广义神经网络在织物热传递性能预测中的应用

在分析织物热传递性能与相关影响因素之间关系的基础上,建立了织物热传递性能预测的广义神经网络模型(GRNN).并与传统的BP网络模型仿真结果进行了比较,结果表明:GRNN网络设计简单,学习收敛快,在解决小样本问题的学习中,具有更好的的预测和泛化能力,验证了GRNN网络预测的优越性和有效性.

纺织品热传递性的应用及检测标准探讨

随着人们对纺织品热湿舒适性要求的提高,纺织品热传递性逐渐作为保暖抗寒面料、凉感面料、吸湿发热面料等功能性面料的重要性能参数而受到重视。本文分类阐述了热传递性在功能性纺织品研发中的应用,并就不同种类功能纺织品热传递性检测标准和方法进行了对比分析,旨在为纺织品热传递性的研究和评价提供一定参考。

一种新型的织物热湿传递性能测试仪

研制一种新型的织物热湿传递性能测试仪，并在模似人体出汗的条件下，对组合双层织物与模拟皮肤之间的水汽分压、温度和热流的动态变化进行了测试根据水汽分压、温度和热流曲线，计算出热湿传递系数。

大豆蛋白纤维织物湿热舒适性能分析

对大豆蛋白纤维织物的湿热舒适性能进行了试验研究。介绍了大豆蛋白纤维织物湿热舒适性能指标的测试方法、试验仪器及使用标准 ,详细对比分析了织物的保暖性、冷暖感、透气性及湿热传递性指标 。

防水透气功能纺织品技术及其性能要求的分析

分析了织物防水透气机理及湿热传递性能的影响因素;总结了织物实现防水透气的条件和技术方法;论述了湿热传递性与服用舒适性之间的关系,包括保暖性与舒适性,透气性与舒适性之间的关系。

拒水整理对纯棉织物舒适性的影响

测试并分析了3种不同类型的拒水整理剂(Repellent ZN、HC305VP、Grafted Polyacrylate)对纯棉织物的拒水性、柔软性、抗静电性、透气性、透湿性和热传递性等与其舒适性密切相关的性能指标的影响。结果表明,纯棉织物经拒水整理后,原有的各项性能会产生一定的变化。因此拒水整理时需要针对各方面影响因素进行综合分析,确保在织物原有的优良性能不受明显影响甚至改善的基础上达到理想的拒水效果。

经编间隔织物的舒适性能

通过对经编间隔织物和海绵材料透气性能和热湿传递性能的测试研究间隔织物的舒适性能,详细介绍性能测试过程中的试样选择、测试仪器、测试方法、测试条件等。对比试验结果表明,间隔织物的透气性能优于同等厚度的海绵,而其热阻和湿阻均小于海绵,因此间隔织物是一种透气、透湿、导热较好的材料,是制作休闲服装、内衣面料、坐椅床垫的理想材料。

出汗假脚的研究与应用

出汗假人是将人体出汗过程从复杂的个体差异中抽象出来,制成模拟出汗人体,用科学的工程技术方法,模拟真人的出汗过程,并用精确的物理状态方程计算、测量和评价服装的热湿传递性能.

基于参数辨识的半导体激光器温度自动控制

以保证半导体激光器的安全稳定运行为目标,提出基于参数辨识的半导体激光器温度自动控制方法。通过分析温度对半导体激光器的影响及温度控制原理,设计半导体激光器温度控制系统,在该系统支持下利用半导体激光器温度控制数学模型描述其一阶纯滞后性,根据半导体激光器的热传递性获取半导体激光器的离散运行数据,建立半导体激光器参数辨识模型,确定其最佳预估量,并将其输入到PID中,利用遗传算法对PID参数进行实时调节,以满足半导体激光器温度变化量对PID参数的自整定需求,实现半导体激光器温度自动控制的目标。实验结果表明,该方法可实现半导体激光器温度的快速控制,能够快速达到预期温度,温度波动范围在0.02℃以内,温度控制后的半导体激光器发光光谱波形平稳,能够保证半导体激光器的安全稳定运行。

冰爽针织面料的冰爽性研究

选取基本原料为锦纶或黏胶,组织结构为纬平针、罗纹和提花的5种冰爽针织面料,分别测试面料的热传递性能和透湿透气性等指标,并采用主成分分析法综合分析冰爽面料的冰爽性能。同时分析热阻、透湿指数、湿阻、透气率等物理指标与冰爽性的关系。结果表明,织物的热阻越小,透湿指数越低,湿阻越小,透气率越高,其冰爽性就越好,该研究为开发冰爽针织面料提供一定的理论依据。

纳米苎麻远红外针织物功能性及服用性能研究

通过对纳米苎麻针织物的远红外发射率、红外照射温升、透气性、湿热传递性、保温性、冷暖感、悬垂性等指标进行测试,并对各指标及其相互间关系进行分析,为苎麻类功能性针织品的开发提供科学依据。

Water and heat transport in hilly red soil of southern China:II. Modeling and simulation

Simulation models of heat and water transport have not been rigorously tested for the red soils of southern China. Based on the theory of nonisothermal water-heat coupled transfer, a simulation model, programmed in Visual Basic 6.0, was developed to predict the coupled transfer of water and heat in hilly red soil. A series of soil column experiments for soil water and heat transfer, including soil columns with closed and evaporating top ends, were used to test the simulation model. Results showed that in the closed columns, the temporal and spatial distribution of moisture and heat could be very well predicted by the model, while in the evaporating columns, the simulated soil water contents were somewhat different from the observed ones. In the heat flow equation by Taylor and Lary (1964), the effect of soil water evaporation on the heat flow is not involved, which may be the main reason for the differences between simulated and observed results. The predicted temperatures were not in agreement with the observed one with thermal conductivities calculated by de Vries and Wierenga equations, so that it is suggested that Kh, soil heat conductivity, be multiplied by 8.0 for the first 6.5 h and by 1.2 later on. Sensitivity analysis of soil water and heat coefficients showed that the saturated hydraulic conductivity, KS, and the water diffusivity, D(θ), had great effects on soil water transport; the variation of soil porosity led to the difference of soil thermal properties, and accordingly changed temperature redistribution, which would affect water redistribution.

Convective Heat Transfer Enhancement of a Rectangular Flat Plate by an Impinging Jet in Cross Flow

Experiments were carried out to study the heat transfer performance of an impinging jet in a cross flow.Several parameters including the jet-to-cross-flow mass ratio(X=2%-8%), the Reynolds number(Red=1434-5735)and the jet diameter(d=2-4 mm) were explored. The heat transfer enhancement factor was found to increase with the jet-to-cross-flow mass ratio and the Reynolds number, but decrease with the jet diameter when other parameters maintain fixed. The presence of a cross flow was observed to degrade the heat transfer performance in respect to the effect of impinging jet to the target surface only. In addition, an impinging jet was confirmed to be capable of enhancing the heat transfer process in considerable amplitude even though the jet was not designed to impinge on the target surface.

Finite element analysis for radiative heat transfer in multidimensional participating media

A finite element model is developed to simulate the radiative transfer in 2D and 3D complex-geome-tric enclosure filled with absorbing and scattering media. This model is based on the discrete ordinates method and finite element theory. The finite element formulations and detailed steps of numerical calculation are given. The discrepancy of the results produced by different space and solid angle discretization is also investigated and compared. The effect of the six-node quadric element on the accuracy is analyzed by a 2D rectangular enclosure. These results indicate that the present model can simulate radiative transfer in multidimensional complex-geometric enclosure with participating media effectively and accurately.

Elasticity solution of laminated beams with temperature-dependent material properties under a combination of uniform thermo-load and mechanical loads

An exact solution for simply-supported laminated beams with material properties variable with temperature under a combination of uniform thermo-load and mechanical loads was investigated,based on the two-dimensional(2-D)thermo-elasticity theory.Firstly,the beam was divided into a series of layers with uniform material properties along the interfaces of the beam.The uniform thermo-load acted on each layer was transformed into a combination of the normal surface forces acted at the two ends and the transverse thermo-load.Secondly,the state space method was employed to obtain the general solutions of displacements and stresses in an arbitrary layer.Thirdly,based on the interfacial continuity conditions between adjacent layers,the relations of displacement and stress components between the top and bottom layers of the beam were recursively derived by use of the transfer-matrix method.The unknowns in the solutions can be solved by the mechanical loads acted on the top and bottom surfaces.The convergence of the present solutions was checked.The comparative study of the present solutions with the Timoshenko’s solutions and the finite element(FE)solutions was carried out.The effects of material properties variable with temperature on the thermo-elastic behavior of laminated beams were discussed in detail.

