WorldWideScience
1

Performance of tubes-and plate fins heat exchangers  

International Nuclear Information System (INIS)

By means of a two-dimensional analysis performance, and using local heat transfer coefficients, the plate fin temperature distribution, the air bulk temperature along the stream path and the fin efficiency can be obtained, for several Reynolds numbers and fin materials. Herein are also presented the average heat transfer coefficients for isothermal plate fins, referring to heat exchangers with central-tube and rear-tube row and to two-row tubes heat exchangers configurations. It is possible to obtain the real tax or the real area of heat transfer, using the average hea transfer coefficients for isothermal plate fins and the fin efficiency. (Author)

2

Heat transfer performance of internally finned tubes in turbulent flow  

Science.gov (United States)

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

Carnavos, T. C.

1980-06-01

3

A Review: Fin and Tube Heat Exchanger Performance with different Fin Pattern  

Directory of Open Access Journals (Sweden)

Full Text Available Various methods are used to increase rate of heat transfer without affecting much the overall performance of the system. These techniques are used in heat exchangers. Heat exchangers are used in various applications in day to day life. Some of the applications of heat exchangers are-in process industries, thermal Power plants, airconditioning equipments, refrigerators, radiators for space vehicles, automobiles etc. The present paper is a review of the various methods used to increase the heat transfer performance by using different types of fins. The performance of different fin types is evaluated at different Reynolds number, fin pitch, number of tube rows etc.

S D Katkade

2014-12-01

4

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

5

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

OpenAIRE

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 an...

Kale, Sandip S.; Bhatkar, V. W.

2014-01-01

6

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

7

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

8

Comparative performance of rippled fin plate fin and tube heat exchangers  

International Nuclear Information System (INIS)

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

9

Experimental study of the air side performance of louver and wave fin-and-tube coils  

Energy Technology Data Exchange (ETDEWEB)

The present paper reports results from an investigation of the air side thermal performance of fin-and-tube coils with herringbone-wavy and convex-louver fins. The tube diameter of the tested coils was 12.7mm. Coils with different fin pitch and tube rows have been tested in order to determine their effect over the thermal performance. In addition, the performance of the convex-louver fins has been evaluated with respect to that of the wavy fins according to the Webb VG1 procedure. The collar diameter Reynolds number covered in the tests varied from 1000 to 6000, corresponding to face velocities of 1-6m/s. It has been found that the fin pitch affects lightly the heat transfer coefficient, its value being incremented of the order of 10% by reducing the fin pitch from 3.17mm to 1.81mm. Opposite trends have been found for the friction factor of wavy and louver fins regarding the effect of the fin pitch. The thermal performance is not affected by the number of tube rows in either of the fin configurations in coils for more than two rows. One and two row coils present non-negligible differences either with respect to the Colburn or friction factors. It has been found that area reductions in louver with respect to wavy fins can attain values of the order of 30% for Reynolds number of the order of 1000 and fin pitch of 3.17mm. (author)

Saiz Jabardo, J.M.; Salamanca, A. [Escuela Politecnica Superior, Universidad de la Coruna, Mendizabal s/n Esteiro, 15403 Ferrol, Coruna (Spain); Bastos Zoghbi Filho, J.R. [Departamento de Engenharia Mecanica, EESC, University of Sao Paulo, Av. Trabalhador Saocarlense 400 Centro, 13566-590 Sao Carlos, SP (Brazil)

2006-07-15

10

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

11

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

International Nuclear Information System (INIS)

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

12

An improved model for predicting performance of finned tube heat exchanger under frosting condition, with frost thickness variation along fin  

Energy Technology Data Exchange (ETDEWEB)

Frost accumulation on a heat exchanger, a direct result of combined heat and mass transfer between the moist air flowing across a cold surface, causes heat transfer performance degradation due to the insulating effect of frost layer and the coil blockage as the frost grows. The complex geometry of finned tube heat exchangers leads to uneven wall and air temperature distribution inside the coil, and causes variations of frost growth rate and densification along the coil. In this study, a general distributed model with frost formation was developed. The equations for finned tube heat exchanger were derived in non-steady-state manner and quasi-steady state in the frost model. In order to make the model more realistic, the variation of frost along fin due to uneven temperature distribution was included. The presented model is able to predict the dynamic behavior of an air cooler both under non-frost and frost condition. Comparisons were made based on the frost mass accumulation, pressure drop across coil and energy transfer coefficient, and results were found to agree well with reported experimental results. (author)

Tso, C.P. [Multimedia University, Jalan Ayer Keroh Lama, Melaka (Malaysia). Faculty of Engineering and Technology; Cheng, Y.C.; Lai, A.C.K. [Nanyang Technological University, Singapore (Singapore). School of Mechanical and Aerospace Engineering

2006-01-15

13

Enhancement of Round Tube and Flat Tube-Louver Fin Heat Exchanger Performance Using Deluge Water Cooling  

OpenAIRE

An experimental study has been conducted to evaluate the performance of a compact round-tube louver-fin condenser, each with frontal areas of 0.25 m2 in both dry and wet conditions. Deluge water cooling is achieved by incorporating a perforated bottom plate-type water distributor on top of the round tube heat exchanger. Water is used as a refrigerant, and enters the heat exchanger tubes at 35°C temperature. Ambient air and deluge cooling water are both maintained at 22°C temperature. Heat e...

Hwang, Yunho; Popli, Sahil; Radermacher, Reinhard

2012-01-01

14

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

International Nuclear Information System (INIS)

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

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

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

Directory of Open Access Journals (Sweden)

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

Du Xueping

2014-01-01

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

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

International Nuclear Information System (INIS)

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

19

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

International Nuclear Information System (INIS)

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

20

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

DEFF Research Database (Denmark)

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

Kærn, Martin Ryhl; Elmegaard, Brian

2009-01-01

21

Comparison of heat pump performance using fin-and-tube and microchannel heat exchangers under frost conditions  

International Nuclear Information System (INIS)

Vapor compression heat pumps are drawing more attention in energy saving applications. Microchannel heat exchangers can provide higher performance via less core volume and reduce system refrigerant charge, but little is known about their performance in heat pump systems under frosting conditions. In this study, the system performance of a commercial heat pump using microchannel heat exchangers as evaporator is compared with that using conventional finned-tube heat exchangers numerically and experimentally. The microchannel and finned-tube heat pump system models used for comparison of the microchannel and finned-tube evaporator performance under frosting conditions were developed, considering the effect of maldistribution on both refrigerant and air sides. The quasi-steady-state modeling results are in reasonable agreement with the test data under frost conditions. The refrigerant-side maldistribution is found remarkable impact on the microchannel heat pump system performance under the frost conditions. Parametric study on the fan speed and the fin density under frost conditions are conducted as well to figure out the best trade-off in the design of frost tolerant evaporators. (author)

22

Experimental Investigation of Gas-Side Performance of a Compact Finned-Tube Heat Exchanger  

Science.gov (United States)

Heat-transfer and pressure-drop data were obtained experimentally for the gas side of a liquid-metal to air, compact finned-tube heat exchanger. The heat exchanger was fabricated from 0.185-inch Inconel tubing in an inline array. The fins were made of 310 stainless-steel- clad copper with a total thickness of 0.010 inch, and the fin pitch was 15.3 fins per inch. The liquid used as the heating medium was sodium. The heat-exchanger inlet gas temperature was varied from 5100 to 1260 R by burning JP fuel for airflow rates of 0.4 to 10.5 pounds per second corresponding to an approximate Reynolds number range of 300 to 9000. The sodium inlet temperature was held at 1400 R with the exception of a few runs taken at 1700 and 1960 R. The maximum ratio of surface temperature to air bulk temperature was 1.45. Friction-factor data with heat transfer were best represented by a single line when the density and viscosity of Reynolds number were evaluated at the average film temperature. At the lower Reynolds numbers reported, the friction data with heat transfer plotted slightly above the friction data without heat transfer. The density of the friction factor was calculated at the average bulk temperature. Heat-transfer results of this investigation were correlated by evaluating the physical properties of air (specific heat, viscosity, and thermal conductivity) at the film temperature.

Gedeon, Louis

1959-01-01

23

Structure optimization and performance experiments of a solar-powered finned-tube adsorption refrigeration system  

International Nuclear Information System (INIS)

Highlights: • New-structure finned-tube adsorption bed for enhancing heat and mass transfer. • Temperatures on different parts of the adsorption tubes differ little. • Maximum COP of 0.122 and maximum daily ice-making of 6.5 kg are achieved by experiments. • Cooling efficiency of system with valve control higher than that without valve control. - Abstract: A large-diameter aluminum-alloy finned-tube absorbent bed collector was designed and optimized by enhancing the heat and mass transfer in the collector. The collection efficiency of the adsorbent bed collector was between 31.64% and 42.7%, and the temperature distribution in the absorbent bed was relatively uniform, beneficial to adsorption/desorption of the adsorbate in the absorbent bed. A solar-powered solid adsorption refrigeration system with the finned-tube absorbent bed collector was built. Some experiments corresponding to the adsorption/desorption process with and without a valve control were conducted in four typical weather conditions: sunny with clear sky, sunny with partly cloudy sky, cloudy sky and overcast sky. Activated carbon–methanol was utilized as the working pair for adsorption refrigeration in the experiments. The experiments achieved the maximum COP of 0.122 and the maximum daily ice-making of 6.5 kg. Under the weather conditions of sunny with clear sky, sunny with partly cloudy sky, and cloudy sky, ice-making phenomenon were observed. Even in the overcast-sky weather condition, the cooling efficiency of the system still reached 0.039 when the total solar radiation was 11.51 MJ. The cooling efficiency of the solar-powered adsorption refrigeration system with a valve control in the adsorption/desorption process was significantly higher than that without a valve control

24

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

International Nuclear Information System (INIS)

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

25

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

OpenAIRE

A tremendous quantity of water can be saved if the air cooling system is used, comparing with the ordinary water-cooling technology. In this study, two kinds of finned tube heat exchangers in an indirect air-cooling tower are experimentally studied, which are a plain finned oval-tube heat exchanger and a wavy-finned flat-tube heat exchanger in a cross flow of air. Four different air inlet angles (90°, 60 °, 45°, and 30°) are tested separately to obtain ...

Du Xueping; Yin Yantao; Zeng Min; Yu Pengqing; Wang Qiuwang; Dong Zhaoyi; Chen Yitung

2014-01-01

26

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

27

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.

28

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

International Nuclear Information System (INIS)

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

29

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

30

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

31

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

Science.gov (United States)

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

Seshimo, Yu

32

Full analysis of low finned tube heat exchangers  

International Nuclear Information System (INIS)

In this paper, first the governing parameters characterizing low-finned tubes are reviewed. Second, the more important of the available performance correlations are compared with the available experimental data. The most reliable one can be employed to develop a pressure drop relationship, which has already been used in an algorithm for exchanger sizing. Also a means for the identification of advantages of low-finned tube heat exchangers over plain tube units has been developed. It has been recognized that for low-finned tube units there are some potential benefits to place certain liquids, particularly with high viscosities, in the shell side of heat exchangers rather than the tube side. These benefits can be obtained in both reduction of surface area and the number of shells required for a given duty. They result in heat exchangers, which are more compact and are also easier to construct. The performance evaluation of low-finned units, in terms of area benefits is not discussed in this paper. However, the results of this study will complete the author's investigation for low-finned tubes heat exchangers

33

Enhance heat transfer for PCM melting in triplex tube with internal–external fins  

International Nuclear Information System (INIS)

Highlights: • Three heating methods were applied to melt the PCM in TTHX without fin. • Heat transfer enhanced by using fin to inner, middle tubes, and both tubes. • Performances of TTHX with fin were compared with finned, internally finned tube. - Abstract: Thermal energy storage is critical for eliminating the discrepancy between energy supply and demand as well as for improving the efficiency of solar energy systems. This study numerically investigates the melting process in a triplex-tube heat exchanger with phase-change material (PCM) RT82. A two-dimensional numerical model is developed using the Fluent 6.3.26 software program. Three heating methods were used to melt the PCM from the inside tube, outside tube, and both tubes. Internal, external, and internal–external fin enhancement techniques were studied to improve the heat transfer between the PCM and heat transfer fluid. Enhancement techniques were compared with the inside tube heating, outside tube heating, both tube heating as well as the finned and internally finned tube. The effects of fin length on the enhancement techniques were investigated. Using a triplex-tube heat exchanger with internal–external fins, predicted results indicated that melting time is reduced to 43.3% in the triplex tube without fins. Experiments were conducted to validate the proposed model. Simulated results correspond with the experimental results

34

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

Directory of Open Access Journals (Sweden)

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

Subodh Bahirat,

2014-08-01

35

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

International Nuclear Information System (INIS)

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

36

Finned Tube With Vortex Generators For A Heat Exchanger.  

Science.gov (United States)

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

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

2005-12-20

37

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

International Nuclear Information System (INIS)

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

38

Vibration behaviour of small-fin extended surface tubes  

International Nuclear Information System (INIS)

Tests in the air channel on small-fin extended surface tubes should lead to conclusions about vibration behaviour. During plant commissioning comparative measurements were made in the steam circuit. These showed that tubes with small fins behave similar to plain surface tubes and that design principles applicable to plain surface tubes can also be applied to finned tubes. The results of the tests in the air channels and of the measurements in the steam circuit are very compatible. (orig.)

39

Enhancenment of In-tube Condensation of Nonazeotropic Refrigerant Mixtures with a Micro-fin Tube  

Science.gov (United States)

Condensation heat transfer and pressure drop characteristics of nonazeotropic refrigerant mixtures (NARMs) of HCFC22 and CFC114 inside horizontal smooth and micro-fin tubes are experimentally investigated. The local Nusselt number for both tubes based on the temperature difference between bulk refrigerant and tube wall is compared. Data for the micro-fin tube are about 50% higher than those for the smooth tube in both cases of pure refrigerants and NARMs. In case of NARMs, however, the decrease of Nesselt number due to vapor mass transfer resistance is observed for the micro-fin tube as well as for the smooth tube. By assuming that heat transfer characteristics of the condensate of NARMs are similar to those for pure refrigerants, the vapor mass transfer coefficient of NARMs is evaluated. Comparison of frictional pressure drop for both tubes is also performed in the Lockharte-Martinelli relation. Data for the micro-fin tube are higer than those for the smooth tube. The maximum increase of the frictional pressure drop is about 30%.

Koyama, Shigeru; Gao, Lei; Hujii, Tetsu

40

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.

41

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)

42

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

43

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

44

Investigations into the dynamic behaviour of finned tube heat exchangers  

International Nuclear Information System (INIS)

Atmospheric disturbances due to thunder storms, side wind effects on the shell or ground inversion can impair the heat dissipation of a cooling tower. These effects react on the overall power plant, which is reflected in the varied electrical output. This uncontrolled behaviour has been investigated in detail for the case of a boiling water reactor nuclear power station with indirect natural draught dry cooling and compared with controlled performance. A computer model, which has been checked out by means of experimental investigations on three different types of tube, is presented to describe the dynamic behaviour of finned tube heat exchangers. (orig.)

45

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

46

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

47

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.

48

Principle of Designing Fin-and-Tube Heat Exchanger With Smaller Tube for Air Condition  

OpenAIRE

The principle of designing fin-and-tube heat exchanger with smaller tubes is proposed in this study. The principle includes designing of fin configuration and designing of refrigerant circuits. In the design principle, the suitable fin configuration for 5 mm diameter tubes is designed by Computational Fluid Dynamic-based method, and the refrigerant circuit with 5 mm diameter tubes is designed by simulation-based method. To verify the results of designing, experiments on air conditioner unit a...

Wu, Wei; Ding, Guoliang; Zheng, Yongxin; Gao, Yifeng; Song, Ji

2012-01-01

49

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)

50

Numerical study of heat transfer enhancement of finned flat tube bank fin with vortex generators mounted on both surfaces of the fin  

Energy Technology Data Exchange (ETDEWEB)

Tube bank fin heat exchanger is one of the most compact heat exchangers, and it is widely used in industry equipments. The flat tube bank fin heat exchangers with vortex generators (VGs) have significant good heat transfer performance, and are used as radiators of locomotive. Here, we study heat transfer enhancement of a new fin where VGs are mounted on both surfaces of the fin. The heat transfer performance of this pattern is evaluated by a numerical method, and the results are compared with those obtained, under identical mass flow rate, when the VGs are mounted only on one surface of the fin. The results reveal that using this new pattern the height of VGs can be reduced and still obtain satisfactory heat transfer enhancement, while the pressure drop is reduced. The results also reveal that if VGs on one surface of the fin is determined, the locations where VGs are mounted on other surface of the same fin are very important, with configurations studied in this paper, depending on the value of Reynolds number, there exists an optimum location with which best heat transfer performance can be obtained. (orig.)

Song, Ke-Wei; Wang, Liang-Bi; Fan, Ju-Fang; Zhang, Yong-Heng; Liu, Song [Lanzhou Jiaotong University, Department of Mechanical Engineering, Lanzhou, Gansu (China)

2008-06-15

51

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)

52

Performance analysis of a small regenerative gas turbine system adopting steam injection and side-wall in finned tube evaporator  

International Nuclear Information System (INIS)

Small gas turbines in power range of several MWs are quite suitable for application in distributed generation as well as Community Energy Systems (CES). Humidification is an effective way to improve gas turbine performance, and steam injection is the most general and practically feasible method. This study intended to examine the effect of steam injection on the performance of several MW class gas turbines. A primary concern is given to the regenerative cycle gas turbine. The steam injection effect on the performance of a system without the regenerator (i.e. a simple cycle) is also examined. In addition, the influence of bypass of some of the exhaust gas on the performance of the gas turbine, especially the regenerative cycle gas turbine, is evaluated.

