window.onload = InitValues;

function InitValues()
{
	f = document.forms['WaterUsage'];
	f.FlowIP.value = fix(1000,0);
	f.FlowSI.value = fix(m3h(1000),0);
	f.HotWaterIP.value = fix(95,2);
	f.HotWaterSI.value = fix(Celsius(95),2);
	f.ColdWaterIP.value = fix(85,2);
	f.ColdWaterSI.value = fix(Celsius(85),2);
	f.WetBulbIP.value = fix(78,2);
	f.WetBulbSI.value = fix(Celsius(78),2);
	f.DriftRate.value = "0.005";
	f.Conc.value = "3";
	InputChange(f.Conc);
}

function InputChange(txtInput)
{
	var x = parseFloat(txtInput.value);
	if (isNaN(x)) x=0;
	var n = txtInput.name;
	var f = txtInput.form;
	if (txtInput == f.FlowIP || txtInput == f.FlowSI)
	{
		if (txtInput == f.FlowSI) x = gpm(x);
		if (x < 10) x=10;
		if (x > 1e6) x=1e6;
		f.FlowIP.value = fix(x,0);
		f.FlowSI.value = fix(m3h(x),0);
	}
	else if (txtInput == f.HotWaterIP || txtInput == f.HotWaterSI)
	{
		if (txtInput == f.HotWaterSI) x = Fahrenheit(x);
		if (x < 40) x=40;
		if (x > 145) x=145;
		f.HotWaterIP.value = fix(x,2);
		f.HotWaterSI.value = fix(Celsius(x),2);
	}
	else if (txtInput == f.ColdWaterIP || txtInput == f.ColdWaterSI)
	{
		if (txtInput == f.ColdWaterSI) x = Fahrenheit(x);
		if (x < 35) x=35;
		if (x > 120) x=120;
		f.ColdWaterIP.value = fix(x,2);
		f.ColdWaterSI.value = fix(Celsius(x),2);
	}
	else if (txtInput == f.WetBulbIP || txtInput == f.WetBulbSI)
	{
		if (txtInput == f.WetBulbSI) x = Fahrenheit(x);
		if (x < 20) x=20;
		if (x > 90) x=90;
		f.WetBulbIP.value = fix(x,2);
		f.WetBulbSI.value = fix(Celsius(x),2);
	}
	else if (txtInput == f.DriftRate)
	{
		if (x < 0.001) x = 0.001;
		if (x > 0.050) x = 0.050;
		f.DriftRate.value = fix(x,3);
	}
	else if (txtInput == f.Conc)
	{
		if (x < 1.5) x = 1.5;
		if (x > 10) x = 10;
		f.Conc.value = x;
	}

	f.EvapIP.value = "";
	f.EvapSI.value = "";
	f.DriftIP.value = "";
	f.DriftSI.value = "";
	f.BlowDownIP.value = "";
	f.BlowDownSI.value = "";
	f.TotalIP.value = "";
	f.TotalSI.value = "";

	var G = parseFloat(f.FlowIP.value);
	var Thw = parseFloat(f.HotWaterIP.value);
	var Tcw = parseFloat(f.ColdWaterIP.value);
	var Twb = parseFloat(f.WetBulbIP.value);
	var DR = parseFloat(f.DriftRate.value);
	var C = parseFloat(f.Conc.value);
	var R = Thw - Tcw;
	var A = Tcw - Twb;
	if (A>=3 && A<=40 && R>=5 && R<=50 && R>=A/4 && R<=A*4)
	{
		var E = G * Evap(Thw, Tcw, Twb);
		var D = G * DR / 100;
		var B = Blowdown(E, D, C);
		var T = E + D + B;
		f.EvapIP.value = fix(E,2);
		f.EvapSI.value = fix(m3h(E),2);
		f.DriftIP.value = fix(D,2);
		f.DriftSI.value = fix(m3h(D),2);
		f.BlowDownIP.value = fix(B,2);
		f.BlowDownSI.value = fix(m3h(B),2);
		f.TotalIP.value = fix(T,2);
		f.TotalSI.value = fix(m3h(T),2);
	}
}

function generateCurves(url, metric)
{
	f = document.forms['WaterUsage'];
	if (url && url.length > 0 && f.EvapIP.value.length > 0)
	{
		var G = parseFloat(f.FlowIP.value);
		var Thw = parseFloat(f.HotWaterIP.value);
		var Tcw = parseFloat(f.ColdWaterIP.value);
		var Twb = parseFloat(f.WetBulbIP.value);
		var DR = parseFloat(f.DriftRate.value);
		var C = parseFloat(f.Conc.value);
		var str = "";
		if (metric)
		{
			str = "?u=SI";
			str += "&flow=" + f.FlowSI.value;
			str += "&hw=" + f.HotWaterSI.value;
			str += "&cw=" + f.ColdWaterSI.value;
			str += "&wb=" + f.WetBulbSI.value;
		}
		else
		{
			str = "?u=IP";
			str += "&flow=" + f.FlowIP.value;
			str += "&hw=" + f.HotWaterIP.value;
			str += "&cw=" + f.ColdWaterIP.value;
			str += "&wb=" + f.WetBulbIP.value;
		}
		str += "&dr=" + f.DriftRate.value;
		str += "&c=" + f.Conc.value;
		window.open(url + str, "_blank");
	}
}


