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

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Journal of Thermal Science 1996年第3期5卷 175-183页

作者： J.G. wei w.q. tao (School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China) School of Energy and Power Engineering Xi’an Jiaotong University Xi’san China

A numerical study of natural convection heat transfer in an inclined cylindrical annulus has been conducted. The inner cylinder of the annulus is maintained at uniform heat flux and the outer cylinder at constant temperature. The two end walls are assumed to be insulated. A numerical code has been developed to calculate the steady state three-dimensional natural convection in an inclined cylindrical annulus, and the research emphasis is placed on the influences of inclination angle or and modified Rayleigh number Ra on the natural convection heat transfer in the annulus. Computations were carried out in the ranges of 0°α 90*, 2.5×105 Ra* and Pr=0.7 with fixed aspect ratio of H=28.97 and radius ratio of K= 3.33. The numerical results are compared with the experimental correlations from the literature and the inclination angle effect on heat transfer is found to be insignificant. Detailed results of heat transfer rate, temperature, and velocity fields are presented for the case of or α=45° and discussion is also made concerning the comparison between the numerical and experimental results for the specific case of α=90°.

关键词： enclosure flows natural convection numerical methods

Pressure　Loss　Through　Sharp　180　deg　Turn　in　a　Relatively　Short　Two－Pass　Smooth　and　Rib－Roughened　Channel

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Journal of Thermal Science 1995年第2期4卷 109-116页

作者： C.Y. Zhao w.q. tao(School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China) School of Energy and Power Engineering Xi’an Jiaotong University Xi’an China

The local pressure distributions and resistance coefficients (f1 and f2) through the sharp 180 deg turn in a relatively short (L/De = 4) two-pass smooth and rib-roughened channel were investigated for a Reynolds number range of 1.0 × 103 - 9.0 × 103. The rib pitch-to-height ratios (p/e) were 5,10, and 20. The rib height-to-hydraulic diameter ratios (e/De) were 0.025, 0.050 and 0.10, and the rib angles of attack (α) were 90, 45, 60, -45, and -60 deg. Ribs were installed not only in before and after turn regions but also in turn region. The results show that the resistance coefficients remain approximately constant when Reynolds number is more than 3.0×104. The effects of the rib condguration (rib spacing, rib height, and rib orientation) on the inlet straight duct resistance coefficient (f2) were significant, however, their effects on the overall resistance coefficient (f1) were diluted by the sharp-180 turn. For this relatively short channel (L/De=4), the overall resistance coefficient (f1) was greatly affected by the sharp turn. Correlations for the overall resistance (f1) and inlet straight duct resistance coefficient (f2) are presented.

关键词： resistance cofficient rib-roughened channel.

Experimental　Study　on　Heat　Transfer　and　Pressure　Drop　Characteristics　of　Four　Types　of　Plate　Fin－and－TUbe　Heat　Exchanger　Surfaces

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Journal of Thermal Science 1994年第1期3卷 34-42页

作者： H.J. Kang w. Li H.Z. Li R.C. Xin w.q. tao(School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China) School of Energy and Power Engineering Xi’an Jiaotong University Xi’an China

In this paper, air side heat transfer and pressure drop characteristics of twelve three-row plate finandtube heat exchanger cores of four types of fin configurations have been experimentally *** heat transfer and friction factor correlations for'the twelve cores are provided in a wide range ofReynolds number. It is found that in the range of Reynolds number tested, the Nusselt number of theslotted fin surface is the largest and that of the plain plate fin is the lowest while the Nusselt numbersof two types of wavy fins are somewhere in between.

关键词： plate fin-and-tube exchanger heat transfer and pressure drop characteristics plain plate fin wavy plate fin slotted plate fin

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

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Journal of Thermal Science 1995年第3期4卷 180-184页

作者： M.J. Lin w.q. tao (School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an, Shabby 710049, China)S.S. Lue (Institute of Chemical Engineering, Southern-China University of Science and Technology, Guangzhou,Guangdong, China) School of Energy and Power Engineering Xi’an Jiaotong University Xi’an China Institute of Chemical Engineering Southern-China University of Science and Technology Guangzhou China

The pressure drops of laminar developing and developed flow in Hnnular-sector ducts with small round corner have been investigated experimentally. Numerical simulation has been performed to study the effect of the small round corner on the friction factor in the developed region. It has been found that with the increase in corner radius, the value of fRe decreases. In the range of rc/ro from 0.031 to 0.12,the decrease in fRe varies from 0.048% to 0.1% for the five apex angle computed.

关键词： laminar flow friction factor.

On Identical Problems of Natural Convection in Enclosures and Applications of the Identity Character

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Journal of Thermal Science 1993年第2期2卷 116-125页

作者： Yang, M. tao, w.q. wang, q.w. Lui, S.S. Xi'an Jiaotong Univ Xi'an China

In this paper, a concept of 'identical problems' of natural convection in enclosures is presented. A pair of problems of natural convection in enclosures is said to be identical if they look different in appearance but with appropriate selection of coordinates and appropriate definition of dimensionless variables for each problem, they will have identical geometric configurations and identical dimensionless governing equations and related boundary conditions. The identical characteristics of a pair of problems of natural convection in enclosures with an internal isolated island are demonstrated via dimensionless mathematical formulation and flow visualization results. Numerical computations are performed and the predicted streamlines agree with the flow visualization results. A number of other possible pairs of identical problems are also presented. Applications of the identical character are provided and assumptions under which the identical problems may exist are discussed.

