{ "metadata": { "name": "", "signature": "sha256:8647345ba179ef2ea9d3fa7f02f9c39fe17f9932a98d0fe8ec5f061488b5ae2f" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "heading", "level": 1, "metadata": {}, "source": [ "Chapter 5 : Some Applications of the Laws of Thermodynamics" ] }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.1" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "import math\n", "\n", "# Variables\n", "#Given:\n", "u1 = 1; \t\t\t #entering velocity of water (m/s)\n", "d_ent = 0.2; \t\t\t#entrance diameter of reducer (m)\n", "d_exit = 0.1; \t\t\t#exit diameter of reducer (m)\n", "P_ent = 105; \t\t\t#pressure at entrance (kPa)\n", "z = 5; \t\t\t #distance between entrance and exit (m)\n", "g = 9.81; \t\t\t #acceleration due to gravity \n", "den = 1000; \t\t\t#density of water (kg/m**3)\n", "\n", "# Calculations\n", "#To calculate the pressure at exit\n", "A1 = (math.pi/4)*d_ent**2; \t\t\t #cross section area of entrance (m**2)\n", "A2 = (math.pi/4)*d_exit**2; \t\t\t#cross section area of exit (m**2)\n", "\n", "#By the equation of continuity and since density of water remains constant\n", "u2 = (A1*u1)/A2;\n", "\n", "#By Bernoulli's equation between section 1 and 2 (Eq 5.20 Page no. 118)\n", "P_exit = (-((u2**2-u1**2)/2)-(g*z)+(P_ent*10**3/den))*(den/10**3)\n", "\n", "# Results\n", "print 'The pressure at exit is %f kPa'%P_exit\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The pressure at exit is 48.450000 kPa\n" ] } ], "prompt_number": 23 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.2" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "P = 1000.; \t\t\t#pressure of saturated steam (kPa)\n", "T = 398.; \t\t\t#temperature of escaping steam (K)\n", "\n", "#Referring steam tables\n", "H_vap = 2778.; \t\t\t#enthalpy of saturated vapour at 1000 kPa (kJ/kg)\n", "H_liq = 763.; \t\t\t#enthalpy of saturated liquid at 1000 kPa (kJ/kg)\n", "H_steam = 2726.; \t\t#enthalpy of superheated steam at 398 K (kJ/kg)\n", "H2 = 2726; \t\t\t #[kJ/kg]\n", "\n", "# Calculations\n", "#No work is done and no heat is exchanged between section 1 and 2\n", "#S0% H1 = H2\n", "x = (H2-H_vap)/(H_liq-H_vap)\n", "\n", "# Results\n", "print 'The steam contains %f percent liquid'%(x*100)\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The steam contains 2.580645 percent liquid\n" ] } ], "prompt_number": 24 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.3, Page no:123" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "m = 10.; \t\t\t#mass flow rate of steam (kg/s)\n", "H1 = 3062.; \t\t\t#enthalpy of entering steam (kJ/kg)\n", "H2 = 2875.; \t\t\t#enthalpy of discharged steam (kJ/kg)\n", "Q = -100./m; \t\t\t#heat loss to the surrounding (kJ/kg)\n", "u1 = 0.; \t\t\t#entering velocity of steam\n", "\n", "# Calculations\n", "import math\n", "H = H2-H1;\n", "u2 = math.sqrt((Q-H)*1000*2)\n", "\n", "# Results\n", "print 'The discharge velocity is %i m/s'%u2\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The discharge velocity is 594 m/s\n" ] } ], "prompt_number": 25 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.4, Page no:125" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "To = 600.; \t\t\t#temperature of air (K)\n", "Po = 2000.; \t\t\t#pressure of air (kPa)\n", "gama = 1.4;\n", "M = 0.8; \t\t\t#Mach number at throat\n", "m = 29.; \t\t\t#molecular mass of air\n", "R = 8.314; \t\t\t#ideal gas constant\n", "\n", "#To determine thermodynamical properties at throat and critical pressure\n", "import math\n", "\n", "# Calculations and Results\n", "#(a)\n", "#Using equation 5.40 (Page no 123).. u**2 = (M**2)*gama*P*V\n", "#Substituting this in eq. 5.39 (Page no. 123) and on rearranging we get\n", "P = Po/((1+(((gama-1)/2)*M**2))**(gama/(gama-1)))\n", "#Using eq. 5.39 and the relation PoVo = RTo/m\n", "u = math.sqrt((2*gama*R*To*1000)/(m*(gama-1))*(1-(P/Po)**((gama-1)/gama)))\n", "#Using eq. 3.23 (Page no. 49)\n", "T = To*(P/Po)**((gama-1)/gama)\n", "#Let d be the density\n", "d_o = (Po*m)/(R*To)\n", "#Since P*(V**gama) = P/(den**gama) = constant...so\n", "d = d_o*((P/Po)**(1/gama))\n", "print '(a). At throat'\n", "print 'Pressure = %i kPa'%P\n", "print 'Temperature = %i K'%T\n", "print 'Velocity = %f m/s'%u\n", "print 'Density = %f kg/cubic m'%d\n", "\n", "#(b)\n", "#Using eq. 5.42 (Page no.124)\n", "Pc = Po*((2/(gama+1))**(gama/(gama-1))) \t\t\t#critical pressure\n", "print '(b).'