提高G142型浆纱机烘燥速度的探讨

本文对影响G142型浆纱机烘燥速度的因素及如何提高烘燥速度进行了分析探讨。提出要提高烘燥速度就应该改进烘房结构和排气系统,使排出的热空缺与循环的热空缺不处在同一个状态。

Atmospheric Sulfur Deposition for a Red Soil Broadleaf Forest in Southern China

A two-year study in a typical red soil region of Southern China was conductedto determine 1) the dry deposition velocity (V_d) for SO_2 and particulate SO_4^(2-) above abroadleaf forest, and 2) atmospheric sulfur fluxes so as to estimate the contribution of variousfractions in the total. Using a resistance model based on continuous hourly meteorological data,atmospheric dry sulfur deposition in a forest was estimated according to V_d and concentrations ofboth atmospheric SO_2 and particulate SO_4^(2-). Meanwhile, wet S deposition was estimated based onrainfall and sulfate concentrations in the rainwater. Results showed that about 99% of the drysulfur deposition flux in the forest resulted from SO_2 dry deposition. In addition, the observeddry S deposition was greater in 2002 than in 2000 because of a higher average concentration of SO_2in 2002 than in 2000 and not because of the average dry deposition velocity which was lower for SO_2in 2002. Also, dry SO_2 deposition was the dominant fraction of deposited atmospheric sulfur inforests, contributing over 69% of the total annual sulfur deposition. Thus, dry SO_2 depositionshould be considered when estimating sulfur balance in forest ecological systems.

Ice Crystal Sizes and Their Impact on Microwave Assisted Freeze Drying

Freeze drying of an aqueous solution would result in the non-uniform distribution of solute concentration.Because ice is almost transparent to microwave, therefore such a non-uniform distribution may affect the microwave assisted freeze drying. The direct observation of the ice crystals formed under microscope reveals that the ice crystal sizes formed from de-ionized water depend on the cooling rate with fast cooling rate giving smaller ice crystals as expected. Once there is a sufficient amount of solute mixed with the de-ionized water, for example the reactive red,the size and its distribution are not very much dependent on either cooling rate or the final temperature provided there is sufficient time of cooling and the final temperature is not too low. The size of ice crystals formed within the solution of reactive red is usually below 100μm with a freezing rate of 1℃·min-1 for a droplet of the size of less than 1 mm. A simplified simulation indicates that such a small ice crystal would not cause a significant non-uniform distribution of temperature for microwave assisted freeze drying. When the ice crystal size is larger than 5 mm, heat conduction from the solute concentrated region to the ice region may need to be considered.

Moving Behavior of an Object in Gas-Solid Fluidized Beds

The settling behavior of coarse particles in a gas-solid fluidized bed was experimentally studied by using magnetic tracer. It is well known that the calculation of terminal velocity is of interest in dense medium separation. However, this problem has not been completely solved up to now. In this work, the terminal velocity of an object mov-ing in a gas-solid fluidized bed was experimentally measured and theoretically calculated. The experimental results in-dicated that the plastic viscosity and yield stress of the bed increase as the size of fluidized particles increases, but it varies little when some coarser particles are mixed with the fluidized particles. The resistance to a rising object was an order magnitude greater than that to a settling object. The efficient buoyancy on a flaky object, which lies flatly on the gas distributor, was much less than that calculated by the Archimedes principle. The object does not always rise or set-tle with minimal projective area owing to radial motion of the fluidized particles. But in the lower part of the bed, the bar-shaped objects were likely with minimal projective area rising or settling.

Hydrodynamic characteristics of Wujiangdu Reservoir during the dry season-a case study of a canyon reservoir

With the development of hydropower in the karst area of Southwest China, a series of cascade canyon reservoirs have been formed through the construction of dams. Given that hydrodynamic conditions in canyon reservoirs play a pivotal role in controlling the spatiotemporal distribution of physical and chemical properties of the stored water, hydrodynamic characteristics are of great importance in understanding biogeochemical cycles in those reservoirs. To further this understanding, a field campaign was conducted in the Wujiangdu Reservoir of Guizhou Province. It was found that from the reservoir inlet to the front of the dam, velocity(v) was negativelycorrelated and had a logarithmic relationship with distance along the ship track(s) under dry-season flow conditions[v =-0.104 ln(s) + 0.4756]. Analysis showed that dryseason flow velocity had no significant correlation with water temperature, p H, or dissolved oxygen(DO). However, when velocity decreased to 0.061 m/s, water depth increased abruptly. In addition, DO displayed a sudden drop and the trend in p H changed from increasing to decreasing, while water temperature showed an opposite trend, indicating the existence of a transition zone from the river to the reservoir.

Optimization of the Design and Drying Process Adapted to Pineapple Slices

The present work is a study on the influence of temperature and the velocity of air on the drying kinetics of pineapple slices. The main objective is to define from this drying kinetics rules to help a designer choose an adequate principle or drying configuration and optimize the design of dryers adapted to the use of it. The experiments were made in an electric dryer using a parallel flow system. The air was used at three different temperatures （40, 50 and 60 ~C） and at four different velocities （0.27, 0.5, 1 and 1.8 m/s） during the experiment. The results show that an increase of 10 ℃ of the drying temperature reduced the drying time by 45% and increased the drying velocity by 30%. On the set of air velocities tested, it was noticed that the influence of air velocity on drying was more striking at the beginning than at the end of the drying process （variation of less than 20%）. Whatever the variation of parameters during the drying process, the best performance was observed when the products water content during the drying process was between 50% and 80%.

THREE-DIMENSIONAL VARIABLES ALLOCATION IN MESOSCALE MODELS

Forecasts and simulations are varied owing to different allocation of 3-dimensional variables in mesoscale models. No attempts have been made to address the issue of optimizing the simulation with a 3-dimensional variables distribution that should come to be. On the basis of linear nonhydrostatic anelastic equations, the paper hereby compares, mainly graphically, the computational dispersion with analytical solutions for four kinds of 3-dimensional meshes commonly found in mesoscale models, in terms of frequency, horizontal and vertical group velocities. The result indicates that the 3-D mesh C/CP has the best computational dispersion, followed by Z/LZ and Z/LY, with the C/L having the worst performance. It is then known that the C/CP mesh is the most desirable allocation in the design of nonhydrostatic baroclinic models. The mesh has, however, larger errors when dealing with shorter horizontal wavelengths. For the simulation of smaller horizontal scales, the horizontal grid intervals have to be shortened to reduce the errors. Additionally, in view of the dominant use of C/CP mesh in finite-difference models, it should be used in conjunction with the Z/LZ or Z/LY mesh if variables are allocated in spectral models.

Effect of drying environment on engineering properties of an expansive soil and its microstructure

This paper investigates the effect of drying environment, i.e. temperature and relative humidity, on the engineering properties and microscopic pore size distribution of an expansive soil. The shrinkage tests under different drying temperatures and relative humidity are carried out in a constant climate chamber. Then, the undisturbed samples, prepared in different drying environment, are used for the triaxial tests and mercury intrusion tests. It is found that the drying environment has noticeable influence on the engineering properties of expansive soils and it can be characterized by the drying rate. The linear shrinkage and strength increase with the decrease of the drying rate. The non-uniform deformation tends to happen in the high drying rate, which subsequently furthers the development of cracks. In addition, during the drying process, the variation of pores mainly focuses on the inter-aggregate pores and inter-particle pores. The lower drying rate leads to larger variation of pore size distribution.

Seismic considerations for spent nuclear fuel storage in dry casks

To aid the United States Nuclear Regulatory Commission,Sandia National Laboratories (SNL) was contracted to investigate the seismic behavior of typical dry cask storage systems. Parametric evaluations characterized the sensitivity of calculated cask response characteristics to input parameters. The parametric evaluation investigated two generic cask designs (cylindrical and rectangular),three different foundation types (soft soil,hard soil,and rock),and three different casks to pad coefficients of friction (0.2,0.55,0.8) for earthquakes with peak ground accelerations of 0.25g,0.6g,1.0g and 1.25g. A total of 1 165 analyses were completed,with regression analyses being performed on the resulting cask response data to determine relationships relating the mean (16 % and 84 % confidence intervals on the mean) to peak ground acceleration,peak ground velocity,and pseudo-spectral acceleration at 1 Hz and 5 % damping. In general,the cylindrical casks experienced significantly larger responses in comparison to the rectangular cask. The cylindrical cask experienced larger top of cask displacements,larger cask rotations (rocking),and more occurrences of cask toppling (the rectangular cask never toppled over). The cylindrical cask was also susceptible to rolling once rocking had been initiated,a behavior not observed in the rectangular cask. Cask response was not overly sensitive to foundation type,but was significantly dependent on the response spectrum employed.

Characterization of Atomization Processes in Suspension/Emulsion Sprays

The characterization of suspension/emulsion sprays plays a decisive role in many industrial processes. A good example of such a process is the drying of a milk spray to produce milk powder, where the process efficiency and product quality is typically controlled by atomization parameters like flow rate, pressure, etc.. However, these parameters influence directly the droplet size and droplet velocity distributions in a spray, so that optimizing a spray drying process often involves adjusting the spray to a desired droplet size and droplet velocity distribution. This requires a measurement technique capable of characterizing in real time, the droplets in a suspension/emulsion spray. To achieve this aim, we present developments to the well-known time-shift technique for spray measurements.

Investigation of drying characteristics of low rank coal of bubbling fluidization through experiment using lab scale

Lignite is a low rank coal which is evenly distributed throughout the world and accounts for 45% of the total coal reserves. As it has a higher moisture content, its moisture content must be reduced in order to utilize it in power plant. In the present work, experiments on lignite has been done using a lab scale fluidized-bed reactor. Drying lignite through fluidized-bed reactor has a higher drying rate because there is good contact between particles and gas in the fluidized-bed reactor. Fluidized-bed drying can use air of 1.5 times of the minimum fluidizing velocity performance at bubbling fluidized-bed. Experiments have been performed on coal particle sizes of 0.3-1 mm, 1-1.18 mm and 1.18-2.8 mm, with operating temperatures being 100℃, 125℃ and 150℃, respectively. It is found that fluidization has a higher drying rate due to the heat transfer rate through air velocity. Hence, moisture content in lignite can be dried to a desired value with a time interval of 10 rain. The experiment through fluidized-bed reactor is expected to be useful for saving money and time.