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Liquefaction: Screencast

Describes the Linde liquefaction cycle for converting a room-temperature gas into a low-temperature liquid.

We suggest you list the important points in this screencast as a way to increase retention.

Important Equations:

Compressors

$T_{1a} > T_1$

$S_{1a} = S_1$

$W_1 = H_{1a}\, -\, H_1$

$T_{1c} > T_{1b}$

$S_{1c} = S_{1b}$

$W_2 = H_{1c} \,-\, H_{1b}$

$T_2 > T_{1d}$

$S_2 = S_{1d}$

$W_3 = H_2 \,-\, H_{1d}$

The subscripts refer to the points on the diagram with three compressors

where $$H$$ = enthalpy per kg

$$S$$ = entropy per kg

$$T$$ = temperature

$$W$$ = work per kg

Cooler

$\dot{m}_1(H_{1b} \,-\, H_{1a}) = \dot{Q}_1$

$\dot{m}_1(H_{1d} \,-\, H_{1c}) = \dot{Q}_2$

$\dot{m}_1(H_3 \,-\, H_2) = \dot{Q}_3$

where $$\dot{Q}$$ = rate of heat transfer (kJ/s)

$$\dot{m}_1$$ = mass flow rate entering the first compressor (kg/s)

Heat exchanger

$\dot{m}_3(H_4 \,-\, H_3) \,+\, \dot{m}_8(H_3 \,-\, H_2) = 0$

$(H_4 \,-\, H_3) \,+\, (1\,-\, y)(H_8 \,-\, H_7) = 0$

where $$y$$ = fraction of flow exiting the Joule-Thomson expansion that is liquid

Joule-Thomson expansion

$H_4 = H_3$

Flash Drum

$H_5 = y\,H_6 \,+\, (1\,-\,y)H_7$