摘要:

This paper emphasizes the established need for a stress based kiln control system. It refers to I) the work which verified that the initial shrinkage rate changes within a board are the result of reduced stress levels and 2) the new statistical method short/long-term slope comparison method used to detect slope changes. The paper continues by giving the explanation for the additional shrinkage slope changes as the equilibrium moisture content changes during fan reversal and kiln schedule advancements. The kiln schedule advancements can cause both shrinkage and swelling. Reduced drying rate resulting in reduced shrinkage rate explains other changes. A stress based automated kiln control system is conceptually possible with 1) shrinkage rate changes understood and 2) a production useful statistical method to detect these changes.

ISSN:0737-3937    

DOI:10.1080/07373930008917751

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

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.

ISSN:0737-3937    

DOI:10.1080/07373930008917752

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

For machine computation of drying, humidification and dehumidification processes it is necessary to have reliable correlations to predict transport and thermodynamic properties of the drying medium as functions of temperature and pressure. In this paper empirical correlations for specific volume, dynamic viscosity, thermal conductivity as well as specific isobaric heat capacity of superheated steam over the temperature range of 160-500°C and the pressure range of 100-500 kPa are presented. The Prandtl numbers at various temperatures and pressures are also presented. Comments on the properties and the use of these correlations are given.

ISSN:0737-3937    

DOI:10.1080/07373930008917753

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

From the time lumber is removed from the kiln to the time the remanufacturer uses it, it can be exposed to many different humidities With exposure to severe humidities, cupping in the final product can occur. This paper considers if humidity conditions during storage and transportation can significantly influence drying stresses and prong lest response. To determine the influence of exposure to different humidities, dried lumber was slowly equilibrated to 7,5% moisture content. It was than cut into blocks. The blocks were exposed to various humidity scenarios lo simulate actual storage and transportation conditions. Stress levels, moisture content and prong response were recorded. The analysis showed that stress level and prong response were strongly influenced by exposure to different humidities. The analysis also indicated that returning lumber to 7.5% equilibrium moisture content did not return the stress level or prong response to the original values. These combined results confirm that the prong test cannot be used as an indicator of how well the lumber has been dried or conditioned after it has been stored and transported. This makes seller/buyer disagreements difficult to resolve.

ISSN:0737-3937    

DOI:10.1080/07373930008917754

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In this work it is shown the application of an experimental method for estimating of time in bin cooling in a silo (7.40 m diameter, 7.60 m height) of com from continuous full-hot dryer. The cool-front evolution was observed with a measuring and acquisition data system. Ten NTC temperature-sensing devices were installed as pairs 2 m apart in a central cable type bus in parallel. The temperature was measured in an autonomous and intelligent module that converts the received signal to digital values and transmits it under demand to a central collector, allowing the access to periodic and request consults. The grain mass temperature was established at 11.8°C after 38 accumulated hours of cooling. This monitoring was given an adequate control of time of cooling needed to carry the grains until temperatures that ensure optimum conditions of conservation. On other hand, when the temperature for sure storage was reached, the following of this variable in real time allowed to observe tends and to analyze the changes on historic information of temperature inside the bin.

ISSN:0737-3937    

DOI:10.1080/07373930008917755

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Sugar cane fibers and arrangements of fibers in cylindrical bundles were dried in a thermoanalyzer and their diffusive coefficients were calculated using the slope method. The effect of temperature, moisture content as well as structural changes were analyzed. Diffusion coefficients changed nanlineariy with moisture content and followed an Arrhenius-like functionality with temperature. The analysis of these effects suggested a liquid diffusion transport mechanism of moisture transfer inside sugar cane fibers and bundles.

ISSN:0737-3937    

DOI:10.1080/07373930008917756

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Thin-layer re-wetting experiments were conducted with medium grain rough rice in the temperature range of 17.8 to 45°C and for relative humidities between 56 and 89.3%, with initial moisture contents in the range of 10.26 to 12.71% dry-basis to determine the diffusion coefficient of rough rice. Recent efforts to characterize the re-wetting characteristics of rough rice are summarized. New equation for temperature dependent liquid diffusion coefficients for medium grain rough rice are presented. The diffusion coefficient in re-wetting was lower than the drying. The results presented here, over typically five day re-wetting, will be useful in studying the longer term moisture transfer process occurring during ventilated storage.

ISSN:0737-3937    

DOI:10.1080/07373930008917757

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Experimental drying curves for Tunisia Deglet Nour dates were obtained in a laboratory dryer under different drying conditions The air temperature was varied from 30 to 69°C, relative humidity from 11.6 to 47.1 % and air velocity from 0.9 to 2.7 m/s. A numerical method to obtain a solution of a diffusion equation in which the diffusivity depends upon temperature and moisture content has been proposed to investigate the moisture movement in a date by assuming the sample to be a homogenous infinite cylinder. To rind the fitting moisture and temperature dependent diffusivity, the calculated drying curves are compared with the observed drying curves and an empirical equation for the moisture diffusivity of the date has presented as a function of temperature and moisture. It has been shown that the moisture distribution in the date during drying can be obtained by using the empirical equation presented.

ISSN:0737-3937    

DOI:10.1080/07373930008917758

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The desorption isotherms of apples of the Granny Smith variety, treated with 0.5% citric acid aqueous solution, were determined using the gravimetric static method. Experiments at three temperature levels: 20°C, 40°C and 60°C and ten water activity levels from 0.112 to 0.856 were carried out. Along with five well known models - modified Chung-Pfost, modified Halsey, modified Oswin, modified Henderson and GAB (Guggenheim-Anderson-de Boer), a new fraction-linear model has been applied to fit the data and to calculate the isosteric heat of desorption determination.

ISSN:0737-3937    

DOI:10.1080/07373930008917759

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Some Chinese popular vegetables are very low in the selenium(Se). The Se enrichment on these vegetables is very beneficial to the health of the local people. Drying and preservin¨g Se-enriched vegetables can provide a valuable food source. Preservation tests on sweet pepper, eggplant and cucumber enriched with Se by different drying methods of microwave, low-vacuum, heated airflow, and high-vacuum after freezing were conducted. Affecting curves have been developed for different drying temperatures. Effects of drying methods, initial selenium contents, sample moisture contents and blanching on keeping quality of Se-enriched sweet pepper bars are discussed.

ISSN:0737-3937    

DOI:10.1080/07373930008917760

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor