Study on Friction Factor of Developing and Developed Laminnr Flow in Annular－Sector Ducts

ＳｔｕｄｙｏｎＦｒｉｃｔｉｏｎＦａｃｔｏｒｏｆＤｅｖｅｌｏｐｉｎｇａｎｄＤｅｖｅｌｏｐｅｄＬａｍｉｎｎｒＦｌｏｗｉｎＡｎｎｕｌａｒ－ＳｅｃｔｏｒＤｕｃｔｓＭ．Ｊ．Ｌｉｎ；Ｗ．Ｑ．Ｔａｏ（ＳｃｈｏｏｌｏｆＥｎｅｒｇｙａｎｄＰｏｗｅｒＥｎｇｉｎｅｅｒｉｎ...     

Local Heat and Mass Transfer for Gas—Solid Two Phase Flow in CFB

ＬｏｃａｌＨｅａｔａｎｄＭａｓｓＴｒａｎｓｆｅｒｆｏｒＧａｓ－ＳｏｌｉｄＴｗｏＰｈａｓｅＦｌｏｗｉｎＣＦＢＦｅｎｇＬｕ；Ｍｉｎｇ－ＨｅｎｇＳｈｉ（Ｄｅｐｔ．ｏｆＰｏｗｅｒＥｎｇ．，ＳｏｕｔｈｅａｓｔＵｎｉｖｅｒｓｉｔｙ，Ｎａｎｊｉｎｇ，２１００１８，...     

A k－ε－PDF Two－Phase Turbulence Model for Simulating Sudden－Expansion Particle－Laden Flows

Ａｋ－ε－ＰＤＦＴｗｏ－ＰｈａｓｅＴｕｒｂｕｌｅｎｃｅＭｏｄｅｌｆｏｒＳｉｍｕｌａｔｉｎｇＳｕｄｄｅｎ－ＥｘｐａｎｓｉｏｎＰａｒｔｉｃｌｅ－ＬａｄｅｎＦｌｏｗｓＡｋ－ε－ＰＤＦＴｗｏ－ＰｈａｓｅＴｕｒｂｕｌｅｎｃｅＭｏｄｅｌｆｏｒＳｉｍｕｌａｔｉｎｇ...     

Local Non－Similarity Solution of Coupled Heat－Mass Transfer of a Flat Plate with Uniform Heat Flux in a Laminar Parallel Flow

ＬｏｃａｌＮｏｎ－ＳｉｍｉｌａｒｉｔｙＳｏｌｕｔｉｏｎｏｆＣｏｕｐｌｅｄＨｅａｔ－ＭａｓｓＴｒａｎｓｆｅｒｏｆａＦｌａｔＰｌａｔｅｗｉｔｈＵｎｉｆｏｒｍＨｅａｔＦｌｕｘｉｎａＬａｍｉｎａｒＰａｒａｌｌｅｌＦｌｏｗＹｕｗｅｎＺｈａｎｇ；ＺｈｏｎｇｑｉＣ...     

Three－Dimensional Numerical Simulation of Natural Convection Heat Transfer in an Inclined Cylindrical Annulus

Ｔｈｒｅｅ－ＤｉｍｅｎｓｉｏｎａｌＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆＮａｔｕｒａｌＣｏｎｖｅｃｔｉｏｎＨｅａｔＴｒａｎｓｆｅｒｉｎａｎＩｎｃｌｉｎｅｄＣｙｌｉｎｄｒｉｃａｌＡｎｎｕｌｕｓＪ．Ｇ．ｗｅｉ；Ｗ．Ｑ．Ｔａｏ（ＳｃｈｏｏｌｏｆＥｎｅｒ...     

