CounterFlow Heat Exchanger - Gas + Gas

The counterflow heat exchanger has four gas ports in two pairs: Input → Output and Input2 → Output2. Two gas streams run separately through the device and exchange heat on the way. The gases themselves do not mix. “Counterflow” means the two streams pass each other in opposite directions.

The principle comes from engineering: at the end of its path the hot stream still meets the freshly entered, coldest part of the other stream. So it can cool further than with a simple equalisation, where both sides only reach a shared middle temperature. The game code models this: the amount of gas passing through in one tick is split into eight portions per side, which are shifted past each other step by step and exchange heat as they go.

A calculation on the energy balance: 10 mol of Carbon Dioxide cool from 400 K to 300 K. At 28.2 J per mole and kelvin they release 10 · 28.2 · 100 = 28,200 J. If a stream of 10 mol of nitrogen (20.6 J per mole and kelvin) takes up all of that heat, it warms by 28,200 / 206 ≈ 137 K. No more than the released heat can pass across.

The exchanger is passive: no power, no data port, no pump of its own. Each tick it lets through as much on each side as makes input and output equal in pressure. So gas only flows while the input has more pressure than the output – plan a pump or a pressure regulator in front, or a consumer with lower pressure behind. All four pipes must be connected, otherwise it exchanges nothing. Below 101.325 kPa the transfer drops in proportion to the pressure: with 50 kPa on one side it manages half, with 50 kPa on both a quarter. Setting (0 to 10), Maximum and Ratio only appear in the logic list; the exchanger never reads Setting.

It is built in two steps: place the Kit (CounterFlow Heat Exchanger), then attach one steel sheet with the welding torch. The same kit also builds the gas + liquid and liquid + liquid versions. When to use which exchanger is covered in Heat exchangers and heat transport: pipe to pipe, gas to liquid.