Engineering Commons^™

Thermal Features Vis A Vis Strain Features Of Fracturing Process In Jointed Rock Layer Under Concentrated Load, Haiqing Yang, Bolong Liu, Shivakumar Karekal

Faculty of Engineering and Information Sciences - Papers: Part B

In case of earthquakes and crustal movement, the concentration of impounding load over a large region of crust can cause disturbances to the stratum. In order to quantitatively investigate crack initiation, propagation and coalescence processes of jointed stratum based on thermal variations caused by concentrated mechanical loading, a series of indention tests were performed on granite specimens. In the experiment, fracture process and resulting infrared radiation fields of specimens were respectively recorded by synchronized digital image correlation system and infrared camera. Then, thermal characteristics of mixed shear-tensile and tensile conical crack were analyzed. Experimental results indicate that the highlighted temperature …

Power Loss And Thermal Impedance Modeling Of Multilevel Power Converter With Discontinuous Modulation, Md Mazharul Islam, Md. Ashib Rahman, Md Rabiul Islam

Faculty of Engineering and Information Sciences - Papers: Part B

The hard switching operation of the insulated gate bipolar transistor (IGBT)-based multilevel converters (MLCs) in the transformer less direct integration of renewable power plants produces a considerable amount of switching and conduction power loss. This eventually causes higher junction temperature and lower thermal stability. The third harmonic sixty-degree bus-clamped pulse width modulation (BCPWM) technique demonstrates reduced switching losses and better harmonic spectra. In this paper, an analytical model for calculating the average and the rms currents for the hard switching operation of IGBTs and antiparallel diodes (APDs) is proposed. Furthermore, to calculate the device turn-on and turn-off losses, a discrete …

Study On Performance Evaluation Of Co2 Heat Pump System Integrated With Thermal Energy Storage For Space Heating, Zhihua Wang, Yuxin Zheng, Fenghao Wang, Mengjie Song, Zhenjun Ma

Faculty of Engineering and Information Sciences - Papers: Part B

CO2 heat pumps have drawn a great deal of attention owing to their advantages of high efficiency and environmental friendly for heating water under low ambient temperature. However, the system performance is not desirable and shows a lower COP for space heating, especially for a radiator as heating terminal, due to the higher inlet water temperature at the gas cooler, which causes a large throttle loss when the refrigerant flow through the throttling device. To tackle this issue, a transcritical CO2 heat pump system integrated with thermal energy storage (TES) systems was developed in this paper. The heating performance of …

A Novel Empirical Heat Transfer Model For A Solar Thermal Storage Process Using Phase Change Materials, Yu Bie, Ming Li, Fei Chen, Grzegorz Krolczyk, Lin Yang, Zhixiong Li, Weihua Li

Faculty of Engineering and Information Sciences - Papers: Part B

Numerical and experimental analyses are often used to evaluate the solar thermal system with latent heat thermal energy storage (LHTES). However, the relationship between the numerical simulation and actual heat transfer process is still unclear. This work compares the simulated average temperature of two different phase change materials (PCMs) with experimental result at different operation conditions for the purpose of developing a temperature correction model. A novel empirical heat transfer model is then established to improve the simulation accuracy of PCM-based solar thermal systems. The contributions of this work include that (1) the system performance could be evaluated by the …

Formulation Of A Model Predictive Control Algorithm To Enhance The Performance Of A Latent Heat Solar Thermal System, Gianluca Serale, Massimo Fiorentini, Alfonso Capozzoli, Paul Cooper, Marco Perino

Faculty of Engineering and Information Sciences - Papers: Part B

Model predictive control has proved to be a promising control strategy for improving the operational performance of multi-source thermal energy generation systems with the aim of maximising the exploitation of on-site renewable resources. This paper presents the formulation and implementation of a model predictive control strategy for the management of a latent heat thermal energy storage unit coupled with a solar thermal collector and a backup electric heater. The system uses an innovative Phase Change Material slurry for both the heat transfer fluid and storage media. The formulation of a model predictive controller of such a closed-loop solar system is …

Thermal Comfort For Occupants Of Nursing Homes: A Field Study, Federico Tartarini, Paul Cooper, Richard Fleming

Faculty of Engineering and Information Sciences - Papers: Part B

The primary aim of this research was to assess the quality of the thermal environment of six Australian nursing homes, and to understand and quantify the impacts of the indoor thermal environment on the perceptions and comfort of staff, residents and other occupants. The impact of the thermal environment on perceptions and comfort of building occupants of six nursing homes was determined through: 1) a long-term building evaluation survey (staff members only); and 2) a point-in-time thermal comfort study, involving 322 residents and 187 non-residents. In addition, a combination of spot-measurements and long-term monitoring of indoor air temperatures was used …

Thermal Perceptions, Preferences And Adaptive Behaviours Of Occupants Of Nursing Homes, Federico Tartarini, Paul Cooper, Richard Fleming

Faculty of Engineering and Information Sciences - Papers: Part B

While the rapid increase in the fraction of people aged over 65 is driving a substantial increase in the number of people living in nursing homes, there has been very limited previous research carried out on how residents of nursing homes perceive their thermal environment and there is a lack of thermal comfort guidelines for the aged care sector. This article reports on a study to investigate thermal perceptions, preferences and adaptive behaviours of occupants in five nursing homes. Participants were asked to complete a questionnaire while local environmental parameters were monitored in their near proximity using portable equipment. Not …

Development Of Microencapsulated Phase Change Material For Solar Thermal Energy Storage, Weiguang Su, Jo Darkwa, Georgios Kokogiannakis

Faculty of Engineering and Information Sciences - Papers: Part A

In this paper a novel microencapsulated phase change material (MF-3) has been developed and tested for solar assisted hot water storage systems. Even though the morphology of the sample was affected by the type of emulsifier used for fabrication it recorded the highest energy storage capacity of 126 kJ/kg with encapsulation efficiency of 97.4% as compared with other developed samples. For the purpose of assessing its thermal effectiveness it was theoretically evaluated in a compacted fixed bed TES unit and found to be capable of achieving a higher energy storage density as well as relatively smaller physical storage size than …

Hybrid Model Predictive Control Of A Residential Hvac System With On-Site Thermal Energy Generation And Storage, Massimo Fiorentini, Josh Wall, Zhenjun Ma, Julio H. Braslavsky, Paul Cooper

Faculty of Engineering and Information Sciences - Papers: Part A

This paper describes the development, implementation and experimental investigation of a Hybrid Model Predictive Control (HMPC) strategy to control solar-assisted heating, ventilation and air-conditioning (HVAC) systems with on-site thermal energy generation and storage. A comprehensive approach to the thermal energy management of a residential building is presented to optimise the scheduling of the available thermal energy resources to meet a comfort objective. The system has a hybrid nature with both continuous variables and discrete, logic-driven operating modes. The proposed control strategy is organized in two hierarchical levels. At the high-level, an HMPC controller with a 24-h prediction horizon and a …

Impact Of Structural Design Solutions On The Energy And Thermal Performance Of An Australian Office Building, Mehdi Robati, Georgios Kokogiannakis, Timothy J. Mccarthy

Faculty of Engineering and Information Sciences - Papers: Part B

Concrete is a heavyweight construction material whose high thermal mass could increase the thermal storage capacity of a building envelope and in turn affect indoor thermal comfort. Selecting an appropriate method for concrete construction and form could also affect the total energy performance and thermal comfort of a building, a fact that is often overlooked by structural engineers. This study presents the results of energy simulations of the potential impact that concrete construction forms, in particular two slab types, and structural materials have on the energy consumption of archetypal commercial office buildings in five major Australia cities (Sydney, Melbourne, Canberra, …

Ventilative Cooling Through Automated Window Opening Control Systems To Address Thermal Discomfort Risk During The Summer Period: Framework, Simulation And Parametric Analysis, Theofanis Psomas, Massimo Fiorentini, Georgios Kokogiannakis, Per K. Heiselberg

Faculty of Engineering and Information Sciences - Papers: Part B

Automated window opening control systems with integrated ventilative cooling strategies may significantly diminish the thermal discomfort and overheating risk of dwellings during cooling periods in temperate climates. One of the challenges with demonstrating the benefits of the systems is the lack of building performance simulation (BPS) tools which may represent precisely how actual algorithms are applied.