Experimental Studieson Gas－Particle Flows and Coal Combustion in New Generation Spouting－Cyclone Combustor

ＥｘｐｅｒｉｍｅｎｔａｌＳｔｕｄｉｅｓｏｎＧａｓ－ＰａｒｔｉｃｌｅＦｌｏｗｓａｎｄＣｏａｌＣｏｍｂｕｓｔｉｏｎｉｎＮｅｗＧｅｎｅｒａｔｉｏｎＳｐｏｕｔｉｎｇ－ＣｙｃｌｏｎｅＣｏｍｂｕｓｔｏｒＤ．Ｘ．Ｗａｎｇ；Ｚ．Ｈ．Ｍａ；Ｘ．Ｌ．Ｗａｎｇ；Ｌ．Ｘ．Ｚ...     

Experimental and Numerical Investigation of Enhancement of Heat and Mass Transfer in Adsorbent Beds

ＥｘｐｅｒｉｍｅｎｔａｌａｎｄＮｕｍｅｒｉｃａｌＩｎｖｅｓｔｉｇａｔｉｏｎｏｆＥｎｈａｎｃｅｍｅｎｔｏｆＨｅａｔａｎｄＭａｓｓＴｒａｎｓｆｅｒｉｎＡｄｓｏｒｂｅｎｔＢｅｄｓＬｉｕＺｈｅｎｙａｎ；ＦｕＺｈｕｍａｎ；ＧｅＸｉｎｓｈｉ；ＳｕＹｕｅｈｏｎｇ；...     

Experimental Research on Heat Transfer and Pressure Drop of Two Configurations of Pin Finned—Tubes in an In—line Array

ＥｘｐｅｒｉｍｅｎｔａｌＲｅｓｅａｒｃｈｏｎＨｅａｔＴｒａｎｓｆｅｒａｎｄＰｒｅｓｓｕｒｅＤｒｏｐｏｆＴｗｏＣｏｎｆｉｇｕｒａｔｉｏｎｓｏｆＰｉｎＦｉｎｎｅｄ－ＴｕｂｅｓｉｎＩｎ－ｌｉｎｅＡｒｒａｙＳｈｏｕＧｕａｎｇＹａｏ；ＤｅＳｈｕＺｈｕ（Ｄｅｐａ...     

Hydrodynamic and Heat Transfer Characteristics of Magnetofluidized Beds

ＨｙｄｒｏｄｙｎａｍｉｃａｎｄＨｅａｔＴｒａｎｓｆｅｒＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆＭａｇｎｅｔｏｆｌｕｉｄｉｚｅｄＢｅｄｓＳ．Ｃ．Ｓａｘｅｎａ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ，ＴｈｅＵｎｉｖｅｒｓｉｔｙｏｆＩｌｌ...     

Two－Phase Critical Discharge of Initially Saturated or Subcooled Water Flowing in Sharp－Edged Tubes at High Pressure

Ｔｗｏ－ＰｈａｓｅＣｒｉｔｉｃａｌＤｉｓｃｈａｒｇｅｏｆＩｎｉｔｉａｌｌｙＳａｔｕｒａｔｅｄｏｒＳｕｂｃｏｏｌｅｄＷａｔｅｒＦｌｏｗｉｎｇｉｎＳｈａｒｐ－ＥｄｇｅｄＴｕｂｅｓａｔＨｉｇｈＰｒｅｓｓｕｒｅＸｕＪｉｎｌｉａｎｇ（ＩｎｓｔｉｔｕｅｏｆＮｕｃ...     

Study of heat transfer enhancement in a nanofluid-cooled miniature heat sink

This paper reports numerical solution for thermally developing temperature profile and analytical solution for fully developed velocity profile in a miniature plate fin heat sink with SiO₂–water nanofluid as coolant. The flow regime is laminar and Reynolds number varies between 0 and 800. The heat sink is modeled using porous medium approach. Modified Darcy equation for fluid flow and the two-equation model for heat transfer between the solid and fluid phases are employed to predict the local heat transfer coefficient in heat sink. Results show that the nanofluid-cooled heat sink outperforms the water-cooled one, having a considerable higher heat transfer coefficient. The effects of channel aspect ratio and porosity on heat transfer coefficient of the heat sink are studied in detail. Based on the results of our analysis, it is found that an increase in the aspect ratio or the porosity of the plate fin heat sink enhances the heat transfer coefficient.     

Numerical study of local heat transfer coefficient and fin efficiency of wavy fin-and-tube heat exchangers

Three-dimensional numerical simulations were performed for laminar flow of wavy fin-and-tube heat exchangers by using body-fitted coordinates (BFC) method with fin efficiency effect accounted. The prediction results of average Nusselt number, friction factor and fin efficiency were compared with the related experimental correlations [R.C. Xin, H.Z. Li, H.J. Kang, W. Li, W.Q. Tao, An experimental investigation on heat transfer and pressure drop characteristics of triangular wavy fin-and-tube heat exchanger surfaces, J. Xi'an Jiaotong Univ. 28 (2) (1994) 77–83] and Schmidt approximation [T.E. Schmidt, Heat transfer calculations for extended surfaces, Refrigerating Engineering (April 1949) 351–357]. For Reynolds numbers based on the tube outside diameter ranging from 500 to 4000, the mean deviation is 3.3% for Nusselt number, 1.9% for friction factor and 3.6% for fin efficiency. The distributions of local Nusselt number and fin efficiency on fin surface were studied at wavy angle equal to 0° (plain plate fin), 10° and 20° respectively. The local Nusselt number decreases along the air flow direction, but fin efficiency increases in general. The wavy angle can greatly affect the distributions of local Nusselt number and fin efficiency, and make the distributions present fluctuation along the flow direction. The result also shows that the fin efficiency at the inlet region of wavy fin is larger than that of plain plate fin at the same region. With the increase of Reynolds number, the effects of wavy angle on the distributions of local Nusselt number and fin efficiency are more and more significant.     

CFD Analysis of Steady Laminar Natural Convection Heat Transfer from a Pin Finned Isothermal Vertical Plate

Heat transfer behavior with both the conductive and nonconductive fins have been analyzed by examining variations of the local and average Nusselt numbers in two‐dimensional flow. The main objective of this study is to quantify and compare the natural convection heat transfer enhancement of fin array with different fin aspect ratio and at different angles of inclination. It is found that significant heat transfer augmentation is obtained for both conductive and nonconductive fins. For conductive fins 20% higher augmentation factor is obtained when the fin aspect ratio is 6, angle of inclination is 60° and the pitch‐to‐length ratio is 0.2. For nonconductive fins, 10% higher augmentation factor is obtained when fin aspect ratio is 8, angle of inclination is 45° and pitch‐to‐length ratio at 0.5. A general correlation has been developed to predict the average Nusselt number and heat transfer augmentation factor for conductive and nonconductive fin arrays as a function of different fin configurations.     

Heat transfer enhancement by using a rectangular wing vortex generator on the triangular shaped fins of a plate‐fin heat exchanger

The present numerical analysis pertains to the heat transfer enhancement in a plate‐fin heat exchanger employing triangular shaped fins with a rectangular wing vortex generator on its slant surfaces. The study has been carried out for three different angles of attack of the wing, i.e., 15°, 20° and 26°. The aspect ratio of the wing is not varied with its angle of attack. The flow considered herein is laminar, incompressible, and viscous with the Reynolds number not exceeding 200. The pressure and the velocity components are obtained by solving the continuity and the Navier– Stokes equations by the Marker and Cell method. The present analysis reveals that the use of a rectangular wing vortex generator at an attack angle of 26° results in about a 35% increase in the combined spanwise average Nusselt number as compared to the plate‐triangular fin heat exchanger without any vortex generator. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20285     

Experimental study of heat transfer coefficient with rectangular baffle fin of solar air heater

This paper presents an experimental analysis of a single pass solar air collector with, and without using baffle fin. The heat transfer coefficient between the absorber plate and air can be considerably increased by using artificial roughness on the bottom plate and under the absorber plate of a solar air heater duct. An experimental study has been conducted to investigate the effect of roughness and operating parameters on heat transfer. The investigation has covered the range of Reynolds number Re from 1259 to 2517 depending on types of the configuration of the solar collectors. Based on the experimental data, values of Nusselt number Nu have been determined for different values of configurations and operating parameters. To determine the enhancement in heat transfer and increment in thermal efficiency, the values of Nusselt have been compared with those of smooth duct under similar flow conditions.     

Battery module thermal management based on liquid cold plate with heat transfer enhanced fin

Battery, as the main energy storage element, directly affects the performance of electric vehicle. Battery thermal management research is required as the battery performance influenced by temperature obviously. This article selects liquid cold plate with different heat transfer enhanced fins as the research object. The angle and length of fins are chosen as the variables. Computational fluid dynamics (CFD) methods and experiments are used in this research. The fin angle of 15°, 30°, and 45° and fin length of 8, 10, 12 mm are selected to compose enhanced fins. The results indicate that heat transfer fins inside liquid cold plate can significantly decrease the highest temperature of battery module and temperature difference among cells. Otherwise, different fin angle and fin length can achieve different heat dissipation performance, which is not positive correlation. Then the design reference of heat transfer enhanced fin in liquid cold plate is offered.     

翅片间距对平直翅片管换热器传热与阻力特性影响试验研究

为了获得翅片间距Pf对平直翅片管换热器的传热与阻力特性的影响规律,根据相似模化原理对3种不同Pf的平直翅片管换热器进行了试验研究。结果表明:雷诺数Rea在4 000~8 000范围内,努赛尔数Nua数随Rea的增大而增加,欧拉数Eua随Rea的增大而降低;同一Rea下,Nua随Pf减小而增加,但增加不明显,Eua随Pf增大而降低;同一Rea下,Pf越大,综合流动传热性能越好,但实际换热面积会减小,需综合考虑。研究成果可为汽轮发电机平直翅片管换热器的结构和性能优化提供依据。     

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

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

电机冷却用翅管换热器传热和阻力特性研究

研究了一种电机冷却用新型翅片开孔结构换热器的性能,对三种结构的翅片管换热器进行了换热和阻力性能测试,新型翅片换热器结构为翅片间距2.1 mm且翅片上具有开孔结构,对照组换热器分别为翅片间距2.1 mm无开孔换热器和翅片间距2.3 mm无开孔换热器。试验结果表明,相同Re数下,该种具有开孔结构换热器在所有换热器中换热性能最好,较2.1 mm无孔提升38%～39%,但同时压降损失也最大,较2.1 mm无孔提升41.9%～42.9%。采用j/f评价综合性能,结果显示,Re>6700时,新型翅片换热器性能优于同翅片间距无开孔换热器。文章还对这三种结构翅片管换热器进行了传热和阻力关联式拟合,可为相关理论研究和工程选用提供参考。     

Numerical validation of natural convection heat transfer with horizontal rectangular fin array using straight knurling patterns on fins—correlation for Nusselt number

Natural convection heat transfer from horizontal rectangular fin array with various knurling patterns has been studied experimentally by the present authors to investigate the effect of knurl‐produced surface roughness of fin on the heat transfer rate. The parameters like knurling height from base, knurling depth, fin spacing, and supply wattage were considered for parametric study. In the present paper, numerical method (CFD) is used to simulate natural convection phenomena with knurled fins and results are validated with the experimental data available from literature. The numerical results show similar trends compared with experimental data and one can use this method to study various fin configurations for knurling patterns. The flow patterns from experiments and numerical method are compared for different supply wattages and fin spacing to back up the conclusion. It is also observed that the variation in nondimensional roughness depth and spacing (D _kn/H and S/H) have more effect on Nusselt number than roughness height parameter (H _kn/H). Further, the method is extended to study numerically large number of fin configurations with knurling patterns to gather sufficient data for Nusselt number with respect to fin geometric parameters as above and establish correlation for heat transfer coefficient for such type of fins.