DWHR bug fixes re multiple showers

Author: chipbarnaby

src/DHWCalc.cpp

@@ -266,7 +266,7 @@ struct DWHRUSE		// info about 1 (shower) draw that could have DWHR
 	DWHRUSE() : wdw_iFx( -1), wdw_coldCnx( 0), wdw_vol( 0.f), wdw_volHR( 0.f), wdw_temp( 0.f)
 	{}
 	DWHRUSE( int iFx, int coldCnx, float vol, float volHR, float temp)
-		: wdw_coldCnx( coldCnx), wdw_vol( vol), wdw_volHR( volHR), wdw_temp( temp)
+		: wdw_iFx( iFx), wdw_coldCnx( coldCnx), wdw_vol( vol), wdw_volHR( volHR), wdw_temp( temp)
 	{}
 	~DWHRUSE() {}
 
@@ -1009,7 +1009,7 @@ void DHWSYS::ws_InitTicks(			// initialize tick data for hour
 	ws_iTkNDWHR = -1;
 }		// DHWSYS::ws_InitTicks
 //----------------------------------------------------------------------------
-RC DHWSYS::ws_DoHourDWHR()		// current hour DHWHEATREC modeling
+RC DHWSYS::ws_DoHourDWHR()		// current hour DHWHEATREC modeling (all DHWHEATRECs)
 {
 	RC rc = RCOK;
 
@@ -1024,62 +1024,86 @@ RC DHWSYS::ws_DoHourDWHR()		// current hour DHWHEATREC modeling
 	// ws_qDWHR = 0.f;			// total heat recovered by all DHWHEATREC devices, Btu
 	// ws_whUseNoHR = 0.;		// check value: hour total hot water use w/o HR, gal
 								//  init'd by caller
-	double qRWHSum = 0.;
+	double qRWHSum = 0.;		// hour total recovered heat to WH inlet, Btu
+	int multiDraw = 0;
 	// int nTk = Top.tp_NHrTicks();
 	for (int iTk=ws_iTk0DWHR; iTk < ws_iTkNDWHR; iTk++)
 	{	DHWTICK& tk = ws_ticks[ iTk];		// DHWSYS tick info
 		if (tk.wtk_nHRDraws == 0)
 			continue;		// no DHWHEATREC draws in this tick
-		float vOther		// non-DHWHEATREC draws that contribute to each
+		if (tk.wtk_nHRDraws > 1)
+			multiDraw++;
+		float whUseOther = tk.wtk_whUse;
+		float vHotOther		// non-DHWHEATREC draws that contribute to each
 							//   feedWH-DHWHEATREC potable-side vol
-			= tk.wtk_whUse / max(ws_wrFeedWHCount, 1);
+			= whUseOther / max(ws_wrFeedWHCount, 1);
+#if defined( _DEBUG)
+		int nReDo = 0;		// debugging aid, see below
+	reDo:
+#endif
 		float whUse = 0.f;		// hot water use, this tick / all DHWHEATREC draws
 		float fxUseMix = 0.f;	// mixed water use
 		float qR = 0.f;			// tick heat recovered
 		float qRWH = 0.f;		// tick heat recovered to WH feed
+		float whUseNoHR = 0.f;	// tick hot water use w/o HR
 		DHWHEATREC* pWR;
 		RLUPC(WrR, pWR, pWR->ownTi == ss)
 		{	DHWHRTICK& wrtk = pWR->wr_ticks[iTk];	// DHWHEATREC tick info
 			if (wrtk.wrtk_draws.size() > 0)
 				whUse += pWR->wr_CalcTick( this,
 					wrtk,			// tick info for *pWR
-					vOther,			// total non-HR hot water use, gal
-					ws_whUseNoHR, fxUseMix, qR, qRWH);	// results accum'd
+					vHotOther,		// total non-HR hot water use, gal
+					whUseNoHR, fxUseMix, qR, qRWH);	// results accum'd
 		}
-		ws_AccumUseTick(		// accum to ws_tick, ws_whUse, and ws_fxMixUse
-			C_DHWEUCH_SHOWER, iTk, fxUseMix, whUse);
+#if defined( _DEBUG)
+		if (!nReDo)
+#endif
+			ws_AccumUseTick(		// accum to ws_tick, ws_whUse, and ws_fxMixUse
+				C_DHWEUCH_SHOWER, iTk, fxUseMix, whUse);
+
+		// water heater inlet temp
 		float tO = ws_tInlet;
 		if (tk.wtk_whUse > 0.)
 			tO += qRWH / (waterRhoCp * tk.wtk_whUse);
-#if defined( _DEBUG)
-		else if (qRWH > 0.f)
-			printf("\nInconsistency: wtk_whUse=%0.3f  qRWHWt=%0.3f",
-				tk.wtk_whUse, qRWH);
-#endif
 		tk.wtk_tInletX = ws_AdjustTInletForSSF(tO);
-		qRWHSum += qRWH;
-		ws_qDWHR += qR;		// accum to hour total heat recovered
-	}  // end tick
 
-#if 0 && defined( _DEBUG)
-	if (frDiff( float( whUseTot), ws_whUse.total, .001f) > .001f)
-		printf( "\nMismatch!");
+#if defined( _DEBUG)
+		// tick energy balance
+		float qXNoHR = (whUseNoHR+whUseOther) * waterRhoCp * (ws_tUse - ws_tInlet);
+		float qX     = tk.wtk_whUse           * waterRhoCp * (ws_tUse - tO);
+		float qXHR = qX + qR;
+		if (frDiff(qXHR, qXNoHR, 1.f) > .001f)
+		{
+			printf("\nDHWSYS '%s': ws_DoHourDWHR tick balance error (md=%d)", name, multiDraw);
+			if (nReDo++ < 2)
+				goto reDo;		// repeat calc (debugging aid)
+		}
 #endif
+		ws_qDWHR += qR;		// hour total heat recovered
+		qRWHSum += qRWH;	// hour total heat to WH inlet
+		ws_whUseNoHR += whUseNoHR;		// hour total WH use w/o HR
+
+	}  // end tick
 
-	// calc hour average adjusted inlet and hot water temps
-	float tInletXNoSSF = ws_tInlet;
+	// hour average adjusted inlet and hot water temps
+	float tInletXNoSSF;
 	if (qRWHSum > 0.)
-	{	tInletXNoSSF = ws_tInlet + qRWHSum / (waterRhoCp * ws_whUse.total);
-		ws_tInletX = ws_AdjustTInletForSSF( tInletXNoSSF);
+	{
+		tInletXNoSSF = ws_tInlet + qRWHSum / (waterRhoCp * ws_whUse.total);
+		ws_tInletX = ws_AdjustTInletForSSF(tInletXNoSSF);
 	}
+	else
+		tInletXNoSSF = ws_tInlet;
 
 #if defined( _DEBUG)
-	float qXNoHR = ws_whUseNoHR   * waterRhoCp * (ws_tUse - ws_tInlet);
+	// hour energy balance
+	float qXNoHR = ws_whUseNoHR * waterRhoCp * (ws_tUse - ws_tInlet);
 	float qX =     ws_whUse.total * waterRhoCp * (ws_tUse - tInletXNoSSF);
-	if (frDiff(qX+ws_qDWHR, qXNoHR, 1.f) > .001f)
-		printf( "\nDHWSYS '%s': ws_DoHourDWHR balance error", name);
+	float qXHR = qX + ws_qDWHR;
+	if (frDiff(qXHR, qXNoHR, 1.f) > .001f)
+		printf("\nDHWSYS '%s': ws_DoHourDWHR balance error (md=%d)", name, multiDraw);
 #endif
-	
+
 	return rc;
 }		// DHWSYS::ws_DoHourDWHR
 //----------------------------------------------------------------------------
@@ -2702,7 +2726,7 @@ RC DHWHEATREC::wr_SetFXConnections(
 float DHWHEATREC::wr_CalcTick(		// calculate performance for 1 tick
 	DHWSYS* pWS,		// parent DHWSYS
 	DHWHRTICK& wrtk,	// current tick info for this DHWHEATREC
-	float vOther,		// hot water draws for other fixtures, gal
+	float vHotOther,	// hot water draws for other fixtures, gal
 						//   included in potable flow if feedsWH
 	float& whUseNoHR,	// returned updated: hot water use w/o heat recovery, gal
 						//   used re energy balance check
@@ -2711,40 +2735,26 @@ float DHWHEATREC::wr_CalcTick(		// calculate performance for 1 tick
 	float& qRWH)		// returned updated: tick recovered heat added to WH inlet water, Btu
 
 // returns hot water use for served fixtures, gal
-//     (not including vOther)
+//     (not including vHotOther)
 {
 	int nD = wrtk.wrtk_draws.size();
 	if (nD == 0)
 		return 0.f;		// no draws, no effect
 
-#if 0 && defined( _DEBUG)
-	// if (Top.jDay == 91 && Top.iHr == 20)
-	// 	printf("  Hit\n");
-	static int nDMulti = 0;
-	if (nD > 1)
-	{
-		if (nDMulti++ == 0)
-			printf("\nMultiple draws: jDay=%d  iH=%d",
-				Top.jDay, Top.iHr);
-	}
-	else
-		nDMulti = 0;
-#endif
-
 	// tick constants
 	float tpI = pWS->ws_tInlet;		// mains temp
 	float tHotFX = pWS->ws_tUse;	// hot water temp at fixture
 
 	float vd = 0.f;			// total mixed use at all fixture(s), all draws, gal
 							//   = drain volume
 	float tdI = 0.f;		// average drain-side entering temp, F
-	float vMixHR = 0.f;		// total mixed use at fixtures with cold side
+	float vMixFXHR = 0.f;	// total mixed use at fixtures with cold side
 							//    connection to DHWHEATREC, gal
 	float vHotFX0= 0.f;		// hot water req'd for fixtures that use
 							//    mains water for mixing, gal
 
 	// re parallel potable-side DHWHEATRECs
-	//   caller allocates vOther equally to all feedsWH-DHWHEATREC(s) in DHWSYS
+	//   caller allocates vHotOther equally to all feedsWH-DHWHEATREC(s) in DHWSYS
 	//    >> DHWHEATER inlet flow for other draws assumed to flow equally via parallel paths
 	//   this-DHWHEATREC fixture flows are assigned to this-DHWHEATREC potable flow
 	//    >> this-DHWHEATER's fixtures DHWHEATER and tempering flows do NOT
@@ -2774,7 +2784,7 @@ float DHWHEATREC::wr_CalcTick(		// calculate performance for 1 tick
 		else
 			// fixture cold comes from DHWHEATREC
 			//   accum mixed vol, compute vHotFX below
-			vMixHR += hru.wdw_vol;
+			vMixFXHR += hru.wdw_vol;
 	}
 	fxUseMix += vd;		// accum to caller's total
 
@@ -2783,16 +2793,16 @@ float DHWHEATREC::wr_CalcTick(		// calculate performance for 1 tick
 	tdI = bracket(tpI, tdI/max( vd, .0001f), tHotFX);
 
 
-	float vp;		// potable-side flow, gal
-	float tpO = 0.f;// potable-side outlet temp, F
-	float vHotFX;	// fixture hot vol, gal
+	float vp = 0.f;		// potable-side flow, gal
+	float tpO = 0.f;	// potable-side outlet temp, F
+	float vHotFX = 0.f;	// fixture hot vol, gal
 
-	if (wr_FeedsFX())
+	if (vMixFXHR > 0.f)		// if any current draw feeds a fixture
 	{	
 		// DHWHEATREC feeds fixture(s) and possibly WH
 		vp = wr_FeedsWH()		// potable volume
-			? vMixHR + vHotFX0 + vOther	//  feeds both
-			: vMixHR / 2.f;				//  fixture only: 1st guess
+			? vMixFXHR + vHotFX0 + vHotOther	//  feeds both
+			: vMixFXHR / 2.f;				//  fixture only: 1st guess
 		int iL;
 		for (iL = 0; iL<10; iL++)
 		{	// cold water temp at wdw_coldCnx fixture(s)
@@ -2808,7 +2818,7 @@ float DHWHEATREC::wr_CalcTick(		// calculate performance for 1 tick
 					vHotFX += hru.wdw_vol * DHWMixF(hru.wdw_temp, tHotFX, tpO);
 			}
 			if (!wr_FeedsWH())
-				vp = vMixHR - vHotFX;	// cold side flow
+				vp = vMixFXHR - vHotFX;
 