\n", "print 'The critical pressure is %f kPa'%Pc\n", "\n", "\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "(a). At throat\n", "Pressure = 1312 kPa\n", "Temperature = 531 K\n", "Velocity = 369.641813 m/s\n", "Density = 8.603873 kg/cubic m\n", "(b).\n", "The critical pressure is 1056.563575 kPa\n" ] } ], "prompt_number": 26 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.7" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "P1 = 1.; \t\t\t#initial pressure (bar)\n", "T1 = 300.; \t\t\t#initial temperature (K)\n", "P2 = 10.; \t\t\t#final pressure (bar)\n", "gama = 1.3; \t\t\t#gama for CO2\n", "V_rate = 100.; \t\t\t#volumetric flow rate (m**3/h)\n", "\n", "# Calculations and Results\n", "#To calculate work required and temperature after compression\n", "Ws = (gama/(gama-1))*P1*10**5*(V_rate/3600)*(1-(P2/P1)**((gama-1)/gama))\n", "print 'The work required is %f kW'%(-Ws/1000)\n", "\n", "#Using equation 3.23 (Page no.49)\n", "T2 = T1*((P2/P1)**((gama-1)/gama))\n", "print 'Temperature of gas after compression is %f K'%T2\n", "\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The work required is 8.441024 kW\n", "Temperature of gas after compression is 510.376284 K\n" ] } ], "prompt_number": 27 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.8" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "P1 = 100.; \t\t\t#initial pressure of saturated steam (kPa)\n", "P2 = 500.; \t\t\t#final pressure (kPa)\n", "eff = 0.8; \t\t\t#compression efficiency\n", "\n", "#Referring steam tables\n", "#Properties of steam entering the compressor\n", "H1 = 2675.5; \t\t\t#enthalpy (kJ/kg)\n", "S1 = 7.3594; \t\t\t#entropy (kJ/kg K)\n", "\n", "#Properties of compressed steam\n", "H2 = 3008.; \t\t\t#enthalpy (kJ/kg)\n", "S2 = S1; \t\t\t#isentropic compression\n", "\n", "\n", "# Calculations and Results\n", "#To calculate work required and temperature\n", "\n", "Hs = H2-H1;\n", "#Using eq. 5.44 (Page no. 128)\n", "W_isentropic = -Hs;\n", "W_act = W_isentropic/eff;\n", "print 'The work required for compression is %f kJ/kg'%-W_act\n", "\n", "H = Hs/eff; \t\t\t#actual change in enthalpy\n", "H_act = H1+H; \t\t\t#actual enthalpy of steam leaving the compressor\n", "#From steam tables for superheated steam at 500 kPa and enthalpy of H_act\n", "T = 586; \t\t\t#temperature (K)\n", "print 'Temperature of exhaust steam is %i K'%T\n", "\n", "\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The work required for compression is 415.625000 kJ/kg\n", "Temperature of exhaust steam is 586 K\n" ] } ], "prompt_number": 28 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.9" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "T1 = 288.; \t\t\t#temperature of surrounding (K)\n", "T2 = 261.; \t\t\t#temperature of solution (K)\n", "Q2 = 1000.; \t\t\t#heat removed (kJ/min)\n", "\n", "# Calculations\n", "#To determine the least amount of power\n", "#Using eq. 5.57 (Page no. 137)\n", "W = Q2*((T1-T2)/T2 )\t\t\t#power in kJ/min\n", "P = (W*1000)/(746.*60) \t\t\t#power in hp\n", "\n", "# Results\n", "print 'Least amount of power necessary is %f hp'%P" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Least amount of power necessary is 2.311177 hp\n" ] } ], "prompt_number": 29 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.10" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "T = 290.; \t\t\t#operating temperature (K)\n", "W = 1000.; \t\t\t#work (J)\n", "tof = 3516.67; \t\t\t#ton of refrigeration (W)\n", "\n", "# Calculations and Results\n", "#To determine COP, heat rejected and lowest temperature\n", "#(a)\n", "Q2 = tof;\n", "COP = Q2/W; \t\t\t#coeffecient of performance\n", "print '(a). COP is %f'%COP\n", "\n", "#(b)\n", "Q1 = Q2+W; \t\t\t#heat rejected\n", "print ' (b). Heat rejected is %f kW'%(Q1/1000.)\n", "\n", "#(c)\n", "#Let T2 be the lowest temperature\n", "T2 = T*(Q2/Q1);\n", "print ' (c). Lowest possible temperature in refrigerator is %f K'%T2\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "(a). COP is 3.516670\n", " (b). Heat rejected is 4.516670 kW\n", " (c). Lowest possible temperature in refrigerator is 225.793405 K\n" ] } ], "prompt_number": 30 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.11" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "T2 = 266.;\n", "T1 = 300.; \t\t\t#operating temperatures of vapour compression refrigeration cycle(K)\n", "\n", "#To determine COP at given conditions\n", "#(a)\n", "Ha = 656.; \t\t\t#(kJ/kg)\n", "Hb = 724.; \t\t\t#(kJ/kg)\n", "Hd = 144.; \t\t\t#(kJ/kg)\n", "Hc = Hd;\n", "\n", "# Calculations and Results\n", "#Using eq. 5.61 (Page no. 139)\n", "COP = (Ha-Hd)/(Hb-Ha);\n", "print '(a). COP = %f'%COP\n", "\n", "#(b)\n", "Ha = 652.; \t\t\t#(kJ/kg)\n", "Hb = 758.; \t\t\t#(kJ/kg)\n", "Hd = 159.; \t\t\t#(kJ/kg)\n", "Hc = Hd;\n", "eff = 0.75; \t\t\t#efficiency of compressor\n", "COP = (Ha-Hd)/((Hb-Ha)*(1./eff));\n", "print ' (b). COP = %f'%COP\n", "\n", "#(c). Ideal Carnot refrigerator\n", "COP = T2/(T1-T2);\n", "print ' (c). COP = %f'%COP\n", "\n", "\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "(a). COP = 7.529412\n", " (b). COP = 3.488208\n", " (c). COP = 7.823529\n" ] } ], "prompt_number": 31 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.12 " ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "\n", "# Variables\n", "#Given:\n", "Tin_cool = 288.; \t\t\t#entering temperature of cooling water (K)\n", "Tout_cool = 300.; \t\t\t#discharge temperature of cooling water (K)\n", "m_c = 0.25; \t\t\t#mass flow rate of coling water (kg/s)\n", "m = 0.5; \t\t\t#mass flow rate of ammonia (kg/min)\n", "Ha = 1426.; \t\t\t#enthalpy of saturated ammonia vapour at 258 K (kJ/kg)\n", "Hd = 281.5; \t\t\t#enthalpy of liquid ammonia at 294 K (kJ/kg)\n", "eff = 0.9; \t\t\t#compressor efficiency\n", "Cp = 4.2; \t\t\t#specific heat of water (kJ/kg K)\n", "tof = 12660.; \t\t\t#ton of refrigeration (kJ/h)\n", "\n", "# Calculations and Results\n", "#To determine the power requirement and refrigeration capacity in tons\n", "Q1 = m_c*Cp*(Tout_cool-Tin_cool); \t\t\t#heat rejected by compressor at constant pressure (kJ/s)\n", "Q2 = (m/60.)*(Ha-Hd); \t\t\t#heat absorbed (kJ/s)\n", "W = Q1-Q2; \t\t\t#work required (kJ/s)\n", "P = (W*1000)/(eff*746); \t\t\t#power requirement of compressor (hp)\n", "print 'Power requirement of the compressor is %f hp'%P\n", "\n", "rc = Q2*3600/tof; \t\t\t#refrigeration capacity (ton)\n", "print ' Refrigeration capacity is %f ton'%rc\n", "\n", "\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Power requirement of the compressor is 4.561364 hp\n", " Refrigeration capacity is 2.712085 ton\n" ] } ], "prompt_number": 32 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.13" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "m1 = 10.; \t\t\t#machine rating (ton)\n", "#Since 5 K approach is necessary\n", "T1 = 293.+5; \t\t\t#temperature of cooling water (K)\n", "T2 = 261.-5; \t\t\t#temperature of cold storage (K)\n", "Ha = 181.; \t\t\t#enthalpy of saturated vapour at 256 K (kJ/kg)\n", "Sa = 0.714; \t\t\t#entropy of saturated vapour at 256K (kJ/kg K)\n", "Hc = 62.; \t\t\t#enthalpy of saturated liquid at 298 K (kJ/kg)\n", "Sc = 0.231; \t\t\t#entropy of saturated liquid at 298 K (kJ/kg K)\n", "Hb = 206.; \t\t\t#enthalpy of superheated vapour (kJ/kg)\n", "Sb = 0.714; \t\t\t#entropy of superheated vapour (kJ/kg)\n", "\n", "# Calculations and Results\n", "#Combining the three relations, we get\n", "Sd = Sc; \t\t\t#isentropic process\n", "Hd = Ha-(T2*(Sa-Sd));\n", "\n", "#Using eq. 5.64 (Page no. 141)\n", "COP = (Ha-Hd)/((Hb-Hc)-(Ha-Hd));\n", "print 'COP = %f'%COP\n", "\n", "#Using equation 5.63 (Page no. 140)\n", "m = (12660*m1)/(Ha-Hd); \t\t\t#refrigerant circulation rate (kg/h)\n", "print ' Refrigerant circulation rate is %f kg/h'%m\n", "\n", "\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "COP = 6.075472\n", " Refrigerant circulation rate is 1023.874224 kg/h\n" ] } ], "prompt_number": 33 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.14" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "m1 = 10.; \t\t\t#machine rating (ton)\n", "#Assuming 5 K approach in refrigerator and cooler\n", "Ta = 261.