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1

Heat transfer performance of internally finned tubes in turbulent flow  

Science.gov (United States)

The heat transfer performance for heating water in turbulent flow was experimentally determined for 11 tubes having integral internal spiral and longitudinal fins. Individual tube performance is presented and compared with a smooth tube datum at constant pumping power. A longitudinal and spiral fin tube from within the 11 tubes and a smooth tube were also tested heating a 50% w/w ethylene glycol-water solution, and these data are included. These data are compared with relevant data available in the literature. Correlating equations are presented for heat transfer and Fanning friction factor that describe the air, water, and ethylene glycol-water data within + or - 10%.

Carnavos, T. C.

1980-06-01

2

Performance Evaluation of Plate-Fin-And Tube Heat Exchanger with Wavy Fins- A Review  

Directory of Open Access Journals (Sweden)

Full Text Available The plate fin-and-tube heat exchangers are widely used in variety of industrial applications, particularly in the heating, air-conditioning and refrigeration, HVAC industries. In most cases the working fluid is liquid on the tube side exchanging heat with a gas, usually air. It is seen that the performance of heat exchangers can be greatly increased with the use of unconventionally shaped flow passages such as plain, perforated offset strip, louvered, wavy, vortex generator and pin. The current study is focused on wavy-fin. The wavy surface can lengthen the path of airflow and cause better airflow mixing. In order to design better heat exchangers and come up with efficient designs, a thorough understanding of the flow of air in these channels is required. Hence this study focuses on the heat transfer and friction characteristics of the air side for wavy fin and tube heat exchanger.

Sandip S. Kale

2014-09-01

3

Performance Prediction of Cross-finned Tube Heat Exchangers  

Science.gov (United States)

An important issue in heat pumps is increasing their efficiency, in order to achieve a significant optimization for heat exchangers. Techniques to simulate the flow length averaged heat transfer coefficient and static pressure drop through the flow passage are presented in this paper. In addition, an analytical evaluation of the cost reduction for a cross-fined tube heat exchanger of outdoor heat pump units is instantiated. The dimensionless factors, Colburn's factor j and Fanning's friction factor f, express the heat transfer performance and frictional characteristics, as a function of Reynolds number. These depend on slit possession, an original parameter used in this study. Further, this paper describes an approximate expression of the fin efficiency, which can be used for to survey the fin parameters. The above three concepts were necessary to forecast the performance on the airside. In the results, the cost minimum point was obtained with a comparable performance.

Kondou, Chieko; Senshu, Takao; Matsumura, Kenji; Oguni, Kensaku

4

Frosting Performance of Fin-and-Tube Evaporators with Small Copper Tubes Diameter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In modern heat pump systems, the heat exchangers use enhanced heat transfer surfaces for both air and refrigerant sides. In air conditioning applications, conventional 9.5 mm (3/8 inch) tube diameter fin-and-tube coils are slowly being replaced by microchannel heat exchangers. However, during heating mode the energy performance of heat pump systems with microchannel outdoor coils are generally lower than those of fin-and-tube direct-expansion evaporators due to a higher frequency of defrost c...

Cremaschi, Lorenzo; Moallem, Ehsan; Fisher, Daniel E.; Hong, Tommy; Padhmanabhan, Sankar

2012-01-01

5

Effect of fin pitch and number of tube rows on the air side performance of herringbone wavy fin and tube heat exchangers  

International Nuclear Information System (INIS)

An experimental study is conducted to investigate the effects of a fin pitch and number of tube rows on the air side performance of fin and tube heat exchangers having herringbone wavy fin configuration at various fin thicknesses. A total of 10 samples of fin and tube heat exchanger with a tube outside diameter of 9.53mm, transverse tube pitch of 25.4mm and longitudinal tube pitch of 19.05mm, having various fin pitches, number of tube rows and fin thicknesses, are tested in a well insulated open wind tunnel. The heat exchangers are made from aluminium plate finned, copper tube. Ambient air is used as a working fluid in the air side while hot water is used for the tube side. The results are presented as the variation of the Colburn factor and the friction factor with the Reynolds number based on the fin collar outside diameter (ReDc). The experimental results reveal that the fin pitch has an insignificant effect on the heat transfer characteristic. The friction factor increases with increasing fin pitch when ReDc>2500, approximately. The Colburn factor and the friction factor decrease with increasing number of tube rows when ReDc<4000, approximately. These results remain the same when the fin thickness is changed

6

Comparative performance of rippled fin plate fin and tube heat exchangers  

International Nuclear Information System (INIS)

Continuous rippled fins are preferred to interrupted fins in applications where fouling by fibrous matter or insects is a problem. The performance characteristic of three rippled fin heat exchangers have been measured in a thermal wind tunnel. The results of these measurements are reported and comparisons are made wtih published data on similar surfaces. The performance evaluation criteria used as the basis for the comparisons were those recommened by Shah (1978). The tested rippled fin surfaces were found to have a higher performance than a similar surface reported in Kay and London (1984). The heat transfer enhancement was found to be dependent upon the profile of the fin

7

Performance of residential air-conditioning systems with flow maldistribution in fin-and-tube evaporators  

DEFF Research Database (Denmark)

Refrigerant and airflow maldistribution in fin-and-tube evaporators for residential air-conditioning was investigated with numerical modeling. Fin-and-tube heat exchangers usually have a pre-defined circuitry. However, the objective in this study was to perform a generic investigation of each individual maldistribution source in an independent manner. Therefore, the evaporator and the condenser were simplified to be straight tubes for the purposes of this study. The numerical model of the R410A system, its verification and an investigation of individual maldistribution sources are presented in this paper. The maldistribution sources of interest were: inlet liquid/vapor phase distribution, feeder tube bending and airflow distribution. The results show that maldistribution reduced the cooling capacity and the coefficient of performance of the system. In particular, different phase distribution and non-uniform airflow distribution reduced the performance significantly. Different feeder tube bendings only caused a minor decrease in performance.

Kærn, Martin Ryhl; Brix, Wiebke

2011-01-01

8

Effect of fin density on the heat transfer and pressure drop performance of low-finned tube banks  

International Nuclear Information System (INIS)

Heat transfer and pressure drop data are presented for equilateral-triangular pitch tube bundles containing low-finned tubes with fin counts between 0.4 and 1.06 fins per mm. Two types of finned tubes were tested. A new low-fin heat transfer correlation was developed which predicted these new data and additional data from five other sources within an error range from minus 20 percent to plus 31 percent. A necessary dimensionless group required to obtain this accuracy was the fin diameter/fin spacing ratio. Existing friction factor correlations were not successful in predicting these new pressure drop results. A new low-fin friction factor correlation was developed which predicted these data and additional published data within an error range from minus 19 percent to plus 27 percent. 14 refs

9

Study on performance of plate fin - oval tube heat exchanger with vortex generators  

International Nuclear Information System (INIS)

An experimental study was carried out to investigate the enhancement of heat transfer from the in-line and staggered arrays of oval tubes in the plate fin - tube heat exchanger with Delta - Wing type Vortex Generators(DWVG). Measurements of average heat(mass) - transfer coefficients on the tube surface were made using a naphthalene sublimation technique, and the flow losses were measured for Reynolds number ranging from 2000 to 3200. The influence of vortex generators parameters such as position and angle of attack was investigated. It was found that the heat transfer enhancement were increased by the existence of a vortex generators and flow losses were decreased by the oval tubes. The results indicate that performance of plate fin - tube heat exchanger can be improved simultanously by using vortex generators and oval tubes

10

Experimental study of the airside performance of tube row spacing in finned tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Almost all of the studies in dehumidifying coils are experimental studies. In this study, effect of tube regulation space on heat and mass transfer and friction factor for heat exchangers made from aluminum fins and cooper tubes are identified experimentally. External surface heat transfer coefficient, Colburn factor and friction factor was calculated by the help of the computer program by using experimental values done. After the diagrams investigated, with the decreasing of tube row spacing the external surface heat transfer in the dry surface and friction factor increased. If wet and dry surfaces are compared, Colburn and friction factor in wet surfaces is larger than Colburn and friction factor in dry surfaces. (orig.)

Halici, Fethi; Taymaz, Imdat [Sakarya University, Mechanical Engineering Department, Adapazari (Turkey)

2006-07-15

11

Investigations on the heat transfer performance of edge-shaped finned-tubes  

Science.gov (United States)

The third generation enhanced heat transfer technologies, such as three-dimensional fin and dimple, are still important means of improving energy efficiency and will continue to be challenging issues. This paper concentrates on the analysis of the condensation heat transfer performance of an edge-shaped finned-tube fabricated by extrusion-ploughing process. Experimental results show that the overall heat transfer coefficient increases with increases of volumetric flow rate of cold water and heat flux whereas the shell side heat transfer coefficient decreases with volumetric flow rate and heat flux increasing. At the similar volumetric flow rate, the shell side heat transfer coefficient of the edge-shaped finned-tube is 4-6 times larger than that of the smooth tube. At the similar volumetric flow rate, the shell side heat transfer coefficient of edge-shaped finned-tube increases with ploughing depth increasing. At the same temperature difference between wall and vapor, the shell side heat transfer coefficient is also higher than what had been reported in the literature.

Wang, Xiao-wu; Wan, Zhen-ping; Tang, Yong

2014-09-01

12

A numerical analysis on heat transfer performance from various gap size between finned tube module and side-wall in finned tube evaporator  

International Nuclear Information System (INIS)

Recently, Heat Recovery Steam Generator(HRSG) is widely used in various commercial places such as hospital, restaurant, and sauna for steam generation equipment due to increasing demand on steam usage for disinfection or fumigation. In HRSG, finned tube type evaporator is usually utilized to enhance heat transfer performance for higher steam generation. Most previous research so far has been focused on heat transfer enhancement aspect from geometry of each individual fin such as pitch distance, length, and thickness. In current study, we have tried to identify the effect from gap size between tube module and side wall on overall heat transfer. We found out that the gap size has considerable effect on total heat transfer rate. We also observed that both heat transfer performance and pressure drop is decreasing with increasing gas size.

13

A numerical investigation of the geometric effects on the performance of plate finned-tube heat exchanger  

International Nuclear Information System (INIS)

This study numerically examines the geometric parameters on the performance of a two-row fin-and-tube heat exchanger. Effects of fin pitch, tube pitch, fin thickness, and tube diameter are termed with. The simulation indicates that the performance, in terms of Q/?P and COP, increases with longitudinal tube pitch or with transverse tube pitch, and it decreases with larger tube diameter or fin thickness. An optimum value for Q/?P occurs at a 6-8 fpi at a fixed flow rate condition. There is not much difference in choosing the index of Q/?P or COP under fixed flow rate condition. However, when the simulation are performed with the actual axial fan whose P-Q curve being implemented. It is found that Q/?P peaks at 12 fpi while COP peaks at 16 fpi.

14

A numerical investigation of the geometric effects on the performance of plate finned-tube heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

This study numerically examines the geometric parameters on the performance of a two-row fin-and-tube heat exchanger. Effects of fin pitch, tube pitch, fin thickness, and tube diameter are termed with. The simulation indicates that the performance, in terms of Q/{delta}P and COP, increases with longitudinal tube pitch or with transverse tube pitch, and it decreases with larger tube diameter or fin thickness. An optimum value for Q/{delta}P occurs at a 6-8 fpi at a fixed flow rate condition. There is not much difference in choosing the index of Q/{delta}P or COP under fixed flow rate condition. However, when the simulation are performed with the actual axial fan whose P-Q curve being implemented. It is found that Q/{delta}P peaks at 12 fpi while COP peaks at 16 fpi. (author)

Lu, Chi-Wen; Huang, Jeng-Min; Nien, W.C. [Department of Refrigeration, Air Conditioning and Energy Engineering, National Chin-Yi University of Technology, No. 35, Lane 215, Chung-Shan Rd., Sec. 1, Taiping City, Taichung County 411 (China); Wang, Chi-Chuan [Department of Mechanical Engineering, National Chiao Tung University, 1001 University Road, 300 Hsinchu (China)

2011-03-15

15

Numerical analysis on the frosting performance of a fin-tube evaporator for a refrigerator  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study is to provide numerical and experimental data that can be used to investigate the performance characteristics of a flat plate fin-tube evaporator in household and commercial refrigerators under frosting conditions. Computer simulations with variations of operating conditions such as air inlet temperature, relative humidity, and geometries were performed to find out optimal design parameters of a fin-tube evaporator for household and commercial refrigerators. The tube-by-tube method was used in the simulation and the frost growth model was considered under frosting conditions. The developed analytical model predicted the decreasing rates of heat transfer capacity and air flow rate ratio within {+-} 10% compared to the experimental results for a refrigerator under real operating conditions. As a result, the frost thickness at 3 .deg. C and 80% is increased 40% than that of -3 .deg. C and 80%, and the frost thickness at 3 .deg. C and 90% is increased 30% than that of 3 .deg. C and 60%. Accordingly, the operating time of the evaporator in the refrigerator was reduced with the increase of the decreasing rate of air flow rate ratio at each condition.

Lee, Moo Yeon; Jang, Yong Hee; Kim, Yong Chan [Korea Univ., Seoul (Korea, Republic of); Lee, Ho Sung [Korea Automotive Technology Institute, Cheonan (Korea, Republic of)

2008-04-15

16

A COMPARISON OF HEAT TRANSFER AROUND A SINGLE SERRATED FINNED TUBE AND A PLAIN FINNED TUBE  

Directory of Open Access Journals (Sweden)

Full Text Available With comparable bundle geometry, serrated fin finned tube heat exchangers transfer more heat than plain finned ones. There are believed to be many factors in this behaviour, and this investigation used CFD to examine the heat transfer and fluid flow patterns around the fins to try to understand the magnitude of the differences in the processes. The study is a first step in developing a new theory-based method to predict the performance of serrated fin tube bundles.

S.R.Mcilwain

2010-02-01

17

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

Directory of Open Access Journals (Sweden)

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.

Du Xueping

2014-01-01

18

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

International Nuclear Information System (INIS)

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.

19

Comparison of the thermal performance of serrated high-finned tubes used in heat-recovery systems  

International Nuclear Information System (INIS)

This paper presents the results of an investigation of the thermal performance of serrated, high-finned tubes in both the staggered and inline arrangements. Comparisons are made with published wind-tunnel data, published correlations, and new results of field tests for a commonly used heat-recovery finned tube configuration in the inline arrangement. For the staggered arrangement, it is shown that reasonable agreement exists between four wind-tunnel data sets and the staggered arrangement correlation of Weierman

20

Experimental study on the performance of a novel fin-tube air heat exchanger with punched longitudinal vortex generator  

International Nuclear Information System (INIS)

Highlights: ? Two novel fin-tube heat exchangers with delta winglet pairs are experimentally studied. ? Heat transfer enhancement accompanying with a reduction of pressure loss is achieved. ? Optimization of the location, orientation and size of delta winglet should be done for practical use. - Abstract: To enhance the heat transfer of fin-tube surface, two kinds of novel fin-tube surfaces with two rows of tubes in different diameter, arranged in staggered pattern are presented. Along the direction of air flow, the diameter of the first transverse row of tubes is smaller than that of the second. Delta winglet pairs working as longitudinal vortex generators are punched only around the first transverse row of tubes in reduced size, with either “common flow up” or “common flow down” orientation. The performances of two new types of air heat exchangers using the novel fin-tube surfaces (referred as SA and SB) and one traditional plain fin-tube heat exchanger (named BL) acting as baseline in contract are experimentally studied under dry-surface conditions. On the condition of the minimum cross velocity in heat exchanger umax = 4.0 m/s, air-side convective heat transfer coefficients of SA and SB increases by 16.5% and 28.2%, respectively, in comparison with that of BL. The air-side pressure drop decreases less than 10% for SA, and slightly decreases for SB, compared with the baseline heat exchanger. The present results show that one can achieve heat transfer enhancement accompanying with a reduction of pressure loss using the strategies of fin-tube surface, longitudinal vortex generator design and appropriate placement on the fin-tube surfaces.

 
 
 
 
21

Three-dimensional performance analysis of plain fin tube heat exchangers in transitional regime  

International Nuclear Information System (INIS)

Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a four-row plain fin-and-tube heat exchanger using the Commercial Computational Fluid Dynamics Code ANSYS CFX 12.0. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 400 to 2000. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models (k-?) with steady and incompressible fluid flow. Model validation is carried out by comparing the simulated case friction factor (f) and Colburn factor (j) with the experimental data of Wang et al.. Reasonable agreement is found between the simulations and experimental data. In this study the effect of geometrical parameters such as fin pitch, longitudinal pitch and transverse pitch of tube spacing are studied. Results are presented in the form of friction factor (f) and Colburn factor (j). For both laminar and transitional flow conditions heat transfer and friction factor decrease with the increase of longitudinal and transverse pitches of tube spacing whereas they increase with fin pitches for both in-line and staggered configurations. Efficiency index increases with the increase of longitudinal and transverse pitches of tube spacing but decreases with increase of fin pitches. For a particular Reynolds number, the efficiency index is higher in in-line arrangement than the staggered case. - Highlights: t than the staggered case. - Highlights: ? 3D CFD simulations for plain-fin-and-tube heat exchanger. ? Validated with experimental data. ? Parametric study for the effects of fluid flow and heat transfer.

22

Effect of refrigerant mal-distribution in fin-and-tube evaporators on system performance  

DEFF Research Database (Denmark)

Refrigerant mal-distribution in fin-and-tube evaporators for residential air-conditioning (RAC) is investigated numerically in this paper. A model of the system is developed in the object-oriented modeling language Modelica. Themodels of the compressor and expansion valve are static, whereas the condenser is a dynamic moving boundary model. The evaporator model is a dynamic distributed one-dimensional homogeneous equilibrium model, in order to capture the distribution phenomena. Fin-and-tube heat exchangers usually have a complex circuitry, however the evaporator will be simplified to be two straight tubes. The refrigerant mal-distribution is then induced to the evaporator by varying the vapor quality at the inlet to each feeder tube, the pressure drop through each feeder tube and the air-flow across each tube. Finally it is shown that air-flow mal-distribution can be compensated by an intelligent distributor, that ensures equal superheat in both tubes. The refrigerant is R410a.

Kærn, Martin Ryhl; Elmegaard, Brian

2009-01-01

23

An experimental study on the performance of plate fin and tube heat exchangers at low Reynolds numbers  

International Nuclear Information System (INIS)

This paper reports on the air side heat transfer and friction performance of plate fin and tube heat exchangers (mainly used in the region of relatively low Reynolds numbers) that were experimentally studied. In this study, 35 heat exchangers with systematically changed geometric parameters were prepared. The, the air side heat transfer and pressure drop performances were measured. Next, the influence of the geometric parameters regarding performance on the basis of these measurements was considered. Finally, by using newly determined characteristic velocity and length with development of the boundary region on the fin's surface being considered, the experimental results were correlated and effective generalized dimensionless correlations of the air side heat transfer and friction factor were obtained

24

The optimum fin spacing of circular tube bank fin heat exchanger with vortex generators  

Science.gov (United States)

In real application, once the pattern of fin is determined, fin spacing of tube bank fin heat exchanger can be adjusted in a small region, and air flow velocity in the front of the heat exchanger is not all the same. Therefore, the effects of fin spacing on heat transfer performance of such heat exchanger are needed. This paper numerically studied the optimal fin spacing regarding the different front flow velocities of a circular tube bank fin heat exchanger with vortex generators. To screen the optimal fin spacing, an appropriate evaluation criterion JF was used. The results show that when front velocity is 1.75 m/s, the optimal fin spacing is 2.25 mm, when front velocity is 2.5 m/s, the optimal fin spacing is 2 mm, and when front velocity is higher than 2.5 m/s, the optimal fin spacing is 1.75 mm.

Hu, Wanling; Su, Mei; Wang, Liangcheng; Zhang, Qiang; Chang, Limin; Liu, Song; Wang, Liangbi

2013-09-01

25

Condensation heat transfer of r134a for single tubes and tube bundles using standard and high performance finned tubes; Kondensatseitiger Waermeuebergang am Einzelrohr und im Rohrbuendel beim Einsatz von Standard- und Hochleistungsrippenrohren mit R134a  

Energy Technology Data Exchange (ETDEWEB)

This work aims at the optimization of the heat transfer of refrigerant R134a on finned tubes in shell-and-tube condensers. The coating and optimization of the fin structure should increase the drainage of the condensate in the space between the fins and therefore the condensation heat transfer on single tubes and tube bundles. (orig.)

Gebauer, Thomas; Leipertz, Alfred; Froeba, Andreas Paul [Erlangen-Nuernberg Univ. (Germany). Lehrstuhl fuer Technische Thermodynamik; Gotterbarm, Achim; El Hajal, Jean; Beutler, Andreas [Wieland-Werke AG, Ulm (Germany)

2011-08-15

26

Impact of delta winglet vortex generators on the performance of a novel fin-tube surfaces with two rows of tubes in different diameters  

International Nuclear Information System (INIS)

Highlights: ? Two novel fin-tube surfaces are presented and numerically simulated. ? The novel fin-tube surfaces bring about heat transfer enhancement. ? Pressure drop reduction of the novel design is another interesting finding. - Abstract: To achieve heat transfer enhancement and lower pressure loss penalty, even pressure loss reduction, two novel fin-tube surface with two rows of tubes in different diameters are presented in this paper. Numerical simulation results show that the fin-tube surface with first row tube in smaller size and second row tube in larger size can lead to an increase of heat transfer and decrease of pressure drop in comparison with the traditional fin-tube surface with two rows of tubes in the same size. Based on this understanding, delta winglet pairs are punched out only from the larger fin area around the first transverse row of tubes in smaller size in the novel fin-tube surfaces. Delta winglet pairs used as longitudinal vortex generator are arranged either in 'common flow up' or 'common flow down' configurations. Numerical simulation results show that delta winglet pairs can bring about a further heat transfer enhancement and pressure drop decrease through the careful arrangement of the location, size and attack angle of delta winglet pairs either in 'common flow up' or 'common flow down' configurations. The traditional knowledge of heat transfer enhancement with necessary pressure drop increase is challenged by the present conclusion. The present work will be helpful to develop more compact, higher heat transfer efficiency, lower fan power and quieter heat exchanger of refrigeration and air condition system.

27

Crystallization fouling of finned tubes during pool boiling: effect of fin density  

Science.gov (United States)

Bubble characteristics such as density, size, frequency and motion are key factors that contribute to the superiority of nucleate pool boiling over other modes of heat transfer. Nevertheless, if heat transfer occurs in an environment prone to fouling, the very same parameters may lead to accelerated deposit formation due to concentration effects beneath the growing bubbles. This has led to the widely accepted design recommendation to maintain the heat transfer surface temperature below the boiling point if fouling may occur, e.g., in seawater desalination. The present paper aims at investigating the formation of deposits on finned tubes during nucleate pool boiling of CaSO4 solutions. The test finned tubes are low finned tubes with fin densities of 19 and 26 fins/in. made from Cu-Ni. The fouling experiments were carried out at atmospheric pressure for different heat fluxes ranging from 100 to 300 kW/m2 and a CaSO4 concentration of 1.6 g/L. For the sake of comparison, similar runs were performed with smooth stainless steel tubes. The results show that: (1) the fouling resistance decreases with increasing fin density, (2) fouling on the finned tubes was reduced with increasing nucleate boiling activity and (3) if any fouling layer occurred on the finned tubes it could be removed easily.

Esawy, M.; Malayeri, M. R.; Müller-Steinhagen, H.

2010-11-01

28

The effects of design and operating factors on the frost growth and thermal performance of a flat plate fin-tube heat exchanger under the frosting condition  

International Nuclear Information System (INIS)

An experimental study of the effects of various factors(fin pitch, fin arrangement, air temperature, air humidity, and air velocity) on the frost growth and thermal performance of a fin-tube heat exchanger has been conducted under the frosting condition. It is found that the thermal performance of a heat exchanger is closely related to the blockage ratio of the air flow passages due to the frost growth. The maximum allowable blockage ratio is used to determine the criteria for the optimal operating conditions of a fin-tube heat exchanger. It is also shown that heat transfer rate of heat exchanger with staggered fin arrangement increases about 17% and the time required for heat transfer rate to reach a maximum value becomes longer, compared with those of an inline fin-tube heat exchanger under the frosting condition. The energy transfer resistance between the air and coolant decreases with the increase of inlet air temperature and velocity and with decreasing inlet air humidity

29

Forecast of winter performances of dry coolers with fin tubes; Voorspelling winterprestaties droge koelers met ribbenbuizen  

Energy Technology Data Exchange (ETDEWEB)

A mathematical model is presented to predict the behaviors of dry coolers by considering the condensing and frosting. It employs one-dimensional transient finite differential formulation with variation of the frost density and thickness. The model is validated by experiments and predicts the heat transfer performance with an accuracy within 2.19%. It is helpful for the operation of dry coolers in winter. [Dutch] In dit artikel wordt een wiskundig model gepresenteerd, waarmee voortschrijdende condens- en ijsvorming op warmteoverdrachtsoppervlakken kunnen worden voorspeld aan de hand van de gevormde condens- en ijslagen. Het model maakt gebruik van eendimensionale transiente formuleringen op basis van een techniek voor lokale uitmiddeling. Hierbij wordt rekening gehouden met de varierende dichtheid en dikte van de ijslaag. Validatie van het model heeft plaatsgevonden door de resultaten te vergelijken met proefgegevens van de fabrikant van de droge koeler.

Yu, Bing [Shanghai DFYH Tech Services Co. Ltd, Shanghai (China); Wang, Xichun [Arup, Shanghai (China); Luscuere, P.G. [Faculteit Bouwkunde, Technische Universiteit Delft, Delft (Netherlands)

2011-01-15

30

Study of the effect of finned tube adsorber on the performance of solar driven adsorption cooling machine using activated carbon-ammonia pair  

Energy Technology Data Exchange (ETDEWEB)

Solar refrigeration represents an important application of solar energy due to the excellent matching between the high sunshine and the refrigeration needs. Solar adsorption refrigeration devices are among the significant techniques used to meet the needs for cooling requirements. Several solar refrigeration systems have been proposed and are under development such as sorption systems including liquid/vapor, solid/vapor absorption, adsorption, vapor compression and others. The purpose of this paper is to identify the influence of a cylindrical adsorber on the performances of a solar adsorption refrigerating machine. The adsorber heated by solar energy contains an activated carbon-ammonia pair; it is composed by many cylindrical tubes welded using external fins. A model based on the conservation equations of energy and mass in the adsorber has been developed and well described. Using real solar irradiance data as well as many initial conditions, the model computes for each point and in the considered time interval during the day, the temperature, the adsorbed mass, the pressure inside the adsorber and the solar performance coefficient (COP). The results show that the optimal diameter of the adsorber with fins is greater than the one without fins. Moreover the mass cycled in the case of an adsorber equipped with external fins is more significant than the one without fins, and the maximal temperature reached in the adsorber with fins attains 97 C while in the adsorber without fins reaches 77 C. Thus, the performances of the solar adsorption refrigerating machine with an adsorber equipped with fins are higher than the machine without fins. (author)

Louajari, Mohamed; Mimet, Abdelaziz [Energetic Laboratory, Sciences Faculty, Abdelmalek Essaadi University, BP 2121, 93000 Tetouan (Morocco); Ouammi, Ahmed [Energetic Laboratory, Sciences Faculty, Abdelmalek Essaadi University, BP 2121, 93000 Tetouan (Morocco); Department of Communication, Computer and System Sciences (DIST), University of Genova, Genova (Italy)

2011-03-15

31

Effectiveness and Fin Efficiency of Plate-fin and Tube Heat Exchangers  

Science.gov (United States)

This paper presents a method for the determination of effectiveness on plate-fin and tube heat exchangers as a function of the parameters, viz. the thermal capacity ratio, the number of transfer unit and the flow arrangement. The analytical model of the heat exchanger which is adopted that of a multi-pass crossflow heat exchanger with one fluid mixed and another unmixed. For three kinds of flow arrangements of plate-fin and tube heat exchangers, equations on the effectiveness were obtained and the experimental verification of these equations was also performed. In addition, this paper is concerned with method which obtains the fin efficiency of the plate-fin and tube heat exchangers. It is usual practice to evaluate the fin efficiency by assuming that the uniform heat transfer and other suppositions. In this paper, a more realistic determination of fin efficiency is reported, which take into account the heat transfer distribution over the fin surface. It was confirmed that the results of fin efficiency by usual manner were almost equal to that of the realistic estimation in this study.

Seshimo, Yu

32

CFD Analysis of Plate Fin Tube Heat Exchanger for Various Fin Inclinations  

Directory of Open Access Journals (Sweden)

Full Text Available ANSYS Fluent software is used for three dimensional CFD simulations to investigate heat transfer and fluid flow characteristics of six different fin angles with plain fin tube heat exchangers. The numerical simulation of the fin tube heat exchanger was performed by using a three dimensional numerical computation technique. Geometry of model is created and meshed by using ANSYS Workbench software. To solve the equation for the fluid flow and heat transfer analysis ANSYS FLUENT was used in the fin-tube heat exchanger. The fluid flow and heat transfer are simulated and result compared for both laminar and turbulent flow models k-epsilon and SST k-omega, with steady state solvers to calculate heat transfer, flow velocity and temperature fields of variable inclined fin angles (? = 00 ,100 , 200 , 300 , 400 ,500 . Model is validate by comparing the simulated value of velocity, temperature and colburn factor with experimental and numerical results investigated by WANG [1] and GHORI KIRAR [10]. Reasonable agreement is found between the simulations and other results, and the ANSYS Fluent software is sufficient for simulating the flow fields in tube fin heat exchanger.

Subodh Bahirat,

2014-08-01

33

Finned Tube With Vortex Generators For A Heat Exchanger.  

Science.gov (United States)

A system for and method of manufacturing a finned tube for a heat exchanger is disclosed herein. A continuous fin strip is provided with at one pair of vortex generators. A tube is rotated and linearly displaced while the continuous fin strip with vortex generators is spirally wrapped around the tube.

Sohal, Manohar S. (Idaho Falls, ID); O'Brien, James E. (Idaho Falls, ID)

2005-12-20

34

Air side flow analysis of fin-tube heat exchanger with vortex generator  

International Nuclear Information System (INIS)

Fin-tube heat exchangers are widely used in refrigeration systems. To improve the performance of fin-tube heat exchangers, the shape of plain fin was developed in slit fin and louver fin. These pins have higher heat transfer performance as well as larger pressure drop. Recent studies of a Delta Winglet Vortex Generator (DWVG) show less heat transfer capacity than louver fin. However, the DWVG has very small pressure drop. This paper compares the performance for the plain fin and DWVG fin in terms of flow characteristics and heat transfer based on CFD analyses. The DWVG generates vortex and delayed flow separation and leads to a reduction of a wake region behind a tube. The results show that the DWVG produces improved heat transfer and reduced pressure drop compared to a plain fin. This result is opposite to the Reynolds analogy.

35

Heat transfer enhancement for fin-tube heat exchanger using vortex generators  

International Nuclear Information System (INIS)

Vortex generators are fabricated on the fin surface of a fin-tube heat exchanger to augment the convective heat transfer. In addition to horseshoe vortices formed naturally around the tube of the fin-tube heat exchanger, longitudinal vortices are artificially created on the fin surface by vortex generators. The purpose of this study is to investigate the local heat transfer phenomena in the fin-tube heat exchangers with and without vortex generators, and to evaluate the effect of vortices on the heat transfer enhancement. Naphthalene sublimation technique is employed to measure local mass transfer coefficients, then analogy equation between heat and mass transfer is used to calculate heat transfer coefficients. Experiments are performed for the model of fin-circular tube heat exchangers with and without vortex generators, and of fin-flat tube heat exchangers with and without vortex generators. Average heat transfer coefficients of fin-flat tube heat exchanger without vortex generator are much lower than those of fin-circular tube heat exchanger. On the other hand, fin-flat tube heat exchanger with vortex generators has much higher heat transfer value than conventional fin-circular tube heat exchanger. At the same time, pressure losses for four types of heat exchanger is measured and compared

36

Transfer coefficients for plate fin and elliptical tube heat exchangers  

International Nuclear Information System (INIS)

In order to determine transfer coefficients for plate fin and elliptical tube exchangers, mass transfer experiments have been performed using the naphthalene sublimation technique. By means of the heat-mass transfer analogy, the results can be converted to heat transfer results. The transfer coefficients were compared with those for circular tube exchangers and the comparison revealed no major differences. This is a positive outcome, since the use of elliptical tubes may reduce substantially the pressure drop, without affecting the transfer characteristics.(Author)

37

Experimental investigation of thermal contact resistance in plain-fin-and-tube evaporators with collarless fins  

Energy Technology Data Exchange (ETDEWEB)

The thermal contact resistance between fins and tubes in a plain-fin heat exchanger has been studied. The test coils have aluminum fins and tubes with no fin-collars. The heat-exchanger configuration under investigation was selected because this fin-tube joint is commonly used in refrigeration applications. Two coils were examined: one in the as-manufactured condition, and the other with brazed fin-tube joints - providing an intimate, metallurgical, bond between fins and tubes. Both heat exchangers were examined under dry and frosting conditions. The results show significant contact resistance in the production heat exchanger when operating under dry conditions. When frost is formed on the surface, the contact resistance is dramatically reduced to an insignificant value. (author)

El Sherbini, A.I.; Jacobi, A.M.; Hrnjak, P.S. [University of Illinois, Urbana, IL (United States). Dept. of Mechanical and Industrial Engineering

2003-08-01

38

Thermal Analysis of Fin and Tube Heat Exchanger  

Directory of Open Access Journals (Sweden)

Full Text Available This paper studied experimentally the effect of heat transfer of fin and tube type heat exchanger for different mass flow rate of fluid. The thermal stresses induced on fin and tube is also studied by ansys software at steady state condition by changing the width of fin and diameter of tube. Readings were taken experimentally by changing mass flow rate of fluid at respective temperatures. Comparison was done on theoretically and experimentally obtained results. It is observed that as the width of fin increases thermal stresses on fin also increases. Likewise for tube, by varying diameter of tube different values of stress are obtained. It is also observed at full valve position maximum thermal stresses are induced on fin as well as tube.

Ms N. B. Rairker

2014-06-01

39

Laminar forced convection inside externally finned tubes  

International Nuclear Information System (INIS)

Analytical solutions are obtained for thermal entry region problems inside ducts with axially varying heat transFer coefficient, by making use of the ideas in the recently advanced generalized integral transform technique. The analysis is applied to stepwise variations of Biot number that simulate intermitent rows of external fins. Numerical results are obtained for different fin arrangements, in a systematic manner, so as to critically examine the relative marits of wider and/or more numerous fin rows. (author)

40

Heat Transfer of Tube-fin Heat Exchanger Having Parallel Louver Continuous Fins  

Science.gov (United States)

Heat transfer from tubes has been numerically simulated in a fan coil unit for an airconditioning equipment. The array of tubes has parallel louver continuous fins, perpendicular to staggered round tubes. Quite a few of slits divide plates into many strips, which are offsetted, so that the heat transfer will be augmented from the plate to the air flow. On the other hand, the conduction of heat in the platemight be prevented with these slits. The conduction retardation due to slit is estimated, and the simulation shows that the retardation is not serious for present fins.

Take-Uchi, Masaaki; Yamada, Jun; Tanaka, Jun-Ichirou

 
 
 
 
41

CFD analysis of tube-fin 'no-frost' evaporators  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of this paper is to assess some aspects of the design of evaporators for household refrigeration appliances using Computational Fluid Dynamics (CFD. The evaporators under study are tube-fin 'no-frost' heat exchangers with forced convection on the air-side and a staggered tube configuration. The calculation methodology was verified against experimental data for the heat transfer rate, thermal conductance and pressure drop obtained for two evaporators with different geometries. The average errors of the heat transfer rate, thermal conductance and pressure drop were 10%, 3% and 11%, respectively. The CFD model was then used to assess the influence of geometric parameters such as the presence and position of the electrical heater coil relative to the tubes, the fin configuration and the width of the by-pass clearance between the outer edge of the fins and the tube bank for conditions typical of the design of household refrigeration appliances

Jader R Barbosa, Jr

2010-12-01

42

3D analysis of thermal exchange in finned batteries. A comparison between round and elliptical tubes  

International Nuclear Information System (INIS)

In this paper a numerical 3D analysis of the thermal exchange in air-cooled finned batteries has been carried out. Speed and temperature values in each hub of the numerical simulation domain have been reckoned both at different air flows and with different shapes of the tubes. The thermal power exchanged between tubes and air is obtained by the simulation of a numerical model of a finned battery with round section tubes and is compared to the values obtained for three batteries with elliptical section tubes. The comparison has been performed for different values of the air input speed

43

Condensation and evaporation of new refrigerants in advanced micro-finned tubes  

Energy Technology Data Exchange (ETDEWEB)

Due to the European deadline for the phase-out of HCFCs, the air-conditioning manufacturers are launching new product range purpose-designed to operate on the non-ozone depleting refrigerants: R404A, R134a or R407C. The micro-finned tubes optimised for finned heat exchangers as for shell and tube evaporators and condensers are one of these recent techniques which may allow increase performance of refrigerating units the new refrigerants. Two models of thermal correlation have been established resulting from experimental measurements on single micro-fin tubes: in evaporation, the model is a modification of Gungor-Winterton which concerns the addition of nucleation and convection processes within the inner grooves. In condensation, this model is a modification of Cavallini-Zecchin correlation. With these models, it is possible to predict the behaviour micro-fin tubes in specific conditions. This permits the necessary adaptation of heat-exchangers. (authors)

Laterrible, P. [Trefimetaux, 92 - Courbevoie (France); Marvillet, C. [CEA/Grenoble, Dept. de Thermohydraulique et de Physique (DTP-GRETH), 38 (France)

1999-07-01

44

Numerical study of a round tube heat exchanger with louvered fins and delta winglets  

Science.gov (United States)

Louvered fin and round tube heat exchangers are widely used in air conditioning devices and heat pumps. In this study the effect of punching delta winglet vortex generators in the louvered fin surface is studied numerically. The delta winglets are located in a common-flow-down orientation behind each tube of the staggered tube layout. It is shown that the generated vortices significantly reduce the size of the tube wakes. Three important heat transfer enhancement mechanisms can be distinguished: a better flow mixing, boundary layer thinning and a delay in flow separation from the tube surface. The compound heat exchanger has a better thermal hydraulic performance then when only louvers or only delta winglets are used. Comparison to other enhanced fin designs clearly shows its potential, especially for low Reynolds number applications.

Huisseune, H.; T'Joen, C.; De Jaeger, P.; Ameel, B.; De Paepe, M.

2012-11-01

45

Study of junction flows in louvered fin round tube heat exchangers using the dye injection technique  

Energy Technology Data Exchange (ETDEWEB)

Detailed studies of junction flows in heat exchangers with an interrupted fin design are rare. However, understanding these flow structures is important for design and optimization purposes, because the thermal hydraulic performance of heat exchangers is strongly related to the flow behaviour. In this study flow visualization experiments were performed in six scaled-up models of a louvered fin round tube heat exchanger. The models have three tube rows in a staggered layout and differ only in their fin spacing and louver angle. A water tunnel was designed and built and the flow visualizations were carried out using dye injection. At low Reynolds numbers the streakline follows the tube contours, while at higher Reynolds numbers a horseshoe vortex is developed ahead of the tubes. The two resulting streamwise vortex legs are destroyed by the downstream louvers (i.e. downstream the turnaround louver), especially at higher Reynolds numbers, smaller fin pitches and larger louver angles. Increasing the fin spacing results in a larger and stronger horseshoe vortex. This illustrates that a reduction of the fin spacing results in a dissipation of vortical motion by mechanical blockage and skin friction. Furthermore it was observed that the vortex strength and number of vortices in the second tube row is larger than in the first tube row. This is due to the thicker boundary layer in the second tube row, and the flow deflection, which is typical for louvered fin heat exchangers. Visualizations at the tube-louver junction showed that in the transition part between the angled louver and the flat landing a vortex is present underneath the louver surface which propagates towards the angled louver. (author)

Huisseune, H.; Willockx, A.; De Paepe, M. [Department of Flow, Heat and Combustion Mechanics, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium); T' Joen, C. [Department of Flow, Heat and Combustion Mechanics, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium); Department Radiation, Radionuclides and Reactors, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); De Jaeger, P. [Department of Flow, Heat and Combustion Mechanics, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium); NV Bekaert SA, Bekaertstraat 2, 8550 Zwevegem (Belgium)

2010-11-15

46

Selection criteria for plain and segmented finned tubes for heat recovery systems  

Science.gov (United States)

Heat recovery heat exchangers with gas as one of the streams depend on the use of finned tubes to compensate for the inherently low gas heat transfer coefficient. Standard frequency welded 'plain' fins were generally used in the past, until the high-frequency resistance welding technology permitted a cost-effective manufacture of 'segmented' fins. The main advantage of this fin design is that it permits higher heat flux and hence smaller, lighter weight units for most operating conditions. While the criteria that dictate optimum design, such as compactness, weight, and cost per unit area favor the segmented fin design, a few other considerations such as fouling, ease of cleaning, and availability of dependable design methods have to be considered. This paper analyzes the performance parameters that affect the selection of either fin type.

Reid, D. R.; Taborek, J.

1994-04-01

47

Design of the Fittest Eddy Current Probe for the Fin Tubes  

International Nuclear Information System (INIS)

The eddy current probe was designed for the test of fin tubes that have uneven outer and inner surfaces to enhance the efficiency of heat emission. Because of the surface roughness of the fin tube, it needs much care to detect flaws in the tube employing eddy current test(ECT). We made ECT probes with different coil lengths and performed eddy current test using these probes for artificially flawed specimens. By the fast Fourier transform and digital filtering, signals from these probes were processed to characterize frequency spectra. From the analysis of eddy current signals and their frequency spectra, we concluded that, for the effective testing of the tubes with the fins of 1mm pitch, 4mm coil length gave the highest S/N ratio

48

CFD analysis of fin tube heat exchanger with a pair of delta winglet vortex generators  

Energy Technology Data Exchange (ETDEWEB)

Among tubular heat exchangers, fin tube types are the most widely used in refrigeration and air-conditioning equipment. Efforts to enhance the performance of these heat exchangers included variations in the fin shape from a plain fin to a slit and louver type. In the context of heat transfer augmentation, the performance of vortex generators has also been investigated. Delta winglet vortex generators have recently attracted research interest, partly due to experimental data showing that their addition to fin-tube heat exchangers considerably reduces pressure loss at heat transfer capacity of nearly the same level. The efficiency of the delta winglet vortex generators widely varies depending on their size and shape, as well as the locations where they are implemented. In this paper, the flow field around delta winglet vortex generators in a common flow up arrangement was analyzed in terms of flow characteristics and heat transfer using computational fluid dynamics methods. Flow mixing due to vortices and delayed separation due to acceleration influence the overall fin performance. The fin with delta winglet vortex generators exhibited a pressure loss lower than that of a plain fin, and the heat transfer performance was enhanced at high air velocity or Reynolds number.

Hwang, Seong Won; Kim, Dong Hwan; Min, June Kee; Jeong, Ji Hwan [Pusan National Univ., Busan (Korea, Republic of)

2012-09-15

49

CFD analysis of fin tube heat exchanger with a pair of delta winglet vortex generators  

International Nuclear Information System (INIS)

Among tubular heat exchangers, fin tube types are the most widely used in refrigeration and air-conditioning equipment. Efforts to enhance the performance of these heat exchangers included variations in the fin shape from a plain fin to a slit and louver type. In the context of heat transfer augmentation, the performance of vortex generators has also been investigated. Delta winglet vortex generators have recently attracted research interest, partly due to experimental data showing that their addition to fin-tube heat exchangers considerably reduces pressure loss at heat transfer capacity of nearly the same level. The efficiency of the delta winglet vortex generators widely varies depending on their size and shape, as well as the locations where they are implemented. In this paper, the flow field around delta winglet vortex generators in a common flow up arrangement was analyzed in terms of flow characteristics and heat transfer using computational fluid dynamics methods. Flow mixing due to vortices and delayed separation due to acceleration influence the overall fin performance. The fin with delta winglet vortex generators exhibited a pressure loss lower than that of a plain fin, and the heat transfer performance was enhanced at high air velocity or Reynolds number

50

CFD analysis of tube-fin 'no-frost' evaporators  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The purpose of this paper is to assess some aspects of the design of evaporators for household refrigeration appliances using Computational Fluid Dynamics (CFD). The evaporators under study are tube-fin 'no-frost' heat exchangers with forced convection on the air-side and a staggered tube configurat [...] ion. The calculation methodology was verified against experimental data for the heat transfer rate, thermal conductance and pressure drop obtained for two evaporators with different geometries. The average errors of the heat transfer rate, thermal conductance and pressure drop were 10%, 3% and 11%, respectively. The CFD model was then used to assess the influence of geometric parameters such as the presence and position of the electrical heater coil relative to the tubes, the fin configuration and the width of the by-pass clearance between the outer edge of the fins and the tube bank for conditions typical of the design of household refrigeration appliances

Jader R, Barbosa, Jr; Christian J. L, Hermes; Cláudio, Melo.

51

CFD analysis of tube-fin 'no-frost' evaporators  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The purpose of this paper is to assess some aspects of the design of evaporators for household refrigeration appliances using Computational Fluid Dynamics (CFD). The evaporators under study are tube-fin 'no-frost' heat exchangers with forced convection on the air-side and a staggered tube configurat [...] ion. The calculation methodology was verified against experimental data for the heat transfer rate, thermal conductance and pressure drop obtained for two evaporators with different geometries. The average errors of the heat transfer rate, thermal conductance and pressure drop were 10%, 3% and 11%, respectively. The CFD model was then used to assess the influence of geometric parameters such as the presence and position of the electrical heater coil relative to the tubes, the fin configuration and the width of the by-pass clearance between the outer edge of the fins and the tube bank for conditions typical of the design of household refrigeration appliances

Jader R, Barbosa, Jr; Christian J. L, Hermes; Cláudio, Melo.

2010-12-01

52

Bundle impact with th condensation of propane at horizontal smooth tubes and finned tubes; Buendeleffekt bei der Kondensation von Propan an horizontalen Glatt- und Rippenrohren  

Energy Technology Data Exchange (ETDEWEB)

With respect to a basic description of the bundling impact in tube bundle condensers, the authors of the contribution under consideration report on the impact of the material properties of the working fluid, tube structure and tube material on the heat transfer. For this, the existing experimental database on the condensate side heat transfer coefficient with 1.1.1.2-tetrafluoroethane (R134a) has been extended by the natural refrigerant propane (R290). In addition to plain tubes, standard finned tubes and high-performance finned tubes consisting of copper, ribbed and grooved steel finned tubes were used. The experimental condensation tests were carried out at the outside of the tube at a saturation temperature of 37 Celsius. By expanding the data base, both analytical models and a CFD model for predicting the condensate side heat transfer coefficient on the smooth and finned tube a well as corresponding single tube bundles could be verified. The results on single smooth tube showed a very good agreement between the condensate side heat transfer coefficients of propane and R134a with the Nusselt theory. The largest side condensate heat transfer coefficients were determined at the single high-performance finned tube made of copper and the corresponding tube bundle with R134a. Compared to the standard finned tubes of both materials, the high-performance finned copper tubes showed a greater bundling effect for both working fluids. Unlike R134a, almost no differences were observed for the experimentally determined behavior of the bundle on standard finned tubes and high-performance finned tube made of steel with propane. The condensation side heat transfer coefficients on the latter two tubes were below the values for the finned copper tubes with propane. The CFD simulations for the single tube were within the experimental uncertainties. In the case of the investigations of bundles, the modeled data showed a larger deviation from the experimental data than the analytical models discussed in the context of this work. This can be explained with the simplifications within the CFD model used.

Gebauer, Thomas; Leipertz, Alfred; Froeba, Andreas Paul [Erlangen-Nuernberg Univ., Erlangen (Germany). Lehrstuhl fuer Technische Thermodynamik (LTT); Gotterbarm, Achim; El Hajal, Jean [Wieland-Werke AG, Ulm (Germany)

2012-07-01

53

Compensation of airflow maldistribution in fin-and-tube evaporators  

DEFF Research Database (Denmark)

Compensation of airflow maldistribution in fin-and tube evaporators for residential air-conditioning is investigated with regards to circuitry design and control of individual channel superheats. In particularly, the interlaced and the face split circuitry designs are compared numerically using a linear velocity profile and a CFD predicted velocity profile obtained from Kærn (2011d) in dry and wet conditions. The circuitry models are validated experimentally in wet conditions, and for this purpose a test case interlaced evaporator (17.58 kW) was reconstructed in order to become a face split evaporator by modifying its U-bend connections. Furthermore, a 14% and 28% blockage of the face split evaporator is studied experimentally with control of individual channel superheats. It is shown that the face split circuitry with compensation gives the best performance in both dry and wet conditions, however with lower gains in wet conditions (around 3% in cooling capacity and 7-9% in UA-value). This performance gain incooling capacity is below the uncertainty in standard experiments, however the gain may be revealed and/or validated by the possible area savings experimentally, i.e. in terms of overall UA-value.

