Sharp JX-9400 Informations techniques télécharger pdf (Page 82)

Inverting this relationship gives the airﬂow rate resulting from a pressure

diﬀerential:

q ¼

b þ

ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ

 4ap

ð4:3Þ

By ﬁtting one of these two models on the measured points on a [q;p] diagram,

the coeﬃcients and the exponent of either of the above models can be assessed

(see Figure 4.2).

Reductive sealing

Global permeability measurement does not provide information on the location

of leakage. Reductive sealing aims to quantify the proportion of the total air

leakage that is attributable to diﬀerent components or groups of components.

One method to locate leakage is to seal components, areas, rooms or zones

suspected of leakage and to perform a new pressurization test. The diﬀerence

is the leakage of the sealed leaks.

The fan pressurization equipment is set up and the dwelling prepared, in

the usual way (see ‘The fan pressurization method’, above). An air leakage

test is then carried out, either pressurizing or depressurizing. A component

or group of components is then chosen (for example, all chimneys and ﬂues)

and sealed with self-adhesive tape, polyethylene sheet, inﬂatable bladder or

modelling clay, as appropriate. It is important that care is taken to make a

good seal on all components. For example, special attention should be given

to corners and around the fasteners.

The air leakage test is then repeated, the diﬀerence between this test and the

ﬁrst test being a measure of the air leakage attributable to the component or

group of components that were sealed.

Further components can then be chosen and the process continued. The

diﬀerence of leakage ﬂow rate at each pressure between two successive tests

is the leakage of the components sealed between these tests. Leakage coeﬃ-

cients for each group of sealed components can be calculated from these leakage

200

400

600

800

1000

010203040

Pressure [Pa]

Airflow rate [m

/h]

Measured points

Power law

Quadratic law

Figure 4.2 Airﬂow rates and pressure diﬀerences as measured in a real

test, together with power law and quadratic ﬁts

Airtightness 61

1 2 ... 77 78 79 80 81 82 83 84 85 86 87 ... 210 211

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