Duncan Fraser

Engineering graduates’ perceptions of how well they were prepared for work in industry

This study investigated how well chemical engineering graduates perceive they were prepared for work in industry. To this end, sixteen interviews were carried out with a purposive sample of recent University of Cape Town chemical engineering graduates. Qualitative analysis of the interview data showed that graduates felt that overall, they were well prepared for work in industry. They perceived their strengths to be their technical background, problem solving skills, formal communication skills and life-long learning abilities. The following areas of weakness were also identified: work in multi-disciplinary teams, leadership, practical preparation and management skills. The use of interviews for data collection is a significant departure from the methods used in other studies in this area. The rich and contextual data gathered from the interviews justified this choice and contributed to the identification of issues not previously mentioned in the literature. For example, an unexpected finding of the study was that there was a clear link between the technical and non-technical attributes of engineering graduates, a result which has clear implications for the design of undergraduate engineering programmes.

Capital cost targets for mass exchange networks A special case: Water minimisation

Abstract Pinch analysis has been applied to mass exchange network synthesis. Until now, minimum utility targets have existed, but not capital cost targets. Previous work minimised the number of units in a network, but this paper shows that this does not necessarily minimise the capital cost. This paper focuses on the special case of water minimisation. It considers a simple example involving a network of absorption columns which use water to remove sulphur dioxide from a set of gas streams. The paper describes the first known method for targeting the minimum number of trays in the network, based on a specified ‘minimum composition difference’. This is then translated into a capital cost target. An interactive design method is presented which allows the targets to be approached to within 5%. The example is then extended to demonstrate how the targets can be used to trade off capital and operating costs in order to optimise the network before design. A further extension deals with multiple water sources. This work may be extended to other absorbents and generalised to other mass exchange networks.

Capital and total cost targets for mass exchange networks: Part 1: Simple capital cost models

Abstract This part of the paper builds on the developments of Part 1. It starts by developing a targeting method for tray columns using detailed capital costing methods. The number of units, column diameters and tray spacings, and the distribution of units and trays will all be considered. The limitations of stages targeting are also discussed, leading to an explanation of why stages targets may be beaten, and showing how continuous contactors are more analogous to heat exchangers than stagewise contactors. A procedure for determining capital cost targets for networks of continuous contactors (usually packed columns) is then developed. Networks featuring different exchanger specifications are also dealt with. As before, capital cost targets are combined with operating cost targets to give total annual cost targets. The design of networks to meet the targets is then discussed. Systems featuring significant differences in exchanger specifications may require some deviation from ideal (vertical) driving force use. The examples presented in this part of the paper demonstrate that the targets are accurate enough for preliminary design as well as pre-design optimisation. The work in both parts of this paper reduces the amount of design work required when evaluating processes at the conceptual stage.

Learning as acquiring a discursive identity through participation in a community: improving student learning in engineering education

In this paper, we propose that learning in engineering involves taking on the discourse of an engineering community, which is intimately bound up with the identity of being a member of that community. This leads to the notion of discursive identity, which emphasises that students’ identities are constituted through engaging in discourse. This view of learning implies that success in engineering studies needs to be defined with particular reference to the sorts of identities that students develop and how these relate to identities in the world of work. In order to achieve successful learning in engineering, we need to recognise the multiple identities held by our students, provide an authentic range of engineering-related activities through which students can develop engineering identities and make more explicit key aspects of the discourse of engineering of which lecturers are tacitly aware. We include three vignettes to illustrate how some of the authors of this paper (from across three different institutions) have applied this perspective of learning in their teaching practice.

Using a Variation Approach to Enhance Physics Learning in a College Classroom.

This article describes an exploration into improving the process and the outcome of learning in interactive teaching at the first-year university physics level, using what is becoming widely known as the “variation approach to learning.” To explore this approach we chose an area of mechanics that is widely known to pose learning difficulties for students—Newtons third law. Test and interview data provided compelling evidence that explicit use of variation made a difference in student learning outcomes.

Teaching in higher education through the use of variation: examples from distillation, physics and process dynamics

Contemporary learning research and development that is embedded in primary and secondary schooling is increasingly acknowledging the significance of a variation approach for enhancing the possibility of learning. However, the variation approach has so far attracted very little attention in higher education, but where it has, the results have been most worthwhile and encouraging. In this article, aspects of the approach that are useful for higher education are described and illustrated using three examples: learning distillation in third-year chemical engineering using a computer simulation, learning Newtons third law in first year physics using an interactive class session, and a proposal for teaching and learning a particular application of Laplace transforms in process dynamics. It is contended that explicit use of variation enhances the possibility of learning for students.

The use of minimum flux instead of minimum approach temperature as a design specification for heat exchanger networks

Abstract In this paper it is proposed that a minimum flux be used in the synthesis of heat exchanger networks as the basic design parameter to be varied in evaluating the utility/area trade-off. The minimum flux replaces the minimum approach temperature which will be derived for each stream from the minimum flux and the stream heat transfer coefficient. This eliminates the multi-variable optimisation which results when stream-dependent minimum approach temperatures are used. Values of minimum flux in the range 1000–3500 W/m 2 are recommended. Typical values of stream heat transfer coefficient for different types of streams lead to a wider range of minimum approach temperatures than have been used in the past. This approach is applied to two practical examples.

A New Approach to Modelling Student Retention through an Application of Complexity Thinking.

Complexity thinking is relatively new to education research and has rarely been used to examine complex issues in physics and engineering education. Issues in higher education such as student retention have been approached from a multiplicity of perspectives and are recognized as complex. The complex system of student retention modelling in higher education was examined to provide an illustrative account of the application of complexity thinking in educational research. Exemplar data was collected from undergraduate physics and related engineering students studying at a Swedish university. The analysis shows how complexity thinking may open up new ways of viewing and analysing complex educational issues in higher education in terms of nested, interdependent and interconnected systems. Whilst not intended to present new findings, the article does illustrate a possible representation of the system of items related to student retention and how to identify such influential items.

Supply-based superstructure synthesis of heat and mass exchange networks

Abstract A new simultaneous mixed integer non-linear programing (MINLP) approach to heat exchange network synthesis (HENS) and mass exchange network synthesis (MENS) is presented. This supply-based superstructure (SBS) approach uses the supply temperatures/compositions of all the streams (including utilities) present in the synthesis problem to define heat/mass exchange superstructure intervals. The intermediate temperatures/compositions are variables used in the optimization of the network total annual cost (TAC). The ability of each stream to exchange heat/mass in any interval in the SBS is subject to thermodynamic/mass transfer feasibility. The paper presents the mathematical formulations for optimizing the TAC for HENS and MENS. The SBS synthesis technique has been applied to nine literature problems involving both HENS and MENS. The solutions obtained are in the same range as those in the literature, with one solution being the lowest of all.

NEW HYBRID METHOD FOR MASS EXCHANGE NETWORK OPTIMIZATION

A new hybrid optimization method is presented that is fairly robust and can be accomplished in an automatic way. The main idea is using integer cuts and bounds, based on driving force plot analysis, for the lean streams to decrease the possibility of being trapped in local optima. A new initial solution is constructed if the MINLP solution is infeasible; otherwise the earlier found best solution is used. In consequence, the MINLP model is modified in the iteration steps. The iteration is stopped when the total annual cost (TAC) in the solution reaches 1.1·TACtarget.