Compressor three stage

Vane compressors tend to be limited to low pressure service, generally less than 100 to 200 psi discharge. They are used extensively as vapor recovery compressors and vacuum pumps. Single-stage vane compressors can develop 27 in. Hg vacuums, two-stage compressors can develop 29.0 in. Hg, and three-stage compressors can develop even higher vacuums. 

A three-stage compressor is required to compress air from 140 kN/m2 and 283 K to 4000 kN/m2. Calculate fee ideal intermediate pressures, the work required per kilogram of gas, and fee isothermal efficiency of fee process. Assume the compression to be adiabatic and the interstage cooling to cool the air to the initial temperature. Show qualitatively, by means of temperature-entropy diagrams, fee effect of unequal work distribution and imperfect intercooling, on the performance of the compressor. 

The objective function for the work requirement for a three-stage compressor can be expressed as (p is pressure)... 

Figure 6.42a Single-stage compressor and three-stage compressor refrigeration...

Build the three-stage-compressor refrigeration cycle as shown in Fig. 6.42a. Assume the compressors are adiabatic with 85% efficiency, and the heater and cooler are isobaric. 

Figure 6.42b Three-stage compressor refrigeration system using R-12. 

Figure 7.18. Heavy-duty centrifugal, axial, and reciprocating compressors, (a) Section of a three-stage compressor provided with steam-sealed packing boxes (DeLaval Steam Turbine Co.), (b) An axial compressor (Clark Brothers Co.), (c) Double-acting, two-stage reciprocating compressor with water-cooled jacket and intercooler (Ingersoll-Rand Co.).

Compression cycles are shown in Figs 8a and 8b. The former indicates the effect of various values of n in PVn = constant and it is seen that the work done is the area under the temperature-entropy curve. Figure 8b illustrates the three-stage compressor of this problem. The final temperature T2, found from T2/T1 = (P2lP ) y X)lr 1S 390 K. The dotted lines illustrate the effect of imperfect interstage cooling. 

Reformed gas is compressed to 100 barg in a 27 MW split, three-stage compressor and injected into the converter loop at the suction of the 5 MW circulating compressor. Converter circulating gas plus make-up gas is heated and fed to a six-bed converter (ZnO/CuO/Al O catalyst). Part of the gas is fed to the inlet of the reactor at 210-240°C and the balance is fed, at a lower temperature, to the lower beds as quench gas. Reactor effluent is cooled both against reactor feed and saturator water feed before passing to the methanol condensers. The crude methanol is then rundown to off-site tankage and the MTG unit. 

Rework Example 9.5(c) for a three-stage compressor, using the optimum interstage pressures. 

Let us consider a three-stage compressor in which the gas is cooled to the inlet gas temperature between stages. The theoretical work is given by ... 

Figure 10.44 shows the mywork3.m file that defines the three-stage compressor work as a function of the intermediate pressures, P2 andpg, which are denoted here asx(l) andx(2). The output of MATLAB built-in fminunc gives x, which minimizes the work. The MATLAB built-in fminunc finds the minimum of a multi-variable, unconstrained function on a fixed interval. 

Figure 10.44 Defining the work of a three-stage compressor with interstage cooling.

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