摘要:

The degradation of product quality during convective drying depends on the temperature and water concentration history of the panicles and drying time. For improving product quality in combination with acceptable operation costs, optimal control of the operation variables is required.

ISSN:0737-3937    

DOI:10.1080/07373939608917111

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The continuously operated Mechanically Spouted Bed (MSB) dryer of high evaporative capacity can be advantageously used to produce fine powder from paste-like materials, slurries, suspensions and sludges. Due to the thin layer formed on the surface of the spherical inert particles intensive heat and mass transfer occur and the drying process takes place in the constant rate period. Steady state drying conditions can be achieved when the total operational time of partial processes of inert bed drying does not exceed the cycle time of the inert particles.

ISSN:0737-3937    

DOI:10.1080/07373939608917112

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Research trials were carried out over a two year period in an industrial skim milk powder production plant to examine the benefits of using an in-line viscometer rather than in-line density meter to control the degree of skim milk concentration in an evaporator prior to spray drying.

ISSN:0737-3937    

DOI:10.1080/07373939608917113

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Single droplets were dried whilst suspended from a rotating thermocouple in a horizontal wind tunnel, to study the effect of skin formation upon the retention of flavours. Native rice starch, wheat starch, or dextrin were used to encapsulate ethanol as a simulated flavour. The ethanol content of the dried droplets was measured using gas liquid chromatography and the crusts were examined using a scanning electron microecope. The effects of variations in encapsulant concentration, drying air temperature, and air flow rates upon flavour retention were determined.

ISSN:0737-3937    

DOI:10.1080/07373939608917114

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The retention of ethanol as a simulated flavour was determined by drying single droplets in a horizontal wind tunnel, with fructose, reconstituted skim milk or coffee as the flavour encapaulant. Droplet temperature histories, ethanol content, and crust structure were evaluated for each encapsulant. No enhancement of volatile retention was obtained with the fructose eolutions irrespective of initial concentration, air velocity, or air temperature. Enhancement of the volatiles retention with the coffee and skim milk solutions correlated with an increase in initial solide concentration. resulting from selective diffusion phenomena and the formation of a resistant skin. In both cases air velocity had no significant effect upon volatiles retention. Skin forming materials with similar characteristics would be advantageous for flavour retention.

ISSN:0737-3937    

DOI:10.1080/07373939608917115

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Ethanol retention in solutions was determined by drying single droplets in a horizontal wind tunnel, with gelatine (Bloom numbers 60 and 150) and gum arabic as encapaulants. The variation in ethanol content, droplet temperature history and crust structure were evaluated in each case. General conclusions are provided for parameters determining volatile- retention in convective drying.

ISSN:0737-3937    

DOI:10.1080/07373939608917116

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Batches of wddv rewened to 18% or 24% moisture content were dried in a sealed rotating drum containing ; preheated sand. For each initial moisture content, all combinations of the following variables were replicated three times: sand patilcle size (0.3 and 0.6mm). residence time (60, 120 and 180 s), sand-to-grain mass ration ( 3:1, 6:1 and 9:1) and initial sand temperture ( 100, 150 and 200°). The dried paddy was shelled and milled and the percentage of whole grain kernels was determined. In general. the paddy starting at 18% mc led to lower final moisture contents than that starting at 24%. For equivalent final moisture contents, milling yields of whole rice were equivalent. Best yields were generally associated with lower energy input (ie. low to intermediate initial sand temperature and sand-to-grain mass ratios below 4.7:1) Residence time was not critical in determining milling yieid. This study indicates that particulate medium drying of paddy is an interesting alternative to traditional drying since it greatly accelerates drying timee without reducing milling yields. Solar preheating of the sand could permit substantial energy savings.

ISSN:0737-3937    

DOI:10.1080/07373939608917117

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Intergranular air movement and its relation with moving drying fmnt in a grain bulk were investigated experimentally. An improved computer simulation model was developed to analyze the drying or cooling process in a bed of grain with non-parallel airflow from a partially or slanted perforated floor. The model first simulates the airflow, then calc lates the heat and mass transfer between air and grain along the airflow streamlines. The results were compared with the simulated and experimental results from a fully perforated floor configuration. The degree of agreement between the computed and the experimental moisture contents depended upon the floor configuration. The model was not capable of predicting the temperatures to the accuracy of the predicted moisture contents, especially when airflow stream lines were not parallel to each other. For further improvement of the drying simulation model, an improved airflow model and computer program is required. Comparison of the simulated results with experimental data also

ISSN:0737-3937    

DOI:10.1080/07373939608917118

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A model is presented to describe the moisture transport inside a partially saturated porous material. The transport is caused by vapour diffusion and liquid diffusion. The evaporation inside the porous material is described with a mass transfer coefficient and a specific evaporating surface. Predictions of the model for moisture profiles are compared to experimentally oblained profiles found in the literature. The model needs further extension in the form of incorporating sorption isotherms.

ISSN:0737-3937    

DOI:10.1080/07373939608917119

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This naver analvzes the surface emission coefficient corresponding to anv diffusion coefficient expressed as an exponential function of the concentration diffusing substance in capillary porous solids. Theoretical equations for surface emission coefficient for both sorption and desorption are presented. Procedures to derive the diffusion coefficient and to verify the corresponding surface emission coefficient are made using experimental sorption data of aspen (Populur sp.) wood. It is of interest to note that the theoretical models for diffusion and surface emission coefficients can be established and/or evaluated using the same set of experimental dara.

ISSN:0737-3937    

DOI:10.1080/07373939608917120

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor