WorldWideScience
1

Thermal performance analysis of a tube finned surface  

Energy Technology Data Exchange (ETDEWEB)

The present work submits an experimental work on the heat transfer and friction loss characteristic, employing a tube finned heating surface kept at a constant temperature in a rectangular channel. The tube fins attached on the surface (o.d.=29 mm) were arranged as either in-line or staggered. The parameters for the study were Reynolds number (3700-30 000), depending on hydraulic diameter, the distance between the tube fins in the flow direction (S{sub y}/D=1.72-3.45) and the fin arrangement. The change in the Nusselt number with these parameters was determined. For both tube fin arrangements, it was observed that increasing Reynolds number increased Nusselt number, and maximum heat transfer occurred at S{sub y}/D=2.59. Thermal performance for both arrangements were also determined and compared with respect to heat transfer from the same surface without fins. With staggered array, a heat transfer enhancement up to 25 per cent for S{sub y}/D=3.45 in staggered array was achieved in constant pumping power. (Author)

Bilen, Kadir [Ataturk Univ., Dept. of Mechanical Engineering, Erzurum (Turkey); Akyol, Ugur [Trakya Univ., Dept. of Mechanical Engineering, Corlu/Tekirdag (Turkey); Yapici, Sinan [Ataturk Univ., Dept. of Chemical Engineering, Erzurum (Turkey)

2002-07-01

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

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

4

Fin-and-tube condenser performance evaluation using neural networks  

Energy Technology Data Exchange (ETDEWEB)

The paper presents neural network approach to performance evaluation of the fin-and-tube air-cooled condensers which are widely used in air-conditioning and refrigeration systems. Inputs of the neural network include refrigerant and air-flow rates, refrigerant inlet temperature and saturated temperature, and entering air dry-bulb temperature. Outputs of the neural network consist of the heating capacity and the pressure drops on both refrigerant and air sides. The multi-input multi-output (MIMO) neural network is separated into multi-input single-output (MISO) neural networks for training. Afterwards, the trained MISO neural networks are combined into a MIMO neural network, which indicates that the number of training data sets is determined by the biggest MISO neural network not the whole MIMO network. Compared with a validated first-principle model, the standard deviations of neural network models are less than 1.9%, and all errors fall into {+-}5%. (author)

Zhao, Ling-Xiao [Institute of Refrigeration and Cryogenics, Shanghai Jiaotong University, Shanghai 200240 (China); Zhang, Chun-Lu [China R and D Center, Carrier Corporation, No. 3239 Shen Jiang Road, Shanghai 201206 (China)

2010-05-15

5

Performance analysis of finned tube and unbaffled shell-and-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

This work considers an optimum design problem for the different constraints involved in the designing of a shell-and-tube heat exchanger consisting of longitudinally finned tubes. A Matlab simulation has been employed using the Kern's method of design of extended surface heat exchanger to determine the behavior on varying the values of the constraints and studying the overall behavior of the heat exchanger with their variation for both cases of triangular and square pitch arrangements, along with the values of pressure drop. It was found out that an optimum fin height existed for particular values of shell and tube diameters when the heat transfer rate was the maximum. Moreover it was found out that the optimum fin height increased linearly with the increase in tube outer diameter. Further studies were also performed with the variation of other important heat exchanger design features and their effects were studied on the behavior of overall performance of the shell-and-tube heat exchanger. The results were thereby summarized which would proclaim to the best performance of the heat exchanger and therefore capable of giving a good idea to the designer about the dimensional characteristics to be used for designing of a particular shell and tube heat exchanger. (author)

Barman, Joydeep; Ghoshal, A.K. [Department of Chemical Engineering, Indian Institute of Technology, Guwahati, North Guwahati 781039, Assam (India)

2007-12-15

6

Enhancement of heat transfer. The performance of micro-fin tubes  

International Nuclear Information System (INIS)

Micro-fin tubes are characterised by numerous, very small integral fins that spiral down the inner surface. A very interesting feature of their performance in flow boiling and condensation is a large heat transfer enhancement accompanied by a low pressure drop penalty. This paper presents a general overview of micro-fin tubes and of their performance in evaporation, condensation and single-phase flow

7

Study on turbulent flow and heat transfer performance of tubes with internal fins in EGR cooler  

Science.gov (United States)

In this paper, flow and heat transfer performances of the tubes with internal longitudinal fins in Exhaust Gas Recirculation (EGR ) cooler were investigated by three-dimension computation and experiment . Each test tube was a single-pipe structure, without inner tube. Three-dimension computation was performed to determine the thermal characteristics difference between the two kinds of tubes, that is, the tube with an inner solid staff as a blocked structure and the tube without the blocked structure. The effects of fin width and fin height on heat transfer and flow are examined. For proving the validity of numerical method, the calculated results were compared with corresponding experimental data. The tube-side friction factor and heat transfer coefficient were examined. As a result, the maximum deviations between the numerical results and the experimental data are approximately 5.4 % for friction factor and 8.6 % for heat transfer coefficient, respectively. It is found that two types of internally finned tubes enhance significantly heat transfer. The heat transfer of the tube with blocked structure is better, while the pressure drop of the tube without blocked structure is lower. The comprehensive performance of the unblocked tube is better to applied in EGR cooler.

Liu, Lin; Ling, Xiang; Peng, Hao

2015-01-01

8

Indoor test for thermal performance evaluation of seven Elcam fin-tube solar collector configurations  

Science.gov (United States)

The test procedure used and the results obtained from an evaluation test program conducted to obtain thermal performance data on seven Elcam fin-tube solar collector configurations under simulated conditions are described. These tests were made using the Marshall Space Flight Center solar facilities. The Elcam fin-tube (liquid) solar collectors each consist of an absorber plate 5.9 inches wide by 83 inches long and a type M copper tube of 0.569 inch nominal inside diameter. No cover plate was used with any of the specimens. The uniqueness of each of the seven configurations is described, and tests were performed on each separate configuration.

1979-01-01

9

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

10

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

International Nuclear Information System (INIS)

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

11

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

Science.gov (United States)

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.

Halici, Fethi; Taymaz, Imdat

2006-07-01

12

Study on heat transfer and flow resistance performance of petal-shaped finned tube oil-cooler with helical baffles  

International Nuclear Information System (INIS)

The heat transfer and flow resistance performance of petal-shaped finned tube oil-cooler with helical baffles was studied, and compared the total heat transfer coefficient of petal-shaped finned tube oil-cooler with helical baffles with that of smooth tube oil-cooler with segmental baffles. The results showed that the total heat transfer coefficient of petal-shaped finned tube oil-cooler with helical baffles was 4-5 times as large as that of smooth tube oil-cooler with segmental baffles at the same oil pressure drop. The correlation equation of the total heat transfer of petal-shaped finned tube oil-cooler petal-shaped finned tube and oil pressure drop with oil velocity were obtained

13

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.

14

Effects of Tube Diameter and Tubeside Fin Geometry on the Heat Transfer Performance of Air-Cooled Condensers  

Science.gov (United States)

A theoretical study has been made on the effects of tube diameter and tubeside fin geometry on the heat transfer performance of air-cooled condensers. Extensive numerical calculations of overall heat transfer from refrigerant R410A flowing inside a horizontal microfin tube to ambient air were conducted for a typical operating condition of the air-cooled condenser. The tubeside heat transfer coefficient was calculated by applying a modified stratified flow model developed by Wang et al.8). The numerical results show that the effects of tube diameter, fin height, fin number and helix angle of groove are significant, whereas those of the width of flat portion at the fin tip, the radius of round corner at the fin tip and the fin half tip angle are small.

Wang, H. S.; Honda, Hiroshi

15

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

International Nuclear Information System (INIS)

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

16

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.

17

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

18

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

19

Filmwise condensation of steam on low integral-finned tubes  

Science.gov (United States)

Filmwise condensation heat-transfer measurements of steam were made on horizontal tubes under vacuum and near-atmospheric pressures. Data were taken for smooth tube and for 21 tubes which contained rectangularly-shaped, low integral fins. The fin geometry was systematically varied in order to investigate the dependence of the steam-side heat-transfer coefficient on fin spacing, thickness and height. The condensation process was found to be most sensitive to fin spacing and to be weakly dependent on fin thickness. When the fin height was increased from 1.0 to 2.0 mm, the increase in the heat-transfer coefficient was about 20 percent, while the increase in condensing area was 51 percent. The best performing finned tube had a fin height of 1.5 mm, a fin thickness of 1.0 mm and a fin height of 2.0 mm. It showed an enhancement over the smooth tube of between 4 to 5 under vacuum conditions and around 6 at atmospheric conditions. Thus, the use of finned tubes may result in a significant reduction in size and weight of present-day steam condensers.

Georgiadis, I. V.

1984-09-01

20

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

OpenAIRE

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 ...

Subodh Bahirat,; Joshi, P. V.

2014-01-01

21

Development of a High-Performance Fin-and-Tube Heat Exchanger with Vortex Generators for a Vending Machine  

Science.gov (United States)

The effect of delta-wing-vortex generators (combination of a delta wing and a delta winglet pair) on the heat transfer performance of fin-and-tube heat exchangers for vending machines has been investegated. Flow visualizations, numerical simulations and heat transfer experiments were conducted to find an optimum geometrical shape and arrangement of the vortex generators. Maximum heat transfer enhancement was achieved by the combination of (a) the delta wing with the apex angle of 86 degrees and (b) the delta winglet pair with the inline angle of 45 degrees. In relatively low Reynolds number range, about 40 % increase in heat transfer coefficient was attained with the above mentioned combination of the vortex generators compared to the ordinary heat exchangers with plain fins. It was revealed that the heat transfer enhancement was attributed to (1) the longitudinal vortexes generated by the delta wing and (2) the reduction of wake area behind the tube. It was also found that an increase in the apex angle of the delta wing brought about heat transfer enhancement, and the scale as well as the streggth of the induced longitudinal vortices played an important role in the heat transfer performance.

Iwasaki, Masamichi; Saito, Hiroshi; Mochizuki, Sadanari; Murata, Akira

22

Performance study of silica gel coated fin-tube heat exchanger cooling system based on a developed mathematical model  

International Nuclear Information System (INIS)

Research highlights: ? A dynamic mathematical model is built to predict the performance of DCHE system. ? Operation time in dehumidification is a crucial parameter to system performance. ? Under ARI summer condition, the largest cooling power can reach to 2.6 kW. ? Under ARI humid condition, the largest cooling power can reach to 3.4 kW. ? System performs better with smaller fin distance and tube diameter. -- Abstract: Desiccant coated heat exchanger (DCHE) system can handle latent and sensible load simultaneously by removing the released adsorption heat in dehumidification process. The system can also be driven by low grade thermal energy such as solar energy. In this paper, a dynamic one-dimensional mathematical model validated by experimental data is established to predict the performance of DCHE system, using conventional silica gel as desiccant material. Cooling performance of DCHE system is calculated under ARI (American Air-conditioning and Refrigeration Institute) summer and humid conditions. Simulated results show that the operation time in dehumidification process is a crucial factor for cooling capacity of DCHE system, which can be enhanced by eliminating the initial period with higher outlet air temperature, the largest cooling power of DCHE system increase from 2.6 kW to 3.5 kW by eliminating first 50 s of operation time under ARI summer condition. The results also prove that the system can provide cooling power to indoor condition with selectivo indoor condition with selective operation time when regeneration temperature varies from 50 oC to 80 oC. Besides, the model is adopted to analyze the effects of some structural parameters on system performance under simulated condition. The system performs well in smaller cobber tube external diameter condition, while both transient heat and mass transfer capacity can be enhanced under the condition of smaller distance between the fins.

23

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

Energy Technology Data Exchange (ETDEWEB)

Highlights: {yields} Two novel fin-tube surfaces are presented and numerically simulated. {yields} The novel fin-tube surfaces bring about heat transfer enhancement. {yields} 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.

Wu, J.M., E-mail: wjmxjtuhd@yahoo.com.cn [State Key Laboratory for Mechanical Structural Strength and Vibration, School of Aerospace, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Tao, W.Q. [School of Energy and Power Engineering, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China)

2011-08-15

24

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

25

Effect of Fin Geometry on Condensation of R134a in a Staggered Bundle of Horizontal Finned Tubes  

Science.gov (United States)

Experimental results are presented that show the effect of fin geometry on condensation of refrigerant R134a in a staggered bundle of horizontal fined tubes. Two kinds of conventional low-fin tubes and three kinds of three-dimensional fin tubes were tested. The refrigerant mass velocity ranged from 8 to 23 kg/m2s and the condensation temperature difference from 1.5 to 12 K. In most cases, the highest performance was obtained by one of the three-dimensional fin tubes. In the case of high mass velocity and high film Reynolds number, however, the highest performance was obtained by one of the low-fin tubes. The results were compared with previous experimental results for bundles of smooth tubes and low-fin tubes.

Honda, Hiroshi; Takata, Nobuo; Takamatsu, Hiroshi; Kim, Jeongsk; Usami, Keiichiro

26

The Effect of Circuiting Arrangement on the Thermal Performance of Refrigeration Mixtures in Tube-and-Fin Condensing Heat Exchangers  

Energy Technology Data Exchange (ETDEWEB)

For the pure or azeotropic refrigerants typically used in present air conditioning and refrigeration applications, the refrigerant changes phase at a constant temperature. Thus, the refrigerant circuiting arrangement such as crossfiow, counterfiow, or cross-counterflow, has no effect on the thermal performance. For zeotropic refrigerant mixtures, however, the phase-change occurs over a temperature range, or "glide", and the refrigerant circuiting arrangement, or flow path through the heat exchanger, can affect the thermal performance of both the heat exchangers as well as the overall efficiency of the vapor compression cooling cycle. The effects of tsvo diflerent circuiting arrangements on the thermal performance of a zeotropic retligerant mixture and an almost azeotropic refrigerant mixture in a four-row cross-countertlow heat exchanger arrangement are reported here. The two condensers differ only in the manner of circuiting the refrigerant tubes, where one has refrigerant always flowing downward in the active heat transfer region ("identical order") and the other has refrigerant alternating flow direction in the active heat transfer region ("inverted order"). All other geometric parameters, such as bce are% fin louver geometry, refrigerant tube size and enhancement etc., are the same for both heat exchangers. One refrigerant mixture (R-41OA) un&rgoes a small temperature change ("low glide") during phase change, and the other retligerant mixture (a multi- component proprietary mixture) has a substantial temperature change ("high glide") of approximately 10"C during the phase change process. The overall thermal conductance, two-phase conductance, and pressure drop are presented. For the flow conditions of these tests, which are representative of resi&ntial cooling conditions, inverted order circuiting is more desirable than identical order. The potential thermal advantages of the i&ntical order arrangement for high-glide zeotropic refrigerant mixtures are negated by the increased parasitic refrigerant-side pressure drop utiortunately resulting from tkbrication requirements of the identical order circuiting.

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

1999-03-15

27

Analysis of spray-cooled finned-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

This paper reports that a mathematical model has been developed for the analysis of spray-cooled finned-tube heat exchangers. An experimental study was conducted on a four-pass, finned-tube heat exchanger in a vertical air/water mist flow to validate the model, and the results compared well with the predicted performance. Significant performance enhancement (up to 3.5 times the dry performance) was found by spraying relatively small amounts of water onto the heat exchanger. The two-phase pressure drop across the heat exchanger was also measured, and the spray water mass flow rate was found to have a significant effect on the pressure drop across the tube bundle. The study helped to identify certain factors, such as the geometry of the finned tubes and the optimum air/spray water ratios, which have to be taken into consideration when designing spray-cooled heat exchangers.

Dreyer, A.A.; Kriel, D.E.; Erens, P.J. (Dept. of Mechanical Engineering, Univ. of Stellenbosch, Stellenbosch, 7600 (South Africa))

1992-12-01

28

Effects of Fin Shape on Condensation Heat Transfer and Pressure Drop inside Herringbone Micro Fin Tubes  

Science.gov (United States)

Experiments of in-tube condensation of R410A have been carried out for as mooth tube, a h elical micro fin tube and five types of herringbone micro fin tubes. In the herringbone micro fin tube, the micro fins work to remove liquid at fin-diverging parts and collect liquid at fin-converging parts. In the high mass velocity region, heat transfer coefficient of all the herringbone tubes is about 2-4 times higher than that of the helical micro fin tube. In the low mass velocity region, however, the heat transfer coefficients of the herringbone micro fin tubes are equal to or smaller than those of the helical micro fin tube. Up to the fin height of 0.18 mm, the heat transfer coefficient is higher for higher fin, whereas that of ah igher fin tube is saturated. The pressure drop increases with increasing fin height. The helix angle strongly affects the heat transfer and pressure drop. Higher helix angle causes higher heat transfer coefficient and higher pressure drop. In the case of the herringbone tube which has shorter fin and/or smaller helix angle, pressure drops are equal to or lower than that of the helical micro fin tube, whereas those of other tubes are higher.

Miyara, Akio; Otsubo, Yusuke; Ohtsuka, Satoshi

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

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

Energy Technology Data Exchange (ETDEWEB)

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.

Hwang, Seong Won; Jeong, Ji Hwan [Pusan National University, Busan (Korea, Republic of)

2009-07-01

31

Eddy current test of fin tubes for a heat exchanger  

International Nuclear Information System (INIS)

Eddy current probes were designed for the test of fin tubes. Fin tubes, often used for heat exchangers, have uneven outer and inner surfaces to enhance the heat emission. The surface roughness make it difficult to detect flaws employing eddy current test(ECT). In order to overcome the difficulties we performed two types of works, one is the delopment of ECT probes, and the other is the signal processing including fast Fourier transform and digital filtering. In the development of ECT probes, we adopted empirical design method. Our ECT probes for fin tubes are inside diameter type. And we are specially concerned about geometric features such as the widths of the coils composing an ECT probe. We fabricated four probes with various coil widths. Eddy current test was performed using those ECT probes on specimens with artificial flaws. After analyzing the output signals, we found that, in order for the effective testing, the width of a coil should be determined considering the pitch of the fins of a tube. And we also learned that the frequency filtering could improve the s/n ratio.

32

Tube an fin assembly exchangers in power plants  

International Nuclear Information System (INIS)

This patent describes a fin and tube assembly for use in a heat exchanger. It comprises: a steel tube provided with an external coating of aluminum; and at least one aluminum fin having aluminum braze cladding in contact with and brazed to the tube. The assembly being characterized by the absence of any appreciable exposed layer of ferrous-aluminum intermetallic compound or intermediate phase on the exterior of the tube in the area of the fin

33

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)

34

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

35

Effect of the Moments of Probability Density Function for Non-uniform Air Flow Distribution on the Hydraulic Performance of a Fin-tube Heat Exchanger  

Directory of Open Access Journals (Sweden)

Full Text Available The work presented in this paper examines the effect of a non-uniform airflow velocity distribution on the air pressure drop through the fin passages of a single row fin-tube heat exchanger. Water flow rate through the tubes and its temperature are taken as constant. Maldistribution of the airflow increases the average pressure drop with respect to that of a uniform flow. As a result of this, the pumping power required by the fan or blower will also increase. The increase of the pumping power is calculated by means of a discretization technique and it is analyzed with respect to the non-uniform distribution statistical moments of probability density function, i.e., the mean, standard deviation, skew and kurtosis. The analysis reveals that the increase of pumping power is dependent on the exchanger NTU, standard deviation and skew of the velocity distribution. Kurtosis has no effect on the pressure drop. Correlations have been developed to predict this increase of pumping power from known statistical moments and resulting air temperatures. These can then be used as design tools to optimize the sizing of the heat exchanger within the air-conditioning unit, hence giving the best energy efficiency performance.

Wai Meng Chin

2011-01-01

36

Development of auto balancing fin tube ECT instrument  

International Nuclear Information System (INIS)

Eddy Current Testing (ECT) instrument for copper fin tube was developed in this research. The instrument was composed of signal generator, signal detector, phase detector, phase controller, digital signal processor and PC software. And this on-line instrument was installed at LG for fin copper tube inspection which enabled small defects to detect and reported for evaluation.

37

Effect of the Moments of Probability Density Function for Non-uniform Air Flow Distribution on the Hydraulic Performance of a Fin-tube Heat Exchanger  

OpenAIRE

The work presented in this paper examines the effect of a non-uniform airflow velocity distribution on the air pressure drop through the fin passages of a single row fin-tube heat exchanger. Water flow rate through the tubes and its temperature are taken as constant. Maldistribution of the airflow increases the average pressure drop with respect to that of a uniform flow. As a result of this, the pumping power required by the fan or blower will also increase. The increase of the pumping power...

Wai Meng Chin; Raghavan, Vijay R.

2011-01-01

38

Impact of air and refrigerant maldistributions on the performance of finned-tube evaporators with R-22 and R-407C. Final Report  

Energy Technology Data Exchange (ETDEWEB)

The report presents basic features of the evaporator model, EVAP5M, and simulation results for an evaporator operating with R-22 and R-407C at non-uniform air and refrigerant distributions. EVAP5M was developed under this project to provide a tool for simulating a finned-tube air-to refrigerant evaporator operating with single-component refrigerants and refrigerant mixtures. The tube-by-tube modeling approach allowed for one-dimensional non-uniformity in the air velocity profile and arbitrary maldistribution on the refrigerant side. The model uses the Carnahan-Starling-DeSantis equation of state for calculating refrigerant thermodynamic properties. Simulations were performed for three evaporator slabs with different refrigerant circuitry designs. For the maldistributions studied, maldistributed air caused much more significant capacity degradation than maldistributed refrigerant. In some cases capacity decreased to as low as 57 percent of the value obtained for uniform velocity profile. Simulation results showed that R-22 and R-407C have similar susceptibility to capacity degradation. Relative change of capacity varied depending on the evaporator design and maldistribution studied. 17 refs., 18 figs., 9 tabs.

Lee, Jangho; Domanski, P.A. [Department of Commerce, Gaithersburg, MD (United States)

1997-07-01

39

Heat transfer characteristics of a tube with elliptic pin fins in crossflow of air  

Science.gov (United States)

Experiments have been performed to investigate the heat transfer characteristics of a tube with elliptic pin fins in crossflow of air. By means of the heat/mass transfer analogy and the naphthalene sublimation technique, the local heat transfer coefficients on pin fins and on the tube surface have been measured respectively. Correlations of the experimental data were obtained to calculate the total mean heat transfer coefficients. Experimental results show that the tube with elliptic pin fins has higher heat transfer coefficients than those of a smooth circular tube.

Li, Qingling; Ma, Lianxiang; Chen, Zhong; Warnecke, Hans-Joachim

2002-11-01

40

Pressure loss and heat transfer studies performed on axial-flow finned-tube bundle heat exchangers  

International Nuclear Information System (INIS)

The experimental studies intend to determine the dependence on the parameters of influence state of flow, tube length, and bundle pitch of the heat transfer and pressure loss characteristic of two tube types in the bundle. By means of suitable parameters for heat flow and pressure loss a comparison will be made of the heat transfer and pressure loss power of the axial-flow furried-tube bundle systems investigated here and conventional heat exchangers. (orig.)

41

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)

42

Effect of Fin Geometry on Condensation of Zeotropic Refrigerant Mixture R407C in a Staggered Bundle of Horizontal Finned Tubes  

Science.gov (United States)

Row-by-row heat transfer data were obtained during condensation of downward-flowing refrigerant mixture R407C in a staggered bundle of horizontal finned tubes. Two kinds of conventional low-fin tubes with flat-sided annular fins and three kinds of three-dimensional fin tubes were tested. The refrigerant mass velocity ranged from 4 to 23 kg/m2s, and the condensation temperature difference from 1.5 to 12 K. At a low to medium film Reynolds number(2000), on the other hand, the highest performance was obtained by one of the low-fin tubes. For all tubes tested, the heat transfer coefficient decreased with decreasing mass velocity. On the basis of previous results for R134a, consideration was given to the characteristics of vapor phase mass transfer of R407C.

Honda, Hiroshi; Takata, Nobuo; Takamatsu, Hiroshi; Kim, Jeongsik; Usami, Keiichiro

43

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

44

Experimental Research on heat transfer enhancement of lubricating-oil cooler with mixing integral pin-fin tubes and plain tubes  

International Nuclear Information System (INIS)

A lot of comparison experimental research has been done to the lubricating-oil cooler with mixing integral pin-fin tubes and plain tubes. It is discovered that the mixing integral pin-fin tubes heat transfer capacity in unit volume is higher, pressure drop is lower, and the very strong heat transfer ability than plain tubes when oil volume flow rate is at constant value. The results show the performance of lubricating-oil cooler with mixing integral pin-fin tubes and plain tubes is superiority. So this can made lubricating-oil cooler miniaturize in the same Heat changing condition. (authors)

45

Chemical milling of Zircaloy tubing to produce integral OD spiral finned tubes (AWBA development program)  

International Nuclear Information System (INIS)

A detailed process description is provided for producing integral spiral fins on the outside surface of Zircaloy nuclear fuel cladding tubes by masking with pressure sensitive tape strips and then chemical milling (pickling) the tube wall between the tape strips to leave the fins in relief. Fins up to 0.020 inch high by 0.05 to 0.12 inch wide were consistently produced on tubes having wall thickness of 0.008 inch or greater after fin pickling. Wall thickness uniformity was excellent. Information is provided on tube surface preparation to maximize tape mask adhesion time during pickling, acid chemistry control to prevent local tube wall thinning near the fin, and pickling techniques to promote uniform material removal. Simple fixture designs are described for quickly and conveniently applying the tape strips to the tube wall in an accurate spiral. 13 figures, 4 tables

46

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

47

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

48

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

International Nuclear Information System (INIS)

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.

49

Effect of Fin Geometry on Condensation Heat Transfer of Refrigerant R134a on Enhanced Finned Tubes  

Science.gov (United States)

This paper presents the experimental results on the outside condensation heat tral1sfer coefficient of horizontal enhanced filmed tubes. Three different fin geometry types of three-dimensional enhanced finned tubes were tested. A low-fin-tube (LFT) 19 fin-per-inch (fpi) was also tested for reference. Experimental refrigerant used was R134a. The heat tral1sfer coefficient test was carried out at a condensing temperature of 40°C, at a cooling water velocity of 1.5 m/s, and the heat flux of 10 to 110 kW/m2K. The outside condensation heat transfer coefficient of all three dimensional enhanced finned tubes were approximately 1.9 times higher than that of LFTl9fpi at high heat flux range. In low heat flux range, the enhanced finned tube of small circumferential segmentation pitches at the fin tip was shown the highest outside heat transfer coefficient for all tubes tested.

Takahashi, Hiroyuki; Saeki, Chikara; Koyama, Shigeru

50

Experimental Study on Condensation of Pure Refrigerants in Horizontal Micro-fin Tubes  

Science.gov (United States)

This paper presents the heat transfer and pressure drop correlations for condensation in micro-fin tubes. Experimental data for eleven micro-fin tubes with different fin dimensions were used, and the refrigerants tested were R22, R123 and R134a. The predicted results using new correlations show good agreement with experimental results within an absolute deviation of ±30%. Experimental results for the micro-fin tubes were also compared with previous correlations for micro-fin Tubes.

Yonemoto, Ryuichiro; Koyama, Shigeru

51

Transfer coefficients in elliptical tubes and plate fin heat exchangers  

International Nuclear Information System (INIS)

Mean transfer coefficients in elliptical tubes and plate fin heat exchangers were determined by application of heat and mass transfer analogy in conjunction with the naphthalene sublimation technique. The transfer coefficients are presented in a dimensionless form as functions of the Reynolds number. By using the least squares method analytical expressions for the transfer coefficients were determined with low scattering. (E.G.)

52

Boiling heat transfer on finned tube bundles - the effect of tube position and intertube spacing  

International Nuclear Information System (INIS)

An experimental investigation is described for measuring boiling heat transfer coefficients for finned tube bundles. The investigation was carried out in R11 at a saturation state of 1 bar. The tube bundle used consists of 18 finned tubes, each tube heated separately with an internal electrical heater. The tubes are arranged with triangular pitch in three vertical rows with six tubes in each row. The intertube spacing was varied. For the regime of fully developed boiling the measurements show that tube position and intertube spacing have only little effect on heat transfer. For the transition regime between natural convection and nucleate boiling and the regime of not fully developed boiling it is found that the tube position and the intertube spacing affect the boiling heat transfer coefficient to a considerable degree. The results of the investigations with three tube bundles with different intertube spacing are correlated in empirical equations

53

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

54

Experimental studies on pressure drop characteristics of cryogenic cross-counter flow coiled finned tube heat exchangers  

Science.gov (United States)

Cross-counter flow coiled finned tube heat exchangers used in medium capacity helium liquefiers/refrigerators were developed in our lab. These heat exchangers were developed using integrated low finned tubes. Experimental studies have been performed to know the pressure drop characteristics of tube side and shell side flow of these heat exchangers. All experiments were performed at room temperature in the Reynolds number range of 3000-30,000 for tube side and 25-155 for shell side. The results of present experiments indicate that available correlations for tube side can not be used for prediction of tube side pressure drop data due to complex surface formation at inner side of tube during formation of fins over the outer surface. Results also indicate that surface roughness effect becomes more pronounced as the value of di/ D m increases. New correlations based on present experimental data are proposed for predicting the friction factors for tube side and shell side.

Gupta, Prabhat Kumar; Kush, P. K.; Tiwari, Ashesh

2010-04-01

55

Three-dimensional optimization of staggered finned circular and elliptic tubes in forced convection  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a three-dimensional numerical and experimental geometric optimization study to maximize the total heat transfer rate between a bundle of finned tubes in a given volume and external flow, for staggered arrangements of circular and elliptic tubes. Experimental results were obtained for circular and elliptic configurations with twelve tubes, starting with an equilateral triangle configuration, which fitted uniformly into the fixed volume with a resulting optimal dimensionless tube-to-tube spacing of S/2b = 1.5, where S is the actual spacing and b is the smaller semi-axis of the ellipse. Several experimental configurations were built by reducing the tube-to-tube spacings, identifying the optimal spacing for maximum heat transfer. Similarly, it was possible to investigate the existence of optima with respect to two other geometric degrees of freedom, such as tube eccentricity and fin-to-fin spacing. The results are reported for air as the external fluid in the laminar regime, for Re{sub L} = 852 and 1065, where L is the swept length of the fixed volume. Circular and elliptic arrangements with the same flow obstruction cross-sectional area were compared on the basis of maximizing the total heat transfer. This criterion allows one to isolate and quantify the heat transfer gain, by studying arrangements with equivalent total pressure drops independently of the tube cross-section shape. This paper continues with three-dimensional numerical optimization results for finned circular and elliptic tubes arrangements, which are validated by direct comparison with experimental measurements. Global optima with respect to tube-to-tube spacing, eccentricity and fin-to-fin spacing (S/2b{approx_equal}0.5, e{approx_equal}0.5, {phi}{sub f}{approx_equal}0.06 for Re{sub L}=852 and 1065) were found and reported in dimensionless terms. A relative heat transfer gain of up to 19% is observed in the optimal elliptic arrangement, as compared to the optimal circular one. The heat transfer gain, combined with the relative material mass reduction of up to 32% observed in the optimal elliptic arrangement in comparison to the circular, show that the elliptical tubes arrangement has better overall performance and lower cost than the traditional circular tubes geometry. (authors)

Matos, R.S.; Vargas, J.V.C. [Departamento de Engenharia Mecanica, Centro Politecnico, Universidade Federal do Parana, Caixa Postal 19011, PR 81531-990, Curitiba (Brazil); Laursen, T.A. [Department of Civil and Environmental Engineering, Duke University, 27708-0287, Durham, NC (United States); Bejan, A. [Department of Mechanical Engineering and Materials Science, Duke University, 27708-0300, Durham, NC (United States)

2004-05-01

56

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

57

A heat exchanger model for air-to-refrigerant fin-and-tube heat exchanger with arbitrary fin sheet  

Energy Technology Data Exchange (ETDEWEB)

A new model for simulating air-to-refrigerant fin-and-tube heat exchangers, with arbitrary fin sheet which encompasses variable tube diameters, variable tube locations, variable tube pitches, internal as well as external jagged edges, variable number of tubes per bank and variable location of fin cuts, is introduced. This model is based on a segment-by-segment approach and is developed to be a general purpose and flexible simulation tool. To account for fin conduction and air propagation through the heat exchanger, it is spatially modeled on a Cartesian grid. A new methodology for air side propagation, required for arbitrary fin sheets, is introduced. The model prediction is validated against experimental data for a condenser using R410A as the working fluid. The predicted results agree within {+-}5% of overall heat load, and {+-}25% for total refrigerant pressure drop. (author)

Singh, Varun; Aute, Vikrant; Radermacher, Reinhard [Department of Mechanical Engineering, University of Maryland, 4164 Glenn L Martin Hall, College Park, MD 20742 (United States)

2009-11-15

58

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

59

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)

60

An experimental investigation of heat transfer and friction losses of interrupted and wavy fins for fin-and-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

The present paper discusses the results of an extensive investigation about the performance of various fin configurations, carried out in the Luve Contardo experimental facilities and aimed to enhance the heat transfer capabilities of air-cooled condensers and liquid coolers. Test results here discussed are relative to 15 coil prototypes, having the same tube and fin geometry (25x21.65 mm staggered 5/8 tube banks, 2 mm fin spacing) but different fin surface geometry, from flat to wavy to louvered to 'winglet'. Different rates of heat transfer and pressure loss enhancement were obtained, also depending on the quality of the pressing process. General approaches to evaluate the 'goodness' of one fin design with respect to another one provided questionable results: pressure loss influence on the air flow cannot be properly evaluated unless the actual fan head curve and the coil dimensions (front area and rows number) are stipulated. The performance of air-cooled condensers was therefore predicted and compared, for various fin design and for coil arrangements of practical interest. The type of fin adopted strongly influences the heat exchanger performance and louvered fins generally provide the best results. (author)

Lozza, G. [Politecnico di Milano (Italy). Dip. di Energetica; Merlo, U. [Luve Contardo, Uboldo (Italy)

2001-07-01

61

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.

62

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

63

Evaporation heat transfer enhancement of R-134a flowing inside smooth and micro-fin tubes using the electrohydrodynamic technique  

Energy Technology Data Exchange (ETDEWEB)

Heat transfer enhancement using the electrohydrodynamic (EHD) technique during evaporation inside horizontal smooth and micro-fin tubes is experimentally investigated. The test section is a counter-flow concentric tube-in-tube heat exchanger with R-134a flowing inside inner tube and heating water flowing in the annulus. Smooth and micro-fin inner tubes are used as test section. The outer diameter and length of inner tubes are 9.52 mm and 2.50 m, respectively. The outer tube is a smooth copper tube having inner diameter of 27 mm. The electrode is made from stainless steel rod of 1.47 mm diameter. Experiments are performed at average saturation temperatures ranging between 10 and 20 C, heat fluxes ranging between 10 and 20 kW/m{sup 2} at mass flux of 400 kg/m{sup 2} s and applied voltage of 2.5 kV. The maximum heat transfer enhancement ratios are 1.25 and 1.15 for smooth tube and micro-fin tube, respectively. New correlations based on the data gathered during this work for predicting the evaporation heat transfer coefficient in smooth tube and micro-fin tube are proposed for practical applications. (author)

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

2009-07-15

64

Evaporation heat transfer enhancement of R-134a flowing inside smooth and micro-fin tubes using the electrohydrodynamic technique  

International Nuclear Information System (INIS)

Heat transfer enhancement using the electrohydrodynamic (EHD) technique during evaporation inside horizontal smooth and micro-fin tubes is experimentally investigated. The test section is a counter-flow concentric tube-in-tube heat exchanger with R-134a flowing inside inner tube and heating water flowing in the annulus. Smooth and micro-fin inner tubes are used as test section. The outer diameter and length of inner tubes are 9.52 mm and 2.50 m, respectively. The outer tube is a smooth copper tube having inner diameter of 27 mm. The electrode is made from stainless steel rod of 1.47 mm diameter. Experiments are performed at average saturation temperatures ranging between 10 and 20 deg. C, heat fluxes ranging between 10 and 20 kW/m2 at mass flux of 400 kg/m2 s and applied voltage of 2.5 kV. The maximum heat transfer enhancement ratios are 1.25 and 1.15 for smooth tube and micro-fin tube, respectively. New correlations based on the data gathered during this work for predicting the evaporation heat transfer coefficient in smooth tube and micro-fin tube are proposed for practical applications.

65

Numerical study of the thermal and hydraulic characteristics of a round tube heat exchanger with louvered fins and delta winglets  

OpenAIRE

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 into the louvered fin surface in the near wake region of each tube was investigated. Numerical simulations were performed on the compound design and the thermal and hydraulic characteristics were evaluated. It was found that the delta winglets can significantly reduce the size of the wake regions. This...

Huisseune, H.; Jaeger, P.; T’joen, Christophe; Ameel, B.; Paepe, M.

2011-01-01

66

Inverse determination of the heat transfer characteristics on a circular plane fin in a finned-tube bundle  

Energy Technology Data Exchange (ETDEWEB)

In this work, we present the numerical results of the average heat transfer coefficients, h{sub {phi}}, over a circular plane fin in a finned-tube bundle for both aligned and staggered arrangements as well as the fin efficiency and the heat flux dissipated from the whole fin. The study covers a wide range of Reynolds number (2 x 10{sup 3}-3 x 10{sup 4}), for three different positions of the finned tube inside the heat exchanger. The temperature distribution on the fins surfaces was obtained experimentally using infrared thermography technique. The predicted values of the heat transfer coefficient were obtained numerically using the finite element method in conjunction with the conjugate gradient algorithm and the measured temperatures. (orig.)

Benmachiche, Abdelmoumene Hakim [University of Biskra, Department of Mechanics, Biskra (Algeria); Bougriou, Cherif [University of Batna, LESEI FSI Department of Mechanics, Batna (Algeria); Abboudi, Said [UTBM, Department of Mechanical Engineering, SET Laboratory, Belfort (France)

2010-12-15

67

Finned tube contact conductance: Characterizing the integrity of the mechanical bond  

Science.gov (United States)

Thermal contact conductance of expanded tube joints is dependent upon the interfacial pressure between the mating parts. A review of the literature indicates that very little work has been done towards relating the joint stresses to the dimensional parameters for mechanically expanded plate finned-tube heat exchangers, commonly called fin coils. This paper presents an experimental testing technique to investigate the fin-to-tube mechanical bond based upon the axial pull strength of the joint. Typical coils from two manufacturers were used in this investigation. They were fabricated from 3/8 in. copper tubes and plate aluminum fins. The coils tested had fin spacings of 6, 7, 8, 12, and 20 fins per inch, fin thicknesses of 0.008 and 0.0055 in. Tube thicknesses of 0.015 and 0.016 in. and diametrical interferences of 0.001, 0.006, and 0.010 in. The maximum force attained during a tube pullout was found to be descriptive of the bond. Plots of this force versus fin number and net interference are presented that illustrate the sensitivity of this force to the fin thickness, fin number, and net interference. These plots show that the fin thickness has the predominant effect on the pullout force and, in turn, the bond between the fin collar and the tube.

Ernest, T. L.; Sheffield, J. W.; Sauer, H. J., Jr.

68

Experimental study of heat transfer enhancement of integral pin-fin tube  

International Nuclear Information System (INIS)

Under the condition of lubricating-oil vertically flowing through the surface of integral pin-fin tube, the experimental investigations of heat transfer characteristics were carried out. Effects of pitch and height of fins, machining direction, inlet temperature of lubricating-oil and velocity of cooling water on heat transfer characteristic were analyzed. In these experiments, total heat transfer coefficient of integral pin-fin tube reached 200-1470 W/m2·K, which increased 1-4 times as compared with the smooth tube. Experimental results showed that the integral pin-fin tube was a new kind of enhanced tube fitting for high-viscosity fluid. (authors)

69

Pressure drop and heat transfer characteristics of turbulent flow in annular tubes with internal wave-like longitudinal fins  

Science.gov (United States)

Measured were pressure drop and heat transfer characteristics with uniform axial heat input using air as the working fluid in both the entrance and fully developed regions of annular tubes with wave-like longitudinal fins. Five series of experiments were performed for turbulent flow and heat transfer in the annular tubes with number of waves equal to 4, 8, 12, 16 and 20, respectively. The test tube has a double-pipe structure with the inner blocked tubes as an insertion. The wave-like fins are in the annulus and span its full width. The friction factor and Nusselt number in the fully developed region were obtained. The friction factor and Nusselt number can be well corrected by a power-law correction in the Reynolds number range tested. In order to evaluate the thermal performance of the longitudinal finned tubes over a plain circular tube, comparisons were made under three conditions: (1) identical pumping power; (2) identical pressure drop and (3) identical mass flow. It was found that under the three constraints all the wave-like finned tubes can enhance heat transfer with the tube with wave number 20 being superior. Finally, discussion on the enhancement mechanism is conducted and a general correlation for the fully developed heat transfer is provided, which can cover all the fifty data of the five tubes with a mean deviation of 9.3%.

Yu, B.; Tao, W. Q.

70

Local Heat Transfer for Finned-Tube Heat Exchangers using Oval Tubes  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with either a circular tube or an elliptical tube in crossflow. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.56 x 10-3 to 15.6 x 10-3 kg/s. These flow rates correspond to a duct-height Reynolds number range of 630 – 6300 with a duct height of 1.106 cm and a duct width-toheight ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. The elliptical tube had an aspect ratio of 3:1 and a/H equal to 4.33. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of circular and oval tubes and their relationship to the complex horseshoe vortex system that forms in the flow stagnation region. Fin surface stagnation-region Nusselt numbers are shown to be proportional to the square-root of Reynolds number.

O' Brien, James Edward; Sohal, Manohar Singh

2000-08-01

71

Improvement of the gas-oil heat exchangers based on the bimetallic finned tubes  

OpenAIRE

The heat exchanger is essential for the process of heat transfer in the industrial equipment. It is widely used in all areas of industry, especially in technology, metallurgy, power, transportation, aviation, aerospace and other sectors. In recent years, with the development of new technologies and energy, the necessity of improving the heat exchanger performance is drawing more and more attention of industry. Devices with finned tubes are one of the most common types of extended surface heat...

Borisov, N. A.

2014-01-01

72

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

International Nuclear Information System (INIS)

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

73

Efficient heat-transfer surfaces assembled from partially finned flat-oval tubes  

Science.gov (United States)

The state of finned convective heat-transfer surfaces and prospects for using them in power engineering and industry are briefly reviewed. The characteristics of a heat-recovery economizer made of partially finned flat-oval tubes are presented by way of comparing them with design versions employing known types of finned tubes, and the results gained from its operation downstream of a PTVM-30M boiler are given.

Pis'mennyi, E. N.

2011-04-01

74

Experimental Study on Cooling Heat Transfer of Supercritical Carbon Dioxide Inside Horizontal Micro-Fin Tubes  

Science.gov (United States)

This paper deals with the experimental study on cooling heat transfer of supercritical carbon dioxide inside micro-fin tubes. The geometrical parameters in micro-fin tubes used in the present study are 6.02 mm in outer diameter, 4.76 mm to 5.11 mm in average inner diameter, 0.15 mm to 0.24 mm in fin height, 5 to 25 in helix angle, 46 to 52 in number of fins and 1.4 to 2.3 in area expansion ratio. Heat transfer coefficients were measured at 8-10 MPa in pressure, 360-690 kg/(m2•s) in mass velocity and 20-75 °C in CO2 temperature. The measured heat transfer coefficients of micro-fin tubes were 1.4 to 2 times higher than those of the smooth tube having 4.42 in inner diameter. The predicted heat transfer coefficients using the correlation equation, which was developed for single-phase turbulent fluid flow inside micro-fin-tubes, showed large deviations to the measured values. The new correlation to predict cooling heat transfer coefficient of supercritical carbon dioxide inside micro-fin tubes was developed taking into account the shape of fins based on experimental data empirically. This correlation equation agreed within ±20% of almost all of the experimental data.

Kuwahara, Ken; Higashiiu, Shinya; Ito, Daisuke; Koyama, Shigeru

75

High temperature design of finned-tube sodium-to-air heat exchanger in a sodium test loop  

Energy Technology Data Exchange (ETDEWEB)

Highlights: • High temperature design of finned-tube heat exchanger (FHX) in SFR were conducted. • Full 3D FE analyses for the sodium-to-air heat exchanger unit were performed. • Stress levels of the FHX unit based on full 3D analyses were not severe. • Creep–fatigue damage as per design rules was evaluated to be within allowable limit. - Abstract: A sodium test loop called ‘SELFA’ (sodium thermal-hydraulic experiment loop for finned-tube sodium-to-air heat exchanger) for simulating thermal hydraulic behavior of the FHX (finned-tube sodium-to-air heat exchanger) unit in a Korean prototype sodium-cooled fast reactor is planned to be constructed at KAERI (Korea Atomic Energy Research Institute). In this study, the elevated temperature design for a model FHX and creep–fatigue damage evaluation have been conducted for the model according to the design codes of ASME section III subsection NH and RCC-MRx based on full 3D finite element analyses. Design optimization for the finned-tubes and tube arrangements in the scaled-down FHX has been performed. The materials of the FHX and piping systems are austenitic stainless steel type 316. The design temperature of the SELFA test loop is 600 °C and the design pressure is 1 MPa. The damage evaluation results have shown that no creep–fatigue damage occurs in the present design of the FHX under the intended test conditions.

Lee, Hyeong-Yeon, E-mail: hylee@kaeri.re.kr; Eoh, Jae-Hyuk; Lee, Yong-Bum

2013-12-15

76

Studi Analitik dan Numerik Perpindahan Panas pada Fin Trapesium (Studi Kasus pada Finned Tube Heat Exchanger  

Directory of Open Access Journals (Sweden)

Full Text Available Penambahan fin pada pipa penukar kalor merupakan suatu upaya memperbesar perpindahan kalor konduksi dan konveksi, dengan cara memperluas bidang geometri. Pada penelitian ini dianalisa secara analitik dan numerik perpindahan kalor pada fin dengan profil longitudinal tidak seragam atau berubah terhadap jarak dari dasar fin, dengan memvariasikan ketebalan ujung fin. Hasil dari kedua studi ini tidak jauh berbeda, pada keduanya menjelaskan bahwa fin dengan ketebalan ujung 0,9 mm (fin trapesium terbalik paling baik dari 5 variasi lainnya; serta perubahan temperatur paling besar terjadi pada sepertiga pertama dari panjang  fin, ini artinya pelepasan kalor terbesar terjadi pada daerah tersebut. Perbedaannya adalah pada persentase penurunan temperatur sepanjang  fin terhadap temperatur dasar fin, untuk ketebalan 0,9 mm pada studi analitik sebesar 91,92% dan pada studi numerik sebesar 91,78%. Hal ini berarti metode penyelesaian persamaan diferensial orde 2 dengan koefisien variabel dengan cara pembedahan koefisien variabel pada ODE, sudah benar dan valid. Namun bila ditinjau dari waktu yang diperlukan untuk komputasinya, studi analitik membutuhkan waktu lebih lama. Waktu yang diperlukan dalam komputasinya tergantung dari fungsi koefisien variabel.

Ahmad Zaini

2013-09-01

77

Parametric study on the performance of a heat exchanger with corrugated louvered fins  

Energy Technology Data Exchange (ETDEWEB)

The Taguchi method is a well-known parametric study tool in engineering quality and experimental design. This study analyzes five experimental factors (flow depth, ratio of fin pitch and fin thickness, tube pitch, number of louvers and angle of louver) affecting the heat transfer and pressure drop of a heat exchanger with corrugated louvered fins using the Taguchi method. Fifteen samples are selected from experimental database and the heat transfer and flow friction characteristics are analyzed. The results show that flow depth, ratio of fin pitch and fin thickness and the number of the louvers are the main factors that influence significantly the thermal hydraulic performance of the heat exchanger with corrugated louvered fins. Therefore, these three factors are considered as the main factors for an optimum design of a heat exchanger. (author)

Qi, Zhao-gang; Chen, Jiang-ping; Chen, Zhi-jiu [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, No. 1954, Huashan Rd., Shanghai 200030 (China)

2007-02-15

78

Prediction of fluid flow and heat transfer in internally finned tubes  

Science.gov (United States)

Fully developed fluid flow and heat transfer characteristics in internally finned tubes were investigated. Both laminar and turbulent flows were considered. Longitudinal fins of trapezoidal profile integrally attached to the tube wall are equally spaced circumferentially in the tube. The assumption of axially constant heat flux per unit length was applied. The tube wall temperature was assumed to be circumferentially uniform at any cross section but varies axially with the change of the bulk temperature. With a fin of finite conductivity, the temperature varies along the fin height. The influence of the ratio of the fin to fluid thermal conductivity ratio, K(sub fin)/K(sub fluid), was investigated for both laminar and turbulent flows. Results for laminar flow case were presented for a fin height to tube radius ratio H/R, ranging from 0.2 to 0.9; the number of fins, NFIN, was varied from 6 to 30; and fin half angles, beta, were varied from 1.5 to 3 degrees. It was found that for any specified geometry the Nusselt number is influenced by a single parameter, K(sub fin)/K(sub fluid). A mixing length model developed by Ivanovic and Patankar was used to predict the results for turbulent fluid flow. Results were presented for a range of fin height to tube radius, H/R, which was varied from 0.2 to 0.4; NFIN ranged from 6 to 22; beta was selected as 1.5 and 3 degrees; and Reynolds number, Re, varied from 10,000 to 100,000. Predicted results for isothermal fins were shown to be in agreement with other researchers. The results provide extensive information on the influence of the fin to fluid thermal conductivities ratio. It is evident from the results that the assumption of isothermal fins is an inaccurate one, especially at high Reynolds number and either high H/R or low K(sub fin)/K(sub fluid) ratio.

Al-Hashem, Mohammed Youssef

1993-03-01

79

Design of Plate-Fin Tube Dehumidifiers for Humidification-Dehumidification Desalination Systems  

OpenAIRE

A two-dimensional numerical model of a plate-fin tube heat exchanger for use as a dehumidifier in a humidification-dehumidification (HDH) desalination systems is developed, because typical heating, ventilating, and air conditioning (HVAC) dehumidifier models and plate-fin tube dehumidifier geometries are not intended for the considerably higher temperature and humidity ratio differences which drive heat and mass transfer in HDH desalination applications. The experimentally validated model is ...

Sievers, Martin; Lienhard, John H.

2014-01-01

80

Further studies in filmwise condensation of steam on horizontal finned tubes  

Science.gov (United States)

Over the years, there has been significant variation in the filmwise steam condensation data at NPS on horizontal low-integral finned tubes. With a view to increasing the accuracy of the data, inserts were used inside the tubes to reduce inside thermal resistance; however, significant discrepancies then occurred in the calculated outside heat-transfer coefficient when compared to data taken without an insert. These discrepancies arose due to the data reduction technique which assumes a known inside heat-transfer resistance and subtracts this from a measured overall resistance. If the assumed value on the inside is inaccurate, then the outside value is equally inaccurate. The present work uses an instrumented smooth tube to obtain accurate inside heat-transfer correlations both with and without inserts and uses these to obtain accurate outside coefficients for a family of uninstrumented finned tubes with a view to finding an optimum fin spacing for steam condensation.

Swensen, Keith A.

1992-03-01

81

Design and optimization of coil finned-tube heat exchangers for cryogenic applications  

Science.gov (United States)

Coiled finned-tube heat exchangers have been used in small and medium helium refrigerators/liquefiers, miniature J-T refrigeration systems for many years. The efficiency of these cryogenic systems strongly depends on the thermal and pressure drop performance of these heat exchangers. A considerable improvement in the performance of heat exchanger is possible by choosing an appropriate geometrical configuration for a given process requirement. In the present study, geometry of heat exchanger has been derived taking into consideration the clearance provided for manufacturing of the heat exchangers and an optimized geometrical configurations have been find out. The results show the possibility of adjusting the thermal and pressure drop performance by varying the clearance. The predictions of four end temperatures from present design method have been compared with the actual experimental results of one of the prototypes fabricated in our lab.

Gupta, Prabhat Kumar; Kush, P. K.; Tiwari, Ashesh

2007-05-01

82

Numerical Investigation of Air-Side Heat Transfer and Pressure Drop in Circular Finned-Tube Heat Exchangers  

OpenAIRE

A three-dimensional numerical study is performed to investigate the heat transfer and pressure drop performance on the air-side of circular finned tube bundles in cross flow. New heat transfer and pressure drop correlations for the air-cooled heat exchangers have been developed with the Reynolds number ranging from 5000 to 70000. The heat transfer and pressure drop results agree well with several existing experimental correlations. In addition, the influence of the geometric parameters on the...

Mon, Mi Sandar

2009-01-01

83

Performance Analysis of FinFET Device at 60nm  

OpenAIRE

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

84

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

85

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

86

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1981-01-01

87

Augmentation of heat transfer by longitudinal vortices in plate-fin heat exchangers with two rows of tubes  

Energy Technology Data Exchange (ETDEWEB)

The thermal performance of fin-tube compact heat exchangers is highly affected by the thermal resistance occurring on the air side, which is much higher than the thermal resistance inside the tubes. Since this kind of heat exchanger is widely used in these days, with applications on air-conditioning, refrigeration, automobilistic industry and many other areas, the development of more efficient and cheaper heat exchangers is highly attractive, because it will permit the manufacturing of more competitive equipments. This work presents results of numerical simulations for fin-tube compact heat exchangers using smooth fins and longitudinal vortex generators. The computational model has two rows of round tubes in staggered arrangement. Built-in delta winglet vortex generators were used, and its geometric dimensions were chosen according to the best results of literature. The steady-state numerical simulations were carried out at Re = 300, with a code based on the finite volume method. The typical configuration, where the vortex generators of both tube rows have identical parameters set, was compared with new ones where the vortex generators of the second row have different attack angles and positions. The global and local influence of vortex generators on heat transfer and flow losses are analyzed by comparison with a smooth fin model without vortex generators. The results show that a best heat transfer performance can be obtained by positioning the vortex generators of the second row at a particular position and angle of attack, when the increasing of the flow losses was smaller than the heat transfer enhancement achieved.

Rodrigues, R. Jr.; Yanagihara, J.I.

1999-07-01

88

Heat transfer characteristics of spirally-coiled circular fin-tube heat exchangers operating under frosting conditions  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study is to investigate the heat transfer characteristics of spirally-coiled circular fin-tube heat exchangers under frosting conditions. The heat transfer rate, pressure drop, frost thickness, and Nusselt number of the heat exchanger were measured and analyzed by varying the fin pitch and number of tube rows under frosting conditions. In addition, the Nusselt number of the spirally-coiled circular fin-tube exchanger was compared with those of flat plate fin-tube heat exchangers with discrete fins. An empirical correlation of the Nusselt number was developed as a function of the Reynolds number, dimensionless fin pitch normalized by the hydraulic diameter, i.e., D{sub h}/F{sub p}, Fourier number, and number of tube rows. The measured Nusselt number was consistent with the predicted value with mean and average deviations of 3.5% and 0.3%, respectively. (author)

Lee, Mooyeon; Kang, Taehyung; Joo, Youngju [Graduate School of Mechanical Engineering, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-713 (Korea, Republic of); Kim, Yongchan [Department of Mechanical Engineering, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-713 (Korea, Republic of)

2011-01-15

89

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

90

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)

91

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

Energy Technology Data Exchange (ETDEWEB)

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)

Jose L Munoz-Cobo; Pena, J. [Universidad Politecnica de Valencia, Department of Chemical and Nuclear Engineering, Camino de Vera 14, Valencia 46022 (Spain); Luis E Herranz [CIEMAT, Departmen of Nuclear Fision, Avenida Complutense 22, Madrid 28040 (Spain)

2005-07-01

92

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

93

Conceptual designs and cost estimates of mechanical draft wet/dry and natural draft dry cooling systems using Curtiss-Wright integral fin-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

This study was performed to establish a conceptual design and cost evaluation of an advanced technology mechanical draft wet/dry and natural draft dry cooling systems for large electric power plants using a high performance integral fin-tube heat transfer surface. This study was part of an overall DOE program to develop and demonstrate advanced concept cooling systems for large electric power plants. The results obtained show significant economic advantages compared to results previously published for conventional cooling systems. These advantages are due to the higher heat transfer and lower pressure loss which occur with the use of the selected multi-port integral fin-tubes.

Haberski, R.J.; Bentz, J.C.

1979-04-01

94

New correlation for natural convection of finned tube A-type air cooler  

Energy Technology Data Exchange (ETDEWEB)

The temperature distribution in a finned tube bundle of an A-type air cooler is investigated. The heat transfer is governed by natural convection. By using a special steam condenser the effect of steam pressure on temperature fields formed outside the bank of finned tubes is studied. It is found that the distribution is approximately the same at various pressures with minor differences. The effects of two-phase flow on temperature distribution are also considered. All 3D temperature contours show maximum values, which highly depend on steam pressures. Moreover, asymmetric steam feeding and probable fouling inside the tubes are possible causes of contour shapes. The experimental Nusselt number as a function of Rayleigh number based on different parameters is investigated separately and simple correlations are presented. (author)

Farhadi, F.; Davani, N.; Ardalan, P. [Department of Chemical and Petroleum Engineering, Sharif University of Technology, Azadi Avenue, 11365-9465 Tehran (Iran)

2005-12-01

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

Effects of winglets to augment tube wall heat transfer in louvered fin heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

The louvered fin heat exchanger, a type of compact heat exchanger, has been used heavily in the automotive and air conditioning industries for the last several decades. The majority of past research, aimed towards improving louvered fin exchanger efficiency, has focused on optimizing various parameters of the louvered fin. The experimental study presented in this paper concentrates instead on augmenting the heat transfer along the tube wall of the compact heat exchanger through the use of winglets placed on the louvers. The experiments were completed on a 20 times scaled model of an idealized louvered fin exchanger with a fin pitch to louver pitch ratio of 0.76 and a louver angle of 27{sup o}. The Reynolds numbers tested, based on louver pitch, were between 230 and 1016. A number of geometrical winglet parameters, including angle of attack, aspect ratio, direction, and shape, were all evaluated based on heat transfer augmentation, friction factor augmentation, and efficiency index (combination of both augmentations). In an attempt to optimize these winglet parameters, tube wall heat transfer augmentations as high as 39% were achieved with associated friction factor augmentations as high as 23%. (author)

Sanders, Paul A.; Thole, Karen A. [Virginia Tech, Blacksburg, VA (United States). Mechanical Engineering Department

2006-10-15

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

Performance and optimum design analysis of convective fin arrays attached to flat and curved primary surfaces  

Energy Technology Data Exchange (ETDEWEB)

A model has been developed analytically to carry out the performance and optimum design analysis of four fin arrays, namely, longitudinal rectangular fin array (LRFA), annular rectangular fin array (ARFA), longitudinal trapezoidal fin array (LTRA) and annular trapezoidal fin array (ATFA) under convective cooling conditions. The performance parameters such as fin efficiency, fin effectiveness and augmentation factor are evaluated for a wide range of design variables. It has been observed that the conduction through the supporting structure and the convection from the interfin spacing have a pronounced effect on the performance of a fin array. The optimum fin dimensions in a fin assembly have been determined by consideration of the constant total height of the fin assembly and interfin spacing. From the results, it can be highlighted that the optimum fin dimensions in fin arrays differ from that of the individual fins. (author)

Kundu, B. [Department of Mechanical Engineering, Jadavpur University, Raja SC Mallick Road, Jadavpur, Kolkata 700 032 (India); Das, P.K. [Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721 302 (India)

2009-05-15

99

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

Energy Technology Data Exchange (ETDEWEB)

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.

Yoo, Jae Hwan; Yoon, Jun Kyu [Gachon Univ., Seongnam (Korea, Republic of)

2013-04-15

100

Experimental study of flow patterns and regimes of condensation in horizontal three-dimensional micro-fin tubes  

Science.gov (United States)

During condensation of R134a the flow patterns inside two three-dimensional (3-D) micro-fin tubes with different fin geometries were investigated. The flow patterns and their transitions were visibly observed and recorded. The experimental findings revealed the following results: a comparison of the condensation flow patterns in the 3-D micro-fin tubes with those in smooth tubes revealed no qualitative differences. The mist flow and the mist-annular flow that appeared in the smooth tube entrance region were not observed in 3-D micro-fin tubes. In the maps of the Mandhane flow regime and the Soliman flow regime, the area of annular flow region of the 3-D micro-fin tube extends towards lower Fr number range in the Soliman map and smaller vapor velocity range in the Mandhane map when compared with that of a smooth tube. The criterion of the flow regime transition between the annular flow and the wavy flow decreases from Fr=7 to Fr=2 in the Soliman flow regime map. However, no significant effect on the criterion for the plug flow transition was observed. The experimental data points of plug flow in the 3-D micro-fin tubes were also obtained in the same regime of smooth tube in Mandhane flow regime map. The Soliman flow regime map indicates the criterion for plug flow transition to be Fr=0.4.

Chen, Q.; Amano, R. S.; Xin, M.

2006-12-01

101

Heat Transfer Enhancement for Finned-tube Heat Exchangers with Winglets  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with a circular tube and/or a delta-winglet pair. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.51 x 10-3 to 14.0 x 10-3 kg/s. These flow rates correspond to a duct-height Reynolds number range of 670 – 6300 with a duct height of 1.106 cm and a duct width-toheight ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of a circular tube, a delta-winglet pair, and a combination of a circular tube and a delta-winglet pair. Comparisons of local and average heat transfer distributions for the circular tube with and without winglets are provided. Overall mean finsurface Nusselt-number results indicate a significant level of heat transfer enhancement associated with the deployment of the winglets with the circular cylinder. At the lowest Reynolds numbers (which correspond to the laminar operating conditions of existing geothermal air-cooled condensers), the enhancement level is nearly a factor of two. At higher Reynolds numbers, the enhancement level is close to 50%.

O' Brien, James Edward; Sohal, Manohar Singh

2000-11-01

102

Heat Transfer Enhancement for Finned-Tube Heat Exchangers with Vortex Generators: Experimental and Numerical Results  

Energy Technology Data Exchange (ETDEWEB)

A combined experimental and numerical investigation is under way to investigate heat transfer enhancement techniques that may be applicable to large-scale air-cooled condensers such as those used in geothermal power applications. The research is focused on whether air-side heat transfer can be improved through the use of finsurface vortex generators (winglets,) while maintaining low heat exchanger pressure drop. A transient heat transfer visualization and measurement technique has been employed in order to obtain detailed distributions of local heat transfer coefficients on model fin surfaces. Pressure drop measurements have also been acquired in a separate multiple-tube row apparatus. In addition, numerical modeling techniques have been developed to allow prediction of local and average heat transfer for these low-Reynolds-number flows with and without winglets. Representative experimental and numerical results presented in this paper reveal quantitative details of local fin-surface heat transfer in the vicinity of a circular tube with a single delta winglet pair downstream of the cylinder. The winglets were triangular (delta) with a 1:2 height/length aspect ratio and a height equal to 90% of the channel height. Overall mean fin-surface Nusselt-number results indicate a significant level of heat transfer enhancement (average enhancement ratio 35%) associated with the deployment of the winglets with oval tubes. Pressure drop measurements have also been obtained for a variety of tube and winglet configurations using a single-channel flow apparatus that includes four tube rows in a staggered array. Comparisons of heat transfer and pressure drop results for the elliptical tube versus a circular tube with and without winglets are provided. Heat transfer and pressure-drop results have been obtained for flow Reynolds numbers based on channel height and mean flow velocity ranging from 700 to 6500.

O' Brien, James Edward; Sohal, Manohar Singh; Huff, George Albert

2002-08-01

103

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

104

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

International Nuclear Information System (INIS)

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 theat 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

105

Performance analysis of rectangular ducts with staggered square pin fins  

International Nuclear Information System (INIS)

This paper presents the heat transfer and friction characteristics and performance analysis of convective heat transfer through a rectangular channel with square cross-section pin fins attached over a flat surface. The pin fins were arranged in a staggered manner. Various clearance ratios (C/H) and interfin distance ratios (Sx/D) were used. The performance analysis was made under a constant pumping power constraint. The experimental results showed that the use of square cross-section pin fins may lead to an advantage on the basis of heat transfer enhancement. For higher thermal performance, lower interfin distance ratio and clearance ratio and comparatively lower Reynolds numbers should be preferred for the staggered arrangement. The results of the staggered configurations were also compared with the results of the inline arrangement

106

Experimental testing of the thermal performance of finned air coolers  

International Nuclear Information System (INIS)

Finned heat exchangers are often used as regenerators in heat recovery systems or as a heat source for heat pump installations. These exchangers are usually operating as air coolers. Heat is extracted from the air flowing through the heat exchanger. If the fin temperature lies below the dew point at the air inlet, water vapour may be condensed, increasing the thermal performance of the cooler. If the air/water heat exchanger is installed outdoors, the blower is usually mounted directly at the exchaner's case. In general this leads to non-ideal air flow conditions. For the sizing of such components the manufacturers dispose of design rules which are based either on theoretical models or on experiments using a uniform air stream. These rules which are mostly internal codes of the individual companies presumably do not take into account some non-ideal conditions such as an inhomogeneous air flow, a poorly sized blower or an increased pressure drop between the fins due to condensed water vapour. Moreover, these codes are possibly not sophisticated enough to enable a correct sizing of the products for any given condition of operation, especially in heat pumps operating under condensation conditions. Therfore, the Swiss Federal Institute for Reactor Research (EIR) carried out a research program dealing with the thermal performance of commercially available finned air coolers. The results give a strong evidence that the sizing of finned air coolers involving a phase change in one of the heat transfer fluids is not yet a procedure belonging to the common knowledge of most of the manufacturers. Moreover, the correct sizing of the blower is at least as important as the sizing of the finned exchanger itself. However, it is evident that there are companies on the Swiss market which use already reliable design tools. 25 refs., 81 figs., 12 tabs

107

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

108

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

Energy Technology Data Exchange (ETDEWEB)

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.

Kang, Tae Hyung; Lee, Moo Yeon; Kim, Yong Chan [Korea University, Seoul (Korea, Republic of); Yun, Sung Jung [Korea Bundy Corporation, Pyeongtaek (Korea, Republic of)

2010-05-15

109

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

110

Combined convection and radiation in a tube with circumferential fins and circular disks  

International Nuclear Information System (INIS)

Combined convection and radiation heat transfer in a circular tube with circumferential fins and circular disks is investigated for various operating conditions. Using a finite volume technique for steady laminar flow, the governing equations are solved in order to study the flow and temperature fields. The P-I approximation and the Weighted Sum of Gray Gases Model (WSGGM) are used for solving the radiation transport equation. The results show that the total Nusselt number of combined convection and radiation is higher than that of pure convection. If the temperatures of the combustion gas and the wall in a tube are high, radiation becomes dominant. Therefore, it is necessary to evaluate the effect of radiation on the total heat transfer

111

Low-temperature radiators with free convection: Finned tube or SPAGHETTI-radiators  

Energy Technology Data Exchange (ETDEWEB)

The aim was to develop a low-temperature radiator for 25/sup 0/-30/sup 0/C water temperature which would not need any powered ventilators for heat dispersion. A finned-tube heat exchanger with 6 mm hard-polyethylene tubes was designed as radiator to be installed underneath plant culture tables in greenhouses with culture grooves. Heat radiation is sufficient to heat a thermopane-greenhouse to 16/sup 0/C at an ambient temperature of -14/sup 0/C and waste heat of 26/sup 0/C (180 W/m/sup 2/ floor area in the test arrangement). Pressure drop corresponds to data of conventional greenhouses. (orig./BWI).

Elsner, B. von.; Elsner, B. von; Bredenbeck, H.

1985-01-01

112

The effects of span position of winglet vortex generator on local heat/mass transfer over a three-row flat tube bank fin  

Energy Technology Data Exchange (ETDEWEB)

The naphthalene sublimation method was used to study the effects of span position of vortex generators (VGs) on local heat transfer on three-row flat tube bank fin. A dimensionless factor of the larger the better characteristics, JF, is used to screen the optimum span position of VGs. In order to get JF, the local heat transfer coefficient obtained in experiments and numerical method are used to obtain the heat transferred from the fin. A new parameter, named as staggered ratio, is introduced to consider the interactions of vortices generated by partial or full periodically staggered arrangement of VGs. The present results reveal that: VGs should be mounted as near as possible to the tube wall; the vortices generated by the upstream VGs converge at wake region of flat tube; the interactions of vortices with counter rotating direction do not effect Nusselt number (Nu) greatly on fin surface mounted with VGs, but reduce Nu greatly on the other fin surface; the real staggered ratio should include the effect of flow convergence; with increasing real staggered ratio, these interactions are intensified, and heat transfer performance decreases; for average Nu and friction factor (f), the effects of interactions of vortices are not significant, fhas slightly smaller value when real staggered ratio is about 0.6 than that when VGs are in no staggered arrangement. (orig.)

Zhang, Y.H.; Wang, L.B.; Ke, F.; Su, Y.X.; Gao, S.D. [Department of Mechanical Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu (China)

2004-09-01

113

Experimental research on heat transfer coefficients for cryogenic cross-counter-flow coiled finned-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

The aim of present experimental research is to find out the suitable correlations for designing the coiled finned-tube heat exchangers used in cryogenic applications. In order to conduct above experimental study, cross-counter-flow coiled finned-tube heat exchangers were developed in our lab and used in actual refrigeration cycle. The experiments were conducted in the range of effective Reynolds number 500-1900. The effect of diametrical clearance on the prediction of overall heat transfer coefficient is also investigated experimentally. The results from present study were compared in the form of overall heat transfer coefficient. Results of present experimental research indicate that different correlations selected in the study can be used with reasonable accuracy for designing the coiled finned-tube heat exchangers, if they are applied with suitable method of calculation of free-flow cross-sectional area. A more accurate new correlation has also been proposed that fitted experimental data within {+-}10% error band. (author)

Gupta, Prabhat Kumar; Kush, P.K. [Cryogenics Section, Raja Ramanna Centre for Advanced Technology (RRCAT), Indore 452013, Madhya Pradesh (India); Tiwari, Ashesh [Institute of Engineering and Technology, DAVV, Indore, Madhya Pradesh (India)

2009-08-15

114

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.

115

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

116

Experimental investigation on condensation heat transfer of R134a on single horizontal copper and stainless steel three-dimensional finned tubes  

Science.gov (United States)

Condensation heat transfer characteristics of R134a on the horizontal copper and stainless steel three-dimensional (3D) finned tubes are experimentally investigated. The objective is to obtain the basic data for film condensation of R134a on low and high thermal conductivity 3D enhanced tubes. Experiments were carried out at saturation temperatures of 39 °C and wall subcoolings from 3.2 to 10.5 °C. The results show that the condensation heat transfer coefficients on the smooth copper and stainless steel tubes are smaller than those predicted by the Nusselt analysis by 4.4% and 4.8%, respectively. The average enhancement factors provided by the copper and stainless steel 3D finned tubes are 7.86 and 3.34, respectively. The copper 3D finned tube has higher enhancement factor than that of the stainless steel 3D finned tube, due to its high fin and thermal conductivity.

Qin, Peng; Zhang, Zhengguo; Xu, Tao; Gao, Xuenong; Wang, Shuangfeng

2013-07-01

117

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 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

118

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

119

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

120

The effects of frost thickness on the heat transfer of finned tube heat exchanger subject to the combined influence of fan types  

Energy Technology Data Exchange (ETDEWEB)

This study conducts a numerical study concerning the effect of frost thickness on the heat transfer performance of a four rows plate finned tube heat exchanger. Calculations are made under constant air volume and variable air volume conditions. It is found that the initial surge of heat transfer rate in the frosted finned tube heat exchanger is mainly associated with the critical radius effect rather than the surface roughness. The frost thermal conductivity plays an important role in the surge phenomenon. There is hardly any initial surge when frost thermal conductivity is below 0.1 W m{sup -1} K{sup -1}. It is also recommended that a refrigerator should defrost when half of a single flow channel area is blocked by frost. The calculations also reveal that a centrifugal fan is recommended with a small fin-pitch heat exchanger. However, if a long term operation at a thick frost situation is unavoidable, an axial fan should be selected. There is no great difference between selection of an axial fan or centrifugal fan for a larger fin pitch heat exchanger. (author)

Huang, Jeng-Min; Hsieh, Wen-Chien; Ke, Xin-Ji [Department of Refrigeration, Air Conditioning National Chin-Yi University of Technology, Taichung County, Taiping City 411 (China); Wang, Chi-Chuan [Energy and Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu 310 (China)

2008-05-15

121

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)

122

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

123

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

International Nuclear Information System (INIS)

This paper presents the results of a theoretical investigation on the influence 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 to Schmidt, VDI and ESCOATM (traditional and revised) as well as a new correlation, which was developed at the Institute for Energy Systems and Thermodynamics, are used. The simulation results show a good agreement in the overall behavior of the boiler between the different correlations. But there are still some important differences found in the detail analysis of the boiler behavior. - Research highlights: ? Numerical simulation is performed to explore the influence of different heat transfer correlations for finned-tubes to the dynamic behavior of a heat recovery steam generator. ? Differences in the steam generator behavior are found. ? In the worst case the boiler can lead to unfavorable operation conditions, e.g. reverse flow.

124

Development and fabrication of seamless Aluminium finned clad tubes for metallic uranium fuel rods for research reactor  

International Nuclear Information System (INIS)

Natural uranium metal or its alloy is used as fuel in nuclear reactors. Usually fuel is clad with compatible material to prevent its direct contact with coolant which prevents spread of activity. One of the methods of producing fuel for nuclear reactor is by co-drawing finished uranium rods with aluminum clad tube to develop intimate contact for effective heat removal during reactor operation. Presently seam welded Aluminium tubes are used as clad for Research Reactor fuel. The paper will highlight entire fabrication process followed for the fabrication of seamless Aluminium finned tubes along with relevant characterisation results

125

Heat transfer and flow characteristics of fin-tube bundles with and without winglet-type vortex generators  

Energy Technology Data Exchange (ETDEWEB)

The objective of this research is to investigate the effect of longitudinal vortices that can be applied to the heat transfer enhancement for fin-tube heat exchangers such as air-cooled condensers. A multichannel test core was designed and fabricated for the determination of overall heat transfer and pressure loss with circular tubes and winglet vortex generators. Heat transfer results were obtained using a transient method referred to as the modified single-blow method. For a three-row tube bundle in an in-line arrangement without winglets, the heat transfer and the pressure loss were 72% and 210% higher, respectively, than for a multichannel test core without any built-in tube or winglet. These increases were caused by vortices around the tube banks. The corresponding increases for a staggered tube bundle are 95% and 310%, respectively. The triangular winglets recommended by the previous studies in a fin-tube bundle in an in-line arrangement increase the overall heat transfer 10-25% and the pressure loss 20-35% for the Reynolds numbers ranging from 300 to 2700. (orig.)

Kwak, K.M.; Torii, K.; Nishino, K. [Department of Mechanical Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, 240-8501 (Japan)

2002-11-01

126

Flow visualization of annular and delta winglet vortex generators in fin-and-tube heat exchanger application  

Energy Technology Data Exchange (ETDEWEB)

This study presents flow visualization and frictional results of enlarged fin-and-tube heat exchangers with and without the presence of vortex generators. Two types of vortex generators and a plain fin geometry were examined in this study. For plain fin geometry at Re=500, the horseshoe vortex generated by the tube row is not so pronounced, and the horseshoe vortex separates into two streams as it flows across the second row and consequently loses its vortical strength. This phenomenon may support the ''maximum phenomenon'' in low Reynolds number region reported by previous studies. With the presence of annular vortex generator, the presence of a pair of longitudinal vortices formed behind the tube is seen. The strength of the counter-rotating vortices increases with the annular height and the strength of the longitudinal vortices is so strong that may swirl with the horseshoe vortices and other flow stream. For the same winglet height, the delta winglet shows more intensely vortical motion and flow unsteadiness than those of annular winglet. This eventually leads to a better mixing phenomenon. However, it is interesting to know that the corresponding pressure drops of the delta winglet are lower than those of annular winglet. Compared to the plain fin geometry, the penalty of additional pressure drops of the proposed vortex generators is relatively insensitive to change of Reynolds number. (author)

Wang, C.-C.; Wei, C.-S. [Energy and Resources Labs., Hsinchu (Taiwan); Lo, J.; Lin, Y.-T. [Yuan Ze Univ., Taiwan (Taiwan). Dept. of Mechanical Engineering

2002-08-01

127

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

128

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

129

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

130

Duct acoustic resonances induced by flow over coiled and rectangular heat exchanger test banks, of plain and finned tubes  

International Nuclear Information System (INIS)

The generation of acoustic resonances in ducts of rectangular and circular cross-section by gas flow over straight and coiled tube heat exchanger banks contained in the ducts has been studied. It has been shown that there is a distinct difference in behaviour between shallow heat exchanger banks, ie less than 40 rows deep, and deep banks, ie greater than 50 rows deep. It has also been shown that there is a distinct difference between the behaviour of finned tubes and plain tubes which is also dependent on the method of supporting the tubes. Some of these features can be predicted from theory but other aspects cannot as yet be explained by theory. (author)

131

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

132

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

133

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

OpenAIRE

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 ...

Walter, H.; Hofmann, R.

2010-01-01

134

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

135

An experimental and theoretical investigation into the heat transfer of a finned water wall tube in a circulating fluidized bed boiler  

Energy Technology Data Exchange (ETDEWEB)

Heat transfer improvement in a water wall tube with fins was investigated in a circulating fluidized bed (CFB) boiler. Experiments were conducted in a 6 MWth CFB boiler then a model was developed to analyse and interpolate the results. Temperatures at discrete points within the wall cross-section of the tube were measured by burying 0.8 mm thermocouples within a tube. Experimental data showed an increase in heat absorption up to 45%. A good agreement between measured and predicted values was noted. The distribution of temperature in the metal wall and of heat flux around the outer wall of a tube with longitudinal and lateral fins was analyzed by numerical solution of a two-dimensional heat conduction equation. Effects of bed-to-wall heat transfer coefficient, water-to-tube inside heat transfer coefficient, bed temperature, water temperature and thermal conductivity of the tube material on the heat flux around water tube are discussed. The effect of the length of the longitudinal fin and the water tube thickness was also investigated. Heat flux was highest at the tip of the longitudinal fin. It decreased but increased again near the root of the lateral fin. 17 refs., 19 figs., 2 tabs.

Basu, P.; Cheng, L. [DalTech Dalhousie University, Halifax, NS (Canada). Dept. of Mechanical Engineering

2000-03-25

136

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

137

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 parcial 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 literaturaThis 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 analysis 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

2004-01-01

138

Heat transfer enhancement accompanying pressure-loss reduction with winglet-type vortex generators for fin-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

This paper proposes a novel technique that can augment heat transfer but nevertheless can reduce pressure-loss in a fin-tube heat exchanger with circular tubes in a relatively low Reynolds number flow, by deploying delta winglet-type vortex generators. The winglets are placed with a heretofore-unused orientation for the purpose of augmentation of heat transfer. This orientation is known as ''common flow up'' configuration. The proposed configuration causes significant separation delay, reduces form drag, and removes the zone of poor heat transfer from the near-wake of the tubes. This enhancement strategy has been successfully verified by experiments in the proposed configuration. In case of staggered tube banks, the heat transfer was augmented by 30% to 10%, and yet the pressure loss was reduced by 55% to 34% for the Reynolds number (based on two times channel height) ranging from 350 to 2100, when the present winglets were added. In case of in-line tube banks, these were found to be 20% to 10% augmentation, and 15% to 8% reduction, respectively. (author)

Torii, K.; Kwak, K.M.; Nishino, K. [Yokohama National Univ. (Japan). Dept. of Mechanical Engineering

2002-08-01

139

The effect of coating and interface resistance on thermal performance of variable thickness annular composite fins  

International Nuclear Information System (INIS)

Highlights: ? The efficiency of composite annular fins with interface resistance is studied. ? It is found that the coating thermal conductivity and thickness effects are governed by a single dimensionless parameter. ? It is found that the interface thermal conductivity and thickness effects are governed by a single dimensionless parameter. ? The effect of interface resistance is more than the coating for the same values of corresponding dimensionless parameters. ? The coating and interface effects are similar for all considered fin profiles. - Abstract: The non-dimensional finite element method is used to study performance characteristics of annular fins when subjected to both interface resistance as well as coating layer over the fin surface. Governing dimensionless parameters are identified for coating and interface resistance effects. It is found that the coating (interface) effects are governed by a single dimensionless parameter that groups all important material and geometric parameters of the fin substrate and coating (interface) layer. The analysis is first conducted for a rectangular profile or constant thickness fin, over the range of fin lateral Biot number 0.001 ? Bizf ? 1, which showed an upper bound of the governing dimensionless parameters for which the coating and interface effects become negligible. The investigation is then extended to variable thickness profile annular fins, which showed the behavior of coating and interfacvior of coating and interface resistances very similar to that of rectangular profile.

140

Indoor solar thermal energy saving time with phase change material in a horizontal shell and finned-tube heat exchanger.  

Science.gov (United States)

An experimental as well as numerical investigation was conducted on the melting/solidification processes of a stationary phase change material (PCM) in a shell around a finned-tube heat exchanger system. The PCM was stored in the horizontal annular space between a shell and finned-tube where distilled water was employed as the heat transfer fluid (HTF). The focus of this study was on the behavior of PCM for storage (charging or melting) and removal (discharging or solidification), as well as the effect of flow rate on the charged and discharged solar thermal energy. The impact of the Reynolds number was determined and the results were compared with each other to reveal the changes in amount of stored thermal energy with the variation of heat transfer fluid flow rates. The results showed that, by increasing the Reynolds number from 1000 to 2000, the total melting time decreases by 58%. The process of solidification also will speed up with increasing Reynolds number in the discharging process. The results also indicated that the fluctuation of gradient temperature decreased and became smooth with increasing Reynolds number. As a result, by increasing the Reynolds number in the charging process, the theoretical efficiency rises. PMID:25879052

Paria, S; Sarhan, A A D; Goodarzi, M S; Baradaran, S; Rahmanian, B; Yarmand, H; Alavi, M A; Kazi, S N; Metselaar, H S C

2015-01-01

141

Steam condensation model onto horizontal finned tubes: first approximation to the containment cooling system of advanced reactors European Designs  

International Nuclear Information System (INIS)

European designs of advanced reactors, such as EPR pr SWR 1000, have considered the use of innovative passive safety systems to preserve containment integrity even in the case of a hypothetical accident. These systems consist of several units of bundles of quasi-horizontal finned tubes. Steam released into the containment atmosphere condenses onto these structures, which are internally cooled by water under natural circulation regime. The energy absorbed by the coolant is then discharged into a pool which acts as a heat sink for at least three days. This paper presents the work carried out under the auspices of European Union within the CONGA project to simulate steam condensation onto the above mentioned quasi-horizontal finned tubes. To date calculation methodologies have been pearly reviewed and and an approximation (''Nusselt type'') has been accepted to be the most suitable for safety studies, because of its mechanistic nature and its compatibility with current safety computation tools. Two versions of this approach have been properly adapted and subsequently implemented into independent codes for their validation. An experimental database built up from the open literature allowed to point out models accuracy, showing error well within the experimental uncertainly margin. Therefore, condensate film resistance to heat transfer has been modelled satisfactorily. Nevertheless, further work remains to be done to account for the effects of noncondensable gas presence ae effects of noncondensable gas presence and aerosol deposition onto heat transfer surfaces. (Author) 22 refs

142

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

143

Experimental study of heat transfer and thermal performance with longitudinal fins of solar air heater.  

Science.gov (United States)

The thermal performance of a single pass solar air heater with five fins attached was investigated experimentally. Longitudinal fins were used inferior the absorber plate to increase the heat exchange and render the flow fluid in the channel uniform. The effect of mass flow rate of air on the outlet temperature, the heat transfer in the thickness of the solar collector, and the thermal efficiency were studied. Experiments were performed for two air mass flow rates of 0.012 and 0.016 kg s(-1). Moreover, the maximum efficiency values obtained for the 0.012 and 0.016 kg s(-1) with and without fins were 40.02%, 51.50% and 34.92%, 43.94%, respectively. A comparison of the results of the mass flow rates by solar collector with and without fins shows a substantial enhancement in the thermal efficiency. PMID:25685486

Chabane, Foued; Moummi, Noureddine; Benramache, Said

2014-03-01

144

Experimental study of heat transfer and thermal performance with longitudinal fins of solar air heater  

Directory of Open Access Journals (Sweden)

Full Text Available The thermal performance of a single pass solar air heater with five fins attached was investigated experimentally. Longitudinal fins were used inferior the absorber plate to increase the heat exchange and render the flow fluid in the channel uniform. The effect of mass flow rate of air on the outlet temperature, the heat transfer in the thickness of the solar collector, and the thermal efficiency were studied. Experiments were performed for two air mass flow rates of 0.012 and 0.016 kg s?1. Moreover, the maximum efficiency values obtained for the 0.012 and 0.016 kg s?1 with and without fins were 40.02%, 51.50% and 34.92%, 43.94%, respectively. A comparison of the results of the mass flow rates by solar collector with and without fins shows a substantial enhancement in the thermal efficiency.

Foued Chabane

2014-03-01

145

Heat transfer and thermal performance analysis of a surface with hollow rectangular fins  

Energy Technology Data Exchange (ETDEWEB)

An experimental study was conducted to investigate the heat transfer and friction loss characteristics in a horizontal rectangular channel having attachments of hollow rectangular profile fins over one of its heated surface. The Reynolds number based on the flow averaged inlet velocity and the hydraulic diameter, ranged from 3000 to 32,000. The hollow rectangular profile fins in 10cm height and axb=2cmx4cm dimensions with a thickness of 0.2cm were mounted on a heating surface vertically. Reynolds number, fin arrangement and fin pitch in the flow direction were the experimental parameters. Both in-line and staggered fin arrangements were studied for one-fixed spanwise (S{sub x}/a=3) and four different streamwise (S{sub y}/b=1.5, 1.875, 2.5 and 3.75) distances. Correlation equations for Nu, f and thermal performances were determined for fin configurations and the straight channel case without fins. (author)

Akyol, Ugur [Department of Mechanical Engineering, Faculty of Corlu Engineering, University of Trakya, 59860 Corlu/Tekirdag (Turkey); Bilen, Kadir [Department of Mechanical Engineering, Faculty of Engineering, University of Ataturk, 25240 Erzurum (Turkey)

2006-02-01

146

Thermal performance of plate fin heat sink cooled by air slot impinging jet with different cross-sectional area  

Science.gov (United States)

Flow and heat transfer characteristics of a plate-fin heat sink cooled by a rectangular impinging jet with different cross-sectional area were studied experimentally and numerically. The study concentrated on investigating the effect of jet width, fin numbers, and fin heights on thermal performance. Entropy generation minimization method was used to define the optimum design and operating conditions. It is found that, the jet width that minimizes entropy generation changes with heat sink height and fin numbers.

Mesalhy, O. M.; El-Sayed, Mostafa M.

2014-11-01

147

Condensation heat transfer coefficients of R1234yf on plain, low fin, and Turbo-C tubes  

Energy Technology Data Exchange (ETDEWEB)

In this study, external condensation heat transfer coefficients (HTCs) of HFC134a and R1234yf are measured on a plain, low fin, and Turbo-C tubes at the saturated vapor temperature of 39 C with the wall subcooling of 3-8 C. R1234yf is a new alternative refrigerant of low greenhouse warming potential for replacing HFC134a, one of the greenhouse gases in Kyoto protocol, used extensively in automobile air conditioners and other refrigeration systems. Test results show that the condensation HTCs of R1234yf are very similar to those of HFC134a for all three surfaces tested. For the development of heat transfer correlations, thorough property measurements are needed for R1234yf in the near future. (author)

Park, Ki-Jung; Kang, Dong Gyu; Jung, Dongsoo [Department of Mechanical Engineering, Inha University, Incheon 402-751 (Korea, Republic of)

2011-01-15

148

Heat Transfer and Flow Characteristics of Flow Boiling of CO2-oil Mixtures in Horizontal Smooth and Micro-fin Tubes  

Science.gov (United States)

Experiments on flow pattern, heat transfer and pressure drop of flow boiling of pure CO2 and CO2-oil mixtures in horizontal smooth and micro-fin tubes have been carried out. The smooth tube is a stainless steel tube with an inner diameter of 3.76 mm. The micro-fin tube is a copper tube with a mean inner diameter of 3.75 mm. Experiments were carried out at mass velocities from 100 to 500 kg?(m2·s), saturation temperature of 10 °C, and the circulation ratio of lubricating oil (PAG) is from 0 to 1.0 mass%. Flow pattern observations mainly showed the slug and wavy flow for the smooth tube, but the annular flow for the micro-fin tube. As compared with flow patterns in case of pure CO2, an increase in frequency of slug occurrence in slug flow region, and a decrease in liquid amount at the top of the tube in annular flow region were observed in case of CO2-oil mixtures. For pure CO2, the flow boiling heat transfer was dominated by nucleate boiling at low vapor quality region, and the heat transfer coefficients for the micro-fin tube were higher than those of the smooth tube. For CO2-oil mixtures, the flow boiling heat transfer was dominated by convective evaporation especially at high vapor quality region. In addition, the heat transfer coefficient decreased remarkably when the oil circulation ratio was larger than 0.1 mass%. For pressure drop characteristics, in case of pure CO2, the homogeneous model agreed with the experimental results within ± 30 % for the smooth tube. The pressure drops of the micro-fin tube were 0˜70 % higher than those predicted with the homogeneous model. Furthermore, the pressure drops increased at the high oil circulation ratio and high vapor quality conditions. The increases in the pressure drops were considered due to the increase in the thickness of the oil film and the decrease in the effective flow cross-sectional area.

Ono, Takashi; Gao, Lei; Honda, Tomohiro

149

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

150

Fin Field Effect Transistors Performance in Analog and RF for High-k Dielectrics  

Directory of Open Access Journals (Sweden)

Full Text Available The high-k is needed to replace SiO2 as the gate dielectric to reduce the gate leakage current. The impact of a high-k gate dielectric on the device short channel performance and scalability of nanoscale double gate Fin Field Effect Transistors (FinFET CMOS is examined by 2-D device simulations. DG FinFETs are designed with high-k at the high performance node of the 2008 Semiconductor Industry Association International Technology Roadmap for Semiconductors (ITRS. DG FinFET CMOS can be optimally designed to yield outstanding performance with good trade-offs between speed and power consumption as the gate length is scaled to < 10 nm. Using technology computer aided design (TCAD tools a 2-D FinFET device is created and the simulations are performed on it. The optimum value of threshold voltage is identified as VT=0.653V with e=23(ZrO2 for the 2-D device structure. For the 2-D device structure, the leakage current has been reduced to 9.47´10-14 A. High-k improves the Ion/Ioff ratio of transistors for future high-speed logic applications and also improves the storage capability.Defence Science Journal, 2011, 61(3, pp.235-240, DOI:http://dx.doi.org/10.14429/dsj.61.695

D. Nirmal

2011-04-01

151

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-09-15

152

Optimization of a stepped circular pin-fin array to enhance heat transfer performance  

Science.gov (United States)

A Stepped circular pin-fin array is formulated numerically and optimized with Kriging metamodeling technique to enhance heat transfer performance. The problem is defined by two non-dimensional geometric design variables composed of height of the channel, height of smaller diameter part of the pin-fins, and smaller diameter of the pin-fins, to maximize heat transfer rate compromising with friction loss. Ten designs generated by Latin hypercube sampling were evaluated by three-dimensional Reynolds-averaged Navier-Stokes solver and the evaluated objectives were used to construct the surrogate model. The predictions of objective function by Kriging model at optimum point show reasonable accuracy in comparison with the values calculated by RANS analysis. Optimum shape of pin-fins strongly depends on the weighting factor which measures importance of the friction loss term in the objective function. The thermal performances are much higher than that of the straight pin-fin at sampling optimum points with different weighting factors.

Kim, Kwang-Yong; Moon, Mi-Ae

2009-11-01

153

Performance comparison of pin fin in-duct flow arrays with various pin cross-sections  

International Nuclear Information System (INIS)

Pin fin arrays are frequently used for cooling of high thermal loaded electronic components. Whereas the pin fin accomplishment regarding heat transfer is always higher than that of other fin configurations, the high pressure drop accompanying pins seriously reduces their overall performance. In order to check how the form of pin cross-section influences the pressure drop and heat transfer capabilities, six forms of pin cross-section were numerically investigated. By employing the conjugate heat transfer boundary conditions, numerical simulations close to realistic working conditions were performed. Two geometric comparison criteria were applied so that the conclusions derived from numerical computations were valid for various possible geometric parameters and working conditions. Both staggered and inline pin arrangements were investigated as these are common in practical applications. The heat transfer and pressure drop characteristics are presented in terms of appropriate dimensionless variables. The final judgment of the performance of the pin fin cross-section was performed based on the heat exchanger performance plot. Such a plot allows the assessment of the pin performance including their heat transfer and the pressure drop

154

Hydrodynamic Performance of an Undulatory Robot: Functional Roles of the Body and Caudal Fin Locomotion  

Directory of Open Access Journals (Sweden)

Full Text Available Both body undulation and caudal fin flapping play essential locomotive roles while a fish is swimming, but how these two affect the swimming performance and hydrodynamics of fish individually is yet to be known. We implemented a biomimetic robotic fish that travel along a servo towing system, which can be regarded as “treadmill” of the model. Hydrodynamics was studied as a function of the principal kinetic parameters of the undulatory body and caudal fin of the model in a self?propelled condition, under which the time?averaged measured axial net force becomes zero. Thrust efficiency was estimated from two?dimensional digital particle image velocimetry (DPIV measurements in the horizontal and mid?caudal fin plane. The Single?Row Reverse Karman wake (2S is commonly observed in many previous studies of live fish swimming. However, we show that a Double?Row Two?Paired vortices (2P wake was generated by the robotic model for most kinetic parameter combinations. Interestingly, the 2S wake emerged within the results of a narrow range of robotic caudal fin pitch angles (0???10°, occurring concurrently with enhanced thrust efficiency. We also show that, compared with the effect of body wavelength (?, the wake structure behind the robotic swimmer is more sensitive to the Strouhal number (St and caudal fin pitch angle (?.

Li Wen

2013-01-01

155

Natural convective performance of perforated heat sinks with circular pin fins  

Science.gov (United States)

This study examines heat transfer performance under natural convection for two different types (Type A and Type B) of pin-fin heat sinks with/without a hollow in the heated base. The effects of the rate of heat transfer, the height of fin and base plate, the heat sink porosity and the perforated base plate on the heat-transfer coefficient and enhancement factor were investigated and evaluated. In order to obtain insight into the fluid flow phenomena, flow visualization was also made to observe the detailed fluid flow characteristics of the present pin-fin heat sinks. Experimental results show that heat transfer, using pin-fin heat sinks, is significantly different for Type A and Type B. Comparisons of the heat transfer coefficients, with respect to the unfinned base plate under the same experimental conditions, for the pin-fin heat sinks were about 1.48-fold-1.64-fold (Type A) and 1.81-fold-1.94-fold (Type B), respectively. In addition, results also show that a Type B-heat sink has a higher enhancement factor than a Type A-heat sink.

Wen, Mao-Yu; Yeh, Cheng-Hsiung

2015-02-01

156

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 fin pitch, fin height, fin length, fin thickness, and wavy amplitude are investigated over a wide range of Reynolds number (600fins have significant effects on the j and f factors as a function of Reynolds number. The computational results have an adequate accuracy when compared to experimental data. The accuracy of the calculations of the j and f factors are evaluated by the values of the absolute average relative deviation (AARD, being respectively 3.8% and 8.2% for the CFD simulation and 1.3% and 1% for the neural network model. Finally, new correlations are proposed to estimate the values of the j and f factors with 3.22% and 3.68% AARD respectively.

M Khoshvaght Aliabadi

2011-09-01

157

SEAKEEPING PERFORMANCE OF SEMI-SWATH IN FOLLOWING SEA USING CONTROLLED FINS STABILIZER  

OpenAIRE

Semi-SWATH ship design is a result of combining the good features of SWATH and Catamaran designs. However, the disadvantage of semi-SWATH is that she has low restoring force at bow that causes a tendency to bow-dive when running in following seas. In some critical conditions, the foredeck was found to be immersed underwater. One of the efforts to improve the ship???s performance is to install fin stabilizers at bow and stern. The fin stabilizers are used to compensate for the low restoring fo...

Rahimuddin

2014-01-01

158

Novel high-gain, improved-bandwidth, finned-ladder V-band Traveling-Wave Tube slow-wave circuit design  

Science.gov (United States)

The V-band frequency range of 59-64 GHz is a region of the millimeter-wave spectrum that has been designated for inter-satellite communications. As a first effort to develop a high-efficiency V-band Traveling-Wave Tube (TWT), variations on a ring-plane slow-wave circuit were computationally investigated to develop an alternative to the more conventional ferruled coupled-cavity circuit. The ring-plane circuit was chosen because of its high interaction impedance, large beam aperture, and excellent thermal dissipation properties. Despite these advantages, however, low bandwidth and high voltage requirements have, until now, prevented its acceptance outside the laboratory. In this paper, the three-dimensional electrodynamic simulation code MAFIA (solution of MAxwell's Equation by the Finite-Integration-Algorithm) is used to investigate methods of increasing the bandwidth and lowering the operating voltage of the ring-plane circuit. Calculations of frequency-phase dispersion, beam on-axis interaction impedance, attenuation and small-signal gain per wavelength were performed for various geometric variations and loading distributions of the ring-plane TWT slow-wave circuit. Based on the results of the variations, a circuit termed the finned-ladder TWT slow-wave circuit was designed and is compared here to the scaled prototype ring-plane and a conventional ferruled coupled-cavity TWT circuit over the V-band frequency range. The simulation results indicate that this circuit has a much higher gain, significantly wider bandwidth, and a much lower voltage requirement than the scaled ring-plane prototype circuit, while retaining its excellent thermal dissipation properties. The finned-ladder circuit has a much larger small-signal gain per wavelength than the ferruled coupled-cavity circuit, but with a moderate sacrifice in bandwidth.

Kory, Carol L.; Wilson, Jeffrey D.

1994-01-01

159

Study of efficiency and optimized dimensions of segmented fins of different cross-section shapes  

International Nuclear Information System (INIS)

Heat recovery of heat exchangers with gas as one of the streams depend on the use of segmented finned tubes to compensate for the inherently low heat transfer coefficient. Segmented fins are of great practical importance in compact heat exchangers, finned tubes, waste heat recovery boilers, etc. For a given fin weight, the fin can dissipate various quantities of heat depending on its shape and geometry. Optimizing the fin, namely finding the shape that would dissipate the maximum heat for a given weight, is an important requirement in fin design. In the paper the temperature profile and the efficiency of four different shapes of segmented fins (rectangular, hyperbolic and parabolic) with variable heat transfer coefficient h, are determined by solving numerically the relevant governing differential equations, it's found that the parabolic fin has the best performance among the four examined shapes, although it has more manufacturing problems

160

Predictive Modeling of Steam Condensation onto Finned Tubes in the Presence of Noncondensable Gases for Passive Safety Reactor Containment Heat Exchangers  

International Nuclear Information System (INIS)

A mechanistic model is presented to predict the steam condensation on containment finned tubes in the presence of noncondensables (NCs). The total thermal resistance from bulk gas to coolant is formulated as a parallel combination of the convective and condensation gas resistances coupled in series to those of the condensate layer, the wall, and the coolant.The condensate layer thermal resistance is calculated by means of an Adamek-based model, while the gas mixture thermal resistance is formulated based on diffusion layer modeling.The model results are compared with the available experimental data of Wanniarachi and Rose for pure steam condensation on finned tubes and with the data of Mazzochi for condensation in the presence of NC gases

161

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

Energy Technology Data Exchange (ETDEWEB)

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 mm{sup 2}. The experiments covered the following ranges: Reynolds number 13500-42,000, clearance ratio (C/H) 0, 0.33 and 1 and interfin spacing ratio (S{sub y}/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 L{sub 9}(3{sup 3}) 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. (author)

Sahin, Bayram [Department of Mechanical Engineering, Faculty of Engineering, University of Ataturk, 25240 Erzurum (Turkey); Demir, Alparslan [Akademi Engineering Ltd, Erzurum (Turkey)

2008-06-15

162

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

163

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.

164

Performance of multi tubes in tube helically coiled as a compact heat exchanger  

Science.gov (United States)

Multi tubes in tube helically coiled heat exchanger is proposed as a compact heat exchanger. Effects of heat exchanger geometric parameters and fluid flow parameters; namely number of inner tubes, annulus hydraulic diameter, Reynolds numbers and input heat flux, on performance of the heat exchanger are experimentally investigated. Different coils with different numbers of inner tubes, namely 1, 3, 4 and 5 tubes, were tested. Results showed that coils with 3 inner tubes have higher values of heat transfer coefficient and compactness parameter (bar{h} Ah ). Pressure drop increases with increasing both of Reynolds number and number of inner tubes. Correlations of average Nusselt number were deduced from experimental data in terms of Reynolds number, Prandtl number, Number of inner coils tubes and coil hydraulic diameter. Correlations prediction was compared with experimental data and the comparison was fair enough.

Nada, S. A.; El Shaer, W. G.; Huzayyin, A. S.

2014-12-01

165

A performance evaluation system for photomultiplier tubes  

Science.gov (United States)

A comprehensive performance evaluation system for Photomultiplier tubes has been built up. The system is able to review diverse cathode and anode properties for PMTs with different sizes and dimensions. Relative and direct methods were developed for the quantum efficiency measurement and the results are consistent with each other. Two-dimensional and three-dimensional scanning platforms were built to test both the cathode and anode uniformity for either the plane type or spherical type photocathode. A Flash Analog-to-Digital Convertor module is utilized to achieve high speed waveforms sampling. The entire system is highly automatic and flexible. Details of the system and some typical experimental results are presented in this paper.

Xia, J.; Qian, S.; Wang, W.; Ning, Z.; Cheng, Y.; Wang, Z.; Li, X.; Qi, M.; Heng, Y.; Liu, S.; Lei, X.

2015-03-01

166

Effect of the inertance tube on the performance of the Stirling type pulse tube refrigerator  

International Nuclear Information System (INIS)

The Pulse Tube Refrigerator(PTR), which has no moving parts at its cold section, is attractive for obtaining higher reliability, simpler construction and lower vibration than in any other small cryocoolers. Commonly used mean to achieve optimum performance of the PTR are orifice or inertance tube. The Stirling type Pulse Tube Refrigerator in the experiments consists of a compressor driven by linear motors, which make pressure waves, a regenerator, a pulse tube with inertance tube, and a buffer. The pressures and temperature are measured to explore the dependency of inertance tube on the performance of the PTR. The results show the dependency of cool-down characteristics, no-load temperature on frequency of operation and inertance tube

167

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

168

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

169

Advanced microchannel heat exchanger with S-shaped fins  

International Nuclear Information System (INIS)

Fin shape effects on thermal-hydraulic characteristics were studied for a Microchannel Heat Exchanger (MCHE) with S-shaped fins using 3D-CFD and changing the fin parameters: fin angle, overlapping length, fin width, fin length, and edge roundness. The fin angle effect on the pressure drop is consistent with the equation obtained experimentally by Weisbach for a circular bent tube: the pressure drop in the S-shaped fin configuration results from bent flow. The overlap of fins with those located immediately downstream at the offset position provides a guide wing effect that reduces the pressure drop remarkably. The overlap was changed by changing the fin radial position and arc length. The pressure drop was minimized when the downstream fins are placed in the middle of the bent flow channels formed by the fins upstream, which differs from Ito's configuration obtained from experiments with a single bent duct. Regarding arc length, the pressure drop is minimized at the standard overlapping length, which was formed to have the longest arc without a change in channel width. Shorter arc lengths from the optimum value by 30 and 50%, respectively, give 2.4 and 4.6% decreases in the heat transfer rate and 17 and 13% increases in the pressure drop. Thinner fins show better thermal-hydraulic performance for fin widths of 0.2-0.8 mm. However, the pressure drop reduced by the longer fin and heat transfer rate was also reduced. Rounded fins with 0.1 mm radius increased the pressure with 0.1 mm radius increased the pressure drop by about 30% compared with that of the fin designed with no roundness. (author)

170

Effect of various parameters on the performance of capillary tube  

OpenAIRE

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; Gupta, Prof R. C.

2011-01-01

171

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

2015-04-01

172

Studying the performance of solid/perforated pin-fin heat sinks using entropy generation minimization  

Science.gov (United States)

Heat transfer and pressure drop characteristics of a set of pin-fins with uniform heat flux were investigated experimentally and numerically. Test set-up was designed to assess the effects of mass flow rate, fin height, and fin density on convection heat transfer and pressure drop. In the numerical investigation, the flow field of various design parameters of the heat sink was simulated. It was found that heat sinks having fin heights of 20 and 30 mm operated at a lower Reynolds number reached minimum value for thermal resistance when the fin density 10 × 10. Which means it is the optimum number of fins for this case. Also, friction factor increased with a decrease in the bypass flow area or inter-fin distance spacing and using perforated fins reduced the pressure losses and thermal resistance for all studied cases.

Elsayed, Mohamed L.; Mesalhy, Osama

2014-10-01

173

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

174

Thermal performance of circular convective–radiative porous fins with different section shapes and materials  

International Nuclear Information System (INIS)

Graphical abstract: - Highlights: • LSM is an accurate technique for simulating heat transfer in circular porous fins. • Rectangular, convex, triangular and exponential variable sections are considered. • Radiation and convection from porous fin are considered. • Effects of material and geometry on heat transfer from fins are studied. - Abstract: In this study, heat transfer and temperature distribution equations for circular convective–radiative porous fins are presented. It’s assumed that the thickness of circular fins varies with radius so four different shapes, rectangular, convex, triangular and exponential, are considered. The heat transfer through porous media is simulated using passage velocity from the Darcy’s model. After deriving equation for each geometry, Least Square Method (LSM) and fourth order Runge–Kutta method (NUM) are applied for predicting the temperature distribution in the porous fins. The selected porous fin’s materials are Al, SiC, Cu and Si3N4. Results reveal that LSM has very effective and accurate in comparison with the numerical results. As a main outcome, Si3N4-exponential section fin has the maximum amount of transferred heat among other fins

175

Numeric Simulation on the Performance of an Undulating Fin in the Wake of a Periodic Oscillating Plate  

Directory of Open Access Journals (Sweden)

Full Text Available A two-dimensional unsteady computational fluid dynamics (CFD method using an unstructured, grid-based and unsteady Navier-Stokes solver with automatic adaptive re-meshing to compute the unsteady flow was adopted to study the hydrodynamic interaction between a periodic oscillating plate and a rigid undulating fin in tandem arrangement. The user-defined function (UDF program was compiled to define the undulating and oscillating motion. First, the influence of the distance between the anterior oscillating plate and the posterior undulating fin on the non-dimensional drag coefficient of the fin was investigated. Ten different distances, D=0.2L, 0.4L, 0.6L, 0.8L, 1.0L, 1.2L, 1.4L, 1.6L, 1.8L and 2.0L, were considered. The performance of the fin for different distances (D is different. Second, the plate oscillating angle (5.7o, 10 o, 20 o, 30 o, 40 o, 45 o, 50 o and frequency (0.5 Hz, 1.0 Hz, 1.5 Hz, 2.0 Hz, 2.5 Hz, 3.0 Hz, 3.5 Hz, 4.0 Hz effects on the non-dimensional drag coefficient of the fin were also implemented. The pressure distribution on the fin was computed and integrated to provide fin forces, which were decomposed into lift and thrust. Meanwhile, the flow field was demonstrated and analysed. Based on the flow structures, the reasons for different undulating performances were discussed. It shows that the results largely depend on the distance between the two objects. The plate oscillating angle and frequency also make a certain contribution to the performance of the posterior undulating fin. The results are similar to the interaction between two undulating objects in tandem arrangement and they may provide a physical insight into the understanding of fin interaction in fishes or bio-robotic underwater propulsors that are propelled by multi fins.

Zhang Yong-Hua

2013-10-01

176

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

177

Leak and burst tests performed on pulled tubes  

International Nuclear Information System (INIS)

The plugging criteria for tubes used in France for PWR plant steam generator tubes allow the presence of through wall cracks during operation. Calculations and tests show the cracks remain stable under accidental conditions and feedback shows that they do not generally result in large leaks. Tests performed on pulled tubes confirm the safety margins provided by the plugging criteria selected with respect to the risks of leakage and sudden propagation of corrosion cracks under accidental conditions. This paper proposes a method for roughly estimating the leakage rate under accidental conditions for a steam generator with corrosion at the top of the tubesheet or at the tube support plate elevation, which is based on tests performed exclusively on pulled tubes and the results of on-site inspections. (authors). 3 figs., 2 tabs., 7 refs

178

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

OpenAIRE

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

179

Effects of EHD on heat transfer enhancement and pressure drop during two-phase condensation of pure R-134a at high mass flux in a horizontal micro-fin tube  

Energy Technology Data Exchange (ETDEWEB)

Effects of electrohydrodynamic (EHD) on the two-phase heat transfer enhancement and pressure drop of pure R-134a condensing inside a horizontal micro-fin tube are experimentally investigated. The test section is a 2.5m long counter flow tube-in-tube heat exchanger with refrigerant flowing in the inner tube and cooling water flowing in the annulus. The inner tube is made from micro-fin horizontal copper tubing of 9.52mm outer diameter. The electrode is made from cylindrical stainless steel of 1.47mm diameter. Positive high voltage is supplied to the electrode wire, with the micro-fin tube grounded. In the presence of the electrode, a maximum heat transfer enhancement of 1.15 is obtained at a heat flux of 10kW/m{sup 2}, mass flux of 200kg/m{sup 2}s and saturation temperature of 40{sup o}C, while the application of an EHD voltage of 2.5kV only slightly increases the pressure drop. New correlations of the experimental data based on the data gathered during this work for predicting the condensation heat transfer coefficients are proposed for practical application. (author)

Laohalertdecha, Suriyan [The Joint Graduate School of Energy and Environment (JGSEE), King Mongkut' s University of Technology Thonburi, Bangmod, Bangkok 10140 (Thailand); Wongwises, Somchai [Fluid Mechanics, Thermal Engineering and Multiphase Flow Research Lab. (FUTURE), Department of Mechanical Engineering, King Mongkut' s University of Technology Thonburi, Bangmod, Bangkok 10140 (Thailand)

2006-07-15

180

Two-Phase Flow and Energy Transfer of a Non-Azeotropic Mixture, R-407c, in a Micro-Fin Tube  

Science.gov (United States)

This study is to determine experimentally the two-phase flow and energy transfer characteristics of a non-azeotropic refrigerant mixture, R-407c (nominal composition: 23% R-32, 25% R-125, and 52% R-134a). R-407c is a fluid with zero ozone depletion potential and one of several alternatives to currently widely used pure refrigerant HCFC-22. As a non-azeotrope, R-407c has distinctly different characteristics from pure fluids. The phase change of a non-azeotrope under constant pressure does not proceed at a constant temperature but rather over a range of temperature. In addition, the momentum, energy transfer, and mass transfer processes are closely linked. The vapor-liquid interfacial mass transfer rate limits the evaporation or condensation rate, and in turns limits the energy transfer rate. The experiments are conducted in a test apparatus with a fluid sampling port to monitor the composition change of the mixture. The test section consists of six horizontal identical passes, constructed as double tube heat exchangers. Each pass is about 2.2 m long and are connected in order by 7.6 cm radius U-bends. The heated or cooled section of each pass is shorter than the pass length and is 1.8 meter long. The inner (mixture) tube of the test section is a nominal 3/8" inch (9.5 mm) copper tube of 0.348 mm wall thickness with 72 axial fins of 0.185 mm height on its inner surface. The apex angle of the fins is 15 deg. and the helix angle is 0. The annulus-side water, serving as heat source (evaporating mode) or heat sink (condensing mode), flows through the annular space between inner and outer tubes. The tests are conducted at 100 deg F dew point temperature and mass flux from 192,000 to 818,000 lb/hr-ft^2 for condensing, and 50 deg F dew point and mass flux from 70,000 to 394,000 lb/hr-ft^2 for evaporating. The experimental results show that, compared to R-22, two-phase flow frictional pressure gradients of R-407c are about 10% less than R-22. Due to the mass transfer resistance, its condensing coefficients are 15% to 30% lower and its evaporating coefficients are about 20% lower, relative to R-22.

Liu, Xin

1996-11-01

181

Thermal-performance evaluation of coolant passages with staggered arrays of pin fins  

Science.gov (United States)

Three-dimensional laminar forced convection including steady-periodic transition is investigated up to periodic-chaotic transition in the fully developed region of coolant passages with staggered arrays of pin fins. Comparative examples concern overall pressure losses and heat transfer characteristics of circular, square and elliptical pins made of nickel and copper. In the numerical model, transient conjugate heat transfer is assumed and space periodicities in pressure, velocity components and temperatures are taken into account. In the range of operative conditions investigated, overall friction factors increase almost linearly with the Reynolds number, while the increase of overall Nusselt numbers with the Reynolds number is characterized by two slope changes connected with the onset of streamwise vortices, and the shedding of transverse vortices, respectively. The use of copper, instead of nickel, increases the overall Nusselt number with all shapes, but is particularly beneficial to the elliptical section. Square pins are characterized by the highest values of friction factors, but are also the best performers as far as convection enhancing is concerned. The reverse is true for the elliptical pins which are characterized by the lowest values of friction factors, but are the worst performers as far as convection enhancing is concerned. On the basis of overall performances, the elliptical pins made of copper are the best choice, at least in the upper range of Reynolds numbers investigated.

D'Agaro, P.; Comini, G.

2008-05-01

182

Evaluation of the thermodynamic performance of pulse tubes  

International Nuclear Information System (INIS)

The thermodynamic performance of pulse tubes (PT) has been studied with emphasis on second law efficiencies and volume effects. The various pulse tube data of operation are compared to small Stirling coolers, characterized by a parameter set similar to the PT specifications. A modified open-quotes thermal shuntclose quotes model (modified open-quotes Bejan modelclose quotes) is utilized for the comparison. The model predicts a small refrigeration load asymptote of the efficiency proportional to the load itself in partial agreement with pulse tube data

183

Numerical simulation of the thermal hydraulic performance of a plate pin fin heat sink  

International Nuclear Information System (INIS)

The computational fluid dynamic software FLUENT is used in assessing the electronics cooling potential of a plate pin fin heat sink (PPFHS), including the conjugate effect. The simulation results are validated with reported experimental data. The simulation shows that pin height and air velocity have significant influences on the thermal hydraulic performances of PPFHS while the influences of in-line/staggered array and neighbor pin flow-directional center distance (NPFDCD) of the PPFHS are less notable. In applying the present design to the cooling of a desktop PC CPU at a heat flux of 2.20 W/cm2, the temperature can be kept at less than 358 K with an air velocity over 6.5 m/s. - Highlights: ? Pin height and air velocity significantly influence thermal performance of PPFHS. ? Less influence by in-line or staggered array. ? Less influence by neighbor pin flow-directional center distance. ? Design with >6.5 m/s air can cool to 2 flux.

184

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

185

Thermal Performance Of Convective-Radiative Heat Transfer In Porous Fins  

OpenAIRE

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 ...

Shahbabaei, Majid; Saedodin, Seyfolah

2014-01-01

186

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)

187

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.

188

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

189

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.)

190

A Comparative Study of Conventional and Tip-Fin Propeller Performance  

DEFF Research Database (Denmark)

During more than a decade several attempts have been made to obtain higher propeller efficiencies by radically modifying the geometry in the tip region of the blade. In the tip-fin propeller a tip fin or winglet is attached to the blade tip and integrated into the blade in such a way that the blade tip is softly curved towards the suction side.Whereas the developments previously have been concentrated mainly on increasing the efficiency of the propeller, the emphasis of current efforts has been on both high efficiency as well as good cavitation properties. This has resulted in a design with a combination of skew and tip fin. To evaluate the design, open-water, self-propulsion and cavitation model tests have been carried out. The tests are done for the conventional propeller originally designed for the ship and for a tip-fin propeller designed for the same ship under the same operation conditions.The results of the model tests show higher open-water efficiency of the tip-fin propeller as well as higher over-all propulsive efficency. Depending on the method used in the full-scale extrapolation this corresponds to reduction in propulsive power of 3.7 to 4.7 per cent. Both propellers suffer from slight wake field behind the ship. The tip-fin propeller suffered a little more from cavitation than the conventional propeller which gave rise to maximum, measured, first-order pressure pulses of 1.3 to 1.4 times those of the conventional propeller.

Andersen, Poul

1997-01-01

191

Performance analysis of a double-pass photovoltaic/thermal (PV/T) solar collector with CPC and fins  

Energy Technology Data Exchange (ETDEWEB)

The use of PV/T in combination with concentrating reflectors has a potential to significantly increase power production from a given solar cell area. A prototype double-pass photovoltaic-thermal solar air collector with CPC and fins has been designed and fabricated and its performance over a range of operating conditions was studied. The absorber of the hybrid photovoltaic/thermal (PV/T) collector under investigation consists of an array of solar cells for generating electricity, compound parabolic concentrator (CPC) to increase the radiation intensity falling on the solar cells and fins attached to the back side of the absorber plate to improve heat transfer to the flowing air. Energy balance equations have been developed for the various nodes of the system. Both thermal and electrical performance of the collector are presented and discussed. (author)

Othman, M.Y.H.; Yatim, B.; Bakar, M.N.A. [Universiti Kebangsaan Malaysia, Selangor (Malaysia). Center for Applied Physics Studies; Sopian, K. [Universiti Kebangsaan Malaysia, Selangor (Malaysia). Dept. of Mechanical and Materials Engineering

2005-10-01

192

Performance tests of Mn-added aluminum heat pipe with micro-sized inner fins and thermal fluid for cooling electronic device  

Science.gov (United States)

Aluminum-5 wt % manganese alloy heat pipe with a nano-fluid of n-butanol and 0.2 wt % carbon nano-tubes was prepared by deep-drawing, and its mechanical and corrosion properties were determined to improve thermal conductivity performance. The heat pipe was designed to have micro-sized inner fins working at temperature higher than 200°C and simultaneously retaining a similar thermal conductivity to that of pure aluminum. The heat pipe formed by aluminum-5 wt % manganese alloys had improved mechanical properties such as 38% micro-hardness, 45.8% yield strength, and 53.5 wt % ultimate tensile strength due to grain size refinement and work hardening effects. The corrosion rate of the aluminum alloy in artificial sea water at room temperature decreased from 0.110 mpy to 0.102 mpy. The nano-fluid of n-butanol and 0.2 wt % carbon nano-tubes improved the thermal conductivity of the heat-pipe by about 250%.

Kim, M. R.; Choi, Y.

2014-12-01

193

Heat exchanger performance calculations for enhanced-tube condenser applications  

Energy Technology Data Exchange (ETDEWEB)

The lack of a prediction method is sometimes used for the rejection of enhanced tubes for some condenser applications even though there is ample data from single-tube condensing experiments. Three methods are discussed that can be used to rate and/or size these multitube units based on the single-tube experimental results. The Kern vertical-number correction appears to be quite adequate for most operating conditions, the exceptions being large sizes and/or deep vacuum operation. The bundle-factor method is preferred for these applications; however, field test results are required to obtain this factor. If performance data are not available, pointwise or numerical methods are required but special care must be taken to insure that the adverse effects of noncondensable gas pockets and the saturation-temperature depression are properly addressed.

Rabas, T.J.

1992-07-01

194

Heat exchanger performance calculations for enhanced-tube condenser applications  

Energy Technology Data Exchange (ETDEWEB)

The lack of a prediction method is sometimes used for the rejection of enhanced tubes for some condenser applications even though there is ample data from single-tube condensing experiments. Three methods are discussed that can be used to rate and/or size these multitube units based on the single-tube experimental results. The Kern vertical-number correction appears to be quite adequate for most operating conditions, the exceptions being large sizes and/or deep vacuum operation. The bundle-factor method is preferred for these applications; however, field test results are required to obtain this factor. If performance data are not available, pointwise or numerical methods are required but special care must be taken to insure that the adverse effects of noncondensable gas pockets and the saturation-temperature depression are properly addressed.

Rabas, T.J.

1992-01-01

195

Effects of regenerator geometry on pulse tube refrigerator performance  

Science.gov (United States)

This paper gives results of the cooling performance of a double-inlet pulse tube refrigerator using various regenerators. The same pulse tube was used for all the experiments and measured 4.76 mm in diameter and 46.2 mm in length. A commercial linear compressor with a swept volume of 4 cm3 was used in these experiments. The operating conditions were held constant at a mean pressure of 2.0 MPa and a frequency of 54 Hz. Using finite difference software called REGEN3.1, developed at NIST, and recent experiment results, we optimized a series of regenerators based on dimensions, materials and screen packing. The values used for calculating the thermal conduction through stacked screens by REGEN3.1 were based on recent experimental results from NIST. The regenerator tubes were designed using 316 stainless steel and titanium materials. The regenerator matrices investigated were 400-mesh and 500-mesh stainless steel screen. The valve settings for both orifices were adjusted to minimize the no-load temperature for all regenerators. A cooling capacity curve from 0 to 3 W was also determined. The performance of the pulse tube refrigerator using the different regenerators is discussed. The experimental results from the various regenerators are evaluated and compared with their corresponding numerically calculated coefficient of performance (COP) and regenerator design as determined by REGEN3.1.

Lewis, M.; Kuriyama, T.; Xiao, J. H.; Radebaugh, R.

1998-01-01

196

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

Energy Technology Data Exchange (ETDEWEB)

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. (orig.)

Tao, W.Q. [Xi' an Jiaotong University, State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an (China); Cheng, Y.P.; Lee, T.S. [National University of Singapore, Laboratory of Fluid Mechanics, Department of Mechanical Engineering, Singapore (Singapore)

2007-11-15

197

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 | Languages: English, 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

198

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

199

Numerical analysis on performance of naphthalene phase change thermal storage system in aluminum plate-fin unit  

Science.gov (United States)

This paper presents a numerical simulation for the prediction of time, temperature and liquid fraction during the melting and solidification process in the latent heat storage of phase changed materials (PCM). The mathematical model, regarding the solid-liquid phase change heat transfer based on the enthalpy formulation, has been proposed. Naphthalene was used as the PCM which is contained in up layer of plate-fin thermal storage. Transient simulations were performed using a commercial computational fluid dynamics package, Fluent, based on the finite volume method. This computational model endeavored to describe both the melting and solidification processes of the PCM. A series of numerical calculations have been done in order to analyses the influence of several heat transfer fluid operating conditions and several fin geometric parameters on the thermal storage unit. Numerical results, which could be used for operating conditions and geometry optimization, provide guideline for the design of the latent thermal energy storage system.

Yang, Lin; Peng, Hao; Ling, Xiang; Dong, Huihua

2015-02-01

200

Performance evaluation of a natural-convection solar air-heater with a rectangular-finned absorber plate  

International Nuclear Information System (INIS)

This paper deals with an experimental investigation to evaluate different thermal characteristics of a natural-convection flat-plate solar air-heater with longitudinal rectangular fins array. Having determined the thermal performance of the system a Nusselt number correlation is presented for such finned duct devices. In the presented empirical model which may have industrial applications, solar radiation and ambient temperature have been considered as independent parameters. Other characteristics of the system such as different dimensionless variables, plates and outflow temperatures, efficiency, and mass flow rate have been empirically modeled based on these variables. The particular difference in this study in comparison with the other similar studies is the presentation of an empirical model for rectangular-finned solar air-heaters. This model proposes design concepts and rules of thumb, and demonstrates the calculations of the design parameters. Based on the order of magnitude analysis, solar radiation has been found to be the main parameter which characterizes the thermal behavior of the system. Besides, exergy analysis has been carried out, and optimum conditions in which the system has the highest performance have been determined.

201

COMPARISON OF TEMPORAL PARAMETERS OF SWIMMING RESCUE ELEMENTS WHEN PERFORMED USING DOLPHIN AND FLUTTER KICK WITH FINS - DIDACTICAL APPROACH  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study was an analysis of the time required to swim to a victim and tow them back to shore, while perfoming the flutter-kick and the dolphin-kick using fins. It has been hypothesized that using fins while using the dolphin-kick when swimming leads to reduced rescue time. Sixteen lifeguards took part in the study. The main tasks performed by them, were to approach and tow (double armpit a dummy a distance of 50m while applying either the flutter-kick, or the dolphin-kick with fins. The analysis of the temporal parameters of both techniques of kicking demonstrates that, during the approach to the victim, neither the dolphin (tmean = 32.9s or the flutter kick (tmean = 33.0s were significantly faster than the other. However, when used for towing a victim the flutter kick (tmean = 47.1s was significantly faster when compared to the dolphin-kick (tmean = 52.8s. An assessment of the level of technical skills in competitive swimming, and in approaching and towing the victim, were also conducted. Towing time was significantly correlated with the parameter that linked the temporal and technical dimensions of towing and swimming (difference between flutter kick towing time and dolphin-kick towing time, 100m medley time and the four swimming strokes evaluation. No similar interdependency has been discovered in flutter kick towing time. These findings suggest that the dolphin-kick is a more difficult skill to perform when towing the victim than the flutter-kick. Since the hypothesis stated was not confirmed, postulates were formulated on how to improve dolphin-kick technique with fins, in order to reduce swimming rescue time

Marek Rejman

2012-12-01

202

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

203

Predicting optimum vortex tube performance using a simplified CFD model  

Energy Technology Data Exchange (ETDEWEB)

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 of tube length. However, it did agree qualitatively for large values. (author)

Karimi-Esfahani, M; Fartaj, A.; Rankin, G.W. [Univ. of Windsor, Dept. of Mechanical, Automotive and Materials Engineering, Windsor, Ontario (Canada)]. E-mail: mki_60@hotmail.com

2004-07-01

204

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)

205

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

206

Experimental investigation of the effects of orientation angle on heat transfer performance of pin-finned surfaces in natural convection  

International Nuclear Information System (INIS)

Natural convection heat transfer in air from a pin-finned surface is investigated experimentally by considering the effect of radiation heat transfer. The plate was oriented as the pin arrays facing either downwards or upwards from vertical axis with different angles and the experiments were performed for different values of heater power input. From the results of the experiments it is observed that the pin fins increase the heat transfer considerably when compared to the unpinned surface. The upfacing pins are more enhancing heat transfer than the downfacing pins and the enhancement is decreasing with increasing orientation angle from the vertical axis. -- Research highlights: ? Effect of orientation in free convection heat transfer from a pin-finned surface. ? The upfacing pins are more enhancing heat transfer than the downfacing pins. ? Radiation view factor is calculated by a modular analysis. ? The radiation is comparable to free convection as not to be neglected. ? The radiative part is 25-40% and increases for low heat transfer rates.

207

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

208

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

209

Performance Study of Concrete-Filled Steel Tubes  

OpenAIRE

Abstract. Concrete-filled steel tubes circular section columns are increasingly used in the design of modernmulti- stories structures. Investigations developed in recent decades confirm their beneficial use. They are used as astructural component system, given their excellent energy absorption and dissipation, or as a rehabilitation tool forrecovery of damaged components after a seismic event. They contribute through their performance to confer highstrength to elements, as high ductility and ...

Chair A.; Djebbar A.; Djebbar N.

2014-01-01

210

Modeling the discontinuous individual channel injection into fin-and-tube evaporators for residential air-conditioning  

DEFF Research Database (Denmark)

In this paper a working principle based upon the novel expansion and distributor device EcoFlowTM is analyzed. The device enables compensation of flow maldistribution by control of individual channel superheat. The working principle is discontinuous liquid injection (pulsating flow) into each individual channels during a specified cycle time. Moreover, the influence of the injection cycle time is investigated together with an optional secondary flow into the other channels with regards to cooling capacity, overall UA-value and COP. The results showed spurious fluctuations in pressure when simulating the pulsating flow, thus the dynamic behavior in the mixture two-phase flow model is insufficient to model the discontinuous liquid injection principle. Despite, the fluctuations and imperfections of the model we found that the cycle time should be kept as low as possible and that the optional secondary flow increases performance. Moreover, the paper reports on the applicability of Modelica developed models to analyze and optimize the working principle and design of expansion devices such that Modelica may be used in future development of novel discontinuous expansion devices.

Kærn, Martin Ryhl; Elmegaard, Brian

2012-01-01

211

Effect of the collector tube profile on Pitot pump performances  

Science.gov (United States)

The pitot pump is composed of the rotating casing with the impeller channel and the pitot tube type collector as the discharge line. The radial impeller feeds water to the rotating casing. The water rotating together with the casing is caught by the stationary pitot tube type collector, and then discharges to the outside. This type pump, as the extra high head pump, is provided mainly for boiler feed systems, and has been designed by trial and error. To optimize the pump profiles, it is desirable to investigate not only performances but also internal flow conditions. This paper discusses experimentally and numerically the relation between the pump performances and the flow conditions in the rotating casing. The moderately larger dimensions of the collector make the pump head and the discharge high with the higher hydraulic efficiency. The flow in the casing is almost the forced vortex type whose velocity is in proportion to the radius but the core velocity is affected with the drag force of the stationary collector. Based upon the above results, the profile of the pitot tube type collector was optimized with the numerical simulation.

Komaki, K.; Kanemoto, T.; Sagara, K.; Umekage, T.

2013-12-01

212

A study on the performance of the boiling and condensation heat transfer of vertical closed two-phase thermosyphons with low integral-fins  

Energy Technology Data Exchange (ETDEWEB)

An experimental study on the boiling and condensation heat transfer performance of thermosyphons with low integral-fins was performed to investigate its heat transfer characteristics. A plain thermosyphon having the same inner and outer diameter as the finned thermosyphons was also tested for comparison. Water and CFC-30 was used as working fluids. The experimental results have been assessed and compared with same existing theories. Good agreement with the theories of Imura and Nusselt was obtained. The vertical closed-type thermosyphons with low integral-fins gave significant increases in the overall heat transfer coefficient compared to plain thermosyphon. In addition, the overall heat transfer coefficients and the operating characteristics was obtained as a function {upsilon}of operating temperature for the practical applications .Also, the closed two-phase thermosyphons with low integral-fins would be highly recommended to achieve some inexpensive and compact heat exchangers in the range of low temperatures. 14 refs., 10 figs.

Cho, D.H. [Daejin University (Korea, Republic of)

1999-03-01

213

Critical heat flux performance for flow boiling of R-134a in vertical uniformly heated smooth tube and rifled tubes  

Energy Technology Data Exchange (ETDEWEB)

In the present paper, critical heat flux (CHF) experiments for flow boiling of R-134a were performed to investigate the CHF characteristics of four-head and six-head rifled tubes in comparison with a smooth tube. Both of rifled tubes having different head geometry have the maximum inner diameter of 17.04 mm while the smooth tube has the average inner diameter of 17.04 mm. The experiments were conducted for the vertical orientation under outlet pressures of 13, 16.5, and 23.9 bar, mass fluxes of 285-1300 kg/m{sup 2}s and inlet subcooling temperatures of 5-40{sup o}C in the R-134a CHF test loop. The parametric trends of CHF for the tubes show a good agreement with previous understanding. In particular, CHF data of the smooth tube for R-134a were compared with well-known CHF correlations such as Bowring and Katto correlations. The CHF in the rifled tube was enhanced to 40-60% for the CHF in the smooth tube with depending on the rifled geometry and flow parameters such as pressure and mass flux. In relation to the enhancement mechanism, the relative vapor velocity is used to explain the characteristics of the CHF performance in the rifled tube. (author)

Chang Ho Kim; In Cheol Bang; Soon Heung Chang [Korea Advanced Institute of Science and Technology, Daejeon (Korea)

2005-07-01

214

Study of the laminar flow of a liquid film between the two radial fins of an horizontal tube using photo-chromic tracers; Etude de l`ecoulement laminaire d`un film liquide entre deux ailettes radiales d`un tube horizontal a l`aide de traceurs photochromiques  

Energy Technology Data Exchange (ETDEWEB)

The problem of laminar film condensate flow over an integral fin tube is investigated using a flow visualisation technique called the photochromic dye method. The dye is activated along narrow lines by passing sharply focused UV light sheet through the solution. The movement of dye traces are recorded, and experimental velocity profiles of liquid condensate film are determined from the resulting pictures. The fin used are of trapezoidal shape. By means of extending this method of investigation, a similarity principle based on both geometric and kinematic criteria is developed. The velocity profiles obtains are presented as function of mass flow. (authors) 6 refs.

Homescu, D.; Desevaux, P.; Speck, P. [Institut de Genie Energetique, Universite de Franche-Comte, 90 - Belfort (France)

1997-12-31

215

Experimental analysis on frosting characteristic of SK-type finned refrigerating heat exchanger with large-diameter circular holes  

International Nuclear Information System (INIS)

This paper presents the construction of both a plane fin-and-tube heat exchanger and a SK-type fin-and-tube heat exchanger. Based on plane fin-and-tube heat exchanger, comparative industrial prototype experiments of SK-type fin-and-tube heat exchanger energy efficiency performance were carried out in the artificial climate chamber. Test results confirmed several findings: when the amount of the refrigerant charged is the same and face velocity u = 3.75 m s?1, SK-type fin-and-tube heat exchanger refrigeration capacity increases by an average of 9.13%; energy consumption reduces by an average of 11.25%, coefficient of performance (COP) of heat exchanger increases by an average of 22.65% with continuous operation during the first 2 h. Also, when the operation time exceeds 2 h, the COP of both types of heat exchangers are both less than 0.6, illustrating that under frost conditions, the defrost interval should not be too long, otherwise energy consumption may sharply spike. - Highlights: •The large holes of SK-type induced the generation of turbulence flow. •The refrigeration capacity and COP of SK-type exceeds that of plane one. •The SK-type fin-and-tube heat exchanger is a new kind of heat transfer equipment. •The defrost interval should not exceed 2 h under frost conditions

216

Heat transfer and pressure loss performance for families of partial length pin fin arrays in high aspect ratio rectangular ducts  

Science.gov (United States)

Arrays of short pin fins are frequently used in narrow high aspect ratio channels to provide heat transfer augmentation for internal cooling of gas turbine engine airfoils. One characteristic of such arrays is that the amount of additional heat transfer area created by the installation of pins is small. Potential increases in performance may be accomplished through removal of a portion of the length of the pins, thereby adding surface area from the pin cross section and reducing flow blockage. For a given pin spacing pattern, such partial length pin fin arrays can be arranged in a large number of variations, both with and without accompanying rib roughness elements. The present paper is a summary of the results of an extensive experimental program which fabricated more than twenty new arrangements to provide designers with additional options. With heat transfer alone as the performance criteria, no partial length pin arrays were found that outperformed the corresponding full length pin array. However, with both heat transfer and pressure loss considered, several new partial length pin arrays were found to be superior.

Steuber, G. D.; Metzger, D. E.

217

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

218

Performance tests and quality control of cathode ray tube displays.  

Science.gov (United States)

Spatial resolution, noise, characteristic curve, and absolute luminance are the essential parameters that describe physical image quality of a display. This paper presents simple procedures for assessing the performance of a cathode ray tube (CRT) in terms of these parameters as well as easy set up techniques. The procedures can be used in the environment where the CRT is used. The procedures are based on a digital representation of the Society of Motion Pictures and Television Engineers pattern plus a few simple other digital patterns. Additionally, measurement techniques are discussed for estimating brightness uniformity, veiling glare, and distortion. Apart from the absolute luminance, all performance features can be assessed with an uncalibrated photodetector and the eyes of a human observer. The measurement techniques especially enable the user to perform comparisons of different display systems. PMID:2085547

Roehrig, H; Blume, H; Ji, T L; Browne, M

1990-08-01

219

Experimental studies on the evaporative heat transfer and pressure drop of CO{sub 2} and CO{sub 2}/propane mixtures flowing upward in smooth and micro-fin tubes with outer diameter of 5 mm for an inclination angle of 45  

Energy Technology Data Exchange (ETDEWEB)

Heat transfer characteristics show different tendency according to the tube orientations such as horizontal, vertical, and inclined positions. In this study, evaporative heat transfer characteristics and pressure drop of CO{sub 2} and CO{sub 2}/propane mixtures flowing upward are investigated in inclined smooth and micro-fin tubes. Smooth and micro-fin tubes with outer diameter of 5 mm and length of 1.44 m with inclination angle of 45 were chosen as test tubes. Average inner diameters of test tubes are 4.0 mm (smooth tube) and 4.13 mm (micro-fin tube). The tests were conducted at mass fluxes from 212 to 656 kg/m{sup 2} s, saturation temperatures from -10 to 30 C and heat fluxes from 15 to 60 kW/m{sup 2} for CO{sub 2}. In addition, for CO{sub 2}/propane mixtures, the test was carried out at inlet temperatures from -10 to 30 C for several compositions (75/25, 50/50, 25/75 wt%) with the same mass fluxes, heat fluxes applied for CO{sub 2}. Heat transfer coefficients in inclined tube are approximately 1.8-3 times higher than those in horizontal tube and the average pressure drop of inclined tube exists between that of horizontal and vertical tubes. (author)

Cho, Jin Min; Kim, Min Soo [School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-744 (Korea); Kim, Yong Jin [School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

2010-08-15

220

High-Rate Performance of Muon Drift Tube Detectors  

CERN Document Server

The Large Hadron Collider (LHC) at the European Centre for Particle Physics, CERN, collides protons with an unprecedentedly high centre-of-mass energy and luminosity. The collision products are recorded and analysed by four big experiments, one of which is the ATLAS detector. In parallel with the first LHC run from 2009 to 2012, which culminated in the discovery of the last missing particle of the Standard Model of particle physics, the Higgs boson, planning of upgrades of the LHC for higher instantaneous luminosities (HL-LHC) is already progressing. The high instantaneous luminosity of the LHC puts high demands on the detectors with respect to radiation hardness and rate capability which are further increased with the luminosity upgrade. In this thesis, the limitations of the Muon Drift Tube (MDT) chambers of the ATLAS Muon Spectrometer at the high background counting rates at the LHC and performance of new small diameter muon drift tube (sMDT) detectors at the even higher background rates at HL-LHC are stud...

Schwegler, Philipp

221

Performance and optimum design analysis of longitudinal and pin fins with simultaneous heat and mass transfer: Unified and comparative investigations  

Energy Technology Data Exchange (ETDEWEB)

In the present paper, the thermal analysis and optimization of longitudinal and pin fins of uniform thickness subject to fully wet, partially wet and fully dry surface conditions are carried out analytically, and also a comparative study is made between the longitudinal and pin fin for a wide range of design parameters. From the results, a significant effect on the temperature distribution in the fin and the fin efficiency with the variations in moist air psychometric conditions is noticed. For partially wet fins, the length of the wet-dry interface depends on the relative humidity RH, fin parameter Z{sub d} and geometry of the fin. From the results, it can also be highlighted that for the same thermo-geometric and psychometric parameters, a longitudinal fin gives higher efficiency than the corresponding pin fin irrespective of surface conditions. Next, a generalized scheme for optimization has been demonstrated in such a way that either heat transfer duty or fin volume can be taken as a constraint selected as per design requirement. From the optimization results, it can be pointed out that the optimum design of both the longitudinal and pin fin under the partially wet surface condition is only possible for a narrow range of relative humidity whereas for the fully wet surface, a wide range is noticed. Finally, design curves have been established for a wide range of thermo-psychometric parameters, which may be helpful to a designer for estimation of the optimum design variables of a fin with a minimum effort. (author)

Kundu, Balaram [Department of Mechanical Engineering, Jadavpur University, Raja SC Mallick Road, Kolkata 700 032, West Bengal (India)

2007-04-15

222

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

223

Heat transfer characteristics of 2t/h class modular water tube type boiler  

International Nuclear Information System (INIS)

A finned tube type evaporator module has been proposed for a 2t/h class water tube type industrial boiler with multiple burners. The geometry of the fins was changed at each module to equalize the evaporation. The modules were designed by considering the energy balance at each row rather than by following a conventional bulk design procedure. The designed module was built into a 2t/h class water tube type boiler, and its performance was tested. A numerical simulation was also conducted to evaluate the two or three dimensional effects of factors such as the inlet conditions. The numerical simulation also included the conjugate heat transfer problem to predict the fin tip temperature. The heat transfer coefficient with fins is lower than that obtained from the empirical correlation of a bare tube. The fin tip temperature from CFD is higher than that from the analytical solution

224

A numerical analysis of the effects of tube plugging on PWR steam generator performance  

International Nuclear Information System (INIS)

The effects of tube plugging on the thermal performance and flow characteristics of a ABB-CE U-tube PWR steam generator have been examined. A three-dimensional numerical analysis was carried out using the ATHOS3 thermal-hydraulics computer code. The 137 tubes were plugged in the periphery of the central cavity region. Some plants have reported tube wear due to flow induced vibration in the same region. The heat transfer area and steam dome pressure with the tube plugging were decreased 1.49% and 0.36% respectively. The change of the other overall parameters was also insignificant. However the difference of local flow characteristics including void fraction, velocities, and quality was indicated clearly and the normal mass flux related to flow induced tube vibration was decreased for the plugged tubes and the no-plugged tubes around the plugged tubes

225

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.

226

Experimental study of boiling phenomena and heat transfer performances of FC-72 over micro-pin-finned silicon chips  

Science.gov (United States)

Experiments were conducted to study the effects of micro-pin-fins on boiling phenomena and heat transfer from square simulated silicon chips immersed in a pool of FC-72. Two kinds of micro-pin-fins having fin thickness of 30 ?m and fin heights of 60 and 200 ?m, respectively, were fabricated on the silicon chip surface with the dry etching technique. The experiments were conducted at the liquid subcoolings of 3, 25, 35 and 45 K. The effects of dissolved air in FC-72 and chip orientation were also investigated. The boiling curve of the micro-pin-finned chips was characterized by a very small increase in wall superheat with increasing heat flux, and the wall temperatures at the CHF point for all the micro-pin-finned chips were less than the upper limit for the reliable operation of LSI chips (Tw=85°C). Liquid subcooling was very effective in elevating CHF for the micro-pin-finned chips compared to the smooth surface and other treated surfaces. The enhanced boiling heat transfer mechanisms for the micro-pin-finned chips were discussed.

Wei, J. J.; Guo, L. J.; Honda, H.

2005-06-01

227

Machining capability of hobbing SNAP cladding fins  

International Nuclear Information System (INIS)

Three helical fins were machined on fifty-one Incoloy 800 cladding tubes by hobbing. This machining technique was to meet SNAP 8 dimensional requirements. The inspection data are presented along with a summary dimensional analysis. (U.S.)

228

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

229

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

230

New x-ray tube performance in computed tomography by introducing the rotating envelope tube technology  

International Nuclear Information System (INIS)

The future demands of computed tomography imaging regarding the x-ray source can be summarized with higher scan power, shorter rotation times, shorter cool down times and smaller focal spots. We report on a new tube technology satisfying all these demands by making use of a novel cooling principle on one hand and of a novel beam control system on the other hand. Nowadays tubes use a rotating anode disk mainly cooled via radiation. The Straton registered x-ray tube is the first tube available for clinical routine utilizing convective cooling exclusively. It is demonstrated that this cooling principle makes large heat storage capacities of the anode disk obsolete. The unprecedented cooling rate of 4.8 MHU/min eliminates the need for waiting times due to anode cooling in clinical workflow. Moreover, an electronic beam deflection system for focal spot position and size control opens the door to advanced applications. The physical backgrounds are discussed and the technical realization is presented. From this discussion the superior suitability of this tube to withstand g-forces well above 20 g created by fast rotating gantries will become evident. Experience from a large clinical trial is reported and possible ways for future developments are discussed

231

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

232

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

233

Prediction of shell and tube thermal energy store performance  

Energy Technology Data Exchange (ETDEWEB)

A one-dimensional transient model has been developed to assist with the design of a shell and tube thermal energy storage unit. The model takes into account the various geometric features of the unit, the latent heat during liquid/solid phase change and the sensible heat storage in the shell, tube material and baffle plates. The model was solved using a multistep predictor-corrector method. The effect of changes to tube diameter, tube length, baffle spacing and PCM fraction were investigated. Certain of the theoretical predictions were compared with experimental results obtained from an 80 MJ thermal energy store using a wax, with a 62 C melting point, as the phase change material. Predicted temperatures were within 8 C of the measured values over the entire charge/discharge periods.

Hofmann, J. [Randcoal Pty Ltd., Johannesburg (South Africa). Dept. of Engineering; Smith, G.D.J. [Univ. of Natal, Durban (South Africa). Dept. of Mechanical Engineering

1995-12-31

234

A comprehensive study of modified Wilson plot technique to determine the heat transfer coefficient during condensation of steam and R-134a over single horizontal plain and finned tubes  

Energy Technology Data Exchange (ETDEWEB)

In the present investigation a comprehensive study of the modified Wilson plot technique has been made and a stepwise methodology has been evolved. This technique can be used to determine the condensing-side heat transfer coefficient during condensation of vapor over a horizontal tube. The necessary experimental data have been acquired by conducting experiments for the condensation of steam and R-134a over a plain tube and different finned tubes (CIFTs and SIFTs). The experimental heat transfer coefficient, based on the test-section wall temperature measurement (wall temperature was measured with thermocouples), h{sub o}, has been compared with that predicted by the modified Wilson plot technique, h{sub mw}. The modified Wilson plot technique underpredicted the condensing-side heat transfer coefficient for the condensation of steam in a range of 7.5-15%. The heat transfer coefficient for the condensation of R-134a is also underpredicted in a range of 13-25% by this technique. (Author)

Kumar, Ravi; Varma, H.K.; Agrawal, K.N.; Mohanty, Bikash

2001-03-01

235

Some aspects of experimental in-tube evaporation  

International Nuclear Information System (INIS)

The heat transfer characteristics of refrigerant-oil mixture for horizontal in-tube evaporator have been investigated experimentally. A smooth copper tube and a micro-fin tube with nominal 9.5 mm outer diameter and 1500 mm length were tested. For the pure refrigerant flow, the dependence of the axial heat transfer coefficient on quality was weak in the smooth tube, but in the micro-fin tube, the coefficients were 3 to 10 times greater as quality increases. Oil addition to pure refrigerant in the smooth tube altered the flow pattern dramatically at low mass fluxes, with a resultant enhancement of the wetting area by vigorous foaming. The heat transfer coefficients of the mixture for low and medium qualities were increased at low mass fluxes. In the micro-fin tube, however, the addition of oil deteriorates the local heat transfer performance for most of the quality range, except for low quality. The micro-fin tube consequently loses its advantage of high heat transfer performance for an oil fraction of 5%. Results are presented as plots of local heat transfer coefficient versus quality

236

An integrated evaluation of the performance effects of steam generator tube plugging  

International Nuclear Information System (INIS)

The integrity of the walls of a small number of steam generator tubes can degrade, with time, during normal operation of a Pressurized Water Reactor. In order to avoid the potential for unacceptable primary-to-secondary leakage, these steam generator tubes must be plugged. This paper presents an integrated evaluation of the impact of tube plugging on plant performance. Such an evaluation is recommended for determining the number of tubes that can be plugged without a significant adverse impact on plant steady state design performance and a large reduction in plant safety analyses margins

237

Effect of the conical-shape on the performance of vortex tube  

Science.gov (United States)

The present study focuses on the effect of conical shape in the cold side of the Ranque-Hilsch vortex tube which is shown to have a considerable influence on the system performance. A vortex tube is a simple circular tube with no moving parts which is capable to divide a high pressure flow into two relatively lower pressure flows with temperatures higher and lower than the incoming flow. A three-dimensional computational fluid dynamic model is used to analyse the mechanisms of flow inside a vortex tube. The SST turbulence model is used to predict the turbulent flow behaviour inside the vortex tube. The geometry of a vortex tube with circumferential inlet slots as well as axial cold and hot outlet is considered. Performance curves temperature separation versus cold outlet mass fraction are calculated for a given inlet mass flow rate and varying outlet mass flow rates.

Guen, M.; Natkaniec, C.; Kammeyer, J.; Seume, J. R.; Adjlout, L.; Imine, O.

2013-04-01

238

Steam-generator tube performance: world 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 during 1978 is reviewed. Tube failures occurred at 31 of the 86 reactors surveyed. The causes of these failures and the procedures designed to deal with them are described. The number of tubes plugged has decreased dramatically in 1978 compared to the previous year. This is attributed to the diligent application of techniques developed through in-plant experience and research and development programs over the past several years

239

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

240

Notes on the voltage performance of accelerator tube sub-modules for the NSF tandem  

International Nuclear Information System (INIS)

Measurements are reported of the d.c. voltage performance of vacuum accelerator tube sub-modules for the Nuclear Structure Facility 30 MV Tandem at Daresbury. Using diagnostic techniques it has been possible to separate out the different processes in the tube which can lead to breakdown. As a result, improved sub-modules have been produced. Tests, have simulated the ion exchange processes which occur in longer tube lengths, and a better understanding has been obtained of the way in which these processes depend on the tube geometry and cleanliness. (U.K.)

241

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

242

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

243

Performance of Closed Tow-Phase Thermosyphon With Double Tube Evaporator  

International Nuclear Information System (INIS)

Experimental studies were carried out for the new thermosyphon type of double tube evaporator. thermosyphons are utilized for transporting large quantities of heat energy. thermosyphons have been widely used in energy and different industrial applications due to their simple construction , small thermal resistance, broad operating limits and low fabrication costs. thermal analysis of thermosyphons performance is experimentally presented in the steady state operation of the closed two-phase thermosyphon of double tube evaporator. the experimental study was performed by inserting an inner pipe into the evaporator of thermosyphon. this study aims to examine the thermosyphons performance against the traditional thermosyphon and analysis of the characteristics of double tube evaporator

244

Heat transfer performance of condenser tubes in an MSF desalination system  

International Nuclear Information System (INIS)

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 Rf 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 resisttube 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

245

Test plan for Fauske and Associates to perform tube propagation experiments with simulated Hanford tank wastes  

International Nuclear Information System (INIS)

This test plan, prepared at Pacific Northwest National Laboratory for Westinghouse Hanford Company, provides guidance for performing tube propagation experiments on simulated Hanford tank wastes and on actual tank waste samples. Simulant compositions are defined and an experimental logic tree is provided for Fauske and Associates (FAI) to perform the experiments. From this guidance, methods and equipment for small-scale tube propagation experiments to be performed at the Hanford Site on actual tank samples will be developed. Propagation behavior of wastes will directly support the safety analysis (SARR) for the organic tanks. Tube propagation may be the definitive tool for determining the relative reactivity of the wastes contained in the Hanford tanks. FAI have performed tube propagation studies previously on simple two- and three-component surrogate mixtures. The simulant defined in this test plan more closely represents actual tank composition. Data will be used to support preparation of criteria for determining the relative safety of the organic bearing wastes

246

Test for Fauske and Associates to perform tube propagation experiments with simulated Hanford tank wastes  

International Nuclear Information System (INIS)

This test plan, prepared at Pacific Northwest National Laboratory for Westinghouse Hanford Company, provides guidance for performing tube propagation experiments on simulated Hanford tank wastes and on actual tank waste samples. Simulant compositions are defined and an experimental logic tree is provided for Fauske and Associates (FAI) to perform the experiments. From this guidance, methods and equipment for small-scale tube propagation experiments to be performed at the Hanford Site on actual tank samples will be developed. Propagation behavior of wastes will directly support the safety analysis (SARR) for the organic tanks. Tube propagation may be the definitive tool for determining the relative reactivity of the wastes contained in the Hanford tanks. FAI have performed tube propagation studies previously on simple two- and three-component surrogate mixtures. The simulant defined in this test plan more closely represents actual tank composition. Data will be used to support preparation of criteria for determining the relative safety of the organic bearing wastes

247

High-performance III-V MOSFET with nano-stacked high-k gate dielectric and 3D fin-shaped structure.  

Science.gov (United States)

A three-dimensional (3D) fin-shaped field-effect transistor structure based on III-V metal-oxide-semiconductor field-effect transistor (MOSFET) fabrication has been demonstrated using a submicron GaAs fin as the high-mobility channel. The fin-shaped channel has a thickness-to-width ratio (TFin/WFin) equal to 1. The nano-stacked high-k Al2O3 dielectric was adopted as a gate insulator in forming a metal-oxide-semiconductor structure to suppress gate leakage. The 3D III-V MOSFET exhibits outstanding gate controllability and shows a high Ion/Ioff ratio?>?105 and a low subthreshold swing of 80 mV/decade. Compared to a conventional Schottky gate metal-semiconductor field-effect transistor or planar III-V MOSFETs, the III-V MOSFET in this work exhibits a significant performance improvement and is promising for future development of high-performance n-channel devices based on III-V materials. PMID:22853458

Chen, Szu-Hung; Liao, Wen-Shiang; Yang, Hsin-Chia; Wang, Shea-Jue; Liaw, Yue-Gie; Wang, Hao; Gu, Haoshuang; Wang, Mu-Chun

2012-01-01

248

Effect of Diameter of Orifice and Nozzle on the Performance of Counter Flow Vortex Tube  

OpenAIRE

Vortex tube is a simple device which will generates cold air stream and hot air stream from the source of compressed air. When high pressure air is injected via tangential nozzle a strong vortex flow will be created which will be split into two air streams. The main factors that affecting the performance of vortex tubes are inlet pressure, L/D ratio, cold mass fraction, diameter of nozzle and orifice. In this paper the performance of the vortex tube is investigated with different diameters of...

Prabakaran J; Vaidyanathan.S

2010-01-01

249

Effect of Diameter of Orifice and Nozzle on the Performance of Counter Flow Vortex Tube  

Directory of Open Access Journals (Sweden)

Full Text Available Vortex tube is a simple device which will generates cold air stream and hot air stream from the source of compressed air. When high pressure air is injected via tangential nozzle a strong vortex flow will be created which will be split into two air streams. The main factors that affecting the performance of vortex tubes are inlet pressure, L/D ratio, cold mass fraction, diameter of nozzle and orifice. In this paper the performance of the vortex tube is investigated with different diameters of orifice and nozzle.

Prabakaran.J

2010-04-01

250

Steady-state and transient heat transfer through fins of complex geometry  

Directory of Open Access Journals (Sweden)

Full Text Available Various methods for steady-state and transient analysis of temperature distribution and efficiency of continuous-plate fins are presented. For a constant heat transfer coefficient over the fin surface, the plate fin can be divided into imaginary rectangular or hexangular fins. At first approximate methods for determining the steady-state fin efficiency like the method of equivalent circular fin and the sector method are discussed. When the fin geometry is complex, thus transient temperature distribution and fin efficiency can be determined using numerical methods. A numerical method for transient analysis of fins with complex geometry is developed. Transient temperature distributions in continuous fins attached to oval tubes is computed using the finite volume - finite element methods. The developed method can be used in the transient analysis of compact heat exchangers to calculate correctly the heat flow rate transferred from the finned tubes to the fluid.

Taler Dawid

2014-06-01

251

Performance characteristics of solar blind UV image intensifier tube  

Science.gov (United States)

The UV radiation of spectrum range of 200~320nm almost is zero on the earth surface because UV radiation is greatly absorbed by ozone in atmosphere. So this spectrum range is called "Solar Blind Range". Because Solar Blind UV(SBUV) can't be influenced by atmosphere, it is easy to detect them as soon as SBUV radiation objects appear in the earth surface. If UV photoelectric image devices are used to observe them, high contrast picture will be acquired, that bright object's image lie in full black background. It is easy to identify the picture by human eye or other optical sensor (CCD). A solar blind UV(Ultra Violet) image intensifier tube(SBUV-IIT) is a special image intensifier tube, which was developed on double proximity focused Generation low-light-level image intensifier tube. It only responses spectrum range of 200~320 nm., SBUV-IIT can be used to observe UV faint radiation object, because UV sensitivity is high and response time is rapid and radiation gain is high. Low-altitude-flying missile can be observed by detecting its tail fog with SBUV-IIT, because its tail fog emits plenty of SBUV. By this way high contrast UV picture can be acquired to achieve missile warning, and this way has been widely used in foreign ordnance equipment. SBUV-IIT has been described in this paper. It is double proximity focused MCP (Micro-channel plate) image intensifier tube. It is 18mm active diameter of photocathode and phosphor screen. Input and output window is quartz glass and fiber optics faceplate respective. Photocathode material and phosphor screen is tellurium cesium compound and P20. It has been developed with a limiting UV resolution of 39 line pair per millimeter, and spectral response of 200~320 nm, photocathode maximum sensitivity of 29.5 milli-ampere per watt at wavelength 254 nm and a mass of 35g. It can be coupled with CCD easily. It has been well suited for fingerprint identify and camera system, It'll be used for UV hail testing, UV earthquake forecasting and so on.

Cheng, Hongchang; Shi, Feng; Feng, Liu; Liu, Hui; Ren, Bing; Zhang, Lian-dong

2009-07-01

252

Numeric Simulation on the Performance of an Undulating Fin in the Wake of a Periodic Oscillating Plate  

OpenAIRE

A two-dimensional unsteady computational fluid dynamics (CFD) method using an unstructured, grid-based and unsteady Navier-Stokes solver with automatic adaptive re-meshing to compute the unsteady flow was adopted to study the hydrodynamic interaction between a periodic oscillating plate and a rigid undulating fin in tandem arrangement. The user-defined function (UDF) program was compiled to define the undulating and oscillating motion. First, the influence of the distance between the anterior...

Zhang Yong-Hua; He Jian-Hui; Low Kin-Huat

2013-01-01

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

Heated ion implantation for high-performance and highly reliable silicon-on-insulator complementary metal–oxide–silicon fin field-effect transistors  

Science.gov (United States)

We have investigated the impact of heated ion implantation (I/I) on the performance and reliability of silicon-on-insulator (SOI) complementary metal–oxide–silicon (CMOS) fin field-effect transistors (FinFETs). An implantation temperature equal to and higher than 400 °C is needed to maintain the crystallinity of the Si substrate during I/I within the experimental conditions of ion species, implantation energy, and ion dose in this study. By heated I/I at 500 °C, the 11-nm-thick SOI layer perfectly maintains the crystallinity even after I/I, and a defect-free crystal is obtained by activation annealing. It was clarified that the cap layer is essential for the suppression of the out-diffusion during heated I/I. Heated I/I on the source and drain improves the on-current–off-current (Ion–Ioff), threshold voltage (Vth) variability, and bias temperature instability (BTI) characteristics of nMOS and pMOS FinFETs as compared with those after room-temperature I/I.

Mizubayashi, Wataru; Onoda, Hiroshi; Nakashima, Yoshiki; Ishikawa, Yuki; Matsukawa, Takashi; Endo, Kazuhiko; Liu, Yongxun; O’uchi, Shinichi; Tsukada, Junichi; Yamauchi, Hiromi; Migita, Shinji; Morita, Yukinori; Ota, Hiroyuki; Masahara, Meishoku

2015-04-01

255

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

256

Effect of Geometric Modifications on the Performance of Vortex Tube - A Review  

Directory of Open Access Journals (Sweden)

Full Text Available The vortex tube is device, which produces hot and cold air streams simultaneously at its two ends from a source of compressed air without any moving part. Literature review of this paper is to understand the effect of various parameters like inlet pressure of air, number of nozzles, cold orifice diameter and hot end valve angle on the performance of vortex tube. Also by the literature review it is clear that there is no theory so perfect, which gives the satisfactory explanation of the vortex tube phenomenon. Due to this reason researcher conduct the series of experimentation to understand the effect of various parameters mentioned above on the performance of vortex tube.

O. M. Kshirsagar

2014-11-01

257

Parametrical study for performances comparison between classic orifice pulse tube and hybrid Stirling pulse tube refrigerators; Etude parametrique comparee des performances des refrigerateurs a tube a gaz pulse classique et hybride  

Energy Technology Data Exchange (ETDEWEB)

An internal dynamic comparative study of orifice pulse tube (OPT) and Stirling hybrid pulse tube (HPT) is made, by thermodynamic modelling of the two systems. Basic structure of the model is established based on mass and energy conservation balances, written for separate control volumes of complete refrigerator. This method makes clear typical common parameters of the two mechanisms and specific importance of pistons phase shift and swept-volumes ratio for HPT. Starting from identical numeric characteristics for the two refrigerators, the study considers principally phases` evolution for pressure and mass flow rate at tube extremities. Greatest setting easiness, lower dimension for equivalent performances, give to the Stirling hybrid pulse tube good chances to be developed in miniature cryo-cooler area. (author) 18 refs.

Nika, Ph. [Universite de Franche-Comte, 90 - Belfort (France). Institut de Genie Energetique

1999-02-01

258

Performance investigation of capillary tubes for machine tool coolers retrofitted with HFC-407C refrigerant  

Science.gov (United States)

The machine tool coolers are the best managers of coolant temperature in avoiding the deviation of spindle centerline for machine tools. However, the machine coolers are facing the compressed schedule to phase out the HCFC (hydro-chloro-floro-carbon) refrigerant and little attention has been paid to comparative study on sizing capillary tube for retrofitted HFC (hydro-floro-carbon) refrigerant. In this paper, the adiabatic flow in capillary tube is analyzed and modeled for retrofitting of HFC-407C refrigerant in a machine tool cooler system. A computer code including determining the length of sub-cooled flow region and the two phase region of capillary tube is developed. Comparative study of HCFC-22 and HFC-407C in a capillary tube is derived and conducted to simplify the traditional trial-and-error method of predicting the length of capillary tubes. Besides, experimental investigation is carried out by field tests to verify the simulation model and cooling performance of the machine tool cooler system. The results from the experiments reveal that the numerical model provides an effective approach to determine the performance data of capillary tube specific for retrofitting a HFC-407C machine tool cooler. The developed machine tool cooler system is not only directly compatible with new HFC-407C refrigerant, but can also perform a cost-effective temperature control specific for industrial machines.

Wang, Fujen; Chang, Tongbou; Chiang, Weiming; Lee, Haochung

2012-09-01

259

Analysis of field-performance data on shell-and-tube heat exchangers in geothermal service  

Energy Technology Data Exchange (ETDEWEB)

Analysis of field performance data from a binary cycle test loop using geothermal brine and a hydrocarbon working fluid is reported. Results include test loop operational problems, and shell-and-tube heat exchanger performance factors such as overall heat transfer coefficients, film coefficients, pinch points, and pressure drops. Performance factors are for six primary heaters having brine in the tubes and hydrocarbon in the shells in counterflow, and for a condenser having cooling water in the tubes and hydrocarbon in the shell. Working fluids reported are isobutane, 90/10 isobutane/isopentane, and 80/20 isobutane/isopentane. Performance factors are for heating each working fluid at supercritical conditions in the vicinity of their critical pressure and temperature and condensing the same fluid.

Silvester, L.F.; Doyle, P.T.

1982-03-01

260

Thermal and Sensitivity Analysis of Multi-Fin Devices  

OpenAIRE

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

261

Optimization of counter flow Ranque-Hilsch vortex tube performance using Taguchi method  

Energy Technology Data Exchange (ETDEWEB)

This study discusses the application of Taguchi method in assessing maximum temperature gradient for the Ranque-Hilsch counter flow vortex tube performance. The experiments were planned based on Taguchi's L27 orthogonal array with each trial performed under different conditions of inlet pressure, nozzle number and fluid type. Signal-to-noise ratio (S/N) analysis, analysis of variance (ANOVA) and regression analysis were carried out in order to determine the effects of process parameters and optimal factor settings. Finally, confirmation tests verified that Taguchi method achieved optimization of counter flow Ranque-Hilsch vortex tube performance with sufficient accuracy. (author)

Pinar, Ahmet Murat [Celal Bayar University, Vocational High School, Department of Machinery, 45400-Turgutlu-Manisa (Turkey); Uluer, Onuralp [Gazi University, Faculty of Technical Education, Mechanical Education Department, Teknikokullar, 06503 Ankara (Turkey); Kirmaci, Volkan [Bartin University, Faculty of Engineering, Mechanical Engineering Department, 74100 Bartin (Turkey)

2009-09-15

262

THERMAL ANALYSIS OF CPU WITH COMPOSITE PIN FIN HEAT SINKS  

OpenAIRE

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...

Mohan, R.; Govindarajan, Dr P.

2010-01-01

263

High Fin Width Mosfet Using Gaa Structure  

OpenAIRE

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 s...

Tripathi, S. L.; Ramanuj Mishra; Mishra, R. A.

2012-01-01

264

Modeling of the thermal performances of an evaporator with graphite spiral-shaped fins; Modelisation des performances thermiques d'un evaporateur a ailettes spiralees en graphite  

Energy Technology Data Exchange (ETDEWEB)

This work concerns the study and modeling of a graphite-made evaporator with internal spiral-shaped fins. The parameters under study are: the Reynolds number of the hot working fluid, the mass flow rate of the falling film and the average inclination of the internal fin which characterize the heating surface. The analysis of the covariance of the experimental data allows to deduce two polynomial models which describe the evolution of the voluminal thermal power and of the specific vaporization ratio with respect to the different parameters under study. (J.S.)

Bessenet, S.; Renaudin, V.; Daroux, M.; Hornut, J.M. [Ecole Nationale Superieure des Industries Chimiques, Lab. des Sciences du Genie Chimique, ENSIC CNRS INPL, 54 - Nancy (France); Hornut, J.M. [Nancy-1 Univ., 54 (France)

2001-07-01

265

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

266

Effects of draft tube on the hydraulic performance of a Francis turbine  

Science.gov (United States)

The draft tube is an important component of a Francis turbine which influences the hydraulic performance. It is located just under the runner and allowed to decelerate the flow velocity exiting the runner, thereby converting the excess of kinetic energy into static pressure. In this study, we have numerically investigated the hydraulic performance of a Francis turbine on the 15MW hydropower generation with various design parameters (three types of draft tube, thickness of guide vane) through a three-dimensional numerical method with the SST turbulent model. The vortex rope characteristics of the draft tube were confirmed. The results of the vortex flow fields and flow characteristics were graphically depicted with different design parameters and operating conditions.

Jeon, J. H.; Byeon, S. S.; Kim, Y. J.

2013-12-01

267

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

268

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)

269

Comparative feeding kinematics and performance of odontocetes: belugas, Pacific white-sided dolphins and long-finned pilot whales.  

Science.gov (United States)

Cetaceans are thought to display a diversity of feeding modes that are often described as convergent with other more basal aquatic vertebrates (i.e. actinopterygians). However, the biomechanics of feeding in cetaceans has been relatively ignored by functional biologists. This study investigated the feeding behavior, kinematics and pressure generation of three odontocetes with varying feeding modes (belugas, Delphinapterus leucas; Pacific white-sided dolphins, Lagenorhynchus obliquidens; and long-finned pilot whales, Globicephala melas). Four feeding phases were recognized in all odontocetes: (I) preparatory, (II) jaw opening, (III) gular depression, and (IV) jaw closing. Belugas relied on a feeding mode that was composed of discrete ram and suction components. Pacific white-sided dolphins fed using ram, with some suction for compensation or manipulation of prey. Pilot whales were kinematically similar to belugas but relied on a combination of ram and suction that was less discrete than belugas. Belugas were able to purse the anterior lips to occlude lateral gape and form a small, circular anterior aperture that is convergent with feeding behaviors observed in more basal vertebrates. Suction generation in odontocetes is a function of hyolingual displacement and rapid jaw opening, and is likely to be significantly enhanced by lip pursing behaviors. Some degree of subambient pressure was measured in all species, with belugas reaching 126 kPa. Functional variations of suction generation during feeding demonstrate a wider diversity of feeding behaviors in odontocetes than previously thought. However, odontocete suction generation is convergent with that of more basal aquatic vertebrates. PMID:19946072

Kane, E A; Marshall, C D

2009-12-01

270

Effect of Fin Passage Length on Optimization of Cylinder Head Cooling Fins  

Science.gov (United States)

The heat transfer performance of baffled cooling fins on cylinder heads of small, air-cooled, general-aviation aircraft engines was analyzed to determine the potential for improving cooling fin design. Flow baffles were assumed to be installed tightly against the fin end edges, an ideal baffle configuration for guiding all flow between the fins. A rectangular flow passage is thereby formed between each set of two adjacent fins, the fin base surface, and the baffle. These passages extend around each side of the cylinder head, and the cooling air absorbs heat as it flows within them. For each flow passage length, the analysis was concerned with optimizing fin spacing and thickness to achieve the best heat transfer for each fin width. Previous literature has been concerned mainly with maximizing the local fin conductance and has not considered the heating of the gas in the flow direction, which leads to higher wall temperatures at the fin passage exits. If the fins are close together, there is a large surface area, but the airflow is restricted.

Siegel, R.; Graham, R. W.

1977-01-01

271

Performance demonstrations for steam generator tubing analysts in the nuclear power plants  

International Nuclear Information System (INIS)

This paper describes personnel training and qualification for nondestructive examination personnel who analyze data for steam generator tubing. The purpose of these qualification requirements is to ensure a continuing uniform knowledge base and skill level for data analysts and contribute to safely operate nuclear power plants. According to the Notice 2004-13 of Ministry of Science and Technology, the qualification for QDA(Qualified Data Analyst) and SSPD(Site-Specific Performance Demonstration) is required to the analysts for steam generator tubing data. The qualification procedures and requirements for QDA and SSPD in Korea are described in detail.

272

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

273

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

Energy Technology Data Exchange (ETDEWEB)

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/cm{sup 2}. Background rates of up to 14 kHz/cm{sup 2} 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 [Max-Planck-Institut für Physik, Munich (Germany); Kroha, Hubert, E-mail: kroha@mppmu.mpg.de [Max-Planck-Institut für Physik, Munich (Germany); Manfredini, Alessandro; Nowak, Sebastian; Ott, Sebastian; Richter, Robert; Schwegler, Philipp; Zanzi, Daniele [Max-Planck-Institut für Physik, Munich (Germany); Biebel, Otmar; Hertenberger, Ralf; Ruschke, Alexander; Zibell, Andre [Ludwig-Maximilians University, Garching (Germany)

2013-12-21

274

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

International Nuclear Information System (INIS)

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

275

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

OpenAIRE

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...

Varthamanan, Y.; Kannan, V.

2013-01-01

276

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

International Nuclear Information System (INIS)

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

277

Performance of the drift tubes for the barrel muon chambers of the CMS detector at LHC  

CERN Document Server

The barrel muon chambers of the CMS experiment are made assembling quadruplets of 4 layers of rectangular drift tubes. We present the performance of a prototype of such quadruplets exposed at a muon beam. Characteristics as noise, efficiency, drift velocity and resolution, are studied for various data taking conditions, as well as the effects of the magnetic field. A special emphasis is given to the performance aspects related to the trigger capability of the chambers.

Lippi, I

1997-01-01

278

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

279

Experimental investigation of heat transfer performance coefficient in tube bundle of shell and tube heat exchanger in two-phase flow  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the results of studies in two phase gasliquid flow around tube bundle in the model of shell tube heat exchanger. Experimental investigations of heat transfer coefficient on the tubes surface were performed with the aid of electrochemical technique. Chilton-Colburn analogy between heat and mass transfer was used. Twelve nickel cathodes were mounted on the outside surface of one of the tubes. Measurement of limiting currents in the cathodic reduction of ferricyanide ions on nickel electrodes in aqueous solution of equimolar quantities of K3Fe(CN6 and K4Fe(CN6 in the presence of NaOH basic solution were applied to determine the mass transfer coefficient. Controlled diffusion from ions at the electrode was observed and limiting current plateau was measured. Measurements were performed with data acquisition equipment controlled by software created for this experiment. Mass transfer coefficient was calculated on the basis of the limiting current measurements. Results of mass transfer experiments (mass transfer coefficient were recalculated to heat transfer coefficient. During the experiments, simultaneously conducted was the the investigation of two-phase flow structures around tubes with the use of digital particle image velocimetry. Average velocity fields around tubes were created with the use of a number of flow images and compared with the results of heat transfer coefficient calculations.

Kara? Marcin

2014-03-01

280

Wave-shaping of pulse tube cryocooler components for improved performance  

Science.gov (United States)

The method of wave-shaping acoustic resonators is applied to an inertance type cryogenic pulse tube refrigerator (IPTR) to improve its performance. A detailed time-dependent axisymmetric experimentally validated computational fluid dynamic (CFD) model of the PTR is used to predict its performance. The continuity, momentum and energy equations are solved for both the refrigerant gas (helium) and the porous media regions (the regenerator and the three heat-exchangers) in the PTR. An improved representation of heat transfer in the porous media is achieved by employing a thermal non-equilibrium model to couple the gas and solid (porous media) energy equations. The wave-shaped regenerator and pulse tube studied have cone geometries and the effects of different cone angles and the orientation (nozzle v/s diffuser mode) on the system performance are investigated. The resultant spatio-temporal pressure, temperature and velocity fields in the regenerator and pulse tube components are evaluated. The performance of these wave-shaped PTRs is compared to the performance of a non wave-shaped system with cylindrical components. Better cooling is predicted for the cryocooler using wave-shaped components oriented in the diffuser mode.

Antao, Dion Savio; Farouk, Bakhtier

2014-11-01

281

Thermal hydraulic performance analysis of a double tube bundle steam generator for a liquid metal reactor  

International Nuclear Information System (INIS)

Highlights: ? Thermal-hydraulic performance of the double tube bundle steam generators was analyzed. ? A numerical method was used with considering properties variation and phase change. ? The separated types are about two times more efficient than the integrated types. ? The integrated types have good heat transfer rate even during small medium flow rate. - Abstract: In this study, thermal-hydraulic performance of a double tube bundle steam generator (DTBSG) using helically coiled tubes was analyzed numerically. For this purpose a one-dimensional thermal-hydraulic analysis computer program was developed. The DTBSG contains hot fluid and cold fluid tube bundles, a medium fluid and a pump for a medium fluid circulation in an SG. Heat is transferred from the hot side to the cold side through a medium fluid which fills the SG shell side. The fluids of the hot, cold and medium side are sodium, water/steam, lead-bismuth respectively. The assessment was made for four different types of the DTBSG at 200 MWt. It showed there is an optimum medium flow rate for each type and the separated bundle type have the best heat transfer efficiency (heat transfer rate per unit area) among the various DTBSG. However, it requires quite a large pumping power and the velocity of the medium fluid. The effect of a medium flow rate change is relatively small in the integrated bundle types while it is very large in the separated type. The developed program can be used for the optimum theam can be used for the optimum thermal design of a double tube bundle steam generator, which is one of the candidates for an Intermediate Heat Transport System (IHTS) simplification concept.

282

Survey of the heat transfer correlations for helically coiled tubes to analyze the performance of the SMART steam generator  

International Nuclear Information System (INIS)

Helically coiled tubes are widely used for making compact heat exchangers. In the nuclear industry, once-through helically coiled heat exchangers are one of the options for small and medium sized reactors. SMART, which has been designed at KAERI, has 12 cassettes of once-through type heat exchangers using helically coiled tubes as a steam generator. To analyze the performance of the steam generator, information on the heat transfer characteristics of the helical coil tubes is required

283

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.

284

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

285

Evaluation of the Performance of a ``Tube-Scanner'' Type STM  

Science.gov (United States)

The performance of a tube-scanner type scanning tunneling microscope (STM) is evaluated. Since tunneling current noise is a basic limitation for the performance of a STM, it is important to eliminate it as far as possible. The dominant noise in tunneling current is the noise in tip-to-sample distance because tunneling current is exponentially dependent on this distance. Minimizing this vibrational noise is achieved by raising the lowest mechanical frequency of the STM. To facilitate this, various dependencies of the lowest resonant frequency are calculated using three simplified models. Resonant frequencies are also measured using both the piezo-electric effect in the tube scanner and the tunneling current. Comparison of the measurements and calculations of the mechanical response of the STM allows us to identify useful improvements in STM designs. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.OSS07.P1.12

Qiu Bao, Xiao; Howald, Craig

2007-05-01

286

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

287

Research on the Pin Fin Efficiency and Structure  

OpenAIRE

The performance of pin fin heat sink can be to measure through the temperature field. The temperature field and efficiency of the Pin Fin were analyzed, Pin fin efficiency curve was drowned also the distribution of the temperature field along the length of the pin fin curve was drawn. Thermal resistance was composed by thermal resistance of Aluminum substrate? thermal resistance of convective heat transfer and the thermal resistance of the cooling liquid. The change rule was studied through...

Fan Bailin; Huang Ganghan; Xu Long; Wang Yanjun; Zhang Pei

2013-01-01

288

Enhancement of Natural Convection Heat Transfer from Perforated Fin  

OpenAIRE

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 te...

Saurabh, D. Bahadure

2014-01-01

289

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

Energy Technology Data Exchange (ETDEWEB)

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.

Paine, Christopher G. [Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Drive, Pasadena CA 91109 (United States)

2014-01-29

290

Plastic Guidance Fins for Long Rod Projectiles .  

Directory of Open Access Journals (Sweden)

Full Text Available Projectile tail fins on long rod kinetic energy (KE penetrators serve the same purpose as fletchings (feathers on an arrow, namely, they help align the projectile axis with its velocity vector. This reduces the projectile's yaw and hence reduces its aerodynamic drag. In addition, a low yaw angle at target impact helps to maximise the projectile's target penetration. It is typical for projectiles to exit the gun muzzle and enter free flight at some ndn-zero yaw angle. Aerodynamic forces acting on yawed tail fins create a stabilising torque about the projectile's centre of gravity (CG. This torque can be increased by making the fin material lighter. Most conventional long rod penetrators fired from high performance guns have tail fins made from aluminium. However, aluminium can undergo catastrophic oxidation (rapid burning in-bore. Coating aluminium with Al/sub 2/O/sub 3/ {hardcoat prevents ignition of the substrate, provided solid propellant grain impacts do not chip the brittle hardcoat off the surface. Plastic is lighter than aluminium and less exothermic when oxidized. Therefore, other factors aside, it is conceivable that plastic fins could increase projectile stability while incurring less thermal erosion than aluminium. However, thermal loads are not the only concern when considering plastic as an alternative tail fin material. The mechanical strength of plastic is also a critical factor. This paper discusses some of the successes and failures of plastic fins, at least relatively thin fins, for use as KE stabilisers.

Mark L. Bundy

2013-04-01

291

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

International Nuclear Information System (INIS)

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

292

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

293

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

294

FinFET- Benefits, Drawbacks and Challenges.  

OpenAIRE

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...

Mayur Bhole; Aditya Kurude; Sagar Pawar

2013-01-01

295

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

296

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

297

Comparison of U-tube boreholes and a thermosiphon on heat pump performance in an aquifer  

Science.gov (United States)

Reducing our energy consumption and dependence on fossil fuels has become a common social, political and engineering goal. Heating and cooling of buildings account for a large percentage of the energy consumption in the United States. Improving HVAC efficiency in buildings can play a major role in reducing energy use. Small scale geothermal systems that utilize low-grade heat have gained popularity as a way to reduce HVAC energy consumption. U-tubes and thermosiphons are two different technologies designed to transfer heat to and from the ground in order to provide building heating and cooling. This thesis presents a short and long term experimental analysis. The short term analysis compares the performance of these technologies. The long term analysis focuses on the U-tubes, looking at the COP of the overall system during the course of a heating season and comparing temperatures for a theoretical air source heat pump system.

Workman, Christopher B.

298

Heat transfer performance during condensation of R-134a inside helicoidal tubes  

International Nuclear Information System (INIS)

This paper reports an experimental investigation of condensation heat transfer and pressure drop of an ozone friendly refrigerant, R-134a, inside a helical tube for climatic conditioning of hot regions. This study concerns the condensation of R-134a flowing through annular helical tubes with different operating refrigerant saturated temperatures. The average pressure drop is measured and compared with data from relevant literature. The measurements of R-134a were performed on mass flow flux ranges from 50 to 680 kg/m2 s. The study provides experimental data that could be used for the design and development of more efficient condensers for refrigeration and air conditioning (A/C) systems working with the same refrigerant

299

Tube vibration in industrial-size test heat exchanger (90/sup 0/ square layout)  

Energy Technology Data Exchange (ETDEWEB)

Tube vibrations in heat exchangers are being systematically investigated in a series of tests performed with an industrial-size test exchanger. Results from waterflow tests of eleven different tube bundles, in six- and eight-crosspass configurations on a 90/sup 0/ square layout with a pitch-to-diameter ratio of 1.25 are reported. The test cases include full tube bundles, no-tubes-in-window bundles, finned tube bundles, and proposed field and design fixes. The testing focused on identification of the lowest critical flowrate to initiate fluidelastic instability (large amplitude tube motion) and the location within the bundle of the tubes which first experience instability. The test results are tabulated to permit comparison with results obtained from previous tests with a 30/sup 0/ triangular layout tube bundle. Instability criteria are evaluated preliminarily. Pressure drop data are also generated and reported.

Halle, H.; Wambsganss, M.W.

1983-02-01

300

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

301

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

302

Effect of Ventilation Tube Diameter on Thermal Performance of Food Refrigerated Warehouse Floor Antifreezing Mechanical Ventilation System  

Directory of Open Access Journals (Sweden)

Full Text Available To investigate the effect of ventilation tube inside diameter on thermal performance of food refrigerated warehouse floor ant freezing mechanical ventilation system, a steady three-dimensional mathematical model of heat transfer is set up in this study. The calculation conditions of the heat transfer model are defined according to the reasonable simplification and heat transfer process. The temperature fields of this system are simulated and calculated by CFD software PHOENICS under different tube inside diameters, 250 or 300 mm. The results show that the effect of ventilation tube inside diameter is greater on thermal performance of food refrigerated warehouse floor antifreezing mechanical ventilation system. The proper tube inside diameter is pointed to be 250 mm for the food refrigerated warehouse floor with 1.5 m tube spacing.

Jing-fu Jia

2015-02-01

303

Development and application of an efficient method for performing modal analysis of steam generator tubes in nuclear power plants  

International Nuclear Information System (INIS)

A typical pressurized water reactor (PWR) steam generator has approximately 10,000 tubes. These tubes have different geometries, supporting conditions, and different material properties due to the non-uniform temperature distribution throughout the steam generator. Even though some tubes may have the same geometry and boundary conditions, the non-uniform distribution of coolant densities adjacent to the tubes causes them to have different added mass effects and dynamic characteristics. Therefore, for a reliable design of the steam generator, a separate modal analysis for each tube is necessary to perform the FIV (flow-induced vibration) analysis. However, the modal analysis of a tube including the finite element modeling is cumbersome and takes lots of time. And when a commercial finite element code is used, interfacing the modal analysis result, such as natural frequencies and mode shapes, with the FIV analysis procedure requires an additional significant amount of time and can possibly incur inadvertent error due to the complexity of data processing. It is therefore impossible to perform the complete FIV analysis for ten thousands of tubes when designing or maintaining a steam generator although it is necessary. Rather, to verify the safe design against the FIV, only a couple of tubes are chosen based on engineering judgment or past experience. In this paper, a computer program, PIAT-MODE, was developed which is able to perform modal analysis of all tubes of a PWR sorm modal analysis of all tubes of a PWR steam generator in a very efficient way. The geometries and boundary conditions of every tube were incorporated into PIAT-MODE using appropriate mathematical formulae. Material property data including the added mass effect was also included in the program. Once a specific tube is selected, the program automatically constructs the finite element model and generates the modal data very quickly. Therefore, modal analysis can be performed for every single tube in a straight way. When PIAT-MODE is coupled with the FIV analysis program, it gives an amazing benefit, which makes the FIV analysis of all tubes possible within a limited time during the design or maintenance period. Using the developed program, the stability ratio regarding the fluid-elastic instability and the amplitude of vibration resulting from the turbulence flow excitation can be calculated for all tubes according the standard ASME Code, therefore, much more reliable design of the steam generator against the FIV related failures can be achieved. For an operating plant, there is a requirement that every single tube must be quantitatively checked whether wear would be more than 40% in thickness during the next operation period. If yes, the tube must be plugged to prevent severe failure including the tube wall penetration. In order to decide the tube plugging, which leads the plant performance degradation, the wear prediction is required. The wear prediction analysis needs wear data by ultrasonic testing and modal property data of tubes. PIAT-MODE will be a power tool enabling the wear prediction in a limited maintenance period by supplying modal data for all tubes.

304

Study on the effect of punched holes on flow structure and heat transfer of the plain fin with multi-row delta winglets  

Science.gov (United States)

Three dimensional numerical simulations are performed to investigate the flow and heat transfer characteristics of the plain fin with multi-row delta winglets punched out from the fin. The Reynolds number based on the tube outside diameter varies from 360 to 1440. The effects of punched holes and their orientations on flow structure and heat transfer are numerically studied. Results show that a down-wash flow is formed through the hole punched at the windward side, which has little influence on the longitudinal vortices in the main flow, and a longitudinal main vortex is formed behind each delta winglet. An up-wash flow is formed through the hole punched at the leeward side, the up-wash flow impinges the longitudinal vortices generated by the delta winglet, and then a counter-rotating pair of main vortices is generated behind each delta winglet. The windward punched holes have little effect on the flow friction and heat transfer of the plain fin with delta winglets, while the leeward punched holes deteriorate the heat transfer and decrease the flow friction of the fin channel, the Nusselt number decreases by 3.5-5.0 % with a corresponding decrease of 3.9-4.8 % in the friction factor. The effect of the punched holes on the heat transfer of the fin can be well explained by the field synergy principle. The overall analysis of the thermal performance is performed for all fin configurations, including the slit fins and the wavy fins with one-row delta winglets, the plain fin with the windward punched delta winglets shows the better thermal performance than one with the leeward punched delta winglets.

Tian, Liting; Liu, Bin; Min, Chunhua; Wang, Jin; He, Yaling

2015-02-01

305

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

306

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

Energy Technology Data Exchange (ETDEWEB)

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

Jo, Nam Hoon [Soongsil University, Seoul (Korea, Republic of)

2010-02-15

307

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

308

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)

309

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

310

Experimental investigation of heat transfer enhancement in a circular duct with circumferential fins and circular disks  

International Nuclear Information System (INIS)

The characteristics of heat transfer and pressure drop for fully developed turbulent flow in a tube with circumferential fins and circular disks were experimentally studied. The various spacing and sizes of circumferential fins and circular disks were selected as design parameters, while the effects of these parameters on heat transfer enhancement and pressure drop were investigated. In order to quantify the effect of heat transfer enhancement and the increase of pressure drop due to the fins and disks in a tube, the Nusselt numbers and the friction factors for various configurations and operating conditions were compared to those for a corresponding smooth tube. The results showed that the heat transfer rate was significantly enhanced by increasing the height of circumferential fins and decreasing the pitch of circumferential fins. On the other hand, the influence of the disk size and the fin-disk spacing were not significant. Based on the experimental results, a correlation for estimating the Nusselt number was suggested

311

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

312

Muscle activity during knee-extension strengthening exercise performed with elastic tubing and isotonic resistance  

DEFF Research Database (Denmark)

BACKGROUND/PURPOSE: While elastic resistance training, targeting the upper body is effective for strength training, the effect of elastic resistance training on lower body muscle activity remains questionable. The purpose of this study was to evaluate the EMG-angle relationship of the quadriceps muscle during 10-RM knee-extensions performed with elastic tubing and an isotonic strength training machine. METHODS: 7 women and 9 men aged 28-67 years (mean age 44 and 41 years, respectively) participated. Electromyographic (EMG) activity was recorded in 10 muscles during the concentric and eccentric contraction phase of a knee extension exercise performed with elastic tubing and in training machine and normalized to maximal voluntary isometric contraction (MVC) EMG (nEMG). Knee joint angle was measured during the exercises using electronic inclinometers (range of motion 0-90°). RESULTS: When comparing the machine and elastic resistance exercises there were no significant differences in peak EMG of the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM) during the concentric contraction phase. However, during the eccentric phase, peak EMG was significantly higher (p70% nEMG) quadriceps muscle activity during the concentric contraction phase, but slightly lower during the eccentric contraction phase, as knee extensions performed using an isotonic trainingmachine. During the concentric contraction phase the two different conditions displayed reciprocal EMG-angle patterns during the range of motion. LEVEL OF EVIDENCE: 5.

