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Design of Soil Vapor Extraction Systems
Published in Jimmy H.C. Wong, Chin Hong Lim, Greg L. Nolen, Design of Remediation Systems, 2020
Jimmy H.C. Wong, Chin Hong Lim, Greg L. Nolen
In general, flow and velocity measuring instruments are calibrated to standard conditions. Standard conditions are defined as pressure at 29.92” Hg (1 atmosphere or 14.7 psi) and temperature at 70°F (some manufacturers use 68°F or 60°F). Despite the actual barometric pressure and temperature conditions, the instruments measure values based on standard conditions, therefore observed readings are referred to as standard values. Thus, the unit for observed flowrates is standard cubic feet per minute (SCFM). Corrected flowrates are presented in ACFM. The conversion from SCFM to ACFM is ACFM=SCFM×14.7(14.7+actualpressure)×(460+actualtemperature)(460+standardtemperature)
Submarine slope stability analysis during natural gas hydrate dissociation: Discussion
Published in Marine Georesources & Geotechnology, 2020
In this short discussion, we presented some concerns about the conditions and parameters used in their model. Generally, a combination of high pressure and low temperature is needed to form gas hydrate. When this condition is changed, gas hydrate can be dissociated (Jia et al., 2016). Zhang et al. (2018) showed that “under the standard conditions where the pressure and temperature are 1.01*105 Pa and 298.15 K, respectively, one volume of natural gas hydrate produces 164.6 volumes of natural gas and 0.87 volumes of water.” However, dissociating one unit volume of hydrate will liberate 164 unit volumes of methane and 0.8 unit volumes of water at standard conditions (Carcione & Gei 2004; Kvenvolden 1993; Max & Dillon 1998; Grauls 2001). The volume change during hydrate dissociation used in their model is imprecise. Most importantly, the standard conditions are defined to be 273.15 K (0 °C) and 1 atm pressure (or 1.01*105 Pa). However the temperature (298.15 K) was used for the standard conditions in their model, which was inaccurate and even false. We found that the two small mistakes used for hydrate dissociation are traceable to Grozic and her students or colleagues (Grozi & Kvalstad 2001; Nixon & Grozic 2006; Nixon & Grozic 2007). They (such as Nixon & Grozic 2006) referenced Max and Dillon (1998) for the above-mentioned condition and parameters; however they made a mindless mistake. Zhang et al. (2018) developed the previous model by Grozic but did not find this mistake.