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The influence of heat transfer limitations on the properties of PET yarn produced by melt spinning
Includes abstract.
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| Main Author: | |
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
Department of Chemical Engineering
2014
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| _version_ | 1867613494683107328 |
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| access_status_str | Open Access |
| author | Kotze, Tyrone |
| author2 | Rawatlal, Randhir |
| author_browse | Kotze, Tyrone Rawatlal, Randhir |
| author_facet | Rawatlal, Randhir Kotze, Tyrone |
| author_sort | Kotze, Tyrone |
| collection | Thesis |
| description | Includes abstract. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/5304 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:37:02.852Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2014 |
| publishDateRange | 2014 |
| publishDateSort | 2014 |
| publisher | Department of Chemical Engineering |
| publisherStr | Department of Chemical Engineering |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/5304 The influence of heat transfer limitations on the properties of PET yarn produced by melt spinning Kotze, Tyrone Rawatlal, Randhir Chemical Engineering Includes abstract. Includes bibliographical references (leaves 121-126). The production of synthetic yarns requires a cost efficient process whilst simultaneously incorporating process methods which ultimately lead to a high quality fibre. A critical part of the production process is the spinning of the molten polymer into individual filaments which are brought together to form the filament bundle. During this process a quench air stream is blown across the filament bundle to aid in cooling the molten polymer. Here, heat transfer limitations may cause inter-filament property variations, which will adversely affect the quality of the yarn. This thesis focuses on the development of a model which allows for an a priori prediction of the influence of major process variables on the degree of fibre property uniformity. Fibre quality is characterised by the high degree of uniformity in the properties which affect the structural features of the yarn. Yarn morphology is dictated by the degree of crystallinity and molecular alignment of the polymer macro-molecules parallel to the fibre axis. These properties are strongly influenced by online tensile stress and local temperature which are, in turn, affected by heat transfer effects between the quench air and filament surface. A model that predicts the influence of heat transfer limitations on the uniformity of the as-spun fibre is therefore needed. Previous research in this field is limited with most work focussed on single filament model development. In this investigation, a monofilament model developed by previous workers (Jarecki et al., 2000) is integrated into a multifilament framework. This model assumes Newtonian behaviour of the polymer with viscosity strongly dependent on local temperature and crystallinity. The development of the multifilament model involves dividing the spinning zone into a number of cells, in which the filament properties are modelled using the monofilament model. The change in quench air temperature is estimated by means of an energy balance incorporating air flow terms and heat transfer through forced convection from the filament surface. A novel iteration approach is proposed in which the temperature of the quench air exiting each cell is iterated for until convergence is met. In simplifying the model, it was found that uniform quench air flow profile could be assumed, since the quench flow channel length was found to fall far short of the length required for turbulent flow to develop. However, it is known that increased contact time for heat transfer would occur if air were dragged down with the filament. Although modelling this effect is beyond the scope of the project, the heat transfer gradients are worsened by air-dragging and hence the model presented in this thesis reveals whether polymer uniformity is possible even under the best possible flow patterns. A negative result therefore indicates that non-uniformity will definitely occur. 2014-07-31T11:09:01Z 2014-07-31T11:09:01Z 2008 Master Thesis Masters MSc http://hdl.handle.net/11427/5304 eng application/pdf Department of Chemical Engineering Faculty of Engineering and the Built Environment University of Cape Town |
| spellingShingle | Chemical Engineering Kotze, Tyrone The influence of heat transfer limitations on the properties of PET yarn produced by melt spinning |
| thesis_degree_str | Master's |
| title | The influence of heat transfer limitations on the properties of PET yarn produced by melt spinning |
| title_full | The influence of heat transfer limitations on the properties of PET yarn produced by melt spinning |
| title_fullStr | The influence of heat transfer limitations on the properties of PET yarn produced by melt spinning |
| title_full_unstemmed | The influence of heat transfer limitations on the properties of PET yarn produced by melt spinning |
| title_short | The influence of heat transfer limitations on the properties of PET yarn produced by melt spinning |
| title_sort | influence of heat transfer limitations on the properties of pet yarn produced by melt spinning |
| topic | Chemical Engineering |
| url | http://hdl.handle.net/11427/5304 |
| work_keys_str_mv | AT kotzetyrone theinfluenceofheattransferlimitationsonthepropertiesofpetyarnproducedbymeltspinning AT kotzetyrone influenceofheattransferlimitationsonthepropertiesofpetyarnproducedbymeltspinning |