air velocity

The aim of our study was to determine the effect of a cooling jet on performance and comfort in warm office environment. We compared cognitive performance, subjective workload, cognitive fatigue, thermal comfort, symptoms, perceived working conditions and perception of airflow in warm temperature (29.5 °C) in two conditions: with and without the jet. Twenty-nine students participated in the experiment in which a repeated measures design was employed. The jet improved the speed of response in a working memory task with increasing exposure time but did not affect other performance measures.

The aim was to study how the cooling jet from the ceiling, with individual control over the airflow, is perceived and how it affects the thermal comfort in warm office environment. 32 undergraduate university students participated in the experiment. Two thermal conditions were tested: (1) no cooling jet and (2) adjustable cooling jet from the ceiling. Subjects were able to use a controller with seven different settings to adjust the airflow coming from the nozzles so that the target velocity varied from 0.3 m/s to 1.5 m/s. The cooling jet was directed into the upper body.

Common experiences, standards, and laboratory studies show that increased air velocity helps to offset warm sensation due to high environmental temperatures. In warm climate regions the opening of windows and the use of desk or ceiling fans are the most common systems to generate increased airflows to compensate for higher environmental temperatures at the expense of no or relatively low energy consumption.

Previous studies have demonstrated that in summertime increased air velocities can compensate for higher room temperatures to achieve comfortable conditions. In order to increase air movement, windows opening, ceiling or desk fans can be used at the expense of relatively low energy consumption.

In many parts of Asia as typified by Japan, conditioning of the indoor thermal and air environments using natural ventilation since ancient times. When indoor thermal and air environments are predicted, the use of simulation technologies such as CFD and Heating and Ventilation Network Model has increased. Those have advantages and disadvantages. In addition, AI programs like Neural Network (NN) and Genetic Algorithm (GA) are increasingly utilized in other research areas. In architectural equipment field, there are examples of airconditioning system models with NN.

In a test cell equipped with an operating table, a medical lamp and a manikin representing the surgeon, air velocity and tracer-gas concentration were automatically measured at more than 700 points. Numerical simulations were performed too for analyzing air quality in operating rooms. The results showed that the distribution of the contaminants depends strongly on the presence of obstacles like medical equipment and staff.

This research proposes a method for task area wide-cover personal air conditioning thatprevents a human body in the task area from being exposed to a largely irregular thermal environment. A Particle Image Velocimeter (PIV) was used in the research to measure air flow fields for conventional spot cooling and wide-cover personal air-conditioning(PAC) around the human body. The wide-cover type PAC formed a calm air flow field of less than 0.18m/s around the human body, while the spot cooling type PAC formed an air current of 0.3-0.6m/s around the area of the neck.

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.

Experiments have been carried out to measure unsteady velocity fields near the coughing subject (mannequin) and also understand unsteady transport process resulting from this type of transient flow. Representative human cough waveforms were reproduced using a flow simulator and the measurements were made using Time Resolved Particle Image Velocimetry (TRPIV). Initial high velocity as well as rapid velocity decay with time and distance were observed, and velocity time history and vorticity variations were characterized.

In this study Particle Streak Velocimetry, PSV, was used to record instantaneous two-dimensional velocities with the help of digital images of streaks created by small water-density particles suspended in the water. This whole-field measuring technique has been improved by substituting the standard chopper technique by a computer-controlled shutter to get a better result in the evaluation process and criteria control for streaks. The vector flow map (direction, speed and position) was also calculated with the help of digital image processing.