SOME FUNDAMENTAL ATTRIBUTES OF FAR INFRARED RADIATION DRYING OF POTATO

ABSTRACT

Drying experiments were carried out using a far infrared heater to examine the drying characteristics of potato slices. The effect of several parameters e.g. radiation intensity, inlet air velocity and relative humidity on moisture and temperature history are presented. FIR drying of potato was observed to be a falling rate process. Drying rates were negatively correlated with air velocity. Relative humidity did not influence the drying rate. It was found that the modified exponential law describes the moisture removal of potato within an acceptable range.     

CTA中空纤维反渗透膜的远红外辐射干燥

本文介绍了三醋酸纤维素（ＣＴＡ）中空纤维反渗透的远红外辐射干燥试验结果及其设备的结构特点，试验结果表明，ＣＴＡ中空纤维反渗透膜远红外辐射干燥可提高其脱盐率，探索最佳干燥条件有可能简化中空纤维反渗透组的生产过程或进一步提高中空纤维反渗透组件的性能。     

基于远红外辐射特性陶瓷坯体的干燥机理

近年来红外干燥技术的应用已深入到各个生产领域之中,针对陶瓷干燥机理进行了探讨.红外辐射源发出的远红外线,被陶瓷坯体吸收之后,产生激烈的共振现象,使辐射能直接转化为热能,坯体温度升高,水分蒸发而达到快速干燥的目的.     

COMBINED CONVECTIVE AND INFRARED DRYING OF A CAPILLARP POROUS BODY

Abstract

This work investigates the effect of spray drying conditions on some properties of tomato powder prepared by spray drying of tomato pulp. A pilot scale spray dryer (Buchi, B-191) with cocurrent regime and a two-fluid nozzle atomizer was employed. Sixty-four different experiments were conducted keeping constant the feed rate, the feed temperature, and the atomizer pressure, and varying the compressed air flow rate, the flow rate of drying air, and the air inlet temperature. Tomato powders were analyzed for moisture, solubility, density (bulk and packed), and hygroscopicity. Analysis of experimental data yielded correlations between powder properties and the above-mentioned variable operating conditions. Regression analysis was used to fit a full second order polynomial, reduced second order polynomials and linear models to the data of each of the properties evaluated. F values for all reduced and linear models with an R ² ≥ 0.70 were calculated to determine if the models could be used in place of full second order polynomials.     

PROCESS DRYING PRACTICE

ABSTRACT

Drying experiments were carried out using a special microwave surface to examine the drying kinetics of corn and potato samples. The process of internal moisture and heat transfer was analyzed in the light of the experimental data obtained. The effects of several dielectric field parameters were also studied. It was found that the modified exponential law describes the water removal proc-ess of both materials within an acceptable confidence range when the specific microwave performance is the driving force for the internal moisture movement. Furthermore, the inner composition of the materials determines their reaction to the effect of microwave fields.     

EFFECT OF INFRARED IRRADIATION ON DRYING CHARACTERISTICS OF WET POROUS MATERIALS

ABSTRACT

We studied infrared drying characteristics of wet porous materials by comparison with the convective drying characteristics, and our attention was focused on the factors influencing their characteristics. By selecting three kinds of membrane filters, we examined the influences of the mean pore diameter and the spectral distribution of irradiation power as variables using a far-infrared heater and a near-infrared heater. The differences between the infrared and convective drying characteristics (drying rate, sample temperature, water content distribution) were experimentally obtained, and the influence of mean pore diameter of the sample on its drying characteristics was observed only in infrared drying but in convective drying. By measuring the diffuse transmittance of the membrane filter in consideration of the drying process, we deliberated that infrared radiation penetrating into the drying sample was absorbed directly by the water in the voids, and that the water vaporized there.     

DRYING CHARACTERISTICS OF GELATINOUS MATERIALS IRRADIATED BY INFRARED RADIATION

ABSTRACT

As a food model for infrared drying, a gelatinous bed composed with agar-gel and powder was used. To study the influences of the bed conditions, the emissivity of the powder materials and their initial-volume fractions were considered. To study the influence of the radiative heat source, the spectral distribution of irradiation power was examined. We selected three kinds and several initial-volume fractions of powders (alumina, silver and stainless steel) and used two types of infrared heaters (a far-infrared heater and a near-infrared heater). Infrared drying of the gelatinous bed was performed, and a heat transfer model for infrared drying of the gelatinous bed was constructed. The model-calculation results were compared with the experimental results, and agreed with the experimental results consistently for FIR drying and qualitatively for NIR drying. The present study shows a fundamental guideline on the application of infrared radiation to the drying operation.     