Kærn, Martin Ryhl; Tiedemann, Thomas

2012-01-01

54

A tube-by-tube reduction method for simultaneous heat and mass transfer characteristics for plain fin-and-tube heat exchangers in dehumidifying conditions  

Science.gov (United States)

This study proposed a new method, namely a tube-by-tube reduction method to analyze the performance of fin-and-tube heat exchangers having plain fin configuration under dehumidifying conditions. The mass transfer coefficients which seldom reported in the open literature, are also presented. For fully wet conditions, it is found that the reduced results for both sensible heat transfer performance and the mass transfer performance by the present method are insensitive to change of inlet humidity. Unlike those tested in fully dry condition, the sensible heat transfer performance under dehumidification is comparatively independent of fin pitch. The ratio of the heat transfer characteristic to mass transfer characteristic (hc,o/hd,o Cp,a) is in the range of 0.6~1.0, and the ratio is insensitive to change of fin spacing at low Reynolds number. However, a slight drop of the ratio of (hc,o/hd,o Cp,a) is seen with the decrease of fin spacing when the Reynolds number is sufficient high. This is associated with the more pronounced influence due to condensate removal by the vapor shear. Correlations are proposed to describe the heat and mass performance for the present plate fin configurations. These correlations can describe 89% of the Chilton Colburn j-factor of the heat transfer (jh) within 15% and can correlate 81% of the Chilton Colburn j-factor of the mass transfer (jm) within 20%.

Pirompugd, Worachest; Wongwises, Somchai; Wang, Chi-Chuan

2005-06-01

55

Quantitative experiments on thermal hydraulic characteristics of an annular tube with twisted fins  

International Nuclear Information System (INIS)

Thermal hydraulic experiments measuring critical heat flux (CHF) and pressure drop of an annular tube with twisted fins, ''annular swirl tube'', has been performed to examine its applicability to the ITER divertor cooling structure. The annular swirl tube consists of two concentric circular tubes, the outer and inner tubes. The outer tube with outer and inner diameters (OD and ID) of 21 mm and 15 mm is made of Cu-alloy that is CuCrZr and oe of candidate materials of the ITER divertor cooling tube. The inner tube with OD of 11 mm and ID of 9 mm is made of stainless steal. It has an external swirl fin with twist ratio (y) of three to enhance its heat transfer performance. In this tube, cooling water flows inside of the inner tube first, and then returns into an annulus between the outer and inner tubes with a swirl flow at an end-return of the cooling tube. The CHF experiments show that no degradation of CHF of the annular swirl tube in comparison with the conventional swirl tube whose dimensions are similar to those of the outer tube of the annular swirl tube. A minimum axial velocity of 7.1 m/s is required to remove the incident heat flux of 28MW/m2, the ITER design value. Applicability of the JAERI's correlation for the heat transfer to the annular swirl tube is also demonstrated by comparing the experimental results with those of the numerical analysis. The friction factor correlation for the annular flow with the twisted fins is also proposed for the hydrodynamic design of the ITER vertical target. The least pressure drop at the end-return is obtained by using the hemispherical end-plug. Its radius is the same as that of ID of the outer cooling tube. These results show that thermal-hydraulic performance of the annular swirl tube is promising in application to the cooling structure for the ITER vertical target. (author)

56

Analysis of internal helically finned tubes for parabolic trough design by CFD tools  

International Nuclear Information System (INIS)

Highlights: ? Parabolic trough collectors life improvement by internally finned tubes. ? Solar thermal oil degradation reduction by homogenization of temperature profile in parabolic trough collectors. ? Efficiency enhancement of parabolic trough collectors by finned tubes. ? CFD analysis of finned parabolic trough collector tubes. -- Abstract: This paper has analysed the effect of the utilization of internal finned tubes for the design of parabolic trough collectors with computational fluid dynamics tools. Our numerical approach has been qualified with the computational estimation of reported experimental data regarding phenomena involved in finned tube applications and solar irradiation of parabolic trough collector. The application of finned tubes to the design of parabolic trough collectors must take into account features as the pressure losses, thermal losses and thermo-mechanical stress and thermal fatigue. Our analysis shows an improvement potential in parabolic trough solar plants efficiency by the application of internal finned tubes.

57

Compensation of flow maldistribution in fin-and-tube evaporators for residential air-conditioning  

DEFF Research Database (Denmark)

Compensation of flow maldistribution in multi-channel fin-and-tube evaporators for residential air-conditioning is investigated by numerical modeling. The considered sources of maldistribution are distribution of the liquid and vapor phases in the distributor and non-uniform airflow distribution. Fin-and-tube heat exchangers usually have a predefined circuitry, however, the evaporator model is simplified to have straight tubes, in order to perform a generic investigation. The compensation of flow maldistribution is performed by control of the superheat in the individual channels. Furthermore, the effect of combinations of individual maldistribution sources is investigated for different evaporator sizes and outdoor temperatures. It is shown that a decrease in cooling capacity and coefficient of performance by flow maldistribution can be compensated by the control of individual channel superheat. Alternatively, a larger evaporator may be used.

Kærn, Martin Ryhl; Brix, Wiebke

2011-01-01

58

Infrared thermography investigation of local heat transfer in a plate fin and two-tube rows assembly  

International Nuclear Information System (INIS)

An experimental study is performed using an infrared thermography system. The experimental method uses the temperature transient variation of a thin plate (tested fin) in order to obtain detailed quantitative heat transfer coefficients. The method developed is similar to the lumped capacitance method usually used to measure heat transfer coefficient on heat exchanger fin models. But the method presented here exploits the capabilities of infrared thermography to measure surface temperatures in a transient technique in order to take into account errors effects due to tangential conduction and radiation of the tested fin. The method is validated using a two-dimensional channel experiment and its advantages are highlighted using a plate fin and two-tube rows assembly experiment. Moreover, convection coefficient variations with fin pitch and frontal air velocity of an automotive plate fin and two-tube rows assembly are also examined

59

Experimental Investigation of Heat Transfer and Pressure Drop Characteristics of H-type Finned Tube Banks  

Directory of Open Access Journals (Sweden)

Full Text Available H-type finned tube heat exchanger elements maintain a high capacity for heat transfer, possess superior self-cleaning properties and retain the ability to effect flue gas waste heat recovery in boiler renovations. In this paper, the heat transfer and pressure drop characteristics of H-type finned tube banks are studied via an experimental open high-temperature wind tunnel system. The effects of fin width, fin height, fin pitch and air velocity on fin efficiency, convective heat transfer coefficient, integrated heat transfer capacity and pressure drop are examined. The results indicate that as air velocity, fin height and fin width increase, fin efficiency decreases. Convective heat transfer coefficient is proportional to fin pitch, but inversely proportional to fin height and fin width. Integrated heat transfer capacity is related to fin efficiency, convective heat transfer coefficient and finned ratio. Pressure drop increases with the increase of fin height and fin width. Finally, predictive correlations of fin efficiency, Nusselt number and Euler Number are developed based on the experimental data.

Heng Chen

2014-11-01

60

Three-dimensional numerical study and field synergy principle analysis of wavy fin heat exchangers with elliptic tubes  

International Nuclear Information System (INIS)

Three dimensional numerical studies were performed for laminar heat transfer and fluid flow characteristics of wavy fin heat exchangers with elliptic/circular tubes by body-fitted coordinates system. The simulation results of circular tube were compared with the experiment data, then circular and elliptic (e = b/a = 0.6) arrangements with the same minimum flow cross-sectional area were compared. A max relative heat transfer gain of up to 30% is observed in the elliptic arrangement, and corresponding friction factor only increased by about 10%. The effects of five factors on wavy fin and elliptic tube heat exchangers were examined: Reynolds number (based on the smaller ellipse axis, 500 ? 4000), eccentricity (b/a, 0.6 ? 1.0), fin pitch (Fp/2b, 0.05 ? 0.4), fin thickness (Ft/2b, 0.006 ? 0.04) and tube spanwise pitch (S1/2b, 1.0 ? 2.0). The results show that with the increasing of Reynolds number and fin thickness, decreasing of the eccentricity and spanwise tube pitch, the heat transfer of the finned tube bank are enhanced with some penalty in pressure drop. There is an optimum fin pitch (Fp/2b = 0.1) for heat transfer, but friction factor always decreases with increase of fin pitch. And when Fp/2b is larger than 0.25, it has little effects on heat transfer and pressure drop. The results were also analyzed from the view point of field synergy principle. It was found that the effects of the five factors on the heat transfer performance can be well described by the field synergy principle

 
 
 
 
61

Two-dimensional fin efficiency of plate fin-tube heat exchangers under partially and fully wet conditions  

Science.gov (United States)

This paper presents the two-dimensional analysis for the efficiency of continuous plate fin-tube heat exchangers in staggered and in-lined arrangements under the dry, partially wet, and fully wet conditions for different heat transfer coefficient ( h=20 W/m2K to h=80 W/m2K) and air relative humidity over the full range from ?=0 % to ?=100%. It is shown that the fin efficiencies of the staggered arrangement are higher than those for the in-lined arrangement, and the fully wet fin efficiency is 10-20% lower than that for a dry fin. The conventional 1-D sector method underestimates the fin efficiency up to 4 % as compared to the 2-D analysis.

Jang, Jiin-Yuh; Lin, Chien-Nan

2002-08-01

62

Quantitative infrared investigation of local heat transfer in a circular finned tube heat exchanger assembly  

International Nuclear Information System (INIS)

Highlights: • Infrared thermography and transient technique are used to estimate local heat transfer. • Calculation model is integrated between local time bounds chosen with an original criterion. • Thermal horseshoe vortices imprints are analyzed by following their angular evolution. -- Abstract: This work deals with the local heat transfer coefficient evaluation over the fin of the second row of a staggered circular finned tube heat exchanger assembly. The coefficient distribution is determined by using a transient technique and by calculating the energy balance during the fin cooling. The calculation model takes into account radiation with the surrounding and lateral heat conduction into the material. The method uses infrared measurements and integration between time bounds that depend on space. It is proposed to choose the integration bounds with an original criterion based on local heat transfer. Validation is performed on the reference case consisting in a thin plate in an aerodynamically and thermally developing channel flow. Then, distributions of Nusselt number on the circular fin are presented for several Reynolds numbers. The high resolution of the whole method and set-up allow detecting thermal imprints of developing horseshoe vortices. These imprints are analyzed by following their angular evolution around the tube

63

Laminar fluid flow and heat transfer in a fin-tube heat exchanger with vortex generators  

Energy Technology Data Exchange (ETDEWEB)

Development of heat transfer enhancement techniques for fin-tube heat exchangers has great importance in industry. In recent years, heat transfer augmentation by vortex generators has been considered for use in plate fin-tube heat exchangers. The present work describes a numerical investigation about the influence of delta winglet pairs of vortex generators on the flow structure and heat transfer of a plate fin-tube channel. The Navier-Stokes and Energy equations are solved by the finite volume method using a boundary-fitted coordinate system. The influence of vortex generators parameters such as position, angle of attack and aspect ratio were investigated. Local and global influences of vortex generators in heat transfer and flow losses were analyzed by comparison with a model using smooth fin. The results indicate great advantages of this type of geometry for application in plate fin-tube heat exchangers, in terms of large heat transfer enhancement and small pressure loss penalty. (author)

Yanagihara, J.I.; Rodriques, R. Jr. [Polytechnic School of Univ. of Sao Paolo, Sao Paolo (Brazil). Dept. of Mechanical Engineering

1996-12-31

64

Carbon-foam finned tubes in air-water heat exchangers  

International Nuclear Information System (INIS)

An engineering model is formulated to account for the effects of porosity and pore diameter on the hydrodynamic and thermal performance of a carbon-foam finned tube heat exchanger. The hydrodynamic and thermal resistances are obtained from well-established correlations that are extended herein to account for the influence of the porous carbon foam. The influence of the foam is characterized on the basis of a unit-cube geometric model that describes the internal structure, the exposed surface, the permeability and the effective conductivity as a function of porosity and pore diameter. The engineering model is validated by comparison with experiments that characterize heat transfer in an air-water radiator made from porous carbon foam. The model is also used in to conduct a parametric study to show the influence of the porosity and pore diameter of the foam. The parametric study suggests that in comparison to conventional aluminum finned-tube radiators, improvements of approximately 15% in thermal performance are possible without changing the frontal area, or the air flow rate and pressure drop. The engineering model developed herein can be used by engineers to assess quantitatively the suitability of porous carbon foam as a fin material in the design of air-water heat exchangers

65

Steam generator tube performance  

International Nuclear Information System (INIS)

A review of the performance of steam generator tubes in 116 water-cooled nuclear power reactors showed that tubes were plugged at 54 (46 percent) of the reactors. The number of tubes removed from service decreased from 4 692 (0.30 percent) in 1981 to 3 222 (0.20 percent) in 1982. The leading causes of tube failures were stress corrosion cracking from the primary side, stress corrosion cracking (or intergranular attack) from the secondary side and pitting corrosion. The lowest incidence of corrosion-induced defects from the secondary side occurred in reactors that have used only volatile treatment, with or without condensate demineralization

66

Steam generator tube performance  

International Nuclear Information System (INIS)

A review of the performance of steam generator tubes in 110 water-cooled nuclear power reactors showed that tubes were plugged at 46 (42 percent) of the reactors. The number of tubes removed from service increased from 1900 (0.14 percent) in 1980 to 4692 (0.30 percent) in 1981. The leading causes of tube failures were stress corrosion cracking from the primary side, stress corrosion cracking (or intergranular attack) from the secondary side and pitting corrosion. The lowest incidence of corrosion-induced defects from the secondary side occurred in reactors that used all-volatile treatment since start-up. At one reactor a large number of degraded tubes were repaired by sleeving which is expected to become an important method of tube repair in the future

67

Burnout in the boiling of water and freon-113 on tubes with annular fins  

International Nuclear Information System (INIS)

This paper presents the results of numerical calculations of burnout heat flux associated with the boiling of Freon-113 and water on an annular fin of constant thickness which have been approximated by simple analytical relations. These are used to calculate the critical burnout parameters of tubes with an annular fin assembly. The calculated data may be used for the analysis of tubes with an annular fin assembly over a wide range of variation of the thermophysical properties of the material and geometrical parameters of the fin assembly

68

Analysis of refrigerant mal-distribution : in fin-and-tube evaporators  

DEFF Research Database (Denmark)

Refrigerant mal-distribution in fin-and-tube evaporators for residential air-conditioning is investigated numerically in this paper. Essentially the influence of refrigerant mal-distribution on capacity of an evaporator is reported. In order to investigate, a model of a fin-and-tube evaporator is developed in the object-oriented modeling language Modelica. The evaporator model is a dynamic distributed one-dimensional homogeneous model, but will be used here to present results in steady state. Fin-and-tube evaporators usually have a complex circuitry, however the evaporator will be simplified to be two straight tubes. The refrigerant maldistribution is then induced to the evaporator by varying the vapor quality at the inlet to each tube and the air-flow across each tube. Finally it is shown that mal-distribution can be compensated by an intelligent distributor, that ensures equal superheat temperature in both tubes. The refrigerant is R410a.

Kærn, Martin Ryhl; Elmegaard, Brian

2009-01-01

69

Investigation on flow and heat transfer for a staggered tube bank of low finned tubes at high Reynolds numbers  

International Nuclear Information System (INIS)

A ten rows deep tube bundle with 15 tubes in each row all of which were cooled has been tested (root diameter of the tubes D = 22,2 mm, fin height h = 1,46 mm, fin pitch t = 1,25 mm). The mean heat transfer coefficient and pressure drop has been determined in the range of 5 .(period on line) 103 5. The results were compared with semiempirical formulas given by Th.E. Schmidt, A. Skrinska and J. Stasiulewitschius and W. Kast. In the same test series the heat transfer of each row has been measured. Besides that the influence of half tubes which were fixed at the walls of the duct on heat transfer and flow resistance was investigated. Finally was made an attempt to judge about the advantes due to finning the tubes. (orig.)

70

Numerical simulation of flow field in a fin tube heat exchanger  

International Nuclear Information System (INIS)

This paper reports on the computation of the flow field and heat transfer between two plate fins of a compact cross flow heat exchanger with staggered arrangement of tubes that has been carried out in Reynolds number range of 40 to 2000. Three Nusselt number plots on the fin show deterioration of heat transfer by 50%, or more in the stagnation zone of the rear tube due to the wake of the preceding tube. The Nusselt number distributions on the tube near the juncture of the tube and the fin deviates substantially from the two dimensional prediction. The Nusselt numbers on the midplane of the first tube in stagnation area compares well available experimental results of Nusselt number distribution on a cylinder in unbounded cross flow

71

The numerical analysis of the flow fields near fin surface of a plate fin-oval tube heat exchanger with delta wing vortex generators  

International Nuclear Information System (INIS)

In present study, the flow field near the fin surface of plate fin - oval tube heat exchanger with delta wing vortex generator was numerically analyzed. As results, the well developed vortex behind delta wing was observed. These vortex can improve heat transfer fin surface behind delta wing vortex generators

72

Steam generator tube performance  

International Nuclear Information System (INIS)

The performance of steam generator tubes in water-cooled nuclear power reactors has been reviewed for 1980. Tube defects occurred at 38% of the 97 reactors surveyed. This is a marginal improvement over 1979 when defects occurred at 41% of the reactors. The number of failed tubes was also lower, 0.14% of the tubes in service in 1980 compared with 0.20% of those in service in 1979. Analysis of the causes of these failures indicates that stress corrosion cracking was the leading failure mechanism. Reactors that used all-volatile treatment of secondary water, with or without full-flow condensate demineralization since start-up showed the lowest incidence of corrosion-related defects

73

Experimental Study on Frost Height of Round Plate Fin-Tube Heat Exchangers for Mobile Heat Pumps  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this study was to provide experimental data that could be used to predict frost growth and frost performance of a round plate fin-tube heat exchanger for low temperature heat pumps used in zero emission vehicles under cold weather conditions. In this study, round plate fin-tube heat exchangers were tested with variation of the fin space, air flow rate, relative humidity, and inlet air temperature. Frost height was measured and considered with the boundary layer interruption between fins. Frost height for 8.0 mm of fin space was increased by approximately 91.9% with an increase of relative humidity from 50.0% to 80.0%. The growth rate of frost height at 1.2 m3/min was observed to be 13.0% greater than that at 0.8 m3/min. Finally, the variation of the blockage ratio with fin space would be an important reference for designing advanced heat exchangers that operate under cold weather conditions.

Dong-Yeon Lee

2012-09-01

74

Experimental research on single phase convection heat transfer in micro-fin tube  

International Nuclear Information System (INIS)

An experimental investigation of heat transfer and flow resistance characteristics of single phase water in three micro-fin tubes with different fin height was conducted. At the same time, the efficiency of micro-fin tubes within the experimental scope was evaluated and the optimal working region was determined. Based on the experimental data in the optimal working region, correlations for predicting the heat transfer and flow resistance were also given by multiple regression method. The result indicates that the micro-fin tubes can greatly enhance the single-phase heat transfer in turbulent flow, and the increase of heat transfer coefficient is higher than the increase of flow resistance. The accuracy of the correlation is very high, of which the deviation from the experimental value is very small. (authors)

75

Numerical analysis of filmwise condensation in a plate fin-and-tube heat exchanger in presence of non-condensable gas  

Science.gov (United States)

In the present paper, a numerical model of a fin-and-tube heat exchanger is proposed. The simulation of water vapor condensation in presence of non-condensable gas (air) between two vertical plane plates and in a plate fin-and-tube heat exchanger in a stationary mode is performed using Fluent software. The differential equations that describe the heat and mass transfer were integrated by the finite volume method, in two and three dimensions.

Benelmir, Riad; Mokraoui, Salim; Souayed, Ali

2009-10-01

76

Numerical analysis of filmwise condensation in a plate fin-and-tube heat exchanger in presence of non-condensable gas  

Energy Technology Data Exchange (ETDEWEB)

In the present paper, a numerical model of a fin-and-tube heat exchanger is proposed. The simulation of water vapor condensation in presence of non-condensable gas (air) between two vertical plane plates and in a plate fin-and-tube heat exchanger in a stationary mode is performed using Fluent software. The differential equations that describe the heat and mass transfer were integrated by the finite volume method, in two and three dimensions. (orig.)

Benelmir, Riad; Mokraoui, Salim; Souayed, Ali [University H. Poincare, Laboratory LERMAB, Faculty of Sciences and Technology, Vandoeuvre-Les-Nancy (France)

2009-10-15

77

Three-dimensional numerical study of heat transfer characteristics of plain plate fin-and-tube heat exchangers from view point of field synergy principle  

International Nuclear Information System (INIS)

In this paper, 3-D numerical simulations were performed for laminar heat transfer and fluid flow characteristics of plate fin-and-tube heat exchanger. The effects of five factors were examined: Re number, fin pitch, tube row number, spanwise and longitudinal tube pitch. The Reynolds number based on the tube diameter varied from 288 to 5000, the non-dimensional fin pitch based on the tube diameter varied from 0.04 to 0.5, the tube row number from 1 to 4, the spanwise tube pitch S 1/d varies from 1.2 to 3, and the longitudinal tube pitch S 2/d from 1.0 to 2.4. The numerical results were analyzed from the view point of field synergy principle, which says that the reduction of the intersection angle between velocity and fluid temperature gradient is the basic mechanism to enhance convective heat transfer. It is found that the effects of the five parameters on the heat transfer performance of the finned tube banks can be well described by the field synergy principle, i.e., the enhancement or deterioration of the convective heat transfer across the finned tube banks is inherently related to the variation of the intersection angle between the velocity and the fluid temperature gradient. It is also recommended that to further enhance the convective heat transfer, the enhancement techniques, such as slotting the fin, should be adopted mainly in the rear part of the fin where the synergy between local velocity and temperature gradient become worsetemperature gradient become worse

78

Performance Analysis of FinFET Device at 60nm  

Directory of Open Access Journals (Sweden)

Full Text Available A Double Gate (DG FinFET device with High K dielectric in 60nm is presented which provides high performance compared to normal MOSFET device in terms of reduction of leakage current. A less leakage current is reported with High-K FinFET device when HfO2 used as High-k material with a dielectric constant of 25. Sentaurus TCAD tool is used to find the performance of the FinFET device

I.Flavia Princess Nesamani#1 , Rijo.P.C

2013-03-01

79

Performance Analysis of FinFET Device at 60nm  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A Double Gate (DG) FinFET device with High K dielectric in 60nm is presented which provides high performance compared to normal MOSFET device in terms of reduction of leakage current. A less leakage current is reported with High-K FinFET device when HfO2 used as High-k material with a dielectric constant of 25. Sentaurus TCAD tool is used to find the performance of the FinFET device

I Flavia Princess Nesamani, Rijo P. C.

2013-01-01

80

Local Heat Transfer Characteristics on Fin Surface of Plate Fin-Oval Tube with Delta Wing Vortex Generators  

International Nuclear Information System (INIS)

In the present study, the effect of delta-wing vortex generators(DWVG) on the local heat transfer of the plate fin-oval tube was experimentally analyzed for Reynolds numbers for 2000, 2500 and 3200. The local heat transfer coefficient of the fin surface for four type DWVGs was measured by the naphthalene sublimation technique. As the results, the distribution of the heat transfer coefficient at rear of DWVGs showed longitudinal contours for common flow down DWVGs and wavy contours for common flow up DWVGs. The distribution showed many cell type contours at near wall and downstream for all DWVGs. Compared to case without DWVGs in present experimental tests, all DWVGs showed the best enhancement of heat transfer at Re=2000. Of 4 cases of DWVGs, D type showed the best enhancement of heat transfer

 
 
 
 
81

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

International Nuclear Information System (INIS)

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

82

New heat transfer and pressure drop correlations for crossflow over low-finned tube banks  

International Nuclear Information System (INIS)

New heat transfer and pressure drop correlations are developed for forced convective turgulent flow over typical low fin tube banks. Only staggered layouts are considered. The proposed correlations cover a Reynolds number range of 800 to 800,000. The data bank assembled by Rabas, Eckels, and Sabatino is expanded with new data sets and tabulated in this paper. Upon comparison, both the new j-factor and f-factor correlations predict 100 percent of the data within +-20 percent error, and 95 percent of the data within +-15 percent error. Recommendations are made for future research needs in the area of fluid flow and heat transfer over low fin tube banks

83

Comparison of fin-and-tube interlaced and face split evaporators with flow maldistribution and compensation  

DEFF Research Database (Denmark)

Flow maldistribution in fin-and tube evaporators for residential air-conditioning is investigated by numerical simulation. In particular, the interlaced and the face split evaporator are compared in flow maldistribution conditions. The considered sources of maldistribution are the liquid/vapor distribution and the airflow distribution. Furthermore, compensation of flow maldistribution by control of individual channel superheat is studied for each evaporator type. It is shown that the interlaced evaporator is better at flow maldistribution than the face split evaporator. However, if individual channel superheats are controlled, the face split evaporator achieves the best performance, i.e. an increase of 7% in overall UA-value and 1.6–2.4% in COP compared to the interlaced evaporator without compensation.

Kærn, Martin Ryhl; Elmegaard, Brian

2013-01-01

84

Multi-objective optimization of a plain fin-and-tube heat exchanger using genetic algorithm  

Science.gov (United States)

In the present paper, a plate fin-and-tube heat exchanger (PFTHE) is considered for optimization with air and water as working fluid, four geometric variables are taken as parameters for optimization, a Genetic Algorithm (GA) was used to search for the optimal structure sizes of the PFTHE, the maximum total heat transfer rate and the minimum total pressure drop are taken as objective functions in GA, respectively. Performance of the optimized result was evaluated and correspondingly the total heat transfer rate, the total pressure drop, the heat transfer coefficient and the local Nusselt number, j-factor and friction factor ? are calculated respectively. Results show that the total heat transfer rate of the optimized heat exchanger increased by about 2.1-9.2% comparing with the original one, the heat transfer coefficient increased by about 8.2-14.7% and the total pressure drop decreased by about 4.4-8% in the range of Re = 1200-14000.

Juan, Du; Qin, Qian Zuo

2014-04-01

85

Heat transfer characteristics of a new helically coiled crimped spiral finned tube heat exchanger  

Science.gov (United States)

In the present study, the heat transfer characteristics in dry surface conditions of a new type of heat exchanger, namely a helically coiled finned tube heat exchanger, is experimentally investigated. The test section, which is a helically coiled fined tube heat exchanger, consists of a shell and a helical coil unit. The helical coil unit consists of four concentric helically coiled tubes of different diameters. Each tube is constructed by bending straight copper tube into a helical coil. Aluminium crimped spiral fins with thickness of 0.5 mm and outer diameter of 28.25 mm are placed around the tube. The edge of fin at the inner diameter is corrugated. Ambient air is used as a working fluid in the shell side while hot water is used for the tube-side. The test runs are done at air mass flow rates ranging between 0.04 and 0.13 kg/s. The water mass flow rates are between 0.2 and 0.4 kg/s. The water temperatures are between 40 and 50°C. The effects of the inlet conditions of both working fluids flowing through the heat exchanger on the heat transfer coefficients are discussed. The air-side heat transfer coefficient presented in term of the Colburn J factor is proportional to inlet-water temperature and water mass flow rate. The heat exchanger effectiveness tends to increase with increasing water mass flow rate and also slightly increases with increasing inlet water temperature.

Srisawad, Kwanchanok; Wongwises, Somchai

2009-02-01

86

Forced convection and entropy generation from elliptic tubes with longitudinal fins  

International Nuclear Information System (INIS)

An experimental investigation has been conducted to clarify heat transfer characteristics and entropy generation for individual elliptic tubes with longitudinal fins. The investigated geometrical parameters included the placement of the fins at the front of the tube, at the rear of the tube and at the front and rear of the tube. The experiments have been carried out on the different cases of electrically heated elliptic tubes which are separately installed in a square tunnel. The surface temperature at different cases of elliptic tubes, have been measured. The testing fluid was air and the Reynolds number ranged from about 4.75 x 103 to 3.96 x 104. The analysis of the entropy generation is based on the principle of minimizing the rate of total entropy generation that includes the generation of entropy due to heat transfer and friction forces are presented. The results indicate that the fin position on the elliptic tube has an effect on the results of heat transfer coefficient, friction factor and irreversibility ratio. The correlations of average Nusselt number, friction factor and irreversibility ratio with Re are presented.

87

HEAT TRANSFER AND FLUID FLOW ANALYSIS IN PLATE-FIN AND TUBE HEAT EXCHANGERS WITH DIFFERENT SHAPED VORTEX GENERATORS  

Directory of Open Access Journals (Sweden)

Full Text Available Numerical analyses were carried out to study the heat transfer and flow in the plate-fin and tube heat exchangers with different shaped vortex generators mounted behind the tubes. The effects of different span angles a (? = 30°, 45° and 60° are investigated in detail for the Reynolds number ranging from 500 to 2500. Numerical simulation was performed by computational fluid dynamics of the heat transfer and fluid flow. The results indicated that the triangle shaped winglet is able to generate longitudinal vortices and improve the heat transfer performance in the wake regions. The case of ? = 45° provides the best heat transfer augmentation than rectangle shape winglet generator in case of inline tubes. Common flow up configuration causes significant separation delay, reduces form drag, and removes the zone of poor heat transfer from the near wake of the tubes.

K.Thirumalai kannan

2012-03-01

88

The influence of the finned-tube assembly on the dimensions of natural-draft dry-type cooling towers  

International Nuclear Information System (INIS)

For various heat exchanger systems the required heights of the towers are evaluated by means of a simplifying mathematical model for dimensioning cooling towers. The characteristics of the cooling systems are for each case taken from literature. The number of tube banks of the heat exchanger systems in flow direction was optimized using the operational data of the Schnehausen dry-type cooling tower. It may be assumed that by changing the tube configuration the performance of very closely spaced, aligned finned systems can be considerably improved. (GL)

89

Degradation of finned tubes heat exchangers in presence of non condensable gases and aerosols  

International Nuclear Information System (INIS)

Full text of publication follows: If a severe accident occurs in a nuclear power plant, then large amounts of steam and aerosols will enter to the containment, increasing the pressure and the temperature inside the containment building. To reduce these thermal and pressure loads, the next generation of European Passive Nuclear Power Plants, incorporates into the containment passive heat exchangers (HX) driven by natural circulation. These passive HX condense the steam inside the containment and transport by natural circulation the heat to a large pool with capability to act as a heat sink at least during 72 hours. These innovative passive systems consist of several units of horizontal or slightly inclined finned tubes bundles internally cooled by water. The cooling water is heated inside the tubes by the condensation heat removed from the containment and moves by natural circulation to a large pool located outside the containment. The main problem that arises in this kind of HX, is the degradation in the heat transfer produced by the non-condensable gases and the aerosols that are present in large amounts after a severe accident inside the containment. This degradation can increase the containment loads after a severe accident and we must be able to predict this effect as better as possible. This paper presents a mechanistic model to predict the steam condensation on containment finned tube heat exchangers in the presence of non-condensable gases (NC) and aerosols. The total thermal resistance from the bulk gas to the coolant is formulated as a parallel combination of the convective and condensation gas resistances coupled in series to those of condensate layer, the aerosol fouling layer, the wall, and the coolant. The condensate layer thermal resistance is calculated by means of an Adamek-based condensation model. The aerosol fouling layer is computed based on diffusiophoresis, settling and impaction mechanisms. The gas mixture (Steam plus NC) thermal resistance is formulated based on a diffusion layer modeling. Finally this paper presents a Monte Carlo method implemented in the Fortran code TAEROSOL that is able to compute the amount of aerosol mass that is deposited by impaction on the top of the finned tubes. The model results are compared with available experimental data of the CONGA European project. Finally we want to mention that Monte Carlo calculations and fluid flow calculations with the code TAEROSOL were performed to compute the amount of aerosols deposited on the top of the fins by impaction during the aerosol phase of Suckow et al. experiments. Also we compute the aerosol mass deposited by diffusiophoresis and settling. The calculations performed show that the mass deposited by settling is always smaller than 3 g in all the cases, and that impaction and diffusiophoresis mechanisms are the main deposition mechanisms for aerosols in CONGA experiments. (authors)

90

Analysis of flow maldistribution in fin-and-tube evaporators for residential air-conditioning systems  

DEFF Research Database (Denmark)

This thesis is concerned with the effects of flow maldistribution in fin-and-tube A-coil evaporators for residential air-conditioning and compensation potentials with regards to system performance. The goal is to create a better understanding of flow maldistribution and the involved physical phenomenons. Moreover, the study investigates the individual and combined effects of non-uniform inlet liquid/vapor distribution, different feeder tube bending and non-uniform airflow. In addition, the possible compensation of these maldistribution sources is investigated by control of individual channel superheat by distributing individual channel mass flow rate continuously (perfect control). The compensation method is compared to the use of a larger evaporator in order to study their trade-off in augmenting system performance (cooling capacity and COP). The studies are performed by numerical modeling in the object-oriented programming language Modelicar and by using the commercial modeling environment Dymola 7.4 (2010). The evaporator model needs to be capable of predicting the flow distribution and circuitry effects, and for these reasons the dynamic distributed one-dimensional mixture two-phase flow model is implemented. The model is verified in steady state with commercial software Coil-Designer (Jiang et al., 2006) and compared to steady state experiments with acceptable results considering the unknown degrees of flow maldistribution for these experiments. Furthermore, the system dynamics in the model were validated and showed that a slip flow model need be used. A test case 8.8 kW residential air-conditioning system with R410A as refrigerant is chosen as baseline for the numerical investigations, and the simulations are performed at standard rating conditions from ANSI/AHRI Standard 210/240 (2008). The investigations are performed on a simplified evaporator tube circuitry (two straight channels), a face split evaporator circuitry and an interlaced evaporator circuitry. The first case is a generic study and serves to provide general results independent of specific type of tube circuitry. The second and third cases are standard tube circuitry designs and these results are thus tube circuitry specific. In addition, a novel method of compensating flow maldistribution is analyzed, i.e. the discontinuous liquid injection principle. The method is based upon the recently developed EcoFlowTM valve by Danfoss A/S, and controls the individual channel superheat by distributing individual mass flow rate discontinuously (on/off injection). The results in this thesis show that flow maldistribution decreases system performance in terms of cooling capacity and COP, but may be compensated significantly by control of individual channel superheat. The generic study (two straight channels) shows that the airflow maldistribution has the largest effect, whereas the liquid/vapor maldistribution has smaller effect and the different feeder tube bending has a minor effect on system performance. The comparison between the face split and interlaced circuitry shows that the face split evaporator performs better at uniform flow conditions, whereas the interlaced evaporator performs better at flow maldistribution conditions. When compensating, the face split evaporator always performs best. A similar result is also obtained as the airflow profile across the A-coil evaporator was predicted by means of CFD simulation software STAR-CD 3.26 (2005) and applied in the numerical model. The main reason for the better face split evaporator performance at uniform conditions or when compensating, is that the superheated "weak" zones with low UA-value is located in the first tube row, where the heat transfer driving potential (temperature difference) is highest. The discontinuous liquid injection principle showed that the cycle time is an important parameter for the performance of this compensation method. The cycle time is essentially the time it takes for distributing mass flow to each evaporator channels. It should be kept as low as possible. Furthermore, it is bett

Kærn, Martin Ryhl

2011-01-01

91

Performance predictions of radiating annular fins of various profile shapes  

Science.gov (United States)

One-dimensional steady-state solutions for radiation from front and rear surfaces of an annular fin having different front and rear emissivities and various profile shapes were obtained by the shooting method along with the use of Runge-Kutta-Verner Fifth and Sixth Order integration method. Fin performance was graphically plotted as a function of variables such as the non-dimensional number, the effective environmental source-to-sink temperature ratio, the radius ratio, and the thickness ratio, over extremely broad ranges. The numerical results are compared with predictions made by two correlation expressions for annular fin performance. These correlations are provided for use in engineering analysis and design.

Truong, H. V.; Mancuso, R. J.

1980-07-01

92

Burnout experiments on the externally-finned swirl tube for steady-state and high-heat flux beam stops  

International Nuclear Information System (INIS)

An experimental study to develop beam stops for the next generation of neutral beam injectors was started, using an ion source developed for the JT-60 neutral beam injector. A swirl tube is one of the most promising candidates for a beam stop element which can handle steady-state and high-heat flux beams. In the present experiments, a modified swirl tube, namely an externally-finned swirl tube, was tested together with a simple smooth tube, an externally finned tube, and an internally finned tube. The major dimensions of the tubes are 10 mm in outer-diameter, 1.5 mm in wall thickness, 15 mm in external fin width, and 700 mm in length. The burnout heat flux (CHF) normal to the externally finned swirl tube was 4.1±0.1 kW/cm2, where the Gaussian e-folding half-width of the beam intensity distribution was about 90 mm, the flow rate of the cooling water was 30 l/min, inlet and outlet gauge pressures were about 1 MPa and 0.2 MPa, respectively, and the temperature of the inlet water was kept to 200C during a pulse. A burnout heat flux ratio, which is defined by the ratio of the CHF value of the externally-finned swirl tube to that of the externally-finned tube, turned out to be about 1.5. Burnout heat fluxes of the tubes with a swirl tape or internal fins increase linearly with an increase of the flow rate. It was found that the tube with external fins has effects that not only reduce the thermal stress but also improve the characteristics of boiling heat transfer. (orig.)

93

Heat transfer and flow characteristics around a finned-tube bank heat exchanger in fluidized bed  

Science.gov (United States)

Principal heat transfer mechanisms in a fluidized bed have been classified into three categories, i.e. solid convection, gas convection and radiation. Among these mechanisms, the solid convection is a dominant mechanism in the bubbling fluidized bed. This solid convection is substantially caused by the bubble movement, thus the visualization of the void fraction distribution becomes a very useful method to understand the characteristics of the fluidized-bed heat exchanger. In this study, the heat transfer coefficient and the void fraction around the heat transfer tube with annuler fin were measured. For the quantitative measurement of the void fraction, neutron radiography and image processing technique were employed. Owing to the existence of the annuler fin, the restriction of the particle movements was put. This restriction suppressed the disturbance caused by tubes, and the influence of the tube arrangement on the flow and heat transfer characteristics could be clearly expressed.

Honda, Ryosuke; Umekawa, Hisashi; Ozawa, Mamoru

2009-06-01

94

Heat transfer and flow characteristics around a finned-tube bank heat exchanger in fluidized bed  

International Nuclear Information System (INIS)

Principal heat transfer mechanisms in a fluidized bed have been classified into three categories, i.e. solid convection, gas convection and radiation. Among these mechanisms, the solid convection is a dominant mechanism in the bubbling fluidized bed. This solid convection is substantially caused by the bubble movement, thus the visualization of the void fraction distribution becomes a very useful method to understand the characteristics of the fluidized-bed heat exchanger. In this study, the heat transfer coefficient and the void fraction around the heat transfer tube with annuler fin were measured. For the quantitative measurement of the void fraction, neutron radiography and image processing technique were employed. Owing to the existence of the annuler fin, the restriction of the particle movements was put. This restriction suppressed the disturbance caused by tubes, and the influence of the tube arrangement on the flow and heat transfer characteristics could be clearly expressed.

95

Flexible Nanoscale High-Performance FinFETs.  

Science.gov (United States)

With the emergence of the Internet of Things (IoT), flexible high-performance nanoscale electronics are more desired. At the moment, FinFET is the most advanced transistor architecture used in the state-of-the-art microprocessors. Therefore, we show a soft-etch based substrate thinning process to transform silicon-on-insulator (SOI) based nanoscale FinFET into flexible FinFET and then conduct comprehensive electrical characterization under various bending conditions to understand its electrical performance. Our study shows that back-etch based substrate thinning process is gentler than traditional abrasive back-grinding process; it can attain ultraflexibility and the electrical characteristics of the flexible nanoscale FinFET show no performance degradation compared to its rigid bulk counterpart indicating its readiness to be used for flexible high-performance electronics. PMID:25185112

Torres Sevilla, Galo A; Ghoneim, Mohamed T; Fahad, Hossain; Rojas, Jhonathan P; Hussain, Aftab M; Hussain, Muhammad Mustafa

2014-10-28

96

Numerical Analysis for Heat Transfer Characteristics of Elliptic Fin-Tube Heat Exchanger with Various Shapes  

International Nuclear Information System (INIS)

In this study, the characteristics of the heat transfer coefficient and pressure drop were numerically analyzed according to the axis ratio (A R), pitch, location of vortex generator, and bump phase of the tube surface about an elliptical fin-tube heat exchanger. The boundary condition for CAD analysis was decided as a tube surface temperature of 348 K and inlet air velocity of 1.5 m/s. RCM 7th turbulent model was chosen as the numerical analysis for the sensitivity level. The analysis results indicated that the A R and transverse pitch decreased whereas the heat transfer coefficient increased. On the other hand, there was little difference in the longitudinal pitch. Furthermore, the heat transfer rate was more favorable when the vortex generator was located in front of the tube. Also, the bump phase of the tube surface indicated that the pressure drop and heat transfer were more favorable with the circle type than with the serrated type

97

Steam generator tube performance  

International Nuclear Information System (INIS)

A survey of steam generator operating experience for 1986 has been carried out for 184 pressurized water and pressurized heavy-water reactors, and 1 water-cooled, graphite-moderated reactor. Tubes were plugged at 75 of the reactors (40.5%). In 1986, 3737 tubes were plugged (0.14% of those in service) and 3148 tubes were repaired by sleeving. A small number of reactors accounted for the bulk of the plugged tubes, a phenomenon consistent with previous years. For 1986, the available tubesheet sludge data for 38 reactors has been compiled into tabular form, and sludge/deposit data will be incorporated into all future surveys

98

Propulsive performance of oscillating batoid-inspired fins  

Science.gov (United States)

Thrust producing ray-like pectoral fins were actuated to drive a low friction carriage through a stationary tow tank. A DC servo motor powered a gear train that produced a traveling wave motion along the chord of the fin. The amplitude of the traveling wave increased linearly along the span from root to tip. A digital optical encoder attached to the carriage tracked the position and velocity as it was propelled through the water by the oscillating fin. Velocity profiles were acquired from trials using different planforms inspired by members of the eagle ray family, as well as an idealized elliptical fin. Traveling wave frequency and wavelength were varied to investigate the propulsive performance of different gaits. Preliminary flow visualization was also performed to describe the structure of the wakes generated by the various planform geometries and locomotory gaits.

Quinn, Daniel; Rein-Weston, Daphne; Dewey, Peter; Green, Melissa; Smits, Alexander

2009-11-01

99

Inverse heat transfer problem in digital temperature control in plate fin and tube heat exchangers  

Science.gov (United States)

The aim of the paper is a steady-state inverse heat transfer problem for plate-fin and tube heat exchangers. The objective of the process control is to adjust the number of fan revolutions per minute so that the water temperature at the heat exchanger outlet is equal to a preset value. Two control techniques were developed. The first is based on the presented mathematical model of the heat exchanger while the second is a digital proportional-integral-derivative (PID) control. The first procedure is very stable. The digital PID controller becomes unstable if the water volumetric flow rate changes significantly. The developed techniques were implemented in digital control system of the water exit temperature in a plate fin and tube heat exchanger. The measured exit temperature of the water was very close to the set value of the temperature if the first method was used. The experiments showed that the PID controller works also well but becomes frequently unstable.

Taler, Dawid; Sury, Adam

2011-12-01

100

Research on air pressure drop in helically-finned tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

In order to establish a reliable procedure for estimation of air pressure drop, extensive investigation of the open literature has been conducted. The equations from mostly cited literature sources were tested against the experimental data given in the open literature and certain level of uncertainty was found. Using published experimental data, new correlations for estimation of air pressure drop in helically-finned tube bundles with in-line and staggered tube arrangement have been established. Chosen form of correlations successfully describes operating regimes for wide range of Reynolds number and geometrical parameters. [Author].

Genic, Srbislav B.; Jacimovic, Branislav M.; Latinovic, Boris R. [Department of Process Engineering, Faculty of Mechanical Engineering, University of Belgrade, Kraljice Marije 16, 11000 Beograd (Serbia and montenegro)

2006-04-01

 
 
 
 
101

Numerical analysis of heat and mass transfer in a compact finned tubes air heat exchanger under dehumidification conditions  

Energy Technology Data Exchange (ETDEWEB)

A simulation model of a fin-and-tube heat exchanger is presented. The effect of the relative humidity, air speed, fin base temperature, and inlet air temperature on the estimation of the overall heat-transfer coefficient and fin efficiency under wet conditions is also investigated. This model considers a non-uniform airflow velocity as well as a variable sensible heat transfer coefficient. (orig.)

Benelmir, Riad; Mokraoui, Salim [Henri Poincare University, Faculty of Sciences and Technology, Lab. LERMAB, Vandoeuvre-Les-Nancy (France)

2012-04-15

102

Performance Improvement of FinFET using Nitride Spacer  

Directory of Open Access Journals (Sweden)

Full Text Available The Double Gate FinFET has been designed for 90nm as an alternative solution to bulk devices. The FinFET with independent gate (IDG structure is designed to control Vth. When the Vth is controlled the leakage current can be decreased by improving its current driving capability. The metal used for the front gate and back gate is TiN. Here the device performance is compared using nitride spacer and device without spacer. The work function is a very important consideration in the selection of metal for the gate structure and also it affects the Vth and the performance of a device

Flavia Princess Nesamani#1, Geethanjali Raveendran*2 , Dr.V. Lakshmi Prabha#3

2013-03-01

103

Upgrading the Performance of VLSI Circuits using FinFETs  

Directory of Open Access Journals (Sweden)

Full Text Available In the world of integrated circuits, CMOS has lost it’s credentialed during scaling beyond 32nm. The main drawback of using CMOS transistors are high power consumption and high leakage current. Scaling causes severe Short Channel Effects (SCE which are difficult to suppress. As technology is scaled down, the importance of leakage current and power analysis for VLSI design is increasing since Short-channel effects cause an exponential increase in the leakage current and power dissipation. Multi-gate MOSFET technologies mitigate these limitations by providing a stronger control over a thin silicon body with multiple electrically coupled gates. Enormous progress has been made to scale transistors to even smaller dimensions to obtain fast switching transistors, as well as to reduce the power consumption. Even though the device characteristics are improved, high active leakage remain a problem. FinFET has become the most promising substitute to bulk CMOS technology because of reducing short channel effect and the similarity of the fabrication steps to the existing standard CMOS technology. FinFET device has a higher controllability, resulting relatively high lon/loff ratio. FinFET devices can be used to increase the performance by reducing the leakage current and power dissipation, because front and back gates both can be controlled.(independently or both simultaneously. In this paper, Dual-gate FinFET with shorted gates of either side is used for better performance to reduce the leakage and hence power consumption. In this work, the basic gates, combinational circuit and are modelled in HSPICE software using CMOS structures and FinFET structure are analysed and their performances like power consumption and speed are compared. Latch based on tied-gate FinFETs is proposed in this paper to simultaneously reduce the power consumption and the circuit area.

Tushar Surwadkar

2014-08-01

104

Development of Design method for a Finned-tube Sodium-to-Air Heat Exchanger in 600MWe demonstration SFR  

Energy Technology Data Exchange (ETDEWEB)

The conceptual design of a 600MWe demonstration sodium-cooled fast reactor (hereafter called DSFR-600) has been performed by the Korea Atomic Energy Research Institute (KAERI). In order to enhance plant safety, reliable decay heat removal (DHR) systems with natural circulation flow have been considered, and different kinds of sodium-to-air heat exchangers were employed as an ultimate heat sink for this type of DHR system. The DHR system comprises two diverse heat removal loops, and the heat load imposed on the primary sodium pool is safely rejected into the environment through different shapes of final aircoolers. Serpentine- and helical-coil type sodium-to-air heat exchangers have been considered for the purpose. The former is called FDHX (Forced-draft sodium-to-air heat exchanger) and the latter is simply called AHX. For a general sodium-to-air heat exchanger design, convection resistance at shell-side air flow path becomes a 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. To this end, performance evaluation of a sodium-to-air heat exchanger is one of the most important tasks to secure the overall performance of a DHR system. This study introduces one-dimensional design approach of a finned-tube sodium-to-air heat exchanger using reasonable heat transfer and pressure drop models, and provides detailed design parameters with heat transfer tube arrangement including the factors of fin-effect. The operational strategy regarding sodium freezing protection of the FDHX unit was briefly discussed as well

Eoh, Jae Hyuk; Choi, Sun Rock; Lee, Hyeong Yeon; Han, Ji Woong; Lee, Tae Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2012-05-15

105

Dehumidification: Prediction of Condensate Flow Rate for Plate-Fin Tube Heat Exchangers Using the Latent j Factor  

Energy Technology Data Exchange (ETDEWEB)

Condensate flow rate is an important factor in designing dehumidifiers or evaporators. In this paper, the latentj fimtor is used to analyze the dehumidification performance of two plate-fin tube heat exchangers. This latent j factor, analogous to the total j factor, is a flmction of the mass transfa coefllcient, the volumetric air flow rate, and the Schmidt number. This latent j factor did predict condensate flow rate more directly and accurately than any other sensiblej factor method. The Iatentj factor has been used in the present study because the sensible j factor correlations presented in the literature failed to predict the condensate flow rate at high Reynolds numbers. Results show that the latent j i%ctor em be simply correlated as a fhnction of the Reynolds number based on the tube outside diameter and number of rows of the heat exchanger.

Baxter, V.D.; Chen, D.T.; Conklin, J.C.

