Question 76Steam Plants - Assistant Engineer
70% to passThe feed water heater shown in the illustration was designed to maintain the required feed water outlet temperature with an approximate 10" (25.4 cm) Hg shell vacuum. If the shell vacuum is increased to approximately 16" (40.64 cm) Hg vacuum, the_______________ Illustration SG-0025
A flow rate of condensate to the feed heater will increase
Boverall plant operating efficiency will increase
Cvacuum in the main condenser will drop as the feed heater shell vacuum increases
Dfeed water outlet temperature will decrease
AI Explanation
The correct answer is D) the feed water outlet temperature will decrease. Explanation: When the shell vacuum of the feed water heater is increased from 10" Hg to 16" Hg, the lower pressure in the shell will result in a lower saturation temperature of the steam inside the heater. This lower steam temperature will, in turn, result in a lower feed water outlet temperature, as the heat transfer from the steam to the feed water will be reduced. The increased shell vacuum does not affect the flow rate of condensate or the overall plant efficiency, and it will not impact the vacuum in the main condenser.
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