ISSN:0737-3937    

DOI:10.1080/07373939508916988

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Designs of heat exchangers for heat recovery from humid air are described. A mathematical model for heat transfer with simultaneous mass transfer is constructed, based on heat and mass balances. Methods for solution are shown for two cases: 1. The water on the exhaust side of the heating surface is only condensate, whose heat content may be neglected. Also, the case of only partially condensing heat transfer surface is discussed. 2. The heating surface is flushed with abundant water. - Each case is illuminated with a calculation example.

ISSN:0737-3937    

DOI:10.1080/07373939508916989

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The technological properties of paper are strongly influenced by the drying conditions. This is the case in particular with M.G. paper and machine performance is limited largely for quality reasons. Therefore, the question as to which extent the drying conditions influence the process of drying and the paper quality is of major importance for industry.

ISSN:0737-3937    

DOI:10.1080/07373939508916990

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The aim of this work was to study mottling in offset printing. The papers studied were coated and princed LWC-papers.The base paper was obtained from a commercial source.Both macroscopic and microscopic analyses were performed.The conventional macroscopic methods take into account variations in nm-cm scale while the microscopic methods consider the nm-pm scale.

ISSN:0737-3937    

DOI:10.1080/07373939508916991

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Many models for simulation of paper drying in multi-cylinder dryer sections exist. In this work. three independently developed models are directly compared using the same reference data The models consired are the Texas A&M model, the Kuiosa model, and the VTT model. Predicted moisture contents plus cylinder and avenge web temperatures along the dryer section are presentcd for the different models. Predicted average evaporation rates during drying are also shown. Three major differences in the model details are highlighted. The effects of these differences on model accuracy evaluated by considering two different paper grades dried with two different machine geometries. This work is the first published direct comparison of different simulation models. The reference machine data provided can be used for comparison of these three models to other models.

ISSN:0737-3937    

DOI:10.1080/07373939508916992

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The development of a mathematical model and a computer program to facilitate the study of thc multi-cylinder paper drying process is presented. Experimentally determined values for different heat and mass transfer coefficients are used to ensure the physical validity of the model. A unique feature of the model is its inclusion of a mass transfer coefficient for the dryer fabric. Thus far. the mass transfer mechanisms in the web have not been included. Two heat transfer coefficients are used to tune the model to actual mill data. They areassigned values that are consistent with experimental data. The agreement between predicted and experimental data, obtained hom nine industrial paper dryers, is generally very good. The investigated basis weights range from 48 to 240 g/m2.

ISSN:0737-3937    

DOI:10.1080/07373939508916993

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Multi-functional radial jet reattachment blow boxes deliver a dry air into the pockets of the dryer section of a paper machine by impinging directly onto the unsuppned sheet in the open diaw. The air flow also maintains or improves the sheet swbility.

ISSN:0737-3937    

DOI:10.1080/07373939508916994

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper is dealing with the mass and heat transport phenomena inside the paper sheet and shows how to deal with shrinkage during drying. The aim is identifying the intrinsic material properties being relevant for internal mass and heat transport. Two approaches will be followed. The first one is based on the description of microscopic mechanisms for mass and heat transport in a porous material, e.g. Darcy flow for liquid due to capillary forces and vapour diffusion due to a vapour pressure gradient, heat flow as a result of the mass flow and a temperature gradient. The contribution of each mechanism in the overall mass resp. heat fluxes is quantified by means of mechanistic transport parameters, such as vapour diffusivity, Darcy permeability, etc. In the second approach the heat and mass fluxes are related to both temperature and moisture gradients and the contribution of each driving force is weighed by a lump transport parameter. Finally, the coupling between the mechanistic and lump parameters is worked out.

ISSN:0737-3937    

DOI:10.1080/07373939508916995

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

During the falling rate period of drying the heat requirements for drying hygroscopic materials may be increased substantially ahove the normal latent heat by the heat of desorption of water. In various new high intensity drying processes which are of increasing interest industrially, the drying material may reach quite high temperatures for periods of time sufficiently short that there is no degradation of the properties of the dried material. However the limited stability of many materials at high temperatures precludes determination of heals of desorption by direct measurements because of the long experimental times required for thermodynamic techniques. The present study develops a thermodymically valid method whereby heats of desorption determined at low lemperatures may be extrapolated reliably to the high temperatures where such information is needed but cannot be measured. A relation between isosteric heat of desorption and latent heat of water is derived in order to compare the new

ISSN:0737-3937    

DOI:10.1080/07373939508916996

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373939508916997

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor