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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.
131

An investigation of thermal conditions in spark ignition engines

Yuen, Hong Chuen Raymond January 1995 (has links)
No description available.
132

Conformational analysis via LIF spectroscopy of jet cooled molecules : hydroxy- and amino-benzoic acid esters

Hepworth, Peter January 1993 (has links)
No description available.
133

Calculations of laser manipulation and evaporative cooling of atoms

Wu, Huang January 1996 (has links)
No description available.
134

EXPERIMENTAL AND CFD STUDY OF EFFUSION COOLING IN AN S-BEND DIFFUSING PASSAGE

Ng, BILLY CHOK NAM 23 December 2013 (has links)
This thesis presents an experimental and computational fluid dynamics (CFD) study on a rectangular S-bend with straight and diffusing passages with passive effusion cooling. Experimental tests were performed at both cold and hot flow conditions over a range of Reynolds numbers from 2.5e5 to 4.5e5. Hot flow testing was conducted with the primary flow temperature up to 300 °C. Severe backpressure penalties occurred with full-surface passive effusion injection in cold flow tests. Moderate penalties occurred with reduced surface coverage whereby the performance was affected by the S-bend secondary fields with injection at different locations. High surface cooling effectiveness with full-coverage of cooling film was measured; the impacts from the S-bend secondary flow fields were measured to be minimal. The CFD study revealed the importance of using experimental flow boundary conditions for simulations. Using the standard k-ε model with wall functions was confirmed as appropriate for simulating the S-bend flow with effusion cooling. A coarse-grid CFD methodology using a porous wall boundary condition to simulate the effects of effusion cooling was investigated. From a design perspective, this model is preferable for quantifying the injection flow rate since the actual mass flow rate is not known. Comparison to the alternative solution using uniform mass flow boundary conditions showed that both models incorrectly predicted the momentum. The porous wall model, however, is promising for practical design applications of S-duct flow fields with effusion injections. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-12-23 14:20:32.38
135

Kyla med värme : En jämförelsestudie med huvudfokus på fjärrvärmedriven kyla

Eliasson, Dennis January 2017 (has links)
Syftet med detta examensarbete är att värdera och jämföra ett antal utvalda kyltekniker, med huvudfokus på värmedriven kyla. Dels för en specifik befintlig byggnad men även en generell jämförelse som kan ligga till grund för andra projekt. Arbetet är utförti samarbete med ÅF i Borlänge. Den specifika byggnaden som har undersökts är belägen i Borlänge och kyls idag av stadsvatten, och har en kyleffektpå 655kW. Borlänge Energis fjärrvärmenät ligger till grund för samtliga beräkningar och antaganden. Huvudsyftet har varit att jämföra de olika kylteknikerna ur ett ekonomiskt perspektiv, men även snudda vid ett miljöperspektiv. Utöver detta så var syftet att undersöka hur en fjärrvärmeleverantör ska kunna leverera kyla till sin kund, utan att behöva gräva ner nya fjärrkylledningar. De kyltekniker som jämförts i detta arbete är absorptionskyla, adsorptionskyla, sorptiv kyla & eldriven kompressorkyla. För att kunna jämföra de olika teknikerna har den totala livscykelkostnaden beräknas. Investeringskostnader och data har erhållits ifrån leverantörer genom kontakt med kunniga säljare. Driftkostnader har beräknats fram med hjälp av driftdata samt energipriser hos Borlänge Energi. Kostnader för installation, frakt och lyft är inte medräknade i detta arbete. För den befintliga byggnaden visade det sig att den mest kostnadseffektiva lösningen är absorptionskyla, tätt följt av att komplettera befintligt system med frikyla i form utav en kylmedelkylare. Absorptionskylan har väldigt låga driftkostnader under sommarhalvåret, då fjärrvärmepriset är som lägst. Dyrast av teknikerna är adsorptionskyla, tack vare den dyra investeringskostnadenoch dess låga verkningsgrad. Även för den generella jämförelsen visade det sig att den mest kostnadseffektiva lösningen är absorptionskyla, tätt följt av eldriven kompressorkyla. Absorptionskylan har mycket låga driftkostnader, men kompressorkylan har istället en lägre investeringskostnad och mycket bättre verkningsgrad. Om Borlänge Energi skulle sälja fjärrvärmeproducerad kyla under sommaren, så skulle de vid 655kW kyleffekt ha en återbetalningstid avett absorptionskylaggregat på endast 2 år. Skulle de istället ha en kyleffekt på 100kW skulle återbetalningstiden vara ca 5 år. Slutsatser kan dras ifrån detta arbete att byggnader med högre kyleffekt är mer fördelaktiga för värmedriven kyla. / The aim of this thesis is to evaluate and compare a number of selected chilling techniques, with a main focus on heat driven cooling. Mainly for an existing building, but also a more general comparison that can be used as a basis for other projects. This thesis has been carried out in cooperationwith ÅF in Borlänge.The building that has been investigated is located in Borlänge. All calculations and assumptions regarding the district heating network are based on Borlänge Energi’s district heating network. The main purpose has been to compare the different cooling techniques from an economical point of view, but also a slight comparison from an environmental point of view. In addition, the purpose has been to investigate how a district heating supplier can deliver cooling to its customers without having to dig down newdistrict cooling pipes. The cooling techniques compared in this thesis are absorption chillers, adsorption chillers, sorptive cooling and conventional electrical compression chillers. In order to compare the different techniques, the total life cycle cost has been calculated. Investment costs and data have been obtained from skillful salesmen representing variouscompanies. Operating costs have been calculated using data and energy prices from Borlänge Energi. Costs for installation, shipping and lifting are not included in this thesis. The most cost-effective solution for the existing building is to install an absorption chiller, closely followed by complementing the existing cooling system with free cooling. The absorption chillers has very low operating costs during the summer, when the price of the district heating is at its lowest. The most expensive technique are adsorption cooling, due to its expensive investment cost and its low efficiency. For the general comparison, it was found that the most cost-effective solution is absorption chiller as well, closely followed by the conventional compressor chiller. The absorption chillers has much lower operating costs than its competitors, but the compressor chiller has a lower investment cost and a much better efficiency. If Borlänge Energi were to sell district heat-produced cooling during the summerusing an adsorption chiller, they would have a payback time of only approximately 2 years, with a cooling power of 655kW. With a cooling power of 100 kW, the payback time would be approximately 5 years. Conclusions can be drawn from this thesis that buildings with higher cooling demand are better suited for heat-driven cooling.
136

