Uncertainty analysis of heat release rate measurement from oxygen consumption calorimetry

Oxygen consumption calorimetry remains the most widespread method for the measurement of the heat release rate from experimental fire tests. In a first step, this paper examines by theoretical analysis the uncertainty associated with this measurement, especially when CO and soot corrections are applied. Application of theoretical equations is presented for chlorobenzene which leads to high values of CO and soot yields. It appears that the uncertainty of CO and soot corrections are high when the fuel composition is unknown. In a second step, a theoretical analysis is provided when the simplest measurement procedure is used for oxygen consumption calorimetry. The overall uncertainty can be dominated either by the uncertainty associated with the oxygen concentration, the assumed heat of combustion, the fumes mass flow rate or the assumed combustion expansion factor depending on the oxygen depletion. Copyright © 2005 John Wiley & Sons, Ltd.     

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.     

Laboratory test of solar distillator with a heat penetrating plate having a bend

A new idea was tested for a solar distillator with wick attached behind an inclined heat penetrating plate.The plate is bended at the center line and a tube is penetrated below the crease of bending. Liquid is fed to the tube and is flooded from two holes near the inlet and then forms a meniscus between the outer surface of the tube and the wick. This meniscus extends along the tube and part of the flow is deliver to the wick. This liquid feeding system is capable of preventing scale formation by forming film flow over the wick surface.The size of the experimental apparatus was 450 mm long and 160 mm wide for one side of the plate. The plate was attached with fibrous sheet as the wick. The idea was tested by using water without heating and satisfactorily uniform film flow was confirmed over all surface of the plate in a feed range between 0.5 and 4.75 kg/h·m.The design procedure was also provided on the basis of process simulation at practical conditions.     

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^*.     

The calculation of the heat release rate by oxygen consumption in a controlled‐atmosphere cone calorimeter

The standard cone calorimeter according to ASTM E 1354 and ISO 5660 enables reaction‐to‐fire tests to be performed in ambient atmospheric conditions. A controlled‐atmosphere chamber modifies the standard apparatus in a way that allows tests to be performed in nonambient conditions as well. The enclosed chamber is placed underneath the standard exhaust hood and does not have a closed connection to the hood. With this open arrangement, the exhaust gases are diluted by excess air drawn in from the laboratory surroundings. Heat‐induced changes in the consequential dilution ratio affect the calculation of fire quantities and, when neglected, lead to deviations of up to 30% in heat release rate. The paper introduces a test protocol and equations to calculate the heat release rate taking dilution effects into account. A mathematical correction is shown that compensates for the dilution effects while avoiding extensive mechanical changes in the equipment. Copyright © 2013 John Wiley & Sons, Ltd.     

高铝耐火砖负载CuO氧载体的化学链氧解耦特性实验

耐火砖常用作高温炉膛材料,具有较高的破碎强度和较强的抗烧结性能。以耐火砖颗粒为惰性载体,采用连续浸渍法制备CuO质量分数为10%～30%的Cu10RefBri、Cu25RefBri和Cu30RefBri氧载体样品,并在热重分析仪（TGA）和批次进料流化床反应器中900～950℃下进行了化学链氧解耦燃烧过程氧载体的释氧-吸氧循环实验测试。结果显示,在上述氧载体样品中Cu25RefBri的释氧速率最高,可达9×10^-5kgO₂/(s?kgOC),流化床中稳定的O₂体积分数可达1.1%。然而,随着循环次数增加,Cu25RefBri的释氧速率逐渐降低至2.0×10^-5kgO₂/(s?kgOC),同时流化床尾气中O₂体积分数降低至0.7%,该值远低于对应温度下的平衡O₂浓度值。氧浓度和释氧速率降低的主要原因在于：循环过程氧载体中形成的低释氧活性的CuAl₂O₄尖晶石含量逐渐增加,导致氧载体总体活性下降。此外,在950℃流化床实验过程,还检测到氧载体颗粒的烧结现象。     

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.     

Speeding up plate drying with bilateral heat input

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

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     

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。     

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     

Parallel plate heat exchanger for heat energy recovery in a farm grain dryer

One of the methods with the most potential to reduce energy consumption in grain drying is heat recovery from the dryer exhaust air. A parallel plate heat exchanger to recover heat energy from the exhaust air of a recirculating batch grain dryer was examined by theoretical assessments as well as by measurements in a scaled-down research dryer and experimental heat exchanger. In addition to the heat transfer performance, the operability in dusty conditions was investigated. Finally, the optimization of the heat exchanger was introduced by the aid of the calculation models and practical measurement. The heat exchanger performed satisfactorily, providing an average energy saving of approximately 18%. A significant improvement in the performance could be achieved by increasing the air velocity. No severe dust accumulation was observed, and a heat exchanger of this type could provide remarkable energy saving possibilities in grain drying. Further tests are necessary to ensure the operability in long-term use.