n. Vp = 22 11. n. Tp Tp − = (1) 22 1 1. n. TV TV − = Compressor without clearance volume . 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. At testing stage the polytropic index \(n\) can be obtained from the test results of suction and discharge pressure temperatures. This is illustrated in Fig. Assume constant work done in each stage and similar stages. Cite 29th Jun, 2017 Calculate the polytropic efficiency η Poly) by Equation 8. e. Calculate the isentropic and polytropic heads by Equations 9 and 10, respectively. Typically, these design curves are given for specific suction conditions. The key difference between adiabatic and polytropic processes is that in adiabatic processes no heat transfer occurs whereas in polytropic processes heat transfer occurs.. Vp. 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 = (−) +. In chemistry, we divide the universe into two parts. The polytropic coefficient can be calculated by knowing the polytropic efficiency of the compressor, given by the manufacturer, and an abacus. It looks that a preference of the polytropic efficiency in a gas compressor community is from a historical background. This page provides an overview of the primary categories of natural gas compressor services and a description of the different classifications and types of compressors available to the industry. An air pollution control device requires 0.23 cu.m./sec of free air. k may be estimated from molecular weight and temperature correlations or obtained from a commercial simulation program. These parameters describe how efficiently a turbine, compressor or nozzle approximates a corresponding isentropic device. Determination of the actual enthalpy change (h 2-h 1). However the isentropic and polytropic efficiencies could be estimated and were used to more accurately assess the performance of the compressor. Blade aspect ratio and pitch-chord ratio are 3 and 0.5. Assume steady state, i.e. In a well-designed subsonic stage, polytropic efficiency could reach around “0.9”. nn = 1 12 21. A trend of decreasing isentropic compressor efficiency is seen when increasing pressure ratio (at constant polytropic efficiency) (Saravanamuttoo et al., 2001, p. 61). … Results and Discussions. This ratio is known as the Isentropic Turbine/Compressor/Nozzle Efficiency. and m p op . The overall efficiencies are given by: m a oa . Determination of the ideal or isentropic (reversible and adiabatic) enthalpy change (h 2Isen-h 1) of the compression process. In recent years, improvement in energy efficiency of each component is desired for the fuel efficiency of any car. In a polytropic compression process infinitesmal changes occur in terms of heat absorbed or heat removed during the entire compression process. I believe that the polytropic process is basically for non-flow type problems and where the mass does not change. Assume the feed composition remain unchanged. overall compressor efficiency will be lower than η s. If , for the . The real-gas equations of polytropic analysis are derived in terms of compressibility functions X and Y which supplement the familiar compressibility factor, Z. DEPARTMENT OF MECHANICAL ENGINEERING, GHOUSIA COLLEGE OF ENGINEERING, RAMANARA -562159 . Relationship to ideal processes. 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 $ % #! Input power is the electric power supplied to the electric motor . b. Inlet stagnation temperature and p° ressure is 288°K and 1 bar. 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. 1 Compression theory; 2 Oil and gas compressor uses. The inlet stagnation conditions are 15°C and 101.3 kPa. The computation compressor efficiency or power involves two steps. The stage loading factor is 0.3, flow coefficient is 0.4, and stage reaction is 0.5. Efficiency of centrifugal compressor To determine head coefficient, preliminary efficiency shall be determine from Fig. 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. The compressor is a standard single-stage barrel/bundle type centrifugal with a polytropic efficiency of >86%. 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. 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. … Figure 1 : principle of an abacus allowing to calculate the polytropic coefficient for a centrifugal compressor . Case Study. - 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. For certain values of the polytropic index, the process will be synonymous with other common processes. k/(k-1) = 0.695 x 1.4 /(1.4-1) = 2.432 assume maximum temperature tdmax = 200 C, Td1max = 473 K n pd Td max ( n −1 ) pressure ratio max. In the previous paper, we introduced the more efficient fixed displacement rotary vane compressors (new CR series) for car air conditioners. 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. After each compression stage, the gas was cooled to the feed temperature of 105 °F (40.6 °C). 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%. 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. 2.11, where the polytropic efficiency of the compressor and turbine is assumed to be 0.87. 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