Jakobsen, Markus Due; Sundstrup, Emil

2012-01-01

313

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

314

A study on heat transfer enhancement using straight and twisted internal fin inserts  

International Nuclear Information System (INIS)

The present study investigated the effect of internal aluminum fins with a star shape cross section on the heat transfer enhancement and pressure drop in a counterflow heat exchanger. A concentric tube heat exchanger was used with water as the working fluid. The heat transfer rate increased by 12-51% over the plain tube value, depending on the internal fin configuration used. However, the pressure drop also increased substantially by an average of 286-338%. The results showed that a straight fin configuration is good enough to produce a heat transfer increase in a counterflow heat exchanger. Twisted fin configurations did not further increase the heat transfer rate

315

Construction and performance of an NMR tube with a sample cavity formed within magnetic susceptibility-matched glass  

OpenAIRE

We describe the construction and performance of an NMR tube with a magnetic susceptibility matched sample cavity that confines the solution within the detection zone in the axial direction and in a quasi-rectangular region in the radial direction. The slot-like sample cavity provides both good sample volume efficiency and tolerance to sensitivity loss in the sample space. The signal-to-noise ratio per unit volume of the constructed tube was 2.2 times higher than that of a cylindrical tube of ...

Takeda, Mitsuhiro; Hallenga, Klaas; Shigezane, Masahiro; Waelchli, Markus; Lo?hr, Frank; Markley, John L.; Kainosho, Masatsune

2011-01-01

316

Design and test of high performance composite tubes for use in deep water drilling and production systems  

Science.gov (United States)

High performance composite tubes to be used as marine risers, in deepwater drilling or in production systems were developed. They are composed of several layers with independant functions. Structural layers made of high resistance fibers set in a resin matrix, are filament wound and consist of circumferential layers, perpendicular to the tube axis, to resist bursting stresses, and longitudinal layers, helically wound, to resist axial forces. The tubes are completed with internal and external liners and are terminated at extremities by steel end pieces to which the composite layers are carefully bonded. The concept of high performance composite tubes is described, including their end fittings. Tests were carried out to verify and improve the properties of the pipes, in ultimate conditions (burst pressure up to 170 MPa, ultimate tensile, collapse), as well as fatigue and aging. Results are satisfactory and real applications are envisaged.

Odru, Pierre; Massonpierre, Yves

1987-10-01

317

Experimental Evaluation of the Energy Performance of an Air Vortex Tube when the Inlet Parameters are Varied  

OpenAIRE

he paper presents the analysis of the energy performance of an air vortex cooling tube under variations of the air inlet properties, with t hree independent experimental tests validated through the energy balance in the device. The experimental analysis includes the following variations of the input conditions: First, the effect of the air inlet pressure to the vortex tube, focused on the analysis of temperature variations in the output cold stream and in the coo...

Torrella Alcaraz, Enrique; Patin?o Pe?rez, Jorge; Sa?nchez Garci?a-vacas, Daniel; Llopis Dome?nech, Rodrigo; Cabello Lo?pez, Ramo?n

2013-01-01

318

Tube vibration in industrial size test heat exchanger (30/sup 0/ triangular layout - six crosspass configuration)  

Energy Technology Data Exchange (ETDEWEB)

Tube vibrations in heat exchangers are being systematically studied in a series of tests performed with an industrial-size test exchanger. Results from flow tests of nine different tube bundles, in a basic 5-baffle, 6-crosspass configuration on a 30/sup 0/-triangular layout with a pitch-to-diameter ratio of 1.25, are reported. the test cases include a full tube bundle, no-tubes-in-window bundle, finned tube bundle, and several proposed field fixes. The testing focused on identification of the lowest critical flowrate to initiate fluidelastic instability (large amplitude tube motion) and the location within the bundle of the tubes which first experience instability. The threshold flowrates are determined from a combination of methods based on sensory observations, vibration amplitude data, and frequency response information. Pressure drop data are also generated and reported.

Wambsganss, M.W.; Halle, H.; Lawrence, W.P.

1981-10-01

319

The numerical analysis of natural convective heat transfer of vertical and horizontal pin-fin arrays of pin-fin air cooling module for electronic packaging applications  

International Nuclear Information System (INIS)

In the present study, the natural convective heat transfer of vertical and horizontal pin-fin arrays of an air cooling module for electronic devices was numerically analyzed with respect to pin-fin shapes. The cross-sectional shapes of the pin-fin were changed from the square (the reference shape) to the long rectangle with same cross-sectional area and height. The vertical pin-fin arrangement had better heat transfer performance that the horizontal pin-fin arrangement. For both vertical and horizontal arrangements the pin-fin arrays had the best heat transfer performance when the aspect ratios had 2.56.

320

Measurement of the performance of a spiral wound polyimide regenerator in a pulse tube refrigerator  

Science.gov (United States)

A regenerator for use in a pulse tube refrigerator has been constructed from a polyimide (polypyromellitimide or PPMI) whose small ratio of thermal conductivity to heat capacity make it a good candidate for a regenerator material in cryocoolers. The regenerator was fabricated using 25 micron thick photoresist strips bonded to a 50 micron thick sheet of PPMI. This composite sheet was wound in jelly-roll fashion around a mandrel and inserted into the regenerator housing. The photoresist strips, formed using a photolithographic technique, provided a 25 micron spacing for the axial flow of gas between each layer of PPMI. Ineffectiveness results are presented for this material under actual operating conditions in a pulse tube refrigerator and compared with a numerical model. The numerical model indicated that a polyimide regenerator would perform much better than one constructed of stainless steel screen, but the experimental results showed the opposite behavior. Measured values for the ineffectiveness were 0.003 for the stainless steel screen and 0.017 for the polyimide.

Rawlins, Wayne; Timmerhaus, Klaus D.; Radebaugh, Ray; Daney, D. E.

1991-01-01

321

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 two 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 two-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. A comparison between data and a detailed Monte Carlo simulation is also presented. The result of the test shows that such a detector can achieve the desired performances. (orig.)

322

Experimental Performance of Window Air Conditioner Using Alternative Refrigerants with Different Configurations of Capillary Tube: A Review  

Directory of Open Access Journals (Sweden)

Full Text Available This review paper presents the work of various researches on the performance of capillary tube ,used in air conditioners with various refrigerants. Research carried out by different authors uses different type of capillary tubes (straight, twisted, coiled in different length and diameter. they determined various parameters like coefficient of performance (COP,cooling capacity, energy efficiency ratio (EER of the system. Various approaches have been used by different authors to predict the performance of capillary in window air conditioner using alternative refrigerant as capillary expansion device.

Richa Soni

2013-08-01

323

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

OpenAIRE

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

324

Heat transfer and pressure drop of a transversely finned concentric annulus with longitudinal flow  

International Nuclear Information System (INIS)

The characteristics of heat transfer and pressure drop have been experimentally studied for the fully developed concentric annular flow with transverse fins normal to the flow direction by the naphthalene sublimation technique. Correlations for calculating the heat transfer coefficient with different inner diameters D0 of the outer tube are presented. A 'characteristic Reynolds number' has been proposed, by which the predominant role of the transverse fins can be evaluated. It has been indicated that the inner diameter D0 has much more effect on pressure drop than on heat transfer. The effect of D0 on the overall performance is also compared under the same flow velocity or flow rate. It has been found that the effect of developing flow on heat transfer is significant and should be taken into account during experiment. (orig.)

325

Enhancement of ECR performances by means of carbon nano-tubes based electron guns  

International Nuclear Information System (INIS)

The CANTES experiment at INFN-LNS tested the use of carbon nano-tubes (CNTs) to emit electrons by field emission effect, in order to provide additional electrons to the plasma core of an ECR ion source. This technique was used with the Caesar source, demonstrating that the total extracted ion current is increased and that a relevant reduction of the number of 'high energy' electrons (above 100 keV) may be observed. The injection of additional electrons inside the plasma increases the amount of cold and warm electrons, and then the number of ionizing collisions. Details of the construction of CNTs based electron gun and of the improvement of performances of the Caesar ECR ion source will be presented. The paper is followed by the associated poster. (authors)

326

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

327

Median fin function during the escape response of bluegill sunfish (Lepomis macrochirus). I: Fin-ray orientation and movement.  

Science.gov (United States)

The fast-start escape response is critically important to avoid predation, and axial movements driving it have been studied intensively. Large median dorsal and anal fins located near the tail have been hypothesized to increase acceleration away from the threat, yet the contribution of flexible median fins remains undescribed. To investigate the role of median fins, C-start escape responses of bluegill sunfish (Lepomis macrochirus) were recorded by three high-speed, high-resolution cameras at 500 frames s(-1) and the 3-D kinematics of individual dorsal and anal fin rays were analyzed. Movement and orientation of the fin rays relative to the body axis were calculated throughout the duration of the C-start. We found that: (1) timing and magnitude of angular displacement varied among fin rays based on position within the fin and (2) kinematic patterns support the prediction that fin rays are actively resisting hydrodynamic forces and transmitting momentum into the water. We suggest that regions within the fins have different roles. Anterior regions of the fins are rapidly elevated to increase the volume of water that the fish may interact with and transmit force into, thus generating greater total momentum. The movement pattern of all the fin rays creates traveling waves that move posteriorly along the length of the fin, moving water as they do so. Flexible posterior regions ultimately act to accelerate this water towards the tail, potentially interacting with vortices generated by the caudal fin during the C-start. Despite their simple appearance, median fins are highly complex and versatile control surfaces that modulate locomotor performance. PMID:22837461

Chadwell, Brad A; Standen, Emily M; Lauder, George V; Ashley-Ross, Miriam A

2012-08-15

328

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

329

Mechanism of tonal noise generation from circular cylinder with spiral fin  

Science.gov (United States)

The pitch of the spiral finned tube influences seriously to the acoustic resonance in the heat exchanger. In this research, the flow characteristics in relating to the aeolian tone from the finned cylinder are studied by the numerical simulation. It is observed that the tonal noise generated from the finned tube at two pitch spaces. The ratio of the fin pitch to the cylinder diameter is changed at 0.11 and 0.27. The tone level increases and the frequency decreases with the pitch shorter. The separation flow from the cylinder generates the span-wise vortices, Karman vortices, and the separation flow from the fin generates the stream-wise vortices. When the fin pitch ratio is small, the stream-wise vortices line up to span-wise and become weak rapidly. Only the Karman vortices are remained and integrate in span. So the Karman vortex became large. This causes the low frequency and the large aeolian tone.

Yamashita, Ryo; Hayashi, Hidechito; Okumura, Tetsuya; Hamakawa, Hiromitsu

2014-12-01

330

Benchmarking the Performance of the ANSYS-FLUENT Standard k- ? Turbulence Model in Fluid Flow and Heat Transfer Predictions for Complex Flows around Circular Pin-Fins Using Various near Wall Functions  

Directory of Open Access Journals (Sweden)

Full Text Available This study compares CFD analyses of the fluid flow and heat transfer phenomena in a popular pin-fin geometry of X/D = 2.5, S/D = 2.5 and H/D = 1 for a range of Re = 5,000 to 30,000 to those from experiment to aid in the benchmarking the performance of the CFD code FLUENT. The CFD analyses use three ANSYS-FLUENT (version 13 near wall treatments available within the code: 1 the Standard Wall Function (SWF, 2 the Non-Equilibrium Wall Function (NEWF and 3 the enhanced wall treatment. Experimental data used in this study were obtained from two papers: 1 by Chyu et al. (1998 for heat transfer predictions and another 2 by Metzgeret al. (1984 for pressure loss predictions, both for the same setup. The study also differentiates between the heat transfer occurring by the body of the pin-fin itself and that by the end-wall areas surrounding it. Results from the CFD analyses based on the fourth pin-fin from the inlet (commonly assumed to have a stable flow around it, show very good prediction accuracies of heat transfer coefficients for the pin-fin body itself but rather low accuracies for the end-wall areas (based on heat flux and inlet temperature values. Better accuracies were obtained when using the enhanced wall treatment where pin-fin body heat transfer coefficients were almost identical between the CFD and experimental results. An alternative definition of heat transfer based on the averaged local temperatures around the fourth pin-fin showed that the heat transfer coefficient then (with CFD's capability to establish the local thermal field is really between 1.5 to 3.5 times that predicted by using the inlet temperature in deducing the local h values. The same accuracies cannot be said about its predictions of pressure loss coefficients where CFD results tended to be lower by 50-100%h.

A. Al-Witry

2013-05-01

331

Performance of Subsurface Tube Drainage System in Saline Soils: A Case Study  

Science.gov (United States)

In order to improve the saline and water logged soils caused due to groundwater table rise, installation of subsurface drainage system is considered as one of the best remedies. However, the design of the drainage system has to be accurate so that the field performance results conform to the designed results. In this investigation, the field performance of subsurface tube drainage system installed at the study area was evaluated. The performance was evaluated on the basis of comparison of the designed value of water table drop as 30 cm after 2 days of drainage and predicted and field measured hydraulic heads for a consecutive drainage period of 14 days. The investigation revealed that the actual drop of water table after 2 days of drainage was 25 cm, about 17 % less than the designed value of 30 cm after 2 days of drainage. The comparison of hydraulic heads predicted by Van Schilfgaarde equation of unsteady drainage with the field-measured hydraulic heads showed that the deviation of predicted hydraulic heads varied within a range of ±8 % indicating high acceptability of Van Schlifgaarde equation for designing subsurface drainage system in saline and water logged soils resembling to that of the study area.

Pali, A. K.

2015-03-01

332

Disruption shape effects on the performance of enhanced tubes with the separation and reattachment mechanism  

Energy Technology Data Exchange (ETDEWEB)

A non-orthogonal, body-fitted numerical code is used to determine the thermo-hydraulic performance of enhanced tubes with transverse periodic sine-, semicircle-, arc-, and trapezoid-shaped disruptions. The turbulence closure was achieved with a two-layer turbulence model. It is shown that there is a tradeoff of the heat-transfer and pressure-drop performances when the disruption shape becomes more contoured; that is, both the heat transfer and the pressure drop increase. The local heat transfer is strongly dependent on the shape in the vicinity of the disruption but it is less dependent in the downstream recirculation region and in the boundary layer development zone. With increasing pitch, effect of the shape on the heat-transfer performance becomes less important. The pressure drop is more dependent on the disruption shape and it continues to decrease when the disruptions become less contoured because of the reduced form drag which is by far the major contribution to the total pressure drop. 27 refs.

Arman, B.; Rabas, T.J.

1992-01-01

333

Disruption shape effects on the performance of enhanced tubes with the separation and reattachment mechanism  

Energy Technology Data Exchange (ETDEWEB)

A non-orthogonal, body-fitted numerical code is used to determine the thermo-hydraulic performance of enhanced tubes with transverse periodic sine-, semicircle-, arc-, and trapezoid-shaped disruptions. The turbulence closure was achieved with a two-layer turbulence model. It is shown that there is a tradeoff of the heat-transfer and pressure-drop performances when the disruption shape becomes more contoured; that is, both the heat transfer and the pressure drop increase. The local heat transfer is strongly dependent on the shape in the vicinity of the disruption but it is less dependent in the downstream recirculation region and in the boundary layer development zone. With increasing pitch, effect of the shape on the heat-transfer performance becomes less important. The pressure drop is more dependent on the disruption shape and it continues to decrease when the disruptions become less contoured because of the reduced form drag which is by far the major contribution to the total pressure drop. 27 refs.

Arman, B.; Rabas, T.J.

1992-08-01

334

Analysis of natural convective heat transfer of nano coated aluminium fins using Taguchi method  

Science.gov (United States)

Rectangular aluminium fins were preferred for analysis and coated by carbon nano tubes using PVD to enhance the heat transfer rate of fins. Convective heat transfer rates for coated and non-coated surfaces were calculated and compared. The temperature and heat transfer characteristics were investigated using Nusselt, Grashof, Prandtl and Rayleigh numbers and also optimized by Taguchi method and ANOVA analysis. The average percentage of increase in fin efficiency is 5 %.

Senthilkumar, R.; Nandhakumar, A. J. D.; Prabhu, S.

2013-01-01

335

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

336

Pollen performance before and during the autotrophic-heterotrophic transition of pollen tube growth.  

OpenAIRE

For species with bicellular pollen, the attrition of pollen tubes is often greatest where the style narrows at the transition between stigmatic tissue and the transmitting tissue of the style. In this region, the tubes switch from predominantly autotrophic to predominantly heterotrophic growth, the generative cell divides, the first callose plugs are produced, and, in species with RNase-type self-incompatibility (SI), incompatible tubes are arrested. We review the literature and present new f...

Stephenson, Andrew G.; Travers, Steven E.; Mena-ali, Jorge I.; Winsor, James A.

2003-01-01

337

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

OpenAIRE

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 r...

Khalid, Asad A.

2001-01-01

338

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

339

Pressure loss and heat transfer through multiple rows of short pin fins  

Science.gov (United States)

Results are presented showing performance in terms of pressure loss and heat transfer for arrays of short pin fins set in a high aspect ratio duct. Seven array configurations were fabricated and tested, typical of those used for heat transfer augmentation in gas turbine airfoil cooling. All configurations have uniform regular pin spacing with alternate rows in the streamwise direction staggered one-half the transverse pitch. The short length of the pins dictates that the uncovered duct walls are a significant fraction of the total heat transfer area. Comparison is made between the present short pin results and established tube bank performance where the tube surfaces account for all the heat transfer area.

Metzger, D. E.; Fan, Z. X.; Shepard, W. B.

340

Boiling of HFE-7100 on a straight pin fin  

Science.gov (United States)

This paper deals with an experimental investigation of pin fin boiling of saturated and subcooled HFE-7100 under atmospheric pressure. Fin base temperature and heat flux data are measured along with the fin tip temperature. The basic features of boiling stability of HFE-7100 boiling on pin fin had been reported for the first time. For a given liquid/heating surface combination there exist upper steady-state (USS) branch and lower steady-state (LSS) branch, and a large, unstable regime located in between. Zones with different stability characteristics are mapped according to boiling on fins with different aspect ratios. Liquid subcooling can largely enhance heat transfer performance. A longer fin can provide a safer operation.

Liu, Z. W.; Lin, W. W.; Lee, D. J.; Hsu, J. P.

2001-03-01

341

A study on the performance of the heat transfer for the liquid filling as the ratio of working fluid volume to total volume of the thermosyphon with axial internal fins  

Energy Technology Data Exchange (ETDEWEB)

This study concerns the performance of the heat transfer of the thermosyphon having 80 internal fins in which boiling and condensation occur. Water has been used as the working fluid. The liquid filling as the ratio of working fluid volume to total volume of thermosyphon have been used as the experimental parameters. The heat flux and heat transfer coefficient at the condenser are estimated from the experimental results. The experimental results have been assessed and compared with existing theories. As a result of the experimental investigation we can state that the maximum heat flow rate in the thermosyphon prove to depend upon the liquid fill quantity. The relatively high rates of heat transfer have been achieved operating in the thermosyphon with axial internal fins. Also, the thermosyphon with internal micro fins can be used to achieve some inexpensive and compact heat exchangers in flow temperature. In addition, it is to obtain the overall heat transfer coefficients and the characteristics as a operating temperature for the practical applications. (author). 12 refs., 8 figs.

Lee, J.H.; Lee, K.B. [Pusan National University, Pusan (Korea); Cho, D.H. [Daejin University, Poch' on (Korea)

2002-03-01

342

Diagnostic performance of liquid crystal and cathode-ray-tube monitors in brain computed tomography  

International Nuclear Information System (INIS)

The aim of this study was to evaluate feasibility of reporting brain CT examinations on liquid crystal display (LCD) flat-screen monitors vs state-of-the-art cathode-ray-tube (CRT) monitors. Ninety-five brain CT examinations of 95 patients were displayed on Picture archiving and communications system (PACS) workstations equipped either with a dedicated medical imaging LCD colour monitor or on a high-resolution CRT which is used for routine reporting of CT, MRI and digital radiography images in our institution. Fifty cases were negative and 45 cases were positive for early brain infarction (EBI), the latter being defined by a combination of one or more signs: dense artery; hypodensity of brain parenchyma; and local brain swelling verified by control scans. Ten radiologists had to rate presence or absence of EBI on a five-point scale. Ratings were evaluated by CORROC2 ROC software and areas under the ROC curve (Az) were computed. Significance of differences between the two viewing conditions were evaluated with Wilcoxon test. Mean Az of the ten observers was 0.7901 with LCD vs 0.7695 with CRT which did not show statistical significance (p=0.2030). In the setting investigated, reporting of CT studies from high-performance LCD monitors seems feasible without significant detriment to diagnostic performance. (orig.)

343

Cooling performance assessment of horizontal earth tube system and effect on planting in tropical greenhouse  

International Nuclear Information System (INIS)

Graphical abstract: - Highlights: • The cooling ability of HETS is studied for planting in tropical greenhouse. • The effective of system was moderate with COP more than 2.0. • Increasing diameter and air velocity increase COP more than other parameters. • The plant growth with HETS was significantly better than no-HETS plant. - Abstract: The benefit of geothermal energy is used by the horizontal earth tube system (HETS); which is not prevalent in tropical climate. This study evaluated geothermal cooling ability and parameters studied in Thailand by mathematical model. The measurement of the effect on plant cultivation was carried out in two identical greenhouses with 30 m2 of greenhouse volume. The HETS supplied cooled air to the model greenhouse (MGH), and the plant growth results were compared to the growth results of a conventional greenhouse (CGH). The prediction demonstrated that the coefficient of performance (COP) in clear sky day would be more than 2.0 while in the experiment it was found to be moderately lower. The parameters study could be useful for implementation of a system for maximum performance. Two plants Dahlias and head lettuce were grown satisfactory. The qualities of the plants with the HETS were better than the non-cooled plants. In addition, the quality of production was affected by variations of microclimate in the greenhouses and solar intensity throughout the cultivation period

344

Performance of a split-type air conditioner matched with coiled adiabatic capillary tubes using HCFC22 and HC290  

International Nuclear Information System (INIS)

This paper experimentally investigated the system performance of a split-type air conditioner matching with different coiled adiabatic capillary tubes for HCFC22 and HC290. Experiments were carried out in a room-type calorimeter. The results have shown that (1) similar cooling effects can be achieved by matching various capillary tubes of different inner diameters; (2) parallel capillary tubes presented better system performance and flow stability with weaker inlet pressure fluctuations than the single capillary tube; (3) with the coil diameter of the capillary tube increasing from 40 mm to 120 mm, the mass flow rate tended to increase slightly. But the cooling capacity, input power and energy efficiency ratio (EER) did not show evident tendency of change; (4) the refrigerant charge and mass flow rate for HC290 were only 44% and 47% of that for HCFC22, respectively, due to the much lower density. And HC290 had 4.7-6.7% lower cooling capacity and 12.1-12.3% lower input power with respect to HCFC22. However, the EER of HC290 can be 8.5% higher than that of HCFC22, which exhibits the advantage of using HC290. In addition, the experimental uncertainties were analyzed and some application concerns of HC290 were discussed.

345

Constructal T-shaped fins  

Energy Technology Data Exchange (ETDEWEB)

This paper reports the geometric (constructal) optimization of T-shaped fin assemblies, where the objective is to maximize the global thermal conductance of the assembly, subject to total volume and fin-material constraints. Assemblies of plate fins and cylindrical fins are considered. It is shown that every geometric feature of the assembly is delivered by the optimization principle and the constraints. These optimal features are reported in dimensionless terms for this entire class of fin assemblies. Corresponding results are developed for more evolved versions of the T-shaped assembly, namely, the tau-shaped assembly where the free ends of the thinner fins are bent, the tau-shaped assembly that is narrower than the space allocated to it, and the umbrella-shaped construct containing cylindrical fins. The results show that some of the optimized geometrical features are relatively robust, i.e.. insensitive to changes in some of the design parameters. (author)

Bejan, A.; Almogbel, M. [Duke Univ., Durham, NC (United States). Dept. of Mechanical Engineering and Materials Science

2000-06-01

346

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

347

Study on the Performance of Inhibitors for a SCC of SG Tube Materials  

Energy Technology Data Exchange (ETDEWEB)

Steam generator (SG) tube materials have severe problems of a stress corrosion cracking (SCC) in nuclear power plants. Most of SCCs have occurred near the top of a sludge pile on a tubesheet and within a tube support plate crevice in which it is thought to be caustic. Some inhibitors have been studied to reduce the SCC problems for a SG tube. Laboratory tests using C-ring and constant extension rate specimens have shown that some chemical compounds may inhibit a SCC of a SG tube. Several titanium compounds have been applied at PWR type nuclear power plants. While they have reported some beneficial effects, there is insufficient evidence as yet that would convince us of its positive effects as an inhibitor. The objectives of this research are to investigate the inhibition effects of a SCC with a variation of SG tube materials and the penetration property in a crevice of the inhibitors.

Kim, Kyung Mo; Lee, Eun Hee; Kim, Uh Chul; Maeng, Wan Young [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2007-07-01

348

Propulsive Forces of a Biomimetic Undulating Fin  

Science.gov (United States)

Understanding gained from much recent work on force production mechanisms of aquatic organisms holds great promise for improved undersea vehicle propulsion and maneuvering. One class of fish locomotion is that of the median fin utilized by animals such as squid, cuttlefish, knifefish, and seahorse. It is characterized by undulatory motion that creates traveling waves along the fin. Results of experiments conducted on a submerged mechanical underwater undulating fin test bed are presented. The 0.5 m long fin is mounted to a cylindrical body and consists of a flexible skin attached to ribs driven by an adjustable cam mechanism and variable speed motor that enables changing the characteristics of the undulating wave(s). Forces produced were measured in a captive mode under quiescent conditions as well in the presence of an ambient current. Propulsive forces are characterized as a function of the fin width, oscillation frequency, amplitude, and wavelength. Free swimming experiments were also conducted to determine the point of self propulsion. Flow field structure visualization using dye tracers is presented for selected cases. Estimates of performance and applications for use with larger scale vehicles are discussed.

Kalumuck, Kenneth; Brandt, Alan; Armand, Mehran

2007-11-01

349

Grid Fin Stabilization of the Orion Launch Abort Vehicle  

Science.gov (United States)

Wind tunnel tests were conducted by Nielsen Engineering & Research (NEAR) and Rose Engineering & Research (REAR) in conjunction with the NASA Engineering & Safety Center (NESC) on a 6%-scale model of the Orion launch abort vehicle (LAV) configured with four grid fins mounted near the base of the vehicle. The objectives of these tests were to 1) quantify LAV stability augmentation provided by the grid fins from subsonic through supersonic Mach numbers, 2) assess the benefits of swept grid fins versus unswept grid fins on the LAV, 3) determine the effects of the LAV abort motors on grid fin aerodynamics, and 4) generate an aerodynamic database for use in the future application of grid fins to small length-to-diameter ratio vehicles similar to the LAV. The tests were conducted in NASA Ames Research Center's 11x11-foot transonic wind tunnel from Mach 0.5 through Mach 1.3 and in their 9x7-foot supersonic wind tunnel from Mach 1.6 through Mach 2.5. Force- and moment-coefficient data were collected for the complete vehicle and for each individual grid fin as a function of angle of attack and sideslip angle. Tests were conducted with both swept and unswept grid fins with the simulated abort motors (cold jets) off and on. The swept grid fins were designed with a 22.5deg aft sweep angle for both the frame and the internal lattice so that the frontal projection of the swept fins was the same as for the unswept fins. Data from these tests indicate that both unswept and swept grid fins provide significant improvements in pitch stability as compared to the baseline vehicle over the Mach number range investigated. The swept fins typically provide improved stability as compared to the unswept fins, but the performance gap diminished as Mach number was increased. The aerodynamic performance of the fins was not observed to degrade when the abort motors were turned on. Results from these tests indicate that grid fins can be a robust solution for stabilizing the Orion LAV over a wide range of operating conditions.

Pruzan, Daniel A.; Mendenhall, Michael R.; Rose, William C.; Schuster, David M.

2011-01-01

350

Optimization Of Tube Hydroforming With Consideration Of Manufacturing Effects On Structural Performance  

Science.gov (United States)

Tube bending and hydroforming processes depend on a multitude of design parameters including geometry of the part and tools, material properties and other process variables. Design by simulation has traditionally been a trial and error process, where the objective is to find a feasible and cost-effective process to manufacture a defect-free product by varying design parameters. This trial and error based design process can become extremely cumbersome as, the number of design variables and the complexity to vary them increases. Consequently, it is important to devise efficient methods that will minimize the tedious human intervention while maintaining a high level of interactivity and flexibility with regards to setting up of the optimization problem. In this study, such an interactive design tool is developed by coupling, nonlinear optimization methods with finite element analysis and morphing technology. The process setup is integrated through a unique software interface that provides complete flexibility in the choice of design variables and objective functions. The optimal design approach developed in this study is applied to improve the formability of a hydroformed part. The design parameters chosen for the study are tool fillets and the hydroforming pressure. The design space for each shape variable is setup by morphing the initial shape. Following the hydroforming optimization, the manufacturing effects (thickness and plastic strain) are transferred to a component level crash model via a mapping tool. The part's crash performance including manufacturing effects is evaluated and compared with nominal conditions.

Kirby, David; Roy, Subir; Kunju, Ravi

2005-08-01

351

Prediction of the burnout performance of some South American coals using a drop-tube furnace  

Energy Technology Data Exchange (ETDEWEB)

An experimental investigation into the combustion burnout behaviour of some South American coals was carried out in a drop-tube furnace. The samples, in two size fractions, were initially pyrolysed at a temperature of 1300{sup o}C, in a 1% of oxygen in nitrogen atmosphere for 200 ms. The re-firing of these pyrolysed chars was performed in the same apparatus, at the same temperature, during 400 ms, in an atmosphere containing 5% of oxygen in nitrogen. The coal samples used in this study were characterised by standard tests along with a specially developed image analysis technique (grey-scale histogram). Data of intrinsic reactivity, morphology, and burnout of the chars were correlated with maceral content of the feed coal by mean of linear regressions. In most cases, the results showed a poor correlation. Subsequently, when the rank of the coals was included in the regressions, the correlations remarkably improved in all cases. When further regressions of char properties with the grey-scale histogram of the coals were carried out, much better correlations were achieved. Therefore, the results indicate that the grey-scale histogram analysis provides a simple and objective technique to predict the combustion behaviour of these coals. 17 refs., 6 figs., 4 tabs.

Richelieu Barranco; Michael Cloke; Edward Lester [University of Nottingham, Nottingham (United Kingdom). Fuel Technology Centre, School of Chemical, Environmental and Mining Engineering

2003-10-01

352

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

353

Performance of the AIRS Pulse Tube Coolers and Instrument—A First Year in Space  

Science.gov (United States)

Launched on NASA's Aqua platform on May 4, 2002, JPL's Atmospheric Infrared Sounder (AIRS) instrument has completed a successful first year in space and captured a number of important lessons. AIRS is designed to make precision measurements of air temperature over the surface of the Earth and uses a redundant pair of TRW 55 K pulse tube cryocoolers to cool its sensitive IR focal plane. Soon after the instrument went cold, contamination of cryogenic surfaces led to increased cooler loads and the need for decontamination cycles. In addition, single event transients occurred while passing through the South Atlantic Anomaly (SAA) necessitating corrective actions. In November 2002 the fundamental operating strategy of the AIRS instrument was changed from the original strategy of running a single cooler and having the second cooler as a non-operating backup. Instead, based on a new system-level reliability analysis, both coolers began operation simultaneously. This change resolved the contamination and SAA driven interruptions and has enabled unprecedented levels of continuous science measurements. A review of the AIRS instrument cryogenic performance over the past year is presented including its contamination buildup and interrupt history. The reliability analysis conducted to justify two-cooler operation is also reviewed.

Ross, R. G.; Rodriguez, J. I.

2004-06-01

354

Monte Carlo study of grid performance in diagnostic radiology: factors which affect the selection of tube potential and grid ratio.  

Science.gov (United States)

A Monte Carlo computational model has been developed for the study of the performance of anti-scatter grids in diagnostic radiology. It is used here to estimate the scatter in the image plane from soft tissue phantoms (representing the patient) and to calculate image contrast and the mean absorbed dose in the phantom. Different scattering conditions, representative of various examinations, have been investigated: adult lumbar spine; small field radiography and fluoroscopy; adult chest and paediatric pelvis and chest. For each scattering condition, the combinations of tube potential and grid ratio have been found which, for a well designed grid, result in the lowest mean absorbed dose in the phantom for a fixed contrast level. In examinations which generate large amounts of scatter, the use of high grid ratios in combination with high tube potentials is favourable with regard to both mean absorbed dose in the phantom and tube charge. When less scatter is generated, either the grid ratio or the tube potential can be varied to achieve the desired contrast level. High grid ratios require shorter exposure times, but need careful alignment in the beam to prevent primary radiation cut-off. It is shown that the air gap technique can be used to reduce patient dose in examinations with small amounts of scatter, but in combinations with a lower tube potential than when a grid is used. PMID:8293262

Sandborg, M; Dance, D R; Carlsson, G A; Persliden, J

1993-12-01

355

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

356

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

357

Design Optimization of Pin Fin Geometry Using Particle Swarm Optimization Algorithm  

OpenAIRE

Particle swarm optimization (PSO) is employed to investigate the overall performance of a pin fin.The following study will examine the effect of governing parameters on overall thermal/fluid performance associated with different fin geometries, including, rectangular plate fins as well as square, circular, and elliptical pin fins. The idea of entropy generation minimization, EGM is employed to combine the effects of thermal resistance and pressure drop within the heat sink. A general dimensio...

Hamadneh, Nawaf; Khan, Waqar A.; Sathasivam, Saratha; Ong, Hong Choon

2013-01-01

358

Thermal performance of direct-flow coaxial evacuated-tube solar collectors with and without a heat shield  

International Nuclear Information System (INIS)

Graphical abstract: Collection efficiency plots and linear characterization of evacuated tube solar collector with a heat shield (ETC-HS) and evacuated tube solar collector without a heat shield (ETC-NHS). - Highlights: • Evacuated solar collector (ETC) with a heat shield had better thermal performance. • Efficiency of ETC with a heat shield is 54.70% at inlet temperature 123.9 °C. • 31.49% higher than efficiency of ETC without a heat shield at this temperature. • Heat loss coefficients of ETC with a heat shield was 1.86 W/(m2 K). • A 50.80% improvement in heat loss reduced compared to ETC without a heat shield. - Abstract: Experimental performance evaluation and comparative analyses based on heat extraction of direct-flow coaxial evacuated-tube solar collectors with and without heat shields are presented in this paper. A test system to evaluate the thermal performance of medium-temperature solar collectors was developed. The experimental analysis shows the evacuated-tube solar collector performed better with a heat shield, especially at higher working temperatures. The collection efficiency of the solar collector with a heat shield was 54.70% at the highest inlet temperature of 123.9 °C during the test period, which is 31.49% higher than for the solar collector without a heat shield. The calculated heat-loss coefficient for the evacuated-tube solar collector with a heat shield was 1.86 W/(m2 K), which is an improvement of 50.80% compared with that of the collector without a heat shield

359

Fully-Implicit Navier-Stokes (FIN-S)  

Science.gov (United States)

FIN-S is a SUPG finite element code for flow problems under active development at NASA Lyndon B. Johnson Space Center and within PECOS: a) The code is built on top of the libMesh parallel, adaptive finite element library. b) The initial implementation of the code targeted supersonic/hypersonic laminar calorically perfect gas flows & conjugate heat transfer. c) Initial extension to thermochemical nonequilibrium about 9 months ago. d) The technologies in FIN-S have been enhanced through a strongly collaborative research effort with Sandia National Labs.

Kirk, Benjamin S.

2010-01-01

360

Benchmarking the Performance of the ANSYS-FLUENT Standard k- ? Turbulence Model in Fluid Flow and Heat Transfer Predictions for Complex Flows around Circular Pin-Fins Using Various near Wall Functions  

OpenAIRE

This study compares CFD analyses of the fluid flow and heat transfer phenomena in a popular pin-fin geometry of X/D = 2.5, S/D = 2.5 and H/D = 1 for a range of Re = 5,000 to 30,000 to those from experiment to aid in the benchmarking the performance of the CFD code FLUENT. The CFD analyses use three ANSYS-FLUENT (version 13) near wall treatments available within the code: 1) the Standard Wall Function (SWF), 2) the Non-Equilibrium Wall Function (NEWF) and 3) the enhanced wall treatment. Experi...

Al-witry, A.; Es-saheb, M.

2013-01-01

361

Thermal enhancement from heat sinks by using perforated fins  

International Nuclear Information System (INIS)

Three-dimensional incompressible laminar fluid flow and heat transfer of a heated array of rectangular perforated and solid fins attached on a flat surface are studied numerically. Perforations with rectangular cross section are along the length of bluff plates and their number varies from 1 to 8. A SIMPLE code using control volume approach is developed for solving Navier-Stokes equations with conjugate energy equations for both fluid and solid regions. The second order upwind technique is used for discretization of momentum and energy equations. Computations were performed for a range of Reynolds numbers 100?ReD?350, based on fin thickness. Thermal performances and effectiveness as well as friction coefficient of perforated and solid fins are determined and compared. Higher performances for perforated fins are observed and effectiveness increased by increasing number of perforations. Higher reduction of weight of fins due to perforation is another major of utilization of the new type of fins structure. Finally a new correlation is proposed to predict perforated fin effectiveness for the range of computation carried out for the considered fins.

362

Thermal enhancement from heat sinks by using perforated fins  

Energy Technology Data Exchange (ETDEWEB)

Three-dimensional incompressible laminar fluid flow and heat transfer of a heated array of rectangular perforated and solid fins attached on a flat surface are studied numerically. Perforations with rectangular cross section are along the length of bluff plates and their number varies from 1 to 8. A SIMPLE code using control volume approach is developed for solving Navier-Stokes equations with conjugate energy equations for both fluid and solid regions. The second order upwind technique is used for discretization of momentum and energy equations. Computations were performed for a range of Reynolds numbers 100{<=}Re{sub D}{<=}350, based on fin thickness. Thermal performances and effectiveness as well as friction coefficient of perforated and solid fins are determined and compared. Higher performances for perforated fins are observed and effectiveness increased by increasing number of perforations. Higher reduction of weight of fins due to perforation is another major of utilization of the new type of fins structure. Finally a new correlation is proposed to predict perforated fin effectiveness for the range of computation carried out for the considered fins. (author)

Shaeri, M.R.; Yaghoubi, M. [Mechanical Engineering Department, School of Engineering, Shiraz University, Shiraz 71348-51154 (Iran)

2009-05-15

363

Modelisation, conception et simulation des performances d'un collecteur solaire aeraulique a tubes sous vide en milieu nordique  

Science.gov (United States)

The global energy consumption is still increasing year after year even if different initiatives are set up to decrease fossil fuel dependency. In Canada 80% of the energy is used for space heating and domestic hot water heating in residential sector. This heat could be provided by solar thermal technologies despite few difficulties originating from the cold climate. The aim of this project is to design a solar evacuated tube thermal collector using air as the working fluid. Firstly, needs and specifications of the product are established in a clear way. Then, three concepts of collector are presented. The first one relies on the standard evacuated tube. The second one uses a new technology of tubes; both sides are open. The third one uses heat pipe to extract the heat from the tubes. Based on the needs and specification as criteria, the concept involving tubes with both sides open has been selected as the best idea. In order to simulate the performances of the collector, a model of the heat exchanges in an evacuated tube was developed in 4 steps. The first step is a model in steady state intended to calculate the stagnation temperature of the tube for a fixed solar radiation, outside temperature and wind speed. As a second step, the model is generalised to transient condition in order to validate it with an experimental setup. A root mean square error of 2% is then calculated. The two remainder steps are intended to calculate the temperature of airflow leaving the tube. In the same way, a first model in steady state is developed and then generalised to the transient mode. Then, the validation with an experimental setup gave a difference of 0.2% for the root mean square error. Finally, a preindustrial prototype intended to work in open loop for preheating of fresh air is presented. During the project, explosion of the both sides open evacuated tube in overheating condition blocked the construction of a real prototype for the test. Different path for further work are also identified. One of these is in relation with CFD simulation of the uniformity of the airflow inside of the collector. Another one is the analysis of the design with a design of experiment plan.

Paradis, Pierre-Luc

364

Multiphase spiral tube as high performance mass exchanger; Das Mehrphasenwendelrohr als Hochleistungsstoffaustauscher  

Energy Technology Data Exchange (ETDEWEB)

In the heated spiral tube, the solution is concentrated into the final product. A separator connected in series with the spiral tube separates the vapours from the sump product; the vapours are condensed or fed into a column for further processing. The viscous polymer is pumped off through a wide-mouthed gear pump. the multiphase spiral tube described here is a simple, low-cost tube system which works in once-through flow and has no rotating elements. Flow instabilities are prevented by installing a single-tube unit in the critical process region. In addition, the self-cleaning effect of the single-tube unit can be utilized. (orig./GL) [Deutsch] Im beheizten Wendelrohr wird die Loesung dann bis zum Endprodukt aufkonzentriert. Der hinter das Wenderohr geschaltete Abscheider hat die Aufgabe, die Brueden vom Sumpfprodukt abzutrennen, die dann kondensiert oder zur Weiterbearbeitung in eine Kolonne eingespeist werden. Das viskose Polymer wird ueber eine breitmaulige Zahnradpumpe ausgetragen. Es handelt sich bei dem Mehrphasenwendelrohr um eine einfache preiswerte Rohrapparatur, die im Durchlauf arbeitet und keine rotierende Elemente besitzt. Da im kritischen Prozessbereich ein Einrohrapparat eingesetzt wird, treten keine Stroemungsinstabilitaeten auf. Zusaetzlich kann der Selbstreinigungseffekt des Einrohrapparats genutzt werden. (orig./GL)

Casper, C. [Bayer AG, Krefeld (Germany); Weinschenck, J. [Bayer AG, Krefeld (Germany)

1996-06-01

365

Integration of an advanced sealed-tube neutron generator into a mobile neutron radiology system and resulting performance  

Science.gov (United States)

The first DIANE ? neutron radiology system is being prepared for operation in the IABG laboratories in Ottobrunn (Germany). It utilizes a new D-T generator, designated GENIE 46, developed by SODERN (France) for this application. The generator is being integrated into an upgraded LTV-produced mobile neutron radiology system suitable for practical nonreactor inspection of components and structures. The maximum output of the present version of the GENIE 46 is 5 × 10 11 n s -1 (14 MeV) with less than 10 mA ion beam current at 225 kV. Tube lifetime at maximum output is approximately 500 h, while at 10 11 n s -1 the tube is designed for a lifetime of 1500 h. The geometry of the neutron tube, VHV connectors, ion source power supply, and cooling tubes comprises a cannister designed to be compatible with the 10-in. diameter opening in the LTV moderator/collimator assembly. 3-D Monte Carlo neutron/photon transport simulations of the new integrated radiology system operation have been performed by IABG. The calculations predict a thermal neutron flux at the collimator exit ( {L}/{D} = 13) of ?th(0 ? En ? 0.3 eV) = 1.2 × 10 5 n cm -2 s -1. Comparisons of this value and other Monte Carlo results with actual performance will be made in the near future with the accrual of operational data.

Dance, William E.; Cluzeau, Serge; Mast, Hans-Ulrich

1991-05-01

366

Study of transient behavior of finned coil heat exchangers  

Science.gov (United States)

The status of research on the transient behavior of finned coil cross-flow heat exchangers using single phase fluids is reviewed. Applications with available analytical or numerical solutions are discussed. Investigation of water-to-air type cross-flow finned tube heat exchangers is examined through the use of simplified governing equations and an up-wind finite difference scheme. The degenerate case of zero air-side capacitance rate is compared with available exact solution. Generalization of the numerical model is discussed for application to multi-row multi-circuit heat exchangers.

Rooke, S. P.; Elissa, M. G.

1993-11-01

367

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

Energy Technology Data Exchange (ETDEWEB)

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 successfully carry out RFT examination of the moisture separator and reheater tube of nuclear power plants.

Nam, Min Woo; Lee, Hee Jong [Korea Electric Power Research Institute, Daejeon (Korea, Republic of); Kim, Cheol Gi [Chungnam National University, Daejeon (Korea, Republic of)

2008-08-15

368

Performance prediction for non-adiabatic capillary tube suction line heat exchanger: an artificial neural network approach  

International Nuclear Information System (INIS)

This study presents an application of the artificial neural network (ANN) model using the back propagation (BP) learning algorithm to predict the performance (suction line outlet temperature and mass flow rate) of a non-adiabatic capillary tube suction line heat exchanger, basically used as a throttling device in small household refrigeration systems. Comparative studies were made by using an ANN model, experimental results and correlations to predict the performance. These studies showed that the proposed approach could successfully be used for performance prediction for the exchanger

369

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

370

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

371

Modelling of in-reactor creep of KOFA cladding tube and performance evaluation of KOFA fuel rod  

International Nuclear Information System (INIS)

Even if a tube is manufactured in accordance with the given specification, creep properties can vary unless all the manufacturing processes are exactly of the same from the ingot fabrication to the final heat treatment. Especially the characterization tests exibit that the thermal creep behavior of KOFA cradding tube made to the KAERI specification which from that of KWU tube but is found almost identical to W tube made to W's own specification which is quite different from the KAERI specification. As the in-reactor creep is assumed to comprise the thermal creep component and the irradiation creep component, the thermal creep model of KOFA cradding tube was developed based on the measured thermal creep data whereas the irradiation creep model of KOFA cladding tube was established based on the referenced data of irradiation creep of W tube. In order to see the effect of newly developed KOFA cladding creep on KOFA fuel performances, the clad strain and rod internal pressure under ANSI I and II operating conditions were investigated with the use of CARO D5-K in which the new KOFA cladding model has replaced the old creep model. The performance calculation displays that the higher the in-reactor creep, the earlier the fuel clad contact occurs, leading to the increased clad strain. Clad strain of a KOFA fuel rod under steady state operating condition increases by 0.46% but still fulfills the design requirement associated with 2.5% plastic strain limit. However, clad strain of a KOFA fuel rod under power transient can increase to a maximum of 0.17% and the most conservative strain exceeds the design limit of 1.0%. It was proposed that the use of Fq burndown curve to reduce the local peak power level to less than 550 W/cm at around the burnup of 19-20 MWd/KgU would result in lower clad strain than 1.0%. On the contrary, the higher clad creep is benificial from the standpoint of rod internal pressure which may be a limiting factor for the high burnup operation. The rod internal pressure was found to decrease by 3 bar. (Author)

372

A Three Dimensional Performance Analysis of a Developed Evacuated Tube Collector using a CFD Fluent Solar Load Model  

OpenAIRE

For the flow through type selected geometry of the designed evacuated tube collector ETC, a three dimensional simulation and analysis of the thermal performance was done, using the ray-tracing solar load model provided by the ANSYS-FLUENT software. In this model the solar radiation heat flux is solved using fair weather condition radiation equations, and then solar radiation load is considered as a heat source term in the energy equation. The thermal effects of the fluid flow and heat transfe...

Ali Basil. H.; Gilani S. I.; Al-Kayiem Hussain H.

2014-01-01

373

A practical plate-fin heat sink model  

International Nuclear Information System (INIS)

This study develops a practical model to predict the hydraulic and thermal performance of a plate-fin heat sink. This all-in-one asymptotic model was developed for a wide range of Reynolds numbers, including laminar, transition, and turbulent flows as Re<5000. It can predict pressure drops with an accuracy within -13.87% to 8.4%. This asymptotic model interprets the heat-transfer behavior of transition flow to within -14% to 12% of error range when Reynolds number ranges from 2000 to 4000. Furthermore, this study achieves optimization in geometry with the present model. While the pressure drop is fixed at 10 mmAq, and the fin height is fixed at 24 mm, optimal values for fin spacing, base thickness, base width, base length, and fin thickness are provided. - Research highlights: ? Friction factor. ? Plate-fin heat sink. ? Electronic cooling.

374

Adaptive vibration damping of fin structures  

Science.gov (United States)

Modern military aircraft are characterized by employment of optimized structural components. New demands on exploitation of lightweight construction technology will arise because even greater flexibility with increased maneuverability is desired. The structural integration of multifunctional, often called 'smart' elements, properly activated to e.g. reduce structural loading, offers great potential to necessary advances in military aircraft design. One major problem of modern military aircraft is the buffet loading on the fin structures. Flying the aircraft at high angles of attack allows vortices, evolving from the leading edge of the wing, to hit the fin and excite structural vibrations. This leads to structural attrition as well as a reduced aircraft maneuverability. With the aim to reduce these fin vibrations, an adaptive structure has been developed which is presented in this paper. A concept is discussed with which the vibrational loads are reduced by introduction of counteracting forces using an 'active interface'. This interface concept is characterized by the integration of active, piezoelectric elements directly into the bending support of the fin structure. To validate the stability of the interface FE calculations and extensive measurements on piezoceramic stack actuators have been performed. The manufactured interface was integrate in an existing test structure and realistically loaded. The result will be given in this presentation.

Stuwing, Michael; Sachau, Delf; Breitbach, Elmar J.

1999-07-01

375

An Experimental Modeling and Investigation of Change in Cold Mass Fraction and Nozzle Numbers on Performance of Counter Flow Vortex Tube  

Science.gov (United States)

An experimental investigation has been performed to realize thorough behavior of a vortex tube system. The vortex tube is a simple device operating as a refrigerating unit without any moving parts. It consists of a principal tube, to which a high pressure gas stream enters tangentially where it splits into two streams: one hot and one cold temperature streams. This paper discusses the experimental investigation of vortex tube performance as it relates to cold mass fraction, and nozzle number. Four different orifices, each with three, four, five and six nozzles respectively, were manufactured and used during the test. The experiments have been conducted with each one of those orifices stated above, and the performance of the vortex tube has been tested with air at inlet pressure of 5 bar and the cold mass fractions of 0.5-0.72.

Mohanty, S. S.; Ray, D. K.

2012-06-01

376

Performance of the superconducting field shielding tube for the CERN 2 meter hydrogen bubble chamber  

CERN Document Server

A superconducting shielding tube to provide a field-free bore 15 cm diameter, 230 cm long through the fringe field of the CERN 2 meter hydrogen bubble chamber has been built and successfully operated with the chamber at full field. Design and construction of the device are described and the results of field measurements in the bore during operation are presented. (3 refs).

Firth, M; Krempasky, L; Schmeissner, F

1973-01-01

377

The design and performance of self-shielded electron processors for filament, wire and tubing applications  

International Nuclear Information System (INIS)

Self-shielded electron cross-linking systems for filament, wire and tubing applications are described, in which both longitudinal and transverse presentations of the product to the unscanned electron beam are employed. Diagnostic techniques for their characterization are described along with systems to 25 kW beam power capable of processing speeds to 20 000 Mrad m/min. (orig.)

378

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

379

Enhancement of the remote field eddy current testing performed from outside of a magnetic tube  

OpenAIRE

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; Tomas Marek

2006-01-01

380

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)

381

Fin shape fluctuations in FinFET: Correlation to electrical variability and impact on 6-T SRAM noise margins  

Science.gov (United States)

Threshold voltage (VT) and drive current (ION) variability of low stand-by power (LSTP)-32 nm FinFETs subject to fin line-edge roughness (LER) is investigated through Technology Computer-Aided Design (TCAD) simulations featuring quantum-corrected hydrodynamic transport. Statistical results provided by an ensemble Monte Carlo (MC) approach highlight an increase in the average VT and a decrease in the average ION with respect to sensitivity analysis based predictions. Correlations of fin shape fluctuations to electrical performance are investigated, thus assessing further limitations of sensitivity analysis and proposing better alternatives to the expensive MC approach. An equivalent fin width is calculated, which allows reducing the spread in ION scatter plots and highlights relative importance of LER in different fin regions. Simplified device instances with linearly varying fin width are simulated to better assess the impact of local thinning/thickening in the channel, source and drain extensions. Asymmetries in the device behavior are observed upon swapping the taper direction and the critical role of extensions is identified. Moreover, the impact of LER on noise margins of FinFET-based Static Random Access Memories (SRAMs) is investigated, considering the hold, read and write operating modes. Results are compared to published data on fabricated cells with similar device features. " ?-6?" statistics extracted from 1000 mixed-mode simulations helps with assessing variability concerns for mainstream integration of aggressively scaled of FinFET-SRAMs.

Baravelli, Emanuele; De Marchi, Luca; Speciale, Nicolò

2009-12-01

382

Metal/ceramic niobium composite fin heat pipes for a low mass radiator  

International Nuclear Information System (INIS)

Niobium/alumina composite materials show promise for providing low mass fin heat pipes for space heat rejection systems. These heat pipes would be incorporated into a large radiator for waste heat rejection from a space nuclear power source. Current fabrication technology limits the heat pipes to straight lengths, although different cross-sections can be fabricated. A radiator analytical model was developed and used to examine the effects of fin pipe cross-section and fin material on radiator mass. Carbon-Carbon, Compglas, and beryllia fins were examined. The overall radiator mass was only slightly affected by the choice of material, however, the carbon-carbon design required fewer fin heat pipes. Radiators with carbon-glass composite (Compglas) fins had a slightly higher mass, but may still be attractive based on the other properties of Compglas, including resistance to atomic oxygen, and the ability to be fabricated into thin sheets. Square Nb/Alumina tubes have already been fabricated, while rectangular niobium composite tube is under development. These tubes will be bonded to carbon-carbon or Compglas fins, and fabricated into sodium heat pipes

383

Synchronized swimming: coordination of pelvic and pectoral fins during augmented punting by the freshwater stingray Potamotrygon orbignyi.  

Science.gov (United States)

Benthic animals live at the juncture of fluid and solid environments, an interface that shapes many aspects of their behavior, including their means of locomotion. Aquatic walking and similar substrate-dependent forms of underwater propulsion have evolved multiple times in benthic invertebrate and vertebrate taxa, including batoid elasmobranchs. Skates (Rajidae) use the pelvic fins to punt across the substrate, keeping the pectoral fin disc still. Other batoids combine pelvic fin motions with pectoral fin undulation in augmented punting, but the coordination of these two modes has not been described. In this study of an augmented punter, the freshwater stingray Potamotrygon orbignyi, we demonstrate the synchrony of pelvic and pectoral fin cycles. The punt begins as the pelvic fins, held in an anterior position, are planted into the substrate and used to push the body forward. Meanwhile, a wave of pectoral fin undulation begins, increasing to maximum height just before the cycle's halfway point, when the pelvic fins reach their furthest posterior extension. The pectoral fin wave subsides as the pelvic fins return to their starting position for subsequent punts. Despite definitive links between pectoral and pelvic fin activity, we find no significant relationship between pectoral fin kinematics (frequency, wave height, and wave speed) and punt performance. However, slip calculations indicate that pectoral undulation can produce thrust and augment punting. Pelvic fin kinematics (frequency and duty factor) have significant effects, suggesting that while both sets of fins contribute to thrust generation, the pelvic fins likely determine punt performance. PMID:23477972

Macesic, Laura J; Mulvaney, Dana; Blevins, Erin L

2013-06-01

384

SIMULATION OF BOILING HEAT TRANSFER AROUND MICRO PIN-FIN HEAT EXCHANGER: PROGRESS AND CHALLENGES  

International Nuclear Information System (INIS)

Boiling at microscales is a challenging problem for the computational models as well as the resources. During boiling, the formation and departure of vapor bubbles from the heated surface involves the physics from nano/micro level to the macro level. Therefore, a hierarchical methodology is needed to incorporate the nano/microscale physics with the macroscale system performance. Using micro-fabrication techniques, microstructures (micropin-fins) can be fabricated around the tubes in the heat exchanger of Pressurized Water Reactors (PWRs) to increase the heat-exchanging efficiency and reduce the overall size of the heat-exchanger for the given heat transfer rates. Combined with high fidelity simulations of the thermal transport in the entire system, optimal design of microstructure patterns and layouts can be worked out pragmatically. Properly patterned microstructures on the pipe in the steam generation zone should create more nuclei for bubble to form and result in a reduced average bubble size and shorter retention time, i.e. the time for the vapor phase sticking on the pipe surface. The smaller average steam bubble size and shorter bubble retention time will enhance the overall thermal efficiency. As a preliminary step, a periodic arrangement of micropin-fins containing four in-line cylindrical fins was modeled. The governing equations for the mass, momentum and energy transport were solved in the fluid in a conjugate heat transfer mode. In the future, several studies will be conducted to simulate different geometric arrangements, different fin cross-sections, and realistic operating conditions including phase-change with boiling by adding complexities in simple steps

385

The Aphrodite boiling crisis program. Analysis of CHF tests performed on a vertical tube  

International Nuclear Information System (INIS)

In order to develop a comprehensive modelling of the boiling crisis phenomenon, the APHRODITE experimental program has been set up at ELECTRICITE DE FRANCE. Aiming at a better mechanistic understanding of this phenomenon, this program will investigate the influence of the experimental conditions (among which the mockup geometry and the boundary conditions) and the two-phase flow patterns via void fraction distributions. It has involved the construction of a R12 test loop, which can deliver a large thermal-hydraulic parameter ranges, and the development of a gamma-ray tomograph. The first experiments have been carried out on a vertical Inconel tube, 6 meters long with a bore diameter of 13 mm and a thickness of 0.5 mm. This electrically heated test section is heavily instrumented with 168 thermocouples welded along the tube, on its outer surface. After a refined calibration of the experimental procedure, a critical heat flux data bank has been collected within large pressure, mass velocity and critical steam quality ranges. These results are firstly compared with other CHF data obtained in similar conditions. Then several empirical correlations and a theoretical model for similar prediction in tubes are tested against these data

386

Evaluation of integrally finned cladding for LMFBR fuel pins  

International Nuclear Information System (INIS)

An integral fin design effectively reduces the coolant temperature gradients within an LMFBR subassembly by redistributing coolant flow so as to reduce the maximum cladding temperature and increase the duct wall temperature. The reduced cladding temperatures are offset by strain concentrations resulting from the fin geometry, so there is little net effect on predicted fuel pin performance. The increased duct wall temperatures, however, significantly reduce the duct design lifetime so that the final conclusion is that the integral fin design is inferior to the standard wire wrap design. This result, however, is dependent upon the material correlations used. Advanced alloys with improved irradiation properties could alter this conclusion

387

Performance tests of a fast-acting valve for the driver tubes of a large blast/thermal simulator  

Science.gov (United States)

This document describes the testing of a fast-acting throat valve element designed by Eaton Consolidated Controls for use in driver tubes, (blast generators) of a Large Blast/Thermal Simulator (LB/TS). An LB/TS is used to simulate decaying blast waves such as are generated by nuclear explosions. The Eaton Throat Valve Element (ETVE) was tested at the Idaho National Engineering Laboratory (INEL) to evaluate its performance against the design criteria. The ETVE was mounted at the end of a driver tube and actuated 16 times at 6 different driver pressures ranging from 396 kPa to 12.4 MPa (57.5 psi to 1,800 psi). The valve seals survived successfully all 16 tests with the driver gas at room temperature and maintained an acceptable leak rate throughout the test program. The average valve lag time was determined to vary from 36 to 120 ms; however, the valve was found to chatter, going through several (up to 20) opening/closing cycles after actuation before settling in the open position. An increase in the pneumatic supply pressure driving the valve showed a minor decrease in the number of chattering cycles. When the valve was actuated with no pressure in the driver tube, no chattering was observed. At the conclusion of the test sequence, the valve seals were inspected and were in good condition. The shock waves appeared to agree with code predictions when the chattering effects were disregarded.

Stacey, Marcela R.

1992-05-01

388

Turbulent Flow Simulations in Complex Multilouvered Fins  

Science.gov (United States)

Air-side resistance makes up roughly 80resistance in compact heat exchangers. Multilouvered fins find widespread use in the automotive and HVAC industry for heat transfer augmentation. We will describe the computational methodology for simulating the complex three-dimensional geometry and present results at a Reynolds number of 1100 based on louver pitch and the average flow velocity. The three-dimensionality in the louver geometry occurs along the height of the fin, where the angled louver transitions to the flat landing and joins with the tube surface. The transition region is characterized by a swept leading edge and decreasing flow area between louvers. Results show the formation of spanwise vortices at the leading edge of the angled portion of the louver which convect downstream in the vicinity of the louver surface. Further there is evidence of a separate louver wake instability which interacts with the vortices shed from the leading edge. In the transition region, a high energy streamwise vortex jet is formed. The jet forms in the vicinity of the louver junction with the flat landing and is drawn under the louver in the transition region. The passage of the jet in the vicinity of the louver surface produces a high pressure stagnant zone directly under the jet with a net effect of reducing heat transfer. On the other hand, the top surface of the louver in the transition region experiences high velocities in the vicinity of the surface and exhibits much higher heat transfer coefficients than the bottom surface.

Tafti, Danesh

2000-11-01

389

Design optimization of pin fin geometry using particle swarm optimization algorithm.  

Science.gov (United States)

Particle swarm optimization (PSO) is employed to investigate the overall performance of a pin fin.The following study will examine the effect of governing parameters on overall thermal/fluid performance associated with different fin geometries, including, rectangular plate fins as well as square, circular, and elliptical pin fins. The idea of entropy generation minimization, EGM is employed to combine the effects of thermal resistance and pressure drop within the heat sink. A general dimensionless expression for the entropy generation rate is obtained by considering a control volume around the pin fin including base plate and applying the conservations equations for mass and energy with the entropy balance. Selected fin geometries are examined for the heat transfer, fluid friction, and the minimum entropy generation rate corresponding to different parameters including axis ratio, aspect ratio, and Reynolds number. The results clearly indicate that the preferred fin profile is very dependent on these parameters. PMID:23741525

Hamadneh, Nawaf; Khan, Waqar A; Sathasivam, Saratha; Ong, Hong Choon

2013-01-01

390