Gas pressure and temperature

For analytieal purposes, eonsider that the mass earrier in the expander with higher temperature and lower pressure eould be thought of as an ideal gas. Beeause exhaust gas pressure and temperature are nearly unehangeable onee seleeted (unless the effieieney degrades), its residual enthalpy may be assumed eonstant. The expander operating eondition mainly depends on the inlet parameters, and the power developed by an expander may be ealeulated from the equation ... 

In porous media, liquid-gas phase equilibrium depends upon the nature of the adsorbate and adsorbent, gas pressure and temperature [24]. Overlapping attractive potentials of the pore walls readily overcome the translational energy of the adsorbate, leading to enhanced adsorption of gas molecules at low pressures. In addition, condensation of gas in very small pores may occur at a lower pressure than that normally required on a plane surface, as expressed by the Kelvin equation, which relates the radius of a curved surface to the equilibrium vapor pressure [25],... 

However, correlations have been established using some experimental investigations, and thus are checked for a restricted range of operating conditions (reactor volume, nature of the liquid, of the gas, pressure and temperature range) and reactor set-up. 

Mass flow through a sonic nozzle is a function of gas pressure and temperature. For a given pressure p and temperature T, mass flow rate through the nozzle is given by... 

Several factors affect the growth of SWNTs in the laser-ablation technique. Extensive studies on the development of the laser-vaporization technique have optimized the process conditions such as laser parameters, composition of graphite and metal, carrier gas, pressure, and temperature. Through these studies, a sigiuficant understanding of the SWNT s growth and propagation under laser-vaporization condition is achieved. ... 

The gravimetric method has in its favour the fact that all variables adsorbed mass, gas pressure and temperature are measured independently. Apparatus are more complicated and more expensive on account of the additional vacuum microbalance. Balance operating requires some skills. The sample is not in direct contact with the thermostat and must be shielded against false heat radiation. Measures to avoid the influence of eddy gas flow may be required. At low pressure the Knudsen pressure difference causes thermal gas flow which seriously interferes in measurements in the Henry region. 

The duration of the compression stroke in the calculated times (Table 6.14) corresponded to approximately 50 ms, signifying that autoignition occurred after top dead centre, as observed experimentally. The choice of bdc as the initial condition is essential to permit the development of spontaneous combustion during the course of the compression stroke as the gas pressure and temperature increase. This definition of the time for ignition differs from that given by, (i) the admission of reactants to a hot, closed reaction vessel, (ii) the end of compression in an RCM, or (iii) the passage of a shock through the reactants in a shock tube. 

The separation of 20 % C2H4 (1) -f 80 % CH4 (2) gas mixture was mathematically simulated using the four-step Skarstrom PSA cycle consisting of adsorption, depressurization, product purge, and product pressurization steps [37]. The feed gas pressure and temperature were 2.08 MPa and 298 K, respectively. The Nuxit charcoal was employed as the adsorbent. An essentially pure stream of CH4 product (99.87 %) could be produced with a recovery of 28.4%. The CH4 productivity was 0.088 kg moles of product/kg of carbon in system/day [37]. 

Applying the Nodal Volume Conservation Equation directly to a gas node would require a full solution for the pressure dynamics in the manner described in Chapter II for a process vessel of fixed volume. However, when the nodal volume is small, the gas pressure and temperature will reach equilibrium quickly, after which time dT/dt = dp/dt = 0. Hence, from equation (18.60), dm/dt = 0. While this last equation will be fully valid only after pressure and temperature have reached equilibrium, it will be acceptable as an approximate characterization of reality at all times provided the nodal volume is small enough to allow very rapid establishment of pressure and temperature equilibria. This is the basis for modelling gas flow in networks under the assumption that steady-state equations for mass balance are valid. 

The axial and radial turbo-expanders may be single- or multi-staged. The application of multi-staged turbo-expanders is expedient when a significant decrease of gas pressure and temperature is needed. Radial turbo-expanders are used mostly in plants operating at a low gas flow rate. Axial turbo-expanders are used for cooling in apparatuses with a high gas flow rate. 

Throttling of the gas, in the course of which the gas pressure and temperature are decreased without doing work and without heat exchange. Throttling is achieved with the aid of a choke restrictor. 

In Figure 2.2 equilibrium adsorption data for carbon dioxide (CO2) on zeolite Na 13X (Linde, UOP) are presented for temperatures 298 K and 303 K. The mol numbers of the Gibbs surface excess amounts per unit mass of sorbent are depicted as function of the sorptive gas pressure and temperature. Relative uncertainties of measurements are about ( ttiGE/ GE)-2%- The subcritical isotherms are in the range of pressure measured of Type I - lUPAC classification [2.20]. 

In Figure 3.10 equilibrium adsorption data of pure gases (CO2, CH4, CO, N2) on activated carbon NORTT R1 EXTRA at pressures (p < 6 MPa) and temperatures 298.15 K are shown [3.27], [3.28]. The mol numbers of Gibbs excess amounts adsorbed per unit mass of sorbent are depicted as function of sorptive s gas pressure (and temperature). Relative uncertainties of data are about (<7 ge/ ge) 1 Measurements were performed with a two beam... 

In gravimetric adsorption measurements of pure gases adsorption of the gas on walls of tubes and vessels does not pose a problem as no mass balances of the gas are necessary. However, in multicomponent adsorption measurements it may influence the sorptive gas concentration to a certain extent, especially at low gas pressures and temperatures (T < 77K), and if- for example in a binary gas mixture -one component is strongly, the other only weakly adsorbed. Electropolishing of inner surfaces of all tubes and vessels, preferably made of stainless steel, can reduce this problem considerably. 

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