# Help with Heat Engines

by Ravey
Tags: engines, heat
 P: 5 1. What is the thermal efficiency for the heat engine shown in the figure? What is the heat extracted from the hot reservoir for the heat engine shown in the figure?t Figure shown here: 2.Wout = 1/2 B*H Also, Qc=Qh-Wout, efficiency: Wout/Qh 3. Wout = .5 * 200KPA* (400x10^-6m^3). I have no idea how to obtain Qc (cold reservoir) or Qh (hot)
 Sci Advisor HW Helper PF Gold P: 2,532 Hi Ravey, welcome to PF. What's the significance of the heat flows marked on the image?
 P: 5 Thanks! I believe that is heat leaving the engine*, but what do I do? Add them? According to some note Qc is the sum of the heat leaving the engine. So I assume so. However, qh is not 280-40 = 240. What's going wrong?
P: 5

## Help with Heat Engines

Stumped too I see ;)
 Sci Advisor HW Helper PF Gold P: 2,532 Hint: No energy is stored in the engine from cycle to cycle.
 P: 5 Got it! Qh=Q_c+W_out = 280J + 40J = 320J. 40/320 = efficiency.
 Sci Advisor HW Helper PF Gold P: 2,532 Sounds good!

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