ThermoFluidCalc Report

Rankine Regenerative โ€” 2026-09-29 07:21:04
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๐Ÿญ Regenerative Rankine Cycle

Analyze steam cycles with open or closed feedwater heaters. Compute extraction fractions and efficiency gains.

โšก Fortran 90 Engine Double Precision (IEEE 754) โœ“ ISO / ASME Validated
Regenerative Rankine Cycle Thermodynamics
๐Ÿ“Š Solver Telemetry โ— ACTIVE
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โšก Solves 109
๐Ÿ’พ Downloads 180 ๐Ÿ“ฆ Fortran Code 11.4 KB
๐Ÿ“… Released Jun 2026
โฑ๏ธ Latency < 1 ms
โšก TOOLS & REPORTS:
๐Ÿ’พ Download Fortran 90

๐Ÿ“ Configuration

๐Ÿ”ฅ Boiler
Must exceed Tsat(Pboiler).
โ„๏ธ Condenser
๐Ÿ”ง Feedwater Heaters
Used only for 2-extraction case.
โš™๏ธ Efficiencies & Flow
Key Equations:

ฮทth = Wnet/Qin
Open FWH: yยทhext+(1โˆ’y)ยทhfw = hf,sat
BWR = Wpump/Wturbine
Wpump = vfฮ”P/ฮทp

๐Ÿ“Š Results

Configure inputs and click Analyze to view results.

๐Ÿ“˜ Methodology

Regenerative Rankine

Extracting steam from the turbine to preheat feedwater raises average temperature of heat addition, improving thermal efficiency. Each extraction stage adds ~1โ€“3% efficiency gain.

Open vs Closed FWH

Open (direct contact) FWH mixes extracted steam with feedwater โ€” simple, effective, requires separate pump per stage. Closed (shell-tube) FWH keeps streams separate โ€” more complex but allows single pump.

Assumptions

  • Simplified water saturation curve fits (educational).
  • Isentropic efficiencies for turbine and pump.
  • Saturated liquid exits each FWH.
  • Steady-state, steady-flow.

๐Ÿ“˜ Calculation Methodology: Regenerative Rankine Cycle (Feedwater Heaters)

Mathematical Model & Theory

Regenerative feedwater heating extracts a fraction $y$ of expanding steam from the turbine to preheat boiler feedwater, raising the average heat addition temperature $\bar{T}_{in}$ and cycle efficiency:

$$y = \frac{h_{fwh} - h_{feed,in}}{h_{bleed} - h_{feed,in}}, \quad w_{net} = (h_1 - h_{bleed}) + (1-y)(h_{bleed} - h_2) - w_{pumps}$$
$$\eta_{regen} = \frac{w_{net}}{h_1 - h_{feed,out}}$$

Assumptions

  • Open or closed feedwater heater at designated extraction pressure.
  • Isentropic turbine stages.

Academic References

  1. Moran, M. J. et al.: Fundamentals of Engineering Thermodynamics, Ch. 8.
  2. Babcock & Wilcox: Steam: Its Generation and Use.

Worked Engineering Example

Problem Statement:
In a regenerative Rankine cycle, boiler inlet enthalpy is $h_1 = 3400\text{ kJ/kg}$, extraction steam is $h_b = 2800\text{ kJ/kg}$, condensate is $h_c = 190\text{ kJ/kg}$, and saturated liquid at extraction is $h_{fwh} = 760\text{ kJ/kg}$. Find extraction fraction $y$.

Step-by-step Solution:
1. Energy balance on Open FWH: $y h_b + (1-y) h_c = h_{fwh}$.
2. $y = (760 - 190) / (2800 - 190) = 570 / 2610 \approx 0.2184 = 21.84\%$.
Final Result:
Extraction bleed fraction is $y = \mathbf{21.8\%}$.
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