocity wind forcing reduces the efficiency of cooling systems and creates preconditions for the development of wind-driven devices. It is noted that

Thermotechnical comparison of possible operation variants for air conditioning system of mine air with high pressure heat exchanger and hydrodistributor

OpenAIRE

Korsun, F. O.

2015-01-01

Problem. There are vast losses of cold that take place during the transition of cold to deep horizons of shafts by the mine air conditioning system (MASC) with high pressure heat exchanger. Cold is transferred by the recuperative way. Vast losses of cold mean vast losses of electricity to in order to supply it. Any enterprise requires the reduction of electricity consumption. This article gives proposals on how to replace HPHE into hydrodistributor which will considerably reduce cold losses. ...

Air conditioner with three stages of indirect regeneration

International Nuclear Information System (INIS)

Worthington, M.N.

1987-01-01

An air conditioner is described comprising: a cabinet defining an internal evaporation chamber and having an air inlet and an air outlet; a heat exchanger mounted in the cabinet and defining an air movement path between the air inlet and the air outlet; means for supplying air to be cooled to the air inlet of the cabinet of movement through the air movement path of the heat exchanger in a heat exchanger relationship; air diversion means for continuously diverting some of the air emerging from the air outlet of the cabinet; and means in the evaporation chamber of the cabinet for recirculating spraying water into the chiller tube of the heat exchanger for interacting with the diverted air moving therethrough to evaporatively cool the heat exchanger

Improving the indoor air quality by using a surface emissions trap

Science.gov (United States)

Markowicz, Pawel; Larsson, Lennart

2015-04-01

The surface emissions trap, an adsorption cloth developed for reducing emissions of volatile organic compounds and particulate matter from surfaces while allowing evaporation of moisture, was used to improve the indoor air quality of a school building with elevated air concentrations of 2-ethyl-1-hexanol. An improvement of the perceived air quality was noticed a few days after the device had been attached on the PVC flooring. In parallel, decreased air concentrations of 2-ethyl-1-hexanol were found as well as a linear increase of the amounts of the same compound adsorbed on the installed cloth as observed up to 13 months after installation. Laboratory studies revealed that the performance of the device is not affected by differences in RH (35-85%), temperature (30-40 °C) or by accelerated aging simulating up to 10 years product lifetime, and, from a blinded exposure test, that the device efficiently blocks chemical odors. This study suggests that the device may represent a fast and efficient means of restoring the indoor air quality in a building e.g. after water damage leading to irritating and potentially harmful emissions from building material surfaces indoors.

Functional design of heat exchange for pneumatic vehicles

Science.gov (United States)

Xu, Z. G.; Yang, D. Y.; Shen, W. D.; Liu, T. T.

2017-10-01

With the increasingly serious environmental problems, especially the impact of fog and haze, the development of air powered vehicles has become an important research direction of new energy vehicles. Quadrature test was done with different materials, i.e. stainless steel and aluminum alloy, at different inlet pressures, using different expansion gases, i.e. air, CO2, for heat exchanging properties for pneumatic vehicles. The mathematics as well as simulation methods are used to analyze the different heat exchanging effects in the multistage cylinder. The research results showed that the stainless steel has better effects in heat exchanging than Aluminum Alloy; the intake pressure has little effect on CO2 than the air in heat exchanging effect. CO2 is better in heat exchanging than air.

Speciated particle dry deposition to the sea surface: Results from ASEPS '97

DEFF Research Database (Denmark)

Pryor, S.C.; Barthelmie, R.J.; Geernaert, L.L.S.

1999-01-01

on Precipitation Scavenging and Atmosphere-Surface Exchange Processes. AMS, Richland, Washington, USA, 12pp.) model to calculate size-segregated dry deposition of particle inorganic nitrogen compounds to the western Baltic during the late Spring of 1997 based on data collected as part of the Air-Sea Exchange...

Comparison of desiccant air conditioning systems with different indirect evaporative air coolers

International Nuclear Information System (INIS)

Pandelidis, Demis; Anisimov, Sergey; Worek, William M.; Drąg, Paweł

2016-01-01

Highlights: • A numerical study of desiccant air conditioning systems is presented. • The ε-NTU model is used for the analysis. • Different arrangements of the desiccant systems were compared. • The systems were compared under different operating conditions. - Abstract: This paper presents a numerical analysis of three desiccant air-conditioning systems equipped with different indirect evaporative air coolers: (1) the cross-flow Maisotsenko cycle heat and mass exchanger (HMX), (2) the regenerative counter-flow Maisotsenko cycle heat and mass exchanger and (3) the standard cross-flow evaporative air cooler. To analyze the desiccant wheel and the indirect evaporative air coolers, the modified ε-NTU-model was used. The simulations were performed under assumption that the desiccant wheel is regenerated with air heated to relatively low temperature values (50–60 °C), which can be produced with solar panels in typical moderate climatic conditions. It was established that the main advantage of the presented solutions is that they can provide comfort conditions even with less effective dehumidification. The different systems were compared under variable selected operational factors (i.e. inlet air temperature, humidity and regeneration air temperature). The analysis allowed establishing the advantages and disadvantages of presented solutions and allowed estimating their application potential.