The effect of thermal plumes on the performance of ventilated ceilings in commercial kitchens

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.author Kosonen, Risto
dc.date.accessioned 2012-02-17T07:47:42Z
dc.date.available 2012-02-17T07:47:42Z
dc.date.issued 2006-06-16
dc.identifier.isbn 951-22-8233-X
dc.identifier.issn 1238-8971
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/2717
dc.description.abstract The efficiency of the exhaust system is especially emphasised with a ventilated ceiling system where the exhaust is located at ceiling level. The removal efficiency of the total system must be guaranteed and the spread of impurities throughout the kitchen should be prevented. At the moment, none of the existing calculation standards are specially tailored for a kitchen ceiling environment. In the normal design practice, empirical knowledge of the existing installations together with heat load based calculation has been used for airflow rate determination. The starting point for this research was to study the effect of the thermal plumes and supply air systems on the efficiency of a ventilated ceiling. A special consideration was to analyze the effect of a capture jet on the contaminant removal efficiency. In that capture air concept, the air jet is projected horizontally across the ceiling, which helps to direct heat and air impurities towards the exhaust. From the practical point of view, the objective of this study was to develop a design process to compute the required air flow rate more accurately. In this study, the measured convection flows of kitchen appliances during idle and cooking modes were compared with the generic plume equation in which the virtual origin is constant. The generic plume equation derived in the region of complete flow similarity is not fully valid in the intermediate zone (0.8-2.0 m from appliances). Still, it is possible to reach a reasonable accuracy for practical applications with the adjusted virtual origin. The cooking process does not have any significant effect on the velocity and temperature distribution of the convection flow. The reason for this is that the mass flow rate of water during boiling is small compared with the induced air flow rate and therefore does not have a significant effect on the convection flow. Thus, the actual convection load and the product specific virtual origin can describe the plume during the cooking process. In the previous studies of thermal plumes, the velocity and temperature distribution factors are much higher than in the present study. In addition, the entrainment factors of the previous studies are much smaller than in this study. The measurements indicate that the heat gain has a significant effect on the spreading angle and the entrainment factor close to the heat source. The plumes with high heat gains are narrower and the convection flow induces more room air than the previous studies have pointed out. The efficiency of the exhaust system can be improved with a small capture jet installed at the ceiling surface. Both the measurement and simulated data give lower contaminant levels when the capture jet was introduced. The plume equation gives a platform to calculate the air flow rate that is theoretically required to remove the convective heat output of the appliance block. In this study, the flush-out factor of the supply air on the theoretical plume equation was derived for the centralized capture jet concept. For practical design work, the target for the containment removal efficiency should be 85 %. To obtain 85 % containment removal efficiency requires to a flush-out factor of 1.2. en
dc.format.extent 55, [56]
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher Helsinki University of Technology en
dc.publisher Teknillinen korkeakoulu fi
dc.relation.ispartofseries Report / Helsinki University of Technology, Laboratory of Heating, Ventilating and Air Conditioning. A en
dc.relation.ispartofseries 11 en
dc.relation.haspart Kosonen Risto, Koskela Hannu, Saarinen Pekka. Thermal plumes of kitchen appliances: part 1 Idle mode. Energy and Buildings, accepted for publication on 29.12.2005. [article1.pdf] © 2006 Elsevier Science. By permission.
dc.relation.haspart Kosonen Risto, Koskela Hannu, Saarinen Pekka. Thermal plumes of kitchen appliances: part 2 Cooking mode. Energy and Buildings, accepted for publication on 29.12.2005. [article2.pdf] © 2006 Elsevier Science. By permission.
dc.relation.haspart Kosonen Risto, Koskela Hannu, Saarinen Pekka. An analysis of thermal plumes. Proceedings of the 17th Air-conditioning and Ventilation Conference. Prague, Czech Republic. 17-19 May 2006.
dc.relation.haspart Kosonen Risto, Mustakallio Panu. The influence of a capture jet on the efficiency of a ventilated ceiling in a commercial kitchen. The International Journal of Ventilation, Volume 1, Number 3, February 2003, pages 189-200. [article4.pdf] © 2003 VEETECH Ltd. By permission.
dc.relation.haspart Kosonen Risto, Mustakallio Panu. Analysis of capture and containment efficiency of a ventilated ceiling. The International Journal of Ventilation, Volume 2, Number 1, June 2003, pages 33-44. [article5.pdf] © 2003 VEETECH Ltd. By permission.
dc.relation.haspart Kosonen Risto. The effect of supply air systems on the efficiency of a ventilated ceiling. Building and Environment, accepted for publication on 5.9.2005. [article6.pdf] © 2006 Elsevier Science. By permission.
dc.subject.other Mechanical engineering en
dc.title The effect of thermal plumes on the performance of ventilated ceilings in commercial kitchens en
dc.type G5 Artikkeliväitöskirja fi
dc.description.version reviewed en
dc.contributor.department Department of Mechanical Engineering en
dc.contributor.department Konetekniikan osasto fi
dc.subject.keyword thermal plumes en
dc.subject.keyword commercial kitchen en
dc.subject.keyword capture jet en
dc.subject.keyword ventilation efficiency en
dc.subject.keyword displacement ventilation en
dc.identifier.urn urn:nbn:fi:tkk-007045
dc.type.dcmitype text en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.type.ontasot Doctoral dissertation (article-based) en
dc.contributor.lab Laboratory of Heating, Ventilating and Air Conditioning en
dc.contributor.lab LVI-tekniikan laboratorio fi


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