Natural convection in porous media—I. Nonfreezing

The Christiansen filter concept is used to visualize natural convection in porous media. Studies are conducted with both permeable and impermeable upper boundaries. The experimental results agree well with the numerical calculations which are based upon Darcy's law. Three different permeabilities as well as different test section aspect ratios (width/height) are examined. It is found that the aspect ratio of the cells does not vary with modified Rayleigh number for the impermeable upper boundary but this ratio increases significantly with modified Rayleigh number for the permeable upper boundary.     

Heat transfer in turbulent fluids—I. Pipe flow

The expression for turbulent Prandtl number obtained from the renormalization group procedure is used to describe the process of heat transfer in turbulent pipe flow. The results are in a good agreement with experimental data over the entire range of experimentally accessible Prandtl numbers, 10^-2<σ₀< 10⁶.     

Moisture transport in silica gel packed beds—II. Experimental study

Experiments have been performed to obtain the transient response of a thin adiabatic packed bed of silica gel after a step change in inlet air conditions. Comparisons are made with predictions using a solid-side resistance model and a pseudo-gas-side controlled model and better agreement obtained with the former model. An apparent dynamic hysteresis for adsorption/desorption with microporous silica gel is clearly in evidence, which could be due to a solid-side effective diffusion coefficient which decreases with increasing moisture content, or to a lesser extent to a hysteresis in the adsorption isotherm itself.     

Moisture transport in silica gel packed beds—I.Theoretical study

Diffusion mechanisms of moisture within silica gel particles are investigated. It is found that for microporous silica gel surface diffusion is the dominant mechanism of moisture transport, while for macroporous silica gel both Knudsen and surface diffusions are important. A model is proposed for simultaneous heat and mass transfer in a thin packed bed of desiccant particles, which accounts for diffusion of moisture into the particles by both Knudsen and surface diffusions. Using finite difference methods to solve the resulting partial differential equations, predictions are made for the response of thin beds of silica gel particles to a step change in air inlet conditions, and compared to a pseudo-gas-side controlled model commonly used for the design of desiccant dehumidifiers for solar desiccant cooling applications.     

Antimony in lead—acid cells IV. Review and design considerations

The literature regarding the dissolution, transport, and sorption of Sb, and its effects in lead—acid batteries is briefly reviewed. Antimony is evol     

Comparison of the evolution of energy intensity in Spain and in the EU15. Why is Spain different?

Energy intensity in Spain has increased since 1990, while the opposite has happened in the EU15. Decomposition analysis of primary energy intensity ratios has been used to identify which are the key sectors driving the Spanish evolution and those responsible for most of the differences with the EU15 energy intensity levels. It is also a useful tool to quantify which countries and economic sectors have had most influence in the EU15 evolution. The analysis shows that the Spanish economic structure is driving the divergence in energy intensity ratios with the EU15, mainly due to strong transport growth, but also because of the increase of activities linked to the construction boom, and the convergence to EU levels of household energy demand. The results can be used to pinpoint successful EU strategies for energy efficiency that could be used to improve the Spanish metric.     

Free convection in a shallow cavity with variable properties—2. Porous media

Free convection in a porous shallow cavity with differentially heated end walls has been studied. The governing differential equations are analytically solved by applying the method of asymptotic expansions. The results show that the constant-property solution (Boussinesq approximation) deviates approximately 3% from the variable-property solution, if the properties in the Boussinesq solution are taken as the arithmetic mean between the hot and cold end wall temperature.     

Studies in the transition from deflagration to detonation in granular explosives—II. Transitional characteristics and mechanisms observed in 91/9 RDX/Wax

The apparatus and instrumentation described in the previous paper have been used to observe the transitional behavior of burning to detonation for a 91/9 RDX/wax mixture. Transitions to detonation were observed for all densities between 67 and 95% TMD. The sequence of observed events following ignition of the explosives charge was: stable propagation of a convective flame front, compaction of the more porous burning charges, formation of a postconvective (compressive) wave in the ignition region, subsequent coalescence of compressive waves some distance beyond the ignition region, and the formation of a detonation wave 1 to 2 cm beyond the intersection of the convective and postconvective fronts. It is proposed that the shock to detonation sequence starts in the region of coalescence of compressive waves. The velocity of the convective flame front was observed to increase with increasing charge density in agreement with earlier results from ammonium picrate. The predetonation column length as a function of charge compaction exhibited a minimum; such minima have been reported by other workers for PETN, RDX, and HMX.     

Free convection in a shallow cavity with variable properties—1. Newtonian fluid

The effect of variable properties on free convection in a shallow cavity with differentially heated end walls has been analytically studied. Compared to the results for the linear theory the Boussinesq approximation usually applied is exact, if the fluid properties are taken at the arithmetic mean between the hot and cold temperature at the end walls. For the parameter range considered the deviation between the results for the quadratic theory and the Boussinesq approximation is less than approximately 2.5%. Hence, it has been demonstrated that the arithmetic mean is a reasonable choice. With this reference temperature the Boussinesq approximation leads to sufficiently accurate results.     

水电厂智能控制.维护.管理集成系统

水电厂智能控制·维护·管理集成系统李朝晖叶鲁卿（华中理工大学，武汉，４３００７４）改革开放以来随着我国电力工业高速发展，电力企业的运行管理机制发生了深刻的变化．无人值班少人值守、安全可靠、经济高效已成为现代电力企业最重要的考核指标．目前的控制系统、维...     

KT ENG.Co.,Ltd.

Introduction KT ENG.CO., LTD is manufacturing educational and vocational equipment in the Refrigeration ＆ Air-conditioning field for the Technical High School, College and University. Our products are Air Handling Unit trainer （KTE-1000AHU）, Standard Refrigeration Trainer （KTE-1000BA）, Temperature, Pressure ＆ Defrost Control Refrigeration Trainer （KTE-1000TP）, Refrigerant Parallel Expansion Refrigeration Trainer（KTE- 2000EV）, Evaporation Pressure Parallel Control Trainer（E.P.R Control） （KTE-2000EP）, 4-Way Reverse Valve Control Heat Pump Heating ＆ Cooling Trainer （KTE-3000HD）,     

关于“S.A.E.”的正确译名问题

“S.A.E.”的原文全文为:“Society fo Automotive Engineers”。长期以来,国内有下列三种译法:①美国汽车工程师学会,②美国自动车工程师学会,③美国机动车工程学会最近,作者赴美参加了在底特律举行,1989年S.A.E.国际会议和展览会。发现上述三种译法都有两个错误: