AIVC - Air Infiltration and Ventilation Centre

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COMIS - an international multizone air-flow and contaminant transport model.

A number of interzonal models have been developed to calculate air flows and pollutant transport mechanisms in both single and multizone buildings. A recent development in multizone air-flow modeling, the COMIS model, has a number of capabilities that go beyond previous models, much as COMIS can be used as either a stand-alone air-flow model with input and output features or as an infiltration module for thermal building simulation programs. COMIS was designed during a 12 month workshop at Lawrence Berkeley National Laboratory (LBNL) in 1988-89.

A numerical study on the role of leakage distribution and internal leakages under unsteady wind conditions

The existence of air leakages in a building has been very clearly stated as an important reason for energy loss. The decrease in the efficiency of the mechanical ventilation has also been clarified. The global demand for achieving nearly zero-energy buildings makes the uncontrolled leakage paths even more undesired. Despite the fact that steady state measurements of in- and exfiltration rates offer a simple and easy way of estimating the airtightness level of an eclosure, a supplement to those methods might be imposed.

Behavior of leakages exposed to dynamic wind loads. A numerical study using CDF on a single zone model

Wind is a potential dominant factor regarding the air infiltration through building envelopes. Due to its dynamic characteristics, quite complex aerodynamic phenomena arise around a structure or through cracks and openings. Energy perfomance is influenced by the climate conditions and thus it should be much more researched. Despite the fact that steady state measurements of infiltration rates offer a simple and easy way of estimating an enclosure’s airtightness level, a supplement to those methods might be imposed.

Simple error reduction in tracer-gas field-measurements of air handling units

Tracer gas measurements are an unparalleled means of measuring air recirculation, leakage, and air flow rates in air handling systems [1-5]. However, such measurements are subject to significant measurement uncertainty in field conditions. A common problem is imperfect mixing of tracer gas.

Application of a Thermal Manikin to Evaluate Heat Loss Rates from People caused by Variations in Air Velocity and Air Temperature

Heat loss monitoring from a thermal manikin was undertaken representing an occupant in a classroom during a lesson period of 80 minutes in which the room temperature was increased from 21 to 24C for various airflow velocity configurations. A group of subjects was exposed to various conditions of temperature and airflow rate so that the impact of these variations on their surface/skin temperature could be determined. It was found that skin temperature remained stable and close to 34C for all conditions of exposure.

ZAER: A Zonal Model for Heat Transfer and Air Flow in Unconditioned Buildings - An Experimental Validation

This paper presents a three-dimensional zonal model, ZAER, for heat transfer and air flow calculations. It is based on an intermediate approach between single-air-node and CFD models. The indoor air volume is divided into macroscopic homogeneous zones. Heat and mass balance equations are written for each zone, while the mass flow rates across the interfaces are calculated by power pressure laws. The simulation tool ZAER allows the determination of temperature fields and air flow distributions inside unconditioned buildings, taking into account external boundary conditions.

Zonal models for indoor air flow - A critical review

A zonal model is an intermediate approach between computational fluid dynamics (CFD) and single-room models. It can give results faster than CFD and be more accurate than single-zone models. It has been used to provide some global information regarding thermal and flow parameters within a room. In this review, due emphasis is given to the commonly used pressurized zonal model - the power law. Qualitative validations show that the power law model reasonably predicts well for natural convection.

A CFD Analysis of the Air Flow Characteristics at an Inflow Opening

In the present study, a numerical simulation to simulate an experiment for evaluating the cross-ventilation performance at an inflow opening by using Large Eddy Simulation (LES), the standard k-e model, and Durbin's k-e model was performed. Results showed that too much turbulent kinetic energy was produced at the leeward opening frame in the standard k-e model. However , Durbin's k-e model improved this defect , and reproduced the wind tunnel results fairly well, as did the LES approach.

A Fundamental Study on the Air Flow Structure of Outflow Openings

A Local Dynamic Similarity Model, applicable to dynamic similarity of cross-ventilation, has been applied to outflow openings. Cross-ventilation performance at the openings on the outflow side has been evaluated, and the structure of air flows around the outflow openings has been studied by LES and wind tunnel experiments. It was found that LES reproduces the wind tunnel experiment results fairly well, such as the extensive increase of discharge coefficient in a small region where dimensionless room pressure, PR*, is low.

AUTOMOBILE HVAC SYSTEMS: AIR FLOW, LEAKAGE AND THEIR EFFECTS ON IN-VEHICLE AIR QUALITY

We have sought to accurately quantify automobile HVAC air flow rates in four passenger vehicles,under a range of different ventilation settings and speeds. We used Sulphur Hexafluoride (SF6) as atracer gas, coupled with a portable doser/sampler system to quantify flow rates and leakage.Results of this work indicate a linear increase in HVAC air flow rate with increasing vehicle speed forall vehicles. Older vehicles were much less airtight than newer vehicles, a likely reflection on improveddesign and reduced door seal deterioration observed in the newer vehicles.

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