# Thermoacoustic hot-head shroud: flame shroud and flue for a vertical 2 in tri-clamp core

> How do I heat the hot exchanger of a vertical thermoacoustic core with a propane torch?

- Category: Stirling engines › Thermoacoustic & fluidyne
- Kind: Hardware
- Basis: Bore = ASME BPE 2 in tube OD Ø50.8; positions from the loop layout in tools/gen_ta_family.py; ISO 273 medium clearance for M4
- Page: https://xemstudio.com/objects/thermoacoustic-hot-shroud/ · JSON: https://xemstudio.com/api/geometry?object=thermoacoustic-hot-shroud · Plain text: https://xemstudio.com/objects/thermoacoustic-hot-shroud/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 loop's core stands vertical with its hot exchanger above the thermal buffer tube, hot end up, so the buffer tube does not convect (Backhaus & Swift ran theirs the same way). A torch cannot fire straight up at the middle of a vertical tube, so the shroud does it: a closed band round the tube at the hot exchanger, with a flue that comes down beside the loop to a torch standing on the bench.
- Flame and hot gas go up the Ø35 flue (132.6 mm), into the chamber, round the tube over a 40 mm band (the top 20 mm of the buffer tube, the hot exchanger, the first 10 mm of the regenerator) and out of the vents in the top. No clamp, gasket or jacket is inside the band.
- Two halves split across the tube: the front half carries the flue; one M4 × 25 and nut each side close them on the tube. The end walls are bored at the tube OD.
- What it is made of is the builder's choice; the file is the geometry. It runs at flame temperature.

## 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 |
|---|---|---|---|---|
| end-wall bores | Ø50.8 | 2 in tube OD | slide | all |
| split | 1.0 total (0.5 per half) | the other half | clamp | all |
| ear holes | Ø4.5 | M4 clearance (ISO 273 medium) | designed | all |
| flue | Ø40 / Ø35 | torch flame from the torch stand below (no contact) | designed | ta-shroud-2in-front* |
| vents | 8 × Ø6, 3 × Ø8 | exhaust (no contact) | designed | all |

## Sizes

| feature | value |
|---|---|
| band | 40 tall, Ø80 round the tube |
| flue | Ø40 / Ø35 × 132.6, 100 in front of the tube axis |
| walls | 2.5 |
| vents | 8 × Ø6 on r 31.5, 3 × Ø8 over the lobe |
| bolts | M4 × 25 + nut, one each side |

## 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): regenerator |Z| 15–30 ρc/A with p and U nearly in phase, thermal buffer tube, inertance and compliance, jet pump against Gedeon streaming](https://sites.science.oregonstate.edu/~hetheriw/energy/topics/doc/thermo/heat_eng/Stirling_engine/thermoacoustic-Stirling.heat.engine.detailed.study.j.acous.soc.2000.pdf) — PDF — journal article; numbers 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-hot-shroud/index.json

- ta-shroud-2in-front: [STEP](https://xemstudio.com/files/hardware/thermoacoustic-hot-shroud/ta-shroud-2in-front.step) · [STL](https://xemstudio.com/files/hardware/thermoacoustic-hot-shroud/ta-shroud-2in-front.stl) — front half (y ≥ 0.5): 40 tall band round the Ø50.8 tube, Ø80 chamber joined to a Ø40 lobe at y 100, 2.5 walls; Ø40 / Ø35 flue 132.6 long down from the chamber; vents in the top; ears with Ø4.5
- ta-shroud-2in-back: [STEP](https://xemstudio.com/files/hardware/thermoacoustic-hot-shroud/ta-shroud-2in-back.step) · [STL](https://xemstudio.com/files/hardware/thermoacoustic-hot-shroud/ta-shroud-2in-back.stl) — back half (y ≤ −0.5) of the same band: Ø80 chamber, vents, ears with Ø4.5

## Questions

**Why not heat it from below?**

The hot exchanger is half way up a vertical core, above the buffer tube; a flame from below would heat the lower clamp, jacket and buffer tube first.

**Where does the torch go?**

On the bench under the flue, its head in the torch stand's ring with the ring top 25 mm below the flue.

## Fits with

- [Torch stand for a horizontal tri-clamp hot leg](https://xemstudio.com/objects/tri-clamp-torch-stand/)
- [Thermoacoustic heat exchangers, hot and cold, parallel plate, for 1.5, 2 and 3 in tri-clamp spools](https://xemstudio.com/objects/thermoacoustic-heat-exchanger/)
- [Thermoacoustic water jacket: 14 mm clamp-on halves for a 2 in tri-clamp tube](https://xemstudio.com/objects/thermoacoustic-water-jacket/)
- [Build list: Thermoacoustic traveling-wave loop, 2 in tri-clamp](https://xemstudio.com/objects/list-ta-loop-2in/)