Thermal Comfort and Building Simulation

Research output: Types of ThesesMaster's Thesis / Diploma Thesis

Abstract

Thermal comfort is an important factor in the daily utilisation of buildings; it is relevant for many kinds of inhabited buildings such as office buildings, schools, houses and any other types of buildings. Most people spend more than 90% of their lives in an artificial climate and therefore it is sensible to design all the influencing parameters of thermal comfort. In the late sixties P.O. Fanger invented a mathematical approach to describe the comfort behavior in buildings. To give this content more significance, it is necessary to handle and optimize the energy consumption with as much emphasis on comfort as possible. Therefore thermal comfort should be an integral part of the design process. The goal of the paper is to find such a coupling method and to investigate its practical relevancy and the possible daily usage of this appendage. The well-established methods in Austria for the calculation of the building energy demand from the “Österreichischen Institut für Bautechnik” (OIB) and the “Passivhaus Projektierungspaket“ (PHPP) can only handle the energy efficiency of buildings. The fundamental question for occupants, according to the thermal behavior and comfort, is not part of these approaches. Simulation packages could offer a method to enhance the design of buildings, which includes the thermal comfort factor neglected by the well established methods for design. This method will optimize the energy efficiency and the comfort factor of buildings. This study aims to investigate if simulations are really able to aid the design process, a key question being how precise the simulations have to be for realistic results. A commonly employed simulation package is TRNSYS which is limited to the star node network model. This restriction leads to a one-node energy balance for each of its defined zones. This is a coarse resolution of the physics. It’s impossible to examine temperature gradients over the height of a room or to give a detailed airflow pattern in a room. A much more specific method is the Finite Volume Method, which is used by FLUENT. Due to the discretization of the domain, each control volume provides a complete energy balance. Each zone is comprised of thousands of finite control volumes. Thus, all phenomena of comfort analysis can be calculated and executed in detail. Obviously, all tools have pros and cons. If the disadvantage of the one package is the advantage of the other then a coupling would make sense. In TRNSYS comfort analysis is very coarse but, on the other hand, it spans over long periods of time and only the calculation of the statistical comfort can be done. On the other hand, in FLUENT, a fine resolution can be made but this is very hardware and time intensive. Unsteady, long-term simulations would be very time consuming and the results would just indicate an approach. Thus, coupling TRNSYS and FLUENT would provide an optimal methodology. The coupling method which has been carried out presents detailed physics of airflow and heat transfer in addition to long-term simulations. As a result of mathematical and physical compromises, all simulation packages are subjected to simplified boundary conditions. The biggest challenge is to give the right limits and represent reality as accurately as possible. This leads to the result that the simulation packages can only be as truthful as the periphery conditions are. A description of the basic steps to realistic results can be found in this assignment.
Translated title of the contributionThermal Comfort and Building Simulation
Original languageGerman
Publication statusIn preparation - 2007

Keywords

  • Gebäudesimulation
  • Behaglichkeit

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