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To reduce inhalable particle and SO(x) pollution from coal-based urban central heating (UCH), China has been vigorously developing natural gas-based UCH for years. The CO(2) emissions of UCH, having an average annual growth rate of 10.3%, accounted for 4.4% of China's total CO(2) emissions in 2009. This paper analyzes the feasibility of replacing UCH with heat pump heating (HPH) in China's climatic suitable regions and evaluates the corresponding potential for energy saving and emission reduction. Current strategy of replacing coal-based UCH with natural gas-based UCH is expected to decrease CO(2) emissions by 63.5%. However, the CO(2) emissions of HPH are 55.4% less than those of natural gas-based UCH. Replacing coal-based UCH with HPH is capable of decreasing CO(2) emissions by 83.7% and consequently decreases the CO(2) emissions per unit of gross domestic product (GDP) by 4.2% by 2020 compared with 2005 level. This contributes about 10.5% to China's 2020 CO(2) emission reduction target. For controlling environmental pollution and protecting ecological environment better, China should adjust its strategy for CO(2) emission reduction by shifting its attention from replacing coal-based UCH with natural gas-based UCH to popularizing HPH in climatic suitable regions.

This paper is concerned with oxygen enrichment. Here, we present a novel method of oxygen enrichment by use of the gradient magnetic field, the essential of which is to use the interception effect of the gradient magnetic field on oxygen molecules. To investigate the feasibility of this method, experimental and numerical studies are carried out. The research results show that the degree of oxygen enrichment is relevant to the macroscopic velocity of flow possessed by the gas. Under the conditions in this paper, the maximum degree of oxygen enrichment reaches 0.65%. Through the method brought forward in this paper, a higher degree of oxygen enrichment can be obtained than other similar methods because it can avoid the remixing of oxygen and nitrogen caused by the gas turbulence and the molecular diffusion. This kind of method has such merits as simpleness, convenience, low cost and low energy consumption, and is suitable for those locations where there is a low demand for oxygen concentration.

A novel oxygen-enriched method is presented. Using two opposite magnetic poles of two magnets with certain distance forms a magnetic space having a field intensity gradient near its borders. When air injected into the magnetic space outflows from the magnetic space via its borders, oxygen molecules in air will experience the interception effect of the gradient magnetic field, but nitrogen molecules will outflow without hindrance. Thereby the continuous oxygen enrichment is realized. The results show that the maximum increment of oxygen concentration reaches 0.49% at 298 K when the maximum product of magnetic flux density and field intensity gradient is 563T2/m. The enrichment level is significantly influenced by the gas temperature and the magnetic field. The maximum increment of oxygen concentration drops to 0.16% when the gas temperature rises to 343 K, and drops to 0.09% when the maximum product of magnetic flux density and gradient is reduced to 101 T2/m from 563 T2/m.

An air separation unit (ASU) represents the largest overall energy consumption (about 15–20%) in a steel production facility. Therefore, improving the operating efficiency of an ASU is an effective way to achieve energy savings and emission reductions. The exergy calculation program for an air separation process is developed, and the detailed exergy calculations and analysis for an actual ASU with capacity of 40,000 Nm3/h in service at Tangshan Tangsteel Gas Co. Ltd. are performed. The results show that the molar exergy contained in oxygen is the largest among all gaseous products, liquid argon contains the largest molar exergy among all liquid products, and liquid products of the same type have larger exergy values than their gaseous equivalents. In a same condition scenario (same environmental condition, same air feed mass flow at rated load operation of the expander), increasing liquids production is an effective way to enhance the process efficiency, especially by increasing liquid argon production at the rated load operation of the expander. The object efficiency of the process from the cleaning unit to production in an actual 40,000 m3/h ASU is 46.84%, while the simple efficiency of the cold box of the ASU is 64.31%. The largest amount of exergy loss is caused by the air compressor (AC), the packed-type air cooling tower (PACT), and the molecular sieve (MS) purifier. The cryogenic ASU itself is well operated from an exergetic viewpoint. On the basis of exergy analysis conducted, this study provides a reference for the improvement of the ASU analyzed and provides a reference for ASUs in general.

