Ciclo Ideal de Rankine Regenerativo – Download as Powerpoint Presentation . ppt /.pptx), PDF File .pdf), Text File .txt) or view presentation slides online. Download scientific diagram | Diagrama T-s Ciclo Rankine regenerativo from publication: Extraction optimal conditions evaluation in regenerative steam power . Regenerative Feedwater Heater problem. Consider an ideal steam regenerative Rankine cycle with two feedwater heaters, one closed and one open.
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Ciclo Rankine Wilkins Download Report. Published on Nov View 53 Download Whereas the ideal diese! The real Rankine cycle used in powerplants is much more complex than the original, simple ideal Rankine cycle. It is by far the most widely used cycle for electric-power generation toda y and will most certainly continue to be so in the future.
This chapter is devoted exclusively to the Rankine cycle, from its simples! Figure shows a simplified flow William John M. Rankine Q was a professor of civil engineering at Gtasgow University. He was an engineer and scientist of many talents whicb, besides civilengineering, included sbipbuilding, di: An exarnination of these figures shows that a great deal of such irreversibility occurs prior to!
The slope of the primary-fluid temperature line is of! Hence, all types of powerplants, fossil-fuel, liquid-metal, gas- or water-cooled nuclear-reactor powerplants, suffer nearly equally from this irreversibil-ity.
This irreversibility can be eliminated if the liquid is added to! This can be done by the process of regeneration, in whicb interna! Regeneration or heat exchange occurs reversibly between! The areas under and denoting heat lost by! The ideal Stirling cycle has!
Thermodynamic Cycle Spreadsheets
This would not have been the case had heat been added from cidlo externa! T 2 4 Figure T-s diagram of Stirling cycle. Arrows indicate beat ‘;, exchange. There will be more on turbines in Chap. No pressure losses are encountered in the condenser process Fig.
The pump process, heing adiabatic and irreversible, also results in an increase in entropy.
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A single-phase liquid process, it results in an increase in temperature and ,g. Thus the actual work h, – h, is greater! In other words, one pays a penalty for inreversibility: The pump inreversibility is also represented se by a pump efficiency r, also called a pump polytropic efficiency and sometimes ” adiabatic or isentropic efficiency. Thus fan teat In both Eqs. The actual pump work may now be obtained by modifying Eq. The path is! Point 5′ at pressure P 1 represents frictional effects in!
Heat los ses from that pipe cause a decrease in entropy to l. Pressure losses between 4 and 1 could he of! Example 23 A superheat steam Rankine cycle has turhine inlet conditions of. The turhine and pump polytropic efficiencies are 0.
dankine Pressure losses bctween pump and turhine inlet are psi. Calculate the turhine exhaust steam quality and cycle efficiency. The now-subcooled water at t; and wet steam at 3 mix in the low-pressure ranoine heater to produce saturated water at 7. Thus the amount of bled steam m3 rankije essentially equal to that that would saturate the subcooled water at 6.
If it were much less, it will result in a much lower temperature than that corresponding to 6, which would partially negate the advantages of feedwater heating.
If it were more, it would result in unnecessary loss of turbine work and in a two-phase mixture that would be difficult to pump. Line in Fig. In practice sorne pressure drop is encountered. The difference between it and the saturated liquid line 5-B is exag-gerated for illustration purposes. The pressure at can be regenerahivo higher than the extraction steam pressure at 3 or else reverse fiow of condensate water would enter the turbine at 3. A second pump must therefore be used to pressurize the saturated water from 7 to a subcooled condition at 8, which is at the pressure of extraction steam at 2.
In the high-pressure feedwatet heater, superheated steam at 2 mixes with subcooled water at 8 to produce saturaled water at 9. This now must be pressurized to 10 in order to enter the steam gcncrator at its pressure. Note, however, that the mass-ftow rate through the turhine is a variable quantity, highest between 1 and 2 and lowest between 3 and 4.
Open-type feedwater heaters also double as deaerators because the breakup of water in the mixing process helps increase the surface area and liberales noncondensible gases such as air, 0 2H2C02 that can be vented to the atmosphere Scc. Hence ihey are sometimes called deaerating heaters, or DA. In order to analyze the system shown in Fig. The mass balance, based on a unit-ftow rate 1 lb. One open-type feedwater heater is placed at psia.
Assuming 1 lb,h ftow at turbine throttle and no ftow pressure drops, calculate the mass-ftow rate in the heater and the pertinent parameters for the cycle and compare them with those of the cycle in Examplewhich has the same conditions except that no feedwater heater was used. There are, however, features that are rather common. This type of heater is the: Occasionally one encounters one more feedwater of this type at a higher-pressure stage. Table is a compilation of the results of calculations similar to and including!
They alt have psia, F steam at turbine inlet, except for cycle A, which is saturated. Cycles G and H have reheat to F. B, and 1 have no feedwater heaters. Tite rest have one feedwater of various types except for cycle H, which has two.
All cycles are ideal, meaning that they are intemally reversible with adiabatic reversible turbines and pumps. Comparison shows large efficiency increases as a result of superheat, reheat, and the use of even one feedwater he a ter.
Tite differences between different types of feedwater heaters are small. It is to be noted, however, that even a fraction of a percent difference in efficiency can mean a very large difference in annual fue! Differences in efficiency also mean differences in plant size heat exchangers, etc. Although the cycles summarized in Table are ideal, the trends they exhibit are applicable to nonideal cycles, so one should expect the sarne relative standings in both cases.
Figure shows a llow diagram of an actualMW powerplant with superheat, reheat, and seven feedwaters: In such diagrams, there are standard notations not al! Steam-jet air ejector condenser Steam packing exhaust condenser Steam sea! Used energy end point, Btuilbm Mass-ftow rate, lb. The thermal efficiency is the ratio of the net work to the heat added lo the cycle or powerplant. The gross efficiency is the one ca! This is the work or power, MW gross, prnduced before power is tapped for the interna!
The net efficiency is ca! What are the pressures at which stearn is to be bled from the turbine that will result in the maximum in crease in efficiency or maximum reduction in heat rate?
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It is expected that the answer to this question can be xiclo most accurately by a complete optimization of the cycle, a job that entails large, complex, and usually not readily available computer programs. There is, however, a simple aoswer based on physical reasoning.
Regenerativ iodicated previously, the role of feedwater heaters is to bring the temperature of the feedwater as close as possible to that of the stearn generator befare the feedwater enters that steam generator. If we were to as sume first for simplicity that ooly one feedwater heater the type is regenerativ importan! A disadvantage of the supercnttcal-pressure cycle, bowever, ts that expansion from point 1 to!
Hence, supercritical-pressure cycles invariably use reheat and otten double reheat. The bigber temperatures after reheat were rznkine by! Condensing is at 1 psia This example is listed as cycle 1 in Tab1e It bas long been used by industries aod municipalities that need proc iJie-dlicienCY o dio cycle. Calcll to the conden: Z-4 Compare thc inlet steam mass and volume ftow rates in pound mass per second and cubic feet l’lf houc.
Each turbine produces megawatts, and exhausts to l psia. Rankine cycles initial tempcraturc water as a heat source, such as sorne typcs of geo’!
Calculate a the mass ftow ratc in pound lllll et. One rankune has no feed heatersw short t 5 the other has one open-type feed heater placed optimally. Why is feed heating not usually resorted IOJiechanical onsd ewl h 1? One fecdwatcr of the closed typc with drlfticiencies, and e ‘ctively.
Calculatc a the mass tlow rate of steam at turbinc inlet in k. Assume the polytropic efficiencies of the at Titere are three feedwater heaters placed optimally as fallows: