Estimation of rate of heat release by means of oxygen consumption measurements

Measurement of the rate of oxygen consumption provides a simple, versatile and powerful tool for estimating the rate of heat release in fire experiments and fire tests. The method is based on the generalization that the heats of combustion per unit of oxygen consumed are approximately the same for most fuels commonly encountered in fires. A measurement of the rate of oxygen consumption can then be converted to a measure of rate of heat release. Data on heats of combustion are presented to support this generalization. The applicability of the technique to combustion under fire conditions is examined, possible sources of error in the measurements are discussed, and applications of the method are reviewed. It is concluded that the accuracy of oxygen consumption based rate of heat release measurements should compare favorably with those derived from conventional calorimetric measurements.     

Rate of heat release by oxygen consumption in an open test arrangement

Equipment has been developed for measuring the rate of heat release from building materials in an open test arrangement. The method is based on an oxygen consumption technique. A vertical sample is placed under an open hood in which the combustion gases and a certain amount of air are collected. The decrease in oxygen concentration and the mass flow of the gases are measured in the exhaust duct. The rate of heat release is then calculated. The equipment has been calibrated with good agreement between input and measured effects. The total response time for the system is 10s. The method has been used for testing building materials at radiation intensities up to 5W Cm^?2. It is able to distinguish between different board materials, and the repeatability is good, The paper describes the equipment, including the weighing of a burning sample and the selection of test condition. Smoke and gas analysis can be added when desirable. Some test results with building materials are also presented.     

Experimental and numerical heat transfer in a plate heat exchanger

In the present study a virtual prototype of a four-channel plate heat exchanger with flat plates was developed using computational fluid dynamics (CFD). Parallel and series flow arrangements were tested and experimental results were compared to numerical predictions for heat load obtained from the 3D CFD model and also from a 1D plug-flow model. The CFD model represents channels, plates and conduits of the exchanger and takes into account the unequal flow distribution among channels and the flow maldistribution inside the channel. CFD results are in good agreement with experimental data, especially for the series arrangement.     

Conjugated heat transfer to laminar flow with internal heat source in a parallel plate channel

A steady heat transfer problem was analyzed as a conjugated problem between a fully-established laminar flow and the duct wall, under two kinds of boundary conditions at the outer wall surface. The internal heat generation is described as a linear function of the fluid temperature. The influence of the heat conduction in the wall was found to be important for the case with small wall conductance under a boundary condition of the first kind, and also for the large wall-conductance case under the second condition. Such influence is more significant for the case with an internal heat source.     

Free convective flow over a vertical plate in a doubly stratified medium with electrophoresis, heat source/sink and chemical reaction effects

We analyzed the problem of unsteady, incompressible free convective doubly stratified flow past a semiinfinite vertical plate with the influence of electrophoresis, heat source/sink and chemical reaction. The partial differential equations governing the flow are solved by employing an implicit finite difference scheme of Crank-Nicolson type. The effect of heat generation and absorption in stratified and unstratified flow are examined and hence the influence of stratification on velocity, temperature and concentration are investigated and presented graphically. Further, the impact of the electrophoresis on particle concentration in the presence of generative and destructive reaction is analyzed. As well, the effects of the physical parameters on local and average values of skin friction, Nusselt number and Sherwood number are also investigated and illustrated graphically. The particular solutions of the present results are compared with the existing solution in literature and are found to be in good agreement.     

Effect of heat transfer conditions on the critical pressure of metal ignition in oxygen

Experimental data on the critical pressure of ignition of titanium alloy fragments in gaseous oxygen are analyzed. The fragments are obtained after fracture of alloy samples in the dynamic mode (p₂^*) and under natural convection conditions (p₁^*). The results are analyzed with allowance for the heat transfer coefficients from material ignition initiators under similar conditions. Based on the shape of the experimental thermograms of plate cooling, the coefficient of heat transfer from microcraters with a juvenile surface formed due to knockout of metal particles from the plate by the high-velocity flow is found: α₂ ≈ 11 kW(m² ·K). The value of α₂ is close to the value of this coefficient calculated with the use of the coefficient α₁ ≈ 5 kW/(m² · K) of heat transfer from titanium rod microfragments (with the size of the order of metal grains) formed during titanium rod fracture in oxygen under conditions of natural convection with allowance for the ratio p₂^*/p₁^*.     

Speeding up plate drying with bilateral heat input

Translated from Steklo i Keramika, No. 12, pp. 13–15, December, 1989.     