The effects of particle size, packed density, thermal conductivity and specific heat capacity on heat transfer between a high-temperature gas fluidized bed and an immersed surface are investigated. Hollow-corundum-sphere, corundum, magnesite and quartz sand particles with different diameters within the range of 0.35–1.21 mm are used. A liquefied petroleum gas fluidized bed furnace with 0.3 m × 0.3 m cross-section at hearth bottom and 0.8 m in height is used. The furnace temperature varies in the range of 990–1010 °C, the immersed object is a silver sphere of 20 mm in diameter and the fluidizing velocity is changed from about 1.0 U mf (the minimum fluidizing velocity) to about 3.0 U mf . The experimental results show that, for small particles, d p d p ⩾0.8 mm, the effects of the properties on heat transfer are limited; and for all particles with diameters in the range of 0.35–1.21 mm, the heat transfer coefficient between the fluidized bed and the immersed surface is insensitive to particle thermal conductivity.

This paper presents a theoretical model for predicting the radiative heat transfer rate between high-temperature fluidized bed and immersed walls, which can be used upon the base of emulsion packet model of heat transfer in bubbling fluidized bed. The model adopted radiative flux computation method to calculate radiative heat transfer between fluidized disperse phase contacting to the wall and immersed walls, in which the absorption and back-scattering coefficients was obtained from the reflectivity and the absorptivity of a layer of disperse media of a single particle thickness. In such a model, many factors, such as particle size, particle emissivity, bed void fraction, fluidized bed and wall temperatures, and so on, are included theoretically to calculate radiative heat transfer between immersed walls and fluidized beds. As a result, the model results provide a reasonable explanation of the experimental observation of that radiative heat transfer rate in fluidized beds increases with the increases of the superficial fluidizing velocity. In addition, the modeling prediction for the trend of radiative heat transfer rate between the fluidized bed and its immersed surface on the variation of wall temperature conforms to the classical experimental trend.

A mathematic model for packed air-cooling tower thermodynamic calculation is set up in this paper on the basis of fundamental heat and mass transfer equations. Based on the Double Film theory, direct equation-solving method is used to simulate air-cooling tower, and variation of parameters is taken to analyze the data and results of the program.

Field synergy characteristics in condensation heat transfer with non-condensable gas (NCG) over a horizontal tube were numerically simulated. Consequently, synergy angles between velocity and pressure or temperature gradient fields, gas film layer thickness, and induced velocity and shear stress on gas–liquid interface were obtained. Results show that synergy angles between velocity and temperature gradient fields are within 73.2°–88.7° and ascend slightly with the increment in mainstream velocity and that the synergy is poor. However, the synergy angle between velocity and pressure gradient fields decreases intensively with the increase in mainstream velocity at θ ≤ 30°, thereby improving the pressure loss. As NCG mass fraction increases, the gas film layer thickness enlarges and the induced velocity and shear stress on gas–liquid interface decreases. The synergy angles between velocity and temperature gradient fields increase, and the synergy angles between velocity and pressure gradient fields change at θ = 70°, decrease at θ < 70°, and rise at θ > 70°. When the horizontal tube circumference angle increases, the synergy angles between velocity and temperature or pressure gradient fields decrease, the synergy between velocity and pressure fields enhances, and the synergy between velocity and temperature fields degrades.

Granular convection/separation of single and binary component particles are studied in a narrow vibration bed, respectively. With filling the single light particles (molecular sieve beads), the bed exhibits five different states successively by increasing the vibration frequency f from 15Hz to 70 Hz (vibration strength Γ>3), as the global convection, symmetrical heap, unsymmetrical heap, local convection and pseudo solid. Comparatively, the granular bed of the single heavy particles (steel beads) is only in pseudo solid state at the above vibration condition. By filling binary component particles (molecular sieve and same size steel beads) instead of the single component, the bed shows similar convection state with that of the single molecular sieve beads, and the heavy steel beads are aggregated in the centre of convention roll as a core. Varying the initial distribution of binary component particles, the final convection and separation are not influenced, although the aggregation process of steel beads changes.

In this paper, we investigate the influences of air flow and vibration on the separation of a binary mixture, when air velocity u is less than the minimums fluidized velocity umf (0

Granular particles systems under vertical vibration exhibit Brazilian Nut separation (BN), Reversed BN (RBN) separation or transitional phases at different vibrating conditions. In the present work, we investigate the influence of rotation on the BN separation of a binary granular particle system by changing rotational speed. 13X molecular sieve particles with diameter 6.00 mm and 0.60 mm are used. Vibration frequency f is 30 Hz and dimensionless acceleration Γ is 1.52 or 1.75, in which the particle system mainly exhibits BN separation tendency. Rotational speed ω varies from 0 to 150rpm, while the upper surface of the particle system maintains flat. We took the pictures of the particles distribution and measured the particles mass layer by layer to obtain the 3-D distribution of the particles. The results show that rotation enhances the BN separation tendency at slow rotational speed. The BN separation becomes strongest when ω is approximately 50rpm, then the BN separation tendency reduces as ω continues to increase. A butterfly pattern appears in the middle particles layer under the simultaneous stimulations of vibration and rotation.

By considering as a thermodynamic system, a minimum energy principle is established, in which the granular system changes its size distribution to make itself to be at the lowest energy state as soon as possible on the precondition that it dissipates all of the energy supplied from the vibrating bottom. A model is presented based on this principle to clarify why and how binary mixture separates under vibration. The small particles tend to sink in order to lower the kinetic energy of system, while the heavy particles sink in order to lower the potential energy. The mixture separates finally based on the competition between the two effects. The results of our model qualitatively agree with the previous researches.

Based on the welding process parameters of high strength pipeline steel, the artificial neural network (ANN) model has been develped to predict Charpy_V notch (CVN) impact toughness of the welded joint. The model with back propagation (BP) algorithm is built in batch mode and optimized using momentum and adaptive learning rate. Futher more, it is also optimized using genetic algorithm (GA). Five process parameters, namely the welding layer, wall thickness, the welding processes, the preheat temperature, the mean energy input, are used as input variables and the CVN of the welded joints is considered as the output variable. The training and testing of the ANN model have been done using 119 datasets which were obtained from practical welding. The number of the testing samples with error less than 20% is about 74% in total testing data. It is found that the CVN of pipeline welded joints can be effectively predicted using the model and the GA outperforms the commonly BP algorithm used as an neural network training technique. Based on this model, the influence of the preheat temperature and the mean energy input on the CVN is also analysed. The results show that the preheat temperature and the mean energy input have little effects on the automatic welding, but large on the semi-automatic welding and the manual welding for root welding. So a reasonable choice of the preheat temperature and the mean energy input is necessary.

The direct nitridation process of silicon added with amorphous silicon nitride powder at atmospheric pressure was investigated and the product was analyzed by XRD and SEM. Based on the relationship between the conversion ratio of silicon and the reaction time at different temperatures, a physical and mathematical model was derived to describe the nitridation process of silicon particles. The results showed that the conversion ratio of silicon increased rapidly at the early stage of reaction. And the reaction would be accelerated by reducing the size of silicon particle and increasing the pressure of N2. At the range of experimental temperature, the conversion ratio of silicon increases with improving temperature.

In this paper an integrated operating simulation system (OSS) for a cryogenic air separation unit (ASU) is developed, which can be used for operators’ training, accident and malfunction analysis and prediction of operating result. Based on the method of modularization an ASU’s components are divided by their physical function. The OSS code includes two parts: the key simulation part which is developed in FORTRAN 5.0 and generally runs in background, and control simulating part which is primary running program and developed in iFix software. The communication between the key simulation part and control part is implemented by boundary module program. The OSS can realize the following operation simulation functions: normal state operation, startup operation and compressor, expander and other machines operations. The OSS has been tested for a 20000Nm3/hr ASU in Jinan Iron and Steel Corporation and 720000Nm3/hr ASU in Bao-Shan Steel Group Corporation in China. The simulating results of the OSS agree with the simulated counterpart.

In the work, the dynamic characteristics of the human skull-dura mater system were studied. For the purpose of our analysis, we adopted a model consisted of a hollow sphere. By using the ‘Patran andAnsys’ finite element processor, a simplified three-dimensional finite element model (FEM) of a human skull was constructed. The model was used to calculate the deformation of human skull with the intracranial pressure changing. This required good representation of the complex anatomy of the skull. Four different entities are distinguished: Tabula externa, Tabula interna, and a porous Diploe sandwiched in between, and dura mater. A thin-walled skull was simulated by composite shell elements. The viscoelasticity of human skull-dura mater system was studied and analyzed by the finite-element Maxwell model. The 1/8 model consisted of 25224 nodes and 24150 three-dimensional 8-nodeisoparametric solid elements. The elastic-viscous mechanical characteristics must be used for the skull. The viscous strains account for about 40% of total strains of human skull and dura mater. And therange of strain errors is from 6.45 to 14.82% after ignoring the viscosity of skull and dura mater.

Because of the dynamic, nonlinear and multi-parameter characteristic of the refrigeration system, it is difficult to keep the system operating under the optimal state. Based on the improved back-propagation (BP) of artificial neural network (ANN) with the momentum factor, the program to predict the performance of refrigeration system at part-load condition is established by Visual C++ 6.0. The training or testing data is from a refrigeration experiment system with HCFC22. The input layer includes 3 neurons, i.e. the indoor and outdoor air temperature and compressor frequency. The prediction result indicates that the artificial neural network method is a kind of effective way to analyze the performance of refrigeration system. This work can provide guidance on the saving-energy control method of refrigeration system at part-load condition.

A large number of split-type air conditioner are widely used in high-rise residential or office buildings in China and the outdoor units of air-conditioner are often installed at the sidewalls or on the roofs in the confined space of a high-rise building. The factors affecting the performance of air-conditioner are the solar radiation, the heat released from the outdoor units, the ventilation of the confined installation space of a building where the outdoor units are installed and so on, which are investigated in this study. The air flow and temperature distribution under steady-state condition near the two outdoor units installed on the same storey in a building are simulated by software FLUENT, in which the porous model and DO radiation model are used. The optimum installation distance from the supporting wall is obtained. The average temperature of the exit surface without wind is 1.18% more than that with wind. The results show that the heat released from the outdoor units and the ventilation of the confined installation space where the outdoor units are installed are the main factors affecting the thermal environment in the confined installation space; The influence of the solar radiation can be neglected.Copyright © 2010 by ASME

Welding is a process for joining similar metals. Heat input and interpass temperature are important technical parameters that affect the welding temperature distribution field. 2D simulation of multi-pass compound groove of welding process for X80 pipeline steel is carried out by finite element software ANSYS, in which the distribution of T8/5 of welding filling layers is analyzed. The results show that the effect of heat input to T8/5 is significant. The T8/5 becomes longer with the increase of the heat input. Because of the obvious preheat influence of the preceding pass to the following, the T8/5 becomes longer with the increase of the weld pass quantity. When interpass temperature is equal to preheat temperature, the difference of the T8/5 on filling layer is tended to be insignificant. The T8/5 will be located within a reasonable range by choosing the appropriate heat input and interpass temperature.Copyright © 2010 by ASME

A general and simple model for simulating the steady behavior of air-to-refrigerant fin-and-tube evaporators, which accounts for detailed flow state inside the tubes, is introduced. To account for the heat transfer between air and the working fluid, the evaporator is divided into a number of control volumes. Space dependent partial differential equations group is obtained from the mass, energy and momentum balances for each one. The corresponding discretized governing equations are solved afterwards. Empirical correlations are also required to estimate the void fraction, the internal and external heat transfer coefficients, as well as the pressure drops. According to the phase of refrigerating fluid, the evaporator can be divided into two distinct zones on the refrigerant-side: the vapor zone and the two-phase zone, while special emphasis is performed on the treatment of the two-phase zone. The distribution of flow pattern has been evaluated with the aim of improving the calculation accuracy. The model prediction is validated against experimental data for an evaporator using R22 as the working fluid, which shows a reasonable level of agreement: the cooling capacity is predicted within the error band of 3%. The developed model will have wide applications in operational optimization, performance assessment and pipeline design.

