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Application of the TEWI Methodology to a Desiccant Cooling System Interacting with a Microcogenerator
Get PDFDesiccant cooling systems, supplied by fossil or renewable fuels, represent a very interesting alternative to conventional electric units based on cooling dehumidification for air conditioning purposes, as they can achieve significant energy and emissions savings. The analysis of environmental impact of energy conversion devices, e.g. in terms of global warming effect, is usually limited to energy-related emissions (indirect contribution), neglecting direct greenhouse gas emissions related to working fluids, such as refrigerants. The Total Equivalent Warming Impact (TEWI) is a more comprehensive methodology, as it takes into account both direct and an indirect contributions to global warming. In this paper, this method is applied to a small scale trigeneration system, in which a microcogenerator, a chiller and a boiler interact with a hybrid desiccant-based cooling system, equipped with a silica-gel desiccant wheel. This trigeneration system is compared with other two systems, in order to assess its potentiality in terms of TEWI reduction. The different direct and indirect contributions of the several equipment are evaluated, and the share of the direct contribution is investigated, considering both the overall TEWI of the complete system, and that of the electric vapour compression device only. Finally, the effect of the greenhouse gas emissions of the electricity production mix and of different values of the Global Warming Potential (GWP) of the refrigerant fluid on the overall TEWI of the three compared systems is investigated
CFD Benchmark Tests for Indoor Environmental Problems: Part 2 Cross-Ventilation Airflows and Floor Heating Systems
Get PDFCommercial Computational Fluid Dynamics (CFD) software is practically applied in indoor environmental design recent years but the prediction accuracy of CFD simulation depends on the understanding for the fundamentals of fluid dynamics and the setting of appropriate boundary and numerical conditions as well. Additionally, deeper understanding to a specific problem regarding indoor environment is also requested. The series of this study aimed to provide with the practical information such as prediction accuracy and problematic areas related to CFD applications in indoor environment, air conditioning and ventilation, then performed benchmark tests and reported the results. In this Part 2, benchmark test results for cross-ventilation airflows and floor heating systems were introduced.
The highest reproducibility of the predicted results compared with the wind tunnel results occurred when the Z0-type wall function was used as the floor-surface boundary condition and the SST k–ω for the turbulence model in case of cross-ventilation flow and SST k–ω model showed also the closest matching results with experiment in case of natural convection in a room with floor heating
Techno-Economic and Environmental Assesment of Compressor Retrofitting Procedure
Get PDFIn this study, retrofitting of a fixed speed refrigeration system to a variable speed refrigeration system is investigated. Economical and technical benefits of the retrofitting procedure are also studied. Refrigeration systems are usually designed to overcome maximum load conditions. However, they work under partial load in most of their life cycle. Hence, in this study a variable speed compressor that equalizes the cooling load to the demand that assures significant energy saving is considered. As a result of this study, the retrofitted variable speed compressor performed 17% decreased energy consumption versus the thermostatic controlled fixed speed system. Also, the retrofitting procedure provided considerable payback time. From the result, 10750 kilograms less carbon emission per year as an environmental benefit within retrofitting procedure is obtained
Application of Bioenergy for Energy or Materials: Future Perspective through Development of Management
Get PDFThe demand for energy continued to outstrip supply and necessitated the development of biomass option. Residues were the most popular forms of renewable energy and currently biofuel production became much promising. Agricultural wastes contained high moisture content and could be decomposed easily by microbes. Agricultural wastes were abundantly available globally and could be converted to energy and useful chemicals by a number of microorganisms. Compost or bio-fertiliser could be produced with the inoculation of appropriated thermophilic microbes which increased the decomposition rate, shortened the maturity period and improved the compost (or bio-fertiliser) quality. The objective of the present research was to promote the biomass technology and involved adaptive research, demonstration and dissemination of results. With a view to fulfill the objective, a massive field survey was conducted to assess the availability of raw materials as well as the present situation of biomass technologies. N the present article, an attempt had also been made to present an overview of present and future use of biomass as an industrial feedstock for production of fuels, chemicals and other materials. We may conclude from the review paper that biomass technology must be encouraged, promoted, invested, implemented, and demonstrated, not only in urban areas but also in remote rural areas
Assessing the Impact of Microwave Treatment on Soil Microbial Populations
Get PDFMicrowave soil treatment can kill weed plants and their seeds in the soil. It has also been demonstrated elsewhere that microwave soil treatment can kill nematodes in the soil; however few studies have considered the effect of microwave soil treatment on other key soil biota. This study explored the effect of microwave soil treatment on soil bacteria, fungi, and various protozoa. The research used a series of experiments using different techniques to verify the effect of varying degrees of microwave treatment on these soil biota. Microwave treatment reduces bacterial populations in the top layers of soil, but populations that are deeper in the soil are relatively unaffected. Bacterial populations increased significantly within a month of microwave treatment. E. coli populations experienced a 10-5 reduction in numbers in the top layer of soil by 500 J cm-2 of microwave energy; however other soil bacteria survived over 3000 J cm-2 of microwave energy applied to the soil surface, suggesting that some species are more susceptible to microwave treatment than others. No significant response of soil fungi, ciliates, amoeba and flagellates could be attributed to a microwave dose response
Soil and Rock Mechanics Investigations for the Assessment of Strata Behaviour of an Opencast Coal Mine