-5; \t\t\t#temperature of air leaving the refrigerator (K)\n", "Tc = 293.+5; \t\t\t#temperature of air leaving the cooler (K)\n", "gama = 1.4;\n", "Cp = 1.008; \t\t\t#sp. heat of air (kJ/kg K)\n", "P1 = 4.052;\n", "P2 = 1.013; \t\t\t#operating pressures in bar\n", "\n", "# Calculations and Results\n", "#To determine the COP and air circulation rate\n", "#Using eq. 5.66 (Page no. 145)\n", "Tb = Ta*(P1/P2)**((gama-1)/gama)\n", "Td = (Tc*Ta)/Tb;\n", "\n", "#Using equation 5.68 (PAge no. 146)\n", "COP = Ta/(Tb-Ta)\n", "print 'COP = %f'%COP\n", "\n", "#Considering energy balance in refrigerator [m*Cp*(Ta-Td) = m1*12660]\n", "m = (m1*12660)/(Cp*(Ta-Td)) \t\t\t#air circulation rate (kg/h)\n", "print ' Air circulation rate is %i kg/h'%m\n", "\n", "\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "COP = 2.057637\n", " Air circulation rate is 2264 kg/h\n" ] } ], "prompt_number": 34 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.15" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "T1 = 300.; \t\t\t#indoor temperatur (K)\n", "T2 = 290.; \t\t\t#outside temperature (K)\n", "W_input = 1.; \t\t\t#1 kW heat pump\n", "W_output = 30.; \t\t\t#given output (kW)\n", "\n", "# Calculations and Results\n", "#To verify that given heat pump is equivalent to 30 kW heater\n", "Q2 = (T2/(T1-T2))*W_input; \t\t\t#heat absorbed\n", "Q1 = Q2 + W_input; \t\t\t#heat rejected\n", "\n", "if(Q1==W_output):\n", " print '1 kW pump if operated reversibly% is equivalent to a 30 kW heater'\n", "else:\n", " print 'The given heat pump is not equivalent to a 30 kW heater'\n", "\n", "\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "1 kW pump if operated reversibly% is equivalent to a 30 kW heater\n" ] } ], "prompt_number": 35 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.16" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "T1 = 295.; \t\t\t#temperature inside building (K)\n", "T2 = 275.; \t\t\t#temperature of outside air (K)\n", "eff = 0.25; \t\t\t#overall efficiency of unit\n", "Hc = 890.9; \t\t\t#heat of combustion of fuel (kJ/mol)\n", "conv = 0.33; \t\t\t#efficiency of conversion of heat of combustion to electricity\n", "Q1 = 10**6; \t\t\t#amount of heat to be delivered\n", "\n", "# Calculations\n", "#To determine the amount of fuel burned\n", "COP = T1/(T1-T2)\n", "W = Q1/COP; \t\t\t#work required to deliver Q1 kJ of heat\n", "W_act = W/eff; \t\t\t#actual amount of electrical energy to be supplied\n", "W_heat = W_act/conv; \t\t\t#heat energy required as heat of combustion\n", "n = W_heat/Hc; \t\t\t#number of moles of fuel burned\n", "\n", "# Results\n", "print 'The amount of fuel burned is %f kmol'%(n/1000)\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The amount of fuel burned is 0.922412 kmol\n" ] } ], "prompt_number": 36 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.17" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "#Referring steam tables at 2.54 bar\n", "H1 = 2717.; \t\t\t#enthalpy of saturated vapour (kJ/kg)\n", "H2 = 538.; \t\t\t#enthalpy of saturated liquid (kJ/kg)\n", "S1 = 7.05; \t\t\t#entropy of saturated vapour (kJ/kg K)\n", "S2 = 1.61; \t\t\t#entropy of saturated liquid (kJ/kg K)\n", "\n", "H = 2700.; \t\t\t#enthalpy of superheated steam at 1 bar and 385 K (kJ/kg)\n", "S = 7.42; \t\t\t#entropy of superheated steam at 1 bar and 385 K (kJ/kg K)\n", "\n", "# Calculations and Results\n", "x = (H-H1)/(H2-H1)\n", "#From steam tables\n", "T = 401.; \t\t\t#temperature of steam (K)\n", "print '(a). For isenthalpic math.expansion'\n", "print ' The fraction of liquid in inlet stream is %f'%x\n", "print ' The temperature of stream is %i K'%T\n", "\n", "#(b)..The math.expansion is isentropic\n", "#Since entropy of saturated vapour at inlet pressure (S1) is less than entropy of steam leaving the turbine (S)\n", "#So% the inlet stream is superheated% therefore\n", "x = 0;\n", "#From steam tales\n", "T = 478.; \t\t\t#temperature of superheated steam having entropy of 7.42 kJ/kg K\n", "print '(b). For isentropic math.expansion'\n", "print ' The fraction of liquid in inlet stream is %i'%x\n", "print ' The temperature of stream is %i K'%T\n", "\n", "\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "(a). For isenthalpic math.expansion\n", " The fraction of liquid in inlet stream is 0.007802\n", " The temperature of stream is 401 K\n", "(b). For isentropic math.expansion\n", " The fraction of liquid in inlet stream is 0\n", " The temperature of stream is 478 K\n" ] } ], "prompt_number": 37 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.18" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "#Referring Fig. 5.15 (Page no. 151)\n", "Hc = 516.; \t\t\t#enthalpy of high pressure gas at 120 bar and 306 K (kJ/kg)\n", "Ha = 526.; \t\t\t#enthalpy of low pressure gas at 2 bar and 292 K (kJ/kg)\n", "Hf = 121.; \t\t\t#entalpy of saturated liquid at 2 bar (kJ/kg)\n", "Hg = 314.; \t\t\t#enthalpy of saturated vapour at 2 bar (kJ/kg)\n", "\n", "#To determine the fraction of air liquified and temperature of air\n", "\n", "# Calculations and Results\n", "#(a)..\n", "#Using equation 5.73 (Page no. 152)\n", "x = (Hc-Ha)/(Hf-Ha) \t\t\t#fraction of air liquified\n", "print '(a). The fraction of liquified air is %f'%x\n", "\n", "#(b)..\n", "#Taking enthalpy balance around heat exchanger\n", "Hd = Hc - (1-x)*(Ha-Hg)\n", "#At enthalpy of Hd kJ/kg% from T-S diagram for air\n", "T = 167.; \t\t\t#temperature in K\n", "print ' (b). Temperature of air on high pressure side of throttle valve is %i K'%T\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "(a). The fraction of liquified air is 0.024691\n", " (b). Temperature of air on high pressure side of throttle valve is 167 K\n" ] } ], "prompt_number": 38 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.19" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "P2 = 2800.; \t\t\t#pressure of superheated steam (kPa)\n", "P1 = 5.; \t\t\t#pressure after math.expansion (kPa)\n", "e_turbine = 0.85; \t\t\t#isentropic turbine efficiency\n", "e_pump = 0.8; \t\t\t#isentropic pump efficiency\n", "V = 1.005*10**-3; \t\t\t#specific volume of saturated liquid at 5 kPaHl = \n", "\n", "#From steam tables:\n", "Hl = 138.; \t\t\t#enthalpy of saturated liquid at 5 kPa (kJ/kg)\n", "Hv = 2562.; \t\t\t#enthalpy of saturated vapour at 5 kPa (kJ/kg)\n", "H3 = 3063.; \t\t\t#enthalpy of superheated steam at 2800 kPa and 598 K (kJ/kg)\n", "Sl = 0.4764; \t\t\t#entropy of saturated liquid at 5 kPa (kJ/kg K)\n", "Sv = 8.3951; \t\t\t#entropy of saturated vapour at 5 kPa (kJ/kg K)\n", "S3 = 6.6875; \t\t\t#entropy of superheated steam at 2800 kPa and 598 K (kJ/kg K)\n", " \n", "\n", "# Calculations and Results\n", "#To determine the ideal Rankine cycle efficiency% thermal efficiency and rate of steam production\n", "\n", "#(a)..The ideal Rankine cycle efficiency for the stated conditions\n", "#Referring fig 5.19(b) (Page no. 155) and considering feed water pump\n", "Ws = V*(P2-P1) \t\t\t#work done by pump (kJ/kg)\n", "H2 = Hl+Ws;\n", "#Considering isentropic math.expansion in turbine\n", "S4 = S3;\n", "x = (S4-Sl)/(Sv-Sl) \t\t\t#fraction of steam that is vapour\n", "H4 = Hl + x*(Hv-Hl)\n", "\t\t\t#Using eq. 5.80 (Page no. 155)\n", "e_r = ((H3-H2)-(H4-Hl))/(H3-H2)\n", "print '(a). The ideal Rankine cycle efficiency for the stated conditions is %i percent'%(e_r*100)\n", "\n", "#(b)..The thermal efficiency of plant\n", "W_act = Ws/e_pump; \t\t\t#actual work requirement in pump\n", "H_2 = Hl + W_act; \t\t\t#enthalpy of water leaving the feed water pump\n", "W_out = e_turbine*(H3-H4) \t\t\t#actual work output\n", "H_4 = H3-W_out; \t\t\t#actual enthalpy of steam leaving the turbine\n", "e_act = ((H3-H_2)-(H_4-Hl))/(H3-H_2)\n", "print ' (b). The actual efficiency is %f percent'%(e_act*100)\n", "\n", "#(c)..The rate of steam production\n", "W_net = e_act*(H3-H_2) \t\t\t#net work output (kJ/kg)\n", "rate = (3.6*10**6)/W_net; \t\t\t#steam produced in boiler (kg/h)\n", "print ' (c). The rate of steam production is %f kg/h'%(rate)\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "(a). The ideal Rankine cycle efficiency for the stated conditions is 34 percent\n", " (b). The actual efficiency is 29.664548 percent\n", " (c). The rate of steam production is 4153.943111 kg/h\n" ] } ], "prompt_number": 39 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.20" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "P2 = 7600.; \t\t\t#pressure of superheated steam (kPa)\n", "P1 = 5.; \t\t\t#pressure after math.expansion (kPa)\n", "V = 1.005*10**-3; \t\t\t#specific volume of saturated liquid (m**3/kg)\n", "\n", "#From steam tables:\n", "H_l1 = 138.; \t\t\t#enthalpy of saturated liquid at 5 kPa (kJ/kg)\n", "S_l1 = 0.4764; \t\t\t#entropy of saturated liquid at 5 kPa (kJ/kg K)\n", "H_v1 = 2562.; \t\t\t#enthalpy of saturated vapour at 5 kPa (kJ/kg)\n", "S_v1 = 8.3951; \t\t\t#entropy of saturated vapour at 5 kPa (kJ/kg K)\n", "H_l2 = 830.; \t\t\t#enthalpy of saturated liquid at 1400 kPa(kJ/kg)\n", "S_l2 = 2.2842; \t\t\t#entropy of saturated liquid at 1400 kPa (kJ/kg K)\n", "H_v2 = 2790.; \t\t\t#enthalpy of saturated vapour at 1400 kPa (kJ/kg)\n", "S_v2 = 6.4693; \t\t\t#entropy of saturated vapour at 1400 kPa (kJ/kg K)\n", "H5 = 3226.; \t\t\t#enthalpy of superheated steam at 1400 kPa and 658 K\n", "S5 = 7.2558; \t\t\t#entropy of superheated steam at 1400 kPa and 658 K\n", "H3 = 3150.; \t\t\t#enthalpy of superheated steam at 7600 kPa and 673 K\n", "S3 = 6.4022; \t\t\t#entropy of superheated steam at 1400 kPa and 673 K\n", "\n", "# Calculations and Results\n", "#Let the fraction of steam in vapour state be x\n", "S4 = S3; \t\t\t#as the math.expansion process is isentropic\n", "x = (S4-S_l2)/(S_v2-S_l2)\n", "H4 = H_l2 + x*(H_v2-H_l2)\n", "W_high = H3-H4;\n", "\n", "#For low pressure turbine\n", "S6 = S5; \t\t\t#isentropic math.expansion\n", "x = (S6-S_l1)/(S_v1-S_l1)\n", "H6 = H_l1 + x*(H_v1-H_l1)\n", "W_low = H5-H6;\n", "\n", "print '(a)'\n", "print ' The work output of high pressure turbine is %i kJ/kg'%W_high\n", "print ' The work output of low pressure turbine is %i kJ/kg'%W_low\n", "\n", "#(b)\n", "#Work output of feed pump is [-Ws = intg(VdP)]\n", "Ws = V*(P2-P1)\n", "H2 = H_l1+Ws;\n", "#Using eq. 5.82 (Page no. 159)\n", "eff = ((H3-H2)+(H5-H4)-(H6-H_l1))/((H3-H2)+(H5-H4))\n", "print ' (b)'\n", "print ' Thermal efficiency is %f percent'%(eff*100)\n", "\n", "#(c)\n", "#The numerator of eq. 5.82 gives net work output\n", "W_net = (H3-H2)+(H5-H4)-(H6-H_l1)\n", "#For 1000 kW of net work output\n", "rate = 3.6*10**6/W_net;\n", "print ' (c)'\n", "print ' The rate of steam circulation is %f kg/h'%rate\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "(a)\n", " The work output of high pressure turbine is 391 kJ/kg\n", " The work output of low pressure turbine is 1012 kJ/kg\n", " (b)\n", " Thermal efficiency is 40.225451 percent\n", " (c)\n", " The rate of steam circulation is 2577.792156 kg/h\n" ] } ], "prompt_number": 40 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.21" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "P2 = 2800.; \t\t\t#pressure of superheated steam (kPa)\n", "P1 = 275.; \t\t\t#pressure of withdrawn steam (kPa)\n", "V = 1.070*10**-3; \t\t\t#specific volume of saturated liquid at 275 kPa\n", "\n", "#From steam tables:\n", "H6 = 138.; \t\t \t#enthalpy of saturated liquid at 5 kPa\n", "S6 = 0.4764; \t\t\t#entropy of saturated liquid at 5 kPa\n", "H_v1 = 2562.; \t\t\t#enthalpy of saturated vapour at 5 kPa\n", "S_v1 = 8.3951; \t\t\t#entropy of saturated vapour at 5 kPa\n", "H1 = 549.; \t\t\t #enthalpy of saturated liquid at 275 kPa\n", "S1 = 1.6408; \t\t\t#entropy of saturated liquid at 275 kPa\n", "H_v2 = 2721.; \t\t\t#enthalpy of saturated vapour at 275 kPa\n", "S_v2 = 7.0209; \t\t\t#entropy of saturated vapour at 275 kPa\n", "H3 = 3063.; \t\t\t#enthalpy of superheated steam at 2800 kPa and 598 K\n", "S3 = 6.6875; \t\t\t#entropy of superheated steam at 2800 kPa and 598 K\n", "\n", "# Calculations and Results\n", "#To determine the fraction of steam withdrawn and thermal efficiency of cycle\n", "#Referring fig. 5.23 (Page no.161)\n", "S4 = S3; \t\t\t#isentropic math.expansion\n", "x = (S4-S1)/(S_v2-S1) \t\t\t#quality of steam\n", "H4 = H1 + x*(H_v2-H1)\n", "H7 = H6; \t\t\t #as the power input to the condensate pump is neglegible\n", "\n", "#Applying energy balance around feed water heater\n", "m = (H1-H7)/(H4-H7 )\t\t\t#fraction of steam extracted\n", "print 'Fraction of steam withdrawn is %f'%m\n", "\n", "W_in = V*(P2-P1) \t\t\t#work input to the feed water pump\n", "H2 = H1+W_in;\n", "#Considering isentropic math.expansion in turbine\n", "S5 = S3;\n", "x = (S5-S6)/(S_v1-S6)\n", "H5 = H6 + x*(H_v1-H6)\n", "#Using eq. 5.85 (Page no.162)\n", "eff = ((H3-H2)-(1-m)*(H5-H6))/(H3-H2)\n", "print ' Thermal efficiency is %f percent'%(eff*100)\n", "\n", "\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Fraction of steam withdrawn is 0.167865\n", " Thermal efficiency is 36.999645 percent\n" ] } ], "prompt_number": 41 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.22" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "r = 8.; \t\t\t#compression ratio\n", "T1 = 290.; \t\t\t#temperature at beginning (K)\n", "P1 = 100.; \t\t\t#pressure at the beginning (kPa)\n", "Q1 = 450.; \t\t\t#heat transferred per cycle (kJ/kg K)\n", "Cp = 1.005; \t\t\t#specific heat of air (kJ/kg K)\n", "Cv = 0.718; \t\t\t#specific heat of air (kJ/kg K)\n", "R = 8.314; \t\t\t#ideal gas constant\n", "M = 29.; \t\t\t#molecular wt of air\n", "\n", "#To determine mean effective pressure\n", "#Basis:\n", "m = 1.; \t\t\t#mass of air (kg)\n", "\n", "# Calculations and Results\n", "#(a)\n", "#Referring fig. 5.24 (Page no. 164)\n", "V1 = (m*R*1000*T1)/(M*P1*10**3)\n", "\n", "#Conditions at state 2\n", "V2 = V1/r;\n", "gama = Cp/Cv;\n", "T2 = T1*(r**(gama-1))\n", "P2 = P1*(r**gama )\n", "print '(a)'\n", "print ' At the end of first process'\n", "print ' Temperature = %f K'%T2\n", "print ' Pressure = %f kPa'%P2\n", "\n", "#Conditions at state 3\n", "#Constant volume process\n", "V3 = V2;\n", "T3 = Q1/Cv + T2;\n", "P3 = (T3/T2)*P2;\n", "print ' At the end of second process'\n", "print ' Temperature = %f K'%T3\n", "print ' Pressure = %f kPa'%P3\n", "\n", "#Conditions at state 4\n", "T4 = T3/(r**(gama-1))\n", "P4 = P3/(r**gama)\n", "print ' At the end of third process'\n", "print ' Temperature = %f K'%T4\n", "print ' Pressure = %f kPa'%P4\n", "Q2 = Cv*(T4-T1) \t\t\t#heat rejected during the constant volume process\n", "\n", "#(b)\n", "#Using eq. 5.88 (Page no. 165)\n", "eff = 1 - ((1./r)**(gama-1))\n", "print ' (b)'\n", "print ' Thermal efficiency is %f'%eff\n", "\n", "#(c)\n", "W = Q1-Q2; \t\t\t#work done\n", "print ' (c)'\n", "print ' Work done is %f kJ/kg'%W\n", "\n", "#(d)\n", "Pm = W/(V1-V2)\n", "print ' (d)'\n", "print ' Mean effective pressure is %f kPa'%Pm\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "(a)\n", " At the end of first process\n", " Temperature = 665.859247 K\n", " Pressure = 1836.853096 kPa\n", " At the end of second process\n", " Temperature = 1292.600195 K\n", " Pressure = 3565.793640 kPa\n", " At the end of third process\n", " Temperature = 562.962905 K\n", " Pressure = 194.125140 kPa\n", " (b)\n", " Thermal efficiency is 0.564473\n", " (c)\n", " Work done is 254.012634 kJ/kg\n", " (d)\n", " Mean effective pressure is 349.170259 kPa\n" ] } ], "prompt_number": 42 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.23" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "r = 15.; \t\t\t#compression ratio\n", "P1 = 100.; \t\t\t#pressure in the beginning (kPa)\n", "T1 = 300.; \t\t\t#temperature in thebeginning (K)\n", "Q1 = 500.; \t\t\t#heat transfer rate (kJ/kg)\n", "M = 29.; \t\t\t#molecular wt of