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1

Performance of tubes-and plate fins heat exchangers  

International Nuclear Information System (INIS)

[en] 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)

1979-01-01

2

Experimental and numerical investigation on air-side performance of fin-and-tube heat exchangers with various fin patterns  

Energy Technology Data Exchange (ETDEWEB)

Air-side heat transfer and friction characteristics of five kinds of fin-and-tube heat exchangers, with the number of tube rows (N = 12) and the diameter of tubes (D{sub o} = 18 mm), have been experimentally investigated. The test samples consist of five types of fin configurations: crimped spiral fin, plain fin, slit fin, fin with delta-wing longitudinal vortex generators (VGs) and mixed fin with front 6-row vortex-generator fin and rear 6-row slit fin. The heat transfer and friction factor correlations for different types of heat exchangers were obtained with the Reynolds numbers ranging from 4000 to 10000. It was found that crimped spiral fin provides higher heat transfer and pressure drop than the other four fins. The air-side performance of heat exchangers with the above five fins has been evaluated under three sets of criteria and it was shown that the heat exchanger with mixed fin (front vortex-generator fin and rear slit fin) has better performance than that with fin with delta-wing vortex generators, and the slit fin offers best heat transfer performance at high Reynolds numbers. Based on the correlations of numerical data, Genetic Algorithm optimization was carried out, and the optimization results indicated that the increase of VG attack angle or length, or decrease of VG height may enhance the performance of vortex-generator fin. The heat transfer performances for optimized vortex-generator fin and slit fin at hand have been compared with numerical method. (author)

Tang, L.H.; Zeng, M.; Wang, Q.W. [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China)

2009-07-15

3

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

4

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

1989-01-01

5

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 indivi...

Kærn, Martin Ryhl; Brix, Wiebke; Elmegaard, Brian; Larsen, Lars Finn Sloth

6

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

7

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

8

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

International Nuclear Information System (INIS)

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

2009-01-01

9

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-03-15

10

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.

2011-01-01

11

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

Directory of Open Access Journals (Sweden)

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

S.R.Mcilwain

2010-01-01

12

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.

2008-01-01

13

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

International Nuclear Information System (INIS)

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

2011-01-01

14

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.

1986-01-01

15

Heat Transfer from Fin-Tube Radiators.  

Science.gov (United States)

A FORTRAN language computer program is developed to calculate the radiation heat transfer characteristics of circular tubes with longitudinal fins. Mutual irradiation effects between the tubes and the fin are included. Arbitrary fin emissivity, fin thickn...

M. F. Sarabia

1964-01-01

16

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

International Nuclear Information System (INIS)

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

2012-01-01

17

A comparison of the heat transfer and pressure drop performance of R-134a-lubricant mixtures in different diameter smooth tubes and micro-fin tubes  

Energy Technology Data Exchange (ETDEWEB)

The average heat transfer coefficients and pressure drops during evaporation and condensation are reported for mixtures of R-134a and an ester lubricant in tubes of 12.7 mm (1/2 in.) outer diameter. The objective of this paper is to evaluate the performance of the R-134a-lubricant mixtures in these tubes and determine the performance benefits of the micro-fin tube. The performance benefits of the tubes with 12.7 mm (1/2 in.) outer diameter are compared to those of smaller tubes with 9.52 mm (3/8 in.) outer diameter. The lubricant used was a 169 SUS penta erythritol ester mixed-acid lubricant. The lubricant concentration was varied from 0--5.1% in the mixture. The average heat transfer coefficients in the 12.7 mm (1/2 in.) micro-fin tube were 50--150% higher than those for the 12.7 mm (1/2 in.) smooth tube, while pressure drops in the micro-fin tube were 5% to 50% higher than in the smooth tube. The addition of lubricant degraded the average heat transfer coefficients in all cases except during evaporation at low lubricant concentrations. Pressure drops were always increased with the addition of lubricant. The experimental results also indicate that tube diameter has some effect on the performance benefits of the micro-fin tube over that of the smooth tube.

Eckels, S.J. [Kansas State Univ., Manhattan, KS (United States). Dept. of Mechanical Engineering; Doerr, T.M.; Pate, M.B. [Iowa State Univ., Ames, IA (United States). Mechanical Engineering Dept.

1998-10-01

18

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: ? 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.

2013-01-10

19

Experimental investigation on the airside performance of fin-and-tube heat exchangers having herringbone wave fins and proposal of a new heat transfer and pressure drop correlation  

International Nuclear Information System (INIS)

The heat transfer and friction characteristics of fin-and-tube heat exchangers having herringbone wave fins were experimentally investigated. Eighteen samples having different fin pitches (1.34 mm to 2.54 mm) and tube rows (one to four) were tested. For all the samples, the waffle depth and the corrugation angle of the fin was 1.14 mm and 11.7 .deg. respectively. Results showed that the j factors were insensitive to fin pitch, while f factors increased as the fin pitch increased. As the number of tube rows increased, both the j and f factors decreased. However, the effect of tube row diminished as the Reynolds number increased, at least for j factors. Existing correlations failed to adequately predict the present data. A new correlation was developed based on existing data, which significantly improved the predictions of the present data

2008-01-01

20

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)

2002-01-00

 
 
 
 
21

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

Science.gov (United States)

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

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

2013-09-01

22

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

1991-01-01

23

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-08-15

24

Effect of circuitry on the condensation performance of a fin-and-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

An experimental study was carried out to investigate the effect of circuitry on the performance of wavy finned condenser. A total of four arrangements was made and tested. Experiments were conducted in an environmental chamber. The test apparatus is based on the air-enthalpy method proposed by ANSI/ASHRAE standard (1993). Cooling capacity was measured from the enthalpy difference of the air flowrate across the test sample. The air flow measuring apparatus is constructed based on ASHRAE 41.2 standard (1991). Refrigerant R-22 was used as the working fluid. The test conditions for the present study is given as follows: Ambient inlet air temperature: 25 {+-} 0.3 C. Saturation refrigerant temperature at the inlet of condenser: 45 {+-} 0.2 C. Notice that the present test samples are all 2-circuit design. One of the unique characteristics of the test results reported in this study is a sudden decrease of pressure drop near the completely condensation point. The phenomenon occurs at one circuit is completely condensed and the other is still in two-phase region, and is due to the direct contact condensation after the combination of these two circuits.

Wang, C.C.; Chang, Y.J.; Jang, J.Y.; Lai, C.C.

1999-07-01

25

Experiments with micro-fin tube in single phase  

Energy Technology Data Exchange (ETDEWEB)

This work shows heat transfer and friction characteristics for water single-phase flow in micro-fin tubes. The analysis of thermal and hydraulic behavior from a laminar to a turbulent flow was carried out in an experimental setup with a 9.52 mm diameter micro-fin tube. The tube was wrapped up with an electrical resistance tape to supply a constant heat flux to its surface. Different operational conditions were considered in the heating tests. The inlet and outlet temperatures, differential wall temperatures along the tube, pressure drop and flow rate were measured. The relationships of heat flux and flow rate with heat transfer coefficient and pressure drop were analyzed. Under the same conditions, comparative experiments with an internally smooth tube were conducted. The micro-fin tube provides higher heat transfer performance than the smooth tube (in turbulent flow h{sub micro-fin}/h{sub smooth}=2.9). In spite of the increase in pressure drop ({delta}p{sub micro-fin}/{delta}p{sub smooth}=1.7) the heat transfer results were significantly higher (about 80%). This shows the advantages of this enhanced configuration in thermal performance related to conventional tubes. The smooth tube results were validated by the comparison with the Dittus-Boelter and Gnielinski correlations. For the micro-fin tube an empirical correlation to the heat transfer coefficient adjusted from the set of measured data is proposed. The values obtained are in conformity with experimental results. (author)

Copetti, J.B.; Macagnan, M.H.; De Souza, D.; Oliveski, R.D.C. [Universidade do Vale do Rio dos Sinos, Sao Leopoldo (Brazil). Department of Mechanical Engineering

2004-12-01

26

Recent developments in finned tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

It is stated that major technological innovations have been achieved in the field of finned tube heat exchangers largely used as cooling or heating units, evaporators or condensers in a very wide range of applications within industry, automotive air conditioning and refrigeration. This is mainly due to competition between Japanese, European and American companies eager to increase the quality and performance of their products and to decrease costs of production and materials. Research and development programmes cover enhanced energy performance of thermodynamic processes, compact and lightweight equipment, improvement of reliability connected with mechanical performance and increased resistance to corrosion, vibration and high temperature. The aim of the publication is to present comprehensive reviews, in the form of articles, of the most important technological innovations that have been made recently in Europe, Japan and USA. The innovations concerning components and overall design related to air conditioning in buildings and the automotive industry are described. Experimental data and correlations regarding heat transfer and pressure drop behaviour found in recent literature is presented, and other special subjects are smooth and enhanced plate fins for operation in humid and dry air, condensation of refrigerants inside smooth and enhanced tubes and evaporation inside these tubes. The authors are employed at six European laboratories working under the Strategic Programme for Innovation and Technology Transfer (SPRINT) of the Commission of European Communities. (AB)

Marvillet, C. (ed.)

1994-01-01

27

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

1999-01-01

28

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

Science.gov (United States)

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

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

29

A study on the thermal contact resistance evaluation for fin-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Usually the contact between fin collar and tube surface for fin-tube heat exchanger is secured by mechanical expansion of the tubes. The objective of the present study is to develop a method of measuring the thermal contact resistance between fin collar and tube surface for fin-tube heat exchanger. Also an experimental work has been performed to evaluate the thermal contact resistance, and a rigorous numerical analysis has been employed to calculate the contact resistance from the measured data. The experiments have been conducted for the fin-tube heat exchangers with the tube of outer diameters 7 and 9.52 mm. (author). 6 refs., 6 figs., 6 tabs.

Jeong, J. [Kyung Hee University Graduate School, Yonjin (Korea); Kim, C.N. [Kyung Hee University, Yongin (Korea); Youn, B.; Gil, S.H. [Samsung Electronics Co., Ltd (Korea); Yang, J.S. [Myongji University, Kyonggi-do (Korea)

2000-11-01

30

A study on the thermal contact resistance evaluation for fin-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Usually the contact between fin collar and tube surface for fin-tube heat exchanger is secured by mechanical expansion of the tubes. The objective of the present study is to develop a method of measuring the thermal contact resistance between fin collar and tube surface for fin-tube heat exchanger. Also an experimental work has been performed to evaluate the thermal contact resistance, and a rigorous numerical analysis has been employed to calculate the contact resistance from the measured data. The experiments have been conducted for the fin-tube heat exchangers with the tube of outer diameters 7 and 9.52 mm.

Jeong, J.; Kim, C. N. [Kyunghee Univ., Seoul (Korea, Republic of); Youn, B.; Gil, S. H. [Samsung Electronics Co., Ltd., Seoul (Korea, Republic of); Yang, J. S. [Myongji Univ., Yongin (Korea, Republic of)

2000-07-01

31

Thermofluid characteristics of frosted finned-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

The performance of frosted finned-tube heat exchangers of different fin types is investigated by experiments in this paper. The effects of the air flow rate, the air relative humidity, the refrigerant temperature, and the fin type on the thermofluid characteristics of the heat exchangers are discussed. The time variations of the heat transfer rate, the overall heat transfer coefficient, and the pressure drop of the heat exchangers are presented. The heat transfer rate, the overall heat transfer coefficient, and the pressure drop for heat exchangers with re-direction louver fins are higher than those with flat plate fins and one-sided louver fins are. The amount of frost formation is the highest for heat exchangers with re-direction louver fins. (author)

Wei-Mon Yan; Hung-Yi Li [Huafan University, Taipei (Taiwan). Department of Mechatronical Engineering; Yeong-Ley Tsay [National Huwei Institute of Technology, Yunlin (Taiwan). Department of Aeronautical Engineering

2005-07-01

32

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

33

A Novel Approach to Study the Performance of Finned-Tube Heat Exchangers under Frosting Conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Frost accumulation due to moist air flowing on a refrigeration coil cold surface impacts negatively on performance. The frost layer growth has an insulating effect in terms of heat transfer and causes the increase of the air pressure drop by blocking the free flow area across the coil. In ...

A.L. Bendaoud; M. Ouzzane; Z. Aidoun; N. Galanis

34

Numerical predictions of wavy fin coil performance  

Energy Technology Data Exchange (ETDEWEB)

The wavy fin-and-tube heat exchanger is widely used in the air-conditioning industry. Hence, the ability of numerical codes to predict the thermo-hydraulic performance of this heat exchanger geometry is of considerable interest. Here, a numerical study has been conducted to predict the air-side heat transfer and pressure drop characteristics of a 2-row finned tube heat exchanger having a herringbone wavy fin geometry. The calculations were performed using the FLUENT CFD code. The calculations were performed in three dimensions and account for conduction within the fins. The computational domain was chosen to cover the entire fin length in the air flow direction. The calculations are implemented for the frontal air velocities between 1.0 and 3.0 m/s yielding hydraulic diameter Reynolds number from 380 to 1,150. The uniqueness of this work is inclusion of the tubes in the wavy channel geometry, and use of a three-dimensional (3D) calculation model. The flow and thermal fields in this finned tube heat exchanger as well as the temperature distribution of the fin are presented and described. The fin efficiency is numerically determined and compared with that given by the Schmidt equation (1966) and found to agree within {+-}2.3%. Predictions were performed for a herringbone channel without and with tubes. The tubes considerably increase the pressure drop, but the effect on the average heat transfer coefficient is much smaller. The calculation results are compared with test data taken by Kang and Webb (1997) for a test sample having the same geometry. The FLUENT over predicts the air-side heat transfer coefficient by 13% and pressure drop by 31%.

Min, J.; Webb, R.L.

1999-07-01

35

A Novel Approach to Study the Performance of Finned-Tube Heat Exchangers under Frosting Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Frost accumulation due to moist air flowing on a refrigeration coil cold surface impacts negatively on performance. The frost layer growth has an insulating effect in terms of heat transfer and causes the increase of the air pressure drop by blocking the free flow area across the coil. In this paper a new modeling approach, accounting for heat and mass transfer as well as the hydrodynamics of the problem, is proposed. A related FORTRAN program was developed, allowing the study of a large range of complex refrigerant circuit configurations. This model predicts the dynamic behavior of a refrigeration coil under dry and frosting conditions. Comparisons were made based on the frost mass accumulation and pressure drop across the coil and the results were found to agree reasonably well with experimental results reported in the literature. The model was then applied to study an evaporator typically employed in supermarkets. In terms of refrigerant temperature glide, it was shown that the glide decrease with time because of the decrease of the refrigeration capacity of the coil during the frosting. Further, the air pressure drop is strongly affected by the variation of the free flow area.

A.L. Bendaoud; M. Ouzzane; Z. Aidoun; N. Galanis

2011-01-01

36

Finned Tube With Vortex Generators For A Heat Exchanger.  

Energy Technology Data Exchange (ETDEWEB)

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 least 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, Monohar S. (Idaho Falls, ID); O' Brien, James E. (Idaho Falls, ID)

2004-09-14

37

Finned Tube With Vortex Generators For A Heat Exchanger.  

Energy Technology Data Exchange (ETDEWEB)

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

38

Heat transfer in bundles of finned tubes in crossflow  

Energy Technology Data Exchange (ETDEWEB)

This book provides correlations of heat transfer and hydraulic data for bundles of finned tubes in crossflow at high Reynolds numbers. Results of studies of the effectiveness of the fin, local, and mean heat transfer coefficients are presented. The effect of geometric parameters of the fins and of the location of tubes in the bundle on heat transfer and hydraulic drag are described. The resistance of the finned tube bundles under study and other factors are examined.

Stasiulevicius, J.; Skrinska, A.; Zukauskas, A.; Hewitt, G.F.

1986-01-01

39

Tube an fin assembly exchangers in power plants  

International Nuclear Information System (INIS)

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

1989-09-12

40

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)

1981-12-18

 
 
 
 
41

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; Vijay R. Raghavan

2011-01-01

42

Heat and mass transfer for compact fin-tube heat exchangers having plain fin geometry  

Energy Technology Data Exchange (ETDEWEB)

The air side heat performance for four compact fin-and-tube heat exchangers having plain fin configuration under dehumidifying conditions were reported in this study. Tests were conducted in a circulation wind tunnel. It consists of a closed loop wind tunnel in which air is circulated by a variable speed centrifugal fan (7.46 kW, 10 HP). The air duct is made of galvanized steel sheet and has a 850 mm x 550 mm cross-section. The dry-bulb and wet-bulb temperatures of the inlet air are controlled by an air-ventilator that can provide a cooling capacity up to 21.12 kW (6RT). The air flowrate measurement station is an outlet chamber setup with multiple nozzles. The test results indicate that the heat transfer coefficients are relatively insensitive to change of inlet condition. However, the pressure drops are strongly related to the inlet conditions and fin pitch. For a larger fin pitch like 1.78 mm, the pressure drops for RH = 90% are approximately 10--20% higher than those of RH = 50%. Further reduction of fin pitch to a smaller value of 1.22 mm would significantly increase the pressure drops. The pressure drops for RH = 90% are approximately 20--45% higher than those of RH = 50%. Possible explanation of this phenomenon may be due to the effect of condensate retention.

Wang, C.C.; Hu, Y.Z.R.; Chi, K.Y.; Chang, Y.P.

1999-07-01

43

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

44

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

International Nuclear Information System (INIS)

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

1981-01-01

45

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)

1988-01-01

46

Microscopic and macroscopic fin-collar effects in the prediction of finned-tube contact  

Energy Technology Data Exchange (ETDEWEB)

This work developed a methodology that will enable the future development of a generalized correlation of thermal-contact conductance for the test samples of plate finned tubes (coils). This was accomplished by determining the local (microscopic) contact conductances and the fin-collar (macroscopic) resistances of coils. These two parameters were not taken into account while formulating the previous correlation. Experimental data for test samples of coils operating under vacuum were obtained from recent American Society of Heating, Refrigeration, and Air-Conditioning Engineers' sponsored projects. These data were utilized to correct the prediction of thermal-contact conductance of the fin by taking into account the effect of fin collars. The only available hypothetical contact pressure distribution in the literature was modified to take into account of a variable local pressure and the interference at the interface of tube and the fin. In turn, this pressure distribution was related to the microscopic contact conductance of the fin. Steady-state heat conduction through the tube to a fin collar resulted in a mixed boundary-value problem. The software Interactive Thermal Analysis System (I/TAS) available for use with a microcomputer based on the nodal method was used to solve a set of these problems. This enabled the determination of the macroscopic thermal contact conductance of fin collars.

Shah, P.R.

1986-01-01

47

Effect of fin spacing on convection in a plate fin and tube heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

We examine the influence of fin spacing on the over-tube side of a single-row fin-tube heat exchanger through flow visualisation and numerical computation. The distance between fins is nondimensionalised by the tube diameter. If this parameter is small, the flow is Hele-Shaw; as it is increased, a horseshoe vortex is formed just upstream of the tube; a separated region is then developed behind the tube; this becomes larger and eventually communicates with the fluid downstream of the heat exchanger. A peak in the Nusselt number occurs at the horseshoe vortex. In the wake region the Nusselt number is very small but increases when there is fluid exchange with that downstream. The ratio of the overall Nusselt number per unit length to the nondimensional pressure drop is found to show a maximum. (Author)

Romero-Mendez, Ricardo; Sen, Mihir; Yang, K.T.; McClain, Rodney [Notre Dame Univ., Dept. of Aerospace and Mechanical Engineering, Notre Dame, IN (United States)

2000-01-01

48

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

Science.gov (United States)

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

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

49

Experimental determination of heat transfer and friction in helically-finned tubes  

Energy Technology Data Exchange (ETDEWEB)

Heat transfer coefficients and friction factors were determined experimentally for eight helically-finned tubes and one smooth tube using liquid water at Reynolds numbers ranging from 12,000 to 60,000. The helically-finned tubes tested in this investigation have helix angles between 25 and 48 , number of fin starts between 10 and 45, and fin height-to-diameter ratios between 0.0199 and 0.0327. An uncertainty analysis was completed and plain-tube results were compared to the Blasius and Dittus-Boelter equations with satisfactory agreement. Power-law correlations for Fanning friction and Colburn j-factors were developed using a least-squares regression. The performance of the correlations was evaluated with data of other researchers with average prediction errors between 30% and 40%. (author)

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

2008-01-15

50

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

Energy Technology Data Exchange (ETDEWEB)

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.

Kang, Soo Young; Lee, Jong Jun; Kim, Tong Seop [Inha Univ., Incheon (Korea, Republic of)

2009-07-01

51

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; P. Selvakumar

2013-01-01

52

Effect of finned tube arrangement on the dimensions of natural draught dry cooling towers  

Energy Technology Data Exchange (ETDEWEB)

Experimental investigations in connection with the dimensioning of natural draught dry cooling towers undertaken by the Department for Heat Transfer and Climatology are aimed at discovering favourable tube arrangements for the heat exchange system, which permit small construction size for such cooling towers. Systematic variations in tube spacing in the direction of flow and of tube arrangement in a system comprising spiral finned tubes indicate that optimum configurations are available for prescribed cooling performance in relation to tower dimensions.

Becker, N.; Renz, U.

1982-02-01

53

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

Directory of Open Access Journals (Sweden)

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

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

2010-01-01

54

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

Scientific Electronic Library Online (English)

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

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

2010-12-01

55

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

Science.gov (United States)

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

Takahashi, Hiroyuki; Saeki, Chikara; Koyama, Shigeru

56

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

Science.gov (United States)

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

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

2012-11-01

57

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

58

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

Science.gov (United States)

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

Yonemoto, Ryuichiro; Koyama, Shigeru

59

Finned tube banks configuration for the utilization of waste heat from a gas turbine station  

Energy Technology Data Exchange (ETDEWEB)

In this work, a computational model was developed to predict and analyze static behavior in two different systems of dual-pressure finned tube banks to be used behind a gas turbine station without a pre-existing heat recovery system. The relevant physical phenomena were accounted for by means of a non-linear approach and the difference between water and steam velocities in finned tubes. Simulations were also done considering the effects of exhaust gas parameters and tube length on the flow-fields of the working fluid. The results revealed the different static performance of these models on the sides of the working fluid and exhaust gas. (authors)

Ngoma, Guyh Dituba [Department of Applied Sciences, University of Quebec in Abitibi-Temiscamingue, 445, Boulevard de l' Universite, Rouyn-Noranda, Quebec, J9X 5E4 (Canada); Sadiki, Amsini [Department of Energy and Power Plant Technology, Darmstadt University of Technology, Petersenstrasse 30, 64287 Darmstadt (Germany)

2005-08-01

60

Experimental investigation of water sprayed finned heat exchanger tube bundles  

International Nuclear Information System (INIS)

[en] 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

1987-01-01

 
 
 
 
61

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

2012-01-01

62

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

63

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.

2001-01-01

64

Evaporation heat transfer and pressure loss in micro-fin tubes and a smooth tube  

Energy Technology Data Exchange (ETDEWEB)

Evaporation heat transfer coefficient and pressure loss were measured for three different micro-fin tubes and a smooth tube. The experiments were carried out with R-22 over a wide range of vapor quality, mass velocity and heat flux. Heat transfer coefficient of the tube with slightly modified fin shape was found to be higher than that of the commercial reference tube by 60%. The improvement of heat transfer has been achieved without noticeable increase of pressure loss. Heat transfer coefficient was increased with increasing quality, refrigerant mass flux, and heat flux. However, the effect of refrigerant mass flux and heat flux was not great. Heat transfer coefficient at bottom was lower than that at top of the tube in low quality region, which suggested the existence of stratification in the micro-fin tube. Pressure drop was linearly increased with increasing refrigerant quality and was proportional to about square of mass flux. 8 refs., 11 figs., 2 tabs.

