English

For the zoning room air conditioning strategy to work properly, it is essential that the supply air is delivered in such a way that it does not block the plumes' way from the lower zone to the upper. The parameter measuring the fulfilment of this condition is the plume penetration. This kind of parameter could be measured by releasing tracer gas into the heat source and measuring the response elsewhere. This was done in our research also, but the tracer gas experiment was supplemented by an alternative method, utilizing small helium-filled soap bubbles instead of gas.

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.

Different measurement procedures are available for the experimental assessment of air change rates inside ventilated enclosures. These mainly consist of tracer gas techniques and can usually be applied to steady-state or moderately transient conditions and when a continuous mixing of the indoor air is assured throughout the test. However, due to the relatively slow response of the gas analysers, none of these procedures can usually be applied to fast transient phenomena that last 15 minutes or less.

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.

Carbon dioxide produced by occupants can be used as a natural tracer gas for analysing air change rates in dwellings. However, a high level of concentration uniformity is necessary for tracer gas measurements. Therefore, mixing fans are usually used. The use of such fans in occupied homes is not convenient, thus the uniformity requirement may not be fulfilled. Experiments in climate chambers were carried out to simulate the distribution of CO2 under different controlled conditions, without additional mixing. Sufficient concentration uniformity was observed in all measured cases.

The segmental equivalent temperature determined by means of a thermal manikin is often correlated with the local thermal sensation of people and is used for indoor environment assessment. It is also used to assess performance of heated/cooled/ventilated car seats, etc. However, the body of the thermal manikins used at present is not as flexible as the human body and is divided into body segments with a surface area that differs from that of the human body in contact with a surface. The area of the segment in contact with a surface will depend on the shape and flexibility of the surface.

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.

In this paper a new test room for thermofluidynamic measurements is presented. The tests have been realised in the Officine Volta (Italy) workrooms as result of a collaboration between researchers of the Department of Fisica Tecnica University of Rome La Sapienza and researchers of the Officine Volta society. The laboratory was thought exploiting the knowledge in the field of thermofluidynamic achieved by the department of Fisica Tecnica in the last few years.

Carbon dioxide exhaled by people can be used as a tracer gas for air change measurements in homes. Good mixing of tracer gas with room air is a necessary condition to obtain accurate results. However, the use of fans in dwellings to ensure mixing is inconvenient. The natural room distribution of metabolic CO2 was simulated in laboratory experiments and verified in a field study. The results of the field measurements presented in this paper support the findings of the laboratory study, i.e. that CO2 is well mixed into the room air even though fans were not used.

Tracer gas sorption in and permeation through building materials influence tracer gas ventilation measurements. The permeation of the commonly used tracer SF6 through three different building materials (gypsum board, wood particle board and MDF-board) with and without paint has been experimentally investigated. The results show that the tracer diffuse through untreated boards and that gypsum board has the largest permeability towards SF6. However, the diffusion rate of tracer is effectively reduced when the boards are coated with two layers of latex paint.