![]() ![]() The isothermal process, however, is seldom used as a basis because the normal industrial compression process is not even approximately carried out at constant temperature.ĭue to practical limitation the compression ratio per stage is often in the range between 2 and 6. ![]() Any one of these processes can be suitably used as a basis for evaluating compression power requirement by either hand or computer calculation. In the compression process there are three ideal processes that can be visualized: 1) an isothermal process, 2) an isentropic process and 3) a polytropic process. The results of a reversible process are then adapted to the real world through the use of an efficiency. Normally, the thermodynamic calculations are performed for an ideal (reversible process). Maddox and Lilly emphasize that using a single value for each variable is not the correct way to evaluate a compression system. Thus the most difficult part of a compressor calculation is specification of a reasonable range for each variable and not the calculation itself. A compressor is going to operate under varying values of the variables affecting its performance. Gas composition is important but a small error here is less important providing it does not involve the erroneous exclusion of corrosive components. įrom a calculation viewpoint alone, the power calculation is particularly sensitive to the specification of flow rate, inlet temperature and pressure, and outlet pressure. Further detail may be found in reference. Rotary screw compressors are gaining in popularity in low to moderate pressure gas boosting service, refrigeration systems and fuel gas compression for gas turbines. Reciprocating and centrifugal compressors are the most popular compressors used in E & P applications. The compression principle is acceleration and deceleration of the gas – kinetic energy is converted to pressure rise. Kinetic or Dynamic: this type of compressor includes centrifugal and axial compressors.The compression principle is volumetric displacement – reducing the gas volume increases pressure. Positive displacement this type of compressor includes reciprocating, rotary screw, sliding vane, liquid ring and rotary lobe.In addition, the impact of thermodynamic properties package has been studied.Ĭompressors can be generally classified in two categories: Variation of polytropic head and efficiencies as a function of gas molecular weight for a given compression ratio, and compressor speed has also been studied. We have considered several “what if” scenarios such as variation of compressor speed as a function of molecular weight, while maintaining the same suction and discharge pressures and mass flow rate. In this tip of the month (TOTM) we will present the results of several case studies showing the effect of gas molecular weight on the performance and efficiencies of centrifugal compressors. ![]()
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