How to calculate throughput efficiency of a gas compressor? How to Calculate Your Current Air Demand Any industry that uses compressed air is subject to inefficiency. Reference  indicates that these overall efﬁciencies include gas friction within the compressor, the mechanical losses (bearings, seals, gear-box, etc. 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. How to Calculate Air Compressor Efficiency. Air compressor efficiency can be drastically reduced in a very short time when dirt, salt water mist, or similar air con taminants enter the inlet air. e. Calculate the ideal enthalpy (h2Isen) at discharge condition for known zi, T2 (or P2) and s2Isen. 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. finally, a procedure can also consider phase equilibria, I know Prode Properties (see http://www.prode.com/docs/pppman.pdf) which includes both Huntington and a proprietary method for solving a polytropic stage with phase equilibria, A comparison with data shown on this website (!) 15, p. 59, 1976. Unfortunately, the CFM rate is often exaggerated by the manufacturers to make more sales. 0 More Detailed Calculation (100-hp Compressor with 30 Power) Annual Electricity Costs = [(Full This is because air compressors inherently consume a lot of energy just to produce the air, and once produced, employees tend to misuse it. Printing, Editors Hubbard, R. and Snow–McGregor, K., Campbell Petroleum Series, Norman, Oklahoma, 2014. Thus it is somewhat of an “average” value representing the true isentropic path. Please clarify me why i am getting wrong. 4. But for the calculation of efficiency should I follow these equations? kսdos. Efficiency was calculated for high pressure compressor with suction pressure 60 kg/cm2. For detail refere to: http://www.nist.gov/pml/high_megawatt/upload/6_1-Approved-Moore.pdf. Home » Blog » How to Calculate Air Compressor Efficiency. In the compression process there are three ideal processes that can be visualized: 1) an isothermal process (PV. Moshfeghian
and the feed composition remain unchanged. The enthalpies and entropies are used to determine the power requirement and the discharge temperatures. Determination of the ideal or isentropic (reversible and adiabatic) enthalpy change (, 2. Since the amount of fuel is relatively small (ratio 1:14.7), compared with the amount of air, we can neglect the fuel mass for volumetric efficiency calculation. Quincy Compressor has long maintained a reputation for manufacturing quality air compressors that combine efficiency and durability. Let’s take a look at the formula and consider how an efficient compressor can help your organization. STROKE 6.5 INCHES 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. Gas analysis and flow rate for the three stages of compression. Air compressors use about 6% of all motor-driven electricity in the industrial sector. 6.5 stroke The process flow diagram is shown in Figure 1. Did you design this weЬsite yourself оr did yоu hire someone t᧐ do it S551 portable data recorder and compressed air analyser. Process flow diagram for a 3-stage compression, Table 1. We are also happy to send out a compressed air expert to conduct a preliminary walkthrough of your facility using the methodology outlined in the efficiency quotient worksheet. Fundam., Vol. When researching air compressors to purchase, there’s a handy tool you can use to calculate a unit’s given efficiency. Table 2 indicates that excellent agreements are obtained for stages 1 and 2. The mechanical efﬁciency varies with compressor size and type, but 95% is a useful planning number. How to calculate and formula for Reducing air pressure form 6 bar to 5 bar in reciprocation air compressor 2 stage 75 KW driving power motor. 2. To evaluate the performance of an existing compressor, the objective is to calculate the compressor efficiency (η) and power requirement. Table 3. For ideal gases, the value would be equal (CP/CV) ratio. a. It is seen in Fig. A compressor is going to operate under varying values of the variables affecting its performance. 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 email@example.com to know more. Campbell, J.M., Gas Conditioning and Processing, Volume 2: The Equipment Modules, 9th Edition, 2nd Printing, Editors Hubbard, R. and Snow–McGregor, K., Campbell Petroleum Series, Norman, Oklahoma, 2014. 1800-2400 RPM Single-stage compressors areIn the for you? Thanks. Important Aspects of Centrifugal Compressor Testing-Part 1. Compressor efﬁciencies vary with compressor type, size, and throughput. 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. The program calculated polytropic and isentropic efficiencies, heads, and compression power. ), and gear-box losses. If I want to neglect the temperature change(too low) which equations should I follow? The calculated isentropic exponent (k) in the ProMax  is not the ideal gas state heat capacity (CP/CV) ratio. Soave, G., Chem. Therefore, only the SRK is used in this work. 1. The heart of any commercial process flow simulation software is an equation of state. The program also calculated the isentropic path exponent (, Table 2 indicates that there are good agreements between the shortcut and the rigorous results. You want to own and operate equipment that runs over long periods of time, using a minimal amount of energy. A compressor has two ratings for delivered flow rate: free air delivery (FAD) and average cylinder charge rate (CR). They can only be determined (afterward) by a compressor test, although compressor manufacturers can usually provide good estimates. After that, our representative can conduct a test using an EQ Analyzer to record how well your system is working. Website by, (Contact us if your Country is not listed. These calculated results are presented in Table 2 for all three stages under SRK headingings. I cannot find the formula for calculating the polytropic path exponent(n). The efficiency of the filter actually improves as dust loads up on the surface of the filter, so an air filter gets better as it gets used. The differences between the rigorous and shortcut method results for facilities calculations and planning purposes are negligible. I ⅼove уour blⲟg.. very nice colors & theme. Eng. 5. “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)
consider non-contant values for properties from pin->pout, It can be seen, for example, that at 3 gal/cfm capacity the part-loaded air compressor might consume 75% of its full load power while delivering 50% of its full load flow. can anyone please help that how to calculate the efficiency of rotary screw air compressor..???? ). f. Calculate the actual enthalpy (h2) at discharge condition for known zi, T2 and P2.
