Sökning: "thermal conduction"

Visar resultat 16 - 20 av 106 avhandlingar innehållade orden thermal conduction.

  1. 16. Predicting the Long-Term Insulation Performance of District Heating Pipes

    Författare :Camilla Persson; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; heat conduction; polyurethane foam; insulation capacity; diffusion; thermal conductivity; cyclopentane; solubility coefficient; long-term performance;

    Sammanfattning : The aim of the studies that comprise this thesis was to predict the heat loss over timefrom a range of district heating pipes insulated with closed-cells foam. The thermalconductivity of the foam changes over time when it is not diffusion-tight encapsulatedagainst the environment, as diffusion alters the cell gas composition until it reachesequilibrium with the surrounding air. LÄS MER

  3. 17. Damage mechanisms for near-infrared radiation induced cataract

    Författare :Zhaohua Yu; Per Söderberg; Konstantin Galichanin; Masami Kojima; Uppsala universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; infrared radiation; photochemical; thermal; forward light scattering; lens; cataract; temperature; Arrhenius equation; heat diffusion;

    Sammanfattning : Purpose: 1) To estimate the threshold dose and the time evolution for cataract induction by near infrared radiation (IRR) in seconds exposure time domain; 2) to determine the ocular temperature development during the threshold exposure; 3) to investigate if near IRR induces cumulative lens damage considering irradiance exposure time reciprocity; 4) to experimentally estimate the temperature in the lens indirectly from the measurement of temperature-induced light scattering increase.Methods: Before exposure, 6-weeks-old albino rats were anesthetized and the pupils of both eyes were dilated. LÄS MER

  4. 18. Thermal and mechanical behaviour of railway wheel steel

    Författare :Johan Ahlström; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; phase transformations; plastic deformation; sliding contact; heat conduction modelling; low cycle fatigue; railway wheel steel Fe-0.5C-0.3Si-0.75Mn-0.05V ; austenitisation; transformation kinetics; heat treatment; friction;

    Sammanfattning : The wish to increase loads and speeds of trains puts higher demand on construc¬tion, engineering and material than ever before. Therefore it is necessary to con¬tinuously develop technology to meet these increasing requirements. LÄS MER

  5. 19. Thin-Film Electrocatalysts for Polymer Electrolyte Fuel Cells - Activity, Durability and Proton Conduction

    Författare :Björn Wickman; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Nafion; thin film evaporation; PEMFC; platinum; titanium oxide; cathode; fuel cell; oxygen reduction reaction; electrocatalyst; proton conduction; model systems;

    Sammanfattning : The polymer electrolyte membrane fuel cell (PEMFC) is a potential technology for future energy conversion in sustainable energy systems. By using hydrogen from renewable energy sources and oxygen from the air, the fuel cell produces electricity with water as the only exhaust. LÄS MER

  7. 20. Heat conduction effects during laser welding

    Författare :Jesper Sundqvist; Lars Pejryd; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Manufacturing Systems Engineering; Produktionsutveckling;

    Sammanfattning : Since the invention of the laser in 1960, its use has been growing steadily. New laser sources with high beam power and high beam quality provide potential for further growth. LÄS MER