air\n", "R = 8.314; \t\t\t#ideal gas constant\n", "gama = 1.3997214\n", "#Specific heats of air (kJ/kg K)\n", "Cp = 1.005;\n", "Cv = 0.718;\n", "\n", "# Calculations and Results\n", "#To determine work done thermal efficiency and mean effective pressure\n", "#(a)\n", "#Isentropic compression 1-2\n", "V1 = (R*1000*T1)/(M*P1*10**3)\n", "T2 = T1*r**(gama-1)\n", "P2 = P1*r**gama;\n", "V2 = V1/r;\n", "print '(a)'\n", "print ' At the end of first process'\n", "print ' Temperature = %f K'%T2\n", "print ' Pressure = %f kPa'%P2\n", "\n", "#Consatnt pressure heat addition 2-3\n", "T3 = Q1/Cp + T2;\n", "V3 = (T3/T2)*V2;\n", "P3 = P2;\n", "print ' At the end of second process'\n", "print ' Temperature = %f k'%T3\n", "print ' Pressure = %f kPa'%P3\n", "\n", "#Isentropic math.expansion 3-4\n", "V4 = V1;\n", "T4 = T3/((V4/V3)**(gama-1))\n", "P4 = P3*((V3/V4)**gama)\n", "print ' At the end of third process'\n", "print ' Temperature = %f K'%T4\n", "print ' Pressure = %f kPa'%P4\n", "Q2 = Cv*(T4-T1) \t\t\t#heat rejected 4-1\n", "\n", "#(b)\n", "Wnet = Q1-Q2;\n", "print ' (b)'\n", "print ' Net work done per cycle per kg air is %f kJ/kg'%Wnet\n", "\n", "#(c)\n", "eff = Wnet/Q1; \t\t\t#thermal efficiency\n", "print ' (c)'\n", "print ' Thermal efficiency is %f'%eff\n", "\n", "#(d)\n", "Pm = Wnet/(V1-V2) \t\t\t#mean effective pressure\n", "print ' (d)'\n", "print ' Mean effective pressure is %f kPa'%Pm\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "(a)\n", " At the end of first process\n", " Temperature = 885.584689 K\n", " Pressure = 4427.923445 kPa\n", " At the end of second process\n", " Temperature = 1383.097127 k\n", " Pressure = 4427.923445 kPa\n", " At the end of third process\n", " Temperature = 559.936687 K\n", " Pressure = 186.645562 kPa\n", " (b)\n", " Net work done per cycle per kg air is 313.365459 kJ/kg\n", " (c)\n", " Thermal efficiency is 0.626731\n", " (d)\n", " Mean effective pressure is 390.374167 kPa\n" ] } ], "prompt_number": 43 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.24" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "#Given:\n", "T1 = 300.; \t\t\t#initial temperature (K)\n", "P1 = 100.; \t\t\t#initial pressure (kPa)\n", "T3 = 1200.; \t\t\t#max temperature (K)\n", "P3 = 500.; \t\t\t#max pressure (kPa)\n", "Cp = 1.005; \t\t\t#(kJ/kg K)\n", "Cv = 0.718; \t\t\t#(kJ/kg K)\n", "\n", "# Calculations and Results\n", "#To determine pressure and temperature work and thermal efficiency\n", "gama = Cp/Cv;\n", "\n", "#(a)\n", "P4 = P1;\n", "P2 = P3;\n", "#Isentropic compression 1-2\n", "T2 = T1*((P2/P1)**((gama-1)/gama))\n", "print '(a)'\n", "print ' At the end of first process'\n", "print ' Temperature = %f K'%T2\n", "print ' Pressure = %f kPa'%P2\n", "\n", "#Process 2-3\n", "print ' At the end of second process'\n", "print ' Temperature = %f K'%T3\n", "print ' Pressure = %f kPa'%P3\n", "\n", "#Isentropic math.expansion 3-4\n", "T4 = T3/((P3/P4)**((gama-1)/gama))\n", "print ' At the end of third process'\n", "print ' Temperature = %f K'%T4\n", "print ' Pressure = %f kPa'%P4\n", "\n", "#(b)\n", "W_comp = Cp*(T2-T1) \t\t\t#work required by compressor\n", "print ' (b)'\n", "print ' Work required by compressor is %f kJ/kg'%W_comp\n", "\n", "#(c)\n", "W_turb = Cp*(T3-T4 )\t\t\t#work done by turbine\n", "print ' (c)'\n", "print ' Work done by turbine is %f kJ/kg'%W_turb\n", "\n", "#(d)\n", "eff = 1-(P1/P2)**((gama-1)/gama)\n", "print ' (d)'\n", "print ' Thermal efficiency is %f'%eff\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "(a)\n", " At the end of first process\n", " Temperature = 475.037193 K\n", " Pressure = 500.000000 kPa\n", " At the end of second process\n", " Temperature = 1200.000000 K\n", " Pressure = 500.000000 kPa\n", " At the end of third process\n", " Temperature = 757.835397 K\n", " Pressure = 100.000000 kPa\n", " (b)\n", " Work required by compressor is 175.912379 kJ/kg\n", " (c)\n", " Work done by turbine is 444.375426 kJ/kg\n", " (d)\n", " Thermal efficiency is 0.368471\n" ] } ], "prompt_number": 44 } ], "metadata": {} } ] }