板式换热器的清洗

板式换热器是一种结构紧凑、高效的换热设备,但其换热温度高、内部流通孔径小,极易结垢,造成板式换热器换热效率降低,从而影响生产的正常进行和设备的安全,所以需采用化学清洗法除垢。本文介绍了板式换热器除垢的两种化学清洗方法——拆卸清洗和不拆卸清洗,清洗后的中和、钝化预膜处理及清洗中的注意事项,为板式换热器的安全除垢提供了可靠的保证。     

平板玻璃的新切桌

本文主要介绍平板玻璃切裁的新切桌，解决了切裁过程产生的玻璃划伤，尺差精度低等难题     

Mass transfer with chemical reaction during gas absorption on a sieve plate

On the basis of measurements of the rate of absorption of carbon dioxide into potassium carbonate—potassium bicarbonate buffer solutions, containing sodium hypochlorite and potassium chloride, and into sodium hydroxide solutions it has been proved that the Danckwerts' pseudo-first order reaction method may be successfully used for the determination of interfacial area and mass transfer coefficients on sieve plates.The values of interfacial area and mass transfer coefficient have been measured by this method for sieve plates of various geometry, at different gas velocities and clear liquid heads. It was found that the interfacial area per unit volume of the froth is almost independent of these parameters.A method of computation of the plate efficiency for absorption with reaction process has been suggested and tested experimentally.The results of investigations of the kinetics of the chemical reactions involved are also given.     

Partial oxidation of methane in a chemical compression reactor with heat regeneration

A method for noncatalytic partial oxidation of methane in a chemical compression reactor with heat regeneration is proposed and the appropriate theory is developed. A reactor is considered that uses the operating principle of an internal combustion engine with a heat regenerator that is located in the channel of a combined exhaust and intake manifold, through which reaction products and reactants alternately pass. Calculations have shown that this method makes it possible to implement noncatalytic conversion of methane in methane-air mixtures with the content of a hydrocarbon of up to 24% at ratios of compression of 14–30 and a maximum process pressure of no more than 10 MPa. The composition of the reaction products in the field of existence of a regenerative cycle as a function of the initial composition of the mixture, the compression ratio, and the crankshaft speed is found. It is shown that the degree of methane conversion can reach above 97% and, in this case, useful power is produced     

钣金展开计算机放样技术

计算机放大样是必然的趋势 ,提醒大家对此应该充分重视 ,及早地进入这个领域     

航空用金属密封板的研制

对金属骨架密封板的胶料及生产工艺进行了初步的研究,确定了低压缩变形氟橡胶的胶料配合体系,并对铝骨架与氟橡胶的粘合工艺进行了对比实验,确定了其密封板的制造工艺。     

Thermal model validation of plate heat exchangers with generalized configurations

Thermal models of plate heat exchangers rely on correlations for the evaluation of the convective heat transfer coefficients inside the channels. It is usual to configure the exchanger with one countercurrent single-pass arrangement for acquiring heat transfer experimental data. This type of configuration approaches the ideal case of pure countercurrent flow conditions, and therefore a simplified mathematical model can be used for parameter estimation. However, it is known that the results of parameter estimation depend on the selected exchanger configuration because the effects of flow maldistribution inside its channels are incorporated into the heat transfer coefficients. This work presents a parameter estimation procedure for plate heat exchangers that handles experimental data from multiple configurations. The procedure is tested with an Armfield FT-43 heat exchanger with flat plates and the parameter estimation results are compared to those obtained from the usual method of single-pass arrangements. It can be observed that the heat transfer correlations obtained for plate heat exchangers are intimately associated with the configuration(s) experimentally tested and the corresponding flow distribution pattern(s).     

切割太阳能硅片用金刚石内圆锯片生产工艺探讨

文章介绍的新生产工艺使产品具有极高的结合强度。生产的锯片刃口锋利、切割平稳、精度高、寿命长。对刀片的基体材质、金刚石粒度、金刚石分布、镀前处理工艺、电镀配方及电镀规范进行独特的选择和改进；通过控制阴极电流密度和上砂时间来实现金刚石在刃口上的合理分布；通过新的“除油、活化、冲击镀”前处理规范，使镀层与基体牢固结合；合理的镀液配方及电镀规范使镀层不仅具有足够高的强度、硬度和耐磨性，还具有足够高的韧性和抗；中击能力，使金刚石发挥出最佳的磨削效果。