CEM Certified Energy Manager: Steam, Industrial and Thermal Storage 2

Question 1

A flash steam recovery system recovers steam from condensate at 150 psig. If condensate is flashed to 15 psig, approximately what percentage of the condensate mass becomes flash steam?

Accepted Answer

About 12–15%

Answer

When high-pressure condensate flashes to a lower pressure, roughly 12–15% of the mass converts to flash steam due to the difference in saturation enthalpies.

Question 2

Which type of steam trap operates on the principle of density differences between steam and condensate?

Accepted Answer

Inverted bucket trap

Answer

The inverted bucket trap uses the buoyancy of steam vapor inside the bucket to keep the valve closed and opens when condensate fills the bucket and sinks.

Question 3

A boiler produces 20,000 lb/hr of steam at 250°F. The feedwater enters at 212°F. If the enthalpy of steam is 1,164 BTU/lb and feedwater enthalpy is 180 BTU/lb, what is the boiler heat output in MMBTU/hr?

Accepted Answer

20.8 MMBTU/hr

Answer

Heat output = 20,000 lb/hr × (1,164 – 180) BTU/lb = 20,000 × 984 = 19,680,000 BTU/hr ≈ 19.7 MMBTU/hr; the closest correct answer based on common exam rounding is 19.7 MMBTU/hr.

Question 4

In a stratified chilled water thermal storage tank, the thermocline is best described as:

Accepted Answer

The thin layer separating warm and cold water zones

Answer

The thermocline is the thin, naturally stable temperature gradient layer that separates the warm return water above from the cold supply water below in a stratified tank.

Question 5

Which industrial heat exchanger configuration provides the highest log mean temperature difference (LMTD) for a given set of inlet and outlet temperatures?

Accepted Answer

Counter flow

Answer

Counter flow configuration maximizes LMTD because the hottest fluid meets the coldest fluid at the same end, maintaining a larger driving temperature difference throughout.

CEM - Certified Energy Manager Practice Test

CEM - Certified Energy Manager Practice Test

CEM Certified Energy Manager: Steam, Industrial and Thermal Storage 2