Fix recuperator bisection bracket failure on wasm#64
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The bisection event handler mapped all SecondLawViolation errors to assume_positive. On wasm, CoolProp enthalpy round-trip noise at the lower bracket endpoint (t_out = t_in) can exceed the ENTHALPY_RELATIVE_ZERO threshold and produce a spurious wrong-direction heat flow. The handler then made both bracket endpoints positive, causing 'no sign change'. Now the handler checks whether t_out is near t_top_in. Near the inlet, the violation is FP noise (UA ≈ 0, negative residual). Farther away, it's a genuine overshoot (positive residual). Closes #63
gdtroszak
approved these changes
Mar 3, 2026
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What
Fixes the recuperator "invalid bracket: no sign change" error on wasm targets with segments > 1.
On wasm (strict IEEE 754, no x86 extended precision), CoolProp's enthalpy round-trip noise at the lower bracket boundary (
t_out = t_in) can exceed theENTHALPY_RELATIVE_ZEROthreshold from #59. When the noise produces a spurious wrong-direction heat flow, the resolve step emits aSecondLawViolation. The event handler was mapping all such violations toassume_positive— correct for genuine overshoots mid-iteration, but wrong at the zero-heat-transfer boundary where UA ≈ 0 and the residual should be negative. Both endpoints end up positive → bracket rejected.How
The event handler now checks whether the candidate
t_outis neart_top_in(within 1e-9 K). Near the inlet, aSecondLawViolationis FP noise →assume_negative. Farther away, it's a real overshoot →assume_positive.The
ENTHALPY_RELATIVE_ZEROthreshold is unchanged — it's still the first line of defense in the resolve step. The event handler is the fallback for when the thermo backend's noise exceeds it.Closes #63