CPT Heat Transfer & Thermodynamics Flashcards

What is 'latent heat' in the context of process thermodynamics?

Answer: Heat absorbed or released during a phase change at constant temperature

Latent heat is the energy absorbed or released when a substance changes phase (e.g., liquid to vapor) without a change in temperature.

A steam trap in a process plant is used to:

Answer: Prevent steam from entering condensate return lines by discharging condensate while retaining steam

A steam trap automatically discharges liquid condensate and non-condensable gases from steam lines while preventing live steam from escaping, maintaining system efficiency.

Fouling in a heat exchanger reduces its performance primarily by:

Answer: Adding thermal resistance that reduces the overall heat transfer coefficient

Scale, biological growth, or deposits on heat transfer surfaces act as insulating layers, increasing thermal resistance and lowering the effective heat transfer rate.

What is the relationship between pressure and boiling point for water in a closed system?

Answer: Higher pressure raises the boiling point

In a closed system, increasing pressure requires more energy to convert liquid to vapor, raising the boiling point — this principle is used in pressure vessels and steam systems.

Which instrument directly measures the enthalpy of steam entering a process unit?

Answer: Combined temperature and pressure measurement used with steam tables

Steam enthalpy is determined from steam tables using both measured temperature and pressure; neither reading alone is sufficient to determine the thermodynamic state.

In a counterflow heat exchanger, fluids flow in opposite directions. What is the main advantage over parallel flow?

Answer: More uniform temperature driving force along the exchanger, enabling greater heat recovery

Counterflow maintains a more consistent temperature difference between streams throughout the exchanger, allowing the cold fluid to be heated closer to the hot fluid inlet temperature.