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.     

THERMAL DYNAMICS OF A DRUM DRYER

The thermal dynamics of a top-loading drum dryer is studied with a view of deriving the transfer function for the thermal process involved. The drum which initially operates at a steady state, is subjected to a step change in the steam pressure and the response of the temperature of the outer surface of the drum is recorded. The normalised time domain response of the temperature T is analysed using the least squares method to a non-linear function. The time domain response is also transformed into the frequency domain using Fourier transforms and the transfer function is derived.     

THERMAL DYNAMICS OF A DRUM DRYER

The thermal dynamics of a top-loading drum dryer is studied with a view of deriving the transfer function for the thermal process involved. The drum which initially operates at a steady state, is subjected to a step change in the steam pressure and the response of the temperature of the outer surface of the drum is recorded. The normalised time domain response of the temperature T is analysed using the least squares method to a non-linear function. The time domain response is also transformed into the frequency domain using Fourier transforms and the transfer function is derived.     

MATHEMATICAL SIMULATION OF A NEWLY-DEVELOPED SEED-COTTON DRYER

The basic analitical method for so-called expression operation, the separation of liquid from solid-liquid systems by compression, are presented in view of the flow through compressible porous media. It has become evident that the expression mechanism consists of two flow phenomena. These types of phenomena can be analyzed by consideration of the flow mechanism through compressible porous beds, first by the filtration theory and second by the so-called consolidation theory. A simplified equation is also presented. It is shown that the simplified equation is well applicable to industrial expression problems even when the creep effects of matarials to be expressed are appreciable     

MATHEMATICAL SIMULATION OF A NEWLY-DEVELOPED SEED-COTTON DRYER

The basic analitical method for so-called expression operation, the separation of liquid from solid-liquid systems by compression, are presented in view of the flow through compressible porous media. It has become evident that the expression mechanism consists of two flow phenomena. These types of phenomena can be analyzed by consideration of the flow mechanism through compressible porous beds, first by the filtration theory and second by the so-called consolidation theory. A simplified equation is also presented. It is shown that the simplified equation is well applicable to industrial expression problems even when the creep effects of matarials to be expressed are appreciable     

UNSTEADY-STATE SIMULATION OF A MDLTI-STAGE CONCURRENT-FLOW MAIZE DRYER

An unsteady - state model of concurrent-flow maize drying was developed. It consists of a set of four partial differential equations (PDE) which are solved by finite differences. The PDE model was verified by comparing it to the steady-state concurrent-flow dryer simulation. The model was used for the development of a process model which in turn is to be employed for the design of an automatic control system of a two-stage concurrent-flow dryer.     

UNSTEADY-STATE SIMULATION OF A MDLTI-STAGE CONCURRENT-FLOW MAIZE DRYER

An unsteady - state model of concurrent-flow maize drying was developed. It consists of a set of four partial differential equations (PDE) which are solved by finite differences. The PDE model was verified by comparing it to the steady-state concurrent-flow dryer simulation. The model was used for the development of a process model which in turn is to be employed for the design of an automatic control system of a two-stage concurrent-flow dryer.     

SIMULATION OF A ROTARY DRYER FOR SUGAR CRYSTALLINE

Dynamic heat and material balances were developed, and residence time, heat and mass transfer rates were calculated using literature correlations. The model equations were solved numerically using the Speedup simulation package and tested against industrial data.

Comparison of model predictions with industrial data show that the model is accurate for steady state operation and predicts dynamic trends that are consistent with engineering judgment. Predicted outlet moisture and temperatures differ by about ±10 % from the industrial data.     

MATHEMATICAL MODEL DEVELOPMENT AND SIMULATION OF HEAT PUMP FRUIT DRYER

ABSTRACT

A mathematical model of a heat pump fruit dryer was developed to study the performance of heat pump dryers. Using the moisture content of papaya glace' drying, the refrigerant temperature at the evaporator and condenser and the performance, was verified. It was found that the simulated results using closed loop heat pump dryer were close to the experimental results. The criteria for evaluating the performance were specific moisture extraction rate and drying rate. The results showed that ambient conditions affected significantly on the performance of the open loop dryer and the partially closed loop dryer. Also, the fraction of evaporator bypass air affected markedly on the performance of all heat pump dryers. In addition, it was found that specific air flow rate and drying air temperature affected significantly the performance of all heat pump dryers.     

