Siemens cycle

In the Siemens cycle the gas is:^{[citation needed]}

1. Heated – by compressing the gas – adding external energy into the gas, to give it what is needed for running through the cycle

2. Cooled – by immersing the gas in a cooler environment, losing some of its heat (and energy)

3. Cooled through heat exchanger with returning gas from next (and last stage)

4. Cooled further by expanding the gas and doing work, removing heat (and energy)

The gas which is now at its coolest in the current cycle, is recycled and sent back to be –

5. Heated – when participating as the coolant for stage 3, and then

6. Resent to stage one, to start the next cycle, and be slightly reheated by compression.

In each cycle the net cooling is more than the heat added at the beginning of the cycle. As the gas passes more cycles and becomes cooler, reaching lower temperatures at the expanding cylinder (stage 4 of the Siemens cycle) becomes more difficult.

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