Jang, S.H.; Jeong, S.Y. [Sogang University, Seoul (Korea); Hong, Y.K. [Samsung Electronics Co., Ltd. (Korea)

1999-03-01

65

Heat transfer coefficients and pressure drops for R-134a and an ester lubricant mixture in a smooth tube and a micro-fin tube  

Energy Technology Data Exchange (ETDEWEB)

This paper reports average heat transfer coefficients and pressure drops during the evaporation and condensation of mixtures of R-134a and a 150 SUS penta erythritol ester branched-acid lubricant. The smooth tube and micro-fin tube tested in this study had outer diameters of 9.52 mm (3/8 in.). The micro-fin tube had 60 fins, a fin height of 0.2 mm (0.008 in), and a spiral angle of 18{degree}. The objective of this study is to evaluate the effectiveness of the micro-fin tube with R-134a and to determine the effect of circulating lubricant. The experimental results show that the micro-fin tube has distinct performance advantages over the smooth tube. For example, the average heat transfer coefficients during evaporation and condensation in the micro-fin tube were 50--200% higher than those for the smooth tube, while the average pressure drops were on average only 10--50% higher. The experimental results indicate that the presence of a lubricant degrades the average heat transfer coefficients during both evaporation and condensation at high lubricant concentrations. Pressure drops during evaporation increased with the addition of a lubricant in both tubes. For condensation, pressure drops were unaffected by the addition of a lubricant.

Eckels, S.J. [Kansas State Univ., Manhattan, KS (United States); Doerr, T.M.; Pate, M.B. [Iowa State Univ., Ames, IA (United States). Mechanical Engineering Dept.

1998-10-01

66

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; R. K. Kirar

2012-01-01

67

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

68

Numerical Investigations for the Optimization of Serrated Finned-Tube Heat Exchangers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Helical serrated finned-tubes are well established in many thermal systems. This paper presents the results of numerical calculations carried out for the performance improvement of these devices. The work is divided into three main investigations conducted for Reynolds numbers betwe...

69

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

70

Heat Transfer and Fin Performance Comparison between Constructal T-shaped Porous and Solid Fin  

Science.gov (United States)

In this literature, constructal theory is applied to compare the heat transfer rate and the fin performance between a T-shaped porous fin and that of solid fin, which are exposed in a convective environment. Adomian decomposition method has been applied for solving governing equation of stem and flange part of the fin. This method provides an explicit form of analytical solution from which temperature distribution and performance analysis can easily be performed. Though the fin performance parameters are reduced a little bit but heat transfer rate can be enhanced as compared to solid fin under same geometric and flow conditions.

Bhanja, D.; Kundu, B.

2010-10-01

71

A study on the development of fouling evaluation method for finned tube heat exchanger  

International Nuclear Information System (INIS)

Heat exchangers in nuclear power plants are used for various purposes, such as safe shutdown of nuclear reactor, increase of thermal efficiency, maintenance of temperature inside building, final heat sink, reduction of thermal stress by cold water injection, etc. As operating time of these heat exchangers progresses, fouling generated by water-borne deposits increases and thermal performance decreases. Even though thermal performance tests for heat exchangers without phase change in domestic nuclear power plants have performed with a fixed interval, thermal performance tests for finned tube heat exchangers with condensation have not performed to date. This paper describes the development of fouling evaluation method for finned tube heat exchangers and the result of prototype evaluation for the heat exchanger using the mixture of C3 and N-C4 as a refrigerant.

2004-01-01

72

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

International Nuclear Information System (INIS)

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

2005-01-01

73

Investigation of enhancement of steam condensation heat transfer on finned tubes with porous drainage strips  

Energy Technology Data Exchange (ETDEWEB)

Condensation of steam on horizontal finned tube with porous drainage strip was investigated experimentally and theoretically. Composite metal screens were used as porous drainage strip. Distilled water was taken in the experiments as working fluid. The experiments were carried out to find the structure effects of composite screen drainage strip on the condensation heat transfer on finned tubes with fin spacing of 0.5mm. Influences of the mesh number of both outer and inner layers and of length and thickness of the drainage strip were investigated. The outer layers of the screens have the mesh numbers of 100, 150, 185 and 220, which lead to different effective pore radius; the inner layers have the mesh numbers of 20, 30 and 40, which lead to different permeability. Strip lengths are 15mm, 20mm and 30mm, while the thickness is 2mm, 4mm and 6mm. Experimental results show that the structure parameters of the porous drainage strip strongly influence condensation on the finned tube. A porous strip having small effective pore radius on the outer layer as well as large permeability, reasonably large length and thickness will lead to excellent performance. In the tested ranges, for steam condensation on a 0.5mm spacing finned tube, the optimum structure of a composite screen drainage strip is of 150 mesh outer layer screen, 20 mesh inner layer screen, 30mm long and 4mm thick. The enhanced condensation heat transfer coefficients are equivalent to 1.15{approximately}1.74 times that of the finned tube and 2.08{approximately}3.08 times that of the plain tube. A new prediction model of condensation on finned tube with porous drainage strip was established. The condensate flow in the interfin grooves and in the porous strip was treated as flow through two kinds of porous medium with different structures. The momentum equation of single phase flow in porous medium was used to solve the condensate flow. The equation was analyzed and several terms were neglected because of their little influences on the present problem. The non-Darcy effect caused by the high Reynolds number in the tiny channels was considered. As a result, micro-scale inertial force term was involved in the control equation. The effective driving force of condensate in the porous drainage strip was defined. It reflects the total effect of forces exerted on the condensate and is helpful to analyze influences of strip parameters. The length of pendant part which could only be obtained by previous experiments was determined by a model based on simulation experiments. The condensation model is validated by present and the other investigation experimental data.

Liu Xijuan; Ma Tongze; Zhang Zhengfang

1999-07-01

74

Experimental study on thermal performance of filled-type evacuated tube with U-tube  

Science.gov (United States)

The filled-type evacuated tube with U-tube, in which the filled layer is used to transfer energy absorbed by working fluid in the U-tube, is proposed to eliminate the effect of thermal resistance between the absorber tube and copper fin of the conventional solar collector. In this paper, the thermal performance of the filled-type evacuated tube was researched by means of experimental study. In order to avoid the effect of some uncertain factors, the single collector tube was considered as investigated objective. The test setup of the thermal performance of the filled-type evacuated tube with U-tube was established. The results show that the filled-type evacuated tube with U-tube has a favorable thermal performance compared with the evacuated tube with copper fin. The heat efficiency of filled-type evacuated tube is higher than that of copper fin evacuated tube by 12%. The useful energy gain of filled-type evacuated tube is 22% higher than that of copper fin evacuated tube at the practical irradiance received I T = 800 W/m2 and flow rate M f = 0.005 L/s. In addition, the exergy efficiency of the filled-type evacuated tube is higher than that of copper fin evacuated tube.

Liang, Ruobing; Ma, Liangdong; Zhang, Jili; Zhao, Dan

2012-06-01

75

Experimental study of R134A condensation heat transfer inside the horizontal micro-fin tubes  

Science.gov (United States)

The Investigation of the two-phase flow patterns and their transitions during the condensation has gained increasing interest and importance from the well-known phenomenon that the heat transfer characteristics are strongly dependent on the flow patterns. Therefore, it is very important to study on which heat transfer enhancement approach is suitable for an individual flow pattern inside a condenser, so that an accurate heat transfer mechanism can be understood that is consistent with the flow patterns. The condensation heat transfer for R134a in the two kinds of in-tube three-dimensional (3-D) micro-fin tubes with different geometries is experimentally investigated. Based on the flow pattern observations, the flow patterns in the Soliman flow regime map are divided into two-flow regimes; one with the vapor-shear-dominant annular regime and the other with the gravitational-force-dominant stratified-wavy regime. The flow regime transition criterion between the annular regime and the stratified-wavy regime is at Fr equal to 2. In the annular regime, the heat transfer coefficients h of the two kinds of in-tube 3-D micro-fin tubes decreases as the vapor quality x decreases. The regressed condensation heat transfer correlation from the experimental data of the annular flow region is obtained. The dispersibility of the experimental data is inside the limits of ±25%. In the stratified-wavy regime, the average heat transfer coefficient h of the two kinds of in-tube 3-D micro-fin tubes increases as the mass flux increases and the number of micro fins in the 3-D micro-fin tube is not the controlling factor for the performance of a condensation heat transfer. The regressed condensation heat transfer correlation of the stratified-wavy flow regime is experimentally obtained. The dispersibility of the experimental data is inside the limits of ±22%. Combined with the criteria of flow pattern transitions, the correlations can be used for the design of a condenser with 3-D micro-fin tubes.

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

2005-07-01

76

Vortex shedding from tube banks with serrated fin; Serrated fin tsuki kangun kara no uzu hoshutsu ni kansuru kenkyu  

Energy Technology Data Exchange (ETDEWEB)

We measured a vortex shedding frequency, gap velocity and the intensity of velocity fluctuation in the fin-tube banks set in a wind tunnel. Two discrete peaks were formed in the spectrum of the velocity fluctuation at the frequencies of 115 Hz and 74 Hz. The vortex shedding phenomena with those frequencies were independent with each other. The peak of 115 Hz mainly formed within the fin-tube banks and the other peak of 74Hz was in the wake of the fin-tube banks. The applicability of the equivalent diameter obtained by a single circular cylinder with serrated fin to the fin-tube banks was examined. Strouhal numbers were calculated by using the measured values of vortex frequency, gap velocity and the equivalent diameter, Strouhal number in case of 115Hz agreed well with Strouhal number 0.3 obtained from Fitz-Hugh map for tube banks without fin, and the other Strouhal number in case of 74Hz was about 0.18 which is similar to vortex shedding from a circular cylinder. (author)

Hamakawa, H. [Oita University, Oita (Japan); Fukano, T. [Kyushu University, Fukuoka (Japan); Nishida, E. [Babcock Hitachi K.K., Tokyo (Japan); Shoda, Y. [Toshiba Corp., Tokyo (Japan); Morooka, T. [Kawasaki Heavy Industries, Ltd., Kobe (Japan)

2000-06-25

77

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

Energy Technology Data Exchange (ETDEWEB)

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

O' Brien, James Edward; Sohal, Manohar Singh

2000-08-01

78

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

International Nuclear Information System (INIS)

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

2010-01-01

79

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

International Nuclear Information System (INIS)

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

2007-01-01

80

Externally finned circular tube immerse in a phase-change material  

Energy Technology Data Exchange (ETDEWEB)

In an attempt to increase the heat transfer rate and reduce the convective currents during the freezing of phase change materials (PCM) in storage tanks, externally finned circular tubes are studied experimentally. The parameters analysed in this work include number of fins, fin length, initial degree of superheat and freezing time.

Alves, C.L.F. [CTA-ITA, Campos, S.P. (Brazil); Ismail, K.A.R. [DEM-FEC-UNICAMP, Campinas, S.P. (Brazil)

1985-07-01

 
 
 
 
81

Heat Transfer between Horizontal Finned Tubes and a Gas-Solid Fluidized Bed  

Energy Technology Data Exchange (ETDEWEB)

The heat-transfer coefficients are measured between electrically heated V-thread tubes and square fluidized beds of alumina and silica sand. The effect of particle size, mass fluidizing velocity, V-thread pitch, and tube pitch on the heat transfer rate is investigated. One-dimensional and two-dimensional heat conduction models are developed for determining the temperature distribution in a V-thread fin. The models are used to calculate the corrected heat-transfer coefficients for the finned tubes. A correlation for the fin effectiveness factor is proposed and is found to be reliable to predict its value for finned tubes with geometry and orientation similar to that in the present investigation. The correlation in conjunction with the existing correlatins for the heat-transfer coefficient for smooth tubes is found, in general, to predict the coefficients for finned tubes immersed in a fluidized bed within + or - 25%.

Grewal, N.S.; Cheung, T.K.; Saxena, S.C.

1985-04-01

82

Heat transfer analysis of a finned-tube evaporator for engine exhaust heat recovery  

International Nuclear Information System (INIS)

Highlights: ? The characteristic of the exhaust waste heat for a light duty diesel engine is analyzed. ? A mathematical model is established for a finned-tube evaporator used in an ORC. ? The heat transfer performance of the finned-tube evaporator is evaluated throughout the engine’s operating region. - Abstract: The organic Rankine cycle (ORC) can be used to recover waste heat from an internal combustion engine. In such a system, the evaporator design is critical. Determining the amount of heat that can be transferred in a designed evaporator is extremely important for a successful ORC system. In this paper, the performance of a finned-tube evaporator used to recover exhaust waste heat from a diesel engine is presented. First, the exhaust heat of the chosen diesel engine is evaluated based on the measured data. Subsequently, a mathematical model of the evaporator is created based on the detailed geometry and the specific ORC working conditions. Then, the heat transfer of the evaporator is estimated as the diesel engine runs through all of its operating regions defined by the engine speed and the engine load. The results show that the exhaust temperature at the evaporator outlet increases with engine speed and engine load. Although the convective heat transfer coefficient of the organic working fluid is significantly larger than that of the exhaust gas, the overall heat transfer coefficient is slightly greater than that of the exhaust gas. Furthermore, the heat transfer rate is the greatest in the preheated zone and least in the superheated zone. Consequently, the heat transfer area for the preheated zone is nearly half of the total area. In addition, the area of the superheated zone is slightly greater than that of the two-phase zone. It is concluded that the heat transfer area for a finned tube evaporator should be selected carefully based on the engine’s most typical operating region.

2013-01-01

83

Optimum dimensions of the continuous plate fin for various tube arrays  

Energy Technology Data Exchange (ETDEWEB)

The finite-difference and sector methods are applied to determine the efficiency of the continuous plate fin pierced by a regularly spaced array of circular tubes in staggered or in-line tube arrays. The comparison of the fin efficiency between the present numerical results, approximate solutions obtained from the sector method, and previous results is made. It is found that the sector method underpredicts the efficiency of the hexagonal and rectangular fins. However, the previous methods can overpredict the fin efficiency for lower r{sub o}/a values. Results also show that the plate fin with the staggered tube array is more efficient than that with the in-line tube array. A simple expression relating the fin efficiency to the tube radius, tube spacing, fin thickness, and material properties is obtained by using the least-squares fitting of numerical data. The main purpose of the present study is to determine the optimum dimensions of the continuous plate fin with various tube arrays that can give the greatest amount of heat dissipation under the conditions of the given physical quantities.

Chen, H.T.; Liou, J.T. [National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Mechanical Engineering

1998-08-07

84

The compact circulating fluidized bed boiler with a finned tube impact separator and a uniflow square cyclone  

Energy Technology Data Exchange (ETDEWEB)

Institute for Thermal Power Engineering, Zhejiang University has introduced a circulating fluidized bed boiler with two stage compact separation. A finned tube impact separator is located at the outlet of the furnace and a uniflow square cyclone is adopted behind the superheater. The flow characteristics of the finned tube separator are measured using a three dimensional particles dynamics analyzer. The measurements show that the reflux flow existing near the front of a finned tube has a very important effect on particle separation. The shape of a uniflow square cyclone is different with a conventional uniflow cyclone and can be laid conveniently in the flue duct of the boiler. A lot of experimental studies have been done focusing on the above separators' performances. The experimental results show that separation efficiency of the uniflow square cyclone can be up to 99% for particles with mean size 0.167 mm and its pressure drop is lower than 1,000 Pa. To change the shape of the cyclone's exhaust pipe is very effective. Based on the results, the optimization design of the separators is reported. The finned tube impact separator has been successfully applied in several circulating fluidized bed boilers. Institute for Thermal Power Engineering, Zhejiang University has designed a compact circulating fluidized bed boiler with the finned tube impact separator and a uniflow square cyclone, and the boilers capacity is 65 t/h (12 MWe).

Li Xiaodong; Chi Yong; Yan Jianhua; Jiang Xuguang; Yang Jialin; Huang Guoquan; Ni Mingjiang; Cen Kefa

1999-07-01

85

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

86

A study on airside performance of geometry combination fins using large scale model  

Energy Technology Data Exchange (ETDEWEB)

This study investigated the pressure drop and heat transfer characteristics of heat exchanger according to the arrangement of fins as well as fin configuration by the similitude experiments with the finned-tube geometry scaled as large as four times. Colburn j factor, Fanning friction factor, f, and goodness factors are compared to each other to estimate performance of each case for four different kinds of fins, which are louver, double side slit, single side slit and plain fin. Results show that heat transfer would be altered by fin arrangement and that friction loss is more affected by fin configurations than by the fin arrangements. In particular, heat transfer depends more on the shape of front row than that of rear row. The heat transfer rate of combined fin arrangement increases a lot more under the same pressure drop than that of conventional fin arrangement. This indicates that the heat exchanger of higher efficiency would be designed by the proper combination of fins of different shapes. (author)

Byun, Ju-Suk; Lee, Jinho [School of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Jeon, Chang-Duk [Department of Mechanical Engineering, Chungju National University, Chung-Buk 380-702 (Korea, Republic of); Mok, Jinho [Samsung Electronics Co., Ltd., Suwon-City, Gyeonggi-Do 443-742 (Korea, Republic of)

2006-09-15

87

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

Energy Technology Data Exchange (ETDEWEB)

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

Rubin, I.R.; Pul' kin, I.N.; Roizen, L.I.

1986-03-01

88

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

International Nuclear Information System (INIS)

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

1986-01-01

89

Experimental study and modelling of heat transfer during condensation of pure fluid and binary mixture on a bundle of horizontal finned tubes  

Energy Technology Data Exchange (ETDEWEB)

An experimental investigation was conducted to measure the local heat transfer coefficient for each row in a trapezoidal finned horizontal tube bundle during condensation of both pure fluid (HFC 134a) and several compositions of the non-azeotropic binary mixture HFC 23/HFC 134a. The test section is a 13x3 (rows x columns) tube bundle and the heat transfer coefficient is measured using the modified Wilson plot method. The inlet vapour temperature is fixed at 40{sup o}C and the water flow rate in each active row ranges from 170 to 600 l/h. The test series cover five different finned tubes all commercially available, K11 (11 fins/inch), K19 (19 fins/inch), K26 (26 fins/inch), K32 (32 fins/inch), K40 (40 fins/inch) and their performances were compared. The experimental results were checked against available models predicting the heat transfer coefficient during condensation of pure fluids on banks of finned tubes. Modelling of heat exchange during condensation of binary mixtures on bundles of finned tubes based on the curve condensation model is presented. (author)

Belghazi, M.; Marvillet, C. [Commissariat a l' Energie Atomique, Grenoble (France). Groupement pour la Recherche sur les Echangeurs thermiques; Bontemps, A. [Universite Joseph Fourier, Grenoble (France). LEGI/GRETh

2003-03-01

90

A study on the thermal contact conductance in fin-tube heat exchangers with 7mm tube  

Energy Technology Data Exchange (ETDEWEB)

The thermal contact resistance has been frequently neglected in the process of design of heat exchangers because of the difficulty of measurement and the lack of accurate data. However, the thermal contact resistance is one of principal parameters in heat transfer mechanism of fin-tube heat exchangers. The objective of the present study is to investigate new factors such as fin types and manufacturing types of the tube affecting the thermal contact conductance and to find a correlation between the thermal contact conductance and the effective factors in fin-tube heat exchangers with 7mm tube. The thermal contact conductances in the 22 heat exchangers with 7mm tube have been investigated through the experimental-numerical method. A numerical scheme has been employed to calculate the thermal contact conductance and the portion of thermal resistances using the experimental data. As a result, the thermal contact conductance has been evaluated quantitatively, and a new correlation including the influence of new factors such as fin types and manufacturing types of the tube has been developed in the fin-tube heat exchanger with 7mm tube. Also, the portion of each thermal resistance has been evaluated in each case. (author)

Jeong, Jin [Department of Mechanical Engineering, Graduate School of KyungHee University, 1 Seochon, Kihung, Yongin, Kyunggi 449-701 (Korea, Republic of); Kim, Chang Nyung [College of Advanced Technology, KyungHee University, 1 Seochon, Kihung, Yongin, Kyunggi 449-701 (Korea, Republic of); Youn, Baek [System Appliances Division, Samsung Electronics Co., Ltd, 416 Maetan-3Dong, Yeongtong, Suwon, Kyunggi 443-742 (Korea, Republic of)

2006-04-15

91

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.

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

2012-01-01

92

Determination of local heat transfer coefficient on the surface of longitudinally finned tubes  

Energy Technology Data Exchange (ETDEWEB)

The distribution of the heat transfer coefficient is calculated from temperature measurements at interior points of the solid, and the measured fluid temperature. The unknown parameters associated with the solution were selected to achieve the closest least squares agreement between the computed and measured temperatures using the Levenberg-Marquardt method. The nonlinear least - squares problem is parameterised by assuming the stair-case changes of the heat transfer coefficient on the boundary, or by expressing the space variations of the heat transfer coefficient in its functional form. The determination of the circumferential heat transfer coefficient distribution on the heated tube with two longitudinal fins in cross flow demonstrates the accuracy of the developed method. The actual experimental data were used. Experiments were performed with an array of vertical tubes arranged in staggered pattern. (orig.)

Sobota, T.; Taler, J. [Cracow Univ. of Technology (Poland). Inst. of Process and Power Engineering

2008-06-15

93

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

2013-01-01

94

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 worse.

2005-01-01

95

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

Energy Technology Data Exchange (ETDEWEB)

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{sub 1}/d varies from 1.2 to 3, and the longitudinal tube pitch S{sub 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 worse. (author)

He, Y.L.; Tao, W.Q.; Song, F.Q.; Zhang, W. [Xian Jiaotong University (China). School of Energy and Power Engineering

2005-06-01

96

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

97

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

1981-01-01

98

Heat transfer analysis of phase change process in a finned-tube thermal energy storage system using artificial neural network  

Energy Technology Data Exchange (ETDEWEB)

In this study, a feed-forward back-propagation artificial neural network (ANN) algorithm is proposed for heat transfer analysis of phase change process in a finned-tube, latent heat thermal energy storage system. Heat storage through phase change material (PCM) around the finned tube is experimentally studied. A numerical study is performed to investigate the effect of fin and flow parameter by the solving governing equations for the heat transfer fluid, pipe wall and phase change material. Learning process is applied to correlate the total heat stored in different fin types of tubes, various Reynolds numbers and different inlet temperatures. A number of hidden numbers of ANN are trained for the best output prediction of the heat storage. The predicted total heat storage values obtained by an ANN model with extensive sets of non-training experimental data are then compared with experimental measurements and numerical results. The trained ANN model with an absolute mean relative error of 5.58% shows good performance to predict the total amount of heat stored. The ANN results are found to be more accurate than the numerical model results. The present study using ANN approach for heat transfer analysis in phase change heat storage process appears to be significant for practical thermal energy storage applications. (author)

Ermis, Kemal [Department of Mechanical Education, Sakarya University, Sakarya, 54187 (Turkey); Faculty of Engineering and Applied Science, University of Ontario Institute of Technology (UOIT), 2000 Simcoe Street North, Oshawa, Ont. (Canada); Erek, Aytunc [Department of Mechanical Engineering, Dokuz Eylul University, Bornova, 35100 Izmir (Turkey); Dincer, Ibrahim [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology (UOIT), 2000 Simcoe Street North, Oshawa, Ont. (Canada)

2007-07-15

99

Finned or serrated rod baffles for finned tube-shell heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

A rod baffle is described comprising: parallel solid for hollow rods; at least some of these rods having longitudinal fins such that they have a cross-section of a serrated circle in at least some areas along the rod; the rods being arranged in the baffle to enable the engagement of the rods with adjacent elements; the rods being mounted as parallel chords across a generally circular support member to form the rod baffle.

