WorldWideScience
 
 
1

Performance of tubes-and plate fins heat exchangers  

International Nuclear Information System (INIS)

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

1979-01-01

2

Heat transfer performance of internally finned tubes in turbulent flow  

Science.gov (United States)

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

Carnavos, T. C.

1980-06-01

3

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

4

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

Energy Technology Data Exchange (ETDEWEB)

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

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)]. E-mail: somchai.won@kmutt.ac.th; Chokeman, Yutasak [Joint Graduate School of Energy and Environment (JGSEE), King Mongkut' s University of Technology Thonburi, Bangmod, Bangkok 10140 (Thailand)

2005-08-15

5

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

Energy Technology Data Exchange (ETDEWEB)

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

Somchai Wongwises [King Mongkut' s University of Technology, Bangkok (Thailand). Dept. of Mechanical Engineering; Yutasak Chokeman [King Mongkut' s University of Technology, Bangkok (Thailand). JGSEE

2005-08-01

6

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

7

Performance of compact louvered fin-and-tube heat exchangers under dehumidifying condition  

Energy Technology Data Exchange (ETDEWEB)

The air side performances of louvered fin surface under dehumidifying conditions were presented in this study. A total of four fin-and-tube heat exchangers were tested and compared. The test results indicated that the effect of fin pitch on the heat transfer performance is very small for Re{sub Dc} > 2,000 and N = 2. For N = 1, the heat transfer performances increase with decrease of fin pitch. Converse to the test results for fully dry condition, the friction factors increase significantly with fin pitch for fully wet conditions.

Wang, C.C.; Shyu, R.J.; Lee, C.J.; Chang, Y.J.

1999-07-01

8

Performance and optimum dimensions of flat fins for tube-and-fin heat exchangers: A generalized analysis  

Energy Technology Data Exchange (ETDEWEB)

The performance of flat fins for tube-fin heat exchangers has been analyzed for both inline and staggered arrangement of tubes. In earlier published studies, regular square and equilateral triangular array tube layouts were considered. No such restriction is put in the present study. The analysis has been done by a semi-analytical technique where the boundary condition at the fin edge is discretely satisfied at a large number of points by a method of collocation. It has also been demonstrated that the approximate results obtained by the sector method closely agree with the prediction of semi-analytical technique. Finally, a generalized scheme of optimization based on Lagrange multiplier technique has been suggested which shows that irrespective of the volume and thickness of the fins, square and equilateral triangular array of tubes are the optimum layout for inline and staggered arrangements, respectively. This result was known so far only intuitively. The optimum dimensions for flat fins for other layout of tubes have also been obtained specifying the ratio of longitudinal to transverse tube pitch.

Kundu, B. [Department of Mechanical Engineering, Jadavpur University, Kolkata 700 032 (India)], E-mail: bkundu123@rediffmail.com; Das, P.K. [Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721 302 (India)

2009-08-15

9

Performance and optimum dimensions of flat fins for tube-and-fin heat exchangers: A generalized analysis  

International Nuclear Information System (INIS)

The performance of flat fins for tube-fin heat exchangers has been analyzed for both inline and staggered arrangement of tubes. In earlier published studies, regular square and equilateral triangular array tube layouts were considered. No such restriction is put in the present study. The analysis has been done by a semi-analytical technique where the boundary condition at the fin edge is discretely satisfied at a large number of points by a method of collocation. It has also been demonstrated that the approximate results obtained by the sector method closely agree with the prediction of semi-analytical technique. Finally, a generalized scheme of optimization based on Lagrange multiplier technique has been suggested which shows that irrespective of the volume and thickness of the fins, square and equilateral triangular array of tubes are the optimum layout for inline and staggered arrangements, respectively. This result was known so far only intuitively. The optimum dimensions for flat fins for other layout of tubes have also been obtained specifying the ratio of longitudinal to transverse tube pitch.

2009-08-01

10

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

DEFF Research Database (Denmark)

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

Kærn, Martin Ryhl; Brix, Wiebke

2011-01-01

11

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

International Nuclear Information System (INIS)

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

2005-11-02

12

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

International Nuclear Information System (INIS)

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

2006-02-01

13

A computer simulation for performance prediction of fin-tube heat exchanger under frosting conditions  

Energy Technology Data Exchange (ETDEWEB)

This study is concerned with the numerical analysis of performance on fin-tube heat exchanger under frosting condition. In this work, tube-by-tube method using LMED is employed. The present results are compared with O`Neal`s experimental and numerical results. A standard evaporator model with 2 rows-2 columns is selected to investigate the effects of the various parameters such as fin pitch, air flow velocity, and humidity. The results show that frost thickness and the amount of frost per unit area decrease as fin-pitch becomes narrower. In the meantime, frost thickness and accumulation rate increase with higher inlet air humidity. It is shown that heat transfer rate increases during 30 minutes and then it decreases. Heat transfer rate and the amount of frost increase with air velocity, however frost thickness does not increase over a certain velocity. (author). 12 refs., 17 figs., 2 tabs.

Lee, Kwan Soo; Pak, Hui Yong; Lee, Wook Yong; Lee, Tae Hui [Hanyang University, Seoul (Korea, Republic of); Lee, Soo Yeop; Lee, Myung Ryul

1995-02-01

14

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.

2009-11-04

15

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

16

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.

2011-03-01

17

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

Science.gov (United States)

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

Wang, H. S.; Honda, Hiroshi

18

Shell-side condensation heat transfer of R-134a. Part 1: Finned-tube performance  

Energy Technology Data Exchange (ETDEWEB)

Shell-side condensation coefficient data are presented for the condensation of refrigerant R-134a on tube bundles constructed from 26-fin-per-inch (fpi) and 40-fpi tubes. The tube bundles tested are five rows wide by five rows deep and have a staggered tube arrangement with a horizontal pitch of 22.2 mm (0.875 in.) and a vertical pitch of 19.1 mm (0.75 in.). The data were obtained at a refrigerant saturation temperature of 35 C (95 F) over a bundle heat flux range of 18,000 to 40,000 W/m{sup 2} (5,700 to 12,700 Btu/[h {center_dot} ft {sup 2}]). Average condensing heat transfer coefficients for the bundle as well as average condensing heat transfer coefficients for the middle tube of each row were calculated. The data show that the 40-fpi tube performs better than the 26-fpi tube. The data also show a marked difference in the row to-row heat transfer coefficient trends between the two tube geometries.

Huber, J.B.; Rewerts, L.E.; Pate, M.B. [Iowa State Univ., Ames, IA (United States). Dept. of Mechanical Engineering

1994-12-31

19

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

2008-04-01

20

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

Energy Technology Data Exchange (ETDEWEB)

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.

Cui, J. [Key Lab. of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Li, W.Z., E-mail: wzhongli@dlut.edu.c [Key Lab. of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Liu, Y.; Zhao, Y.S. [Key Lab. of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024 (China)

2011-02-15

 
 
 
 
21

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.

2011-02-01

22

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

23

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.

2012-05-01

24

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

25

An experimental study on the performance of fin-tube heat exchanger under frosting condition  

Energy Technology Data Exchange (ETDEWEB)

In this study, the experiment with 2 rows-2 columns fin-tube heat exchanger under forced convection and frosting condition is performed. The influence of each operating condition(the temperature of air, the humidity of air, the velocity of air, the temperature of coolant) on the growth of frost layer, air-side pressure drop, and characteristics of heat transfer is investigated. The experimental results show that the frost thickness increases rapidly in the early stage of frost formation and increases linearly after sometime. The frost thickness increases with the increase of the inlet air humidity and velocity and the decrease of inlet air temperature and coolant temperature. It is also found that the total energy transfer rate increases with the increase of inlet air temperature and velocity and with the decrease of inlet air humidity and coolant temperature. (author). 6 refs., 17 figs., 1 tab.

Lee, Kwan Soo; Pak, Hee Yong; Lee, Tae Hee; Lee, Nam Gyo [Hanyang University, Seoul (Korea, Republic of); Lee, Soo Yeop; Lee, Myung Ryul

1995-05-01

26

The effect of conduction between rows on the heat transfer performance of fin-tube heat exchanger  

International Nuclear Information System (INIS)

This study was to investigate the effect of conduction characteristics between rows of the fin-tube heat exchanger. Experiments were performed for the 7mm tube diameter heat exchangers using air-enthalpy type calorimeter. Fin patterns of the heat exchangers were slit and louver types. Equivalent fin spacing with 18FPI was used for all samples, and the number of tube rows were 2. In order to investigate the conduction effects, one sample was physically separated between two rows, but the other was connected. The air velocity was varied from 0.7 to 2.5 m/s with 0.3 m/s interval. Heat transfer for each row are evaluated. It was observed that conduction effects between rows on the overall heat transfer performance was considerable and have to be considered for determination of heat transfer coefficients for individual row

2002-11-13

27

The effect of conduction between rows on the heat transfer performance of fin-tube heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

This study was to investigate the effect of conduction characteristics between rows of the fin-tube heat exchanger. Experiments were performed for the 7mm tube diameter heat exchangers using air-enthalpy type calorimeter. Fin patterns of the heat exchangers were slit and louver types. Equivalent fin spacing with 18FPI was used for all samples, and the number of tube rows were 2. In order to investigate the conduction effects, one sample was physically separated between two rows, but the other was connected. The air velocity was varied from 0.7 to 2.5 m/s with 0.3 m/s interval. Heat transfer for each row are evaluated. It was observed that conduction effects between rows on the overall heat transfer performance was considerable and have to be considered for determination of heat transfer coefficients for individual row.

Lee, M. K.; Chang, K. S.; Park, T. J. [Sunmoon Univ., Asan (Korea, Republic of); Jeong, J. H. [Cheonan Univ. of Foreign Studies, Cheonan (Korea, Republic of); Lee, C. S.; Hong, K. S. [LG Electronics, Seoul (Korea, Republic of)

2002-07-01

28

Performance of HC and HFC Refrigerants in a Finned-Tube Evaporator and Its Effect on System Efficiency.  

Science.gov (United States)

The paper presents a comparable evaluation of isobutane (R600a), propane (R290), R134a, R22, R410A, and R32 in an optimized finned-tube evaporator, and analyzes the impact of evaporator effects on the system coefficient of performance (COP). The study rel...

D. Yashar M. Kim P. A. Domanski

2003-01-01

29

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

DEFF Research Database (Denmark)

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

Kærn, Martin Ryhl; Elmegaard, Brian

2009-01-01

30

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Refrigerant mal-distribution in fin-and-tube evaporators for residential air-conditioning (RAC) is investigated numerically in this paper. A model of the system is developed in the object-oriented modeling language Modelica. Themodels of the compressor and expansion valve are static, whereas the condenser is a dynamic moving boundary model. The evaporator model is a dynamic distributed one-dimensional homogeneous equilibrium model, in order to capture the distribution phenomena. ...

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

2009-01-01

31

Heat and mass transfer performances on plate fin and tube heat exchangers with dehumidification  

Energy Technology Data Exchange (ETDEWEB)

The authors discuss how they conducted an experimental study on the air side performance of a single-row plate fin and tube heat exchanger in moist air where mass transfer exist under a relatively low driving potential. The results are as follows: The heat transfer with dehumidification is about 20% greater than that with only sensible heat transfer. Also the air side pressure drop is about 30-40% greater. The reason, as clarified by visual observations, comes from the condensate effect. To study how the condensate film affects performance, the presence of the stagnant condensate in the heat exchanger was modeled as an apparent change of the heat exchanger geometry, and the equivalent thickness of the condensate film was calculated from the increase in the air side pressure drop. As a result, if the presence of condensate in the heat exchanger is considered, then the heat transfer with dehumidification can be treated in the same way as with only sensible heat transfer. The analogy between heat and mass transfer does not strictly hold, the experimental results being closed to the Lewis Law.

Seshimo, Y.; Ogawa, K.; Marumoto, K.; Fujii, M. (Mitsubishi Electric Corp. (JP))

1990-09-01

32

A Numerical Study on the Performance of the Fin-Tube Heat Exchanger Operated under the Frosting Condition  

Energy Technology Data Exchange (ETDEWEB)

This study is concerned with the numerical analysis on the performance of the finned-tube heat exchanger under the frosting conditions. A tube-by-tube method using LMED is employed in the analysis, and the present results are compared with O`Neal`s experimental and numerical results. The performance analysis has been done using a standard model with a 2-row;2-column heat exchanger. The effects of various parameters such as fin pitch, air flow velocity, and humidity, are examined. As the inlet air humidity becomes higher, the frost thickness and the amount of frost increase. It is also found that the amount of frost and heat transfer rate increase with increasing air velocity, but frost thickness is nearly constant over a certain velocity range. (author). 12 refs., 2 tabs., 17 figs.

Lee, Kwan Soo; Pak, Hi Yong [Hanyang University, Seoul (Korea, Republic of); Lee, Wook Yong [LG Electronics Co., Seoul (Korea, Republic of); Lee, Tae Hee [Hanyang University, Seoul (Korea, Republic of)

1996-09-15

33

Cooling output performance of a prototype adsorption heat pump with fin-type silica gel tube module  

Energy Technology Data Exchange (ETDEWEB)

Silica gel/water type adsorption heat pump (AHP) is considered to be a promising low-temperature heat utilization system because of its ability to utilize waste heat below 353 K and to generate cooling energy for air conditioning. However, the widespread realization of AHP system has not yet been achieved due to its large footprint, which results from the low power density of the AHP system. In order to improve cooling output performance of the AHP by enhancing heat and mass transfer rates of the adsorber, a fin-type silica gel tube (FST) module consisting of circular finned-tube heat exchanger with silica gel packed between the fins was developed in our previous work. Further, based on the numerical analysis, the optimal fin pitch and fin length of the module were proposed. In this study, a prototype AHP with the new adsorber consisting of the optimized FST modules was made and cooling output performance of this prototype AHP was investigated under various operating conditions. As a result, the ability of the AHP to continuously generate cooling energy, by utilizing a heat source of around 333-353 K, was confirmed. Further, cooling output and COP were found to increase with an increase in hot water inlet temperature. Finally, it was experimentally verified that the optimized FST module can achieve more than twice higher cooling output per unit adsorber volume than the un-optimized module. (author)

Kubota, Mitsuhiro; Ueda, Takeshi; Fujisawa, Ryo [Department of Energy Engineering and Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya-shi, Aichi 464-8603 (Japan); Kobayashi, Jun [Center for Cooperative Research in Advanced Science and Technology, Nagoya University, Furo-cho, Chikusa-ku, Nagoya-shi, Aichi 464-8603 (Japan); Watanabe, Fujio [Research Institute for Industrial Technology, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota-shi, Aichi 470-0392 (Japan); Kobayashi, Noriyuki [EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya-shi, Aichi 464-8603 (Japan); Hasatani, Masanobu [Department of Mechanical Engineering, Faculty of Engineering, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota-shi, Aichi 470-0392 (Japan)

2008-02-15

34

Fin Distance Effect at Tube-Fin Heat Exchanger  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Article deals with numerical simulation of the Tube-Fin heat exchanger. Several distances between fins are examined with intence of increasing the cooling output of the heat exchanger. Geometrical model consists of set of 2 fins with input and output area. Calculations covers the area of the gap from 2.25 mm to 4 mm with new fin geometry. For the numerical silumation was used software Ansys Fluent.

Lemfeld F.; Muller M.; Frana K.

2013-01-01

35

Fin Distance Effect at Tube-Fin Heat Exchanger  

Directory of Open Access Journals (Sweden)

Full Text Available Article deals with numerical simulation of the Tube-Fin heat exchanger. Several distances between fins are examined with intence of increasing the cooling output of the heat exchanger. Geometrical model consists of set of 2 fins with input and output area. Calculations covers the area of the gap from 2.25 mm to 4 mm with new fin geometry. For the numerical silumation was used software Ansys Fluent.

Frana K.

2013-04-01

36

Fin Distance Effect at Tube-Fin Heat Exchanger  

Science.gov (United States)

Article deals with numerical simulation of the Tube-Fin heat exchanger. Several distances between fins are examined with intence of increasing the cooling output of the heat exchanger. Geometrical model consists of set of 2 fins with input and output area. Calculations covers the area of the gap from 2.25 mm to 4 mm with new fin geometry. For the numerical silumation was used software Ansys Fluent.

Lemfeld, F.; Muller, M.; Frana, K.

2013-04-01

37

Heat and mass transfar performance on plate fin and tube heat exchangers under dehumidification  

Energy Technology Data Exchange (ETDEWEB)

When moist air is cooled and the temperature on the cooling surface is 0/sup 0/C or less, heat transfer and mass transfer occur simultaneously on that surface. Condensation in a plate fin tube heat exchanger placed in moist air atmosphere was studied under the condition of relatively low propulsive force. The findings are as follows: The flow loss involved in condensation is 30% to 40% higher than that with single phase because condensed water is present. Also, the apparent behavior of the condensed water remaining in the heat exchange was simulated as a model representing changes in the shape of the heat exchanger; the equivalent water film thickness was calculated from the increase in flow loss. The results of this calculation almost agreed with the results of visual observation. When mass transfer was involved, the heat transfer rate was 20% higher than that with single phase. Whthin the scope of this experiment, exacting analogy does not hold. When mass transfer is involved, the ratio between the heat transfer rate and mass transfer rate, h/h/sub 0/, is about 0.29 W-h/(kg-K), suggesting an approximate Lewis relation. (11 figs, 1 tab, 16 refs)

Seshimo, Yu; Ogawa, Kazuhiko; Marumoto, Kenji; Fujii, Masao

1988-03-25

38

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

Energy Technology Data Exchange (ETDEWEB)

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

Ge, T.S. [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200240 (China); Dai, Y.J., E-mail: yjdai@sjtu.edu.c [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang, R.Z. [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200240 (China)

2011-06-15

39

An experimental study on the effects of design factors for the performance of fin-tube heat exchanger under frosting conditions  

Energy Technology Data Exchange (ETDEWEB)

In this study, the effects of design factors of finned-tube heat exchanger, such as fin spacing and fin array on the frost growth and heat exchanger performance are investigated under a frosting condition. The results show that the amount of frost, frost density and blockage ratio of air flow passage increase with decreasing fin spacing. Heat transfer rate increases momentarily at the initial stage of frosting and then decreases. After that heat transfer rate continues to increase again to reach a maximum value and then decreases dramatically. It is shown that the time required for heat transfer rate to reach a maximum value becomes shorter with decreasing fin spacing, and after a maximum value, heat transfer rate decreases very fast. The maximum allowable blockage ratio is introduced to determine the operation limit of a finned-tube heat exchanger operating under frosting condition and is obtained as a function of fin spacing. It is also shown that heat transfer rate of heat exchanger with staggered fin array increases about 17% and the amount of pressure drop of air increases about 1{approx}2 mmH{sub 2}O, compared with those of in-line type heat exchanger under frosting condition. (author). 13 refs., 13 figs., 2 tabs.

Lee, K.S.; Kim, W.S. [Hanyang University, Seoul (Korea, Republic of); Lee, T.H. [Hanyang University Graduate School, Seoul (Korea, Republic of)

1995-10-01

40

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

 
 
 
 
41

The Effects of Operating Factors on the Performance of Fin-Tube Heat Exchanger under Frosting Conditions  

Energy Technology Data Exchange (ETDEWEB)

In this study, the experiment with a 2-column, 2-row finned-tube heat exchanger under forced convection and frosting condition is performed. The influence of each operating condition(air temperature air humidity, air velocity, coolant temperature) on the growth of frost layer, air-side pressure drop, and characteristics of heat transfer is investigated. The experimental results show that the frost thickness increase rapidly at the early stage of frost formation and then increases linearly. The frost thickness increases with the increase in the inlet air velocity and with the decrease inlet air temperature and coolant temperature. It is also found that the total energy transfer rate increases with the increase in inlet air temperature and velocity and with the decrease in inlet air humidity and coolant temperature. (author). 6 refs., 1 tab., 17 figs.

Lee, Tae Hee; Lee, Kwan Soo; Ahn, Kang Ho [Hanyang University, Seoul (Korea, Republic of); Lee Nam Gyo [LG Electronics Co., Changwon (Korea, Republic of)

1996-09-15

42

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

1999-12-01

43

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  

Energy Technology Data Exchange (ETDEWEB)

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 humidi0008.

Lee, Kwan Soo; Kim, Woo Seung [Hanyang Univ., Seoul (Korea, Republic of)

1999-12-01

44

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

45

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

International Nuclear Information System (INIS)

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

2000-11-02

46

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

47

The effect of circuiting arrangement on the thermal performance of refrigerant 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 crossflow, counterflow, 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 two different circuiting arrangements on the thermal performance of a zeotropic refrigerant mixture and an almost azeotropic refrigerant mixture and an almost azeotropic refrigerant mixture in a four-row cross-counterflow 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 face area, fin louver geometry, refrigerant tube size and enhancement, etc., are the same for both heat exchangers. One refrigerant mixture (R-410A) undergoes a small temperature change (low glide) during phase change, and the other refrigerant 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 residential cooling conditions, inverted order circuiting is more desirable than identical order. The potential thermal advantages of the identical order arrangement for high-glide zeotropic refrigerant mixtures are negated by the increased parasitic refrigerant-side pressure drop unfortunately resulting from fabrication requirements of the identical order circuiting.

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

1999-07-01

48

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

49

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

Science.gov (United States)

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

Miyara, Akio; Otsubo, Yusuke; Ohtsuka, Satoshi

50

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 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 s...

2011-01-01

51

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 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 rang...

2011-01-01

52

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

2011-01-01

53

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-07-01

54

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

International Nuclear Information System (INIS)

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

2009-04-23

55

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

International Nuclear Information System (INIS)

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

2002-01-01

56

Study on thermo-conductive plastic finned tube radiators  

DEFF Research Database (Denmark)

This paper discusses thermo-conductive plastic finned tube radiators used in water saving type power stations. First, the development of thermo-conductive plastics is introduced. Second, in order to determine the rational geometric dimensions of thermo-conductive plastic finned tubes, an objective function which takes the minimum volume of the consumed material for making finned tubes as an object is introduced. On the basis of the function, the economy comparison between thermo-conductive plastic finned tubes and metal finned tubes is conducted.

Yang, J.; Cheng, L.

1997-01-01

57

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

58

Eddy current test of fin tubes for a heat exchanger  

International Nuclear Information System (INIS)

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

1992-05-01

59

Performance analysis and optimization of eccentric annular disk fins  

Energy Technology Data Exchange (ETDEWEB)

In the first part of the paper, a semi-analytical method has been described for solving the two-dimensional heat conduction equation in an eccentric annular disk fin circumscribing a circular tube, subjected to convective cooling. Analysis has been done considering both convective and insulated conditions at the fin tip. The effects of surface and tip heat transfer coefficients and eccentricity on the performance of the fin have been studied. Comparative studies have also been made between the performance of concentric and eccentric fins with same radius ratio. Next, the optimum dimensions for eccentric annular fins have been determined using Lagrange multiplier technique. In the scheme, either the fin volume or the heat transfer duty can be taken as the constraint. Finally, it has been shown that when space restriction is imposed on one side of the tube, eccentric annular fins can be designed to have lesser volumes compared to concentric annular fins above a certain heat transfer duty.

Kundu, B.; Das, P.K. [Indian Inst. of Tech., Kharagpur (India). Dept. of Mechanical Engineering

1999-02-01

60

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

 
 
 
 
61

Tube an fin assembly exchangers in power plants  

Energy Technology Data Exchange (ETDEWEB)

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.

Cottone, A.J.; Saperstein, Z.P.

1990-08-21

62

Fin spacing optimization of a fin-tube heat exchanger under frosting conditions  

Energy Technology Data Exchange (ETDEWEB)

Optimal values of the design parameters for a fin-tube heat exchanger of a household refrigerator under frosting conditions are proposed to improve its thermal performance and extend its operating time. In the optimization procedure, fin spacings of the heat exchanger are selected as the design parameters, and the average heat transfer rate, frost mass, and operating time are considered to be objective functions. The response surface and Taguchi methods are employed to optimize the design parameters. As a result, the average heat transfer rate and operating time of the optimum models increases by up to 6.3% and 12.9% compared to that of the reference model, respectively. (author)

Yang, Dong-Keun; Lee, Kwan-Soo; Song, Simon [School of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Sungdong-gu, Seoul 133-791 (Korea, Republic of)

2006-07-15

63

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

Directory of Open Access Journals (Sweden)

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

Wai Meng Chin

2011-01-01

64

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Wai Meng Chin; Raghavan, Vijay R.

2011-01-01

65

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

66

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

67

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

Science.gov (United States)

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

Song, Ke-Wei; Wang, Liang-Bi; Fan, Ju-Fang; Zhang, Yong-Heng; Liu, Song

2008-06-01

68

Numerical Analysis for Optimal Design of Fin and Tube Type Adsorber  

Science.gov (United States)

Adsorption cooling systems driven by low temperature waste heat (below 100°C) or renewable energy sources have gained considerable attention as one of the solutions for both energy and environment related problems. In this study, a two dimensional numerical analysis is carried out to evaluate the adsorption characteristics and to determine the performance of a fin and tube type adsorber/desorber heat exchanger; activated carbon fiber (ACF) of type A-20, which has relatively higher surface area, and ethanol are used as adsorbent/refrigerant pair. The effects of heat exchanger design configurations such as fin height, fin thickness, fin pitch, tube diameter and apparent density of ACF bed on the performance are examined numerically. The simulation results show that the cooling capacity can be optimized in the condition of fin height 15mm and fin pitch 5.5mm when other parameters are fixed.

Kariya, Keishi; Kuwahara, Ken; Shigeru, Koyama

69

Augmenting the nucleate pool-boiling characteristics of GEWA-T finned tubes in R-113  

International Nuclear Information System (INIS)

A series of pool-boiling heat-transfer measurements in R-113 were made using seven specially fabricated GEWA-T finned copper tubes to study ways to improve upon the performance of this type of surface. One tube was tested under three conditions: (a) as received, (b) with shrouds to direct the liquid-vapor flow in the inter-fin channels, and (c) with small wires wrapped within the inter-fin channels. The other six tubes had two different fine densities (0.75 and 1.02 fins/mm) and three fin-tip gaps of 0.15, 0.25 and 0.35 mm. It was shown that, at heat fluxes less than 70 kW/m/sup 2/, the use of a shroud can increase the boiling heat-transfer coefficient over the value for the as-received GEWA-T tube. Increases as large as 80 percent were measured for a shroud with a 60"0 opening at the top and an 8.5"0 opening at the bottom. At heat fluxes in excess of 70 kW/m/sup 2/, however, the presence of the shroud deteriorated the boiling performance. When wire wraps were provided, the heat-transfer coefficient was improved at all heat fluxes. The use of three wires gave the best performance with a 140 percent increase in the heat-transfer coefficient at 10 kW/m/sup 2/. The effect of fin-tip gap was studied using the six tubes described above. For each of the fin densities tested, the 0.25 mm fin-tip gap produced the best boiling performance at all heat fluxes. Also, for a given fin-tip gap, the boiling performance increased with increasing fin density. The importance of bubble nucleation and volumetric flow within the inter-fin channels and techniques to influence these parameters are described

1985-01-01

70

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

71

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

72

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

International Nuclear Information System (INIS)

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

2001-05-01

73

Numerical Analysis on Optimization of a Fin and Tube Type Adsorber/Desorber Heat Exchanger using ACF/C2H5OH Pair  

Science.gov (United States)

This study deals with a two dimensional numerical analysis of the fin and tube type adsorber/desorber heat exchanger design such as fin height, fin pitch, fin thickness and tube diameter effect on the performance of closed adsorption cooling system with activated carbon fiber (ACF) of type A-20, which has relatively higher surface area, and ethanol pair. The simulation results show that the fin tube diameter is effective on the performance of the heat exchanger. It is also found that the cycle COP can be optimized in the condition of fin pitch 4.5mm and fin height 20mm, respectively when other parameters are fixed.

Kariya, Keishi; Kuwahara, Ken; Koyama, Shigeru

74

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

Directory of Open Access Journals (Sweden)

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

Jader R Barbosa, Jr

2010-12-01

75

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-11-15

76

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

77

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 exchangers were tested with variation of the fin space, air flow rate, relative humidity, and inlet air temperature. Frost height was measured and considered with the boundary layer interruption b...

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

2012-01-01

78

Experimental study of air side pressure drop and heat transfer characteristics of enhanced fin-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Heat transfer and pressure drop for {phi}10.07 dry surface fin-tube heat exchanger with wave and wave-slit fins were measured for different fin spacings and number of tube rows. Longitudinal and transverse tube spacings of the heat exchangers are 21.65 mm and 25 mm respectively, and wave depth of wave fin is 1.5 mm. The experiments were performed for 4 different fin spacings, 1.3, 1.5, 1.7 and 2.0 mm, and the number of tube rows were 1, 2 and 3 rows. The present results were compared with the previous results for the wave depth of 2 mm. Also hydrophilic coated and bare fins were tested. Correlations for Colburn j-factor and friction factor were developed. (author). 22 refs., 10 figs., 3 tabs.

Youn, Baek; Kil, Y.H.; Park, H.Y.; Kim, Y.S. [Sam Sung Electronics Corporation Limited (Korea, Republic of)

1998-11-01

79

Transfer coefficients in elliptical tubes and plate fin heat exchangers  

International Nuclear Information System (INIS)

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

1979-01-01

80

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

2012-09-01

 
 
 
 
81

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-09-15

82

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

83

Mixed convection heat transfer between a steam / non-condensable gas mixture and an inclined finned tube bundle  

Energy Technology Data Exchange (ETDEWEB)

An experimental and analytical program was performed at PSI to study the performance of a finned-tube condenser in the presence of non-condensable gases at low gas mass fluxes. The model developed for this application includes mixed convection heat transfer between the vapour/non-condensable mixture and the finned-tubes, heat conduction through the fins and tubes, and evaporative heat transfer inside the tubes. The finned-tubes condenser model has been assessed against data obtained at the PSI LINX facility with two test condensers. For the 62 LINX experiments performed, the model predictions are very good, i.e., less than 10 % standard deviation between experimental and predicted results. (authors)

Cachard, F. de; Lomperski, S.; Monauni, G.R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland). Lab. for Thermal-Hydraulics

1999-07-01

84

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

85

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

Scientific Electronic Library Online (English)

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

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

86

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-11-15

87

Numerical Analysis of Tube-Fin Heat Exchanger using Fluent  

Directory of Open Access Journals (Sweden)

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

M. V. Ghori

2012-08-01

88

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

International Nuclear Information System (INIS)

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

2011-11-01

89

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

International Nuclear Information System (INIS)

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

2003-01-01

90

Comparison of one-dimensional and two-dimensional models for wet-surface fin efficiency of a plate-fin-tube heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

This paper investigates the wet-surface fin efficiency of a plate-fin-tube heat exchanger. Depending on the compromise made between accuracy and complexity, a one-dimensional analytical model, a one-dimensional numerical model and a two-dimensional numerical model are proposed respectively for fin efficiency together with the corresponding computation algorithms. The one-dimensional numerical model considers the local mass transfer effect. The two-dimensional model takes into account of the complex fin geometry and the variation of moist air properties over the fin. In the analytical model, two parameters M and T{sub a} are employed in the solution in place of the C parameter that is commonly used in the literature. A quantitative comparison of these models together with a widely used method by McQuiston is presented. Meanwhile, the fin performance of a plate-fin-tube heat exchanger is investigated under a variety of fin geometric parameters and airflow conditions, especially for a wide range of air relative humidity (from 20 to 95%). Due to the different simplifications made in each model, the differences among the calculation results are found to be significant. Finally, the applications and limitations of these models are discussed along with the error analysis. (author)

Liang, S.Y.; Wong, T.N.; Nathan, G.K. [Nanyang Technological University, Singapore (Singapore). School of Mechanical and Production Engineering

2000-07-01

91

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

92

Air-side flow and heat transfer for an inclined offset strip fin-tube heat exchanger with grooves  

Energy Technology Data Exchange (ETDEWEB)

A numerical study has been performed to suggest the 1-row inclined offset strip fin-tube heat exchanger with grooves which has a similar performance to the 2-row plain offset strip fin-tube heat exchanger and to predict their air-side local flow and heat transfer characteristics. The results indicated that the reversed geometry of the main slit between the front half and the rear half of the heat exchanger causes more pressure drop than the identical one. In addition, the heat transfer rate of the 1-row A-type inclined offset strip fin-tube heat exchanger with grooves reached about 96% {approx} 99% of the 2-row offset strip fin-tube heat exchanger, and the fan power representing the energy consumption rate was reduced to 90% {approx} 99%. (author). 6 refs., 9 figs., 1 tab.

Bae, J.H.; Park, M.H. [Korea Power Engineering Company (Korea, Republic of)

1998-04-01

93

Three-dimensional numerical study of wavy fin-and-tube heat exchangers and field synergy principle analysis  

Energy Technology Data Exchange (ETDEWEB)

In this paper, 3-D numerical simulations were performed for laminar heat transfer and fluid flow characteristics of wavy fin-and-tube heat exchanger by body-fitted coordinates system. The effect of four factors were examined: Reynolds number, fin pitch, wavy angle and tube row number. The Reynolds number based on the tube diameter varied from 500 to 5000, the fin pitch from 0.4 to 5.2 mm, the wavy angle from 0 to 50 , and the tube row range from 1 to 4. The numerical results were compared with experiments and good agreement was obtained. The numerical results show that with the increasing of wavy angles, decreasing of the fin pitch and tube row number, the heat transfer of the finned tube bank are enhanced with some penalty in pressure drop. The effects of the four factors were also 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 for enhance convective heat transfer. It is found that the effects of the four factors on the heat transfer performance of the wavy fin-and-tube exchangers can be well described by the field synergy principle. (author)

Tao, Y.B.; He, Y.L.; Huang, J.; Wu, Z.G.; Tao, W.Q. [State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi' an Jiaotong University, Xi' an, Shaan xi 710049 (China)

2007-03-15

94

An Experimental-Numerical Evaluation of Thermal Contact Conductance in Fin-Tube Heat Exchangers  

Science.gov (United States)

The contact between fin collar and tube surface of a fin-tube heat exchanger is secured through mechanical expansion of tubes. However, the characteristics of heat transfer through the interfaces between the tubes and fins have not been clearly understood because the interfaces consist partially of metal-to-metal contact and partially of air. The objective of the present study is to develop a new method utilizing an experimental-numerical method for the estimation of the thermal contact resistance between the fin collar and tube surface and to evaluate the factors affecting the thermal contact resistance in a fin-tube heat exchanger. In this study, heat transfer characteristics of actual heat exchanger assemblies have been tested in a vacuum chamber using water as an internal fluid, and a finite difference numerical scheme has been employed to reduce the experimental data for the evaluation of the thermal contact conductance. The present study has been conducted for fin-tube heat exchangers of tube diameter of 7mm with different tube expansion ratios, fin spacings, and fin types. The results show, with an appropriate error analysis, that these parameters as well as hydrophilic fin coating affect notably the thermal contact conductance. It has been found out that the thermal contact resistance takes fairly large portion of the total thermal resistance in a fin-tube heat exchanger and it turns out that careful consideration is needed in a manufacturing process of heat exchangers to reduce the thermal contact resistance.

Kim, Chang Nyung; Jeong, Jin; Youn, Baek; Kil, Seong Ho

95

Modeling for predicting frosting behavior of a fin-tube heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

A mathematical model is proposed to evaluate the frosting behavior of a fin-tube heat exchanger under frosting conditions. Empirical correlations of the heat transfer coefficients for the plate and tube surfaces and a diffusion equation for the frost layer are used to establish the model. The correlations for the heat transfer coefficients, derived from various experimental data, were obtained as functions of the Reynolds number and Prandtl number. The proposed model is validated by comparing the numerical results with experimental data for the frost thickness, frost accumulation, and heat transfer rate. The numerical results agree well with the experimental data. It is also found that this model can be applied to evaluate the thermal performance of a common fin-tube heat exchanger under frosting conditions. (author)

Yang, Dong-Keun [Digital Appliance Research Laboratory, LG Electronics Inc., 222-22 Guro3-dong, Seoul 152-848 (Korea, Republic of); Lee, Kwan-Soo; Song, Simon [School of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Sungdong-gu, Seoul 133-791 (Korea, Republic of)

2006-04-15

96

Experimental comparison and analysis on silica gel and polymer coated fin-tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

In this paper, two desiccant-coated heat exchangers, which are actually fin-tube heat exchanging devices coated with silica gel and polymer materials respectively, are investigated experimentally. Due to the hygroscopic properties of the desiccant materials, both the sensible heat and the latent heat of the process air can be handled by using this kind of heat exchanger. An experimental setup was designed and built to test the performance of this unit. It is found that this desiccant-coated fin-tube heat exchanger well overcomes the side effect of adsorption heat which occurs in desiccant dehumidification process, and achieves good dehumidification performance under given conditions. The silica gel coated heat exchanger behaves better than the polymer one. The influences of regeneration temperature, inlet air temperature and humidity on the system performance in terms of average moisture removal rate D{sub avg} and thermal coefficient of performance COP{sub th} were also analyzed. (author)

Ge, T.S.; Dai, Y.J.; Wang, R.Z.; Peng, Z.Z. [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200240 (China)

2010-07-15

97

Finishing of disk tools for rolling spiral fins on tubes  

Energy Technology Data Exchange (ETDEWEB)

At the All-Union Scientific-Research and Design Institute for Chemical and Petroleum Apparatus Building Technology, Volgograd, a special machine has been designed and built and investigations have been made to provide tool working surfaces with high quality. Finds that the increase in surface quality of the rolling tools as a result of abrasive grinding with a belt on the special machine makes it possible to reduce external friction in the rolling zone, as a result of which there is an improvement in the conditions of radial flow of the tube metal. Savings are obtained as a result of a decrease in the power required by the electric motors for rolling of finned tubes. This is an indication of a reduction in the forces of friction in the source of change in form of the fins and approximately doubles the life of the rolling tool. The production operation of grinding the parts of the rolling tool with an abrasive belt and a special machine has been introduced into the Lauristin Tallin Machine Building Plant.

Sultanov, T.A.; Buneev, B.G.; Yurova, T.I.

1982-09-01

98

Numerical Analysis on Adsorption Characteristics of Activated Carbon/Ethanol Pair in Finned Tube Type Adsorber  

Science.gov (United States)

The cycle performance of adsorption cooling system depends on the thermophysical properties of the adsorbent/refrigerant pair and configuration of the adsorber/desorber heat exchanger. In this study, a twodimensional analysis is carried out in order to clarify the performance of the finned tube type adsorber/desorber heat exchanger using a highly porous activated carbon powder (ACP)/ethanol pair. The simulation results show that the average cooling capacity per unit volume of adsorber/desorber heat exchanger and coefficient of performance (COP) can be improved by optimizing fin thickness, fin height, fin pitch and tube diameter. The performance of a single stage adsorption cooling system using ACP/ethanol pair is also compared with that of activated carbon fiber (ACF)/ethanol pair. It is found that the cooling capacities of each adsorbent/refrigerant pair increase with the decrease of adsorption/desorption time and the cooling capacity of ACP/ethanol pair is approximately 2.5 times as much as that of ACF/ethanol pair. It is also shown that COP of ACP/ethanol pair is superior to that of ACF/ethanol pair.

Makimoto, Naoya; Kariya, Keishi; Koyama, Shigeru

99

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

2010-04-01

100

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

Energy Technology Data Exchange (ETDEWEB)

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

Kim, Sung Jool; Choi, Ho Jin; Ha, Man Yeong [Pusan National University, Busan (Korea, Republic of); Kim, Seok Ro; Bang, Seon Wook [Home Appliance Company, LG Electronics, Changwon (Korea, Republic of)

2010-04-15

 
 
 
 
101

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

International Nuclear Information System (INIS)

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

2013-12-01

102

Heat transfer enhancement in plate fin-tube heat exchanger by longitudinal vortex generators  

Energy Technology Data Exchange (ETDEWEB)

An experimental study about the influence of longitudinal vortex generators when applied to a single row plate fin-tube heat exchanger model is described. A set of configurations of delta wing let pair over the fins surface was studied. For each vortex generators position the Reynolds number was varied from 1000 to 2000. The results indicate that it is possible to achieve about 15% of intensification when comparing with a flat plate fin-tube heat exchanger. (author)

Yanagihara, Jurandir I.; Sabanai, Hamilton J. [Sao Paulo Univ., SP (Brazil). Escola Politecnica. Dept. de Engenharia Mecanica

1996-07-01

103

Modelling analysis on fin-tube heating coil of air handling unit  

Energy Technology Data Exchange (ETDEWEB)

One of the fundamental components in engineering practice is the heat exchanger. The fin-tube heating coil of an air handling unit (AHU) is one important component in an HVAC system. In order to study the fault detection and diagnosis (FDD) strategy for an HVAC system, a general model of a fin-tube heat exchanger which is accurate and adaptable is necessary. On the basis of the physical conservation law, a dynamic discretization parameter model is built by Simulink. The heat exchanger is split into small elements to increase the accuracy of the model. The dynamic behaviour of the fin-tube heat exchanger is studied under the condition of step changes on the opening of the control valve. Research has been performed on an AHU and the simulation results show good accordance with the measurements. Correction on heat transfer coefficient has been introduced to increase the accuracy. Matlab S-function is used to decrease the computational time of the simulation. (Author)

Yu, B.; Jong, W. de; Paassen, A.H.C. van [Delft Univ. of Technology, Energy Technology, Delft (Netherlands)

2003-12-01

104

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

International Nuclear Information System (INIS)

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

1991-01-01

105

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

106

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

107

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

International Nuclear Information System (INIS)

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

1986-03-01

108

Carbon-foam finned tubes in air-water heat exchangers  

International Nuclear Information System (INIS)

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

2006-02-01

109

A general steady state mathematical model for fin-and-tube heat exchanger based on graph theory  

Energy Technology Data Exchange (ETDEWEB)

Fin-and-tube heat exchangers are widely used in air conditioners, chillers, etc. A lot of factors, including arrangement of refrigerant circuits, configure specification of fins and tubes, and operating conditions, have significant influence on the performance of fin-and-tube heat exchangers. For the purpose of fast design of high performance heat exchangers, a simulator reflecting the influence of these factors is necessary. In this paper, a general steady state mathematic model based on the graph theory is presented. With the help of the directed graph and graph-based traversal methods (Breadth-first search and Depth-first search), this model is capable to describe any flexible refrigerant circuit arrangement, and quantify the refrigerant distribution in the refrigerant circuit and heat conduction through fins. An alternative iteration method is also developed to solve the conservation equations, which can shorten the simulating time effectively. The model is verified with the experimental results, and the maximum error is within {+-}10.0%. A simulator based on this model has been used for designing practical fin--and-tube heat exchangers. (author)

Jian Liu; WenJian Wei; GouLiang Ding; Chunlu Zhang [Shanghai Jiaotong University (China). Institute of Refrigeration and Cryogenics, Department of Power and Energy Engineering; Fukaya, M.; Kaijian Wang; Inagaki, T. [Fujitsu General Institute of Air-Conditioning Technology Ltd., Kawasaki (Japan)

2004-12-01

110

Thermal behavior of spiral fin-and-tube heat exchanger having fly ash deposit  

Energy Technology Data Exchange (ETDEWEB)

This research investigates the effect of fly-ash deposit on thermal performance of a cross-flow heat exchanger having a set of spiral finned-tubes as a heat transfer surface. A stream of warm air having high content of fly-ash is exchanging heat with a cool water stream in the tubes. In this study, the temperature of the heat exchanger surface is lower than the dew point temperature of air, thus there is condensation of moisture in the air stream on the heat exchanger surface. The affecting parameters such as the fin spacing, the air mass flow rate, the fly-ash mass flow rate and the inlet temperature of warm air are varied while the volume flow rate and the inlet temperature of the cold water stream are kept constant at 10 l/min and 5 C, respectively. From the experiment, it is found that as the testing period is shorter than 8 h the thermal resistance due to the fouling increases with time. Moreover, the deposit of fly-ash on the heat transfer surface is directly proportional to the dust-air ratio and the amount of condensate on heat exchange surface. However, the deposit of fly-ash is inversely proportional to the fin spacing. The empirical model for evaluating the thermal resistance is also developed in this work and the simulated results agree well with those of the measured data. (author)

Nuntaphan, Atipoang [Thermal Technology Research Laboratory, Mae Moh Training Center, Electricity Generating Authority of Thailand, Mae Moh, Lampang 52220 (Thailand); Kiatsiriroat, Tanongkiat [Department of Mechanical Engineering, Chiang Mai University, Chiang Mai 50200 (Thailand)

2007-08-15

111

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

DEFF Research Database (Denmark)

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

Kærn, Martin Ryhl; Elmegaard, Brian

2009-01-01

112

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

International Nuclear Information System (INIS)

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

2008-11-05

113

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

114

Numerical simulation of flow field in a fin tube heat exchanger  

International Nuclear Information System (INIS)

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

1990-11-25

115

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2011-01-01

116

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Refrigerant mal-distribution in fin-and-tube evaporators for residential air-conditioning is investigated numerically in this paper. Essentially the influence of refrigerant mal-distribution on capacity of an evaporator is reported. In order to investigate, a model of a fin-and-tube evaporator is developed in the object-oriented modeling language Modelica. The evaporator model is a dynamic distributed one-dimensional homogeneous model, but will be used here to present results i...

Kærn, Martin Ryhl; Elmegaard, Brian

2009-01-01

117

Performance Analysis of FinFET Device at 60nm  

Directory of Open Access Journals (Sweden)

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

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

2013-03-01

118

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-10-15

119

Steam generator tube performance  

International Nuclear Information System (INIS)

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

1984-01-01

120

Steam generator tube performance  

International Nuclear Information System (INIS)

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

1983-01-01

 
 
 
 
121

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

122

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

123

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

124

Pulse tube refrigerator performance  

International Nuclear Information System (INIS)

The performance of pulse tube coolers is being studied in order to determine their suitability for development into long-life space coolers. Coolers based on the pulse tube phenomenon appear to be attractive for long-life space application because of their inherent simplicity. Single-stage and two-stage pulse tube test coolers have been designed and tested. In these early tests a single stage cooler has achieved a low temperature of 53 K while rejecting heat above 300 K. An unoptimized two-stage cooler has reached 26 K while rejecting heat above 300 K. Performance measurements for the coolers is presented. 15 refs

1989-07-24

125

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

126

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Mon, Mi Sandar

2009-01-01

127

Investigation of heat transfer characteristics on various kinds of fin-and-tube heat exchangers with interrupted surfaces  

Energy Technology Data Exchange (ETDEWEB)

This study experimentally investigates the effects of the shapes of interrupted surfaces on the performance of the fin-and-tube heat exchanger used in home air conditioners. The scaled-up model experiments are conducted to evaluate the heat transfer coefficient and pressure drop, and prototype experiments are also performed to examine the validity of the scaled-up experiments. Their results are in agreement with the available experimental data. These results are confined to the sensible heat transfer characteristics. It is shown that the scaled-up model experiments are very useful for estimating the heat transfer characteristics of a heat exchanger. In this study, the heat transfer and pressure drop characteristics of the three kinds of newly designed fin shapes are also compared to one another, and an optimal fin shape for home air conditioners is recommended. (author)

Yun, J.Y. [LG Electronics Co., Seoul (D.P.R. of Korea). Living System Research Lab.; Lee, K.S. [Hanyang University, Seoul (D.P.R. of Korea). School of Mechanical Engineering

1999-07-01

128

High-frequency welded finned tubes - finning of 9% chromium steel X10CrMoVNb91 (P91/T91)  

Energy Technology Data Exchange (ETDEWEB)

During the past two years, a research programme was set up to investigate the feasibility of producing, in an economical way, finned tubes in modified 9% chromium steel, by using the high frequency resistance welding (finning) process and to evaluate their properties and product reliability for the intended high temeprature application area, at temepratures above 530 C. The basic aim was to produce T91/P91 finned tubes and to demonstrate their applicability in the `as-welded` condition. Therefore, the influence of omitting any post weld heat treatment on the short and longer term behaviour was evaluated. The programm was performed by Mannesmann-Carnoy and realised in collaboration with the Research Centre of the Belgian Welding Institute, with support of the Minister of Economic Affairs of the Flemish Region. (orig.) [Deutsch] In den letzten zwei Jahren wurde ein Untersuchungsprogramm durchgefuehrt, in dem die Moeglichkeit einer wirtschaftlichen Herstellung von Rippenrohren aus 9%igem modifizierten Chromstahl untersucht wurde durch Anwendung des Hochfrequenz-Widerstandsschweissprozesses. Die Eigenschaften und die Zuverlaessigkeit des Produktes fuer die Anwendung im Hochtemperaturbereich (ueber 530 C) wird beurteilt. Es kamen T91/P91-Rippenrohre zum Einsatz, um ihre Verwendbarkeit im nicht waermebehandelten Zustand zu zeigen. Insbesondere wurde ueberprueft, welchen Einfluss der nicht waermebehandelten Zustand nach dem Schweissen auf das Kurz- und Langzeitverhalten der Rippenrohre hat. Das Programm wurde von Mannesmann Carnoy in Zusammenarbeit mit dem Untersuchungszentrum des belgischen Schweissinstitutes, und mit Unterstuetzung durch das Wirtschaftsministerium der flaemischen Regierung durchgefuehrt. (orig.)

Coussement, C.J. [Belgian Welding Inst., Gent (Belgium); Bruehl, F.H. [Mannesmann Carnoy N.V., Gent (Belgium); Donckt, E. van der [Mannesmann Carnoy N.V., Gent (Belgium)

1995-07-01

129

Steam generator tube performance  

International Nuclear Information System (INIS)

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

1982-01-01

130

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

Science.gov (United States)

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

Juan, Du; Qin, Qian Zuo

2014-04-01

131

Forced convection and entropy generation from elliptic tubes with longitudinal fins  

International Nuclear Information System (INIS)

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

2009-08-01

132

Forced convection and entropy generation from elliptic tubes with longitudinal fins  

Energy Technology Data Exchange (ETDEWEB)

An experimental investigation has been conducted to clarify heat transfer characteristics and entropy generation for individual elliptic tubes with longitudinal fins. The investigated geometrical parameters included the placement of the fins at the front of the tube, at the rear of the tube and at the front and rear of the tube. The experiments have been carried out on the different cases of electrically heated elliptic tubes which are separately installed in a square tunnel. The surface temperature at different cases of elliptic tubes, have been measured. The testing fluid was air and the Reynolds number ranged from about 4.75 x 10{sup 3} to 3.96 x 10{sup 4}. The analysis of the entropy generation is based on the principle of minimizing the rate of total entropy generation that includes the generation of entropy due to heat transfer and friction forces are presented. The results indicate that the fin position on the elliptic tube has an effect on the results of heat transfer coefficient, friction factor and irreversibility ratio. The correlations of average Nusselt number, friction factor and irreversibility ratio with Re are presented. (author)

Ibrahim, E. [Faculty of Engineering, Zagazig University, Zagazig 44519 (Egypt); Moawed, M. [Faculty of Engineering Shoubra, Benha University, Cairo, 108 Shoubra Street, Shoubra, Cairo 11689 (Egypt)

2009-08-15

133

Optimum parameters of transversely finned tubes in the case of simultaneous sooling by natural convection and radiations  

International Nuclear Information System (INIS)

The optimum parameters of minimum-weight finned tubes for the case of heat transfer by free convection and radiation are determined using the mathematical model with boundary conditions of the 3-type by the method of calculational experiment. The effects of the coolant and air temperatures diameter and thickness of the bimetallic wall, contamination and other factors on optimal finning parameters are investigated. It is obtained that for the case of heat transfer by free convection and radiation, the optimum finning parameters for the heat transfer surface of minimum-weight tubes by absolute value are larger than those of tube finning with forced convection

1983-01-01

134

Optimum parameters of transversely finned tubes in the case of simultaneous sooling by natural convection and radiations  

Energy Technology Data Exchange (ETDEWEB)

The optimum parameters of minimum-weight finned tubes for the case of heat transfer by free convection and radiation are determined using the mathematical model with boundary conditions of the 3-type by the method of calculational experiment. The effects of the coolant and air temperatures diameter and thickness of the bimetallic wall, contamination and other factors on optimal finning parameters are investigated. It is obtained that for the case of heat transfer by free convection and radiation, the optimum finning parameters for the heat transfer surface of minimum-weight tubes by absolute value are larger than those of tube finning with forced convection.

Volodin, V.I.; Mikhalevich, A.A.; Nesterenko, V.B.

1983-01-01

135

The effect of the number of tube rows on heat, mass and momentum transfer in flat-plate finned tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

The effect of the number of tube rows on heat, mass and momentum transfer is experimentally investigated for flat-plate, finned-tube heat exchangers which consist of aluminum fins and copper tubes. Four flat-plate finned-tube heat exchangers are identical except for changes in the number of tube rows (1 to 4). Heat-transfer coefficients for wet and dry surface conditions are obtained for both heating and cooling of moist air flowing over finned tubes. The air velocity was varied from 0.9 to 4 m/s. Heat transfer, Colburn and friction factors are determined for different tube rows numbers while the Reynolds number were being warned. It is found that the values of Colburn and friction factors for wet surfaces are higher than for dry surfaces and for both conditions the Colburn and friction factors decrease with an increase in the tube row numbers. (author)

Hal, F.; Taymaz, I.; Gunduz, M. [University of Sakarya (Turkey). Mechanical Engineering Dept.

2001-11-01

136

Measurement of the longitudinal thermal conductivity for spiral tube-fin heat exchanger structure for helium facilities  

International Nuclear Information System (INIS)

The results on measuring the spiral tube fin heat exchanger (HE) longitudinal heat conductivity are given. This HE is made from coiled copper tubes spirally finned with a copper wire. This type of HE will be used in the cryogenic system for accelerator-storage ring complex. 9 refs.; 3 figs.; 1 tab

1989-01-01

137

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 he...

2004-01-01

138

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

International Nuclear Information System (INIS)

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

2004-12-01

139

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

140

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

 
 
 
 
141

I-B-R ratings for baseboard and finned tube (commercial) radiation  

Energy Technology Data Exchange (ETDEWEB)

This book lists the certified I-B-R ratings for 53 models of baseboard and 35 models of commercial finned tube in a variety of production enclosures. It shows the physical dimensions and the BTU outputs at various temperatures for hot water and for steam.

1990-01-01

142

Horizontal Convective Condensation of Alternative Refrigerants within a Micro-Fin Tube.  

Science.gov (United States)

This paper presents local convective condensation measurements for four refrigerants: R134a, R410A(R32/R125, 50/50 % mass), R125, and R32 in a micro-fin tube. Both heat transfer and pressure drop measurements are provided. The heat transfer degradation as...

M. A. Kedzierski J. M. Goncalves

1997-01-01

143

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

144

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

Energy Technology Data Exchange (ETDEWEB)

An experimental study has been performed to investigate the heat transfer characteristics of a plate fin and tube heat exchanger. Existing transient and steady methods are inappropriate for the measurement of heat transfer coefficients of the thin heat transfer model. In this study, the lumped capacitance method based on liquid crystal thermography was adopted. The method is validated through impinging jet and plate flow experiments. The two experiments showed very good agreements with those of the well-known transient method with the thick acryl model. And the lumped capacitance method showed similar results regardless of the thickness of the polycarbonate model if the Bi of the fin is small enough. The method was also applied for the heat transfer coefficient measurements of a fin and tube heat exchanger. Quantitative heat transfer coefficients of the plate fin were successfully obtained. (author)

Kim, Ye Yong [LGE PC Division 19-1, Chengho-Ri Jinwuy-Myun Pyungtaik Gyunggi-Do 451-713 (Korea, Republic of); Kim, Kui Soon; Jeong, Sooin [Department of Aerospace Engineering, Pusan National University, Busan 609-735 (Korea, Republic of); Jeong, Gi Ho [SAMSUNG Electro-Mechanics, 314 Metan3-Dong Yeongtong-Gu Suwon Gyunggi-Do 443-743 (Korea, Republic of)

2006-01-15

145

On the heat and mass analogy of fin-and-tube heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

This study examines the heat and mass analogy of the fin-and-tube heat exchanger under dehumidifying process. A total of 36 fin-and-tube heat exchangers having plain fin geometry are experimentally examined. It is found that the ratio of h{sub c,o}/h{sub d,o}C{sub p,a} is in the range of 0.6-1.1 and is insensitive to change of fin spacing at low Reynolds number. However, it is noted that this ratio is not a constant throughout the test range. A slight drop of the ratio of h{sub c,o} /h{sub d,o}C{sub p,a} is seen with the decrease of fin spacing and with the rise of the Reynolds number. This is associated with the more pronounced influence during condensate removal. Moreover, during the dehumidifying process, the temperature gradient is directly responsible for establishing the concentration gradient, suggesting the heat transfer and mass transfer are not independent. Based on a simple analysis, one can easily find that the increasing rate of ((dc)/(dT)) vertical stroke {sub i} slightly exceeds that of ({delta}c)/({delta}T). As a result, the ratio of h{sub c,o}/h{sub d,o}C{sub p,a} can be proved to be slightly decreased with the rise of the Reynolds number. (author)

Wang, Chi-Chuan [Energy and Environment Research Laboratory, Industrial Technology Research Institute, Hsinchu, Taiwan 310 (China)

2008-04-15

146

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

International Nuclear Information System (INIS)

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

2009-06-21

147

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-04-15

148

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

International Nuclear Information System (INIS)

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

2013-04-01

149

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

150

Performance Improvement of FinFET using Nitride Spacer  

Directory of Open Access Journals (Sweden)

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

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

2013-03-01

151

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-04-15

152

Entropy generation in tube and fin radiating systems; Geracao de entropia em sistemas radiantes de tubos aletados  

Energy Technology Data Exchange (ETDEWEB)

The entropy generation minimization method is applied to tube and fin radiative systems. The mathematical modeling of the systems lead to a non-linear integro-differential systems of equations, which is solved numerically. The entropy generation in the fin is computed. This is obtained as result of the thermal analysis of the system which gives the fin temperature distributions and the radiative heat transfer rates. Examples of optimized design are considered and discussed. (author)

Santos, Marcio Bueno dos; Saboya, Sergio Mourao [Instituto Nacional de Pesquisas Espaciais (INPE), S Jose dos Campos, SP (Brazil). Lab. de Integracao e Testes]. E-mail: bueno@lit.inpe.br; saboya@mec.ita.cta.br

1997-07-01

153

Experimental testing of the thermal performance of finned air coolers  

International Nuclear Information System (INIS)

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

1988-01-01

154

Condensation of Downward-Flowing Zeotropic Mixture HCFC-123/HFC-134a on a Staggered Bundle of Horizontal Low-Finned Tubes  

Science.gov (United States)

Expenmentswere conducted to obtain row-by-row heat transfer data during condensation of downward-flowing zeotropic refrigerant mixture HCFC-123/HFC-134 a on a staggered bundle of horizontal low-finned tubes. The vapor temperature and the HFC-134a m ass fraction at the tube bundle inlet were maintained at about 50°C and 14% respectively. The refrigerant mass velocity ranged from 9 to 33 kg/m2s, and the condensation temperature difference from 2 to 12K. Four kinds of low-finned tubes with different fin geometry were tested. The highest heat transfer coefficient was obtained with a tube which showed the highest performance for HCFC-123. However, the effect of fin geometry was much smaller for the mixture than for HCFC-123. The heat transfer coefficient and the vapor-phase mass transfer coefficient decreased significantly with decreasing mass velocity. On the other hand, the mass transfer coefficient increased with condensation temperature difference. This was due to the effect of suction associated with condensation. On the basis of the analogy between heat and mass transfer, a dimensionless correlation of the mass transfer coefficient was developed for each tube.

Honda, Hiroshi; Takamatsu, Hiroshi; Takata, Nobuo

155

Heat transfer during condensation of HFC-134a and R-404A inside of a horizontal smooth and micro-fin tube  

Energy Technology Data Exchange (ETDEWEB)

In recent small and medium capacity refrigeration systems, the condenser tubes are provided with micro-fins from inside. The vapour refrigerant at the compressor outlet and the condenser inlet is in superheat state. As it advances in the condenser it is in two phases and at the outlet it is in sub cooled liquid. The heat transfer coefficient (HTC) during condensation of HFC-134a and R-404A in a smooth (8.56 mm ID) and micro-fin tubes (8.96 mm ID) are experimentally investigated. Different from previous studies, the present experiments are performed for various condensing temperatures, with superheating and sub cooling and using hermetically sealed compressor. The test runs are done at average saturated condensing temperatures ranging from 35 C to 60 C. The mass fluxes are between 90 and 800 kg m{sup -2} s{sup -1}. The experimental results indicate that the average HTC increases with mass flux but decreases with increasing condensing temperature for both smooth and micro-fin tubes. The average condensation HTCs of HFC-134a and R-404A for the micro-fin tubes were 1.5-2.5 and 1.3-2 times larger than that in smooth tube respectively. The HTCs for R-404A are less than that of HFC-134a. New correlations based on the data gathered during the experimentation for predicting condensation HTCs are proposed for wide range of operating conditions. (author)

Sapali, S.N. [Govt. College of Engineering, Department of Mechanical Engineering, Shivaji Nagar, Pune, Maharashtra 411 005 (India); Patil, Pradeep A. [AISSMS College of Engineering, Pune University, Mechanical Engineering Department, Kennedy Road, Near R.T.O., Pune, Maharashtra 411 001 (India)

2010-11-15

156

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

157

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

158

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

159

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

2010-05-01

160

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

 
 
 
 
161

Application of mechanistic models for flow distribution and heat transfer in finned tube bundles  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The focus of this thesis was heat transfer and pressure drop in staggered tube bundles with solid and serrated fins. The first part of the work dealed with five prediction models, namely PFR's model (1976), Nir's model (1991), Ralston et al.'s HTFS1 model (1997), Chu and Ralston's HTFS2 model (1998) and McIlwain's HTFS3 model (2003). The models all had correlations for prediction of heat transfer and pressure drop, but only PFR and Nir had specific correlations for se...

2013-01-01

162

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

International Nuclear Information System (INIS)

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

2012-07-01

163

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

164

Propulsion performance of a skeleton-strengthened fin.  

Science.gov (United States)

We examine numerically the performance of a thin foil reinforced by embedded rays resembling the caudal fins of many fishes. In our study, the supporting rays are depicted as nonlinear Euler-Bernoulli beams with three-dimensional deformability. This structural model is then incorporated into a boundary-element hydrodynamic model to achieve coupled fluid-structure interaction simulation. Kinematically, we incorporate both a homocercal mode with dorso-ventral symmetry and a heterocercal mode with dorso-ventral asymmetry. Using the homocercal mode, our results demonstrate that the anisotropic deformability of the ray-reinforced fin significantly increases its capacity of force generation. This performance enhancement manifests as increased propulsion efficiency, reduced transverse force and reduced sensitivity to kinematic parameters. Further reduction in transverse force is observed by using the heterocercal mode. In the heterocercal model, the fin also generates a small lifting force, which may be important in vertical maneuvers. Via three-dimensional flow visualization, a chain of vortex rings is observed in the wake. Detailed features of the wake, e.g. the orientation of the vortex rings in the heterocercal mode, agree with predictions based upon particle image velocimetry (PIV) measurements of flow around live fish. PMID:18552298

Zhu, Qiang; Shoele, Kourosh

2008-07-01

165

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2011-01-01

166

Numerical approach for modeling air-to-refrigerant fin-and-tube heat exchanger with tube-to-tube heat transfer  

Energy Technology Data Exchange (ETDEWEB)

A new model for simulating air-to-refrigerant heat exchangers, which accounts for conduction along the fins (tube-to-tube), is introduced. This model is based on a segment-by-segment approach and is developed to be general purpose and flexible simulation tool. To account for fin conduction, the heat exchanger is spatially modeled on a Cartesian grid. A set of equations that conserve energy over a segment of a heat exchanger is introduced. A sub-dividable segment model is introduced that accounts for changing flow regimes, and associated wall temperatures, within a tube segment. The model prediction is validated against experimental data obtained from experiments and the literature. The predicted results agree within {+-}3% of overall heat load and all tube-bend temperatures agree within {+-}3.9 C of measured temperatures for the first set of experiments. For the second set of experiments, all predicted tube-bend temperatures agree within {+-}8.5 C and overall heat load agrees within {+-}5%. (author)

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

2008-12-15

167

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

International Nuclear Information System (INIS)

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

1993-10-10

168

Effect of strip location on the air-side pressure drop and heat transfer in strip fin-and-tube heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

This work discusses about the pressure drop and heat transfer characteristics of plain fin, a strip fin and combinations thereof in the fin-and-tube heat exchanger. Experimental apparatus and test algorithm using scale-up model fin geometry are discussed. The present work uses the electric heaters inside of the tube as the heating source to simulate the hot water loop in the wind tunnel test. The test results of the plain and strip fins are composed with the existing correlation and experimental data. It was found that a hybrid fin, plain fin at front row and strip fin at rear row, was more effective to enhance the heat transfer than that of the whole strip fin at the same fan power. (Author)

Hiechan Kang [Kunsan National Univ., School of Mechanical Engineering, Kunsan (Korea); Moohwan Kim [Pohang Univ. of Science and Technology, Dept. of Mechanical Engineering, Pohang (Korea)

1999-06-01

169

The effect of ionisation of spray in cooling air on the wetting characteristics of finned tube heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

A major concern when introducing a water spray to pre-cool the air flowing into a finned tube heat exchanger is that wetting of the heat exchanger surface may cause corrosion. In an attempt to prevent droplets from impacting and wetting the heat exchanger, the use of an electrostatically charged spray was investigated. Experiments were performed whereby electrostatically charged spray was sprayed on a heat exchanger with an electric charge having the same polarity as the droplets. The results indicated that droplet deposition decreased significantly as the charge on presdroplets was increased. However, total prevention of deposition could not be achieved, since the equipment used could not produce high enough voltages. This concept shows some promise, and it is recommended that further research be performed on it. (author)

Esterhuyse, B.D. [P.O. Box 5214, Secunda 2302 (South Africa); Kroeger, D.G. [Mechanical Engineering Department, Stellenbosch University, Stellenbosch 7600 (South Africa)

2005-12-01

170

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

Energy Technology Data Exchange (ETDEWEB)

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

Lin, Chia-Wen; Jang, Jiin-Yuh [National Cheng-Kung University, Department of Mechanical Engineering, Tainan (Taiwan)

2005-05-01

171

Fan supplied heat exchanger fin performance under frosting conditions  

Energy Technology Data Exchange (ETDEWEB)

In this paper, a validated numerical model for frost growth on heat exchange fins is modified to simulate a fan-supplied finned heat exchanger under refrigeration frosting conditions. It is found that frost growth on refrigeration heat exchangers causes a dramatic drop in the fin heat rate, airflow rate, and fin efficiency while the pressure drop increases. A sensitivity study shows the effects of changing several design parameters including the type of fan. (Author)

Hong Chen; Besant, Robert W. [Saskatchewan Univ., Dept. of Mechanical Engineering, Saskatoon, SK (Canada); Thomas, Leena [Corning Cable Systems, Saskatoon, SK (Canada)

2003-01-01

172

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

International Nuclear Information System (INIS)

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

1982-01-01

173

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

174

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

International Nuclear Information System (INIS)

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

2008-02-01

175

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

Energy Technology Data Exchange (ETDEWEB)

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

Sahin, Besir [Cukurova University, Faculty of Engineering and Architecture, Department of Mechanical Engineering, 01330 Adana (Turkey)], E-mail: bsahin@cu.edu.tr; Ozturk, Nurhan Adil [Mustafa Kemal University, Faculty of Engineering and Architecture, Department of Mechanical Engineering, 01330, Adana (Turkey); Gurlek, Cahit [Cukurova University, Faculty of Engineering and Architecture, Department of Mechanical Engineering, 01330 Adana (Turkey)

2008-02-15

176

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-10-15

177

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

Science.gov (United States)

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

Zhou, Feng; Catton, Ivan

2012-10-01

178

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

Scientific Electronic Library Online (English)

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

Sérgio Nascimento, Bordalo; Francisco Eduardo Mourão, Saboya.

179

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

Directory of Open Access Journals (Sweden)

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

Ahmed F. Khudheyer

2011-07-01

180

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

Scientific Electronic Library Online (English)

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

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

 
 
 
 
181

The effect of Water Contact Angles of the Fin Surfaces of the Fin-and-Tube Heat Exchangers on the Water Hold-up  

Energy Technology Data Exchange (ETDEWEB)

An experimental study on the behavior of the water hold-up by condensation of a fin-and-tube heat exchanger with regard to the surface characteristics, i.e., contact angles, was conducted. The static and dynamic contact angles were measured, and condensation experiments were conducted. Flow patterns on the fins with different surface characteristics were visualized. Results showed that the static contact angle is proportional to the dynamic contact angle within the range of this study. The water hold-up of the heat exchanger increases as the static or dynamic contact angle of its surfaces increases. Existence of transition of flow patterns was found as the static or dynamic angle increase. Due to the transition in the flow patterns, changes in the gradient of the water hold-up is occurred around the static angle of 80 degree. 10 refs., 8 figs.

Shin, Jongmin; Lee, Nam Gyo; Han, Sungjoo; Ha, Samchul [Digital Appliance Research Laboratory, LG Electronics, Changwon (Korea)

2001-06-01

182

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

183

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

Directory of Open Access Journals (Sweden)

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

Atipoang Nuntaphan

2004-05-01

184

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)

2009-11-03

185

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

186

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)

2006-07-17

187

Experimental study on effect of interwall tube cylinder on heat/mass transfer characteristics of corrugated plate fin-and-tube exchanger configuration  

Energy Technology Data Exchange (ETDEWEB)

The major characteristics of the corrugated plate fin-and-tube heat exchanger, as compared to the plain duct, are the existence of wall corrugation and the interwall tube cylinders, which serve as the passage for the in-tube fluid and also as the holder of the corrugated plate fins. The purpose of this work is to investigate experimentally the effect of the interwall tube cylinders on the heat/mass transfer characteristics of corrugated channel. To facilitate the test process, the naphthalene sublimation technique was used. In the study mass transfer measurements were done for the test section with interwall cylinders and for that without interwall cylinders, with other geometric dimensions remained the same. Mass transfer results may be converted to heat transfer results by application of the analogy between the two processes. Since the focus of this study is to make a relative comparison, this inversion will not be completed and the presentation is limited to mass transfer aspect.

Xiao, Q.; Cheng, B.; Tao, W.Q. (Xi' an Jiaotong Univ. (China))

1992-08-01

188

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

Science.gov (United States)

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

189

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

International Nuclear Information System (INIS)

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

2012-02-27

190

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

International Nuclear Information System (INIS)

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

1965-09-01

191

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

International Nuclear Information System (INIS)

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

2013-06-01

192

Free convection on finned-tube air coolers; Beschreibung der freien Konvektion an Lamellenrohr-Luftkuehlern  

Energy Technology Data Exchange (ETDEWEB)

Convective heat transfer on finned-tube heat exchangers was measured, and a theoretical approach was developed on the basis of the measurements. The method describes convective heat transfer on parallel vertical plates by a semi-empirical approach with correction factors for different operating and installation conditions. (orig.) [Deutsch] Ueber die durchgefuehrten Untersuchungen erfolgte die Bestimmung der Waermeaufnahme an Lamellenrohrwaermeaustauschern, die ueberwiegend durch die sich einstellende freie Konvektion bestimmt wird. Realitaetsnahe Messungen an zwei in der Praxis eingesetzten Kuehlern zeigten den Einfluss auf, den verschiedene Einbau- und Betriebsbedingungen auf die Waermeaufnahme an den Kuehlern haben. Aufbauend auf den Ergebnissen der durchgefuehrten Messungen wurde auf der Basis in der Literatur bestehender Ansaetze zur Beschreibung der Waermeabgabe an parallelen senkrechten Platten infolge freier Konvektion ein halbempirischer Ansatz aufgestellt, bei dem ueber Korrekturfaktoren der Einfluss unterschiedlicher Einbau- und Betriebsbedingungen auf die Waermeuebergangsbedingungen an den Kuehlern Beruecksichtigung findet. Die Anpassung der in dem Ansatz enthaltenen Konstanten erfolgte ueber Regressionsrechnungen, wobei die ueber die Messungen fuer beide Kuehler ermittelten Nusselt-Zahlen zugrunde gelegt wurden. (orig.)

Mengede, B. [Universitaet - GH - Essen, Institut fuer Angewandte Thermodynamik und Klimatechnik (Germany)

1997-12-31

193

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

194

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

195

Heat transfer and pressure loss for smoke gas in finned tube heat exchangers. Varmeovergang og tryktab for roeggas i ribberoersvarmevekslere  

Energy Technology Data Exchange (ETDEWEB)

The aim was to investigate heat transfer and pressure loss in relation to transverse flow round bunches of pipes fitted into a finned tube heat exchanger. Conditions of both condensing and non-condensing operation were dealt with. Various pipe types were examined in order to discover potentials for utilization in gas-fired boilers. Measurements were taken on ribbed pipe heat exchangers, and computer calculations were made to determine convection conditions. (AB).

Krighaar, M.; Wit, J. de; Ingerslev, I.; Paulsen, O. (Energiteknologi, Dansk Teknologisk Institut (DK))

1990-01-01

196

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

International Nuclear Information System (INIS)

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

1979-01-01

197

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

198

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

1989-02-20

199

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

International Nuclear Information System (INIS)

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

2012-02-01

200

Application of a genetic algorithm to optimize the refrigerant circuit of fin-and-tube heat exchangers for maximum heat transfer or shortest tube  

Energy Technology Data Exchange (ETDEWEB)

Optimization of the refrigerant circuit (RC) of a fin-and-tube heat exchanger can increase its heat exchange capacity or decrease its cost. The genetic algorithm is one of the suitable optimization methods, however it needs to be improved for RC optimization of fin-and-tube heat exchangers. An improved genetic algorithm (IGA) is proposed for RC optimization. In the IGA, the RC solutions are represented by one-dimensional integer strings which can save both computer memory and decoding time. RC correction operators are developed and embedded in the entire genetic process with the goal of avoiding physically impossible solutions. The knowledge-based RC generation method, greedy RC crossover method, greedy RC mutation method and all-previous-population based selection method are developed in order to improve the efficiency of the genetic evolution process for RC optimization. Case studies with 3 different heat exchangers show that both the optimization speed and the quality of the output optimal solution of IGA are better than those of the conventional genetic algorithm. A 0-40% decrease in total length of joint tubes is obtained after optimization with the IGA with the target of obtaining the shortest joint tubes. In addition, a 2.8-7.4% increase in heat exchange capacity is obtained after IGA optimization with the target of maximum heat transfer. (author)

Zhigang Wu; Guoliang Ding [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Kaijian Wang; Fukaya, Masaharu [Fujitsu General Institute of Air-Conditioning Technology Limited, 1116 Suenaga, Takatsu-Ku, Kawasaki 213-8502 (Japan)

2008-08-15

 
 
 
 
201

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

Scientific Electronic Library Online (English)

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

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

202

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

Directory of Open Access Journals (Sweden)

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

M.T. Martínez

2004-01-01

203

Performance and optimum design of convective-radiative rectangular fin with convective base heating, wall conduction resistance, and contact resistance between the wall and the fin base  

International Nuclear Information System (INIS)

This paper investigates the performance and optimum design of a longitudinal rectangular fin attached to a convectively heated wall of finite thickness. The exposed surfaces of the fin lose heat to the environmental sink by simultaneous convection and radiation. The tip of the fin is assumed to lose heat by convection and radiation to the same sink. The analysis and optimization of the fin is conducted numerically using the symbolic algebra package Maple. The temperature distribution, the heat transfer rates, and the fin efficiency data is presented illustrating how the thermal performance of the fin is affected by the convection-conduction number, the radiation-conduction number, the base convection Biot number, the convection and radiation Biot numbers at the tip, and the dimensionless sink temperature. Charts are presented showing the relationship between the optimum convection-conduction number and the optimum radiation-conduction number for different values of the base convection Biot number and dimensionless sink temperature and fixed values of the convection and radiation Biot numbers at the tip. Unlike the few other papers which have applied the Adomian's decomposition and the differential quadrature element method to this problem but give illustrative results for specific fin geometry and thermal variables, the present graphical data are generally applicable and can be used by fin designers without delving into the mathematical details of the computational techniques.

2009-10-01

204

MODERN MANUFACTURING TECHNIQUES OF PRECISED MISSILE REAR FIN ASSEMBLY  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2013-01-01

205

Steam generator tubing NDE performance  

International Nuclear Information System (INIS)

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

1997-02-01

206

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

207

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-08-01

208

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

2013-01-01

209

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

International Nuclear Information System (INIS)

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

2001-11-01

210

Design and performance of shroud tubes  

International Nuclear Information System (INIS)

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

211

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

Directory of Open Access Journals (Sweden)

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

2006-01-01

212

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

Directory of Open Access Journals (Sweden)

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

D. Nirmal

2011-05-01

213

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

Directory of Open Access Journals (Sweden)

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

DR. S.N. Sapali

2009-11-01

214

Internally finned ethylene coils  

Energy Technology Data Exchange (ETDEWEB)

Ways of maximising heat transfer and operating temperatures in ethylene furnaces are described. During the conversion of ethane or liquefied petroleum gas and steam to ethylene in a pyrolysis or steam cracker furnace, the feedstock is passed at 0.2-0.5 N/mm{sup 2} through high alloy steel coils heated to 950-1150C. The importance of using cast alloys is stressed and their advantages over wrought alloys shown in a histogram. To improve heat flux in response to developments in furnace design, conventional coil designs were replaced with tubes with an increased internal surface area obtained using integral longitudinal fins. Initially these new coils were made of wrought iron, but the problems caused by coke deposits led to the development by Doncasters Paralloy of PEP (Paralloy Ethylene Profiled) tubes. These are centrifugal cast tubes with integral bore fins made of high carbon cast alloys. The performance of wrought finned and cast PEP tubes are compared in terms of carburisation resistance, surface finish, macrostructure and microstructure.

Barker, T.; Jones, John [Doncasters Paralloy (United Kingdom)

2000-10-01

215

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

Directory of Open Access Journals (Sweden)

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

Ahmed F. Khudheyer

2011-08-01

216

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

Energy Technology Data Exchange (ETDEWEB)

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

Sahin, B. [Department of Mechanical Engineering, Cukurova University, 01330 Adana (Turkey)]. E-mail: bsahin@cu.edu.tr; Akkoca, A. [Department of Mechanical Engineering, Mersin University, 33342 Mersin (Turkey); Oztuerk, N.A. [Department of Mechanical Engineering, Cukurova University, 01330 Adana (Turkey); Akilli, H. [Department of Mechanical Engineering, Cukurova University, 01330 Adana (Turkey)

2006-06-15

217

A numerical analysis of three-dimensional turbulent fluid flow and heat transfer in plate-fin and tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Fluid flow and heat transfer over a multi-row (1-5 rows) plate-fin and tube heat exchanger are studied numerically. Flow is incompressible, three-dimensional and turbulent. The effects of tube arrangements and tube row numbers are investigated in detail for the Reynolds number ReH (based on the fin spacing H) ranging from 2000 to 10000. The effects of turbulence are simulated by the k-{epsilon} turbulence model. Stream and isothermal lines through the whole tube bank, local and average Nusselt number and pressure coefficient in the streamwise direction are presented. The numerical results for the average heat transfer coefficient agree well with the previously published experimental data.

Jang, Jiin-Yuh [National Cheng-Kung Univ., Tainan (Taiwan, Province of China); Chang, Wen-Jen; Lin, Min-Sheng [Feng-Chia Univ., Taichung (Taiwan, Province of China)

1996-12-31

218

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

Directory of Open Access Journals (Sweden)

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

Li Wen

2013-01-01

219

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

Science.gov (United States)

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

Ono, Takashi; Gao, Lei; Honda, Tomohiro

220

MODERN MANUFACTURING TECHNIQUES OF PRECISED MISSILE REAR FIN ASSEMBLY  

Directory of Open Access Journals (Sweden)

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

Md Akhtar khan

2013-11-01

 
 
 
 
221

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

Directory of Open Access Journals (Sweden)

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

Foued Chabane

2013-01-01

222

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

Directory of Open Access Journals (Sweden)

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

M Khoshvaght Aliabadi

2011-09-01

223

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

Science.gov (United States)

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

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

2014-03-01

224

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

International Nuclear Information System (INIS)

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

2001-09-01

225

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

International Nuclear Information System (INIS)

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

2007-07-01

226

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

International Nuclear Information System (INIS)

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

2010-12-01

227

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

228

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 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 pe...

2013-01-01

229

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

International Nuclear Information System (INIS)

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

2007-04-01

230

Effect of various parameters on the performance of capillary tube  

Directory of Open Access Journals (Sweden)

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

Rahul Gulati

2011-08-01

231

Effect of various parameters on the performance of capillary tube  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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.

2011-01-01

232

Performance of a tapered pulse tube  

International Nuclear Information System (INIS)

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

1998-05-26

233

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

Energy Technology Data Exchange (ETDEWEB)

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

Paeng, Jin Gi; Kim, Kyung Hwan; Yoon, Young Hwan [Changwon National University, Changwon (Korea, Republic of)

2009-02-15

234

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

International Nuclear Information System (INIS)

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

2009-02-01

235

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

International Nuclear Information System (INIS)

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

2013-06-17

236

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

Science.gov (United States)

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

Müller-Menzel, T.; Hecht, T.

237

Lumped Parameter Model for Dynamic Performances of Plate-Fin Recuperator  

International Nuclear Information System (INIS)

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

2006-07-17

238

A Comparative Study of Conventional and Tip-Fin Propeller Performance  

DEFF Research Database (Denmark)

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

Andersen, Poul

1997-01-01

239

Norplant capsules perform better with soft tubing.  

Science.gov (United States)

Norplant is a contraceptive method which, when used, prevents women from becoming pregnant for 5 years. It has been approved in 60 countries, and at least 6 million women have used it. The Norplant implants function by releasing small amounts of levonorgestrel, a synthetic progestin, through 6 capsules implanted under the skin of a woman's upper arm. Results published in the September 1998 issue of Obstetrics & Gynecology of the first 5-year study of the soft-tubing Norplant contraceptive since its approval in the US in 1990 found that the implant's efficacy is comparable to that of being surgically sterilized. The prospective multicenter trial involving 511 female volunteers, who accumulated 1642 woman-years of method use, at clinics in California, New Jersey, and New York observed a pregnancy rate for the method of 3/1000/year. This rate is one-third of that stated on the Norplant product label. The scientific literature on Norplant understates the method's ability to prevent pregnancy because most of the data were collected based upon using hard-tubing implants. The soft-tubing version of the method was first distributed in the US in 1991, with the difference between the two tubings being the amount of silicate used to strengthen the capsule. More than 80% of women continued using the method from year to year over the 5-year period, for a median of 47 months. The soft-tubing Norplant system is highly effective in women of all weights, even among those in their later reproductive years. PMID:12321877

1998-09-01

240

Condensation of ammonia on the outside of smooth and fluted tubes at various tube positions  

Energy Technology Data Exchange (ETDEWEB)

Experiments were conducted to determine the heat transfer performance obtained for ammonia condensing on the outside of six tubes of four distinct types: (1) a smooth tube, (2) two single-fluted tubes, (3) two double-fluted tubes, and (4) an external-finned tube. All tubes tested were 2.54 cm (1.0 in.) in nominal diameter and 1.22 m (4.9 ft) in length. Condensing heat transfer coefficients are reported as composite coefficients (including the resistances of both condensing film and tube wall) for (1) a smooth tube condensing in the horizontal position and at various tilt angles, (2) two single-fluted tubes condensing in the vertical position, and (3) a finned tube condensing in the horizontal position. Overall heat transfer data are given for both double-fluted tubes. Data show that for a given heat flux, a horizontal smooth tube can increase composite coefficients by up to 2.1 times the vertical smooth-tube values. For a single-fluted tube, composite coefficients increased by up to 5.2 times the corresponding vertical smooth-tube values. However, on a horizontal position, the finned tube gave the lowest performance of any other tube tested in this study. Finally, for one double-fluted tube, inside fluting increased the overall heat transfer coefficient by as much as 25% more than that for a tube with identical external flutes and a smooth inside surface.

Domingo, N.

1982-02-01

 
 
 
 
241

Evacuated-tube solar collector--performance evaluation  

Science.gov (United States)

Report gives thermal performance test procedures and results for commercially produced, water-filled, 8-tube collectors. Tests include efficiency, time constant for temperature drop after solar flux is cut, change in efficiency as function of sun angle, and test to see if tubes break when filled with hot water.

1980-01-01

242

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

Scientific Electronic Library Online (English)

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

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

243

Performance demonstration requirements for eddy current steam generator tube inspection  

International Nuclear Information System (INIS)

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

1992-10-21

244

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

Directory of Open Access Journals (Sweden)

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

Marek Rejman

2012-12-01

245

WWER Steam Generators Tubing Performance and Aging Management  

International Nuclear Information System (INIS)

At WWER NPPs the horizontal steam generators (SGs), are used that differ in design concept from vertical SGs mostly used at western NPPs. Reliable operation of SG heat-exchanging tubes is the crucial worldwide problem for NPP of various types. According to the operation feedback the water chemistry is the governing factor affecting operability of SG tubing. The secondary side corrosion is considered to be the main mechanism of SG heat-exchanging tubes damage at WWER plants. To make the assessment of the tubing integrity the combination of pressure tests and eddy-current tests is used. Assessment of the tubing performance is an important part of SG life extension practice. The given paper deals with the description of the tube testing strategy and the approach to tube integrity assessment based on deterministic and probabilistic methods of fracture mechanics. Requirements for eddy-current test are given as well. Practice of condition monitoring and implementing the database on steam generators operation are presented. The approach to tubes plugging criteria is described. The research activities on corrosion mechanism studies and residual lifetime evaluation are mentioned. (authors)

2006-07-17

246

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

Science.gov (United States)

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

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

2014-06-01

247

Evaluation of the thermodynamic performance of pulse tubes  

International Nuclear Information System (INIS)

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

1995-07-17

248

Combustion characteristics and performance of U type radiation tube burner  

Energy Technology Data Exchange (ETDEWEB)

Present study deals with combustion characteristics and performance of U type radiation tube burner which combustion capacity is 30,000 kcal/he and the maximum capacity of supply fuel is 3.0 Nm{sup 3}/hr. temperature range of radiation tube is maximum 170 deg.C and minimum 150 deg.C and this displays relatively small temperature range. And thermal efficiency is satisfactory as 75 {approx} 80 %. Also, radiative efficiency of radiation tube is 52 {approx} 63 %. (author). 4 refs., 7 figs., 8 tabs.

Lee, H.C.; You, H.S.; Lee, J.S. [Korea Gas Corporation, Seongnam (Korea)

2000-11-01

249

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

250

Performance characterization of the TRW 35K pulse tube cooler  

International Nuclear Information System (INIS)

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

1995-07-17

251

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

252

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

253

Indications and complications of tube thoracostomy performed by general surgeons.  

Science.gov (United States)

The cross-sectional study conducted at the Isra University Hospital, Hyderabad was to determine the frequencies of various indications and complications of tube thoracostomy performed by general surgeons between February 2003 and January 2006. The data was analyzed and compared with other local and international studies. One hundred and five tube thoracostomies were performed over the above mentioned last three years. The most common indication for tube thoracostomy was tuberculous effusion (38/105, 36.1%). Most of the complications were categorized as positional complications and these occurred in about 9.5% (10/105) of the patients. Insertional complications occurred in 5.7% (6/105) of the patients whereas infective complication was noticed in only one patient. The most common complication was nonfunctioning of tube and this occurred in about 7.6% (8/105) of the patients. Tube thoracostomy is a relatively simple but invasive procedure and carries less risk of complications if performed carefully and cautiously. PMID:18297976

Khanzada, Tariq Wahab; Samad, Abdul

2008-01-01

254

Analysis of radial fin assembly heat transfer with dehumidification  

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. An individual finned tube geometry is a reasonable representation of heat exchangers used in air conditioning. The condensation process involves both heat and mass transfer and the cooling takes place by the removal of sensible as well as latent heat. The ratio of sensible to total heat is an important quantity that defines the heat transfer process during a dehumidifier operation. A one-dimensional model for heat transfer in the fin and the heat exchanger block is developed to study the effects of condensation on the fin surface. The combined heat and mass transfer process is modeled by incorporating the ratio of sensible to total heat in the formulation. The augmentation of heat transfer due to fin was established by comparing heat transfer rate with and without fins under the same operating conditions. Numerical calculations were carried out to study the effects of relative humidity and dry bulb temperature of the incoming air, and cold fluid temperature inside the coil on the performance of the heat exchanger. Results were compared to those published for rectangular fin under humid condition showed excellent agreement when the present model was used to compute that limiting condition. It was found that the heat transfer rate increased with increment in both dry bulb temperature and relative humidity of the air. The augmentation factor, however, decreased with increment in relative humidity and the dry bulb temperature.

Rosario, L.; Rahman, M.M. [Univ. of South Florida, Tampa, FL (United States). Dept. of Mechanical Engineering

1996-12-31

255

In-reactor performance of pressure tubes in CANDU reactors  

International Nuclear Information System (INIS)

The pressure tubes in CANDU reactors have been operating for times up to about 25 years. The in-reactor performance of Zr-2.5Nb pressure tubes has been evaluated by sampling and periodic inspection. This paper describes the behaviour and discusses the factors controlling the behaviour of these components in currently operating CANDU reactors. The mechanical properties (such as ultimate tensile strength, UTS, and fracture toughness), and delayed-hydride-cracking properties (crack growth rate Vc, and threshold stress intensity factor, KIH) change with irradiation; the former reach a limiting value at a fluence of 25 n m-2, while Vc and KIH reach a steady-state condition after a fluence of about 3 x 1025 n m-2 and 3 x 1024 n m-2, respectively. At saturation the UTS is raised by about 200 MPa, toughness is reduced to about 40% of its initial value, Vc increases by about a factor of ten while KIH is only slightly reduced. The role of microstructure and trace elements in these behaviours is described. Pressure tubes exhibit elongation and diametral expansion. The deformation behaviour is a function of operating conditions and material properties that vary from tube-to-tube and as a function of axial location. Semi-empirical predictive models have been developed to describe the deformation response of average tubes as a function of operating conditions. For corrosion and, more importantly deuterium pickup, semi-empirical predictive models have also been developed to represent the behaviour of an average tube. The effect of material variability on corrosion behaviour is less well defined compared with other properties. Improvements in manufacturing have increased fracture resistance by minimising trace elements, especially H and Cl, and reduced variability by tightening controls on forming parameters, especially hot-working temperatures

2008-12-15

256

Energy saving device: AP-Fin (Aperture Fin)  

Energy Technology Data Exchange (ETDEWEB)

The energy-saving device named AP-Fin (Aperture Fin) was developed to improve the propulsive performance by reducing the rotational energy loss behind propeller, and not impairing the superiority of the optimized stern and propeller. AP-Fin is a simple curved plate fitted to the upper part of the propeller aperture and its features are easy design and construction, low cost, and wide applicability. Series model tests systematically varying skew and length of AP-Fin are performed to study the effects on resistance, interaction, flow field and rudder force. As a result of these experiments, power-saving effect of AP-Fin was confirmed to be about 4% in full load condition and approximately 2% in ballast condition for VLCC. The semicontainer ship, the first full-scale vessel adopting AP-Fin, will be in service before the end of 1988.

Koshiba, Y.; Shirose, Y.

1988-01-01

257

Effects of regenerator geometry on pulse tube refrigerator performance.  

Science.gov (United States)

This paper gives results of the cooling performance of a double-inlet pulse tube refrigerator using various regenerators. The same pulse tube was used for all the experiments and measured 4.76 mm in diameter and 46.2 mm in length. A commercial linear compressor with a swept volume of 4 cm3 was used in these experiments. The operating conditions were held constant at a mean pressure of 2.0 MPa and a frequency of 54 Hz. Using finite difference software called REGEN3.1, developed at NIST, and recent experiment results, we optimized a series of regenerators based on dimensions, materials and screen packing. The values used for calculating the thermal conduction through stacked screens by REGEN3.1 were based on recent experimental results from NIST. The regenerator tubes were designed using 316 stainless steel and titanium materials. The regenerator matrices investigated were 400-mesh and 500-mesh stainless steel screen. The valve settings for both orifices were adjusted to minimize the no-load temperature for all regenerators. A cooling capacity curve from 0 to 3 W was also determined. The performance of the pulse tube refrigerator using the different regenerators is discussed. The experimental results from the various regenerators are evaluated and compared with their corresponding numerically calculated coefficient of performance (COP) and regenerator design as determined by REGEN3.1. PMID:11543212

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

1998-01-01

258

Predicting optimum vortex tube performance using a simplified CFD model  

Energy Technology Data Exchange (ETDEWEB)

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

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

2004-07-01

259

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

260

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.

2011-08-01

 
 
 
 
261

Performance of the CMS Drift Tube Chambers with Cosmic Rays  

CERN Document Server

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

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

2010-01-01

262

Performance analysis of double basin solar still with evacuated tubes  

International Nuclear Information System (INIS)

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

2013-01-01

263

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

Science.gov (United States)

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

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

2013-09-15

264

Heat exchanger with transpired, highly porous fins  

Science.gov (United States)

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

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

2002-01-01

265

Experimental investigation on flow and heat transfer performance of a novel heat fin-plate radiator for electronic cooling  

Energy Technology Data Exchange (ETDEWEB)

Within the electronics industry, high degree of integration and enhanced performance has led to high heat dissipation electronic devices. This has identified the future development of very high heat flux components. In this paper, a novel and high efficient diffusion welded heat fin-plate radiator (HFPR) was proposed and designed. Various parameters affect the thermal performance of HFPR. The effect of three parameters: the working fluid filling ratios (8% < FR < 70%), the vacuum degrees (0.001 Pa < VD < 0.1 Pa), and the air flow velocities (0.5 m/s < u < 6 m/s) were investigated experimentally. Using distilled water and ethanol as working fluids, a series of tests were carried out to find the influence of the above parameters on steady-state heat transfer characteristics of HFPR. The experimental results indicated that the filling ratio and vacuum degree had a significant influence on thermal performance of HFPR. Also compared with cooling performance using distilled water and ethanol, the HFPR cooling component using distilled water had a stronger heat dissipation capacity for the same filling ratio. The results also can provide a basis for optimal design of HFPR structure. (orig.)

Peng, Hao; Ling, Xiang [Nanjing University of Technology, Department of Mechanical and Power Engineering, Nanjing (China)

2009-10-15

266

Experimental investigation on flow and heat transfer performance of a novel heat fin-plate radiator for electronic cooling  

Science.gov (United States)

Within the electronics industry, high degree of integration and enhanced performance has led to high heat dissipation electronic devices. This has identified the future development of very high heat flux components. In this paper, a novel and high efficient diffusion welded heat fin-plate radiator (HFPR) was proposed and designed. Various parameters affect the thermal performance of HFPR. The effect of three parameters: the working fluid filling ratios (8% < FR < 70%), the vacuum degrees (0.001 Pa < VD < 0.1 Pa), and the air flow velocities (0.5 m/s < u < 6 m/s) were investigated experimentally. Using distilled water and ethanol as working fluids, a series of tests were carried out to find the influence of the above parameters on steady-state heat transfer characteristics of HFPR. The experimental results indicated that the filling ratio and vacuum degree had a significant influence on thermal performance of HFPR. Also compared with cooling performance using distilled water and ethanol, the HFPR cooling component using distilled water had a stronger heat dissipation capacity for the same filling ratio. The results also can provide a basis for optimal design of HFPR structure.

Peng, Hao; Ling, Xiang

2009-10-01

267

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

Science.gov (United States)

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

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

2010-10-01

268

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

Energy Technology Data Exchange (ETDEWEB)

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

Pu, Hui; Ding, Guo-liang; Hu, Hai-Tao [Shanghai Jiaotong University, Institute of Refrigeration and Cryogenics, Shanghai (China); Gao, Yi-feng [International Copper Association Shanghai Office, Shanghai (China)

2010-10-15

269

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

Directory of Open Access Journals (Sweden)

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

M. R. Beigh

2013-03-01

270

Development and performance of a double diaphragm shock tube  

International Nuclear Information System (INIS)

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

1972-01-01

271

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

1988-11-09

272

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

Science.gov (United States)

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

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

2013-02-01

273

Condenser performance test and replacement tubing material evaluation: Final report  

Energy Technology Data Exchange (ETDEWEB)

This document describes the experiences of a utility in evaluating condenser performance and in performing testing to identify and correct performance deficiencies and related problems. A comprehensive evaluation of the steam surface condenser performance at Kewaunee Nuclear Plant (KNP) was undertaken by Wisconsin Public Service Corporation (WPSC) in the first half of 1984. This evaluation was prompted by the projected need to retube the steam surface condenser. Stainless steel alloys were considered the only acceptable replacement candidates because of the contribution of copper to nuclear plant steam generator corrosion. All of the stainless steel alloys have lower heat transfer coefficients than the Admiralty brass tubing originally installed in the condenser. The potential impact on the unit heat rate coupled with apparent condenser performance deficiences led to this extensive analysis.

Bell, R.J.; Hardy, C.D.

1988-04-01

274

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

Science.gov (United States)

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%...