1999-03-15

106

In-service inspection method for low-finned ferritic stainless steel tubes for new heat exchanger  

International Nuclear Information System (INIS)

Conventional inner eddy current test cannot obtain sufficient evaluation for low finned ferritic stainless steel tube inspection. The authors tried various methods and developed special partial saturation eddy current method. This paper summarizes typical experimental results of fundamental studies and trials, and introduces developed ECT data acquisition and evaluation system. Moisture Separator Heater (MSH) used in ABWR (Advanced Boiling Water Reactor) plant is a new type heat exchanger to increase plant thermal efficiency. There are four single tubesheet heaters in a MSH vessel. Each heater has hundreds of low finned tubes made of ferritic stainless steel. In nuclear power plants, non-magnetic materials (austenitic stainless steel, titanium, aluminum brass, etc.,) are mainly used as heat exchanger tubes such as the tubes of feedwater heater, condenser, evaporator and so on. Conventional ECT (Eddy Current Test) method are easily applied for the inspection of these heat exchanger tubes. In recent years, the authors started using ferritic stainless steel tube for new heat exchangers such as MSH because of its superior heat transfer efficiency. However, high permeability of ferritic stainless steel prevents the inspection of these tubes using conventional ECT method. To inspect MSH tubes periodically is important to confirm and maintain reliability of MSH. They tried applying various inspection methods and have developed special ECT method for low finned ferritic stainl ECT method for low finned ferritic stainless steel tubes

107

High-fin staggered tube banks: Heat transfer and pressure drop for turbulent single phase gas flow  

Science.gov (United States)

This Data Item ESDU 86022 is an addition to the Heat Transfer Sub-series. New correlations are presented for external heat transfer coefficient and static pressure loss for single phase flow over plain circular fins of either retangular or tapered cross section on round tubes. The correlations were derived by a regression analysis of experimental results extracted from the literature for a wide range of tube bundle configurations. Fin densities of 4 to 11 per inch (equivalent to fin pitches of 6.4 to 2.3 mm) tube outside diameters of 3/8 to 2 inch (10 to 51 mm), fin heights of 1/4 to 5/8 inch (6 to 16 mm), and ratios of fin tip to fin root diameter of 1.2 to 2.4 were covered. For heat transfer the range of Reynolds number based on tube outer diameter was from 2,000 to 40,000 and for pressure drop from 5,000 to 50,000. Comparison of the prediction with experiment shows that for heat transfer 85% of the data points were within 10% of estimated and for pressure drop 72% were within 10%. A comprehensive worked example showing the use of the method for an air cooled heat exchanger bundle is included. The applicability of this method to nonintegral fins is considered and factors influencing the thermal resistance of the interface are discussed. Effects of fouling are also briefly covered.

1986-10-01

108

Research on the air pressure drop in plate finned tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

In order to establish a reliable procedure for estimation of air pressure drop, experiments on plate finned tube heat exchangers have been conducted, as well as the research on the open literature. The procedure of Kays and London was tested against the experimental data and significant level of uncertainty was found. Using own experimental data, as well as previously published data of Kays and London, new correlation for estimation of air pressure drop has been established. Statistical parameters of new correlation enable the conclusion that it can be used for wide range of Reynolds numbers. (author)

Jacimovic, Branislav M.; Genic, Srbislav B. [Department of Process Engineering, Faculty of Mechanical Engineering, University of Belgrade, Kraljice Marije 16, 11000 Beograd (Serbia and Montenegro); Latinovic, Boris R. [Innovation Center, Faculty of Mechanical Engineering, University of Belgrade, Kraljice Marije 16, 11000 Beograd (Serbia and Montenegro)

2006-11-15

109

Experimental investigation of forced-convection in a finned rhombic tube of the flat-plate solar collectors  

DEFF Research Database (Denmark)

Due to scarcity of literature on forced-convection heat transfer in a solar collector with rhombic cross-section absorbing tubes, a series of experiments was arranged and conducted to determine heat transfer coefficient. In this study, a typical rhombic cross-section finned tube of flat-plate collectors used as the test section. Two correlations were proposed for the Nusselt number as a function of the Reynolds number and the Prandtl number based on hydraulic diameter for various heat fluxes. The temperature distribution along the finned tube for the fluid and the wall were also illustrated.

Yazdanshenas, Eshagh

2006-01-01

110

A nonlinear inverse problem for the prediction of local thermal contact conductance in plate finned-tube heat exchangers  

Science.gov (United States)

A nonlinear inverse problem utilizing the Conjugate Gradient Method (CGM) of minimization is used successfully to estimate the temporally and circumferentially varying thermal contact conductance of a plate finned-tube heat exchanger by reading the simulated transient temperature measurement data from the thermocouples located on the plate. The thermal properties of the fin and tube are assumed to be functions of temperature, and this makes the problem nonlinear. It is assumed that no prior information is available on the functional form of the unknown thermal contact conductance in the present study, thus, it is classified as the function estimation in the inverse calculation. The accuracy of the inverse analysis is examined by using the simulated temperature measurements. Finally the inverse solutions with and without the consideration of temperature-dependent thermal properties are compared. Results show that when the nonlinear inverse calculations are performed an excellent estimation on the thermal contact conductance can be obtained with any arbitrary initial guesses within a couple of minute's CPU time on a HP-730 workstation.

Huang, C.-H.; Hsu, G.-C.; Jang, J.-Y.

111

Experimental Study on the Air-Side Heat Transfer Characteristics of a Spirally- Coiled Circular Fin-Tube Heat Exchanger According to Geometric Parameters  

International Nuclear Information System (INIS)

The objective of this study is to investigate the air-side heat transfer characteristics of a spirally-coiled circular fin tube heat exchanger for various geometric parameters under non-frosting conditions. The heat transfer characteristics of the heat exchanger were analyzed with respect to heat exchanger geometries, and then, the characteristics were compared with those of rectangular-plate fin-tube heat exchangers with discrete fins. The heat transfer coefficient increased with a decrease in the number of tube rows and an increase in the fin pitch. The optimum length of the L-foot was 2.7 mm. In addition, the heat transfer rate increased with a decrease in the tube pitch and the tube thickness. The heat transfer coefficient of the spirally coiled circular fin-tube heat exchanger was 24.3% higher than that of the rectangular-plate fin-tube heat exchanger

112

Comparison of Streak Tube Performance  

Energy Technology Data Exchange (ETDEWEB)

The performance of four streak tubes in six streak camera configurations is reported. Evaluations were made as part of a search for a streak tube to replace the obsolete RCA C73435 used in the ICF Program's optical streak cameras. Characteristics measured include linearity, spatial and temporal resolution, line-spread function, contrast transfer ratio (CTR), and dynamic range. Tubes evaluated are the RCA C73435, Photonis P510, Photek ST-Y, and Hamamatsu N8059. The RCA C73435 was evaluated in three camera configurations: large format CCD coupled directly to the streak tube, CCD directly coupled to an image intensifier tube (IIT), and the original configuration with a smaller CCD lens coupled to the IIT output. The Photonis and Photek tubes were characterized in configurations where they were directly coupled to large format CCDs. Optimum spatial resolution is achieved when the IIT is removed. Maximum dynamic range requires a configuration where a single photoelectron from the photocathode produces a signal that is {approx}5 times the CCD read noise. The Photonis P510 tube with the E2V CCD forms a well-optimized streak camera system.

Lerche, R A; Andrews, D S; Bell, P M; Griffiths, R L; Huey, A W; McDonald, J W; de Dios, G V

2004-11-04

113

Heat transfer from a horizontal finned tube bundle in bubbling fluidized beds of small and large particles  

Energy Technology Data Exchange (ETDEWEB)

Steady state average heat transfer coefficient measurements were made by the local thermal simulation technique in a cold, square, bubbling air-fluidized bed (0.305 m x 0.305 m) with immersed horizontal finned tube bundles (in-line and staggered) with integral 60{degree} V-thread. Studies were conducted using beds of small (average particle diameter less than 1 mm) sand particles and of large (average particle diameter greater thin 1 mm) particles (raagi, mustard, millet and coriander). The fin pitch varied from 0.8 to 5.0 mm and the fin height varied from 0.69 to 4.4 mm. The tube pitch ratios used were 1.75 and 3.5. The influence of bed particle diameter, fluidizing velocity, fin pitch, and tube pitch ratio on average heat transfer coefficient was studied. Fin pitch and bed particle diameter are the most significant parameters affecting heat transfer coefficient within the range of experimental conditions. Bed pressure drop depends only on static bed height. New direct correlations, incorporating easily measurable quantities, for average heat transfer coefficient for finned tube bundles (in-line and staggered) are proposed.

Devaru, C.B. [Jayachamaraja College of Engineering, Mysore (India). Dept. of Mechanical Engineering; Kolar, A.K. [Indian Inst. of Technology, Madras (India). Dept. of Mechanical Engineering

1995-12-31

114

3D Numerical heat transfer and fluid flow analysis in plate-fin and tube heat exchangers with electrohydrodynamic enhancement  

Science.gov (United States)

Three-dimensional laminar fluid flow and heat transfer over a four-row plate-fin and tube heat exchanger with electrohydrodynamic (EHD) wire electrodes are studied numerically. The effects of different electrode arrangements (square and diagonal), tube pitch arrangements (in-line and staggered) and applied voltage (VE=0-16 kV) are investigated in detail for the Reynolds number range (based on the fin spacing and frontal velocity) ranging from 100 to 1,000. It is found that the EHD enhancement is more effective for lower Re and higher applied voltage. The case of staggered tube pitch with square wire electrode arrangement gives the best heat transfer augmentation. For VE=16 kV and Re = 100, this study identifies a maximum improvement of 218% in the average Nusselt number and a reduction in fin area of 56% as compared that without EHD enhancement.

Lin, Chia-Wen; Jang, Jiin-Yuh

2005-05-01

115

Manufacturing techniques and quality level of low fin tubes for a moisture separator-reheater in nuclear power plant  

International Nuclear Information System (INIS)

In order to increase the overall efficiency of nuclear power plants, moisture separator-reheaters (MSR) are installed or are going to be installed in light water reactors. Ferritic stainless steel is considered as an alternative material for low fin MSR tube. However, by utilizing 13Cr-Ti and 18Cr-Ti steel, low fin tubes with superior corrosion resistance have been developed, the required content of Ti in chemical composition clarified, and manufacturing techniques established. This paper introduces the manufacturing process and their quality data. (author)

116

Horseshoe vortex studies in the passage of a model plate-fin-and-tube heat exchanger  

International Nuclear Information System (INIS)

An experimental investigation is reported using particle image velocimetry of the flow structure in the flow through a rectangular duct containing a circular cylinder with axis normal to the flow. A duct with a narrow gap was designed to simulate a fin-tube heat exchanger containing a single circular cylinder. The time-averaged velocity vectors map, , patterns of streamlines, and corresponding vorticity contours, were obtained using 490 instantaneous images. Development of the entrainment process between the main flow and wake-flow regions is magnified by a helical horseshoe vortex system emerging upstream of the cylinder. The occurrence and development of boundary layer separation and the formation of horseshoe vortices upstream of the cylinder close to both upper and lower plate surfaces and the merging of these developing horseshoe vortices into a primary horseshoe vortex system were also observed in the side-view plane for the Reynolds number range of 1500 ? Red ? 6150

117

Volume Averaging Theory (VAT) based modeling and closure evaluation for fin-and-tube heat exchangers  

Science.gov (United States)

A fin-and-tube heat exchanger was modeled based on Volume Averaging Theory (VAT) in such a way that the details of the original structure was replaced by their averaged counterparts, so that the VAT based governing equations can be efficiently solved for a wide range of parameters. To complete the VAT based model, proper closure is needed, which is related to a local friction factor and a heat transfer coefficient of a Representative Elementary Volume (REV). The terms in the closure expressions are complex and sometimes relating experimental data to the closure terms is difficult. In this work we use CFD to evaluate the rigorously derived closure terms over one of the selected REVs. The objective is to show how heat exchangers can be modeled as a porous media and how CFD can be used in place of a detailed, often formidable, experimental effort to obtain closure for the model.

Zhou, Feng; Catton, Ivan

2012-10-01

118

Comparison of fin-and-tube interlaced and face split evaporators with flow mal-distribution and compensation  

DEFF Research Database (Denmark)

Flow mal-distribution in fin-and tube evaporators for residential air-conditioning is investigated by numerical simulation. In particularly, the interlaced and the face split evaporator are compared in flow maldistribution conditions. The considered sources of mal-distribution are: Liquid/vapor distribution and airflow distribution. Furthermore, compensation of flow mal-distribution by control of individual channel superheat is studied for each type of evaporator. It is shown that the interlaced evaporator is better at flow maldistribution than the face split evaporator. However, if individual channel superheats are controlled, the face split evaporator achieves the best performance, i.e. an increase of 7% in UA-value and 1.6% to 2.4% in COP compared to the interlaced evaporator without compensation.

Kærn, Martin Ryhl; Elmegaard, Brian

2011-01-01

119

Numerical analysis of fin-tube plate heat exchanger by using CFD technique  

Directory of Open Access Journals (Sweden)

Full Text Available Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a two-row plain fin-and-tube heat exchanger using Open FOAM, an open-source CFD code. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 330 to 7000. Model geometry is created, meshed, calculated, and post-processed using open source software. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models (k-epsilon, and Menter SST k-omega, with steady-state solvers to calculate pressure drop, flow, and temperature fields. Model validation is carried out by comparing the simulated case friction factor f and Colburn factor j to experimental results from the literature. For friction factor determination, little difference is found between the flow models simulating laminar flow, while in transitional flow, the laminar flow model produced the most accurate results and the k-omega SST turbulence model was more accurate in turbulent flow regimes. The most accurate simulations for heat transfer in laminar flow are found using the laminar flow model, while heat transfer in transitional flow is best represented with the SST k-omega turbulence model, and heat transfer in turbulent flow is more accurately simulated with the k-epsilon turbulence model. Reasonable agreement is found between the simulations and experimental data, and the open-source software has been sufficient for simulating the flow fields in tube-fin heat exchangers.

Ahmed F. Khudheyer

2011-07-01

120

Numerical simulation and experimental verification on thermal performance of a novel fin-plate thermosyphon  

International Nuclear Information System (INIS)

Numerical investigation of a novel fin-plate thermosyphon (FPT), used to cool the high heat dissipation electronic devices, was performed. Three dimensional model of FPT is established using the Fluent software. The effects of fin pinch, fin thickness and fin type at the air side on thermal characteristics of FPT are presented with the air flow velocity various from 1.0 m/s to 4.0 m/s. The numerical results showed a good agreement with the corresponding experimental data. The heat transfer efficiency and pressure drops of FPT for plain fins were reduced by increasing the fin space. It also can be indicated that the cooling performance of FPT with serrated fins was better than plain fins for the same structural parameters. - Highlights: ? A novel diffusion welded fin-plate thermosyphon (FPT) was designed and performed. ? The plain fins heat transfer efficiency increases with the decrease of fin spaces. ? The fin thickness is less influential on FPT performance. ? Thermal performance of serrated fins is significantly much higher than that of plain fins.

 
 
 
 
121

Pressure drop coefficients for elliptic and circular sections in one, two and three-row arrangements of plate fin and tube heat exchangers  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The objective of the present work is the experimental determination of pressure drop coefficients (loss coefficients) for elliptic and circular sections in one, two and three-row arrangements of plate fin and tube heat exchangers. The experiments permitted to correlate the dimensionless loss coeffic [...] ient with the flow Reynolds number in the rectangular channel formed by the plate fins. The experimental technique consisted of the measurement of the longitudinal pressure distribution along the flow channel, for several values of air mass flow rate. The total number of data runs, each one characterized by the flow Reynolds number, was 216. The present geometry is used in compact heat exchangers for air conditioning systems, heaters, radiators, and others. Also, it is verified the influence of the utilization of elliptic tubes, instead of circular ones, in the pressure drop. The measurements were performed for Reynolds numbers ranging from 200 to 1900.

Sérgio Nascimento, Bordalo; Francisco Eduardo Mourão, Saboya.

1999-12-01

122

Pressure drop coefficients for elliptic and circular sections in one, two and three-row arrangements of plate fin and tube heat exchangers  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The objective of the present work is the experimental determination of pressure drop coefficients (loss coefficients) for elliptic and circular sections in one, two and three-row arrangements of plate fin and tube heat exchangers. The experiments permitted to correlate the dimensionless loss coeffic [...] ient with the flow Reynolds number in the rectangular channel formed by the plate fins. The experimental technique consisted of the measurement of the longitudinal pressure distribution along the flow channel, for several values of air mass flow rate. The total number of data runs, each one characterized by the flow Reynolds number, was 216. The present geometry is used in compact heat exchangers for air conditioning systems, heaters, radiators, and others. Also, it is verified the influence of the utilization of elliptic tubes, instead of circular ones, in the pressure drop. The measurements were performed for Reynolds numbers ranging from 200 to 1900.

Sérgio Nascimento, Bordalo; Francisco Eduardo Mourão, Saboya.

123

Numerical study of the pressure drop in a plain fin-and-circular tube heat exchanger under frost condition  

International Nuclear Information System (INIS)

Full text: Three-dimensional computational fluid dynamics (CFD) simulations are carried out to study the pressure drop behavior in a plain fin-and-four staggered layout and circular tube rows for different fin pitches under frost conditions using FLUENT 6.3 CFD code. Models geometry is created and meshed using GAMBIT 2.3. Fluid flow and heat transfer are simulated and results calculated using (Transitional SST k-omega) turbulence model, with steady-state solver. Model validation is carried out by comparing the pressure drop of a simulated case with experimental results from the literature. It was found that Fluent 6.3 software has been sufficient for simulating the flow characteristics in tube-fin heat exchangers. (author)

124

Thermal behavior of crimped spiral fin tube bank under dehumidifying process: A case study of inline arrangement  

Directory of Open Access Journals (Sweden)

Full Text Available Cross flow heat exchangers having crimped spiral fin and inline arrangement configurations under dehumidification are studied. The effect of tube diameter, fin spacing, fin height, transverse tube pitch are examined. From the experiment, it is found that the heat transfer and the frictional characteristics of the heat exchanger under dehumidification is close to that of the non-dehumidifying process. However, the air stream pressure drop and the heat transfer coefficient of the wet surface heat exchanger are higher and lower than those of the dry surface respectively. Moreover, equations are developed for predicting the f and the j factors of a tested heat exchanger. Results from the developed equations agree well with the experimental data.

Atipoang Nuntaphan

2004-05-01

125

3D-CFD simulation and neural network model for the j and f factors of the wavy fin-and-flat tube heat exchangers  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english A three dimensional (3D) computational fluid dynamics (CFD) simulation and a neural network model are presented to estimate the behaviors of the Colburn factor (j) and the Fanning friction factor (f) for wavy fin - and - flat tube (WFFT) heat exchangers. Effects of the five geometrical factors of fi [...] n pitch, fin height, fin length, fin thickness, and wavy amplitude are investigated over a wide range of Reynolds number (600

M, Khoshvaght Aliabadi; M, Gholam Samani; F, Hormozi; A, Haghighi Asl.

2011-09-01

126

Fluid-structure interactions of skeleton-reinforced fins: performance analysis of a paired fin in lift-based propulsion.  

Science.gov (United States)

We investigate the thrust generation capacity of a thin foil consisting of a membrane strengthened by embedded rays that is geometrically, structurally and kinematically similar to pectoral fins of bony fishes during lift-based labriform locomotion. Our numerical model includes a fully nonlinear Euler-Bernoulli beam model of the skeleton and a boundary-element model of the surrounding flow field. The fin undergoes a dorso-ventral flapping activated by rotations of the rays. Both the trailing edge vortices (TEV) and the leading edge vortices (LEV) are accounted for and modeled as shear layers. The thrust generation and propulsion efficiency are examined and documented. Our results show that synchronization of rays is pivotal to the performance of the system. A primary factor that determines the performance of the fin is phase lags between the rays, which create variations of the effective angle of attack at the leading edge as well as shape changes throughout the fin surface. Structural flexibility of the rays leads to passive deformations of the fin, which can increase the thrust generation and the propulsion efficiency. PMID:19648413

Shoele, Kourosh; Zhu, Qiang

2009-08-01

127

Non-Destructive Testing Methods Applied to Multi-Finned SAP Tubing for Nuclear-Fuel Elements  

International Nuclear Information System (INIS)

The Danish Atomic Energy Commission has undertaken a design study oi an organic-cooled, heavy- water-moderated power reactor. The fuel element for the reactor is a 19-rod bundle; the fuel rods contain sintered uranium-dioxide pellets canned in 2-m long, helically-finned tubes of Sintered Aluminium Product (SAP). A very high quality of the canning tubes is necessary to obtain the optimum heat-transfer conditions and to maintain the integrity of the fuel element during reactor service. Two examples of tube design illustrate the narrow dimensional tolerances. In order to ensure an adequate quality of the canning tubes, a stringent quality control has been established, to a wide extent based upon non-destructive methods. An account is presented of the non-destructive techniques developed for measuring wall thickness and diameters and for detecting defects. The complex 24-finned cross-section prevents the application of ultrasonic or eddy-current methods for wall-thickness measurements. Therefore, a special recording beta-gauge has been developed, based upon the attenuation of beta radiation from a Sr90 source placed inside the tube. An ultrasonic immersion resonance method is used for the continuous recording of the wall thickness of the more simple 12-finned tube design. Inner and outer (across fin tips) diameters are continuously recorded by rapid air-gauge systems. Flaw detection is carried out by the ultrasonic pulse-echo immersion technique and by eddy-cure-echo immersion technique and by eddy-current inspection.. Transverse cracks can easily be detected by the ultrasonic method whereas inspection for longitudinal flaws has not appeared feasible with this method. Therefore, eddy-current inspection is applied in addition to the ultrasonic testing. (author)

128

Experimental Study of Heat Transfer Enhancement in Fin Tube Heat Exchanger by Vortex Generator-A Review  

Directory of Open Access Journals (Sweden)

Full Text Available This review paper presents the work of various researchers on the heat transfer enhancement of fin tube heat exchanger. In this research author used different type of vortex generator like delta winglet, rectangular winglet, curved trapezoidal winglet pair. The vortex generator can be embedded in the plate fin and that too in a low cost with effect the original design and setup of the commonly used heat exchangers. The various design modifications which are implemented and studied numerically and experimentally is been discussed in the paper.

Dhananjay Kumar*1

2014-05-01

129

DRY/WET PERFORMANCE OF A PLATE-FIN AIR COOLED HEAT EXCHANGER WITH CONTINUOUS CORRUGATED FINS  

Science.gov (United States)

The report describes work to (1) determine experimentally the performance and operating characteristics of a plate-fin heat exchanger during dry/wet or 'deluge' operation and (2) continue developing the deluge heat/mass transfer model. This work supports the improvement of power ...

130

Geometrical optimization and mould wear effect on HPD type steel offset strip fin performance  

International Nuclear Information System (INIS)

Aiming at studying the influence and importance of the geometrical parameters on steel HPD type offset strip fin performance, this paper reports experimental and numerical studies at low Reynolds number. A novel test rig with electrically heated single layer fin assembly as test object was constructed. Only the effects of fin height and fin wavelength on the fin characteristics were considered because of the pressing mould limitation. Through comparisons of experimental, simulated and Muzychka's results, the tendencies agree well. The deviations between them are due to the difference of fin material and the influences of the pressing mould process technique on the fins. Based on the Taguchi method and uniform design, the importance of the geometrical factors on the fin thermal-hydraulic performance was investigated. The sequence of degrees of effect for each parameter is s, h, ?, s 0, b and t. The paper obtained the optimum model and numerically proved its validity among the considered ranges. Eleven sample fins were collected during different periods of the mould life time, and the influences of mould wear on fin friction performance were examined. The mould wear includes three stages, and the performance of fins pressed during 100 thousand times to 1,050 thousand times is more stable. The recommended life time for the mould type is about 1,050 thousand times

131

Operating performance of CANDU pressure tubes  

International Nuclear Information System (INIS)

The performance of Zircaloy-2 and Zr-2.5 Nb pressure tubes in CANDU reactors is reviewed. The accelerated hydriding of Zircaloy-2 in reducing water chemistries can lower the toughness of this material and it is essential that defect-initiating phenomena, such as hydride blister formation from pressure tube to calandria tube contact, be prevented. Zr-2.5 Nb pressure tubes are performing well with low rates of hydrogen pick-up and good retention of material properties

132

Steam generator tubing NDE performance  

International Nuclear Information System (INIS)

Steam generator (SG) non-destructive examination (NDE) is a fundamental element in the broader SG in-service inspection (ISI) process, a cornerstone in the management of PWR steam generators. Based on objective performance measures (tube leak forced outages and SG-related capacity factor loss), ISI performance has shown a continually improving trend over the years. Performance of the NDE element is a function of the fundamental capability of the technique, and the ability of the analysis portion of the process in field implementation of the technique. The technology continues to improve in several areas, e.g. system sensitivity, data collection rates, probe/coil design, and data analysis software. With these improvements comes the attendant requirement for qualification of the technique on the damage form(s) to which it will be applied, and for training and qualification of the data analysis element of the ISI process on the field implementation of the technique. The introduction of data transfer via fiber optic line allows for remote data acquisition and analysis, thus improving the efficiency of analysis for a limited pool of data analysts. This paper provides an overview of the current status of SG NDE, and identifies several important issues to be addressed

133

Effects of hydrophilic coating on air side heat transfer and friction characteristics of wavy fin and tube heat exchangers under dehumidifying conditions  

International Nuclear Information System (INIS)

The air side heat transfer and friction characteristics of wavy fin and tube heat exchangers with and without hydrophilic coating are studied under dehumidifying conditions experimentally. The effects of a hydrophilic coating on air side performance are investigated. The results indicated that the influence of the hydrophilic coating on heat transfer performance is mainly related to the flow conditions of condensation water on the fin surface without hydrophilic coating. The hydrophilic coating can enhance the heat transfer performance when plenty of condensation water flows and weakens the heat transfer performance when little condensation water forms on the fin surface. The pressure drops for the hydrophilic coating surface are lower than those of the corresponding uncoated surface. A maximum 44% reduction is observed. The proposed heat transfer coefficient ratio correlation and pressure drop ratio have a mean deviation of 9.9% and 8.2% from experimental data and can predict 76.6% and 82.8% of the experimental data within the deviation limit of ±15%, respectively

134

The impact of fin profile and interface condition on performance characteristics of heat sinks  

International Nuclear Information System (INIS)

Thermal management of electronic products relies mainly on the effective dissipation of heat. Heat sinks (containing multiple extended surfaces or fin array) are commonly used for heat dissipation network. The performance of an individual fin depends on its geometry, material properties and operating environment (i.e. free or forced convection). In the first part of this paper, the four most commonly used fin profiles are studied for pin, longitudinal and annular fins using non-dimensional finite element formulation. In the second part, the performance of different thermal interfaces is studied for polymer and metallic fins. Polymer composite materials result in significant increase in the performance of a fin; however manufacturing can be a constraint to construct an effective heat sink due to interface conditions at the fin and base plate junction. It is found that the joint at fin base plate has considerable stress effect in the heat sink system. The press fit joint must have high contact pressure to maintain an appropriate thermal contact conductance (TCC) in order to have thermal performance comparable to an adhesive joint, but the two joints have different state of thermal and contact stresses. -- Highlights: ? The effect of fin profile on performance for pin, longitudinal and annular fins is studied. ? The significant effect is found only for pin fins under considered conditions. ? The effect of interface at orthotropic pin fin and metallic base plate is studied. ? Two interface conditions called epoxy-bonded and press-fitted are studied. ? The contact pressure and stresses decrease at high temperature for press-fitted interface

135

Study of flexible fin and compliant joint stiffness on propulsive performance: theory and experiments.  

Science.gov (United States)

The caudal fin is a major source of thrust generation in fish locomotion. Along with the fin stiffness, the stiffness of the joint connecting the fish body to the tail plays a major role in the generation of thrust. This paper investigates the combined effect of fin and joint flexibility on propulsive performance using theoretical and experimental studies. For this study, fluid-structure interaction of the fin has been modeled using the 2D unsteady panel method coupled with nonlinear Euler-Bernoulli beam theory. The compliant joint has been modeled as a torsional spring at the leading edge of the fin. A comparison of self-propelled speed and efficiency with parameters such as heaving and pitching amplitude, oscillation frequency, flexibility of the fin and the compliant joint is reported. The model also predicts the optimized stiffnesses of the compliant joint and the fin for maximum efficiency. Experiments have been carried out to determine the effect of fin and joint stiffness on propulsive performance. Digital image correlation has been used to measure the deformation of the fins and the measured deformation is coupled with the hydrodynamic model to predict the performance. The predicted theoretical performance behavior closely matches the experimental values. PMID:24737004

Kancharala, A K; Philen, M K

2014-09-01

136

How can the heat transfer correlations for finned-tubes influence the numerical simulation of the dynamic behavior of a heat recovery steam generator?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract This paper presents the results of a theoretical investigation on the influ- ence of different heat transfer correlations for finned-tubes to the dynamic behavior of a heat recovery steam generator (HRSG). The investigation was done for a vertical type natural circulation HRSG with 3 pressure stages under hot start-up and shutdown conditions. For the calculation of the flue gas side heat transfer coefficient the well known correlations for segmented finned-tubes according ...

2010-01-01

137

Experimental Study on Flow Boiling of CO2 and CO2-PAG Oil Mixture in Smooth and Micro-fin Tubes  

Science.gov (United States)

In this study, experiments on the flow boiling of nearly pure CO2 and CO2-PAG oil mixture are carried out using a 2.064 m long double-pipe counter-flow heat exchanger, in which the refrigerant flows inside the inner tube and the heat source water flows counter-currently in the outer annulus. A smooth copper tube and a micro-fin copper tube are used as the inner tube. In case of nearly pure CO2, the present experimental results of heat transfer coefficient in smooth tube with rough surface agree well with the predicted results using Yu et al. correlation [5], in which the surface roughness effect is taken into account. It is also confirmed that the values of heat transfer coefficient for both smooth and micro-fin tubes are almost analogous, while the values of pressure drop for micro-fin tube are slightly higher than those of smooth tube. By comparing the experimental results between nearly pure CO2 and CO2-oil mixture, it is confirmed that the oil concentration effects on heat transfer coefficient and pressure drop in micro-fin tube have different characteristics from those of smooth tube.

Koyama, Shigeru; Ito, Daisuke; Lee, Sang-Mu; Kuwahara, Ken; Saeki, Chikara

138

Evaluación de Intercambiadores de Calor Compactos de Tubos Aletados / Evaluation of Compact Finned-Tube Heat Exchangers  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish En este trabajo, se presenta el análisis térmico teórico de un intercambiador de calor compacto, con y sin condensación de agua en el lado del aire. El fenómeno de la condensación del vapor de agua en la corriente de aire entrante produce una película de agua en la superficie cubriéndola en forma pa [...] rcial o completa. El análisis considera varias configuraciones geométricas con respecto a: la superficie de las aletas y a la forma de los tubos considerando la forma circular tradicional y también un caso para tubos planos. Los resultados obtenidos reflejan la eficiencia de la aleta en ambos casos: una aleta totalmente seca (sin condensación) y a una totalmente húmeda es decir, totalmente cubierta por la película de condensado. Se concluye que la metodología propuesta es una buena alternativa de análisis y caracterización de un intercambiador, ya que los resultados obtenidos coinciden con los reportados en la literatura Abstract in english This study presents a theoretical thermal analysis of a compact heat exchanger, with and without water condensation on the air side. The phenomenon of condensation of water vapor in the entering air current produces a film of water on the surface, partially or completely covering the surface. The an [...] alysis considers various geometric configurations with respect to the surfaces of the fins and the form of the tubes, including the traditional round form as well as flattened tubes. The results obtained reflect the efficiency of the fins in both cases , including a completely dry fin (no condensation) and a completely wet fin, that is completely covered with a film of condensate. It is concluded that the methodology proposed is a good alternative for the analysis and characterization of a heat exchanger since the results agree with those reported in the literature

M.T., Martínez; E., Torres; J.A., Soto.

139

Performance of a shell-and-tube heat exchanger with spiral baffle plates  

International Nuclear Information System (INIS)

In a conventional shell-and-tube heat exchanger, fluid contacts with tubes flowing up and down in a shell, therefore there is a defect in the heat transfer with tubes due to the stagnation portions. Fins are attached to the tubes in order to increase heat transfer efficiency, but there exists a limit. Therefore, it is necessary to improve heat exchanger performance by changing the fluid flow in the shell. In this study, a highly efficient shell-and-tube heat exchanger with spiral baffle plates is simulated three-dimensionally using a commercial thermal-fluid analysis code, CFX4.2. In this type of heat exchanger, fluid contacts with tubes flowing rotationally in the shell. It could improve heat exchanger performance considerably because stagnation portions in the shell could be removed. It is proved that the shell-and-tube heat exchanger with spiral baffle plates is superior to the conventional heat exchanger in terms of heat transfer

140

Levenberg-Marquardt application to two-phase nonlinear parameter estimation for finned-tube coil evaporators  

Directory of Open Access Journals (Sweden)

Full Text Available A procedure for calculation of refrigerant mass flow rate is implemented in the distributed numerical model to simulate the flow in finned-tube coil dry-expansion evaporators, usually found in refrigeration and air-conditioning systems. Two-phase refrigerant flow inside the tubes is assumed to be one-dimensional, unsteady, and homogeneous. In the model the effects of refrigerant pressure drop and the moisture condensation from the air flowing over the external surface of the tubes are considered. The results obtained are the distributions of refrigerant velocity, temperature and void fraction, tube-wall temperature, air temperature, and absolute humidity. The finite volume method is used to discretize the governing equations. Additionally, given the operation conditions and the geometric parameters, the model allows the calculation of the refrigerant mass flow rate. The value of mass flow rate is computed using the process of parameter estimation with the minimization method of Levenberg-Marquardt minimization. In order to validate the developed model, the obtained results using HFC-134a as a refrigerant are compared with available data from the literature.

2006-01-01

 
 
 
 
141

Investigations of flow characteristics in a plate fin and tube heat exchanger model composed of single cylinder  

International Nuclear Information System (INIS)

The flow structure in a plate fin and tube heat exchanger model composed of single cylinder located between two parallel plates for duct height-to-cylinder diameter ratio of 0.365 for Reynolds numbers of 4000 and 7500 is investigated experimentally. Particle image velocimetry (PIV) technique is employed to obtain instantaneous, time-averaged and phase-averaged turbulent flow characteristics in the heat exchanger flow passage. Interactions between the main flow and the secondary flow are examined in detail in the horizontal and vertical planes of the flow passage. Horseshoe vortex system formed in close region of cylinder-plate junction and convected downstream in the main flow direction and its evolution in the circumference of the cylinder is also investigated in detail

142

Two-Phase condensation Heat Transfer Coefficients Heat Transfer Coefficients and Pressure drops of R-404A for different Condensing Temperatures in a smooth and Micro-Fin Tube  

Directory of Open Access Journals (Sweden)

Full Text Available Two phase heat transfer coefficients and pressure drops of R-404A in a smooth (8.56 mm ID and micro-fin tube (8.96 mm ID are experimentally investigated. Different from previous studies, the present experiments are performed for different condensing temperatures, with superheating and sub cooling and using hermetically sealed compressor. The test runs are done at average saturated condensing temperatures ranging from 35oC to 60oC. The mass fluxes are between 90 and 800 kg m-2s-1 . The experimental results from both smooth and micro-fin tubes show that the average heat transfer coefficient and pressure drop increases with mass flux but decreases with increasing condensing temperature. The average heat transfer coefficient is 30-210% higher for micro-fin tube than that of smooth tube, with moderate increase in pressure drop ranging from 10-55%. New correlations based on the data gathered during the experimentation for predicting condensation heat transfer coefficients are proposed for wide range of practical applications.

DR. S.N. Sapali

2009-11-01

143

Enhanced hydrodynamic performance of flexible fins using macro fiber composite actuators  

Science.gov (United States)

Recent studies on the role of body flexibility in propulsion suggest that fish have the ability to control the shape or modulate the stiffness of the fins for optimized performance. Inspired by nature’s ability to modulate stiffness and shape for different operating conditions, this paper investigates active control of flapping foils for thrust tailoring using Macro Fiber Composites (MFCs). A coupled piezohydroelastic model has been developed to predict the propulsive performance of an actively deforming fin. The effect of important parameters such as oscillation frequency, flexibility of the fin, applied voltage and the phase difference between applied voltage and heaving on propulsive performance are studied and reported. It is observed that distributed actuation along fin produces maximum performance through proper selection of the phase difference between heaving and voltage. The optimal phase for lower values of fin stiffness is approximately 90° and it approaches 0° for higher stiffness values. Experiments performed to determine the effect of active control using MFCs validate the theoretical results.

Kancharala, A. K.; Philen, M. K.

2014-10-01

144

MAPLE research reactor beam-tube performance  

International Nuclear Information System (INIS)

Atomic Energy of Canada Limited (AECL) has been developing the MAPLE (Multipurpose Applied Physics Lattice Experimental) reactor concept as a medium-flux neutron source to meet contemporary research reactor applications. This paper gives a brief description of the MAPLE reactor and presents some results of computer simulations used to analyze the neutronic performance. The computer simulations were performed to identify how the MAPLE reactor may be adapted to beam-tube applications such as neutron radiography

145

Study the effect of flow bypass on the performance of a shrouded longitudinal fin array  

Directory of Open Access Journals (Sweden)

Full Text Available Theoretical and experimental studies were carried out to investigate the effects of duct velocity, fin density and tip-to-shroud clearance on the flow bypass and its impact on the pressure drop across a longitudinal aluminum fin array and its thermal performance. The clearance was varied parametrically, stating with the fully shrouded case and variations of the channel height giving partially shrouded configuration of different clearance ratios were also carried out. The flow bypass was found to increase with increasing fin density and insensitive to the air flow rate. That effect of fin density decreased as the clearance increased. The calculated total pressure was greatly affected by fin density. For fully-shrouded fin array, with Hf /S equals to 8 and 12.75, the pressure drop increased by a factor of 4.3 and 20 of that with Hf /S equals to 3.4, respectively. The total pressure drop and the average convective heat transfer coefficients corresponding to the fully and partially shrouded fin array of Hf /S = 3.4 were compared. Going from fully to partially shrouded one of the largest clearance ratio (C/Hf = 0.89, the total pressure drop reduced by about 50%. For clearance ratios equal to 0.36, 0.56, and 0.89, the average heat transfer coefficients were reduced by about 12, 17, and 30 percent of those for the fully shrouded configuration at ReD of about 3 x 103. That percentage reduction in heat transfer coefficients decreased with the increase of air flow rate.

Ahmed F. Khudheyer

2011-08-01

146

A study of heat and fluid flow phenomena on the gas side of circular-tube plate-fin heat exchangers  

Science.gov (United States)

The heat transfer and pressure drop characteristics of a circular-tube, plate-fin heat exchanger geometry were investigated. These parameters, expressed as the Colburn J factor and a friction factor f, are presented for Reynolds numbers from 100 to 3200, for exchanger samples with 1, 2 and 4 tube rows and 8, 10 and 12 fins per inch. These results are presented graphically and as a mathematical predictor model. The Taylor first order expansion and a Monte-Carlo numerical simulation of data were used to estimate the uncertainty in the values of J and f due to instrument discretization and random error. Comparisons with earlier work by other authors using simplified equations were undertaken. Dye-streak flow visualization was undertaken to study the flow field in four times scale models of circular-tube exchanger geometries with louvred and un-louvred plate-fins. Local heat transfer coefficients were obtained for the plain exchanger using a phase change paint in a transient condition. Correlations between the flow field and local heat transfer coefficient distribution were identified on the plain geometry and used to estimate the trends in heat transfer coefficient distribution for a louvred geometry. Numerical prediction of the flow fields present in a three dimensional plain circular-tube, plate-fin exchanger geometry, and two designs of multi-fin louvre bank were undertaken using the PHOENICS 81 code. Comparisons of predicted flow fields and experimental flow visualization showed good qualitative agreement. The development and manufacture of the various rigs, tools, and techniques used in the investigation are described.

Baldwin, Stephen

147

Verification of the performance of impact limiting fins for transportation containers  

International Nuclear Information System (INIS)

Empirical data are frequently applied in designing the crush limiting fins for the special transport containers used for shipping radioactive materials. One of the most widely accepted sets of design curves was derived from research work done at Oak Ridge National Laboratories (ORNL) in 1971. This report presents the results of experimental work aimed at verifying particular aspects of the applicability of the ORNL design curves. The main objective was to check the fundamental assumption inherent in the ORNL data - namely that the design curve data can be extrapolated to any fin configuration regardless of the length and number of fins. Using a drop facility similar to ORNL, but with a modern computerized data capture system, data were collected from 625 specimens. These comprised both single and multiple fin types, that differed in height, thickness, length, angle of inclination and orientation. Included were several duplicate ORNL fin specimens for reference. Results obtained from the work reported here indicate that the basic premise regarding the extrapolation from the design curve data is reasonable. However, the results do not produce curves consistent with the ORNL curves. The newer curves of absorbed energy versus percent deformation are flatter, indicating that the percent deformation for a given energy input can sometimes vary considerably. For plots of the peak force per fin width versus height/thickness ratios the sharp upward trend for height/thickness ratios below 10 is not observed. The results obtained indicate that further work should be performed to determine the reason for the differences between the ORNL data and those data obtained from this project

148

3D analysis of thermal exchange in finned batteries. A comparison between round and elliptical tubes; Analisi tridimensionale dello scambio termico nelle batterie alettate. Confronto fra tubi tondi e tubi ellittici  

Energy Technology Data Exchange (ETDEWEB)

In this paper a numerical 3D analysis of the thermal exchange in air-cooled finned batteries has been carried out. Speed and temperature values in each hub of the numerical simulation domain have been reckoned both at different air flows and with different shapes of the tubes. The thermal power exchanged between tubes and air is obtained by the simulation of a numerical model of a finned battery with round section tubes and is compared to the values obtained for three batteries with elliptical section tubes. The comparison has been performed for different values of the air input speed. [Italian] In questo lavoro e' stata condotta un'analisi numerica tridimensionale dei fenomeni di scambio termico in batterie alettate raffreddate ad aria. I valori di velocita' e temperatura nei singoli nodi del dominio di simulazione numerica sono stati calcolati sia al variare della portata dell'aria sia della forma dei tubi. La potenza termica scambiata tra tubi ed aria, ottenuta dalle simulazioni in un modello numerico di batteria alettata composta da tubi di sezione circolare, e' stata confrontata con i valori ottenuti per tre batterie formate da tubi di sezione elittica. Il confronto e' stato eseguito per diversi valori della velocita' d'ingresso dell'aria.

Valdiserri, P. [Bologna Univ., Bologna (Italy). Facolta' di Ingegneria, Dipartimento di Ingegneria Energetica, Nucleare e del Controllo Ambientale

2001-05-01

149

Experimental analysis on thermal performance of a solar air collector with longitudinal fins in a region of Biskra, Algeria  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a thermal performance of a single pass solar air heater with fins attached was investigated experimentally. Longitudinal fins were used inferior the absorber plate for an increase the heat exchange and uniform the flow fluid in the channel. The effects of mass flow rate of air on the outlet temperature, the heat transfer in a thickness of solar collector and thermal efficiency were studied. Experiments were performed for two air mass flow rates of 0.012 kg/s., Moreover; the maximum efficiency was obtained by using five longitudinal fins and without fins. The maximum efficiency obtained for the 0.012 kg/s with and without fins were 40.02 % and 34.92 %, respectively. Comparison of the results as an effect the solar collector’s with and without fins shows a substantial enhancement in the thermal efficiency.

Foued Chabane

2013-01-01

150

MODERN MANUFACTURING TECHNIQUES OF PRECISED MISSILE REAR FIN ASSEMBLY  

Directory of Open Access Journals (Sweden)

Full Text Available Missile rear fin is mainly used for direction control. The fin includes number of components likepanels, pins, tubes, lamina and caps. The performance of actuation system plays a decisive role indetermining the performance of the flight control system for a highly maneuverable missile. To controlthe missiles by aerodynamics, control surfaces, sometimes called fins, are used. The manufacturingprocess of missile fin components involves different operations like CNC turning, CNC milling,drilling, EDM, grinding, and surface treatments. The paper presents the study of manufacturingprocesses of missile rear fin assembly.

Md Akhtar khan

2013-11-01

151

The Study of Local Heat Transfer Characteristics of the Surface of a Plate Fin - Oval Tube with Delta Wing Vortex Generators  

International Nuclear Information System (INIS)

In the present paper, the effect of Delta-Wing Vortex Generators(DWVGs) on heat transfer of the plate fin-oval tube heat exchanger was experimentally studied. The local heat transfer coefficient of the tube surface of one kind of DWVGs arrangement were measured by naphthalene sublimation technique for Reynolds numbers of 2000 ? 3200 and angles of attack of DWVG of 30 .deg. ? 60 .deg.. As the results, compared to the case without DWVGs, the heat transfer of the plate fin surface with DWVGs was enhanced from upstream to downstream in the test region. The heat transfer were significantly affected by angles of attack of DWVGs as well as Reynolds number. It showed that the result of 45 .deg. was best within test angles

152

Thermal performance analysis and optimum design parameters of heat exchanger having perforated pin fins  

International Nuclear Information System (INIS)

This paper reports the heat transfer enhancement and corresponding pressure drop over a flat surface equipped with circular cross section perforated pin fins in a rectangular channel. The channel had a cross section area of 100-250 mm2. The experiments covered the following ranges: Reynolds number 13500-42,000, clearance ratio (C/H) 0, 0.33 and 1 and interfin spacing ratio (Sy/D) 1.208, 1.524, 1.944 and 3.417. Correlation equations were developed for the heat transfer, friction factor and enhancement efficiency. The experimental results showed that the use of circular cross section pin fins may lead to heat transfer enhancement. Enhancement efficiencies varied between 1.4 and 2.6 depending on clearance ratio and interfin spacing ratio. Using a Taguchi experimental design method, optimum design parameters and their levels were investigated. Nusselt number and friction factor were considered as performance parameters. An L9(33) orthogonal array was selected as an experimental plan. First of all, each goal was optimized separately. Then, all the goals were optimized together, considering the priority of the goals, and the optimum results were found to be Reynolds number of 42,000, fin height of 50 mm and streamwise distance between fins of 51 mm

153

Atomic Layer Deposition of SiO2 for the Performance Enhancement of Fin Field Effect Transistors  

Science.gov (United States)

Atomic layer deposition (ALD) of SiO2 by using a tetraethoxysilane (TEOS) or a bis(ethylmethylamino)silane (BEMAS) have been studied for the side-wall spacer formation of the fin field effect transistor (FinFET). The ALD-SiO2 can be deposited conformally at 50 °C for the TEOS and at 250 °C for the BEMAS precursor. As a result, FinFETs with a 25-nm-long extension of the source/drain using the ALD grown SiO2 sidewall spacer have been successfully fabricated. The performance of the FinFET has been successfully improved by reduction of the parasitic resistance.

Endo, Kazuhiko; Ishikawa, Yuki; Matsukawa, Takashi; Liu, Yongxun; O'uchi, Shin-ichi; Sakamoto, Kunihiro; Tsukada, Junichi; Yamauchi, Hiromi; Masahara, Meishoku

2013-11-01

154

Dynamic performances of plate-fin recuperator with infinite core heat capacitance  

International Nuclear Information System (INIS)

A lumped parameter model was proposed to research dynamic performances of plate-fin recuperator in high-temperature gas-cooled reactor with direct helium turbine cycle(HTGR-GT). The model with infinite core heat capacitance could be numerically solved by fourth-order Rounge-Kutta method. Based on this lumped parameter model, transient responses of outlet temperature of recuperator were analyzed when step and ramp changed of inlet temperatures and mass flow rate took place in hot side. Moreover, transient responses of outlet temperature and core temperature were analyzed while power of HTGR-GT was regulated in normal operation condition and total electric load was rejected from full power. The model can be applied to analyze dynamic performances of plate-fin recuperator. (authors)

155

Parametric study of the swimming performance of a fish robot propelled by a flexible caudal fin  

International Nuclear Information System (INIS)

In this paper, we aim to study the swimming performance of fish robots by using a statistical approach. A fish robot employing a carangiform swimming mode had been used as an experimental platform for the performance study. The experiments conducted aim to investigate the effect of various design parameters on the thrust capability of the fish robot with a flexible caudal fin. The controllable parameters associated with the fin include frequency, amplitude of oscillation, aspect ratio and the rigidity of the caudal fin. The significance of these parameters was determined in the first set of experiments by using a statistical approach. A more detailed parametric experimental study was then conducted with only those significant parameters. As a result, the parametric study could be completed with a reduced number of experiments and time spent. With the obtained experimental result, we were able to understand the relationship between various parameters and a possible adjustment of parameters to obtain a higher thrust. The proposed statistical method for experimentation provides an objective and thorough analysis of the effects of individual or combinations of parameters on the swimming performance. Such an efficient experimental design helps to optimize the process and determine factors that influence variability.

156

Parametric study of the swimming performance of a fish robot propelled by a flexible caudal fin  

Energy Technology Data Exchange (ETDEWEB)

In this paper, we aim to study the swimming performance of fish robots by using a statistical approach. A fish robot employing a carangiform swimming mode had been used as an experimental platform for the performance study. The experiments conducted aim to investigate the effect of various design parameters on the thrust capability of the fish robot with a flexible caudal fin. The controllable parameters associated with the fin include frequency, amplitude of oscillation, aspect ratio and the rigidity of the caudal fin. The significance of these parameters was determined in the first set of experiments by using a statistical approach. A more detailed parametric experimental study was then conducted with only those significant parameters. As a result, the parametric study could be completed with a reduced number of experiments and time spent. With the obtained experimental result, we were able to understand the relationship between various parameters and a possible adjustment of parameters to obtain a higher thrust. The proposed statistical method for experimentation provides an objective and thorough analysis of the effects of individual or combinations of parameters on the swimming performance. Such an efficient experimental design helps to optimize the process and determine factors that influence variability.

