Compressor stages. determining

By the theoretical analysis the filtering units are considered as independent elements. Proceeding from this, the availability factor of the compressor is determined as a derivative of availability factors of these two units. As in the previous case, at the first stage of calculations the same assumptions are accepted according to which all other elements included in the system are deemed absolutely reliable. 

Several constraints were faced in the design phase of the project. For example, special attention was given to the fact that 400 Series stainless steel, carbon, and some grades of aluminum were not compatible with the process. Additionally, the expander discharge temperature was required to stay between 35-70°F. The operating rpm of the expander wheel was determined by the rpm required by the third stage of the air compressor. 

To start, convert the flow to values estimated to be the compressor inlet conditions. Initially, the polytropic head equation (Equation 2.73) will be used with n as the polytropic compression exponent. If prior knowledge of the gas indicates a substantial nonlinear tendency, the real gas compression exponent (Equation 2.76) should be substituted. As discussed m Chapter 2, an approximation may be made by using the linear average ut the inlet and outlet k values as the exponent or for the determination of the polytropic exponent. If only the inlet value of k is known, don t be too concerned. The calculations will be repeated several times as knowledge of the process for the compression cycle is developed. After selecting the k value, u,se Equation 2.71 and an estimated stage efficiency of 15 / to de clop the polytropic compression exponent n. 

Thus, in all compressors of two or more stages, the volumetric efficiency of the low-pressure cylinder determines the volumetric efficiency of the entire compressor (not recognizing packing leaks). ... 

A natural gas (methane) pipeline is to be designed to transport the gas at a rate of 50,000 scfm. The pipe is to be 6 in. ID, and the maximum pressure that the compressors can develop is 10,000 psig. The compressor stations are to be located in the pipeline at the point at which the pressure drops to 100 psi above that at which choked flow would occur (this is the suction pressure for the compressors). If the design temperature for the pipeline is 60°F, the compressors are 60% efficient, and the compressor stations each operate with three stages and interstage cooling to 60°F, determine... 

In a two-stage continuous compression process, methane (stream 1) enters the first compressor at 300 K and 1 bar. The methane (stream 2) leaves the second compressor at 300 K and 60 bar. The flow rate of methane is 0.5kg/s. The total power input is 400kW. The intercooler between the compressors uses cooling water. The surroundings are at 295 K. Determine the energy dissipated. 

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