added gravity function for calculating local g updated config for faster testing and changed the symbols at physical pos

src/coolprop-node/src/index.js

@@ -3,11 +3,61 @@ const customRefs = require('./refData.js');
 
 class CoolPropWrapper {
     constructor() {
+
         this.initialized = false;
         this.defaultRefrigerant = null;
         this.defaultTempUnit = 'K';    // K, C, F
         this.defaultPressureUnit = 'Pa' // Pa, kPa, bar, psi
         this.customRef = false;
+        this.PropsSI = this._propsSI.bind(this);
+
+
+        // 🔹 Wastewater correction options (defaults)
+        this._ww = {
+            enabled: true,
+            tss_g_per_L: 3.5,       // default MLSS / TSS
+            density_k: 2e-4,        // +0.02% per g/L
+            viscosity_k: 0.07,      // +7% per g/L (clamped)
+            viscosity_max_gpl: 4    // cap effect at 4 g/L
+        };
+
+        this._initPromise = null;
+        this._autoInit({ refrigerant: 'Water' });
+
+    }
+
+    _isWastewaterFluid(fluidRaw) {
+        if (!fluidRaw) return false;
+        const token = String(fluidRaw).trim().toLowerCase();
+        return token === 'wastewater' || token.startsWith('wastewater:');
+    }
+
+    _parseWastewaterFluid(fluidRaw) {
+        if (!this._isWastewaterFluid(fluidRaw)) return null;
+            const ww = { ...this._ww };
+            const [, tail] = String(fluidRaw).split(':');
+            if (tail) {
+                tail.split(',').forEach(pair => {
+                    const [key, value] = pair.split('=').map(s => s.trim().toLowerCase());
+                    if (key === 'tss' && !Number.isNaN(Number(value))) {
+                        ww.tss_g_per_L = Number(value);
+                    }
+                });
+            }
+        return ww;
+    }
+
+    _applyWastewaterCorrection(outputKey, baseValue, ww) {
+        if (!Number.isFinite(baseValue) || !ww || !ww.enabled) return baseValue;
+        switch (outputKey.toUpperCase()) {
+            case 'D': // density
+                return baseValue * (1 + ww.density_k * ww.tss_g_per_L);
+            case 'V': // viscosity
+                const effTss = Math.min(ww.tss_g_per_L, ww.viscosity_max_gpl);
+                return baseValue * (1 + ww.viscosity_k * effTss);
+            default:
+                return baseValue;
+        }
     }
 
     // Temperature conversion helpers
@@ -407,13 +457,31 @@ class CoolPropWrapper {
         }
     }
 
-    // Direct access to CoolProp functions
-    async getPropsSI() {
-        if(!this.initialized) {
-            await coolprop.init();
+    _autoInit(defaults) {
+        if (!this._initPromise) {
+            this._initPromise = this.init(defaults);
         }
-        return coolprop.PropsSI;
+        return this._initPromise;
     }
+
+    _propsSI(outputKey, inKey1, inVal1, inKey2, inVal2, fluidRaw) {
+        if (!this.initialized) {
+            // Start init if no one else asked yet
+            this._autoInit({ refrigerant: this.defaultRefrigerant || 'Water' });
+            throw new Error('CoolProp is still warming up, retry PropsSI in a moment');
+        }
+        const ww = this._parseWastewaterFluid(fluidRaw);
+        const fluid = ww ? 'Water' : (this.customRefString || fluidRaw);
+        const baseValue = coolprop.PropsSI(outputKey, inKey1, inVal1, inKey2, inVal2, fluid);
+        return ww ? this._applyWastewaterCorrection(outputKey, baseValue, ww) : baseValue;
+    }
+
+    //Access to coolprop
+    async getPropsSI() {
+        await this._ensureInit({ refrigerant: this.defaultRefrigerant || 'Water' });
+        return this.PropsSI;
+    }
+    
 }
 
 module.exports = new CoolPropWrapper();