Page 11 – The Gas Circuit and Fins

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The schematic of the engine shown previously, represents the patented design of 1816.

I call that design the “simple beta” or “tin can” design.
The air flows around the plunger/displacer.

In the diagram opposite, the base of the displacer has a piston ring. This makes it possible for the displacer to pump air around a gas circuit. I call it the “pumped beta”.

The advantage is that gas can be routed through a larger number of narrow channels.
This increases the contact area between hot metal and the gas – better gas heating.

In the diagram the green displacer is at mid stroke moving downwards.
Air beneath the displacer is being pumped through ports located around the cylinder
into slots
within the water cooler.
The gas then passes upward through the
orange regenerator section.
Then through slots inside the hot cap (red).
Finally, gas exits
the slotting, passing through ports, into the space above the displacer.

The whole of the inside of the hot cap and cooler cylinder is slotted with very narrow slots.
This dramatically increases the heat transfer surface area. Gas molecules are only heated/cooled when they touch the metal surface.
The gas is kept in the slots by a liner which fits inside, against the fins. This liner also
acts as the cylinder for the piston and the piston ring at the base of the displacer.

There is a gap in the slotting, between the hot cap and the cold end.
This void is where
the regenerator wire is packed.

So, in summary, in the pumped beta, the gas is circulated, with every stroke,
through a very much increased
area of contact with the hot fins, the regenerator wire
and the cold fins.

This larger heat transfer area allows far larger heat transfer and more power.