Defining “efficiency ratio” in steam turbines Evaluate the statement: “The efficiency ratio is the ratio of the total useful heat drop to the total isentropic heat drop.” Is this definition correct in turbine performance terminology?

Introduction / Context:
Steam-turbine literature uses several related ratios to express how much of the ideal (isentropic) enthalpy drop is actually realized as useful work. One such term is the “efficiency ratio,” which compares realized heat drop to the ideal benchmark across the overall expansion.

Given Data / Assumptions:

• Overall turbine expansion from inlet to exhaust.
• Isentropic reference between the same two states.
• Useful heat drop is the enthalpy fall contributing to shaft work, excluding kinetic energy carry-over and losses.

Concept / Approach:
If the useful (actual) heat drop equals the sum of effective stage enthalpy drops contributing to rotor work, then comparing this with the ideal isentropic drop provides a global efficiency-type index. While terminology can vary by text (overall or internal efficiency), the statement captures the intended ratio known as “efficiency ratio.”

Step-by-Step Solution:
Define ideal reference: total isentropic heat drop between inlet and exhaust states.Define useful heat drop: actual enthalpy decrease converted to shaft work, net of kinetic carry-over.Form the ratio: efficiency ratio = useful heat drop / isentropic heat drop.Interpretation: values less than 1 indicate losses due to friction, incidence, leakage, and residual kinetic energy.

Verification / Alternative check:
Manufacturer performance sheets often present “internal/overall efficiency” calculated against an isentropic baseline; the described ratio is consistent with that practice.

Why Other Options Are Wrong:
Choosing “Disagree” would conflict with common usage where realized heat-drop ratios against isentropic references define efficiency-type quantities.

Common Pitfalls:
Mixing this ratio with “reheat factor,” which compares cumulative stage drops to the isentropic drop; related but conceptually distinct measures.

Final Answer:
Agree