Low, K H; Chong, C W, E-mail: mkhlow@ntu.edu.s, E-mail: ch0018ee@ntu.edu.s [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

2010-12-15

157

Performance of a Miniature Pulse Tube Cryocooler  

Science.gov (United States)

Fuji Electric Group has developed a miniature pulse tube cryocooler (PTC) of U-shaped configuration with a specific cooling capacity of 2W at 70K and requiring 100W of electrical input power. The emphasis has been on compactness, light weight, high performance, high reliability and low cost. This PTC is for commercial applications: for example, semiconductivity and high temperature superconductivity (HTS) devices used in wireless telecommunication systems and imaging sensors. The dimensions of the PTC have been reduced to 246mm wide by 232mm high and a weight of 8.5kg as integral configurations. The linear compressor motor uses two sets of moving coils to drive twin pistons supported by flexure bearings in a dual opposed configuration. The phase shifter, consisting of an inertance tube and reservoir tank, has been optimized. We produced and tested a prototype reduced-cost PTC. The prototype has a cooling capacity greater than 2.5W at 70K with 100W of electrical input power. The vibration of the cold head is less than 2 micrometers (peak to peak) when the hot-end side flange of the expander is fixed. This paper describes in detail its performance including inclination and vibration.

Matsumoto, N.; Yasukawa, Y.; Ohshima, K.; Minematsu, S.; Takeuchi, T.; Yoshizawa, K.; Matsushita, T.; Mizoguchi, Y.

2006-04-01

158

Performance of photomultiplier tubes for cryogenic applications  

International Nuclear Information System (INIS)

The use of noble liquid detectors draws a great interest in particle physics research, especially for direct searches of Dark Matter. This kind of experiments requires to go to several tons of noble liquid in order to explore deeper regions of the parameter space. The signal produced in large tons of liquid is usually read out by photomultipliers. In this paper we report on results of tests performed on 2 in. and 3 in. photomultiplier tubes developed by Electron Tubes Ltd. for operation at cryogenic temperatures in the WArP experiment. The measurements have been performed at the Photomultipliers Test Facility set-up in Naples laboratory. The Photomultipliers Test Facility cryogenic equipment uses fused silica fibers driven LED/LASER generated light in the 400 nm region. The photomultipliers have been tested in liquid nitrogen (77 K). The behaviour of photomultipliers at cryogenic temperature has been studied on more than 350 samples. All the photomultipliers show typical gain behaviour when immersed in liquid nitrogen. Generally, this gain exponentially decreases to asymptotic values, some 20-30% lower. Charge resolution and signal-to-noise ratio show a long-term stability in cryogenic environment.

159

A robotic fish caudal fin: effects of stiffness and motor program on locomotor performance.  

Science.gov (United States)

We designed a robotic fish caudal fin with six individually moveable fin rays based on the tail of the bluegill sunfish, Lepomis macrochirus. Previous fish robotic tail designs have loosely resembled the caudal fin of fishes, but have not incorporated key biomechanical components such as fin rays that can be controlled to generate complex tail conformations and motion programs similar to those seen in the locomotor repertoire of live fishes. We used this robotic caudal fin to test for the effects of fin ray stiffness, frequency and motion program on the generation of thrust and lift forces. Five different sets of fin rays were constructed to be from 150 to 2000 times the stiffness of biological fin rays, appropriately scaled for the robotic caudal fin, which had linear dimensions approximately four times larger than those of adult bluegill sunfish. Five caudal fin motion programs were identified as kinematic features of swimming behaviors in live bluegill sunfish, and were used to program the kinematic repertoire: flat movement of the entire fin, cupping of the fin, W-shaped fin motion, fin undulation and rolling movements. The robotic fin was flapped at frequencies ranging from 0.5 to 2.4 Hz. All fin motions produced force in the thrust direction, and the cupping motion produced the most thrust in almost all cases. Only the undulatory motion produced lift force of similar magnitude to the thrust force. More compliant fin rays produced lower peak magnitude forces than the stiffer fin rays at the same frequency. Thrust and lift forces increased with increasing flapping frequency; thrust was maximized by the 500× stiffness fin rays and lift was maximized by the 1000× stiffness fin rays. PMID:22162853

Esposito, Christopher J; Tangorra, James L; Flammang, Brooke E; Lauder, George V

2012-01-01

160

Improving the performance of photomultiplier tubes  

Energy Technology Data Exchange (ETDEWEB)

Photomultipliers are ubiquitous detectors of low level light signals, but their performance is limited by the complexity of photocathode technology. Two contributory problems are that light is lost both by surface reflection and by transmission through the photocathode layer. Knowledge of the dielectric constants has allowed predictive modelling of the reflectivity and absorption of the light as a function of angle of incidence, cathode thickness and polarization. The predictions have stimulated designs of extremely simple and very low cost retrofit approaches to improve the overall effectiveness of photomultipliers. One simple design presented here exploits signal that is normally lost by the surface reflection. A simple external conical torch reflector is clipped over the photomultiplier end face. The reflector raised the efficiency of an S20 multialkali photocathode by between 20% and 10% across the blue to red spectral range. An alternative semi-cylindrical glass coupler has improved the absorption efficiency by allowing the input signal to arrive at 60{sup 0} incidence to the photocathode surface, rather than normal incidence as in the standard head-on geometry. Enhancements are from 30% to 500% across the spectral range. The greater gains are at long wavelengths, and so are particularly valuable as this is the region of lowest quantum efficiency. The latter high-incidence angle approach, when applied to a low-efficiency C grade tube, has raised the performance to greater than the best of the A grade tubes, as used in the normal head-on operation. Both methods are equally applicable to other cathode compositions.

Harmer, S W [Department of Engineering and Technology, Manchester Metropolitan University, Manchester M1 5GD (United Kingdom); Townsend, P D, E-mail: pdtownsend@googlemail.co [Science and Technology, University of Sussex, Brighton BN1 9QH (United Kingdom)

2010-10-20

 
 
 
 
161

Improving the performance of photomultiplier tubes  

Science.gov (United States)

Photomultipliers are ubiquitous detectors of low level light signals, but their performance is limited by the complexity of photocathode technology. Two contributory problems are that light is lost both by surface reflection and by transmission through the photocathode layer. Knowledge of the dielectric constants has allowed predictive modelling of the reflectivity and absorption of the light as a function of angle of incidence, cathode thickness and polarization. The predictions have stimulated designs of extremely simple and very low cost retrofit approaches to improve the overall effectiveness of photomultipliers. One simple design presented here exploits signal that is normally lost by the surface reflection. A simple external conical torch reflector is clipped over the photomultiplier end face. The reflector raised the efficiency of an S20 multialkali photocathode by between 20% and 10% across the blue to red spectral range. An alternative semi-cylindrical glass coupler has improved the absorption efficiency by allowing the input signal to arrive at 60° incidence to the photocathode surface, rather than normal incidence as in the standard head-on geometry. Enhancements are from 30% to 500% across the spectral range. The greater gains are at long wavelengths, and so are particularly valuable as this is the region of lowest quantum efficiency. The latter high-incidence angle approach, when applied to a low-efficiency C grade tube, has raised the performance to greater than the best of the A grade tubes, as used in the normal head-on operation. Both methods are equally applicable to other cathode compositions.

Harmer, S. W.; Townsend, P. D.

2010-10-01

162

Caudal fin allometry in the white shark Carcharodon carcharias: implications for locomotory performance and ecology  

Science.gov (United States)

Allometric scaling analysis was employed to investigate the consequences of size evolution on hydrodynamic performance and ecology in the white shark Carcharodon carcharias. Discriminant analysis using the power equation y=axb was negative for caudal fin span (S) versus fork length (FL) in C. carcharias. In contrast in two delphinid species, Delphinus capensis and Tursiops aduncus, the span of the flukes versus fork length rises in positive allometric fashion, and strong positive allometry of S versus ?A (area) was also recorded. The latter reflects a high lift/drag ratio. S versus ?A in C. carcharias displays negative allometry and consequently a lower lift/drag ratio. A lower aspect ratio (AR) caudal fin in C. carcharias compared to that of the delphinids (mean 3.33 and 4.1, respectively) and other thunniform swimmers provides the potential for better maneuverability and acceleration. The liver in sharks is frequently associated with a buoyancy function and was found to be positively allometric in C. carcharias. The overall findings suggest that the negatively allometric caudal fin morphometrics in C. carcharias are unlikely to have deleterious evolutionary fitness consequences for predation. On the contrary, when considered in the context of positive liver allometry in C. carcharias it is hereby suggested that buoyancy may play a dominant role in larger white sharks in permitting slow swimming while minimizing energy demands needed to prevent sinking. In contrast hydrodynamic lift is considered more important in smaller white sharks. Larger caudal fin spans and higher lift/drag ratio in smaller C. carcharias indicate greater potential for prolonged, intermediate swimming speeds and for feeding predominantly on fast-moving fish, in contrast to slow-swimming search patterns of larger individuals for predominantly large mammalian prey. Such data may provide some answers to the lifestyle and widespread habitat capabilities of this still largely mysterious animal.

Lingham-Soliar, Theagarten

2005-05-01

163

OTEC performance tests of the Union Carbide enhanced-tube condenser  

Energy Technology Data Exchange (ETDEWEB)

Results of performance tests conducted on a Union Carbide enhanced-tube condenser with wire wrapping on the ammonia side and internal axial fins on the water side are reported. This unit performed satisfactorily and was free of operational difficulties. At design operating conditions (a heat duty of 3.2 million Btu/h, an inlet water temperature of 40/sup 0/F, and a water flow rate of 3200 gpm) the steady-state value of the overall heat transfer coefficient was found to be 818 Btu/h.ft/sup 2/./sup 0/F, and the ammonia-side and water-side heat transfer coefficients were 5180 and 1130 Btu/h.ft/sup 2/./sup 0/F, respectively. The water-side pressure drop was 1.8 psi. Varying the heat duty from 2.4 million to 4.0 million Btu/h had a negligible effect on thermal performance. The value obtained for the ammonia-side heat transfer coefficient at nominal conditions is about two times that predicted by the Nusselt expression for condensation on a smooth tube. The water-side coefficient is within 3% of the value predicted by the Noranda correlation for finned tubes.

Yung, D T; Hillis, D L; Lorenz, J J; Sather, N F

1979-05-01

164

Windsurfer Fin  

Science.gov (United States)

A NASA report detailing a wind tunnel investigation of a variable camber and twist could effectively reduce drag, thus improving performance. The resulting VooDoo fin is made of composite materials, has a rigid internal spar and a flexible polymer exterior coating. It is computer-designed and exceptionally durable.

1994-01-01

165

A novel 1D/2D model for simulating conjugate heat transfer applied to flow boiling in tubes with external fins  

Science.gov (United States)

This study presents a novel, simplified model for the time-efficient simulation of transient conjugate heat transfer in round tubes. The flow domain and the tube wall are modeled in 1D and 2D, respectively and empirical correlations are used to model the flow domain in 1D. The model is particularly useful when dealing with complex physics, such as flow boiling, which is the main focus of this study. The tube wall is assumed to have external fins. The flow is vertical upwards. Note that straightforward computational fluid dynamics (CFD) analysis of conjugate heat transfer in a system of tubes, leads to 3D modeling of fluid and solid domains. Because correlation is used and dimensionality reduced, the model is numerically more stable and computationally more time-efficient compared to the CFD approach. The benefit of the proposed approach is that it can be applied to large systems of tubes as encountered in many practical applications. The modeled equations are discretized in space using the finite volume method, with central differencing for the heat conduction equation in the solid domain, and upwind differencing of the convective term of the enthalpy transport equation in the flow domain. An explicit time discretization with forward differencing was applied to the enthalpy transport equation in the fluid domain. The conduction equation in the solid domain was time discretized using the Crank-Nicholson scheme. The model is applied in different boundary conditions and the predicted boiling patterns and temperature fields are discussed.

Oc?o?, Pawe?; ?opata, Stanis?aw; Nowak, Marzena

2014-09-01

166

Numerical analysis for the air-side convective heat transfer characteristics in a compact heat exchanger with flat tubes and plate fins according to the aspect ratio  

International Nuclear Information System (INIS)

Numerical analysis has been carried out to investigate air-side convective heat transfer characteristics in a compact heat exchanger with flat tubes and continuous plate fins according to the aspect ratio. RNG k-? model is applied for turbulence analysis. Simulation results such as air velocity and temperature distributions are presented, and heat transfer coefficients are compared with previous correlations for circular tubes. The numerical conditions are considered for the aspect ratios ranging from 3.06 to 5.44 and Reynolds number ranging from 1000 to 10,000. The results showed that heat transfer coefficients decreased with the increase of aspect ratio. From the calculated results a correlation of Colburn j factor for the considered aspect ratio in the compact heat exchanger system is suggested. The predicted results in this study can be applied to the optimal design of air conditioning system

167

Effect of various parameters on the performance of capillary tube  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper analysis the performance of capillary tube under the different condition. The following condition :condensing temperature 40-55°c , subcooling 0-5°c , capillary tube diameter 1.2 – 2.4mm , mass flow rate 5 – 50 g/s , various friction factor given by different authors is used to predict the performance of capillary tube withR-22 , R-134a , R-410A refrigerant.

Rahul Gulati

2011-08-01

168

Performance of a tapered pulse tube  

International Nuclear Information System (INIS)

In a well instrumented pulse tube refrigerator having 1,500 W of cooling power at 125 K, the authors have measured the figure of merit of a tapered pulse tube at several operating points. At operating points near the operating point for which the taper was designed, the figure of merit is 0.96. This is close to the theoretical optimum figure of merit 0.97 calculated for this pulse tube considering only two loss mechanisms: heat conduction in the metal pulse tube wall and ordinary thermoacoustic heat transport in the gas within a few thermal penetration depths of the wall. At operating points farther from the design operating point, the measured figure of merit is much lower, as streaming driven convection adds a third loss mechanism

169

Steam condensation on finned tubes, in the presence of non-condensable gases and aerosols: Influence of impaction, diffusiophoresis and settling on aerosol deposition  

International Nuclear Information System (INIS)

This paper presents a mechanistic model to predict the steam condensation on containment finned tube heat exchangers in the presence of non-condensable gases (NC) and aerosols. The total thermal resistance from the bulk gas to the coolant is formulated as a parallel combination of the convective and condensation gas resistances coupled in series to those of condensate layer, the aerosol fouling layer, the wall, and the coolant. The condensate layer thermal resistance is calculated by means of an Adamek-based condensation model. The aerosol fouling layer is computed based on diffusiophoresis, settling and impaction mechanisms. The gas mixture (steam plus NC) thermal resistance is formulated based on a diffusion layer modeling. Finally, this paper presents a Montecarlo method implemented in the FORTRAN code TAEROSOL that is able to compute the amount of aerosol mass that is deposited by impaction on the top of the finned tubes. The model results are compared with the available experimental data of the CONGA European project

170

Characteristics of near wake behind a circular cylinder with serrated fins (IV): Comparison of vortex formation regions  

International Nuclear Information System (INIS)

An experimental study is performed to investigate characteristics of near wakes of circular cylinders with serrated fins using a hot-wire anemometer for various freesteam velocities. The main focus of this paper is to investigate a reason why a vortex formation length is increased suddenly. Velocity of the fluid which flow through fins decreases as fin's height and freestream velocity increases and fin pitch decreases, and a thickness of boundary layer increases. The finned tube has a lower velocity gradient when the higher boundary layer grows. This velocity gradient on finned tube makes a weak shear force in the wake and moves to downstream in a state of lower momentum transfer between the freestream and the wake. The phenomenon makes a vortex formation length increased suddenly. The fluctuations of the velocity distributions on the finned tube and U/Uo=1.0 contour line in the vortex formation region decreases when the fin height increases and the pitch decreases

171

Design and performance of a straw tube drift chamber  

International Nuclear Information System (INIS)

The design and performance of the straw drift chambers used in E735 is reported. The chambers are constructed from 2.5 cm radius aluminized mylar straw tubes with wall thickness less than 0.2 mm. Also, presented are the results of tests with 2 mm radius straw tubes. The small tube has a direct detector application at the Superconducting Super Collider. (orig.)

172

Performance Investigation of a two Reflector Box Type Solar Cooker with a Finned Absorber Plate : A Review  

Directory of Open Access Journals (Sweden)

Full Text Available This review paper presents the work of various researchers on the performance of solar cooker. In this research author used finned absorber plate inside bottom surface of solar cooker and The top cover (Glazing is tilted at 23.16° corresponding to the latitude of jabalpur (the location of the test site. To provide the tilt, the height of the back side will made 25.47 cm while it will made 10 cm for the front one. Four caster wheels have been provided under the cooker This review paper presents, the work of various researchers on the performance of solar to change orientation of the cooker towards the sun. According to given above specification, A two reflector box type solar cooker with a finned absorber plate will be fabricated and performance compared with a box type solar cooker without reflector mirror and finned absorber plate.

Pradeep Kumar*1,

2014-04-01

173

Performance demonstration requirements for eddy current steam generator tube inspection  

International Nuclear Information System (INIS)

This paper describes the methodology used for developing performance demonstration tests for steam generator tube eddy current (ET) inspection systems. The methodology is based on statistical design principles. Implementation of a performance demonstration test based on these design principles will help to ensure that field inspection systems have a high probability of detecting and correctly sizing tube degradation. The technical basis for the ET system performance thresholds is presented. Probability of detection and flaw sizing tests are described

174

Experimental analysis on thermal performance of a solar air collector with longitudinal fins in a region of Biskra, Algeria  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents a thermal performance of a single pass solar air heater with fins attached was investigated experimentally. Longitudinal fins were used inferior the absorber plate for an increase the heat exchange and uniform the flow fluid in the channel. The effects of mass flow rate of air on the outlet temperature, the heat transfer in a thickness of solar collector and thermal efficiency were studied. Experiments were performed for two air mass flow rates of 0.012 kg/s., Moreover; th...

Foued Chabane; Noureddine Moummi; Said Benramache

2013-01-01

175

High Rate Performance of Drift Tubes  

CERN Document Server

This article describes calculations and measurements of space charge effects due to high rate irradiation in high resolution drift tubes. Two main items are studied: the reduction of the gas gain and changes of the drift time. Whereas the gain reduction is similar for all gases and unavoidable, the drift time changes depend on the kind of gas that is used. The loss in resolution due to high particle rate can be minimized with a suitable gas. This behaviour is calculable, allowing predictions for new gas mixtures.

Scherberger, G; Waldmann, V; Landgraf, U; Herten, G; Mohr, W

1999-01-01

176

High Rate Performance of Drift Tubes  

CERN Document Server

This article describes calculations and measurements of space charge effects due to high rate irradiation in high resolution drift tubes. Two main items are studied: the reduction of the gas gain and changes of the drift time. Whereas the gain reduction is similar for all gases and unavoidable, the drift time changes depend on the kind of gas that is used. The loss in resolution due to high particle rate can be minimized with a suitable gas. This behaviour is calculable, allowing predictions for new gas mixtures.

Scherberger, Guenter; Landgraf, Ulrich; Mohr, Wolfgang; Paschhoff, Volker; Waldmann, Viola

1998-01-01

177

Numerical Analysis for the Air-Side Convective Heat Transfer Characteristics in a Compact Heat Exchanger with Circular Tubes and Continuous Plate Fins  

International Nuclear Information System (INIS)

Numerical analysis has been carried out to investigate air-side convective heat transfer characteristics in a compact heat exchanger with circular tubes and continuous plate fins. Simulation results such as air velocity and temperature distributions are presented, and heat transfer coefficients are compared with previous experimental correlations. Three models of standard and RNG k-?, and Reynolds stress are applied for turbulence model applicability. Predicted heat transfer coefficient from the models of standard and RNG k-? are very close to those of the heat transfer correlations while there are relatively large difference, more than 17 percentage in the result from the Reynolds stress model. From the calculated results a correlation for Colburn j factor in the compact heat exchanger system is suggested

178

Experimental measurement and numerical computation of the air side convective heat transfer coefficients in a plate fin-tube heat exchanger  

International Nuclear Information System (INIS)

The air-side forced convective heat transfer of a plate fin-tube heat exchanger is investigated by experimental measurement and numerical computation. The heat exchanger consists of a staggered arrangement of refrigerant pipes with a diameter of 10.2 mm and a fin pitch of 3.5 mm. In the experimental study, the forced convective heat transfer was measured at Reynolds numbers of 1082, 1397, 1486, 1591 and 1649 based on the diameter of the refrigerant piping and on the maximum velocity. The average Nusselt number for the convective heat transfer coefficient was also computed for the same Reynolds number by using the commercial software STAR-CD with the standard k .? turbulent model. It was found that the relative errors of the average Nusselt numbers between the experimental and numerical data were less than 6 percent in a Reynolds number range of 1082?1649. The errors between the experiment and other correlations from literature ranged from 7% to 32.4%. However, the literature correlation of Kim et al. is closest to the experimental data within a relative error of 7%

179

Global Analysis and Structural Performance of the Tubed Mega Frame  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Tubed Mega Frame is a new structure concept for high-rise buildings which is developed by Tyréns. In order to study the structural performance as well as the efficiency of this new concept, a global analysis of the Tubed Mega Frame structure is performed using finite element analysis software ETABS. Besides, the lateral loads that should be applied on the structure according to different codes are also studied. From the design code study for wind loads and seismic design response spectru...

Zhang, Han

2014-01-01

180

Finned heat exchanger. Ib. General and basic aspects  

International Nuclear Information System (INIS)

This paper is a review of the main literature studies about the finned heat exchanger modelling and simulation. Finned heat exchangers are used in cryogenic industry, nuclear industry, food industry, medicine, etc.. The aspects concerning the air circulation through the heat exchanger component tubes are studied, as well as those involved in the thermal transfer from technological fluid to wall or from fin to air. A particular attention is devoted to the physical and mathematical complete models of finned heat exchangers, as well as to the criterial relationship for the calculation of the partial heat transfer to air (?2), fin efficiency (?a) and friction coefficient (f). Details are also given about the influence of the thermal contact resistance on the finned heat exchanger performance. This study is a useful tool for a correct technological sizing of this type of heat exchangers. (authors)

 
 
 
 
181

Finned heat exchangers. Ia. General and basic aspects  

International Nuclear Information System (INIS)

This paper is a review of the main literature studies about the finned heat exchanger modelling and simulation. Finned heat exchangers are used in cryogenic industry, nuclear industry, food industry, medicine, etc. The aspects concerning the air circulation through the heat exchanger component tubes are studied, as well as those involved in the thermal transfer from technological fluid to wall or from fin to air. A particular attention is devoted to the physical and mathematical complete models of finned heat exchangers, as well as to the criterial relationship for the calculation of the partial thermal transfer to air, ?2, fin efficiency, ?a and friction coefficient, f. Details are also given about the influence of the thermal contact resistance on the finned heat exchanger performance. This study is a useful tool for a correct technological sizing of this heat exchanger type. (authors)

182

Thermal and friction drop characteristic of heat exchangers with elliptical tubes and smooth fins / Caracterización térmica e hidráulica de intercambiadores de calor con tubos elípticos y aletas lisas  

Scientific Electronic Library Online (English)

Full Text Available SciELO Cuba | Language: English Abstract in spanish Caída de presión y transferencia de calor son importantes parámetros en intercambiadores de calor. Existe falta de información cuando de intercambiadores de calor y tubos elípticos se trata. El objetivo del trabajo fue caracterizar experimentalmente modelos de intercambiadores de calor con tubos elí [...] pticos y aletas lisas. El numero de Reynolds y los espaciamientos fueron variados, dentro del régimen laminar. Los experimentos fueron desarrollados en un túnel de viento de circuito abierto usando la sublimación de naftaleno y la analogía calor y masa. Los números de Nusselt medio, locales y el factor de fricción fueron obtenidos en forma de correlaciones de Factores de Fricción y Colburn. Las correlaciones, validas para 200 Abstract in english Pressure drop and heat transfer are the most important parameters in compact heat exchanger. There is a lack of information in the literature about heat exchanger with elliptical tube. The objective of this work was the experimental characterization of compact heat exchangers models using elliptical [...] tube with eccentricity of 0,5 and smooth fins. The Reynolds numbers and the spacing were varied and always inside laminar regime. The experiments were conducted in an open wind tunnel using sublimation of naphthalene and the heat and mass transfer analogy. As results, the average and local Nusselt number and friction factor for 36 models were obtained. Correlations for Colburn and friction factors were presented. This correlations were obtained for 200

Rubén, Borrajo-Pérez; Jurandir, Ititzo Yanagihara; Juan José, González-Bayón.

183

Lumped Parameter Model for Dynamic Performances of Plate-Fin Recuperator  

International Nuclear Information System (INIS)

A lumped parameter model was developed to study dynamic performances of plate-fin recuperator in high temperature gas-cooled reactor with direct helium turbine cycle (HTGR-GT). For the core heat capacitance of recuperator was far larger than heat capacitance and thermal flow rate of helium, it was reasonable to ignore the influence of heat capacitance of fluid on dynamic characteristics of recuperator and develop the lumped parameter model with infinite core heat capacitance. The model was solved by four-order Runge-Kutta method, considering the influence of temperature on helium thermal properties. Based on the lump parameter model, transient response of outlet temperatures of recuperator was analyzed when step and ramp changes of inlet temperatures of recuperator took place in hot side, as well as mass flow rate of recuperator. Transient responses of the core temperature and outlet temperatures of helium were also analyzed while power was regulated in course of normal operation and total electric load was rejected from full power. (authors)

184

Performance of double –pass solar collector with CPC and fins for heat transfer enhancement  

International Nuclear Information System (INIS)

The temperature of photovoltaic modules increases when it absorbs solar radiation, causing a decrease in efficiency. This undesirable effect can be partially avoided by applying a heat recovery unit with fluid circulation (air or water) with the photovoltaic module. Such unit is called photovoltaic / thermal collector (pv/t) or hybrid (pv/t). In this unit, photovoltaic cells were pasted directly on the flat plate absorber. An experimental study of a solar air heater with photovoltaic cell located at the absorber with fins and compound parabolic collector for heat transfer enhancement and increasing the number of reflection on the cells have been conducted. The performance of the photovoltaic, thermal, and combined pv/t collector over range of operating conditions and the results was discussed. Results at solar irradiance of 500 W/m2 show that the combined pv/t efficiency is increasing from 37.28 % to 81.41 % at mass flow rates various from 0.029 to 0.436 kg/s.

185

Plate-fin heat exchanger performance reduction in special two-phase flow conditions  

Science.gov (United States)

This paper discusses the occurrence of various flow patterns of a cold, upflowing two-phase stream in an aluminium plate-fin heat exchanger (PFHE) and their impact on the overall heat exchanger performance. Various flow patterns were observed in a flow visualization rig comprising a single PFHE passage. At high gas mass fluxes both phases flow uniformly upwards. When decreasing the gas flow, a reversing slug flow becomes more and more pronounced. In this flow pattern fluid particles of significantly different temperatures can mix within the same passage. If the number of transfer units (NTU) is high, the effective temperature difference against a hot stream of the exchanger decreases. At very low gas mass fluxes a sudden static instability with liquid logging was observed. The liquid zones thus appearing can cover and thus deactivate large portions of the heating area. In PFHE design both phenomena should be taken into account, particularly for exchangers with low mean temperature differences and heated multicomponent streams with large boiling ranges.

Müller-Menzel, T.; Hecht, T.

186

On the heat transfer in the pool boiling at tightly finned steel tubes; Zum Waermeuebergang beim Behaeltersieden an eng berippten Stahlrohren  

Energy Technology Data Exchange (ETDEWEB)

Process-integrated energy efficiency in power plants and process plants can only be achieved with new innovative apparatus concepts. There exist no sufficient reference applications, no data to assist in interpretation a well as no certificates of operational safety for these apparatus concepts. Thus, these concepts are not applied despite of the significant energetic advantages. Under this aspect, industrial companies (plant fabricators, plant operators and engineering offices) and five universities have affiliated to a multi-institutional project in order to explore unused opportunities on the integration of heat. The Department of Technical Thermodynamics at the University of Kassel (Federal Republic of Germany) regards to apparatuses which effectively and securely transfer a heat flow at especially low differences of temperatures between the heat dissipating and heat absorbing side of an evaporator with structured ducts. It has been known for many decades that ribbed structures are one of the most efficient methods to transfer heat. Ribbed ducts in heat exchangers are used in the refrigeration technology as well as in the technology of air conditioning. Nevertheless, plain tubes still are the technical standard in the chemical and process industry. The objective of this research project consists of a presentation of macrostructures and microstructures which can be produced efficiently with regard to the heat transfer, at a relatively low cost as well as in large quantities with a consistent structure. Furthermore, a substantial database for the design of evaporators with such surface textures is set up. Thus, evaporators being produced by the project partner Wieland-Werke AG (Ulm, Federal Republic of Germany) were investigated on a laboratory scale as well as in small tube bundles. Subsequently, selected structures were applied in the technical centre of the project partner Linde AG (Pullach, Federal Republic of Germany) in order to validate the transferability from the laboratory scale (single tube, mini-bundle) to the technical scales. On this occasion, the authors investigate the impact of tightly finned steel tubes with trapezoidal cross-sectional ribs on the heat transfer during the boiling in case of free convection over a wide range of pressures from the beginning up to the fully developed nucleate boiling. Hydrocarbons such as n-pentane and i-octane as a natural refrigerant in the process industry are used as a boiling fluid. The results of the investigations at an electrically heated and horizontally placed test tube consisting of structural steel are compared with correlations from the literature. First results from a mixture of both hydrocarbons show that the heat transfer deteriorates if only a little amount of the heavier boiling component is added.

Bujok, Patrick; Wang, Yabai; Luke, Andrea [Kassel Univ. (Germany). Lehrstuhl fuer Technische Thermodynamik

2012-07-01

187

Effect of tube plugging in the thermalhydraulic performance of 'U' tube steam generators  

International Nuclear Information System (INIS)

The thermalhydraulic performance of Angra II steam generator has been simulated using the model developed by Braga, C.V.M., 'Thermohydraulic model for steam generator of PWR power plants', in steady state, with plugging up to 40% of total number of tubes. (E.G.)

188

Performance characterization of the TRW 35K pulse tube cooler  

International Nuclear Information System (INIS)

The TRW 35K pulse tube cooler is configured as an integral cooler, with the pulse tube attached perpendicular to a pair of compressors operating into a common compression chamber. The cooler was optimized for 35K operation and has a nominal cooling capacity of 850 mW at 35 K with a cooler input power of 200 W. It also provides 2 W of cooling at 60 K for 90 W of input power. The cooler was extensively characterized by JPL, measuring the thermal performance and the cooler-generated vibration and EMI as a function of piston stroke and offset position. The thermal performance was found to be quite sensitive to the piston offset position. The pulse tube parasitic conduction levels were also measured and shown to have a strong angular dependence relative to gravity. Magnetic shielding studies were performed to examine radiated magnetic emission levels from compressors with and without shielding

189

Optimum fin geometry in flat plate solar collector systems  

International Nuclear Information System (INIS)

The width and thickness of the fins is optimized by minimizing the cost per unit useful heat flux. The proposed procedure allows computation of the necessary collection surface area. A rather involved, but still simple, flat plate solar collector model is used in the calculations. Model implementation requires a specific geographical location with a detailed meteorological data base available. Both fins of uniform and variable thickness were considered. In the case of fins with uniform thickness, the optimum distance between tube centres is decreased by increasing the operation temperature, while the optimum fin thickness is relatively the same, whatever the operation temperature and meteorological factors. The optimized width of the collection surface decreases when the operation temperature increases. The best economical performance is obtained in the case of fins with optimized space variable thickness. Optimal control techniques are used in this case. The optimum fin cross section is very close to an isosceles triangle. The fin width is shorter and the seasonal influence is weaker at lower operation temperatures. Fin width and thickness at the base depend on season. The optimum distance between the tubes is increased by increasing the inlet fluid temperature, and it is larger in the cold season than in the warm season

190

Complicações em lipoaspiração clássica para fins estéticos / Complications of classical liposuction performed for cosmetic purposes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese A lipoaspiração realizada para procedimentos estéticos tem como objetivo a retirada de gordura em pacientes saudáveis e redução do acúmulo de gordura localizada, a chamada lipodistrofia, levando à melhora no contorno corporal. Nas últimas três décadas, a lipoaspiração vem sendo aperfeiçoada; porém, [...] como qualquer outro procedimento cirúrgico, não é isenta de complicações. O objetivo deste estudo é realizar revisão da bibliografia, por meio do PubMed, identificando as complicações após lipoaspiração clássica, incluindo apenas aquelas realizadas com finalidade estética. Foram encontrados 210 artigos empregando a expressão "complication in liposuction", 86 artigos com "complication after liposuction", 27 artigos com "fat embolism after liposuction", 7 artigos com "fat embolism following liposuction" e 16 artigos com "deaths related to liposuction". Dentre esses artigos, apenas 84 foram considerados relacionados ao assunto, sendo encontrados casos de embolia gordurosa após lipoaspiração, perfuração visceral, lesão vascular, cegueira e infecção por herpes zoster, entre outros relatos. Com base nos artigos analisados foi possível concluir que a lipoaspiração é um procedimento altamente eficaz quando bem indicado e bem realizado, porém existem riscos inerentes ao ato cirúrgico. Este levantamento constatou que existem muitos artigos abordando complicações após lipoaspiração para fins estéticos, e a embolia gordurosa pulmonar apresenta alta incidência. Abstract in english Liposuction for esthetic purposes aims to remove fat in healthy patients and reduce localized fat accumulation, called lipodystrophy, in order to improve body contour. In the last 3 decades, the liposuction technique has improved dramatically. However, like any other surgical procedure, it is not wi [...] thout complications. Here, we reviewed the literature on PubMed to identify complications after classic liposuction performed solely for esthetic purposes. In total, 210 articles were found using the term "complication in liposuction," 86 with "complication after liposuction," 27 with "fat embolism after liposuction," 7 with "fat embolism following liposuction," and 16 with "deaths related to liposuction." Among these articles, only 84 including cases of fat embolism after liposuction, visceral perforation, vascular injury, blindness, and herpes zoster infection among others were considered to be related to the subject. Based on the analyzed articles, we can conclude that liposuction is a highly effective procedure when well indicated and performed accurately. Despite this, there are inherent risks. This review found many articles addressing complications, predominantly pulmonary fat embolism, after liposuction for esthetic purposes.

Fernando Fabrício, Franco; Rafael de Campos Ferreira, Basso; Alfio José, Tincani; Paulo, Kharmandayan.

191

Complicações em lipoaspiração clássica para fins estéticos Complications of classical liposuction performed for cosmetic purposes  

Directory of Open Access Journals (Sweden)

Full Text Available A lipoaspiração realizada para procedimentos estéticos tem como objetivo a retirada de gordura em pacientes saudáveis e redução do acúmulo de gordura localizada, a chamada lipodistrofia, levando à melhora no contorno corporal. Nas últimas três décadas, a lipoaspiração vem sendo aperfeiçoada; porém, como qualquer outro procedimento cirúrgico, não é isenta de complicações. O objetivo deste estudo é realizar revisão da bibliografia, por meio do PubMed, identificando as complicações após lipoaspiração clássica, incluindo apenas aquelas realizadas com finalidade estética. Foram encontrados 210 artigos empregando a expressão "complication in liposuction", 86 artigos com "complication after liposuction", 27 artigos com "fat embolism after liposuction", 7 artigos com "fat embolism following liposuction" e 16 artigos com "deaths related to liposuction". Dentre esses artigos, apenas 84 foram considerados relacionados ao assunto, sendo encontrados casos de embolia gordurosa após lipoaspiração, perfuração visceral, lesão vascular, cegueira e infecção por herpes zoster, entre outros relatos. Com base nos artigos analisados foi possível concluir que a lipoaspiração é um procedimento altamente eficaz quando bem indicado e bem realizado, porém existem riscos inerentes ao ato cirúrgico. Este levantamento constatou que existem muitos artigos abordando complicações após lipoaspiração para fins estéticos, e a embolia gordurosa pulmonar apresenta alta incidência.Liposuction for esthetic purposes aims to remove fat in healthy patients and reduce localized fat accumulation, called lipodystrophy, in order to improve body contour. In the last 3 decades, the liposuction technique has improved dramatically. However, like any other surgical procedure, it is not without complications. Here, we reviewed the literature on PubMed to identify complications after classic liposuction performed solely for esthetic purposes. In total, 210 articles were found using the term "complication in liposuction," 86 with "complication after liposuction," 27 with "fat embolism after liposuction," 7 with "fat embolism following liposuction," and 16 with "deaths related to liposuction." Among these articles, only 84 including cases of fat embolism after liposuction, visceral perforation, vascular injury, blindness, and herpes zoster infection among others were considered to be related to the subject. Based on the analyzed articles, we can conclude that liposuction is a highly effective procedure when well indicated and performed accurately. Despite this, there are inherent risks. This review found many articles addressing complications, predominantly pulmonary fat embolism, after liposuction for esthetic purposes.

Fernando Fabrício Franco

2012-03-01

192

Complicações em lipoaspiração clássica para fins estéticos / Complications of classical liposuction performed for cosmetic purposes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese A lipoaspiração realizada para procedimentos estéticos tem como objetivo a retirada de gordura em pacientes saudáveis e redução do acúmulo de gordura localizada, a chamada lipodistrofia, levando à melhora no contorno corporal. Nas últimas três décadas, a lipoaspiração vem sendo aperfeiçoada; porém, [...] como qualquer outro procedimento cirúrgico, não é isenta de complicações. O objetivo deste estudo é realizar revisão da bibliografia, por meio do PubMed, identificando as complicações após lipoaspiração clássica, incluindo apenas aquelas realizadas com finalidade estética. Foram encontrados 210 artigos empregando a expressão "complication in liposuction", 86 artigos com "complication after liposuction", 27 artigos com "fat embolism after liposuction", 7 artigos com "fat embolism following liposuction" e 16 artigos com "deaths related to liposuction". Dentre esses artigos, apenas 84 foram considerados relacionados ao assunto, sendo encontrados casos de embolia gordurosa após lipoaspiração, perfuração visceral, lesão vascular, cegueira e infecção por herpes zoster, entre outros relatos. Com base nos artigos analisados foi possível concluir que a lipoaspiração é um procedimento altamente eficaz quando bem indicado e bem realizado, porém existem riscos inerentes ao ato cirúrgico. Este levantamento constatou que existem muitos artigos abordando complicações após lipoaspiração para fins estéticos, e a embolia gordurosa pulmonar apresenta alta incidência. Abstract in english Liposuction for esthetic purposes aims to remove fat in healthy patients and reduce localized fat accumulation, called lipodystrophy, in order to improve body contour. In the last 3 decades, the liposuction technique has improved dramatically. However, like any other surgical procedure, it is not wi [...] thout complications. Here, we reviewed the literature on PubMed to identify complications after classic liposuction performed solely for esthetic purposes. In total, 210 articles were found using the term "complication in liposuction," 86 with "complication after liposuction," 27 with "fat embolism after liposuction," 7 with "fat embolism following liposuction," and 16 with "deaths related to liposuction." Among these articles, only 84 including cases of fat embolism after liposuction, visceral perforation, vascular injury, blindness, and herpes zoster infection among others were considered to be related to the subject. Based on the analyzed articles, we can conclude that liposuction is a highly effective procedure when well indicated and performed accurately. Despite this, there are inherent risks. This review found many articles addressing complications, predominantly pulmonary fat embolism, after liposuction for esthetic purposes.

Fernando Fabrício, Franco; Rafael de Campos Ferreira, Basso; Alfio José, Tincani; Paulo, Kharmandayan.

2012-03-01

193

Performance enhancement by an innovative tube cleaning application  

International Nuclear Information System (INIS)

Clinton Power Station (CPS) performance had degraded over the past four operation cycles. A large portion of this performance degradation was due to the main condenser not performing as designed. Clinton lake water chemistry has pH of an average above 8.0. This has resulted in an extensive deposition of hard calcium carbonate scale in the 53,160 stainless steel tubes of the main condenser. In the past, attempts were made to clean the condenser tubes with standard mechanical scrapers. These scrapers removed a layer of soft material but did little to remove the hardened deposits. By third refueling outage, the average deposit was 20 mils thick resulting in condenser performance producing a backpressure that was 1.3 inches of mercury (inHg) greater than design. This translated to plant generation losses of $2.6 Million. The majority of these losses occurred during the summer months when CPS has its peak loads. This paper discusses the development of a new product which functions as a scale cutter and tube cleaner; its application on a trial basis and subsequently on a full scale condenser for the first time. It also describes station's experience, plant performance, the improvement, and the cost savings associated with tube cleaning

194

Similarity curve in the solidification process of latent heat energy storage unit with straight fins. 2nd Report. ; Effect of heat transfer tube on the formation of the similarity rule. Tate fin tuki sennetsu chikunetsuki no gyoko katei ni okeru soji kyokusen. 2. ; Sojisoku no seiritsu ni oyobosu dennetsukan no eikyo  

Energy Technology Data Exchange (ETDEWEB)

Using a latent heat storage unit with straight fins, an experiment is made on conditions for clarifying thermal properties in the solidification process of a latent heat storage unit in the relation of similarity functions and frozen fraction (similarity curves). The condition for the similarity curve being similar to different Biot numbers is that the Stefan number is small, a thermal conducting Laplace equation of quasi-stationary similarity is formed, and as boundary conditions, solid-liquid interface temperature is uniform, and surface heat flux by convection from heat transfer surface to heat medium is also uniformly distributed. When thermal conductivity of the heat transfer tube is large, the similarity rule is formed regardless of thickness of the heat transfer tube. This is because the tube circumferential heat conductance is large and ununiform distribution of heat flux caused by fins is relaxed. When thermal conductivity of the heat transfer tube is small, the thicker the tube is, the more easily the similarity rule is formed. This is because tube radial heat resistance increases and surface heat flux distribution becomes more uniform. The paper also indicates temperature distribution at the time of formation of the similarity rule and the similarity equation on forms of the solid-liquid interface position. 5 refs., 12 figs.

Kaino, K. (Toyota Technological Institute, Nagoya (Japan))

1993-02-25

195

Comprehensive methodology for finned air-cooled condensers and spray cooling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study consists of two discrete topics important to the design of two-phase cooling systems, fin-and-tube condensers and spray cooling modules. ^ The first part describes a comprehensive method for predicting pressure drop and thermal performance of three different types of fin-and-tube condensers. Detailed airside heat transfer coefficient condensation side, a series of correlations for the laminar/turbulent single-phase cooling regions and two-phase condensation region are presente...

Lee, Hyoungsoon

2011-01-01

196

Thermal Performance Of Convective-Radiative Heat Transfer In Porous Fins  

Directory of Open Access Journals (Sweden)

Full Text Available Forced and natural convection in porous fin with convective coefficient at the tip under radiation and convection effects are investigated in this letter. Aluminum and copper as materials of fins are determined. In forced and natural convection, the air and water, are applied as working fluids, respectively. In order to solution of this nonlinear equation, HPM and VIM has been used . For verifying the accuracy of the solution methods, compare them with exact solutions (BVP. In this work the effects of porosity parameter ( , Radiation parameter (? and Temperature-Ratio parameter (µ on temperature distribution for both of the flows have been shown. The results shows that the effects of (? and (µ on temperature distribution in natural convection are based on porosity and in forced convection are uniform, approximately. Also, its shown that both VIM and HPM are capables to solving this nonlinear heat transfer equation.

Majid SHAHBABAEI

2014-11-01

197

In-reactor performance of pressure tubes in CANDU reactors  

Science.gov (United States)

The pressure tubes in CANDU reactors have been operating for times up to about 25 years. The in-reactor performance of Zr-2.5Nb pressure tubes has been evaluated by sampling and periodic inspection. This paper describes the behaviour and discusses the factors controlling the behaviour of these components in currently operating CANDU reactors. The mechanical properties (such as ultimate tensile strength, UTS, and fracture toughness), and delayed-hydride-cracking properties (crack growth rate Vc, and threshold stress intensity factor, KIH) change with irradiation; the former reach a limiting value at a fluence of <1 × 10 25 n m -2, while Vc and KIH reach a steady-state condition after a fluence of about 3 × 10 25 n m -2 and 3 × 10 24 n m -2, respectively. At saturation the UTS is raised by about 200 MPa, toughness is reduced to about 40% of its initial value, Vc increases by about a factor of ten while KIH is only slightly reduced. The role of microstructure and trace elements in these behaviours is described. Pressure tubes exhibit elongation and diametral expansion. The deformation behaviour is a function of operating conditions and material properties that vary from tube-to-tube and as a function of axial location. Semi-empirical predictive models have been developed to describe the deformation response of average tubes as a function of operating conditions. For corrosion and, more importantly deuterium pickup, semi-empirical predictive models have also been developed to represent the behaviour of an average tube. The effect of material variability on corrosion behaviour is less well defined compared with other properties. Improvements in manufacturing have increased fracture resistance by minimising trace elements, especially H and Cl, and reduced variability by tightening controls on forming parameters, especially hot-working temperatures.

Rodgers, D. K.; Coleman, C. E.; Griffiths, M.; Bickel, G. A.; Theaker, J. R.; Muir, I.; Bahurmuz, A. A.; Lawrence, S. St.; Resta Levi, M.

2008-12-01

198

In-reactor performance of pressure tubes in CANDU reactors  

Energy Technology Data Exchange (ETDEWEB)

The pressure tubes in CANDU reactors have been operating for times up to about 25 years. The in-reactor performance of Zr-2.5Nb pressure tubes has been evaluated by sampling and periodic inspection. This paper describes the behaviour and discusses the factors controlling the behaviour of these components in currently operating CANDU reactors. The mechanical properties (such as ultimate tensile strength, UTS, and fracture toughness), and delayed-hydride-cracking properties (crack growth rate V{sub c}, and threshold stress intensity factor, K{sub IH}) change with irradiation; the former reach a limiting value at a fluence of <1 x 10{sup 25} n m{sup -2}, while V{sub c} and K{sub IH} reach a steady-state condition after a fluence of about 3 x 10{sup 25} n m{sup -2} and 3 x 10{sup 24} n m{sup -2}, respectively. At saturation the UTS is raised by about 200 MPa, toughness is reduced to about 40% of its initial value, V{sub c} increases by about a factor of ten while K{sub IH} is only slightly reduced. The role of microstructure and trace elements in these behaviours is described. Pressure tubes exhibit elongation and diametral expansion. The deformation behaviour is a function of operating conditions and material properties that vary from tube-to-tube and as a function of axial location. Semi-empirical predictive models have been developed to describe the deformation response of average tubes as a function of operating conditions. For corrosion and, more importantly deuterium pickup, semi-empirical predictive models have also been developed to represent the behaviour of an average tube. The effect of material variability on corrosion behaviour is less well defined compared with other properties. Improvements in manufacturing have increased fracture resistance by minimising trace elements, especially H and Cl, and reduced variability by tightening controls on forming parameters, especially hot-working temperatures.

Rodgers, D.K.; Coleman, C.E.; Griffiths, M. [Atomic Energy of Canada Ltd., Chalk River, Ontario, K0J IJ0 (Canada); Bickel, G.A. [Atomic Energy of Canada Ltd., Chalk River, Ontario, K0J IJ0 (Canada)], E-mail: bickelg@aecl.ca; Theaker, J.R.; Muir, I.; Bahurmuz, A.A.; Lawrence, S. St.; Resta Levi, M. [Atomic Energy of Canada Ltd., Chalk River, Ontario, K0J IJ0 (Canada)

2008-12-15

199

Thermal performance in circular tube fitted with coiled square wires  

International Nuclear Information System (INIS)

The effects of wires with square cross section forming a coil used as a turbulator on the heat transfer and turbulent flow friction characteristics in a uniform heat flux, circular tube are experimentally investigated in the present work. The experiments are performed for flows with Reynolds numbers ranging from 5000 to 25,000. Two different spring coiled wire pitches are introduced. The results are also compared with those obtained from using a typical coiled circular wire, apart from the smooth tube. The experimental results reveal that the use of coiled square wire turbulators leads to a considerable increase in heat transfer and friction loss over those of a smooth wall tube. The Nusselt number increases with the rise of Reynolds number and the reduction of pitch for both circular and square wire coils. The coiled square wire provides higher heat transfer than the circular one under the same conditions. Also, performance evaluation criteria to assess the real benefits in using both coil wires of the enhanced tube are determined

200

Investigation of process-induced performance variability and optimization of the 10 nm technology node Si bulk FinFETs  

Science.gov (United States)

we propose a process and device design strategy for Lg = 14 nm Si bulk n/p-FinFETs based on the effects of process-induced geometry variability on device performance. A calibrated TCAD simulation was used to design and optimize structures and these were also tested under various process split conditions. By comparing the I-V data from process-changed devices with nominal CMOS, relationships between process- induced geometry variation and device performance were investigated and analyzed. Moreover a DC/RF compact model was executed to observe the geometry variability effects on ring oscillator and RF applications. Finally key circuit design factors to mitigate process variability are suggested.

Baek, Rock-Hyun; Kang, Chang Yong; Sohn, Chang-Woo; Kim, Dae Mann; Kirsch, Paul

2014-06-01

 
 
 
 
201

Predicting optimum vortex tube performance using a simplified CFD model  

International Nuclear Information System (INIS)

The Ranque-Hilsch tube is a particular type of vortex tube device. The flow enters the device tangentially near one end and exits from the open ends of the tube. The inlet air is of a uniform temperature throughout while the outputs are of different temperatures. One outlet is hotter and the other is colder than the inlet air. This device has no moving parts and does not require any additional power for its operation other than that supplied to the device to compress the inlet air. It has, however, not been widely used, mainly because of its low efficiency. In this paper, a simplified 2-dimensional computational fluid dynamics model for the flow in the vortex tube is developed using FLUENT. This model makes use of the assumption of axial symmetry throughout the entire flow domain. Compared to a three-dimensional computational solution, the simplified model requires significantly less computational time. This is important because the model is to be used for an optimization study. A user-defined function is generated to implement a modified version of the k-epsilon model to account for turbulence. This model is validated by comparing a particular solution with available experimental data. The variation of cold temperature drop and efficiency of the device with orifice diameter, inlet pressure and cold mass flow ratio qualitatively agree with experimental results. Variation of these performance indices with tube length did not agree with the experiments for small values ree with the experiments for small values of tube length. However, it did agree qualitatively for large values. (author)

202

A computer program for detailed estimates of the refrigerant and air specifications of bundled finned-tube evaporators. PC-Programm zur detaillierten kaeltemittel- und luftseitigen Berechnung eines Lamellenrohrbuendel-Verdampfers  

Energy Technology Data Exchange (ETDEWEB)

A model-simulation for estimating the specifications of a round-tube bundled finned-tube evaporator is described. The evaporator is divided into several small segments. The segments are seperately estimated and then combined through coupling and marginal factors. Division into numerous single segments permits the simulation of any desired type of air or refrigerant flow. In order to handle the resulting very large linear equation set on a personal computer, it was necessary to develop a special computational technique that economized the space needed in the memory. (orig.).

Koehler, J. (KONVEKTA/IPEK-Entwicklungszentrum, Marburg (Germany, F.R.)); Antonetty, F.; Keuper, A.; Beer, H. (Technische Hochschule Darmstadt (Germany, F.R.). Fachgebiet Technische Thermodynamik)

1991-06-01

203

Similarity curve in the solidification process of a latent-heat energy-storage unit with longitudinally straight fins (effect of heat-transfer tube on the applicability of the similarity rule)  

Energy Technology Data Exchange (ETDEWEB)

The applicability of the similarity rule that the relationship between the similarity function and the frozen fraction is independent of the Biot number is known to have a connection with the uniformity of heat-flux distribution on a heat-transfer surface. A latent-heat thermal-energy storage unit with straight fins, which has the nature of losing such uniformity inherently, has been adopted to examine how the applicability of the similarity rule will be affected by the thickness and thermal conductivity of the heat-transfer tube serving as the base of the straight fins. It is proved that, if the heat-transfer tube is made of a high-thermal-conductivity material, the applicability of the similarity rule can be ensured over wide variations in the thickness of the tube. On the other hand, if the heat-transfer tube has a lower thermal conductivity, the similarity rule is valid only in the situation in which the tube is considerably thick. The temperature distribution inside the storage unit, as well as the position of the solid-liquid interface, is shown for the purpose of discussing the results.

Kaino, Koji

1994-10-01

204

Performance of the CMS Drift Tube Chambers with Cosmic Rays  

CERN Document Server

Studies of the performance of the CMS drift tube barrel muon system are described, with results based on data collected during the CMS Cosmic Run at Four Tesla. For most of these data, the solenoidal magnet was operated with a central field of 3.8 T. The analysis of data from 246 out of a total of 250 chambers indicates a very good muon reconstruction capability, with a coordinate resolution for a single hit of about 260 microns, and a nearly 100% efficiency for the drift tube cells. The resolution of the track direction measured in the bending plane is about 1.8 mrad, and the efficiency to reconstruct a segment in a single chamber is higher than 99%. The CMS simulation of cosmic rays reproduces well the performance of the barrel muon detector.

Chatrchyan, S; Sirunyan, A M; Adam, W; Arnold, B; Bergauer, H; Bergauer, T; Dragicevic, M; Eichberger, M; Erö, J; Friedl, M; Frühwirth, R; Ghete, V M; Hammer, J; Hänsel, S; Hoch, M; Hörmann, N; Hrubec, J; Jeitler, M; Kasieczka, G; Kastner, K; Krammer, M; Liko, D; Magrans de Abril, I; Mikulec, I; Mittermayr, F; Neuherz, B; Oberegger, M; Padrta, M; Pernicka, M; Rohringer, H; Schmid, S; Schöfbeck, R; Schreiner, T; Stark, R; Steininger, H; Strauss, J; Taurok, A; Teischinger, F; Themel, T; Uhl, D; Wagner, P; Waltenberger, W; Walzel, G; Widl, E; Wulz, C E; Chekhovsky, V; Dvornikov, O; Emeliantchik, I; Litomin, A; Makarenko, V; Marfin, I; Mossolov, V; Shumeiko, N; Solin, A; Stefanovitch, R; Suarez Gonzalez, J; Tikhonov, A; Fedorov, A; Karneyeu, A; Korzhik, M; Panov, V; Zuyeuski, R; Kuchinsky, P; Beaumont, W; Benucci, L; Cardaci, M; De Wolf, E A; Delmeire, E; Druzhkin, D; Hashemi, M; Janssen, X; Maes, T; Mucibello, L; Ochesanu, S; Rougny, R; Selvaggi, M; Van Haevermaet, H; Van Mechelen, P; Van Remortel, N; Adler, V; Beauceron, S; Blyweert, S; D'Hondt, J; De Weirdt, S; Devroede, O; Heyninck, J; Kalogeropoulos, A; Maes, J; Maes, M; Mozer, M U; Tavernier, S; Van Doninck, W; Van Mulders, P; Villella, I; Bouhali, O; Chabert, E C; Charaf, O; Clerbaux, B; De Lentdecker, G; Dero, V; Elgammal, S; Gay, A P R; Hammad, G H; Marage, P E; Rugovac, S; Vander Velde, C; Vanlaer, P; Wickens, J; Grunewald, M; Klein, B; Marinov, A; Ryckbosch, D; Thyssen, F; Tytgat, M; Vanelderen, L; Verwilligen, P; Basegmez, S; Bruno, G; Caudron, J; Delaere, C; Demin, P; Favart, D; Giammanco, A; Grégoire, G; Lemaitre, V; Militaru, O; Ovyn, S; Piotrzkowski, K; Quertenmont, L; Schul, N; Beliy, N; Daubie, E; Alves, G A; Pol, M E; Souza, M H G; Carvalho, W; De Jesus Damiao, D; De Oliveira Martins, C; Fonseca De Souza, S; Mundim, L; Oguri, V; Santoro, A; Silva Do Amaral, S M; Sznajder, A; Fernandez Perez Tomei, T R; Ferreira Dias, M A; Gregores, E M; Novaes, S F; Abadjiev, K; Anguelov, T; Damgov, J; Darmenov, N; Dimitrov, L; Genchev, V; Iaydjiev, P; Piperov, S; Stoykova, S; Sultanov, G; Trayanov, R; Vankov, I; Dimitrov, A; Dyulendarova, M; Kozhuharov, V; Litov, L; Marinova, E; Mateev, M; Pavlov, B; Petkov, P; Toteva, Z; Chen, G M; Chen, H S; Guan, W; Jiang, C H; Liang, D; Liu, B; Meng, X; Tao, J; Wang, J; Wang, Z; Xue, Z; Zhang, Z; Ban, Y; Cai, J; Ge, Y; Guo, S; Hu, Z; Mao, Y; Qian, S J; Teng, H; Zhu, B; Avila, C; Baquero Ruiz, M; Carrillo Montoya, C A; Gomez, A; Gomez Moreno, B; Ocampo Rios, A A; Osorio Oliveros, A F; Reyes Romero, D; Sanabria, J C; Godinovic, N; Lelas, K; Plestina, R; Polic, D; Puljak, I; Antunovic, Z; Dzelalija, M; Brigljevic, V; Duric, S; Kadija, K; Morovic, S; Fereos, R; Galanti, M; Mousa, J; Papadakis, A; Ptochos, F; Razis, P A; Tsiakkouri, D; Zinonos, Z; Hektor, A; Kadastik, M; Kannike, K; Müntel, M; Raidal, M; Rebane, L; Anttila, E; Czellar, S; Härkönen, J; Heikkinen, A; Karimäki, V; Kinnunen, R; Klem, J; Kortelainen, M J; Lampén, T; Lassila-Perini, K; Lehti, S; Lindén, T; Luukka, P; Mäenpää, T; Nysten, J; Tuominen, E; Tuominiemi, J; Ungaro, D; Wendland, L; Banzuzi, K; Korpela, A; Tuuva, T; Nedelec, P; Sillou, D; Besancon, M; Chipaux, R; Dejardin, M; Denegri, D; Descamps, J; Fabbro, B; Faure, J L; Ferri, F; Ganjour, S; Gentit, F X; Givernaud, A; Gras, P; Hamel de Monchenault, G; Jarry, P; Lemaire, M C; Locci, E; Malcles, J; Marionneau, M; Millischer, L; Rander, J; Rosowsky, A; Rousseau, D; Titov, M; Verrecchia, P; Baffioni, S; Bianchini, L; Bluj, M; Busson, P; Charlot, C; Dobrzynski, L; Granier de Cassagnac, R; Haguenauer, M; Miné, P; Paganini, P; Sirois, Y; Thiebaux, C; Zabi, A; Agram, J L; Besson, A; Bloch, D; Bodin, D; Brom, J M; Conte, E; Drouhin, F; Fontaine, J C; Gelé, D; Goerlach, U; Gross, L; Juillot, P; Le Bihan, A C; Patois, Y; Speck, J; Van Hove, P; Baty, C; Bedjidian, M; Blaha, J; Boudoul, G; Brun, H; Chanon, N; Chierici, R; Contardo, D; Depasse, P; Dupasquier, T; El Mamouni, H; Fassi, F; Fay, J; Gascon, S; Ille, B; Kurca, T; Le Grand, T; Lethuillier, M; Lumb, N; Mirabito, L; Perries, S; Vander Donckt, M; Verdier, P; Djaoshvili, N; Roinishvili, N; Roinishvili, V; Amaglobeli, N; Adolphi, R; Anagnostou, G; Brauer, R; Braunschweig, W; Edelhoff, M; Esser, H; Feld, L; Karpinski, W; Khomich, A; Klein, K; Mohr, N; Ostaptchouk, A; Pandoulas, D; Pierschel, G; Raupach, F; Schael, S; Schultz von Dratzig, A; Schwering, G; Sprenger, D; Thomas, M; Weber, M; Wittmer, B; Wlochal, M; Actis, O; Altenhöfer, G; Bender, W; Biallass, P; Erdmann, M; Fetchenhauer, G; Frangenheim, J; Hebbeker, T; Hilgers, G; Hinzmann, A; Hoepfner, K; Hof, C; Kirsch, M; Klimkovich, T; Kreuzer, P; Lanske, D; Merschmeyer, M; Meyer, A; Philipps, B; Pieta, H; Reithler, H; Schmitz, S A; Sonnenschein, L; Sowa, M; Steggemann, J; Szczesny, H; Teyssier, D; Zeidler, C; Bontenackels, M; Davids, M; Duda, M; Flügge, G

2010-01-01

205

Performance analysis of double basin solar still with evacuated tubes  

International Nuclear Information System (INIS)

Solar still is a very simple device, which is used for solar distillation process. In this research work, double basin solar still is made from locally available materials. Double basin solar still is made in such a way that, outer basin is exposed to sun and lower side of inner basin is directly connected with evacuated tubes to increase distillate output and reducing heat losses of a solar still. The overall size of the lower basin is about 1006 mm x 325 mm x 380 mm, the outer basin is about 1006 mm x 536 mm x 100 mm Black granite gravel is used to increase distillate output by reducing quantity of brackish or saline water in the both basins. Several experiments have conducted to determine the performance of a solar still in climate conditions of Mehsana (latitude of 23 degree 59' and longitude of 72 degree 38'), Gujarat, like a double basin solar still alone, double basin solar still with different size black granite gravel, double basin solar still with evacuated tubes and double basin solar still with evacuated tubes and different size black granite gravel. Experimental results show that, connecting evacuated tubes with the lower side of the inner basin increases daily distillate output of 56% and is increased by 60%, 63% and 67% with average 10 mm, 20 mm and 30 mm size black granite gravel. Economic analysis of present double basin solar still is 195 days. (authors)

206

3D numerical simulation on fluid flow and heat transfer characteristics in multistage heat exchanger with slit fins  

Science.gov (United States)

In this paper, a numerical investigation is performed for three-stage heat exchangers with plain plate fins and slit fins respectively, with a three-dimensional laminar conjugated model. The tubes are arranged in a staggered way, and heat conduction in fins is considered. In order to save the computer resource and speed up the numerical simulation, the numerical modeling is carried out stage by stage. In order to avoid the large pressure drop penalty in enhancing heat transfer, a slit fin is presented with the strip arrangement of “front coarse and rear dense” along the flow direction. The numerical simulation shows that, compared to the plain plate fin heat exchanger, the increase in the heat transfer in the slit fin heat exchanger is higher than that of the pressure drop, which proves the excellent performance of this slit fin. The fluid flow and heat transfer performance along the stages is also provided.

Tao, W. Q.; Cheng, Y. P.; Lee, T. S.

2007-11-01

207

Performance of a lead radiator, gas tube calorimeter  

International Nuclear Information System (INIS)

Design and performance of a 4.2 radiation length lead-sandwich, gas tube hodoscope are discussed. The device, measuring 1 /times/ 2 m2 in area and 12 cm in depth, was employed in Fermi National Accelerator Laboratory experiment 705. Multiple samplings of anode wires situated within three-walled aluminum tubes were used to generate an X coordinate; similarly, capacitively coupled copper-clad strips were ganged together to yield a Y coordinate. The results reviewed are based on an analysis of electron calibration data taken during a recent six-month running period. In particular, position resolution (in millimeters) is seen to be 0.8 + 3.3/?E + 31/E for the 9.92 mm spaced wires and 0.6 + 3.2/?E + 32/E for the 12.5 mm strips, where E represents the electron beam energy in GeV. 5 refs., 6 figs

208

Performance of a lead radiator, gas tube calorimeter  

Energy Technology Data Exchange (ETDEWEB)

Design and performance of a 4.2 radiation length lead-sandwich, gas tube hodoscope are discussed. The device, measuring 1 /times/ 2 m/sup 2/ in area and 12 cm in depth, was employed in Fermi National Accelerator Laboratory experiment 705. Multiple samplings of anode wires situated within three-walled aluminum tubes were used to generate an X coordinate; similarly, capacitively coupled copper-clad strips were ganged together to yield a Y coordinate. The results reviewed are based on an analysis of electron calibration data taken during a recent six-month running period. In particular, position resolution (in millimeters) is seen to be 0.8 + 3.3/..sqrt..E + 31/E for the 9.92 mm spaced wires and 0.6 + 3.2/..sqrt..E + 32/E for the 12.5 mm strips, where E represents the electron beam energy in GeV. 5 refs., 6 figs.

Spiegel, L.; Arenton, M.; Chen, T.Y.; Conetti, S.; Cox, B.; Delchamps, S.W.; Etemadi, B.; Fortney, L.; Guffey, K.; Haire, M.

1989-03-13

209

Heat transfer performance of condenser tubes in an MSF desalination system  

International Nuclear Information System (INIS)

tube is 0.56 of the fouling thermal resistance of the smooth tube after140 running hours of the experiment are concluded. Overall, in the case of real brine, results prove that heat performance for the corrugated tube is superior to the plain tube over the studied time period (140 hrs) for the chosen range of flow speeds

210

Effects of intraspecific variation in reproductive traits, pectoral fin use and burst swimming on metabolic rates and swimming performance in the Trinidadian guppy (Poecilia reticulata)  

DEFF Research Database (Denmark)

There is considerable intraspecific variation in metabolic rates and locomotor performance in aquatic ectothermic vertebrates; however, the mechanistic basis remains poorly understood. Using pregnant Trinidadian guppies (Poecilia reticulata), a livebearing teleost, we examined the effects of reproductive traits, pectoral fin use and burse-assisted swimming on swimming metabolic rate, standard metabolic rate (MO2std) and prolonged swimming performance (Ucrit). Reproductive traits included reproductive allocation and pregnancy stage, the former defined as the mass of the reproductive tissues divided by the total body mass. Results showed that the metabolic rate increased curvilinearly with swimming speed. The slope of the relationship was used as an index of swimming cost. There was no evidence that reproductive traits correlated with swimming cost, MO2std or Ucrit. In contrast, data revealed strong effects of pectoral fin use on swimming cost and Ucrit. Poecilia reticulata employed body-caudal fin (BCF) swimming at all tested swimming speeds; however, fish with a high simultaneous use of the pectoral fins exhibited increased swimming cost and decreased Ucrit. These data indicated that combining BCF swimming and pectoral fin movement over a wide speed range, presumably to support swimming stability and control, is an inefficient swimming behaviour. Finally, transition to burst-assisted swimming was associated with an increase in aerobic metabolic rate. Our study highlights factors other than swimming speed that affect swimming cost and suggests that intraspecific diversity in biomechanical performance, such as pectoral fin use, is an important source of variation in both locomotor cost and maximal performance.

Svendsen, Jon Christian; Banet, Amanda I.

2013-01-01

211

Commissioning, Operation and Performance of the CMS Drift Tube Chambers  

CERN Document Server

The CMS muon spectrometer, designed to trigger, identify, reconstruct and measure muons with high efficiency and accuracy, is equipped with Drift Tube chambers (DT) in the barrel region. The DT system has been fully commissioned using cosmic muons with and without magnetic field, and during months of cosmic data taking has provided millions of triggers to the rest of the CMS detector. This contribution will describe the challenges in the operation of the DT system, including calibration procedures, monitoring and reconstruction performance, and the result of the analysis of the collected cosmic data.

Cerminara, Gianluca

2010-01-01

212

Performance of 2mm radius straw tube drift cells  

International Nuclear Information System (INIS)

The performance of a 128 channel test module made with straw tubes of 2mm radius has been studied in a test beam and with cosmic rays. Different gases were used and for each one the time-to-distance relation and the hit efficiency was measured. Comparison are made between results when two different electronics readouts were used. The information was recorded with 106 MHz FADC units and also with TDCs (50ps resolution). The best resolution, of 135 ?m, was obtained using 50% ethane, 50% argon and reading out the information with the TDCs, at an operating HV of 1,750V

213

Effect of external recycle on the performances of flat-plate solar air heaters with internal fins attached  

Energy Technology Data Exchange (ETDEWEB)

The influence of external recycle on the collector efficiency in solar air heaters with internal fins attached, has been investigated theoretically. The application of external recycle operation to solar air heaters actually has two conflict effects. One is the increase in fluid velocity to decrease the heat-transfer resistance, which is good for performance, while the other is lowering the driving force (temperature difference) of heat-transfer, due to the remixing at the inlet, which is bad for performance. It is found that considerable improvement in collector efficiency is obtainable if the operation is carried out with an external recycle, where the desirable effect overcomes the undesirable effect. The enhancement increases with increasing reflux ratio, especially for operating at lower air flow rate with higher inlet air temperature. (author)

Yeh, Ho-Ming; Ho, Chii-Dong [Energy and Opto-Electronic Materials Research Center, Department of Chemical and Materials Engineering, Tamkang University, 151 Ying-Chuan Road, Tamsui, Taipei County 25137 (China)

2009-05-15

214

Felipe Neto em performance no YouTube: uma responsabilidade mútua entre performer e audiências  

Directory of Open Access Journals (Sweden)

Full Text Available This paper aims at understanding to what extent Felipe Netos performance on his video Desabafo e coisas da madrugada published on YouTube explicits a responsibility between performer and audiences. We understand performance as a relacional practice that is performed for different audiences that are called together to participate therein. We also emphasize the espetacular and entertained dimension of Netos performance on web.

Tiago Barcelos Pereira Salgado

2012-12-01

215

Effect of Gate Length Scaling on Various Performance Parameters in DG-FinFETs: a Simulation Study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents a simulation study on the gate length scaling of a double gate (DG) FinFET. To achieve channel lengths smaller than 20 nm, innovative device architectures will be necessary to continue the benefits previously acquired through scaling. In order to obtain desirable control of short channel effects (SCEs), the thickness or the horizontal width of a fin in a FinFET should be less than two-third of its gate length and the semiconductor fin should be thin enough in the channel r...

Rakesh Vaid; Meenakshi Chandel

2012-01-01

216

Steam generator tube performance. Experience with water-cooled nuclear power reactors during 1985  

International Nuclear Information System (INIS)

The performance of steam generator tubes at water-cooled reactors during 1985 has been reviewed. Seventy-three of 168 reactors in the survey experienced tube degradation sufficient for the tubes to be plugged. The number of tubes plugged was 6837 or 0.28% of those in service. The leading cause of tube failure was stress corrosion cracking from the primary side. Stress corrosion cracking or intergranular attack from the secondary side and pitting were also major causes of tube failure. Unlike most previous years, fretting was a substantial problem at some reactors. Overall, corrosion continued to account for more than 80% of the defects. 20 refs

217

Subcooled boiling heat transfer on a finned surface  

International Nuclear Information System (INIS)

Experimental and numerical studies have been performed to determine the heat transfer coefficients from a finned cylindrical surface to subcooled boiling water. The heat transfer rates were measured in an annular test section consisting of an electrically heated fuel element simulator (FES) with eight longitudinal, rectangular fins enclosed in a glass tube. A two-dimensional finite-element heat transfer model using the Galerkin method was employed to determine the heat transfer coefficients along the periphery of the FES surface. An empirical correlation was developed to predict the heat transfer coefficients during subcooled boiling. The correlation agrees well with the measured data. (6 figures) (Author)

218

Flow splits and lowing performances of fuel fins in wire wrapped FBR fuel assemblies  

International Nuclear Information System (INIS)

In a LMFBR fuel subassembly, the coolant temperature difference between the wall and the inner subchannels is considerably large due to the edge flow effect. The coolant temperature difference causes thermal and swelling bowings of fuel bundles and depresses an allowable burnup with consequent increase of fuel cycle cost. So, at first, it is required to obtain precise informations about the flow splits since the temperature form factor of a subchannel is almost proportional to the flow split parameter X2 (= Vwall/anti V) where wall is an average axial velocity in wall subchannels while anti V is a bundle average velocity. Secondly, it is required to analyze bowing performances of the fuel pins accurately using the flow splits. In this paper, flow splits and bowing performances of fuel pins in a wire wrapped LMFBR fuel subassembly are discussed on the basis of fuel subassembly flow tests using a water loop, and on computer analyses. (orig.)

219

Effects of intraspecific variation in reproductive traits, pectoral fin use and burst swimming on metabolic rates and swimming performance in the Trinidadian guppy (Poecilia reticulata).  

Science.gov (United States)

There is considerable intraspecific variation in metabolic rates and locomotor performance in aquatic ectothermic vertebrates; however, the mechanistic basis remains poorly understood. Using pregnant Trinidadian guppies (Poecilia reticulata), a live-bearing teleost, we examined the effects of reproductive traits, pectoral fin use and burst-assisted swimming on swimming metabolic rate, standard metabolic rate (O2std) and prolonged swimming performance (Ucrit). Reproductive traits included reproductive allocation and pregnancy stage, the former defined as the mass of the reproductive tissues divided by the total body mass. Results showed that the metabolic rate increased curvilinearly with swimming speed. The slope of the relationship was used as an index of swimming cost. There was no evidence that reproductive traits correlated with swimming cost, O2std or Ucrit. In contrast, data revealed strong effects of pectoral fin use on swimming cost and Ucrit. Poecilia reticulata employed body-caudal fin (BCF) swimming at all tested swimming speeds; however, fish with a high simultaneous use of the pectoral fins exhibited increased swimming cost and decreased Ucrit. These data indicated that combining BCF swimming and pectoral fin movement over a wide speed range, presumably to support swimming stability and control, is an inefficient swimming behaviour. Finally, transition to burst-assisted swimming was associated with an increase in aerobic metabolic rate. Our study highlights factors other than swimming speed that affect swimming cost and suggests that intraspecific diversity in biomechanical performance, such as pectoral fin use, is an important source of variation in both locomotor cost and maximal performance. PMID:23737561

Svendsen, Jon C; Banet, Amanda I; Christensen, Rune H B; Steffensen, John F; Aarestrup, Kim

2013-09-15

220

Fins improve the swimming performance of fish sperm: a hydrodynamic analysis of the Siberian sturgeon Acipenser baerii.  

Science.gov (United States)

The flagella of sturgeon sperm have an ultrastructure comprising paddle-like fins extending along most of their length. These fins are seen in several other marine and freshwater fish. The sperm of these fish are fast swimmers and are relatively short lived: it is therefore tempting to think of these fins as having evolved for hydrodynamic advantage, but the actual advantage they impart, at such a small length scale and slow speed, is unclear. The phrase "the fins improve hydrodynamic efficiency" is commonly found in biological literature, yet little hydrodynamic analysis has previously been used to support such conjectures. In this paper, we examine various hydrodynamic models of sturgeon sperm and investigate both swimming velocity and energy expenditure. All of the models indicate a modest hydrodynamic advantage of finned sperm, in both straight line swimming speed and a hydrodynamic efficiency measure. We find a hydrodynamic advantage for a flagellum with fins, over one without fins, of the order of 15-20% in straight line propulsive velocity and 10-15% in a hydrodynamic efficiency measure. PMID:23233331

Gillies, Eric A; Bondarenko, Volodymyr; Cosson, Jacky; Pacey, Allan A

2013-02-01

 
 
 
 
221

Effect of gravity opientation on the thermal performance of Stirling-type pulse tube cryocoolers  

Science.gov (United States)

This paper extends the investigation of angular orientation effects to the refrigeration performance of high frequency (-40 Hz) Stirling-type pulse tube cryocoolers typical of those used in long-life space applications. Strong orientation effects on the performance of such cryocoolers have recently been observed during system-level testing of both linear and U-tube type pulse tubes. To quantify the angular dependency effects, data have been gathered on both U-tube and linear type pulse tubes of two different manufacturers as a function of orientation angle, cold-tip temperature, and compressor stroke.

Ronald, Ross G., Jr.; Johnson, D. L.

2003-01-01

222

Threshold Voltage Sensitivity to Metal Gate Work-Function Based Performance Evaluation of Double-Gate n-FinFET Structures for LSTP Technology  

Directory of Open Access Journals (Sweden)

Full Text Available This paper investigates the threshold voltage sensitivity to metal gate work-function for n-channel double gate fin field-effect transistor (FinFET structures and evaluates the short channel performance of the device using threshold voltage dependence on metal gate work-function analysis. We carried out the study for a double gate n-channel fin field-effect transistor (n-FinFET with parameters as per the projection report of International Technology Roadmap for Semiconductors, ITRS-2011 for low standby power (LSTP 20 nm gate length technology node. In the present study device simulation have been carried out using PADRE simulator from MuGFET, which is based on the drift-diffusion theory. Our results show the accuracy and validity of classical drift-diffusion simulation results for transistor structures with lateral dimensions 10nm and above. The subthreshold behavior of device improves with increased metal gate work-function. The results also show that a higher gate work-function (?5 eV can fulfill the tolerable off-current as projected in ITRS 2011 report. The SCE in FinFET can reasonably be controlled and improved by proper adjustment of the metal gate work-function. DIBL is reduced with the increase in gate work function.

M. R. Beigh

2013-03-01

223

Effect of salt spray corrosion on air-side hydrophilicity and thermal-hydraulic performance of copper-fin heat exchangers  

Science.gov (United States)

The effect of salt spray corrosion on the air-side hydrophilicity and the thermal-hydraulic performance of copper-fin heat exchangers were experimentally investigated. Artificial accelerated method of salt spray corrosion on the copper-fin heat exchangers was used for simulating the actual corroded heat exchangers. The experimental results show that, the contact angles increase with the increase of salt spray corrosion hours, which results in the degradation of the hydrophilicity of copper fin. The air-side heat transfer coefficients decrease and pressure drops increase with the increase of corrosion hours. The effect of salt spray corrosion on the heat transfer coefficients and pressure drops become more obvious with the increase of inlet air velocity. The heat transfer coefficients of the corroded copper-fin heat exchangers decrease by 4.4-34.0% and the pressure drop increase by 5.2-26.1% comparing with those of the uncorroded copper-fin heat exchanger at the inlet air velocity ranging from 0.5 to 2.0 m/s.

Pu, Hui; Ding, Guo-Liang; Hu, Hai-Tao; Gao, Yi-Feng

2010-10-01

224

Forced convection heat transfer and pressure drop for a horizontal cylinder with vertically attached imperforate and perforated circular fins  

International Nuclear Information System (INIS)

Highlights: ? The effect of holes placed on perforated finned heat exchangers on convective heat transfer experimentally investigated. ? Six millimeter-diameter holes were opened on each circular fin on a heating tube in order to increase convective heat transfer. ? These holes were placed on the circular fins in such a way as to follow each other at the same chosen angle. ? The holes created turbulence in a region near the heating tube surface on the bottom of the fin. - Abstract: In this study, the effect of holes placed on perforated finned heat exchangers on convective heat transfer experimentally investigated. Six millimeter-diameter holes were opened on each circular fin on a heating tube in order to increase convective heat transfer. These holes were placed on the circular fins in such a way as to follow each other at the same chosen angle. The holes created turbulence in a region near the heating tube surface on the bottom of the fin. Some experiments were then performed to analyze the effect of this turbulence on heat transfer and pressure drop. These experiments were carried out at six different angular locations in order to determine the best angular location. In addition, a perforated finned heater was compared with an imperforate finned heater to observe the differences. In the cases of the Re above the critical value, Nusselt numbers for the perforated finned positions are 12% higher than the Nusselt numbers for the imperforate state. Moreover, athe imperforate state. Moreover, a correlation has been obtained between the Re and Nu in the Re number above the critical value and the Re below the critical value. Meanwhile, correlations regarding pressure drops in the flow areas have been obtained.

225

High-Performance Three-Terminal Fin Field-Effect Transistors Fabricated by a Combination of Damage-Free Neutral-Beam Etching and Neutral-Beam Oxidation  

Science.gov (United States)

Three-terminal fin field-effect transistors (3T-FinFETs) were fabricated by neutral-beam oxidation (NBO) to form gate silicon dioxide (SiO2). The 3T-FinFET fabricated by NBO showed higher device performance - namely, a higher subthreshold slope and a higher effective mobility - than that fabricated by conventional thermal oxidation. It is considered that those improved subthreshold slope and mobility are due to the fact that the three-dimensional structure of a SiO2 film fabricated by NBO has a lower interfacial state density and a lower roughness than a similar structure fabricated by the conventional thermal oxidation of a SiO2 film. The reasons for the lower interfacial state density and lower roughness are the low temperature and lattice plane independence of NBO in comparison with conventional thermal oxidation processes.

Wada, Akira; Sano, Keisuke; Yonemoto, Masahiro; Endo, Kazuhiko; Matsukawa, Takashi; Masahara, Meishoku; Yamasaki, Satoshi; Samukawa, Seiji

2010-04-01

226

Study of the thermal performance of external and internal finned plate-heat exchangers for nuclear steam generator application  

International Nuclear Information System (INIS)

The present study points out two main categories of steam generators for nuclear plants with PWR reactor, on one side of the Babcok and Wilcox type, and on the other side of the Westinghouse type. The present study examines, from a recent patent, the possibility to add internal and external fins in the steam generator exchangers of PWR reactors. The finned-plate heat exchanger is first described. The thermal characteristics of a finned-plate and of an exchanger including these plates are tested. The theoretical study and the experiment are both presented. The study deals more particularly with the evaluation of the global heat exchange coefficient that the internal fins allow to improve. The experiment has been carried out for different flow rates and at different temperatures

227

Critical heat flux test on saw-toothed fin duct under one-sided heating conditions  

International Nuclear Information System (INIS)

Critical heat flux (CHF) tests on a new type of rectangular cooling tube, 'saw-toothed fin duct, SFD' for high heat flux components were performed under one-sided heating conditions. The tube has internal triangle fins at the heating side to enhance the CHF characteristics. Hydraulic conditions were as follows: axial flow velocity ranged from 2 to 12 m/s. Local pressure at the center of the test sample was 1 MPa and inlet water temperature was 21-25 deg. C. In the present work, SFD, which has a fin height of 3.46 mm and an installation angle of the fin of 70 deg., results in the highest CHF of 43 MW/m2 at the axial flow velocity of 10 m/s. This value is 1.3 times higher than that obtained with a Hypervapotron

228

Critical heat flux test on saw-toothed fin duct under one-sided heating conditions  

Energy Technology Data Exchange (ETDEWEB)

Critical heat flux (CHF) tests on a new type of rectangular cooling tube, 'saw-toothed fin duct, SFD' for high heat flux components were performed under one-sided heating conditions. The tube has internal triangle fins at the heating side to enhance the CHF characteristics. Hydraulic conditions were as follows: axial flow velocity ranged from 2 to 12 m/s. Local pressure at the center of the test sample was 1 MPa and inlet water temperature was 21-25 deg. C. In the present work, SFD, which has a fin height of 3.46 mm and an installation angle of the fin of 70 deg., results in the highest CHF of 43 MW/m{sup 2} at the axial flow velocity of 10 m/s. This value is 1.3 times higher than that obtained with a Hypervapotron.

Ezato, K. E-mail: ezatok@fusion.naka.jaeri.go.jp; Suzuki, S.; Sato, K.; Taniguchi, M.; Hanada, M.; Araki, M.; Akiba, M

2001-10-01

229

Performance of a 20-in. photoelectric lens image intensifier tube  

CERN Document Server

We have evaluated a 20-in. photoelectric lens image intensifier tube (PLI) to be mounted on the spherical focal surface of the Ashra light collectors, where Ashra stands for All-sky Survey High Resolution Air-shower Detector, an unconventional optical collector complex that images air showers produced by very high energy cosmic-ray particles in a 42$^\\circ$-diameter field of view with a resolution of a few arcminutes. The PLI, the worlds largest image intensifier, has a very large effective photocathode area of 20-in. diameter and reduces an image size to less than 1-inch diameter using the electric lens effect. This enables us to use a solid-state imager to take focal surface images in the Ashra light collector. Thus, PLI is a key technology for the Ashra experiment to realize a much lower pixel cost in comparison with other experiments using photomultiplier arrays at the focal surface. In this paper we present the design and performance of the 20-in. PLI.

Asaoka, Yoichi; 10.1016/j.nima.2011.05.036

2011-01-01

230

Thermal-hydraulic performance of heavy liquid metal in straight-tube and U-tube heat exchangers  

International Nuclear Information System (INIS)

Motivated by an increased interest in heavy liquid metal (lead or lead alloy) cooled fast reactors (LFR) and accelerator-driven system (ADS), the present paper presents a study on resistance characteristics and heat transfer performance of liquid lead bismuth eutectic (LBE) flow through a straight-tube heat exchanger and a U-tube heat exchanger. The investigation is performed on the TALL test facility at KTH. The heat exchangers have counter-current flow arrangement, and are made from a pair of 1-m-long concentric ducts, with the LBE flowing in the inner tube of 10 mm I.D. and the secondary coolant flowing in the annulus. The inlet temperature of LBE into the heat exchangers is from 200 deg. C to 450 deg. C with temperature drops from 0 deg. C to 100 deg. C within the LBE flow range of Re = 104-105. Analysis of the experimental results obtained provides a basic understanding and quantification of the regimes of lead-bismuth flow and heat transfer through a straight tube and a U-shaped tube. The unique data base also serves as benchmark and improvement for system thermal-hydraulic codes (e.g. RELAP, TRAC/AAA) whose development and testing were dominantly driven by applications in water-cooled systems. Lessons and insights learnt from the study and recommendations for the heat exchanger selection are discussed.

231

Steam generator tube performance: experience with water-cooled nuclear power reactors during 1979  

International Nuclear Information System (INIS)

The performance of steam generator tubes in water-cooled nuclear power reactors has been reviewed for 1979. Tube failures occurred at 38 of the 93 reactors surveyed. Causes of these failures and procedures designed to deal with them are described. The defect rate was twice that in 1978 but still lower than the two previous years. Methods being employed to detect defects include increasing use of multifrequency eddy-current testing and a trend to full-length inspection of all tubes. To reduce the incidence of tube failures by corrosion, plant operators are turning to full-flow condensate demineralization and more leak-resistant condenser tubes. (author)

232

Experimental investigation on carbon nano tubes coated brass rectangular extended surfaces  

International Nuclear Information System (INIS)

Finned surface has been extensively used for free convection cooling of internal combustion engines and several electronic kits etc. Here rectangular brass fin was preferred for analysis. Thermocouples were attached all over the surface of the fin in equal distances. The measurement of surface temperature and calculated convective heat transfer rate were reported for several heat input values. The overall system performance can be improved by enhancing heat transfer rate of extended surfaces. Based on the above requirement, brass surface was coated by carbon nano tubes. The temperature and heat transfer characteristics were investigated using Taguchi method for experimental design. Finally the performances of coated and non-coated rectangular brass fins were compared. The average percentage of increase in heat transfer rate was proved around 12% for carbon nanocoated rectangular brass fins. - Graphical abstract: The designed Natural and Forced convection Heat Transfer Test Rig measures the enhanced rate of heat transfer for nano coated rectangular fins than in non-coated fins. Highlights: ? Rectangular brass fins were preferred for convective heat transfer process. ? The rectangular brass fins are coated with multi wall carbon nano tubes in EBPVD process with nanometer thickness. ? Temperature and heat transfer rate were investigated for nanocoated and non-coated fins by using Taguchi method. ? Multi wall carbon nanotubes act as a pin fin to enhance surface aras a pin fin to enhance surface area for effective convective heat transfer rate.

233

New ferritic stainless steel tube for heat exchangers  

International Nuclear Information System (INIS)

Newly developed processes have made ferritic alloy tube competitive in cost and performance to Type 304 stainless steel in heat exchanger applications. The new corrosion-resistant alloys are being used in integrally finned moisture separator reheater tubes for nuclear power plant retubing projects

234

Single endoscopist-performed percutaneous endoscopic gastrostomy tube placement  

Directory of Open Access Journals (Sweden)

Full Text Available AIM: To investigate whether single endoscopist-performed percutaneous endoscopic gastrostomy (PEG is safe and to compare the complications of PEG with those reported in the literature. METHODS: Patients who underwent PEG placement between June 2001 and August 2011 at the Baskent University Alanya Teaching and Research Center were evaluated retrospectively. Patients whose PEG was placed for the first time by a single endoscopist were enrolled in the study. PEG was performed using the pull method. All of the patients were evaluated for their indications for PEG, major and minor complications resulting from PEG, nutritional status, C-reactive protein (CRP levels and the use of antibiotic treatment or antibiotic prophylaxis prior to PEG. Comorbidities, rates, time and reasons for mortality were also evaluated. The reasons for PEG removal and PEG duration were also investigated. RESULTS: Sixty-two patients underwent the PEG procedure for the first time during this study. Eight patients who underwent PEG placement by 2 endoscopists were not enrolled in the study. A total of 54 patients were investigated. The patients’ mean age was 69.9 years. The most common indication for PEG was cerebral infarct, which occurred in approximately two-thirds of the patients. The mean albumin level was 3.04 ± 0.7 g/dL, and 76.2% of the patients’ albumin levels were below the normal values. The mean CRP level was high in 90.6% of patients prior to the procedure. Approximately two-thirds of the patients received antibiotics for either prophylaxis or treatment for infections prior to the PEG procedure. Mortality was not related to the procedure in any of the patients. Buried bumper syndrome was the only major complication, and it occurred in the third year. In such case, the PEG was removed and a new PEG tube was placed via surgery. Eight patients (15.1% experienced minor complications, 6 (11.1% of which were wound infections. All wound infections except one recovered with antibiotic treatment. Two patients had bleeding from the PEG site, one was resolved with primary suturing and the other with fresh frozen plasma transfusion. CONCLUSION: The incidence of major and minor complications is in keeping with literature. This finding may be noteworthy, especially in developing countries.

Askin Erdogan

2013-01-01

235

Measured performance of a solar water heater with a parallel tube polymer absorber  

Energy Technology Data Exchange (ETDEWEB)

We performed calibrated side-by-side measurements of the thermal performance of solar water heaters with spaced polypropylene tube absorbers in identical glazed and insulated collector boxes. This was to determine the influence of tube spacing and tube height above the back insulation. A low flow rate (4.32 g s[sup [minus]1] m[sup [minus]2]) was used. As the number of tubes (spaced over the same aperture) is increased by 76.3% (from 38 to 67), the mean mid day efficiency increases by only 12.9% (7.4 percentage points), from 57.2% to 64.6%. It may therefore be more cost effective to use fewer, more widely spaced tubes. As tube height h above the insulation increased from the lowest value (3 mm) to the next (8 mm), the thermal efficiency dropped 1.4 percentage points. From h = 8 to 28 mm, the efficiency was almost independent of h.

Van Niekerk, W.M.K.; Scheffler, T.B. (Univ. of Pretoria (South Africa))

1993-11-01

236

Assessment of beam tube performance for the maple research reactor  

International Nuclear Information System (INIS)

The MAPLE research reactor is a versatile new research facility that can be adapted to meet the requirements of a variety of reactor applications. A particular group of reactor applications involves the use of beams of radiation extracted from the reactor core via tubes that penetrate through the biological shield and terminate in the reflector surrounding the fuelled core. An assessment is given of the neutron and gamma radiation fields entering beam tubes that are located radially or tangentially with respect to the core

237

Assessment of beam tube performance for the MAPLE research reactor  

International Nuclear Information System (INIS)

The MAPLE research reactor is a versatile new research facility that can be adapted to meet the requirements of a variety of reactor applications. A particular group of reactor applications involve the use of beams of radiation extracted from the reactor core via tubes that penetrate through the biological shield and terminate in the reflector surrounding the fuelled core. An assessment of the neutron and gamma radiation fields entering beam tubes that are located radially or tangentially with respect to the core is given

238

AIRS PFM Pulse Tube Cooler System-level Performance  

Science.gov (United States)

JPL's Atmospheric Infrared Sounder (AIRS) instrument is being built to make precision measurements of air temperature over the surface of the Earth as a function of elevation; the flight instrument is in the final stages of assembly and checkout at this time, and uses a pair of TRW pulse tube cryocoolers operating at 55K to cool its sensitive IR focal plane.

Ross, R.; Johnson, D.; Collins, S.; Green, K.; Wickman, H.

1998-01-01

239

Condensation of Refrigerant-11 on the outside of horizontal and inclined enhanced tubes  

Energy Technology Data Exchange (ETDEWEB)

Heat transfer condensation tests with Refrigerant-11 were performed on the outside of a smooth tube and a variety of enhanced tubes oriented horizontally and at various tube inclinations. One smooth tube and seven enhanced (externally fluted, roped, spiraled, and externally finned) tubes of 2.54-cm (1-in.) nominal outside diameter and 1.17-m (4-ft) length were tested. Several of the tested tubes featured internal enhanced geometries, which were caused by the heat transfer enhancing geometry on the tube's external surface. Condensing heat transfer coefficients are reported as composite coefficients, which combine the resistance of the condensing film and the tube wall, and are based on total tube outside surface area. Results show that in the horizontal condensing mode, the rank order (best to worst) of the tube geometries tested was spiral-shaped tubes, rope-shaped tubes, smooth tube, externally finned tube, and externally fluted tube. For a spiral-shaped tube, horizontal composite coefficients were up to 2.0 times the corresponding horizontal smooth tube values. For tilt angles greater than or equal to 60/sup 0/ from the horizontal, the condensing performance of the externally fluted tube was best of all the tubes tested.

Domingo, N.

1982-12-01

240

Numerical optimization of louvered fin heat exchanger with variable louver angles  

Science.gov (United States)

Several studies of the louvered fin heat exchanger have already been done. Both experimental and numerical studies are available. Investigations to the optimal louver angle have been performed, many times in combination with other fin parameters such as louver pitch and fin thickness. Most studies assume a single louver angle for all the louvers in the heat exchanger. Hsieh and Jang [1] on the other hand studied the effect of a variable louver angle for 5 different cases with successively increasing or decreasing louver angles. Tube-fin interactions were not taken into account. In this study, a round tube and fin geometry with individually varying louver angles is analyzed. The thickness of the fin was neglected. Any interactions between the optimal louver angles and the fin thickness are hence not captured. A laminar and steady calculation was performed, with symmetric boundary conditions. For the Reynolds number on the hydraulic diameter (ReDh) of 535 that was studied, a Von Karman vortex street is present behind the last tube row of heat exchanger. The steady calculation is hence only an approximation of the reality, but is shown to give reasonable results. An ordinary kriging response surface model was used to explore the entire parameter space. Updates to the model were made on the basis of improving the Pareto front, visualizing the tradeoff between heat transfer and pressure drop. It is shown that the use of individually varying louver angles allows increasing the Colburn j factor by 1.3% for the same friction factor, with respect to the optimal uniform louvered fin configuration.

Ameel, B.; Degroote, J.; Huisseune, H.; De Jaeger, P.; Vierendeels, J.; De Paepe, M.

2012-11-01

 
 
 
 
241

Numerical optimization of louvered fin heat exchanger with variable louver angles  

International Nuclear Information System (INIS)

Several studies of the louvered fin heat exchanger have already been done. Both experimental and numerical studies are available. Investigations to the optimal louver angle have been performed, many times in combination with other fin parameters such as louver pitch and fin thickness. Most studies assume a single louver angle for all the louvers in the heat exchanger. Hsieh and Jang [1] on the other hand studied the effect of a variable louver angle for 5 different cases with successively increasing or decreasing louver angles. Tube-fin interactions were not taken into account. In this study, a round tube and fin geometry with individually varying louver angles is analyzed. The thickness of the fin was neglected. Any interactions between the optimal louver angles and the fin thickness are hence not captured. A laminar and steady calculation was performed, with symmetric boundary conditions. For the Reynolds number on the hydraulic diameter (ReDh) of 535 that was studied, a Von Karman vortex street is present behind the last tube row of heat exchanger. The steady calculation is hence only an approximation of the reality, but is shown to give reasonable results. An ordinary kriging response surface model was used to explore the entire parameter space. Updates to the model were made on the basis of improving the Pareto front, visualizing the tradeoff between heat transfer and pressure drop. It is shown that the use of individually varying louver angles allows individually varying louver angles allows increasing the Colburn j factor by 1.3% for the same friction factor, with respect to the optimal uniform louvered fin configuration.

242

Steam generator tube performance: experience with water-cooled nuclear power reactors during 1982  

International Nuclear Information System (INIS)

A review of the performance of steam generator tubes in 116 water-cooled nuclear power reactors showed that tubes were plugged at 54 (46%) of the reactors. The number of tubes removed from service decreased from 4692 (0.30%) in 1981 to 3222 (0.20%) in 1982. Leading causes of tube failures were stress corrosion cracking from the primary side, stress corrosion cracking (or intergranular attack) from the secondary side, and pitting corrosion. From the secondary side, the lowest incidence of corrosion-induced defects occurred in reactors that have used only volatile treatment, with or without condensate demineralization

243

Development and performance of resistive seamless straw-tube gas chambers  

International Nuclear Information System (INIS)

A new straw-tube gas chamber which is made of seamless straw-tubes, instead of ordinary wound-type straw-tubes is developed. Seamless straw-tubes have various advantages over ordinary wound-type ones, in particular, in terms of mechanical strength and lesser wall thickness. Our seamless straw-tubes are fabricated to be resistive so that the hit positions along the straw axis can be read by cathode planes placed outside the straw-tube chambers, where the cathode strips run transverse to the straw axis. A beam test was carried out at KEK to study their performance. As a result of the beam test, the position resolution of the cathode strips of 220?m is achieved, and an anode position resolution of 112?m is also obtained

244

Steam generator tube performance: experience with water-cooled nuclear power reactors during 1983 and 1984  

International Nuclear Information System (INIS)

A review of the performance of steam generator tubes in water-cooled nuclear power reactors showed that tubes were plugged at 47 (35.6%) of the reactors in 1983 and at 63 (42.6%) of the reactors during 1984. In 1983 and 1984 3291 and 3335 tubes, respectively, were removed from service, about the same as in 1982. The leading causes assigned to tube failure were stress corrosion cracking from the primary side and stress corrosion cracking or intergranular attack from the secondary side. In addition 5668 tubes were repaired for further service by installation of internal sleeves. Most of these were believed to have deteriorated by one of the above mechanisms or by pitting. There is a continuing trend towards high-integrity condenser tube materials at sites cooled by brackish or sea water. 31 refs

245

Improving the RF Performance of Carbon Nano tube Field Effect Transistor  

International Nuclear Information System (INIS)

Compact model of single-walled semiconducting carbon nano tube field-effect transistors (CNTFETs) implementing the calculation of energy conduction subband minima under VHDLAMS simulator is used to explore the high-frequency performance potential of CNTFET. The cutoff frequency expected for a MOSFET-like CNTFET is well below the performance limit, due to the large parasitic capacitance between electrodes. We show that using an array of parallel nano tubes as the transistor channel combined in a finger geometry to produce a single transistor significantly reduces the parasitic capacitance per tube and, thereby, improves high-frequency performance.

246

Effect of Gate Length Scaling on Various Performance Parameters in DG-FinFETs: a Simulation Study  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a simulation study on the gate length scaling of a double gate (DG FinFET. To achieve channel lengths smaller than 20 nm, innovative device architectures will be necessary to continue the benefits previously acquired through scaling. In order to obtain desirable control of short channel effects (SCEs, the thickness or the horizontal width of a fin in a FinFET should be less than two-third of its gate length and the semiconductor fin should be thin enough in the channel region to ensure forming fully depleted device. The effect of decreasing gate length (Lg is to deplete more of the region under the inversion layer, which can be easily visualized if the source and drain are imagined to approach one another. If the channel length L is made too small relative to the depletion regions around the source and drain, the SCEs associated with charge sharing and punch through can become intolerable. Thus, to make L small, the depletion region widths should be made small. This can be done by increasing the substrate doping concentration and decreasing the reverse bias. Drain induced barrier lowering (DIBL increases as gate length is reduced, even at zero applied drain bias, because the source and drain form pn junction with the body, and have associated built-in depletion layers associated with them that become significant partners in charge balance at short channel lengths, even with no reverse bias applied to increase depletion width. The subthreshold slope increases as the device becomes shorter. In fact, when the device becomes very short, the gate no longer controls the drain current and the device cannot be turned off. This is caused by punch through effect. The subthreshold swing (SS changes with the drain voltage.

Rakesh Vaid

2012-10-01

247

Heat transfer performance of condenser tubes in an MSF desalination system  

Energy Technology Data Exchange (ETDEWEB)

The present research examines the amount of condensed fresh water off the outer-side surface of heat exchangers in an MSF system. The quantitative modeling of condensed water on the outer surface of comparable tubes, enhanced and plain, in a simulated MSF technique is investigated. An adapted simulation design on a test-rig facility, accounting for the condenser tubing in actual industrial desalination plate-form, is used with corrugated and smooth aluminum-brass material tubes 1100mm long and 23mm bore. A single phase flow of authentic brine water that typifies real fouling is utilized to simulate the actual environmental life of a multi-stage flashing desalination system, with coolant flow velocity 0.1 m/s in the two delineated types of condenser tubing. It is demonstrated that the condensate water amount from the specified enhanced tube is about 1.22 times the condensate water amount from the smooth tube, adaptive for 140 running hours under deliberated constrains. The topic covers a comparative analysis of thermal performance. Comparing results with fresh water confirm the effect of fouling on significantly lowering the value of the overall heat transfer coefficient versus time. Fouling resistance R{sub f} is reported with the critical coolant flow speed of 0.1 m/s. Comparison between the fouling resistance for both smooth and corrugated tubes versus time is performed. The fouling thermal resistance of the corrugated tube is 0.56 of the fouling thermal resistance of the smooth tube after140 running hours of the experiment are concluded. Overall, in the case of real brine, results prove that heat performance for the corrugated tube is superior to the plain tube over the studied time period (140 hrs) for the chosen range of flow speeds

Galal, T.; Kalendar, A.; Al Saftawi, A.; Zedan, M. [Public Authority for Applied Education and Training, Shuwaikh (Kuwait)

2010-11-15

248

Effect of marine biofouling on the heat transfer performance of titanium condenser tubes  

International Nuclear Information System (INIS)

The fouling of the sea water side surfaces of condenser tubes lowers their heat transfer and affects the efficiency of thermal and nuclear power stations. Recently, with the rise of energy cost, the economical and technical interests on this problem have increased. Titanium tubes have very excellent corrosion resistance in sea water, but are apt to undergo biofouling since they are non-poisonous. In this study, titanium tubes and aluminum brass tubes were compared regarding biofouling, and as the countermeasures, the effect of the frequent cleaning with Carborundum balls was compared with other methods. On the basis of these results, the heat transfer performance of the titanium tubes cleaned frequently with Carborundum balls was examined. A model condenser in the Atsumi Power Station, Chubu Electric Power Co., Inc., was used for the experiment. The experiment was commenced on November 6, 1976, and finished on April 5, 1979. The tubes tested, the test conditions, and the measurement of the coefficient of overall heat transmission and the calculation of the fouling factor are explained. For the prevention of the biofouling of titanium tubes, the frequent cleaning with Carborundum balls was very effective, and these titanium tubes showed the same coefficient of overall heat transmission as the aluminum brass tubes cleaned with sponge balls. (Kako, I.)

249

Performance comparison of high speed microchannel plate photomultiplier tubes  

Science.gov (United States)

The transit time spread characteristics of high speed microchannel photomultipliers has improved since the upgrade of the NASA CDSLR network to MCP-PMT's in the mid-1980's. The improvement comes from the incorporation of 6 micron (pore size) microchannels and offers significant improvement to the satellite ranging precision. To examine the impact on ranging precision, two microchannel plate photomultiplier tubes (MCP-PMT) were evaluated for output pulse characteristics and temporal jitter. These were a Hamamatsu R 2566 U-7 MCP-PMT (6 micron) and an ITT 4129f MCP-PMT (12 micron).

Varghese, Thomas; Selden, Michael; Oldham, Thomas

1993-01-01

250

Performance of a Compact Gamma Tube Interrogation Source  

International Nuclear Information System (INIS)

Active interrogation with high-energy monoenergetic gammas can induce photofission signals in fissile materials while minimizing absorbed radiation dose and background from surrounding materials. A first-generation axial-type gamma generator has been developed that utilizes the 11B(p,?)12C nuclear reaction at a 163 keV resonance to produce monoenergetic 12-MeV gamma-rays. The gamma tube employs a water-cooled cylindrical radio frequency (if) induction ion source capable of producing a proton current density of up to 100 mA/cm2. The extracted proton beam bombards a lanthanum hexaboride (LaB6) target at energies up to 200 keV. The 12-MeV gamma intensity was measured as a function of proton energy, beam current, and angle. Photofission-induced neutrons from depleted uranium (DU) were measured and compared to MCNPX calculations. After extended operation, the high power density of the proton beam was observed to cause damage to the LaB6 target and the gamma tube improvements currently being made to mitigate this damage are discussed.

251

Performance of a Compact Gamma Tube Interrogation Source  

Science.gov (United States)

Active interrogation with high-energy monoenergetic gammas can induce photofission signals in fissile materials while minimizing absorbed radiation dose and background from surrounding materials. A first-generation axial-type gamma generator has been developed that utilizes the 11B(p,?)12C nuclear reaction at a 163 keV resonance to produce monoenergetic 12-MeV gamma-rays. The gamma tube employs a water-cooled cylindrical radio frequency (if) induction ion source capable of producing a proton current density of up to 100 mA/cm2. The extracted proton beam bombards a lanthanum hexaboride (LaB6) target at energies up to 200 keV. The 12-MeV gamma intensity was measured as a function of proton energy, beam current, and angle. Photofission-induced neutrons from depleted uranium (DU) were measured and compared to MCNPX calculations. After extended operation, the high power density of the proton beam was observed to cause damage to the LaB6 target and the gamma tube improvements currently being made to mitigate this damage are discussed.

King, Michael J.; Antolak, Arlyn J.; Leung, Ka-Ngo; Morse, Dan H.; Raber, Thomas N.; Doyle, Barney L.

2009-03-01

252

Relationship between pressure tube processing, impurity/alloying element concentrations and performance in CANDU reactors  

International Nuclear Information System (INIS)

In a CANDU reactor, pressure tubes of cold-worked Zr-2.5 Nb material are used in the reactor core to contain the fuel bundles and the heavy water (D2O) coolant. Under normal operating conditions the pressure tubes are exposed to an operating environment of high fast neutron flux, D2O coolant flow rate and temperature for up to 30 years. To ensure that these tubes will perform acceptably over their design life in such an environment, their behaviour has been monitored in relation two variations in the manufacturing processes used to produce them and their alloying/impurity element concentrations. For example, elongation data are available for all tubes in most reactors, over 2000 deuterium concentration measurements are available from operating tubes, transverse strain profiles have been determined by inspection of approximately 100 tubes and mechanical properties, fracture toughness and microstructural data are available from about 50 tubes removed from reactors, the largest proportion of which were taken from the Pickering 3 and 4 Nuclear Generating Stations when these reactors were re-tubed. Evaluations of the information provided by these measurements of the characteristics of tubes that have seen power reactor service, combined with corresponding results from laboratory experiments of unirradiated pressure tube material and similar material irradiated in research reactors, have yielded relationships between the property changes and the manufaetween the property changes and the manufacturing process and alloying/impurity concentration levels of the tubes. This information is being exploited to improve the performance of pressure tubes in present and future CANDU reactors. For example, evidence is presented to show that reductions in Cl and, to a lesser extent, P and C, substantially increase the fracture toughness after irradiation, and that increasing the Fe concentration will result in a significant reduction in the elongation rate of the tubes. Some of the relationships found in these studies have already been factored into the pressure tube specification for recent reactors while others will be included in the near future. These changes will allow the pressure tubes to reach their design lives with greater margins

253

Thermal-hydraulic performance of Vipertex 1EHT enhanced heat transfer tubes  

International Nuclear Information System (INIS)

Heat transfer enhancement plays an important role in improving energy efficiency. Transition from laminar to turbulent flow for smooth tubes is typically assumed to occur for a Reynolds Number of approximately 2,300. Vipertex 1EHT enhanced tubes produce an early transition at Reynolds Numbers near 750 and for the same conditions they can provide the same amount of heat transfer that smooth tubes produce for flows that are twenty times greater. Low Reynolds Number flow (sometimes due to the lack of process water) is a typical process requirement in many areas of the world and can cause major design challenges. Use of Vipertex 1EHT enhanced heat transfer tubes can decrease process water requirements and provide higher performance levels within the same equipment footprint. In a comparison of the heat transfer for some constant flow rates, the Vipertex 1EHT surface can produce heat transfer increases of more than 500% when compared to smooth tubes. Advantages of the Vipertex 1EHT design (when compared to smooth tubes) include the maximization of heat transfer; minimization of operating costs; and/or minimization of the rate of surface fouling. These enhanced tubes recover more energy and provide an opportunity to advance the design of many heat transfer products. -- Highlights: • Vipertex 1EHT tubes produce heat transfer increases of almost 550% for a friction factor penalty of only 33%. • 1EHT tubes at a Re = 750 provides the same amount of heat transfer that smooth tube does for twenty times that value. • Vipertex 1EHT series of tubes provides a means to significantly advance many heat exchange processes

254

Tube-type heat exchanger  

International Nuclear Information System (INIS)

The tube-type heat exchanger consists of a cylindrical casing in which are mounted U shaped heat exchange tubes anchored in a tube plate. The individual tubes of the inlet and outlet branch are fitted in support partitions normal to the axis of the tubes and provided with fins. The length of the fin equals half of the length of the chord of the support partition. The fins of the partitions of the inlet branch fit close to the partitions of the outlet branch and vice versa. The fin nearest to the tube plate comes into contact with the inner wall of the tube plate. Support partitions, fins and the inner surface of the casing thus form a helical throughflow channel to which are tangentially connected the inlet and outlet necks. (E.S.)

255

A biorobotic model of the sunfish pectoral fin for investigations of fin sensorimotor control  

Energy Technology Data Exchange (ETDEWEB)

A comprehensive understanding of the control of flexible fins is fundamental to engineering underwater vehicles that perform like fish, since it is the fins that produce forces which control the fish's motion. However, little is known about the fin's sensory system or about how fish use sensory information to modulate the fin and to control propulsive forces. As part of a research program that involves neuromechanical and behavioral studies of the sunfish pectoral fin, a biorobotic model of the pectoral fin and of the fin's sensorimotor system was developed and used to investigate relationships between sensory information, fin ray motions and propulsive forces. This robotic fin is able to generate the motions and forces of the biological fin during steady swimming and turn maneuvers, and is instrumented with a relatively small set of sensors that represent the biological lateral line and receptors hypothesized to exist intrinsic to the pectoral fin. Results support the idea that fin ray curvature, and the pressure in the flow along the wall that represents the fish body, capture time-varying characteristics of the magnitude and direction of the force created throughout a fin beat. However, none of the sensor modalities alone are sufficient to predict the propulsive force. Knowledge of the time-varying force vector with sufficient detail for the closed-loop control of fin ray motion will result from the integration of characteristics of many sensor modalities.

Phelan, Chris; Tangorra, James [Department of Mechanical Engineering, Drexel University, Philadelphia, PA 19104 (United States); Lauder, George [Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138 (United States); Hale, Melina, E-mail: tangorra@coe.drexel.ed [Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637 (United States)

2010-09-15

256

A biorobotic model of the sunfish pectoral fin for investigations of fin sensorimotor control  

International Nuclear Information System (INIS)

A comprehensive understanding of the control of flexible fins is fundamental to engineering underwater vehicles that perform like fish, since it is the fins that produce forces which control the fish's motion. However, little is known about the fin's sensory system or about how fish use sensory information to modulate the fin and to control propulsive forces. As part of a research program that involves neuromechanical and behavioral studies of the sunfish pectoral fin, a biorobotic model of the pectoral fin and of the fin's sensorimotor system was developed and used to investigate relationships between sensory information, fin ray motions and propulsive forces. This robotic fin is able to generate the motions and forces of the biological fin during steady swimming and turn maneuvers, and is instrumented with a relatively small set of sensors that represent the biological lateral line and receptors hypothesized to exist intrinsic to the pectoral fin. Results support the idea that fin ray curvature, and the pressure in the flow along the wall that represents the fish body, capture time-varying characteristics of the magnitude and direction of the force created throughout a fin beat. However, none of the sensor modalities alone are sufficient to predict the propulsive force. Knowledge of the time-varying force vector with sufficient detail for the closed-loop control of fin ray motion will result from the integration of characteristics of many sensor modalities.

257

Optimized transcritical CO{sub 2} heat pumps: Performance comparison of capillary tubes against expansion valves  

Energy Technology Data Exchange (ETDEWEB)

A capillary tube based CO{sub 2} heat pump is unique because of the transcritical nature of the system. The transcritical cycle has two independent parameters, pressure and temperature, unlike the subcritical cycle. In the present study, a steady state simulation model has been developed to evaluate the performance of a capillary tube based transcritical CO{sub 2} heat pump system for simultaneous heating and cooling at 73 C and 4 C, respectively against optimized expansion valve systems. Capillary tubes of various configurations having diameters of 1.4, 1.5 and 1.6 mm along with internal surface roughness of 0.001-0.003 mm have been tested to obtain the optimum design and operating conditions. Subcritical and supercritical thermodynamic and transport properties of CO{sub 2} are calculated employing a precision in-house property code. It is observed that the capillary tube system is quite flexible in response to changes in ambient temperature, almost behaving to offer an optimal pressure control. System performance is marginally better with a capillary tube at higher gas cooler exit temperature. Capillary tube length turns out to be the critical parameter that influences system optimum conditions. A novel nomogram has been developed that can be employed as a guideline to select the optimum capillary tube. (author)

Agrawal, Neeraj; Bhattacharyya, Souvik [Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

2008-05-15

258

Steam generator tube performance: experience with water-cooled nuclear power reactors during 1978  

International Nuclear Information System (INIS)

The performance of steam generator tubes in water-cooled nuclear power reactors has been reviewed for 1978. Tube failures occurred at 31 of the 86 reactors surveyed. Causes of these failures and procedures designed to deal with them are described. A dramatic decrease in the number of tubes plugged was evident in 1978 compared to the previous year. This is attributed to diligent application of techniques developed from in-plant experience and research and development programs over the past several years. (auth)

259

Steam-generator tube performance: world experience with water-cooled nuclear power reactors during 1977  

International Nuclear Information System (INIS)

The performance of steam-generator tubes in water-cooled nuclear power reactors in various countries is reviewed for 1977. Tube failures were reported at 34 of the 79 reactors surveyed. The causes of these failures and the inspection and repair procedures designed to deal with them are presented. Although denting caused by corrosion remained the leading cause of tube failures, specific mechanisms have been identified, and methods of dealing with them have been developed. These methods are being applied and should lead to a reduction of corrosion failures in the future

260

Evaluation of a Fin and Tube Type Adsorber/Desorber Heat Exchanger using =ACF/C2H5OH Pair  

Science.gov (United States)

This study deals with the experiment to clarify the characteristics of adsorption refrigeration system employing activated carbon fiber (ACF) and ethanol pair and to evaluate the performance of adsorber/desorber heat exchanger defined by two kind of index to the system performance. The experiments are carried out by varying system running parameters such as regeneration temperature for adsorber, ethanol temperature in the evaporator, pre-heating/cooling cycle time, adsorption/desorption cycle time. Regeneration temperature for adsorber is from 60 to 90 °C and ethanol temperature is from 0 to 20 °C and pre-heating/cooling cycle time is 60 and 120 second and adsorption/desorption cycle time is from 120 to 300 second. Results show that the system can be operated with regeneration temperature of 60 °C and the system performance improves with increase of ethanol temperature. It is also found that the system performance is affected by regeneration temperature for adsorber and the pre-heating/cooling cycle time and adsorption/desorption cycle time.

Kariya, Keishi; Makimoto, Naoya; Kuwahara, Ken; Koyama, Shigeru

 
 
 
 
261

Experimental investigation of thermal-hydraulic performance of PCCS with horizontal tube heat exchangers: single U-tube test  

Energy Technology Data Exchange (ETDEWEB)

JAERI and JAPC started a cooperative study to verify performance of a PCCS (Passive Containment Cooling System) using horizontal heat exchanger for next-generation BWR in 1998. A test facility with a horizontal single U-tube was constructed in JAERI in 1999 to investigate fundamental condensation behavior under influences of non-condensable gas. Preliminary pre-test analyses were performed using RELAP5/ MOD3.2.1.2 code to expect the experimental outcomes by incorporating a correlation for condensation degradation because of non-condensable gas by Ueno et al. for better prediction. Preliminary results from both experiments (shakedown) and pre-test analyses indicated that the PCCS using horizontal U-tube heat exchanger is promising. Steam generated under assumed severe accident conditions; steam generation rate approx. = 1% core power, non-condensable gas concentration of 1% and simulated containment vessel pressure of 0.7 MPa, was totally condensed with a small differential pressure across inlet and outlet plenum. Experimental data will be accumulated to develop models and correlations for a better prediction of responses of the PCCS using horizontal heat exchanger during postulated severe accidents. (author)

Nakamura, Hideo; Anoda, Yoshinari [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Tabata, Hiroaki; Obata, Hiroyuki [Japan Atomic Power Co., Tokyo (Japan); Arai, Kenji; Kurita, Tomohisa [Nuclear Engineering Lab., Toshiba Co., Kawasaki, Kanagawa (Japan)

2000-11-01

262

Experimental investigation of thermal-hydraulic performance of PCCS with horizontal tube heat exchangers: single U-tube test  

International Nuclear Information System (INIS)

JAERI and JAPC started a cooperative study to verify performance of a PCCS (Passive Containment Cooling System) using horizontal heat exchanger for next-generation BWR in 1998. A test facility with a horizontal single U-tube was constructed in JAERI in 1999 to investigate fundamental condensation behavior under influences of non-condensable gas. Preliminary pre-test analyses were performed using RELAP5/ MOD3.2.1.2 code to expect the experimental outcomes by incorporating a correlation for condensation degradation because of non-condensable gas by Ueno et al. for better prediction. Preliminary results from both experiments (shakedown) and pre-test analyses indicated that the PCCS using horizontal U-tube heat exchanger is promising. Steam generated under assumed severe accident conditions; steam generation rate approx. = 1% core power, non-condensable gas concentration of 1% and simulated containment vessel pressure of 0.7 MPa, was totally condensed with a small differential pressure across inlet and outlet plenum. Experimental data will be accumulated to develop models and correlations for a better prediction of responses of the PCCS using horizontal heat exchanger during postulated severe accidents. (author)

263

High Fin Width Mosfet Using Gaa Structure  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes the design and optimization of gate-all-around (GAA MOSFETs structures. The optimum value of Fin width and Fin height are investigated for superior subthreshold behavior. Also the performance of Fin shaped GAA with gate oxide HfO2 are simulated and compared with conventional gate oxide SiO2 for the same structure. As a result, it was observed that the GAA with high K dielectric gate oxide has more possibility to optimize the Fin width with improved performance. All the simulations are performed on 3-D TCAD device simulator.

S.L.Tripathi

2012-11-01

264

Heat transfer augmentation due to surface radiative exchange effect of internal fins in an annulus  

International Nuclear Information System (INIS)

Heat transfer augmentation due to surface radiation in an annulus with fins was investigated both theoretically and experimentally for fully developed laminar flow. The system considered in the present study was an array of axially internal and straight fins attached to the outer tube wall. Analytical solutions were given for 4, 8, 16, 24, 32 fins and for the ratios of the fin height to the passage clearance, 0, 0.2, 0.4, 0.5, 0.6, 0.8. The experiments were performed with air as the working fluid for radius ratio of 1.45, 16 fins and for Reynolds numbers ranging from 500 to 2000. The numerically predicted results of the convective/radiative heat transfer for the present case were in good agreement with the experimental data. It was found that the heat transfer augmentation coefficient attained a maximum value of 1.45 for 32 fins and for a dimensionless fin height of 0.65

265

Performance studies of tubular flat plate collectors  

International Nuclear Information System (INIS)

Computations have been performed for flat plate efficiency factor, heat removal factor, heat gained by fluid for different materials used for the tubes and fins of flat plate tubular solar collectors. 3 refs, 17 figs, 4 tabs

266

Experimental investigation of self heating effect (SHE) in multiple-fin SOI FinFETs  

Science.gov (United States)

In this work, the self-heating effect (SHE) on metal gate multiple-fin SOI FinFETs is studied by adopting the ac conductance technique to extract the thermal resistance and temperature rise in both n-channel and p-channel SOI FinFETs with various geometry parameters. It is shown that the SHE degrades by over 10% of the saturation output current in the n-channel and by over 7% in the p-channel. The extracted thermal resistances Rth increase with the scaled down gate length, reducing the number of fin and shrinking the fin width. The temperature rise caused by the SHE increases with the scaled down gate length, increasing the number of fin and shrinking the fin width under the saturated operation condition. Additionally, due to a larger power density in the n-channel SOI FinFETs under the same bias condition, the temperature in the n-channel FinFETs is higher than that in the p-channel FinFETs. Because the Si thermal conductivity decreases as the temperature increases, Rth is larger in the n-channel FinFETs than in the p-channel FinFETs. Therefore, tradeoffs have to be made between the thermal properties and the device’s electrical performance by careful design optimizations of SOI FinFETs.

Jiang, Hai; Xu, Nuo; Chen, Bing; Zeng, Lang; He, Yandong; Du, Gang; Liu, Xiaoyan; Zhang, Xing

2014-11-01

267

Performance Study of Concrete-Filled Steel Tubes  

Directory of Open Access Journals (Sweden)

This type of structure can be used in Algeria for rehabilitating old buildings, or strengthening reinforced concretecolumns to improve their structural performance. However, new regulatory measures should be considered in order tointroduce this compound element in the construction.

Chair A.

2014-04-01

268

Steam generator tube performance: experience with water-cooled nuclear power reactors during 1980  

International Nuclear Information System (INIS)

The performance of steam generator tubes in water-cooled nuclear power reactors has been reviewed for 1980. Tube defects occurred at 38% of the 97 reactors surveyed. This is a marginal improvement over 1979, when defects occurred at 41% of the reactors. The number of failed tubes was also lower, 0.14% of the tubes in service in 1980 compared with 0.20% of those in service in 1979. Causal analysis of these failures indicates that stress-corrosion cracking was the leading failure mechanism. Reactors that used all-volatile treatment of secondary water with or without full-flow condensate demineralization since startup showed the lowest incidence of corrosion-related defects

269

HEAT TRANSFER EVALUATION OF HFC-236EA WITH HIGH PERFORMANCE ENHANCED TUBES IN CONDENSATION AND EVAPORATION  

Science.gov (United States)

The report gives results of an evaluation of the heat transfer performance of pure hydrofluorocarbon (HFC)-236ea for high performance enhanced tubes which had not been previously used in Navy shipboard chillers. Shell-side heat transfer coefficient data are presented for conde...

270

The Effect of the Capillary Tube Coil Number on the Refrigeration System Performance  

Directory of Open Access Journals (Sweden)

Full Text Available The capillary tube performance for (R134a is experimentally investigated. The experimental setup is a real vapor compression refrigeration system. All properties of the refrigeration system are measured for various mass flow rate from (13 – 23 kg/hr and capillary tube coil number (0-4 with fixed length (150 cm and capillary diameter(2.5mm.The results showed that the theoretical compression power increases by (65.8 % as the condenser temperature increases by (2.71%, also the theoretical compression power decreases by (10.3 % as the capillary tube coil number increases.The study shows also that the cooling capacity increases by (65.3% as the evaporator temperature increases by (8.4 %, and the cooling capacity increases by (1.6%as the capillary tube coil number increases in the range (0-4.The coefficient of performance decreases by (43.4 %, as the mass flow rateincreases by (76.9%, also the coefficient of performance increases by (13.51 % as thecapillary tube coil number increases in the range (0-4.Through this study, it was found that the best coil number in refrigeration cycle at the lowest mass flow rate (31 Kg/hr and at high mass flow rate (23 Kg/hr is (coil number = 4, this will give the highest performance, cooling capacity and lowest theoretical compression power.

Thamir K. Salim

2012-06-01

271

The effect of fins on vortex shedding from a cylinder in cross-flow  

International Nuclear Information System (INIS)

A bare tube and three segmented-finned tubes have been tested to investigate the effect of the fins on vortex shedding from cylinders in cross-flow. The addition of the fins is found to enhance the process of vortex shedding. It is shown that the fins increase the correlation length and the amplitude of velocity fluctuation at the vortex shedding frequency. The fins also increase the non-linear nature of the flow in the wake, as evidenced by a remarkable increase in the number and in the amplitude of the higher harmonic components of vortex shedding. However, the correlation length in the wake of the finned tubes is found to change with angular rotation of the tube around its axis. This phenomenon seems to be related to an irregular wavy pattern of the fin distribution along the tube axis. (authors)

272

Thermal and Sensitivity Analysis of Multi-Fin Devices  

Digital Repository Infrastructure Vision for European Research (DRIVER)

As device dimensions shrink into the nanometer range, power and performance constraints prohibit the longevity of traditional MOS devices in circuit design. A finFET, a quasi-planar double-gated device, has emerged as a replacement. FinFETs are formed by creating a silicon em fin which protrudes out of the wafer, wrapping a gate around the fin, and then doping the ends of the fin to form the source and drain. Wider finFETs are formed using multiple fins between the source and drain regions. W...

Swahn, B.; Hassoun, S.

2006-01-01

273

A modular straw drift tube tracking system for the solenoidal detector collaboration experiment. Pt. II. Performance  

International Nuclear Information System (INIS)

For pt.I see ibid., p.355-71, 1996. Several investigations were conducted to demonstrate the capabilities of a straw drift tube outer tracking system for the SDC detector as described in the previous article. These include electrical properties and aging properties of the tubes as well as measurements of electron drift times in a 2 T magnetic field. Measurements characterizing the radiation hardness of the processes used to fabricate the front-end electronics are also included. We present the performance characteristics of prototype straw modules read out through this front-end electronics as well as some data on the performance of the track trigger system. (orig.)

274

Features of plate and fin type heat exchanger made of stainless steel. Stainless kosei plate fin gata netsukokanki no tokucho  

Energy Technology Data Exchange (ETDEWEB)

A plate and fin type heat exchanger has such features that it can increase heat transfer area per unit cubage; it can adopt different kinds of flow patterns; it can select types of fins in a wide range enabling optimal designs for particular applications; and it can reduce pressure loss because it can use lower flow rate for one specific performance requirement. Further, the capability of integrating multiplicity of heat exchangers enables making the entire plant more compact. The heat exchanger consists basically of cores, and header tanks and stub pipes to flow fluids into paths in the cores. A core comprises three kinds of parts, i.e., tube plates, corrugated fins, and spacer bars. These parts are bonded together using vacuum brazing into an integrated structure. Plate and fin type heat exchangers made of stainless steel are beginning to be used one after another in applications that require compactness, high-temperature resistance, corrosion resistance, or cleanliness, which are the features of the heat exchanger. 9 figs., 1 tab.

Iwata, K. (Sumitomo Precision Products Co. Ltd., Hyogo (Japan))

1992-06-01

275

Effect of draft tube size on the performance of a cross-flow turbine  

Energy Technology Data Exchange (ETDEWEB)

The cross-flow turbine has attracted the attention of several investigators working in the area of microhydroelectric power generation. This type of turbine, although primarily an impulse type, is suitable for operation at low and medium heads. This article describes the effect of using different sizes of draft tubes on the performance of a 5-kW cross-flow turbine. An effort is made to arrive at an optimum size for the particular turbine tested, as the existing draft tube (203 mm) had an adverse effect on the performance at higher heads. The study involved variation of different performance parameters such as output, efficiency, runaway speed, and speed ratio for four different cases, viz., without the draft tube and with three different sizes of draft tubes (203, 250, and 300 mm) in the head range 3--9 m. The investigation shows that a properly sized draft tube enhances the efficiency of a cross-flow turbine over the entire space of its operation.

Reddy, H.; Seshadri, V.; Kothari, D.P.

1996-03-01

276

Does size matter? An assessment of quota market evolution and performance in the Great Barrier Reef fin-fish fishery  

Directory of Open Access Journals (Sweden)

Full Text Available In fisheries managed using individual transferable quotas (ITQs it is generally assumed that quota markets are well-functioning, allowing quota to flow on either a temporary or permanent basis to those able to make best use of it. However, despite an increasing number of fisheries being managed under ITQs, empirical assessments of the quota markets that have actually evolved in these fisheries remain scarce. The Queensland Coral Reef Fin-Fish Fishery (CRFFF on the Great Barrier Reef has been managed under a system of ITQs since 2004. Data on individual quota holdings and trades for the period 2004-2012 were used to assess the CRFFF quota market and its evolution through time. Network analysis was applied to assess market structure and the nature of lease-trading relationships. An assessment of market participants’ abilities to balance their quota accounts, i.e., gap analysis, provided insights into market functionality and how this may have changed in the period observed. Trends in ownership and trade were determined, and market participants were identified as belonging to one out of a set of seven generalized types. The emergence of groups such as investors and lease-dependent fishers is clear. In 2011-2012, 41% of coral trout quota was owned by participants that did not fish it, and 64% of total coral trout landings were made by fishers that owned only 10% of the quota. Quota brokers emerged whose influence on the market varied with the bioeconomic conditions of the fishery. Throughout the study period some quota was found to remain inactive, implying potential market inefficiencies. Contribution to this inactivity appeared asymmetrical, with most residing in the hands of smaller quota holders. The importance of transaction costs in the operation of the quota market and the inequalities that may result are discussed in light of these findings.

James Innes

2014-09-01

277

Performance demonstration tests for eddy current inspection of steam generator tubing  

Energy Technology Data Exchange (ETDEWEB)

This report describes the methodology and results for development of performance demonstration tests for eddy current (ET) inspection of steam generator tubes. Statistical test design principles were used to develop the performance demonstration tests. Thresholds on ET system inspection performance were selected to ensure that field inspection systems would have a high probability of detecting and and correctly sizing tube degradation. The technical basis for the ET system performance thresholds is presented in detail. Statistical test design calculations for probability of detection and flaw sizing tests are described. A recommended performance demonstration test based on the design calculations is presented. A computer program for grading the probability of detection portion of the performance demonstration test is given.

Kurtz, R.J.; Heasler, P.G.; Anderson, C.M.

1996-05-01

278

Performance demonstration tests for eddy current inspection of steam generator tubing  

International Nuclear Information System (INIS)

This report describes the methodology and results for development of performance demonstration tests for eddy current (ET) inspection of steam generator tubes. Statistical test design principles were used to develop the performance demonstration tests. Thresholds on ET system inspection performance were selected to ensure that field inspection systems would have a high probability of detecting and and correctly sizing tube degradation. The technical basis for the ET system performance thresholds is presented in detail. Statistical test design calculations for probability of detection and flaw sizing tests are described. A recommended performance demonstration test based on the design calculations is presented. A computer program for grading the probability of detection portion of the performance demonstration test is given

279

Improving heat exchanger performance by using on-line automatic tube cleaning system  

Energy Technology Data Exchange (ETDEWEB)

In this presentation, OVIVO demonstrates an innovative solution for enhancing the performance and output of heat exchangers used in oil recovery plants. The solution proposed for reducing tube failure due to deposit buildup, corrosion, micro fouling, and scaling caused by the high mineral content of the water used, is to use an on-line automatic tube cleaning system (ATCS). The first ATCS type is the ball type, which injects rubber balls into the water entering the heat exchanger. The scrubbing and wiping action of the balls keeps the tubes clean, and the balls are subsequently collected by means of a strainer and can be re-circulated as needed. A second system aligns a brush and basket to each tube and, by periodically reversing water flow using a diverter valve, cleans each tube several times daily without process interruption or the need for unit shut down. The use of ATCS has been proven to improve plant performance and increase output while reducing operating and maintenance costs.

Someah, Kaveh; Beauchesne, Guy [OVIVO Water (United States)], email: kaveh.someah@ovivowater.com, email: guy.beauchesne@ovivowater.com

2011-07-01

280

Performance evaluation of a dual GM Tube based 85Kr monitor  

International Nuclear Information System (INIS)

The performance of a dual GM based 85Kr monitor used in reprocessing facility-I was evaluated with the help of a single GM Tube based 85Kr monitor used in reprocessing facility-Il. The 85Kr concentration was also simultaneously measured by TLD for independently estimating the activity. (author)

 
 
 
 
281

The ATLAS Transition Radiation Tracker (TRT) proportional drift tube: design and performance  

International Nuclear Information System (INIS)

A straw proportional counter is the basic element of the ATLAS Transition Radiation Tracker (TRT). Its detailed properties as well as the main properties of a few TRT operating gas mixtures are described. Particular attention is paid to straw tube performance in high radiation conditions and to its operational stability

282

Experimental study of heat transfer of parallel louvered fins by laser holographic interferometry  

International Nuclear Information System (INIS)

Recently many compact air-cooled heat exchanger begin to utilize the enhanced fins to upgrade the performance of a heat exchanger. The study of heat transfer characteristics of these enhanced fins has been focused on as calculated by heat transfer performances in two-dimensional plate array neglecting the effects of tubes. Proposed correlations of the Colburn j-factor and the friction factor for triangular tube arrangement to design the heat exchanger are made. The effects of louver's geometry and their arrangement on heat transfer of louvered fins are studied. A number of informations are available concerning theoretical analyses and global heat transfer performances in a heat exchanger with louvered fins; however, little amount of experimental information to clarify the mechanism of heat transfer around louvers so far has prevailed. The objectives of this paper are experimentally to study the mechanism of heat transfer in a louver-array and to develop the preferable geometrical arrangement of louvers from the point of view of improving the performance of a heat exchanger

283

Performance of drift-tube detectors at high counting rates for high-luminosity LHC upgrades  

Science.gov (United States)

The performance of pressurized drift-tube detectors at very high background rates has been studied at the Gamma Irradiation Facility (GIF) at CERN and in an intense 20 MeV proton beam at the Munich Van-der-Graaf tandem accelerator for applications in large-area precision muon tracking at high-luminosity upgrades of the Large Hadron Collider (LHC). The ATLAS muon drift-tube (MDT) chambers with 30 mm tube diameter have been designed to cope with ? and neutron background hit rates of up to 500 Hz/cm2. Background rates of up to 14 kHz/cm2 are expected at LHC upgrades. The test results with standard MDT readout electronics show that the reduction of the drift-tube diameter to 15 mm, while leaving the operating parameters unchanged, vastly increases the rate capability well beyond the requirements. The development of new small-diameter muon drift-tube (sMDT) chambers for LHC upgrades is completed. Further improvements of tracking efficiency and spatial resolution at high counting rates will be achieved with upgraded readout electronics employing improved signal shaping for high counting rates.

Bittner, Bernhard; Dubbert, Jörg; Kortner, Oliver; Kroha, Hubert; Manfredini, Alessandro; Nowak, Sebastian; Ott, Sebastian; Richter, Robert; Schwegler, Philipp; Zanzi, Daniele; Biebel, Otmar; Hertenberger, Ralf; Ruschke, Alexander; Zibell, Andre

2013-12-01

284

Statistical analysis of duplex-tube performance in Experimental Breeder Reactor II superheater SU-712  

International Nuclear Information System (INIS)

A detailed investigation was made of historical data recorded at Experimental Breeder Reactor II during operation with superheater SU-712. The objective of this study was to analyze and characterize the performance of 72 duplex steam tubes that became unbonded during a long period of operation. The information processing system ANALYZE was developed to perform the required numerical manipulations, statistical analyses, and correlation analyses with a large data base containing some five million data values. The ANALYZE system was successfully employed (a) to characterize the performance of all the steam tubes in terms of frequency and relative severity of unbonding, and (b) to establish a correlation between the observed anomalous behavior of the superheater and its operating parameters. Results from this investigation were used to select sections for materials examinations and physical tests that were performed after SU-712 was removed from operation

285

Nursing care for patients with orotracheal tube: evaluation performed at intensive care unit  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: to evaluate the care dispensed by the nursing team of the Intensive Care Unit of the Hospital Public of Gurupi to patients using orotracheal tube. Methods: this is about a descriptive, observational research, from quantitative analysis. The observation of care, according to the protocol aimed at the handling of the endotracheal tube, occurred for seven days in March 2009 for 14 hours a day, with a total of 105 hours. The study was approved by the Research Ethics Committee of the University Castelo Branco (0169/2008. Results: checking blood pressure of the cuff every 12 hours and hydration of the lips every four hours was not performed by nursing staff, the oral hygiene was performed only once a day, but was assured by professionals an alternative means of communication intubated patients, the exchange and holding the lace was made daily, the use of gauze on the sides of the oral cavity was placed when it was apparent some aggression to the skin of the patient, the aspiration of endotracheal tube with aseptic technique, was performed to avoid complications. Conclusion: the nursing team observed presented failures in attendance which could be reduced through implanting specific protocols for handling of the orotracheal tube.

Giselle Pinheiro Lima Aires Gomes, Adriana Arruda Barbosa Rezende, Joana D’Arc Ponce de Almeida, Iris Lima e Silva, Heron Beresford

2009-10-01

286

Performance of PCCS with horizontal U-tube type heat exchanger  

International Nuclear Information System (INIS)

The passive containment cooling system (PCCS) using a shell-and-tube type heat exchanger has been developed as a decay heat removal system following a severe accident. It requires no active devices and no operator action to start and maintain its function. A horizontal heat exchanger has been studied for the PCCS heat exchanger since it has several advantages over a vertical large diameter tube heat exchanger that was originally proposed for the SBWR. The fundamental heat removal performance and pressure loss characteristics has been investigated by conducting a thermal-hydraulic test using single horizontal U-shape heat exchanger tube. Comparing with the experimental results, the analysis model has been adopted for estimating the heat transfer performance and the pressure loss of a PCCS horizontal heat exchanger. The analysis model was applied to the sizing of the PCCS horizontal heat exchanger for the next generation BWR. The effect of heat transfer tube diameter and length on the PCCS performance has been estimated. According to the analysis results, the economical benefits of the horizontal heat exchanger type PCCS over the original vertical heat exchanger have been clarified. (author)

287

Undulating fins produce off-axis thrust and flow structures.  

Science.gov (United States)

While wake structures of many forms of swimming and flying are well characterized, the wake generated by a freely swimming undulating fin has not yet been analyzed. These elongated fins allow fish to achieve enhanced agility exemplified by the forward, backward and vertical swimming capabilities of knifefish, and also have potential applications in the design of more maneuverable underwater vehicles. We present the flow structure of an undulating robotic fin model using particle image velocimetry to measure fluid velocity fields in the wake. We supplement the experimental robotic work with high-fidelity computational fluid dynamics, simulating the hydrodynamics of both a virtual fish, whose fin kinematics and fin plus body morphology are measured from a freely swimming knifefish, and a virtual rendering of our robot. Our results indicate that a series of linked vortex tubes is shed off the long edge of the fin as the undulatory wave travels lengthwise along the fin. A jet at an oblique angle to the fin is associated with the successive vortex tubes, propelling the fish forward. The vortex structure bears similarity to the linked vortex ring structure trailing the oscillating caudal fin of a carangiform swimmer, though the vortex rings are distorted because of the undulatory kinematics of the elongated fin. PMID:24072799

Neveln, Izaak D; Bale, Rahul; Bhalla, Amneet Pal Singh; Curet, Oscar M; Patankar, Neelesh A; MacIver, Malcolm A

2014-01-15

288

Performance of Multi-anode Photomultiplier Tubes for the LHCb RICH detectors  

Energy Technology Data Exchange (ETDEWEB)

An array of Multi-anode Photomultiplier Tubes (MaPMT) was evaluated for use in the LHCb Ring Imaging Cherenkov (RICH) detectors using a prototype RICH detector in a charged particle beam. The MaPMT performance was measured with different radiator gases with and without lenses. The performance of the MaPMTs in terms of photon yield and pixel cross-talk is presented.

Bibby, J. [University of Oxford, Oxford (United Kingdom); Buckley, A. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Chamonal, R. [University of Edinburgh, Edinburgh (United Kingdom); Easo, S. [CCLRC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire (United Kingdom); Eisenhardt, S. [University of Edinburgh, Edinburgh (United Kingdom); Gibson, V. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Harnew, N. [University of Oxford, Oxford (United Kingdom); Muheim, F. [University of Edinburgh, Edinburgh (United Kingdom); Howard, A. [Imperial College, London (United Kingdom); Lawrence, J. [University of Edinburgh, Edinburgh (United Kingdom); Pickford, A. [Kelvin Building, Department of Physics and Astronomy, University of Glasgow, Glasgow (United Kingdom)]. E-mail: a.pickford@physics.gla.ac.uk; Plackett, R. [Imperial College, London (United Kingdom); Price, D. [Imperial College, London (United Kingdom); Rademacker, J. [University of Oxford, Oxford (United Kingdom); Smale, N. [University of Oxford, Oxford (United Kingdom); Soler, F.J.P. [CCLRC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire (United Kingdom); Kelvin Building, Department of Physics and Astronomy, University of Glasgow, Glasgow (United Kingdom); Somerville, L. [University of Oxford, Oxford (United Kingdom); Storey, J. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Websdale, D. [CCLRC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire (United Kingdom); Wilkinson, G. [University of Oxford, Oxford (United Kingdom); Wotton, S. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom)

2005-07-01

289

Performance of the Hamamatsu R11410 Photomultiplier Tube in Xenon Environments  

CERN Document Server

The Hamamatsu R11410 photomultiplier, a tube of 3'' diameter and with a very low intrinsic radioactivity, is an interesting light sensor candidate for future experiments using liquid xenon (LXe) as target for direct dark matter searches. We have performed several experiments with the R11410 with the goal of testing its performance in environments similar to a dark matter detector setup. In particular, we examined its long-term behavior and stability in LXe and its response in various electric field configurations.

Baudis, Laura; Ferella, Alfredo; Kish, Alexander; Undagoitia, Teresa Marrodan; Mayani, Daniel; Schumann, Marc

2013-01-01

290

Performance of the Hamamatsu R11410 photomultiplier tube in cryogenic xenon environments  

International Nuclear Information System (INIS)

The Hamamatsu R11410 photomultiplier, a tube of 3'' diameter and with a very low intrinsic radioactivity, is an interesting light sensor candidate for future experiments using liquid xenon (LXe) as target for direct dark matter searches. We have performed several experiments with the R11410 with the goal of testing its performance in environments similar to a dark matter detector setup. In particular, we examined its long-term behavior and stability in LXe and its response in various electric field configurations.

291

Performance of the Hamamatsu R11410 photomultiplier tube in cryogenic xenon environments  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Hamamatsu R11410 photomultiplier, a tube of 3" diameter and with a very low intrinsic radioactivity, is an interesting light sensor candidate for future experiments using liquid xenon (LXe) as target for direct dark matter searches. We have performed several experiments with the R11410 with the goal of testing its performance in environments similar to a dark matter detector setup. In particular, we examined its long-term behavior and stability in LXe and its response in...

Baudis, Laura; Behrens, Annika; Ferella, Alfredo; Kish, Alexander; Undagoitia, Teresa Marrodan; Mayani, Daniel; Schumann, Marc

2013-01-01

292

Performance of Multi-anode Photomultiplier Tubes for the LHCb RICH detectors  

CERN Document Server

An array of Multi-anode Photomultiplier Tubes (MaPMT) was evaluated for use in the LHCb Ring Imaging Cherenkov (RICH) detectors using a prototype RICH detector in a charged particle beam. The MaPMT performance was measured with different radiator gases with and without lenses. The performance of the MaPMTs in terms of photon yield and pixel cross-talk is presented1).

Bibby, J; Chamonal, R; Easo, S; Eisenhardt, S; Gibson, V; Harnew, N; Muheim, F; Howard, A; Lawrence, J; Pickford, A; Plackett, R; Price, D; Rademacker, J; Smale, N; Soler, F J P; Somerville, L; Storey, J; Websdale, D M; Wilkinson, G; Wotton, S; 10.1016/j.nima.2005.03.043

2005-01-01

293

Effect of Tube Arrangement on the Thermal Performance of a High Temperature Generator of the Absorption System  

Science.gov (United States)

The present study numerically investigated the effect of tube arrangement on the thermal performance of the high temperature generator (HTG) of a double effect LiBr-water absorption system with the cooling capacity of 210 refrigeration tons. The HTG tubes were located behind the pre-mixed surface flame burner. The HTG was consisted with a set of circular tubes and flattened tubes in series. LiBr aqueous weak solution was flowed into the HTG tube, and then turned to strong solution at the exit of the HTG tube. FLUENT, as a commercial code, was used to estimate the thermal performance of the HTG. Standard k-? model was applied for the turbulent flow of combustion gas around the HTG tubes. Key parameters were the diameter of the circular tube and tube pitch ratio of flattened and circular tubes in the HTG. The combustion gas temperature was increased and its heat transfer rate was decreased as the circular tube diameter was increased, and the pitch ratios of both circular and flattened were decreased.

Lee, Insong; Cho, Keumnam

294

Medical Thoracoscopy Performed Using a Flexible Bronchoscope Inserted through a Chest Tube under Local Anesthesia  

Directory of Open Access Journals (Sweden)

Full Text Available Background and Objectives. Many cases of pleural effusion can remain undiagnosed following thoracentesis. We evaluated our own technique for performing thoracoscopy under local anesthesia using a 32?Fr chest tube and a flexible fiberoptic bronchoscope without a rigid thoracoscope for the diagnosis, inspection, and management of patients with pleurisy. Methods. Seven patients with pleural effusion who underwent thoracoscopy under local anesthesia using a 32?Fr chest tube and a flexible fiberoptic bronchoscope were retrospectively studied. Results. Thoracoscopy was safely performed in the diagnosis and management of pleural effusion in all cases. The visualization of the pleura, diaphragm, and lung using this instrumentation was excellent in comparison to that normally obtained during surgical thoracoscopy. A forceps biopsy of the pleura or diaphragm could therefore be easily and effectively performed. Conclusion. This technique is considered to have clinical utility as a diagnostic tool for pleurisy; furthermore, this method is safe, effective and inexpensive, not only for surgeons but also for physicians.

Toshinobu Yokoyama

2009-01-01

295

Medical Thoracoscopy Performed Using a Flexible Bronchoscope Inserted through a Chest Tube under Local Anesthesia  

Science.gov (United States)

Background and Objectives. Many cases of pleural effusion can remain undiagnosed following thoracentesis. We evaluated our own technique for performing thoracoscopy under local anesthesia using a 32 Fr chest tube and a flexible fiberoptic bronchoscope without a rigid thoracoscope for the diagnosis, inspection, and management of patients with pleurisy. Methods. Seven patients with pleural effusion who underwent thoracoscopy under local anesthesia using a 32 Fr chest tube and a flexible fiberoptic bronchoscope were retrospectively studied. Results. Thoracoscopy was safely performed in the diagnosis and management of pleural effusion in all cases. The visualization of the pleura, diaphragm, and lung using this instrumentation was excellent in comparison to that normally obtained during surgical thoracoscopy. A forceps biopsy of the pleura or diaphragm could therefore be easily and effectively performed. Conclusion. This technique is considered to have clinical utility as a diagnostic tool for pleurisy; furthermore, this method is safe, effective and inexpensive, not only for surgeons but also for physicians. PMID:19536345

Yokoyama, Toshinobu; Toda, Reiko; Tomioka, Ryusuke; Aizawa, Hisamichi

2009-01-01

296

Performance comparison of the commercial CFD software for the prediction of turbulent flow through tube bundles  

International Nuclear Information System (INIS)

Because turbulent flow through tube bundles can be found in many important industrial applications, such as PWR reactor, steam generator, CANDU calandria and lower plenum of the VHTR, extensive studies have been made both experimentally and numerically. Although recently licensing applications supported by commercial CFD software are increasing, there is no commercial CFD software which obtains a licensing from the regulatory body until now. Therefore, it is necessary to perform the systematic assessment for the prediction performance of the commercial CFD software. The main objective of the present study is to numerically simulate turbulent flow through both staggered and in line tube bundle using the two popular commercial CFD software, ANSYS CFX and FLUENT and to compare the simulation results with the experimental data for the assessment of these software's prediction performance

297

Experimental Study of Convective Heat Transfer and Thermal Performance in the Heat-Sink Channel with Various Geometrical Configurations Fins  

Directory of Open Access Journals (Sweden)

Full Text Available An experimental study was conducted to investigate the heat transfer & friction loss characteristics in a heat sink channel with various geometrical configurations under constant heat flux conditions. The experiments are performed for the Reynolds number and heat flux in the ranges of 300 to 900 and 1.50-5.50kw/m2, respectively. The heat sink with two different channel heights and two different channel widths are accomplished. Different geometrical configurations parameters effect of the microchannel and heat flux on the heat transfer haracteristics and pressure drop are considered. For those configurations the average heat transfer coefficient and Nusselt number were determined experimentally. The micro-channel geometry configuration has significant effect on the enhancement heat transfer and pressure drop. The results of this study are expected to lead to guidelines that will allow the design of the micro-channel heat exchangers with improved heat transfer performance of the electronic devices.

