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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Befuktning : Installationer, processer och hälsofördelar. / Humidification : Installations, processes and health benefits.

Cavallius, Matilda, Rehnstedt, Oskar January 2017 (has links)
Det finns tydliga hälsofördelar med en relativ fuktighet på 40–60% inomhus. Trots detta finns det idag inga direktiv på hur man ska styra den relativa fuktigheten inomhus. Många gånger diskuteras det kring avfuktning men i denna rapport tas befuktning upp ur ett hälsoperspektiv.I denna studie har det undersökts huruvida befuktningssystem skulle kunna användas i större utsträckning till fördel för människors hälsa.I rapporten redogörs för olika befuktningmetoder samt deras termofysiska processer - adiabatisk eller isotermisk. Dessutom undersöks vad som händer med energin i luften och vattenångan vid olika temperaturer samt vad olika relativ fuktighet har för hälsomässiga för- och nackdelar.Resultatet visar på att det finns både etablerade befuktningssystem samt ett behov av befuktning. Däremot är efterfrågan av befuktning inte speciellt stor i bostäder och branschen ställer sig negativ till befuktning i ventilationssystem. / There are clear health benefits of having a relative humidity between 40–60% indoors. Despite this, there are currently no directives on what level the relative humidity should be indoors. Today dehumidification is a common matter but this report is about humidification, from a health perspective.In this study, it has been investigated whether humidification could be used to a greater extent, to the benefit of humans’ health.This report describes various humidification methods and their thermophysical processes - adiabatic and isothermal. It is also explained what happens to the energy in the air and water vapor at different temperatures and how the relative humidity affects our health at different levels.The result shows that there is a need for humidification and that there are several technical solutions available today. However, the demand is low and the industry is not very positive to the idea of humidification in ventilation systems.
22

Aktiv befuktning vid mekaniskventilation : En integrerad litteraturstudie / Active humidification in mechanical ventilation : An integrated literature review

Lindström, Karl-Johan, Carling, Anna January 2017 (has links)
Introduktion: Befuktning vid mekanisk ventilation är nödvändigt för att inte skador skall uppstå i luftvägarna. Luften kan befuktas aktivt eller passivt och då tekniken ständigt utvecklas kan tidigare riktlinjer för vilken metod som är bäst behöva revideras. Syfte: Studiens syfte var att undersöka evidensen för användning av aktiv befuktning hos intuberade eller trakeostomerade patienter. Metod: I enlighet med Whittemore & Knafls metod utfördes en integrerad litteraturstudie. Litteratursökning gjordes i databaserna PubMed, CINAHL och Cochrane. Även en manuell sökning i referenslistor utfördes och ledde till att totalt 14 artiklar valdes ut, varav 13 var kvantitativa och 1 kvalitativ. Resultat: Analysen av de 14 artiklarna resulterade i fyra huvudkategorier med efterföljande underrubriker: Aktiv befuktnings påverkan på nosokomiala infektioner: Infektionsincidens och Infektionstyp; Aktiv befuktnings påverkan på luftvägsproblem: Ocklusionsproblemoch Sekretviskositet/sekretmängd; Aktiv befuktnings påverkan på mekanisk ventilation: Vårdtid med mekanisk ventilation och Påverkan på andningsarbete;Upplevelse av aktiv befuktning: Upplevd påverkan på hälsa och Negativ påverkanpå vårdmiljön. Konklusion: Denna studie var att aktiv befuktning har en viktigfunktion att fylla hos vissa patienter, men borde inte användas slentrianmässigt.Sjuksköterskan har en viktig roll i att hitta de patienter som är mest hjälpta av det. / Introduction: Humidification during mechanical ventilation is necessary to avoid damage in the airways. The air can be humidified actively or passively and since thetechnique is constant developing the guidelines for which of the alternative that’sthe best may need to be revised. Aim: The aim of the study was to examine the evidence of using active humidification in intubated patients or in patients withtracheostomy. Method: An integrated literature review according to Whittemore &Knafl was carried through. The literature search was done in the databases PubMed, CINAHL and Cochrane. A manual search in reference lists was also made and resulted in a total of 14 articles whereof 13 were quantitative and one was qualitative. Result: The analysis of the 14 articles led to four main categories with the following subcategories: Active humidifications influence on nosocomial infections: Infectionincidence and Infection type; Active humidifications influence on airway problems: Occlusion problems and Mucus viscosity/mucus volume; Active humidifications influence on mechanical ventilation: Time on mechanical ventilation and Influenceon respiratory work; Experience of active humidification: Experienced influence on health and Negative impact on hospital environment. Conclusion: The conclusion of this study was that active humidification is the better choice among certain patientgroups but should not be used routinely. The nurse plays an important role in finding the patients who can benefit the most of it.
23

