Analysis of the indoor environment in a room with diffuse ceiling ventilation
Author
Andersen, Rune Baldur Kessler
Term
4. term
Publication year
2018
Abstract
Formålet med dette projekt er at evaluere indeklimakvaliteten i et rum med diffus loftventilation med fokus på termisk og atmosfærisk komfort. Arbejdet er opdelt i to dele: laboratoriemålinger og numeriske CFD-simuleringer. I forsøgsdelen blev varmebelastningens fordeling, forureningskildens placering og ventilationsluftskiftet varieret, mens temperatur, lufthastighed og sporstof (N2O) blev målt i opholdszonen for at vurdere komfort samt mål som lokalt luftkvalitetsindeks og forureningsfjernelseskoefficient. Resultaterne bekræfter, at diffus loftventilation kan levere acceptabel termisk og atmosfærisk komfort med ensartede temperaturfordelinger, små lodrette temperaturgradienter og trækfri forhold i opholdszonen. Ændringer i kildeplacering, luftskifte og varmebelastning gav forskellige forureningsmønstre og påvirkede de lokale luftkvalitetsmål. Den numeriske model, der repræsenterer rummet i 3D og loftet som porøst medie, viste mindre afvigelser i temperatur og hastighed, men beskrev N2O-fordelingen utilstrækkeligt, når kilden var placeret uden for den termiske fane. På trods af måleusikkerheder og energi-/masseubalance indikerede sammenligningerne, at modelsættet var rimeligt; en justeret model med ekstra energikilde og reduceret kontaminationsflow blev derfor afprøvet, og resultaterne præsenteres i appendiks. Rapporten afsluttes med konklusioner, usikkerheder og forslag til fremtidigt arbejde.
This project evaluates indoor environmental quality in a room with diffuse ceiling ventilation, focusing on thermal and atmospheric comfort. The work comprises two parts: laboratory experiments and numerical CFD analyses. In the experiments, the distribution of heat loads, the position of the pollutant source, and the ventilation flow rate were varied, while temperature, air velocity, and tracer gas (N2O) were measured in the occupied zone to assess comfort and metrics such as the local air quality index and contaminant removal coefficient. Results confirm that diffuse ceiling ventilation can provide acceptable thermal and atmospheric comfort with uniform temperature fields, small vertical temperature gradients, and draught-free conditions in the occupied zone. Changes in source position, air change rate, and heat load produced distinct contamination patterns that affected local air quality metrics. The numerical model, representing the room in 3D and the ceiling as a porous medium, showed small discrepancies in temperature and velocity, but it did not accurately predict N2O distribution when the source was outside the thermal plume. Despite measurement uncertainties and energy/mass imbalances, comparisons suggested the model setup was reasonable; an adjusted model with an additional energy source and reduced contamination flow was therefore tested, with results reported in the appendix. The thesis concludes with key findings, measurement uncertainties, and directions for future work.
[This summary has been generated with the help of AI directly from the project (PDF)]
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