Air flow

Magnetic resonance imaging (MRI) and other techniques are being used to investigate moisture transport in textiles. MRI revealed that moisture distribution in carpet is significantly influenced by the vacuum extraction procedure. Industrially relevant through-flow drying of carpet has been simulated on a laboratory through-flow dryer (LTFD) as well as inside a MRI scanner. The effects of the moisture distribution and

Relative spectral reflectance is an illumination invarient image feature that is related to many ecological phenomena that are difficult to measure, such as plant CO2 uptake. We describe a procedure to estimate the relative spectral reflectance of known subject using ...

The aim of this study was to investigate the deposition of particles in three types of synthetic fabric filter by scanning electron microscope (SEM) and to determine the experimental adhesive force of filter cakes in fabric filters. The fabrics used were acrylic, polypropylene and polyester. The particulate matter was phosphate rock. The particles were deposited in the filters during 10 filtration cycles, with a superficial filtration velocity of 0.10 m/s and maximum pressure drop of 980 Pa across the filter. The cleaning technique used was reverse air flow at 0.12 m/s. The results showed that the deposition depth of particles in the polypropylene filter was lower than those observed in the polyester and acrylic filters. Nevertheless, the residual pressure drop of the polypropylene at the beginning of the filtration assays was highest, owing to the greater accumulation of particles at the surface of the filter and the characteristics of the filter itself. It was also observed that the adhesion force was higher in the polypropylene filter than in the other filters, making it hard to remove the filter cake from that filter.► The behavior of the particle deposition and adhesion forces can improve the understanding of the cycles of filtration. ► The polypropylene filter exhibited the highest number of particles retained on the surface of the filter. ► The acrylic and polyester filters trapped greater numbers of particles internally than the polypropylene filter. ► The adhesion force was higher in the polypropylene filter, making it difficult to remove the cakes from the filter.

ABSTRACT One of the most efficient ways to reduce the pollution and fuel consumption of an automotive engine is to downsize the engine, whilst maintaining a high level of power and torque. This is achieved by using turbochargers. In urban, and often in suburban, traffic conditions the engine power demand is weak in relation to the maximum power available, so the turbocharger runs at low speed. To appreciate and improve engine performance, it is necessary to know the characteristics of the turbomachinery in this functioning area, characteristics which are not given by turbocharger manufacturer. The reason for this lack of information will be explained and the experiments we are currently conducting at low turbocharger speed are presented. Experimentally, it has been demonstrated that the measured performances of the compressor are dependent on heat exchange (convection and conduction) and are also linked to the pressure and temperature of the lubricating oil. At the CNAM laboratory, the turbocharger test rig has been equipped with a special torquemeter, allowing rotation speeds of up to 120000 rpm, set up between the turbine and the compressor. The turbine is thus separated from the compressor and could be considered as a drive which provides mechanical power to the turbocharger (torquemeter + compressor + bearing unit). Temperature and pressure of the lubricating oil can be adjusted to an experiment’s requirements. The test bench lay out is described. To achieve accurate measurements and evaluate the influence of heat exchanges, tests have been carried out with the whole compressor thermally isolated and with preheated inlet air. The compressor can be assumed to be adiabatic, and the power given to the air flow can be calculated using the first law of thermodynamics. Mechanical bearing losses can be deduced from this calculation and torquemeter power, but also from measurements of lubricating oil flow, and oil temperature at inlet and outlet. The results of experiments for different lubricating oil temperatures and pressures and turbocharger speeds are presented. Real compressor characteristics curves are set up and a comparison of experimental mechanical power losses with a journal bearing CFD model is presented.

A summary of the evaluation of an air flow and contaminant model as part of the IEA-ECBCS Annex 23 `Multizone Airflow Modelling' is presented. Evaluation, rather validation, is the goal. The most important points of the cases analyzed during this project are presented and commented from the point of view of analytical evaluation, comparison with experimental data and user sensitivity. The conclusion addresses the need for user-friendly tools and guidelines for the analysis of simulation output.