Mc Clintock, W.A.

1987-04-14

100

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

Energy Technology Data Exchange (ETDEWEB)

Solar flat plate collectors can be used to produce domestic hot water or to preheat ventilation air through connection to the space heating system. There are several types of solar flat plate collectors. In terms of flat plate collector design, obtaining a heat transfer coefficient is necessary. There are varieties of flat plate collectors with different cross-sections such as circular, rectangular, hexagonal, and rhombic. Sunstrip fins manufactured by Thermo Dynamics Ltd, has a rhombic and cross section with round corners. This type is widely used in solar thermal systems, offering advantages over other fins such as, high thermal performance, light weight and high rigidity due to their construction. Due to the lack of literature on forced-convection heat transfer in a solar collector with rhombic cross-section absorbing tubes, a series of experiments was prepared and conducted to determine the heat transfer coefficient. A typical rhombic cross-section finned tube of flat-plate collectors was 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 the hydraulic diameter for various heat fluxes. The temperature distribution along the finned tube for the fluid and the wall were also illustrated. 8 refs., 6 figs.

Taherian, H.; Yazdanshenas, E. [Mazandaran Univ., Babol (Iran, Islamic Republic of). Faculty of Mechanical Engineering

2006-07-01

 
 
 
 
101

Effects of oil on boiling R-123 and R-134a flowing normal to an integral-finned tube bundle  

Energy Technology Data Exchange (ETDEWEB)

Local, experimental heat transfer coefficients have been measured for boiling refrigerant flowing up and across a tube bundle segment representing a full flooded evaporator tube bundle. R-123 and R-134a data with 26 fins per inch (1,024 fins per meter) tubes have been obtained. The refrigerant enters at 15% vapor quality and exits at nearly 100% vapor in order to simulate an actual flooded evaporator bundle. The nominal area heat flux was varied from 2,607 to 10,427 Btu/h{center{underscore}dot}ft{sup 2} (8,224 to 32,893 W/m{sup 2}) as the tube bundle oil content ranged from 0 to 15% (by weight) for each refrigerant/tube combination. The performance of R-22 without oil has also been determined. Local tube and bulk fluid temperatures were measured directly by thermocouples to calculate the refrigerant-side heat transfer coefficients. The bundle segment saturation temperature set point (taken at the top of the tube bundle) is 40 F (4.4 C).

Tatara, R.A.; Payvar, P.

1999-07-01

102

Numerical prediction of flow and heat transfer in a tube with circumferential fins and circular disks  

Energy Technology Data Exchange (ETDEWEB)

The characteristics of fluid flow and heat transfer were numerically analyzed for hydrodynamically and thermally developing laminar flow in a tube with circumferential fins and circular disks. Computations were carried out for a variety of flow conditions and geometric arrangements for the fins and disks, and the effects of these on heat transfer enhancement and pressure drop were studied. In order to quantify the heat transfer enhancement effects of the fins and disks in a tube, the Nusselt numbers for various configurations were compared to those for a corresponding smooth tube. In addition, the flow pattern and the local Nusselt number of developing flow as well as the overall Nusselt numbers for both developing and fully developed flows were presented with associated increase in pressure drop. It was found that the flow was fully developed after passing two consecutive fins from the entrance, and that not only heat transfer enhancement but also pressure drop increase were significant with the fins and disks. And, it was known that heat transfer enhancement and pressure drop increase are strongly dependent on Reynolds number and the fin height rather than the size of the disk.

Jeon, K.; Seo, T.; Lee, C.; Kim, C.

1999-07-01

103

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

104

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; B.Senthil Kumar

2012-01-01

105

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

Energy Technology Data Exchange (ETDEWEB)

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. (author)

Jin Jeong [Kyunghee University (Korea). Dept. of Mechanical Engineering; Chang Nyung Kim [Kyunghee University (Korea). College of Advanced Technology; Baek Youn; Young Saeng Kim [Samsung Electronics Co. Ltd (Korea)

2004-12-01

106

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

Energy Technology Data Exchange (ETDEWEB)

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.

Jeong, Jin; Nyung Kim, Chang; Youn, Baek; Saeng Kim, Young

2004-12-01

107

Optimal configuration of cross flow plate finned tube condenser based on the second law of thermodynamics  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a mathematical model for determining optimal configuration of plate finned tube condensers widely used in air conditioning system. The condenser investigated in this work is a cross-flow air-refrigerant type with aluminium plain fin geometry. Refrigerant HFC 134a flows inside while air flows outside the copper tubes. Minimum entropy change of air and refrigerant is used as the criterion for analysis. This entropy change resulting from losses due to heat transfer and pressure drop can be represented in a form of entropy generation number, N{sub s}. The proposed mathematical model is divided into three regions: superheated, two-phase and sub-cooled regions. Effects of heat transfer and pressure drop of air side and refrigerant side on entropy generation rate are simultaneously analyzed through the implicit method. Results from the mathematical model show that entropy generation number decreases with increasing fin pitch and decreasing number of rows and tube diameter. In addition, this work also presents an optimal configuration of condenser. The optimal tube diameter and the number of fin per inch are 6.35-12.7 mm ((1)/(4)-(1)/(2) inch) and 11-12, respectively. (author)

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

2008-11-15

108

Condensation of r-134a on horizontal integral-fin titanium tubes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Experimental research was conducted to evaluate the condensation of R-134a on horizontal smooth and integral-fin (32 fpi) titanium tubes of 19.05 mm outer diameter. Experiments were carried out at saturation temperatures of 30, 40 and 50 °C and wall subcoolings from 0.5 to 9 °C. The...

109

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

110

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

International Nuclear Information System (INIS)

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

1989-01-01

111

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

International Nuclear Information System (INIS)

[en] 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.

2009-06-21

112

A new model for forced-convection condensation on integral-fin tubes  

Energy Technology Data Exchange (ETDEWEB)

Integral-fin tubes are extensively used in shell-and-tube condensers for refrigeration. This work investigates the effects of vapor shear during pure vapor external condensation on horizontal integral-fin tubes. More than 220 experimental data-points in a wide range of operative conditions and enhanced surface geometries are reported together with the visual observation of the condensate flow patterns. The effects of vapor shear are relevant only for vapor Reynolds numbers greater than 70,000--100,000, while heat transfer enhancement is linked to the geometry of the extended surface. A simple semi-empirical equation was developed to account for the shear stress contribution in forced-convection condensation: this equation, applied in conjunction with the model by Briggs and Rose (1994) for stationary vapor condensation, displays a good ability in reproducing all the available data with relevant vapor velocities.

Cavallini, A.; Doretti, L.; Klammsteiner, N.; Longo, G.A.; Rossetto, L. [Univ. di Padova (Italy). Ist. di Fisica Tecnica

1995-12-31

113

Heat transfer coefficients of individual rows for fin-and-tube heat exchangers  

International Nuclear Information System (INIS)

The row-by-row heat transfer characteristics of fin-and-tube heat exchangers having wavy fins were experimentally investigated. Three samples having different rows (one, tow and three) were tested. Results show that the heat transfer coefficient is strongly dependent on the tube row. The heat transfer coefficient of the first row is larger than those of second or third rows. However, the difference decreases as the Reynolds number increases. The heat transfer coefficients of the second and the third row are approximately the same, probably due to increased mixing of bulk flow by wavy channels. Although samples have different tube row, the heat transfer coefficients of same row are approximately the same.

2004-01-01

114

Heat transfer and friction correlations for wavy plate fin-and-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

This paper deals with heat exchangers having plate fins of herringbone wave configuration. Correlations are developed to predict the air-side heat transfer coefficient and friction factor as a function of flow conditions and geometric variables of the heat exchanger. Correlations are provided for both staggered and in-line arrays of circular tubes. A multiple regression technique was used to correlate 41 wavy fin geometries by Beecher and Fagan (1987), Wang et al. (1995) and Beecher (1968). For the staggered layout, 92% of the heat transfer data are correlated within {+-}10%, and 91% of the friction data are correlated within {+-}15%.

Kim, N.H. [Univ. of Inchon (Korea, Republic of). Dept. of Mechanical Engineering; Youn, J.H. [Korea Academy of Industrial Technology, Seoul (Korea, Republic of); Webb, R.L. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical Engineering

1996-12-31

115

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

Science.gov (United States)

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

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

2006-12-01

116

Heat Transfer Enhancement for Finned-tube Heat Exchangers with Winglets  

Energy Technology Data Exchange (ETDEWEB)

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

O' Brien, James Edward; Sohal, Manohar Singh

2000-11-01

117

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-08-01

118

Film-wise condensation of R134a and R23/R134a mixture on horizontal finned tubes, influence of fin spacing  

Energy Technology Data Exchange (ETDEWEB)

The condensation of a pure fluid (R123a) and of a zeotropic mixture (R134a/R123) outside an horizontal bundle of finned tubes have been studied to understand the behaviour of the new refrigerants. Experimental results with pure R134a and several compositions of mixture R134a/R123 have been obtained during condensation on a bundle equipped with finned tubes of three different types: K26 (1024-fpm), K19(748-fpm), K11(433-fpm). The experimental data show the important effect of fin spacing and the different tubes has been made. The experimental data have also been compared to values calculated with the classical Bell and Ghaly model and a good agreement has been noticed. (authors)

Belghazi, M.; Signe, J.C.; Marvillet, Ch. [CEA/Grenoble, Dept. de Thermohydraulique et de Physique (DTP-GRETh), 38 (France); Bontemps, A. [Universite Joseph-Fourier, Institut Universitaire de Technologie 1Grenoble I, 38 (France)

1999-07-01

119

Steam generator tube performance  

International Nuclear Information System (INIS)

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

1992-01-01

120

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

2013-01-01

 
 
 
 
121

Flow induced vibrations in heat exchangers equipped with helical finned tubes; Stroemungsinduzierte Schwingungen in Spiralrippenrohrbuendelwaermetauschern  

Energy Technology Data Exchange (ETDEWEB)

Flow-induced vibrations resulting from acoustic resonance or fluid-elastic instability cause severe damage to finned-tube heat exchangers. There are hardly any publications on spiral finned tubes. This contribution presents experimental data on intrinsic frequencies and damping of spiral finned tubes as well as equations for calculating intrinsic frequencies. Stability limits for fluid-elastic instabilities were defined in flow experiments. Examples are presented to illustrate the applicability of the calculation method in preventing vibration-induced damage. [German] Stroemungsinduzierte Schwingungen in Rippenrohrwaermetauschern aufgrund von akustischer Resonanz bzw. fluidelastischer Instabilitaet fuehren immer wieder zu schweren Schadensfaellen. Hinsichtlich ihres Schwingungsverhaltens sind Spiralrippenrohre in der Literatur bislang vernachlaessigt worden, obwohl sie in der industriellen Anwendung immer mehr an Bedeutung gewinnen. Im vorliegenden Beitrag werden die Eigenfrequenzen und Daempfungen von Spiralrippenrohren experimentell untersucht und Berechnungsformeln fuer die Eigenfrequenzen angegeben. In Stroemungsexperimenten werden Stabilitaetsgrenzen fuer fluidelastische Instabilitaeten ermittelt. Anhand einiger Beispielfaelle wird aufgezeigt, dass das daraus entwickelte Berechnungsschema zur Absicherung gegen Schwingungsschaeden geeignet ist. (orig.)

Fischer, M.

2003-08-01

122

Effect of electroplating on the thermal conductance of fin-tube interface  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the experimental results of thermal contact conductance, heat transfer and interfacial temperature drop of finned tube heat exchanger test specimens. The results were based on the measured temperatures at several locations on the test specimen so that the thermal contact conductance could be directly determined. Each test specimen was assembled by mechanically expanding seven tubes into a single fin. The geometry of the specimens was based on a commonly used model of heat exchangers. The specimens included one bare tube (non-coated) specimen and four electroplated tube specimens. The plating metals were zinc, tin, silver and gold. The thickness of the plating in each case was 5{mu}m. Experiments have been conducted in both vacuum and nitrogen. Maximum enhancement was obtained when the tube was coated with tin. This indicates that, although the thermal conductivity is important, the softness of the plating material also plays an important role in enhancing the thermal conductance of the interface. The presence of an interstitial gas such as nitrogen is beneficial for the heat transfer and the thermal contact conductance. It is also noted that the interfacial temperature drop alone does not fully reflect the efficiency of the heat exchanger. (author)

Cheng, Wui-wai; Madhusudana, Chakravarti [School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia)

2006-12-15

123

Heat transfer and pressure drop of finned tube banks with a staggered arrangement in forced convection. 1st Report. ; Heat transfer characteristics and correlation of spirally finned tube banks. Fin tsuki dennetsukan no dennetsu ryudo tokusei ni kansuru kenkyu. 1. ; Enkan fin tsuki dennetsukangun no dennetsu tokusei to tokusei yosokushiki  

Energy Technology Data Exchange (ETDEWEB)

Heat transfer characteristics of a finned heat transfer tube bank for heat exchange with hot gas are experimentally grasped and new prediction equations of heat transfer characteristics are introduced. Heat transfer characteristics are investigated in the experiment on heat exchange of the air flowing outside the tube through a heat transfer wind tunnel and hot water which is run inside the heat transfer tube. The heat transfer tube bank is with a staggered configuration and has symmetry property as a whole by installing dummy tubes which are finned heat transfer tubes divided in two at the upper and lower parts of the tube bank in even-number lines. Briggs and others cite fin height (hf) and fin spacing (S) as most controlling factors, but there are found to be insufficient. Heat transfer characteristics prediction equations newly derived including S/hf correspond well to the experimental results. Moreover, limited application conditions of this prediction equation are shown as functions of pipe pitch and equivalent diameter. Physical meaning of the tube arrangement parameter in the prediction equation is clarified, grasping local heat flux distribution experimentally. 5 refs., 15 figs., 2 tabs.

Kawamura, T.; Kanzaka, M.; Iwabuchi, M. (Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)); Takahashi, Y. (Hiroshima Inst. of Technology, Hiroshima (Japan). Faculty of Engineering)

1991-05-25

124

Dehumidification: Prediction of condensate flow rate for plate-fin tube heat exchangers using the latent j factor  

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-07-01

125

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-03-15

126

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

2010-01-01

127

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

128

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

DEFF Research Database (Denmark)

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

Taherian, Hessam; Yazdanshenas, Eshagh

2006-01-01

129

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

Energy Technology Data Exchange (ETDEWEB)

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

Huang, C.H.; Hsu, G.C. [Dept. of Naval Architecture and Marine Engineering, National Cheng Kung Univ., Tainan (Taiwan); Jang, J.Y. [Dept. of Mechanical Engineering, National Cheng Kung Univ., Tainan (Taiwan)

2001-07-01

130

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

International Nuclear Information System (INIS)

[en] 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.

2012-01-01

131

Comparison of Streak Tube Performance  

Energy Technology Data Exchange (ETDEWEB)

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

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

2004-11-04

132

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

133

Experimental study of single-phase pressure drop and heat transfer in a micro-fin tube  

Energy Technology Data Exchange (ETDEWEB)

The single-phase pressure drop and heat transfer in a micro-fin tube were measured using oil and water as the working fluids. The Prandtl number varied from 3.2 to 220 and the Reynolds number ranged from 2500 to 90,000. The results show that there is a critical Reynolds number, Re{sub cr}, for heat transfer enhancement. For Refin tube is the same as that in a smooth tube, but for Reynolds numbers higher than Re{sub cr}, the heat transfer in the micro-fin tube is gradually enhanced compared with a smooth tube. It reaches more than twice that in a smooth tube for Reynolds numbers greater than 30,000 with water as the working fluid. The Nusselt number is proportional to Pr {sup 0.56} in the enhanced region and is proportional to Pr {sup 0.3} in the non-enhanced region. For the high Prandtl number working fluid (oil, 80< Pr <220), the critical Reynolds number for heat transfer enhancement is about 6000, while for the low Prandtl number working fluid (water, 3.2< Pr <5.8), the critical Reynolds number for heat transfer enhancement is about 10,000. The friction factors in the micro-fin tube are almost the same as for a smooth tube for Reynolds numbers below 10,000. For Reynolds numbers higher than 30,000, the friction factor is about 40-50% higher than for a smooth tube. (author)

Li, Xiao-Wei; Meng, Ji-An; Li, Zhi-Xin [School of Aerospace, Tsinghua University, Beijing 100084 (China)

2007-11-15

134

Some insights on heat transfer augmentation by vortex generators in fin-tube compact heat exchangers with two rows of staggered tubes  

Energy Technology Data Exchange (ETDEWEB)

This work presents numerical simulations of fin-tube compact heat exchangers with smooth fins and built-in vortex generators. The computational model has two rows of round tubes in staggered arrangement. Delta winglet vortex generators were used, and its geometric dimensions were fixed according to the best results of literature. The steady state numerical simulations were carried out at Re=300 with the PHOENICS code (based on finite volume method). Local and global influences of vortex generators in heat transfer and flow losses were analyzed. The results provide important information about the use of longitudinal vortex generators to enhance the heat transfer on this kind of heat exchanger. (author)

Rodrigues Junior, Rogerio; Yanagihara, Jurandir Itizo [Sao Paulo Univ., SP (Brazil). Escola Politecnica. Dept. de Engenharia Mecanica

1998-07-01

135

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

Science.gov (United States)

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

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

2013-07-01

136

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 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 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 dis (more) tribution 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.

Bordalo, Sérgio Nascimento; Saboya, Francisco Eduardo Mourão

1999-12-01

137

Thermal performance analysis of the glass evacuated tube solar collector with U-tube  

Energy Technology Data Exchange (ETDEWEB)

In this paper, based on the energy balance for the glass evacuated tube solar collector with U-tube, the thermal performance of the individual glass evacuated tube solar collector is investigated by analytical method. The solar collector considered in this study is a two-layered glass evacuated tube, and the absorber film is deposited in the outer surface of the absorber tube. The heat loss coefficient and heat efficiency factor are analyzed using one-dimensional analytical solution. And the influence of air layer between the absorber tube and the copper fin on the heat efficiency is also studied. The results show that the function relation of the heat loss coefficient of the glass evacuated tube solar collector with temperature difference between the absorbing coating surface and the ambient air is nonlinear. In the different ambient temperatures, the heat loss coefficient of the solar collector should be calculated by different expressions. The heat efficiency factor will be subject to influence of air layer between absorber tube and the copper fin. Specially, the influence is remarkable when the heat loss coefficient of the collector is large. When the synthetical conductance amounts to 5 W/m K, the solar collector efficiency decreases 10%, and the outlet fluid temperature decreases 16% compared with the case which the air thermal resistance is neglected. And the surface temperature of the absorbing coating increases 30 C due to the effect of air thermal resistance. So the surface temperature of the absorbing coating is an important parameter to evaluate the thermal performance of the glass evacuated tube solar collector. (author)

Ma, Liangdong; Lu, Zhen; Zhang, Jili; Liang, Ruobing [School of Civil and Hydraulic Engineering, Dalian University of Technology, Dalian (China)

2010-09-15

138

In-tube heat transfer and pressure drop of R-134a and ester lubricant mixtures in a smooth tube and a micro-fin tube. Part 2: Condensation  

Energy Technology Data Exchange (ETDEWEB)

Average in-tube heat transfer coefficients and pressure drops during condensation are reported for condensation of refrigerant R-134a/lubricant mixtures in a smooth tube and a micro-fin tube of 9.52-mm (3/8-in.) outer diameter. The lubricants tested were 169-SUS and 369-SUS penta erythritol ester mixed acids. Lubricant concentrations ranged from 0% to 5%. The average saturation temperature in the test tube was approximately 40 C (104 F). The mass flux of the refrigerant-lubricant mixtures was varied from 85 kg/m{sup 2}{center_dot}s (62,700 lb/ft{sup 2}{center_dot}h) to 375 kg/m{sup 2}{center_dot}s (276,640 lb/ft{sup 2}{center_dot}h). Heat transfer coefficients during condensation decreased with the addition of lubricants in all cases. Condensation pressure drops increased with the addition of the 169-SUS ester lubricant in both the smooth tube and the micro-fin tube. The addition of the 369-SUS lubricant did not affect pressure drops in the smooth tube, but it decreased the pressure drops in the micro-fin tube. Pure R-134a heat transfer coefficients in the micro-fin tube were 100% to 200% higher than those in the smooth tube, with the higher values occurring at the lower mass fluxes. Pressure drops in the micro-fin tube were 20% to 50% higher than those in the smooth tube. Design equations are presented that aid in predicting the heat transfer coefficients and pressure drops of R-134a/lubricant mixtures in the smooth and micro-fin tubes.

Eckels, S.J. [Kansas State Univ., Manhattan, KS (United States). Dept. of Mechanical Engineering; Doerr, T.M.; Pate, M.B. [Iowa State Univ., Ames, IA (United States). Dept. of Mechanical Engineering

1994-12-31

139

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-05-15

140

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

International Nuclear Information System (INIS)

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

2009-01-01

 
 
 
 
141

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

Directory of Open Access Journals (Sweden)

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

Atipoang Nuntaphan; Tanongkiat Kiatsiriroat

2004-01-01

142

Generalized Pressure Drop Correlation for Evaporation and Condensation of Alternative Refrigerants in Smooth and Micro-Fin Tubes.  

Science.gov (United States)

This paper presents a pressure drop correlation for evaporation and condensation in smooth and micro-fin tubes. The correlation was developed from a database consisting of the following pure and mixed refrigerants: R125, R134a, R32, R410A (R32/R125 50/50 ...

H. Y. Choi M. A. Kedzierski P. A. Domanski

1999-01-01

143

Modelling of plate finned tube evaporators and condensers working with R134A  

Energy Technology Data Exchange (ETDEWEB)

A model to predict the behaviour of finned tube evaporators and condensers working with R134a has been developed. For modelling of the refrigerant phase change, evaporation or condensation, the heat transfer and the pressure drop for the two-phase flow have to be calculated. Therefore, a number of correlations, the most recommended ones in the reviewed literature, have been analysed and compared. The results of this comparison are presented for the evaporation and condensation heat transfer coefficients and for the evaporator frictional pressure drop. Once the correlations have been implemented in the model and compared with the experimental results, the ones that work best for the studied heat exchangers have been ultimately selected. The experimental study to validate the model has been carried out in a small air-conditioning unit with cross-flow air-refrigerant type heat exchangers. The results are compared with model predictions for thermal capacity, refrigerant superheat or subcooling, and tube-side pressure drop. (Author)

Corberan, J.M.; Melon, M.G. [Universidad Politecnica de Valencia (Spain). E.T.S.I.I., Applied Thermodynamics Dept.

1998-06-01

144

Performance Assessment of Sodium to Air Finned Heat Exchanger for FBR  

International Nuclear Information System (INIS)

In pool type Fast Breeder Reactors (FBR) a passive Safety Grade Decay Heat Removal (SGDHR) system removes decay heat produced in the core when normal heat removal path through steam water system is not available. This is essential to maintain the core temperatures within limits. A Decay Heat Exchanger (DHX) picks the heat from the pool and transfers the heat to atmosphere through sodium to Air Heat Exchanger (AHX) situated at high elevation. Due to the temperature differences existent in the system density differences are generated causing a buoyant convective heat transfer. The system is completely passive as primary sodium, secondary sodium and air flows under natural convection. DHX is a sodium to sodium counter flow heat exchanger with primary sodium on shell side and secondary sodium on tube side. AHX is a cross flow heat exchanger with sodium on tube side and air flows in cross flow across the finned tubes. Capacity of a single loop of SGDHR is 8 MW. Four such loops are available for the decay heat removal. It has been seen that the decay heat removal to a large extent depends on the AHX performance. AHX tested have shown reduced heat removal capacity much as 30 to 40%, essentially due to the bypassing of the finned tubes by the air. It was felt that a geometrically similar AHX be tested in sodium. Towards this a 2 MW Sodium to air heat exchanger (AHX) was tested in the Steam Generator Test Facility (SGTF) constructed at Indira Gandhi Center for Atomic Research (IGCAR), Kalpakkam. The casing arrangement of the AHX was designed to minimise bypassing of air. (authors)

2006-01-01

145

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.

2010-01-01

146

Condensate retention on a louver-fin-and-tube air cooling coil  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a study of condensate retention on a louver-fin-and-tube air cooling coil, which is commonly used in air conditioning (A/C) systems. Compared to previously related work focusing on the influence of condensate retention on the heat and mass transfer between air and a cooling coil, the present study emphasizes the impacts of operating parameters on condensate retention on a cooling coil. A new method to describe the steady-state condensation has been suggested and a new mathematical model to represent the force balance of retained condensate developed. The mass of condensate retained has been measured experimentally under various operating conditions of a direct expansion (DX) air cooling and dehumidification system. The influences of air dry-bulb temperature, moisture content and Reynolds Number on condensate retention are discussed. The model developed relates the mass of condensate retained to condensing rate, and is successful in predicting the trends of condensate retention under normal operating conditions for air cooling applications. (author)

Xu, Xiangguo; Chan, Mingyin; Deng, Shiming [Department of Building Services Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR (China); Leung, Chunwah [Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR (China)

2007-05-15

147

In-tube heat transfer and pressure drop of R-134a and ester lubricant mixtures in a smooth tube and a micro-fin tube. Part 1: Evaporation  

Energy Technology Data Exchange (ETDEWEB)

In-tube heat transfer coefficients and pressure drops during evaporation are reported for mixtures of refrigerant R-134a and a penta erythritol ester mixed-acid lubricant. The ester lubricant was tested at viscosities of 169 SUS and 369 SUS over a lubricant concentration range of 0% to 5% in both a smooth tube and a micro-fine tube. The average saturation temperature used was 1 C (33.8 F). Measurements were taken for the refrigerant-lubricant mixture over a mass flux range of 85 kg/m{sup 2}{center_dot}s (62,700 lb/ft{sup 2}{center_dot}h) to 375 kg/m{sup 2}{center_dot}s (276,640 lb/ft{sup 2}{center_dot}h) in test tubes with an outer diameter of 9.52 mm (3/8 in.). Heat transfer coefficients during evaporation increased at low concentrations of the 169-SUS ester lubricant and then dropped off at high lubricant concentrations in both the smooth tube and the micro-fin tube. The higher viscosity 369-SUS lubricant decreased the heat transfer coefficients in both tubes over the range of lubricant concentrations tested. Pressure drops during evaporation increased in both the smooth tube and the micro-fin tube with the addition of ester lubricant of either viscosity. The heat transfer coefficients for the micro-fin tube were 100% to 50% higher than those for the smooth tube, with the higher values occurring at low mass fluxes. Pressure drops in the micro-fin tube were 10% to 20% higher than those in the smooth tube.

Eckels, S.J. [Kansas State Univ., Manhattan, KS (United States). Dept. of Mechanical Engineering; Doerr, T.M.; Pate, M.B. [Iowa State Univ., Ames, IA (United States). Dept. of Mechanical Engineering

1994-12-31

148

High Performance Pulse Tube Cryocoolers  

Science.gov (United States)

Lockheed Martin's Advanced Technology Center has been developing pulse tube cryocoolers for more than ten years. Recent innovations include successful testing of four-stage coldheads, no-load temperature below 4 K, and the recent development of a high-efficiency compressor. This paper discusses the predicted performance of single and multiple stage pulse tube coldheads driven by our new 6 kg ``M5Midi'' compressor, which is capable of 90% efficiency with 200 W input power, and a maximum input power of 1000 W. This compressor retains the simplicity of earlier LM-ATC compressors: it has a moving magnet and an external electrical coil, minimizing organics in the working gas and requiring no electrical penetrations through the pressure wall. Motor losses were minimized during design, resulting in a simple, easily-manufactured compressor with state-of-the-art motor efficiency. The predicted cryocooler performance is presented as simple formulae, allowing an engineer to include the impact of a highly-optimized cryocooler into a full system analysis. Performance is given as a function of the heat rejection temperature and the cold tip temperatures and cooling loads.

Olson, J. R.; Roth, E.; Champagne, P.; Evtimov, B.; Nast, T. C.

2008-03-01

149

An experimental study on quantitative interpretation of local convective heat transfer for the fin and tube heat exchanger using lumped capacitance method  

Energy Technology Data Exchange (ETDEWEB)

An experimental study has been performed to investigate the heat transfer characteristics of fin and tube heat exchanger. The existing transient and steady methods are very difficult to apply for the measurements of heat transfer coefficients of a thin heat transfer model. In this study the lumped capacitance method was adopted. The heat transfer coefficients were measured by using the lumped capacitance method based on the liquid crystal thermography. The method is validated through impinging jet and flat plate flow experiments. The two experiments showed that the results of the lumped capacitance method with polycarbonate model showed very good agreements with those of the transient method with acryl model. The lumped capacitance method showed similar results regardless of the thickness of polycarbonate model. The method was also applied for the heat transfer coefficient measurements of a fin and tube heat exchanger. The quantitative heat transfer coefficients of the plate fin were successfully obtained. As the frontal velocity increased, the heat transfer coefficients were increased, but the color-band shape showed similar patterns regardless of frontal velocity. (author). 17 refs., 15 figs., 1 tab.

Kim, Y.Y.; Kim, K.S. [Pusan National University, Pusan (Korea); Jung, K.H. [Samsung Electronics Co., Ltd. (Korea)

2001-02-01

150

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

International Nuclear Information System (INIS)

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

2007-01-01

151

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

1989-01-01

152

The effect of surface contact angle on the behavior of frost formation in the fin-tube heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

The effect of surface contact angle on the behavior of frost formation in the fin-tube heat exchanger is investigated experimentally. It is shown that both heat exchangers with hydrophilic and hydrophobic surfaces appear to have a better thermal performance than bare aluminium heat exchanger, but the improvements are very small. There is a little increase in the amount of the frost deposited onto the heat exchanger with both hydrophilic and hydrophobic surface. However, the effect of contact angle on the frost density is observed : the frost with high density forms on the heat exchanger with hydrophilic surface : and the frost with low density is deposited onto the heat exchanger with hydrophobic surface when compared with the frost deposited onto the heat exchanger with bare aluminium surface. This may be attributed to the fact that the shape of water droplets which condense on the surface of heat exchanger at the early stage of frosting varies with contact angle, and thus makes a difference on the structure of frost formation. From the experiments with different relative humidity of inlet air, it is shown that the variations of operating parameter make no influence on the effect of surface contact angle on the frosting behavior in the heat exchanger. (author). 10 refs., 9 figs.

Lee, K.S. [Hanyang University, Seoul (Korea); Jhee, S.; Lee, D.W. [Hanyang University, Graduate School, Seoul (Korea)

1999-11-01

153

Verification of the performance of impact limiting FINS-II  

International Nuclear Information System (INIS)

Atomic Energy Control Board (AECB) repeated drop test experiments, by Oak Ridge National Laboratories (ORNL) in 1971, to: a) investigate the influence of impact velocity in order to determine whether it was a cause of the difference between the two sets of curves, and b) extend the range of application of the design curves; specifically to higher deformation, to stainless steel material, and to non-square (oblique) impact conditions. Using the same drop test facility, instrumentation and experimental procedure as the previous study, data were collected from 272 specimens. These were primarily of the single fin type, similar to the ORNL design; only the oblique impact test specimens had a special double fin configuration. Results from the impact velocity tests showed that while this did influence the shape of the first part of the curves, it did not explain the difference in magnitude between the two sets of curves. Changing the fin material to type 304 stainless steel showed that for vertical fins essentially the same curves were obtained. However, for the 30 degree inclined specimens, the stainless steel fins showed lower energy absorption capabilities. Measurements from the high deformation tests indicated that there is no tendency for the curves to change slope at the higher deformations. The oblique impact tests attempted to extend the application of the design curves to a 'one end first' type of container impact condition. Results confirmed expected higher values of deformation per input (energy/fin width), but there was no correlation between the curves for normal impact conditions and those for oblique impact conditions.

1986-01-01

154

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

155

Models for Automated Tube Performance Calculations  

International Nuclear Information System (INIS)

High power radio-frequency systems, as typically used in fusion research devices, utilize vacuum tubes. Evaluation of vacuum tube performance involves data taken from tube operating curves. The acquisition of data from such graphical sources is a tedious process. A simple modeling method is presented that will provide values of tube currents for a given set of element voltages. These models may be used as subroutines in iterative solutions of amplifier operating conditions for a specific loading impedance.

2002-01-01

156

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

Directory of Open Access Journals (Sweden)

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

M.T. Martínez; E. Torres; J.A. Soto

2004-01-01

157

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

Scientific Electronic Library Online (English)

Full Text Available 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 parcial o completa. El análisis considera varias configuraciones geométricas con respecto a: la superficie de las aletas y a la forma de los tubos considerando la forma (more) 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 analysis considers various geometric configurations with respect to the surfaces of the fins and the form of the tubes, including the traditional round form as well as flattened (more) 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

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

2004-01-01

158

Design and performance of shroud tubes  

International Nuclear Information System (INIS)

[en] Shroud tubes were conceived as a means of preventing the rearrangement and wedging of broken fuel pieces in sodium-bonded advanced-fuel elements. The specific design of a thin-walled tube with slots that fits closely around the fuel was arrived at by consideration of a number of competing mechanical and heat-transfer requirements. Postirradiation examination results obtained to date indicate that shroud tubes are meeting the design requirement of retaining fuel fragments. No cladding failures have been observed in any sodium-bonded element using a shroud tube. The excellent irradiation performance of sodium-bonded elements with shroud tubes as compared to similar elements without shroud tubes demonstrates the utility of the shroud-tube concept

1977-10-10

159

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

Directory of Open Access Journals (Sweden)

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

S. S. Bueno; J. P. Dias; A. L. Seixlack; J. B. Aparecido

2006-01-01

160

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

Directory of Open Access Journals (Sweden)

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

DR. S.N. Sapali; Pradeep A.Patil

2009-01-01

 
 
 
 
161

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.

2003-01-01

162

Modeling of partially wet radial fin assembly used as a dehumidifier coil  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the analysis of heat transfer in a radial fin assembly during the process of dehumidification. In past studies, both fully-dry and fully-wet fins have been analyzed. New analytical formulation leading to a closed-form solution has been developed for a partially wet fin which is most common in dehumidifier coil operation during air conditioning. The parameters that influenced the heat transfer rate in the finned tube structure are ratio of fin to wall thermal conductivity, ratio of fin thickness to fin pitch, ratio of wall thickness to fin pitch, ratio of fin length to fin pitch, cold fluid Biot number, ambient Biot number, the relative humidity and dry bulb temperature of the incoming air, and the cold fluid temperature inside the coil. Calculations were carried out to study the performance of the heat exchanger. The computed results included the temperature distribution in the wall and the fin and the fin efficiency.

Rosario, L.; Rahman, M.M.

1998-07-01

163

Development of prediction technique for cooling performance of a heatsink with plate fins; Kushigata fin no dennetsu seino yosokuho no kaihatsu  

Energy Technology Data Exchange (ETDEWEB)

Numerical calculation was carried out on flow and temperature fields around a heatsink with plate fins subjected to a uniform flow, varying the ratio of fin length L to the half-pitch of fins s. The average flow velocity between fins Uf, became lower, as Re0s/ s/L decreased, where Re0 was Reynolds number defined by uniform flow velocity and s. It was also found that friction resistance and heat transfer of the fins showed excellent agreement with those of parallel plates with uniform inlet flow velocity equal to Uf. A prediction technique for the cooling performance of the heatsink was developed in which Uf, was estimated under the condition of constant pressure distribution at its downwind edge. The present technique can predict the heat transfer of the fins with error level below 30% under practical conditions of electronics design, while it underestimates Uf, in the region of small Re0 s/L. 7 refs., 9 figs., 1 tab.

Sata, Y.; Iwasaki, H.; Ishizuka, M. [Toshiba Corp., Tokyo (Japan)

1995-10-25

164

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

Directory of Open Access Journals (Sweden)

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

Ahmed F. Khudheyer

2011-01-01

165

Performance Analysis of Spiral Tube Heat Exchanger  

Directory of Open Access Journals (Sweden)

Full Text Available In the present study, the performance of the spiral tube heat exchanger can be carried out. The heat exchanger consists of a shell and tube unit. Each coil is fabricated by bending a 12 mm diameter straight copper tube into a spiral coil tube of four turns. Cold water and hot oil are used as working fluids in shell side and tube side, respectively. The experiments are done at the cold water and hot oil mass flow rates ranging between 0.075 and 0.25 kg/s, and between 0.008 and 0.04 kg/s, respectively. The inlet temperatures of cold and hot water are between 29 and 37 °C, and between 70 and 56 °C, respectively. The cold water entering the heat exchanger at the shell inlet side and outer from the shell outside. The hot water enters the heat exchanger at the inner tube side and flows along the outside of the tube. The effects of the inlet conditions of both working fluids flowing through the test section on the heat transfer characteristics are discussed..

JAY J. BHAVSAR,; DR. V K. MATAWALA,; S.B.DIXIT

2013-01-01

166

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; Jianhong Liang; Qi Shen; Lei Bao; Qian Zhang

2013-01-01

167

Performance of Elliptical Pin Fin Heat Exchanger ?with Three Elliptical Perforations  

Directory of Open Access Journals (Sweden)

Full Text Available Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} A computational investigation has been carried out to assess the heat transfer and pressure drop characteristics of elliptical pin fins arranged in a rectangular duct in a staggered manner. Two types of elliptical pin fins have been considered for this purpose, namely, solid elliptical and perforated elliptical pin fins. Three perforations of elliptical cross sections are considered in the elliptical pin fins. Pressure, temperature and velocity profiles at different locations within the computational domain are considered for different inlet velocities. The heat transfer and pressure drop characteristics along the computational domain are presented and the overall performance, which is defined here as the heat transfer per unit pressure drop, of the heat exchanger is also assessed. The results show that the perforated elliptical pin fins perform better than the solid elliptical pin fin both in terms of heat transfer and pressure drop characteristics.

Monoj Baruah; Anupam Dewan; Pinakeswar Mahanta

2011-01-01

168

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

1985-01-01

169

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; Noureddine Moummi; Said Benramache

2013-01-01

170

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

Directory of Open Access Journals (Sweden)

Full Text Available A three dimensional (3D) computational fluid dynamics (CFD) simulation and a neural network model are presented to estimate the behaviors of the Colburn factor (j) and the Fanning friction factor (f) for wavy fin - and - flat tube (WFFT) heat exchangers. Effects of the five geometrical factors of fin pitch, fin height, fin length, fin thickness, and wavy amplitude are investigated over a wide range of Reynolds number (600fins have significant effects on the j and f factors as a function of Reynolds number. The computational results have an adequate accuracy when compared to experimental data. The accuracy of the calculations of the j and f factors are evaluated by the values of the absolute average relative deviation (AARD), being respectively 3.8% and 8.2% for the CFD simulation and 1.3% and 1% for the neural network model. Finally, new correlations are proposed to estimate the values of the j and f factors with 3.22% and 3.68% AARD respectively.

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

2011-01-01

171

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english A three dimensional (3D) computational fluid dynamics (CFD) simulation and a neural network model are presented to estimate the behaviors of the Colburn factor (j) and the Fanning friction factor (f) for wavy fin - and - flat tube (WFFT) heat exchangers. Effects of the five geometrical factors of fin pitch, fin height, fin length, fin thickness, and wavy amplitude are investigated over a wide range of Reynolds number (600(more) the geometrical parameters of wavy fins have significant effects on the j and f factors as a function of Reynolds number. The computational results have an adequate accuracy when compared to experimental data. The accuracy of the calculations of the j and f factors are evaluated by the values of the absolute average relative deviation (AARD), being respectively 3.8% and 8.2% for the CFD simulation and 1.3% and 1% for the neural network model. Finally, new correlations are proposed to estimate the values of the j and f factors with 3.22% and 3.68% AARD respectively.

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

2011-09-01

172

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

173

MAPLE research reactor beam-tube performance  

International Nuclear Information System (INIS)

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

1989-01-01

174

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

175

Experimental study on the effect of frost parameters on domestic refrigerator finned tube evaporator coils  

Energy Technology Data Exchange (ETDEWEB)

In this study, parameters affecting the frost formation on the evaporator of a refrigerator and the structure of frost were examined. Air velocity measurements both at the air inlet and outlet channels of the evaporator were performed, and the effect of air velocity on frost formation was examined. The rate of evaporation of water inside the refrigerator cabin was also recorded. (author)

OEzkan, Derya Burcu; OEzil, Eralp [Department of Mechanical Engineering, Yildiz Technical University, 34349 Istanbul (Turkey)

2006-12-15

176

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

UK PubMed Central (United Kingdom)

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

Esposito CJ; Tangorra JL; Flammang BE; Lauder GV

2012-01-01

177

The performance in shell-and-tube heat exchangers with configuration and surface characteristics of tube  

International Nuclear Information System (INIS)

This paper presents an improved performance of heat transfer for shell-and-tube and thermal analysis based on the Bell-Delaware method for single tube. Heat transfer has been compared for a smooth tube, helical tube and surface-coated tube. In general, the results showed that properly designed helical tube and surface-coated tube offer a significant improvement in heat transfer. The numerical results derived from the Bell-Delaware method for the shell-side heat transfer coefficient were verified with experimental results. The thermal analysis aids significantly in the solution of the design problem.

2008-01-01

178

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 thresho...

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

179

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

International Nuclear Information System (INIS)

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

2003-01-01

180

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

 
 
 
 
181

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

UK PubMed Central (United Kingdom)

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.

Zhang Y; Du Y; Chen Y; Lil X; Yang X; Han W; Yang F

2013-02-01

182

Heat transfer in a finned dehumidifier coil under partially wet condition  

Energy Technology Data Exchange (ETDEWEB)

The aim of this paper is the analysis of heat transfer in a radial fin assembly during the process of dehumidification. A numerical simulation of the fin with dry, wet, and partially wet boundary conditions have been carried out using a control volume based finite-difference method and compared with past analytical studies. The augmentation of heat transfer due to fin was calculated by comparing heat transfer rate with and without fins under the same operating conditions. In addition, the fin efficiency was calculated. The parameters that influenced the heat transfer rate in the finned tube structure are ratio of fin and wall thermal conductivities, ratio of fin thickness to fin pitch, ratio of wall thickness to fin pitch, ratio of fin length to fin pitch, cold fluid Biot number, ambient Biot number, the relative humidity and dry bulb temperature of the incoming air, and the cold fluid temperature inside the coil. Numerical calculations were carried out to study the performance of the heat exchanger for various combinations of these parameters. It was found that the heat transfer increased with increment in both dry bulb temperature and the relative humidity of the air. The results suggested that fin efficiency can be very significantly altered by the condensation phenomenon on the fin surface and designs with dry fin data may result in serious over or under prediction of coil performance. The present results are expected to be very useful for the design of dehumidifier (cooling) coils for air conditioning applications.

Rosario, L.; Rahman, M.M.

1999-07-01

183

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

International Nuclear Information System (INIS)

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

2002-01-01

184

Finned heat exchanger. Ib. General and basic aspects  

International Nuclear Information System (INIS)

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

1995-01-01

185

Finned heat exchangers. Ia. General and basic aspects  

International Nuclear Information System (INIS)

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

1995-01-01

186

Effect of various parameters on the performance of capillary tube  

Directory of Open Access Journals (Sweden)

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

Rahul Gulati; Prof. R.C.Gupta

2011-01-01

187

Performance of a tapered pulse tube  

Energy Technology Data Exchange (ETDEWEB)

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

Swift, G.; Allen, M.; Woolan, J.J. [Cryenco Inc., Denver, CO (United States)

1998-02-01

188

Performance of the hybrid photomultiplier tube (HPMT)  

Energy Technology Data Exchange (ETDEWEB)

The HPMT, which may be an alternative for PhotoMultiplier Tubes (PMT`s) in many applications, is a vacuum tube in which the latest technologies of photocathodes and photodiodes are combined. Photo-electrons are accelerated and bombarding a reversely biased PIN diode, where they create many electron-hole-pairs. The resulting charge pulse can be amplified and further processed. The HPMT shows many superior characteristics compared to regular PMT`s, because it does not suffer the statistical fluctuations common for electron multiplication processes. An energy resolution of up to 14 photo-electrons will be presented, together with striking figures for dynamic range and timing behavior.

Schomaker, R.J. [B.V. Delft Electronische Producten, Roden (Netherlands)

1995-12-31

189

Forced convective boiling of R22 and R407C inside horizontal smooth and micro-fin tubes; Ebullition en convection forcee du R22 et du R407C a l'interieur de tubes horizontaux, lisse et micro-ailetes  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study is to experimentally obtain the boiling heat transfer coefficients and pressure drops of pure refrigerant R22 and non azeotropic refrigerant mixture R407C inside smooth and micro-fin tubes. To investigate the in-tube flow-boiling, an experimental apparatus was set up. The tests have been carried at constant heat flux uniformly distributed all along the tube length. The effects of the tube geometry, the heat flux and the mass flow rate on the local heat transfer coefficient and the local pressure drops have been studied. The contribution of each boiling mechanism to heat transfer is also investigated. When compared to smooth tube, the micro-fin tubes exhibit a significant heat transfer enhancement, up to 180 %, with less important pressure drop increase (75 %). In comparison to R22, the R407C heat transfer coefficients and pressure drops of smooth and micro-fin tubes are 15 at 35 % and 5 at 20 % lower. The best heat transfer enhancement is obtained at low heat flux and mass flow rate. A water-evaporator model has been developed taking into account the experimental laws. Using a micro-fin tube allows to reduce from 21 at 40 % the evaporator surface, compared to a smooth tube, respectively. (author)

Branescu, C.N.

2000-05-31

190

Optimum fin geometry in flat plate solar collector systems  

Energy Technology Data Exchange (ETDEWEB)

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. (author)

Badescu, Viorel [Candida Oancea Institute of Solar Energy, Faculty of Mechanical Engineering, Polytechnic University of Bucharest, Spl. Independentei 313, Bucharest 79590 (Romania)

2006-09-15

191

Optimum fin geometry in flat plate solar collector systems  

International Nuclear Information System (INIS)

[en] 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

2006-01-01

192

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.

1987-09-03

193

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

194

High rate performance of drift tubes  

Energy Technology Data Exchange (ETDEWEB)

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

Scherberger, G. E-mail: scherbe@physik.uni-freiburg.de; Paschhoff, V.; Waldmann, V.; Landgraf, U.; Herten, G.; Mohr, W

1999-03-21

195

High Rate Performance of Drift Tubes  

CERN Document Server

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

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

1998-01-01

196

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 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 elípticos y aletas lisas. El numero de Reynolds y los espaciamientos fueron variados, dentro del régimen laminar. Los experimentos fueron desarrollados en un túnel de vien (more) to 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 win (more) d 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

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

2012-12-01

197

Evaluation of the thermodynamic performance of pulse tubes  

Energy Technology Data Exchange (ETDEWEB)

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

Pinsky, C.; Yoshida, S.; Ravikumar, K.V.; Frederking, T.H.K. [Univ. of California, Los Angeles, CA (United States)] [and others

1996-12-31

198

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

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

199

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

Scientific Electronic Library Online (English)

Full Text Available 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, (more) 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 without complications. Here, we reviewed the literature on PubMed to identify complications after classic liposuction performed solely for esthetic purposes. In total, 210 articl (more) es 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.

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

2012-03-01

200

Factors affecting cathode ray tube display performance.  

UK PubMed Central (United Kingdom)

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.

Compton K

2001-06-01

 
 
 
 
201

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

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

202

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.)

1981-01-01

203

Identifying pitfalls in chest tube insertion: improving teaching and performance.  

UK PubMed Central (United Kingdom)

OBJECTIVE: Chest tube thoracostomies are common surgical procedures, but little is known about how practitioners learn the skill. This study evaluates the frequency with which correctly performed tasks are executed by subjects during chest tube thoracostomies. DESIGN: In this prospective study, we developed a mobile-learning module, containing stepwise multimedia guidance on chest tube insertion. Next, we developed and tested a 14-item checklist, modeled after key skills in the module. Participants, defined as "novice" (fewer than 10 chest tubes placed) or "expert" (10 or more placed), were assigned to either the video or control group. A trained clinician used the checklist to rate participants while they inserted a chest tube on a TraumaMan simulator. SETTING: University of Miami, Miller School of Medicine, a tertiary care academic institution. PARTICIPANTS: Current medical students, residents, and the United States Army Forward Surgical Team members rotating through the institution. One hundred twenty-eight subjects entered and finished the study. RESULTS: One hundred twenty-eight subjects enrolled in the study; 86 (67%) were residents or US Army Forward Surgical Team members, 66 (77%) were novices, and 20 (23%) were experts. Novices most frequently connected the tube to suction (91%), adequately dissected the soft tissue (82%), and scrubbed or anesthetized appropriately (80%). They least frequently completed full finger sweeps (33%), avoided the neurovascular bundle (35%), and performed a controlled pleural puncture (39%). Comparing the novice video group with the novice control group, the video group was more likely to correctly perform a finger sweep (42%, p<0.001) and clamp the distal end of the chest tube (42%, p<0.001). Of all the steps, experts least frequently completed full finger sweeps (70%) and avoided the neurovascular bundle (75%). Comparing the expert video group with the expert control group, the video group was more likely to correctly perform finger sweeps, the incision, and clamping the distal chest tube (20%, p = not significant). CONCLUSIONS: Avoiding the neurovascular bundle, controlled pleural entry, and finger sweeps are most often performed incorrectly among novices. This information can help instructors to emphasize key didactic steps, possibly easing trainees' learning curve.

Davis JS; Garcia GD; Jouria JM; Wyckoff MM; Alsafran S; Graygo JM; Withum KF; Schulman CI

2013-05-01

204

Performance Analysis of Cross Flow Plate Fin Heat Exchanger for Immiscible System Using ANN  

Directory of Open Access Journals (Sweden)

Full Text Available An experimental investigation on heat transfer study on a solvent and solution were made using cross flow plate fin heat exchanger. Steam is the hot fluid, whereas Steam and Toluene-Steam immiscible solution serves as cold fluid. A series of runs were made between steam and water, steam and Toluene solution. In addition to, the volume fraction of Toluene was varied and the experiment was held. The flow rate of the cold fluid is maintained from 120 to 720 lph and the volume fraction of Toluene is varied from 10-50%. Experimental results such as exchanger effectiveness, overall heat transfer coefficients were calculated. Simulation studies were carried out to predict Nusselt number of the cold fluid (NNu), Fin Effectiveness (?), Cold Side Efficiency (?c) and Hot Side Efficiency (?h) for the heat exchanger using ANN. General regression is used to train and test the network since the target data was continuous. It is shown that the predicted results are close to experimental data by ANN approach. The model was compared with the experimental findings and found to be valid.

Thirumarimurugan M.; Kannadasan T.; Gopalakrishnan S.

2010-01-01

205

Performance of the CMS drift tube chambers with cosmic rays  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 2...

Chatrchyan, S; Khachatryan, V; Sirunyan, AM; Adam, W; Arnold, B; Bergauer, H; Bergauer, T; Dragicevic, M; Eichberger, M

206

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

207

Heat exchanger performance calculations for enhanced-tube condenser applications  

Science.gov (United States)

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.

208

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

209

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

210

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

UK PubMed Central (United Kingdom)

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

Svendsen JC; Banet AI; Christensen RH; Steffensen JF; Aarestrup K

2013-09-01

211

A generalised approximation equation for the efficiency of fins on circular and elliptical tubes. Verallgemeinerte Naeherungsgleichung fuer den Wirkungsgrad von Rippen auf kreisfoermigen und elliptischen Kernrohren  

Energy Technology Data Exchange (ETDEWEB)

With the aid of numerical calculation, the accuracy of the Schmidt approximation equation for the determination of fin-efficiency for different fin-configurations is investigated, and based on that a generalised formula is proposed, which gives a better reproduction of the exact values. (orig.)

Zeller, M. (Lehrstuhl fuer Waermeuebertragung und Klimatechnik, RWTH Aachen (Germany)); Grewe, M. (Lehrstuhl fuer Waermeuebertragung und Klimatechnik, RWTH Aachen (Germany))

1994-06-01

212

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

213

Constructal tree-shaped fins  

Energy Technology Data Exchange (ETDEWEB)

A tree-like fin is investigated and optimized by the constructal optimization method. The tree shape is not mimicked. Rather, the T-shaped fin - which was optimized in a previous paper - is enhanced geometrically. This fin is allowed to grow new branches to allow more of the fin-material to get to the surface area and transfer heat directly to the reservoir. For that, the new fin is adding more branches in each major step of the optimization process until an optimum shape - that delivers the maximum base heat - is found. Fin material (volume fraction) and fin allocated volume (frontal area) are constrained. In this paper the tree-shaped fin is kept uniform as in uniform thicknesses of the stem and the branches, and an equal length and equal thicknesses of all branches. The thermal performance of the optimized tree-shaped fin is found to be much better than the performance of the longitudinal fin and the optimized T-shaped fins, and it has a compact size. (authors)

Almogbel, Majed A. [Refrigeration and Air-Conditioning Division, Riyadh College of Technology (Saudi Arabia)

2005-04-01

214

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

2004-01-01

215

Performance of the CMS drift tube chambers with cosmic rays  

Energy Technology Data Exchange (ETDEWEB)

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 {mu}m, 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.

NONE

2010-03-15

216

Performance of the CMS Drift Tube Chambers with Cosmic Rays  

CERN Multimedia

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

217

Performance of the CMS drift tube chambers with cosmic rays  

International Nuclear Information System (INIS)

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 ?m, 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.

2010-01-01

218

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1997-12-31

219

Flow visualisation in inclined louvered fins  

Energy Technology Data Exchange (ETDEWEB)

In this study the flow within an interrupted fin design, the inclined louvered fin, is investigated experimentally through visualisation. The inclined louvered fin is a hybrid of the offset strip fin and standard louvered fin, aimed at improved performance at low Reynolds numbers for compact heat exchangers. The flow behaviour is studied in six geometrically different configurations over a range of Reynolds numbers and quantified using the concept of 'fin angle alignment factor'. The transition from steady laminar to unsteady flow was studied in detail. The fin geometry had a very large impact on the transitional flow behaviour, especially on vortex shedding. (author)

T' Joen, C.; De Paepe, M. [Department of Flow, Heat and Combustion Mechanics, Ghent University-UGent, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium); Jacobi, A. [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, IL 61801 (United States)

2009-04-15

220

Performance of a lead radiator, gas tube calorimeter  

International Nuclear Information System (INIS)

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

1989-01-01

 
 
 
 
221

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

222

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, 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.

2011-01-01

223

Steady-state performance in a thermosyphon with tube separator  

Energy Technology Data Exchange (ETDEWEB)

A one-dimensional steady-state mathematical model describing natural circulation two-phase flow in a thermosyphon with tube separator is presented. The theoretical results show that a single liquid region in the lower part of the evaporator is available if the heat rate and operating temperature are low. At high performance operations the total mass flux changes weakly with variations in the operating temperature and heat rate. Void fraction distributions along the thermosyphon length are obtained under various operating conditions. Liquid fill ratios for steady flow are suggested. (Author)

Lanchao Lin; Faghri, A. [Connecticut Univ., Storres, CT (United States). Dept. of Mechanical Engineering

1997-07-01

224

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

Science.gov (United States)

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

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

2013-06-04

225

Heat exchanger with transpired, highly porous fins  

Energy Technology Data Exchange (ETDEWEB)

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

226

Effect of lubricant on spray evaporation heat transfer performance of R-134a and R-22 in tube bundles  

Energy Technology Data Exchange (ETDEWEB)

This study evaluates the effects of lubricant on spray evaporation heat transfer performance. Tests were conducted with refrigerant R-134a and triangular-pitch tube bundles made from enhanced-condensation, enhanced-boiling, low-finned, and plain-surface tubes. A 340-SUS polyol-ester (POE) oil was used for the R-134a testing because this lubricant is being integrated into industry for use with this refrigerant. Refrigerant was sprayed onto the tube bundles with low-pressure-drop, wide-angle nozzles located directly above the bundle. Collector testing was conducted with both R-134a and R-22 to determine the percentage of refrigerant contacting the tue bundle. It was found that small concentrations of the polyol-ester lubricant yielded significant improvement in the heat transfer performance of R-134a. The shell-side heat transfer coefficient was more dependent on lubricant concentration than on film-feed supply rate within the range of the respective parameters evaluated in this study. As expected, pure R-22 results show higher heat transfer coefficients than those obtained with pure R-134a at the same saturation temperature of 2.0 C (35.6 F).

Moeykens, S.A. [Trane Co., La Crosse, WI (United States); Pate, M.B. [Iowa State Univ., Ames, IA (United States)

1996-11-01

227

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

Directory of Open Access Journals (Sweden)

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

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

2013-01-01

228

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

UK PubMed Central (United Kingdom)

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

Gillies EA; Bondarenko V; Cosson J; Pacey AA

2013-02-01

229

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

Science.gov (United States)

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

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

2012-12-11

230

A method for assessing the arm movement performance: probability tube.  

UK PubMed Central (United Kingdom)

Quantification of motor performance is an important component of the rehabilitation of humans with sensory-motor disability. We developed a method for assessing arm movement performance of trainees (patients) termed "probability tube" (PT). PT captures the stochastic characteristics of a desired movement when repeated by an expert (therapist). The PT is being generated automatically from data recorded during point-to-point movement executed not more than 15 repetitions by the clinician and/or other non-expert programmer in just a few minutes. We introduce the index, termed probability tube score (PTS), as a single "goodness-of-fit" value allowing quantified analysis of the recovery and effects of the therapy. This index in fact scores the difference between the movement (velocity profile) executed by the trainee and the velocity profile of the desired movement (executed by the expert). We document the goodness of the automatic method with results from studies which included healthy subjects and show the use of the PTS in healthy and post-stroke hemiplegic subjects.

Kosti? M; Popovi? MB; Popovi? DB

2013-08-01

231

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

Science.gov (United States)

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.

Duffy, R.; Shayesteh, M.

2011-01-01

232

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.

2011-01-07

233

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

International Nuclear Information System (INIS)

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

2012-01-01

234

DKV joint project: reduction of CFC-emissions in air conditioning and refrigeration. Subproject 6. Pool boiling of new refrigerants and their mixtures at single plain and finned tubes. Final report; DKV-Verbundvorhaben: Minderung von FCKW-Emissionen in der Klima- und Kaeltetechnik. Teilvorhaben 6; Waermeuebergang bei der Verdampfung neuer Kaeltemittel an einzelnen Glatt- und Rippenrohren. Abschlussbericht  

Energy Technology Data Exchange (ETDEWEB)

Heat transfer at pool boiling from three novel finned tubes with different fin geometry to the new refrigerants R134a (CH{sub 2}F.CF{sub 3}), R152a (CH{sub 3}.CHF{sub 2}), R227 (CF{sub 3}.CHF.CF{sub 3}) and to a nearly equimolar mixture of R134a and R152a has been investigated within extended ranges of heat flux and saturation pressure. The main new features of the tubes are: K-shaped fins with very narrow fin distances/T-shaped fins with additional grooves between the fins/Y-shaped fins with additional grooves between the fins. The results show that especially the tubes with T-shaped and Y-shaped fins are significantly superior to plain tubes at pool boiling of the new refrigerants at saturation pressures up to approximately 10 bar. The biggest enhancement has been achieved using the tube with Y-shaped fins, thus energy consumption can be reduced by smaller temperature differences on the pool side, if these tubes will be applied, and the amount of refrigerants as well as construction material for the evaporators can be reduced by more compact design, being possible, because the heat flow rate transferred per unit of tube length may be chosen higher. (orig.). 11 refs., 1 tab., 12 figs. [Deutsch] Durch Waermeuebergangsmessungen bei der Verdampfung von neuen, teilfluorierten Kaeltemitteln an neuentwickelten Hochleistungs-Verdampferrohren sollten verlaessliche Auslegungsgrundlagen fuer optimierte Rohrbuendelverdampfer bereitgestellt werden, die mit geringerem Energiebedarf und durch kompakte Bauweise mit reduziertem Material- und Kaeltemittelaufwand auskommen und dadurch einerseits kein Ozongefaehrdungspotential und andererseits einen geringeren Beitrag zum Treibhauseffket liefern als die z.Zt. noch verwendete Technik. Zu Beginn des Vorhabens existierten entsprechende Unterlagen in der Literatur nicht. Als Versuchsstoffe dienten die neuen Kaeltemittel R134a(CH{sub 2}F.CF{sub 3}), R152a(CH{sub 3}.CHF{sub 2}), R227(CF{sub 3}.CHF.CF{sub 3}) sowie ein etwa aequimolares Gemisch aus R134a und R152a. Die Waermestromdichte und der Siededruck wurden in weiten Bereichen variiert. Eines der Rohre besass K-foermige Rippen mit sehr engem Rippenabstand, die beiden anderen waren sog. Hochleistungsrohre mt Veraenderungen an Rippenspitze (T-Form bzw. Y-Form) und Rippengrund (``X``-Kerben). Die Versuchsergebnisse zeigen, dass besonders die beiden Hochleistungsrohre bei Siededruecken bis etwa 10 bar erhebliche Vorteile im Vergleich zu Glattrohren versprechen. Die groesste Verbesserung lieferte das YX-rohr, so dass bei Verwendung dieses Rohres der Energiebedarf und zugleich die notwendige Kaeltemittelmenge und der Materialaufwand fuer die Verdampfer reduziert werden kann. (orig.)

Gorenflo, D.; Rott, W.; Sokol, P.; Caplanis, S; Kuenstler, W.

1993-03-01

235

Performance measurements of sealed-tube electron beam windows  

Energy Technology Data Exchange (ETDEWEB)

This paper describes the performance of the thin-film windows used in a new sealed-tube electron gun. Measurements include beam current, power, and power density along with window transmission, temperature, electron scattering and window life tests. A number of novel beam diagnostic tools were developed as part of this effort. Results are compared to Monte Carlo computer predictions and show good agreement. Transmitted beam powers in excess of 200 watts have been achieved, with current densities exceeding 30 milliamperes per square centimeter at sixty kilovolts beam energy. Predicted window wearout time exceeds several thousand hours at a current density of two milliamperes per square centimeter and a beam accelerating voltage of 60 kilovolts. This work was carried out under a Cooperative Research and Development Agreement (CRADA) between Lawrence Livermore National Laboratory and American International Technologies, Inc.

Myers, B.R.; Chen, H.L.; Meyer, G.; Wakalopulos, G.

1996-02-23

236

Performance of water-in-glass evacuated tube solar water heaters  

Energy Technology Data Exchange (ETDEWEB)

The performance of water-in-glass evacuated tube solar water heaters is evaluated using experimental measurements of optical and heat loss characteristics and a simulation model of the thermosyphon circulation in single-ended tubes. The performance of water-in-glass evacuated tube solar collector systems are compared with flat plate solar collectors in a range of locations. The performance of a typical 30 tube evacuated tube array was found to be lower than a typical 2 panel flat plate array for domestic water heating in Sydney. (author)

Budihardjo, I.; Morrison, G.L. [School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney 2052 (Australia)

2009-01-15

237

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

International Nuclear Information System (INIS)

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

238

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

239

Fin efficiency of serrated fins. 1st Rejport. Analysis of theoretical fin efficiency and experimental results; Serrated fin no fin koritsu. 1. Riron fin koritsu no kaiseki to jikken kekka  

Energy Technology Data Exchange (ETDEWEB)

The fin efficiency of serrated fins was analyzed and an analytical solution was derived as a function of modified Bessel functions. Two assumptions, i.e., thermal insulation at the end surfaces of segmented sections, and a uniform heat transfer coefficient over the fin surface, were employed in this analysis. To determine the effect of these assumptions, a heat transfer experiment was performed. From a comparison of the experimentally evaluated fin efficiencies with the analytical solution, a correction factor was obtained for a typical serrated fin configuration. 5 refs., 11 figs., 1 tab.

Hashizume, K.; Matsue, T.; Koyama, T. [Hiroshima Institute of Technology, Hiroshima (Japan). Faculty of Engineering

1997-12-25

240

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents a simulation study on the gate length scaling of a double gate (DG) FinFET. To achieve channel lengths smaller than 20 nm, innovative device architectures will be necessary to continue the benefits previously acquired through scaling. In order to obtain desirable control of shor...

Rakesh Vaid; Meenakshi Chandel

 
 
 
 
241

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.

2004-01-01

242

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

Science.gov (United States)

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 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. PMID:15487753

Schardt, Peter; Deuringer, Josef; Freudenberger, Jörg; Hell, Erich; Knüpfer, Wolfgang; Mattern, Detlef; Schild, Markus

2004-09-01

243

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

244

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; Meenakshi Chandel

2012-01-01

245

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

International Nuclear Information System (INIS)

[en] 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[fr] La presente etude fait apparaitre deux grandes categories de generateurs de vapeur pour les centrales nucleaires a reacteur PWR, d'une part du type Babcok et Wilcox et d'autre part du type Westinghouse. L'essentiel de la presente etude a consiste a examiner, a partir d'un brevet recent, la possibilite d'introduire des ailettes exterieures et interieures dans les echangeurs generateurs de vapeur pour reacteurs PWR. L'echangeur a plots est tout d'abord decrit. Les caracteristiques thermiques du plot a ailettes et d'un echangeur construit avec ces plots sont ensuite testees. L'etude theorique et l'etude experimentales sont presentees. On s'interesse plus particulierement a l'evaluation du coefficient global d'echange que les ailettes interieures permettent d'ameliorer. L'experience a ete faite pour differents debits et a differentes temperatures

1982-01-01

246

Safety and feasibility of interventional pulmonologists performing bedside percutaneous endoscopic gastrostomy tube placement.  

UK PubMed Central (United Kingdom)

BACKGROUND: Prior to the 1980s, permanent feeding tube placement was limited to an open surgical procedure until Gauderer and colleagues described the safe placement of percutaneous endoscopic gastrostomy (PEG) tubes. This procedure has since expanded beyond the realm of surgeons to include gastroenterologists, thoracic surgeons, and interventional radiologists. In some academic centers, interventional pulmonologists (IPs) also perform this procedure. We describe the safety and feasibility of PEG tube placement by IPs in a critically ill population. METHODS: Prospectively collected data of patients in a medical ICU undergoing PEG tube placement from 2003 to 2007 at a tertiary-care center were reviewed. Inclusion criteria included all PEG tube insertions performed or attempted by the IP team. Data were collected on mortality, PEG tube removal rate, total number of days with PEG tube, and complication rates. Follow-up included hospital length of stay and phone contact after discharge. Procedural and long-term PEG-related complications were recorded. RESULTS: Seventy-two patients were studied. PEG tube insertion was completed successfully in 70 (97.2%), with follow-up data in 69 of these 70. Thirty-day mortality was 11.7%. No deaths or immediate complications were attributed to PEG tube placement. PEG tube removal occurred in 27 patients, with a median time to removal of 76 days. CONCLUSIONS: Bedside PEG tube placement can be performed safely and effectively by trained IPs. Because percutaneous tracheostomy is currently performed by IPs, the ability to place both PEG and tracheostomy tubes at the same time has the potential for decreased costs, anesthesia exposure, procedural times, ventilator times, and ICU days.

Yarmus L; Gilbert C; Lechtzin N; Imad M; Ernst A; Feller-Kopman D

2013-08-01

247

Tube-type heat exchanger  

International Nuclear Information System (INIS)

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

1979-03-08

248

High Fin Width Mosfet Using Gaa Structure  

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

249

Development of a high performance air heater through use of an evacuated tube cover design. Final report  

Energy Technology Data Exchange (ETDEWEB)

Work leading to the development of a high performance air heater through use of an evacuated tube cover design is detailed. Work consisted of a literature survey, fabrication of the tubes, solar transmittance tests, thermal conductance tests, collector design, prototype construction; prototype testing, and finally performance and cost evaluation. Two types of evacuated tubes were manufactured, clear tubes and tubes with an infrared reflective coating. The tubes were arranged parallel in a close packed flat array to form a transparent cover for the collector. The array transmittance of clear tubes is similar to that of two flat sheets of low absorptance glass. The coated tube array had substantially reduced transmittance. Thermal conductance tests indicated that the tube arrays perform similar to two flat sheets of glass with an evacuated space. Convection off the lower and upper surface of the tube arrays was enhanced by the larger surface area which somewhat offset the advantage of the vacuum. Two prototype collectors were designed, built, and tested: (1) clear tube array over a selective surface; (2) coated tube array over a non-selective surface. The collectors were tested side by side with two baseline collectors, a selective surface collector without a tube array and a standard Solaron collector. Test results indicate the tube collector performs better at higher temperatures than either baseline or the coated tube collector, but the performance increase is not outstanding. Inclusion of the evacuated tube cover concept is probably not cost competitive with other collectors in either the high or low temperature range.

Jones, D.E.; Shaw, L.E.; Loef, G.O.G.

1981-01-01

250

Performance of Closed Tow-Phase Thermosyphon With Double Tube Evaporator  

International Nuclear Information System (INIS)

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

2004-01-01

251

Transient heat transfer in a functionally graded convecting longitudinal fin  

Science.gov (United States)

The study investigates the transient thermal performance of a constant area longitudinal fin made of a functionally graded material. Such a fin offers advantages that are not attainable with a traditional fin made of a homogeneous material. A numerical approach has been used to study the transient response of the fin with a step change in its base temperature. The fin is assumed to have an adiabatic tip. Three types of variations in the thermal conductivity with the longitudinal distance along the fin are considered: (a) linear, (b) quadratic, and (c) exponential. New analytical solutions for the steady state performance of the fin are derived in terms of the Bessel functions for cases (a) and (c) and in terms of the Legendre functions for case (b). These solutions provide a check on the accuracy of the transient numerical predictions for large times. The thermal performance of the fin is governed by the classical fin parameter, N c, and the fin thermal conductivity grading parameter, a. Results are presented for the transient temperature distribution, base heat flow, convective heat loss, the energy stored in the fin and the fin efficiency for representative values of N c and a. It is found that the transient, as well the steady state performance of the fin, is significantly affected by the functional grading of the fin material. The results presented are not only of fundamental interest but can also be used to design a functionally graded fin with the desirable steady and transient thermal characteristics.

Khan, W. A.; Aziz, A.

