# Annular regenerator screen ring: 100 mesh, Ø47.5 / Ø41.5, for a 2 in tri-clamp Stirling

> How do I make an annular regenerator for a 2 in tri-clamp free-piston Stirling?

- Category: Hardware › Stirling & thermoacoustic
- Kind: Hardware
- Basis: Urieli & Berchowitz screen relations: porosity 1 − π m d / 4, hydraulic diameter d·β/(1 − β); heat transfer and friction from Gedeon & Wood (1996)
- Page: https://xemstudio.com/objects/fpse-regenerator-screen-ring/ · JSON: https://xemstudio.com/api/geometry?object=fpse-regenerator-screen-ring · Plain text: https://xemstudio.com/objects/fpse-regenerator-screen-ring/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

- 389 rings of 100 mesh, 0.1 mm wire screen stacked 77.8 mm high in the annulus between the liner (Ø41.5) and the hot spool's bore (Ø47.5), on the liner's spokes and under its rim.
- Porosity 0.691, hydraulic diameter 0.223 mm, frontal area 419 mm². At the design point the regenerator's NTU is 165 (effectiveness 0.9940), its enthalpy loss 5.4 W.
- Stack the rings with the weave of each layer turned a little against the last; fill the annulus exactly, so the rim holds the stack.

## 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 |
|---|---|---|---|---|
| OD | Ø47.5 | hot spool bore | slide | all |
| ID | Ø41.5 | liner tube OD | slide | all |

## Sizes

| feature | value |
|---|---|
| ring | Ø47.5 / Ø41.5 × 0.2 |
| count | 389 |
| screen | 100 mesh, 0.1 mm wire |
| porosity | 0.691 |
| hydraulic Ø mm | 0.223 |

## Where the files are

- Ohio University (Urieli): [Stirling cycle machine analysis: ideal adiabatic and simple analysis (after Urieli & Berchowitz, Stirling Cycle Engine Analysis, 1984)](https://www.ohio.edu/mechanical/stirling/) — web — author's site
- NASA (NTRS, public domain): [Gedeon & Wood (1996), Oscillating-flow regenerator test rig: correlations for screens and felts, NASA CR-198442 (f = 129/Re + 2.91 Re^-0.103; Nu = (1 + 0.99 Pe^0.66) β^1.79)](https://ntrs.nasa.gov/citations/19960015878) — PDF — US Government work, public domain
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/fpse-regenerator-screen-ring/index.json

- regen-ring-41.5x47.5x0.2: [STEP](https://xemstudio.com/files/hardware/fpse-regenerator-screen-ring/regen-ring-41.5x47.5x0.2.step) · [STL](https://xemstudio.com/files/hardware/fpse-regenerator-screen-ring/regen-ring-41.5x47.5x0.2.stl) — regenerator ring: one layer of 100 mesh woven screen (0.1 mm wire) cut to Ø47.5 / Ø41.5, drawn 0.2 thick (two wire diameters)

## Questions

**Why 100 mesh?**

At 40–50 Hz in helium the gas needs a fine matrix to give up and take back its heat each stroke; 100 mesh keeps the effectiveness above 0.99 while the friction stays a fraction of the cycle's work.

## Fits with

- [Free-piston displacer liner: Ø40 bore, regenerator inner wall, rim clamped in the tri-clamp joint](https://xemstudio.com/objects/fpse-displacer-cylinder/)
- [Regenerator matrix disc Ø44 / Ø32 × 0.5 mm (mesh counts #40–#200)](https://xemstudio.com/objects/regenerator-mesh-disc/)
- [Build list: Free-piston Stirling generator, 2 in tri-clamp (pressurised, linear alternator)](https://xemstudio.com/objects/list-fpse-generator-2in/)