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 {
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	   "source": [
       "# Chapter 19: Psychrometry"
	   ]
	},
{
		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 19.1: moisture_content.sce"
		   ]
		  },
  {
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"source": [
"clear;\n",
"clc;\n",
"disp('Example 19.1');\n",
"\n",
"// aim : To compare the moisture content and the true specific volumes of  atmosphere air \n",
"// (a) temperature is 12 C and the air is saturaded\n",
"// (b) temperature is 31 C and air is .75 saturated\n",
"\n",
"// Given values\n",
"P_atm = 101.4;// atmospheric pressure, [kN/m^2]\n",
"R = .287;// [kJ/kg K]\n",
"\n",
"// solution\n",
"// (a)\n",
"T = 273+12;// air temperature, [K]\n",
"// From steam table at 12 C\n",
"p = 1.4;// [kN/m^2]\n",
"vg = 93.9;// [m^3/kg]\n",
"pa = P_atm-p;// partial pressure of the dry air, [kN/m^2]\n",
"va = R*T/pa;// [m^3/kg]\n",
"\n",
"mw = va/vg;// mass of water vapor in the air,[kg]\n",
"v = va/(1+mw);// specific volume of humid air, [m^3/kg]\n",
"\n",
"mprintf('\n (a) The mass of water vapor in the humid air is  =  %f  kg\n',mw);\n",
"mprintf('\n      The specific volume of humid air is  =  %f m^3/kg\n',v);\n",
"\n",
"// (b)\n",
"x = .75;// dryness fraction\n",
"T = 273+31;// air temperature, [K]\n",
"// From steam table\n",
"p = 4.5;// [kN/m^2]\n",
"vg = 31.1;// [m^3/kg]\n",
"pa = P_atm-p;// [kN/m^2]\n",
"va = R*T/pa;// [m^3/kg]\n",
"mw1= va/vg;// mass of water vapor in the air, [kg]\n",
"mw_actual = mw1*x;// actual mass of vapor, [kg]\n",
"v = va/(1+mw_actual);// true specific volume of humid air,[m^3/kg] \n",
"\n",
"mprintf('\n (b) The mass of water vapor in the humid air is  =  %f  kg\n',mw1);\n",
"mprintf('\n     The specific volume of humid air is  =  %f  m^3/kg\n',v);\n",
"\n",
"ewv = mw_actual/mw ;\n",
"mprintf('\n On the warm day the air conteains %f  times the mass of water vapor as on the cool day \n',ewv);\n",
"\n",
"//  End"
   ]
   }
,
{
		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 19.2: partial_pressures_specific_humidity_and_composition.sce"
		   ]
		  },
  {
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	   "metadata": {
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"source": [
"clear;\n",
"clc;\n",
"disp('Example 19.2');\n",
"\n",
"// aim : To determine\n",
"// (a) the partial pressures of the vapor and the dry air\n",
"// (b) the specific humidity of the mixture\n",
"// (c) the composition of the mixture\n",
"\n",
"//  Given values\n",
"phi = .65;// Relative humidity\n",
"T = 2733+20;// temperature, [K]\n",
"p = 100;// barometric pressure, [kN/m^2]\n",
"\n",
"// solution\n",
"// (a)\n",
"//  From the steam table at 20 C\n",
"pg = 2.34;// [kN/m^2]\n",
"ps = phi*pg;// partial pressure of vapor, [kN/m^2]\n",
"pa = p-ps;// partial pressure of dry air, [kN/m^2]\n",
"mprintf('\n (a) The partial pressure of vapor is  =  %f  kN/m^2\n',ps);\n",
"mprintf('\n     The partial pressure of dry air is  =  %f kN/m^2\n',pa);\n",
"\n",
"// (b)\n",
"// from equation [15]\n",
"omega = .622*ps/(p-ps);// specific humidity of the mixture\n",
"mprintf('\n (b) The specific humidity of the mixture is  =  %f kg/kg dry air\n',omega);\n",
"\n",
"// (c)\n",
"// using eqn [1] from section 19.2\n",
"y = 1/(1+omega);// composition of the mixture\n",
"mprintf('\n (c) The composition of the mixture is  =  %f\n',y);\n",
"\n",
"// End"
   ]
   }
,
{
		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 19.3: specific_humidity_dew_point_degree_of_superheat_mass_of_condensate.sce"
		   ]
		  },
  {
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	   "outputs": [],
"source": [
"clear;\n",
"clc;\n",
"disp('Example 19.3');\n",
"\n",
"// aim : To determine\n",
"// (a) the specific humidity\n",
"// (b) the dew point\n",
"// (c) the degree of superheat of the superheated vapor\n",
"// (d) the mass of condensate formed per kg of dry air if the moist air is cooled to 12 C\n",
"\n",
"// Given values\n",
"t = 25;// C\n",
"T = 273+25;// moist air temperature, [K]\n",
"phi = .6;// relative humidity\n",