53

Effective Heat Transfer Enhancement in Finned Tube Heat Exchanger with Different Fin Profiles  

Directory of Open Access Journals (Sweden)

Full Text Available During cross flow in a heat exchanger, heat transfer in the front portion of the tube is more compared to back portion of the tube. This is due to less formation of vortices at the backside of the tube. For uniform heat transfer to take place throughout the tube, it is necessary to increase the vortex formation at the rear side of the tube. The aim of this study is to explore the possibilities of improving the flow structure and thereby increasing uniform heat transfer around the tubes by introducing special type of fin arrangement over the tubes. The effect of shape and orientation of the fin on vortex generation and respective heat transfers are studied numerically. It have been identified that by introducing special type of fin arrangement over the tube there is a possibility for increase the vortex formation at the rear portion of the tube, which significantly leads to creation of uniform heat transfer all around the tube.

J.A.Livingston

2013-04-01

54

Heat and mass transfer studies on plate fin-and-elliptical tube type metal hydride reactors  

International Nuclear Information System (INIS)

In the present work a two-dimensional transient model to study the heat and mass transfer characteristics of plate fin-and-elliptical tube type metal hydride reactors is presented. The relevant governing equations are solved numerically. The heat transfer coefficient and pressure drop on external fin side are estimated using available correlations. Effects of external fluid flow rate and temperature on the fin-and-tube metal hydride reactor are studied. Results show that the use of elliptical metal hydride tubes in place of the standard circular tubes give rise to compact systems in addition to considerably lower fan power consumption, with very little change in the average heat and hydrogen transfer rates. Even though the performance of the reactor depends very much on the fin-and-tube arrangement, for all the arrangements considered here, the reactors with elliptical tubes were found to perform better in terms of compactness, weight and fan power consumption. Considering the aspects of mean hydride bed thickness, tube wall thickness, tube mass, compactness, heat and hydrogen transfer rates and fan power consumption, elliptical tubes of 0.6 eccentricity appear to offer the best solution for the given application.

55

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

OpenAIRE

The objective of this study was to provide experimental data that could be used to predict frost growth and frost performance of a round plate fin-tube heat exchanger for low temperature heat pumps used in zero emission vehicles under cold weather conditions. In this study, round plate fin-tube heat exchangers were tested with variation of the fin space, air flow rate, relative humidity, and inlet air temperature. Frost height was measured and considered with the boundary layer interruption b...

Dong-Yeon Lee; Moo-Yeon Lee; Yongchan Kim

2012-01-01

56

Experimental investigation of water sprayed finned heat exchanger tube bundles  

International Nuclear Information System (INIS)

Experimental investigations have been made to study the performance of two finned tube-bundle heat exchangers (FORGO type) when wetted by water sprays. The heat exchangers are designed to cool water in a dry cooling tower. The test-elements had a frontal area of 1 m2. The water sprays were created by 20 nozzles, 200 mm in front of the heat exchangers. Air velocities at the inlet of the coolers were in the range 0,8 m/s to 12 m/s and initial temperature differences ITD reached 45 degrees C. The test facility was designed to determine the combined latent and sensible heat fluxes in the wetted heat exchanger, the airside pressure drop and the air humidity and temperature at the exchanger inlet and outlet, and to measure the weight of the water wetting the cooler's surface. The sprayed test elements were investigated in different positions, but most of the experiments were carried out in the position with the fins horizontal

57

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

58

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.)

59

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

International Nuclear Information System (INIS)

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

60

Fouling of HVAC fin and tube heat exchangers  

International Nuclear Information System (INIS)

Fin and tube heat exchangers are used widely in residential, commercial and industrial HVAC applications. Invariably, indoor and outdoor air contaminants foul these heat exchangers. This fouling can cause decreased capacity and efficiency of the HVAC equipment as well as indoor air quality problems related to microbiological growth. This paper describes laboratory studies to investigate the mechanisms that cause fouling. The laboratory experiments involve subjecting a 4.7 fins/cm (12 fins/inch) fin and tube heat exchanger to an air stream that contains monodisperse particles. Air velocities ranging from 1.5-5.2 m/s (295 ft/min-1024 ft/min) and particle sizes from 1-8.6(micro)m are used. The measured fraction of particles that deposit as well as information about the location of the deposited material indicate that particles greater than about 1(micro)m contribute to fouling. These experimental results are used to validate a scaling analysis that describes the relative importance of several deposition mechanisms including impaction, Brownian diffusion, turbophoresis, thermophoresis, diffusiophoresis, and gravitational settling. The analysis is extended to apply to different fin spacings and particle sizes typical of those found in indoor air

61

Fouling of HVAC fin and tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Fin and tube heat exchangers are used widely in residential, commercial and industrial HVAC applications. Invariably, indoor and outdoor air contaminants foul these heat exchangers. This fouling can cause decreased capacity and efficiency of the HVAC equipment as well as indoor air quality problems related to microbiological growth. This paper describes laboratory studies to investigate the mechanisms that cause fouling. The laboratory experiments involve subjecting a 4.7 fins/cm (12 fins/inch) fin and tube heat exchanger to an air stream that contains monodisperse particles. Air velocities ranging from 1.5-5.2 m/s (295 ft/min-1024 ft/min) and particle sizes from 1--8.6 {micro}m are used. The measured fraction of particles that deposit as well as information about the location of the deposited material indicate that particles greater than about 1 {micro}m contribute to fouling. These experimental results are used to validate a scaling analysis that describes the relative importance of several deposition mechanisms including impaction, Brownian diffusion, turbophoresis, thermophoresis, diffusiophoresis, and gravitational settling. The analysis is extended to apply to different fin spacings and particle sizes typical of those found in indoor air.

Siegel, Jeffrey; Carey, Van P.

2001-07-01

62

Evaporation of R407C/oil mixtures inside corrugated and micro-fin tubes  

Energy Technology Data Exchange (ETDEWEB)

The paper reviews the evaporation of R407C data currently available in the literature. The experimental rig and procedure are discussed. Experimental data about the evaporation for the pure R407C and R407C/oil mixtures in two smooth tubes and two enhanced tubes are also presented. The performance benefits of the micro-fin tube and corrugated tube are quantified and discussed. During tests inlet vapour quality was set 0 and outlet quality 0.7. Mass flux density varied from about 250 to 500 kg/m{sup 2} s. The experiments have been conducted for average saturation temperature 0{sup o}C. (author)

Targanski, Waldemar; Cieslinski, Janusz T. [Faculty of Mechanical Engineering, Gdansk University of Technology, Narutowicza 11/12, 80952 Gdansk (Poland)

2007-09-15

63

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

64

Numerical Analysis of Tube-Fin Heat Exchanger using Fluent  

Directory of Open Access Journals (Sweden)

Full Text Available Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of two-row plain Tube and Fin heat exchanger using FLUENT software. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 330 to 7000. Model geometry is created and meshed by using GAMBIT software. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models k-, and SST k-omega, with steady-state solvers to calculate pressure drop, flow, and temperature fields. Model validation is carried out by comparing the simulated value friction factor f and Colburn factor j to experimental results investigate by Wang. Reasonable agreement is found between the simulations and experimental data, and the fluent software has been sufficient for simulating the flow fields in tube-fin heat exchangers.

M. V. Ghori

2012-08-01

65

Compensation of Airflow Maldistribution in Fin-and-Tube Evaporators  

OpenAIRE

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 p...

Kærn, Martin Ryhl; Tiedemann, Thomas

2012-01-01

66

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.

67

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

68

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

International Nuclear Information System (INIS)

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

69

Condensation heat transfer in horizontal elliptical tubes with internal fins  

International Nuclear Information System (INIS)

In this paper condensation heat transfer inside horizontal elliptical tubes is investigated for a stratified, concurrent two-phase flow of vapor and liquid. The analysis takes into account the effects of interfacial shear, axial pressure gradient, saturation temperature level and the development of the stratified angle associated with the accumulated condensate layer at the bottom of the tube. The governing equations are solved numerically with finite difference method. The results are presented for two cases; i.e. with and without fins. Also different values of ellipticity (b/a) are considered and discussed. At first, the results for special case of circle (b/a=1) are compared with available data in the literature that shows good agreement. Also, comparing of obtained results for different values of ellipticity shows that for ellipticity values of less than one, condensation heat transfer is greater than circular tubes; both above cases show greater transfer than those corresponding to ellipticity values bigger than one

70

The structure of heat transfer equations for bundles of staggered tubes with external annular fins, operating in cross flow  

International Nuclear Information System (INIS)

It is shown on the basis of a study of heat transfer coefficients in thirty-two bundles of staggered tubes with external annular fins, operating in cross flow, that the exponent m in the expression Nu/sub ann/ = CR/sub e//sup m/ depends significantly on the relative tube spacing and the fin geometry. The studies were performed by complete thermal simulation at Re/sub d/ between 2 x 103 and 6 x 104

71

The structure of heat transfer equations for bundles of staggered tubes with external annular fins, operating in cross flow  

Energy Technology Data Exchange (ETDEWEB)

It is shown on the basis of a study of heat transfer coefficients in thirty-two bundles of staggered tubes with external annular fins, operating in cross flow, that the exponent m in the expression Nu/sub ann/ = CR/sub e//sup m/ depends significantly on the relative tube spacing and the fin geometry. The studies were performed by complete thermal simulation at Re/sub d/ between 2 x 10/sup 3/ and 6 x 10/sup 4/.

Legkiy, V.; Pis' menny, Y.N.

1985-01-01

72

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

73

Heat transfer analysis of flat and louvered fin-and-tube heat exchangers using CFD  

OpenAIRE

This paper analyzes the fluid flow and heat exchange on the air side of a multi-row fin-and-tube heat exchanger. A comparison is given between fin-and-tube heat exchanger characteristics with flat and louvered fins in a wider range of operating conditions defined by Reynolds number (based on fin spacing and air frontal velocities). The detailed representation of calculated data for the louvered heat exchanger shows significantly better heat transfer characteristics and a ...

Carija, Z.; Frankovic, B.

2008-01-01

74

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

OpenAIRE

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...

Mun?oz Anto?n, Javier; Aba?nades Velasco, Alberto

2011-01-01

75

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

International Nuclear Information System (INIS)

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

76

An experimental study of ECT for fin-type copper alloy tubes  

International Nuclear Information System (INIS)

Eddy current detecting probes with inner and encircling coils were designed for the fin-type tubes that have uneven outer and inner surface to enhance the efficiency of heat emission. As the uneven surface of them, it is difficult to detect flaws in the tubes by eddy current test. In this paper, standard and artificial specimens with flaws for the different types of the tubes were manufactured. Eddy current test was performed with the designed probes, which have inner and encircling coils, for the prepared specimens. From the signals of the eddy current detecting probes, the phase and amplitude variation were analyzed and the best conditions of the flaw detection for the tubes were found.

77

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

International Nuclear Information System (INIS)

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

78

Steam generator tube performance  

International Nuclear Information System (INIS)

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

79

Steam generator tube performance  

International Nuclear Information System (INIS)

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

80

Air-side heat transfer characteristics of spiral-type circular fin-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study is to investigate the air-side heat transfer characteristics of spiral-type circular fin-tube heat exchangers used as evaporators in household refrigerators. The j-factors of the tested heat exchangers under non-frosting conditions were measured by varying the fin pitch, number of tube rows, and fin alignment. The j-factors of the spiral-type circular fin-tube heat exchangers were analyzed as a function of heat exchanger geometries and then compared with those of the flat plate fin-tube heat exchangers with discrete fins. Two empirical correlations of the j-factors were developed separately for the inline and the staggered fin alignment as a function of the Reynolds number, number of tube rows, and dimensionless fin pitch normalized by the hydraulic diameter. The mean deviation of the predictions using the present correlations from the measured data was 4.78% for the inline fin alignment and 6.02% for the staggered fin alignment. (author)

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

2010-03-15

81

Natural convection heat transfer in a horizontal annulus from an inner tube with two vertical fins  

International Nuclear Information System (INIS)

Natural convection heat transfer in a horizental annulus from an inner tube with two vertical fins has been studied for the effect of dimensionless fin length and Rayleigh number. The maximum local Nusselt number of inner tube was obtained at ??145deg and that of outer cylinder at ?=0deg for the case of lF=0.3. Local Nusselt Number distributions for the lower fins show higher values tham that of the upper fins. The mean Nusselt Number of inner tube was increased with the values of dimensionless fin lengths. The mean Nusselt Number can be represented in an exponential function of Grashof number at various fin lengths. As compared with experimental and numerical results, isotherms and local Nusselt Number show good agreement. (Author)

82

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-12-31

83

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

DEFF Research Database (Denmark)

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

Kærn, Martin Ryhl; Elmegaard, Brian

2009-01-01

84

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

85

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

International Nuclear Information System (INIS)

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

86

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

OpenAIRE

Numerical analyses were carried out to study the heat transfer and flow in the plate-fin and tube heat exchangers with different shaped vortex generators mounted behind the tubes. The effects of different span angles a (? = 30°, 45° and 60°) are investigated in detail for the Reynolds number ranging from 500 to 2500. Numerical simulation was performed by computational fluid dynamics of the heat transfer and fluid flow. The results indicated that the triangle shaped winglet is able to gene...

Thirumalai Kannan, K.; Senthil Kumar, B.

2012-01-01

87

Correlation equations for friction factors and convective coefficients in tubes containing bundles of internal, longitudinal fins  

Science.gov (United States)

Finned tubes are commonly employed in tubular heat exchangers to augment the heat transfer rates between two dissimilar fluid streams. The goal of this study is two-fold: a) to determine the laminar, fully developed velocity and temperature fields for long, internal, longitudinal finned tubes; and b) to construct empirical correlation equations applicable for the asymptotic friction factor and the asymptotic Nusselt numbers as a function of the number of fins and the relative fin height in the bundle. Neither the fluid dynamics nor the heat transfer literature provides information for the second goal, which can be extremely useful to thermal engineers for the implementation of Computer-Aided Design (CAD) of internal, longitudinal finned tubes in heat exchange devices. Moreover, for the validity of the correlation equations, a seldom adopted criterion for the critical Reynolds number has also been introduced as an indispensable guideline to warrant laminar regimes.

Campo, A.; Chang, J.

88

Numerical simulation of flow field in a fin tube heat exchanger  

International Nuclear Information System (INIS)

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

89

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

90

A technical note on application of internally finned tubes in solar parabolic trough absorber pipes  

OpenAIRE

The heterogeneous incoming heat flux in solar parabolic trough absorber tubes generates huge temperature difference in each pipe section. Helical internal fins can reduce this effect, homogenising the temperature profile and reducing thermal stress with the drawback of increasing pressure drop. Another effect is the decreasing of the outer surface temperature and thermal losses, improving the thermal efficiency of the collector. The application of internal finned tubes for the design of pa...

Aba?nades Velasco, Alberto; Mun?oz Anto?n, Javier

2011-01-01

91

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

International Nuclear Information System (INIS)

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

92

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

Directory of Open Access Journals (Sweden)

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

Dong-Yeon Lee

2012-09-01

93

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-10-15

94

Experimental study of flow friction characteristics of integral pin-fin tubes  

International Nuclear Information System (INIS)

Friction characteristics of integral pin-fin tubes, through which lubricating-oil flowed vertically, were studied experimentally. Effects of the pitch, the height of fins and the machining direction on friction coefficient were analyzed. The experimental results showed that the friction coefficient of the integral pin-fro tube was obviously lager than that of smooth tube. Compared with other influential factors, the effect of the height of fins was dominant. Because the three-dimensional pin fin could disturb and destroy the boundary layer, when the Reynolds Number reached 200-300, the friction coefficient curve began to bend, that was, a turning point was appeared in the friction coefficient curve. (authors)

95

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

International Nuclear Information System (INIS)

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

96

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

97

Effective Heat Transfer Enhancement in Finned Tube Heat Exchanger with Different Fin Profiles  

OpenAIRE

During cross flow in a heat exchanger, heat transfer in the front portion of the tube is more compared to back portion of the tube. This is due to less formation of vortices at the backside of the tube. For uniform heat transfer to take place throughout the tube, it is necessary to increase the vortex formation at the rear side of the tube. The aim of this study is to explore the possibilities of improving the flow structure and thereby increasing uniform heat transfer...

Livingston, J. A.; Selvakumar, P.

2013-01-01

98

Method and equipment for the non-destructive material testing of a finned tube using ultrasonic testing  

International Nuclear Information System (INIS)

A method for the non-destructive material testing of a finned tube by ultrasonic testing according to the pulse-echo method is described in which the test probe support and the tube rotate relative to one another and the echos made in the region of the fins can be distinguished from the echos in the remainder of the tube. (RW)

99

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

100

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

101

Influence of fins on tractor-type podded propulsor performance  

Science.gov (United States)

A mathematical model of podded propulsors was established in order to investigate the influence of fins. The hydrodynamic performance of podded propulsors with and without fins was calculated, with interactions between propellers and pods and fins derived by iterative calculation. The differential equation based on velocity potential was adopted and hyperboloidal panels were used to avoid gaps between surface panels. The Newton-Raphson iterative procedure was used on the trailing edge to meet the pressure Kutta condition. The velocity distribution was calculated with the Yanagizawa method to eliminate the singularity caused by use of the numerical differential. Comparisons of the performance of podded propulsors with different fins showed that the thrust of propeller in a podded propulsor with fins is greater. The resistance of the pod is also reduced because of the thrust of the fin. The hydrodynamic performance of a podded propulsor with two fins is found to be best, the performance of a podded propulsor with one fin is not as good as two fins, and the performance of the common type is the worst.

Xie, Xue-Shen; Huang, Sheng

2009-09-01

102

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

103

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

104

Heat Transfer of HC290-OIL Mixtures in a Horizontal Condensing Micro-Fin Tube  

Science.gov (United States)

Heat transfer coefficients was experimentally determined for a horizontal micro-fin tube (2m in length, 11.44mm ID) with HC290-oil mixtures. The oil is Suniso 3GS, which is a widely used oil in refrigerant systems. The micro-fin tube is a internally enhanced tube, which has 60 fins with a height of 0.25mm and 20° spiral angle. The condensation temperatures varied from 40° to 45° and the refrigerant mass flux was varied from 40kg/(m2s) to 220kg/(m2s). The results showed that the mean condensation heat transfer coefficients on the test section (inlet vapor quality 1, outlet vapor quality 0.1~0.25) decreased as the oil concentrations were increased and the condensation temperature had negligible effect on the heat transfer coefficients.