Influence of Some Factors on the Efficiency of Heat Storage Accumulator in the Bed of a Stone in a Plastic Tunnel

The study was conducted in a plastic tunnel in which the heat storage system was installed in the stone accumulator. The system consists of a suction pipe warm air fan and perforated pipes placed in the stone＇s accumulator. The accumulator used a bed of stone （porphyry-type stones of dimension in the range 37 mm to 65 ram）. In the accumulator, there are four sections with dimensions of 1.7 m × 11 m, each of which contains a perforated pipe for hot air distribution within the battery, and separate conduits for supplying air to the interior of the tunnel. The paper presents the results of analysis related to performance （as a result of heat and mass transfer） in cycles of charging and discharging of the accumulator.

Testing Thermal Properties of Cooling Device with Heat Pipes to Improve His Heat Transfer Ability

This paper deals about testing thermal properties of the cooling device with heat pipes at inclination position, in consequence of using the natural convection to improve heat transfer properties. Head point testing of cooling device is monitoring temperature on the aluminium block of energy converter, heat pipes and ribs under temperature condition 30 ℃ in thermostatic chamber. Testing of the device was performed at tilt angles positions 0, 10 and 20° from the vertical level. The heat flux loaded to energy converter was 450 W. The next goal of the paper is to research on influence working position of the wick heat pipe on their thermal performance. In this research heat pipes were made with capillary structure sintered from copper powder granularity 100, 63 and 50 μm filled with water and ethanol. Next heat pipe thermal performance was performed by measuring heat source and working positions. Knowledge of these two research goals can bring potential improvements in purpose of cooling device for effective heat sink from high power electronic components.

Finite element formulation of axisymmetric heat transfer problem for orthotropic materials

By using Galerkin’s method, the finite element formulation is made for axisymmtric heat transfer problems for anisotropic materials from the heat transfer differential equations expressed in terms of heat fluid density. Results of an example show that the heat transfer anisotropy has an important effect on temperature field.

The synthesis of micro-sized silicon carbide whiskers and the application for heat transfer enhancement

This paper presents a simple and cost-effective method for the production of micro-sized silicon carbide whiskers at high yield and the effect on heat transfer enhancement for the whisker laden fluids. For SiC whisker synthesis, the starting powder mix- ture is obtained by milling short carbon fibers with the white ashes of rice hulls. Calcina：ion in argon, together with the subse- quent purification process, results in a high yield of SiC whiskers, which possess a diameter of 200-400 nm and a length of several tens of microns. The formation of the whiskers is discussed according to VS growth mechanism. Convective heat transfer performance in small channel tubes is then studied for fluid systems mixed with those micro-sized SiC whiskers at different concentrations. The heat transfer coefficient of SiC containing fluid can be significantly improved in comparison to the base fluid.

Experimental Study on Condensation Heat Transfer Characteristics of R410A in Short Vertical Tubes

An experimental study on condensation heat transfer of R410 A in short vertical tubes(8.02 mm ID and 10.7mm ID) was presented. Experiments were performed in eight short copper tubes length varied from 300 mm to 600 mm at mass fluxes range of 58–246 kg m-2s-1 and saturation temperature of 38℃. Effects of mass flux, tube length on condensation heat transfer coefficient were investigated. The distribution of temperature, thickness of condensate film and local condensation heat transfer coefficient along the tube were also analyzed.. It is indicated that the entrance effect played an important role in condensation heat transfer of vertical tube, and the influence of entrance effect on average condensation heat transfer coefficients will weaken with the length of tube in the experimental condensation. The experimental results were compared with four well known correlations available in literatures, and the Chen correlation shows good agreement with the experimental data but with ±40% deviation. A new modified condensation heat transfer correlation with 12.7% mean deviation was developed to predict the condensation heat transfer coefficients in short vertical tube based on the experimental data.