关键词： natural convection enclosure flow identical problems

Effect of lamellarization on the microstructure and mechanical properties of marine 10Ni5CrMoV steel

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International Journal of Minerals,Metallurgy and Materials 2025年第2期32卷 402-413页

作者： tao Zou Yanwu Dong Zhouhua Jiang Shuyang Du Yushuo Li School of Metallurgy Northeastern UniversityShenyang 110819China Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China Key Laboratory for Ecological Metallurgy of Multimetallic Ores(Ministry of Education) Northeastern UniversityShenyang 110819China

Multistage heat treatment involving quenching(q),lamellarizing(L),and tempering(T)is applied to marine 10Ni5CrMoV *** microstructure and mechanical properties were studied by multiscale characterizations,and the kinetics of reverse austenite transformation,strain hardening behavior,and toughening mechanism were further *** lamellarized specimens possess low yield strength but high toughness,especially cryogenic *** leads to the development of film-like reversed austenite at the martensite block and lath boundaries,refining the martensite structure and lowering the equivalent grain *** analysis of austenite reversion based on the JMAK model shows that the isothermal transformation is dominated by the growth of reversed austenite,and the maximum transformation of reversed austenite is reached at the peak temperature(750℃).The strain hardening behavior based on the modified Crussard-Jaoul analysis indicates that the reversed austenite obtained from lamellarization reduces the proportion of martensite,significantly hindering crack propagation via martensitic transformation during the *** a consequence,the qLT specimens exhibit high machinability and low yield *** with the qT specimen,the ductile-brittle transition temperature of the qLT specimens decreases from-116 to-130℃due to the low equivalent grain size and reversed austenite,which increases the cleavage force required for crack propagation and absorbs the energy of external load,*** work provides an idea to improve the cryogenic toughness of marine 10Ni5CrMoV steel and lays a theoretical foundation for its industrial application and comprehensive performance improvement.

关键词： 10Ni5CrMoV steel lamellarizing reversed austenite cryogenic toughness ductile-brittle transition temperature

Forced Convective Heat Transfer and Pressure Drop of Air Flowing in a Rectangle Duct with Cross-Ribs on the Opposite walls

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Journal of Thermal Science 2002年第3期11卷 259-270页

作者： B.Deng T.T.wong w.q.tao School of Power and Energy Xi’an Jiaotong University Xi’an China Department of Mechanical Engineering The Hong Kong Polytechnic University Hong Kong

Experiments were conducted to investigate the forced convective heat transfer and flow friction of turbulent airflow in a rectangular duct with cross-ribs attached at the two principal walls in the Reynolds number range from 5000 to 40000. The effect of the rib cross angle (45° 60° 75° and the height (4 mm, 5 mm) of the cross-ribs on the forced convection and flow friction were tested. Non-dimensional correlations for the duct average Nusselt number and friction factor of cross-ribs duct were developed from the test data. Experiments were also conducted for the corresponding parallel ribs to compare their relative performance. The experimental results show that both of the convective heat transfer coefficient and friction factor were increased with cross-ribs, with 45°cross-ribs being the best. Compared with parallel ribs normal to the flow direction under identical flow rate and identical pumping power constraints, the cross-ribs can enhance heat transfer in the lower Reynolds number region, while

关键词： cross-ribs forced convection heat transfer enhancement.

Experimental Study on Transient Natural Convection in a Cube Enclosure with an Isolated Vertical Cyclically Heated Plate

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Journal of Thermal Science 1999年第1期8卷 51-58页

作者： C. M. Ling q. w. wang w. q. tao H. Ozoe School of Energy and Power Engineering Xi’an Jiaotong University Xi’an China Institute of Advanced Material Study Kyushu University 86 Kasuga Japan

The low frequency cyclical transient natural convection in a cube enclosure with an internal isolated vertical heated plate was investigated experimentally. A computer-aided experimental system was designed to generate the cyclical heating power input and also used for data reduction. The effects of the cyclic heating power input amplitude (from 0 to 8 w) and frequency (from 1/5400 s-1 to 1/600 s-1)as well as the per-cycle time-average power input (from 8 to 24 w) on the transient and time-average Nusselt number were parametrically studied. It was found that for such cyclical transient natural convection with low frequency, the plate heating power input amplitude and frequency have little effects on the time-average Nusselt number as long as the cyclical time-average heating power input remains the same, although the transient Nusselt number may be significantly affected. Therefore, the modified Grashof number based on the plate average heat flux can be used to characterize the time-average heat transfer process. The plate time-average Nusselt number is about 15% less than the infinite-space Nusselt number. The location of the isolated plate in enclosure does not appreciably influence the time-average heat transfer characteristics of the plate.

关键词： natural convection in enclosure isolated plate transient cyclically heating power input.

Two Dimensional Numerical Simulation of Transient Natural Convection in Freezer

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Journal of Thermal Science 1993年第3期2卷 170-179页

作者： C. M. Ling (1) w. q. tao (1) 1. Department of Power Machinery Engineering Xi’an Jiaotong University 710049 Xi’an Shaanxi China

A two dimensional model of the transient natural convection in a freezer is studied numerically by finite volume *** temperatures of the freezer outside surfaces and the evaporator vary in specified manners,which were taken from an experimental *** fluid in the freezer is of the Bousinnesq type and the flow is assumed laminar,The transient heat conduction in the insulating layers and the temperature and velocity fields of the fluid are solved *** radiation heat transfer between the freezer inner surfaces is taken into account by using the additional source term *** distributions of the local Nusselt number along the upper and lower surfaces of the evaporator and their average values in the period of periodically unsteady operation are *** are made between the results with and without consideration of inner surface radiative heat *** is found that the radiative heat transfer between the inner surfaces has a profound effect on the evaporator heat transfer characteristics.

关键词： freezer natural convection flow pattern radiative heat transfer Nusselt number