Tong, M. W.; Dong, M. L.; Li, Y.

105

Performance evaluation of plate-fin heat exchangers  

Science.gov (United States)

The performance parameters proposed by Soland et al. were used to perform a comparison of the Kays and London plate - finned surfaces for heat exchangers constructed from stainless steel, mild steel, aluminum, and cooper. Three additional comparison criteria were also investigated by modifying the proposed parameters. When using stainless steel, the louvered plate - finned surface 1/4 (b) 0 11.1, is the best, but when using mild steel, aluminum, or copper, the wavy - fin plate - finned surface 17.8 - 3/8w is the best of those considered.

Ceci, David M.

1987-06-01

106

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

Energy Technology Data Exchange (ETDEWEB)

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

Shin, Seok Won; Chung, In Kee; Kim, Soo Youn [Yeungnam University, Gyeongsan (Korea, Republic of)

2009-10-15

107

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

International Nuclear Information System (INIS)

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

108

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

109

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

Directory of Open Access Journals (Sweden)

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

K.Thirumalai kannan

2012-03-01

110

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

DEFF Research Database (Denmark)

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

Kærn, Martin Ryhl; Elmegaard, Brian

2013-01-01

111

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)

112

Influence of refrigeration oil on evaporation heat transfer characteristics of R-290 inside micro fin tube  

Energy Technology Data Exchange (ETDEWEB)

Recently, micro fin tube is widely used to heat exchanger for high performance. And, as the alternative refrigerants for R-22, hydrocarbons such as R-290, R-600 and R-600a are very promising because of their low GWP and ODP. Thus, R-290 was used as working fluid in this study. Most design of heat exchanger had been based on heat transfer characteristics of pure refrigerant although refrigerant oil exists in the refrigeration cycles. So, the influence of oil on heat transfer characteristics have to be considered for investigating exact evaporation heat transfer characteristics. But, this is an unresolved problem of refrigeration heat transfer. Therefore the influence of the refrigeration oil to the evaporation heat transfer characteristics of R-290 were conducted in a horizontal micro fin tube. The mineral oil was used as refrigeration oil. The experimental apparatus consisted of a basic refrigeration cycle and a system for oil concentration measurement. Test conditions are as the follows: evaporation temperature 5 deg.C, mass velocity 100 kg/m{sup 2}s, heat flux 10 kW/m{sup 2}, oil concentration 0, 1.3, 3.3, 5.7 wt.%, and quality 0.07 {approx} 1.0. When refrigeration oil was entered, oil foaming was observed at the low quality region. And, very small bubbles were observed as quality was increased. Pressure drop and heat transfer coefficient increased as the concentration of refrigeration oil increased to 5 wt.%.. The performance index of heat exchanger was the highest near 3.3 wt.%. (author). 7 refs., 8 figs., 1 tab.

Park, C.M; An, Y.T.; Lee, W.H. [Pukyong National University Graduate School, Pusan(Korea); Kim, J.H.; Kim, J.S. [Pukyong National University, Pusan(Korea)

2000-07-01

113

A study on the correlation between the thermal contact conductance and effective factors in fin-tube heat exchangers with 9.52 mm tube  

International Nuclear Information System (INIS)

The thermal contact resistance is a principal parameter interfering with heat transfer in a fin-tube heat exchanger. However, the thermal contact resistance in the interface between tubes and fins has not been clearly investigated. The objective of the present study is to examine the thermal contact conductance for various fin-tube heat exchangers with tube diameter of 9.52 mm and to find a correlation between the thermal contact conductance and effective factors such as expansion ratio, fin type, fin spacing and hydrophilic coating. In this study, experiments have been conducted only to measure heat transfer rate between hot and cold water. To minimize heat loss to the ambient air by the natural convection fin-tube heat exchangers have been placed in an insulated vacuum chamber. Also, a numerical scheme has been employed to calculate the thermal contact conductance with the experimental data. As a result, a new correlation including the influences of expansion ratio, slit of fin and fin coating has been introduced, and the portion of each thermal resistance has been estimated in the fin-tube heat exchangers with 9.52 mm tube

114

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

International Nuclear Information System (INIS)

Full text of publication follows: If a severe accident occurs in a nuclear power plant, then large amounts of steam and aerosols will enter to the containment, increasing the pressure and the temperature inside the containment building. To reduce these thermal and pressure loads, the next generation of European Passive Nuclear Power Plants, incorporates into the containment passive heat exchangers (HX) driven by natural circulation. These passive HX condense the steam inside the containment and transport by natural circulation the heat to a large pool with capability to act as a heat sink at least during 72 hours. These innovative passive systems consist of several units of horizontal or slightly inclined finned tubes bundles internally cooled by water. The cooling water is heated inside the tubes by the condensation heat removed from the containment and moves by natural circulation to a large pool located outside the containment. The main problem that arises in this kind of HX, is the degradation in the heat transfer produced by the non-condensable gases and the aerosols that are present in large amounts after a severe accident inside the containment. This degradation can increase the containment loads after a severe accident and we must be able to predict this effect as better as possible. This paper presents a mechanistic model to predict the steam condensation on containment finned tube heat exchangers in the presence of non-condensable gases (NC) and aerosols. Thon-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)

115

Free convection heat transfer from the outside of radial fin tubes  

Science.gov (United States)

Heat transfer rates for a variety of finned tubes in water and asphalt-water emulsion were determined experimentally. From these data, free convection heat transfer coefficients on the outside of the tube were calculated as a function of the Rayleigh number. A correlation of the form Nusselt number = a constant times the Rayleigh number to second constant power was then determined by a least-squares fit of the data.

Wiebelt, J. A.; Parker, J. D.; Henderson, J. B.

1980-06-01

116

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

117

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

Energy Technology Data Exchange (ETDEWEB)

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

Honda, Ryosuke [Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan); Umekawa, Hisashi [Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan)], E-mail: umekawa@kansai-uac.jp; Ozawa, Mamoru [Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan)

2009-06-21

118

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

International Nuclear Information System (INIS)

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

119

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

120

Evaporation heat transfer characteristics of R-290 in a micro fin tube  

Energy Technology Data Exchange (ETDEWEB)

Hydrocarbons are very suitable alternative refrigerants, because of their low GWP and ODP. These alternative refrigerants have been expected to have different heat transfer characteristics from that of HCFC-22 when the phase is changed in the evaporator. Thus, in this study, evaporation heat transfer coefficient, pressure drop and flow regimes of pure R-290(Propane) inside a micro fin tube were experimentally investigated. The length of test section was 500 mm and average diameter of a micro fin copper tube was 8.62 mm. Test conditions were as follows: saturation temperature 5 deg.C; mass velocity 100, 150 kg/m{sup 2}s; heat flux 10, 20 kW/m{sup 2}; inlet quality 0.08{approx}1.0. The observed flow regimes agreed with that of Breber's flow map. However, annular flow pattern appeared at the low quality, which was different from the flow pattern in a smooth tube. Pressure drop of R-290 was three times higher than that of R-22 at the same mass velocity and heat flux. Among the local surface temperature difference in circumferential direction of a micro fin tube, temperature difference of upper part was smallest and lower one was largest. Evaporation heat transfer coefficient of R-290 was two times higher than that of R-22 at the same mass velocity and heat flux. (author). 16 refs., 13 figs., 1 tab.

Park, C.M.; Im, Y.B.; Lee, W.H. [Pukyong National University Graduate School, Pusan (Korea); Kim, J.S. [Pukyong National University, Pusan (Korea)

1999-12-01

121

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

Science.gov (United States)

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

Taler, Dawid; Sury, Adam

2011-12-01

122

Research on the Desulfurization Gypsum of the Rotary Kiln with the Finned Tube  

OpenAIRE

The calcination technology of the desulfurization gypsum decides the product quality directly. The production process and property of the desulfurization gypsum has been described and themerits and faults of the conventional calcination technologies have been analyzed. The calcination technology of the desulfurization gypsum of the rotary kiln with the finned tube was chose for the research. The structure and workflow of the calcinatory has been analyzed, and the results showed the advantages...

Zhang, Zongyu; Xin, Zhaoxiang; Li, Jie; Zhao, Hongming

2010-01-01

123

Performance Improvement of FinFET using Nitride Spacer  

Directory of Open Access Journals (Sweden)

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

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

2013-03-01

124

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

International Nuclear Information System (INIS)

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

125

Upgrading the Performance of VLSI Circuits using FinFETs  

Directory of Open Access Journals (Sweden)

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

Tushar Surwadkar

2014-08-01

126

Linear correlation of heat transfer and friction in helically-finned tubes using five simple groups of parameters  

Energy Technology Data Exchange (ETDEWEB)

A linear regression approach was used to correlate experimentally-determined Colburn j-factors and Fanning friction factors for flow of liquid water in helically-finned tubes. Experimental data came from eight enhanced tubes with helix angles between 25 and 48 , number of fin starts between 10 and 45, fin height-to-diameter ratios between 0.0199 and 0.0327, and Reynolds numbers ranging from 12,000 to 60,000. The current study revealed that, in helically-finned tubes, logarithms of both friction and Colburn j-factors can be correlated with linear combinations of the same five simple groups of parameters and a constant. The proposed functional relationship was tested with independent experimental data yielding excellent results. (author)

Zdaniuk, Gregory J. [Ramboll Whitbybird Ltd., 60 Newman Street, London W1T 3DA (United Kingdom); Luck, Rogelio; Chamra, Louay M. [Department of Mechanical Engineering, Mississippi State University, 210 Carpenter Engineering Building, P.O. Box ME, MS 39762-5925 (United States)

2008-07-01

127

Performance Improvement of FinFET using Nitride Spacer  

OpenAIRE

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

Flavia Princess Nesamani, Geethanjali Raveendran

2013-01-01

128

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

129

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

130

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

131

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

132

Stress analysis of finned-tube water-walls of boilers  

International Nuclear Information System (INIS)

The effects of tube pressure, furnace pressure and attachment forces acting on plain walls, walls with simple attachment plates or brackets, and corners with brackets have been studied using three-dimensional photoelastic models. In all configurations the tube axes were vertical. The simple horizontal attachment plates extended from crown to crown over three pitches and were integral with the tubewall; they were loaded by horizontal forces normal or parallel to the wall. The bracket attachments consisted of two horizontal plates or ribs integral with the tubewall and extending over five pitches, with the bracket itself fitting between these ribs and joined to them along the edges; the applied loads were horizontal or vertical forces at the bracket, and furnace pressure. Detailed surface stress distributions have been determined. The critical positions were found to be in the fillets at the fin-tube and plate-tube junctions. The application of the model results to the prediction of stresses in boiler walls is discussed

133

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

OpenAIRE

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 stu...

Dhananjay Kumar*1; Prof. Alok choube2

2014-01-01

134

Development of a plate-pin fin heat sink and its performance comparisons with a plate fin heat sink  

Energy Technology Data Exchange (ETDEWEB)

Based on plate fin heat sinks (PFHSs), a new type of plate-pin fin heat sink (PPFHS) is constructed, which is composed of a PFHS and some columnar pins staggered between plate fins. Numerical simulations and some experiments were performed to compare thermal performances of these two types of heat sinks. The simulation results showed that thermal resistance of a PPFHS was about 30% lower than that of a PFHS used to construct the PPFHS under the condition of equal wind velocity. Another obvious advantage of PPFHSs is that users can change an existing unsuitable PFHS into a required PPFHS by themselves to achieve better air-cooling results. (author)

Xiaoling Yu; Jianmei Feng; Quanke Feng; Qiuwang Wang [Xi' an Jiaotong Univ. (China). School of Energy and Power Engineering

2005-02-01

135

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

Science.gov (United States)

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

Lin, Chia-Wen; Jang, Jiin-Yuh

2005-05-01

136

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

Energy Technology Data Exchange (ETDEWEB)

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

Takaishi, K.; Nasu, S.; Yamashita, S. (Kobe Steel Ltd., Shimonoseki, Yamaguchi (Japan). North Chofu Plant); Fujiwara, K.; Tsuda, K.; Tsujino, N.

1982-01-01

137

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

International Nuclear Information System (INIS)

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

138

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.

139

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

140

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

Directory of Open Access Journals (Sweden)

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 coefficient 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

1999-12-01

141

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

Scientific Electronic Library Online (English)

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

Sérgio Nascimento, Bordalo; Francisco Eduardo Mourão, Saboya.

1999-12-01

142

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

143

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

Energy Technology Data Exchange (ETDEWEB)

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. (orig.)

Zhou, Feng; Catton, Ivan [University of California, Department of Mechanical and Aerospace Engineering, Los Angeles, CA (United States)

2012-10-15

144

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

Directory of Open Access Journals (Sweden)

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

Ahmed F. Khudheyer

2011-07-01

145

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

OpenAIRE

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

Taherian, Hessam; Yazdanshenas, Eshagh

2006-01-01

146

Experimental study of convective heat transfer from a rotating finned tube in transverse air flow  

Science.gov (United States)

The convective heat transfer from fins to air has been evaluated using rotating annular fins subjected to an air flow parallel to the fins. The fin cooling is studied using infrared thermography. The thermal balance in a fin during its cooling process allows us to obtain the heat transfer coefficient from the temperature time evolution of the fin. Moreover, Particle Image Velocimetry allows us to obtain the flow field in the mid-plane between two fins. The influence of the fin spacing on the convective heat transfer is studied for various velocities of the superposed air flow and various fin rotational speeds. These tests were carried out for air flow Reynolds numbers (based on the shaft diameter and the velocity of the superposed air flow) between 2550 and 18200 and rotational Reynolds numbers (based on the shaft diameter and the peripheral speed) between 800 and 2.9×104, for different fin spacings.

Watel, B.; Harmand, S.; Desmet, B.

2000-12-01

147

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

148

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.

149

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

150

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

International Nuclear Information System (INIS)

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

151

Prediction method for condensation heat transfer coefficient of pure refrigerants in horizontal micro-fin tubes; Tan`itsu reibai suihei mizotsuki kannai gyoshuku netsudentatsuritsu no yosoku shuho  

Energy Technology Data Exchange (ETDEWEB)

The condensation heat transfer coefficients of pure refrigerants in horizontal micro-fin tubes were predicted by solving the modeled equations. In the model, film condensation on the inner fins was estimated from the total unwetted area, while the forced convection condensation heat transfer coefficient of the liquid film was set to be equal to that of the smooth tube. The predicted results showed good agreement with the experimental results, and it was shown that effects of the parameters that characterize the micro-fin tube, i. e., pipe diameter, fin height, fin pitch and fin tip angle, were well predicted. Furthermore, the high heat transfer coefficient was reproduced in the high-quality range using the present model, which assumes that the liquid phase is distributed in the valley between the grooves in this region. 10 refs., 11 figs., 1 tab.

Shikazono, N.; Ito, M.; Uchida, M.; Fukushima, T.; Hatada, T. [Hitachi, Ltd., Tokyo (Japan)

1997-07-25

152

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

153

Steam generator tubing NDE performance  

Energy Technology Data Exchange (ETDEWEB)

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.

Henry, G. [Electric Power Research Institute, Charlotte, NC (United States); Welty, C.S. Jr. [Electric Power Research Institute, Palo Alto, CA (United States)

1997-02-01

154

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

155

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

International Nuclear Information System (INIS)

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

156

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

Science.gov (United States)

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

157

Self-Heating Effects and Analog Performance Optimization of Fin-Type Field-Effect Transistors  

Science.gov (United States)

The self-heating effects (SHEs) of bulk and silicon-on-insulator (SOI) fin-type field-effect transistors (FinFETs) and their impacts on circuit performance have been investigated on the basis of a realistic thermal conductivity of silicon. The heat dissipation via interconnect wires and interface thermal resistance in the high-? gate stack were incorporated in simulations. It is shown that the depth of the shallow trench isolation (STI) of bulk FinFETs cannot be decreased to less than 100 nm owing to the increase in off-state leakage current. We observed that the thermal resistance Rth of SOI FinFETs greatly decreases upon thinning the buried oxide (BOX) layer. When the BOX thickness tBOX is less than 50 nm, the Rth of SOI FinFETs is smaller than that of bulk FinFETs with an STI thickness of 100 nm, indicating a lower operation temperature of the thin-BOX SOI FinFETs than that of bulk FinFETs. The lower operation temperature of the 5-nm BOX SOI FinFET was confirmed under a practical bias condition for analog operations. In fin width, Wfin, versus Rth characteristics, a strong Wfin dependence of Rth was observed only in the bulk FinFETs, implying that fluctuations in Wfin result in the variability of the operation temperature of the bulk FinFETs. Analog performance has been analyzed by calculating the cutoff frequency fT and the maximum oscillation frequency fmax. We demonstrated that both fT and fmax can be maximized in SOI FinFETs by optimizing tBOX with regard to electrical and thermal properties. Better analog performance, and hence the optimization of tBOX, are indispensable for the device design of a FinFET-based system-on-a-chip (SoC) platform.

Takahashi, Tsunaki; Beppu, Nobuyasu; Chen, Kunro; Oda, Shunri; Uchida, Ken

2013-04-01

158

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

International Nuclear Information System (INIS)

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

159

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

OpenAIRE

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 optim...

Nirmal, D.; Vijaya Kumar, P.

2011-01-01

160

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

161

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

162

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

Scientific Electronic Library Online (English)

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

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

163

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

Science.gov (United States)

Work to determine experimentally the performance and operating characteristics of a plate-fin heat exchanger during dry/wet of deluge operation is discussed, as well as the development of the deluge heat/mass transfer model. The work supports the improvement of power plant cooling systems that conserve fresh water in an environmentally and economically viable manner. The experiments identified important trade-offs concerning deluge cooling; these are discussed. The earlier deluge model was refined and extended to the simultaneous calculation of heat transfer and evaporation from wetted surfaces. Experiments showed the model to be an excellent predictor of heat exchanger performance during deluge operation.

