Condenser terminology — definition of vacuum State whether the following is correct: “The condenser vacuum is the difference between atmospheric pressure and the absolute pressure in the condenser.”

Introduction / Context:
Vacuum readings in steam surface or jet condensers quantify how far below atmospheric the condenser absolute pressure has been reduced. Correct interpretation of vacuum is essential for diagnosing condenser performance and turbine/engine back-pressure losses.

Given Data / Assumptions:

• Atmospheric pressure p_atm is the local barometric pressure.
• Condenser absolute pressure p_abs is the sum of partial pressures of steam and non-condensable gases.
• Vacuum gauges are typically calibrated in “centimetres or millimetres of mercury” or “bar/kPa below atmosphere.”

Concept / Approach:
By definition, condenser vacuum V is the difference between local atmospheric pressure and the absolute pressure existing in the condenser space: V = p_atm − p_abs. This expresses how much of the atmospheric pressure has been “removed.” A higher vacuum (larger difference) means a lower absolute back pressure on the exhaust side, improving cycle efficiency.

Step-by-Step Solution:
Write the relationship: V = p_atm − p_abs.Recognize that p_abs includes steam and air partial pressures.Hence the statement as given is correct.

Verification / Alternative check:
Indicator diagrams for condensing engines show the back-pressure line below the atmospheric line by an amount corresponding to the indicated vacuum.

Why Other Options Are Wrong:

• Disagree and conditional variants conflict with the standard definition.
• “Gauge minus absolute” is not a meaningful expression for vacuum.

Common Pitfalls:
Forgetting that p_atm varies with weather and altitude; vacuum must always be referenced to local barometric pressure.

Final Answer:
Agree