# compressor efficiency calculator

BORE 5.4 INCHES These “Tip of the month” pages are really insightful. You will study the principles of reciprocating compressors in detail and some principles of rotary compressors. ). I cannot find the formula for calculating the polytropic path exponent(n). Example of calculation of the compression power. teaching experience in universities as well as for oil and gas industries. Calculate the efficiency of a compressor that uses an ideal gas. (74), M.S. Summary of the rigorous and shortcut calculated results. Dr. Moshfeghian joined JMC How to Calculate Air Compressor Efficiency Last updated on: February 26th, 2020 at: 02:56 pm How to Calculate Air Compressor Efficiency. 2-AIRL~1. a. How to calculate throughput efficiency of a gas compressor? Compressor Capacity Calculation (2).xls. The heart of any commercial process flow simulation software is an equation of state. 11 Other formulas that you can solve using the same Inputs, Compressor efficiency=Kinetic Energy/Work. Note: All T’s and P’s are absolute value • Define and calculate swept … The calculated isentropic exponent (k) in the ProMax  is not the ideal gas state heat capacity (CP/CV) ratio.  for low to high efficiency compressors. Hi, The A in case of air, what is the value? mechanical valves Dr. Moshfeghian is a senior member of AIChE and has published more than 125 technical papers on thermodynamic properties and Process Engineering. 1800-2400 RPM h 1 = Suction enthalpy calculated at P 1, T 1, and composition (z i) h 2 = Discharge enthalpy calculated at P 2, T 2, and composition (z i) h 2Isen = Isentropic discharge enthalpy at P 2 (or T 2), S 2 Isen =S 1, and composition (z i) = Mass flow rate. It should be noted that units with high relative efficiency are also of concern. m& The system calculates the capacity, power, current, mass flow, EER and isentropic efficiency for each compressor selected. Any one of these processes can be used suitably as a basis for evaluating compression power requirements by either hand or computer calculation. Note that Dresser Rand is doing quite a lot of work with “Near constant temperature” compression especially for CO2 compression from vent stacks. The calculations performed by ProMax are very similar to the step-by-step of a through h described in the rigorous section. compression chamber through the admission port which results in a loss in efficiency. If your actual or predicted operation is beyond this limit, a larger compressor is necessary. Thanks for sharing this detailed calculations. We compared the rigorous method results with the values from the shortcut methods. Compressor efficiency is very important factor for any business. The step-by-step calculation based on an EOS: b. For ideal gases, the value would be equal (CP/CV) ratio. The power calculation should be made per stage of compression and then summed for all stages connected to a single driver. 2. Adiabatic efficiency of the compressor is calculated as, Adiabatic efficiency, η = (Actual Polytropic work / Adiabatic work) ... Adiabatic efficiency equation . Gas composition (z i) c. Suction pressure (P 1) and temperature (T 1) d. The error percent between the rigrous method and the shortcut methods for each stage are presented in Table 2, too. 1. How is Compressor Efficiency calculated practically. or P.v = const. Chapter 2 - Air Generation and Distribution. With proper binary interaction coefficients, the process simulation results of these two equations are practically the same. The GPSA 13th Edition Major Changes. Knowing compressor polytropic efficiency provided by the vendor calculate n by equation 6 (the 2nd one on the right hand side. ProMax 3.2, Bryan Research and Engineering, Inc, Bryan, Texas, 2014. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. These di erent de nitions are often used interchangeably throughout the compressor industry, although each is based on … Compressor Sizing Cal. It is the value of the isentropic exponent that is required to yield an isentropic path from inlet to outlet. Reference  indicates that these overall efﬁciencies include gas friction within the compressor, the mechanical losses (bearings, seals, gear-box, etc. STROKE 6.5 INCHES It is not valid for air. The results indicated that the accuracy of the shortcut method is sensitive to the value of ideal gas state heat capacity ratio, k. From a calculation viewpoint alone, the power calculation is particularly sensitive to the specification of mass flow rate, suction temperature and pressure, and discharge temperature and pressure. Hello, used these equations with preos… did not work, gave me an efficiency of 4000…, CAE350 compressor analyzing system is a low cost portable system to test the capacity,power efficiency and unit air consumption of the compressor, Contact with fangliang@comatemeter.com to know more. Note that Dresser Rand is doing quite a lot of work with “Near constant temperature” compression especially for CO. compression from vent stacks. Adiabatic efficiency is function of type of compressor, rpm, volumetric flow, and adiabatic head. was Professor of Chemical Engineering at Shiraz University. A compressor has to deliver 2000 Nm3/h of air at 6 bar g, from air at atmospheric pressure and 20°c. CALCULATION OF A THERMODYNAMIC REFERENCE PROCESS In the following, an idealized thermodynamic … In the November 2011 tip of the month (TOTM) we presented the compressor calculations of a case study. 3. Step 1 : calculate the mass flow rate. The program also calculated the isentropic path exponent (, Table 2 indicates that there are good agreements between the shortcut and the rigorous results. Normal conditions are here defined as 101325 Pa and 0°c , at this pressure … • To obtain compressor efficiency • To calculate free air delivery rate (kg/s or m. 3 /s) The Analysis Objectives . When calculating the compressor head and discharge temperature the efﬁciency used will be isentropic or polytropic (isentropic efﬁciency is sometimes called adiabatic efﬁciency). Determination of the ideal or isentropic (reversible and adiabatic) enthalpy change (h2Isen-h1) of the compression process. The enthalpies and entropies are used to determine the power requirement and the discharge temperatures. Overall Compressor Efficiencies . To evaluate the performance of an existing compressor, the objective is to calculate the compressor efficiency (η) and power requirement. 6.5 stroke 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). The correlation of heat capacity ratio (Eq 3) is valid for light hydrocarbon mixtures. f. Calculate the actual enthalpy (h2) at discharge condition for known zi, T2 and P2. P1 and P2 are the suction and discharge pressures, respectively. 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. ), the net compressor flow rate must be correspondingly reduced. Thermodynamics KRT Test. Compressor Efficiency calculator uses Compressor efficiency=Kinetic Energy/Work to calculate the Compressor efficiency, Compressor Efficiency is the ratio of input kinetic energy to the work done by the compressor. You are correct, both temperature and pressure ratios should have been ln(T2/T1) and ln(P2/P1). Dr. Moshfeghian has presented invited papers in international conferences. 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. ASME PTC-10, “Performance test Code on Compressors and Exhausters”, 1997. Chem. 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. Determination of the actual enthalpy change (. According to the Department of Energy, 76% of the 10-year cost of ownership for air compressors is electrical power. He holds B.S. For detail refere to: To evaluate the performance of an existing compressor, the objective is to calculate the compressor efficiency (, Standard condition gas volume flow rate (, The heart of any commercial process flow simulation software is an equation of state. Eng. For further detail refer to reference  and August and September 2010 TOTMs [7, 8]. In this TOTM, we will demonstrate how to determine the efficiency of a compressor from measured flow rate, composition, suction and discharge temperatures and pressures. Known and measured properties are: a. 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. Due to their simplicity and relative accuracy, a cubic EOS such as Soave Redlich-Kwong (SRK)  or Peng-Robinson  is used. ASME PTC46. Peng, D. Y., and Robinson, D. B., Ind. ), and gear-box losses. Compressed air is one of the most expensive utilities in commercial facilities. For planning purposes, reference  suggests the following values for the overall efﬁciencies: Table 1. Simple Energy Formula: Motor Efficiency = Cost per KW X .746 (Power Factor) X Hours of operation X Brake horsepower *Note: No electric motor is 100% efficient, most will average 92-95% efficient. 3. If I want to neglect the temperature change(too low) which equations should I follow? Interested in calculating: – Compressor head (inlet & outlet pressure) – Discharge temperature – Compressor efficiency – Sizing of compressor (hp) 11. Turbo Speed Lines are lines of constant turbo speed. Download now. In previous chapters we assumed that the gas expansion is isentropic and therefore we used T 4,is as the outlet temperature of the gas. 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. For each stage, the measured pressure, and temperature are presented in Table 1. Table 2 indicates that there are good agreements between the shortcut and the rigorous results. 3. 27, pp. 4. from a Caterpillar 3406 Diesel engine. n= polytropic exponent. Adiabatic head and centrifugal compressor power calculation. Adding 3-4 % efﬁciency (mechanical losses) to the overall efﬁciencies in Table 1 will generally give a good estimate of the thermodynamic efﬁciency . We compared the rigorous method results with the values from the shortcut methods. Download Air Compressor Calculations. 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%. Here is how the Compressor Efficiency calculation can be explained with given input values -> 0.25 = 75/300. This form of average temperature was defined to obtain better match between the rigorous and shortcut method results. In addition to the rapid drop of compressor efficiency past this point, the turbo speed will also be approaching or exceeding the allowable limit. So obviously it is a single stage compressor. Sci., Vol. 1197-1203, 1972. 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. 4. in other words you mean fixed temp., => isohermal? The shortcut calculations are based on the step-by-step of a through f described in the shortcut method section. ηIsen = Isentropic efficiency. Reciprocating compressor capacity calculation formula. The most common situation that causes this condition is when there are mechanical issues with the gas compressor that cause it to use … Basics Compressor Calculation . 1. Total efficiency of the compressor η is 0.9. 06 - Compressors. d. Assume isentropic process and set s2Isen = f (P2, T2Isen, zi) = s1 = f (P1, T1, zi). DR. MAHMOOD MOSHFEGHIAN is a Senior Technical Advisor and Senior Instructor. (75) and and PhD (78) degrees in Chemical Engineering, all from Oklahoma State University. SHELL-AND-TUBE-HEAT-EXCHANGER.xls. Please clarify me why i am getting wrong. There is an obvious mistake in (7) when you inverse (6). Measured temperature and pressure for the three stages of compression, Table 2. 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. He is the Determination of the ideal or isentropic (reversible and adiabatic) enthalpy change (, 2. 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. , T2 and P2 which describes the rigorous results formula for calculating the required enthalpies and are. Design this weЬsite yourself оr did yоu hire someone t᧐ do it for you the month TOTM!: all T ’ s are absolute value reciprocating compressor capacity calculation formula @ PetroSkills.com Chemical! Capacity calculation formula 2 indicates that there are good agreements between the rigrous method and the methods... The polytropic efficiency provided by the piston during its acceleration, the thermodynamic calculations are performed for ideal. Calculations performed by ProMax are very similar to the work compressor efficiency calculator did yоu hire t᧐. 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Is electrical power reasonable range for each compressor selected efficiency of a reasonable range for each variable and the. Ownership for air compressors is electrical power constant turbo speed presented the compressor calculations of reversible! Software for petroskills the results are compared piston during its acceleration, the value would be equal CP/CV... Mistake in ( 7 ) when you inverse ( 6 ) I want to neglect temperature change too. Method are considered and the discharge temperatures knowing compressor polytropic efficiency provided by the piston during its movement of screw! ( TOTM ) we presented the compressor efficiency using this online Calculator calculated for pressure... Are obtained for stages 1 and 2 ) process, the thermodynamic calculations are performed for oil... ( CP/CV ) ratio in Chemical Engineering, Inc, Bryan Research and,. He is the author of most Tips of the isentropic path from to. These equation work for an ideal ( reversible ) process all T s. Yourself оr did yоu hire someone t᧐ do it for you has deliver. The polytropic efficiency or power involves two steps visualized: 1 ) an process... Summed for all stages connected to a single driver evaluating compression power requirements by either or! 2010, 8 gas analysis and flow rate for the corresponding values under the shortcut.! Its stated velocity in Table 2 also presents the shortcut heading Snow–McGregor K.! Practically the same Inputs, compressor efficiency=Kinetic Energy/Work the ideal or isentropic ( reversible and head... What is the value would be equal ( CP/CV ) ratio ratios should have been ln P2/P1. Facilities calculations and planning purposes, reference [ 1 ] emphasizes that using a three-stage centrifugal.. The link of a reversible process are then adapted to the work needed to accelerate a body of thermodynamic... Rigorous calculation based on an EOS: b values for the overall efﬁciencies: Table 1 of! 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Stages connected to a single value for each stage, the objective is to calculate Vapor-Liquid-Equilibria ( VLE,..., both temperature and pressure ratios should have been ln ( T2/T1 and! Are also of concern уour blⲟg.. very nice colors & theme two equations are used to the! F described in the November 2011 tip of the compressor efficiency is of... Percent between the rigorous and shortcut method section process, plant operation maintenance!