Bio-Inspired CACO<sup>3</sup> Nanocomposite for Efficient Radiative Cooling

Zixuan Zhao (6636170) 14 May 2019 (has links)
Passive radiative cooling favors the transfer of energy to the deep space (2.7K) by emitting in the transparent atmosphere region (8-13m) and reflecting incoming solar irradiation. To achieve desired daytime or night time cooling performance, scientists have explored various fine-tuned photonic material combinations and layering techniques. However, the high cost, UV absorption or telecommunication interferences due to the metallic material used. Scalable and low-cost nonmetal materials have been studied, but the absorption in the UV range still remains a limitation. Single crystal CaCO_3was found to be highly reflective in the UV range, but it has not been explored for radiative cooling applications yet. In this work we first studied the reflectance in the solar range of seashells of multi-millimeters thick, and found over 70% reflectance. Inspired by this promising result, we fabricated a bio-inspired material — CaCO_3 acrylic nanocomposite, and optimized the nanoparticle size to most strongly reflect the sunlight. We analyzed its performance using Mie Theory and Monte Carlo Simulation for multiple size distribution with dependent scattering correction. The results are in excellent agreement with the experimental data. With 60% volume concentration, the simulation results showed that the total solar reflectance of CaCO_3 can achieve up to 97% . Insights obtained from this work will aid researchers in selecting economical, scalable, and manufacturable materials for radiative cooling applications. <br>
137

Correlations for the specific volume of nanostructured Pd₈₂Si₁₈ alloys. / 納米鈀硅合金比容的硏究 / Correlations for the specific volume of nanostructured Pd₈₂Si₁₈ alloys. / Na mi ba gui he jin bi rong de yan jiu

January 2001 (has links)
Tsui Pui Yuen = 納米鈀硅合金比容的硏究 / 徐沛源. / Thesis submitted in 2000. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Tsui Pui Yuen = Na mi ba gui he jin bi rong de yan jiu / Xu Peiyuan. / Abstract --- p.i / 摘要 --- p.ii / Acknowledgments --- p.iii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- A New Age of Materials --- p.1 / Chapter 1.2 --- Nanocrystalline Materials --- p.1 / Chapter 1.3 --- Fabrication of Nanocrystalline Materials --- p.2 / Chapter 1.4 --- Phase Transformation --- p.3 / Chapter 1.5 --- Nucleation and Growth --- p.5 / Chapter 1.6 --- Spinodal Decomposition --- p.7 / Chapter 1.7 --- The Relation of Undercooling and the Morphology of SD --- p.9 / Chapter 1.8 --- Method to Obtain Large Undercooling --- p.9 / References --- p.11 / Figures --- p.12 / Chapter Chapter 2 --- Experimental --- p.19 / Chapter 2.1 --- Method --- p.19 / Chapter 2.2 --- Preparation of Fused Silica Tubes --- p.19 / Chapter 2.3 --- Sample Preparation --- p.19 / Chapter 2.3.1 --- Alloying --- p.19 / Chapter 2.3.2 --- Fluxing --- p.20 / Chapter 2.3.3 --- Controlled Undercooling --- p.20 / Chapter 2.4 --- Analyzing Method --- p.20 / Chapter 2.4.1 --- Measurement of density --- p.20 / Chapter 2.4.1.1 --- Theory --- p.20 / Chapter 2.4.1.2 --- Experimental Setup --- p.21 / Chapter 2.4.2 --- Microstxucture Analysis --- p.21 / References --- p.23 / Figures --- p.24 / Chapter Chapter 3 --- Results and Discussions --- p.28 / References --- p.32 / Table --- p.33 / Figures --- p.34
138

Matrix solution for linear and nonlinear buckling of hyperboloids of revolution

Pan, Chen January 2011 (has links)
Typescript (photocopy). / Digitized by Kansas Correctional Industries
139

Analysis of Cooling Capability in Polish District Heating Substations

Markowicz, Catarina January 2012 (has links)
For a district heating company it is of importance to have an efficient and well performing system. A central part in the work to lower temperature levels in district heating networks is to acknowledge and improve cooling capability in substations. The aim of this thesis is to analyse substations in Polish district heating systems in order to identify reasons of poor cooling and to present suggestions of implementable measures. Furthermore, the economical saving potential from an improved cooling is evaluated. The analysis was carried out for two of the five Polish companies included in this report; Sydkraft EC Slupsk and MEC Koszalin. It was followed by two scenarios created for evaluation of improvement possibilities based on calculated financial savings from reduction of distribution heat losses and distribution pumping. The results show that there are significant improvement possibilities. From the carried out scenarios a saving potential between 15 000 to 20 000 PLN/substation is possible to achieve for selected worst substations, if their individual annual average cooling is set to 30°C. The analysis further shows that causes of poor cooling in substations are highly individual but points out that customer owned substations are represented in the majority of worst substations.
140

Single-phase forced convection in a microchannel with carbon nanotubes for electronic cooling applications

Dietz, Carter Reynolds 10 July 2007 (has links)
A comparative study was conducted to determine whether it would be advantageous to grow carbon nanotubes on the bottom surface of anisotropically-etched silicon microchannels to facilitate greater heat removal in electronic cooling applications. The effect of the samples was evaluated based on the fluid temperature rise through the channels, the silicon surface temperature increase above ambient, and the pressure drop. The height and deposition pattern of the nanotubes were the parameters investigated in this study. The working fluid, water, was passed through the microchannels at two different volumetric flow rates (16 mL/min and 28 mL/min). Additionally, two different heat fluxes were applied to the backside of the microchannel (10 W/cm2 and 30 W/cm2). Extensive validation of the baseline channels was carried out using a numerical model, a resistor network model, and repeatability tests. Finally, the maximum enhancement when using carbon nanotubes under single-phase, laminar, internal, forced convection was investigated using basic principles in regard to the additional surface area created by the carbon nanotubes, as well as their high thermal conductivity. For the devices tested, the samples with carbon nanotubes not only had a higher pressure drop, but also had a higher surface temperature. Therefore, the baseline samples had the best performance. Furthermore, based on a basic principles investigation, the increase to thermal performance gained by increasing the surface area with CNTs is overshadowed by the decrease in mass flow rate for a fixed pressure drop. The analysis suggests that the limiting factor for heat transfer in single-phase, laminar pressure driven flows is not convection heat transfer resistance, but the bulk resistance of the fluid.

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