O. S. Tatone R. L. Tapping

1988-01-01

275

Environment-friendly heat exchangers. CO2 applications and tubes with internal finning for glycol air coolers; Umweltfreundliche Waermetauscher. CO{sub 2}-Anwendungen und innen geriffelte Rohre fuer Glykol-Luftkuehler  

Energy Technology Data Exchange (ETDEWEB)

The contribution discusses two different aspects: 1. The use of tubes with internal finning for glycol air coolers. These special tubes have a higher internal HI even with very low REynolds numbers (1800 + 3000) without internal pressure loss. This makes for a new line of highly efficient glycol air coolers. 2. Identification of key parameters for the design of efficient CO2 heat exchangers. An air cooler analysis shows that simple battery reforming provides good results at higher pressure levels in spite of different CO2 characteristics. Gas coolers, on the other hand, necessitate a new design for higher pressure resistance and optimum utilisation of CO2 properties. Correct operation necessitates special mechanical solutions for the material and ocmponents. A new method of heat exchanger design was developed. In order to ensure high gas cooler efficiency especially in the summer season, LU-VE developed innovative designs for spraying of the battery surface with demineralized water. (orig.)

Filippini, S. [LU-VE CONTARDO S.p.A., Uboldo-Varese (Italy)

2006-07-01

276

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

277

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

Energy Technology Data Exchange (ETDEWEB)

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.

Ahn, Joon [Kookmin Univ., Seoul (Korea, Republic of); Hwang, Sang Soon [Univ. of Incheon, Incheon (Korea, Republic of)

2012-11-15

278

Experimental performance of single and double pass solar air heater with fins and steel wire mesh as absorber  

Energy Technology Data Exchange (ETDEWEB)

Thermal performance of a single and double pass solar air heater with fins attached and using a steel wire mesh as absorber plate was investigated experimentally. The effects of air mass flow rate range between 0.012 kg/s and 0.038 kg/s on the outlet temperature and thermal efficiency was studied. The bed heights were 7 cm and 3 cm for the lower and upper channels respectively. Result shows that, the efficiency increase with increasing air mass flow rate. For the same flow rate, the efficiency of the double pass is found to be higher than the single pass by 7-19.4%. Maximum efficiency obtained for the single and double pass air heater was 59.62% and 63.74% respectively for air mass flow rate of 0.038 kg/s. Moreover, the thermal efficiency further decreases by increasing the height of the first pass of the double pass solar air heater. The temperature difference between the outlet flow and the ambient, {delta}T, reduces as the air mass flow rate increase The result of a single or double solar air heater using steel wire mesh arrange in layers as an absorber plate and packing material when compared with a conventional solar air heater shows a much more substantial enhancement in the thermal efficiency. (author)

Omojaro, A.P.; Aldabbagh, L.B.Y. [Mechanical Engineering Dept., Eastern Mediterranean University, Gazimagusa, Mersin 10 (Turkey)

2010-12-15

279

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

280

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

Science.gov (United States)

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

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

2014-04-01

 
 
 
 
281

Steam Generator Tube Performance: Experience with Water-Cooled Nuclear Power Reactors During 1983 and 1984.  

Science.gov (United States)

A review of the performance of steam generator tubes in water-cooled nuclear power reactors showed that tubes were plugged at 47 (35.6%) of the reactors in 1983 and at 63 (42.6%) of the reactors during 1984. In 1983 and 1984 3291 and 3335 tubes, respectiv...

O. S. Tatone P. Meindl G. F. Taylor

1986-01-01

282

Steam Generator Tube Performance. Experience with Water-Cooled Nuclear Power Reactors During 1982.  

Science.gov (United States)

A review of the performance of steam generator tubes in 116 water-cooled nuclear power reactors showed that tubes were plugged at 54 (46 percent) of the reactors. The number of tubes removed from service decreased from 4,692 (0.30 percent) in 1981 to 3,22...

O. S. Tatone R. S. Pathania

1984-01-01

283

Steam Generator Tube Performance. Experience with Water-Cooled Nuclear Power Reactors During 1981.  

Science.gov (United States)

A review of the performance of steam generator tubes in 110 water-cooled nuclear power reactors showed that tubes were plugged at 46 (42 percent) of the reactors. The number of tubes removed from service increased from 1900 (0.14 percent) in 1980 to 4692 ...

O. S. Tatone R. S. Pathania

1983-01-01

284

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

285

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

286

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

Science.gov (United States)

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

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

2012-01-01

287

Performance characteristics of an electromagnetic streamer tube calorimeter  

International Nuclear Information System (INIS)

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

1987-05-01

288

Equipment for performance testing of steam generator tube-to-tube plate joints  

International Nuclear Information System (INIS)

The demands are discussed placed on tests of operating resistance of tube-to-tube plate joints for steam generators of nuclear power plants with WWER-440 and WWER-1000 reactors. The heat exchange tubes are made of austenitic stainless steel 08Ch18N10T, the tube plates of the WWER-440 reactor of the same steel and for the WWER-1000 reactor of low-alloyed 10GN2MFA steel. The demands are presented which are placed on testing equipment which allows to expose test joints in conditions approaching the actual operation of a nuclear plant. The equipment consists of three water circuits which correspond to the primary and secondary parts of the steam generator, the third circuit is a cooling one. The system includes a water treatment unit, auxiliary technological circuits, inspection and control circuits. Operating parameters of the testing equipment are: primary water temperature 290 degC, secondary water temperature 259 degC pressure of secondary water or 4.8 Mpa, and power input of the heater 85 kW. During the first implemented experiment corrosion occurred of the test module after 1840 hours. The results of the experiments will serve to optimize the technology of the tube-to-tube plate joints in steam generators and to increase the corrosion resistance of certain steam generator parts of major importance. (Z.M.). 7 figs., 8 refs

1988-07-01

289

Engineer, Design, Construct, Test, and Evaluate a Pressurized Fluidized Bed Pilot Plant Using High Sulfur Coal for Production of Electric Power. Phase I: Preliminary Engineering. Technology Support Test Results PFB Heat Exchanger Fin and Tube Materials Erosion Rig Evaluation Test Period July 1976--April 1977.  

Science.gov (United States)

A test environment was created simulating the temperature and particle velocity conditions to which tube and fin alloys will be exposed in the Curtiss-Wright PFB Combustor. Sample pieces of seven candidate alloys were exposed to the environment for 1000 h...

1978-01-01

290

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

Energy Technology Data Exchange (ETDEWEB)

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

Domingo, N.

1982-12-01

291

Implementation status of performance demonstration program for steam generator tubing analysts in Korea  

Energy Technology Data Exchange (ETDEWEB)

Some essential components in nuclear power plants are periodically inspected using non destructive examinations, for example ultrasonic, eddy current and radiographic examinations, in order to determine their integrity. These components include nuclear power plant items such as vessels, containments, piping systems, pumps, valves, tubes and core support structure. Steam generator tubes have an important safety role because they constitute one of the primary barriers between the radioactive and non radioactive sides of the nuclear power plant. There is potential that if a tube bursts while a plant is operating, radioactivity from the primary coolant system could escape directly to the atmosphere. Therefore, in service inspections are critical in maintaining steam generator tube integrity. In general, the eddy current testing is widely used for the inspection of steam generator tubes due tube integrity. In general, the eddy current testing is widely used for the inspection of steam generator tubes due to its high inspection speed and flaw detectability on non magnetic tubes. However, it is not easy to analyze correctly eddy current signals because they are influenced by many factors. Therefore, the performance of eddy current data analysts for steam generator tubing should be demonstrated comprehensively. In Korea, the performance of steam generator tubing analysts has been demonstrated using the Qualified Data Analyst program. This paper describes the performance demonstration program for steam generator tubing analysts and its implementation results in Korea. The pass rate of domestic analysts for this program was 71.4%.

Cho, Chan Hee; Lee, Hee Jong; Yoo, Hyun Ju; Nam, Min Woo [KHNP Central Research Institute, Daejeon (Korea, Republic of); Hong, Sung Yull [Yeungnam Univ., Gyeongsan (Korea, Republic of)

2013-02-15

292

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

CERN Document Server

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

Asaoka, Yoichi; 10.1016/j.nima.2011.05.036

2011-01-01

293

Determination of heat transfer and friction characteristics of an adapted inclined louvered fin  

Energy Technology Data Exchange (ETDEWEB)

An experimental study of a fin-and-tube heat exchanger was performed. To this end a test rig was constructed to measure the heat transfer rate on the air and waterside of the heat exchanger. A wide range of Reynolds numbers on the airside was investigated. The resulting data was used to determine the convective heat transfer correlation (expressed using the Colburn factor) and the friction factor on the airside. The fin type used in the heat exchanger of this research is an adaptation of the standard inclined louvered type. A thorough error analysis was performed, to validate the results. (author)

T' Joen, C.; Steeman, H.-J.; Willockx, A.; De Paepe, M. [Department of Flow, Heat and Combustion Mechanics, Ghent University-UGent, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium)

2006-03-01

294

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

International Nuclear Information System (INIS)

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

295

High Fin Width Mosfet Using Gaa Structure  

Directory of Open Access Journals (Sweden)

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

S.L.Tripathi

2012-11-01

296

R 134a makes tube bundle apparatus more compact. Rohrbuendelapparate noch kompakter mit R 134a. Untersuchung des Leistungsverhaltens von Hochleistungs-Rippenrohren bei der Verdampfung und Verfluessigung in Rohrbuendeln und an Einzelrohren mit dem Ersatzkaeltemittel R 134a  

Energy Technology Data Exchange (ETDEWEB)

This article contains a report on measuring results obtained during experiments with liquefaction and evaporation of the refrigerant substitute R 134a. Performance of standard- and high-efficiency finned tubes is studied for single tubes and tube bundles. Both types of tubes are subjected to a comparison with the known refrigerants R 22 and R 12. The high-efficiency finned tube's performance was 40% higher when R 134a was used. Performance increases of between 40 and 50% compared to standard finned tubes are achievable. Varying proportions of oil mass in the R 134a have an influence on performance in single tubes and tubes bundles. (orig./BWI)

Kriegsmann, A. (Anwendungstechnik Waermeuebertragung, Wieland-Werke AG, Ulm (Germany))

1993-10-01

297

Recent progress in enhancing film condensation heat transfer on horizontal tubes  

International Nuclear Information System (INIS)

An assessment of several promising techniques which use surface tension forces to enhance film condensation heat transfer on horizontal tubes is made. Recent progress on integral-fin tubes is stressed, including experimental findings on fin spacing, geometry and material, and the latest theoretical developments to predict performance. Condensation heat transfer enhancement on wire-wrapped tubes is also examined, as well as the use of non-wetting strips and porous drainage devices. The effect of condensate inundation on plain and enhanced tubes is briefly reviewed, and future research directions are discussed

1986-01-01

298

Simulation of Grid-Fin Control Surfaces  

Science.gov (United States)

Conference poster using previously disclosed techniques and methods (see ARC 16210 & 16212). We present simulations of grid-fin control surfaces to demonstrate geometric complexity and numerical robustness. These results have relevance to high-performance computing and performance of grid-fin-based control systems.

Aftosmis, Michael J.

2011-01-01

299

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

International Nuclear Information System (INIS)

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

1980-01-01

300

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

Energy Technology Data Exchange (ETDEWEB)

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

Tatone, O.S.; Pathania, R.S.

1980-11-01

 
 
 
 
301

Time-dependent heat transfer in a fin-wall assembly. New performance coefficient: thermal reverse admittance  

Energy Technology Data Exchange (ETDEWEB)

Transient thermal fields and heat fluxes due to step-harmonic temperature excitation and their dependence on frequency are studied in a fin-wall assembly. Application of the currently used efficiency coefficient to transient-harmonic processes is discussed. A new coefficient, thermal reverse transfer admittance, and others, including the augmentation factor, have been used to characterise the behaviour of the system. In a thermal frequency response analysis, module, phase, real and imaginary components have been obtained. For the calculation a network model (whose admittance is identical to the thermal admittance of the system) has been designed for the whole system. The network simulation method provides the numerical response of the system by running the network in circuit resolution software. (authors)

Alarcon, M. [Murcia Univ., Thermal Machines and Heat Engines Area (Spain); Alhama, F.; Gonzalez-Fernandez, C.F. [University of Cartagena, Dept. of Amplied Physics, Tech., Cartagena, Murcia (Spain)

2002-04-01

302

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

Energy Technology Data Exchange (ETDEWEB)

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

Tatone, O.S.; Pathania, R.S.

303

Steam generator tube performance: experience with water-cooled nuclear power reactors during 1981  

Energy Technology Data Exchange (ETDEWEB)

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

Tatone, O.S.; Pathania, R.S.

304

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

Energy Technology Data Exchange (ETDEWEB)

A review of the performance of steam generator tubes in water-cooled nuclear power reactors showed that tubes were plugged at 47 (35.6%) of the reactors in 1983 and at 63 (42.6%) of the reactors during 1984. In 1983 and 1984, 3291 and 3335 tubes, respectively, were removed from service - about the same as in 1982. The leading causes assigned to tube failure were stress corrosion cracking from the primary side and stress corrosion cracking or intergranular attack from the secondary side. In addition, 5668 tubes were repaired for further service by installation of internal sleeves. Most of these were believed to have deteriorated by one of the preceding mechanisms or by pitting. A trend continues toward high-integrity condenser tube materials at sites cooled by brackish water or seawater. 31 refs., 3 figs., 12 tabs.

Tatone, O.S.; Meindl, P.; Taylor, G.F.

305

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

International Nuclear Information System (INIS)

A review of the performance of steam generator tubes in water-cooled nuclear power reactors showed that tubes were plugged at 47 (35.6%) of the reactors in 1983 and at 63 (42.6%) of the reactors during 1984. In 1983 and 1984, 3291 and 3335 tubes, respectively, were removed from service - about the same as in 1982. The leading causes assigned to tube failure were stress corrosion cracking from the primary side and stress corrosion cracking or intergranular attack from the secondary side. In addition, 5668 tubes were repaired for further service by installation of internal sleeves. Most of these were believed to have deteriorated by one of the preceding mechanisms or by pitting. A trend continues toward high-integrity condenser tube materials at sites cooled by brackish water or seawater. 31 refs., 3 figs., 12 tabs

306

Steam generator tube performance: experience with water-cooled nuclear power reactors during 1981  

International Nuclear Information System (INIS)

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

307

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

International Nuclear Information System (INIS)

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

308

Steam Generator Tube Performance: Experience with Water-Cooled Nuclear Power Reactors During 1978.  

Science.gov (United States)

The performance of steam generator tubes in water-cooled nuclear power reactors has been reviewed for 1978. Tube failures occurred at 31 of the 86 reactors surveyed. Causes of these failures and procedures designed to deal with them are described. A drama...

O. S. Tatone R. S. Pathania

1980-01-01

309

Steam Generator Tube Performance. Experience with Water-Cooled Nuclear Power Reactors During 1980.  

Science.gov (United States)

The performance of steam generator tubes in water-cooled nuclear power reactors has been reviewed for 1980. Tube defects occurred at 38% of the 97 reactors surveyed. This is a marginal improvement over 1979 when defects occurred at 41% of the reactors. Th...

O. S. Tatone R. S. Pathania

1982-01-01

310

Steam Generator Tube Performance: Experience with Water-Cooled Nuclear Power Reactors During 1979.  

Science.gov (United States)

The performance of steam generator tubes in water-cooled nuclear power reactors has been reviewed for 1979. Tube failures occurred at 38 of the 93 reactors surveyed. Causes of these failures and procedures designed to deal with them are described. The def...

O. S. Tatone R. S. Pathania

1981-01-01

311

Performance of Closed Tow-Phase Thermosyphon With Double Tube Evaporator  

International Nuclear Information System (INIS)

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

2004-01-01

312

The effects of fin parameters on the radiation and free convection heat transfer from a finned horizontal cylindrical heater  

Energy Technology Data Exchange (ETDEWEB)

A series of experiments has been carried out to determine the influence of fin parameters upon natural convection from a finned horizontal cylindrical heater. Due to its numerous applications, the fin geometry is chosen to be circular. The test section is constructed from a central heating tube, aluminium collars, and copper fins. Therefore, the experimental set-up is capable of analysing the effect of the fin diameter and spacing on heat transfer. In respect to the experimental results, the effect of [gamma], the ratio between fin space and body diameter, within the range studied (0.25 [<=] [gamma] [<=] 1.5), appears to be indiscernible on natural convection. However, the [lambda]-effect, the ratio between diameter of fin and cylindrical body, has been considered in the stated correlations. (Author).

Karabacak, R. (Dokuz Eyluel Univ., Denizli (Turkey). Dept. of Mechanical Engineering)

1992-11-01

313

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

International Nuclear Information System (INIS)

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

1987-01-01

314

Undulating fins produce off-axis thrust and flow structures.  

Science.gov (United States)

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

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

2014-01-15

315

Ultra-high aspect-ratio FinFET technology  

Science.gov (United States)

FinFETs with ultra-large height-to-width ratio have been processed on (1 1 0) bulk silicon wafers by employing crystallographic etching of silicon with TMAH, which results in nearly vertical sidewalls with a (1 1 1)/ surface orientation. Tall fins, which corresponds to wide transistor channels per single fin offer more efficient use of the silicon area and improved performance for multi-fin devices in high-frequency analog applications. N-channel FinFETs with 1.9-nm-wide fins demonstrate the downscaling potential of the technology and devices with a height of the active part of the fin of 625 nm have the largest aspect-ratio of the fins reported thus far. Both devices with highly and moderately scaled fin-widths exhibit excellent subthreshold performance while electrons have higher mobility in 15-nm-wide FinFETs, which gives them larger on-state currents. The comparison between FinFETs and wide tri-gate devices shows that FinFETs have better current drivability in this simple process, even with larger source/drain series resistances. The differences in threshold voltage and low-field electron mobility between 1.9-nm-wide and 15-nm-wide FinFETs have been related to the increase in subband energies due to carrier confinement in the extremely narrow fins.

Jovanovi?, Vladimir; Suligoj, Tomislav; Poljak, Mirko; Civale, Yann; Nanver, Lis K.

2010-09-01

316

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

317

Tube expanding machine  

Science.gov (United States)

A machine includes a casing disposed in a housing for receiving one or more tubes and a number of fins engaged around the tubes. A frame is slidably received in the housing, and one or more rods are secured to the frame and moved to engage into and to expand the tubes to engage with the fins when the rods are moved toward the tubes. A bracket and a seat have one or more pipes slidably received in the barrels for slidably receiving the rods and for preventing the rods from being bent. The rods each includes a mold piece for further expanding the tubes.

2000-12-26

318

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

International Nuclear Information System (INIS)

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

1980-01-01

319

Performance of long straw tubes using dimethyl ether  

Energy Technology Data Exchange (ETDEWEB)

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{Phi}NE, the Frascati {phi}-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 {mu}m can be reached. (orig.).

Benussi, L. [Lab. Nazionali di Frascati (Italy); Bertani, M. [Lab. Nazionali di Frascati (Italy); Bianco, S. [Lab. Nazionali di Frascati (Italy); Fabbri, F.L. [Lab. Nazionali di Frascati (Italy); Gianotti, P. [Lab. Nazionali di Frascati (Italy); Giardoni, M. [Lab. Nazionali di Frascati (Italy); Guaraldo, C. [Lab. Nazionali di Frascati (Italy); Lanaro, A. [Lab. Nazionali di Frascati (Italy); Lucherini, V. [Lab. Nazionali di Frascati (Italy); Mecozzi, A. [Lab. Nazionali di Frascati (Italy); Passamonti, L. [Lab. Nazionali di Frascati (Italy); Russo, V. [Lab. Nazionali di Frascati (Italy); Sarwar, S. [Lab. Nazionali di Frascati (Italy)

1995-07-01

320

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

 
 
 
 
321

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

International Nuclear Information System (INIS)

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

1996-01-01

322

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

323

Test plan 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. [Pacific Northwest National Lab., Richland, WA (United States); Babad, H. [Westinghouse Hanford Co., Richland, WA (United States)

1996-05-01

324

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

Science.gov (United States)

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

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

325

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

International Nuclear Information System (INIS)

The performance of steam generator tubes in water-cooled nuclear power reactors is reviewed for 1979. Tube failures occurred at 38 of the 93 reactors surveyed. The causes of these failures and the procedures designed to deal with them are described. The defect rate, although higher than that in 1978, was still lower than the rates of the two previous years. Methods being employed to detect defects include the increased use of multifrequency eddy-current testing and a trend to full-length inspection of all tubes. To reduce the incidence of tube failure by corrosion, plant operators are turning to full-flow condensate demineralization and more leak-resistant condenser tubes. 10 tables

1981-01-01

326

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

Energy Technology Data Exchange (ETDEWEB)

The performance of steam generator tubes in water-cooled nuclear power reactors is reviewed for 1979. Tube failures occurred at 38 of the 93 reactors surveyed. The causes of these failures and the procedures designed to deal with them are described. The defect rate, although higher than that in 1978, was still lower than the rates of the two previous years. Methods being employed to detect defects include the increased use of multifrequency eddy-current testing and a trend to full-length inspection of all tubes. To reduce the incidence of tube failure by corrosion, plant operators are turning to full-flow condensate demineralization and more leak-resistant condenser tubes. 10 tables.

Tatone, O.S.; Pathania, R.S.

1981-09-01

327

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

International Nuclear Information System (INIS)

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

2013-10-15

328

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

Energy Technology Data Exchange (ETDEWEB)

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 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. (author)

Wang, D.C.; Zhang, J.P. [College of Electromechanical Engineering, Qingdao University, Qingdao 266071 (China)

2009-05-15

329

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.

2009-05-01

330

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-09-15

331

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

International Nuclear Information System (INIS)

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

332

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

Energy Technology Data Exchange (ETDEWEB)

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

Pathania, R.S.; Tatone, O.S.

1979-09-01

333

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

International Nuclear Information System (INIS)

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

1979-01-01

334

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

International Nuclear Information System (INIS)

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

335

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

Directory of Open Access Journals (Sweden)

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

J.S. Wang

2008-01-01

336

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

International Nuclear Information System (INIS)

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

2000-11-01

337

High-performance silicon field emitter arrays for microwave power tube cathodes  

Energy Technology Data Exchange (ETDEWEB)

Microwave power tube cathodes set the most demanding performance standards for any application of field emitter arrays. The devices described in this work are fabricated at MCNC using a new process. The resulting devices have tips on 2 {micro}m columns and gate aperture diameters of less than 2 {micro}. The tips are formed by either anisotropic or isotropic etch techniques, and are oxidation sharpened to produce uniform emitters with tip radii less than 100 angstroms. Measurement of the electrical characteristics is performed by an automated data acquisition system. The current-voltage characteristics are then plotted in Fowler-Nordheim format. From this plot and the RF impedance of the device, the parameters that determine the ultimate performance in a microwave tube can be extracted. Based on measurements of these high-performance arrays, a power gain of approximately 10 dB can be expected when these arrays are used as cathodes in an inductive output amplifier tube.

Palmer, D.; Shaw, J.; True, R.B. [and others

1996-12-31

338

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1982-03-01

339

Performance Study of Concrete-Filled Steel Tubes  

Directory of Open Access Journals (Sweden)

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

Chair A.

2014-04-01

340

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

 
 
 
 
341

Performance characteristics of the pulsed high power klystron tube for PLS 2-GeV Linac  

International Nuclear Information System (INIS)

PLS 2-GeV Linac employs the E-3712 klystron tubes manufactured by TOSHIBA as one of the pulsed high power microwave sources. The rated power of the tube is 80-MW at 4 ps pulse width with 6OHz pulse repetition rate. As a part of the main linac the authors have completed the installation of two units of the E-3712 klystron tubes and the matching 200-MW modulators together with the accompanying waveguide networks and the accelerating columns. Since all the components are exposed as a virgin to high power microwave, careful power conditioning procedures are underway. The rest of linac components installation is also underway. The authors present the performance characteristics of the E-3712 klystron tube measured with the water load. The result of the initial power conditioning operation for the waveguide network and the accelerating structures installed as a part of the PLS 2-GeV linac is also presented

1993-05-17

342

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

International Nuclear Information System (INIS)

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

343

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

Energy Technology Data Exchange (ETDEWEB)

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

Tatone, O.S.; Pathania, R.S.

344

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

Science.gov (United States)

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

Arslanturk, Cihat

2011-02-01

345

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

Directory of Open Access Journals (Sweden)

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

Thamir K. Salim

2012-06-01

346

Effect of flame-tube head structure on combustion chamber performance  

Science.gov (United States)

The experimental combustion performance of a premixed, pilot-type flame tube with various head structures is discussed. The test study covers an extensive area: efficiency of the combustion chamber, quality of the outlet temperature field, limit of the fuel-lean blowout, ignition performance at ground starting, and carbon deposition. As a result of these tests, a nozzle was found which fits the premixed pilot flame tube well. The use of this nozzle optimized the performance of the combustion chamber. The tested models had premixed pilot chambers with two types of air-film-cooling structures, six types of venturi-tube structures, and secondary fuel nozzles with two small spray-cone angles.

Gu, Minqqi

1986-01-01

347

Performance demonstration tests for eddy current inspection of steam generator tubing  

International Nuclear Information System (INIS)

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

1996-01-01

348

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

Science.gov (United States)

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

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

2013-12-01

349

Steam Generator Tube Performance: Experience with Water-Cooled Nuclear Power Reactors During 1977.  

Science.gov (United States)

The performance of steam generator tubes in water-cooled nuclear power reactors has been reviewed for 1977. Failures were reported in 34 of the 79 reactors surveyed. Causes of these failures and inspection and repair procedures designed to deal with them ...

R. S. Pathania O. S. Tatone

1979-01-01

350

Quench gas and preamplifier selection influence on 3He tube performance for spent fuel applications  

International Nuclear Information System (INIS)

Current 3He tubes utilized in neutron coincidence counting use different quench gas admixtures to shorten the avalanche process. In addition amplifier modules with different shaping characteristics are used to process detector signals. Both of these aspects affect the detector response. In the current paper, 3He tubes with several quench gas admixtures (CO2, N2, Ar+CH4 and CF4) and amplifier modules (PDT, AMPTEK, BOT) are compared. The plateau characteristics, gamma-sensitivity and deadtime of individual counters in combination with the listed amplifier modules are compared to determine optimum amplifier module/counter performance for the spent fuel applications.

2012-06-01

351

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

Energy Technology Data Exchange (ETDEWEB)

The performance of pressurized drift-tube detectors at very high background rates has been studied at the Gamma Irradiation Facility (GIF) at CERN and in an intense 20 MeV proton beam at the Munich Van-der-Graaf tandem accelerator for applications in large-area precision muon tracking at high-luminosity upgrades of the Large Hadron Collider (LHC). The ATLAS muon drift-tube (MDT) chambers with 30 mm tube diameter have been designed to cope with ? and neutron background hit rates of up to 500 Hz/cm{sup 2}. Background rates of up to 14 kHz/cm{sup 2} are expected at LHC upgrades. The test results with standard MDT readout electronics show that the reduction of the drift-tube diameter to 15 mm, while leaving the operating parameters unchanged, vastly increases the rate capability well beyond the requirements. The development of new small-diameter muon drift-tube (sMDT) chambers for LHC upgrades is completed. Further improvements of tracking efficiency and spatial resolution at high counting rates will be achieved with upgraded readout electronics employing improved signal shaping for high counting rates.

Bittner, Bernhard; Dubbert, Jörg; Kortner, Oliver [Max-Planck-Institut für Physik, Munich (Germany); Kroha, Hubert, E-mail: kroha@mppmu.mpg.de [Max-Planck-Institut für Physik, Munich (Germany); Manfredini, Alessandro; Nowak, Sebastian; Ott, Sebastian; Richter, Robert; Schwegler, Philipp; Zanzi, Daniele [Max-Planck-Institut für Physik, Munich (Germany); Biebel, Otmar; Hertenberger, Ralf; Ruschke, Alexander; Zibell, Andre [Ludwig-Maximilians University, Garching (Germany)

2013-12-21

352

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

Science.gov (United States)

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

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

2013-12-01

353

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

International Nuclear Information System (INIS)

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

2013-12-21

354

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,

2010-07-01

355

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

Directory of Open Access Journals (Sweden)

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

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

2009-10-01

356

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 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 measure...

2010-01-01

357

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

CERN Document Server

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

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

2005-01-01

358

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

International Nuclear Information System (INIS)

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

2005-07-01

359

An approach to optimal fin diameter based on entropy minimization  

Directory of Open Access Journals (Sweden)

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

Masoud Asadi

2013-04-01

360

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Oppedal, Douglas; Goldsmith, Matthew I.

2010-01-01

 
 
 
 
361

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

Science.gov (United States)

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

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

2013-08-01

362

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

International Nuclear Information System (INIS)

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

2013-08-01

363

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

International Nuclear Information System (INIS)

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

1995-09-01

364

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

365

Performance Assessment of Passive Heat Exchanger with Horizontal Tube using RELAP5  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-10-15

366

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

367

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

Science.gov (United States)

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

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

2014-05-01

368

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)

2006-11-01

369

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

2007-08-01

370

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

Energy Technology Data Exchange (ETDEWEB)

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

Halle, H.; Wambsganss, M.W.

1983-02-01

371

Optimization of a reversed trapezoidal fin  

Energy Technology Data Exchange (ETDEWEB)

A reversed trapezoidal fin with the fluid in the inside wall is analyzed and optimized in this study. As a fin base boundary condition, the heat transfer from inside wall fluid to the fin base is considered. The values of fin base temperature with the variations of inside wall fluid convection characteristic number and fin base length are listed. The heat transfer, fin effectiveness, fin length and fin base height are optimized as a function of fin base length, convection characteristic number ratio, fin shape factor and fin volume.

Kang, Hyung Suk [Kangwon National University, Chuncheon (Korea, Republic of)

2006-10-15

372

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2000-01-01

373

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

Science.gov (United States)

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

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

2014-05-01

374

Source Drain Engineering in FinFET – A Review  

Directory of Open Access Journals (Sweden)

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

I.Flavia Princess Nesamani

2014-02-01

375

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

376

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

377

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

378

Analysis of a finned heat exchanger working in an adsorption refrigeration system using zeolite and methanol  

Energy Technology Data Exchange (ETDEWEB)

A new refrigeration system that uses a specially designed finned plate heat exchanger and works with zeolite and methanol is proposed. The integration of heat transfer and adsorption via a finned surface coated with zeolite CBV 901 and the use of a connected, twin active bed system to enable heat recuperation are novel features. The thermophysical properties of zeolite and methanol were first studied with the intention of designing a high performance heat exchanger (generator) for the adsorption refrigeration system. Here, the major problem is related to poor conductivity at the interface between the heat exchanger and the zeolite. The adsorbent must be heated (desorption phase) and then cooled (adsorption phase) back to ambient temperature in order to complete a thermodynamic cycle. To manufacture a sufficiently small system, there must be high rates of heat transfer in and out of the adsorbent. Therefore, the surface of the heat exchanger is finned in order to increase the heat transfer area (the fins are coated with 2 mm layer of specially prepared zeolite paste). The following characteristics were estimated from initial calculation: heating temperature, 120 deg C; outside tube temperature, 119.6 deg C; middle fin temperature 117 deg C, and coated layer of zeolite paste temperature, 115.3 deg C. The mathematical code developed to calculate the effects of operating conditions and the Coefficient of Performance (COP) was presented at HPC 2001 in Paris. It is based on the Dubinin-Astakhov equation and thermodynamic analyses. The results obtained shows that 0.535 is the COP for a single bed and 0.925 for a double bed. (Author)

Waszkiewicz, S.; Jenkins, S.; Saidani-Scott, H.; Tierney, M. [Bristol Univ., Mechanical Engineering Dept., Bristol (United Kingdom)

2003-12-01

379

Propulsive Forces of a Biomimetic Undulating Fin  

Science.gov (United States)

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

Kalumuck, Kenneth; Brandt, Alan; Armand, Mehran

2007-11-01

380

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

International Nuclear Information System (INIS)

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

2010-02-01

 
 
 
 
381

Performance model of metallic concentric tube recuperator with counter flow arrangement  

Science.gov (United States)

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

Sharma, Harshdeep; Kumar, Anoop; Goel, Varun

2010-03-01

382

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

International Nuclear Information System (INIS)

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

2010-06-13

383

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

International Nuclear Information System (INIS)

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

2013-07-25

384

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2013-01-01

385

Grid Fin Stabilization of the Orion Launch Abort Vehicle  

Science.gov (United States)

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

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

2011-01-01

386

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

International Nuclear Information System (INIS)

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

1996-01-01

387

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

Energy Technology Data Exchange (ETDEWEB)

Manufacturing processes of Zr-2.5Nb pressure tube used in CANDU reactor, effects of impurities on the properties of the pressure tube, exper