Heat Recovery from Dryer Exhaust Air

The classical problem of heat recovery from convective dryer exhaust air is considered under modern easy-to-programming techniques towards effective decision making environment. Heat exchangers as well as heat pumps are considered versus various dryer performance characteristics.     

Heat Recovery from Dryer Exhaust Air

Abstract

The classical problem of heat recovery from convective dryer exhaust air is considered under modern easy-to-programming techniques towards effective decision making environment. Heat exchangers as well as heat pumps are considered versus various dryer performance characteristics.     

RECENT DEVELOPMENT OF GHE SOLAR DRYING IN INDONESIA

Prototypes of greenhouse effect GHE solar dryer have been tested and their technical performances for drying of tropical products have been obtained. Quality of the dried products was comparable to the existing standard used in estate plantation. The latest drying experiment with fermented cocoa beans using mechanical stirrer, and with a stationary rectangular bin for coffee berries, showed that the developed drying system was capable of reducing the total specific energy to 6.2 MJ/kg and 5.2 MJ/kg water evaporated, respectively. Therefore, the results of the study suggest that the current design could now be used in helping the farmers and fishermen to produce better quality products.     

SIMULATION OF THERMAL AND DISINFESTATION CHARACTERISTICS OF A FORAGE DRYER

The thermal morality data for the cocoon stage of the insect Sitodiplosis mosellana (Gehin) were fitted to a normal distribution function and a probit viability equation was developed. The equation was included in a new tunnel dryer simulation program to compute the cumulative mortality of the insect during baled- forage drying. From the analysis it became clear that the temperature of dried forage remained at or above 60 C during drying and thus 99.99% kill of the insect was assured.     

硬脂酸脂肪酯作为温室控温相变材料的制备及性能研究

相变材料可对室内温度进行调控,采用酰氯醇解法将硬脂酸及直链脂肪醇合成系列硬脂酸酯(18-8,18-10,18-12,18-14)作为温室控温相变材料,并通过傅里叶变换红外光谱(FT—IR)、核磁共振(1H NMR)、差示扫描量热仪(DSC)、热重分析仪(TGA)、导热仪等对其结构、热性能及导热性能等进行了测定。结果表明:该系列硬脂酸酯的相变温度为22.2~44.8oC,相变焓为138.7~155.7 kJ·kg~(-1),并具有良好的热稳定性和导热性能,适于作为温室控温相变材料。     

An Experimental Study of Wheat Drying in Thin Layer and Mathematical Simulation of a Fixed-Bed Convective Dryer

Drying of wheat (Algerian cultivar: Hadba03) in thin layers was studied and mass flux phenomenon was used to characterize the thin-layer drying process. Thin-layer drying of wheat was determined for drying air temperature range of 40–60°C, relative humidity of drying air from 10 to 30%, air velocity of 0.7 m/s, and initial grain moisture from 26 to 31% (dry basis). Equilibrium moisture content of wheat was determined using desorption isotherms obtained from the thin-layer drying data. An equilibrium model for a stationary deep bed with drying air moving vertically upward was developed using mass and energy balance between grain and drying air in the bed and drying air characteristics obtained from thin-layer drying experiments. The developed model was validated by drying wheat in a laboratory dryer using different drying air temperatures and initial moisture contents.     

转筒干燥机热效率研究现状与趋势

本文介绍了近年来国内外转筒干燥机的改进情况,包括直接加热式、间接加热式转筒干燥机的结构优化、内部模型优化等方法。将现有的转筒干燥机的优化方法分类,针对如何提高干燥强度和热效率的问题进行了分析与讨论,并给出了提高转筒干燥机效率的研究方向。     

A review of “ FLUID DYNAMICS: THEORETICAL AND COMPUTATIONAL APPROACHES ” By Z.U.A. WARSI Published by CRC Press, 2000 Corporate Blvd. N.W. Boca Raton,Fl. 33431, U.S.A. 1992, 683 pages

ABSTRACT

A mathematical model is presented for exergy analysis of an industrial system for high-temperature forage drying. It allows qualitative analysis of the individual components as well as the entire system using a software package. This paper presents, as an example, the application of the model and the software, for forage drying, the changes of exergy and the basic elements and system operation quality indicators depending on the significant parameters.     

旋转闪蒸干燥机的设计

介绍了旋转闪蒸干燥机的结构、工作原理及相关参数的计算与确定。     

Optimization of Plate Dryer Design for Polyformaldehyde Production

Polyformaldehyde (POM) is a modern engineering plastic with excellent characteristics and there is a huge demand for it in China and the world. An industrial plate dryer process with nitrogen protection was newly developed to meet the emerging needs for big-scale and energy-efficient dryers in the production of POM. The plate dryer developed has a production capacity of 43 tons/day POM powder and a thermal efficiency of 78%. A field test report shows that the dryer allows a reliable and smooth operation and meets the quality specifications for POM powders.     

玻璃池窑的热平衡测试及节能评价

通过对玻璃池窑的热平衡测试、计算及分析,得到了该池窑玻璃液带出显热、潜热,池窑表面散热,观察孔口辐射散热、溢流气体显热以及烟气带走的显热等各项热指标。计算了玻璃液单位耗热、热效率、重油单耗及熔化率等主要技术经济指标。在这基础上,对该玻璃池窑的技术特点进行了分析和评价,最后,给出了今后进一步提高热效率的技术措施建议。     

AC-anodising of aluminium: Contribution to electrical and efficiency study

AC-anodising of AA1050 aluminium alloy in sulphuric and phosphoric acid solutions has been examined, with the contributions of the anodic and cathodic processes evaluated from the electrical signal analysis. The porous anodic film morphology and the potential-time behaviour confirm the similarity with DC-anodising, although lower anodic charge and film formation efficiencies are evident from gravimetric measurements. The anodic charge loss is mainly related to the capacitive current required to re-establish (between successive charge cycles) the electric field strength for ionic migration across the pre-existing and healed barrier layer oxide. Cathodic hydrogen gas evolution is considered to proceed at flaw sites in the barrier layer oxide, leading to high localized current densities that result in high cathodic potentials. Hydrogen gas retention at flaws and pores of the anodic film also contributes to the high cathodic potentials.     

Tailored thermal expansion and electrical properties of α-Cu2V2O7/Al

α-Cu₂V₂O₇/Al composites (with 5–80 wt% of Al) were prepared by a solid state method. Their structural stability, thermal expansion, hardness and electrical properties were studied in detail. The coefficient of thermal expansion (CTE) and hardness of α-Cu₂V₂O₇/Al composites sample can be tailored with the content of Al. The CTE is only 0.49×10⁻⁶ K⁻¹ (RT–780 K) when the Al content is 10 wt%, which is near-zero thermal expansion. The electrical conductivity of α-Cu₂V₂O₇/Al composites increases with increasing the content of Al. When the content of Al is larger than 40 wt%, the α-Cu₂V₂O₇/Al composites exhibit excellent electrical conductivity, which can be mainly attributed to the conductive percolation phenomena of Al in the α-Cu₂V₂O₇/Al composites.     

Online measurement and control of solids moisture in fluidised bed dryers

Currently, two main methods are used to take online measurement of the solids moisture in fluidised bed dryers, namely microwave resonance and near infrared spectroscopy. In this paper, a new online approach to solids moisture measurement of batch fluidised bed dryers by electrical capacitance tomography (ECT) is presented for the first time. Based on online measurement of solids moisture, it is possible to implement feedback control and process optimisation of batch fluidised bed drying processes, aiming to increase the operation efficiency and to improve product quality. A twin-plane ECT sensor with eight electrodes in each plane is mounted in the bottom of a glass fluidisation chamber. From the adjacent electrode pairs, the water content of the solids is estimated based on the correlation between the moisture content and the permittivity value. To reduce measurement error, the effect of temperature on moisture measurement is compensated. The fluidisation velocity is estimated by a semi-empirical function based on the measured water content. The acquired information is sent to a controller to adjust the air flow rate of the fluidised bed dryer. To validate the moisture measurement by ECT, a mathematical model has been developed, based on the measured temperature and relative humidity of the outlet air. The Landweber iteration method is applied to reconstruct images. The averaged solids concentration along the radial direction at different fluidisation conditions is given and compared with results by the linear back-projection (LBP) method. Results from batch drying processes with online measurement and feedback control are given and compared with no feedback control. To compare the operation efficiency, the thermal efficiency is considered and the results show the possibility of online control and optimisation of the fluidised bed drying processes, based on online measurement of solids moisture by ECT. Some challenges and future work are discussed.     

Electrical discharge machining of B4C-TiB2 composites

The interrelationships between the microstructure and electrical discharge machining (EDM) behaviour of B₄C-TiB₂ composites with respectively 30, 40 and 60 vol.% TiB₂ are investigated. Special attention was given to the influence of the grain size on the EDM behaviour by producing composites with an ultrafine TiB₂ phase using in situ synthesis during PECS. The experimental work revealed that 40 vol.% of TiB₂ results in an optimal material removal rate while the surface roughness for rough cut EDM decreases with increasing TiB₂ content. The finer microstructure of the ultrafine composite shows higher MRR's and lower R_a values than the commercial powder based composites. The major material removal mechanism for the PECS based composites was melting. The 3 point bending strength of all composites after grinding, EDM rough cut and EDM finish cut was not statistically different and about 800 MPa. The EDM recast layer was analysed by X-ray photoelectron spectroscopy.