exhaust

The aim of ventilation for commercial kitchens is capturing fumes and odours, providing fire protection measures and insuring comfort. But the technologies concerning extraction and introduction of fresh air are not numerous.In this article, the author explains how difficult are the dimensioning of the equipment and the calculation of the airflow to extract.The author also refers to guide and regulations related to commercial kitchens.

The author gives practical advices in the design of local exhaust ventilation system (mainly hoods) to capture the contaminant and general ventilation systems to dilute the offending chemical contaminant to acceptable effects. The effect on local environment is studied too.

The objective of this paper was to illustrate the potential of the CFD technique to compare the effectiveness of different general ventilation systems in reducing the workers' exposure to styrene vapour in a workroom. . Thanks to the CFD technique predicted airflow velocities and styrene distribution are shown for the 3 different ventilation arrangements at identical planes across the room. And predicted values of styrene concentration at workers'position are given.

2 examples of extract systems are presented in this paper : the first one concerns dust removal in a public waste plant and the second smoke separation in a smoker/non-smoker zone with no visual impact (i.e. no walls).Thanks to the CFD simulation, proper exhaust systems for dust and smoke have been successfully designed and optimised for each case with simulation results. The proposed solutions were then realized and with few minor modifications led to excellent working conditions on the one hand and excellent smoke caption on the other hand.

This paper deals with measurement of the capture efficiency of REEXS (Reinforced Exhaust System). For the experiment a local exhaust hood was designed with the possibility of working either as a traditional circular exhaust hood or as a REEXS. Experimental measurements were done both for the traditional hood and the REEXS, with the same exhaust flow rate. The results were then compared.The results proved that the main weaknesses of the traditional local exhaust hood can be improved by using REEXS hood.

The aim of that study was to measure the performance of local ventilation for various parameter settings (nozzles and slots REEXS) and to demonstrate the benefit for real working situations.A test cabin was built, to measure the capture efficiency under reproducible cross draughts. Optimised REEXS hoods were used for the experiment : they proved to have a larger capture range compared to the conventional flanged hood. The results were so encouraging that an exhaust installation for 6 welding working places was completed.

This paper aims at showing the difference between the two approaches used to evaluate the capture efficiency of a local ventilation system : an experimental research using the tracer gas method ( CO2) and the numerical modelling using CFD code ( STAR-CD). Comparison between the two methods show that the CFD modelling can provide results in good agreement with the experiment.

Attempts to examine the relationship between ventilation rate and sick building syndrome symptoms. Uses a cross sectional population based study of 399 workers in 14 mechanically ventilated office buildings without air recirculation or humidification in Finland. Air flow was measured through exhaust air outlets in the room. A questionnaire was also used. States that the results suggest that outdoor air ventilation rates below the optimal increase the risk of sick building syndrome symptoms.

Presents new empirical formulae for the prediction of the air velocity in front of rectangular (slot) openings. Infers the equations from an experimental study of a common type of local exhaust opening. The formulae describe the three-dimensional velocity field near a rectangular exhaust hood, providing the velocity gradients along suitable directions, parallel to the slot axis. Testing of the formulae showed a good fit to the experimental data.

In mechanical exhaust ventilated buildings in cold climates, the supply air through vents in the perimeter may cause draught and reduce the zone of occupancy. One way to prevent this is to preheat the outdoor air by a vent-convector. An experimental study of the performance of a vent-convector is reported in this paper. Measurements have been conducted in a test room and in a school equipped with vent-convectors. Air flow and pressure drop characteristics were investigated for one type of vent-convector. the temperature variation at a step change of the air flow was also investigated.