Effect of Reactor Ambient Pressure on the Morphology of Spray Dried Magnesium Sulphate Powders

The effect of reducing the reactor air pressure on the morphology of spray dried magnesium sulphate powders is investigated, experimentally. A reactor, capable of drying and pyrolyzing solution sprays at low pressures, is designed and manufactured. A vibrating mesh nebulizer is employed to generate the spray. Four different pressures, starting from 60 Torr to the atmospheric pressure, and two different reactor air temperatures of 130°C and 420°C, are considered. In addition, two different concentrations of magnesium sulphate solutions are tested. The results are explained based on the effect of reactor air pressure on the droplet evaporation rate.     

Determination of gas dispersion in vapor extraction of heavy oil and bitumen

In this work, a mathematical model is developed and simulated to determine gas dispersion along with solubility during the vapor extraction (Vapex) of live oil from a laboratory scale physical model. The physical model is a rectangular block of homogenous porous medium saturated with heavy oil and bitumen. At a given temperature and pressure, the block is initially exposed on its side to a solvent gas, which diffuses into the medium and gets absorbed. The absorption of gas reduces the viscosity of heavy oil and bitumen causing it to drain under gravity. The low-viscosity “live oil” is produced at the bottom of the porous block. The production of live oil with time is accompanied by the shrinkage of oil in the block as well as its increased exposure to gas from top. These phenomena of Vapex are described by the mathematical model, which is used to calculate live oil production with various values of gas solubility and dispersion. Their optimal values are determined for the vapor extraction of Cold Lake bitumen with butane by matching calculated live oil production with its experimental values published earlier.     

VARIATIONS IN ALFALFA JUICE SOLUTE CONCENTRATIONS AS WATER IS EVAPORATED

Alfalfa juice was extracted from plants during the graving phases of the first and second crops. The alfalfa juice was dried and solute concentrations were measured periodically during the process using freezing point depression (FPD) as an indicator. Solute/solvent weight ratios were calculated from the freezing point depression of fresh unconcentrated 'uice extracted from both firsc and second crops. At the time of harvest, tie FPD was a function of this ratio. The first and second crops behaved distinctively different during the drying process, with the second having a larger soluce concentration and a greater FPD at a given moisture content. The appearance of preci itate during the drying process and the general1 large FPD makes this materiay a questionable product for drying vitg low temperature processes.     

Experimental Investigation of the Recovery of Soaked Paper Using Evaporative Freeze Drying

The aim of this article is to develop an experiment and a procedure to investigate the restoration of water-damaged paper and archival materials using freeze drying in order to allow a reproducible test and comparison of the influence of different operating conditions on drying time and restored paper quality. Firstly, a reproducible method for the preparation of soaked samples simulating water-damaged paper has been developed. Then, the samples have been freeze-dried in a laboratory-scale apparatus that allowed monitoring the temperature as well as the weight of the samples. The technique of evaporative freezing, which reduces the drying time required, has been used in this case. An innovative procedure for the visualization of the progress of the drying process has been validated, thus allowing the validation of a simple phenomenological model of the time evolution of the ice core volume; in addition, data on the residual moisture of the dried paper sheets in different zones have been given. Finally, optimization of this particular drying process by using simple or more sophisticated approaches has been discussed.     

Computations of Explosive Boiling in Microgravity

Dynamics of the explosive growth of a vapor bubble in microgravity is investigated by direct numerical simulation. A front tracking/finite difference technique is used to solve for the velocity and the temperature field in both phases and to account for inertia, viscosity, and surface deformation. The method is validated by comparison of the numerical results with the available analytical formulations such as the evaporation of a one-dimensional liquid/vapor interface, frequency of oscillations of capillary waves, and other numerical results. Evolution of a three-dimensional vapor nucleus during explosive boiling is followed and a fine scale structure similar to experimental results is observed. Two-dimensional simulations yield a similar qualitative instability growth.     

提高拉刀耐用度的挤压工艺

拉刀在刃磨过程中存在不易获得定值前角且会降低刀具硬度等问题，为此设计了拉刀前刀面挤压工艺．该工艺简便易行，一把拉刀可挤压5—8次，效益好。使用证明，经挤压加工后的拉刀加工的零件精度高，且拉刀的使用寿命可提高30%以上。     

Optimal Control of Solar Sludge Dryers

Optimal control (OC) methodology is used to develop a control policy for a batch-operated solar sludge dryer with ventilation as the dominant control. Batch performance criteria and instantaneous optimization criteria are developed for two economic environments: quota limited and capital limited. The general formulation, as well as simplifications resulting from the multiplicative form of the evaporation (drying) rate model, are presented. The multiplicative form results in a single constant number, called here “control intensity,” which is used to guide the on-line control decisions. These decisions turn out to be independent of the dry solids content (DSC) of the sludge. Further simplification, by assuming a strictly constant weather, is used to demonstrate the general effects of the economic and physical (weather) environment on the solution.

The OC approach is used to address, via simulation under realistic weather conditions, several design, operation, and pricing problems. In particular, the following have been considered: sizing of the ventilation fans, determination of a fair fee for sludge disposal, finding the best final DSC, and evaluating the effect of the price of electricity. Regarding the particular location represented by the data, it has been shown that the installed capacity of the ventilation fans should be increased and that there seems to be sufficient economic incentive for solar drying.     

Experimental Study on Energy Consumption of Combined Conventional and Dehumidification Drying

Conventional drying, dehumidification drying, and combined conventional-dehumidification drying of wood were experimentally studied in this article. The results showed that the energy consumption in the dehumidification drying is the least but its drying time is the longest. The energy consumption in the combined drying is more than that in the dehumidification drying but less than that in the conventional drying, and the drying time is half of that in the dehumidification drying. The advantages of the combined conventional and dehumidification drying are discussed from the experiments results.     

Whey Drying on Porous Carriers

Whey is an undurable product. treated very often as a waste which pollutes the natural environment. Whey which is a valuable source of protein, lactose, vitamins and mineral salts should be utilized completely. The present paper is a proposal of whey drying on porous carriers. It is proved experimentally that the proposed drying method guarantees good product quality.     

PROPAGATION OF GASLESS COMBUSTION FRONTS: NONZERO REACTION RATE IN THE WHOLE DOMAIN

This paper deals with the gasless combustion problem in an infinite one-dimensional medium. The possibility of the existence of steadily propagating reaction waves is stated for system models with nonzero reaction rates everywhere but at the boundaries. Two forms for the chemical reaction rate dependence on the temperature are considered: the classical Arrhenius, and a modified Arrhenius incorporating and ignition temperature. The equations for the steadily propagating waves are studied in the phase-plane of the temperature and its derivative. The analysis first addresses the question of whether steadily propagating waves are admissible. Then bounds for the propagation velocity are sought and found. The results of the closed-form analysis are successfully tested against numerical experiments. Non-steady propagation regimes are also found, and regions in the parameter space associated with different asymptotic dynamical behaviour are identified.