ELECTROCHEMICAL AND THERMAL SIMULATION OF A SOLID OXIDE FUEL CELL

The lack of accurate modeling of solid oxide fuel cells (SOFC's) and their systems has resulted in limitations in identifying key operating parameters and allowing for system configuration. The purpose of this study is to address each level of modeling needed to identify key parameters as well as integrating each level of modeling. The first level deals with the single cell and its electrochemical and thermal issues. The second level deals with the bundling of cells to form an SOFC stack while the third level incorporates the stack results into an overall thermal system.     

SIMULATION OF FORESTRY BIOMASS DRYING IN A ROTARY DRYER

Drying of forestry biomass in a rotary dryer has been performed. The raw material used was Erica Arborea belonging to the ever-green, broad leaves ecosystem which covers Central Greece and other Mediterranean countries. The study was part of a project concerning a Greek biomass pyrolysis demonstration plant where drying of biomass is very important in the contribution to the global energy balance and product yields of pyrolysis.

The study includes two parts. First, the experimental part concerns the influence of air flowrate, temperature, rotation speed and inclination of a laboratory rotary dryer to biomass residence time and biomass outlet moisture content. The second part concerns the development of a mathematical model for biomass drying in a rotary dryer. Experimental measurements in a rotary dryer were compared to the data from the model, in order to check the validity of the model.     

SIMULATION OF FORESTRY BIOMASS DRYING IN A ROTARY DRYER

ABSTRACT

Drying of forestry biomass in a rotary dryer has been performed. The raw material used was Erica Arborea belonging to the ever-green, broad leaves ecosystem which covers Central Greece and other Mediterranean countries. The study was part of a project concerning a Greek biomass pyrolysis demonstration plant where drying of biomass is very important in the contribution to the global energy balance and product yields of pyrolysis.

The study includes two parts. First, the experimental part concerns the influence of air flowrate, temperature, rotation speed and inclination of a laboratory rotary dryer to biomass residence time and biomass outlet moisture content. The second part concerns the development of a mathematical model for biomass drying in a rotary dryer. Experimental measurements in a rotary dryer were compared to the data from the model, in order to check the validity of the model.     

INDIRECT THERMAL DRYING OF LIGNITE: DESIGN ASPECTS OF A ROTARY DRYER

An investigation of the thermal drying of lignite has been carried out, by using an indirect heat pilot rotary drum. The process aims at the production of dry lignite and clean steam as part of a gasification procedure. Both flighted and bare drum modes have been employed. Temperature profiles along the dryer length, the amount of evaporation (moisture conversion) and the solids residence time distribution (RTD) were measured. A non-isothermal model was tested under three different regimes of solids flow. Model integration, by taking account of experimental amount of evaporation at dryer exit and temperature profiles along the dryer length, has been utilized in the validation of drying kinetics and heat transfer correlations. Model predictions compare satisfactorily with the operating data of an indirect heat industrial lignite dryer. Overall heat transfer coefficients of the pilot rotary dryer were found to agree well with those reported for direct heat dryers.     

MODELING AND OPTIMIZATION OF A DRYER

This study deals with the modeling and the search for the optimum production capacity of a tunnel-dryer of the Californian type. The model is obtained from the heat and mass transfer balances at two levels, the product (fruits) level and inside the tunnel itself. The optimum condition is given by the maximum production capacity of a plum dryer satisfying the final product quality. This choice is determined by the fact that a large amount of fruit must be dried in a short time to have a minimum of loss. Recirculation of a proportion of the exhaust air improves the dryer efficiently in terms of energy.     

