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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.
1

Värmestrålning i ugn för hushållsbruk, modellering – simulering - experiment / Heat radiation in ovens for domestic use, modeling – simulation - experiment

Wahlström, Krister January 2005 (has links)
I många mikrovågsugnar finns grillelement som kan färgsätta matens yta. Vissa kommande modeller av mikrovågsugnar planeras vara utan roterande tallrik och maten blir då stillastående. Därför måste grillelementen och tillhörande reflektorer optimeras så värmestrålningen om möjligt blir jämnt fördelad i ugnen. Syftet med examensarbetet är att undersöka hur värmestrålningen i ugnarna kan beräknas så optimeringar kan göras. Värmestrålningen i en befintlig mikrovågsugn har simulerats och mätts. Simuleringarna och mätningarna visar att värmestrålningens fördelning bör kunna beräknas med tillräcklig noggrannhet då quartzglasen som omger grillelementens värmetrådar försummas, reflektionerna ansätts som diffusa och ytorna ansätts som grå. Väggarnas emissionstal har troligen mindre betydelse för strålningsfördelningen, men påverkar den absoluta strålningen. / In many microwave ovens are grill elements, which give color to the food surface. Some future models of microwave ovens are designed with no turning table and the food will therefore be stationary. The grill elements and their reflectors must therefore be optimized so the heat radiation if possible will be evenly distributed in the oven. The purpose of this work is to examine how the heat radiation in the ovens can be calculated, thus the optimization can be carried out. The heat radiation in an existing microwave oven has been simulated and measured. The simulations and measurements show that the distribution of the heat radiation should be calculated with sufficient accuracy when the quartz glass that surrounds the filament of the grill element is neglected, reflections are assumed to be diffuse and the surfaces are assumed to be mathematically grey. The emissivities of the surfaces
2

Demonstrating the significance of microclimate on annual building energy simulations using RadTherm

Sommerfeldt, Nelson January 2012 (has links)
Buildings account for over 35% of the energy demand in OECD countries, making them a prime target for improvement. (EIA 2011) To help building owners reduce energy usage, ratings systems such as LEED have been developed. A prerequisite for certification is the demonstration of energy efficiency through computer modeling; however, the complex nature of building energy simulations too often leads to errors of up to 30% (Turner and Frankel 2008). One source of significant error can be the assumptions made of environmental conditions, which are often simplified to speed up simulations. To demonstrate the significance of active microclimate modeling, a building energy model combined with a microclimate model has been created in RadTherm, a commercial CAE thermal solver. Simulations are run using Passive House construction in three types of environments, and demonstrate an increase in energy demand over an annual time scale when microclimatic components are included. The increase in demand is less than 1%, however the decrease in radiant heat losses are up to 30%. Using the same methodology with revisions to the building construction and urban geometry, a larger increase in energy demand is expected.

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