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อัปเดต 2026-09-07
Ambient heat transfer
buried / above-ground U
On the marching engine, a pipe can lose or gain heat to its surroundings. We compute a per-length overall heat-transfer coefficient from the insulation/soil/air resistance network and apply it segment by segment.
เมื่อไรจึงใช้
- Heat-losing or heat-gaining lines — buried pipe, above-ground exposed pipe, insulated runs, cooldown of a hot fluid.
ค่าที่ต้องกรอก
| ค่า | คำอธิบาย |
|---|---|
| Environment | Buried (soil) or above-ground (air) — sets the outer resistance. |
| Insulation | Material and thickness — the dominant resistance when present. |
| Ambient temperature | The sink/source the pipe exchanges with. |
คำนวณอย่างไร
The overall U comes from series thermal resistances (fluid film, wall, insulation, and soil or air). Per marching segment we add q = U·(T − T_amb) to the enthalpy update; U = 0 (no config) is a bit-identical no-op.
สมการ
Per-length heat exchange
q′ = heat per unit length (W/m), applied to the stream enthalpy each segment. Positive = loss to a cooler ambient.
Overall coefficient (series resistances)
Each conduction resistance is ln(r₂/r₁)/(2πk); the soil resistance uses the buried-cylinder form, air uses a convective film.
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