In order to study analytically the nature of the size separation in granular mixture, we present the maximum entropy production principle based on kinetic temperature of granular mixture. For simplicity we apply this principle to size separation of a sphere binary mixture in vibrated bed, and we find a new thermodynamic mechanism of size separation phenomenon. With the irreversible processes such as elastic collisions and frictions, the kinetic energy is dissipated rapidly in system, which induces the entropy production. By the fact that the entropy production rate always has the absolute maximum at the stable state of granular mixture, we find the crossover from “Brazil Nut Effect” to its reverse by changing particles size and density, and our result is about satisfied with Schnautz’s experiment.Copyright © 2009 by ASME

To enhance the practicality of the separate type heat tube in large-scale industrial application, the authors have adopted a non-vacuum separate type heat tube in which quantitatively predicting condensation heat transfer of vapor in the presence of stagnant high partial pressure non-condensable (NC) gases is vital to the task of design. So the condensation heat transfer in a V-shape tube with high partial pressure non-condensable gases was simulated based on a 3D steady state VOF model coupled with the MS (Maxwell-Stefan) equation for considering the effect of stagnant high partial pressure non-condensable gases on condensation heat transfer. The results show that the high partial pressure non-condensable gases have a limited influence on the condensation heat transfer, and they are constrained in a narrow space at the rear of the tube due to the forced convective vapor, therefore, a small part of the pipe wall has lower local heat flux and condensation heat transfer coefficient, while most part of pipe wall has higher performance of condensation heat transfer. The calculated results are in agreement with the experimental data.Copyright © 2009 by ASME

The mechanical properties of welding material is correlative with the chemical composition Artificial neural network (ANN) program to predict mechanical properties — yield strength, tensile strength, elongation and average Charpy impact toughness — of welding material is established by Visual C + + 6.0 based on improved BP arithmetic with momentum factor, in which one input layer with 13 nodes, one hidden layer with 23 nodes, one output layer with 4 nodes, and Sigmoid activation function are included. The 20 samples are from the experimental data of semi-automatic welding material of X70. The average maximum relative error of the 4 mechanical properties is less than 0.5%. Based on the program, the influence of the chemical composition, such as C, S, P, Si, Mn, Cr, Ni and Al on the mechanical properties is analyzed. The results show that the different element has different influence on the mechanical properties. For non-metallic elements, the mechanical properties are becoming worse with the increase of composition, in which the influence of C is primary, then P and then S. For metallic elements, the influence is greater and more complex than that of non-metallic ones.Copyright © 2008 by ASME

Microwave heating has been extensively used in the area of food handling, and many investigators have been studying the effect of microwave heating on the quality of food. However, the phenomenon concerning on the hard-cores in steamed breads caused by microwave heating is poorly understood. A series of experiments are designed in this paper to investigate the impact of microwave heating on the quality of steamed breads under different heating conditions. The experiment results show that the hardness and cohesiveness can be used to measure the hard-core of steamed breads. The mechanism of hard-core caused by microwave heating is discussed. According to the results of experiments, the hardness of the steamed breads increases with the increment of the power, the duration and the times of microwave heating. The cohesiveness of the steamed breads shows a trend, which drops at first, then increases, and decreases finally with the duration of microwave heating. According to the experiment data, a hard-core in a steamed-bread appears under the following conditions: when it is heated for 50s with the power of 900W when the overheating time is 20s, for 65s with the power of 720W when the overheating time is 25s, or for 80s with the power of 540W when the overheating time is 30s. Heated twice with the same heating time, the steamed bread begins to appear hard-core phenomenon under the following conditions: when it is heated for 55s with the power of 540W, for 40s with the power of 720W, or for 30s with the power of 900W.Copyright © 2007 by ASME