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

1982-04-01

164

A High Efficiency, Miniaturized Ka Band Traveling Wave Tube Based on a Novel Finned Ladder RF Circuit Design  

Science.gov (United States)

Space communications architectures are being planned to meet the high rate data distribution requirements of future NASA Enterprise missions. These will require the use of traveling wave tube amplifiers (TWTAs) to provide the high frequency, RF (radio frequency) power and efficiency needed for many of the communications links. A program addressing these requirements is currently underway at NASA Glenn Research Center (GRC) for the development of a high efficiency, 20 watt, 32 GHz TWT of reduced size and weight that is based on a novel high gain n circuit design, termed the 'finned ladder'.

Wintucky, E. G.; Wilson, J. D.; Vaden, K. R.; Force, D. A.; Freeman, J. C.; Lesny, G. G.; Kory, C. L.; Chevalier, C. T.; Ebihara, B.; Dayton, J. A.; Williams, W. D. (Technical Monitor)

2001-01-01

165

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

Science.gov (United States)

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

Xu, Bin; Shi, Yumei; Chen, Dongsheng

2014-03-01

166

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

OpenAIRE

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 coefficient 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 f...

Sérgio Nascimento Bordalo; Francisco Eduardo Mourão Saboya

1999-01-01

167

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

168

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

International Nuclear Information System (INIS)

The air-side particulate fouling in the heat exchangers of HVAC applications degrades the performance of cooling capacity, pressure drop across a heat exchanger, and indoor air quality. Indoor and outdoor air contaminants foul heat exchangers. The purpose of this study is to investigate the fouling characteristics trough accelerated tests. The fouling characteristics are analyzed as functions of a dust concentration (1.28 and 3.84 g/m3), a face velocity (0.5, 1.0, and 1.5 m/s), and a surface condition. The cooling capacity in the slitted finned-tube heat exchangers at the face velocity of 1 m/s decreases about 2% and the pressure drop increases up to 57%. The rate of build-up of fouling is observed to be 3 times slower for this three-fold reduction of dust concentration whilst still approaching the same asymptotic level

169

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

170

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

International Nuclear Information System (INIS)

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

171

Performance and cost benefits analysis of double-pass solar collector with and without fins  

International Nuclear Information System (INIS)

Highlights: • The thermal performances and cost analysis of the double-pass solar collector with and without fins absorber were discussed. • The theoretical and experimental study on the double-pass solar air collector with and without fins absorber was conducted. • The ratio of AC/AEG or the cost benefit ratio was presented. • The double-pass solar collector with fins absorber is more cost-effective compared to without fins absorber. - Abstract: The performance and cost benefit analysis of double-pass solar collector with and without fins have been conducted. The theoretical model using steady state analysis has been developed and compared with the experimental results. The performance curves of the double-pass solar collector with and without fins, which included the effects of mass flow rate and solar intensity on the thermal efficiency of the solar collector, were obtained. Results indicated that the thermal efficiency is proportional to the solar intensity at a specific mass flow rate. The thermal efficiency increased by 9% at a solar intensity of 425–790 W/m2 and mass flow rate of 0.09 kg/s. The theoretical and experimental analysis showed a similar trend as well as close agreement. Moreover, a cost-effectiveness model has been developed examine the cost benefit ratio of double-pass solar collector with and without fins. Evaluation of the annual cost (AC) and the annual energy gain (AEG) of the collector were also performed. The results show that the double-pass solar collector with fins is more cost-effective compared to the double-pass solar collector without fins for mass flow rate of 0.01–0.07 kg/s. Also, simulations were obtained for the double-pass solar collector with fins at Nusselt number of 5.42–36.21. The energy efficiency of collector increases with the increase of Nusselt number. The results show that by increasing the Nusselt number simultaneously would drop the outlet temperature at any solar intensity. Increase in Nusselt number causes an increase in energy efficiency. On the other hand, the exergy efficiency has been obtained, which the fluctuation of exergy efficiency was based on the Nusselt number, collector length and solar intensity level

172

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

173

Numerical analysis of the flow and heat transfer characteristics for forced convection-radiation in entrance region of an internally finned tubes  

International Nuclear Information System (INIS)

The flow and heat transfer characteristics of combined forced convection and radiation in the entrance region of internally finned tubes are investigated numerically in this paper. The uniform flow is considered for an inlet flow condition. A three dimensional parabolic problem is solved by a marching-type procedure envolving a series of two dimensional elliptic problems in the cross-stream plane. The SIMPLER-algorithm and Raithby's pressure-velocity coupling method are employed to analyze the flow and heat transfer characteristics. For the calculation of radiative heat transfer, the P1-approximation and the Weighted Sum of Gray Gases Method (WSGGM) are used. The effects of fin height, number of fins, optical thickness, reference temperature, and Planck number on the flow and heat transfer characteristics are examined. It was found that the effect of fin-height on the heat transfer characteristic is more dominant than that of number of fins. The present results show that the optimal non-dimensional fin height and number of fins are 0.4 and 16, respectively

174

MODERN MANUFACTURING TECHNIQUES OF PRECISED MISSILE REAR FIN ASSEMBLY  

Directory of Open Access Journals (Sweden)

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

Md Akhtar khan

2013-11-01

175

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

Science.gov (United States)

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

Baldwin, Stephen

176

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

177

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

178

Performance of photomultiplier tubes for cryogenic applications  

International Nuclear Information System (INIS)

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

179

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

180

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

Directory of Open Access Journals (Sweden)

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

Foued Chabane

2013-01-01

181

Verification of the performance of impact limiting fins for transportation containers  

International Nuclear Information System (INIS)

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

182

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

International Nuclear Information System (INIS)

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

183

Influence of bending mode shape and trailing edge deflection on propulsive performance of flexible heaving fins using digital image correlation  

Science.gov (United States)

The propulsive performance of flexible flapping fins greatly depends on the stiffness of the fins along with the oscillating parameters. The bending mode shape and trailing edge deflection of the oscillating fins play a major role in the generation of thrust and efficiency. This paper examines the deformation pattern of heaving flexible foils and its dependency on propulsive performance. Experimental investigation has been carried out on fins of various lengths oscillating at their leading edge. A LaVision 2D/3D StrainMaster Digital Image Correlation (DIC) system was used to measure the deformation of the fins. It is observed that the propulsive performance can be maximized by operating at frequencies close to resonance. Trailing edge amplitude and deformation pattern together play an important role in achieving high propulsive performance even when the oscillation frequency is not close to resonant frequency.

Kancharala, Ashok K.; Dewillie, Kevin; Philen, Michael K.

2014-03-01

184

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

185

Optimization of Surface Orientation for High-Performance, Low-Power and Robust FinFET SRAM  

OpenAIRE

We analyze the impact of surface orientation on stability and performance of FinFET SRAMs. We show that devices with proper orientations can improve static noise margin (SNM, 23-35%) and access time (22-33%) of 32nm FinFET SRAM compared to a design with devices of single (110) orientation.

Gangwal, Saakshi; Mukhopadhyay, Saibal; Roy, Kaushik

2006-01-01

186

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

International Nuclear Information System (INIS)

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

187

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.

188

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-12-15

189

Evaluation of Heat Transfer and Pressure Loss Performances of Louvered Fins by Modified Single-blow Method  

Science.gov (United States)

The modified single-blow transient testing technique was applied to evaluate heat transfer and pressure loss performances of actual louvered fin heat exchanger cores. A systematic measurement was conducted for the louvered fin surfaces varying transverse fin pitch in order to investigate the effect of the channel cross section shape as well as the Reynolds number, Re. In this study, the ratio of louver pitch and hydraulic diameter, l/dh, was used as a parameter to represent the channel cross section shape. Empirical equations were obtained for heat transfer and pressure loss performances in terms of Gz, Pr and l/dh.

Yagi, Yoshinao; Mochizuki, Sadanari

190

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

Science.gov (United States)

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

Lingham-Soliar, Theagarten

2005-05-01

191

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

Science.gov (United States)

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

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

2014-09-01

192

Performance demonstration requirements for eddy current steam generator tube inspection  

International Nuclear Information System (INIS)

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

193

Steam generator tube performance in Ontario Hydro CANDU PHWRS  

International Nuclear Information System (INIS)

The performance of steam generator tubing in Ontario Hydro reactors has been excellent with only a few failures after more than 110 reactor years of operation. Specifics of steam generator performance are discussed by examining operating history, results from in-situ inspections, and examinations of removed tubes. Reasons for the observed performance are discussed. Ontario Hydro operates by 16 CANDU (Canadian Deuterium Uranium) pressurized heavy water reactors (PHWRs) which provide a net capacity of 10 550 MWe

194

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

195

Low-temperature performance of accumulation-mode p-channel wrap-gated FinFETs.  

Science.gov (United States)

In this work, accumulation-mode (AM) p-channel wrap-gated FinFETs and AM p-channel planar FETs are fabricated using top-down strategies, and compared in performance at temperatures from 6 K to 295 K. The threshold voltage variation of the AM wrap-gated FinFET is slightly larger than that of the AM planar FET. The drain current and the peak transconductance in the AM wrap-gated FinFET are larger than those in the AM planar FET, and those differences are temperature dependent. We attribute those to the body current enhancement in the AM wrap-gated FinFET as temperature increases. The subthreshold swings (SS) of both types of the FETs improve with temperature decreasing and get lower than 10 mV/dec at 6 K. The higher SS in the AM wrap-gated FinFET is likely due to a high interface state density at the fin sidewalls arising from the fin patterning induced defects. PMID:23646519

Zhang, Yanbo; Du, Yandong; Chen, Yankun; Lil, Xiaoming; Yang, Xiang; Han, Weihua; Yang, Fuhua

2013-02-01

196

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

International Nuclear Information System (INIS)

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

197

Windsurfer Fin  

Science.gov (United States)

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

1994-01-01

198

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

199

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

International Nuclear Information System (INIS)

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

200

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

OpenAIRE

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 ...

Beigh, M. R.; Mustafa, M.; Bhat, Tawseef A.

2013-01-01

201

Global Analysis and Structural Performance of the Tubed Mega Frame  

OpenAIRE

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

Zhang, Han

2014-01-01

202

Performance evaluation of a wavy-fin heat sink for power electronics  

Energy Technology Data Exchange (ETDEWEB)

The almost daily increase in dissipated power per unit area of electronic components sets higher and higher demands on the performance of the heat sinks. These must not only be able to dissipate high heat fluxes, but must also keep costs to a minimum and exhibit a reliable behaviour. In this paper a novel, modular heat sink consisting of elements with wavy fin profile which can be pressed together to construct the component is presented. Its performance under steady-state conditions are assessed for the case of forced convection in terms of velocity distribution in the channels and global thermal resistance. Configurations with uniform and non-uniform heat flux are studied and some considerations are made as to the influence of the spacers between fan and heat sink proper.

Lorenzini, Marco [Dipartimento di Ingegneria Energetica, Nucleare e del Controllo Ambientale, DIENCA, via Terracini 34, I-40136 Bologna (Italy)]. E-mail: marco.lorenzini@unibo.it; Fabbri, Giampietro [Dipartimento di Ingegneria Energetica, Nucleare e del Controllo Ambientale, DIENCA, viale Risorgimento 2, I-40131 Bologna (Italy); Salvigni, Sandro [Dipartimento di Ingegneria Energetica, Nucleare e del Controllo Ambientale, DIENCA, viale Risorgimento 2, I-40131 Bologna (Italy)

2007-04-15

203

Performance evaluation of a wavy-fin heat sink for power electronics  

International Nuclear Information System (INIS)

The almost daily increase in dissipated power per unit area of electronic components sets higher and higher demands on the performance of the heat sinks. These must not only be able to dissipate high heat fluxes, but must also keep costs to a minimum and exhibit a reliable behaviour. In this paper a novel, modular heat sink consisting of elements with wavy fin profile which can be pressed together to construct the component is presented. Its performance under steady-state conditions are assessed for the case of forced convection in terms of velocity distribution in the channels and global thermal resistance. Configurations with uniform and non-uniform heat flux are studied and some considerations are made as to the influence of the spacers between fan and heat sink proper

204

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

205

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

206

(1 1 0) and (1 0 0) Sidewall-oriented FinFETs: A performance and reliability investigation  

Science.gov (United States)

The performance and reliability of (1 0 0) and (1 1 0) sidewall, silicon-on-insulator (SOI) FinFETs with a Hf-based gate dielectric were evaluated. Unlike the typical planar MOSFET mobility orientation dependence, (1 1 0) FinFET sidewalls do not impair electron mobility and result in good short channel performance compared to (1 0 0) FinFET sidewall devices. Hot carrier injection (HCI) degradation was also investigated with nMOS and pMOS high-? FinFETs on both sidewall surface orientations. Impact ionization at the source, as well as at the traditional drain side, was found to enhance HCI degradation when gate voltage (Vg) = drain voltage (Vd). The degradation becomes more pronounced as the gate length decreases, with a negligible dependence on substrate orientation. However, the orientation dependence of negative bias temperature instability (NBTI) on FinFETs demonstrates that the (1 1 0) orientation is slightly worse than (1 0 0). The kinetics of ?NIT(t) under negative bias stress conditions suggests the interface trap density (NIT) is generated by a mechanism similar to that in planar devices.

Young, C. D.; Akarvardar, K.; Baykan, M. O.; Matthews, K.; Ok, I.; Ngai, T.; Ang, K.-W.; Pater, J.; Smith, C. E.; Hussain, M. M.; Majhi, P.; Hobbs, C.

2012-12-01

207

Factors affecting cathode ray tube display performance.  

Science.gov (United States)

Monitors are a complex combination of analog circuits that perform absolutely amazing feats of current and voltage control at both low and high frequency. Digital circuits can reduce the complexity of interfacing with the adjustments and even be used to build complex waveforms, but they cannot replace the point at which pure power is required. Five main topic areas are covered, each building on the other in how they relate to display performance. They are glass composition, resolution and addressability, phosphor selection and aging characteristics, light output and uniformity, and the tools available to assess display performance. PMID:11440259

Compton, K

2001-06-01

208

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

International Nuclear Information System (INIS)

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

209

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

International Nuclear Information System (INIS)

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

210

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.)

211

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

OpenAIRE

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 f...

Marek Rejman; Wojciech Wiesner; Piotr Silakiewicz; Andrzej Klarowicz; Arturo Abraldes, J.

2012-01-01

212

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.

213

Performance enhancement by an innovative tube cleaning application  

International Nuclear Information System (INIS)

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

214

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

Scientific Electronic Library Online (English)

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

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

2012-12-01

215

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

216

Performance of storage walls with highly conductive covering plates and connecting fins  

Science.gov (United States)

The thermal behavior of a storage wall, constructed of concrete with highly conductive covering plates and connecting vertical fins, is investigated. The results demonstrate that, during the charging mode, the amount of energy released from the front surface is significantly reduced. A portion of the saved energy is stored for future discharge, but a large portion is transferred to the back surface and released. A selective front surface further reduces the energy released from the front surface, and this energy is stored. By properly selecting the fin spacing, plate-fin thickness, and plate-fin thermal conductivity, the rate and direction of thermal discharge can be controlled. The improved heat transfer capability and added thermal control provide new alternatives for interzonal heat transfer and multizone passive building designs.

Ortega, J. K. E.; Bingham, C. E.; Connolly, J. M.

1980-07-01

217

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

218

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

Science.gov (United States)

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

Müller-Menzel, T.; Hecht, T.

219

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)

220

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

Science.gov (United States)

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.

Alfegi, Ebrahim M. A.; Abosbaia, Alhadi A. S.; Mezughi, Khaled M. A.; Sopian, Kamaruzzaman

2013-06-01

221

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.

222

Comprehensive methodology for finned air-cooled condensers and spray cooling  

OpenAIRE

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

Lee, Hyoungsoon

2011-01-01

223

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

224

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

225

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

226

Thermal/hydraulic design and performance of an LMFBR double wall tube seven tube steam generator model  

International Nuclear Information System (INIS)

This paper describes the thermal/hydraulic design and performance of a full-length LMFBR steam generator. This seven-tube model (the few tube model-FTM), uses straight, prestressed double wall tubes with third fluid leak detection capabilities. This paper describes the FTM design and instrumentation, the test facility including digital data acquisition system, and a comparison between pretest predictions and actual experimental thermal/hydraulic performance results for 100 percent load. 7 refs

227

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)

228

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

229

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

230

Performance analysis of double basin solar still with evacuated tubes  

International Nuclear Information System (INIS)

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

231

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

232

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

233

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

Scientific Electronic Library Online (English)

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

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

2012-03-01

234

Comparison of Temporal Parameters of Swimming Rescue Elements When Performed Using Dolphin and Flutter Kick with Fins - Didactical Approach  

Science.gov (United States)

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. Key points The source of reduction of swimming rescue time was researched. Time required to approach and to tow the victim while doing the flutter kick and the dolphin-kick with fins was analyzed. The propulsion generated by dolphin-kick did not make the approach and tow faster than the flutter kick. More difficult skill to realize of dolphin-kick than the flutter-kick was postulated. The criteria for how improve dolphin kick technique with fins were formulated. PMID:24150079

Rejman, Marek; Wiesner, Wojciech; Silakiewicz, Piotr; Klarowicz, Andrzej; Abraldes, J. Arturo

2012-01-01

235

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

236

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

237

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.

238

Development and performance of a double diaphragm shock tube  

International Nuclear Information System (INIS)

After recalling the techniques used to produce intense shocks in gases, the double diaphragm shock tube (T.C.D.2), studied and developed at the Vaujours Research Center, is presented. The theoretical and experimental performances were compared, argon being used as the test gas. In this way, it was shown that shock waves having velocities as high as 15 km/s could be produced. Various diagnostic techniques were employed to measure the velocity of the wave front and its attenuation, as well as the thickness of the gas heated by the shock (expressed generally by the test time, ?, at a given point). An estimation of the temperature and electron number density of the plasma behind the shock was effected spectroscopically. The experimental results obtained confirm theoretical predictions. It is shown that the velocity gain of T.C.D.2 over a simple shock tube may be as high as 60 per cent. (author)

239

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

240

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

241

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

242

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

243

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

244

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

Directory of Open Access Journals (Sweden)

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

Tiago Barcelos Pereira Salgado

2012-12-01

245

Differential methods for the performance prediction of multistream plate-fin heat exchangers  

Science.gov (United States)

Use of traditional methods of rating can prove inaccurate or inadequate for many plate-fin heat exchanger applications. The superiority in practical situations of differential methods, based on dividing the heat exchanger into several sections and a step-wise integration of the heat transfer and pressure loss functions, is discussed. Differential methods are developed for counterflow, crossflow, and cross-counterflow heat exchangers. The methods developed also avoid iterations at the section level calculations. Design of computer algorithms based on these methods is outlined. Two computer programs developed using the methods are presented and the results for a few typical cases are discussed.

