Teaching mathematical modelling: a research based approach

A collaborative, research based laboratory experiment in mathematical modelling was included in a bioprocess engineering laboratory module, taught as part of an interdisciplinary program in biotechnology. The class was divided into six groups of three students and given the task of investigating a novel diafiltration process that is currently the focus of international research. Different aspects of the problem were assigned to each group and inter-group communication via email was required to ensure that there was a coherent set of objectives for each group and for the class as a whole. The software package, Berkeley Madonna, was used for all calculations. As well as giving the students an introduction to mathematical modelling and computer programming, this approach helped to illustrate the importance of research in bioprocess engineering. In general, the experiment was well received by the students and the fact that they were discovering new knowledge generated a degree of enthusiasm. However, many students were consumed by the technical demands of computer programming, especially the attention to detail required. Thus, they did not think too deeply about the physical aspects of the system they were modelling. In future years, therefore, consideration will be given to giving the student prior instruction in the use of the software

Using peer review to enhance the quality of engineering laboratory reports

Peer review of third year bioprocess engineering laboratory reports was introduced in an attempt to improve the standard of report writing in the BSc in Biotechnology degree programme at DCU. Preliminary results suggest that the review process leads to improved report writing skills. The student response to the initiative was very positive but it was strongly felt that the process should be anonymous. On average, marks awarded by students were higher than those awarded by the lecturer but there was a slight tendency to award more extreme marks

Is there a transition flux? Incorporating a research element into an undergraduate engineering laboratory

It is frequently remarked that the modern student has an excellent ability to recall information but cannot think independently and does not show initiative. While the secondary school curriculum is a major factor in this regard, it must be said that large parts of the third level experience perpetuate this problem. However, increased use of active learning, problem based learning and research-based learning should help to encourage independent thinking. In most degree courses in Engineering/Science, a final year project is the first true taste of scientific research encountered by undergraduate students. The final year research project can often prove an extremely daunting task, and the amount of time and effort required by the undergraduate student to settle into this new type of work can be detrimental to the work of the student on core subjects that are assessed by written examination. We present here the incorporation of real research into an engineering laboratory module taught in the third year of a Biotechnology degree program. This is achieved by challenging the students with a hypothesis to be investigated using the laboratory session, rather than the traditional prescriptive approach resulting in a defined laboratory report. Each laboratory group conducts their experiment using unique experimental conditions and the results are collated into a body of work to challenge the hypothesis presented to the students. The students learn to disseminate their results effectively by including the requirement that the report be constructed in the form of a journal article. By adopting this approach to teaching in the laboratory, students are introduced at an earlier stage to the skills needed to conduct meaningful scientific research. In particular, it encourages students to evaluate experimental data without bias. By performing experiments for which the outcome is not known in advance, student interest and enthusiasm is significantly increased

Dead-end filtration of yeast suspensions: correlating specific resistance and flux data using artificial neural networks

The specific cake resistance in dead-end filtration is a complex function of suspension properties and operating conditions. In this study, the specific resistance of resuspended dried bakers yeast suspensions was measured in a series of 150 experiments covering a range of pressures, cell concentrations, pHs, ionic strengths and membrane resistances. The specific resistance was found to increase linearly with pressure and exhibited a complex dependence on pH and ionic strength. The specific resistance data were correlated using an artificial neural network containing a single hidden layer with nine neurons employing the sigmoidal activation function. The network was trained with 104 training points, 13 validation points and 33 test points. Excellent agreement was obtained between the neural network and the test data with average errors of less than 10%. In addition, a network was trained for prediction of the filtrate flux directly from the system inputs and this approach is easily extended to crossflow filtration by adding inputs such as the crossflow velocity and channel height. An attempt was made to interpret the network weights for both the specific resistance and flux networks. The effective contribution of each input to the system output was computed in each case and showed trends that were as expected. Although network weights, and consequently the computed effect of each parameter, is different each time a network is changed (depending on the initial weights used in the training process), the variation was low enough for information contained in the network to be interpreted in a meaningful way

A project and competition to design and build a simple heat exchanger

To address a declining interest in process engineering, a project to design and build a compact heat exchanger was initiated in the second year of a four-year, multidisciplinary degree programme in biotechnology. The heat exchangers had a double-pipe configuration and employed plastic outer pipes and copper inner pipes of various diameters. Designs produced ranged from coiled inner pipes to various multi-pass arrangements and were assessed on the basis of heat transfer achieved per unit mean temperature difference per unit cost. The project, which also formed the basis of a competition, was very well received by students and gave them hands-on experience of engineering design and construction, as well as team work, problem solving, engineering drawing and the use of simple tools. Based on the success of this project, a similar problem based learning approach will be initiated in the third year of the same degree programme and will focus on bioethanol production

High-efficiency generation of nanomaterials via laser ablation synthesis in solution with in-situ diagnostics for closed-loop control

