Fix BPHX mass flux per-side channels so pressure drop is visible.

Mass flux used all plate gaps instead of half the pack per fluid, underestimating G and making ΔP look like zero in the UI (0.000 bar). Also show ΔP in kPa/Pa and sync the web example.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/web/public/examples/bphx_evaporator_condenser.json

@@ -33,6 +33,7 @@
           "target_subcooling_k": 5.0,
           "emergent_pressure": true,
           "correlation": "Longo2004",
+          "dp_correlation": "SimplifiedChannel",
           "ua": 2500.0
         },
         {
@@ -52,6 +53,7 @@
           "target_superheat_k": 5.0,
           "emergent_pressure": true,
           "correlation": "Longo2004",
+          "dp_correlation": "SimplifiedChannel",
           "ua": 2000.0
         },
         {

apps/web/src/components/panels/PropertiesPanel.tsx

@@ -903,10 +903,24 @@ function ModelicaResultsView({
 
       <div className="grid grid-cols-2 gap-1.5">
         {inspector.delta_p_bar != null && (
-          <MiniMetric label="ΔP" value={`${inspector.delta_p_bar.toFixed(3)} bar`} />
+          <MiniMetric
+            label="ΔP"
+            value={
+              Math.abs(inspector.delta_p_bar) * 100 >= 0.05
+                ? `${(inspector.delta_p_bar * 100).toFixed(2)} kPa`
+                : `${(inspector.delta_p_bar * 1e5).toFixed(1)} Pa`
+            }
+          />
         )}
         {inspector.delta_p_sec_bar != null && (
-          <MiniMetric label="ΔP sec" value={`${inspector.delta_p_sec_bar.toFixed(3)} bar`} />
+          <MiniMetric
+            label="ΔP sec"
+            value={
+              Math.abs(inspector.delta_p_sec_bar) * 100 >= 0.05
+                ? `${(inspector.delta_p_sec_bar * 100).toFixed(2)} kPa`
+                : `${(inspector.delta_p_sec_bar * 1e5).toFixed(1)} Pa`
+            }
+          />
         )}
         {inspector.q_primary_kw != null && (
           <MiniMetric label="Q̇" value={`${Math.abs(inspector.q_primary_kw).toFixed(2)} kW`} />
@@ -977,43 +991,6 @@ function ModelicaResultsView({
   );
 }
 
-function SolvedVariablesBlock({
-  items,
-  title,
-}: {
-  items: SolvedVariable[];
-  title: string;
-}) {
-  if (items.length === 0) return null;
-  return (
-    <div className="overflow-hidden rounded-md border border-[var(--line)]">
-      <div className="border-b border-[var(--line)] bg-[var(--chrome-2)] px-2 py-1 text-[9px] font-semibold uppercase tracking-wide text-[var(--ink-faint)]">
-        {title}
-      </div>
-      <table className="w-full text-[10px]">
-        <thead>
-          <tr className="text-left text-[9px] text-[var(--ink-faint)]">
-            <th className="px-1.5 py-1 font-medium">Var</th>
-            <th className="px-1 py-1 font-medium">Value</th>
-            <th className="px-1 py-1 font-medium">Min</th>
-            <th className="px-1 py-1 font-medium">Max</th>
-          </tr>
-        </thead>
-        <tbody>
-          {items.map((sv) => (
-            <tr key={sv.id} className="border-t border-[var(--line)]">
-              <td className="mono px-1.5 py-1 text-[var(--ink)]">{sv.variable}</td>
-              <td className="mono px-1 py-1 text-[var(--ink)]">{fmtOpt(sv.value, 4)}</td>
-              <td className="mono px-1 py-1 text-[var(--ink-dim)]">{fmtOpt(sv.min, 3)}</td>
-              <td className="mono px-1 py-1 text-[var(--ink-dim)]">{fmtOpt(sv.max, 3)}</td>
-            </tr>
-          ))}
-        </tbody>
-      </table>
-    </div>
-  );
-}
-
 function MiniMetric({ label, value }: { label: string; value: string }) {
   return (
     <div className="rounded border border-[var(--line)] bg-[var(--chrome-2)] px-1.5 py-1">

