Enter the h3 − h2, the h4 − h1, and the h2 − h1 (specific enthalpy differences, e.g., kJ/kg) into the calculator to determine the Rankine Cycle Efficiency. 

Rankine Cycle Efficiency Calculator

Enter the three specific enthalpy differences (per unit mass). Leave outputs blank.

Results Summary (not inputs)
qin: — kJ/kg
qout: — kJ/kg
wp: — kJ/kg
wt: — kJ/kg
wnet: — kJ/kg
Back‑work ratio: —
Heat rate: — kJ/kWh (— Btu/kWh)
Steam rate: — kg/kWh

Rankine Cycle Efficiency Formula

The following formula is used to calculate the Rankine Cycle Efficiency.

Erank = [(h3-h2) - (h4-h1)] / (h3-h2) * 100
  • Where Erank is the Rankine Cycle (thermal) efficiency (%)
  • h3 − h2 is the heat added in the boiler per unit mass (e.g., kJ/kg)
  • h4 − h1 is the heat rejected in the condenser per unit mass (e.g., kJ/kg)
  • h2 − h1 is the pump work input per unit mass (e.g., kJ/kg); it does not change the efficiency if h3 − h2 and h4 − h1 are already known, but it is used for other results like turbine work and back‑work ratio

How to Calculate Rankine Cycle Efficiency?

The following example problems outline how to calculate the Rankine Cycle Efficiency.

Example Problem #1

  1. First, determine the heat added h3 − h2. In this example, h3 − h2 is given as 30 kJ/kg.
  2. Next, determine the heat rejected h4 − h1. For this problem, h4 − h1 is given as 20 kJ/kg.
  3. Next, determine the pump work h2 − h1. In this case, h2 − h1 is found to be 15 kJ/kg.
  4. Finally, calculate the Rankine Cycle Efficiency using the formula above: 

Erank = [(h3-h2) - (h4-h1)] / (h3-h2) * 100

Inserting the values from above and solving yields: 

Erank = [30 - 20] / (30) * 100 = 33.33 (%)

FAQ

What is the Rankine Cycle?

The Rankine cycle is a thermodynamic cycle used to generate electricity in the majority of thermal power plants. It is the fundamental operating cycle of all thermal power plants where an operating fluid is continuously evaporated and condensed. The cycle includes the generation of steam in a boiler, expansion of steam in a turbine, condensation of steam into water in a condenser, and then the pumping of the condensed water back into the boiler.

Why is Rankine Cycle Efficiency important?

Rankine Cycle Efficiency is a critical measure as it determines how effectively a power plant converts the thermal energy from fuel into electrical energy. Higher efficiency means more electricity is generated from a given amount of fuel, which can lead to lower operational costs and reduced environmental impact due to lower emissions per unit of electricity produced.

How can Rankine Cycle Efficiency be improved?

Improvements in Rankine Cycle Efficiency can be achieved through various methods, including increasing the boiler pressure, superheating the steam to higher temperatures, and using multiple reheat and regenerative feedwater heating stages. Additionally, employing advanced materials that can withstand higher temperatures and pressures can also lead to efficiency gains. Each of these methods helps in extracting more work from the steam, thereby improving the overall efficiency of the cycle.