Back Work Ratio (BWR)
Calculate the back work ratio (BWR) of a power cycle, BWR = w_compressor ÷ w_turbine, dividing the work consumed by the compressor (or pump) by the gross work produced by the turbine. The dimensionless result shows what fraction of turbine work is reinvested to compress the fluid. In gas turbines (Brayton cycle) the BWR is high (0.4–0.6), since compressing gas is costly; in steam Rankine cycles it is tiny (~0.01), since pumping liquid is cheap. A high BWR makes the cycle sensitive to component efficiencies. Enter the compressor work and the turbine work.
Resultado
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Back work ratio (razão de trabalho reverso)
Toda turbina produz trabalho, mas parte dele tem de ser devolvida para acionar o compressor (ou a bomba) que comprime o fluido de trabalho. O back work ratio (BWR) mede essa fatia: BWR = w_compressor ÷ w_turbina. É a fração do trabalho bruto da turbina que não sobra como saída útil porque foi reinvestida na compressão. O valor revela o caráter do ciclo. Em uma turbina a gás (ciclo Brayton), comprimir ar é caro e o BWR fica entre 0,4 e 0,6 — mais da metade do trabalho da turbina volta ao compressor! Isso torna a turbina a gás muito sensível às eficiências de seus componentes: pequenas quedas no rendimento do compressor ou da turbina podem zerar o trabalho líquido. Já em um ciclo Rankine a vapor, como a bomba comprime líquido (trabalho mínimo), o BWR é ínfimo, da ordem de 0,01. Por isso ciclos a vapor toleram componentes menos eficientes sem deixar de gerar potência. Informe o trabalho do compressor e o da turbina.
Related Tools
Regenerator Effectiveness
Calculate the effectiveness of a regenerator (heat recuperator), ε = (T_out − T_in) ÷ (T_hot − T_in), comparing the actual heating of the cold fluid with the maximum possible (if it reached the hot exhaust gas temperature). The result (between 0 and 1, or ×100%) measures heat-exchange effectiveness: a regenerator uses a gas turbine's exhaust heat to preheat the air before the combustor, cutting fuel use and raising the regenerative Brayton cycle efficiency. Typical effectiveness is 0.7–0.9. Enter the inlet, outlet and hot-gas temperatures.
Rankine Cycle Efficiency
Calculate the thermal efficiency of a Rankine cycle, η = (w_turbine − w_pump) ÷ q_boiler × 100%, dividing the net work (turbine work minus pump work) by the heat added in the boiler, all in kJ/kg. The Rankine cycle is the basis of steam power plants: water is pumped, heated and vaporized in the boiler, expands through the turbine producing work, then condenses. The result, in %, measures how much boiler heat becomes useful work; real cycles run 30–45%. Enter the turbine work, the pump work and the boiler heat.
Compressor Work (Isentropic)
Compute the specific compression work in an ideal refrigeration cycle, W = h₂ − h₁, the enthalpy difference between the compressor outlet and inlet (isentropic compression, at constant entropy). It is the energy the compressor adds to the refrigerant per kilogram — the cycle's 'electricity bill'. Together with the refrigerating effect, it defines the COP (COP = refrigerating effect/work). Enter the outlet and inlet enthalpies.
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