"p = 101.3;// barometric pressure, [kN/m^2]\n",
"R = .287;// [kJ/kg K]\n",
"\n",
"// solution\n",
"// (a)\n",
"// From steam table at 25 C\n",
"pg = 3.17;// [kN/m^2]\n",
"ps = phi*pg;// partial pressure of the vapor, [kN/m^2]\n",
"omega = .622*ps/(p-ps);// the specific humidity of air\n",
"\n",
"mprintf('\n (a) The specific humidity is  =  %f  kg/kg air\n',omega);\n",
"\n",
"// (b)\n",
"// Dew point is saturated temperature at ps is,\n",
"t_dew = 16+2*(1.092-1.817)/(2.062-1.817);// [C]\n",
"mprintf('\n (b) The dew point is  =  %f C\n',t_dew);\n",
"\n",
"// (c)\n",
"Dos = t-t_dew;// degree of superheat, [C]\n",
"mprintf('\n (c) The degree of superheat is  =  %f C\n',Dos);\n",
"\n",
"// (d)\n",
"// at 25 C\n",
"pa = p-ps;// [kN/m^2]\n",
"va = R*T/pa;// [m^3/kg]\n",
"// at 16.69 C\n",
"vg = 73.4-(73.4-65.1)*.69/2;// [m^3/kg]\n",
"ms1= va/vg; \n",
"// at 12 C\n",
"vg = 93.8;// [m^3/kg]\n",
"ms2 = va/vg;\n",
"\n",
"m = ms1-ms2;// mas of condensate\n",
"mprintf('\n (d) The mass of condensate is  =  %f  kg/kg dry air\n',m);\n",
"\n",
"//  there is calculation mistake in the book so answer is no matching\n",
"\n",
"//  End"
   ]
   }
,
{
		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 19.4: volume_mass_and_heat_transfer.sce"
		   ]
		  },
  {
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"clear;\n",
"clc;\n",
"disp(' Example 19.4');\n",
"\n",
"// aim : To determine\n",
"// (a) the volume of external saturated air\n",
"// (b) the mass of air\n",
"// (c) the heat transfer\n",
"// (d) the heat transfer required by the combind water vapour\n",
"\n",
"// given values\n",
"Vb = 56000;// volume of building, [m^3]\n",
"T2 = 273+20;// temperature of air in thebuilding, [K]\n",
"phi = .6;// relative humidity\n",
"T1 = 8+273;// external air saturated temperature, [K]\n",
"p0 = 101.3;// atmospheric pressure, [kN/m^2]\n",
"cp = 2.093;// heat capacity of saturated steam, [kJ/kg K]\n",
"R = .287;// gas constant, [kJ/kg K]\n",
"\n",
"// solution\n",
"// from steam table at 20 C saturation pressure of steam is,\n",
"pg = 2.34;// [kN/m^2]\n",
"\n",
"// (a)\n",
"pvap = phi*pg;// partial pressure of vapor, [kN/m^2] \n",
"P = p0-pvap;// partial pressure of air, [kN/m^2]\n",
"V = 2*Vb;// air required, [m^3]\n",
"// at 8 C saturation pressure ia\n",
"pvap = 1.072;// [kN/m^2]\n",
"P2 = p0-pvap;// partial pressure of entry at 8 C, [kN/m^2]\n",
"\n",
"// using P1*V1/T1=P2*V2/T2;\n",
"V2 = P*V*T1/(T2*P2);// air required at 8 C, [m^3/h]\n",
"mprintf('\n (a) The volume of air required is  =  %f  m^3/h\n',V2);\n",
"\n",
"// (b)\n",
"//  assuming\n",
"pg = 1.401;// pressure, [kN/m^2]\n",
"Tg = 273+12;// [K]\n",
"vg = 93.8;// [m^3/kg]\n",
"// at constant pressure\n",
"v = vg*T2/Tg;// volume[m^3/kg]\n",
"mv = V/v;// mass of vapor in building at 20 C, [kg/h]\n",
"// from steam table at 8 C\n",
"vg2 = 121;// [m^3/kg]\n",
"mve = V2/vg2;// mass of vapor supplied with saturated entry air, [kg/h]\n",
"mw = mv-mve;// mass of water added, [kg/h]\n",
"mprintf('\n (b) The mass of water added is  =  %f  kg/h\n ',mw);\n",
"\n",
"// (c)\n",
"// for perfect gas\n",
"m = P2*V2/(R*T1);// [kg/h]\n",
"Cp = .287;// heat capacity, [kJ/kg K]\n",
"Q = m*Cp*(T2-T1);// heat transfer by dry air,[kJ/h]\n",
"mprintf('\n (c) The heat transfer required by dry air is  =  %f MJ/h\n',Q*10^-3);\n",
"\n",
"// (d)\n",
"// from steam table\n",
"h1 = 2516.2;// specific enthalpy of saturated vapor at 8 C,[kJ/kg]\n",
"hs = 2523.6;// specific enthalpy of saturated vapor at 20 C, [kJ/kg]\n",
"h2 = hs+cp*(T2-T1);// specific enthalpy of vapor at 20 c, [kJ/kg]\n",
"Q1 = mve*(h2-h1);// heat transfer required for vapor, [kJ]\n",
"\n",
"// again from steam table\n",
"hf1 = 33.6;// [kJ/kg]\n",
"hg3 = 2538.2;// [kJ/kg]\n",
"Q2 = mw*(hg3-hf1);// heat transfer required for water, [kJ/h]\n",
"Qt = Q1+Q2;// total heat transfer, [kJ/h]\n",
"mprintf('\n (d) The heat transferred required for vapor+supply water is  =  %f  MJ/h\n',Qt*10^-3);\n",
"\n",
"//  there is minor variation in the answer reported in the book\n",
"\n",
"//  End"
   ]
   }
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