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air flow

Development of a Temperature-Based Sensor for Airflow Pattern Control in Mechanically Ventilated Buildings

To satisfy the optimal environment in agricultural buildings, much effort is made to controlventilation rate and indoor temperature. However, distribution of fresh air is equally important for animal performance and welfare. So far, no sensor is available to measure and to control airflow pattern continuously in a ventilated building. Therefore, an airflow pattern sensor was developed to measure the trajectory of a nonisothermal air jet in a building with a single or multiple air inlet(s).

Impact of the thermal load on the room airflow pattern

The maximum velocity in the occupied space is an important aspect of the thermal comfort. The velocity field is controlled by the position of the inlet devices, the introduced momentum flux and the thermal load of a room. Isothermal room air flow velocities depend on the position of the inlet devices and the introduced momentum flux only. Increasing the thermal load of the room leads to a more and more unstable flow situation. Finally, the flow field is dominated by buoyancy effects and it develops a new stable flow structure.

Thermal Sensation of Tropically Acclimatized Subjects under Fixed Air Flow of Personalized Ventilation

Thermal sensation of tropically acclimatized subjects performing sedentary tasks under personalized ventilation (PV) was explored in this study. The study was conducted in an Indoor Air Quality (IAQ) chamber, which is capable of simulating typical office conditions in Singapore. An experimental design involving interventions in indoor ambient temperature, PV supply temperature and PV supply airflow rate, introduced blind to subjects, was conducted.

Duct Airflow Measurement by Tracer Gas – Development of a New Portable Device for convenient HVAC Auditing

The development of a new device for the injection of tracer gas is discussed with the objective of practical application in the field of HVAC airflow measurements. The uniform tracer gas dispersion for very short distances, when measuring airflow by the constant emission method is of great interest. This new injection device has a compact tubular shape, with magnetic fixation to be easy to apply to duct walls. After a preliminary study with an initial prototype already tested, further detailed experiments had been carried out, culminating in a second prototype.

Monitoring Airflow in Occupied Buildings, the Dynamics of Balloons

Carrying out tests on occupied buildings presents several challenges. Typical instrumentation that can be used in unoccupied test cells cannot be used in occupied spaces. We have videotaped the behavior of helium filled balloons to track the airflow patterns within the building. If the balloons closely follow the local average airflow behavior they will provide substantial insight. For neutrally buoyant balloons, the observed horizontal motions should provide an accurate picture of the corresponding air motions.

Evaluation of the Ventilation Rate via Four Different Measuring Methods

In this study, the houses located in the northern region of Japan had been investigated. The investigation included the measurement of the ventilation rate using four different methods, namely the constant concentration method, measurement of airflow at inlet/outlet and two kinds of PFT method. This paper shows the relationship between the measurement results of ventilation rate via these four measurement methods. It is found that the amount of outdoor air introduced is insufficient for many houses and some of the used ventilation systems are not properly operated.

Complex Air Flow Behaviour in Complex Spaces - Design Optimization by CFD, Realization and Visualization

This paper shows the successful application of CFD simulations for analyzing complex room air flow problems in real applications and deriving optimized solutions.

Natural ventilation of a room with vents at multiple heights

The natural ventilation of a room with a source of uniformly distributed heating at the base andwith vents at multiple heights is investigated both theoretically and experimentally. It is shown that the impact of additional vents can be predicted by determining the height of neutral buoyancy. As a room is heated it heats up to a uniform state and the relative height of neutral buoyancy depends on the ratio of the upper and lower vent areas. When a simple additional intermediate level vent is introduced a unique solution can be used to predict the resulting air flow.

Experimental and Numerical Analysis of Wind Driven Natural Ventilation in a Building Scale Model

Airflow through openings in a cross ventilated building scale model was investigated in a windtunnel and by numerical predictions. Predictions for a wind direction perpendicular to the building showed an airflow pattern consisting of streamlines entering the room, that originated from approximately the same upstream area in the undisturbed boundary layer and a direction of the flow into the room dependent on opening location with velocity vectors pointing away from the stagnation point.

The Characteristics of Wall Confluent Jets for Ventilated Enclosures

This paper reports experimental measurements on the diffusion of confluent jets thatform a wall jet. The experiments were carried out at a fixed air flow rate and fixed temperaturedifference between the supply and room air in the cooling mode. Based on these experiments, theresults presented show the behaviour of the wall confluent jet in the form of velocity profiles, thespreading ratio of jet on the wall, etc. The empirical equations derived are compared with othertypes of air jets, such as the free confluent jet, free plane wall jet, and free plane jet.