apps/web/src/lib/componentInspector.ts

@@ -182,8 +182,22 @@ export function buildComponentInspector(
   }
 
   const summaryLines: string[] = [];
-  if (delta_p_bar != null) summaryLines.push(`ΔP = ${fmt(delta_p_bar, 3)} bar`);
+  if (delta_p_bar != null) {
-  if (delta_p_sec_bar != null) summaryLines.push(`ΔP sec = ${fmt(delta_p_sec_bar, 3)} bar`);
+    const dp_kpa = delta_p_bar * 100.0;
+    summaryLines.push(
+      Math.abs(dp_kpa) >= 0.05
+        ? `ΔP = ${fmt(dp_kpa, 2)} kPa`
+        : `ΔP = ${fmt(delta_p_bar * 1e5, 1)} Pa`,
+    );
+  }
+  if (delta_p_sec_bar != null) {
+    const dp_kpa = delta_p_sec_bar * 100.0;
+    summaryLines.push(
+      Math.abs(dp_kpa) >= 0.05
+        ? `ΔP sec = ${fmt(dp_kpa, 2)} kPa`
+        : `ΔP sec = ${fmt(delta_p_sec_bar * 1e5, 1)} Pa`,
+    );
+  }
   if (q_primary_kw != null) summaryLines.push(`Q̇ = ${fmt(Math.abs(q_primary_kw), 2)} kW`);
   if (q_secondary_kw != null) summaryLines.push(`Q̇ sec = ${fmt(Math.abs(q_secondary_kw), 2)} kW`);
   if (work_kw != null) summaryLines.push(`Ẇ = ${fmt(work_kw, 2)} kW`);

crates/components/src/heat_exchanger/bphx_exchanger.rs

@@ -498,7 +498,8 @@ impl BphxExchanger {
         let dp_hot = self.side_channel_dp(state[m_h], rho_hot, z_dp)?;
         let dp_cold = self.side_channel_dp(state[m_c], rho_cold, z_dp)?;
 
-        let a_flow = self.geometry.channel_flow_area() * self.geometry.n_channels() as f64;
+        let a_flow =
+            self.geometry.channel_flow_area() * self.geometry.n_channels_per_side() as f64;
         if a_flow <= 1e-30 {
             return Err(ComponentError::InvalidState(
                 "BPHX channel flow area too small for pressure-drop Jacobian".into(),

crates/components/src/heat_exchanger/bphx_geometry.rs

@@ -170,20 +170,29 @@ impl BphxGeometry {
         self.channel_spacing * self.plate_width
     }
 
-    /// Returns the total number of channels (n_plates - 1).
+    /// Returns the total number of inter-plate gaps (n_plates − 1).
     pub fn n_channels(&self) -> u32 {
         self.n_plates.saturating_sub(1)
     }
 
-    /// Returns the mass flux for a given mass flow rate.
+    /// Channels available to **one** fluid in a single-pass counterflow pack.
     ///
-    /// G = m_dot / (A_channel × n_channels)
+    /// Alternating hot/cold channels split the gaps roughly in half:
+    /// `⌊n_plates / 2⌋` (at least 1). Using the full `n_channels` for mass flux
+    /// underestimates G by ~2× and ΔP by ~4×.
+    pub fn n_channels_per_side(&self) -> u32 {
+        (self.n_plates / 2).max(1)
+    }
+
+    /// Returns the mass flux for a given mass flow rate on one fluid side.
+    ///
+    /// G = m_dot / (A_channel × n_channels_per_side)
     ///
     /// # Arguments
     ///
-    /// * `mass_flow` - Total mass flow rate (kg/s)
+    /// * `mass_flow` - Total mass flow rate on that side (kg/s)
     pub fn mass_flux(&self, mass_flow: f64) -> f64 {
-        let n_channels = self.n_channels() as f64;
+        let n_channels = self.n_channels_per_side() as f64;
         if n_channels < 1e-10 {
             return 0.0;
         }
@@ -460,8 +469,12 @@ mod tests {
             .unwrap();
 
         let mass_flow = 0.1;
+        // 10 plates → 5 channels per side; A_ch = 0.002 × 0.1 = 2e-4 m²
+        // G = 0.1 / (2e-4 × 5) = 100 kg/(m²·s)
         let g = geo.mass_flux(mass_flow);
-        assert!(g > 0.0);
+        assert!((g - 100.0).abs() < 1e-9, "got G={g}");
+        assert_eq!(geo.n_channels_per_side(), 5);
+        assert_eq!(geo.n_channels(), 9);
     }
 
     #[test]