# A 3D-printed fridge that runs on a flame

Ben Krasnow printed a clear Einstein-Szilard absorption refrigerator in resin, heated it with an open flame, and got it 5 °C below ambient.

- Category: Hardware (build)
- Made by: Ben Krasnow on Hackaday
- Original: https://www.youtube.com/watch?v=doZ5e4YVdEs
- On Afterware: https://afterware.xyz/p/a-3d-printed-fridge-that-runs-on-a-flame

## Can I build this?

- Difficulty: Expert
- AI-buildability: 2/5 (AI can help with CAD and thermodynamic sizing, but the work is mostly resin printing, leak-free sealing, handling ammonia and an open flame, and troubleshooting bubble airlocks by hand.)
- Time: A few weeks
- Cost: $150–400
- Parts: 3D-printed clear resin body, copper block, perfluoropentane
- Tools: 3D printer, soldering iron, propane torch

Estimates based on the original write-up. How the AI-buildability score works: https://afterware.xyz/ai-buildability

## Build sheet

- Method: Absorption, Einstein-Szilard
- Heat source: Open flame
- Body: 3D-printed clear resin
- Result: 5 °C below ambient

## Starter prompt

```
Based on "A 3D-printed fridge that runs on a flame" on Afterware: https://afterware.xyz/p/a-3d-printed-fridge-that-runs-on-a-flame

Help me design a 3D-printable transparent Einstein-Szilard absorption refrigerator model. Give me a single internal fluid path layout for a resin body with a copper boiler block heated by a flame, and list the ammonia-water and perfluoropentane fill steps. Flag where bubbles are most likely to airlock the loop.
```

## Story

Most absorption fridges need pressures a glass or plastic body can't hold. The Einstein-Szilard design sidesteps that with a third liquid as the refrigerant, so Ben Krasnow could build the whole thing in clear resin and watch the cycle run.

A copper block carries heat from an open flame into the boiler, which separates ammonia from a strong ammonia-water solution. The ammonia gas lowers the refrigerant's partial pressure so it evaporates and pulls heat away. He used nonflammable perfluoropentane instead of the usual butane, since there's a flame right next to it. The single internal path is finicky: a stray bubble in the wrong place airlocks the whole loop. He got it to 5 °C below ambient.

Copper and ammonia don't mix long term, so this is a demo, not a keeper. It's still the clearest way to see how an absorption cycle works, and the clear body means you can track every bubble.

## Resources

- [Build video](https://www.youtube.com/watch?v=doZ5e4YVdEs)

Tags: absorption refrigerator, einstein-szilard, 3d printed, resin, perfluoropentane, copper, transparent

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