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.     

DRYING OF BIOLOGICAL PRODUCTS WITH SIGNIFICANT VOLUME VARIATION. EXPERIMENTAL AND MODELING RESULTS FOR POTATO DRYING.

ABSTRACT

This work is devoted to the experimental investigation and theoretical modeling of biological products with high initial moisture content which implies significant volume contraction. Firstly, experimental equipment which was designed to continuously determine variations in the global moisture content and in the temperature of the sample is introduced. Furthermore, the equipment is controlled by a PC which records experimental information in real time. In particular, measurement of the radial and temporal distributions of moisture content and temperature during the drying process of the homogeneous porous media potato are given. The mean moisture content and temperature curves are also given.     

EFFECT OF OSMOTIC PRE-TREATMENT AND INFRARED RADIATION ON DRYING RATE AND COLOR CHANGES DURING DRYING OF POTATO AND PINEAPPLE

A combination of intermittent infrared and continuous convection heating was used to dry various osmotically pretreated sample of potato (in solutions of 10%, 20% and 30% NaCl) and pineapple (in solutions of 30%, 50%, 70% Brix). The effect of drying conditions on color changes of potato and pineapple was investigated. The Hunter color scale parameters (redness, yellowness and lightness) were measured to quantify the color changes. With appropriate choice of infrared intermittency as well as osmotic pretreatment, it is possible to reduce the overall color change while maintaining high drying rates. As expected, osmotic pretreatment resulted in a shift in the sorption isotherms for both products.     

EFFECT OF OSMOTIC PRE-TREATMENT AND INFRARED RADIATION ON DRYING RATE AND COLOR CHANGES DURING DRYING OF POTATO AND PINEAPPLE

A combination of intermittent infrared and continuous convection heating was used to dry various osmotically pretreated sample of potato (in solutions of 10%, 20% and 30% NaCl) and pineapple (in solutions of 30%, 50%, 70% Brix). The effect of drying conditions on color changes of potato and pineapple was investigated. The Hunter color scale parameters (redness, yellowness and lightness) were measured to quantify the color changes. With appropriate choice of infrared intermittency as well as osmotic pretreatment, it is possible to reduce the overall color change while maintaining high drying rates. As expected, osmotic pretreatment resulted in a shift in the sorption isotherms for both products.     

SIMULATION OF INFRARED DRYING PROCESS

ABSTRACT

A control volume formulation for the solution of a set of two-way coupled heat and diffusive moisture transfer equations with an infrared source term is presented in three dimensions. The solution procedure developed uses a fully implicit time stepping scheme for the solution of the coupled set of equations and is applied to study the infrared drying of potato using two different drying systems. The maximum deviation between experimental and simulation results were 9.0°C in temperature for potato drying, and 10% (d.b.) for moisture predictions. The overall predictions agreed well with the available experimental data from the two systems and show a good potential for application in infrared drying of food grains and biomaterials.     

SIMULATION OF INFRARED DRYING PROCESS

A control volume formulation for the solution of a set of two-way coupled heat and diffusive moisture transfer equations with an infrared source term is presented in three dimensions. The solution procedure developed uses a fully implicit time stepping scheme for the solution of the coupled set of equations and is applied to study the infrared drying of potato using two different drying systems. The maximum deviation between experimental and simulation results were 9.0°C in temperature for potato drying, and 10% (d.b.) for moisture predictions. The overall predictions agreed well with the available experimental data from the two systems and show a good potential for application in infrared drying of food grains and biomaterials.     

PULSED MICROWAVE-VACUUM DRYING OF FOOD MATERIALS

ABSTRACT

Microwave drying of food materials has been investigated over several years as a potential means for reducing the total drying time. However, some quality loss almost always accompanied when foods were dried completely using microwaves due to nonuniform temperature and moisture distribution. Some strategies used to improve dried product quality include combination of microwave and conventional hot air drying. pulsed or intermittent drying, and microwave-vacuum drying. Combination of pulsing and vacuum drying is a useful technique to maximize energy use efficiency and product quality especially for temperature sensitive products such as fruits. Some results of pulsed, microwave-vacuum drying of cranberries are presented. Pulsed drying is more energy efficient than continuous drying. In pulsed drying, the longer the pulsing ratio (i.e. longer power-off time in relation to power-on time) was more energy efficient. The quality of pulse-dried product was also generally better than that of continuous-dried product. The cycle power-on time and pulsing ratio should be carefully selected to obtain maximize the benefits of pulsed, microwave vacuum drying     

EXPERIMENTAL INFRARED DRYING STUDY OF A MODEL WATER-BASED EPOXY-AMINE PAINTING COATED ON IRON SUPPORT

ABSTRACT

The aim of this work is to study the infrared drying and curing kinetics of a model water-based epoxy-amine painting coaled on iron support. After a presentation of the model painting elaborated in our laboratory, experimental and theoretical data of the curing kinetics are presented. Then, we described the special laboratory-scale infrared dryer set up in our laboratory. This dryer was able to carry on drying experiments with uniform infrared flux densities between 0 to 25 kW,m^-2 The study of the painting drying as a function of the infrared flux density and of the film thickness shows the influence of these two main physical parameters.     

含水粒子层的红外线干燥

用数值和实验两种方法研究了玻璃球粒子层的红外线干燥特性．首先建立了基于一维假设下的热量和质量传递的动态数学模型,并用有限差分法进行数值求解.得到含水率、温度与时间的关系曲线和干燥特性曲还建立了一套实验装置,测量了干燥过程中含水率和层内温度随时间的变化曲线．计算结果与实验结果吻合很好．结果表明,层内温度分布和干燥速度受辐射线波长、入射热量、粒子直径、粒子层厚度的影响．远红外线比近红外线具有更高的能量效率和干燥速度．     

远红外聚丙烯纤维的力学特性

分析了远红外聚丙烯（ＰＰ）纤维的拉伸性能、形态结构及有色远红外ＰＰ纤维的力学性能。结果表明,在拉伸过程中,随拉伸倍数的提高,纤维的断裂强度不断提高,伸长降低较多,纤维的模量和耐热性有些增加,纤维截面形态结构是均匀和充实的。随着纤度的降低,纤维的力学性能迅速增加,有色远红外ＰＰ纤维仍能保持优良的力学特性。     

过渡金属氧化物体系红外辐射陶瓷的研制

采用常规相烧结法制备了Ｆｅ２Ｏ３－ＭｎＯ２－Ｃｏ２Ｏ３－ＣｕＯ系过渡金属氧化物陶瓷及其分别与堇青石和高岭土组成的复合体系陶瓷,研究了材料的结构及其在８～１４ｕｍ波段的常温红外辐射率。研究结果表明,过渡金属氧化物陶瓷的常温红外辐射率达到０．９３０,反尖晶石及混合尖晶石结构的形成是过注金属氧化物陶瓷中产生高的红外辐射率的内在原因。在复合体系陶瓷中获得了０．９１０～０．９３０的常温红外辐射率,其中过渡金     

远红外功能陶瓷的防污性能研究

在陶瓷釉浆中添加多功能健康陶瓷材料，经研磨、施釉，制得辐射远红外线功能陶瓷。用板磁共振技术(NMR)研究了远红外功能陶瓷的防污机理。结果表明：远红外功能陶瓷可活化水，降低水分子缔合度，增强油污的乳化效果。从而避免油水分离现象的产生，达到陶瓷制品的防污目的。     

DRYING KINETICS OF SOME FRUITS

ABSTRACT

Drying kinetics of four Fruits (namely, apple, pear, kiwi and banana) were studied by introducing an one-parameter empirical mass transfer model, involving a characteristic parameter (drying constant), as a function of process variables. The model was tested with data produced in a laboratory dryer, using non-linear regression analysis. The investigation involved a wide range of characteristic dimensions of samples and air conditions (temperature, humidity, and superficial velocity). The parameters of the model considered were found to be greatly affected by sample characteristic dimension and air temperature. The model also involved the equilibrium material moisture content which was formulated in the form of the GAB equation. Its parameters were evaluated by means of non-linear regression analysis to independent experiments covering two process variables (temperature and water activity of the surrounding air).