2012-10-01

252

Heat transfer performance of condenser tubes in an MSF desalination system  

International Nuclear Information System (INIS)

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

2010-01-01

253

Development of a high performance air heater through use of an evacuated tube cover design  

Energy Technology Data Exchange (ETDEWEB)

Development of a high performance air heater through use of an evacuated tube cover design is described. The cover design utilizes evacuated fluorescent light tubes laid parallel in a close packed array to form an inner transparent glazing over a conventional metal absorber plate with flow behind the plate. A tempered flat glass plate was used as an outer glazing. Both clear and infrared reflective (IR) tubes were investigated. Solar transmittance tests indicate that the clear tube array has a higher transmittance than two flat sheets of low-iron glass. The IR coating produced substantial transmittance loss. Thermal conductance tests indicate that the tubes behave similar to two flat glass sheets with a vacuum in between. The IR reflective coating was only marginally effective at reducing heat conductance. Final prototype designs are presented along with collector performance estimates.

Jones, D.E.; Shaw, L.E.

1980-01-01

254

Performance of long straw tubes using dimethyl ether  

International Nuclear Information System (INIS)

A cylindrical tracking detector with an inner radius of one meter employing straw tubes is being envisaged for the FINUDA experiment aimed at hyper-nuclear physics at DA?NE, the Frascati ?-factory. A prototype using several 10 mm and 20 mm diameter, two meter long aluminized mylar straws has been assembled and tested with a one GeV/c pion beam. While operating with dimethyl ether, gas gain, space resolution, and device systematics have been studied. A simple method of correction for systematics due to straw eccentricity has been developed and, once applied, a space resolution better than 40 ?m can be reached. (orig.).

1995-01-01

255

Heat removal from a triangular finned flat-plate solar-energy collector  

Energy Technology Data Exchange (ETDEWEB)

For a fin-and-tube header-and-riser arrangement of a flat-plate solar-energy collector, the effect of triangular tapering of the absorber fins attached to each riser has been analysed. The heat-removal factor for each triangular fin is greater than for a rectangular fin of the same base width but lower than that of a rectangular fin of the same magnitude of absorber surface area. (author).

Norton, B.; Hobson, P.A.; Probert, S.D. (Cranfield Inst. of Tech., Bedford (GB). Solar Energy Technology Centre)

1989-01-01

256

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

Energy Technology Data Exchange (ETDEWEB)

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

Carlson, C.D.

1996-02-01

257

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

International Nuclear Information System (INIS)

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

1996-01-01

258

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; Vaidyanathan.S

2010-01-01

259

Design and performance prediction of an adsorption heat pump with multi-cooling tubes  

International Nuclear Information System (INIS)

Widespread application of adsorption heat pumps has been delayed not only by poor heat and mass transfer performance but also by low operating reliability because high vacuum must be maintained in the adsorption cooling system, especially in a water system. An adsorption cooling tube is a tube in which an adsorber, a condenser and an evaporator are all completely housed to construct a small scale adsorption cooling unit. In this work, an adsorption cooling tube and an adsorption heat pump with multi-cooling tubes are designed. A theoretical model is built to simulate the performance of the designed chiller. According to the results, the coefficient of performance and specific cooling power reach about 0.5 and 85 W/kg adsorbent, respectively, at the hot water temperature of 85 deg. C. These results indicate that the designed heat pump in this work would provide a better choice if the operating reliability became crucial for an adsorption heat pump.

2009-01-01

260

Performance of fine grained photon position detector using proportional tubes  

Energy Technology Data Exchange (ETDEWEB)

As part of the NA24 experiment at the CERN-SPS a photon position detector serves to separate direct photons from abundantly produced ..pi../sup 0/ decay photons: electromagnetic showers are measured with an energy- and position-resolution sufficiently good to give a two-gamma resolving power of 1.2 cm. The shower detector covers 3 x 3 m/sup 2/ and consists of 12 layers of triangular proportional tubes (7.73 mm pitch) sandwiched with lead (altogether 9.6 X/sub 0/). For eight layers the analog information is provided by an ADC system. Ambiguities are resolved by the digital information of four additional layers inclined by 45/sup 0/. Prototypes were built in order to test gas mixtures and electronics. The electromagnetic shower development in the PPD and the prototypes are reproduced by Monte Carlo calculations. The homogeneity of the PPD has been checked by calibration measurements.

Artemiev, V.; Galaktionov, Y.; Gordeev, A.; Gorodkov, Y.; Kamishkov, Y.; Lubimov, V.; Plyaskin, V.; Pojidaev, V.; Shevchenko, V.; Shumilov, E. (Institut Teoreticheskoj i Ehksperimental' noj Fiziki, Moscow (USSR))

1984-07-15

 
 
 
 
261

Performance of fine grained photon position detector using proportional tubes  

International Nuclear Information System (INIS)

As part of the NA24 experiment at the CERN-SPS a photon position detector serves to separate direct photons from abundantly produced ?0 decay photons: electromagnetic showers are measured with an energy- and position-resolution sufficiently good to give a two-gamma resolving power of 1.2 cm. The shower detector covers 3 x 3 m2 and consists of 12 layers of triangular proportional tubes (7.73 mm pitch) sandwiched with lead (altogether 9.6 X0). For eight layers the analog information is provided by an ADC system. Ambiguities are resolved by the digital information of four additional layers inclined by 450. Prototypes were built in order to test gas mixtures and electronics. The electromagnetic shower development in the PPD and the prototypes are reproduced by Monte Carlo calculations. The homogeneity of the PPD has been checked by calibration measurements. (orig.)

1984-07-15

262

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

263

Fin efficiency of serrated fins. 3rd Report. Correction factor for the theoretical fin efficiency; Serrated fin no fin koritsu. 3. Riron fin koritsu no hosei keisu  

Energy Technology Data Exchange (ETDEWEB)

A correction factor for the theoretical fin efficiency of serrated fins was derived from an experiment. This correction factor compensates the influence of the assumptions made in the analytical model used for evaluating the fin efficiency, which has been derived theoretically in the 1st report of our study and has been expressed as an approximate equation in the 2nd report. Using this correction factor together with the theoretical fin efficiency, the actual fin efficiency can be estimated for serrated fins of various fin geometries, including plain or solid fins. (author)

Hashizume, K.; Morikawa, R.; Matsue, T.; Koyama, T. [Hiroshima Institute of Technology, Hiroshima (Japan)

2000-08-25

264

Comparison of Analytical and Experimental Effectiveness of Four-Row Plate-Fin-Tube Heat Exchangers with Water, R-22, and R-410A  

Energy Technology Data Exchange (ETDEWEB)

The analytical solutions of heat exchanger effectiveness for four-row crcmilow, cross-countertlow and cross-paralleltlow have been derived in the recent study. The main objective of this study is to investigate the etlkct of heat exchawger tlow conllguration on thermal performance with refrigerant mixtures. Difference of heat exchanger effectiveness for all flow arrangements relative to an analytical many-row solution has been analyzed. A comparison of four-row cross cou~ltet-ilow heat exchanger effectiveness between analytical solutions and experimental data with water, R-22, and R-4 10A is presented.

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

1998-11-15

265

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-09-15

266

Analysis of critical heat flux during subcooled boiling for finned fuel elements  

Energy Technology Data Exchange (ETDEWEB)

Experimental and analytical studies were performed to determine the critical heat flux (CHF) during subcooled boiling on finned fuel elements. Tests were conducted in a vertical, concentric-annulus test section consisting of a glass tube containing a finned heater element with either six, eight, or ten longitudinal fins. The phenomena leading to CHF are described and the parametric trends are discussed.A two-dimensional finite-element heat transfer model using the Galerkin method was used to analyse the experimental data to obtain CHF values. A dimensionless correlation was derived to predict the CHF values during subcooled boiling. Over 90% of the predicted CHF values agreed with those obtained from the two-dimensional analysis within [+-]30%. ((orig.))

Kowalski, J.E. (Thermalhydraulics Branch, Whiteshell Laboratories, AECL Research, Pinawa, Man. R0E 1L0 (Canada)); Buell, J.R. (Thermalhydraulics Branch, Whiteshell Laboratories, AECL Research, Pinawa, Man. R0E 1L0 (Canada)); Tran, T.V. (Thermalhydraulics Branch, Whiteshell Laboratories, AECL Research, Pinawa, Man. R0E 1L0 (Canada))

1994-09-01

267

How fish swim: flexible fin thrusters as an EAP platform  

Science.gov (United States)

Fish are capable of remarkable locomotor performance and use their fins extensively for both propulsion and maneuvering. Recent interest in using fishes as inspiration for the design of a new generation of autonomous underwater vehicles has prompted both new experimental studies of fish locomotor function and efforts to use electroactive polymers (EAP) as actuators in fish-inspired propulsive devices. The fins of fishes allow precise control over body position and vectoring of thrust during propulsion and maneuvering. Recent experimental studies of fish locomotion have revealed that fins exhibit much greater flexibility than previously suspected and that there is considerable deformation of the fin surface during locomotion. The fins of the large group known as ray-finned fishes are supported by fin rays, which have a bilaminar structure that allows active curvature control of the ray and fin surface by the fin musculature. Fish have up to seven different fins, and these fins may interact with each other hydrodynamically during locomotion. Fish fins provide an excellent test platform for the use of electroactive polymer actuators as the frequency of movement is typically less than 5 Hz, and fin muscle strains typically range from 2 to 10%. Recent developments of biorobotic fish pectoral fins actuated with EAP are reviewed.

Lauder, George V.

2007-04-01

268

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

Science.gov (United States)

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

269

Filtration model of longitudinal flow in a finned cylindrical channel  

Science.gov (United States)

The problem of laminar flow of a viscous incompressible fluid in a finned circular tube is considered. A solution is obtained in the form of series in eigenfunctions of the Laplace operator; the coefficients in the series are found numerically. For the same problem, a simpler filtration approximation is proposed in which the system of fins is modeled by a radially inhomogeneous porous layer, and fluid flow in it is described by the Brinkman equation. A formula for the effective permeability of the porous medium is obtained by varying the number and height of fins. The formula provides an accurate evaluation of the mean flow velocity and viscous drag coefficient in finned channels.

Mosina, E. V.; Chernyshev, I. V.

2012-05-01

270

An evaluation of the ASHRAE method for predicting capillary tube-suction line heat exchanger performance  

Energy Technology Data Exchange (ETDEWEB)

The ASHRAE method of predicting capillary tube performance, including the effect of suction line heat exchange, was experimentally evaluated for R-12. Capillary tube-suction line heat exchangers are commonly used in household refrigerator application. For this study, performance test data were taken over a range of operating conditions and heat exchanger geometries applicable to household refrigerators. Measured mass flow rates and calculated effective subcooling values were compared to predictions using the appropriate ASHRAE design charts. Most mass flow rate data points fell within 5% of prediction, and all fell within 10% of prediction. Effective subcooling data were within 3 F (1.7 C) of prediction.

Bittle, R.R. [Texas Christian Univ., Fort Worth, TX (United States). Dept. of Engineering; Stephenson, W.R.; Pate, M.B. [Iowa State Univ., Ames, IA (United States)

1995-12-31

271

Performance of a novel pressure release valve for cuff pressure control in pediatric tracheal tubes.  

UK PubMed Central (United Kingdom)

BACKGROUND: Acute and chronic hyperinflation of tracheal tube cuffs represents a persistent risk factor for airway damage in children when cuffed tracheal tubes are used. In order to overcome this particular risk, a cuff pressure (CP) pop-off valve has been designed to avoid CP exceeding 20 cmH(2)O. METHODS: The performance of the novel pop-off valve has been evaluated in an in vitro set-up during slow and rapid air insufflation by a syringe or a CP manometer or inadvertent compression of the cuff pilot balloon while measuring cuff and tracheal wall pressure (WP) in ID 3.0 mm cuffed tracheal tubes. Steady-state performance was evaluated during nitrous oxide exposure of tracheal tube cuffs (ID 3.0 mm). RESULTS: The novel CP pop-off valve avoided cuff hyperinflation during rapid air volume changes and showed reliable performance during steady-state nitrous oxide exposure to the tube cuff. CONCLUSIONS: These preliminary results show that the CP pop-off valve limits the effect of rapid, potentially dangerous manual cuff inflation maneuvers and reliably prevents CP exceeding the predetermined level of 20 cmH(2)O when exposed to nitrous oxide.

Dullenkopf A; Bernet-Buettiker V; Maino P; Weiss M

2006-01-01

272

Thermal and Sensitivity Analysis of Multi-Fin Devices  

Digital Repository Infrastructure Vision for European Research (DRIVER)

As device dimensions shrink into the nanometer range, power and performance constraints prohibit the longevity of traditional MOS devices in circuit design. A finFET, a quasi-planar double-gated device, has emerged as a replacement. FinFETs are formed by creating a silicon em fin which protrudes out...

Swahn, B.; Hassoun, S.

273

Performance demonstration tests for eddy current inspection of steam generator tubing  

International Nuclear Information System (INIS)

[en] 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

1996-01-01

274

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

J.S. Wang; W.J. Luo; S.P. Hsu

2008-01-01

275

Small-bore chest tubes seem to perform better than larger tubes in treatment of spontaneous pneumothorax.  

UK PubMed Central (United Kingdom)

INTRODUCTION: The aim of this study was to compare the efficacy and complications of surgical (large-bore) chest tube drainage with smaller and less invasive chest tubes in the treatment of non-traumatic pneumothorax (PT).  MATERIAL AND METHODS: This was a retrospective study of 104 cases (94 patients) of non-traumatic PT treated with chest tubes - either by pulmonary physicians (daytime and weekdays) using small-bore chest tubes, or by orthopaedic surgeons (remaining time slots) using large-bore chest tubes.  RESULTS: A total of 62 had primary spontaneous PT, 30 had secondary spontaneous PT and 12 had iatrogenic PT. A total of 62 patients were treated with large-bore (20-28 Fr) chest tubes placed with traditional thoracotomy, 42 patients were treated by a pulmonary physician, and in 30 of these cases a True-Close thoracic vent (11-13 Fr) was inserted. Patients treated with surgical chest tubes were comparable with patients treated with smaller chest tubes in terms of demographic data and type and size of PT. Compared with patients treated with smaller chest tubes, patients with surgical large-bore tubes had more complications (27.4% versus 9.5%; p = 0.026), a lower success rate (56.5% versus 85.7%; p = 0.002), and longer duration of chest tube (8.3 versus 4.9 days; p = 0.001) and of hospitalisation (11.8 versus 6.9 days; p = 0.004).  CONCLUSION: We found small chest tubes to be superior to large-bore chest tubes with regard to short-term outcomes in the treatment of non-traumatic PT.  FUNDING: not relevant. TRIAL REGISTRATION: The project was approved by the Danish Data Protection Agency, file no. 2012-41-0554. 

Iepsen UW; Ringbæk T

2013-06-01

276

Performance of a large limited streamer tube cell in drift mode  

CERN Multimedia

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

277

Performance evaluation of a dual GM Tube based 85Kr monitor  

International Nuclear Information System (INIS)

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

2012-01-01

278

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 o...

Chatrchyan, S; Khachatryan, V; Sirunyan, AM; Adam, W; Arnold, B; Bergauer, H; Bergauer, T; Dragicevic, M; Eichberger, M

279

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

Science.gov (United States)

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

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

2013-07-01

280

Performance study of an evaporator tube working under high heat fluxes  

Energy Technology Data Exchange (ETDEWEB)

The performance of an evaporator tube operating under high fluxes with water is studied analytically for possible thermal conditions in the pre- and post-burnout regions. A correlation is proposed for predicting the critical heat flux under slow burnout conditions making use of the concept proposed by Mozharov that the dry-out conditions in the tube arise due to tearing of the liquid film on the periphery due to shearing action of the lighter phase flowing in the core. The correlation is found to reasonably satisfy experimental data in the Russian literature. Besides a computational procedure is employed to describe the nature of variation of both heat transfer coefficient and thermal potential (T{sub W}-T{sub S}) all along the length of the evaporator tube. (author)

Sarma, P.K.; Srinivas, V. [GITAM, Rishikonda, Visakhapatnam 530 045 (India); Sharma, K.V. [JNTU, Hyderabad (India); Rao, V. Dharma; Subramanyam, T. [College of Engineering, Andhra University, Visakhapatnam 530 002 (India); Bergles, A.E. [Rensselear Polytechnic Institute, Troy, New York (United States)

2006-12-15

 
 
 
 
281

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

282

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

2009-01-01

283

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-07-01

284

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

285

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

2013-01-01

286

Experimental determination of shell side heat transfer coefficient and pressure drop for an oil cooler shell-and-tube heat exchanger with three different tube bundles  

Energy Technology Data Exchange (ETDEWEB)

In this paper, the heat transfer coefficient and pressure drop on the shell side of a shell-and-tube heat exchanger have been experimentally obtained for three different types of copper tubes (smooth, corrugated and with micro-fins). Also, experimental data has been compared with theoretical data available. Correlations have been suggested for both pressure drop and Nusselt number for the three tube types. A shell-and-tube heat exchanger of an oil cooler used in a power transformer has been modeled and built for this experimental work in order to investigate the effect of surface configuration on the shell side heat transfer as well as the pressure drop of the three types of tube bundles. The bundles with the same geometry, configuration, number of baffles and length, but with different external tube surfaces inside the same shell were used for the experiment. Corrugated and micro-fin tubes have shown degradation of performance at a Reynolds number below a certain value (Re<400). At a higher Reynolds number the performance of the heat exchanger greatly improved for micro-finned tubes. (author)

Hosseini, R.; Hosseini-Ghaffar, A. [Faculty of Mechanical Engineering Amirkabir University of Technology, 424 Hafez Avenue, P.O. Box 15875-4413, Tehran (Iran); Soltani, M. [Mechanical Systems Department, Niroo research Institute (NRI), End of Pounak Bakhtari Blvd., P.O. Box 14665-517, Shahrak Gharb, Tehran (Iran)

2007-04-15

287

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

International Nuclear Information System (INIS)

[en] 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

2012-01-01

288

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

Directory of Open Access Journals (Sweden)

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

Toshinobu Yokoyama; Reiko Toda; Ryusuke Tomioka; Hisamichi Aizawa

2009-01-01

289

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; Dr.P.Govindarajan

2010-01-01

290

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

International Nuclear Information System (INIS)

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

2011-01-01

291

Development of an Accordion-type Offset-fin Heat Exchanger for Air-conditioners  

Science.gov (United States)

To reduce the depth of the indoor heat exchanger in room air-conditioners, we studied fin and tube heat exchangers, and found that we could make the heat transfer coefficient of fins 30% higher than of conventional fins by reducing louver width and fin pitch. We also improved water drainage on the surface of the fins by adopting accordion-type offset-fin heat exchangers. We found that the material cost of a heat exchanger was minimized when the heat exchanger had a tube 7 mm in diameter, and we could increase the heat transter coefficient of the refrigerant side by developing a new grooved tube 7 mm in diameter. We succeeded in making the heat exchanger 40% thinner than conventional types.

Itoh, Masaaki; Kogure, Hiroshi; Miyagi, Masahiro; Mochizuki, Sadanari; Yagi, Yoshinao; Kunugi, Yoshifumi

292

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

Energy Technology Data Exchange (ETDEWEB)

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

Guentay, A.D.S.

1995-09-01

293

EXPERIMENTAL HEAT TRANSFER ANALYSIS ON ANNULAR CIRCULAR AND ELLIPTICAL FINS .  

Directory of Open Access Journals (Sweden)

Full Text Available Most of the engineering problems require high performance heat transfer components with progressively less weights, volumes, accommodating shapes and costs. Extended surfaces (fins) are one of the heat exchanging devices that are employed extensively to increase heat transfer rates. The rate of heat transfer depends on the surfacearea of the fin. Radial or annular fins are one of the most popular choices for exchanging the heat transfer rate from the primary surface of cylindrical shape. In this paper the heat transfer rate and efficiency for circular and elliptical annular fins were analyzed for different environmental conditions.. Elliptical fin efficiency is more than circular fin. If space restriction is there along one particular direction while the perpendicular direction is relatively unrestricted elliptical fins could be a good choice.

N.Nagarani,; K.Mayilsamy

2010-01-01

294

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; Nasrin Dindar Mehrabani

2013-01-01

295

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

Science.gov (United States)

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

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

2012-12-20

296

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

International Nuclear Information System (INIS)

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

2007-01-01

297

Thermal performance of a circular tube filled with a high porous material  

International Nuclear Information System (INIS)

This paper describes the heat transfer and flow characteristics of a heat exchanger tube filled with a high porous material. Fine copper wire (diameter: 0.5 mm) was inserted in a circular tube dominated by thermal conduction and forced convection. The porosity was from 0.98 to 1.0. Working fluid was air. Hydraulic equivalent diameter was cited as the characteristic length in Nusselt number and Reynolds number. Nusselt number and friction factor were expressed as functions of Reynolds number and porosity. Thermal performance was evaluated by the ratio of Nusselt number with and without a high porous material and the entropy generation. It was recognized that the high porous material was effective in low Reynolds number and the Reynolds number which minimized the entropy generation, existed. (author)

2006-01-01

298

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

299

El fin del fin del mundo  

Directory of Open Access Journals (Sweden)

Full Text Available En este ensayo la profesora Ivette Fred discute la utilización del lenguaje científico en las discusiones sobre el cambio climático en la tierra. Absteniéndose a cuestionar la validez de los planteamientos científicos, se limita a analizar la forma en la cual los científicos transmiten estas ideas. Considera que el lenguaje utilizado para referirse a los cambios climáticos es similar al que se emplea en los discursos religiosos de corte apocalíptico. Compara ambos discursos, como describen el fin del mundo en un lenguaje muy similar. Termina por plantear las siguientes preguntas: ¿Por qué los científicos recurren al lenguaje apocalíptico? ¿Cómo los seres se pueden unir como humanidad? ¿Cómo se podría describir una catástrofe sin sonar catastrófico?

Ivette Fred

2009-01-01

300

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.

2009-01-01

 
 
 
 
301

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

302

Fin efficiency of serrated fins. 2nd Report. Approximation equation for theoretical fin efficiency; Serrated fin no fin koritsu. 2. Riron fin koritsu no kinjishiki  

Energy Technology Data Exchange (ETDEWEB)

An analytical solution for the theoretical fin efficiency of serrated fins was derived in the 1st report. This solution was given as a function of the modified Bessel functions, therefore, a computer having any solver for the modified Bessel functions is needed to calculate the fin efficiency. In this report, an approximation equation is presented for the theoretical fin efficiency, which enables the calculation with a pocked calculator. The deviation of the calculated result from the analytical solution is within {+-} 1.5% for the industrially practical ranges. (author)

Hashizume, K.; Morikawa, R.; Matsue, T.; Koyama, T. [Hiroshima Institute of Technology, Hiroshima (Japan)

1999-04-25

303

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

Energy Technology Data Exchange (ETDEWEB)

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.

Gonczy, J.D.; Boroski, W.N.; Larson, E.T.; Nicol, T.H.; Niemann, R.C.; Otavka, J.G.; Ruschman, M.K.

1988-12-01

304

Electronic imaging system using a high-performance HARPICON tube for neutron radiography  

International Nuclear Information System (INIS)

[en] A high-performance HARPICON tube has been equipped to an electronic imaging camera of Musashi Image Processing System for neutron radiography (NRG). A vertical limiting resolution of 1600 TV lines was obtained with an imaging size of 2048 x 2048 pixels using the EIAJ test chart-A. The camera was applied to neutron radiography at the NRG facility of JRR-3M at Japan Atomic Energy Research Institute and excellent neutron radiographs have been obtained. Durability of the HARPICON camera against neutron and gamma rays was proved. (orig.)

