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41.
高温炉内的辐射传热是工业生产中常遇到的问题。过去,人们在应用热流法计算辐射传热时遇到了一定的困难,使计算结果与实际有一定的偏差。本文运用文献[1]中给出的新热流数学模型,开发出由新热流方程与能量方程相耦合的计算机程序,其中的比热流参数由线加热热源情况下计算得到。用该程序计算了实验室用马弗炉内的温度场,并且用热电偶实测了炉内的一些温度值,理论计算与实测值符合很好。 相似文献
42.
Sensitivity analysis is used to show how uncertainties in basic factors, such as heat transfer, pressure drop, compressor efficiency, and thermophysical properties, influence the result of heat pump cycle performance estimations. By comparing the results of this analysis with uncertainty levels of estimations and experimental determinations, it is established to what extent improvements in accuracy are needed. The investigation was carried out for several different applications and, as working fluids, both pure substances and non-azeotropic mixtures were examined. It was found that evaporation heat transfer and compressor efficiency are two areas where improvements are needed. It is also shown that estimates using very accurate, substance-specific, equations of state differ from those using more general types by up to 1 % for COP and 2% for capacity. 相似文献
43.
快速凝固高碳铁基合金脉冲激光非平衡热处理 总被引:1,自引:0,他引:1
利用脉冲Nd:YAG激光辐照对快速凝固高碳铁基合金进行非平衡相变热处理,发现在高能脉冲激光辐照时,原快速凝固共晶碳化物(Fe3C)异常迅速地石墨化,获得了含超细石墨球和既含超细石墨球又含快速凝固共晶Fe3C的两种新材料,研究表明,这种快速石墨化及上述两类新型材料的形成主要归因于脉冲激光光速辐照产生强烈周期性起伏温度场的“微退火(micro-annealing)效应。 相似文献
44.
Dmitri E. Nikonov George I. Bourianoff Paolo A. Gargini 《Journal of Superconductivity and Novel Magnetism》2006,19(6):497-513
Quantum limits of power dissipation in spintronic computing are estimated. A computing element composed of a single electron
in a quantum dot is considered. Dynamics of its spin due to external magnetic field and interaction with adjacent dots are
described via the Bloch equations. Spin relaxation due to magnetic noise from various sources is described as coupling to
a reservoir. Resulting dissipation of energy is calculated and is shown to be much less than the thermal limit, ∼kT per bit,
if the rate of spin relaxation is much slower than the switching rate. Clues on how to engineer an energy efficient spintronic
device are provided. 相似文献
45.
Comparative studies on Ar and He closed-cycle MHD power plants combined with fossil fuel are performed. The sizes of a regenerative heat exchanger and a boiler are expected to be smaller for He than for Ar. The pressure loss of a working gas in a regenerative heat exchanger is reduced for He. The purification subsystem for He is expected to be more compact and economical than that for Ar; but a larger compressor is required for He than for Ar. 相似文献
46.
C Riverol V Napolitano 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(5):594-600
Pasteurization is an important, if not the most important, process step in the packaging of milk. It is subject to alterations stemming from the variation in the temperature, pH and raw milk quality. The variability may manifest itself in changes in the formation of the deposit (fouling) in the pasteurization unit, such that there is a need for tools, both instrumentation and computational, to help in monitoring the process and keeping it on the desired course. In this paper we describe a practical procedure based on artificial neural networks (ANN) that allows prediction of the deposit thickness, the overall heat transfer coefficient and the critical time (the time that the unit has to be stopped for cleaning) for reducing the impact of fouling on such processes. The procedure determines when the cleaning operation is required once the system is under critical conditions of operations. A combination of fundamental studies and plant measurements were used for study of the operating conditions and thus evaluation of the trades‐offs between operating conditions and longer operating life span. The results are encouraging, enough to validate current operating industrial techniques. Copyright © 2005 Society of Chemical Industry 相似文献
47.
利用保温裸露因数的概念来反映保温层保温性能的变化,提出采用统一原则来建立适用于单元系统和复合系统保温层热经济寿命的数学模型,并通过实例证明在热经济寿命终了时更新保温层,可使系统的运行具有最大的经济性。 相似文献
48.
49.
50.
40000m~3/h空分设备主换热器的设计及制造 总被引:1,自引:0,他引:1
通过对进口 4 0 0 0 0m3 /h空分设备主换热器进行结构分析及对比模拟计算 ,用国产传热翅片进行设计、采用真空钎焊工艺制造的主换热器 ,经并网运行 ,设计指标优于原空分设备 ,为今后成套大型空分设备板翅式换热器国产化设计、制造创造了条件。 相似文献