Machines in which thermodynamics are significant are often made up of components which individually may be analyzed as simple control volumes.
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⚠️ The following equations are all simplifications of the general energy rate balance for a control volume. These shortcut formulas make assumptions that may not be the case for any given problem, such as that $Q=0$. Be careful to check all assumptions
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$$ \dot{U}=0=\dot{Q}{{CV}}-\dot{W}{{CV}}+\Sigma\dot{m}(h+\frac{\bold{v}^2}{2}+gz) $$
Remember that for all of these components, the mass rate balance also applies.
$$ \Sigma \dot{m}=0=\dot m_i-\dot m_e $$
These bring about changes in specific volume change pressure change
$$ 0=(h_1-h_2)+(\frac{\bold{v}_1^2-\bold{v}_2^2}{2}) $$
These have an exchange of work with the substance. Compressors operate on gas, pumps on liquids.
$$ \dot{W}=\dot{m}(h_1-h_2) $$
Reduces pressure by flow restriction
$$ h_1=h_2 $$