Influence of kinetic energy sources and internal obstructions on room air conditioning strategy, efficiency of ventilation and room velocity conditions

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en Hagström, Kim 2012-02-10T09:32:33Z 2012-02-10T09:32:33Z 2002-08-30
dc.identifier.isbn 951-22-6088-3
dc.identifier.issn 1238-8971
dc.description.abstract There is a variety of different methods consulting engineers use to design room system, room air diffusion, such as assumption of perfect mixing, design methods employing the empirical relations determined through research, air jet theory and computational fluid dynamics (CFD) codes. The most common design methods based on air jet theory allows only for the prediction of extreme values of air velocities and air temperatures in the occupied zone. However, the results of most analytical and experimental studies has been received from tests in empty rooms and do not reflect the influence of the obstructions or other kinetic energy sources on the room conditions, air distribution and ventilation efficiency. The objectives of the study have been to investigate the influence of different factors on the room air conditions, airflow pattern and efficiency of ventilation and to utilize the collected information to improve current design practices. Scale models and full scale experiments and computational fluid dynamics simulations were conducted in order to study the influence of an occupied zone obstruction level, air distribution method, air change rate, heat and contaminant source plus non-uniformity on the room system performance and the efficiency of ventilation. A new room air conditioning strategy classification was developed. In classification the zonal strategy is introduced to separate room flow situations that cannot be explained by mixing strategy. It is suggested the room air conditioning strategy should be used as a target for design of the room air conditioning system. A simple method for the calculation of the room average velocity conditions was developed. The method is based on the kinetic energy balance of the room space, thus taking into account both air jets and heat sources. Following the presented design algorithm, a designer can estimate the average velocity level within a ventilated room and furthermore utilize it for evaluation of comfort conditions. The calculation method developed is reasonably accurate in mixed conditions, but additional development is needed to take into account zone effects. The room obstructions do not influence on room contaminant distribution within the studied ranges and air distribution methods. The room heat sources are important factors for contaminant removal effectiveness and contaminant uniformity inside the occupied zone with zonal air distribution methods. There exists non-uniformity of the contaminant concentrations within the occupied zone that should not be neglected when designing room air distribution. The non-uniform distribution of heat and contaminant sources within the ventilated space can have a remarkable influence on the contaminant removal effectiveness and especially on the contaminant distribution within the occupied zone. A straightforward comparisons between the measurement data and CFD simulation results is difficult because the comfort oriented, omni-directional air speed measurements are not directly comparable with the air velocity computed with the turbulence models. The use of an artificial, modified velocity method gives especially in low speed areas better correspondence between the measured and calculated speeds. en
dc.format.extent 37, [121]
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 4 en
dc.relation.haspart Hagström K, Zhivov A M, Sirén K, Christianson L L, Influence of the floor-based obstructions on contaminant removal efficiency and effectiveness. Building & Environment 37 (2002), 55-66.
dc.relation.haspart Hagström K, Sirén K, The Influence of heat and contaminant source non uniformity on the performance of three different room air distribution methods, ASHRAE Transactions, Vol. 105, Part 2, 1999, pp. 750-758.
dc.relation.haspart Hagström K, Sandberg E, Koskela H, Hautalampi T, Classification for the room air conditioning strategies, Building & Environment 35 (2000), 699-707.
dc.relation.haspart Hagström K, Sandberg E, Koskela H, Hautalampi T., A strategic approach for the room air conditioning design, Proceedings of the RoomVent 2000 conference, Reading, 9-12 July 2000.
dc.relation.haspart Hagström K, Sirén K, Calculation of the Room Velocity Using Kinetic Energy Balance, ASHRAE Transactions, Vol. 106, Part 2, 2000, pp. 3-12.
dc.relation.haspart Alajuusela J, Heikkinen J, Hagström K, Numerical and Experimental Studies on room airflow, HUT, Laboratory of Applied Thermodynamics, Report 132, August 08, 2001, 66pp.
dc.subject.other Mechanical engineering en
dc.title Influence of kinetic energy sources and internal obstructions on room air conditioning strategy, efficiency of ventilation and room velocity conditions 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 indoor air en
dc.subject.keyword contaminants en
dc.subject.keyword air velocity en
dc.subject.keyword air distribution en
dc.subject.keyword computational fluid dynamics en
dc.subject.keyword CFD en
dc.subject.keyword simulation en
dc.subject.keyword heat sources en
dc.subject.keyword calculation methods en
dc.identifier.urn urn:nbn:fi:tkk-001867
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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