The study supported herein aims to present a framework of how to simulate an advanced ventilative cooling algorithm of a window system on coupled BPS environments (ESP-r and BCVTB tools). Parametric analysis has been conducted to verify specific operational functions of the system. The …

Preparation Of Microencapsulated Phase Change Materials (Mepcm) For Thermal Energy Storage, Weiguang Su, Jo Darkwa, Georgios Kokogiannakis, Tongyu Zhou, Yilin Li

Faculty of Engineering and Information Sciences - Papers: Part B

Microencapsulated phase change materials (MEPCM) could be used for energy saving applications in buildings due to their relatively high energy storage capacities at constant temperature, which could passively reduce peak cooling loads in summer. In this study, poly(methyl methacrylate-co-methacrylic acid) (PMMA-MAA) was used as a shell material to fabricate MEPCM by crosslinking methyl methacrylate (MMA) and methacrylic acid (MAA) through in-situ suspension-like polymerization method. The effects of initiator weight percentage and the ratio of shell monomers for the preparation of MEPCM were also investigated. The experimental results showed that the best MEPCM sample was achieved with a shell monomer weight …

Performance Simulation Of A Ground Source Heat Pump System Integrated With Solar Photovoltaic Thermal Collectors For Residential Application, Lei Xia, Zhenjun Ma, Georgios Kokogiannakis

Faculty of Engineering and Information Sciences - Papers: Part B

This paper presents the simulation and performance evaluation of a ground source heat pump (GSHP) system integrated with water-based solar photovoltaic thermal (PVT) collectors for residential buildings. A dynamic simulation system is developed using TRNSYS and used to facilitate the performance evaluation of the system. A 20-year life-time performance simulation is performed under three operation scenarios with different sizes of the PVT collectors. The results showed that the performance of the system is highly dependent on the size of the PVT collectors. Furthermore, an economic analysis is carried out to determine the optimum size of the PVT collectors for the …

Development Of A Dynamic Model For A Hybrid Photovoltaic Thermal Collector - Solar Air Heater With Fins, Wenke Fan, Georgios Kokogiannakis, Zhenjun Ma, Paul Cooper

Faculty of Engineering and Information Sciences - Papers: Part A

A dynamic model for a hybrid Photovoltaic Thermal Collector-Solar Air Heater (PVT-SAH) with longitudinal fins was developed to enable assessment of the potential of the system to provide high temperature outlet air (60-90 °C) under dynamic boundary conditions. The model description includes the method for discretising the system into a number of control volumes, the energy balance equations for each control volume and the implementation of the numerical solution. Model validation has been successfully undertaken by using empirical verification of model predictions with an experimental facility and by comparing the model outputs with the reference data from the literature. The …

Dynamic Exergy Analysis For The Thermal Storage Optimization Of The Building Envelope, Valentina Bonetti, Georgios Kokogiannakis

Faculty of Engineering and Information Sciences - Papers: Part A

As a measure of energy "quality", exergy is meaningful for comparing the potential for thermal storage. Systems containing the same amount of energy could have considerably different capabilities in matching a demand profile, and exergy measures this difference. Exergy stored in the envelope of buildings is central in sustainability because the environment could be an unlimited source of energy if its interaction with the envelope is optimised for maintaining the indoor conditions within comfort ranges. Since the occurring phenomena are highly fluctuating, a dynamic exergy analysis is required; however, dynamic exergy modelling is complex and has not hitherto been implemented …

Thermal Comfort Evaluation Of A Mixed-Mode Ventilated Office Building With Advanced Natural Ventilation And Underfloor Air Distribution Systems, Xiang Deng, Georgios Kokogiannakis, Zhenjun Ma, Paul Cooper