 #if 0 && defined( _DEBUG)
 			if (iL > 7)
@@ -2818,20 +2828,31 @@ float DHWHEATREC::wr_CalcTick(		// calculate performance for 1 tick
 				break;
 			wr_EffAdjusted(vp, tpI, vd, tdI);		// update efficiency
 		}
+		vHotFX += vHotFX0;		// total fixture hot water
 	}
 	else
-	{	// DWHR feeds WH only -- flows known
-		vHotFX = vHotFX0;
-		vp = vHotFX + vOther;
-		wr_EffAdjusted(vp, tpI, vd, tdI);	// derive wr_eff
-		tpO = wr_HX(vp, tpI, vd, tdI);
+	{	// no current fixture draw uses tempered cold-side water
+		//   all flows known
+		vHotFX = vHotFX0;		// hot water needed
+		if (wr_FeedsWH())
+		{	// potable side feeds water heater
+			//    recovered heat boosts tInlet
+			vp = vHotFX + vHotOther;
+			wr_EffAdjusted(vp, tpI, vd, tdI);	// derive wr_eff
+			tpO = wr_HX(vp, tpI, vd, tdI);
+		}
+		else
+		{	// does not feed WH
+			//   no heat recovered
+			vp = 0.f;		// no potable-side flow
+			tpO = tpI;		// outlet temp = inlet temp (insurance)
+		}
 	}
 
 	float qR1 = vp * waterRhoCp * (tpO - tpI);	// recovered heat
 	qR += qR1;
-	qRWH += wr_FeedsWH() && vp > 0.f			// recovered heat to WH
-		? qR1 * (vHotFX + vOther) / vp
-		: 0.f;
+	if (wr_FeedsWH() && vp > 0.f)
+		qRWH += qR1 * (vHotFX + vHotOther) / vp;			// recovered heat to WH
 	return vHotFX;
 
 }		// DHWHEATREC::wr_CalcTick

test/DWHR.cse

@@ -4546,14 +4546,21 @@ DO0( "DS0",   "Elec0",   FX0,    WH0,    1)
 DO1( "DS0a",  "Elec0a",  FX0a,   WH0a,   1, 1, 0, Yes,  0)
 DO1( "DS0b",  "Elec0b",  FX0b,   WH0b,   0, 0, 0, No,  0)
 
-// fixed heat recovery -- these 2 should get same results
+// fixed heat recovery -- should get same results
 DO0DU( "DSX0",   "ElecX0",   FXX0,   WHX0,    "4D7FixedHR", 1)
 DO1DU( "DSX0a",  "ElecX0a",  FXX0a,  WHX0a,   "4D7",        1, SetEF, 1, 1, No,  .5)
 
 DO1( "DSEQ",  ElecEQ,  FXEQ,  WHEQ,  1, 1, 1, Yes, .5)
 DO1( "DSUSH", ElecUSH, FXUSH, WHUSH, 1, 1, 1,  No, .5)
 DO1( "DSUWH", ElecUWH, FXUWH, WHUWH, 1, 1, 0, Yes, .5)
 
+// 2 showers, 1 DHWHEATREC
+DO1( "DS2S0Y", Elec2S0Y,  FX2S0Y,  WH2S0Y, 2, 2, 0, Yes, .6)
+DO1( "DS2S1N", Elec2S1N,  FX2S1N,  WH2S1N, 2, 2, 1, No,  .6)
+DO1( "DS2S1Y", Elec2S1Y,  FX2S1Y,  WH2S1Y, 2, 2, 1, Yes, .6)
+DO1( "DS2S2N", Elec2S2N,  FX2S2N,  WH2S2N, 2, 2, 2, No,  .6)
+DO1( "DS2S2Y", Elec2S2Y,  FX2S2Y,  WH2S2Y, 2, 2, 2, Yes, .6)
+
 // todo -- drain TD
 //////////////////////////////////////////////////////////////////////