摘要:

In this article a procedure for designing a multitray agricultural dryer, capable of producing uniform drying of product, is given. An analytical solution based on heat and mass transfer for air and product inside the dryer is used. In the solution, there is an attempt to keep the drying rates of the products on different trays constant during the whole drying period. This could be realized by changing the dryer shape and dimensions for every specific product in accordance with the conditions of the inlet air. It was found that a dryer of pyramidal shape is most suitable for fulfilling the requirement of good quality dried product. The method has been verified experimentally and shows good agreement with the analytical solution. Based on the obtained results, the design of a dryer for many kinds of fruits is obtained with the analytical solution.

ISSN:0090-8312    

DOI:10.1080/00908319708908860

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The binary (methane + pentane) and tricomponent (methane + butane + pentane) systems composed of individual gases of high purity have been researched. Then with help of mathematical methods of experimental data processing the moment of the more characteristic changes of the mass transfer process was discovered. Processing of experimental data for tricomponent system by statistical differentiation allowed the discovery of a pressure below of which lightening of the vented gas was observed.

ISSN:0090-8312    

DOI:10.1080/00908319708908861

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Four industrial coal-fired atmospheric fluidized bed systems used to produce process steam and hot oil were investigated. Chemical and particle size analysis of the coal, bed ash, and fly ash samples taken from the investigated fluidized bed systems were performed. Minimum fluidization velocity was calculated for each combustion system and compared to its operation velocity. The combustible parts of the fly ash samples were determined and related to the operation conditions. The reasons for inefficient combustion were indicated and some suggestions were made to increase combustion efficiency.

ISSN:0090-8312    

DOI:10.1080/00908319708908862

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This article presents an analytical model for analyzing transient heat transfer between a brick particle and air flow during heating in a fluidized bed combustor. Both experimental and theoretical studies were carried out. The experimental investigation provided the temperature distributions at the centers of the spherical particles during heating. These data were presented in the dimensionless form and were compared with the results of the present analytical model The modeling includes two heat transfer coefficient cases. In the first case, heat transfer coefficient is the only convection heat transfer coefficient, and in the second case, it is the sum of the convection and radiation heat transfer coefficients. In the comparison between experimental data and theoretical results, better agreement was found for the second case. The present results indicate that the radiation heat transfer coefficient has a significant effect on transient heat transfer from the single object and should be taken into consideration.

ISSN:0090-8312    

DOI:10.1080/00908319708908863

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The cost of supplying electricity in a grid is minimized in a nonlinear optimization framework The formulation of the problem gives the incentive-compatible trading prices of electricity among many independently operating state utilities. The problem is solved both for a central planner (central grid operator) and for the case of a slate planner (independent state utility). It is proved that there exist trading prices that are compatible with both. Finally, as an example, the theorem is applied to the case of the Indian National Grid.

ISSN:0090-8312    

DOI:10.1080/00908319708908864

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Finite-time thermodynamics is used to determine the maximum power output and the corresponding thermal efficiency for an irreversible closed-cycle Brayton heat engine. A realistic model is presented, which includes three types of irreversibilities: finite thermal conductance between the working fluid and the reservoirs, heat leaks between the reservoirs, and internal irreversibility inside the Brayton heat engine. The effects of heat leaks, hot-to-cold reservoir temperature ratios, and component efficiencies on the maximum power output and the corresponding thermal efficiency are studied. With component efficiencies less than 100%, the optimum ratio of the hot-end heat exchanger conductance to the total conductance of the two heat exchangers is found to be less than 0.5. Moreover, this ratio increases as the component efficiencies and the total conductance of the two heat exchangers are increased, and decreases as the hot-to-cold reservoir temperature ratio is increased.

