# Thermoacoustic buffer-tube liner: 2 in, 0.5 wall, 180 and 140 mm

> What holds the hot exchanger in a thermoacoustic core, and what is the thermal buffer tube?

- Category: Stirling engines › Thermoacoustic & fluidyne
- Kind: Hardware
- Basis: Bore Ø47.5; lengths from the core layouts in tools/gen_ta_power.py
- Page: https://xemstudio.com/objects/thermoacoustic-buffer-tube-liner/ · JSON: https://xemstudio.com/api/geometry?object=thermoacoustic-buffer-tube-liner · Plain text: https://xemstudio.com/objects/thermoacoustic-buffer-tube-liner/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part.

## Notes

- The thermal buffer tube is the open length between the hot exchanger and the secondary ambient exchanger: the gas oscillates in it without touching anything, so the heat stays at the hot end. It runs hot end up (hot gas over cold), so it does not convect.
- The liner is what the hot exchanger stands on: a thin tube at the bore, 0.5 wall, so it conducts as little heat as it can (the model counts its conduction with the tube wall's).
- 180 mm in the ring engine's cores, 140 mm in the twin engine's: in the model the ring's gas moves about ±9 mm at the liner's ends, well inside its length.
- Fit: outside slide in the bore; the ends bear on the exchanger inserts.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| outside | Ø47.5 | 2 in spool bore | slide | all |
| inside | Ø46.5 (0.5 wall) | gas passage (no contact) | designed | all |
| end faces | flat ring Ø46.5–Ø47.5 | hot and secondary exchanger inserts | designed | all |

## Sizes

| file | outside_mm | inside_mm | length_mm |
|---|---|---|---|
| tbt-liner-2in-140 | 47.5 | 46.5 | 140.0 |
| tbt-liner-2in-180 | 47.5 | 46.5 | 180.0 |

## Where the files are

- J. Acoust. Soc. Am. (S. Backhaus, G. W. Swift): [A thermoacoustic-Stirling heat engine: detailed study, JASA 107(6), 3148 (2000): torus with inertance and compliance, thermal buffer tube, jet pump against Gedeon streaming](https://doi.org/10.1121/1.429343) — web — journal article; cited (verify at link)
- G. W. Swift (Acoustical Society of America / LANL): [Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (Rott's equations, the energy equation, screen relations; the method behind DeltaEC)](https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/) — web, book — cited (verify at link)
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (2 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/thermoacoustic-buffer-tube-liner/index.json

- tbt-liner-2in-140: [STEP](https://xemstudio.com/files/hardware/thermoacoustic-buffer-tube-liner/tbt-liner-2in-140.step) · [STL](https://xemstudio.com/files/hardware/thermoacoustic-buffer-tube-liner/tbt-liner-2in-140.stl) — thermal buffer tube liner Ø47.5 / Ø46.5 × 140 (0.5 wall)
- tbt-liner-2in-180: [STEP](https://xemstudio.com/files/hardware/thermoacoustic-buffer-tube-liner/tbt-liner-2in-180.step) · [STL](https://xemstudio.com/files/hardware/thermoacoustic-buffer-tube-liner/tbt-liner-2in-180.stl) — thermal buffer tube liner Ø47.5 / Ø46.5 × 180 (0.5 wall)

## Questions

**Why so thin?**

Every square millimetre of wall carries heat from the hot end to the cold end by conduction; the liner only has to locate the exchangers.

## Fits with

- [Thermoacoustic bore spacers and liners for 2 in tri-clamp spools: 8.4, 60 and 61.7 mm](https://xemstudio.com/objects/thermoacoustic-bore-spacer/)
- [Thermoacoustic slotted exchanger insert: 2 in bore, 14 and 12 mm](https://xemstudio.com/objects/thermoacoustic-slotted-exchanger-insert/)
- [Build list: Thermoacoustic-Stirling ring generator, three 2 in units, pressurised](https://xemstudio.com/objects/list-ta-ring-3x2in/)