All Rights Reserved. The step-by-step calculation for shortcut method. We compared the rigorous method results with the values from the shortcut methods. when I try to calculate the polytropic exponent with the T1 = 40.6, T2 = 129.4, P1 = 793.1, P2 = 2275.9 the n = 1.808666. but in the table the value is n = 1.3097. Compressed Air System Economics Improving Compressed Air System Performance F9-2 A Sourcebook for Industry April 1998 - Rev. Adjustment of the ideal work requirement for compressor efficiency. Using a Flow Meter to Calculate CFM (Airflow) Another easy way to calculate your CFM is by using an airflow meter. 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. Determination of the actual enthalpy change (. Watch our latest video to learn what can happen when you choose an air compressor provider that offers low-quality products and services. Its value is calculated as an integration of that path. Peng, D. Y., and Robinson, D. B., Ind. From there, you’ll be well equipped to make decisions regarding cost savings. volumetric efficiency of the compressor Ev should be calculated rigourously thanks to the actual volume and swept volume, but for quick estimations, the volumetric efficiency can be estimated thanks to the following expression Any one of these processes can be used suitably as a basis for evaluating compression power requirements by either hand or computer calculation. 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. These equations are used to calculate Vapor-Liquid-Equilibria (VLE), enthalpy (, 1. It is the value of the isentropic exponent that is required to yield an isentropic path from inlet to outlet. a. Pl do needful how to calculate in reduction of Pressure in Reciprocation air compressor. Assume steady state, i.e. We invite you to take advantage of a professional’s opinion on how your compressor system is functioning and where you can increase efficiency. This would mean the specific power at the 50% point would be roughly 50% higher than at full load (75/50 = 1.5 times full load sp). BORE 5.4 INCHES these variations may originate large errors (see the example provided in Huntington’s paper), These “Tip of the month” pages are really insightful. The program also calculated the isentropic path exponent (k), and polytropic path exponent (n). The process flow diagram shown in Figure 1 was simulated by ProMax software  to perform the rigorous calculations using the SRK EOS. d. Assume isentropic process and set s2Isen = f (P2, T2Isen, zi) = s1 = f (P1, T1, zi). 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. However, at Quincy Compressor, we strive to make it easier. from a Caterpillar 3406 Diesel engine. Summary of the rigorous and shortcut calculated results. … 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. Norman, OK. 73072. Mechanical valves Normally, the thermodynamic calculations are performed for an ideal (reversible) process. He holds B.S. 27, pp. The results of a reversible process are then adapted to the real world through the use of a thermodynamic efficiency. 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. (75) and and PhD (78) degrees in Chemical Engineering, all from Oklahoma State University. DR. MAHMOOD MOSHFEGHIAN is a Senior Technical Advisor and Senior Instructor. Owning a machine that uses energy in an economical way is a goal that consumers in both the personal and professional realms share. dear Faisal, you want to neglect temperature change? Dr. Moshfeghian has presented invited papers in international conferences. A rigorous calculation based on an equation of state and a shortcut method are considered and the results are compared. air-compressor is best shown on a pressure-volume (p-V) diagram. g. Calculate isentropic efficiency by Equation 1: µIsen = (h2Isen – h1)/(h2 – h1). Please can u write the formula for calculating polytropic path exponent. Contaminants will accumulate in the air compressor and reduce its compression 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. Reference  emphasizes that using a single value for each variable is not the correct way to evaluate a compression system. ASME PTC-10, “Performance test Code on Compressors and Exhausters”, 1997. The power calculation should be made per stage of compression and then summed for all stages connected to a single driver. The rigorous method was based on an equation of state like the Soave-Redlich-Kwong (SRK) for calculating the required enthalpies and entropies. In the single-stage compressor, air is drawn in from the atmosphere and compressed to final pressure in a single stroke. is 85% practical? f. Calculate the required power per stage by either Equation 11 or 12. The results of a reversible process are then adapted to the real world through the use of a thermodynamic efficiency. Thanks for sharing this detailed calculations. The error percent between the rigrous method and the shortcut methods for each stage are presented in Table 2, too. 1800-2400 RPM 6. By using the second equation, we get power requirement is 0.594 hp. For preliminary calculation we choose 70% adiabatic efficiency. This parameter reduces the overall efficiency and work output. AIR One of the most important factors determining how powerful an air compressor is CFM that stands for cubic feet per minute. Dr. Moshfeghian joined JMC