Mohit Taneja, 2 Sandeep Nandal, 3Arpan Manchanda, 4Ajay Kumar Agarwal

2013-06-01

298

Thermal performance of a solar pressure cooker based on evacuated tube solar collector  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the thermal performance of a community type solar pressure cooker based on evacuated tube solar collector. The developed design of solar pressure cooker has separate parts for energy collection and cooking unit and both are coupled by heat exchanger. The paper has presented the performance results of experimental study conducted on solar pressure cooker and a simulation model has been developed for predicting the cooker performance under a variety of operating and climatic conditions. The theoretical model is validated against the experimental results. The obtained results have suggested a possibility of several batches of solar cooking on a clear sunny day under typical conditions of Delhi. (author)

Kumar, R.; Adhikari, R.S.; Garg, H.P. [Indian Institute of Technology, New Delhi (India). Centre for Energy Studies; Kumar, A. [Ministry of Non-Conventional Energy Sources, New Delhi (India). Solar Energy Centre

2001-11-01

299

COMPARATIVE ANALYSIS OF REVERSIBLE LOGIC BASED CARBON NANO TUBE FIELD EFFECT TRANSISTOR MULTIPLEXER PERFORMANCE  

Directory of Open Access Journals (Sweden)

Full Text Available This study is about the design and analysis of a reversible logic based multiplexer, that is realized using carbon nano tube transistor. Reversible logic realization of the digital circuits offers numerous advantages over conventional circuit design. Power analysis was performed using HSPICE simulation software and the results are obtained for the 2Ã?1 and 4Ã?1 multiplexer transient behavior. The power consumption is also obtained. Comparative analysis was performed with the conventional CMOS multiiplexer design to validate the proposed design performance.

Y. Varthamanan

2013-01-01

300

High-performance BWR core and fuel using zirconium liner tubings  

International Nuclear Information System (INIS)

The high-performance core and fuel using zirconium liner tubings developed by Toshiba has come to be introduced into BWRs. This fuel allows rapid power increase without fuel failure, as already verified by the out-of-pile tests, as well as demonstration test in test reactors and power reactors. This characteristic has advanced nuclear design as to provide 10- % increase of burnup. This core and fuel provide not only easy load following but also better fuel-cycle economy. (author)

 
 
 
 
301

Thermal performance testing of two Thales 9310 pulse-tube cryocoolers for PHyTIR  

International Nuclear Information System (INIS)

PHyTIR is a NASA-funded technology demonstration for a near-term earth-observing instrument in the thermal infrared spectrum, intended for use in the HyspIRI mission. PHyTIR will use two Thales 9310 single-stage pulse tube cryocoolers, one to directly cool the FPA, the other to simulate a passive radiator. We report performance measurements for the two Thales 9310 cryocoolers intended for inclusion in the PHyTIR demonstrator

302

The waveform digitiser of the Double Chooz experiment: performance and quantisation effects on photomultiplier tube signals  

International Nuclear Information System (INIS)

We present the waveform digitiser used in the Double Chooz experiment. We describe the hardware and the custom-built firmware specifically developed for the experiment. The performance of the device is tested with regards to digitising low light level signals from photomultiplier tubes and measuring pulse charge. This highlights the role of quantisation effects and leads to some general recommendations on the design and use of waveform digitisers

303

The results of our external dacryocystorhinostomy performed with single flap and bicanalicular silicone tube intubation  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: To assess the results of external dacryocystorhinostomy(EDSR performed with single flap and bicanalicularsilicone tube intubation (STI surgery in ourpatients with nasolacrimal duct obstruction.Methods: A total of 27 EDSR with single flap + STI operationsthat were performed under general anesthesia onpatients with nasolacrimal duct obstruction aged 7 to 72(median 43.2 years were evaluated.Results: Five patients (18.5% were male and 22 (81.4%were female. All of operations were initial. Median postoperativefollow up period was 20.7 ± 7.2 months (10 to 36months. In three patients (11.1% the passages of theeyes were closed. Of these patients, one patient (3.7%had completely closed passage. The remaining 2 patients(7.4% had partially closed passage. Major complicationwas observed in any patient during the surgery. Woundhematoma or fistula was observed during follow-up in anypatient. There were no complications due to silicone tubing.As a result, patients with nasolacrimal duct obstructionin 24 of 27 (88.9%, success was achieved by ensuringa clear passage.Conclusion: External DSR with single flap + STI is a safeand effective procedure and it may be performed as anoperation in patients with nasolacrimal duct obstructionKey words: External dacryocystorhinostomy, single flap,silicone tube intubation

Çi?dem Harmanc?

2013-09-01

304

A model for the performance of a vertical tube condenser in the presence of noncondensable gases  

Energy Technology Data Exchange (ETDEWEB)

Some proposed vertical tube condensers are designed to operate at high noncondensable fractions, which warrants a simple model to predict their performance. Models developed thus far are usually non self-contained as they require the specification of the wall temperature to predict the local condensation rate. The present model attempts to fill this gap by addressing the secondary side heat transfer as well. Starting with momentum balance which includes the effect of interfacial shear stress, a Nusselt-type algebraic equation is derived for the film thickness as a function of flow and geometry parameters. The heat and mass transfer analogy relations are then invoked to deduce the condensation rate of steam onto the tube wall. Lastly, the heat transfer to the secondary side is modelled to include cooling by forced, free or mixed convection flows. The model is used for parametric simulations to determine the impact on the condenser performance of important factors such as the inlet gas fraction, the mixture inlet flowrate, the total pressure, and the molecular weight of the noncondensable gas. The model performed simulations of some experiments with pure steam and air-steam mixtures flowing down a vertical tube. The model predicts the data quite well.

Guentay, A.D.S.

1995-09-01

305

FinFET- Benefits, Drawbacks and Challenges.  

Directory of Open Access Journals (Sweden)

Full Text Available FinFET is a promising alternative to conventional MOSFET - which has reached its limits and has too much leakage for too little performance gain. FinFET is being recommended as the basis for future IC processes because of its power/performance benefits, scalability, superior controls over short channel effects etc. However, it brings with itself new challenges andundesirable characteristics such as Corner effects, Quantum effects, Width quantization, Layout dependencies, additional parasitics etc. This paper discusses the major advantages, disadvantages and challenges of FinFET technology.

Mayur Bhole

2013-11-01

306

Performance Assessment of Passive Heat Exchanger with Horizontal Tube using RELAP5  

International Nuclear Information System (INIS)

In the world nuclear industry to enhance safety and reliability of nuclear power plant, passive safety system design has been introducing. Especially, passive auxiliary feedwater system (PAFS) has been applied to the advanced power reactor plus (APR+) in our domestic industry. According to PAFS design concept, PAFS makes role completely for the existing auxiliary feedwater system. PAFS can remove the residual heat in the core and then prevent the core damage when the feedwater is not available. The passive heat removal system has essentially heat exchanger with vertical or horizontal tubes. PAFS is a kind of passive heat exchanger with an inclined horizontal U tube bundle. Heat transfer phenomena in horizontal tubes play an important role in passive safety systems for the next generation of nuclear power plants. To assess the performance of the system, it is required to carry experiment and code analysis. NOKO experiment facility for investigating the emergency condenser effectiveness in SWR1000, is similar to PAFS. So the experiment result can be useful to evaluate the cooling performance of passive system like PAFS. The purpose of this study is to simulate the TH phenomena such as natural circulation and horizontal condensation heat transfer in NOKO experiment using RELAP5, and to compare the results between experimental data and RELAP5 code analysis

307

Performance Assessment of Passive Heat Exchanger with Horizontal Tube using RELAP5  

Energy Technology Data Exchange (ETDEWEB)

In the world nuclear industry to enhance safety and reliability of nuclear power plant, passive safety system design has been introducing. Especially, passive auxiliary feedwater system (PAFS) has been applied to the advanced power reactor plus (APR+) in our domestic industry. According to PAFS design concept, PAFS makes role completely for the existing auxiliary feedwater system. PAFS can remove the residual heat in the core and then prevent the core damage when the feedwater is not available. The passive heat removal system has essentially heat exchanger with vertical or horizontal tubes. PAFS is a kind of passive heat exchanger with an inclined horizontal U tube bundle. Heat transfer phenomena in horizontal tubes play an important role in passive safety systems for the next generation of nuclear power plants. To assess the performance of the system, it is required to carry experiment and code analysis. NOKO experiment facility for investigating the emergency condenser effectiveness in SWR1000, is similar to PAFS. So the experiment result can be useful to evaluate the cooling performance of passive system like PAFS. The purpose of this study is to simulate the TH phenomena such as natural circulation and horizontal condensation heat transfer in NOKO experiment using RELAP5, and to compare the results between experimental data and RELAP5 code analysis

Lee, Kyung Jin; Hong, Soon Joon; Lee, Byung Chul [FNC Tech., SNU, Seoul (Korea, Republic of)

2011-10-15

308

Signal-to-noise performance analysis of streak tube imaging lidar systems. I. Cascaded model.  

Science.gov (United States)

Streak tube imaging lidar (STIL) is an active imaging system using a pulsed laser transmitter and a streak tube receiver to produce 3D range and intensity imagery. The STIL has recently attracted a great deal of interest and attention due to its advantages of wide azimuth field-of-view, high range and angle resolution, and high frame rate. This work investigates the signal-to-noise performance of STIL systems. A theoretical model for characterizing the signal-to-noise performance of the STIL system with an internal or external intensified streak tube receiver is presented, based on the linear cascaded systems theory of signal and noise propagation. The STIL system is decomposed into a series of cascaded imaging chains whose signal and noise transfer properties are described by the general (or the spatial-frequency dependent) noise factors (NFs). Expressions for the general NFs of the cascaded chains (or the main components) in the STIL system are derived. The work presented here is useful for the design and evaluation of STIL systems. PMID:23262622

Yang, Hongru; Wu, Lei; Wang, Xiaopeng; Chen, Chao; Yu, Bing; Yang, Bin; Yuan, Liang; Wu, Lipeng; Xue, Zhanli; Li, Gaoping; Wu, Baoning

2012-12-20

309

Optical MCP image tube with a quad Timepix readout: initial performance characterization  

Science.gov (United States)

A photon counting, microchannel plate (MCP) optical imaging tube has been fabricated using a 2 × 2 array of Timepix application specific integrated circuits (ASICs) as the readout anode. A Timepix ASIC is a 256 × 256 pixellated CMOS readout chip with each pixel containing an amplifier, discriminator and counter. The counter values, representing either time of arrival, total count or time over threshold, can record the position and time of arrival of the electron pulses from the MCP if the charge collected on its input pads exceed the adjustable lower threshold value. Below we present initial results of the tube's performance, the quantum efficiency of the bi-alkali photocathode, uniformity of response, spatial and temporal resolution, and dynamic range. Planned improvement to the design based on the new Timepix3 chip will be discussed.

Vallerga, J.; Tremsin, A.; DeFazio, J.; Michel, T.; Alozy, J.; Tick, T.; Campbell, M.

2014-05-01

310

Performance of the CMS drift-tube chamber local trigger with cosmic rays  

International Nuclear Information System (INIS)

The performance of the Local Trigger based on the drift-tube system of the CMS experiment has been studied using muons from cosmic ray events collected during the commissioning of the detector in 2008. The properties of the system are extensively tested and compared with the simulation. The effect of the random arrival time of the cosmic rays on the trigger performance is reported, and the results are compared with the design expectations for proton-proton collisions and with previous measurements obtained with muon beams.

311

Performance of the CMS drift-tube chamber local trigger with cosmic rays  

CERN Document Server

The performance of the Local Trigger based on the drift-tube system of the CMS experiment has been studied using muons from cosmic ray events collected during the commissioning of the detector in 2008. The properties of the system are extensively tested and compared with the simulation. The effect of the random arrival time of the cosmic rays on the trigger performance is reported, and the results are compared with the design expectations for proton-proton collisions and with previous measurements obtained with muon beams.

Chatrchyan, S; Sirunyan, A M; Adam, W; Arnold, B; Bergauer, H; Bergauer, T; Dragicevic, M; Eichberger, M; Erö, J; Friedl, M; Frühwirth, R; Ghete, V M; Hammer, J; Hänsel, S; Hoch, M; Hörmann, N; Hrubec, J; Jeitler, M; Kasieczka, G; Kastner, K; Krammer, M; Liko, D; Magrans de Abril, I; Mikulec, I; Mittermayr, F; Neuherz, B; Oberegger, M; Padrta, M; Pernicka, M; Rohringer, H; Schmid, S; Schöfbeck, R; Schreiner, T; Stark, R; Steininger, H; Strauss, J; Taurok, A; Teischinger, F; Themel, T; Uhl, D; Wagner, P; Waltenberger, W; Walzel, G; Widl, E; Wulz, C E; Chekhovsky, V; Dvornikov, O; Emeliantchik, I; Litomin, A; Makarenko, V; Marfin, I; Mossolov, V; Shumeiko, N; Solin, A; Stefanovitch, R; Suarez Gonzalez, J; Tikhonov, A; Fedorov, A; Karneyeu, A; Korzhik, M; Panov, V; Zuyeuski, R; Kuchinsky, P; Beaumont, W; Benucci, L; Cardaci, M; De Wolf, E A; Delmeire, E; Druzhkin, D; Hashemi, M; Janssen, X; Maes, T; Mucibello, L; Ochesanu, S; Rougny, R; Selvaggi, M; Van Haevermaet, H; Van Mechelen, P; Van Remortel, N; Adler, V; Beauceron, S; Blyweert, S; D'Hondt, J; De Weirdt, S; Devroede, O; Heyninck, J; Kalogeropoulos, A; Maes, J; Maes, M; Mozer, M U; Tavernier, S; Van Doninck, W; Van Mulders, P; Villella, I; Bouhali, O; Chabert, E C; Charaf, O; Clerbaux, B; De Lentdecker, G; Dero, V; Elgammal, S; Gay, A P R; Hammad, G H; Marage, P E; Rugovac, S; Vander Velde, C; Vanlaer, P; Wickens, J; Grunewald, M; Klein, B; Marinov, A; Ryckbosch, D; Thyssen, F; Tytgat, M; Vanelderen, L; Verwilligen, P; Basegmez, S; Bruno, G; Caudron, J; Delaere, C; Demin, P; Favart, D; Giammanco, A; Grégoire, G; Lemaitre, V; Militaru, O; Ovyn, S; Piotrzkowski, K; Quertenmont, L; Schul, N; Beliy, N; Daubie, E; Alves, G A; Pol, M E; Souza, M H G; Carvalho, W; De Jesus Damiao, D; De Oliveira Martins, C; Fonseca De Souza, S; Mundim, L; Oguri, V; Santoro, A; Silva Do Amaral, S M; Sznajder, A; Fernandez Perez Tomei, T R; Ferreira Dias, M A; Gregores, E M; Novaes, S F; Abadjiev, K; Anguelov, T; Damgov, J; Darmenov, N; Dimitrov, L; Genchev, V; Iaydjiev, P; Piperov, S; Stoykova, S; Sultanov, G; Trayanov, R; Vankov, I; Dimitrov, A; Dyulendarova, M; Kozhuharov, V; Litov, L; Marinova, E; Mateev, M; Pavlov, B; Petkov, P; Toteva, Z; Chen, G M; Chen, H S; Guan, W; Jiang, C H; Liang, D; Liu, B; Meng, X; Tao, J; Wang, J; Wang, Z; Xue, Z; Zhang, Z; Ban, Y; Cai, J; Ge, Y; Guo, S; Hu, Z; Mao, Y; Qian, S J; Teng, H; Zhu, B; Avila, C; Baquero Ruiz, M; Carrillo Montoya, C A; Gomez, A; Gomez Moreno, B; Ocampo Rios, A A; Osorio Oliveros, A F; Reyes Romero, D; Sanabria, J C; Godinovic, N; Lelas, K; Plestina, R; Polic, D; Puljak, I; Antunovic, Z; Dzelalija, M; Brigljevic, V; Duric, S; Kadija, K; Morovic, S; Fereos, R; Galanti, M; Mousa, J; Papadakis, A; Ptochos, F; Razis, P A; Tsiakkouri, D; Zinonos, Z; Hektor, A; Kadastik, M; Kannike, K; Müntel, M; Raidal, M; Rebane, L; Anttila, E; Czellar, S; Härkönen, J; Heikkinen, A; Karimäki, V; Kinnunen, R; Klem, J; Kortelainen, M J; Lampén, T; Lassila-Perini, K; Lehti, S; Lindén, T; Luukka, P; Mäenpää, T; Nysten, J; Tuominen, E; Tuominiemi, J; Ungaro, D; Wendland, L; Banzuzi, K; Korpela, A; Tuuva, T; Nedelec, P; Sillou, D; Besancon, M; Chipaux, R; Dejardin, M; Denegri, D; Descamps, J; Fabbro, B; Faure, J L; Ferri, F; Ganjour, S; Gentit, F X; Givernaud, A; Gras, P; Hamel de Monchenault, G; Jarry, P; Lemaire, M C; Locci, E; Malcles, J; Marionneau, M; Millischer, L; Rander, J; Rosowsky, A; Rousseau, D; Titov, M; Verrecchia, P; Baffioni, S; Bianchini, L; Bluj, M; Busson, P; Charlot, C; Dobrzynski, L; Granier de Cassagnac, R; Haguenauer, M; Miné, P; Paganini, P; Sirois, Y; Thiebaux, C; Zabi, A; Agram, J L; Besson, A; Bloch, D; Bodin, D; Brom, J M; Conte, E; Drouhin, F; Fontaine, J C; Gelé, D; Goerlach, U; Gross, L; Juillot, P; Le Bihan, A C; Patois, Y; Speck, J; Van Hove, P; Baty, C; Bedjidian, M; Blaha, J; Boudoul, G; Brun, H; Chanon, N; Chierici, R; Contardo, D; Depasse, P; Dupasquier, T; El Mamouni, H; Fassi, F; Fay, J; Gascon, S; Ille, B; Kurca, T; Le Grand, T; Lethuillier, M; Lumb, N; Mirabito, L; Perries, S; Vander Donckt, M; Verdier, P; Djaoshvili, N; Roinishvili, N; Roinishvili, V; Amaglobeli, N; Adolphi, R; Anagnostou, G; Brauer, R; Braunschweig, W; Edelhoff, M; Esser, H; Feld, L; Karpinski, W; Khomich, A; Klein, K; Mohr, N; Ostaptchouk, A; Pandoulas, D; Pierschel, G; Raupach, F; Schael, S; Schultz von Dratzig, A; Schwering, G; Sprenger, D; Thomas, M; Weber, M; Wittmer, B; Wlochal, M; Actis, O; Altenhöfer, G; Bender, W; Biallass, P; Erdmann, M; Fetchenhauer, G; Frangenheim, J; Hebbeker, T; Hilgers, G; Hinzmann, A; Hoepfner, K; Hof, C; Kirsch, M; Klimkovich, T; Kreuzer, P; Lanske, D; Merschmeyer, M; Meyer, A; Philipps, B; Pieta, H; Reithler, H; Schmitz, S A; Sonnenschein, L; Sowa, M; Steggemann, J; Szczesny, H; Teyssier, D; Zeidler, C; Bontenackels, M; Davids, M; Duda, M; Flügge, G

2010-01-01

312

Ground plane fin-shaped field effect transistor (GP-FinFET): A FinFET for low leakage power circuits  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, a fin-shaped field effect transistor (FinFET) structure which uses ground plane concept is proposed and theoretically investigated. The ground plane reduces the coupling of electric field between the source and drain reducing drain-induced barrier lowering (DIBL). To assess the performance of the proposed structure, some device characteristics of the structure have been compared with those of silicon on insulator-FinFET (SOI-FinFET) and Bulk-FinFET structures (where the BOX lay...

Saremi, Mehdi; Afzali-kusha, Ali; Mohammadi, Saeed

2012-01-01

313

Transient Response of a Spiral Fin with its Base Subjected to the Variation of Heat Flux  

Directory of Open Access Journals (Sweden)

Full Text Available INTRODUCTION The problem of response in fins has been of much interest for many researchers and engineers due to its magnificently industrial applications. The use of Fins to enhance the heat dissipation from a hot surface is very extensive in many areas of engineering applications. Besides the traditional applications, such as power generator, plants and vehicles, fines are also used in heat removal devices foe electronic components. Park et al. (2007 used the pin-fin type heat sinks for different fin shapes to enhance the heat transfer of a heat sink and the optimum values of the design variables such as fin height, fin width or fin diameter and fan-to-heat sink distance at the junction of a heat sink and a heat source are investigated. T'joen et al. (2007 applied an experimental study to investigate the performance of a fin-and-tube heat exchanger in two different configurations. In a conventional heat exchanger heat is transferred from one fluid to another through a metallic wall. The rate of heat transfer is directly proportional to the extent of the wall surface, the heat transfer coefficient and to the temperature difference between one fluid and the adjacent surface. It might be expected that the rate of heat transfer per unit of the base surface area would increase in direct proportion. However, the average surface temperature of the fins tends to decrease approaching the temperature of the surrounding fluid so the effective temperature difference is decreased and the net increase of heat transfer would not be in direct proportion to the increase of the surface area and may be considerably less than that would be anticipated on the basis of the increase of surface area alone. The performance of fin under steady state conditions has been studied in considerable detail but the transient response of such surfaces to changes in either base temperature or base heat flux has not received much attention. Both of one-dimensional and two-dimensional circular fin have been studied broadly. Chu et al. (1982, 1983a, b has applied the Fourier series inversion technique to determine the transient response of two-dimensional straight fins and circular fins, one-dimensional annular fin and the composite straight fins. His results showed a good agreement in the physical circumstances. The transient temperature response of the annular fins, a special case (pitch equal zero for the spiral fin, was well studied. Cheng et al. (1994, 1998 studied the transient response of annular fins of various shapes subjected to constant base heat fluxes. In their work, the inverse method was applied. Yu and Chao-Kuang Chen (1999 applied the Taylor transformation to the transient temperature response of annular fin. When the end of the fin is not insulated, Harper and Brown (1992 have shown that, under certain circumstances, an equivalent fin with end insulated can be obtained by suitably increasing its length. It is also assumed that one-dimensional analysis is valid. One-dimensional analysis has been shown to be valid under steady state conditions for small Biot number by Crank and Parker (1996. Performance and optimum dimensions of longitudinal and annual fins and spines with a temperature-dependent heat transfer coefficient have been presented by Laor and Kalman (1996. In this study, considered the heat transfer coefficient as a power function of temperature and used exponent values in the power function that represent different heat transfer mechanisms such as free convection, fully developed boiling and radiation. The optimum dimensions of circular fins with variable profile and temperature-dependent thermal conductivity have been obtained by Zubair et al. (1996. Campo and Stuffle (1996 presented a simple and compact form correlation that facilitates a rapid determination of fin efficiency and tip temperature in terms of fin controlling parameters for annular fins of constant thickness. Mokheimer (2002 investigated the performance of annular fins of different profiles subject to locally variable heat transfer coefficient.

J.S. Wang

2008-01-01

314

Estimation and optimization of thermal performance of evacuated tube solar collector system  

Science.gov (United States)

In this study, artificial neural networks (ANNs) and adaptive neuro-fuzzy (ANFIS) in order to predict the thermal performance of evacuated tube solar collector system have been used. The experimental data for the training and testing of the networks were used. The results of ANN are compared with ANFIS in which the same data sets are used. The R2-value for the thermal performance values of collector is 0.811914 which can be considered as satisfactory. The results obtained when unknown data were presented to the networks are satisfactory and indicate that the proposed method can successfully be used for the prediction of the thermal performance of evacuated tube solar collectors. In addition, new formulations obtained from ANN are presented for the calculation of the thermal performance. The advantages of this approaches compared to the conventional methods are speed, simplicity, and the capacity of the network to learn from examples. In addition, genetic algorithm (GA) was used to maximize the thermal performance of the system. The optimum working conditions of the system were determined by the GA.

Dikmen, Erkan; Ayaz, Mahir; Ezen, H. Hüseyin; Küçüksille, Ecir U.; ?ahin, Arzu ?encan

2014-05-01

315

Elimination of plume in laser welding of small diameter tubes with YAG high performance laser  

International Nuclear Information System (INIS)

Bushing technique is the practical method for repairing the damaged tubes of the steam generators in operation. In this case, a bush of smaller diameter is inserted in a small diameter tube. The damaged place is in the supporting plate and on tube walls, and the welding must be carried out in very narrow space. The authors developed a YAG high performance welding system with optical fibers of 2 kW. The 2 kW YAG laser oscillator is placed outside the safety container, and laser beam is transmitted through optical fibers to the end part, therefore, it is very important to protect the optical components from the damage by plume arising at an adjoining place of welding. First, the behavior of plume was studied in Ar, Nz and He atmosphere by using a 20 kW CO2 laser. The action of O2 concentration in protecting gas on penetration depth was examined. The welding condition for YAG laser welding, the condition of gas to help eliminate plume, and the results of practical application of this laser welding of bushes are reported. (K.I.)

316

Scoping assessment of design characteristics for an enhanced calandria tube  

International Nuclear Information System (INIS)

Highlights: ? Both a finned tube and a spiral ribbed tube design showed improved design performance relative to the current bare tube. ? The addition of longitudinal fins has the potential to increase the effective heat transfer surface area by a factor of 1.35. ? The addition of ribs has the potential to increase the effective heat transfer surface area by a factor of 11. ? The addition of longitudinal fins or ribs has the potential to decrease the natural displacement and the bending stress applied to the CT. ? The ribbed design option appears to provide better structural integrity than the finned design option. ? Both designs do not have a significant first order effect on the neutronics although further investigation is required to confirm. - Abstract: Over the lifetime of a CANada Deuterium Uranium (CANDU) type reactor, the pressure tubes and calandria tubes undergo creep deformation via static, dynamic and thermal stresses accelerated by neutron bombardment. Creep deformation leads to fuelling issues, potential contact between the calandria tube (CT) and the liquid injection shutdown system or between the CT and the pressure tube (PT). As such, this aging phenomenon limits the lifetime of these components. Also, in the event of Loss of Coolant Accident (LOCA) and Loss of Emergency Coolant Injection (LOECI) scenarios, PT/CT contact may occur and if sufficient cooling is not provided, PT/CT rupture may also occur. Conceptual designs were assessed to deal designs were assessed to determine their potential for reducing the effects of aging by improving CT rigidity and thermal performance of the CT. Two different design options for a CT have been investigated using numerical simulation techniques. The CT design options include fins and ribs of different sizes and combinations. The fins and ribs provide improved structural integrity and improved thermal performance over the reactors lifetime. Analyzed results have shown that the design options yield an increased overall strength with a minimal impact on fuel efficiency. The analysis has determined that the finned design option is superior in terms of CT strength enhancement yet the ribbed design is superior for improving heat transfer in accident scenarios.

317

On the performance of copper foaming metal in the heat exchangers of pulse tube refrigerator  

Science.gov (United States)

As key components in pulse tube refrigerators (PTRs), heat exchangers have great influence on the performance of the PTRs, especially the cold end heat exchangers which dominate the cooling effect between the cold gas and heat load. Filling copper screens are widely used to improve the performance of heat exchange and laminar flow. Whereas, the heat transfer rate of copper screens is still not good enough for the actual requirements of PTRs. Furthermore, the flow resistance of the copper screen is growing up quickly with the increase of screen mesh. In this paper, we propose a new type of copper foaming metal with high heat transfer area and low flow resistance in the heat exchanger instead of the copper screens. The heat transfer performances of the copper screens and the copper foaming metal are firstly compared by theoretical calculation, which shows that the performance of the copper foaming metal with 600 ?m pore size is better than that of 20 and 80 mesh copper screens, verified by experimental results. A four valve pulse tube refrigerator (FVPTR) with copper foaming metal of 600 ?m pore size as filling material of the heat exchanger achieved 69.5 K, 2.5 K lower than that of using 20 mesh copper screens, 1.7 K lower than that of using 80 mesh copper screens.

Wang, K.; Ju, Y. L.; Lu, X. S.; Gu, A. Z.

2007-01-01

318

Performance model of metallic concentric tube recuperator with counter flow arrangement  

Science.gov (United States)

A performance model for counter flow arrangement in concentric tube recuperator that can be used to utilize the waste heat in the temperature range of 900-1,400°C is presented. The arrangement consists of metallic tubular inner and outer concentric shell with a small annular gap between two concentric shells. Flue gases pass through the inner shell while air passes through the annular gap in the reverse direction (counter flow arrangement). The height of the recuperator is divided into elements and an energy balance is performed on each elemental height. Results give necessary information about surface, gas and air temperature distribution, and the influence of operating conditions on recuperator performance. The recuperative effectiveness is found to be increased with increasing inlet gas temperature and decreased with increasing fuel flow rate. The present model accounts for all heat transfer processes pertinent to a counterflow radiation recuperator and provide a valuable tool for performance considerations.

Sharma, Harshdeep; Kumar, Anoop; Goel, Varun

2010-03-01

319

Performance Evaluation of SG Tube Defect Size Estimation System in the Absence of Defect Type Classification  

International Nuclear Information System (INIS)

In this paper, we study a new estimation system for the prediction of steam generator tube defects. In the previous research works, defect size estimators were independently designed for each defect types in order to estimate the defect size. As a result, the structure of estimation system is rather complex and the estimation performance gets worse if the classification performance is degraded for some reason. This paper studies a new estimation system that does not require the classification of defect types. Although the previous works are expected to achieve much better estimation performance than the proposed system since it uses the estimator specialized in each defect, the performance difference is not so large. Therefore, it is expected that the proposed estimator can be effectively used for the case where the defect type classification is imperfect

320

Comparative study of photocatalytic performance on different TiO2 nano-tubes arrays  

International Nuclear Information System (INIS)

Highlights: • Two different TiO2 nano-tubes arrays were fabricated through anodic oxidization. • Different electrolytes could result in different nano-tubes with morphology. • The relationship between morphology and activity of TNTAs was investigated. • TNTAs-NH4F exhibited higher OCP, photovoltage and photo-convention efficiency. • Highly ordered structure favors the separation of photoinduced charge carriers. -- Abstract: Two different TiO2 nano-tubes arrays (TNTAs) have been successfully fabricated through constant potential anodic oxidization method, followed with post-annealing treatment. Morphologies and crystal structures of the as-fabricated TNTAs were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that both TNTAs were comprised of anatase and rutile phase, while TNTAs-NH4F exhibited highly ordered nano-tubular structure. In addition, their photoelectrochemical (PECH) properties were investigated through open circuit potential (OCP) and photocurrent response. As a result, TNTAs-NH4F performed higher OCP (0.16 mA cm?2), photovoltage (0.1897 V cm?2) and photo-convention efficiency (0.18%) than that of TNTAs-NaF which could result in the more effective separation and transfer of photoinduced electrons and holes. Furthermore, the analysis of photocatalytic (PC) performance and output of hydroxyl radicals (·OH) demonstrated that TNTAs-NH4F photoanode possessed higher PC activity than that of TNTAs-NaF for photodegradation of methyl blue (MB). The higher PECH and PC performance could be ascribed to the highly ordered nano-tubular structure and higher separation and transfer efficiency of photoinduced charge carriers

 
 
 
 
321

Comparative study of photocatalytic performance on different TiO{sub 2} nano-tubes arrays  

Energy Technology Data Exchange (ETDEWEB)

Highlights: • Two different TiO{sub 2} nano-tubes arrays were fabricated through anodic oxidization. • Different electrolytes could result in different nano-tubes with morphology. • The relationship between morphology and activity of TNTAs was investigated. • TNTAs-NH{sub 4}F exhibited higher OCP, photovoltage and photo-convention efficiency. • Highly ordered structure favors the separation of photoinduced charge carriers. -- Abstract: Two different TiO{sub 2} nano-tubes arrays (TNTAs) have been successfully fabricated through constant potential anodic oxidization method, followed with post-annealing treatment. Morphologies and crystal structures of the as-fabricated TNTAs were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that both TNTAs were comprised of anatase and rutile phase, while TNTAs-NH{sub 4}F exhibited highly ordered nano-tubular structure. In addition, their photoelectrochemical (PECH) properties were investigated through open circuit potential (OCP) and photocurrent response. As a result, TNTAs-NH{sub 4}F performed higher OCP (0.16 mA cm{sup ?2}), photovoltage (0.1897 V cm{sup ?2}) and photo-convention efficiency (0.18%) than that of TNTAs-NaF which could result in the more effective separation and transfer of photoinduced electrons and holes. Furthermore, the analysis of photocatalytic (PC) performance and output of hydroxyl radicals ({sup ·}OH) demonstrated that TNTAs-NH{sub 4}F photoanode possessed higher PC activity than that of TNTAs-NaF for photodegradation of methyl blue (MB). The higher PECH and PC performance could be ascribed to the highly ordered nano-tubular structure and higher separation and transfer efficiency of photoinduced charge carriers.

Cheng, Xiuwen [State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), Department of Environmental Science and Engineering, Harbin Institute of Technology, Huanghe Road 73, Nangang District, Harbin 150090 (China); Liu, Huiling, E-mail: hlliu2002@163.com [State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), Department of Environmental Science and Engineering, Harbin Institute of Technology, Huanghe Road 73, Nangang District, Harbin 150090 (China); Chen, Qinghua; Li, Junjing [State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), Department of Environmental Science and Engineering, Harbin Institute of Technology, Huanghe Road 73, Nangang District, Harbin 150090 (China); Yu, Xiujuan [Department of Environmental Science and Engineering, Heilongjiang University, Xuefu Road 74, Nangang District, Harbin 150080 (China)

2013-07-25

322

Study on the manufacturing process, causes of the pressure tube failure and methods for improving its performance  

International Nuclear Information System (INIS)

Manufacturing processes of Zr-2.5Nb pressure tube used in CANDU reactor, effects of impurities on the properties of the pressure tube, experiences and causes of the pressure tube cracking accident and the development programs on the fuel channel at AECL have been described. Fabrication processes on the pressure tube have been explained in detail from the sponge production step to the final product. Test methods that are performed to verify the integrity of the final product have also been described. Most of the pressure tube rupture accidents were caused by DHC (Delayed Hydride Cracking). In cases of Pickering units 3 and 4 and Bruce unit 2, excessive residual stresses induced by improper rolled joint process had played a role to cause DHC. In Pickering unit 2, cracks formed by contact between pressure and calandria tubes due to the movement of garter spring were direct cause of failure. After the accidents, a lot of R and D programs on each component of the fuel channel have been carried out. The study on the improvement of manufacturing processes such as increasing cold working rate, performing the intermediate and final annealing and adding the third element like Fe, V, Cr for enhancing the pressure tube performance are on progress. To suppress hydrogen uptake into the pressure tube, the methods such as zirconia coating on the pressure tube, Cr-plating on the end fitting and placing the yttrium getter on the pressure tube are considered. Experiments on each test specimen are currently under way. Owing to such an effort, more advanced fuel channel can be installed in the next CANDU reactor. 6 tabs., 20 figs., 20 refs. (Author)

323

Thermal performance measurements of a graphite tube compact cryogenic support for the Superconducting Super Collider  

International Nuclear Information System (INIS)

The magnet cryostat development program for the Superconducting Super Collider (SSC) High Energy Physics Proton-Proton Collider has produced an innovative design for the structural support of the cold mass and thermal radiation shields. This work updates the continuing development of the support known as the Compact Cryogenic Support (CCS). As the structural and thermal requirements of the SSC became better defined, a CCS was developed that employs an innermost tube comprised of a graphite composite material. Presented is the thermal performance to 4.5K of the graphite CCS model. 8 refs., 6 figs., 2 tabs

324

OTEC performance tests of the Carnegie-Mellon University vertical fluted-tube condenser  

Energy Technology Data Exchange (ETDEWEB)

Results of performance tests on a vertical fluted-tube condenser designed by Carnegie-Mellon University are reported. The condenser was free of operational problems and performed in a stable and repeatable manner. At nominal design conditions (a heat duty of 3.2 million Btu/hr and a water flow rate of 3200 gpm), the overall heat transfer coefficient (U/sub 0/) was 1040 Btu/hr.ft/sup 2/./sup 0/F and the water-side pressure drop was 3.3 psi. Varying the quality of the ammonia vapor feed to the condenser (in the range of 90 to 100%) did not affect performance. On the other hand, when the heat duty was increased from 2.3 million to 4.0 million Btu/hr, U/sub 0/ rose from 1024 to 105 Btu/hr.ft/sup 2/./sup 0/F. This trend resulted from an increase in the ammonia-side coefficient (from 3270 to 3730 Btu/hr.ft/sup 2/./sup 0/F) over this range of heat duties. Finally, the water-side coefficient was about 2.45 times greater than that calculated from the Sieder-Tate equation for smooth circular tubes of the same cross-sectional area. This enhancement ratio of 2.45 was some 20% greater than the enhancement factor of 2.07 expected from the increase in surface area alone.

Lewis, L G; Sather, N F

1979-05-01

325

The effects of area contraction on the performance of UNITEN's shock tube: Numerical study  

International Nuclear Information System (INIS)

Numerical study into the effects of area contraction on shock tube performance has been reported in this paper. The shock tube is an important component of high speed fluid flow test facility was designed and built at the Universiti Tenaga Nasional (UNITEN). In the above mentioned facility, a small area contraction, in form of a bush, was placed adjacent to the diaphragm section to facilitate the diaphragm rupturing process when the pressure ratio across the diaphragm increases to a certain value. To investigate the effects of the small area contraction on facility performance, numerical simulations were conducted at different operating conditions (diaphragm pressure ratios P4/P1 of 10, 15, and 20). A two-dimensional time-accurate Navier-Stokes CFD solver was used to simulate the transient flow in the facility with and without area contraction. The numerical results show that the facility performance is influenced by area contraction in the diaphragm section. For instance, when operating the facility with area contraction using diaphragm pressure ratio (P4/P1) of 10, the shock wave strength and shock wave speed decrease by 18% and 8% respectively.

326

Optimum Design of Thin Walled Tube on the Mechanical Performance of Super Lock Nut  

Science.gov (United States)

The bolts and nuts are widely used in various fields as important joining elements with long history. However, loosening induced by the vibration and external loads is still a big problem. For example, the loosening sometimes causes very serious accident without notice. This paper deals with a special nut named “Super Lock Nut (SLN)” which can prevent loosening effectively. There is a thin walled tube between the upper and lower threads, which can be deformed along the axial direction so that the phase difference of lower and upper threads is produced and SLN is developed. This phase difference induces the contrary forces on the surfaces of the upper and lower threads, which bring out the anti-loosening performance. In this study, the anti-loosening performance is analyzed and realized with the finite element method. Moreover, the anti-loosening performances under various phase difference of lower and upper threads are compared and finally best dimensions for SLN are examined.

Noda, Nao-Aki; Xiao, Yang; Kuhara, Masahiro; Saito, Kinjiro; Nagawa, Masato; Yumoto, Atsushi; Ogasawara, Ayako

327

The shark's fin  

International Nuclear Information System (INIS)

Initial plain film studies of seven patients with facet fracture-dislocations of the cervical spine were examined retrospectively. Rotation of the cross-table lateral film from a standard vetical viewing orientation to a simulated brow-down position allowed easier appreciation of the dislocated pillar in six of the seven patients. The displaced pillar had an appearance similar to that of the dorsal fin of a shark. We conclude that the finding of a shark's fin appearance of an articular pillar in a traumatized patient warrants further radiographic studies. (author). 8 refs.; 3 figs

328

Development of colburn ` j' factor and fanning friction factor ` f' correlations for compact heat exchanger plain fins by using CFD  

Science.gov (United States)

A numerical model has been developed for plain fin of plate fin heat exchanger. Plain fin performance has been analyzed with the help of CFD by changing the various parameters of the fin, Colburn ` j' and fanning friction ` f' factors are calculated. These values compared with the standard values. The correlations have been developed between Reynolds number Re, fin height h, fin thickness t, fin spacing s, Colburn factor ` j' and friction factor ` f'.

Bala Sundar Rao, R.; Ranganath, G.; Ranganayakulu, C.

2013-07-01

329

THERMAL ANALYSIS OF CPU WITH COMPOSITE PIN FIN HEAT SINKS  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes about pin fin and slot parallel plate heat sinks with copper and carbon carbon composite(CCC base plate material mounted on CPU’s. The parameters such as fin geometry, base plate material, base plate thickness, number of fins, fin thickness are considered and primarily in this paper fin geometry, base platethicknesses, base plate materials are optimized for improving the thermal performance of a heat sink in the next generation. In this research work, the thermal model of the computer system with various fin geometry heat sink design has been selected and the fluid flow, thermal flow characteristics of heat sinks have been studied. The plate, pin and Elliptical fin geometry heat sinks have been used with base plate to enhance the heat dissipation. In this study a complete computer chassis with different heat sinks are investigated and the performances of the heat sinks are compared.

R.Mohan

2010-09-01

330

Performance of M5TM alloy as cladding tube and structural component material  

International Nuclear Information System (INIS)

Based on an extensive program of optimization and industrial development, the M5TM alloy proposed by Framatome-ANP as cladding tube and structural components material meets the fuel users requirements (high reliability, dimensional stability, high corrosion resistance, low hydrogen pick-up) and complies with PCI, RIA and LOCA criteria for the increasingly challenging operating conditions. To date the M5TM alloy is the reference alloy for PWR cladding-tubes, guide-tubes and spacer grids offered by Framatome ANP on the market. Alloy M5TM is fully optimised and industrially mastered, its out-of-pile properties are reproducible and stable under irradiation. In-pile testing and, most important, experience feedback from irradiation in PWRs clearly demonstrate that the M5TM features all properties required for upgraded reactor operation under normal conditions. To date more than 400,000 fuel rods with M5TM cladding are under irradiation or discharged in 36 PWRs worldwide including 40 full reloads; more over 36 all-M5TM LTAs (M5TM cladding, guide-tube and spacers) are under irradiation in 10 PWRs. An extensive post-irradiation surveillance program has shown that compared with low-tin Zircaloy-4, M5TM cladding and structural components exhibit impressive gains at extended burnup related to corrosion, hydriding, creep and growth. To address the behavior of the fuel during a RIA or a LOCA traior of the fuel during a RIA or a LOCA transient, full-scale tests and comprehensive analyses have been performed on M5TM and for comparison with SRA low-tin Zircaloy-4. These tests demonstrate that M5TM shows identical or even better performance than SRA Zircaloy-4 in all phase of a LOCA and a RIA. This paper will focus on the behavior of the M5TM cladding-tube, guide-tube and spacer-grids in normal operating and accidental conditions. Regarding the behavior of the M5TM under LOCA conditions, the post-quench mechanical properties between 1000 and 1200 .deg. C of M5TM cladding for three types of mechanical tests, are similar to those of Zircaloy-4 and are combined with positive residual ductility. Other tests performed on Zircaloy-4 and other Nb-containing alloys type have led to different conclusions. As a prerequisite for licensing a complete core with fuel elements having M5TM cladding, a 5 cycle and a 6 cycle fuel rod with respectively a local burnup of 63 and 75 GWd/tU were subjected to a RIA test in the Cabri loop under conditions causing Zircaloy-4 and other Zr alloys to fail but no failure occurred in M5TM. End 2002, the authorisation for loading M5 cladding into KSNP fuel assembly was granted by Korean Safety Authorities

331

Performance of a prototype aerogel counter readout by fine mesh photo-tubes  

International Nuclear Information System (INIS)

The BABAR experiment, in order to achieve its physics program, requires pion/kaon identification capability up to 4.3 GeV/c. The recent development of new processes has lead to the fabrication of low density silica aerogel with high optical quality. An aerogel threshold counter using the combination of 2 refractive indices (1.055 and 1.007) can be used to complete the angular coverage of the particle identification system in the forward region of the BABAR experiment. We present final test-beam results on a 2 layer aerogel prototype, readout by Hamamatsu fine mesh photo-tubes, as required by the high magnetic field environment of the BaBar experiment. Several configurations have been tested, with different aerogels, photo-tubes and reflective materials. We have performed a Monte-Carlo simulation, in order to understand the sensitivity of light collection to the optical parameters. The result of the test shows that such a detector can achieve the desired performances. (authors). 14 refs., 19 figs., 1 tab

332

Prediction of ice slurry performance in a corrugated tube heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

Ice slurry performance in a concentric corrugated tube heat exchanger is experimentally studied in this work in order to compare experimental results to theoretical prediction obtained using the correlations proposed in previous papers. Once the validity of those correlations is verified, the behaviour of the studied heat exchanger is analyzed for different ice slurry flow conditions and compared to the results obtained when a heterogeneous storage is used and only carrier fluid flows through the heat exchanger. According to the performance evaluation criterion used - variation in heat transfer rate for equal pressure drop and surface area - the most remarkable conclusion obtained is that slurry improves the behaviour of the heat exchanger studied for all the cases analyzed, although the increase in heat transfer rate is always lower than 15%, being in most cases lower than 5%. (author)

Illan, F.; Viedma, A. [Departamento de Ingenieria Termica y de Fluidos, Universidad Politecnica de Cartagena, Campus de la Muralla del Mar, 30202 Cartagena (Spain)

2009-09-15

333

Drift Tubes Trigger System of the CMS Experiment at LHC : Commissioning and Performances  

CERN Document Server

In this thesis the performances of the CMS Drift Tubes Local Trigger System of the CMS detector are studied. CMS is one of the general purpose experiments that will operate at the Large Hadron Collider at CERN. Results from data collected during the Cosmic Run At Four Tesla (CRAFT) commissioning exercise, a globally coordinated run period where the full experiment was involved and configured to detect cosmic rays crossing the CMS cavern, are presented. These include analyses on the precision and accuracy of the trigger reconstruction mechanism and measurement of the trigger efficiency. The description of a method to perform system synchronization is also reported, together with a comparison of the outcomes of trigger electronics and its software emulator code.

Battilana, Carlo

2009-01-01

334

Performance of a flash-lamp-pumped Nd:YAG laser with short-wavelength-cut tubes.  

Science.gov (United States)

Performance of a flash-lamp-pumped Nd:YAG laser with optically coated short-wavelength-cut tubes has been investigated. The laser rod or the flash lamps were covered with the coated tubes, which reflect radiation of wavelengths less than 0.5 µm. The experimental results show a 10% increase in the polarized laser output power and a 40% reduction of the rod-heating power when coated tubes are used for either the flash lamps or the rod. PMID:20861954

Takehisa, K; Yano, M; Kuwabara, K

1993-12-20

335

SEISMIC RESISTING PERFORMANCE OF A NEW DOUBLE TUBE HYBRID SYSTEM FOR MULTI-STORY BUILDINGS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Investigation on Double Tube Hybrid System (DTHS) through experimental work and analytical study are conducted as a part of the proposal on the seismic design method for Double Tubes Hybrid System (DTHS) for buildings. This structural system comprises Energy Dissipation Structural Walls (EDSW) as the interior tube and Spandrel Wall Frame (SWF) as the exterior tube. EDSW is composed of two reinforced concrete walls linked by steel coupling girders. The RC walls are not anchored to the foundati...

Nasruddin*

2012-01-01

336

Improvement of high-voltage performance of acceleration tubes by cleaning the walls with a high-pressure water jet  

Science.gov (United States)

We cleaned electrostatic accelerator tubes by applying a high-pressure water jet and examined their high-voltage performances at 1 and 3 MV. The cleaning was very effective in reducing discharge activities at their rated voltages. We did some experimental investigations with the tubes and their ceramic insulators. We found that removal of microparticles loosely bound on the vacuum-side ceramic surfaces had an important effect in eliminating the discharge activities.

Takeuchi, S.; Nakanoya, T.; Kabumoto, H.; Yoshida, T.

2003-11-01

337

Improvement of high-voltage performance of acceleration tubes by cleaning the walls with a high-pressure water jet  

International Nuclear Information System (INIS)

We cleaned electrostatic accelerator tubes by applying a high-pressure water jet and examined their high-voltage performances at 1 and 3 MV. The cleaning was very effective in reducing discharge activities at their rated voltages. We did some experimental investigations with the tubes and their ceramic insulators. We found that removal of microparticles loosely bound on the vacuum-side ceramic surfaces had an important effect in eliminating the discharge activities

338

Enhancement of Natural Convection Heat Transfer from Perforated Fin  

Directory of Open Access Journals (Sweden)

Full Text Available A comprehensive theoretical and experimental study was carried out on the thermal performance of a pin fin heat sink. An experimental model was shows that have the capability of predicting influence of effective surface area of pin fin on thermal heat transfer coefficient. Pin fin array are used in many applications to enhance heat transfer and also shows enhancement of heat transfer coefficient for different material of fin. Several different type of experiment test were run out with corresponding variation including the material of pin fin and different perforation on pin fin .Perforation with circular cross section are along the height of pin fin and there number varies from 1 to 3. The result indicates that the material having higher thermal conductivity with higher number of perforation gives more heat transfer coefficient. The effect of perforation on heat transfer was investigated.

