The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Implementation and Evaluation of Air Flow and Heat Transfer Routines for Building Simulation Tools

Pekka Tuomaala

Dissertation for the degree of Doctor of Science in Technology to be presented, with permission of the Department of Mechanical Engineering of the Helsinki University of Technology (Espoo, Finland), for public examination and debate in Auditorium K216 on the 23rd of August, 2002, at 12 o'clock noon.

Overview in PDF format (ISBN 951-38-5996-7)   [214 KB]
VTT Publications 471, ISSN 1455-0849

Dissertation is also available in print (ISBN 951-38-5995-9)
Copyright © 2002 VTT Technical Research Centre of Finland
VTT Publications 471, ISSN 1235-0621


Environmental, epidemiological and economical reasons increase the pressure to design, construct and maintain better buildings in the future. Therefore, a new assembly of simulation routines for predicting both ventilation and heat transfer processes of buildings were studied. The work was limited to implementation and evaluation of new air flow and heat transfer routines for building simulation tools. Development of simulation tool user-interfaces, post-processors and component database have all been excluded.

The simulation routines were implemented in a new building simulation tool BUS++, which was based on discretisation and solution of mass, momentum, and heat balance equations. Ventilation fans, external wind and thermal buoyancy were included as driving forces for air infiltration and ventilation process. Two completely new routines were developed and implemented to obtain more reliable estimations of dynamic and multi-mode heat transfer covering thermal convection, conduction, and radiation. The first new routine focused on defining a rational thermal calculation network, and the second one concentrated on simulation of thermal radiation in a room. Finally, a rigorous set of tests were conducted to validate the air flow and heat transfer routines implemented in BUS++. The test set included commonly utilised analytical verifications and inter-model comparisons as well as completely new empirical validation test cases.

The new rational gridding method reduced simulation times by 44 % to 86 % in a typical slab test case with a cyclic excitation, and the new routine for thermal radiation was up to ten times faster than the conventional matrix radiosity method. In addition, the simulation and validation data showed good agreement, especially for the analytical verifications and inter-model comparisons with typical differences less than 2 %. Despite these promising results, more research work is needed to further develop the simulation routines. In the future, special attention ought to be paid to simulation tool user-interfaces to facilitate full utilisation of the simulation tool by a wide range of users.

This thesis consists of an overview and of the following 5 publications:

  1. Tuomaala, P. 1993. New Building Air Flow Simulation Model: Theoretical Basis. Building Services Engineering Research and Technology, Vol. 14, Number 4, pp. 151-157.
  2. Tuomaala, P. and Rahola, J. 1995. Combined Air Flow and Thermal Simulation of Buildings. Building and Environment, Vol. 30, Number 2, pp. 255-265.
  3. Tuomaala, P., Piira, K. and Vuolle, M. 2000. A Rational Method for the Distribution of Nodes in Modelling of Transient Heat Conduction in Plane Slabs. Building and Environment, Vol. 35, pp. 397-406.
  4. Tuomaala, P. and Piira, K. 2000. Thermal radiation in a Room: An Improved Progressive Refinement Method. Building Services Engineering Research and Technology, Vol. 21, Number 1, pp. 9-17.
  5. Tuomaala, P., Simonson, C. J. and Piira, K. 2002. Validation of Coupled Airflow and Heat Transfer Routines in a Building Simulation Tool. Accepted for publication in ASHRAE Transactions, Vol. 108, Number 1, pp. 435-449.

Keywords: air conditioning, HVAC systems, heat transfer, air flow, air quality, buildings, simulation, BUS++, networks, data processing

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© 2004 Helsinki University of Technology

Last update 2011-05-26