When the same compressor is rated using these two methods, the results are dramatically different - average charge rate will exceed free air delivery. You are correct, both temperature and pressure ratios should have been ln(T2/T1) and ln(P2/P1). The computation compressor efficiency or power involves two steps 1. Would these equation work for an oil injected twin rotary screw compressor? Sci., Vol. Adiabatic efficiency Figure above shows that for centrifugal compressor, adiabatic efficiency is ranging from 60% to 80%. 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). Once completed, you’ll be able to estimate how much you currently spend on your air system. 3. Screw compressors are inefficient in the unload condition and, thus, a larger compressor will use more energy and consumables than a right-sized compressor for a given air requirement. For example, if a compressor produces 500 cubic feet per minute (CFM) but the air requirement is only 300 CFM, then the compressor will be in unload condition for a significant portion of the time. Adding 3-4 % efﬁciency (mechanical losses) to the overall efﬁciencies in Table 1 will generally give a good estimate of the thermodynamic efﬁciency . The shortcut calculations are based on the step-by-step of a through f described in the shortcut method section. 1. These parameters describe how efficiently a turbine, compressor or nozzle approximates a corresponding isentropic device. These results will be taken into consideration, and you will have access to a full report detailing specific ways in which you can save money with recommendations for creating a more efficient system. For further detail refer to reference  and August and September 2010 TOTMs [7, 8]. 5.4 bore The single-stage reciprocating compressor is illustrated in (Figure 1). The measured feed composition, flowrates, and calculated molecular weight and relative density are presented in Table 2. Here is the link of a new article, which describes the rigorous calculation of the polytropic efficiency based on thermodynamics of real gases. 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 We compared the rigorous method results with the values from the shortcut methods. An air compressor uses an electric motor or gas engine to take in air at one condition and release it at an increased pressure to power a range of industrial or commercial equipment. Improving air compressor efficiency is not just a trend anymore: it’s a competitive advantage in the world of growing energy costs and increasing accessibility of modern energy-saving technologies. You value your time and money, and so do we. PetroSkills offers consulting expertise on this subject and many others. 4 that the maximum exergy efficiency exists at design point C (94.44%), while the compressor cost rate is the greatest at this point (33.1 $ h −1). (74), M.S. Honeywell, J. Donaldson air filters in Donaldson air cleaner housings have a 99.95+% minimum overall efficiency. or P.v = const. In the November 2011 tip of the month (TOTM) we presented the compressor calculations of a case study. You may be surprised to learn how much you can save by making a few simple tweaks to your system. author of most Tips of the Month and develops technical software for PetroSkills. Air heat capacity ratio is about 1.4 in the range of -40 deg F to 200 deg F. 1215 Crossroads Blvd.Suite 230
to find out wһere u got this from. in 1990 as a part time consultant and then as full time instructor/consultant in 2005. The step-by-step calculation based on an EOS: b. Energy calculators and measurement tools for your compressed air system. 4 that the total compressor cost increases moderately as the compressor exergy efficiency increases up to about 92%. For more information about these services, visit our website at http://petroskills.com/consulting, or email us at consulting@PetroSkills.com. g. Calculate isentropic efficiency by Equation 1: ) can be calculated by the correlation presented in the May 2013 TOTM: Similarly, the actual discharge temperature based on a polytropic path can be estimated, = Universal gas constant, 848 kg-m/(kmol-K) or (1545 ft-lb, = Standard condition pressure, kPa (psia), = Gas volumetric rate at the standard condition, Sm, = Gas compressibility factor at the suction condition, = Gas compressibility factor at the discharge condition, c. Calculate the polytropic coefficient (, The process flow diagram shown in Figure 1 was simulated by ProMax software  to perform the rigorous calculations using the SRK EOS. 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. To do this, take the number of cubic feet found in Step 7 and divide it by the number of seconds it took to pump this amount. Table 2 also presents the shortcut caculation results for the corresponding values under the shortcut heading. It can be complicated to determine the efficiency of an air compressor. Download Air Compressor Calculations. Free templates compressor power calculation spreadsheet, centrifugal compressor power calculation spreadsheet, compressor efficiency calculation xls, compressor calculation spreadsheet, centrifugal compressor calculation spreadsheet, centrifugal compressor performance calculation excel, compressor efficiency calculation formula, centrifugal compressor calculation spreadsheet, … Measured temperature and pressure for the three stages of compression, Table 2. This form of average temperature was defined to obtain better match between the rigorous and shortcut method results. A screw compressor is available designed for air pressure boosting from P 1 =0.6 MPa to P 2 =1.8 MPa. Filter pressure drop, air usage and leakage, installation pipework and more. For planning purposes, reference  suggests the following values for the overall efﬁciencies: Table 1. 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 %. The calculations performed by ProMax are very similar to the step-by-step of a through h described in the rigorous section. Determination of the ideal or isentropic (reversible and adiabatic) enthalpy change (h2Isen-h1) of the compression process. These details are often lost in the day to day array of operations occurring at your facility. P2 = absolute final pressure after compression (psi) V = volume of air at atmospheric pressure - standard or free air (scfm, ft3/min) adiabatic compression (or expansion) takes place without transmission of heat He has 40 years
In the calculation adiabatic efficiency η ad is assumed to c At Quincy Compressor, we make air compressors that are built to last. mechanical valves Calculate the isentropic efficiency (ηIsen) by Equation 5. c. Calculate the polytropic coefficient (n) by Equation 7. d. Calculate the polytropic efficiency (ηPoly) by Equation 8. e. Calculate the isentropic and polytropic heads by Equations 9 and 10, respectively. The polytropic efficiency calculation formula is the following : Ep = 0.61+0.03*log (0.5885*Qv) You want to own and operate equipment that runs over long periods of time, using a … “Important Aspects of Centrifugal Compressor Testing-Part 1”, Tip of the Month, August 2010, 8. Honeywell, J. 2. To get to the bottom of how much your air compressor system is costing your organization, careful attention is needed to provide a thorough analysis. The differences between the rigorous and shortcut method results for facilities calculations and planning purposes are negligible. Hi, The A in case of air, what is the value? Determination of the actualh 2-h 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. Promoting air compressor system efficiency is a smart way to make your organization run more effectively and sustainably. Note that Dresser Rand is doing quite a lot of work with “Near constant temperature” compression especially for CO2 compression from vent stacks. 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. Calculate the isentropic exponent (k) by Equation 3 using the average temperature defined by T = (T1+3T2)/4. There is an obvious mistake in (7) when you inverse (6). Determination of the actual enthalpy change (h2-h1). was Professor of Chemical Engineering at Shiraz University. 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. Table 2 indicates that there are good agreements between the shortcut and the rigorous results. I built an air compressor with a quick return mechanism and a bike pump. • It is known as an indicator diagram for the compressor. ProMax 3.2, Bryan Research and Engineering, Inc, Bryan, Texas, 2014. Due to their simplicity and relative accuracy, a cubic EOS such as Soave Redlich-Kwong (SRK)  or Peng-Robinson  is used. It can be seen in Fig. By opting to switch to our new QGD and QGDV units, you can expect efficiency gains of up to 20%. How to maintain efficiency of an air compressor, volumetric efficiency, bumping clearance, effects of compressor valve leaking, air bottle pressure test. For turbines, the value of ηT is … teaching experience in universities as well as for oil and gas industries. Centrifugal compressor efficiency calculation with heat transfer December 2017 IIUM Engineering Journal 18(2):225 DOI: 10.31436 /iiumej.v18i2.695 Project: … Convert this number to minutes. Caterpillar 3406 Diesel Engine in other words you mean fixed temp., => isohermal? 2. For each stage, the measured pressure, and temperature are presented in Table 1.