CALCULATION OF A THERMODYNAMIC REFERENCE PROCESS In the following, an idealized thermodynamic … If your actual or predicted operation is beyond this limit, a larger compressor is necessary. The measured feed composition, flowrates, and calculated molecular weight and relative density are presented in Table 2. 11 Other formulas that you can solve using the same Inputs, Compressor efficiency=Kinetic Energy/Work. Here is how the Compressor Efficiency calculation can be explained with given input values -> 0.25 = 75/300. The enthalpies and entropies are used to determine the power requirement and the discharge temperatures. Thanks for sharing this detailed calculations. ASME PTC46. The compressor is to deliver 2000 Nm3/h of air. The shortcut calculations are based on the step-by-step of a through f described in the shortcut method section. 3. Kinetic Energy is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. AIR Recieve follow up comments updates: RSS 2.0, View all posts by: Dr. Mahmood Moshfeghian, thanks for the article, To find the turbine efficiency, a robust technique is to use the turbocharger power balance to obtain the combined aerodynamic/mechanical turbine efficiency. Download Air Compressor Calculations. CheCalc Chemical engineering calculations to assist process, plant operation and maintenance engineers. The program also calculated the isentropic path exponent (k), and polytropic path exponent (n). On completion you should be able to the following. To learn more about similar cases and how to minimize operational problems, we suggest attending our G4 (Gas Conditioning and Processing), PF4 (Oil Production and Processing Facilities), ME46 (Compressor Systems–Mechanical Design and Specifications) and ME44 (Fundamentals of Pump and Compressors Systems), courses. h1 = Suction enthalpy calculated at P1, T1, and composition (zi), h2 = Discharge enthalpy calculated at P2, T2, and composition (zi), h2Isen = Isentropic discharge enthalpy at P2 (or T2), S2Isen =S1, and composition (zi), The computation compressor efficiency or power involves two steps. can also be found, under: http://www.degruyter.com/view/j/tjj.ahead-of-print/tjj-2016-0029/tjj-2016-0029.xml?format=INT, Please calculate or estimate overall efficiency of the following Theoretical Coefficient of Performance of a refrigerator, Theoretical Coefficient of Performance=Heat Extracted from Refrigerator/Work, Theoretical Coefficient of Performance=Heat Delivered to Body/Work, Nozzle efficiency=Change in Kinetic Energy/Kinetic Energy, Cooled Compressor Efficiency=Kinetic Energy/Work, thermal efficiency of heat engine=Work /Heat, mean effective pressure=Work /Displacement, Coefficient of Performance of absorption system, Coefficient of Performance of Refrigerator, Equipartition energy for molecule having n degrees of freedom, Thermal efficiency given Mechanical energy, Coefficient of Performance of Refrigerator given the heat in the cold and hot reservoir, Coefficient of Performance of Heat Pump given the heat in the cold and hot reservoir, Coefficient of Performance of Heat Pump given work and heat in the cold reservoir, Coefficient of Performance of Refrigerator given work and heat in the cold reservoir, Temperature Ratio When Isentropic Pressure is Given, Temperature Ratio when Isentropic Specific Volume is Given, Isentropic temperature 2 given pressure ratio, Isentropic temperature 1 given pressure ratio, Isentropic temperature 1 given specific volume, Isentropic temperature 2 given specific volume, Compressor Efficiency is the ratio of input kinetic energy to the work done by the compressor and is represented as, Compressor Efficiency is the ratio of input kinetic energy to the work done by the compressor is calculated using. 1. With proper binary interaction coefficients, the process simulation results of these two equations are practically the same. I tried using the same formulas for calculating the compressor efficiency but results are good in one case but in other cases error is more than 20 %. Printing, Editors Hubbard, R. and Snow–McGregor, K., Campbell Petroleum Series, Norman, Oklahoma, 2014. For planning purposes, reference [2] suggests the following values for the overall efﬁciencies: Table 1. Solving the above equation for the polytropic path coefficient (n): Similarly, the actual discharge temperature based on a polytropic path can be estimated (ηPoly) by: Similarly, the polytropic head is calculated by, For an isentropic (reversible and adiabatic) process the power is calculated by, Or for a polytropic process the power is calculated by, R = Universal gas constant, 848 kg-m/(kmol-K) or (1545 ft-lbf/(lbmol-°R)), PS = Standard condition pressure, kPa (psia), TS = Standard condition temperature, K (°R), qS = Gas volumetric rate at the standard condition, Sm3/d (scf/day), Za = Average gas compressibility factor = (Z1+Z2)/2, Z1 = Gas compressibility factor at the suction condition, Z2 = Gas compressibility factor at the discharge condition. P1 and P2 are the suction and discharge pressures, respectively. Honeywell, J. m& Adiabatic head and centrifugal compressor power calculation. 6.5 stroke Compressor E ciency De nitions K. Ueno, PhD, and R. E. Bye, VAIREX Corporation K. S. Hunter, PhD, University of Colorado May 12th, 2003 Many standard e ciency de nitions exist that qualify the mass ow and power performance characteristics of a compressor. These assumptions are only applicable with ideal cycles. If I want to neglect the temperature change(too low) which equations should I follow? g. Calculate isentropic efficiency by Equation 1: µIsen = (h2Isen – h1)/(h2 – h1). The program calculated polytropic and isentropic efficiencies, heads, and compression power. For the first stage friction loss coefficient β f is 0.007, leakage loss coefficient β l is 0.009, and let’s assume that for subsequent stages the losses will increase by 1%. Not all the cylinder volume can be used for the compression as there is always the clearance at the end of the cylinder that remains with some … Note that Dresser Rand is doing quite a lot of work with “Near constant temperature” compression especially for CO. compression from vent stacks. kսdos. Worked Example for Calculating the Performance of a Gas Turbine F.1 THE REQUIREMENTS AND DATA GIVEN A 12 MW gas turbine generator is required to operate at sea level with an ambient temperature T 1 of 20 C and a combustion temperature T 3 of 950 C. The following data apply. Assume the feed composition remain unchanged, c. Calculate suction enthalpy h1=f(P1, T1, and zi) and entropy s1=f(P1, T1, and zi) by EOS. Calculate the isentropic exponent (k) by Equation 3 using the average temperature defined by T = (T1+3T2)/4. It should be noted that units with high relative efficiency are also of concern. ), the net compressor flow rate must be correspondingly reduced. The results indicate that the heat pump COP increases almost linearly with compressor efficiency. The results indicated that the accuracy of the shortcut method is sensitive to the value of ideal gas state heat capacity ratio, Normally, the thermodynamic calculations are performed for an ideal (reversible) process. 2. 5.4 bore Compressor efficiency and is denoted by CE symbol. Turbo Speed Lines are lines of constant turbo speed. The results of a reversible process are then adapted to the real world through the use of a thermodynamic efficiency. 7. The most common situation that causes this condition is when there are mechanical issues with the gas compressor that cause it to use … Compressor Efficiency Calculation. when there is a change of phase it is difficult to evaluate and adopt a value for efficiency in different conditions…, Please may I know the equation seven. ASME PTC-10, “Performance test Code on Compressors and Exhausters”, 1997. A system and method for calculating the performance of a compressor wherein the user can select a compressor from a database or retrieve a list of compressors to select from based on application conditions. Monitoring of air quality or compressor efficiency is often done through third party contractors on a periodic audit basis and this may be sufficient for a particular need but will always be limited by the length of time the survey gathered data from. The polytropic efficiency calculation formula is the following [1] : Ep = 0.61+0.03*log(0.5885*Qv) With : Ep = polytropic efficiency (-) f. Calculate the actual enthalpy (h2) at discharge condition for known zi, T2 and P2. It may also be worth noting that when trending ‘n’ and the polytropic efficiency to evaluate machine condition, the relative accuracy of measurement instrument/equipment (temperature and pressure transducers) and mapping of compressor performance to the original performance curve (actual gas volume flow rate vs speed), introduces many potential erroneous sources into this daily evaluation. Standard condition gas volume flow rate (qS) or gas mass rate (), c. Suction pressure (P1) and temperature (T1), d. Discharge pressure (P2) and temperature (T2). Soave, G., Chem. Compressor efficiency is very important factor for any business. In addition to the rapid drop of compressor efficiency past this point, the turbo speed will also be approaching or exceeding the allowable limit. They can only be determined (afterward) by a compressor test, although compressor manufacturers can usually provide good estimates. In the compression process there are three ideal processes that can be visualized: 1) an isothermal process (PV1=C1), 2) an isentropic process (PVk=C2) and 3) a polytropic process (PVn=C3). We compared the rigorous method results with the values from the shortcut methods. 27, pp. Maddox, R. N. and L. L. Lilly, “Gas conditioning and processing, Volume 3: Advanced Techniques and Applications,” John M. Campbell and Company, 2nd Ed., Norman, Oklahoma, USA, 1990. As turbo speed … these variations may originate large errors (see the example provided in Huntington’s paper), Compressor Capacity Calculation (2).xls. For more information about these services, visit our website at http://petroskills.com/consulting, or email us at consulting@PetroSkills.com. 1. [54] for low to high efficiency compressors. mechanical valves Calculate the efficiency of a compressor that uses an ideal gas. 1800-2400 RPM (74), M.S. Isentropic Efficiency – Turbine, Compressor, Nozzle. is 85% practical? Peng, D. Y., and Robinson, D. B., Ind. 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. Compressor efficiency is the ratio of input kinetic energy to the work done. Chapter 2 - Air Generation and Distribution. ProMax 3.2, Bryan Research and Engineering, Inc, Bryan, Texas, 2014. Thermodynamics KRT Test. Compressor Pressure ratio of the compressor r pc 11.0 Compressor efﬁciency η c 0.85 Ratio … DR. MAHMOOD MOSHFEGHIAN is a Senior Technical Advisor and Senior Instructor. b. For stage 3, due to high-pressure operation and deviating too far from the ideal gas state condition, a larger error is observed for the isentropic exponent (, It may also be worth noting that when trending ‘, Note that the accuracy of the shortcut methods is dependent on the values of, To learn more about similar cases and how to minimize operational problems, we suggest attending our, 1. The program calculated polytropic and isentropic efficiencies, heads, and compression power. These “Tip of the month” pages are really insightful. The enthalpies and entropies are used to determine the power requirement and the discharge temperatures. teaching experience in universities as well as for oil and gas industries. In a reciprocating compressor, the capacity depends on the volume displaced by the piston during its movement. This error in ‘k’ also illustrates the importance of specifying which correlation is to be used when ordering a performance test (ie, refer to ASME PTC-10 for additional details), so that client and vendor are on the same agreement moving forwards with regard to molecular weight (MW) and k for the test fluid. You are on … “Important Aspects of Centrifugal Compressor Testing-Part 2”, Tip of the Month, September 2010, Categories: Gas Processing, Mechanical, Pipeline, Process Facilities, Recieve new post updates: Entries (RSS) or P.v = const. Any one of these processes can be used suitably as a basis for evaluating compression power requirements by either hand or computer calculation. Sci., Vol. Laurent: For further detail refer to reference [6] and August and September 2010 TOTMs [7, 8]. n= polytropic exponent. Compressor Sizing Cal. The program also calculated the isentropic path exponent (, Table 2 indicates that there are good agreements between the shortcut and the rigorous results. The computation compressor efficiency or power involves two steps. There is an obvious mistake in (7) when you inverse (6). For stage 3, due to high-pressure operation and deviating too far from the ideal gas state condition, a larger error is observed for the isentropic exponent (k). How is Compressor Efficiency calculated practically. 5. 06 - Compressors. Important Aspects of Centrifugal Compressor Testing-Part 1. I built an air compressor with a quick return mechanism and a bike pump. Here is the link of a new article, which describes the rigorous calculation of the polytropic efficiency based on thermodynamics of real gases. He has 40 years If this is not available, you can approximate the polytropic efficiency of centrifugal compressors as the polytropic efficiency is linked to the flow at inlet of the compressor. cooling or other purposes belong to the losses and have not to be considered in the efficiency calculation. The swept volume of one piston can be calculated the following way . Reference [1] emphasizes that using a single value for each variable is not the correct way to evaluate a compression system. The process flow diagram is shown in Figure 1. The process flow diagram shown in Figure 1 was simulated by ProMax software [5] to perform the rigorous calculations using the SRK EOS. Hi, The A in case of air, what is the value? 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