f. Calculate the required power per stage by either Equation 11 or 12. Determination of the ideal or isentropic (reversible and adiabatic) enthalpy change (h 2Isen-h 1) of the compression process. These parameters describe how efficiently a turbine, compressor or nozzle approximates a corresponding isentropic device. Cite 29th Jun, 2017 Polytropic efficiency calculations are the preferred method for (one dimensional) performance simulation of Gas Turbines. The real-gas equations of polytropic analysis are derived in terms of compressibility functions X and Y which supplement the familiar compressibility factor, Z. At testing stage the polytropic index \(n\) can be obtained from the test results of suction and discharge pressure temperatures. If the volumetric efficiency is 78%, mechanical efficiency is 94% and the isothermal compression efficiency is 66%, Find: a) the metered flow per second (0.795 cu.m./sec) b) the indicated power in KW (181 KW) c) the power required to drive this compressor in KW ( 193 KW) d) the adiabatic compression efficiency ( 82%) 20. DEPARTMENT OF MECHANICAL ENGINEERING, GHOUSIA COLLEGE OF ENGINEERING, RAMANARA -562159 . In the previous paper, we introduced the more efficient fixed displacement rotary vane compressors (new CR series) for car air conditioners. The computation compressor efficiency or power involves two steps. After each compression stage, the gas was cooled to the feed temperature of 105 °F (40.6 °C). The step-by-step calculation based on an EOS: a. December 2018 ; Acta Polytechnica CTU Proceedings 20:65-72; DOI: 10.14311/APP.2018.20.0065. 11, EFp= 0.695. n/(n-1) = EFp. The key difference between adiabatic and polytropic processes is that in adiabatic processes no heat transfer occurs whereas in polytropic processes heat transfer occurs.. Relationship to ideal processes. This parameter reduces the overall efficiency and work output. Contents. Inlet stagnation temperature and p° ressure is 288°K and 1 bar. Using polytropic efficiency gives a more accurate calculation of power required. The polytropic coefficient can be calculated by knowing the polytropic efficiency of the compressor, given by the manufacturer, and an abacus. This paper describes the technology involved in analysis of compressor power, used in development of new series of Compressors . However the isentropic and polytropic efficiencies could be estimated and were used to more accurately assess the performance of the compressor. The part we are going to … and m p op . In chemistry, we divide the universe into two parts. The use of the polytropic efficiency requires the specification of the polytropic exponent (n) which will change depending on the working real gas and operating conditions, which would be inconsistent with the original intent. RE: Polytropic efficiency … same example , we assume that each stage has the same . One of the great interests of the polytropic concept lies in the simplicity of equation (4.1.9), which generalizes that of isentropic Pvγ = Const. nn = 1 12 21. Calculate the polytropic efficiency η Poly) by Equation 8. e. Calculate the isentropic and polytropic heads by Equations 9 and 10, respectively. The inlet stagnation conditions are 15°C and 101.3 kPa. RE: Polytropic efficiency of turbomachinery sailoday28 (Mechanical) 11 Aug 05 18:35. results of polytropic head and efficiency versus design compressor curves provided by the Manufacturer. An increase in centrifugal compressor speed will result in an increase in compressor polytropic head by a value equal to the square of the speed. OME tool can … k may be estimated from molecular weight and temperature correlations or obtained from a commercial simulation program. overall compressor efficiency will be lower than η s. If , for the . Stagnation temperature rise for each stage is 15K. Functions X and Y are generalized and plotted for gases in corresponding states. Inserting this into the definition of the normal Isentropic Efficiency allows one to compute it in terms of η Poly and the finite pressure or temperature ratio: $ % 1 # c $ % #! Determination of the actual enthalpy change (h 2-h 1). The compressor, the defrosting cycles, to manage air humidity, air heating and alarms. Double flow ducted dehumidifier line The DPG-DF series highly efficient dehumidifiers with energy recycling (double flow) are high quality appliances with the following specifications: Full insulation for indoor use. For an ideal gas in a closed system undergoing a slow process with negligible changes in kinetic and potential energy the process is polytropic, such that (−) + =where C is a constant, =, =, and with the polytropic coefficient = (−) +. A polytropic head factor, f, is introduced to adjust test results for deviations from perfect-gas behavior. The stage loading factor is 0.3, flow coefficient is 0.4, and stage reaction is 0.5. Input power is the electric power supplied to the electric motor . The compressor is a standard single-stage barrel/bundle type centrifugal with a polytropic efficiency of >86%. It can be seen from Equations 2.41 and 2.43 that, for a given polytropic efficiency, the compressor isentropic efficiency decreases, whereas the turbine isentropic efficiency increases with increase in pressure ratio. The basics of these methods have been defined by Mr. Dzung who was working for Brown Boveri & Cie in the forties of the last century. c " = c $ % & c % 1 $ % 1 # c $! The polytropic head is a function of pressure ratio across the compressor and therefore will result in a pressure rise, assuming the inlet pressure is not changed. 11 2 2 12. pV pV TT = 11 2 2. pV pV. … Assume steady state, i.e. The compressor is directly coupled to a standard mechanical drive aero-derivative gas turbine package. The polytropic compressor efficiency is approximately equal to the hydraulic efficiency η p ... Lower COPs (4.78–6.55) correspond to lower compressor efficiency η comp s = 0.7) and lower ejector element efficiency (η pr = 0.85, η sec = 0.85, η mc = 0.95, η d = 0.60 (η ej = 0.30–0.35, T ′ = 22–29°C)). The relationship between polytropic exponent and efficiency can be used at design stage, to estimate the value of polytropic index \(n\) when the design stage polytropic efficiency \(\eta_p\) is known. In this research, the design data of axial flow compressor used in gas turbine engine is picked up from the Ta Dar Ooairway in Myanmar. Authors: Jiří Oldřich. If you plot a P-V curve for the compression process and … b. Blade aspect ratio and pitch-chord ratio are 3 and 0.5. Efficiency of centrifugal compressor To determine head coefficient, preliminary efficiency shall be determine from Fig. In a well-designed subsonic stage, polytropic efficiency could reach around “0.9”. Case Study. polytropic efficiency ... the compressor inlet and outlet, which is of type: Pvk = Const (4.1.9) k is called the polytropic coefficient of the process. Shaft power is the power supplied by the electric motor to compressor. Figure 1 : principle of an abacus allowing to calculate the polytropic coefficient for a centrifugal compressor . It looks that a preference of the polytropic efficiency in a gas compressor community is from a historical background. 1 Compression theory; 2 Oil and gas compressor uses. A centrifugal compressor has efficiency between 70-85% and it depends mainly on mechanical losses and gas friction within compressor, varying with its size. Stage efficiency and polytropic efficiency is 84 % and 87 %. A compression or expansion process caused by movment of a piston in a cylinder. NPTEL Phase-I under grant in aid NMEICT, MHRD, New Delhi . Ie. A 16-stage axial flow air compressor is to have a stagnation pressure ratio of 5.5 and tests have shown that the stage polytropic efficiency (or small stage efficiency) is 90%. Adiabatic and polytropic compression theory are discussed with supporting definition of terminology. Assume constant work done in each stage and similar stages. Since then formulas were used, which describe the (average) energy conversion in compressor and turbine bladings in gas turbines. - OME tool (OME stands for 'Online Monitoring of Efficiency') is a thermodynamic tool primarily intended for the monitoring of polytropic efficiency and head of a centrifugal compressor section with known end points (i.e. The polytropic efficiency of 86, 80, and 79 % based on the actual inlet volumetric rate (from Figure 13.23 of GPA Data book [2]) was specified for stages 1, 2, and 3 respectively. Assume the feed composition remain unchanged. 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