Characterization of residential chimney conditions for flue gas flow measurements

A literature survey and a theoretical study were performed to characterize residential chimney conditions for flue gas flow measurements. The focus is on Pitot-static probes to give sufficient basis for the development and calibration of a velocity pressure averaging probe suitable for the continuous dynamic (i.e. non steady state) measurement of the low flow velocities present in residential chimneys. The flow conditions do not meet the requirements set in ISO 10780 and ISO 3966 for Pitot-static probe measurements, and the methods and their uncertainties are not valid. The flow velocities in residential chimneys from a heating boiler under normal operating condi-tions are shown to be so low that they in some conditions result in voiding the assumptions of non-viscous fluid justifying the use of the quadratic Bernoulli equation. A non-linear Reynolds number dependent calibration coefficient that is correcting for the viscous effects is needed to avoid significant measurement errors. The wide range of flow velocity during normal boiler operation also results in the flow type changing from laminar, across the laminar to turbulent transition region, to fully turbulent flow, resulting in significant changes of the velocity profile during dynamic measurements. In addition, the short duct lengths (and changes of flow direction and duct shape) used in practice are shown to result in that the measurements are done in the hydrodynamic entrance region where the flow velocity profiles most likely are neither symmetrical nor fully developed. A measurement method insensitive to velocity profile changes is thus needed, if the flow velocity profile cannot otherwise be determined or predicted with reasonable accuracy for the whole measurement range. Because of particulate matter and condensing fluids in the flue gas it is beneficial if the probe can be constructed so that it can easily be taken out for cleaning, and equipped with a locking mechanism to always ensure the same alignment in the duct without affecting the calibration. The literature implies that there may be a significant time lag in the measurements of low flow rates due to viscous effects in the internal impact pressure passages of Pitot probes, and the significance in the discussed application should be studied experimentally. The measured differential pressures from Pitot-static probes in residential chimney flows are so low that the calibration and given uncertainties of commercially available pressure transducers are not adequate. The pressure transducers should be calibrated specifically for the application, preferably in combination with the probe, and the significance of all different error sources should be investigated carefully. Care should be taken also with the temperature measurement, e.g. with averaging of several sensors, as significant temperature gradients may be present in flue gas ducts.

Är Mjukvaru-EQ:s så bra som utvecklarna lovar? : En jämförelse av hårdvaru- och mjukvaru-EQ:s

I denna uppsats undersöks skillnaden mellan EQ:s som analog hårdvara och dess digitala motsvarigheter, dvs. emuleringar i pluginformat. I uppsatsen undersöks enheterna genom tekniska mätningar samt lyssningstest. I mätningarna gick det att se tydliga skillnader i övertonsdistortionen även om resterande parametrar var bra emulerade. I lyssningstesten uppfattade lyssningspanelen relativt stora skillnader mellan enheterna. Detta visar på att emuleringarna inte är så bra och exakta som utvecklarna påstår.

Charterturisme som en produkt : en sociologisk analyse af agens i oplevelsesøkonomien

Charter tourism as a product: a sociological analysis of agency in the experience economy In recent years charter tourism as a convenient and cost-effective mode of travelling has been declining. This may be related to dominating societal ideals promoting self-actualization, individual exploration and spontaneity. However, not much is known about the development of ideals and practices among charter tourists. By use of ethnographic fieldwork methodology, including pre-departure and post-travel telephone interviews, this exploratory study investigated a group of Danish charter tourists travelling to Gran Canaria. Results show that the charter tourists were active in navigating between a series of central dilemmas posed by the consumption of a mass product in an individualized societal context, thereby shaping their experiences to form a desirable tourist product.

Kreativitet under stress : En studie i att vara kreativ på beställning

En grafisk designer måste kunna producera oavsett vilka förhållanden som råder. Rapporten behandlar vad korta och långa deadlines har för inverkan på denna förmåga och hur kreativiteten kan främjas vid stressiga situationer. Semistrukturerade djupintervjuer utfördes med åtta Art- och Creative directors i Gävledala-regionen för att undersöka hur de upplevde att vara kreativa under stressiga förhållanden. Resultatet visade att det generellt inte var ett problem för studiens respondenter att vara kreativa på beställning men att de inte heller följde några specifika metoder för att underlätta arbetsflödet. Det visade sig även att det snarare var arbetsbördan och mängden arbetsuppgifter som påverkade stressfaktorn än en specifik tidsram.