Humid gas density

Volumetric humidity Y Mass of vapor per unit volume of gas-vapor mixture. It is sometimes, confusingly, called the absolute humidity, but it is really a vapor concentration preferred units are kg/m or Ib/fT, but g/nV and gr/ft are also used. It is inconvenient for calculations because it depends on temperature and pressure and on the units system absolute humidity Y is always preferAle for heat and mass balances. It is proportional to the specific humidity (wet basis) Yy = Yy/pg, where pg is the humid gas density (mass of gas-vapor mixture per unit volume, wet basis). Also... 

To measure the internal flow velocity in the duct, dust sampling was taken at various points along the vertical diameter. A pitot static tube and magnehelic gauge, shown in Figure 1, was the equipment used for these measurements. The duct humidity, tempertaure, and static pressure were measured to calculate the gas density. In determining the humidity, the wet and dry bulb temperature of a continuous sample stream was used. To prevent dust buildup on the wet bulb thermometer, an inline metal filter was inserted into the line. 

Figure 7. Velocity vectors and gas density contours under very low humidity operation (a) in the middle and (b) at the exit of a 10 cm PEFC. ...

Feed surface tension Chamber inlet gas humidity bulk density ib) product moisture content, chamber wall build-up (a) particle size (b)... 

Xg, Cp, and pg are the thermal conductivity, specific heat, and density of the humid gas, respectively and Mg are the molar mass of the moisture and dry gas, respectively... 

Observation Membrane Catalyst Gas Flow rate Pressure Temperature (°C) Relative humidity Current density Source... 

Carrier gas Temperature Pressure Humidity Density Viscosity Dewpoint of all condensibles Corrosiveness Inflammability Toxicity... 

Engineering factors include (a) contaminant characteristics such as physical and chemical properties - concentration, particulate shape, size distribution, chemical reactivity, corrosivity, abrasiveness, and toxicity (b) gas stream characteristics such as volume flow rate, dust loading, temperature, pressure, humidity, composition, viscosity, density, reactivity, combustibility, corrosivity, and toxicity and (c) design and performance characteristics of the control system such as pressure drop, reliability, dependability, compliance with utility and maintenance requirements, and temperature limitations, as well as size, weight, and fractional efficiency curves for particulates and mass transfer or contaminant destruction capability for gases or vapors. 

According to the state equation of ideal gas, the partial density of dry air in humid air is... 

Transport properties of hydrated PFSA membranes strongly depend on nanophase-segregated morphology, water content, and state of water. In an operational fuel cell, these characteristics are indirectly determined by the humidity level of the reactant streams and Faradaic current densities generated in electrodes, as well as the transport properhes of catalyst layers, gas diffusion layers, and flow... 

O2 consumption rate becomes smaller under 0.7 V, the O2 concentration at the reaction surface recovers, thus leading to an increase in the cell current density. The current rise time corresponds well with the characteristic time scale of gas phase transport as analyzed above. The rise in the cell current, however, experiences an overshoot because the polymer membrane still maintains a higher water content corresponding to 0.6 V. It then takes about 15 s for the membrane to adjust its water content at the steady state corresponding to 0.7 V. This numerical example clearly illustrates the profound impact of water management on transient dynamics of low humidity PEFC engines where the polymer membrane relies on reaction water for hydration or dehydration. 

Six different regimes of fluidization are identified in Figure 6.11 and its legend. Particulate fluidization, class (b) of the figure, is desirable for most processing since it affords intimate contacting of phases. Fluidization depends primarily on the sizes and densities of the particles, but also on their roughness and the temperature, pressure, and humidity of the gas. Especially small particles are subject to electrostatic and interparticle forces. 

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