1996-07-21

305

Electronic imaging system using a high-performance HARPICON tube for neutron radiography  

Science.gov (United States)

A high-performance HARPICON tube has been equipped to an electronic imaging camera of Musashi Image Processing System for neutron radiography (NRG). A vertical limiting resolution of 1600 TV lines was obtained with an imaging size of 2048 × 2048 pixels using the EIAJ test chart-A. The camera was applied to neutron radiography at the NRG facility of JRR-3M at Japan Atomic Energy Research Institute and excellent neutron radiographs have been obtained. Durability of the HARPICON camera against neutron and gamma rays was proved.

Mochiki, Koh-Ichi; Uno, Takayuki; Murata, Yutaka; Kobayashi, Hisao; Matsubayashi, Masahito; Tsuruno, Akira

1996-02-01

306

Electronic imaging system using a high-performance HARPICON tube for neutron radiography  

Energy Technology Data Exchange (ETDEWEB)

A high-performance HARPICON tube has been equipped to an electronic imaging camera of Musashi Image Processing System for neutron radiography (NRG). A vertical limiting resolution of 1600 TV lines was obtained with an imaging size of 2048 x 2048 pixels using the EIAJ test chart-A. The camera was applied to neutron radiography at the NRG facility of JRR-3M at Japan Atomic Energy Research Institute and excellent neutron radiographs have been obtained. Durability of the HARPICON camera against neutron and gamma rays was proved. (orig.).

Mochiki, K. [Musashi Inst. of Tech., Tokyo (Japan). Dept. of Electrical and Electronic Engineering; Uno, T. [Musashi Inst. of Tech., Tokyo (Japan). Dept. of Electrical and Electronic Engineering; Murata, Y. [Musashi Inst. of Tech., Tokyo (Japan). Dept. of Electrical and Electronic Engineering; Kobayashi, H. [Rikkyo Univ., Yokosuka, Kanagawa (Japan). Inst. for Atomic Energy; Matsubayashi, M. [Japan Atomic Energy Research Institute, Shirakata-Shirane, Tokai-mura, Naka-gun, Ibaraki-ken, 319-11 (Japan); Tsuruno, A. [Japan Atomic Energy Research Institute, Shirakata-Shirane, Tokai-mura, Naka-gun, Ibaraki-ken, 319-11 (Japan)

1996-07-21

307

A performance comparison of lithium, helium, and flibe cooled tube/header fusion blankets  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study is to provide a comparison of thermal-hydraulic and structural performance of lithium, helium, and flibe cooled fusion blankets based on a tube/header geometry in a liquid lithium breeder. Type 316 stainless steel and TZM are considered as representative near-term and long-term, high temperature blanket structural materials, respectively, to show the potentials of each coolant. The flibe-TZM system has the best characteristics, while lithium-316SS, helium-316SS, and helium-TZM are comparable but definitely more limited in operating conditions. These results suggest that molten salt-refractory metal systems deserve more attention.

Chao, J.; Gierszewski, P.; McManamy, T.J.; Mikic, B.B.; Todreas, N.E.

1982-04-01

308

Optical absorption and photoelectrochemical performance enhancement in Si tube array for solar energy harvesting application  

Science.gov (United States)

We studied large-scale fabrication and photovoltaic properties of Si tube array (SiTA) for solar energy harvesting application. The SiTA is fabricated with photolithography by using Poisson spot effect, followed by investigating its light absorption properties and photoelectrochemical performance to compare its solar energy harvesting property with the well studied Si hole and Si pillar array. It was found that SiTA has the highest onset potential and photocurrent among the three Si micro/nanostructures because of its ``hole-in-pillar'' hierarchal structures. The result suggests an alternative strategy in enhancing the efficiency of Si photovoltaic devices using this hierarchal structure.

Zhang, Ying; Wang, Hui; Liu, Zhen; Zou, Bin; Duan, Chunyang; Yang, Tian; Zhang, Xiujuan; Zheng, Caijun; Zhang, Xiaohong

2013-04-01

309

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

310

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 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.

2008-10-01

311

Effect of surface conditions on boiling heat transfer of refrigerants in shell-and-tube evaporators  

International Nuclear Information System (INIS)

Experimental results are presented for the boiling heat transfer performance of R 22 and R 717 on surfaces with porous metallized coatings. A calculational-theoretical model is given for predicting the heat transfer of refrigerants boiling on a bundle of finned tubes.

1990-01-01

312

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

Directory of Open Access Journals (Sweden)

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

A. Al-Witry; M. Es-Saheb

2013-01-01

313

Performance comparisons of enhanced tubes with discrete and wavy disruption shapes  

Energy Technology Data Exchange (ETDEWEB)

This paper presents comparisons of the friction factors and heat-transfer coefficients obtained with enhanced tubes with transverse discrete and almost transverse wavy two-dimensional disruptions. Both experimental data and numerical predictions were used for the comparisons. For the latter a two-layer turbulence model incorporated in a body-fitted, finite-volume method was used. The disruption shape, discrete or wavy, depends on the manufacturing process. If an extrusion process is used, discrete disruptions (ribs) of various profiles are obtained that are separated from each other by a flat or unaltered inside diameter. If a spirally indenting process is used, a wavy proflie is obtained with a continuously varying inside diameter between two adjacent disruption peaks. These disruptions are transverse or almost transverse to the tube axis and separated by a distance that exceeds the reattachment length. Based on these comparisons, the following conclusions are obtained: (1) the disruption shape is not an important correlating parameter for discrete disruptions, (2) only the friction factor is influenced by the shape for wavy disruptions, and (3) there are major differences between both the friction-factor and heat-transfer performance of discrete and wavy disruptions with the same maximum disruption height and spacing. However, the most important finding is that the groove radius of spirally indented tubes should be increased because of the substantial reduction of the friction factor but only a small decrease in the thermal performance. Additional comparisons of predicted results were made to obtain a fundamental understanding of the influence of these different shapes.

Arman, B.; Rabas, T.J.

1993-08-01

314

Research on Under-actuated Flexible Pectoral Fin of Labriform Fish  

Directory of Open Access Journals (Sweden)

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

Qiang Liu

2012-01-01

315

Performance of a two-phase closed thermosyphon solar collector with a shell and tube heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

In the present study, a two-phase closed thermosyphon flat-plate solar collector with a shell and tube heat exchanger was investigated experimentally under the field conditions of Cairo, Egypt. The collector was designed, constructed, and tested at transient conditions to study its performance for different cooling water mass flow rates at different inlet cooling water temperatures. Also the effect of the number of the thermosyphon tubes on the performance of the collector was investigated. Under different climate conditions, the experimental results showed that the optimal mass flow rate is very close to the ASHRAE standard mass flow rate for testing conventional flat-plate solar collectors. Also, the experimental results indicated that the number of the thermosyphon tubes has a significant effect on the collector efficiency. The performance of the present collector with optimum number of thermosyphon tubes was compared with the performance of two-phase closed thermosyphon flat-plate solar collectors with tube in tube heat exchangers of previous investigators and a better performance for the present collector was obtained at high inlet water temperature. (author)

Nada, S.A. [Benha High Institute of Technology (Egypt). Dept. of Mechanical Engineering; El-Ghetany, H.H.; Hussein, H.M.S. [National Research Center, Dokki (Egypt). Dept. of Solar Energy

2004-09-01

316

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

International Nuclear Information System (INIS)

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

1996-01-01

317

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-03-01

318

Optimum profiles for asymmetrical longitudinal fins in annular ducts  

Energy Technology Data Exchange (ETDEWEB)

In the present work the geometry of annular ducts with asymmetrical longitudinal fins is optimized in order to enhance the heat transfer under laminar coolant flow conditions. The heat transferred is also maximized for a given amount of material or hydraulic resistance. Polynomial profiles are assigned to the two lateral fin surfaces. Velocity and temperature distributions on the annular duct cross section are determined with the help of a finite-element model. A global heat transfer coefficient and an equivalent Nusselt number are then calculated. Lastly, optimum asymmetrical fins obtained by means of a genetic algorithm are shown for different situations and their performance is compared with those of optimum symmetrical fins.

Fabbri, G.

2000-04-01

319

Optimization of convective trapezoidal profile circular pin fins  

Energy Technology Data Exchange (ETDEWEB)

Circular pin fins or spines are frequently used as heat exchange devices in air conditioners. Here, circular convective pin fins of trapezoidal profile are analyzed. The results are presented in a manner which is more useful than the conventional efficiency graphs given in the textbooks and handbooks. The solution of the optimal problem can be used to determine the optimum heat dissipation or volume and optimum dimensions of the pin fin. Performance of the pin fins for off-optimum conditions is also discussed.

Das, S.; Razelos, P. [Coll. of Staten Island, NY (United States). Dept. of Applied Sciences

1997-07-01

320

Constructal T-shaped fins  

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-06-01

 
 
 
 
321

Net Shape Fins for Compact Heat Exchanger Produced by Cold Spray  

Science.gov (United States)

This work explores the manufacturability of pyramidal fin arrays produced using the cold spray process. Near-net shaped pyramidal fin arrays of various sizes and fin densities were manufactured using masks made of commercially available steel wire mesh. The feedstock powders used to produce the fins are characterized using scanning electron microscopy. Obstruction of the masks was investigated. The standoff distances between the substrate, mesh, and nozzle were empirically determined. Fin array characterization was performed using digital microscopy. The fin arrays' heat transfer performance was assessed experimentally for a range of Reynolds number relevant to the application sought. The fins produced using the cold spray process outperform traditional straight (rectangular) fins at the same fin density and it is hypothesized that this is due to increased fluid mixing and turbulence.

Cormier, Yannick; Dupuis, Philippe; Jodoin, Bertrand; Corbeil, Antoine

2013-10-01

322

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

323

An acute control improves the performances of a cogeneration installation; Un pilotage fin ameliore les performances d'une cogeneration  

Energy Technology Data Exchange (ETDEWEB)

In order to reduce the space heating costs of its occupiers, the OPAC company of Paris (France) is testing the use of cogeneration for the space heating of its residential buildings. The fuel heating plant of the Charenton-Meuniers bloc of flats was replaced by a natural gas cogeneration unit of 695 kW of electrical power and 1053 kW of thermal power which in order to supply 506 apartments in hot water between November and March. Three auxiliary gas heating plant of a total 3350 kW power are used as a complement of cogeneration during winter and for the production of sanitary hot water during the rest of the year. A tele-management and supervision system is used to control the performances of the cogeneration system and to manage the contract for the supply of natural gas. (J.S.)

Anon.

1999-09-01

324

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

International Nuclear Information System (INIS)

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

2003-11-11

325

FinFET analogue characterization from DC to 110 GHz  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this work the analogue performance of 50 nm gate length FinFETs is investigated under static and dynamic conditions up to 110 GHz. The fin width is shown to have a large impact on some analogue figures of merit such as the Early voltage because it determines the existence of volume inversion, ful...

Lederer, Dimitri; Kilchytska, Valeriya; Rudenko, T.; Collaert, Nadine; Flandre, Denis; Dixit, A; De Meyer, K; Raskin, Jean-Pierre

326

Influence of lubricant oil on heat transfer performance of refrigerant flow boiling inside small diameter tubes. Part I: Experimental study  

Energy Technology Data Exchange (ETDEWEB)

Two-phase flow pattern and heat transfer characteristics of refrigerant-oil mixture flow boiling inside small tubes with inside diameters of 6.34 mm and 2.50 mm are investigated experimentally. The test condition of nominal oil concentration is from 0% to 5%, mass flux from 200 to 400 kg m{sup -2} s{sup -1}, heat flux from 3.2 to 14 kW m{sup -2}, evaporation temperature of 5 C, inlet quality from 0.1 to 0.8, and quality change from 0.1 to 0.2. Wavy, wavy-annular, annular and mist-annular flow pattern in 6.34 mm tube are observed, while only slug-annular and annular flow pattern are observed in 2.50 mm tube. Oil presence can make annular flow to form early and to retard to diminish in quality direction at nominal oil concentration {>=}3%. Augmentation effect of oil on heat transfer coefficient becomes weakened or even diminishes for small diameter tube while detrimental effect of oil on small tube performance becomes more significant than large tube. For both test tubes, variation of heat transfer coefficient and enhanced factor with oil concentration is irregular. Two-phase heat transfer multiplier with refrigerant-oil mixture properties increases consistently and monotonically with local oil concentration at different vapor quality. (author)

Wei, Wenjian; Ding, Guoliang; Hu, Haitao [Refrigeration and Cryogenics Institute, Shanghai JiaoTong University, ShangHai 200030 (China); Wang, Kaijian [Fujitsu General Institute of Air-Conditioning Technology Limited, Kawasaki 213-8502 (Japan)

2007-10-15

327

A new nanoscale and high temperature field effect transistor: Bi level FinFET  

Science.gov (United States)

In this paper, we propose a new Bi Level Fin Field Effect Transistor (BL-FinFET) where the fin regions consist of Bi level. The novel features of the BL-FinFET are simulated and compared with a Conventional FinFET (C-FinFET). The three-dimensional and two-carrier device simulation demonstrate that the application of Bi level to the FinFET structure results in an ideal threshold voltage roll-off, reduced DIBL, excellent behavior in voltage gain at high temperatures and the gate capacitance improvement when compared with the C-FinFET. Also, this paper illustrates the benefits of the high performance BL-FinFET device over the conventional one and expands the application of Silicon on Insulator Metal Oxide Semiconductor Field Effect Transistors (SOI MOSFETs) to high temperature.

Mehrad, Mahsa; Orouji, Ali A.

2011-12-01

328

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

Directory of Open Access Journals (Sweden)

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

Syed S. Daood; Aamir Ijaz; Muhammad A. Butt

2007-01-01

329

Apparatus to reduce or eliminate fluid bed tube erosion  

Energy Technology Data Exchange (ETDEWEB)

Apparatus to reduce or eliminate fluid bed erosion in fluid bed combustion boilers by increasing the fire-side tube temperature by adding appropriately dimensioned longitudinal or circumferential fins to the inbed heat exchange tubes in the reactor.

McCoy, D.E.; Garver, D.L.; Hileman, G.

1988-04-13

330

Experimental Comparisons between Tetrakis(dimethylamino)titanium Precursor-Based Atomic-Layer-Deposited and Physical-Vapor-Deposited Titanium--Nitride Gate for High-Performance Fin-Type Metal--Oxide--Semiconductor Field-Effect Transistors  

Science.gov (United States)

In this study, we successfully introduced an atomic-layer-deposited (ALD) titanium nitride (TiN) gate grown with a tetrakis(dimethylamino)titanium (TDMAT) precursor into fin-type metal--oxide--semiconductor field-effect transistor (FinFET) fabrication for the first time, and comparatively investigated the electrical characteristics, including mobility and threshold voltage (Vth) variation, of the fabricated ALD and physical-vapor-deposited (PVD)-TiN gate FinFETs. The ALD-TiN gate FinFETs showed superior conformality to the PVD-TiN gate FinFETs. The electron mobilities of the ALD- and PVD-TiN gate FinFETs were comparable in the small Lg region. It was also confirmed that the ALD-TiN gate FinFETs showed a smaller Vth variation than the PVD-TiN gate FinFETs.

Hayashida, Tetsuro; Endo, Kazuhiko; Liu, Yongxun; O'uchi, Shin-ichi; Matsukawa, Takashi; Mizubayashi, Wataru; Migita, Shinji; Morita, Yukinori; Ota, Hiroyuki; Hashiguchi, Hiroki; Kosemura, Daisuke; Kamei, Takahiro; Tsukada, Junichi; Ishikawa, Yuki; Yamauchi, Hiromi; Ogura, Atsushi; Masahara, Meishoku

2012-04-01

331

Fouling of augmented heat transfer tubes  

Energy Technology Data Exchange (ETDEWEB)

Comparisons are made between fouling of augmented and plain heat transfer tubes. Results from the literature are analyzed on a consistent basis to emphasize differences between extended and enhanced surfaces. Tubes with internal and external fins are considered, as well as different types of enhanced tubes. Based on the analysis of this data, recommendations are given for assigning fouling resistances for augmented tubes of the corresponding plain-tube fouling resistances.

Watkinson, A.P. (University of British Columbia, Vancouver (CA))

1990-01-01

332

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

2007-04-07

333

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

Energy Technology Data Exchange (ETDEWEB)

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

Arman, B.; Rabas, T.J.

1992-01-01

334

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

Energy Technology Data Exchange (ETDEWEB)

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

Arman, B.; Rabas, T.J.

1992-08-01

335

Inspection performance of eddy current probe for in-service inspection of HTTR intermediate heat exchanger tubes  

International Nuclear Information System (INIS)

An experimental study was carried out to clarify the inspection performance of an eddy current probe for the inservice inspection of the intermediate heat exchanger (IHX) tubes of the high-temperature engineering test reactor. Test tubes were made of the same material (Hastelloy XR) and dimensions as those of the IHX, and had artificial discontinuities with reference to the standards of steam generator tubes in ASME Boiler and Pressure Vessel Code which were conservative for the IHX tubes. It was confirmed that the inspection performance of the probe satisfied the ASME standards in the base metal. The probe also could detect discontinuities such as a 90deg circumferential groove with 0.5 mm in width and 20% through from the outer tube surface, and a 100% through-wall hole with 0.5 mm in diameter. The inspection performance was lowered for discontinuities in the welded joint, and flat bottom holes with 1.7 mm in diameter were not detected. The inspection limit of 90deg circumferential grooves with 1.5 mm in width, was above 60% in depth for outer surface and 20% in depth for inner surface in the welded joint. (author).

1993-01-01

336

Seed celler having dual drives for turning fin and seed cell knife  

UK PubMed Central (United Kingdom)

An apparatus for coring and seed celling pears, apples, honeydew melons, cantaloupe and other fruits is provided in which a seed celler support tube is utilized to drive a seed celler knife and wherein a coring tube is utilized to rotate said fruit by one or more turning fins mounted on the coring tube. Separate and independent stepper motor drives are provided for the coring tube and the seed celler support tube. During a portion of the peeling process, the turning fin and seed celler knife are rotated at the same speed. In order to sever the seed cell, the seed celler blade is caused to either rotate faster or slower than the turning fin to sever the seed cell.

POLACO II JOSEPH V; BLICKENSDERFER DWIGHT A; HOWARTH MATTHEW S; CAMPBELL BARRY M; MILLER STANLEY M; FRITZ MICHAEL H

337

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

338

Supercritical heat exchanger field test (SHEFT), I. Field performance data on shell-and-tube heat exchangers in geothermal service  

Energy Technology Data Exchange (ETDEWEB)

Field performance data on shell-and-tube heat exchangers in geothermal service are presented. The test data were taken for geothermal brine on the tube side and hydrocarbon on the shell side in counterflow for six primary heat exchangers, and for hydrocarbon on the shell side and cooling water on the tube side for the condenser. Test data were for heating isobutane, 1 90/10 isobutane/isopentane mixture, and a 80/20 isobutane/isopentane mixture at supercritical conditions in the vicinity of their critical pressure and temperature, and for condensing the same fluids. The test data were used in a preliminary data analysis to determine the reported heat exchanger performance parameters.

Silvester, L.F.; Beaulaurier, L.O.; Mirk, K.F.; Fulton, R.L.

1981-06-01

339

Research on Under-actuated Flexible Pectoral Fin of Labriform Fish  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The new propulsor, whose inspiration is from pectoral fins of fishes, has arisen increasing attention. To improve the performance of the existing labriform bionic pectoral fin, based on the structure and control mechanism of real fish pectoral fin, the under-actuated technology was utilized...

Qiang Liu

340

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

International Nuclear Information System (INIS)

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

2007-01-01

 
 
 
 
341

An experimental evaluation of capillary tube-suction line heat exchanger performance with refrigerant HFC-134a  

Energy Technology Data Exchange (ETDEWEB)

Capillary tube-suction line heat exchanger performance with refrigerant HFC-134a was experimentally evaluated for a range of heat exchanger geometries and operating conditions typically found in household refrigerators. Due to the number of variables that could potentially influence heat exchanger performance, statistical methods were employed in designing the experimental test plan and in reducing the data. Key variables and their respective ranges tested included: capillary tube inner diameter (0.66 to 0.79 mm), capillary tube length (2,440 to 3,300 mm), heat exchanger length (1,000 mm to 1,780 mm), condensing temperature (29.4 to 55.6 C, which corresponds to a condensing pressure of 758 kPa and 1,516 kPa), evaporator pressure (131 to 165 kPa), capillary tube inlet condition (2.8 to 5.6 C subcool), and oil concentration level (0 to 3%). For these experiments, the measured HFC-134a mass flow rates ranged between 2.7 and 9.5 kg/hr, and measured effective subcooling level ranged between 13 and 33 C. Based on the resulting performance database, design correlations predicting mass flow rate and the heat exchanger effectiveness were developed and verified. The HFC-134A results were also compared to measured heat exchanger performance with refrigerants HFC-152a and CFC-12.

Bittle, R.R. [Texas Christian Univ., Fort Worth, TX (United States). Dept. of Engineering; Pate, M.B. [Iowa State Univ., Ames, IA (United States). Dept. of Mechanical Engineering

1996-12-31

342

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 of the designed drier varies from 38.61% to 43.7% where as the efficiency of sun drying varies from 12.5% to 14.15%. It is observed that the efficiency of the drier increases with increase in air velocity flow rates. Initial moisture content of amla ranges between 83.6% and 84.3% and the equilibrium moisture content ranges between 0.1% and 0.6%. Solar drying takes 5 to 7 hours to reach safe moisture content where as sun drying takes 13 to15 hours. Also the quality of solar dried amla is better in terms of colour, odour, flavour and appearance than the sun dried amla. The observed result of the present work shows that the proposed solar drier is good for drying amla in this region.

AR. Umayal Sundari; P. Neelamegam; C.V. Subramanian

2013-01-01

343

Evaluation performance of helix tube solar collector from nano carbon composite  

Energy Technology Data Exchange (ETDEWEB)

Hot fluid is an essential requirement in both the domestic and industrial sectors. Reducing electricity consumption and energy costs as well as reducing environmental pollution are concerns that have led to the search for more viable and efficient renewable energy sources. A helix tube solar oil heater was designed and manufactured for preheating water in the distillation process of natural products and to preheat seed oil or vegetable oil in the production of bio-diesel. The thermal performance was evaluated by using solar radiation data from the province of Phitsanuloke, Thailand as well as optical parameter absorbance and infrared emissions of nano carbon composite. A solar collector is a device that absorbs the incoming solar radiation, converts it into heat, and then subsequently transfer this heat to a fluid (usually air, water, or oil) flowing through the collector. The design, thermal analysis of collectors, and results and discussion were presented in this paper. It was concluded that there is a good capability of the system to convert the solar energy to heat. 15 refs., 6 tabs., 4 figs.

Boonchom, K. [Rajabhat ChiangMai Univ., ChiangMai (Thailand). Faculty of Science and Technology; Vorasingha, A.; Bongran, T. [Naresuan Univ., Phitsanuloke (Thailand). Faculty of Science; Ketjoy, N. [Naresuan Univ., Phitsanuloke (Thailand). School of Renewable Energy; Souvakon, C. [Rajabhat Uttaradit Univ., Uttaradit , (Thailand). Faculty of Science and Technology

2006-07-01

344

A New Rounded Edge Fin Field Effect Transistor for Improving Self-Heating Effects  

Science.gov (United States)

In this paper, a new rounded edge fin field-effect transistor (RE-FinFET) is proposed, where the edges of fins near source and drain regions are rounded in order to reduce self-heating effects. The key idea in this work is to control self-heating by reducing the thermal resistance. Moreover, our simulation results demonstrate that current of the device increases. Also, the series resistance reduces due to the rounded edges of fins near source and drain. Furthermore, using three-dimensional (3D) and two-carrier device simulator, we have examined various design issues of the RE-FinFET and provided the reasons for the improved performance in terms of self-heating and short channel effects. Our results suggest that RE-FinFET is an alternate structure for FinFETs, and expands the application of FinFETs to high temperature.

Orouji, Ali A.; Mehrad, Mahsa

2011-12-01

345

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

Science.gov (United States)

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

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

1993-12-01

346

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

UK PubMed Central (United Kingdom)

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

Sandborg M; Dance DR; Carlsson GA; Persliden J

1993-12-01

347

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

348

Performance comparison of high quantum efficiency and normal quantum efficiency photomultiplier tubes and position sensitive photomultiplier tubes for high resolution PET and SPECT detectors.  

UK PubMed Central (United Kingdom)

PURPOSE: Recently, photomultiplier tubes (PMTs) and position sensitive PMTs (PSPMTs) with higher quantum efficiencies (HQE) have been developed. However, it remains unclear whether they actually improve such performances as the energy and spatial resolution for PET and SPECT detectors. METHODS: The authors evaluated the quantum efficiencies (QEs) for PMTs and PSPMTs and measured the energy resolution of a 3-in. round HQE PMT combined with various scintillators and compared the results with a conventional normal quantum efficiency (NQE) PMT of the same type. The authors also measured the position and energy performance of a 2-in. square HQE PSPMT combined with scintillator blocks and compared them with a NQE PSPMT of the same size. RESULTS: The energy resolution of the 3-in. round HQE PMT showed higher energy resolution than the NQE with all scintillators. The improvement of the energy resolution was smaller, for all measurements, than the expected value from the quantum efficiency of the PMT but was higher for the scintillators with smaller light outputs. The energy and position performance of the HQE PSPMT based block detectors showed higher position and energy performance than those with NQE. CONCLUSIONS: From these results, the authors conclude that both HQE PMT and PSPMT contribute to improve the energy and position performance for PET and SPECT detectors. Significant performance improvements will be expected in PET and SPECT systems by the use of the HQE PMTs or PSPMTs.

Yamamoto S; Watabe H; Kato K; Hatazawa J

2012-11-01

349

Tube performance at EdF 900MWe units - an update  

Energy Technology Data Exchange (ETDEWEB)

French experience with steam generator tubes is updated to 1986, and trends to be expected in 1987 are discussed. The total number of tubes plugged in EdF PWRs each year since 1983, and the reasons for plugging them are discussed. Corrosion on the primary side has been the most important cause to date. Corrosion on the secondary side has been very limited, while 1986 saw an increase in the incidence of fretting wear at antivibration bars. (U.K.).

Surgy, J. de; Hutin, J.P.; Serres, R.

1988-01-01

350

Tube performance at EdF 900MWe units - an update  

International Nuclear Information System (INIS)

[en] French experience with steam generator tubes is updated to 1986, and trends to be expected in 1987 are discussed. The total number of tubes plugged in EdF PWRs each year since 1983, and the reasons for plugging them are discussed. Corrosion on the primary side has been the most important cause to date. Corrosion on the secondary side has been very limited, while 1986 saw an increase in the incidence of fretting wear at antivibration bars. (U.K.)

1988-01-01

351

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

UK PubMed Central (United Kingdom)

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

Macesic LJ; Mulvaney D; Blevins EL

2013-06-01

352

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

Energy Technology Data Exchange (ETDEWEB)

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

Richard A. Corbett; Dave Severance

2005-02-01

353

3D modeling of dual-gate FinFET.  

UK PubMed Central (United Kingdom)

The tendency to have better control of the flow of electrons in a channel of field-effect transistors (FETs) did lead to the design of two gates in junction field-effect transistors, field plates in a variety of metal semiconductor field-effect transistors and high electron mobility transistors, and finally a gate wrapping around three sides of a narrow fin-shaped channel in a FinFET. With the enhanced control, performance trends of all FETs are still challenged by carrier mobility dependence on the strengths of the electrical field along the channel. However, in cases when the ratio of FinFET volume to its surface dramatically decreases, one should carefully consider the surface boundary conditions of the device. Moreover, the inherent non-planar nature of a FinFET demands 3D modeling for accurate analysis of the device performance. Using the Silvaco modeling tool with quantization effects, we modeled a physical FinFET described in the work of Hisamoto et al. (IEEE Tran. Elec. Devices 47:12, 2000) in 3D. We compared it with a 2D model of the same device. We demonstrated that 3D modeling produces more accurate results. As 3D modeling results came close to experimental measurements, we made the next step of the study by designing a dual-gate FinFET biased at Vg1 >Vg2. It is shown that the dual-gate FinFET carries higher transconductance than the single-gate device.

Mil'shtein S; Devarakonda L; Zanchi B; Palma J

2012-01-01

354

Constructal design of Y-shaped assembly of fins  

Energy Technology Data Exchange (ETDEWEB)

This work relies on constructal design to perform the geometric optimization of the Y-shaped assembly of fins. It is shown numerically that the global thermal resistance of the Y-shaped assembly of fins can be minimized by geometric optimization subject to total volume and fin material constraints. A triple optimization showed the emergence of an optimal architecture that minimizes the global thermal resistance: an optimal external shape for the assembly, an internal optimal ratio of plate-fin thicknesses and an optimal angle between the tributary branches and the horizontal. Parametric study was performed to show the behavior of the minimized global thermal resistance. The results also show that the optimized Y-shaped structure performs better than the optimized T-shaped one. (author)

Lorenzini, Giulio [Department of Agricultural Economics and Engineering, Alma Mater Studiorum-University of Bologna, viale Giuseppe Fanin no. 50, 40127 Bologna (Italy); Oliveira Rocha, Luiz Alberto [Departamento de Fisica, Fundacao Universidade Federal do Rio Grande, Cx.P. 474, Rio Grande, RS 96201-900 (Brazil)

2006-11-15

355

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

International Nuclear Information System (INIS)

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

1993-01-01

356

Characteristics of near wake behind a circular cylinder with serrated fins (III): mechanism of velocity recovery  

International Nuclear Information System (INIS)

The characteristics of near wakes of circular cylinders with serrated fins are investigated experimentally using a hot-wire anemometer for various freesteam velocities. Near wake structures of the fin tubes are observed using a phase average technique. With increasing fin height and decreasing fin pitch, oscillation of steamwise velocity increases. While oscillation of lateral velocity decreases. The time averaged V-component velocity distribution of the finned tube is contrary to that of the circular cylinder due to the different strength of entrainment flow. This strength is affected by the distance of U/Uo=1.0 contour lines. U/Uo=1.0 contour line approaches to the wake center line when the fin density is increased. When the distance between U/Uo=1.0 contour lines comes close, the shear force should be increased and the flow toward the wake center line can be more strengthened because of the shear force. Factors related to the velocity recovery in the near wake of the finned tube are attributed to the turbulent intensity, the boundary layer thickness, the position and strength of entrainment process.

2003-01-01

357

Analysis of predicted and measured performance of an integrated compound parabolic concentrator (ICPC)  

Energy Technology Data Exchange (ETDEWEB)

A variety of configurations of evacuated Integrated Compound Parabolic Concentrator (ICPC) tubes have been under development for many years. A particularly favorable optical design corresponds to the unit concentration limit for a fin CPC solution which is then coupled to a practical, thin, wedge-shaped absorber. Prototype collector modules using tubes with two different fin orientations (horizontal and vertical) have been fabricated and tested. Comprehensive measurements of the optical characteristics of the reflector and absorber have been used together with a detailed ray trace analysis to predict the optical performance characteristics of these designs. The observed performance agrees well with the predicted performance.

Winston, R.; O' Gallagher, J.J.; Muschaweck, J.; Mahoney, A.R.; Dudley, V.

1999-07-01

358

A prospective randomized controlled trial to assess the diagnostic performance of reduced tube voltage for coronary CT angiography.  

UK PubMed Central (United Kingdom)

OBJECTIVE: Tube voltage reduction has been shown to be an effective method to reduce radiation dose in nonobese patients undergoing coronary CT angiography. To date, the impact of reduced tube voltage on objective measures of diagnostic accuracy, as defined by quantitative coronary angiography (QCA), has not been established. The purpose of this article was to investigate the impact of tube voltage reduction on the diagnostic performance of coronary CTA compared with QCA. SUBJECTS AND METHODS: We performed a prospective randomized trial evaluating 50 consecutive patients referred for catheter angiography with a body mass index (BMI) ? 35 kg/m². Patients were randomly assigned to reduced (n = 24) or standard tube voltage (n = 26). Reduced tube voltage was defined as 80 or 100 kVp for individuals with BMI < 25 kg/m² or 25-35 kg/m², respectively; whereas standard tube voltage was defined as 100 or 120 kVp for individuals with BMI < 25 kg/m² or 25-35 kg/m², respectively. Tube current was fixed by study protocol as 600 mA (BMI < 30 kg/m²) or 650 mA (BMI ? 30 kg/m²). Coronary CTA examinations were interpreted by two blinded experienced readers with a third reader providing consensus. QCA was performed by an independent experienced core laboratory blinded to coronary CTA findings. Coronary artery segments were graded for stenosis as < 50%, 50-69%, and ? 70% by coronary CTA and as percentage stenosis by QCA. In an intention-to-diagnose fashion, all segments were included for final analysis, with nonevaluable segments by coronary CTA graded as obstructive. Signal and noise; contrast (mean signal-signal in left ventricular myocardium); and signal-to-noise ratio (SNR) and contrast-to-noise (CNR) ratio were compared. RESULTS: Mean age of the study cohort was 60.2 years; 78% were men. Prospective ECG gating was used in all patients, and no differences existed in scan length between groups (p = 0.19). Standard versus reduced tube voltage was associated with a reduction in effective radiation dose (2.6 ± 0.4 vs 1.3 ± 0.5 mSv, p < 0.001). The patient prevalence of luminal stenosis ? 50% was 56% (28/50). For detection of ? 50% stenosis in the standard versus reduced kVp groups, there were no differences in per-segment sensitivity (87% vs 84%, p = 0.73), specificity (92% vs 93%, p = 0.81), or accuracy (92% vs 91%, p = 0.70). No differences were noted for reduced versus standard tube current for SNR (13 ± 4 vs 13 ± 3, p = 0.59), CNR (10 ± 3 vs 10 ± 2, p = 0.99), or graded (0-4) image quality score (3.4 ± 0.8 vs 3.5 ± 0.6, p = 0.19). CONCLUSION: Compared with standard tube voltage, coronary CTA using reduced tube voltage results in lower effective radiation dose with comparable diagnostic performance.

Leipsic J; LaBounty TM; Mancini GB; Heilbron B; Taylor C; Johnson MA; Hague C; Earls JP; Ajlan A; Min JK

2011-04-01

359

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

Science.gov (United States)

The first DIANE* neutron radiology system is being prepared for operation in the IABG laboratories in Ottobrunn (Germany). It utilizes a new D-T generator, designated GENIE 46, developed by SODERN (France) for this application. The generator is being integrated into an upgraded LTV-produced mobile neutron radiology system suitable for practical nonreactor inspection of components and structures. The maximum output of the present version of the GENIE 46 is 5 × 1011 n s-1 (14 MeV) with less than 10 mA ion beam current at 225 kV. Tube lifetime at maximum output is approximately 500 h, while at 1011 n s-1 the tube is designed for a lifetime of 1500 h. The geometry of the neutron tube, VHV connectors, ion source power supply, and cooling tubes comprises a cannister designed to be compatible with the 10-in. diameter opening in the LTV moderator/collimator assembly. 3-D Monte Carlo neutron/photon transport simulations of the new integrated radiology system operation have been performed by IABG. The calculations predict a thermal neutron flux at the collimator exit (L/D = 13) of ?th(0 <= En <= 0.3 eV) = 1.2 × 105 n cm-2 s-1. Comparisons of this value and other Monte Carlo results with actual performance will be made in the near future with the accrual of operational data.

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

1991-05-01

360

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

1982-01-01

 
 
 
 
361

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

Energy Technology Data Exchange (ETDEWEB)

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

Tyagi, M.; Maha, A.; Singh, K. V.; Li, G.; and Pang, S.S.

2006-07-01

362

Wind Fins: Novel Lower-Cost Wind Power System  

Energy Technology Data Exchange (ETDEWEB)

This project evaluated the technical feasibility of converting energy from the wind with a novel “wind fin” approach. This patent-pending technology has three major components: (1) a mast, (2) a vertical, hinged wind structure or fin, and (3) a power takeoff system. The wing structure responds to the wind with an oscillating motion, generating power. The overall project goal was to determine the basic technical feasibility of the wind fin technology. Specific objectives were the following: (1) to determine the wind energy-conversion performance of the wind fin and the degree to which its performance could be enhanced through basic design improvements; (2) to determine how best to design the wind fin system to survive extreme winds; (3) to determine the cost-effectiveness of the best wind fin designs compared to state-of-the-art wind turbines; and (4) to develop conclusions about the overall technical feasibility of the wind fin system. Project work involved extensive computer modeling, wind-tunnel testing with small models, and testing of bench-scale models in a wind tunnel and outdoors in the wind. This project determined that the wind fin approach is technically feasible and likely to be commercially viable. Project results suggest that this new technology has the potential to harvest wind energy at approximately half the system cost of wind turbines in the 10kW range. Overall, the project demonstrated that the wind fin technology has the potential to increase the economic viability of small wind-power generation. In addition, it has the potential to eliminate lethality to birds and bats, overcome public objections to the aesthetics of wind-power machines, and significantly expand wind-power’s contribution to the national energy supply.

David C. Morris; Dr. Will D. Swearingen

2007-10-08

363

Field experience and performance summary using the EPRI EMAT-based gaging system for boiler tubing  

Energy Technology Data Exchange (ETDEWEB)

The Electric Power Research Institute (EPRI) and the Babcock & Wilcox (B&W) Company have developed a boiler tube thickness gage using EMATs (Electromagnetic Acoustic Transducers) which can be used in either a spot measuring or a scanning mode to identify localized wall thinning due to corrosion or erosion. A field-hardened, prototype version has been constructed and tested in a wide range of utility boilers. The prototype has been refined into a commercial grade system that is being utilized by B&W to supply services to utilities. This paper describes the EMAT gaging system and presents results of field applications in utility boilers. The EMAT system in its current configuration is capable of measuring tube wall thickness as thin as 0.070 inches with an accuracy comparable to conventional ultrasonic measurements, {+-}0.005 inches. Thickness readings can be obtained on tube wall surfaces which have been sandblasted or ground free of scale, and on tube wall surfaces which have uniform layers of scale. The presence of scale, in some instances, can greatly enhance the ultrasonic signal strength, allowing thickness measurements on tubes without any surface preparation as long as the scale layer is uniform.

Schlader, D.; Stevens, D. [B & W Lynchberg Research Center, Lynchburg, VA (United States); Nakoneczny, G. [B & W, Barberton, OH (United States); Tilley, R. [Electric Power Research Institute, Palo Alto, CA (United States)

1996-07-01

364

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

International Nuclear Information System (INIS)

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

2009-01-01

365

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

International Nuclear Information System (INIS)

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

1982-07-27

366

Design Consideration in the Development of Multi-Fin FETs for RF Applications  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, we propose multi-fin FET design techniques targeted for RF applications. Overlap and underlap design configuration in a base FinFET are compared first and then multi-fin device (consisting of transistor unit up to 50) is studied to develop design limitations and to evaluate their effects on the device performance. We have also investigated the impact of the number of fins (up to 50) in multi-fin structure and resulting RF parameters. Our results show that as the number of fin increases, underlap design compromises RF performance and short channel effects. The results provide technical understanding that is necessary to realize new opportunities for RF and analog mixed-signal design with nanoscale FinFETs.

Peijie Feng; Prasanta Ghosh

2012-01-01

367

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)

1991-01-01

368

Comparison of product drying performance in molded and serum tubing vials using gentamicin sulfate as a model system.  

UK PubMed Central (United Kingdom)

In a previous study, heat transfer coefficients of different 10 mL tubing and molded vials were determined gravimetrically via sublimation tests with pure water. Contrary to "conventional wisdom", only small differences in K(v) values between tubing and molded vials were found in the pressure range relevant for pharmaceutical freeze-drying. In order to investigate the impact of these relatively small differences on the primary drying time of an actual product, freeze-drying experiments with 5% gentamicin sulfate solution as a model system were performed at 68, 100 and 200 mTorr. The primary drying times of the API in recently developed molded (EasyLyo™), tubing (TopLyo™) and polymer vials (TopPac™) were compared. At 68 and 100 mTorr the primary drying time of the drug in the glass vials only differed by 3% to 4%, while the polymer vial took around 9% longer. At 200 mTorr, the API in the EasyLyo™ vials dried approximately 15% faster compared to the other vial types. The present study suggest that molded vials that have been modified in design to have better heat transfer properties can achieve drying times comparable to tubing vials.

Hibler S; Wagner C; Gieseler H

2012-09-01

369

Pool boiling of R-114/oil mixtures from single tubes and tube bundles. Master's thesis  

Energy Technology Data Exchange (ETDEWEB)

An apparatus was designed, fabricated, and operated for the testing of horizontal tube bundles for boiling of R-114 with various concentrations of oil. Preliminary data were taken on the top tube in the bundle, with and without the other tubes in operation. Results showed up to a 37% increase in the boiling heat-transfer coefficient as a result of the favorable bundle effect. In a separate single-tube apparatus, three enhanced tubes were tested at a saturation temperature of 2.2 C with oil mass concentrations of 0, 1, 2, 3, 6 and 10%. The tubes were: 1) a finned tube with 1024 fins per meter, 2) a finned tube with 1575 fins per meter and 3) a Turbo-B tube. These tubes resulted in enhancement ratios in pure refrigerant of 2.8, 3.8 and 5.2, respectively, at a practical heat flux of 30 kW/sq. meter. With 3% oil, these ratios were decreased to 2.6, 3.5 and 5, while with 10% oil, these ratios were further reduced to 2.6, 3.2 and 4.7, respectively. Based on these results, the use of Turbo-B tubes is expected to result in significant savings in weight and size of evaporators over the finned tubes presently in use on board some naval vessels.

Murphy, T.J.

1987-09-01

370

Projectile fin damage from propellant combustion  

Science.gov (United States)

A novel fin heating experiment was designed to emulate in-bore heating conditions of a normal launch, without actually launching the fin. The fins are exposed to roughly the same hot gases encountered during normal launch, as well as some of the same mechanical abrasion. The test procedure allows for the post-firing examination of the fins, and is used to determine the fin damage mechanism for the non-launched fins, and apply the fin damage mechanism to normally launched fins. An interior ballistics code is used to model fin temperature for both the normal launch and the static firing (test) case, for both granular and stick propellant configurations. Qualitative comparison is made between the effects expected from modeling and those actually observed. It is found that the non-launched fins underwent mostly leading edge damage, with loss of hardcoat followed by uneven downstream ablation.

Bundy, M. L.; Horst, A. W.; Robbins, F. W.

1990-06-01

371

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

International Nuclear Information System (INIS)

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

1979-08-30

372

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

Directory of Open Access Journals (Sweden)

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

Tomas Marek; Daniela Gombarska

2006-01-01

373

In-pile performance of a double-walled tube and a tritium permeation barrier  

International Nuclear Information System (INIS)

In two recent irradiation experiments in the HFR Petten, tritium permeation rates through representative materials to be used as cooling tubes of the water-cooled lithium-lead blanket have been measured in-pile. These latest experiments in the EXOTIC 8 series (E 8.9 and E 8.10) are made of a double wall tube (DWT) and a T91 tube with an Fe-Al/Al2O3 layer acting as tritium permeation barrier (TPB). These tubes contain annular pebble beds of ceramic breeder materials for the helium-cooled pebble bed concept blanket as tritium breeding material. Both experiments are built up of two concentric and independently purged containments allowing on-line tritium release rate and permeation rate measurements. In-pile operation has ended in March 2001 after 450 full power days and resulted in an irradiation damage of approximately 2.6 and 3.2 dpa, respectively in T91 steel. This paper reports on the experimental results obtained for in-pile tritium permeation and discusses the influence of purge gas compositions, temperature and irradiation on tritium permeation through the DWT and TPB

2002-01-01

374

In-pile performance of a double-walled tube and a tritium permeation barrier  

Energy Technology Data Exchange (ETDEWEB)

In two recent irradiation experiments in the HFR Petten, tritium permeation rates through representative materials to be used as cooling tubes of the water-cooled lithium-lead blanket have been measured in-pile. These latest experiments in the EXOTIC 8 series (E 8.9 and E 8.10) are made of a double wall tube (DWT) and a T91 tube with an Fe-Al/Al{sub 2}O{sub 3} layer acting as tritium permeation barrier (TPB). These tubes contain annular pebble beds of ceramic breeder materials for the helium-cooled pebble bed concept blanket as tritium breeding material. Both experiments are built up of two concentric and independently purged containments allowing on-line tritium release rate and permeation rate measurements. In-pile operation has ended in March 2001 after 450 full power days and resulted in an irradiation damage of approximately 2.6 and 3.2 dpa, respectively in T91 steel. This paper reports on the experimental results obtained for in-pile tritium permeation and discusses the influence of purge gas compositions, temperature and irradiation on tritium permeation through the DWT and TPB.

Magielsen, A.J. E-mail: magielsen@nrg-nl.com; Bakker, K.; Chabrol, C.; Conrad, R.; Laan, J.G. van der; Rigal, E.; Stijkel, M.P

2002-12-01

375

Prospect of charge enhancement by increasing top oxide thickness of silicon-on-insulator fin field effect transistors  

Science.gov (United States)

The variation of electrostatic and transport characteristics of silicon-on-insulator fin field effect transistors (FinFETs) having sub-10 nm fin dimensions is investigated with the variation of top oxide thickness. Capacitance voltage and ballistic transport characteristics of double gate (DG) and triple gate (TG) FinFETs are obtained by self-consistently solving the coupled Schrödinger's and Poisson's equations. Performance enhancement can be obtained in terms of both on-state current and inversion capacitance by increasing the top oxide thickness of highly scaled FinFETs. The work suggests limiting values of the device parameter to differentiate the DG and TG variants of FinFET.

Zunaid Baten, Md.; Islam, Raisul; Amin, Emran Md.; Khosru, Quazi D. M.

2011-09-01

376

Heat Transfer Analysis of Cylindrical Perforated Fins in Staggered Arrangement  

Directory of Open Access Journals (Sweden)

Full Text Available The present paper gives the experimental analysis of on heat transfer enhancement and the corresponding pressure drop over a flat surface equipped with cylindrical cross-sectional perforated pin fins in a rectangular channel. The channel had a cross-sectional area of 250-100 mm2. The experiments covered the following range: Reynolds number 13,500–42,000, the clearance ratio (C/H) 0, 0.33 and 1, the inter-fin spacing ratio (Sy/D) 1.208, 1.524, 1.944 and 3.417. Nusselt number and Reynolds number were considered as performance parameters. Correlation equations were developed for the heat transfer, friction factor and enhancement efficiency. The experimental implementation shows that the use of the cylindrical perforated pin fins leads to heat transfer enhancement than the solid cylindrical fins. Enhancement efficiencies vary depending on the clearance ratio and inter-fin spacing ratio. Both lower clearance ratio and lower inter-fin spacing ratio and comparatively lower Reynolds numbers are suggested for higher thermal performance.

Mr. Amol. B. Dhumne,; Prof. Hemant S. Farkade,

2013-01-01

377

Performance Analysis of Shell and Tube Heat Exchanger Using Miscible System  

Directory of Open Access Journals (Sweden)

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

M. Thirumarimurugan; T. Kannadasan; E. Ramasamy

2008-01-01

378

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

Energy Technology Data Exchange (ETDEWEB)

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

Kolarik, Robert V.

2005-11-11