摘要:

In order to reduce cross machine (CD) moisture deviations and their detrimental effects in tissue production, control components are more frequently used today. The CORRECTA hood, a high temperature/high velocity hood with an integrated correction system, is described. It controls both wet and dry streaks by re-distributing the drying capacity of the hood. Test results from a commercial installation in a twin wire tissue machine are reported. The experimental data agree to a great extent with theoretical calculations undertaken beforehand to predict the correction potential of the CORRECTA hood. Economic evaluation shows a high return on investment for such a CD moisture profile control unit.

ISSN:0737-3937    

DOI:10.1080/07373938608916323

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The functioning of a conventional heated platen laboratory press for paper or board press dry experiments is considered analytically and in the light of experimental results from the literature. A press dry sample dries so that the evaporation zone recedes from the edges toward the center. Since the dwell time of the web within a certain moisture content range influences the resulting strength characteristics, a conventional press dry experiment will not produce a uniformly strong web. To study the possible distribution of the strength deviation, a strength development function is generated and used in computer simulation of a web being press dried. The results emphasize the importance of dwell time as a factor in press dry strength devel oprnent. Finally, basic principles are reviewed or evolving an improved press dry laboratory device, and a model is proposed.

ISSN:0737-3937    

DOI:10.1080/07373938608916324

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The theory of radio frequency and microwave heating is presented with particular regard to moisture profile correction of paper and board. The electrical parameters, and the aspects of heat and mass transfer relevant to this form of drying are discussed and thence a mathematical model developed. This model is validated against experimental results taken from industrial installations. The major factors in the design of r.f. equipment for moisture profiling are detailed.

ISSN:0737-3937    

DOI:10.1080/07373938608916325

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

High-intensity contact drying denotes drying under suf- ficiently intensive heating conditions that, following a brief warmup period, the mist paper web operates at internal tem- peratures in excess of the ambient boiling point.A simplified, two-zone analytical model is first presented. The paper is depicted as having a dry layer, of ever-increasing thickness, adjacent to the hot surface. Heat conduction through this layer (the rate-limiting step) causes evaporation at the interface with the “wet zone.” The vapor is then considered to flow through the wet zone into the ambient.Results of bench-scale experiments are discussed. Drying rates as much as twenty times conventional rates are indicated. The drying rate increases with hot surface/boiling point tem- perature difference and applied mechanical pressure. The instsn- taneous drying rate decreases continuously after a brief warmup period. The vapor pressure at the hot surfacelpaper interface rises quickly to a peak value, followed by a continuously- diminishing level. The heat flux shows a rapid rise to boiling- like conditions, followed by a drop to a range compatible with measured drying rates. The temperature of the open side of the sheet is constant during drying, after its initial rise to the boiling point. The experimental results are compatible with pre- dictions of the model.

ISSN:0737-3937    

DOI:10.1080/07373938608916326

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This paper describes and diacusses various impinging jet systems used commercially to aerodynamically support flat sheets (e.g. paper web). Certain design aspects of auch systems are discussed. Some mass transfer results are also presented.

ISSN:0737-3937    

DOI:10.1080/07373938608916327

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The structure of a conventional Mollier’s psychrometric chart is described. The mathematics of the perspective transformation is presented. The humidity range of the transformed i,x -diagram is from 0 to ∞ and the temperature range from -20° to 400° The use of the diagram for drying calculations is illustrated.

ISSN:0737-3937    

DOI:10.1080/07373938608916328

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373938608916329

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373938608916330

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373938608916322

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor