Sharp JX-9400 Technical Information PDF herunterladen (Seite 59)

with

R ¼

Q

ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ

ð1 þ RÞ

ð2:73Þ

Or method C

R ¼ 1 

with

R ¼

ﬃﬃﬃ

Q

ð1  RÞð2:74Þ

assuming that the relative error Q=Q is the same for both airﬂow rates, and

taking into account that Q

¼ð1  RÞQ

The accuracy of the three methods for determining R is compared in

Figure 2.12. Me thod B (Equation 2.73) should be preferred at low recirculation

ratios, while meth od C (Equation 2.74) is best at large recirculation ratios.

Method A could be applied where the other methods cannot be used. Note

that the relative error R=R becomes very large for small recirculation ratios.

It is interesting to see that some interpretation methods of the same

measurements provide more accurate results than others, and that the best

way depends on the unit measured. Therefore, care should be taken to select

the most appropriate method.

10%

15%

0% 20% 40% 60% 80% 100%

Confidence interval of R

Recirculation ratio

Figure 2.12 Conﬁdence interval of the recirculation ratio as a function of the

recirculation ratio itself for three assessment metho ds

Note: For this ﬁgure, the relative conﬁdence intervals of injection rate and concentra-

tions are 5 per cent.

38 Ventilation and Airﬂow in Buildings

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Sharp JX-9400 Technical Information Seite 59