Get PDFAbstract: The Singareni Collieries Company Limited (SCCL) planned for deepening the Opencast projects from the present depth of 250m to 400m. For successful operation and forecasting of strata behaviour in pre-mining was recognized. In this direction, SCCL had tie-up with CSIRO, Australia to work jointly, with a lead research provider. As part of these studies, to meet the requirement of generating needy data to conduct Numerical Modelling, extensive program was organized to take up different Physico Mechanical Properties (PMP) tests. In light of this, different tests suggested were taken up in SCCL and NIRM laboratories. The data thus generated were analyzed statistically to make use of the same for Numerical Modelling by CSIRO, Australia. The data generated during the course of organizing different tests, are synthesized and discussed in this paper. The paper deals with the methodology evolved in generation of desired soil and Rock Mechanics data to assess the stability of pit slopes, internal dump and OB dumps
Construction and Operation of an Electronic Automatic Transfer Switch (Ats)
Get PDFThe inconsistency of power supply in Nigeria has been a major stumbling block to the advancement of her economy and as such it is an issue that requires immediate attention. Uninterrupted power supply is critical in so many applications especially in cases like hospital operations or financial transactions. This work was born out of the need to provide a cost effective and locally available way to automate the switching between various power sources. This issue can be addressed by implementing an Automatic transfer switch which automatically switches on a backup generator in the absence of the utility supply and transfers the load to the generator. The automatic transfer switch also switches off the backup generator and connects back to the utility supply when the power comes back. The circuitry consists of time delay integrated circuits and switching relays. The present effort is a prototype design to create an automatic transfer switch that can be used in an average Nigerian household because of its affordability and simplicity of operation
A Preliminary Assessment of the Transmutation Potentialities for an ITER-like FW Sector Loaded with MA
Get PDFThe fusion-fission hybrid reactor is a promising technology that is likely to assume an increasingly important role in the global energy scene in the coming years. This kind of reactor can use both the nuclear fusion and fission processes to produce energy: neutrons from fusion reactions are used to sustain the fission of a sub-critical system. This method allows to have an intrinsically safe facility, with higher efficiency than a fusion reactor itself and with a harder neutron energy spectrum than a fission reactor, which could be suitable for nuclear waste transmutation. This paper, in particular, analyzes a type of hybrid reactor for the transmutation of Minor Actinides (MA). Nuclear waste, in the oxide form, is inserted as an element of the First Wall (FW) of an ITER-like fusion reactor. The aim is to demonstrate the feasibility of the transmutation of the MA characterized by higher long term radiotoxicity into shorter lived nuclides. The neutron transport in a detailed 3D geometrical model of the ITER reactor (B-lite) was performed by MCNP6 code, while the transmutation of the MA loaded in a single element of the FW was performed by SERPENT2 code. A pulsed ITER-like irradiation scenario was used. The analysis, which must be considered as a preliminary feasibility study, lead to very promising results, which could be further improved with a longer DEMO-like irradiation scenario and a larger number of MA loaded (“fission waste”) elements loaded in the FW
The Magic in 2-Channel Sound Reproduction - Why is it so Rarely Heard?
Get PDFHearing, finding the direction, distance and significance of a source of sound in various acoustic environments, is a survival mechanism in the evolution of living organisms. Hearing two strongly correlated sources of sound, either from earphones or two loudspeakers, is an unnatural phenomenon, from which the ear-brain apparatus is asked to draw an illusion of reality. Misleading cues must be eliminated from the sound presentation for the illusion to happen convincingly. In the case of earphone presentation, which typically suffers from a high degree of distance distortion, i.e. distance foreshortening, the ear signals must change with head movement to externalize the illusion. In the case of loudspeaker presentation there is already the distance between listener and speakers, which typically is perceived as the minimum distance to the illusionary aural scene or phantom scene. But that scene is usually hard bounded by the speakers, which are recognized as such by the ear-brain perceptual apparatus. One or the other speaker is preferred as the source, when the listener moves a short distance away laterally from the "sweet spot". In a reverberant room, where the listener not only hears the direct sound but also the reflected sound, i.e. the off-axis radiated sound, the ear-brain perceptual apparatus must be allowed to withdraw attention from room and speakers and focus attention upon the direct sound to create a convincing illusion of the reproduced acoustic event. For this to happen misleading perceptual cues must be eliminated. The speakers must be placed so that reflections are delayed relative to the direct sound. The speakers must be free from spurious resonant radiation and their off-axis radiation must follow their on-axis frequency response for the reverberant sound to be neutral. The polar radiation pattern must be essentially either omni-directional, cardioid or dipolar, aiming for constant directivity. The speakers must be acoustically small, yet capable of realistic volume levels at low non-linear distortion. Two prototype speakers and the evolution of their radiation pattern design will be discussed: a full-range, acoustically small dipole and a hybrid, omni-cardioid-dipole design. Either speaker is capable of disappearing from perception and rendering an aural scene in a reverberant room that is like a magic act
Condensation Heat Transfer Enhancement on Surfaces with Interlaced Wettability
Get PDFThis study investigated the effect of surfaces with interlaced wettability on steam–air mixture condensation. Experiments were conducted on various types of surface with different modified strip widths. In general, surfaces exhibiting high hydrophobic wettability yield a high condensation heat-transfer rate because dropwise condensation is easily formed. However, the experimental results of this study revealed that surfaces with interlaced wettability demonstrated superior condensation heat-transfer performance to those with homogeneous high hydrophobic wettability. Such an observation implies that the configuration of surface modification can enhance condensation heat transfer. In addition, the data indicated an optimal area ratio of modified surfaces to unmodified surfaces