PROPOSAL FOR A NOVEL CHEMICAL HEAT PUMP DRYER

ABSTRACT

A new chemical heat pump (CHP) system for ecofriendly effective utilization of thermal energy in drying is proposed from the viewpoints of energy saving and environmental impact. CHPs can store thermal energy in the form of chemical energy by an endothermic reaction and release it at various temperature levels for heat demands by exo/endothermic reactions. CHPs have potential for heat recovery and dehumidification in the drying process by heat storage and high/law temperature heat release. In this study, we estimate the potential of the CHP application to drying systems for industrial use. Some combined systems of CHPs and dryers are proposed as chemical heat pump dryers (CHPD). The potential for commercialization of CHPDs is discussed.     

A PROPOSAL FOR DIGITIZATION OF LIQUID-LIQUID DISTRIBUTION DATA

Abstract

A spline function has been employed to interpolate liquid-liquid distribution data by producing a function representing a smoothed curve through the points. The data for divalent metal extraction by trioctylamine, tributyl-phosphate and hydroxyoxime are examined in order to test the utility of interpolation with this function.     

PROPOSAL FOR A NOVEL CHEMICAL HEAT PUMP DRYER

A new chemical heat pump (CHP) system for ecofriendly effective utilization of thermal energy in drying is proposed from the viewpoints of energy saving and environmental impact. CHPs can store thermal energy in the form of chemical energy by an endothermic reaction and release it at various temperature levels for heat demands by exo/endothermic reactions. CHPs have potential for heat recovery and dehumidification in the drying process by heat storage and high/law temperature heat release. In this study, we estimate the potential of the CHP application to drying systems for industrial use. Some combined systems of CHPs and dryers are proposed as chemical heat pump dryers (CHPD). The potential for commercialization of CHPDs is discussed.     

A NEW MODEL FOR SINGLE-LAYER DRYING

This paper presents a new empirical model for single layer drying process, which was verified with selected experimental data. The present model is also compared with other single layer drying models available in the literature, using laboratory as well as field data from literature.     

A NEW MODEL FOR SINGLE-LAYER DRYING

ABSTRACT

This paper presents a new empirical model for single layer drying process, which was verified with selected experimental data. The present model is also compared with other single layer drying models available in the literature, using laboratory as well as field data from literature.     

A MODEL FOR THIN-LAYER DRYING OF LENTILS

A procedure was developed based on a three-component physical model to simulate the drying characteristics of Laird lentils. In this model, the cotyledons were simplified as a homogeneous slab where moisture transfer was governed by a one-dimensional diffusion equation, and the hilum and seedcoat were considered as two parallel routes for moisture to escape from a seed. The simulation procedure was verified with the experimental data from thin-layer drying testing on samples of 19.0 to 24.5% initial moisture content at temperatures from 23 to 80°C and relative humidities from 5 to 70%. Using previously obtained information on the transport properties of the cotyledons, the seedcoat, and the hilum, the simulation followed the drying data closely over temperatures between 23 and 60°C.     

A NEW MODEL FOR FLUID BED DRYING

ABSTRACT

A new model is proposed which calculates fluid bed drying curves without any adaptation of the Sherwood number between panicles and gas. Even the fine-structure of experimental data, i.e. the influence of bed height and gas flow rate, is predicted reliably. This is achieved by considering backmixing of the suspension gas in the kinetic parameter and not in the driving potential. A traditional derivation with reduced driving potential fails in the comparison with experimental results.     

A NEW MODEL FOR FLUID BED DRYING

A new model is proposed which calculates fluid bed drying curves without any adaptation of the Sherwood number between panicles and gas. Even the fine-structure of experimental data, i.e. the influence of bed height and gas flow rate, is predicted reliably. This is achieved by considering backmixing of the suspension gas in the kinetic parameter and not in the driving potential. A traditional derivation with reduced driving potential fails in the comparison with experimental results.     

A UNIFIED COLLOCATION ALGORITHM FOR PACKED-BED CHEMICAL REACTOR SIMULATION

Mathematical models of packed-bed catalytic reactors are aimed to predict the conversions and temperature profiles in both fluid and solid phases within the reactor. Although very general models can be mathematically formulated, usually several simplifying hypothesis are introduced for the fluid phase and/or the solid phase, in order to overcome computational difficulties

We describe in this paper a computational algorithm based on Orthogonal Collocation Method on finite elements, with elimination of the knot unknown functions, coupled with an integration method for stiff ordinary differential equations. This has been used in the development of a computer code, which allows us to find the transient behavior of the reactor by solving the equation relative to the external field, coupled with those describing the transient behavior in the catalyst particles, for a wide class of reactor models. The most general examined model includes axial dispersion in the external fluid phase, interphase mass and heat transfer resistances, intraphase mass resistance and any given kinetic scheme with complex reaction rate expressions.     

ANALYSIS OF RECENT PATENT LITERATURE ON DRYING AND DRYERS

ABSTRACT

A preliminary semi-quantitative analysis is made of the recent patent literature related to drying and dryers. United States patents granted in the period January 1998 to June 1999 were examined. For this preliminary study, only the abstracts were used to classify the patents by subject area and arrive at some general conclusions. An in-depth overview covering a larger database and full texts of the patents is required to confirm the results presented.     

A SIMULATION MODEL FOR SOLAR THIN-LAYER DRYING PROCESS

A mathematical formulation of the physical process of solar drying based on conventional heat and mass transfer equations is presented. The model Includes: a a technique of estimating the solar radiation on a south-facing tilted panel using the meteorological and geographical parameters for a typical location; b the procedures for obtaining the thermal performance of a solar air-heater for a flat-plate flow-over-absorber design; c an analysis of the drying process based on the Lewis analogy and the Equilibrium Moisture Content concept. Results predicted by the simulation model are presented.     

STRATEGIES FOR DRYING TOMATOES IN A TUNNEL DEHYDRATOR

A tunnel dehydrator can be operated using batch or semi-batch modes and while a batch mode is the simplest, it has the inherent characteristic of producing non-uniform moisture content. Although semi-batch mode does not have this problem, because all product experiences the same drying conditions, it is not used when drying tomatoes in Australia. The operation of most dehydrators is based on operator experience and rules of thumb, methods that are not likely to give optimum performance. A model that is suitable for simulating the operation of a tunnel dehydrator with any fruit has been developed. This model has been applied to the development of strategies for drying tomatoes with the objective of achieving optimum throughput, colour and drying efficiency. The results of these simulations are presented in this paper.     

A MATHEMATICAL MODEL FOR DRYING OF SHRINKING MATERIALS

ABSTRACT

A mathematical model has been developed to describe heat and mass transfer within materials undergoing shrinkage during drying. Both heat and mass transfer equations are solved simultaneously using a numerical technique A beat pump dryer has been used to conduct experiments to validate the model. Several samples were placed in the drver and after the commencement of each drying test one sample was taken oat at rceular time interval: The bone-dry mass of each piece was also determined. This enables to determine moisture distribution within the materials. Temperatures at different locations of the material were measured with thermocouples. The predicted temperature and moisture distribution within the material agreed fairly well with the experimental results.     

A PROPOSAL FOR TREATMENT OF TURBULENT MIXING IN A TWO-PHASE SUBCHANNEL FLOW

We propose a practical method for the treatment of turbulent mixing rate in a two-phase subchannel flow in a hydrodynamic non-equilibrium state. Based on the assumption that the fundamental modes of the inter-subchannel fluid transfer in such a state are turbulent mixing, void drift, and diversion cross flow, the turbulent mixing rate is considered to be equal to that in the hydrodynamic equilibrium state that the flow will attain. The applicability of the method is examined by experiments concerning the axial variation in tracer concentration in a non-equilibrium flow without diversion cross flow. A good agreement is seen between the calculations and the measurements.     

A MATHEMATICAL MODEL FOR DRYING OF SHRINKING MATERIALS

A mathematical model has been developed to describe heat and mass transfer within materials undergoing shrinkage during drying. Both heat and mass transfer equations are solved simultaneously using a numerical technique A beat pump dryer has been used to conduct experiments to validate the model. Several samples were placed in the drver and after the commencement of each drying test one sample was taken oat at rceular time interval: The bone-dry mass of each piece was also determined. This enables to determine moisture distribution within the materials. Temperatures at different locations of the material were measured with thermocouples. The predicted temperature and moisture distribution within the material agreed fairly well with the experimental results.     

STRATEGIES FOR DRYING TOMATOES IN A TUNNEL DEHYDRATOR

ABSTRACT

A tunnel dehydrator can be operated using batch or semi-batch modes and while a batch mode is the simplest, it has the inherent characteristic of producing non-uniform moisture content. Although semi-batch mode does not have this problem, because all product experiences the same drying conditions, it is not used when drying tomatoes in Australia. The operation of most dehydrators is based on operator experience and rules of thumb, methods that are not likely to give optimum performance. A model that is suitable for simulating the operation of a tunnel dehydrator with any fruit has been developed. This model has been applied to the development of strategies for drying tomatoes with the objective of achieving optimum throughput, colour and drying efficiency. The results of these simulations are presented in this paper.     

A DIFFUSIONAL MODEL FOR DRYING WITH VOLUME CHANGE

A diffusional model to study the drying process when volume change is significant is proposed. The effect of the foodstuff shape is taken into account. An empirical relation between moisture content and volume is presented. The resulting differential equations are numerically solved using a moving boundary finite differences technique. A good agreement between numerical results and experimental data is obtained.     

A DIFFUSIONAL MODEL FOR DRYING WITH VOLUME CHANGE

A diffusional model to study the drying process when volume change is significant is proposed. The effect of the foodstuff shape is taken into account. An empirical relation between moisture content and volume is presented. The resulting differential equations are numerically solved using a moving boundary finite differences technique. A good agreement between numerical results and experimental data is obtained.