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101.
自行设计了一台单填料函滑动管板式换热器代替进口设备,运转良好。本文着重介绍该设备密封结构的设计。 相似文献
102.
管壳式换热器管束振动分析及防振措施 总被引:7,自引:0,他引:7
针对管壳式换热器常见的振动破坏形式 ,全面分析了管束振动的机理 ,并提出了相应的抗振措施 相似文献
103.
A heating process for obtaining free-standing carbon nanotube emitters is presented with the aim of improving field-emission properties from the screen-printed multiwalled carbon nanotube (MWCNT) films. Using an atmosphere with an optimum combination of nitrogen and air for heat treatment of CNT films, the CNT emitters can be made to protrude from the surface. This allows for a high emission current and the formation of very uniform emission sites without special surface treatment. The morphological change of the CNT film by this technique has eliminated additional processing steps, such as surface treatment which may result in secondary contamination and damage to the film. Despite its simplicity the process provides a high reproducibility in emission current density which makes the films suitable for practical applications. 相似文献
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The evaporative heat transfer of the non-boiling annular two-phase flow of air-water in a small vertical tube with uniform wall heat flux was studied both theoretically and experimentally. A simplified two-phase flow boundary layer model was used to calculate the thickness of the water film attached to the wall, and from the liquid film thickness the evaporative heat transfer coefficients of the annular two-phase flow were obtained. Theoretical equations and semi-theoretical equations were proposed for predicting the evaporative heat transfer of the annular two-phase flow of air-water in a small vertical tube. The semi-theoretical prediction agrees well with the experimental data. The mechanism of the heat transfer enhancement is the evaporation of the thin liquid film attached on the wall. 相似文献
107.
Robert R LuiseBryan B Sauer 《Polymer》2003,44(4):1095-1101
Wholly aromatic thermotropic main chain liquid crystalline copolymers (LCPs) with varying glass transitions (Tg) were tested for wear resistance, particularly under high friction conditions, where surface temperatures can rise. Dynamic mechanical spectroscopy and DSC were used to characterize molecular relaxations. Three copolyester LCPs which all contain a substantial fraction of main chain 1,4-phenyl groups were chosen for this study. These included semi-crystalline Vectra® A900, a semi-crystalline LCP containing phenyl hydroquinone (phHQ-LCP), and a low crystallinity LCP containing t-butyl substituted hydroquinone (t-butylLCP). These have glass transitions of 100, 160 and 175 °C, respectively, and heat deflection temperatures (HDTs) of 170, 260 and 174 °C, respectively. HDT is dependent in part on crystallinity. The wear performance was found to depend mainly on Tg and not HDT, suggesting a microscopic failure mechanism related to the amorphous phase. This is supported by the relatively poor elevated temperature wear performance of Vectra® compared to the higher Tg LCPs. Shear strength measurements on the neat LCP resins did not correlate with wear properties of the blends, most likely because the measurements were made at room temperature and not elevated temperatures. 相似文献
108.
Rama Subba Reddy Gorla Jorge E. Gatica Bahman Ghorashi Pijarn Ineure Larry W. Byrd 《Chemical Engineering Communications》2004,191(5):718-731
Heat transfer enhancement in an evaporating thin liquid film utilizing a electric field under isothermal interfacial condition is presented. A new mathematical model subjected to van der Waals attractive forces, capillary pressure, and an electric field is developed to describe the heat transfer enhancement in the evaporating thin liquid film. The effect of the electrostatic field on the curvature of the thin film, evaporative flux, pressure gradient distribution, heat flux, and heat transfer coefficient in the thin film is presented. The results show that applying an electric field can enhance heat transfer in a thin liquid film significantly. In addition, utilizing electric fields on the evaporating film will be a way to expand the extended meniscus region to attain high heat transfer coefficients and high rates of heat flux. 相似文献
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The inverse problem approach by conjugate gradient with adjoint equations is adapted to the context of a non-isothermal bioprocess, controlled by internal heat generation from microbial oxidation, as could be found in a composting reactor for instance, to determine the heat source from internal temperature measurements. The volumetric heat source is assumed proportional to the rate of consumption of a substrate by a biomass, as described by a Monod model. Computations are performed for Rayleigh numbers equal to 0.25 and 25, for a representative biochemical reaction under typical boundary conditions, for constant and temperature-dependent model parameters. The influence of noisy input data is also considered. It is found that good solutions can be obtained when heat release and diffusion occur over very different time scales. The variation of the model parameters with temperature must be taken into account, but single sensor solutions are possible at relatively small Rayleigh numbers when convection is present. 相似文献