- #1

Andrew1234

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- Homework Statement
- Explain why the work done in process 2-3 is zero.

- Relevant Equations
- ΔH = ΔQ-ΔW

Is there a mathematical explanation for why the work done in the condenser (in process 2 to 3) is zero? I am aware that ammonia does not expand or compress in the condenser, only changes phase, but without knowing that the process takes place in a condenser and only considering the graph, according to which temperature is constant for process 2-3, how can it be seen that no work is done in this process?

In process 2-3 the temperature and pressure are both constant. Because the cycle is reversible, Q = ∫Tds.

Substituting this in the energy balance, -m'(Δh)+∫Tds = ΔW. Because temperature is constant, ΔW = T(Δs)-m'(Δh).

W = TΔs - ΔH = T(sf-sg) + m(hg - hf)

It is not clear to me why this quantity is zero for process 2-3.

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