Driven by an ever-increasing demand for nanomaterials with specific functionalities, physical synthesis techniques such as Laser Ablation Synthesis in Solution (LASiS) have gained significant interest over in recent years. Commercial wet chemical synthesis methods, while having significantly higher nanomaterial yields than LASiS, typically have considerable negative environmental impact through the use of harmful reagents and solvents. LASiS therefore represents a route towards the sustainable “green” production of nanomaterials however the significant challenge to its commercialization is that of comparably low nanomaterial yields. Significant effort has been made towards increasing the production rates of LASiS, however many of the reported advances have relied on the use of high power (>20 W) or short pulse (<10 ps) laser systems which have high capital costs. Other advances have examined moving from batch production in small volumes towards the use of continuous production through the use of solvent flow systems. Combining these advances, we have developed a new system for nanomaterial generation via LASiS incorporating a low cost, low power (< 4W) Nd:YAG laser and solvent flow system for high-efficiency nanomaterial generation. This study has shown an increase in productivity from 2.5± 0.5 mg/hr for an 11 mL batch colloid, to continuous production yields of 17± 0.7 mg/hr under flow conditions

Development of a heat transfer and artificial neural networks teaching laboratory practical for biotechnology students

The paper describes a newly developed laboratory practical that teaches students how to develop an Artificial Neural Network model and its possible use in bio-processing. An emphasis is placed on giving students "hands on" experience with bio-processing equipment, namely bio-reactors and data acquisition systems in an attempt to help prepare them for work in bio-processing and chemical engineering industries

Engineering of pervaporation systems: Modelling of dehydration modules, including recycles

Assuming a concentration-independent flux with an Arrhenius dependence on temperature, and using temperature- and composition-averaged physical properties, an exact analytical expression is derived for the average flux in an adiabatic, single-pass pervaporation module. The envelope of industrially feasible operating conditions for alcohol dehydration systems is completed. The range of feasible activation energies of permeation is established for IPA-water and ethanol–water systems. Within this range a simple approximation to the exact analytical expression is derived. A parameter Jr/Jreheat is proposed where Jreheat is the flux at the retentate composition and feed temperature. It can be used to determine the optimum membrane area within an adiabatic module for systems with concentration-dependent flux and concentration-independent flux. Results indicate that permeate-to-feed ratios above the current industry norm of 5% are economically feasible in some cases. The impact of a recycle on the average flux, retentate composition, retentate temperature and permeate-to-feed ratio is explored. Equations are developed relating flowrates and compositions to the recycle ratio. A module is modelled for concentration-independent flux, concentration-dependent flux and desalination. The results indicate that increases in average flux can be achieved through use of a recycle for some industrial applications including desalination. Ó Súilleabháin, C., Foley, G., Engineering of pervaporation systems: Exact and approximate expressions for the average flux during alcohol dehydration by single-pass pervaporation, Sep. Purif. Technol. 152 (2015) 160–163. Santoso, A., Cheng-Ching, Y., Ward, J.D., Analysis of local recycle for membrane pervaporation systems, Ind. Eng. Chem. Res., 2012, 51, 9790-9802

Modelling the activity of seawater and implications for desalination exergy analyses

Exergy analysis has been applied to desalination membrane processes in an effort to characterise energy consumption and to optimise energy efficiency. Several models have been used to this end in the literature. One assumption that is common in these analyses is that of ideal solution behavior. However, seawater and other aqueous solutions of interest do not behave ideally. Indeed, even when ideal behavior is not assumed, there are several approaches to calculate these activity values, which are typically a function of the molality and ionic strength of the electrolytic solution. What is not clear from the published literature is the impact that the choice of activity calculation model has on the exergy analysis results. The objective of this research was to undertake the exergy analysis of a seawater membrane desalination plant using the Szargut chemical exergy approach and to compare the activity calculation approaches. The chemical exergy of the seawater was calculated using several activity coefficient modelling approaches including, (a) ideal mixture model, (b) the Debye-Huckel limiting law, (c) the Davies model, and finally, (d) the Pitzer model, which is more appropriate for higher ionic strength solutions such as seawater. The results showed considerable differences in the chemical exergy rates and the magnitude of chemical exergy destruction rates calculated using the various models. For example, there were percentage differences of 61.8% and 44.7% between the magnitude of chemical exergy destruction rates calculated using the Pitzer model when compared with the Debye-Huckel limiting law for the nanofiltration and reverse osmosis processes respectively

Stable nano-silver colloid production via Laser Ablation Synthesis in Solution (LASiS) under laminar recirculatory flow

As nanomaterials find applications in an increasingly diverse range of fields such as wastewater treatment, biotechnology and flexible electronics, the demand for nanomaterials with specific properties has increased. This increase is coupled with an increasing emphasis on nanomaterials with highly specific properties for specialised applications. Industrially, nanomaterials are produced via wet- chemical techniques which employ the use of solvents and reagents which are environmentally harmful. As we move forward with the use of nanomaterials, the ability to produce nanomaterials in a sustainable manner has become a topic of great significance. Towards this end, Laser Ablation Synthesis in Solution (LASiS) is a physical production technique capable of producing tailored nanomaterial colloids in a sustainable manner. These colloids are produced by ablating a solid target immersed in a solvent using a laser. Typically, LASiS is conducted in a batch process and in small volumes limiting commercial viability. To overcome this, there has been a move towards the use of continuous production via LASiS using flow systems. This allows an increase in nanomaterial yield, resulting in colloid concentrations approaching those of commer- cial colloids. This work investigates a new production technique incorporating a laminar recirculatory flow system to produce stable high concentration nano-silver colloids