ISSN:0090-8312    

DOI:10.1080/00908319708908865

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This investigation was concerned with the effects of coal properties and process variables, such as fluidized bed depth, superficial gas velocity, coal to magnetite feed weight ratio, and processing time, on coal cleaning efficiency in a bubbling fluidized bed dry coal purifier. The coal cleaning experiments were carried out on various size fractions of Pennsylvania's bituminous coal, Rushton coal. Angular magnetite was used as the host material to enhance segregation. The performance of the coal cleaning process was measured with the aid of sulfur and ash removal efficiencies. Previous experimental results and those obtained in this study showed that coal particle sizes smaller than 30 mesh and larger than 140 mesh can be cleaned with high efficiency in the fluidized bed separator. For coal particle sizes smaller than 140 mesh, bed slugging and channeling occurred due to high interparticle cohesive forces, resulting in a relatively poor cleaning performance. The results also indicated that the air fluidized bed should be operated using shallow bed depths and processing times of 30 s or more. Experiments were also performed to determine the optimum values of superficial air velocity and the effect of feed weight ratio of coal to magnetite on cleaning performance. It was observed that batch bed should be operated with a superficial air velocity between about 1.75 and 2.75 times the minimum fluidization velocity. However, coal cleaning performance in the case of a shallow bed of 3 cm was found to be relatively insensitive to the ratio of coal to magnetite feed weight.

ISSN:0090-8312    

DOI:10.1080/00908319708908866

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Concentrations of the elements As, B, Br, Cl, Cr, Mn, Na, Sb, Th, U, V, and Zn were determined in ply-by-ply samples from two sections of subbituminous coal from seam 3, Vesta Mine, Alberta Plains. The elemental mean concentrations in section 1 were As l.0 ppm, B 215ppm, Br 2.3ppm, Cl 29ppm, Cr 7.4ppm, Co 1.1 ppm, Mn 24.5 ppm, Mo 2.5 ppm, Na 4900ppm, Sb 0.4 ppm, Se 0.8 ppm, Ti 270 ppm, U 1.4 ppm, Th 2.8 ppm, V 2.9 ppm, and Zn 9.5 ppm. In section 2, the mean concentrations were As 0.7 ppm, B 201 ppm, Br 1.6 ppm, CI 24 ppm, Cr20ppm, Co 1.7 ppm, Mn 30.0ppm, Mo 2.8ppm, Na 4200ppm, Sb 0.3 ppm, Se 0.7ppm, Ti 340ppm, U 0.8 ppm, Th 1.8 ppm, V 4.4 ppm, and Zn 68 ppm. Total sulfur content averaged 0.44% in section 1 and 0.48% in section 2. Mean concentrations of these elements are low when compared to western Canadian coals of similar rank, or to world coals (Swaine, 1990). Antimony, barium, and boron are enriched, with the latter being a reflection of the coal-forming environment. Despite the short lateral distance between the sections (∼100 m), seam 3 in section 1 has slightly higher mean concentrations of As, B, Br, Cl, Na, Sb, Se, U, and Th than in section 2. Seam 3 in section 2 has slightly higher mean concentrations of Cr, Co, Mn, Mo, Ti, V, Zn, and S than in section 1. Elements were differentiated on the basis of their inorganic association, organic association, or intermediate (mixed) association. Thus, As, Ba, Cr, Mo, K, Na, and U in section 1 have a positive correlation with ash and aluminum contents of the coal, while Ca and Co show a weak to moderate relationship with ash content. Iron and Mn do not exhibit a clear relationship to ash in coal from section 1. In section 2, the elements As, Ba, Fe, Mg, Mo, K, Na, Th, U, V, Cr, and Co show a weak to strong relationship with ash content, while Ca and Mn show a moderate relationship. The halogens show a negative relationship with ash content in both sections. An inertinite-rich layer in section 1 has higher concentrations of Ca, Mn, and Fe, when compared to huminite-rich layers above and beneath. It also has the lowest boron concentration (25 ppm), lowest sulfur content (0.19%), and highest fixed carbon value in the section. The high boron concentrations in the Vesta Mine coals (mean is 208 ppm) indicate interaction of the peat with brackish waters during deposition, except for the inertinite-rich layer. The study also shows that sulfur content in coal does not always show a correlation to marine influence during coal formation. Perhaps, differences in the paleoenuiron-mental setting may be responsible for the boron/sulfur relationship in the Vesta Mine coals.

ISSN:0090-8312    

DOI:10.1080/00908319708908867

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Various policies and programs have been created to promote energy conservation in Asia. Energy conservation centers, energy conservation standards and labeling, commercial building codes, industrial energy use regulations, and utility demand-side management (DSM) are but a few of them. This article attempts to analyze the roles of these different policies and programs in seven typical Asian countries: China, Indonesia, Japan, Pakistan, South Korea, the Philippines, and Thailand. The conclusions show that the two most important features behind the success policies and programs are (1) government policy support and (2) long-run self-sustainability of financial support to the programs.

ISSN:0090-8312    

DOI:10.1080/00908319708908868

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor