1,721,052 research outputs found
The integration of heat pumps with biomass boiler flue gas for generating hot water
No full textAchieving the goal of net zero greenhouse gases by 2050 requires reducing demand and switching from fossil fuels to renewables. Process heat in New Zealand is a significant source of greenhouse gas emissions. Transitioning to biomass boilers could lower emissions and offer opportunities for waste heat recovery by integrating heat pumps with the flue gas.
This thesis evaluates heat pump integration for hot water production, supplying low temperature process heat. Using an industrial case study, a boiler model is developed and confirmed against industrial measurements. Flue gas composition is modelled to determine temperature-enthalpy profiles, and therefore the heat available for recovery and upgrade. Combustion is modelled for different biomass fuels and varying flue gas oxygen levels. The higher moisture fuels showed increased availability of heat for utilisation, which decreased as flue gas oxygen levels increased.
Three heat pump cycles are explored to maximise efficiency. Refrigerant selection is considered with respect to environmental factors and thermodynamic suitability. Using a basic cycle heat pump the three most promising refrigerants, ammonia, propane and cyclopropane, were identified and considered in more detail for the industrial case. Subcooling improved efficiency and should be maximised. An internal heat exchanger also improves efficiency and reliability and should be considered. Two zeotropic mixtures were investigated to take advantage of the temperature glide. The propane-pentane (50wt%-50wt%) blend matched the temperature profile more closely and provided increases in COP.
To make the most of the latent heat in the flue gas, the evaporator temperature must be much lower than the dew point. However, absorbing heat from low source temperatures results in lower COPs, but higher volumes of hot water generated
An investigation of self-learning and self-protection for Adaptive Digital Twins
Full text linkAdaptive Digital Twins are applicable to a number of fields, including the cybersecurity of industial control systems. This thesis prototypes a Self-Learning adaptive digital twin and posits an architecture for the creation of digital twins based on the learnings gained from the prototype. The prototype shows the efficacy of control theoretical approaches for adaptive digital twins for both modelling and protecting a system, and the architecture posits a generalised method for developing adaptive digital twins
Energy Investment and Emissions Planning for Electricity Generation in Myanmar
No full textHydropower plays a critical role in supplying electricity generation in the developing nation of Myanmar. Over the next 15 years (2015 – 2030) with anticipated rapid social and economic development in Myanmar, the demand for electricity is expected to increase from 23718 GWh in 2015 to 136605 GWh in 2030, which is nearly a six-fold increase. The aim of this thesis is to investigate the critical role of hydropower in the Myanmar electricity sector in meeting projected demand in 2030. As a result this thesis presents a detailed analysis of electricity generation in Myanmar using chiefly two methods: Energy Return on Investment (EROI) and Carbon Emissions Pinch Analysis (CEPA).
The contributions of this thesis to literature and Myanmar include: (1) the development of a low energy investment, low emissions roadmap towards achieving electricity demand in 2030 for Myanmar; (2) the identification of 20 storage-type hydropower stations that with excellent EROI values and low energy payback times, which help form the foundation of the future development roadmap; and (3), the determination of dam-type-specific empirical correlations for EROI by inputting the estimated electricity output (based on head, water flow, overall efficiency and capacity factor) and dam volume.
By implementing the recommendation of a further 20 hydropower plants, beyond the currently installed and under-construction plants, Myanmar can achieve its ambitious 2030 electricity supply target, 136605 GWh, in which a major of generation comes from hydropower (69%). The remaining generation comes from natural gas (24%), coal 3340 GWh (2.5%) and other renewables such as solar, wind and biomass (4.5%). Compared to the Myanmar’s current National Electricity Master Plan (2014-2030) adopted by Ministry of Electric Power, the recommendations in this thesis can lead to 41% mitigation of carbon emissions with 7% less energy investment
Vacuum Steam Desuperheating and Condensation: An Experimental Investigation
No full textSteam condensation plays an essential role in supplying and removing heat in many industrial applications, including the energy sector. It therefore is a phenomena of significance that requires deep understanding. This thesis presents effective vacuum steam condensation on the shell-side of vertical shell and tube condenser (VSTC) accompanying steam desuperheating. It describes a fundamental study of heat transfer in VSTC with considerations of several factors; explicitly degree of superheat related with each vacuum steam pressure, temperature waviness in desuperheating section, and steam condensation in absence of non-condensable gas (NCG). Experiments performed on the VSTC are:
Steam desuperheating and condensation in the shell-side VSTC at a variety of vacuum steam pressures and respective steam flowrates, vacuum steam desuperheating and condensation in the shell-side of VSTC at reduced steam flowrates, and vacuum steam desuperheating and condensation at tube wall temperatures up to steam saturation temperature (T₂ ≥ Tsat) to analyse dry heat transfer in the desuperheating section. To examine the stated aim, test facility was built in the laboratory of the University of Waikato.
By generating desuperheating and condensation models for each test pressure, this investigation proves that vacuum steam condensation best occurs without involvement of superheat. About 60% of the VSTC occupied with desuperheating, and the heat transfer involved in desuperheating is minor approximately 1 kW, whereas, the condensation section of VSTC has heat transfer about 10 kW. By reducing the steam flowrate, 10% reduction in the desuperheating section and 20% to 50% reduction in the Reynolds number was observed. After raising the tube wall temperature up to the steam saturation temperature, a smooth temperature profile across the desuperheating the section was seen with significant sensible heat transfer. Obstruction linked with superheated steam condensation in the dairy industrial leads to poor heat transfer area utilization by the desuperheating section and therefore, reduction of the evaporator rating or oversizing of the heat exchangers to attain appropriate duty
Multi-Level process integration of heat pumps in a non-continuous processing site
No full textIndustrial process heat demands contribute significantly to New Zealand’s greenhouse gas emissions. With a global push towards decarbonization, including New Zealand’s Climate Change Response Amendment Act 2019, there is a need for methods and technologies that can be applied to replace industrial fossil fuel boiler use. With an increasing range of renewable energy sources, electrification provides a promising alternative to fossil fuel use; however, it is also critical to reduce process heat demands where possible. This can be done through the reuse of industrial waste heat via direct heat exchange, thermal storage, or heat pump installations. Existing Heat Integration methods provide a means of identifying waste heat recovery opportunities; however, these methods are typically aimed at steady state industries. In New Zealand, many industries operate in a non-continuous manner, creating challenges in the accurate application of these existing Heat Integration methods.
This thesis presents a multi-level process integration method for heat pump and thermal storage retrofit on non-continuous industrial processing sites. This method aims to address several gaps in current Heat Integration methodology through the novel amalgamation of several tools discussed in four main chapters: (1) A multi-level heat pump integration tool is developed that sequentially identifies heat pump opportunities to both upgrade waste heat for reuse, and shift remaining waste process heat towards more favorable temperature ranges, (2) A multi steady state time slice investigation develops a tool for selecting appropriate time slice sizes to accurately represent variable, non-continuous industrial sites, (3) a multi steady state thermal storage identification tool is developed by applying the previously identified time slices to existing heat integration methods with an aim to further buffer fluctuations in heat demand, and optimize the thermal loads on the previously identified heat pump opportunities.
The tools are combined into a final method and applied to a meat processing case study site that is representative of the variable, non-continuous industries that dominate the food sector in New Zealand. In this case study, hourly time slices were used to identify multiple successive heat pump opportunities including a 1.9 MW MVR that recompresses waste steam from the rendering dryers with a COP of 10, and a central 1.5 MW heat pump that supplies heat at 70°C to the site ring main with a COP of 3.4. In addition, it was found that the 90°C heat pump, already installed on the case study site, would have the potential to increase utilization on the case study site if the two other heat pump opportunities identified were implemented. Thermal storage opportunities were also identified that can be used to buffer heat demands on the 70°C heat pump opportunity, thereby allowing the heat pump to be resized to 1.04 MW in comparison to the initially hypothesized 1.5 MW, reducing both capital and operational costs of the heat pump.
This amalgamated method provides novel Total Site Heat Integration additions, which when compared to conventional heat integration methods, provide more accurate and more useful heat pump decarbonization strategies for non-continuous industrial sites, ultimately aiding in industrial decarbonization
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Heat Integrated Milk Powder Production
No full textDairy processing is critical to New Zealand’s (NZ) economy producing NZ3 million and internal rate of return of 71 %. This tool will empower industry with greater confidence to uptake exhaust heat recovery technology as a vital method for improving the heat integration of MPPs in NZ
- …
