From 529c957cfea9cc9f0323c27cf5b45b6aab47a10e Mon Sep 17 00:00:00 2001 From: Ethan Hill Date: Tue, 6 Oct 2026 21:57:29 -0400 Subject: [PATCH] psychro-chart: mix OA and RA through Psychro.mixAir, by mass (#228 step 1) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The chart blended OA and RA inline: W and h weighted by the % OA, the dry-bulb backed out of h, then buildState — which clamps W to saturation and keeps the cold, pre-#236 dry-bulb when the mix fogs. The engine's mixAir (step 0, #651) does the same blend through the mixStreams kernel and re-solves a fogged mix onto the curve, so the page now calls it and the #236 ruling reaches this surface. Clear of saturation the displayed MA state is unchanged: six of the seven engine-standardization §1 rows read identically off the built page before and after, in both unit systems. The fog-corner row moves 10.4 -> 17.7 °F, 9.4 -> 13.4 gr/lb, h 3.93 -> 6.29 Btu/lb — the intended correction (design note §1: 10.42 -> 17.67 °F). - html/tools/psychrometric-chart.html: solveChain's MA step calls Psychro.mixAir({ basis: 'mass' }) and takes exact; an ok:false result mutes the MA readouts and sets the status message like the other stages. The % OA label reads "Outdoor air (% by mass)" and the MA ref-note says the % is of dry-air mass flow, not CFM, and what happens when the mixed point lands past the curve. Refs: codebase-issues#228 Co-Authored-By: Claude Fable 5.1 --- html/tools/psychrometric-chart.html | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/html/tools/psychrometric-chart.html b/html/tools/psychrometric-chart.html index 7e1f8eb0..7d4404c1 100644 --- a/html/tools/psychrometric-chart.html +++ b/html/tools/psychrometric-chart.html @@ -331,10 +331,10 @@

Air handler

- +
-

Mass-weighted mix of OA and RA. The mixed point falls on the straight line between OA and RA on the chart, at the OA% fraction of the way from RA to OA.

+

Mass-weighted mix of OA and RA — the % is a share of the dry-air mass flow, not of CFM. The mixed point falls on the straight line between OA and RA on the chart, at the OA% fraction of the way from RA to OA. If that point lands past the saturation curve, the excess moisture condenses as fog and the mixed point settles onto the curve instead.

MA dry-bulb (°F)—
MA humidity ratio (gr/lb)—
MA rel. humidity (%)—
@@ -661,19 +661,24 @@

OA r.ra = Psychro.solveState(eRa.mode, eRa.tdb, eRa.second, P); if (!r.ra.ok) setErr('RA: ' + r.ra.error); - // MA — mass-weighted enthalpy + humidity-ratio mix + // MA — mass-weighted enthalpy + humidity-ratio mix. % OA is a + // MASS fraction (the editor label says so): the engine blends + // W and h, which conserve by mass, and recovers the dry-bulb — + // re-solved onto the saturation curve when the mix fogs + // (codebase-issues #228 / #236, docs/engine-standardization.md). if (r.oa.ok && r.ra.ok) { const pct = parseFloat(document.getElementById('ma-pct').value); if (!isFinite(pct) || pct < 0 || pct > 100) { r.ma = { ok: false, error: '% OA must be 0–100' }; setErr('MA: % OA must be 0–100'); } else { - const fOa = pct / 100, fRa = 1 - fOa; - const W_ma = fOa * r.oa.W + fRa * r.ra.W; - const h_ma = fOa * r.oa.h + fRa * r.ra.h; - // back out tdb from h = (0.240 + 0.444·W)·tdb + 1061·W - const tdb_ma = (h_ma - 1061 * W_ma) / (0.240 + 0.444 * W_ma); - r.ma = Psychro.buildState(tdb_ma, W_ma, P); + const mix = Psychro.mixAir({ + streams: [{ state: r.oa, share: pct }, { state: r.ra, share: 100 - pct }], + basis: 'mass', + P, + }); + r.ma = mix.ok ? mix.exact : mix; + if (!r.ma.ok) setErr('MA: ' + r.ma.error); } } else { r.ma = { ok: false, error: 'awaiting OA / RA' };