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The global energy system faces a dual challenge; the need for more energy and less carbon emission. Out of the 50 billion tonnes of greenhouse gases emitted each year, 24.2 % comes from energy use in industries such as processing and manufacturing that require constant heating and cooling. Heat transfer improvements in heating and cooling industries cause energy saving thus reducing operational costs, increase the operational life of heat transfer systems and reducing greenhouse gas emissions. While nanofluids usage in heat exchangers presents a critical step for emission reduction, several factors including instability of suspended nanoparticles, the effect of a surfactant on physical property measurements and combining nanofluids with inserts have not been adequately assessed. This thesis investigates the use of highly conductive nanofluids as a potential alternative to conventional working fluids with low thermal conductivity, such as water, currently used in heat exchangers for heating and cooling systems. A distinguishing feature of this study is the consideration of the effect of surfactants on the stability of nanofluids, the physical properties of the nanofluids and the thermal performance of the nanofluids. The use of nanofluids in combination with hiTRAN® heat transfer inserts was also investigated. Activated carbon (C), copper oxide (CuO) and alumina (Al₂O₃) nanoparticles were suspended in distilled water (H₂O) and Ethylene glycol (EG). Surfactants were added including sodium dodecyl benzene sulfonate (SDBS), cetyltrimethyl ammonium bromide (CTAB), sodium lauryl sulphate (SDS) and Arabinogalactan (ARB) to create 20 combinations of nanofluids. ARB as a surfactant kept C/H₂O and CuO/EG nanofluid stable for 29 days. Whereas CTAB and SDBS surfactants kept C/H₂O and Al₂O₃/H₂O nanofluids stable for 17 and 11 days respectively. Viscosity results showed that in some cases the surfactant caused a slight increase in viscosity and in some cases viscosity decreased.

The ocean covers approximately 70 % of the earth’s surface and contains an immense source of renewable energy, in terms of ocean waves. However, this resource is unevenly distributed throughout the world, and so, therefore, converting waves into a useful form of energy will require the identification of potential Wave Energy Farm (WEF) locations. This should be undertaken in tandem with selecting an appropriate Wave Energy Converter (WEC), as the characteristics of these devices are critical in capturing the available wave power. This thesis presents a novel integrated methodology to select and assess potential installation sites for WEFs, identify appropriate WECs, and overcome the limitations of current methods. Original contributions of this thesis include: (i) a robust method for identifying generic WEF sites based on the dimensions of sustainability, which includes a cultural dimension, and utilises limiting conditions to reduce large study areas; (ii) a suite of MATLAB tools—which thoroughly assesses potential WEF sites, in terms of the available resource as well as temporal, directional, and spectral characteristics; (iii) a WEC database which identifies all devices currently in development; and (iv) a WEC classification scheme that classifies devices in a practical and meaningful manner in order to streamline the selection process of WECs for wave energy projects. Several of the developed methods have been applied to a New Zealand (NZ) case study. Results confirm that with the application of the proposed site selection method, that 12 suitable WEF sites, clustered within four regions along the west and south coast of NZ, were identified from the initial study area of approximately 4.1 million km². In terms of site assessment, the utilisation of the MATLAB tools established that a higher-energy area comprised the south of NZ and that as expected, the available resource at all sites was subjected to seasonal variability, with a maximum and minimum wave power a

In a large industrial processing plant, a significant amount of process heat is generated using fossil fuels, contributing to New Zealand’s overall greenhouse gas emissions. While New Zealand’s renewable energy sources present potential alternatives to fossil fuels, reducing the process heat demand of industrial processing plants is another critical step for emissions reduction, with multiple long-term economic and environmental benefits. Reducing process heat demand often centres on retrofitting the heat exchanger network to improve heat recovery and lower the hot utility consumption. This thesis presents a comprehensive automated retrofit design method for heat exchanger networks, fulfilling several gaps in current knowledge. The novel contributions are presented and discussed in four main chapters: (1) two retrofit tools are developed that enable visualisation of the problem – the Modified Energy Transfer Diagram and the Heat Surplus-Deficit Table, (2) an algorithm called Automated Retrofit Targeting that searches for all possible retrofit modifications of the heat exchanger network that unlocks energy savings, (3) a comprehensive energy retrofit planning tool that uses a multi-stage retrofit analysis to provide strategic long-term and cost-effective retrofit plans, and (4) an heat exchanger network simulation method, incorporating using Monte Carlo Simulation, to quantify the effect of variable process flows and temperatures on flexibility and steady state performance. The developed methods are illustrated using a simple four-stream network and then applied to two industrial case studies that are representative of some of the large industrial energy-users in New Zealand: a paper mill at a Kraft pulp and paper mill cluster and a petrochemical complex. In both case studies, numerous potential retrofit designs have been identified. These options are reduced to those that ranked as the most cost-effective, using thermodynamic and economic constraints with Pareto fro

Process industries in New Zealand use 214.3 PJ of process heat, of which approximately 65 % is fossil fuels. Despite increasing energy demands, depleting fossil fuel resources, and pressure to reduce Greenhouse Gas emissions, low grade heat in large-scale processing sites is still not fully utilised. This thesis presents methods to target, optimise and design more practical heat recovery systems for large industrial sites, i.e. Total Sites, and overcome technical limitations of current methods. Original contributions of this thesis to literature include novel developments and applications in six areas: i) a new Total Site Heat Integration (TSHI) targeting method – Unified Total Site Targeting (UTST) – which sets realistic targets for isothermal and non-isothermal utilities and heat recovery via the utility system; ii) a new TSHI optimisation and utility temperature selection method to optimise Total Cost of the utility system; iii) a new Utility Exchanger Network synthesis and design method based on the targets achieved by the UTST method and optimal temperatures from optimisation method; iv) a new method for calculating assisted heat transfer and shaft work to further improve TSHI cogeneration and performance; v) examination of heat transfer enhancement techniques in TSHI to achieve higher heat recovery and lower required area by substituting conventional utility mediums by nanofluids in the utility system; and vi) a spreadsheet software tool called Unified Total Site Integration to apply the developed methods to real industrial cases. The developed methods have been applied to three large industrial case studies. Results confirm that heat recovery and utility targets obtained from the UTST method were lower but more realistic to achieve in practice when compared to conventional TSHI methods. The three industrial case studies represent a wide variety of processing industries. In summary, the over-estimation of TSHI targets for the three case studies from using the

Dairy processing is critical to New Zealand’s (NZ) economy producing NZ$13 billion in exports for 2012 while consuming 32 PJ of fossil fuels for process heat. Three quarters of NZ dairy exports are milk powders. This thesis presents methods to reduce process heat use in Milk Powder Plants (MPP) through improved heat integration and addresses key technical challenges preventing industrial implementation. My original contributions to literature include: (1) a novel design method called the Cost Derivate Method (CDM) that cost optimally allocates area in direct heat exchange networks, (2) a new design methodology for integration of semi-continuous process clusters using a Heat Recovery Loop (HRL) with a Variable Temperature Storage (VTS) system for improved heat recovery, (3) an experimentally validated deposition model for predicting critical air conditions that cause milk powder fouling, and (4) a thermo-economic assessment tool for the optimisation of industrial spray dryer exhaust heat recovery projects via a Liquid Coupled Loop Heat Exchanger (LCHE) system. By applying Pinch Analysis to an industrial MMP, this work confirms that heat must be recovered from the milk spray dryer exhaust air (~75 °C) to achieve maximum heat integration in MPPs. For stand-alone MPPs exhaust heat is best used to indirectly preheat the inlet dryer air reducing steam use by 12.7 % for a 55 °C exhaust outlet. Additional economic heat recovery from condensate and vapour flows decreased steam use by a further 6.9 %. Application of the CDM to the liquid and vapour sections of new MMP maximum energy recovery networks reduced total cost by 5.8 %. For multi-plant dairy factories, a second industrial case study showed the exhaust heat may be integrated with neighbouring plants via a HRL with VTS to increase site heat recovery by 10.8 MW including 5.1 MW of exhaust heat recovery, compared to 7.9 MW using a conventional HRL design method with constant temperature storage. A key barrier preventing

Pressure screens are used for contaminant removal and fibre length fractionation in the production of pulp and paper products. Axial variations and entry effects in the screen are known to occur and these variations have not been adequately quantified. This thesis describes a fundamental study of the axial variations of several factors that occur within an industrial pressure screen; namely, pulp consistency, fibre length distribution, rotor pressure pulse, and feed annulus tangential velocity. Axial variations of pulp consistency in the screen annulus and the accept chamber of the screen were studied using an internal radial sampling method. Localised pulp samples were taken and evaluated and common measures of screen performance such as fibre passage ratio and fractionation efficiency were calculated along the screen. Consistency generally increased along the length of the screen although under certain conditions the consistency toward the front of the screen was lower than the feed consistency. A two passage ratio model that incorporated forward and reverse passage ratio was derived to elucidate the flow of both fibre and fluid through the screen and their effects on overall screen performance. The passage of fibre through the screen decreased with screen length which generally had a positive effect on the fractionation efficiency toward the back of the screen. The passage of individual fibre length fractions was also studied and it was found that long fibre had a much lower passage than short fibre which caused the average fibre length in the annulus to increase. Rotor induced pressure pulse variations along the screen length were also investigated. The magnitude of the pressure pulse was significantly lower (up to 40 %) at the rear of the screen. The variation in pressure caused by the rotor is due to a Venturi effect and the shape of the rotor. The relative velocity of the fluid and the rotor, called the slip factor, also directly affects the size of the press