Question

Identify the \(p\text{-}h\) diagram that denotes a vapor compression refrigeration cycle with flash intercooling from the following.
The pressure and specific enthalpy of the working fluid are represented by \(p\) and \(h\) respectively.

• A.

  

• B.

  

• C.

  

• D.

  

Hint:

Count how many states the working fluid passes through and check whether both throttling steps around the flash chamber are drawn.

Answer 1

The Correct Option is D

A cycle described as "with flash intercooling" always needs a flash chamber sitting between two compression stages, so the correct diagram must carry seven states, not four.

1. Option A: shows only four states, 1, 2, 3 and 4, inside the dome. That is a plain single stage vapor compression cycle with no flash chamber and no intermediate pressure line, so it cannot be the flash intercooling cycle.
2. Option B: also has only four states, 1, 2, 3 and 4, same idea as A just redrawn further right. It still has no flash chamber, so it fails for the same reason as A.
3. Option C: has the right skeleton of seven states, with an intermediate pressure line carrying 7, 4 and 3, and a high pressure line carrying 6 and 5. But the throttling step that takes the saturated liquid out of the flash chamber down to state 1 in the evaporator is not shown as its own marked expansion, so the two step throttling path is incomplete.
4. Option D: keeps the same seven states in the same layout, and now both throttling legs are shown clearly: the high pressure liquid at 6 expands to 7 on entering the flash chamber, and the saturated liquid leaving the flash chamber expands again from 7 down to 1 before the evaporator. Both compression legs, 1 to 2 and 4 to 5, and the mixing of the flash vapor 3 into 4, are also drawn correctly.

Since only option D shows the complete two stage compression, the flash chamber mixing, and both throttling legs that define a flash intercooling cycle, option D is the correct diagram.