Implementation and evaluation of air flow and heat transfer routines for building simulation tools
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Doctoral thesis (article-based)
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VTT publications, 471
AbstractEnvironmental, 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.
air conditioning, HVAC systems, heat transfer, air flow, air quality, buildings, simulation, BUS++, networks, data processing
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