AC pressurisation: Analysis by non-linear optimisation

Abstract

The paper briefly describes the AC pressurisation method of building airtightness measurement and the disadvantages of earlier analysis methods. A new analysis method is described, based on fitting a non-linear function of the unknowns to data. The function is derived from the differential equations of the system components. The new method performed well with simulated data. With real data, the method produced good estimates of the leakage flow rate at 4 Pa pressure loss, leakage length/area and enclosure flexing, but poor estimates of the leakage exponent. It is suspected that this problem was due to measurement errors. List of symbolsA Leak cross sectional area (m2) a Leakage coefficient in I Apf = a IQI2 + b IQ (Pa sl m~) b Leakage coefficient in I Apf = at I Q 1 2 + b I Q (Pa s m-3) c Leakage coefficient in I Apf c I Q 1,1 (Pa at 1 m3 s' air flow rate) d Leak diameter (m) g Index of polytropic expansion and compression of air in enclosure K Enclosure flexing coefficient (m3 Pa') coefficient in (sin crx + k sin 2 at) L Leak equivalent length (m) tri Mass of air in enclosure (kg) n Leakage exponent in I Apf = c I Q n p Absolute pressure of air in enclosure (Pa) pa Atmospheric pressure (Pa) p. Mean absolute pressure of air in enclosure (Pa) 4p~ Friction pressure loss through leak (Pa) Q Flow rate through leak (m3 S-1) R Gas constant of air in enclosure (J kg-I K-1) T Absolute temperature of air in enclosure (K) T Mean absolute temperature of air in enclosure (K) t Time (s) u Air velocity through leak (m s-1) h Volume of air in enclosure (m3)

Modeling air leakage in buildings caused by the cyclic variation of the atmospheric pressure

“…Further developments have centered around the diversification of the measuring equipment [52][53][54][55][56][57][58][59] and the implementation of Fourier analysis on this kind of signals. 60,61 Several measurement procedures are detailed in Cooper et al 56 and Cooper and Etheridge. 62 This study selects some mathematical procedures from these techniques as we ascertained that there are closed similarities between the natural oscillation of the atmospheric pressure and the induced harmonics of pressure.…”

“…Further developments have centered around the diversification of the measuring equipment 52–59 and the implementation of Fourier analysis on this kind of signals. 60,61 Several measurement procedures are detailed in Cooper et al. 56 and Cooper and Etheridge.…”

Building Air Tightness: Research and Practice

“…In looking at large datasets, one hopes that the central limit theorem will apply and that all of the biases and other uncertainties will be reflected in the standard deviations of the data themselves. Gusdorf (2003) Hamlin 1997Buchan (1996, Proskiw (1998) Buchan (1992, Fugler (1994) Scanada 2001Elmahdy 2003, Proskiw (1995) Fugler (1999 Petrone Architects 2000Air-Ins Inc. (1998, 1998b) Among the largest database to date on air tightness of single-family dwellings is the LBNL Residential Diagnostics Database which has over 73,000 measurements from across the US. Data collection is an ongoing effort by the Energy Performance of Buildings Group at LBNL.…”

“…In a pair of papers, Dewsbury (1996Dewsbury ( , 1996a has examined some additional analysis approaches involving low frequencies, Fourier analysis and non-linear optimization strategies. The lower the frequency the less susceptible the analysis is to effects of inertia and flexing of the envelope.…”

Swine finishing room air infiltration quantification-modelling and use in ventilation system design

“…Other advanced topics in AI measurement, such as pulse pressurization, AC pressurization, and acoustic tests, were explored by Dewsbury (1996), Sherman & Modera (1986), and Sherman & Modera (1988). The results highlighted that the frequency of air flow or pressure fluctuations and related assumptions made to simplify the analysis affects the leakage measurement accuracy (Sherman and Modera, 1986).…”