Environmental considerations have led to the phase out of chlorofluorocarbon (CFC) refrigerants from the domestic refrigeration industry. One intriguing aspect is that the chlorine in CFCs is a good lubricating agent and any deterioration of system performance may adversely influence other environmental considerations. Based on the above, the aim of this research is to address the sustainable development of domestic refrigeration systems using the replacement refrigerant HFC-134a. The work focuses on the emissions that may arise if the electrical consumption of the product deteriorates or its durability is curtailed. Tribological characteristics on compressor components influence both of these product attributes and therefore a thorough system analysis was carried out. An in-house built experimental test rig, which monitored slight variations in the electrical power drawn by a reciprocating hermetic compressor, was used under different experimental conditions. Furthermore, a detailed life cycle assessment on a domestic refrigerator was performed to help quantify the ensuing environmental burdens. In this way, a relation between tribological characteristics, power consumption and environmental impact was studied. Results have shown that the CFC substitute will increase friction and wear characteristics on the aluminium alloy connecting rod and the steel gudgeon pin. These characteristics led to an increase in the electrical energy consumption of the compressor such that the indirect global warming implications are set to rise with HFC-134a. If the sustainable development of this product is to be ascertained then a change in refrigerants alone will not suffice. New design considerations, primarily aimed at servicing and extending the life of the hermetic compressor itself, are considered. This work helps stimulate new ideas to address environmental issues influenced by traditional engineering disciplines. For this reason additional future research work, which will help determine these implications further, is outlined.

International environmental concern led to the control and phase out of traditional chlorofluorocarbon refrigerants (CFCs) under the terms of the Montreal protocol. CFCs used in domestic applications were initially replaced with hydrofluorocarbons (HFCs) such as R134a which has a zero ozone depletion potential (ODP). The use of HFCs has also come under scrutiny as they have high global warming potential (GWP) and inferior thermodynamic and lubricating properties and have been replaced by hydrocarbon (HC) refrigerants such as R600a in much of the domestic European and Asian markets. Despite this, there has been little research into the long-term environmental consequences of their application. Domestic refrigeration compressors were analysed to ascertain the tribological contact conditions for both R600a and R134a systems. A novel pressurised micro-friction test machine was developed to simulate the tribological conditions of the critical components using aluminium on steel samples. Refrigerant charges of R600a with mineral oil (MO) and poly-ol-ester (POE) lubricant and R 134a with POE were tested for their tribological performance within the test rig. Experimental tribological information is presented from the physical test procedures to establish wear mechanisms and friction coefficients within the critical components. The tribological performance is used to predict deterioration in energy consumption and system durability. Results indicate that for higher contact stresses R600a MO charges provide a lower wear regime than R600a and R134a POE charges. At lower contact stresses the R600a and R134a POE charges provide a very low wear, very low friction regime. Despite contact conditions lead to a faster deterioration in durability, hence increase in energy consumption compared to the R600a system.

The application of computers in the manufacturing industry has substantially altered the control procedures used to program a whole manufacturing process. Currently, one the problems which automated manufacturing systems are experiencing is the lack of a good overall control system. The subject of this research has been centred on the identification of the problems involved in current methods of control and their advantages and disadvantages in an automated manufacturing system. As a result, a different type of control system has been proposed which distributes both the control and the decision making. This control model is an hybrid of hierarchical and hierarchical control systems which takes advantage of the best points offered by both types of control structures. The Durham FMS rig has been used as a testbed for an automated manufacturing system to which the hybrid control system has been applied. The implementation of this control system would not have been possible without the design and development of a System Integration Tool (SIT). The system is capable of real-time scheduling of the system activities. Activities within the system are monitored in real-time and a recording of the system events is available, which allows the user to analyse the activities of the system off-line. A network independent communication technique was developed for the Durham FMS which allowed the manufacturing cells to exercise peer-to-peer communication. The SIT also allowed the integration of equipment from different vendors in the FMS.

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The work reported in this thesis is related to the development of a generic model for a 'make-to-stock’ manufacturing organisation. This research is based upon the hypothesis that every type of manufacturing company should have a generic model. The objectives of the model are first, to help SNIEs (Small and Medium sized Enterprises) who cannot afford external help and second, to fulfil the need for modelling that arose from a review of modelling literature. These were the basic driving forces in carrying out this research and from which the objectives are derived. A survey of various system design and analysis methods was carried out. Initially SSADM, SADT, IDEFO, NMRISE, STRIM and GRAI were selected for the study. The reason for the selection of these methods was that each contained graphical tools and fulfilled the requirements for modelling. Further investigation showed GRAI and IDEFO to be the most suitable methods for modelling manufacturing systems and these were selected for further investigation. A direct comparison of the GRAI and IDEFO methods was carried out using a case study. The results of this indicated that the GRAI method was the most suitable for the analysis and design of manufacturing systems and demonstrated advantages over the IDEFO method. For this reason the GRAI method was selected and applied to case study 'make-to-stock! manufacturing organisations. The case studies demonstrated that several similar characteristics existed in 'make-to-stock’ manufacturing organisations, supporting the hypothesis of the research. The case studies also indicated that the application methodology had some significant drawbacks. On the basis of this investigation, a detailed methodology to apply the GRAI method was formulated and validated using a further detailed case study. After the methodology had been validated, it was used to develop a generic model for a 'make-to-stock' manufacturing organisation. The model developed presents the activities carried out at the strategic, tactical and operational levels of the management hierarchy. Details of typical decision horizon and review periods are also included in the model. The thesis presents the first detailed methodology for applying the GRAI method and first application to develop a generic model. It also presents the first detailed comparison between the IDEFO and GRAI methods. The findings of this research and recommendations for future work are presented in the final chapter.

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