Prasad, B. S. V.; Gurukul, S. M. K. A.

1992-02-01

246

Heat transfer performance test of a prototype plate-fin condenser - boiler for industrial usage  

Science.gov (United States)

A 1 metre long prototype plate-fin condenser-boiler section was constructed with two boiling channels on either side of a central condensing channel. Liquid nitrogen is evaporated inside the boiling channel at atmospheric pressure while the condensing nitrogen at a higher pressure returns to a reboiler and evaporates again in the reboiler due to electric heating. At heat fluxes less than 6000 w/m 2 the total temperature difference for boiling and condensing heat transfer is less 1.1 K, decreased by 0.3-0.8 K in comparison with the practical operating condenser-boiler.

Yuyuan, Wu; Yongzhong, Liu; Liufang, Chen; Yanzhong, Li; Hongqi, Xie

247

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

DEFF Research Database (Denmark)

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

Svendsen, Jon Christian; Banet, Amanda I.

2013-01-01

248

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

249

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.

250

Analytic method for thermal performance and optimization of an absorber plate fin having variable thermal conductivity and overall loss coefficient  

Energy Technology Data Exchange (ETDEWEB)

The absorber of a collector receives solar energy which is delivered to the transport medium to be carried away as useful energy. During this process, temperature of the absorber plate increases and therefore, thermophysical parameters engaged to determine the thermal performance of an absorber plate varies with temperature of the plate. The present study demonstrates analytically to determine the performance of an absorber plate fin with temperature dependent both thermal conductivity and overall heat loss coefficient. The decomposition method is proposed for the solution methodology. An optimum design analysis has also been carried out. A comparative study has been executed among the present results and that of existed in the published work, and a notable difference in results has been found. Finally, unlike published work, dependency parameters on the performances and optimum design have been highlighted. (author)

Kundu, B. [Department of Mechanical Engineering, Jadavpur University, Kolkata 700 032 (India); School of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Sungdong-gu, Seoul 133-791 (Korea)

2010-07-15

251

The heat transfer performance of horizontal tube bundles in large falling film evaporators  

Energy Technology Data Exchange (ETDEWEB)

The performance of the horizontal heat transfer tube bundles in falling film evaporators in large compression refrigeration systems was investigated with numerical simulation in this paper. Four types of tubes, including plain tubes, and enhanced surface tubes of Turbo-B, Turbo-BII and Turbo-EHP, were employed in the simulation. Some factors, such as tube kind, tube pass arrangement, dry patch area on tube surface, liquid refrigerant flow rate, and number of flooded tubes, were analyzed based on simulated results. In the study, the maldistribution of liquid refrigerant flow caused by the distributor apparatus was discussed, which severely affects the performance of falling film evaporators according to the simulation. Some calculated results were verified by the experiment. These discussions and results can be used to guide the design of falling film evaporators under realistic flow conditions. (author)

Yang, Li; Wang, Wen [Institute of Refrigeration and Cryogenics, Shanghai Jiao tong University, 800 Dongchuan Road, Shanghai 200240 (China)

2011-01-15

252

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

International Nuclear Information System (INIS)

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

253

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

Energy Technology Data Exchange (ETDEWEB)

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

Karabacak, Rasim [Department of Mechanical Engineering, Pamukkale University, 20070 Kinikli, Denizli (Turkey); Yakar, Guelay, E-mail: gyakar@pau.edu.tr [Department of Mechanical Engineering, Pamukkale University, 20070 Kinikli, Denizli (Turkey)

2011-08-15

254

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

OpenAIRE

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

Rakesh Vaid; Meenakshi Chandel

2012-01-01

255

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

256

New ferritic stainless steel tube for heat exchangers  

International Nuclear Information System (INIS)

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

257

Bonded molar tubes: a retrospective evaluation of clinical performance.  

Science.gov (United States)

This study investigated time to first failure of stainless steel orthodontic first permanent molar tubes (Ormco Corp) bonded with a light-cured resin adhesive (Transbond) and assessed whether this was related to patient gender, age of the patient at the start of treatment, the presenting malocclusion, or the operator. All first molar tubes were bonded to intact buccal enamel, free of any restoration. Survival analysis was carried out on data from 483 patients with 1190 bonded first molar tubes. For each case, a single molar tube, either that which was first to fail or had the shortest follow-up time, was chosen for analysis. The median time until first bonded tube failure was 699 days with an overall failure rate of 21% recorded. There was no significant difference in time to first failure of molar tubes with respect to patient gender or presenting malocclusion but significant differences were recorded with respect to the patients' age at the start of treatment and the operator. Age at the start of treatment and operator were identified as independently useful predictors of bonded molar tube survival. PMID:10358250

Millett, D T; Hallgren, A; Fornell, A C; Robertson, M

1999-06-01

258

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 ( T Fin/ W Fin) 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 I on/ I off 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.

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

2012-08-01

259

Performance characteristics of an electromagnetic streamer tube calorimeter  

International Nuclear Information System (INIS)

We have tested an electromagnetic streamer tube calorimeter in an electron beam in the energy range 1-70 GeV. Also the dependence of the response and energy resolution on the particle rate and magnetic field were investigated. A magnetic field transverse to the streamer tubes has no effect, while a field parallel to the wires deteriorates the energy resolution. (orig.) With 14 figs

260

Heat exchanger with transpired, highly porous fins  

Science.gov (United States)

The heat exchanger includes a fin and tube assembly with increased heat transfer surface area positioned within a hollow chamber of a housing to provide effective heat transfer between a gas flowing within the hollow chamber and a fluid flowing in the fin and tube assembly. A fan is included to force a gas, such as air, to flow through the hollow chamber and through the fin and tube assembly. The fin and tube assembly comprises fluid conduits to direct the fluid through the heat exchanger, to prevent mixing with the gas, and to provide a heat transfer surface or pathway between the fluid and the gas. A heat transfer element is provided in the fin and tube assembly to provide extended heat transfer surfaces for the fluid conduits. The heat transfer element is corrugated to form fins between alternating ridges and grooves that define flow channels for directing the gas flow. The fins are fabricated from a thin, heat conductive material containing numerous orifices or pores for transpiring the gas out of the flow channel. The grooves are closed or only partially open so that all or substantially all of the gas is transpired through the fins so that heat is exchanged on the front and back surfaces of the fins and also within the interior of the orifices, thereby significantly increasing the available the heat transfer surface of the heat exchanger. The transpired fins also increase heat transfer effectiveness of the heat exchanger by increasing the heat transfer coefficient by disrupting boundary layer development on the fins and by establishing other beneficial gas flow patterns, all at desirable pressure drops.

Kutscher, Charles F. (Golden, CO); Gawlik, Keith (Boulder, CO)

2002-01-01

261

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.)

262

Performance and stability testing of a low circulation ratio LMFBR double-wall tube evaporator  

International Nuclear Information System (INIS)

This paper describes the performance of a full-length, seven tube LMFBR Evaporator that was designed, built, and tested by Westinghouse as part of a DOE contract to develop a steam generator for a large scale LMFBR plant. This Few Tube Model (FTM) has straight, prestressed, double-walled tubes with third fluid leak detection. The tubes have a 0.436 inch (1.11 cm) inside diameter, a 0.812 inch (2.07 cm) outside diameter, a 68.25 foot (20.8 m) under sodium tube length, and a 77.1 foot (23.5 m) total tube length. The evaporator model was tested under low circulation ratio (CR = 1.1) at six different operating conditions ranging from 40 percent load to near full power. This paper describes the design, the thermal/hydraulic performance, and the dynamic stability of the test model when operated under evaporator conditions of the DOE Large Development Plant

263

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

264

FinFET Doping; Material Science, Metrology, and Process Modeling Studies for Optimized Device Performance  

International Nuclear Information System (INIS)

In this review paper the challenges that face doping optimization in 3-dimensional (3D) thin-body silicon devices will be discussed, within the context of material science studies, metrology methodologies, process modeling insight, ultimately leading to optimized device performance. The focus will be on ion implantation at the method to introduce the dopants to the target material.

265

Assessment of beam tube performance for the MAPLE research reactor  

International Nuclear Information System (INIS)

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

266

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

267

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

268

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

269

Improving the RF Performance of Carbon Nano tube Field Effect Transistor  

International Nuclear Information System (INIS)

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

270

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

International Nuclear Information System (INIS)

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

271

The effect of tube arrangement on a flat plate solar water heater performance  

Energy Technology Data Exchange (ETDEWEB)

Indonesia has abundant solar energy and plans to use it as an alternative energy source to heat up fluids. The sun's electromagnetic energy can be converted to thermal energy in solar collectors. Flat plate collectors are commonly used for water heating, room heating and some drying processes. A tube in a flat plate solar collector circulates water from a tank. The solar collector then heats the water. The tube can be either below, between or above the flate absorber plate. The tube arrangement may result in different heat transfer modes and heat losses from the collector. As such, the arrangement may influence the performance of a flat plate solar water heater, notably the temperature difference of the water flowing at the inlet and outlet of the collector and its flow rate. The affect of tube arrangement on heat transfer was the focus of this study. Three models were developed to represent the 3 tube arrangements. Experiments were conducted from January to February 2008 in Surabaya, Indonesia. The experiments showed that the placement of tubes below the flat plate was suitable for cloudy and windy circumstances while the placement of tubes above the flat plate was suitable for locations that are sunny with still air. The best performance was achieved with tubes placed between the flat plates. This latter arrangement resulted in the hottest water temperature in the storage tank and the highest temperature difference of water flowing in and out of the collector. 5 refs., 1 tab., 6 figs.

Handoyo, E.A.; Kristianto, A. [Petra Christian Univ., Surabaya (Indonesia). Dept. of Mechanical Engineering

2009-07-01

272

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

273

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

274

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

275

Improving on-product performance at litho using integrated diffraction-based metrology and computationally designed device-like targets fit for advanced technologies (incl. FinFET)  

Science.gov (United States)

In order to meet current and future node overlay, CD and focus requirements, metrology and process control performance need to be continuously improved. In addition, more complex lithography techniques, such as double patterning, advanced device designs, such as FinFET, as well as advanced materials like hardmasks, pose new challenges for metrology and process control. In this publication several systematic steps are taken to face these challenges.

Chen, Kai-Hsiung; Huang, GT; Chen, KS; Hsieh, C. W.; Chen, YC; Ke, CM; Gau, TS; Ku, YC; Bhattacharyya, Kaustuve; Huang, Jacky; den Boef, Arie; v. d. Schaar, Maurits; Maassen, Martijn; Plug, Reinder; Zhang, Youping; Meyer, Steffen; van Veen, Martijn; de Ruiter, Chris; Wu, Jon; Xu, Hua; Chow, Tatung; Chen, Charlie; Verhoeven, Eric; Li, Pu; Hinnen, Paul; Storms, Greet; Pao, Kelvin; Zhang, Gary; Fouquet, Christophe; Mori, Takuya

2014-04-01

276

Eddy current testing performed on steam generator tubes  

International Nuclear Information System (INIS)

In the Beznau nuclear power plants the eddy current method for early detection of defective steam generator tubing. Thanks to extensive measurement campaigns, we are able to return to what is likely to be the largest data base for measured values in a single plant. Through the comparison of such measured values carried out in 1982, we have come to doubt the information value of the testing method. Concerning in particular the qualification of the method for certain types of defects as well as exactitude of measurement and reproducibility, reservations were made. We have agreed with the Swiss Security Authorities to outline and carry out a measurement programme on test pipes in order to define the problems under consideration. Our main objective will be to examine to what extent precisely defined defect geometries and test values can influence test results. Phase 1 of the series of tests is due to be concluded by the end of 1983. (orig./RW)

277

The Voith Turbo Fin (VTF) A New System To Improve The Performance Of Escort Tractor Voith Tugs  

Science.gov (United States)

The geometry of the skeg in the Escort Tractor Voith tugs is the result of a series of intense investigations in the forms of the tug and its fins, oriented to get a significant improvement in the forces on the towing line when the indirect method is used in the escort towing. For that, and with the aim of getting the best behaviour of this fin, a variety of options have been investigated for years, evaluating its merits in terms of lift force and complexity to reach the present designs, which are adapted to the functions which the tug is destined to carry out. With the object of optimizing the lift force in the skeg when the indirect method is used in the escort towing, and after long investigations, the Voith Turbo Marine has incorporated a rotating cylinder at the leading edge to its design in escort towing for the first time at the beginning of 2005. The leading edge is the part over which the water flow first falls upon in normal escort operation conditions, calling this new development Voith Turbo Fin (VTF) to the system as a whole (skeg and rotating cylinder). This fin is analyzed in this article especially with regard to its basis, ways of operation and efficiency of the novel joining rotating cylinder.

Iglesias Baniela, Santiago; García Melón, Enrique

278

Performance Of Window Air Conditioner Using Alternative Refrigerants With Different Configurations Of Capillary Tube  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this study is to present test results on the basis of experimental data of capillary tubes for R-22 and its alternative R-410A (R-32/125, 50/50 wt.%.Three capillary tubes with different length (500mm, 900mm, and 1500 mm and inner diameter (1.3mm, 1.4mm, and 1.6mm respectively were selected as test sections. Compressor work, heat rejected in the condenser, coefficient of performance (COP and mass flow rate through capillary tubes were calculated for several ambient temperature. Compressor work, heat rejected in the condenser, coefficient of performance (COP and mass flow rate of R-410A were compared with R-22 for the same test conditions. The results of single capillary tubes were also compared with the results of combination of two capillary tubes. The air-conditioner was 1 TR unit designed for R-22 and R410A. The performance of the air-conditioner with R-410A was compared with the baseline performance of the air-conditioner with R-22.The experiment result shows that (1 the coefficient of performance (COP for R-410A is lowers than R-22. And the mass flow rate, heat rejected in the condenser and compressor work done for R-410A are higher than R-22 for all capillary tubes. (2For this experiment the combination of two capillary tubes with inner diameter of 1.4mm and length 900 mm has higher coefficient of performance (COP than single capillary tubes with inner diameter of 1.3 mm, 1.6 mm and length 500 mm, 1500 mm respectively.(3 The coefficient of performance (COP of capillary tube with inner diameter of 1.6 mm and length 1500 mm is higher than the capillary tube with inner diameter of 1.3 mm and length 500 mm.(4 For R-22, the coefficient of performance (COP of combination of two capillary tubes with inner diameter of 1.4mm and length 900 mm is 17.10 % higher than the straight capillary tube with inner diameter of 1.3 mm and length 500 mm. And 13.07 % higher than the straight capillary tube with inner diameter of 1.6 mm and length 1500 mm at 40ºC ambient temperature. (5And for R- 410A, the coefficient of performance (COP of combination of two capillary tubes with inner diameter of 1.4mm and length 900 mm is 13.00 % higher than the straight capillary tube with inner diameter of 1.3 mm and length 500 mm. And 11.15% higher than the straight capillary tube with inner diameter of 1.6 mm and length1500 mm at 40ºC ambient temperature.

Richa Soni*1

2014-06-01

279

Convective boiling performance of refrigerant R-134a in herringbone and microfin copper tubes  

Energy Technology Data Exchange (ETDEWEB)

This paper reports an experimental investigation of convective boiling heat transfer and pressure drop of refrigerant R-134a in smooth, standard microfin and herringbone copper tubes of 9.52mm external diameter. Tests have been conducted under the following conditions: inlet saturation temperature of 5{sup o}C, qualities from 5 to 90%, mass velocity from 100 to 500kgs{sup -1}m{sup -2}, and a heat flux of 5kWm{sup -2}. Experimental results indicate that the herringbone tube has a distinct heat transfer performance over the mass velocity range considered in the present study. Thermal performance of the herringbone tube has been found better than that of the standard microfin in the high range of mass velocities, and worst for the smallest mass velocity (G=100kgs{sup -1}m{sup -2}) at qualities higher than 50%. The herringbone tube pressure drop is higher than that of the standard microfin tube over the whole range of mass velocities and qualities. The enhancement parameter is higher than one for both tubes for mass velocities lower than 200kgs{sup -1}m{sup -2}. Values lower than one have been obtained for both tubes in the mass velocity upper range as a result of a significant pressure drop increment not followed by a correspondent increment in the heat transfer coefficient. (author)

Bandarra Filho, Enio P. [Faculdade de Engenharia Mecanica, Universidade Federal de Uberlandia, Av. Joao Naves de Avila, 2160 Bloco 1M, Santa Monica, Uberlandia, MG (Brazil); Saiz Jabardo, Jose M. [Escuela Politecnica Superior, Universidad de la Coruna, Calle Mendizabal s/n, 15403 Ferrol, Espana (Spain)

2006-01-01

280

The pulse tube engine: A numerical and experimental approach on its design, performance, and operating conditions  

International Nuclear Information System (INIS)

The pulse tube engine is a simple heat engine based on the pulse tube process. Due to its simplicity it has a high potential to be applicable in waste heat usage and energy harvesting purposes. In this work, mathematical and experimental design tools are developed to study a pressurized laboratory scale pulse tube engine. The mathematical model is based on the transient numerical solution of the governing differential equations for mass, momentum and energy. The Modelica environment of SimulationX is used to solve the equations numerically and the model is employed to design the experimental test engine with helium as working fluid. The transient behavior of the pulse tube engine's underlying thermodynamic properties is studied numerically and experimentally under different design parameters as well as for different heat input temperatures, filling pressures and operating frequencies. The measured engine characteristics are compared with the calculated predictions. Internal and external power losses are quantified. Design studies for a further development of the pulse tube engine are performed experimentally. The developed numerical tool provides a rational framework for up-scaling the current laboratory model to industrial scale. - Highlights: • We developed a mathematical model and an experimental test engine to study the pulse tube engine. • The experimental test engine is able to operate with pressurized helium of up to 12 bar filling pressure. • We characterized and compared the engine's behavior under different design features and operating conditions. • Design studies for a further development of the pulse tube engine are performed experimentally

281

Design and performance of a rapid piston expansion tube for the investigation of droplet condensation  

Energy Technology Data Exchange (ETDEWEB)

A piston expansion tube (pex-tube) is described which has been developed for the investigation of homogeneous nucleation in a supersaturated vapor and subsequent droplet growth. The design of the tube with periphery is discussed as well as the underlying gasdynamics. Examples for the measurement of nucleation and growth rates in a binary mixture of n-propanol/water carried in nitrogen demonstrate performance and range. The focus of the paper is on the determination of the nucleation state. It is shown that this state may not be based on an adiabatic expansion when helium is used as carrier gas instead of argon or nitrogen. (orig.) With 11 figs., 17 refs.

Peters, F.; Rodemann, T. [Essen Univ. (Gesamthochschule) (Germany). Lehrstuhl fuer Stroemungslehre

1998-04-01

282

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

International Nuclear Information System (INIS)

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

283

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

284

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

International Nuclear Information System (INIS)

The performance of steam generator tubes in water-cooled nuclear power reactors has been reviewed for 1977. Failures were reported in 34 of the 79 reactors surveyed. Causes of these failures and inspection and repair procedures designed to deal with them are presented. Although corrosion remained the leading cause of tube failures, specific mechanisms have been identified and methods of dealing with them developed. These methods are being applied and should lead to a reduction of corrosion failures in future. (author)

285

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

286

Performance test of inservice inspection equipment for HTTR intermediate heat exchanger tubes  

International Nuclear Information System (INIS)

Experimental study was carried out to clarify the performance of eddy current testing probes and a probe inserting equipment for the inservice inspection of the intermediate heat exchanger tubes of the high-temperature engineering test reactor. The inspection performance of the probes were investigated using test tubes, made of Hastelloy XR and containing artificial discontinuities made with reference to the ASME standards of steam generator tubes in a light-water reactor. It was confirmed that the probe could detect the discontinuities of the ASME standards and the smaller ones, such as a 100% through-wall hole with 0.5-mm diameter and a groove with 0.5-mm width, in the base metal tube. For the tube support and the welded joint, the multi-frequency method could remove the noise. The inspection performance, however, lowered. The probe inserting equipment was manufactured by way of trial. It could be settled stably in the hot header of a mock-up model, and could smoothly insert and extract the probe. The winding of a cable cause the scattering of the probe traveling velocity and the measurement error of the probe location in the tube. (author)

287

Development of Performance Demonstration Programs for Steam Generator Tubing Analysts in Korea  

International Nuclear Information System (INIS)

Korea Electric Power Research Institute developed the performance demonstration programs for non-destructive examination personnel who analyze eddy current data for steam generator tubes of the nuclear power plant. The purpose of these programs is to ensure a continuing uniform knowledge base and skill level for data analysts and contribute to safely operate the nuclear power plant. In Korea, there have been many changes for the non-destructive examination of steam generator tubing in the nuclear power plant such as inspection scope, plugging criteria and qualification requirements. According to the Notice 2004-13 revised by the Ministry of Science and Technology in Korea, the analysts for steam generator tubing shall be qualified as the Qualified Data Analyst, and the Site Specific Performance Demonstration program shall be implemented for them. KEPRI developed these performance demonstration programs and they are being successfully implemented. The analyst performance is expected to be improved by the implementation of theses programs. (authors)

288

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

289

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-09-15

290

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

Science.gov (United States)

A comprehensive understanding of the control of flexible fins is fundamental to engineering underwater vehicles that perform like fish, since it is the fins that produce forces which control the fish's motion. However, little is known about the fin's sensory system or about how fish use sensory information to modulate the fin and to control propulsive forces. As part of a research program that involves neuromechanical and behavioral studies of the sunfish pectoral fin, a biorobotic model of the pectoral fin and of the fin's sensorimotor system was developed and used to investigate relationships between sensory information, fin ray motions and propulsive forces. This robotic fin is able to generate the motions and forces of the biological fin during steady swimming and turn maneuvers, and is instrumented with a relatively small set of sensors that represent the biological lateral line and receptors hypothesized to exist intrinsic to the pectoral fin. Results support the idea that fin ray curvature, and the pressure in the flow along the wall that represents the fish body, capture time-varying characteristics of the magnitude and direction of the force created throughout a fin beat. However, none of the sensor modalities alone are sufficient to predict the propulsive force. Knowledge of the time-varying force vector with sufficient detail for the closed-loop control of fin ray motion will result from the integration of characteristics of many sensor modalities. PMID:20729572

Phelan, Chris; Tangorra, James; Lauder, George; Hale, Melina

2010-09-01

291

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

Directory of Open Access Journals (Sweden)

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

Rakesh Vaid

2012-10-01

292

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

293

Single endoscopist-performed percutaneous endoscopic gastrostomy tube placement  

OpenAIRE

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 met...

Askin Erdogan

2013-01-01

294

Study of the sealing performance of tubing adapters in gas-tight deep-sea water sampler  

Science.gov (United States)

Tubing adapter is a key connection device in Gas-Tight Deep-Sea Water Sampler (GTWS). The sealing performance of the tubing adapter directly affects the GTWS's overall gas tightness. Tubing adapters with good sealing performance can ensure the transmission of seawater samples without gas leakage and can be repeatedly used. However, the sealing performance of tubing adapters made of different materials was not studied sufficiently. With the research discussed in this paper, the materials match schemes of the tubing adapters were proposed. With non-linear finite element contact analysis and sea trials in the South China Sea, it is expected that the recommended materials match schemes not only meet the requirements of tubing adapters' sealing performance but also provide the feasible options for the following research on tubing adapters in GTWS

Huang, Haocai; Yuan, Zhouli; Kang, Wuchen; Xue, Zhao; Chen, Xihao; Yang, Canjun; Ye, Yanying; Leng, Jianxing

2014-09-01

295

Thermal performance characteristics of STC [solar tube collector] system with phase change storage  

Energy Technology Data Exchange (ETDEWEB)

Storing solar heat using Phase Change Materials (PCM) is an effective method. The combination of solar collector and PCM in one unit is studied. The performance characteristics of the proposed Solar Tube Collector (STC) are analysed analytically and experimentally. Experiments were performed to simulate a direct contact solar storage system, using two vertical cylindrical concentric tubes with the annular space between them fill with Stearic acid (C[sub 18] H[sub 38] O[sub 2], melting temperature 70[sup o]C). (Author)

Al-Jandal, S.S.; Sayigh, A.A.M. (Reading Univ. (United Kingdom))

1994-08-01

296

Energy-efficient flat-tube heat exchangers for indirectly cooled display cabinets  

Energy Technology Data Exchange (ETDEWEB)

Different designs of flat-tube heat exchangers with plain fins have been evaluated theoretically in a parameter study in order to evaluate their performance potential in indirectly cooled display cabinets. Two different types of flat-tube heat exchangers were considered; one with serpentine fins and one with continuous plate fins. Both flat-tube heat exchanger types were adapted to the laminar flow regime on the liquid as well as on the air side. The performance of the two heat exchanger types had previously been verified experimentally under dehumidifying conditions. The results from this parameter study show that considerable savings in the required electric drive power to compressors, pumps and fans can be obtained in comparison with the traditional cooling coil. The savings may be up to 15%. In addition, the required temperature difference for the flat-tube heat exchangers is so small that frost-free operation is possible, which would result in even larger savings. (author)

Stignor, Caroline Haglund [SP Technical Research Institute of Sweden, Energy Technology, P.O. Box 857, SE-501 15 Boraas (Sweden); Sunden, Bengt [Lund University, Faculty of Engineering, Division of Heat Transfer, P.O. Box 118, SE-221 00 Lund (Sweden); Fahlen, Per [Chalmers University of Technology, Building Services Engineering, SE-412 96 Gothenburg (Sweden)

2009-09-15

297

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

298

Performance demonstration tests for eddy current inspection of steam generator tubing  

International Nuclear Information System (INIS)

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

299

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

300

Vertical-tube aqueous LiBr falling film absorption using advanced surfaces  

Energy Technology Data Exchange (ETDEWEB)

A heat and mass transfer test stand was fabricated and used to investigate nonisothermal falling film absorption of water vapor into a solution of aqueous lithium bromide. The absorber was made of borosilicate glass for visual inspection of the failing film. Experiments were conducted on internally cooled tubes of about 0.019 m outside diameter and of 1.53 m length. Testing evaluated a single absorber tube`s performance at varying operating conditions, namely different cooling-water flow rates, solution flow rates, pressures, temperatures, and concentrations. Advanced surfaces were identified that enhanced absorber load and the mass of absorbed vapor. A pin-fin tube with 6.4mm pitch absorbed about 225% more mass than did a smooth tube. A grooved tube was the d best performer with 175% enhancement over the smooth tube. Increasing the cooling water flow rate to 1.893 {times} 10{sup {minus}4} m{sup 3}/s caused about a 300% increase in the mass absorbed for the grooved tube compared with the smooth tube. Results showed that the pin-fin tube with 6.4-mm pitch and the grooved tubes may enhance absorption to levels comparable to chemical enhancement in horizontal smooth tube absorbers. Absorber load, the transport coefficients, and pertinent absorption data are presented as functions of dimensionless numbers. These experimental data will prove useful in formulating analytical tools to predict vertical-tube absorber performance.

Miller, W.A. [Oak Ridge National Lab., TN (United States); Perez-Blanco, H. [Pennsylvania State Univ., University Park, PA (United States)

1993-10-01

301

Effect of inundation for condensation of steam on smooth and enhanced condenser tubes  

Energy Technology Data Exchange (ETDEWEB)

The paper presents new measurements on the effect of inundation during condensation of steam in tubes banks. Most of the data relate to wire-wrapped enhanced tubes but measurements are also reported for low-finned and smooth tubes. The technique of artificial inundation has been used where liquid is supplied above a single horizontal test condenser tube to simulate condensate draining from higher tubes. Inundation rates have been used to simulate a column of up to almost 30 tubes. The surface temperature of the condenser tube was measured at four locations around the tube using buried thermocouples. The heat transfer and hence condensation rate was determined from the mass flow rate and temperature rise from coolant. The temperature and flow rate of the simulated inundation was carefully controlled. All tests were carried out at atmospheric pressure with constant vapour downflow approach velocity and constant coolant flow rate. For the given coolant and vapour flow rates and temperatures (same for all tests), and in the absence of inundation, the vapour-side heat-transfer coefficient for the finned tube was around four times that of the smooth tube while the heat-transfer coefficient for the wire-wrapped tubes was independent of winding pitch and around 30% higher than for the smooth tube. For inundation conditions the smooth tube data are in line with the widely used Kern equation relating the heat-transfer coefficient to the depth of a tube in the bank. The heat-transfer coefficient for the finned tube was virtually unaffected by inundation up to the maximum used which was equivalent to a depth of about 20 finned tubes in a bank. At this depth level the heat-transfer coefficient for the finned tube was around six times that of the smooth tube. For the wire-wrapped tubes the deterioration in performance with increasing inundation was least for the smallest winding pitch used for which the heat-transfer coefficient fell by around 9% at an equivalent depth in a bank of 25 tubes. At this depth level the heat-transfer coefficient for the wire-wrapped tube was almost twice that of the smooth tube. (author)

Murase, T.; Wang, H.S.; Rose, J.W. [Department of Engineering, Queen Mary, University of London, London E1 4NS (United Kingdom)

2006-08-15

302

Effect of Image Intensifier Tube Equivalent Background Illumination on Range Performance of Passive Night Sight  

OpenAIRE

Effect of increase in equivalent background illumination (EBI) with temperature of second generation (18 mm) proximity focused image intensifier tube on the range performance of a passive night sight has been studied using the image intensifier minimum resolvable contrast model. It has been shown that for ambient temperatures of 40 oC and above, the range performance of sight goes down drastically under low-illumination level due to increase in the EBI. Deterioration in range performance is n...

Musla, A. K.; Jaiswal, A. K.

2007-01-01

303

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

International Nuclear Information System (INIS)

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

304

Enhanced Thomson TSN 506 Electronic Camera Performance Through New Image Converter Tubes  

Science.gov (United States)

The general characteristics of an electronic camera used in the analysis of high speed photonic phenomena and consequently those of an automatic image acquisition and processing system built around these cameras can be divided into two categories : - The first covers the characteristics specific to the image converter tube used, such as the size and spectral response of the photocathode, its spatial and temporal resolutions, dynamic geometric distorsion, cut-off ratio, etc. - The second are those related to the performance of the electronic control circuits : . sweep ramp linearity, . triggering delay and jitter, . sweep times, . transients that occur while the tube's internal voltages are established during aperture control, etc. The major criteria for evaluating a tube with respect to dynamic operation, which by itself is of interest to the user, will be presented during a brief review of theory. The effect on the quality of the image obtained in terms of the duration and number of Nyquist points in the time analysis window, the resulting Bandwith, spatial resolution and cross-talk will also be shown. These criteria can also be used to determine the improvements in the performance of the TSN 506 camera and the NORMA system obtained by using RTC P 510 and ITT F 4157 image converter tubes. We shall conclude with a brief review of tubes currently being developed, their proven and expected characteristics and their impact on the development of electronic cameras and automatic photon measuring systems.

Hammer, E.; Imhoff, C.

1989-02-01

305

Development of a theoretical model for predicting the thermal performance characteristics of a vertical pin-fin array heat sink under combined forced and natural convection with impinging flow  

Energy Technology Data Exchange (ETDEWEB)

A comprehensive theoretical and experimental study was carried out on the thermal performance of a pin-fin heat sink. A theoretical model was formulated that has the capability of predicting the influence of various geometrical, thermal, and flow parameters on the effective thermal resistance of the heat sink. An experimental technique was developed for measuring the thermal performance of the heat sink, and the overall convective heat transfer coefficient for the fin bundle. Experiments were carried out, and correlations obtained, for a wide range of parameters for pure natural convection and for combined forced and natural convection. The predictive capability of the theoretical model was verified by comparison with experimental data including the influence of various fin parameters and the existence of an optimum fin spacing. (Author)

Kobus, C.J.; Oshio, T. [Oakland Univ., School of Engineering and Computer Science, Rochester, MI (United States)

2005-03-01

306

Performance of a large limited streamer tube cell in drift mode  

International Nuclear Information System (INIS)

The performance of a large (3x3 cm2) streamer tube cell in drift mode is shown. The detector space resolution has been studied using cosmic muons crossing a high precision silicon telescope. The experimental results are compared with a GARFIELD simulation

307

Performance of a large limited streamer tube cell in drift mode  

CERN Document Server

The performance of a large (3x3 $cm^2$) streamer tube cell in drift mode is shown. The detector space resolution has been studied using cosmic muons crossing an high precision silicon telescope. The experimental results are compared with a GARFIELD simulation.

Battistoni, G; Campagnolo, R; Meroni, C; Scapparone, E

2002-01-01

308

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

309

Fundamental study on high performance heat transfer tube for intermediate heat exchanger of HTGR  

International Nuclear Information System (INIS)

In this research on the IHX for the HTGR, the heat tubes having the combined effects of extended surface and turbulence promoter were tested and it was suggested the possibility of the reduction of the cost in the IHX by achieving the higher performance on IHX

310

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

Science.gov (United States)

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.

ATLAS TRT Collaboration; Abat, E.; Addy, T. N.; Åkesson, T. P. A.; Alison, J.; Anghinolfi, F.; Arik, E.; Arik, M.; Atoian, G.; Auerbach, B.; Baker, O. K.; Banas, E.; Baron, S.; Bault, C.; Becerici, N.; Beddall, A.; Beddall, A. J.; Bendotti, J.; Benjamin, D. P.; Bertelsen, H.; Bingul, A.; Blampey, H.; Bocci, A.; Bochenek, M.; Bondarenko, V. G.; Bychkov, V.; Callahan, J.; Capeáns Garrido, M.; Cardiel Sas, L.; Catinaccio, A.; Cetin, S. A.; Chandler, T.; Chritin, R.; Cwetanski, P.; Dam, M.; Danielsson, H.; Danilevich, E.; David, E.; Degenhardt, J.; Di Girolamo, B.; Dittus, F.; Dixon, N.; Dogan, O. B.; Dolgoshein, B. A.; Dressnandt, N.; Driouchi, C.; Ebenstein, W. L.; Eerola, P.; Egede, U.; Egorov, K.; Evans, H.; Farthouat, P.; Fedin, O. L.; Fowler, A. J.; Fratina, S.; Froidevaux, D.; Fry, A.; Gagnon, P.; Gavrilenko, I. L.; Gay, C.; Ghodbane, N.; Godlewski, J.; Goulette, M.; Gousakov, I.; Grigalashvili, N.; Grishkevich, Y.; Grognuz, J.; Hajduk, Z.; Hance, M.; Hansen, F.; Hansen, J. B.; Hansen, P. H.; Hare, G. A.; Harvey, A., Jr.; Hauviller, C.; High, A.; Hulsbergen, W.; Huta, W.; Issakov, V.; Istin, S.; Jain, V.; Jarlskog, G.; Jeanty, L.; Kantserov, V. A.; Kaplan, B.; Kapliy, A. S.; Katounine, S.; Kayumov, F.; Keener, P. T.; Kekelidze, G. D.; Khabarova, E.; Khristachev, A.; Kisielewski, B.; Kittelmann, T. H.; Kline, C.; Klinkby, E. B.; Klopov, N. V.; Ko, B. R.; Koffas, T.; Kondratieva, N. V.; Konovalov, S. P.; Koperny, S.; Korsmo, H.; Kovalenko, S.; Kowalski, T. Z.; Krüger, K.; Kramarenko, V.; Kudin, L. G.; LeBihan, A.-C.; LeGeyt, B. C.; Levterov, K.; Lichard, P.; Lindahl, A.; Lisan, V.; Lobastov, S.; Loginov, A.; Loh, C. W.; Lokwitz, S.; Long, M. C.; Lucas, S.; Lucotte, A.; Luehring, F.; Lundberg, B.; Mackeprang, R.; Maleev, V. P.; Manara, A.; Mandl, M.; Martin, A. J.; Martin, F. F.; Mashinistov, R.; Mayers, G. M.; McFarlane, K. W.; Mialkovski, V.; Mills, B. M.; Mindur, B.; Mitsou, V. A.; Mjörnmark, J. U.; Morozov, S. V.; Morris, E.; Mouraviev, S. V.; Muir, A. M.; Munar, A.; Nadtochi, A. V.; Nesterov, S. Y.; Newcomer, F. M.; Nikitin, N.; Novgorodova, O.; Novodvorski, E. G.; Ogren, H.; Oh, S. H.; Oleshko, S. B.; Olivito, D.; Olszowska, J.; Ostrowicz, W.; Passmore, M. S.; Patrichev, S.; Penwell, J.; Perez-Gomez, F.; Peshekhonov, V. D.; Petersen, T. C.; Petti, R.; Placci, A.; Poblaguev, A.; Pons, X.; Price, M. J.; hne, O. Rø; Reece, R. D.; Reilly, M. B.; Rembser, C.; Romaniouk, A.; Rousseau, D.; Rust, D.; Ryabov, Y. F.; Ryjov, V.; Söderberg, M.; Savenkov, A.; Saxon, J.; Scandurra, M.; Schegelsky, V. A.; Scherzer, M. I.; Schmidt, M. P.; Schmitt, C.; Sedykh, E.; Seliverstov, D. M.; Shin, T.; Shmeleva, A.; Sivoklokov, S.; Smirnov, S. Yu; Smirnova, L.; Smirnova, O.; Smith, P.; Sosnovtsev, V. V.; Sprachmann, G.; Subramania, S.; Suchkov, S. I.; Sulin, V. V.; Szczygiel, R. R.; Tartarelli, G.; Thomson, E.; Tikhomirov, V. O.; Tipton, P.; Valls Ferrer, J. A.; Van Berg, R.; Vassilakopoulos, V. I.; Vassilieva, L.; Wagner, P.; Wall, R.; Wang, C.; Whittington, D.; Williams, H. H.; Zhelezko, A.; Zhukov, K.

2008-02-01

311

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

312

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.

313

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

International Nuclear Information System (INIS)

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

314

Energy Absorption Performances of Square Winding Kenaf Fiber Reinforced Composite Tubes  

Directory of Open Access Journals (Sweden)

Full Text Available This paper investigates the energy absorption response of winding kenaf fiber composite tubes when subjected to an axial quasi-static crushing test. The square composites were prepared firstly by submerging the kenaf yarn into resin bath before it is warped around the mould for different number of layers and fiber orientations. The parameters measured were peak load, mean load and specific energy absorption. Collapse mechanisms during the progressive collapses were observed as a function of tube length. It is found that as-expected, number of layers played an important role in increasing the energy absorption performances. However, fiber alignments have insignificant effect on the absorbed energy. A surface bulge appeared on the one side of the tube walls responsible for premature failure of the composite prior to the progressive collapse.

A.E Ismail

2014-12-01

315

Measurement of the optical performance of liquid scintillator filled Teflon-fiber tubes  

Energy Technology Data Exchange (ETDEWEB)

A study of the optical performance of a liquid scintillator (BC517L) filled Teflon tube of inner diameter 0.06 cm, was carried out using a rectangular array of those tubes. Two experimental methods, the cosmic ray telescope and the direct scouce method, were used in measuring the light output (in photoelectrons) and the light attenuation length through the scintillator. Results showed the light output from this array for minimum ionizing charged particles to ba a fraction of a photoelectron (about 10{sup {minus}2}) and the attenuation length to be about 20.0 cm, for high energy particles, suggesting a limiting value for the tube diameter of the Teflon that can be used in scintillating fiber calorimeters for high energy physics experiments. 18 refs., 16 figs., 4 tabs.

Zaman, S.M.

1990-05-01

316

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

317

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

318

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

319

Performance of PCCS with horizontal U-tube type heat exchanger  

International Nuclear Information System (INIS)

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

320

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

Directory of Open Access Journals (Sweden)

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

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

2009-10-01

321

Performance of the Hamamatsu R11410 Photomultiplier Tube in Xenon Environments  

CERN Document Server

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

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

2013-01-01

322

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

323

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

Energy Technology Data Exchange (ETDEWEB)

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.

Lee, Gong Hee; Bang, Young Seok; Woo, Sweng Woong [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

2012-10-15

324

A comparison of heat transfer enhancement in a medium temperature thermal energy storage heat exchanger using fins  

Energy Technology Data Exchange (ETDEWEB)

An experimental energy storage system has been designed using a horizontal concentric tube heat exchanger incorporating a medium temperature phase change material (PCM) Erythritol, with a melting point of 117.7 C. Three experimental configurations, a control system with no heat transfer enhancement and systems augmented with circular and longitudinal fins have been studied. The results presented compare the system heat transfer characteristics using isotherm plots and temperature-time curves. The system with longitudinal fins gave the best performance with increased thermal response during charging and reduced subcooling in the melt during discharging. The experimentally measured data for the control, circular finned and longitudinal finned systems have been shown to vindicate the assumption of axissymmetry (direction parallel to the heat transfer fluid flow) using temperature gradients in the axial, radial and angular directions in the double pipe PCM system. (author)

Agyenim, Francis; Smyth, Mervyn [Centre for Sustainable Technologies, University of Ulster, Newtownabbey BT37 0QB (United Kingdom); Eames, Philip [Electronic and Electrical Engineering, Loughborough University, Leicestershire LE11 3TU (United Kingdom)

2009-09-15

325

Numerical analysis on heat removal from Y-shaped fins: Efficiency and volume occupied for a new approach to performance optimisation  

Energy Technology Data Exchange (ETDEWEB)

This paper faces the problem of geometric optimisation for exchanger profiles with innovative shapes. In particular it was analysed the Y shape, keeping the dimensionless thermal conductance as reference parameter like in the thematic technical literature. The use of suitable geometrical constraints allows wide comparisons with papers in literature using different kinds of geometries. The methodological approach here chosen is numerical and utilises a CFD software. The geometries examined are obtained by varying the angle between the two arms of the Y, starting from the T-shaped profile that allows the best performances, as obtained in a previous work. Results show that the new shape proposed for the fins, together with the assessment of the horizontal width, leads to a novel performance evaluation criterion. (author)

Lorenzini, Giulio; Moretti, Simone [Alma Mater Studiorum-University of Bologna, Department of Agricultural Economics and Engineering viale Giuseppe Fanin, 50-40127 Bologna (Italy)

2007-06-15

326

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

327

Undulating fins produce off-axis thrust and flow structures.  

Science.gov (United States)

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

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

2014-01-15

328

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

329

Mechanical performance of oxidized Zr-Nb-O nuclear cladding tubes  

Science.gov (United States)

Ring compression and tensile tests on oxidized Zr-Nb-O cladding tubes were performed, to examine the reliability of nuclear cladding tubes after oxidation. The oxidation rate was observed to be far greater at 700°C than 600°C, because of the increased volume fraction of less protective porous oxide. The tensile strength of oxidized Zr-1Nb cladding tubes at 600°C for 3 h increased, with no appreciable loss of ductility. After heat treatment at 600°C for 24 h and 700°C for 3 h, the yield strength and the initial flow stress increased, and the flow stress decreased rapidly with strain, resulting in decreased ductility. The increase of yield strength after heat treatment at 600°C in Zr-1Nb was associated with the presence of strong and protective oxide film. In compressive loading, for cladding tubes oxidized at 600°C for 24 h and 700°C for 3 h, a small drop of load, resulting from cracking of the surface oxide layer, was observed at the total displacement of 1.3 ˜ 1.5 mm. The catastrophic fracture that was observed at the total displacement of 5.7 mm in Zr-Nb-Sn-Fe did not occur in Zr-Nb-O. The absence of sudden drop and catastrophic fracture at the displacement of 5 ˜ 7 is thought to be associated with the softer matrix of annealed Zr-Nb-O.

Jeong, Gu Beom; Choi, Yong; Hong, Sun Ig

2014-12-01

330

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

International Nuclear Information System (INIS)

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

331

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

332

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

333

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.

334

Scoping assessment of design characteristics for an enhanced calandria tube  

Energy Technology Data Exchange (ETDEWEB)

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 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.

Harvel, Glenn D., E-mail: Glenn.Harvel@uoit.ca [Faculty of Energy Systems and Nuclear Science, University of Ontario Institute of Technology, 2000 Simcoe St. North, Oshawa, Ontario, L1H 7K4 (Canada); Scrannage, Richard C.; Hobbs, Daniel M. [Faculty of Energy Systems and Nuclear Science, University of Ontario Institute of Technology, 2000 Simcoe St. North, Oshawa, Ontario, L1H 7K4 (Canada)

2011-08-15

335

Performance Assessment of Passive Heat Exchanger with Horizontal Tube using RELAP5  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-10-15

336

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

337

Effect of Image Intensifier Tube Equivalent Background Illuminationon Range Performance of Passive Night Sight  

Directory of Open Access Journals (Sweden)

Full Text Available Effect of increase in equivalent background illumination (EBI with temperature of secondgeneration (18 mm proximity focused image intensifier tube on the range performance of apassive night sight has been studied using the image intensifier minimum resolvable contrastmodel. It has been shown that for ambient temperatures of 40 oC and above, the range performanceof sight goes down drastically under low-illumination level due to increase in the EBI.Deterioration in range performance is negligible when ambient illumination is relatively high asin case of clear-starlit condition.

A. K. Musla

2007-11-01

338

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

Science.gov (United States)

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

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

2014-05-01

339

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

340

Experimental and numerical characterization of a mechanical expansion process for thin-walled tubes  

OpenAIRE

Air heat exchangers are made with tubes joined to finned pack. The connection between tubes and fins can be obtained through a mechanical process where an ogive is pushed inside the tube with smaller internal diameter causing its expansion. Residual plastic deformation provides the assembly with the fins. Accurate connection over the whole contact area of the tubes and fins is essential for maximum heat exchange efficiency. The goal of this work is to study and develop a finite element model ...

Priarone, Paolo Claudio; Scattina, Alessandro; Avalle, Massimiliano

2014-01-01

341

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.

342

Performance model of metallic concentric tube recuperator with counter flow arrangement  

Energy Technology Data Exchange (ETDEWEB)

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. (orig.)

Sharma, Harshdeep [HIET, Department of Mechanical Engineering, Ghaziabad, Uttar Pradesh (India); Kumar, Anoop; Goel, Varun [NIT, Department of Mechanical Engineering, Hamirpur, Himachal Pradesh (India)

2010-03-15

343

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

344

Performance of horizontal U-tube type passive containment cooling system in a BWR  

International Nuclear Information System (INIS)

To enhance countermeasures against important severe accident (SA) phenomena, SA mitigation systems with passive features are being developed to protect containment integrity and prevent release of a large amount of radioactive materials to environment after SA including core melt. Passive mitigation systems are preferable considering accident sequences with loss of power, which are dominant in Probabilistic Safety Assessment (PSA). The dedicated passive SA mitigation systems, i.e. passive containment cooling system (PCCS) combined with core catcher can be introduced to containment design of BWRs or Advanced BWRs (ABWRs) in the future. Heat removal capability of the PCCS has been verified through fundamental tests using single tube and full-scale bundle as well as its capability of non-condensable gases (NCG) purges from the tubes. An analysis models for the steam condensation inside of the tubes, boiling heat transfer outside of the tubes and two-phase flow pressure drop, including the degradation of steam condensation by the NCG, have been developed and validated. Furthermore, a system integral test for the PCCS performance has been conducted in order to demonstrate it using TIGER test facility. It showed good heat removal capability of the PCCS. MAAP code was applied to SA sequence analysis considering heat removal by the PCCS. The analysis showed that the PCCS combined with the core catcher could protect the integrity of the containment and avoid containment ventine containment and avoid containment venting in passive manner during SA. Although the passive heat removal models due to the steam condensation in the MAAP are not same as those developed by the PCCS tests, it was found that the MAAP models were more conservative. (authors)

345

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

OpenAIRE

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 ...

Richa Soni; Gupta, P. K. Jhinge R. C.

2013-01-01

346

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

347

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-07-25

348

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)

349

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

350

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

Energy Technology Data Exchange (ETDEWEB)

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 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.

Rhee, Huinam [Dept of Mechanical and Aerospace Engineering, Sunchon National University, Sunchon, 540-742 (Korea, Republic of); Boo, Myung-Hwan [Korea Hydro and Nuclear Power Company, Yuseong-Gu, Daejeon 305-343 (Korea, Republic of); Park, Chi-Yong [KEPCO Research Institute, Yuseong-Gu, Daejeon 305-380 (Korea, Republic of); Ryu, Ki-Wahn, E-mail: kwryu@chonbuk.ac.k [Department of Aerospace Engineering, Chonbuk National University, 664-14, Deogjin-Dong, Jeonju 561-756 (Korea, Republic of)

2010-10-15

351

Study on heat transfer performance of an aluminum flat plate heat pipe with fins in vapor chamber  

International Nuclear Information System (INIS)

Highlights: • A novel flat plate heat pipe (FPHP) was designed and performed. • Maximum HS temperature is lower than 60 °C when the heat load reaches 100 W. • The FPHP will spend less time to start up with the increase of heat flux. • Liquid FR and VD have a significant influence on thermal performance of FPHP. - Abstract: The heat transfer performance of a novel flat plate heat pipe (FPHP) for electronic cooling was investigated experimentally. A variety of performance tests of FPHP were carried out with different air flow velocities (1.5 m/s < u < 6 m/s), working fluid filling ratios (10% < FR < 50%), and the vacuum degrees (0.002 Pa < VD < 0.25 Pa). Using distilled water and acetone as working fluids, the influence of the above parameters on steady-state heat transfer characteristics of the FPHP was also examined. The experimental results indicated that the filling ratio and vacuum degree had a significant influence on thermal performance of FPHP. Compared with cooling performance using distilled water and acetone, the FPHP cooling component using acetone had a stronger heat dissipation capacity for the same filling ratio

352

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

353

Performance Evaluation of a Forced Convection Solar Drier with Evacuated Tube Collector for Drying Amla  

OpenAIRE

A forced convection solar drier is designed with evacuated tube collector and a blower. The performance of the designed drier is evaluated by carrying drying experiments at Thanjavur District, Tamilnadu, India with amla. Solar drying of amla is carried at different air velocity flow rates – 4m/s, 4.25m/s and 4.5m/s and is compared with natural sun drying. The temperature of the dryingchamber ranges from 53ºC to 82ºC while the ambient temperature ranges from 29ºC to 32ºC. The efficiency ...

Ar, Umayal Sundari; Neelamegam, P.; Subramanian, C. V.

2013-01-01

354

FinFET- Benefits, Drawbacks and Challenges.  

Directory of Open Access Journals (Sweden)

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

Mayur Bhole

2013-11-01

355

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

Energy Technology Data Exchange (ETDEWEB)

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

Lewis, L G; Sather, N F

1979-05-01

356

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

357

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

358

Optimum thermal analysis of annular fin heat sink by adjusting outer radius and fin number  

Energy Technology Data Exchange (ETDEWEB)

The theoretical exploration of the optimum cooling effect of a heat sink equipped with annular fins is presented in this study. The optimum equation is derived in transcendental form and the formula of the thermal resistance is also provided. With the input data of dimensionless parameter, C, heat transfer coefficient ratios, H and H{sub e}, this optimum equation can be utilized to find the optimum outer radius of annular fins and fin number on a heat sink that affect the overall thermal effectiveness of a heat sink. Finally, examples are offered to illustrate the cooling performance of a heat sink including annular fins. [Author].

Lai, Chi-Yuan; Kou, Hong-Sen; Lee, Ji-Jen [Department of Mechanical Engineering, Tatung University, No. 40, Chung-shan North Road, Section 3, Taipei City 104, Taiwan (China)

2006-06-15

359

Performance analysis and optimization of radiating fins with a step change in thickness and variable thermal conductivity by homotopy perturbation method  

Science.gov (United States)

Although tapered fins transfer more rate of heat per unit volume, they are not found in every practical application because of the difficulty in manufacturing and fabrications. Therefore, there is a scope to modify the geometry of a constant thickness fin in view of the less difficulty in manufacturing and fabrication as well as betterment of heat transfer rate per unit volume of the fin material. For the better utilization of fin material, it is proposed a modified geometry of new fin with a step change in thickness (SF) in the literature. In the present paper, the homotopy perturbation method has been used to evaluate the temperature distribution within the straight radiating fins with a step change in thickness and variable thermal conductivity. The temperature profile has an abrupt change in the temperature gradient where the step change in thickness occurs and thermal conductivity parameter describing the variation of thermal conductivity has an important role on the temperature profile and the heat transfer rate. The optimum geometry which maximizes the heat transfer rate for a given fin volume has been found. The derived condition of optimality gives an open choice to the designer.

Arslanturk, Cihat

2011-02-01

360

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

361

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

362

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

OpenAIRE

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 micr...

Mohit Taneja, Sandeep Nandal

2013-01-01

363

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

Energy Technology Data Exchange (ETDEWEB)

Performance tests were conducted with the Carnegie-Mellon University (C-MU) vertical fluted-tube evaporator. Under nominal operating conditions (3200 gpm water flow, 3.2 million Btu/hr heat duty, and 100 gpm ammonia feed rate), the overall heat transfer coefficient (U/sub 0/) was 825 Btu/hr ft/sup 2/ /sup 0/F and the ammonia-side and water-side heat transfer coefficients were 1800 and 2610 Btu/hr ft/sup 2/ /sup 0/F, respectively. The water-side pressure drop was 3.2 psi. Tests were conducted at heat duties ranging from 2.4 million to 4.0 million Btu/hr and ammonia feed rates from 30 to 110 gpm. Over these ranges, U/sub 0/ increased with ammonia feed rate and decreased with heat duty. For all runs the quality of the ammonia vapor leaving the evaporator exceeded 99.9%. The measured U/sub 0/ values were very stable and repeatable for any continuous run at fixed operating conditions; however, they were not always repeatable following operating state changes or shutdown of the ammonia feed. These repeatability problems were attributed to variations in tube wetting and to the poor design of the ammonia applicator. Test results suggested that to ensure sufficient wetting and good thermal performance, the system should be started with a high ammonia feed rate and then cut back to the desired operating value.

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

1979-07-01

364

Thermal performance of capillary micro tubes integrated into the sandwich element made of concrete  

DEFF Research Database (Denmark)

The thermal performance of radiant heating and cooling systems (RHCS) composed of capillary micro tubes (CMT) integrated into the inner plate of sandwich elements made of High Performance Concrete (HPC) was investigated in the article. Temperature distribution in HPC elements around integrated CMT was studied. Thermal heat flux on the inner surface of HPC element was carefully investigated. Calculations were carried out for different temperatures of the circulating fluid, different spacing between CMT and different thicknesses of the inner HPC layer covering the CMT. This paper shows that CMT integrated into the thin plate of sandwich element made of HPC can supply the energy needed for heating and cooling. The investigations were conceived as a low temperature concept, where the difference between the temperature of circulating fluid and air in the room was kept in range of 1 to 4°C. © (2013) Trans Tech Publications, Switzerland.

Mikeska, Tomas; Svendsen, Svend

2013-01-01

365

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

366

Computer program for performance and sizing analysis of compact counter-flow plate-fin heat exchangers, research and development report  

Science.gov (United States)

This report presents a computer program for preliminary design analysis of counter-flow, compact, plate-fin heat exchangers. The program method is based on the effectiveness-NTU relationship analysis. The heat exchanger design begins with assumptions for counter-flow length, total frontal flow area and core matrix fin geometry. Using these constraints, the program proceeds to calculate the resulting effectiveness and pressure drop based on specified air-side and gas-side fin types; the pressures, temperatures, and mass flows of the air and gas streams; fuel-air ratio; as well as, the maximum air-side inlet header velocity. Heat exchanger designs may be generated based on four different fin types (i.e., plain, louvered, strip/offset or wavy fins) over a varied number of core dimensions. Program output includes inlet and exit conditions on air and gas sides, effectiveness, fin characteristics, core length and volume, total frontal units, overall weight, and air-side header diameters and velocities. This report presents the analysis method, description of input and output with sample cases, and a program listing.

Ness, J. C.

1982-12-01

367

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

368

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

OpenAIRE

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

Nasruddin

2012-01-01

369

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

370

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

371

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

372

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)

373

Temperature stability of high-performance GM pulsed tube chillers; Temperaturstabilitaet von leistungsstarken GM-Pulsrohrkuehlern  

Energy Technology Data Exchange (ETDEWEB)

Experiments on temperature stability of Gifford-McMahon pulsed tube chillers showed that their performance may become unstable in certain operating conditions. The reasons for this, as well as the available countermeasures, were investigated in detail. [German] Im Rahmen des BMBF-Verbundprojektes 'Pulsrohrkuehler' wurden zahlreiche experimentelle Untersuchungen zur Temperaturstabilitaet von Pulsrohrkuehlern des Gifford-McMahon-Typs durchgefuehrt. Ein Ergebnis dieser Untersuchungen ist, dass es mit diesem Pulsrohrtyp unter bestimmten Bedingungen zu einem nicht stabilen Betriebsverhalten kommen kann. Die Gruende fuer dieses Verhalten, sowie Moeglichkeiten einen stabilen Betrieb sicherzustellen werden eingehend beschrieben. Dieser Vortrag schliesst damit an den letztjaehrigen DKV-Vortrag 'Untersuchungen zum Langzeit-Betriebsverhalten von GM-Pulsrohrkuehlern' an. (orig.)

Siegel, A. [Leybold Vakuum GmbH, Koeln (Germany)

2002-07-01

374

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

CERN Document Server

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

Giorgini, M

2002-01-01

375

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

CERN Document Server

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

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

2004-01-01

376

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

377

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

378

Heat transfer and thermal performance characteristics of heat exchanger tube fitted with perforated twisted-tapes  

Science.gov (United States)

Twisted tape insert was applied as a swirling flow generator for the passive heat transfer enhancement in the present work. The influences of the perforated twisted tapes (PTs) on the heat transfer, pressure loss and thermal performance characteristics were investigated experimentally. The experiments were performed under uniform wall heat flux condition by using PTs with y/W = 3, 4 and 5, d/W = 0.11, 0.14 and 0.17 and s/W = 0.4, 0.6 and 0.8 where y is a twist length, d is a perforation hole diameter, s is a spacing between holes (pitch) and W is a tape width. The experimental results reveal that Nusselt number increased with decreasing s/W and y/W and increasing d/W. For the present range, the maximum heat transfer was obtained by utilizing the tape with s/W = 0.4, d/W = 0.17 and y/W = 3, which is higher than those obtained from the plain tube with and without typical twisted tape by around 27.4 and 86.7%, respectively. In addition, the empirical correlations for Nusselt number, friction factor and thermal performance are also proposed in the present paper.

Thianpong, Chinaruk; Eiamsa-ard, Petpices; Eiamsa-ard, Smith

2012-06-01

379

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

International Nuclear Information System (INIS)

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

380

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

381

Scroll heat sink: A novel heat sink with the moving fins inserted between the cooling fins  

Energy Technology Data Exchange (ETDEWEB)

In this paper, a new type of a fan-integrated heat sink named a scroll heat sink is proposed and demonstrated. The most striking feature of the scroll heat sink is that heat dissipation and fluid pumping occurs simultaneously in the whole cooling space without requiring any additional space for a fan module. In the scroll heat sink, the moving fins, which rotate with two eccentric shafts, are inserted between the fixed (cooling) fins. By a relative motion between the moving fins and the cooling fins, a coolant is drawn into the space between them, takes heat away from the cooling fins, and the heated coolant is discharged out of the heat sink. In the present study, an experimental investigation is performed in order to demonstrate the concept of the scroll heat sink. Average coolant velocities and thermal resistances of the scroll heat sink are measured for various rotating speeds of the moving fins from 200 rpm to 500 rpm. Experimental results show that measured flow rates of the coolant are almost linearly proportional to the rotating speed of the moving fins. A theoretical model is also developed to estimate the required pumping power and the thermal resistance, and validated using experimental results. The theoretical model shows that optimized scroll heat sinks have lower thermal resistances than optimized plate-fin heat sinks under the fixed pumping power condition. (author)

Kim, Tae Young; Kim, Dong-Kwon; Kim, Sung Jin [School of Mechanical, Aerospace and System Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea)

2008-07-01

382

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

383

An approach to optimal fin diameter based on entropy minimization  

Directory of Open Access Journals (Sweden)

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

Masoud Asadi

2013-04-01

384

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

Directory of Open Access Journals (Sweden)

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

V.S.Daund*

2014-08-01

385

Study of thermal performance of capillary micro tubes integrated into the building sandwich element made of high performance concrete  

DEFF Research Database (Denmark)

The thermal performance of radiant heating and cooling systems (RHCS) composed of capillary micro tubes (CMT) integrated into the inner plate of sandwich elements made of high performance concrete (HPC) was investigated in the article. Temperature distribution in HPC elements around integrated CMT was studied. Thermal heat flux on the inner surface of HPC element, and the increase of heat losses to the outside environment were carefully investigated. Calculations were carried out for different temperatures of the circulating fluid, different spacing between CMT and different thicknesses of the inner HPC layer covering the CMT. This paper shows that CMT integrated into the thin plate of sandwich element made of HPC can supply the energy needed for heating (cooling) and at the same time create the comfortable and healthy environment for the occupants. This solution is very suitable for heating and cooling purposes of future low energy buildings. The investigations were conceived as a low temperature concept, where the difference between the temperature of circulating fluid and air in the room was kept in range of 1–4 °C.

Mikeska, Tomas; Svendsen, Svend

2013-01-01

386

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

387

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.

388

The shark's fin  

International Nuclear Information System (INIS)

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

389

Plasma doping and reduced crystalline damage for conformally doped fin field effect transistors  

Science.gov (United States)

Low frequency noise and hot carrier reliability analysis of the plasma doping scheme are investigated for advanced fin field effect transistor (FinFET) conformal doping. Plasma doping improves device performances and hot carrier reliability for both fin resistors and FinFETs due to the absence of crystalline damage for narrow fins. One decade lower noise level and Coulomb scattering coefficient related to the crystalline damage suppression are observed for the plasma doping compared to the standard ion-implantation.

Woo Lee, Jae; Sasaki, Yuichiro; Ju Cho, Moon; Togo, Mitsuhiro; Boccardi, Guillaume; Ritzenthaler, Romain; Eneman, Geert; Chiarella, Thomas; Brus, Stephan; Horiguchi, Naoto; Groeseneken, Guido; Thean, Aaron

2013-06-01

390

[Toxicity of puffer fish fins].  

Science.gov (United States)

Puffer fish is prized as a Japanese traditional food and its fin is also used in the cuisine. However, whether the fin is edible or not is determined for convenience from the toxicity of skin, since little information is available about the toxicity of puffer fish fins. In the present study, we examined the toxicity of fins and skin of three toxic species, Takifugu vermicularis, T. snyderi, and T. porphyreus. The toxicity of T. vermicularis fins (skin (skin. The toxicity (puffer fish with toxic skin also have toxic fins. PMID:18027550

Honda, Shunichi; Ichimaru, Shunichi; Arakawa, Osamu; Takatani, Tomohiro; Noguchi, Tamao; Ishizaki, Shoichiro; Nagashima, Yuji

2007-10-01

391

Comparison between one-dimensional uncoupled and convection-conduction conjugated approaches in finned surface heat transfer  

OpenAIRE

This work studies the forced convection problem in internal flow between concentric annular ducts, with radial fins at the internal tube surface. The finned surface heat transfer is analyzed by two different approaches. In the first one, it is assumed one-dimensional heat conduction along the internal tube wall and fins, with the convection heat transfer coefficient being a known parameter, determined by an uncoupled solution. In the other way, named conjugated approach, the mathematical mode...

Andrade, Cla?udia R.; Zaparoli, Edson L.

2000-01-01

392

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

393

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

International Nuclear Information System (INIS)

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 CO2 molecules in the Ar:CO2 (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 ? ray background fluences. The chambers have a spatial resolution better than 40 ?m at the nominal background rates expected at the Large Hadron Collider design luminosity of 1034 cm-2s-1 and a resolution better than 50 ?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.

394

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

Science.gov (United States)

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

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

2012-07-01

395

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-07-15

396

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

397

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-08-15

398

Source Drain Engineering in FinFET – A Review  

OpenAIRE

Scaling poses many challenges beyond 22nm technology. In this paper, the various designs proposed by researchers about the double gate FinFET with raised source and drain have been studied. Also the significance of various parameters, different modes of operation of the FinFET, effect of fin thickness over the performance, doping level, effect of height of source and drain, advantages of using metal gate electrodes along with high-k dielectrics have been studied. Different designing technique...

Flavia Princess Nesamani, I.; Rekha Puthenpurayil Divakaran; Lakshmi Prabha, Dr V.; Sujith M.B

2014-01-01

399

Characteristics of a micro-fin evaporator: Theoretical analysis and experimental verification  

OpenAIRE

A theoretical analysis and experimental verification on the characteristics of a micro-fin evaporator using R290 and R717 as refrigerants were carried out. The heat capacity and heat transfer coefficient of the micro-fin evaporator were investigated under different water mass flow rate, different refrigerant mass flow rate, and different inner tube diameter of micro-fin evaporator. The simulation results of the heat transfer coefficient are fairly in good a...

Zheng Hui-Fan; Fan Xiao-Wei; Wang Fang; Liang Yao-Hua

2013-01-01

400

Dermoskeleton morphogenesis in zebrafish fins  

OpenAIRE

Zebrafish fins have a proximal skeleton of endochondral bones and a distal skeleton of dermal bones. Recent experimental and genetic studies are discovering mechanisms to control fin skeleton morphogenesis. Whereas the endochondral skeleton has been extensively studied, the formation of the dermal skeleton requires further revision. The shape of the dermal skeleton of the fin is generated in its distal growing margin and along a proximal growing domain. In these positions, dermoskeletal fin m...

Mari?-beffa, Manuel; Murciano, Carmen

2010-01-01

401

Visualization Study of the Effect of the Prolonged Vertical Tube on the Separation Performance of a Cyclone  

Science.gov (United States)

Cyclones have been widely used in different industrial processes. The most widely used experimental observation techniques for the flow pattern include Pitot tubes; hot-wire anemometers, as well as the non-intrusive techniques such as laser Doppler anemometry (LDA). However, all these available techniques have the limitation of only one-point measurement at a time, by which the whole-field fluid characterization in cyclones cannot be obtained simultaneously. Particle image velocimetry (PIV) is a novel non-intrusive visualization experimental technique to measure the whole-field three-dimensional fluid velocity instantaneously. However, only a few papers that examined the flow pattern in cyclones with PIV have been found. The objective of this work is to carry out an elementary experimental investigation of the effect of the prolonged vertical tube on the separation performance of a cyclone by PIV. Since the tangential velocity results in the centrifugal force for particle separation, and is regarded as the most important component of the gas flow in a cyclone, this paper only presents this velocity component. To facilitate visual observation all cyclone parts are constructed of perspex. The lengths of the prolonged vertical tube (attaching a vertical tube at the bottom of the dust outlet) are 0.30m, 0.40m and 0.50m, respectively. Experiments were conducted at 18m/s inlet gas velocity. The model cyclone is set horizontally in order to take images by charge coupled device (CCD) easily. Particles of about 1 ?m in diameter are added as tracer particles. They are generated by the atomizer. Air with tracer particles is sucked into the cyclone through the entry, subsequently travels through outlet tube of the cyclone and the gate valve, and is discharged into the atmosphere. The experimental results show that a typical Rankine vortex with inner quasi-forced vortex and outer quasi-free vortex in the vertical tube and dustbin which are the same as that in the body of the cyclone; the tangential velocity in the dustbin reduces1 greatly when the prolonged vertical tube attaching into the dust outlet, which can avoid the re-entrainment of already separated dust effectively. The results also indicate that PIV technique can be used to measure the strong swirl gas flow such as cyclones, and the prolonged vertical tube has practical significance for improving the separation performance of a cyclone.

Qian, Fuping; Zhang, Mingyao

2007-06-01

402

Critical heat flux experiments using a screw tube under DEMO divertor-relevant cooling conditions  

International Nuclear Information System (INIS)

As part of the development of plasma-facing components (PFCs) for fusion machines, JAEA has been developing high-performance cooling tubes with pressurized water flow. Along this line, a cooling tube with a helical triangular fin on its inner surface has been recently proposed for application in a fusion DEMO to enhance heat removal. Since the fin can be machined via simple mechanical threading, this tube is called as a 'screw tube'. The divertor cooling conditions for the JAEA DEMO design will be a pressure of 4 MPa and an outlet temperature of 200 deg. C, in order to improve the thermal efficiency of power generation. In the this study, the effect of subcooling on the critical heat flux (CHF) by the screw tube has been investigated under DEMO divertor-relevant conditions, with the local pressure of 4 MPa and the inlet coolant temperature up to 180 deg. C. A test sample of the screw tube is made of pure Cu instead of F82H, a candidate structural material for the DEMO divertor. The results show that the ICHF values of the screw tube are more than double the values of the smooth tube at the inlet coolant temperature of 180 deg. C, although the temperature rise of the cooling water by 140 K leads to a reduction in the ICHF by almost half as compared with those values at room temperature

403

Source Drain Engineering in FinFET – A Review  

Directory of Open Access Journals (Sweden)

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

I.Flavia Princess Nesamani

2014-02-01

404

High heat load test of CFC divertor target plate with screw tube for JT-60 superconducting modification  

International Nuclear Information System (INIS)

A flat carbon fiber composite (CFC) tile mock-up with screw tubes, which have helical fins like a nut, was fabricated aiming at further improvement of the heat removal performance of the cost-effectively manufactured divert or target for JT-60SC (modified JT-60 as a superconducting coil tokamak). The heat removal performance of the mock-up was successfully demonstrated on the JAERI Electron Beam Irradiation Stand. The estimated heat transfer coefficient of the screw tube at the non-boiling region was roughly three times higher than that of the smooth tube. This corresponds to 1.5 times that of the swirl tube. A heat cycle test of 10 MW/m2 showed that the mock-up with the screw tubes could withstand for 1400-cycles. These results indicate that the divertor target plate with the flat CFC tile and the screw tube can be a promising candidate for the JT-60SC divertor target

405

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

Science.gov (United States)

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

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

2011-01-01

406

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)

407

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

408

Stability of tube rows in crossflow  

International Nuclear Information System (INIS)

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

409

The Waveform Digitiser of the Double Chooz Experiment: Performance and Quantisation Effects on PhotoMultiplier Tube Signals  

CERN Document Server

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

Abe, Y; Cabrera, A; Courty, B; Dawson, J V; Gonzalez, L F G; Hourlier, A; Ishitsuka, M; de Kerret, H; Kryn, D; Novella, P; Obolensky, M; Perasso, S; Remoto, A; Roncin, R

2013-01-01

410

Successful euthanasia of a juvenile fin whale.  

OpenAIRE

A stranded juvenile fin whale was successfully euthanized with an intravenous injection of sedative and cardioplegic drugs. Veterinarians may face a number of serious difficulties if called to perform this task, and advance preparation is required for successful euthanasia of these animals.

Daoust, P. Y.; Ortenburger, A. I.

2001-01-01

411