Biomedical subjects

F Marzal

Publications and source records attributed to F Marzal.

5 recordsLinked to original sources

PubMed2002

Influence of push element geometry on the capture efficiency of push-pull ventilation systems in surface treatment tanks.

A full-scale installation which simulates a surface treatment tank provided with a push-pull ventilation system has been designed. This study examines the influence of the geometry of the push element on the capture efficiency of the system. It is observed that: (i) capture efficiency increases with the number of holes because of the continuous curtain formed, the size of the holes having no significant effect within the range studied (5-20 mm diameter); (ii) the push element is best supported on the tank wall so that no air from outside penetrates below the emitting jets because in this way the impact of the curtain on the tank occurs earlier and losses are less; (iii) the best results are obtained when the holes are directed downwards towards the tank surface at an angle of between 22 and 45 degrees.

Air Pollutants, Occupational↗

PubMed2002

Determination and interpretation of total and transversal linear efficiencies in push-pull ventilation systems for open surface tanks.

A real-scale pilot installation simulating an open surface treatment tank with a push-pull ventilation system has been designed. From experiments carried out, typical representations of the total and transversal linear efficiencies show that when total efficiency is related to push flow rate, taking as a parameter the pull flow rate, a parabolic profile is obtained with a maximum point or plateau that increases as the pull flow increases. When the transversal linear efficiency is analysed, three general zones where losses occur to the exterior can be detected: (i) when the push flow rate is low, any distortion in the wall jet, whether external (e.g. in the air flow inside the workshop) or internal (e.g. thermal effects), provokes an escape from contaminant; (ii) in the impact zone, where the push flow impacts on the tank surface, distortion increases as the push flow rate increases; (iii) when the push/pull flow rate ratio increases and preferential currents are produced inside the exhaust hood, these escape and cause substantial losses in efficiency.

Air Pollutants, Occupational↗

PubMedDate not supplied

Analytical model for evaluating lateral capture efficiencies in surface treatment tanks.

A pilot scale installation 1.8 m long and 1.6 m wide was designed to simulate a surface treatment tank incorporating a lateral capture system and a distribution network that permits the surface emission of tracer (SF6). The capture efficiency, ET, was determined as a function of the specific capture flow qc, m3/sm2, for three tank lengths, L, (1.2, 1.53, and 1.8 m) and several temperatures, T, from ambient to 95 degrees C, keeping the surrounding air velocity low (v < or = 0.1 m/sec). The data showed a satisfactory fit to a model that related capture efficiency with two exponential functions: the first dependent on the ratio capture velocity/air velocity in the vicinity of the tank, and the second on the ratio capture velocity/velocity of rising drafts provoked by the temperature of the tank.

Air Movements↗

PubMedDate not supplied

Methodologies for determining capture efficiencies in surface treatment tanks.

Methodologies are proposed for determining capture efficiencies in the ventilation systems of surface treatment tanks, using test-scale equipment. The equipment, which incorporates a lateral and push-pull ventilation system, can measure and control the variables of interest because it incorporates a tracer gas generator (sulfur hexafluoride, the concentration of which is measured by infrared spectrometer). The experimental methodologies described determine total efficiency (when the tracer is emitted uniformly from the whole surface of the tank) and the so-called transversal linear efficiency (when the tracer is emitted linearly through a perforated tube situated over the tank, parallel to the exhaust hood face). The analytical and graphical relationships that can be are established between the two efficiencies make it possible to detect where the emissions not captured by the ventilation system are produced (i.e., losses to the outside). At the same time, such losses can be quantified. Several experiments, results of which are analyzed by the methods described, are included.

Air Pollutants↗

PubMedDate not supplied

Visualization of airflows in push-pull ventilation systems applied to surface treatment tanks.

A pilot installation was designed that simulates a surface treatment tank fitted with a push-pull ventilation system. The installation contained elements for measuring and controlling the operational variables (flow rate and tank temperature) and smoke generating equipment for injecting smoke through the holes of the push unit and from the tank surface. Visual observation and video recording of the flows involved meant it was possible to follow the qualitative behavior of the push flow rate along the tank surface and to identify any emissions not captured by the exhaust system. It was possible to differentiate the initial semifree push curtain, its impact with the tank surface, the wall jet that moved toward the exhaust, and its entrance into the exhaust. The methodology proposed is complemented by a quantitative technique for measuring the efficiency, using sulfur hexafluoride as tracer, which permits the causes and location of losses in the ventilation system to be determined.

Air Movements↗