Two-step compression

Two-Step Compression. We can compress the gas in two steps. For example, a mass Mi/2 is lifted onto the pan, and after the gas has been partially compressed, Mj is put onto the pan in place of Mi/2 to finish the compression. In this case the total work required for the compression is... 

The fugacityy) of pure compressed liqiiid i must be evaluated at the T and P of the equilibrium mixture. This is done in two steps. First, one calculates the fugacity coefficient of saturated vapor 9i = by an integrated form of Eq. (4-161), written for pure species i and evalu-atea at temperature T and the corresponding vapor pressure P = Equation (4-276) written for pure species i becomes... 

For two step cooling, now with irreversible compression and expansion, Fig. 4.7 shows that the turbine entry temperature is reduced from Ti. to by mixing with the cooling air i/ H taken from the compressor exit, at state 2, pressure p2, temperature T2 (Fig. 4.7a). After expansion to temperature Tg, the turbine gas flow (1 + lp ) is mixed with compressor air at state 7 (mass flow i/h.) at temperature Tg. This gas is then expanded to temperature T g. 

A system undergoes a two-step process. In step 1, it absorbs 50. J of heat at constant volume. In step 2, it releases 5 J of heat at 1.00 atm as it is returned to its original internal energy. Find the change in the volume of the system during the second step and identify it as an expansion or compression. 

Yin et al. [73,74] prepared new microgel star amphiphiles and stndied the compression behavior at the air-water interface. Particles were prepared in a two-step process. First, the gel core was synthesized by copolymerization of styrene and divinylbenzene in diox-ane using benzoylperoxide as initiator. Microgel particles 20 run in diameter were obtained. Second, the gel core was grafted with acrylic or methacryUc acid by free radical polymerization, resulting in amphiphilic polymer particles. These particles were spread from a dimethylformamide/chloroform (1 4) solution at the air-water interface. tt-A cnrves indicated low compressibility above lOmNm and collapse pressnres larger than 40 mNm With increase of the hydrophilic component, the molecnlar area of the polymer and the collapse pressure increased. 

In the high-pressure process for the production of polyethylene, ethylene is compressed in a two-step process. In the primary step, the gas is compressed in a two-stage compressor to 25 to 30 MPa. This is followed by compression in a hypercompressor to 150 to 320 MPa. 

Compression moulding of thermoplastics comprises at least two steps ... 

Fig. 5.9 Thermal hydrogen compression with a two-step process...

The difference between PLS and PCR is the manner in which the x data are compressed. Unlike the PCR method, where x data compression is done solely on the basis of explained variance in X followed by subsequent regression of the compressed variables (PCs) to y (a simple two-step process), PLS data compression is done such that the most variance in both x and y is explained. Because the compressed variables obtained in PLS are different from those obtained in PCA and PCR, they are not principal components (or PCs) Instead, they are often referred to as latent variables (or LVs). 

Articles formed from UHMWPE polymers can be prepared in a one step process by using high temperature compression, or in a two step process comprising cold compaction molding followed by high temperature compression molding. 

The calculation of liquid density at pressures above the bubble point is a two-step procedure. First, the density at the bubble point must be computed using one of the methods previously described. Then this density must be adjusted to take into account the compression due to the increase in pressure from bubble-point pressure to the pressure of interest. 

Panzer t al. (5) extracted Athabasca tar sand in two steps, the first with compressed n-pentane (Tc = 570 K, Pc = 3.37 MPa) and the second with compressed benzene (Tc = 563 K, Pc = 4.92 MPa). At 533-563 K and 2.0-7.7 MPa, n-pentane extracted 95% of the maltenes and asphaltenes from the tar sand, whereas at atmospheric pressure only 75% was extracted. Further extraction with benzene at 633 K and 2.0 MPa removed the remaining higher molecular weight asphaltenes. This indicates that the chemical nature of the dense gas is important in some applications. 

Figure 8.21 Simplified flow schematic of the PRISM membrane system to recover hydrogen from an ammonia reactor purge stream. A two-step membrane system is used to reduce permeate compression costs...

In Fig. 8, step I is an isothermal expansion, step II is an adiabatic expansion, step III is an isothermal compression, and step IV is an adiabatic compression. Note that zero heat is transferred in the adiabatic expansion and compression (steps II and IV) that we have added to complete the cycle, and that the work terms in these two steps exactly cancel, being equal to TC Cv dT in the expansion and Th Cv dT in the compression. (The work in an adiabatic... 

The ammonia synthesis takes place in two steps at different pressures (see Figure 6.15). In the first step, makeup gas is compressed to about 110 bar in a two-stage, intercooled compressor. The makeup gas is then fed to a three-bed, intercooled, once-through converter to produce about one-third of the ammonia. About 85% of the ammonia product is separated from the gas, which is then compressed to the standard pressure of up to 210 bar for the second-stage ammonia synthesis loop215,218. 

As shown in Chap. 6, ideal-gas heat capacities, rather than the actual heat capacities of gases, are used in the evaluation of thermodynamic properties such as internal energy and enthalpy. The reason is that thermodynamic-property evaluation is conveniently accomplished in two steps first, calculation of ideal-gas values from ideal-gas heat capacities second, calculation from PVT data of the differences between real-gas and ideal-gas values. A real gas becomes ideal in the limit as P - 0 if it were to remain ideal when compressed to a finite pressure, its state would remain that of an ideal-gas. Gases in these hypothetical ideal-gas states have properties that reflect their individuality just as do real gases. Ideal-gas heat capacities (designated by Cf and Cy) are therefore different for different gases although functions of temperature, they are independent of pressure. 

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