capture efficiency

Particles generated from cooking activities are the biggest contributor to the concentration of indoor particles in most homes, and they are not easily removed without natural or mechanical ventilation. As more focus is directed on human health, kitchen range hoods have drawn increasing attention and their performance in various conditions needs to be evaluated. Consequently, in this study, we performed measurements to establish the particle capture efficiency of a kitchen range hood for various particle diameters at different exhaust flow rates.

Cooking can be a major source of exposure to particulate matter. Range hoods can be used to reduce odours, moisture and contaminants resulting from cooking. The capture efficiency with regard to these contaminants is determined by the thermal plume and the aerodynamic properties of the range hood. There is a new ASTM (an international standards organization) test method: ASTM E3087. It measures capture efficiency under specific conditions that permits standardized comparison of range hoods under controlled laboratory conditions.

Residential cooking can be a significant indoor source of odour, pollutants and particulate matter. Conventionally, range hoods expel the air into the ambient. A number of studies have investigated their contaminant capture performance. However, for highly energy efficient houses the installation of extracting range hoods can pose certain challenges, e.g. high ventilation losses, additional thermal bridges and potential air leakage sites.

In typical Chinese commercial kitchens, the large amount of heat and moisture that is generated must be removed. The ventilation and energy consumption rates can be huge. Middle and small scale commercial kitchens in China produce an exhaust airflow rate so large that without a reasonably effective ventilation system, the temperature and contaminant concentrations are far more than acceptable levels. To fulfil all the requirements of indoor air conditioning in an economical manner, a new air distribution pattern called air curtain ventilation (ACV) is presented in this study.

In a commercial kitchen, a large ventilation rate is needed and energy consumption can be large because a large amount of effluence of heat and moisture need to be removed. To improve kitchen environment and to save the energy, low radiative cooking equipment with concentrated exhaust chimney was developed. Although a ventilation rate may be decreased by using this equipment, the effluence needs to be captured well. To predict indoor air and thermal environment of commercial kitchen using this equipment, CFD analysis is useful.

INRS has evaluated the performance of fume extraction systems on road pavement asphalt pavers over a two year period between 2009 and 2011. These systems are used to reduce operator exposure by capturing fumes at the auger, where most emissions are generated, and discharging them above the paver at sufficient velocity to prevent fumes blowing back towards the operator cab. Evaluation was conducted using a tracer gas (SF6), based on the NIOSH-proposed protocol (1997).

A buoyancy-capture principle is firstly revisited as the most important fluid dynamics mechanism in kitchen range hoods. A recent new derivation of the capture efficiency of a kitchen range hood, which eliminates the inconsistencies and inadequacies of existing derivations, shows that the capture efficiency equals the ratio of capture flow rate to total plume flow rate in a confined space. The result is applied here, together with the buoyancy-capture principle, to derive a simple formula for determining capture efficiency.