Indoor airflow characteristics under increased heat load conditions

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

A healthy, comfortable and intelligent indoor environment is a key objective in comprehensive well-being. This is also a main target of advanced HVAC-technology. The major challenge in indoor air distribution is to provide occupants with clean air for breathing and maintain their thermal comfort. Consequently, a careful study based on systematic understanding and critical awareness of knowledge has been carried out to recognize main characteristics of indoor airflows under different heat load conditions. The research methods were experimental and modeling methods. The motivation was to improve knowledge on airflow characteristics and indoor air movement. The main objective was to create a physical basis for characterizing indoor airflows and to investigate the effects of heat load strength and distribution on the airflow field. The diffuse ceiling ventilation enabled locally a low-momentum supply airflow field that disturbs little the buoyancy driven flows from heat sources. The airflow characteristics can be used to assess dependencies, regularities and relations from the experimental and numerical data. In this way, novel mathematical models can be investigated and new indicators can be developed. The study adds to the knowledge on airflow characteristics by conducting the laboratory measurements and the field studies. The numerical modeling was used to provide detailed data from indoor airflow field under the given boundary conditions. The experiments indicate that the average of mean air speeds, the spatial deviation of mean air speeds and the temporal deviation of instantaneous air speeds increase with heat load strength. The asymmetric heat load distribution generated a circulating airflow pattern that was not found with the symmetric heat load distribution. Hence, the results show a clear cause-effect relationship between the heat sources and the indoor airflow field. Furthermore, the significance on reducing heat loads has been realized while minimizing the draught discomfort. It was found that the category A for thermal environment is difficult to achieve according to standard EN ISO 7730. In the multipurpose arena, the large-scale air movement was considerably affected by the ventilation airflow rates, the air temperature differences, retractable stand position and share of lower and the upper air distribution. In the small ice rink, the indoor air movement was quiescent in the ice rink zone compared to the upper zone, in which the air movement occurred.The airflow characteristics offer parameters for assessing indoor airflows, thermal conditions and draught. Those parameters are necessary when controlling indoor environmental quality (IEQ) by combining the measured, modeled and perceived data in the future. Thus, airflow characteristics is an essential part of human well-being and performance indoors. Further targets for healthy, comfortable and intelligent indoor environment can be evolved by using an artificial intelligence.
Translated title of the contributionSisäilman virtauksen ominaispiirteet suurilla lämpökuormilla
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Kosonen, Risto, Supervisor
Publisher
Print ISBNs978-952-60-8313-1
Electronic ISBNs978-952-60-8314-8
Publication statusPublished - 2018
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • indoor airflows
  • thermal environment
  • airflow characteristics
  • convection flows
  • airflow interaction
  • heat load
  • air distribution

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