Adventures with Stirling Engines

[mahashma]

Where do they draw their "external" or "cold side" temp from? I have one set up in naked Mars atmosphere so by rights ambient temperature should never get above 300K *maybe*, but my engines are reading into the 800's. All the pipework leading in and out is insulated.

Currently pulling 650W with an infeed of 3.5MPa and 3MPa volatile coolant but no idea why my cold side temps are so high when the whole machine is sitting in 280K ambient air.

https://steamcommunity.com/sharedfiles/filedetails/?id=3444092021

Any help, ideas, ridicule even?

[G-Man]

The "cold side" is for the gas inside the stirling engine's compression cylinder. That gas is cooled by exchanging heat with the outside air. The reason the "cold side" temperature is so high is probably because the Martian atmosphere is so thin at 2 kPa that it can't exchange heat very well. You need the surrounding air to be at least 100 kPa for full effectiveness on the heat exchanger.

[mahashma]

Originally posted by G-Man:

The "cold side" is for the gas inside the stirling engine's compression cylinder. That gas is cooled by exchanging heat with the outside air. The reason the "cold side" temperature is so high is probably because the Martian atmosphere is so thin at 2 kPa that it can't exchange heat very well. You need the surrounding air to be at least 100 kPa for full effectiveness on the heat exchanger.

That makes sense. I'll do some experimenting with pressurization and see how it goes.

[fixius01]

Originally posted by mahashma:

Originally posted by G-Man:

The "cold side" is for the gas inside the stirling engine's compression cylinder. That gas is cooled by exchanging heat with the outside air. The reason the "cold side" temperature is so high is probably because the Martian atmosphere is so thin at 2 kPa that it can't exchange heat very well. You need the surrounding air to be at least 100 kPa for full effectiveness on the heat exchanger.

That makes sense. I'll do some experimenting with pressurization and see how it goes.

or increase the surface area and or the heat capacity and conductivity of the coolant.