Advanced controllers for building energy management systems : advanced controllers based on traditional mathematical methods (MIMO P+I, state-space, adaptive solutions with constraints) and intelligent solutions (fuzzy logic and genetic algorithms) are investigated for humidifying, ventilating and air-conditioning applications

Ghazali, Abu Baker Mhd January 1996 (has links)
This thesis presents the design and implementation of control strategies for building energy management systems (BEMS). The controllers considered include the multi PI-loop controllers, state-space designs, constrained input and output MIMO adaptive controllers, fuzzy logic solutions and genetic algorithm techniques. The control performances of the designs developed using the various methods based on aspects such as regulation errors squared, energy consumptions and the settling periods are investigated for different designs. The aim of the control strategy is to regulate the room temperature and the humidity to required comfort levels. In this study the building system under study is a 3 input/ 2 output system subject to external disturbances/effects. The three inputs are heating, cooling and humidification, and the 2 outputs are room air temperature and relative humidity. The external disturbances consist of climatic effects and other stochastic influences. The study is carried out within a simulation environment using the mathematical model of the test room at Loughborough University and the designed control solutions are verified through experimental trials using the full-scale BMS facility at the University of Bradford.
24

Studies on Poly(N,N-dimethylaminoethyl methacrylate) Composite Membranes for Gas Separation and Pervaporation

Du, Runhong January 2008 (has links)
Membrane-based acid gas (e.g., CO2) separation, gas dehydration and humidification, as well as solvent dehydration are important to the energy and process industries. Fixed carrier facilitated transport membranes can enhance the permeation without compromising the selectivity. The development of suitable fixed carrier membranes for CO2 and water permeation, and understanding of the transport mechanism were the main objectives of this thesis. Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) composite membranes were developed using microporous polysulfone (PSF) or polyacrylonitrile (PAN) substrates. The PDMAEMA layer was crosslinked with p-xylylene dichloride via quaternization reaction. Fourier transform infrared, scanning electron microscopy, adsorption tests, and contact angle measurements were conducted to analyze the chemical and morphological structure of the membrane. It was shown that the polymer could be formed into thin dense layer on the substrates, while the quaternary and tertiary amino groups in the side chains of PDMAEMA offered a high polarity and hydrophilicity. The solid-liquid interfacial crosslinking of PDMAEMA led to an asymmetric crosslinked network structure, which helped minimize the resistance of the membrane to the mass transport. The interfacially formed membranes were applied to CO2/N2 separation, dehydration of CH4, gas humidification and ethylene glycol dehydration. The membranes showed good permselectivity to CO2 and water. For example, a CO2 permeance of 85 GPU and a CO2/N2 ideal separation factor of 50 were obtained with a PDMAEMA/PSF membrane at 23oC and 0.41 MPa of CO2 feed pressure. At 25oC, the permeance of water vapor through a PDMAEMA/PAN membrane was 5350 GPU and the water vapor/methane selectivity was 4735 when methane was completely saturated with water vapor. On the other hand, the relative humidity of outlet gas was up to 100 % when the membrane was used as a hydrator at 45oC and at a carrier gas flow rate of 1000 sccm. For used for dehydration of ethylene glycol at 30oC, the PDMAEMA/PSF membrane showed a permeation flux of ~1 mol/(m2.h) and a permeate concentration of 99.7 mol% water at 1 mol% water in feed. This work shows that the quaternary and tertiary amino groups can be used as carriers for CO2 transport through the membrane based on the weak acid-base interaction. In the presence of water, water molecules in the membrane tend to form a water "path" or water "bridge" which also help contribute to the mass transport though the membrane. In addition, CO2 molecules can be hydrated to HCO3-, which reaction can be catalyzed by the amino groups, the hydrated CO2 molecules can transport through the water path as well as the amino groups in the membrane. On the other hand, for processes involving water (either vapor or liquid) permeation, the amino groups in the membrane are also helpful because of the hydrogen bonding effects.
25

Studies on Poly(N,N-dimethylaminoethyl methacrylate) Composite Membranes for Gas Separation and Pervaporation