MODELING AND OPTIMIZATION OF A DRYER

This study deals with the modeling and the search for the optimum production capacity of a tunnel-dryer of the Californian type. The model is obtained from the heat and mass transfer balances at two levels, the product (fruits) level and inside the tunnel itself. The optimum condition is given by the maximum production capacity of a plum dryer satisfying the final product quality. This choice is determined by the fact that a large amount of fruit must be dried in a short time to have a minimum of loss. Recirculation of a proportion of the exhaust air improves the dryer efficiently in terms of energy.     

INDIRECT THERMAL DRYING OF LIGNITE: DESIGN ASPECTS OF A ROTARY DRYER

ABSTRACT

An investigation of the thermal drying of lignite has been carried out, by using an indirect heat pilot rotary drum. The process aims at the production of dry lignite and clean steam as part of a gasification procedure. Both flighted and bare drum modes have been employed. Temperature profiles along the dryer length, the amount of evaporation (moisture conversion) and the solids residence time distribution (RTD) were measured. A non-isothermal model was tested under three different regimes of solids flow. Model integration, by taking account of experimental amount of evaporation at dryer exit and temperature profiles along the dryer length, has been utilized in the validation of drying kinetics and heat transfer correlations. Model predictions compare satisfactorily with the operating data of an indirect heat industrial lignite dryer. Overall heat transfer coefficients of the pilot rotary dryer were found to agree well with those reported for direct heat dryers.     

EXPERIMENTAL INVESTIGATION ON FLOW AND DRYING CHARACTERISTICS OF A VERTICAL AND SEMI-CYCLIC COMBINED IMPINGING STREAMS DRYER

Abstract

Flow characteristics of a vertical and semi-cyclic combined impinging streams dryer(VSCIS) was investigated. Results show that centrifugation and gravity have obvious influences on pressure drop and on momentum commutation between gas and particles in impingement zones. The effects of various operating parameters on water removal from particles have been studied experimentally. It is found that initial hot air temperature Tin, μ and initial moisture content of particles X₀ play important roles on water removal from particles. Based on the experimental data, dimensionless correlations for flow and drying characteristics in the system were obtained. VSCIS has shown to be a good way to overcome the shortcomings of single configuration of either vertical or semi-cyclic impinging streams. It can take full advantages of both arrangement to remove more water from particles.     

EXPERIMENTAL INVESTIGATION ON FLOW AND DRYING CHARACTERISTICS OF A VERTICAL AND SEMI-CYCLIC COMBINED IMPINGING STREAMS DRYER

Flow characteristics of a vertical and semi-cyclic combined impinging streams dryer(VSCIS) was investigated. Results show that centrifugation and gravity have obvious influences on pressure drop and on momentum commutation between gas and particles in impingement zones. The effects of various operating parameters on water removal from particles have been studied experimentally. It is found that initial hot air temperature Tin, μ and initial moisture content of particles X₀ play important roles on water removal from particles. Based on the experimental data, dimensionless correlations for flow and drying characteristics in the system were obtained. VSCIS has shown to be a good way to overcome the shortcomings of single configuration of either vertical or semi-cyclic impinging streams. It can take full advantages of both arrangement to remove more water from particles.     

DYNAMIC MATHEMATICAL MODEL OF A ROTARY DRYER: METHOD OF CHARACTERISTICS

A mathematical model for the dynamic behavior of a countercurrent rotary dryer has been developed and solved. The model consists of four hyperbolic partial differential equations with split boundary conditions. The equations are solved numerically using an algorithm based on the method of characteristics. The solution is stable and rapid. Sample results of a dryer simulation are presented.     

电石渣与石灰石热分解特性比较及电石渣热分解动力学

用热分析曲线比较电石渣和石灰石分解特性.通过热分析得到电石渣中氢氧化钙和石灰石中碳酸钙分解热耗分别为72.253kJ/mol和142.933kJ/mol;热力学计算氢氧化钙和碳酸钙理论分解热耗分别为101.625kJ/mol和166.232kJ/mol,热分析结果比热力学计算值低.采用Melak法求得电石渣中氢氧化钙分解的活化能Ea=124.01kJImoi,反应机理函数微分形式为,f(a)=(1-a)2/3(其中a为相应物质转化率),动力学因子为20.92.