Infiltration has traditionally been assumed to affect the energy load of a building by an amount equal to the product of the infiltration flow rate and the enthalpy difference between inside and outside. Results from detailed computational fluid dynamics simulations of five wall geometries over a range of infiltration rates show that heat transfer between the infiltrating air and walls can be substantial, reducing the impact of infiltration.
Simulations have been performed to investigate the performance of intelligent algorithms for control of indoor air quality through natural ventilation strategies whilst simultaneously meeting the requirements of thermal and visual comfort. The proposed control algorithms are founded on the knowledge base of the building physics and support the control of natural ventilation through control of the window opening, whilst simultaneously controlling the lighting, heating and cooling systems of the building.
Similar to supply air jets in mixing ventilation this paper describes a comprehensive flow model for displacement ventilation derived from the integrated Navier-Stokes differential equations for boundary layers. A new test method for low velocity diffusers in displacement ventilation is developed based on this new flow model. Contrary to jet flow, it is shown that the only independent variable in the new model is the buoyancy flux.
The air leakages can have a large impact on heating needs and thermal comfort in industrial buildings. This is sometimes poorly taken into account, both due to the lack of theoretical approach and knowledge of air tightness.
The air distribution effects of floor mounted swirl diffusers are investigated and described inthis paper. Results are based on a case study of an office typical of those in urban commercialenvironments. The effects of the swirl applied to the supply air as well as temperaturedifferentials between supply and room air are explored. The investigation is restricted tosituations where cooling is required.The results of the work, which is undertaken by way of CFD analysis, are presented in termsof appropriate ventilation effectiveness parameters.
The design of natural, including passive, ventilation systems assumes one of two genericforms: the nasty design problem where the designer seeks to size ventilation openings givenclimatic conditions and thermal comfort criteria or the nice design problem where the designerseeks to size ventilation openings given climatic conditions, indoor temperature distributions,and specified airflow rates - presumably determined from separate thermal or air qualityconsiderations.
The inadequate dissipation of hurnidity fiom living spaces and bathrooms has become asignificant problem area in recent years. This can be attributed both to the replacement of old,poorly sealed windows by new windows with better seals, and to the increasing use of tilesand other building materials which hinder an adequate absorption of water vapour.The residents tend to reject repeated opening of the windows for ventilation purposes ongrounds of the ensuing energy costs.
A self administrated questionnaire was mailed to over 300 dwellings in blocks of flats usingthe wall exhaust. In almost all the dwellings there was a controllable ventilation unit. Theunits were either a mechanical exhaust ventilation system type with outdoor air inlets ormechanical supply and exhaust ventilation system with heat recovery and outdoor air intakeon the wall. In the questionnaire, the daily use of ventilation unit, noise levels as well as odorsand their sources in the dwellings were asked.
The Dutch organization for applied scientific research TNO in Delft developed asystem of Controlled Natural Ventilation (CNV). It is produced by the Dutchventilation fm Brake1 in Uden.
Airtightness measurements are not yet common in the Italian dwelling stock. In the frameworkof the MICA-ENEA contract, three dwellings were chosen to study the energy performanceon the influence of natural agents. The majority of the dwellings in Italy still nowdays rely onnatural ventilation and records of the fluidynamic and energy performance are not contractualdocuments among the parties involved.
Login