Du, Runhong January 2008 (has links)
Membrane-based acid gas (e.g., CO2) separation, gas dehydration and humidification, as well as solvent dehydration are important to the energy and process industries. Fixed carrier facilitated transport membranes can enhance the permeation without compromising the selectivity. The development of suitable fixed carrier membranes for CO2 and water permeation, and understanding of the transport mechanism were the main objectives of this thesis. Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) composite membranes were developed using microporous polysulfone (PSF) or polyacrylonitrile (PAN) substrates. The PDMAEMA layer was crosslinked with p-xylylene dichloride via quaternization reaction. Fourier transform infrared, scanning electron microscopy, adsorption tests, and contact angle measurements were conducted to analyze the chemical and morphological structure of the membrane. It was shown that the polymer could be formed into thin dense layer on the substrates, while the quaternary and tertiary amino groups in the side chains of PDMAEMA offered a high polarity and hydrophilicity. The solid-liquid interfacial crosslinking of PDMAEMA led to an asymmetric crosslinked network structure, which helped minimize the resistance of the membrane to the mass transport. The interfacially formed membranes were applied to CO2/N2 separation, dehydration of CH4, gas humidification and ethylene glycol dehydration. The membranes showed good permselectivity to CO2 and water. For example, a CO2 permeance of 85 GPU and a CO2/N2 ideal separation factor of 50 were obtained with a PDMAEMA/PSF membrane at 23oC and 0.41 MPa of CO2 feed pressure. At 25oC, the permeance of water vapor through a PDMAEMA/PAN membrane was 5350 GPU and the water vapor/methane selectivity was 4735 when methane was completely saturated with water vapor. On the other hand, the relative humidity of outlet gas was up to 100 % when the membrane was used as a hydrator at 45oC and at a carrier gas flow rate of 1000 sccm. For used for dehydration of ethylene glycol at 30oC, the PDMAEMA/PSF membrane showed a permeation flux of ~1 mol/(m2.h) and a permeate concentration of 99.7 mol% water at 1 mol% water in feed. This work shows that the quaternary and tertiary amino groups can be used as carriers for CO2 transport through the membrane based on the weak acid-base interaction. In the presence of water, water molecules in the membrane tend to form a water "path" or water "bridge" which also help contribute to the mass transport though the membrane. In addition, CO2 molecules can be hydrated to HCO3-, which reaction can be catalyzed by the amino groups, the hydrated CO2 molecules can transport through the water path as well as the amino groups in the membrane. On the other hand, for processes involving water (either vapor or liquid) permeation, the amino groups in the membrane are also helpful because of the hydrogen bonding effects.
26

An Investigation of Low Temperature Direct Propane Fuel Cells

Parackal, Bhavana January 2017 (has links)
This research is directed toward the investigation of a low temperature direct propane fuel cell (DPFC). Modeling included a parametric study of a direct propane fuel cell using computational fluid dynamics (CFD), specifically FreeFem++ software. Polarization curves predicted by the CFD model were used to understand fuel cell performance. The predictions obtained from the computational fluid dynamics mathematical model for the fuel cell were compared with experimental results. The computational work identified some critical parameters (exchange current density, pressure, temperature) for improving the overall performance of the fuel cell. The model predictions clearly highlighted the role of catalysts in significantly enhancing the overall performance of a DPFC. Experiments were performed using commercial Nafion-Pt based membrane electrode assemblies (MEAs) to obtain a basis for comparison. It is the first report in the literature that a Pt-Ru (Platinum-Ruthenium) MEA was used in the investigation of a DPFC. Also, it was the first study that fed liquid water continuously to a DPFC by using interdigitated flow field (IDFF) at the anode to humidify the dry propane feed gas. During the experiments oscillations were observed at very low current densities i.e. in nA/cm2, which is a rare case and not reported in the literature to date. This observation has raised serious concerns about the existence of absolute open-circuit cell potential difference for a DPFC. The cycling behaviour observed with DPFC indicated the presence of a continuous degradation-regeneration process of the catalyst surface near open-circuit potential. The experimental work further evaluated the performance of fuel cell by measurement of polarization curves.
27

Vzduchotechnika knihovny / Air conditioning in the library

Pospíšilová, Lucie January 2018 (has links)
Dissertation offers a plan for air – conditioning equipment of library building in Brno and it involves air filter experimental measurement. The proposal is divided into three parts. The first part explains air filter theory with detailed description of atmospheric air filters for separation of particles for general ventilation - filter parameter determination. Theory part ends specifically with pocket air filters and their construction. The second part focuses on experimental pocket air filter measurement execution, which calculates with variable filter cartridges and pocket count. Measurement also evaluates pressure drop and their efficiency. The last part of the dissertation looks at air – conditioning equipment design for specified building, concretely library building. The project solves fresh air traffic into interior of selected library rooms and it counts with thermal heat gain in summer season, heat loss in winter season and air humidity modification.
28

Adiabatické chlazení vzduchu / Adiabatic air cooling

Silbernágl, Petr January 2016 (has links)
The diploma thesis deals deals with the designing and assessment of the two variants of cooling and humidifying the air in the production hall for cotton in Humpolec. The system is proposed to fulfil hygienic, operational, economic and functional requirements for indoor microclimate of the production hall. The task of this system is the transport of cooler air to interior and the covering of heat gains all year round. The equipment is also designed for the regulation of air humidity in the interior. The theoretical part is devoted to air humidification and air humidification device. Calculation of the project and then a specific proposal, two variants for air distribution level studies. Both variants are treated as project documentation. Experimental part is devoted to the measurement on the measuring path containing adiabatic humidifier in the laboratory. The benefit of the experiment is to verify the data from the manufacturer adiabatic humidifier which we can assess the practical use of the product.
29

Advanced controllers for building energy management systems. Advanced controllers based on traditional mathematical methods (MIMO P+I, state-space, adaptive solutions with constraints) and intelligent solutions (fuzzy logic and genetic algorithms) are investigated for humidifying, ventilating and air-conditioning applications.

Ghazali, Abu Baker MHD. January 1996 (has links)
This thesis presents the design and implementation of control strategies for building energy management systems (BEMS). The controllers considered include the multi PI-loop controllers, state-space designs, constrained input and output MIMO adaptive controllers, fuzzy logic solutions and genetic algorithm techniques. The control performances of the designs developed using the various methods based on aspects such as regulation errors squared, energy consumptions and the settling periods are investigated for different designs. The aim of the control strategy is to regulate the room temperature and the humidity to required comfort levels. In this study the building system under study is a 3 input/ 2 output system subject to external disturbances/effects. The three inputs are heating, cooling and humidification, and the 2 outputs are room air temperature and relative humidity. The external disturbances consist of climatic effects and other stochastic influences. The study is carried out within a simulation environment using the mathematical model of the test room at Loughborough University and the designed control solutions are verified through experimental trials using the full-scale BMS facility at the University of Bradford.
30

The Formation and Growth of Marine Aerosols and the Development of New Techniques for their In-situ Analysis.

Johnson, Graham Richard January 2005 (has links)
Marine aerosols have attracted increasing attention over the past 15 years because of their potential significance for global climate modelling. The size distribution of these aerosols extends from super-micrometer sea salt mode particles down through 150 nm accumulation mode particles, 40 nm Aitken mode particles and nucleation mode particles which extend from 25 nm right down to clusters of a few molecules. The process by which the submicrometer modes form and grow and their composition have remained topics of debate throughout this time in large part because of the difficulties associated with determining their composition and relating it to proposed models of the formation process. The work compared the modality of marine aerosol influencing the South-east-Queensland region with that of other environmental aerosols in the region. The aerosol was found to be consistent with marine aerosols observed elsewhere with concentrations below 1000 cm-3 and frequently exhibiting the distinct bimodal structure associated with cloud processing, consisting of an Aitken mode at approximately 40 nm, an accumulation mode in the range 100-200 nm and a coarse mode attributed to sea salt between 600 and 1200 nm. This work included the development of two new techniques for aerosol research. The first technique measures aerosol density using a combination of aerosol size distribution and gravimetric mass concentration measurements. This technique was used to measure the density of a number of submicrometer aerosols including laboratory generated NaCl aerosol and ambient aerosol. The densities for the laboratory generated aerosols were found to be similar to those for the bulk materials used to produce them. The technique, extended to super-micrometer particle size range may find application in ambient aerosol research where it could be used to discriminate between periods when the aerosol is dominated by NaCl and periods when the density is more representative of crustal material or sulfates. The technique may also prove useful in laboratory or industrial settings for investigating particle density or in case where the composition is known, morphology and porosity. The second technique developed, integrates the existing physicochemical techniques of volatilisation and hygroscopic growth analysis to investigate particle composition in terms of both the volatilisation temperatures of the chemical constituents and their contribution to particle hygroscopic behaviour. The resulting volatilisation and humidification tandem differential mobility analyser or VH-TDMA, has proven to be a valuable research tool which is being used in ongoing research. Findings of investigations relating the composition of the submicrometer marine aerosol modes to candidate models for their formation are presented. Sea salt was not found in the numerically dominant particle type in coastal nucleation mode or marine Aitken and accumulation modes examined on the Southeast Queensland coast during periods where back trajectories indicated marine origin. The work suggests that all three submicrometer modes contain the same four volatile chemical species and an insoluble non-volatile residue. The volatility and hygroscopic behaviours of the particles are consistent with a composition consisting of a core composed of sulfuric acid, ammonium sulfate and an iodine oxide coated with a volatile organic compound. The volume fraction of the sulfuric acid like species in the particles shows a strong dependence on particle size.

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