The proposed research methodology consists of four stages:
1. Review of research background, making hypothesis and definition of scope 2. Framework and software tool development
3. Testing and validation of research concept and case studies 4. Discussion and research conclusions
The methodology adopted is in line with those commonly used within typical engineering research (John W. Creswell, 2003). Figure 6.1 provides an overview of the research approach, highlighting how various elements of the research are grouped within the four stages.
6.3.1 Review of Research Background, Research Questions and Define Scope
The initial research assertion “How do we identify the quantity, quality and availability of waste heat energy from a manufacturing process, and determine the most appropriate technology for recovery?” was defined based on the author’s prior knowledge and a number of industrial visits one of which was to a chemical etching facility and the other to a large automotive engine casting plant. The knowledge was then further developed by conducting an extensive review of the literature, regarding the energy management systems within manufacturing, state-of-the-art technologies used for waste energy recovery and current research carried out in this field. During the establishment of the research background for the thesis, via literature survey and industrial visits, it became apparent that just like the proactive and reactive approaches that are adopted for materials recycling, there was also an opportunity for energy to be considered via the reactive approach to explore energy recovery, options including tools and technologies that are capable of harnessing waste energy and reutilising this within a manufacturing environment. The research assertion was then refined to acknowledge that waste energy recovery is an area of broad aspects, including waste mechanical, light, sound, and chemical energy which are generally more difficult to harvest and of insignificant value compared to waste heat which is easier to recover and is of more benefit to the manufacturers There are numerous waste heat recovery technologies on the market, however because of the lack
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of knowledge and informed decision making, industrial waste heat is often not recovered in a systematic and therefore optimised way.
6.3.2 Research Activities and Framework Development
The final establishment of the aim, objective and scope of the research led the work into the second stage (i.e. Research activities and framework development). Based on the definition of research assertion and questions, the research is focused on the development of a framework for waste heat energy recovery, by which different scenarios of waste heat sources, sinks and recovery technologies can be defined, assessed and compared. From the research objectives, the evaluation methodology adopted in the framework is required to evaluate quantity and quality of waste heat energy source in a manufacturing facility with quantitative and qualitative descriptors such as temperature, pressure, contaminant, temporal availability etc., so as to compare the waste heat sources with suitable uses within a factory. Subject to the information obtained from the comparison between waste heat sources and potential uses, the framework also allows for identification of appropriate methods and technologies to harness waste heat provided by the knowledge of technology database from extensive literature survey and waste heat energy survey. This provides a structured approach, identifying advantages and disadvantages of each method and technology, and visually compares many different solutions to give decision making guidance for complex problems. Interpretation of obtained information and calculation is also required to process data and make informed decisions for industries to quickly react. Thus a software tool is implemented to aid the framework in an accessible way. In addition, information provided by a cost and benefit analysis also enables evaluation of economic and environmental impact for the chosen solution in order to provide an optimised decision.
6.3.3 Testing and Validation of Research Concept and Case Studies
After the framework was structured, the software tool required validation by case studies. The objective of carrying out this additional step was to test the software with practical issues by gathering real data and its ability produce consistent results. In order to verify the performance of the framework and software tool, two different cases examples were carried out. In this thesis one example is in the low temperature manufacturing industry while another example focuses on a high temperature processes. The purpose of having such arrangement of case studies is to: 1) validate the functionality of the framework and software tool when applied to the two extreme ends of the spectrum, and 2) to compare recoverability, economic benefit and reutilisation method of each case. The use of case studies to validate the framework and software tool allows findings to be analysed and further improvement of the framework, potential iteration process to be incorporated within
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the decision making system. A systematic approach was developed to conduct both of the case studies with data from both provided and collected via onsite sources.
6.3.4 Discussion and Research Conclusions
The completion of the case studies marks the start of the final stage of the research which discusses all research results documented in the thesis in order to draw overall conclusions. The purpose of the discussion is to explain the results and their potential implications and limitations. It also scrutinises the results obtained and discusses the possible influence of methodological biases and errors on data validity. The discussion also addresses general limitations and weakness of the study and comments on these. The conclusions section summarises the answers to the research questions and assertions raised in Chapter 2, which then leads to the generation of concluding statements based on the findings.
6.4 Chapter Summary
This chapter has identified the different types of research utilised in the thesis, based on the requirement to address the research aim and objectives identified in Chapter 2. The research methodology adopted in the thesis has been presented by following the aforementioned general overview. The four stages of research methodology have been illustrated schematically, showing the stepwise development of this thesis. The research supported by the first stage of the methodology is reported in the earlier part of the thesis, in Chapters 1-5. Similarly, stages two and three of the research methodology are documented in Chapters 7-9 and Chapters 10-11 respectively, and finally Chapters 12 and 13 cover the fourth stage of the research methodology. Although the methodology presented in Figure 6.1 suggests a linear progression through the four stages defined in this section, it is acknowledged that research has an iterative nature, such that specific aspects may require revisiting and refinement in light of new findings, as the research progresses.
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Waste Heat Recovery Framework
Chapter 7
7.1 Introduction
This chapter introduces a framework that has been generated by this research to aid manufacturers in making decisions regarding the most suitable solution to recover waste heat from their activities. The framework describes a methodology to identify sources of waste heat throughout a manufacturing plant, production processes and product levels, and provides an overview of waste heat hotspots within the production system. This analysis is used to highlight opportunities for heat recovery, by capturing available waste heat with suitable recovery technologies and reuse, recycle or energy storage options in order to improve overall energy efficiency.