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伴随有水蒸气凝结的烟气对流换热的实验研究 总被引:13,自引:0,他引:13
本文通过实验研究了冷凝式燃气热水器中烟气伴随有水蒸气凝结的受迫对流换热过程。着重介绍实验系统、测试方法和对塔板式换热器和肋片板式换热器的实验研究结果。实验表明,有水蒸气凝结时的烟气对流换热系数远大于无凝结时的换热系数,可提高数倍。在冷凝式换热器中,塔板式换热器的换热系数大于肋片板式换热器。 相似文献
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对一种斜翅型外翅片带内螺纹的冷凝强化换热管进行传热性能的实验研究。管外冷凝换热的制冷剂为R134a,管内对流换热的介质为水。分别在定热流密度与定水流速的条件下进行一系列工况的实验,得到相应的实验数据。在定热流密度条件下,利用Wilson图解法得到管内的换热系数数据及相应的计算关联式。在定水流速的条件下,利用分离方法得到管外冷凝换热系数数据及相应的计算关联式。将强化管换热系数数据与光管换热系数的理论计算值进行了比较,结果表明:冷凝强化换热管管内对流换热的强化倍率为2.4,管外凝结换热系数随壁面过冷度的增加而增大,管外凝结换热的强化倍率为:1.78~3.92。 相似文献
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We present a study of the one-dimensional flame structure of combusting solid propellants that focuses on the effects of thermal expansion and variable thermal properties in the condensed phase. A nonlinear heat equation is derived for a burning thermo-elastic solid with temperature-dependent specific heat, thermal expansion, and thermal conductivity coefficients. It is solved for different modelling approximations both analytically and numerically. Explicit expressions are derived for the regression rate of the propellant surface as functions of surface temperature and thermal expansion parameters. A simple one-step reaction model of the gas phase is used to study the full structure of propellent flame and illuminate the influence of temperature-dependent material properties on the regression rate, surface temperature, and flame stand-off distance. Results are displayed for HMX and compared with experimental data and numerical simulation with fair success. 相似文献
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Efficient and economical utilization of industrial waste heat would result in reduced energy use and thereby contribute to reduction of greenhouse gas emissions to the atmosphere. Two-phase thermosyphon technology has demonstrated the potential capability for waste heat recovery, but it has not been yet utilized in large-scale industrial applications. As a part of an industrial project, various types of thermosyphon heat pipes have been designed and tested for extraction of waste heat and process control in aluminum industry. This article presents the heat and mass transfer model, developed to provide a fast and accurate simulation tool for industrial application of thermosyphon heat pipe technology for waste heat utilization. The mathematical model considers the energy, momentum, and mass transfer equations, in their one-dimensional form, to predict output parameters of the thermosyphon and enable parametric and sensitivity analysis. The mathematical model structure is set up in a way that the least numerical cost and time is spent while the model accuracy is kept at acceptable level for the defined application. To provide experimental data for validation of the simulation model, the proposed thermosyphon was tested experimentally using a test set-up instrumented for this purpose. The simulation results are found to be in good agreement with the experimental data. The developed model and code are viable to be used as a simple and fast tool for modeling, design, and optimization of the thermosyphon as an element in a heat recovery module. 相似文献
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In this study, we present empirical analysis of statistical properties of mating networks in genetic algorithms (GAs). Under the framework of GAs, we study a class of interaction network model—information flux network (IFN), which describes the information flow among generations during evolution process. The IFNs are found to be scale-free when the selection operator uses a preferential strategy rather than a random. The topology structure of IFN is remarkably affected by operations used in genetic algorithms. The experimental results suggest that the scaling exponent of the power-law degree distribution is shown to decrease when crossover rate increases, but increase when mutation rate increases, and the reason may be that high crossover rate leads to more edges that are shared between nodes and high mutation rate leads to many individuals in a generation possessing low fitness. The magnitude of the out-degree exponent is always more than the in-degree exponent for the systems tested. These results may provide a new viewpoint with which to view GAs and guide the dissemination process of genetic information throughout a population. 相似文献
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The primary mission of ocean color remote sensing is to provide accurate marine bio-optical properties from satellite data. We propose a new algorithm that uses symbolic regression to estimate chlorophyll a (chl a) concentrations from remote sensing reflectance. We compared the accuracy and computational efficiency of the new algorithm to that of the explicit empirical algorithms (OC4v4 and OC4v6), and implicit algorithms based on neural networks or support vector machines (SVM). Results show that the accuracy of the symbolic regression algorithm is higher than that of the OC4 algorithms and comparable to that of implicit algorithms. The improvement is particularly important for high biomass areas (chl a?≧?3 mg?m-3) that are often found in optically complex waters. The computational efficiency of the explicit algorithm developed by symbolic regression is comparable to that of the two versions of OC4 algorithms and better than that of implicit algorithms based on SVM. With its good precision and fast processing, the symbolic regression algorithm is a powerful tool for remote sensing of chl a that could be used advantageously in the reprocessing of large datasets. 相似文献
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The asymptotic behavior of the operator exponent related to the Cauchy problem for a parabolic equation with periodic coefficients
is studied either under the reduction of the periodicity cell or for large times. Estimates for the closeness of the operator
exponentials (the original and the limit) with respect to the L
2-operator norm and the related H
1-estimates are obtained under minimal assumptions concerning the smoothness of the heat matrix and of the initial data.
Financially supported by RFBR under grant no. 05-01-00621. 相似文献
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S. T. Surzhikov 《Doklady Physics》2018,63(2):76-81
The problem of the radiation gas dynamics of super-orbital entry into dense layers of the Earth’s atmosphere of the command module of Apollo 4 is solved numerically in the two-dimensional formulation of the flow around an aerodynamic frontal shield at the velocity V∞= 10.7 km/s in the altitude range H = 91.5?76.2 km. The density distributions of the spectral and integral radiation heat fluxes on the surface flowed around are obtained. The considerable role of atomic spectral lines in the radiation heating of the surface is shown. The results of calculations are compared with the flight experimental data and the calculated data of other authors. 相似文献
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Computation of leading edge film cooling from a CONSOLE geometry (CONverging Slot hOLE) 总被引:1,自引:0,他引:1
The aim of this study is to investigate the effect of mass flow rate on film cooling effectiveness and heat transfer over a gas turbine rotor blade with three staggered rows of shower-head holes which are inclined at 30° to the spanwise direction, and are normal to the streamwise direction on the blade. To improve film cooling effectiveness, the standard cylindrical holes, located on the leading edge region, are replaced with the converging slot holes (console). The ANSYS CFX has been used for this computational simulation. The turbulence is approximated by a k-ε model. Detailed film effectiveness distributions are presented for different mass flow rate. The numerical results are compared with experimental data. 相似文献
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A symbolic analysis of observed time series requires a discrete partition of a continuous state space containing the dynamics. A particular kind of partition, called "generating," preserves all deterministic dynamical information in the symbolic representation, but such partitions are not obvious beyond one dimension. Existing methods to find them require significant knowledge of the dynamical evolution operator. We introduce a statistic and algorithm to refine empirical partitions for symbolic state reconstruction. This method optimizes an essential property of a generating partition, avoiding topological degeneracies, by minimizing the number of "symbolic false nearest neighbors." It requires only the observed time series and is sensible even in the presence of noise when no truly generating partition is possible. 相似文献
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M. V. Bayaskhalanov M. N. Vlasov A. S. Korsun I. G. Merinov 《Bulletin of the Lebedev Physics Institute》2017,44(2):50-52
The results of numerical simulation of the sodium coolant flow in the fuel assembly with partial blocking of its cross section are presented. A comparison of the results obtained with experimental data confirmed the operability of the APMod module intended for simulating heat exchange processes in cores and heat exchange equipment of promising nuclear reactors. 相似文献