Mr. Saurabh ,D. Bahadure , Mr. G. D. Gosavi

2014-01-01

339

An approach to optimal fin diameter based on entropy minimization  

Directory of Open Access Journals (Sweden)

Full Text Available Pin fin geometries provide a large surface area of heat transfer and reduce the thermal resistance of the package. One of the important features of this type of fins is that they often take less space and contribute less to the weight and cost of the product. Pin fin arrays are used widely in many applications such as gas turbine or electronic circuits cooling, where pin fin geometries use due to their low cost of manufacturing and easy installing. In gas turbine application heat transfer from the blade to the coolant air can be increased by installing pin fins. In fact, Pin fin arrays increase heat transfer by increasing the flow turbulence and surface area of the airfoil exposed to the coolant. The overall performance of a heat exchanger with pin-fin typically depends on a number of parameters including the fin diameter, dimensions of the baseplate and pin-fins, thermal joint resistance and location heat sources. These parameters have an impact on the optimal design of a heat exchanger. Fin diameter is a key parameter to determine overall heat exchanger efficiency and entropy generation. In this paper, our objective is introducing an Equation to calculate optimal fin diameter based on minimizing entropy generation.

Masoud Asadi

2013-04-01

340

The influences of recycle on performance of baffled double-pass flat-plate solar air heaters with internal fins attached  

Energy Technology Data Exchange (ETDEWEB)

A new device for inserting an absorber plate to divide a flat-plate channel into two parts with fins attached by baffles and external recycling at the ends is presented. The proposed device substantially improves the heat-transfer efficiency. Experimental and theoretical investigations into the device efficiency are presented. The theoretical prediction agreement with the measured values from the experimental results is good. The experimental and theoretical results are represented graphically and compared with data from the downward-type single-pass solar air heaters of the same size without recycling. Considerable heat-transfer improvement is obtained by employing baffled double-pass operations with external recycling and fin attached over and under the absorber plate. The recycle ratio and absorber plate location influences on the heat-transfer efficiency and on the power consumption increment are also discussed. (author)

Ho, C.D.; Yeh, H.M.; Cheng, T.W.; Chen, T.C.; Wang, R.C. [Energy and Opto-Electronic Materials Research Center, Department of Chemical and Materials Engineering, Tamkang University Tamsui, Taipei 251 (China)

2009-09-15

 
 
 
 
341

Study on a Concentric Tube Bulb Manometer and its Performance Compared to U-shaped Manometer  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents comparative study of a new type of manometer calledconcentric tube bulb (C.T.B manometer. Its performance of measuring differential heightis studied against conventional U-shaped manometer. Pressure drops and mass flow ratesare calculated by taking various systems comprising of different flow measuring devicessuch as orifice and venturimeters using both U- shaped and C.T.B manometers.Comparison between the physically measured values of differential pressure drops andmass flow rates with the calculated values based on theoretical equations is also made.Experiments are carried out using mercury and CCl4 in these manometers as sensing fluids.Water is used as flowing fluid for mass flow rate and pressure drop measurements, whereasin gauge pressure measurements air is used.

Muhammad A. Butt

2007-11-01

342

Performance of the MACRO limited streamer tubes for estimates of muon energy  

CERN Document Server

The MACRO limited streamer tubes can be operated in drift mode by using the TDCs included in the QTP system. In this way a considerable improvement in the space resolution is obtained, allowing the analysis of muon tracks in terms of multiple scattering effects and the energy estimates of muons crossing the detector. We present the results of two dedicated tests, performed with the CERN PS-T9 and SPS-X7 beams, to provide a full check of the electronics and to exploit the feasibility of the analysis. Using a neural network, we are able to estimate the muon energies up to E/sub mu / approximately = 40 GeV. The test beam data provide then an absolute energy calibration, which allows to apply the method to the MACRO data. (5 refs).

Giorgini, M

2002-01-01

343

Study of the performance of the ATLAS monitored drift tube chambers under the influence of heavily ionizing $\\alpha$-particles  

CERN Document Server

The MDT chambers of the ATLAS Muon Spectrometer will operate in a heavy LHC background environment mainly from photons and neutrons. The ionization produced by neutron recoils is much higher than the one from photons or muons and can be simulated by the use of alpha particles. A systematic study of the behavior of the ATLAS Monitored Drift Tubes (MDTs) under controlled irradiation has been performed. The presence of alpha particles results in the reduction of the gas gain due to space charge effects. The gas gain reduction has been studied in a single tube set up using a well controlled radium (/sup 226/Ra) source in order to enrich the tube gas (Ar/CO/sub 2/) with the alpha emitter /sup 220/Rn and irradiate the tubes internally. The results are confronted with Garfield simulations.

Sampsonidis, Dimitrios; Liolios, Anastasios; Manolopoulou, Metaxia; Petridou, C

2004-01-01

344

Performance comparison between three intraoral image receptors of different technology at a variety of tube potential, tube current and exposure time settings using a stepwedge phantom  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: To comparatively evaluate the per-formance of three intraoral image receptors of different technology when exposed to different X-ray beam spectra, dose and dose rate levels using a stepwedge phantom. Materials and methods: The intraoral radiographic receptors evaluated were: the Kodak Insight F speed class film, the Kodak RVG 6000, and the Duerr Vis-tascan Combi PSP system. A dental quality control phantom made of Plexiglas, containing an aluminium stepwedge with 12 steps and 7 holes drilled in each step was radiographed using a dental X-ray unit offering a wide range of tube potential, tube current and exposure time settings. The visibility of the holes in the images produced with each one of the three receptors was assessed by three independent observers. For each image the total image quality score (TS was derived from the summation of the number of visible holes in each step. The numbers of perceptible holes in each experimental condition (TSs were statistically analyzed through use of analysis of variance. Intraobserver and interobserver agree-ment was also measured. Results: Vistascan ex-hibited the most extended useful exposure range, followed by RVG 6000 and Insight. RVG 6000 exhibited the largest TS values in all tube potential settings except 70 kV where the Vistascan performed better. Insight performed better than Vistascan only at 60 and 63 kV. Vistascan performed better at 66 and 70 kV, Insight at 60 and 66 kV, whereas RVG performed equally well at all tube potential settings, except than at 52 and 70 kV. For the Insight the largest TS values were obtained with the smallest ESAK values whereas with the Vistascan the largest TS were obtained with ESAK values that where the largest observed. Conclusions: The performance of all receptors tested was greatly dependent on the exposure parameters and mainly on the kV settings. Overall, the RVG 6000 offered the best image quality at doses somewhere in between those required by the Insight and the Vistascan.

Elli Katsoni

2011-01-01

345

Use of biorobotic models of highly deformable fins for studying the mechanics and control of fin forces in fishes.  

Science.gov (United States)

Bony fish swim with a level of agility that is unmatched in human-developed systems. This is due, in part, to the ability of the fish to carefully control hydrodynamic forces through the active modulation of the fins' kinematics and mechanical properties. To better understand how fish produce and control forces, biorobotic models of the bluegill sunfish's (Lepomis macrochirus) caudal fin and pectoral fins were developed. The designs of these systems were based on detailed analyses of the anatomy, kinematics, and hydrodynamics of the biological fins. The fin models have been used to investigate how fin kinematics and the mechanical properties of the fin-rays influence propulsive forces and to explore kinematic patterns that were inspired by biological motions but that were not explicitly performed by the fish. Results from studies conducted with the fin models indicate that subtle changes to the kinematics and mechanical properties of fin rays can significantly impact the magnitude, direction, and time course of the 3D forces used for propulsion and maneuvers. The magnitude of the force tends to scale with the fin's stiffness, but the direction of the force is not invariant, and this causes disproportional changes in the magnitude of the thrust, lift, and lateral components of force. Results from these studies shed light on the multiple strategies that are available to the fish to modulate fin forces. PMID:21653544

Tangorra, James; Phelan, Chris; Esposito, Chris; Lauder, George

2011-07-01

346

Crash Performance Evaluation of Hydro-formed DP-steel Tubes Considering Welding Heat Effects, Formability and Spring-back  

International Nuclear Information System (INIS)

In order to numerically evaluate hydro-formed DP-steel tubes on crash performance considering welding heat effects, finite element simulations of crash behavior were performed for hydro-formed tubes with and without heat treatment effects. Also, finite element simulations were performed for the sequential procedures of bending and hydro-forming of tubes in order to design process parameters, particularly for the boost condition and axial feeding, considering formability and spring-back. Effects of the material property including strain-rate sensitivity on formability as well as spring-back were also considered. The mechanical properties of the metal active gas (MAG) weld zone and the heat affected zone (HAZ) were obtained utilizing the continuous indentation method in this work

347

Effect of Low Aspect Ratio on Convective Heat Transfer from Rectangular Fin Array in Natural Convection  

Directory of Open Access Journals (Sweden)

Full Text Available Experimental and CFD analysis is conducted in order to establish effect of geometrical fin parameters for natural convection heat transfer from vertical rectangular fin arrays.Natural convective heat transfer from rectangular vertical plates has been reviewed. Study revealed that most of the work was carried out considering various configurations. Experimental work carried on steady state natural convection heat transfer from vertical rectangular fins made of aluminum. Experimental work carried investigates the effect of fin spacing, fin height, fin length on the performance of heat dissipation from the fin arrays. It is found that convection heat transfer rate depends on fin height and fin length. For a given fin spacing, the convection heat transfer rate from fins increases with fin height. For a given fin spacing, the convection heat transfer rate from fins increases with fin length .This trend is observed for every fin configuration. It is found that convection heat transfer rate is more for less aspect ratio fin array for same power input.

V.S.Daund*

2014-08-01

348

Finite Element and Experimental Analysis for the Performance of Hybrid Composite Tubes under Crushing  

Directory of Open Access Journals (Sweden)

Full Text Available An experimental and finite element analysis for axial crushing of hybrid composite tubes of different fiber combinations as cotton, glass and carbon has been carried out throughout this investigation. One size of tube has been selected with a length of 110 and 90 mm diameter. This composite tubes were fabricated using the filament winding process. Cotton, glass and carbon fibers were selected to be the reinforcement materials. While epoxy resin and hardener have been used to form the matrix required for the fabrication of the composite tubes. All the composite tubes were fabricated from six layers. The first three types of tubes were of fully cotton, fully glass and fully carbon type fibers. The other three tubes were done by using all the three types of fibers to form a hybrid type. Each two layers have been made of the same type of fiber. Compression tests were carried out for all the tubes fabricated. Three tests were done for each type in order to get better results consistency. Load-displacement graphs were drawn for each test. The initial crushing and mean loads were obtained for each case and then drawn against the type of hybrid. The specific energy absorption has also been plotted for each case. Finite element analysis for tubes of the same dimensions and materials were done for the elastic behavior region. A comparison was done for the tested composite tubes between the finite element and the experimental results. Results obtained from this study shows that carbon fiber tubes stands higher load than glass fiber and cotton fibers. For hybrid types tested, tubes with the external layer of carbon shows higher strength than those of internal carbon fiber layers. It has also been found that the difference between the experimental and finite element results at the elastic region of load-displacement response falls in the range of 1.3 to 14%.

Asad A. Khalid

2001-01-01

349

A Chemical Screen to Identify Novel Inhibitors of Fin Regeneration in Zebrafish  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We performed a chemical screen to look for novel inhibitors of zebrafish caudal fin regeneration. In a pilot screen, 520 compounds were tested. Two compounds, budesonide and AGN192403, abrogated fin regeneration. One compound in particular, AGN192403, targets the imidazoline receptor, a pathway not previously linked to fin regeneration. In addition to inhibiting regeneration of the adult fin, AGN192403 also blocked regeneration of the larval fin fold. Finally, the inhibitory effect of AGN1924...

Oppedal, Douglas; Goldsmith, Matthew I.

2010-01-01

350

Measurement of Work Generation and Improvement in Performance of a Pulse Tube Engine  

Science.gov (United States)

Apart from double acting type engines, Stirling engines have either 2 pistons in 2 cylinders or 2 pistons in a single cylinder. Typically, the heater, regenerator and cooler are installed between the 2 pistons. The pulse tube engine, on the other hand, consists of a single piston in a single cylinder, a pulse tube, a heater, a regenerator, a cooler and a second cooler. For this paper, a simple prototype engine that uses air at normal atmospheric pressure as the working gas was fabricated. The oscillating velocity of the working gas in the pulse tube was measured using LDV, and the work flow emitting out of the pulse tube was observed. In addition, the effect of inserting heat storage material in the pulse tube on shaft power and indicated power was examined experimentally. A dramatic increase in the shaft power was achieved.

Hamaguchi, Kazuhiro; Futagi, Hiroaki; Yazaki, Taichi; Hiratsuka, Yoshikatsu

351

Experimental examination of heat removal limitation of screw cooling tube at high pressure and temperature conditions  

Energy Technology Data Exchange (ETDEWEB)

For development of high heat flux components for fusion machines, JAERI has developed high performance cooling tubes using pressurized water flow. A cooling tube with triangular fins on its inner surface has been tested. Because the fins can be machined by a simple mechanical threading, this tube is called a screw tube. The present study is intended to investigate heat transfer characteristics of the screw tube with M10 thread of 1.5-mm-pitch, which has the highest critical heat flux (CHF) in the previous experimental campaign compared with the tubes with various threads of different pitches. In addition, another CHF tests have been performed to examine the reduction of the heat removal performance of the screw tube caused with the increase of cooling water temperature up to 100 deg. C at the local pressure of 2 and 4 MPa. The results of CHF experiments are compared with an existing correlation for a smooth tube to evaluate its heat removal limitation at higher temperature condition compared with the previous ones.

Ezato, Koichiro [Blanket Engineering Lab, Department of Fusion Research Establishment, Japan Atomic Energy Research Institute, JAERI, Naka-shi, Naka-gun, Ibaraki-ken 311-0193 (Japan)]. E-mail: ezatok@fusion.naka.jaeri.go.jp; Suzuki, Satoshi [Blanket Engineering Lab, Department of Fusion Research Establishment, Japan Atomic Energy Research Institute, JAERI, Naka-shi, Naka-gun, Ibaraki-ken 311-0193 (Japan); Dairaku, Masayuki [Blanket Engineering Lab, Department of Fusion Research Establishment, Japan Atomic Energy Research Institute, JAERI, Naka-shi, Naka-gun, Ibaraki-ken 311-0193 (Japan); Akiba, Masato [Blanket Engineering Lab, Department of Fusion Research Establishment, Japan Atomic Energy Research Institute, JAERI, Naka-shi, Naka-gun, Ibaraki-ken 311-0193 (Japan)

2006-02-15

352

Source Drain Engineering in FinFET – A Review  

Directory of Open Access Journals (Sweden)

Full Text Available Scaling poses many challenges beyond 22nm technology. In this paper, the various designs proposed by researchers about the double gate FinFET with raised source and drain have been studied. Also the significance of various parameters, different modes of operation of the FinFET, effect of fin thickness over the performance, doping level, effect of height of source and drain, advantages of using metal gate electrodes along with high-k dielectrics have been studied. Different designing techniques of double gate FinFETs and its advantages are noted so as to create a new design for better drive current and low leakage.

I.Flavia Princess Nesamani

2014-02-01

353

Compound heat transfer enhancement for shell side of double-pipe heat exchanger by helical fins and vortex generators  

Science.gov (United States)

To improve heat transfer performance of shell side of double-pipe heat exchanger with helical fins on its inner tube, some vortex generators (VGs) were installed along the centerline of the helical channel. Heat transfer performance and pressure drop characteristic of the enhanced heat exchangers were investigated using air as the working fluid and steam as the heating medium. The helical fins were in the annulus and span its full width at different helical pitch. Wing-type VGs (delta or rectangular wing) and winglet-type VGs (delta or rectangular winglet pair) were used to combine with helical fins. The friction factor and Nusselt number can be well correlated by power-law correlations in the Reynolds number range studied. In order to evaluate the thermal performance of the shell side enhanced over the shell side without enhancement, comparisons were made under three constraints: (1) identical mass flow rate, IMF; (2) identical pressure drop, IPD and (3) identical pumping power, IPP. The results show the shell side enhanced by the compound heat transfer enhancement has better performance than the shell side only enhanced by helical fins at shorter helical pitch under the three constraints.

Zhang, Li; Guo, Hongmei; Wu, Jianhua; Du, Wenjuan

2012-07-01

354

Compound heat transfer enhancement for shell side of double-pipe heat exchanger by helical fins and vortex generators  

Energy Technology Data Exchange (ETDEWEB)

To improve heat transfer performance of shell side of double-pipe heat exchanger with helical fins on its inner tube, some vortex generators (VGs) were installed along the centerline of the helical channel. Heat transfer performance and pressure drop characteristic of the enhanced heat exchangers were investigated using air as the working fluid and steam as the heating medium. The helical fins were in the annulus and span its full width at different helical pitch. Wing-type VGs (delta or rectangular wing) and winglet-type VGs (delta or rectangular winglet pair) were used to combine with helical fins. The friction factor and Nusselt number can be well correlated by power-law correlations in the Reynolds number range studied. In order to evaluate the thermal performance of the shell side enhanced over the shell side without enhancement, comparisons were made under three constraints: (1) identical mass flow rate, IMF; (2) identical pressure drop, IPD and (3) identical pumping power, IPP. The results show the shell side enhanced by the compound heat transfer enhancement has better performance than the shell side only enhanced by helical fins at shorter helical pitch under the three constraints. (orig.)

Zhang, Li [School of Chemical Engineering, Shenyang University of Chemical Technology, Shenyang, Liaoning (China); School of Chemical Engineering, Tianjin University, Tianjin (China); Guo, Hongmei; Du, Wenjuan [School of Chemical Engineering, Shenyang University of Chemical Technology, Shenyang, Liaoning (China); Wu, Jianhua [School of Chemical Engineering, Tianjin University, Tianjin (China); School of Mechanical Engineering, Shenyang University of Chemical Technology, Shenyang, Liaoning (China)

2012-07-15

355

Effect of interior guide tubes in cross-flow turbine runner on turbine performance  

Energy Technology Data Exchange (ETDEWEB)

The cross-flow turbine has attracted much attention as a source of hydropower generation for small and micro-systems, especially for low head establishments. Such turbines have a distinct advantage of lower initial and operating costs over other small scale turbines, but their efficiency is lower than others. Efficiency predictions of these turbines are generally based on the assumption that the entire flow crosses from the first stage to the second stage of the turbine runner. In this study, interior guide tubes were designed and used inside the runner of a cross-flow turbine to collect and guide the crossing flow towards the second stage of the runner. The interior guide tubes were designed on the basis of observed flow patterns inside the runner. Experimentally, three different types of tubes were tested. The laboratory tests were conducted to calculate the turbine efficiency with different gate openings of nozzle and different positions of interior guide tubes. Results of this work with and without interior tubes have been presented in this paper. When the experiments were done with and without interior guide tubes, it has been found that turbine efficiency with the interior guide tube decreased about 5 per cent. (Author)

Olgun, Hayati [Tubitak Marmara Research Center, Energy Systems and Environmental Research Inst., Kocaeli (Turkey)

2000-07-01

356

Comparison of charge transfer device and photomultiplier tube performance for extremely low photon fluxes  

Science.gov (United States)

New solid state silicon arrays which outperform photon counting photomultiplier tubes (PMTs) under extreme low light fluxes are described. The results of the evaluation of the spectroscopically pertinent characteristics of several charge transfer device (CTD) detectors are presented. The characteristics of these multichannel detectors include peak quantum efficiencies exceeding 80 percent, read noises of approximately ten charge carriers and virtually no dark current. The potential for these non-intensified silicon devices to outperform PMTs in many low light level situations is demonstrated. The signal-to-noise ratios for several CTD detectors are contrasted to the signal-to-noise ratio performance of the best photon counting PMTs for a variety of low flux situations. Two approaches to creating a single element detector with the same optical format and larger dynamic range than common photon PMTs are described. The results of the evaluation of a prototype large single element charge injection device are presented. Combining a 1,000,000 simple dynamic range with the ability to vary integration times over four orders of magnitude allows this detector to quantity photon fluxes ranging over ten orders of magnitude.

Sweedler, Jonathan V.; Denton, M. B.

1988-02-01

357

Analytical and experimental performance of a dual-mode traveling wave tube and multistage depressed collector  

Science.gov (United States)

A computational procedure for the design of traveling-wave-tube(TWT)/refocuser/multistage depressed collector (MDC) systems was used to design a short, permanent-magnet refocusing system and a highly efficient MDC for a medium-power, dual-mode, 4.8- to 9.6-GHz TWT. The computations were carried out with advanced, multidimensional computer programs which model the electron beam and follow the trajectories of representative charges from the radiofrequency (RF) input of the TWT, through the slow-wave structure and refocusing section, to their points of impact in the depressed collector. Secondary emission losses in the MDC were treated semiquantitatively by injecting representative secondary-electron-emission current into the MDA analysis at the point of impact of each primary beam. A comparison of computed and measured TWT and MDC performance showed very good agreement. The electrodes of the MDC were fabricated from a particluar form of isptropic graphite that was selected for its low secondary electron yield, ease of machinability, and vacuum properties.

Ramins, Peter; Force, Dale A.; Kosmahl, Henry G.

1987-01-01

358

Research on Under-actuated Flexible Pectoral Fin of Labriform Fish  

Directory of Open Access Journals (Sweden)

Full Text Available The new propulsor, whose inspiration is from pectoral fins of fishes, has arisen increasing attention. To improve the performance of the existing labriform bionic pectoral fin, based on the structure and control mechanism of real fish pectoral fin, the under-actuated technology was utilized to design a new flexible bionic pectoral fin. Then, the kinematic model of pectoral fin during fish forward steady swimming and the dynamic model of bionic pectoral was built. Finally, Matlab was used to simulate the kinematic and dynamic performance of bionic pectoral fin. The simulation result shows that the new flexible bionic pectoral fin can imitate the propulsion motion morphology of pectoral fin during fish forward steady swimming well. However, due to the restriction of kinematic model of pectoral fin and structure as well as physical properties of bionic fin ray, there is still tolerance between the locomotion morphology of bionic pectoral fin and that of real fish. Therefore, it is necessary to develop further research on kinematic modeling of pectoral fin and bionic design of fin ray. Additionally, the new bionic pectoral fin reduces the number of the driving variables, providing the possibility and the basis of further reducing the volume as well as the complexity of bionic device of pectoral fin.

Qiang Liu

2012-06-01

359

Estimation of heat transfer performance of surface condenser with titanium tubes  

International Nuclear Information System (INIS)

The heat transfer characteristic of titanium tube expected for use for the condenser is described. Titanium is inferior in heat conductivity to copper alloys. But this problem is solved at the design level. Since contaminant adhesion to the tube is thought to differ from plant to plant, the cleaning condition must be worked out while the vacuum is observed. This report shows an example of sponge-ball cleaning test and investigates the effect of a sponge ball with carborundum on the wear of tubing material. The test results indicate that even when chlorination is not used, the ball cleaning is sufficient heat transfer measure. (author)

360

Study of the performance of ATLAS muon drift-tube chambers in magntic fields and at high irradiation rates  

Energy Technology Data Exchange (ETDEWEB)

The performance of ATLAS muon drift-tube (MDT) chambers has been studied in detail using high-energy muon beams. The measurements of the drift tube properties in magnetic fields showed that inelastic collisions of the drifting electrons with the CO{sub 2} molecules in the Ar:CO{sub 2} (93:7) gas mixture of the MDT chambers have to be taken into account in the simulation of the drift properties. Such inelastic collisions are now correctly treated by the Garfield simulation programme from version 9 providing an accurate description of the behaviour of the ATLAS muon drift tubes, in particular in the magnetic field. Measurements at the Gamma Irradiation Facility at CERN were performed to study the performance of the MDT chambers in the presence of high {gamma} ray background fluences. The chambers have a spatial resolution better than 40 {mu}m at the nominal background rates expected at the Large Hadron Collider design luminosity of 10{sup 34} cm{sup -2}s{sup -1} and a resolution better than 50 {mu}m for up to five times higher background rates. Efficient muon detection up to background counting rates of 500 kHz per tube corresponding to 35% occupancy was demonstrated.

Valderanis, Chrysostomos

2012-07-26

 
 
 
 
361

Final Technical Report - High-Performance, Oxide-Dispersion-Strengthened Tubes for Production of Ethylene adn Other Industrial Chemicals  

Energy Technology Data Exchange (ETDEWEB)

This project was undertaken by Michigan Technological University and Special Metals Corporation to develop creep-resistant, coking-resistant oxide-dispersion-strengthened (ODS) tubes for use in industrial-scale ethylene pyrolysis and steam methane reforming operations. Ethylene pyrolysis tubes are exposed to some of the most severe service conditions for metallic materials found anywhere in the chemical process industries, including elevated temperatures, oxidizing atmospheres and high carbon potentials. During service, hard deposits of carbon (coke) build up on the inner wall of the tube, reducing heat transfer and restricting the flow of the hydrocarbon feedstocks. About every 20 to 60 days, the reactor must be taken off-line and decoked by burning out the accumulated carbon. This decoking costs on the order of $9 million per year per ethylene plant, accelerates tube degradation, and requires that tubes be replaced about every 5 years. The technology developed under this program seeks to reduce the energy and economic cost of coking by creating novel bimetallic tubes offering a combination of improved coking resistance, creep resistance and fabricability not available in current single-alloy tubes. The inner core of this tube consists of Incoloy(R) MA956, a commercial ferritic Fe-Cr-Al alloy offering a 50% reduction in coke buildup combined with improved carburization resistance. The outer sheath consists of a new material - oxide dispersion strengthened (ODS) Alloy 803(R) developed under the program. This new alloy retains the good fireside environmental resistance of Alloy 803, a commercial wrought alloy currently used for ethylene production, and provides an austenitic casing to alleviate the inherently-limited fabricability of the ferritic Incoloy(R) MA956 core. To provide mechanical compatibility between the two alloys and maximize creep resistance of the bimetallic tube, both the inner Incoloy(R) MA956 and the outer ODS Alloy 803 are oxide dispersion strengthened materials produced using mechanical alloying technology. To minimize cost, the bimetallic tube is produced by direct powder co-extrusion. This technology has potential for domestic energy savings of up to 4.1 trillion BTU/year (4.3 x 1015J/year) and a reduction of 370,000 tons (340,000 tonnes) of CO2 emissions in short-residence-time ethylene furnaces. This represents an energy savings and CO2 emissions reduction of about 3.3%. If the technology is also applied to other types of ethylene pyrolysis furnaces, total energy savings and CO2 emissions reductions could increase by up to five times. The work involved: Developing powder and consolidation processing protocols to produce an oxide-dispersion strengthened variant of Alloy 803 exhibiting creep strength comparable to Incoloy? Alloy MA956, Developing a direct powder co-extrusion protocol for fabricating co-extruded bimetallic Incoloy? Alloy MA956 / ODS Alloy 803 tubes, Characterizing the properties of the ODS Alloy 803 material, the welding characteristics of the bimetallic tubes, and the coking characteristics of the Incoloy? MA956 alloy, and Documenting the potential energy savings and user requirements for these bimetallic pyrolysis furnace tubes. The project demonstrated that oxide dispersion strengthened Alloy 803 can be produced successfully using conventional mechanical alloying technology. The oxide dispersion strengthened bimetallic radiant coil technology explored under this program has significant potential for energy savings and productivity improvements for domestic ethylene producers. In today's competitive market, however, domestic furnace manufacturers and ethylene producers appear reluctant to pay any cost premium for higher-performance coil materials offering either higher temperature capabilities or longer service life. Interest in oxide dispersion strengthened radiant coils is likely to increase if furnace and ethylene producers begin to focus more on increasing tube wall temperatures to improve productivity.

McKimpson, Marvin G.

2006-04-06

362

DEVELOPMENT OF A REPRODUCIBLE SCREENING METHOD TO DETERMINE THE MECHANISM AND EFFECT OF ORGANIC ACIDS AND OTHER CONTAMINANTS ON THE CORROSION OF ALUMINUM-FINNED COPPER-TUBE HEAT EXCHANGE COILS  

Energy Technology Data Exchange (ETDEWEB)

Formicary corrosion is an insidious form of localized pitting corrosion. Notoya (1997b) wrote, ?In Japan, this type of corrosion is found in approximately 10% of cases of premature failure of copper tubes.? Attack characteristically features very small surface pits which are not visible to the un-aided eye, and random directional changes in the underlying copper metal. Attack is rapid. Failures have occurred before installation, shortly thereafter, or within several years later. Objectives of this Research Project Conduct an in depth literature search on the subject of formicary corrosion. Define the corrosion mechanism. Develop a test method that will reproduce formicary corrosion. Develop a test method for screening candidate materials that could cause formicary corrosion.

Richard A. Corbett; Dave Severance

2005-02-01

363

PWR RCCA Rodlet Performance for Cladding Tube Cracking caused by Absorber Swelling  

International Nuclear Information System (INIS)

The swelling of the rod tip due to neutron irradiation is one of the important degradation mechanisms of the control rods of a PWR. In Japan, the diameter measurements of RCCAs (Rod Cluster Control Assembly) have been carried out at several reactor sites in order to investigate the relation between the diameter increase of the rod tip and neutron fluence. During these inspections, an axial crack was found in a rod tip which had a high neutron exposure. Then, the cracked rodlet was examined in a hot-cell to identify the cause of crack. As a result of the examination, it is concluded that the crack in the rodlet tip was caused by a decrease in elongation of the cladding tube due to neutron irradiation and an increase in hoop strain caused by swelling of the absorber. The critical hoop strain for crack initiation is estimated to be approximately 0.7 % from the hot-cell studies and this agrees well with the threshold in the diameter increase at which cracking was observed during site inspections. In addition, mechanical tests were performed on the absorber material using unirradiated specimens to investigate the contribution of mechanical deformation of the absorber on the diameter increase of the rod. Test results show that the contribution of mechanical deformation of the absorber is negligible. The crack in the tip of a rodlet is considered to have no impact on the performance and the integrity of the RCCA because the crack is longitudinal, and the absorber material is resistant to corrosion in the primary water environment of a PWR. In Japan, however, a management guideline has been established to prevent cracks based on the above studies, i.e., the RCCA is replaced when the neutron fluence at the rod tip exceeds critical values. For the purpose of farther life extension of the RCCA, an improved RCCA in which the diameter of the absorber is reduced at the tip has been introduced. At this time, more than 700 improved RCCAs are in service and have experienced up to 5 operating cycles. The follow-up program on the improved RCCAs is being conducted for estimating their life time. Recently, diameter measurements were carried out on the improved RCCAs. The results show good performance of the improved RCCA, i.e. no obvious diameter increase was observed and the diameter increase seems smaller than that of a conventional RCCA although the neutron fluence is not so large at this time

364

Toward quantum FinFET  

CERN Document Server

This book reviews a range of quantum phenomena in novel nanoscale transistors called FinFETs, including quantized conductance of 1D transport, single electron effect, tunneling transport, etc. The goal is to create a fundamental bridge between quantum FinFET and nanotechnology to stimulate readers' interest in developing new types of semiconductor technology. Although the rapid development of micro-nano fabrication is driving the MOSFET downscaling trend that is evolving from planar channel to nonplanar FinFET, silicon-based CMOS technology is expected to face fundamental limits in the near future. Therefore, new types of nanoscale devices are being investigated aggressively to take advantage of the quantum effect in carrier transport. The quantum confinement effect of FinFET at room temperatures was reported following the breakthrough to sub-10nm scale technology in silicon nanowires. With chapters written by leading scientists throughout the world, Toward Quantum FinFET provides a comprehensive introductio...

Wang, Zhiming

2013-01-01

365

Electron Optics Design and Performance of a New Large-Format Two-Frame Framing Tube  

Energy Technology Data Exchange (ETDEWEB)

We have developed a framing tube with 80-mm photocathode for capturing two frames in less than 100-ns onto a 50-mm phosphor screen. A proven electron optics trajectory code was used to design the tube for imaging fidelity over wide dynamic range. This code's full accounting of space charge effects is essential for its ability to simulate accurately the distributed photoelectronic trajectories from the entire large photocathode area. Our approach and guideline for designing the electron optics are described. Results of trajectory simulation and test measurement are reported. Substantial correlations between the code expectation and the measured results are observed on relative resolution and distortion of the frame images. This tube has been integrated into an active framing camera system for field application.

Lai, C C

2002-11-08

366

Hydrothermal Preparation of Gd3+Doped Titanate Nano tubes: Magnetic Properties and Photovoltaic Performance  

International Nuclear Information System (INIS)

Pure and Gd3+ doped titanate nano tubes (TNTs) materials were synthesized by a hydrothermal method. Their morphology, optical properties, thermal stability, and magnetic properties were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), UV-Vis spectroscopy, thermal analysis, and magnetic measurements. It was found that doping renders Gd3+ TNT visible light active and results in smaller crystallite size and larger surface area as well as higher thermal stability compared to pure titanate nano tubes. The estimated magnetic moments point to presence of weak antiferromagnetic interaction. Application of the prepared Gd3+ TNT for modifying conventional photoanodes in polymer solar cells was attempted. Preliminary results show slightly improved photovoltaic energy conversion efficiency in the devices containing the newly designed Gd3+ doped nano tubes.

367

Sensitization and performances of S1 image converter tubes designed for laser fusion experiments  

International Nuclear Information System (INIS)

S1 streak cameras with time resolution better than 10 ps are now currently available at the Centre d'Etudes de Limeil. They integrate a standard P 500 image converter tube slightly modified to allow the S1 photocathode's deposition. Almost 70% of the tubes have 1.06 ?m sensitivity greater than 50 ?A/w and 60% are in the 100 to 400 ?A/w range. It is also possible to regenerate the 1.06 ?m sensitivity when necessary, thus solving the difficult lifetime problem of these tubes. Dynamic range of a few hundreds is possible for 47 ps I.R. laser pulses and more than 64 for 12 ps pulses

368

A comparison of R-22, R-134a, R-410a, and R-407c condensation performance in smooth and enhanced tubes: Part 1, Heat transfer  

Energy Technology Data Exchange (ETDEWEB)

Local and average heat transfer coefficients during condensation are reported for R-22, R-134a, R-410a, and R-407c in one smooth tube and three enhanced surface tubes. The test tubes included a 3/8 inch outer diameter smooth tube, a 3/8 inch outer diameter microfin tube, a 5/16 inch outer diameter microfin tube, and a 5/8 inch outer diameter microfin tube. The local and average heat transfer coefficients were measured over a mass flux range of 92,100 lb/ft{sup 2}{center_dot}h to 442,200 lb/ft{sup 2}{center_dot}h and at saturation temperatures of 104 F and 122 F. A comparison of the performance of the different refrigerants reveals that R-134a has the highest heat transfer performance followed by R-22 and R-410a, which have similar performances. In general, R-407c had the lowest performance of the refrigerants tested. The microfin tube more than doubles the heat transfer coefficient compared to the smooth tube for all refrigerants at the low mass fluxes, but only increases the heat transfer coefficients by 50% at the highest mass flux tested. The measured heat transfer coefficients are also compared with a number of correlations for condensation.

Eckels, S.J.; Tesene, B.A.

1999-07-01

369

Effect of fins and repeated-rib roughness on the performance characteristics of a reactor vessel air cooling system for LMFBR shutdown heat removal  

International Nuclear Information System (INIS)

The use of a totally passive cooling system for shutdown heat removal that rejects heat from the reactor vessel by radiation to the guard vessel and from the guard vessel to a circulating air stream driven by natural convection is a key feature of the US Department of Energy's liquid-metal reactor advanced design study concepts. General Electric refers to the system as the Reactor Vessel Auxiliary Cooling System (RVACS) and Rockwell International as the Reactor Auxiliary Cooling System (RACS). The circulating air stream is contained in the annular passage formed with guard vessel wall and the duct wall surrounding the guard vessel. Specifically, the RVACS/RACS is designed to assure adequate cooling of the reactor vessel under abnormal operational conditions associated with loss of heat removal through the normal heat transport path via the steam generator system or the DRACS, if available. To enhance the heat transfer, longitudinal radial fins or repeated ribs can be attached to the duct wall and/or the guard vessel. The purpose of the present paper is to summarize the status of the analytical work on the development of an optimum design configuration for the RVACS/RACS

370

Numerical simulation of a pectoral fin during labriform swimming.  

Science.gov (United States)

We numerically examine the fluid-structure interaction and force generation of a skeleton-reinforced fin that geometrically, structurally and kinematically resembles the pectoral fin of a fish during labriform swimming. This fin contains a soft membrane with negligible bending stiffness and 12 embedded rays (modeled as beams). A potential flow-based boundary element model is applied to solve the fluid flow around the fin, in which the vorticity field is modeled as thin vorticity sheets shed from prescribed locations (the sharp trailing edge). The fin motion is actuated by dorsoventral and anteroposterior rotations of the rays (the motion of each ray is controlled individually), as well as pitching motion of the baseline. Consequently, the fin undergoes a combination of flapping (lift-based) and rowing (drag-based) motions typical in labriform swimming. The fin motion contains two strokes: a recovery stroke and a power stroke. The performance of the fin depends upon kinematic parameters such as the Strouhal number, the phase lag between rays, the pitching motion of the baseline and the passive deformations of the rays. The most interesting finding is that the strengthening of the ray at the leading edge plays a pivotal role in performance enhancement by reducing the effective angle of attack and decreasing the power expenditure during the recovery stroke. PMID:20511517

Shoele, Kourosh; Zhu, Qiang

2010-06-15

371

An Evaluation of Performance Metrics for High Efficiency Tube-and-Wing Aircraft Entering Service in 2030 to 2035  

Science.gov (United States)

An analysis of basic vehicle characteristics required to meet the Fundamental Aeronautics Program s 70 percent energy consumption reduction goal for commercial airliners in the 2030 to 2035 timeframe was conducted. A total of 29 combinations of vehicle parasitic drag coefficient, vehicle induced drag coefficient, vehicle empty weight and engine Specific Fuel Consumption were used to create sized tube-and-wing vehicle models. The mission fuel burn for each of these sized vehicles was then compared to a baseline current technology vehicle. A response surface equation was generated of fuel burn reduction as a function of the four basic vehicle performance metrics, so that any values of the performance metrics up to a 50 percent reduction could be used to estimate fuel burn reduction of tube-and-wing aircraft for future studies.

Perkins, H. Douglas; Wilson, Jack; Raymer, Daniel P.

2011-01-01

372

A study of the high vacuum engineering for the accelerator tube construction has performed  

International Nuclear Information System (INIS)

Failure of the accelerator tube vacuum systems due to construction and physical chemistry aspect are reported in this study. The problem solving are presented in this paper, where the results of this engineering concepts are met with the requirement of the technical specifications. (author)

373

Design and performance of a charge-coupled device /CCD/-streak tube  

International Nuclear Information System (INIS)

A new 'streak' tube has been developed for use in diagnostic applications involving very high-speed optical transients such as the Shiva laser-fusion studies at the University of California's Lawrence Livermore Laboratory. The tube combines the direct read-out characteristics of a CCD (charge-coupled device) with the high-speed deflection system incorporated in the light-shutter image tube to give immediate electronic read-out of information suitable for data processing. The front section of the tube is an image-intensifier stage with an infrared-sensitive photocathode (S-1) sensitive to the laser wavelength of 1.06 micrometers. When the laser beam is incident on the photocathode, the emitted stream of electrons is accelerated and deflected by a ramp voltage applied to deflecting electrodes. The deflected beam impacts the CCD, producing several thousand electron-hole pairs per photoelectron. The charge pattern is then scanned out providing a time-intensity profile of the laser beam

374

Enhancement of the Remote Field Eddy Current Testing Performed from Outside of a Magnetic Tube  

Directory of Open Access Journals (Sweden)

Full Text Available The paper deals with design of remote field eddy current probe for non-destructive testing dedicated for inspection of ferromagnetic tubular material from outside. The remote field effect inside the tube wall is achieved by the medium of a magnetic shield covering the probe. Results of numeric simulations made for verification of probe characteristics confirmed the effectiveness of probe design.

Daniela Gombarska

2006-01-01

375

50 CFR 600.1204 - Shark finning; possession at sea and landing of shark fins.  

Science.gov (United States)

... 2010-10-01 2010-10-01 false Shark finning; possession at sea and landing of shark fins. 600.1204 Section 600.1204 ...COMMERCE MAGNUSON-STEVENS ACT PROVISIONS Shark Finning § 600.1204 Shark finning;...

2010-10-01

376

Stability of tube rows in crossflow  

International Nuclear Information System (INIS)

A mathematical model for the instability of tube rows subjected to crossflow is examined. The theoretical model, based on the fluid-force data for a pitch-to-diameter ratio of 1.33, provides additional insight into the instability phenomenon. Tests are also conducted for three sets of tube rows. The effects of mass ratio, tube pitch, damping, detuning and finned tubes are investigated. Theoretical results and experimental data are in good agreement

377

Performance evaluation of a non-adiabatic capillary tube in a transcritical CO{sub 2} heat pump cycle  

Energy Technology Data Exchange (ETDEWEB)

A non-adiabatic capillary tube in a transcritical CO{sub 2} heat pump cycle has been simulated to investigate the effect of parameters such as gas cooler and evaporator temperature, capillary tube diameter and heat exchanger length on various performance indicators. The homogeneous flow model is employed to simulate two-phase flow in the non-adiabatic capillary tube. Fundamental equations of mass, energy and momentum are solved simultaneously through an iterative process. Single and two-phase heat transfer coefficients are calculated by employing appropriate empirical correlations. Subcritical and supercritical thermodynamic and transport properties of CO{sub 2} are calculated employing an in-house precision property code. Lowering evaporator temperature is found to be more effective for heat transfer from the capillary tube compared to the gas cooler temperature. Heat transfer rate variation with respect to gas cooler temperature in case of CO{sub 2} is distinctly different compared to conventional refrigerants due to its transcritical nature and is influenced by initial quality, mass flow rate of the refrigerant and the prevailing temperature difference at the gas cooler. Increase in gas cooler temperature causes the heat transfer rate to first increase and then to decrease. Lowering evaporator and gas cooler temperature increases the cooling capacity. Throttling effect decreases rapidly as internal tube diameter becomes larger leading to higher mass flow rate of the refrigerant. Shorter inlet adiabatic capillary length with larger heat exchanger length is better for heat transfer. This study is an attempt to allay the scepticism prevailing in the parlance of CO{sub 2} based transcritical systems overemphasising the need for a throttle valve to control the optimum discharge pressure. (author)

Agrawal, Neeraj; Bhattacharyya, Souvik [Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

2008-04-15

378

Subcooled freon-11 flow boiling in top-heated finned coolant channels with and without a twisted tape  

Science.gov (United States)

An experimental study was conducted in top-heated finned horizontal tubes to study the effect of enhancement devices on flow boiling heat transfer in coolant channels. The objectives are to examine the variations in both the mean and local (axial and circumferential) heat transfer coefficients for circular coolant channels with spiral finned walls and/or spiral fins with a twisted tape, and improve the data reduction technique of a previous investigator. The working fluid is freon-11 with an inlet temperature of 22.2 C (approximately 21 C subcooling). The coolant channel's exit pressure and mass velocity are 0.19 M Pa (absolute) and 0.21 Mg/sq. ms, respectively. Two tube configurations were examined; i.e., tubes had either 6.52 (small pitch) or 4.0 (large pitch) fins/cm of the circumferential length (26 and 16 fins, respectively). The large pitch fins were also examined with a twisted tape insert. The inside nominal diameter of the copper channels at the root of the fins was 1.0 cm. The results show that by adding enhancement devices, boiling occurs almost simultaneously at all axial locations. The case of spiral fins with large pitch resulted in larger mean (circumferentially averaged) heat transfer coefficients, h sub m, at all axial locations. Finally, when twisted tape is added to the tube with large-pitched fins, the power required for the onset of boiling is reduced at all axial and circumferential locations.

Smith, Alvin; Boyd, Ronald D., Sr.

1989-01-01

379

Unsteady thermal response of a porous fin under the influence of natural convection and radiation  

Science.gov (United States)

In this study, the effects of transient thermal performance of a rectangular porous fin in the presence of radiation and natural convection heat transfer are considered. The porous fin allows the flow to infiltrate through it and solid-fluid interaction takes place. This study is performed using Darcy's model to formulate heat transfer equation. To study the thermal performance, three types of cases are considered, namely, long fin, finite length fin with insulated tip and finite length fin with tip exposed. The effects of the porosity parameter Sh, radiation parameter G and the temperature ratio CT on the dimensionless transient temperature distribution and heat transfer rate are discussed.

Darvishi, M. T.; Gorla, Rama Subba Reddy; Khani, F.

2014-09-01

380

Performance Analysis of Shell and Tube Heat Exchanger Using Miscible System  

Directory of Open Access Journals (Sweden)

Full Text Available An experimental investigation on comparative heat transfer study on a solvent and solution were made using 1-1 Shell and Tube Heat Exchanger. Steam is the hot fluid, whereas Water and Acetic acid-Water miscible solution serves as cold fluid. A series of runs were made between steam and water, steam and Acetic acid solution. In addition to, the volume fraction of Acetic acid was varied and the experiment was held. The flow rate of the cold fluid is maintained from 120 to 720 lph and the volume fraction of Acetic acid is varied from 10-50%. Experimental results such as exchanger effectiveness, overall heat transfer coefficients were calculated. A mathematical model was developed for the outlet temperatures of both the Shell and Tube side fluids and was simulated using MATLAB program. The model was compared with the experimental findings and found to be valid.

M. Thirumarimurugan

2008-01-01

 
 
 
 
381

Controlled Thermal-Mechanical Processing of Tubes and Pipes for Enhanced Manufacturing and Performance  

Energy Technology Data Exchange (ETDEWEB)

The Alloy Steel Business of The Timken Company won an award for the controlled thermo-mechanical processing (CTMP) project and assembled a strong international public/private partnership to execute the project. The premise of the CTMP work was to combine Timken's product understanding with its process expertise and knowledge of metallurgical and deformation fundamentals developed during the project to build a predictive process design capability. The CTMP effort succeeded in delivering a pc-based capability in the tube optimization model, with a virtual pilot plant (VPP) feature to represent the desired tube making process to predict the resultant microstructure tailored for the desired application. Additional tasks included a system for direct, online measurement of grain size and demonstration of application of CTMP via robotically enhanced manufacturing.

Kolarik, Robert V.

2005-11-11

382

Condensation heat transfer coefficients of flammable refrigerants on various enhanced tubes  

Energy Technology Data Exchange (ETDEWEB)

In this study, external condensation Heat Transfer Coefficients (HTCs) of six flammable refrigerants of propylene (R1270), propane (R290), isobutane (R600a), butane (R600), dimethylether (RE170), and HFC32 were measured at the vapor temperature of 39 .deg. C on a 1023 fpm low fin and turbo-C tubes. All data were taken under the heat flux of 32{approx}116 and 42{approx}142 kW/m{sup 2} for the low fin and turbo-C tubes respectively. Flammable refrigerants' data obtained on enhanced tubes showed a typical trend that external condensation HTCs decrease with increasing wall subcooling. HFC32 and DME showed up to 30% higher HTCs than those of HCFC22 due to their excellent thermophysical properties. Propylene, propane, isobutane, and butane showed similar or lower HTCs than those of HCFC22. Beatty and Katz' correlation predicted the HTCs of the flammable refrigerants obtained on a low fin tube within a mean deviation of 7.3%. Turbo-C tube showed the best performance due to its 3 dimensional surface geometry for fast removal of condensate.

Park, Ki Jung; Jung, Dong Soo [Inha Univ., Incheon (Korea, Republic of)

2005-10-15

383

Evaluating the Fin-ray Trajectory Tracking of Bio-inspired Robotic Undulating Fins via an Experimental-numerical Approach  

Directory of Open Access Journals (Sweden)

Full Text Available In the past decade, biomimetic undulating fin propulsion has been one of the main topics considered by scientists and researchers in the field of robotic fish. This technology is inspired by the biological wave-like propulsion of ribbon-finned fish. The swimming modes have aquatic application potentials with greater manoeuvrability, less detectable noise or wake and better efficiency at low speeds. The present work concentrates on the evaluation of fin-ray trajectory tracking of biorobotic undulating fins at the levels of kinematics and hydrodynamics by using an experimental-numerical approach. Firstly, fin-ray tracking inconsistence between the desired and actual undulating trajectories is embodied with experimental data of the fin prototype. Next, the dynamics' nonlinearity is numerically and analytically unveiled by using the computational fluid dynamics (CFD method, from the viewpoint of vortex shedding and the hydro-effect. The evaluation of fin-ray tracking performance creates a good basis for control design to improve the fin-ray undulation of prototypes.

Xiaojia Xiang

2014-07-01

384

Development of Remote Weld Testing Technique for Moisture Separator and Reheater Tubes in Nuclear Power Plants  

International Nuclear Information System (INIS)

The heat exchanger tube in nuclear power plants is mainly fabricated from nonferromagnetic material such as a copper, titanium, and inconel alloy, but the moisture separator and reheater tube in the turbine system is fabricated from ferromagnetic material such as a carbon steel or ferrite stainless steel which has a good mechanical properties in harsh environments of high pressure and temperature. Especially, the moisture separator and reheater tubes, which use steam as a heat transfer media, typically employ a tubing with integral fins to furnish higher heat transfer rates. The ferromagnetic tube typically shows superior properties in high pressure and temperature environments than a nonferromagnetic material, but can make a trouble during the normal operation of power plants because the ferrous tube has service-induced damage forms including a steam cutting, erosion, mechanical wear, stress corrosion cracking, etc. Therefore, nondestructive examination is periodically performed to evaluate the tube integrity. Now, the remote field testing(RFT) technique is one of the solution for examination of ferromagnetic tube because the conventional eddy current technique typically can not be applied to ferromagnetic tube such as a ferrite stainless steel due to the high electrical permeability of ferrous tube. In this study, we have designed RFT probes, calibration standards, artificial flaw specimen, and probe pusher-puller necessary for field application, and have successfulfor field application, and have successfully carry out RFT examination of the moisture separator and reheater tube of nuclear power plants.