Effects of temperature and composition on the viscosity of respiratory gases

Turner, Martin J.; MacLeod, I.M.; Rothberg, A. D.

doi:10.1152/jappl.1989.67.1.472

Cited by 33 publications

(17 citation statements)

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“…See References [19]. The viscosity of air varies by less than 0.5 % as the humidity changes from dry to fully saturated [20]. We do not expect to see this crossover in our experiments.…”

Section: Continuum Modelsmentioning

confidence: 66%

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Dynamic effective mass of granular media and the attenuation of structure-borne sound

et al. 2009

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We report a theoretical and experimental investigation into the fundamental physics of why loose granular media are effective deadeners of structure-borne sound. Here we demonstrate that a measurement of the effective mass,M (ω), of the granular medium is a sensitive and direct way to answer the question: What is the specific mechanism whereby acoustic energy is transformed into heat? Specifically, we apply this understanding to the case of the flexural resonances of a rectangular bar with a grain-filled cavity within it. The pore space in the granular medium is air of varying humidity. The dominant features ofM (ω) are a sharp resonance and a broad background, which we analyze within the context of simple models. We find that: a) On a fundamental level, dampening of acoustic modes is dominated by adsorbed films of water at grain-grain contacts, not by global viscous dampening or by attenuation within the grains. b) These systems may be understood, qualitatively, in terms of a height-dependent and diameter-dependent effective sound speed [∼ 100 − 300 (m · s −1 )] and an effective viscosity [∼ 5 × 10 4 Poise]. c) There is an acoustic Janssen effect in the sense that, at any frequency, and depending on the method of sample preparation, approximately one-half of the effective mass is borne by the side walls of the cavity and one-half by the bottom. d) There is a monotonically increasing effect of humidity on the dampening of the fundamental resonance within the granular medium which translates to a non-monotonic, but predictable, variation of dampening within the grain-loaded bar.

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“…See References [19]. The viscosity of air varies by less than 0.5 % as the humidity changes from dry to fully saturated [20]. We do not expect to see this crossover in our experiments.…”

Section: Continuum Modelsmentioning

confidence: 66%

“…And finally, there may be structure due to the fact that the springs themselves exhibit a non-trivial frequency dependence, an example of which is given by Eq. (20).…”

Section: Continuum Modelsmentioning

confidence: 99%

Dynamic effective mass of granular media and the attenuation of structure-borne sound

et al. 2009

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“…The physical properties of the gas ow through the PNT (room air during inspiration, alveolar gas with body temperature and pressure saturated (BTPS) conditions during expiration) can be corrected [21]. In contrast to the FTT, it can be used in conjunction with techniques requiring airway occlusions (e.g.…”

Section: Relative Advantages and Limitations Of The Two Methodsmentioning

confidence: 99%

Effect of apparatus dead space on breathing parameters in newborns: “flow-through”versusconventional techniques

et al. 2001

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Commercial devices for tidal breathing measurements in newborns allow only short-term measurements, due to the high apparatus dead space of the face mask and pneumotachometer. The¯ow-through technique (FTT) minimizes the dead space by a background¯ow, thereby allowing long-term measurements. The aim of this study was to investigate the comparability of tidal breathing parameters using both techniques.Paired measurements of tidal breathing were performed in 86 sleeping infants (median (range) body weight 2.8 kg (1.9±5.3 kg), age 65 days (3±150 days)), using the FTT and SensorMedics 2600 (SM 2600).There was a signi®cant bias (pv0.001) in all tidal breathing parameters. Compared with the FTT, increases (95% con®dence interval (CI)) in tidal volume (VT), respiratory frequency (fR), and minute ventilation (V'E) were 0.74 (0.5±1.0) mL . kg -1 , 9.0 (6.9±11.2) . min -1 and 92 (74±109) mL . min -1 . kg -1 when measured with the SM 2600, representing average increases of 13, 17 and 30%, respectively, in response to the added dead space. By contrast, time to peak tidal expiratory¯ow as a proportion of expiratory time (tPTEF/tE) was changed by -0.09 (-0.11±-0.08). The mean (95% CI) change in tPTEF/tE of -54 (-62±-45)%, when measured in infants by the SM 2600, was remarkably similar to that observed during in vitro validation studies (-59 (-73±-44)%), suggesting that the discrepancies in timing parameters may be largely attributable to differences in signal processing.In conclusion, differences in measurement technique and precision of the devices used can result in signi®cant differences in tidal breathing parameters. This may impede the comparison of results within and between infants and the clinical interpretation of tidal breathing measurements in newborns. Eur Respir J 2001; 17: 108±114.

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“…The greater the gas viscosity, the larger the pressure drop across a pneumotachometer of fixed flow resistance. The viscosity of ambient air at different temperatures can be calculated by Sutherland's formula [280,281], and for a gas mixture by Wilke's [282] or Turner's equation [283]. The following is a worked example taken from [279] (see table 12, data reproduced with permission from [279]).…”

Section: P·vit =Cmentioning

confidence: 99%