Theoretical and Experimental Simulation of Exhaust Hoods.

The paper presents a criterion to assess the performance of mechanical exhaust hoods for dome stic kitchens and a procedure to experimentally test them; an analysis of the relevant parameters which affect their performance is made, the test results are shown, and finally these are compared with the results of a numerical fluid dynamic code. Experiments were performed using the tracer gas technique, and attention has been drawn rather on the hood efficiency in the removal of pollutants than on the IAQ in the test room. It was first shown that the choice of the tracer gas has no influence on the results of the experiments. Then, the influence of the following parameters has been investigated: distance from hood to pollution source, thermal power dissipated under the source itself, extracted air flow rate, and hood-towalls geometry. The repeatibility of the experimental apparatus was less than 10 9%. A simplified empirical expression based on nondimensional parameters has been derived, which provides a precise estimate of hood efficiency. Furthemre, a number of tests have been simulated by means of a CFD model. The results provide an interesting insight on the hood fluidynamic behaviour, yet the calculated efficiency is underestimated by 20 - 30 % respect to the measured values.