Abstract For indoor environments, thermal discomfort must be clearly distinguished from the air pollution caused by outdoor air as well as by inside polluting agents. Full air conditioning of a room requires the introduction of a minimum ventilation air flow whose characteristics ...

Natural losses from fruit and vegetable products stored in cold conditions are investigated. A mathematical model describing heat and mass transfer processes taking place during storage time is presented and the resulting governing equations are solved using Software Mathcad7. The relative humidity of the ventilating air and the temperature field of an apple bulk are found for different cold storage conditions; namely the initial air relative humidity and air flow rate. It was found that the relative humidity of the ventilating air approaches a limiting value as the apple bulk depth increases up to 4.2 m. In addition, when the relative humidity is larger than the equilibrium relative humidity value, an increase in the ventilating air rate reduces the losses of the product during the period of its storage while larger losses occur when the relative humidity values are lower than the equilibrium one.

... The appropriateness of a glazing for warm climates may be measured by an index called the glazing luminous efficacy, K e , sometimes called the 'coolness index', which is defined as the visible transmittance divided by the shading coefficient [3]: ...

Silver conductive ink is widely used to form conductive electrode in printed electronics applications. However, rapid rise in silver price is driving the need for alternative conductive ink that is significantly more cost-effective [1]. Copper based conductive ink is a promising alternative due to inherently lower material cost compared with silver conductive ink. In addition, copper conductive ink will provide solderable printed interconnects unlike those using silver conductive ink [2]. A key limitation of copper based conductive ink is inherently higher electrical resistivity compared with silver conductive ink. This study focuses on large area screen printing, low temperature ink curing and electrical characterization. The selected copper conductive ink has a metal loading of 65wt.%, and viscosity range of 25,000 to 35,000 cps. Two test vehicles on Polyethylene Terephthalate (PET) substrate were used for performance characterization: 1) printed conductive circuit 2) printed frequency selective electromagnetic interference (EMI) shield. By optimising key screen printing parameters including screen mesh size, printing speed and squeegee pressure, a minimum printed line width of 100 μm was achieved for a printed area of 500 mm × 500 mm. A low curing temperature of 60°C was achieved by optimising air-flow rate and curing profile. Good printing uniformity was achieved, translating to a 10% tolerance for measured electrical resistance in printed conductive circuit. High-frequency characterization was also performed on printed frequency selective EMI shield. A shielding effectiveness of 24 dB was achieved at the tuned rejection frequency of 1.8 GHz for a narrow band topology. The shielding performance is comparable with that of printed frequency selective EMI shield using silver conductive ink.

Progress in understanding dance communication in honeybees is reviewed. The behaviour of both dancers and follower bees contain flexible and stereotypic elements. The transfer of specific information about direction and distance probably involves more than one sensory modality. The follower bees need to stay behind the dancer (within the angle of wagging) during at least one waggle run in order to perceive the specific information. Within this zone, a small stationary air-flow receiver (like the antenna of a follower bee) experiences a well-defined maximum when the abdomen of the wagging dancer passes by. Within 1 mm from the tip of the abdomen, the maximum may be caused by oscillating flows generated by the wagging motion. At other positions and distances (up to several millimetres from the dancer) the maximum is due to a spatially narrow jet air flow generated by the vibrating wings. The time pattern of these maxima is a function of the angular position of the receiver relative to...

Abstract Fluid flow phenomena in a cylindrical bath stirred by a top submerged lance (TSL) gas injection was investigated by using the computational fluid dynamic (CFD) modeling technique for an isothermal air–water system. The multiphase flow simulation, based on ...

The use of solar chimneys in buildings is one way to increment natural ventilation and, as a consequence, to improve indoor air quality. They are similar to conventional chimneys except that the south wall is replaced by a glazing. In order to compare the behaviour of a solar chimney with a conventional one, one of each was built in Porto. Results of measurements carried out in both chimneys are shown in this paper, as well as results of a thermal model specially developed for simulating solar chimneys, taking into account the wind effect. It was concluded that there is a significant increase in ventilation rate with solar chimneys, and that the thermal model predicts with good accuracy the measurements carried out.