Faculty of Engineering and Information Sciences - Papers: Part A

This study uses field monitoring and post occupancy evaluation (POE) surveys to investigate the indoor thermal comfort of an office building that is located in subtropical zone. The building is special as it combines advanced natural ventilation (ANV) strategies and underfloor air distribution (UFAD) systems. A comparison between a static thermal comfort model and a dynamic thermal comfort model is also conducted. The results show that the thermal comfort conditions in the case study building are satisfactory in summer while in winter there is evidence of thermal discomfort. For the case study building, the static thermal comfort model gives outputs …

Thermal Environment And Thermal Sensations Of Occupants Of Nursing Homes: A Field Study, Federico Tartarini, Paul Cooper, Richard Fleming

Faculty of Engineering and Information Sciences - Papers: Part B

A demographic shift is underway in Australia; the number of people aged 65 and over is rapidly increasing. Regulations have been implemented to enhance the quality of care being provided in nursing homes; however, in the aged care sector there is little by way of guidance addressing design and performance issues in regards to Indoor Environmental Quality (IEQ), and there is still uncertainty as to the perceptions of residents on specific IEQ factors. The objectives of this study are to determine: how accredited facilities are performing in regards to thermal comfort conditions; how indoor environmental factors can be assessed in …

Numerical Analysis Of Indoor Thermal Comfort In A Cross-Ventilated Space With Top-Hung Windows, Xiang Deng, Paul Cooper, Zhenjun Ma, Georgios Kokogiannakis

Faculty of Engineering and Information Sciences - Papers: Part B

Natural ventilation can be used in residential buildings in several Australian climatic zones and well-designed windows have the potential to facilitate indoor thermal comfort by allowing occupants to control volumetric outdoor airflow and indoor air velocities. Top-hung window is one of the most popular window types in Australia. This paper investigates the effect of the attributes of top-hung windows (i.e. window length, aspect ratio, height above the ground, window opening angle and the fly screen porosity) and outdoor air conditions (i.e. outdoor air temperature, wind speed and direction) on indoor thermal comfort during cross ventilation using CFD simulations. The Taguchi …

Thermal Performance Evaluation Of An Integrated Photovoltaic Thermal-Phase Change Material System Using Taguchi Method, Haoshan Ren, Wenye Lin, Zhenjun Ma, Wenke Fan

Faculty of Engineering and Information Sciences - Papers: Part B

This paper presents the performance evaluation of an integrated photovoltaic thermal (PVT) collector-phased change material (PCM) thermal energy storage (TES) system. The PVT collectors can generate both electricity and low-grade thermal energy during the daytime, and the thermal energy generated can be temporarily stored in the PCM TES unit and used for space heating during the night-time. Taguchi method and analysis of variance are used for the simulation design and data analysis, respectively. The thermal performance of the proposed system was evaluated in terms of the useful energy stored in the TES system. The results showed that the outlet air …

Field Study Of Air Conditioning And Thermal Comfort In Residential Buildings, Jungsoo Kim, Richard De Dear, Tom Parkinson, Christhina Candido, Paul Cooper, Zhenjun Ma, Wasim Saman

Faculty of Engineering and Information Sciences - Papers: Part A

The aim of this study is to better understand the external and internal drivers that affect residential air-conditioning (A/C) use decisions and occupant comfort. Field observations were carried out using instrumental measurements and smartphone questionnaires, recording householder's A/C usage patterns, indoor/outdoor climatic factors, perception of thermal comfort and adaptive behaviours.

Development And Performance Evaluation Of A Liquid Desiccant Air Conditioning System With Hybrid Electrodialysis And Thermal Regeneration, Yi Guo, Zhenjun Ma, Ali Hussein Al-Jubainawi, Paul Cooper, Long D. Nghiem

Faculty of Engineering and Information Sciences - Papers: Part A

Liquid desiccant air conditioning (LDAC) systems have gained increasing attention due to the improved energy performance and reduced environmental impacts. This paper presents an LDAC system using electrodialysis (ED) as well as low grade heat generated from a hybrid photovoltaic thermal and evacuated tube (PVT-ET) collector for liquid desiccant regeneration. As ED regenerator is a key component in the proposed system, a modified mathematical model is used to simulate the mass transfer of the ED stack. The performance of the model was validated using the experimental data generated based on a lab-scale experimental setup. It is shown that the model …

Thermal Performance Evaluation And Optimal Design Of Buildings With Integrated Air-Based Photovoltaic Thermal Collectors And Phase Change Materials Using The Hooke-Jeeves Pattern Search Method, Wenye Lin, Zhenjun Ma, Paul Cooper

Faculty of Engineering and Information Sciences - Papers: Part A

Over the last several decades, many low energy technologies have been developed and deployed to reduce building energy consumption. Among various solutions, solar photovoltaic thermal (PVT) collectors and phase change materials (PCMs) are among the most promising methods receiving increasing attention. This paper presents a thermal performance evaluation and optimal design of buildings integrated with air-based solar PVT collectors and PCMs embedded in the building envelope by using The Hooke-Jeeves pattern search method. The Hooke-Jeeves generalized pattern search is used to search for optimal solutions of the optimization problem. The variables optimized include the PVT air flow rate, additional wall …

Incorporating Environmental Evaluation And Thermal Properties Of Concrete Mix Designs, Mehdi Robati, Timothy J. Mccarthy, Georgios Kokogiannakis

Faculty of Engineering and Information Sciences - Papers: Part A

One of the main challenges in sustainable design of buildings is to improve the energy efficiency of the building during its lifetime along with reducing the environmental impact of the design. Recent advances in concrete technology offer lower embodied emission through the application of supplementary cementitious materials and recycled aggregates. There are also improvements to thermal properties with the application of admixtures. However, the relationships between the environmental impact (Cradle to Gate) and thermal performance of concrete mix designs have not been researched adequately. The Green House Gas (GHG) emissions associated with each individual concrete component and its production need …

Optimization Of A Ceiling Ventilation System With Integrated Photovoltaic Thermal Collectors And Phase Change Materials, Zhenjun Ma, Wenye Lin, Mohammed I. Sohel

Faculty of Engineering and Information Sciences - Papers: Part A

This paper presents the performance evaluation and design optimization of a ceiling ventilation system with integrated solar photovoltaic thermal (PVT) collectors and phase change materials (PCMs) by using a hybrid Particle Swarm Optimization and Hooke-Jeeves Pattern search (PSO-HJ) algorithm. In this novel ceiling ventilation system, the PVT collectors are used to generate electricity and provide the low-grade heating energy for buildings by using the winter daytime solar radiation, while the PCM is integrated into the building ceiling as part of the ceiling insulation and at the same time, as a centralized thermal energy storage unit to temporally store the low-grade …

Coupling A Thermal Comfort Model With Building Simulation For User Comfort And Energy Efficiency, Katharina Boudier, Massimo Fiorentini, Sabine Hoffmann, Raghuram Kalyanam, Georgios Kokogiannakis

Faculty of Engineering and Information Sciences - Papers: Part B

This paper describes a methodology for coupling an advanced model of the thermo-regulatory system of the human body that describes its physiological processes, a comfort model that evaluates thermal sensation and comfort, and the ESP-r building simulation software that computes the transient thermal response of a building model. The objective of this study was to utilise the physiology and comfort models to dynamically modify the heating and cooling temperature set points of a zone controller in ESP-r, in accordance with the computed human thermal sensation and achieve realtime thermal comfort management. The comunication between the software is managed by the …

Development And Optimization Of An Innovative Hvac System With Integrated Pvt And Pcm Thermal Storage For A Net-Zero Energy Retrofitted House, Massimo Fiorentini, Paul Cooper, Zhenjun Ma

