After heating, the gas temperature is 1000oC. 7. In this turbines the high-pressure stage receives gas (point 3 at the figure; p 3 = 6.7 MPa; T 3 = 1190 K (917°C)) from a heat exchanger and exhaust it to another heat exchanger, where the outlet … Your lab report is to include the following: The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. We will see this effect later in the Power Plant Efficiency lab. EXAMPLE 7–14 Isentropic Efficiency of a Steam Turbine Steam enters an adiabatic turbine steadily at 3 MPa and 4008C and leaves at 50 kPa and 1008C. The usual way of representing the steam consumption of a turbine is the willans line, for example.... Often, a willans line for a specific turbine is not available, and one only has has incomplete information about an installed steam turbine; namely the rated power and (perhaps a guesstimate) the isentropic efficency or specific steam … If the expansion is not isentropic (i.e. A steam turbine with an isentropic efficiency of 85% operates between steam pressures of 1500 and 100 psia . If the inlet steam is at 1000°F, determine the actual work and the 2nd Law Efficiency of the turbine. Where . Assuming an isentropic efficiency of 80 percent for the compressor and 86 percent for the turbine, determine the mass flow rate of air through the cycle. As shown on the H-S coordinates, the difference in enthalpy, (H1-H2), is maximum when the lowest enthalpy (H2) is reached at the exit conditions. [ "article:topic", "license:ccby", "program:bcc", "authorname:beyenirboskovic" ], https://workforce.libretexts.org/@app/auth/3/login?returnto=https%3A%2F%2Fworkforce.libretexts.org%2FBookshelves%2FHVAC_and_Power_Plant_Operations%2FBook%253A_Sim_Labs_for_Thermodynamics_and_Thermal_Power_Plant_Simulator_(Beyenir_and_Boskovic)%2F01%253A_Sim_Labs%2F1.02%253A_Turbine_Efficiency. {\displaystyle \eta _ {\text {t}}= {\frac {\text {actual turbine work}} {\text {isentropic turbine work}}}= {\frac {W_ {a}} {W_ {s}}}\cong {\frac {h_ {1}-h_ {2a}} {h_ {1}-h_ {2s}}}.} Isentropic efficiency of the steam turbine: The isentropic efficiency of an optimized steam turbine is 90% for an advanced power plant. The isentropic efficiency of the turbine is 0.85. : A turbine is a mechanical machine used to produce continuous power. The real-world efficiency of a device is always less than the isentropic efficiency. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. On the diagram above, T1, P1 and P2 are known process variables, for example, H1 is determined by using T1 and P1. For these compressors, the isentropic power calculation is therefore relevant and can be used to calculate the reciprocating compressor power. Non-ideal processes or real processes, however, do not present straight lines as shown on the Mollier diagram due to such factors as friction. Due to the losses the compression is irreversible. Calculate the minimum power input required and T 2: b.) the isentropic turbine efficiency is ηT = 0.91 (91%) and exhaust it to another heat exchanger, where the outlet pressure is (point 4): p 4 = 2.78 MPa T 4,is = ? ΔS is the change in entropy and S 1, S 2 are initial and final entropies of the system. The difference in enthalpy H2’-H2 is called the reheat factor and is the basis for multi-stage turbines. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Typical Isentropic efficiencies range from 70-90%. Missed the LibreFest? H 2 then can be found drawing a vertical line from P 1 to P 2 by following adiabatic isentropic expansion (expansion at constant entropy). Chapter 8 - Thermodynamics of Flow Processes, Isentropic and 2nd Law Efficiencies of a Steam Turbine, A steam turbine with an isentropic efficiency of. The Isentropic efficiency of a turbine is a comparison of the actual power output with the Isentropic case. Isentropic Efficiency of Turbines. The outlet temperature from a real, adiabatic compressor that accomplishes the same compression is 520K.Calculate the actual power input and the isentropic efficiency of the real compressor. The ideal process’ isentropic efficiencies of the steam turbine and the pump are at a value of 100 %, and pressure losses in the condenser and the steam generator are non-existent, which would result in the thermal efficiency being equal to the Carnot efficiency. Calculate the enthalpy at exit and the power output. In a steam turbine… Isentropic efficiency of a turbine: t = m(hi he ) Q Wactual = Wisentropic m(hi hes ) … Turbine efficiency. The mass flow rate is We can calculate the isentropic work of the turbine because. Assume an isentropic expansion of helium (3 → 4) in a gas turbine. Operate the Plant at the following generating capacities to compute the isentropic change in enthalpy and thermal efficiency for the HP turbine. entropy is not constant but it increases), the lowest enthalpy (H2) cannot be reached at the exit conditions, in other words, H2’ > H2. On the diagram above, T 1, P 1 and P 2 are known process variables, for example, H 1 is determined by using T 1 and P 1. On the diagram above, T 1, P 1 and P 2 are known process variables, for example, H 1 is determined by using T 1 and P 1. The internal turbine efficiency is therefore given by, \[\eta_{\text {Turbine}}=\frac{\text {Actual change in enthalpy}}{\text {Isentr opic change in enthalpy}}\], \[\eta_{\text {Turbine}}=\frac{\left(H_{1}-H_{2}\right)}{\left(H_{1}-H_{2}\right)}\]. Some examples of theoretical isentropic systems are pumps, turbines, gas compressors, etc. Use constant specific heats at room temperature, cp 1.005 kJ/kg. All rights reserved. Pressure and temperature of air at inlet to compressor = 1… The isentropic efficiency of turbine can then be written as η T (h 2a - h 1)/(h 2s - h 1) where h 1 = enthalpy at the inlet h 2a = enthalpy of actual process at the exit h 2s = enthalpy of isentropic process at the exit : Isentropic Efficiency of Compressors and Pumps © B-Cubed, 2003, 2005, 2006. An isentropic process can also be called a constant entropy process. Steam enters a turbine at 350 C, and exits at 50 kPa. H2 then can be found drawing a vertical line from P1 to P2 by following adiabatic isentropic expansion (expansion at constant entropy). The inlet and exit pressures are constant and fixed for an adiabatic turbine that is subject to a steady-flow process. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. Turbine Steam Consumption Calculations. Determine the work output of the turbine per unit mass of steam if the process is reversible. Changes in kinetic and potential energies are negligible. 1. Evaluating an Isentropic Steam Turbine: Steam turbines are a fundamental component in thermodynamics. It expands this to the atmospheric pressure of 1 bar. It is a reversible adiabatic process. We can calculate the isentropic work of the turbine because S2 = S1 gives us the additional … The turbine’s desired output is the isentropic work output. View Isentropic efficiency of a turbine.pdf from ENGINEERIN 48651 at University of Technology Sydney. It is important to be able to calculate power … As can be seen on the Mollier diagram, the pressure curves are divergent. Solution for A steam at 3 MPa and 5 kg/s is entering into an isentropic steam turbine and leave with 100 kPa and 200°C (see Figure Q1). Non-ideal processes or real processes, however, do not present straight lines as … Isentropic turbine efficiency is the ratio of actual work to the maximum theoretical work per mass flow. Thus the turbine curves are divergent see this effect later in the solution of this the! To compute the isentropic efficiency of 0.88 % in our analyses inlet to =. Gas compressors, etc enters a turbine is adiabatic gas compressors, nozzles and pumps enthalpy exit. The turbine ’ S desired output is the free expansion where,... only if inlet... 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