function Fahrenheit(t)
{
	return t*1.8+32;
}

function Celsius(t)
{
	return (t-32)/1.8;
}

function gpm(f)
{
	return f/0.227124707;
}

function m3h(f)
{
	return f*0.227124707;
}

function fix(x, n)
{
	return (new Number(x)).toFixed(n);
}

function Evap(Thw, Tcw, Twb)
{
	var R = Thw - Tcw;
	var LG1 = LG(Thw, Tcw, Twb);
	var Tdb = DryBulb(Twb, 0.5); //assume 50% relative humidity
	var hIn = Enthalpy(Twb, Tdb);
	var Win = HumidityRatio(Twb, Tdb);
	var Wout = Win + 0.0008 * R * LG1;
	var Wprev, hOut, TwbOut;
	for (var i=0; i<5; i++)
	{
		Wprev = Wout;
		hOut = hIn + R * LG1 + (Wout - Win) * (Tcw - 32);
		TwbOut = WetBulb(hOut);
		Wout = HumidityRatio(TwbOut, TwbOut);
		if (Math.abs(Wout-Wprev) <= 0.00001) break;
	}
	return (Wout - Win) / LG1;
}

function Blowdown(Evap, Drift, Conc)
{
	return (Evap - Drift * (Conc-1)) / (Conc-1);
}

function LG(Thw, Tcw, Twb)
{
	var F = Fr(Thw, Tcw, Twb);
	var LG = 1.3 / Math.pow(F, 1.15);
	return LG;
}

function Fr(Thw, Tcw, Twb)
{
	var R = Thw - Tcw;
	var A = Tcw - Twb;
	var Fr = 0.60589436;
	Fr += -0.00562416 * Twb;
	Fr += -0.00002268 * Twb * Twb;
	Fr += 0.04609405 * R;
	Fr += -0.00010031 * Twb * R;
	Fr += -0.00074946 * R * R;
	Fr += -0.06167657 * A;
	Fr += 0.00008363 * Twb * A;
	Fr += 0.0010762 * A * A;
	Fr = Math.pow(10, Fr);
	return Fr;
}

//Psychrometrics
//Reference: 2005 ASHRAE Handbook - Fundamentals

function Enthalpy(Twb, Tdb)
{
	var W = HumidityRatio(Twb, Tdb);
	var h = 0.24 * Tdb + W * (1061 + 0.444*Tdb);
	return h;
}

function HumidityRatio(Twb, Tdb)
{
	var T = Twb + 459.67;
	var pws, Ws, W;
	if (Twb >= 32)
	{
		pws = -1.0440397e4 / T;
		pws += -1.129465e1;
		pws += -2.7022355e-2 * T;
		pws += 1.289036e-5 * T * T;
		pws += -2.4780681e-9 * T * T * T;
		pws += 6.5459673 * Math.log(T);
		pws = Math.exp(pws);
		Ws = 0.62198 * pws / (14.7 - pws);
		W = ((1093-0.556*Twb)*Ws - 0.24*(Tdb-Twb)) / (1093+0.444*Tdb-Twb);
	}
	else
	{
		pws = -1.0214165e4 / T;
		pws += -4.8932428;
		pws += -5.3765794e-3 * T;
		pws += 1.9202377e-7 * T * T;
		pws += 3.5575832e-10 * T * T * T;
		pws += -9.0344688e-14 * T * T * T * T;
		pws += 4.1635019 * Math.log(T);
		pws = Math.exp(pws);
		Ws = 0.62198 * pws / (14.7 - pws);
		W = ((1220-0.036*Twb)*Ws - 0.24*(Tdb-Twb)) / (1220+0.444*Tdb-0.48*Twb);
	}
	return W;
}

function RelativeHumidity(Twb, Tdb)
{
	var W = HumidityRatio(Twb, Tdb);
	var pw = 14.7 * W / (0.62198 + W);
	var Ws = HumidityRatio(Tdb, Tdb);
	var pws = 14.7 * Ws / (0.62198 + Ws);
	return pw / pws;
}

function WetBulb(h)
{
	var Twb = 32;
	var hTest = Enthalpy(Twb, Twb);
	var TwbPrev = Twb
	var hPrev = hTest;

	if (h > 12)
		Twb = 38 * Math.log(h) - 63.5;
	else
		Twb = 2.8 * h - 0.8;

	var n = 0;
	var dhdT, dT;
	for (var i=0; i<10; i++)
	{
		hTest = Enthalpy(Twb, Twb);
		dhdT = (hTest - hPrev) / (Twb - TwbPrev);
		dT = (hTest - h) / dhdT;
		if ((Twb<=32 && Twb-dT>=32) || (Twb>=32 && Twb-dT<=32))
			if (++n > 2) return 32;
		TwbPrev = Twb;
		hPrev = hTest;
		Twb = Twb - dT;
		if (Math.abs(dT) < 0.0005) break;
	}
	return Twb;
}

function DryBulb(Twb, RH)
{
	var Tdb = Twb;
	var RHtest = 1;
	var TdbPrev = Tdb;
	var RHprev = RHtest;

	Tdb = Twb + 0.12*Math.pow(Twb,1.5)*Math.pow(1-RH,2.5);
	var dRHdT, dT;
	for (var i=0; i<10; i++)
	{
		RHtest = RelativeHumidity(Twb, Tdb);
		dRHdT = (RHtest - RHprev) / (Tdb - TdbPrev);
		dT = (RHtest - RH) / dRHdT;
		TdbPrev = Tdb;
		RHprev = RHtest;
		Tdb = Tdb - dT;
		if (Math.abs(dT) < 0.0005) break;
	}
	return Tdb;
}