Faculty of Engineering and Information Sciences - Papers: Part A

This paper describes a novel solar-assisted HVAC system developed for the Team UOW 'Illawarra Flame' Solar Decathlon house, the winner of the Solar Decathlon China 2013 competition. This HVAC system consists of an air-based photovoltaic-thermal (PVT) collector and a phase change material (PCM) thermal storage unit integrated with a reverse cycle heat pump, in a ducted system. The system was designed for operation during both winter and summer using daytime solar radiation and night-time sky radiative cooling, respectively. The PVT collector heats or cools fresh air from ambient and thereby provides heating or cooling either directly to the indoor space, …

Experimental Investigation Of An Innovative Hvac System With Integrated Pvt And Pcm Thermal Storage For A Net-Zero Energy Retrofitted House, Massimo Fiorentini, Paul Cooper, Zhenjun Ma, Josh Wall

Faculty of Engineering and Information Sciences - Papers: Part A

This paper presents the experimental investigation of a novel solar assisted HVAC system developed for the Team UOW Solar Decathlon house, the overall winner of the Solar Decathlon China 2013 competition. This novel HVAC system consists of an air based photovoltaic-thermal (PVT) system and a phase change material (PCM) thermal storage unit integrated with a ducted system with a reverse-cycle heat pump. The system has been designed for operation during both winter and summer, using daytime solar radiation and night sky radiative cooling to increase the energy efficiency of the air-conditioning system. The PVT system can exchange heat with the …

Thermal Stability And Properties Of Deformation-Processed Cu-Fe In Situ Composites, Keming Liu, Zhengyi Jiang, Jingwei Zhao, Jin Zou, Lei Lu, Deping Lu

Faculty of Engineering and Information Sciences - Papers: Part A

This paper investigated the thermal stability, tensile strength, and conductivity of deformation-processed Cu-14Fe in situ composites produced by thermo-mechanical processing. The thermal stability was analyzed using scanning electronic microscope and transmission electron microscope. The tensile strength and conductivity were evaluated using tensile-testing machine and micro-ohmmeter, respectively. The Fe fibers in the deformation-processed Cu-14Fe in situ composites undergo edge recession, longitudinal splitting, cylinderization, break-up, and spheroidization during the heat treatment. The Cu matrix experiences recovery, recrystallization, and precipitation phase transition. The tensile strength and conductivity first increase with increasing temperature of heat treatment, reach peak values at different temperatures, and then …

Sodium Borohydride Hydrazinates: Synthesis, Crystal Structures, And Thermal Decomposition Behavior, Jianfeng Mao, Qinfen Gu, Zaiping Guo, Hua-Kun Liu

Faculty of Engineering and Information Sciences - Papers: Part A

Metallic borohydride hydrazinates are novel boron- and nitrogen-based materials that appear to be promising candidates for chemical hydrogen storage. Herein, sodium borohydride hydrazinates, including NaBH₄·N2H₄ and NaBH₄·2N₂H₄, were synthesized via a facile solution synthesis approach based on the solid-liquid reaction between NaBH₄ and hydrazine in tetrahydrofuran (THF) solution. The crystal structure of NaBH₄·2N₂H₄ was solved to a monoclinic structure with unit cell parameters a = 8.4592(2) Å, b = 11.7131(2) Å, c = 6.4584(1) Å, and β = 100.0777(14)°, with space group A1a1 (9). Each …

Uncertainty Management In Multiobjective Hydro-Thermal Self-Scheduling Under Emission Considerations, Jamshid Aghaei, Abdollah Ahmadi, Abdorreza Rabiee, Vassilios G. Agelidis, Kashem M. Muttaqi, H A. Shayanfar

Faculty of Engineering and Information Sciences - Papers: Part A

In this paper, a stochastic multiobjective framework is proposed for a day-ahead short-term Hydro Thermal Self-Scheduling (HTSS) problem for joint energy and reserve markets. An efficient linear formulations are introduced in this paper to deal with the nonlinearity of original problem due to the dynamic ramp rate limits, prohibited operating zones, operating services of thermal plants, multi-head power discharge characteristics of hydro generating units and spillage of reservoirs. Besides, system uncertainties including the generating units' contingencies and price uncertainty are explicitly considered in the stochastic market clearing scheme. For the stochastic modeling of probable multiobjective optimization scenarios, a lattice Monte …