Question

An engineer devises a scheme for extracting some power from waste process steam. The engineer claims that the steam enters the device at 340 F and quality 75%, and exits at 220 F and 65% quality.
Does this device violate the first law of thermodynamics?

Answer 1

Answer:

This device does not violate the first law of thermodynamics

Explanation:

First law of thermodynamics states that  any change in the internal energy (∆E) of a system is given by the sum of the heat (q) that flows across its boundaries and the work (w) done on the system by the surroundings:

i.e (∆E)= q + w

The operation of the device is coherent with the first law of thermodynamics because the work extracted from the steam causes a drop in the internal energy and quality of the steam. This is reflected by the drop in temperature which is from 340 F to 220 F.

This drop in temperature and quality shows that work is extracted from the total energy of the system, proving that the device obeys the first law of thermodynamics.