{ "metadata": { "name": "" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "heading", "level": 1, "metadata": {}, "source": [ "Chapter 5 : Second law of thermodynamics and its applications" ] }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.2 Page No : 161" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "import math \n", "\n", "# Variables\n", "Q = 1000.;\t\t \t #amount of energy absorbed by the heat engine in kJ/s\n", "W = 650.;\t\t\t #work delivered by the heat engine in kW\n", "T_source = 500. \t\t #temperature of the source in degree celsius\n", "T_sink = 25.\t\t\t #temperature of the sink in degree celsius\n", "\n", "# Calculations\n", "n_claimed = W/Q\n", "T1 = T_source+273.15\n", "T2 = T_sink+273.15\n", "n_carnot = 1-(T2/T1)\n", "\n", "# Results\n", "print \" The efficiency of the Carnot engine = %0.3f \"%(n_carnot);\n", "print \" The efficiency of the engine claimed by the inventor = %0.2f \"%(n_claimed);\n", "if n_claimed0 or S_G == 0 :\n", " print \" As the first and second law of thermodynamics are satisfied, the device is theoretically feasible \"\n", "else:\n", " print \" As both the first and second law or either the first or second law of thermodynamics \\\n", " are not satisfied, the device is not feasible \"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ " The LHS of the equation applied to the flow device to check if the first law of thermodynamics is satisfied = 2745.4 kJ\n", " The RHS of the equation applied to the flow device to check if the first law of thermodynamics is satisfied = 2745.5 kJ\n", " The entropy generated by applying the second law of thermodynamics to the flow device = 0.3552 kJ/kgK\n", " As the first and second law of thermodynamics are satisfied, the device is theoretically feasible \n" ] } ], "prompt_number": 21 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.18 Page No : 185" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "Pi = 30.\t\t\t #pressure of superheated steam entering the turbine in bar\n", "Ti = 300.\t\t\t #temperature of superheated steam entering the turbine in degree celsius\n", "Pe = 0.1\t\t\t #pressure at which steam exits the turbine in bar\n", "Xe = 0.9\t\t\t #quality of steam at the exit (no unit)(for the actual turbine)\n", "\n", "# Calculations\n", "#For superheated steam at Pi and Ti\n", "hi = 2995.1;\t\t\t #enthalpy of superheated steam at the entrance in kJ/kg\n", "si = 6.5422;\t\t\t #entropy of superheated steam at the entrance in kJ/kgK\n", "\n", "#For steam at Pe\n", "hf = 191.83;\t\t\t #enthalpy of saturated liquid in kJ/kg\n", "hg = 2584.8;\t\t\t #enthalpy of saturated vapour in kJ/kg\n", "sf = 0.6493;\t\t\t #entropy of saturated liquid in kJ/kgK\n", "sg = 8.1511;\t\t\t #entropy of saturated vapour in kJ/kgK\n", "\n", "X2 = (si-sf)/(sg-sf)\n", "h2 = (hf*(1-X2))+(X2*hg)\n", "he = (hf*(1-Xe))+(Xe*hg)\n", "n_T = (hi-he)/(hi-h2)\n", "\n", "# Results\n", "print \" The isentropic efficiency of the turbine = %f \"%(n_T);\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ " The isentropic efficiency of the turbine = 0.703395 \n" ] } ], "prompt_number": 22 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.19 Page No : 186" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "Ti = 25.\t\t\t #temperature of air taken in by the adiabatic air compressor in degree celsius\n", "Pi = 0.1\t\t\t #pressure of air taken in by the adiabatic air compressor in MPa\n", "Pe = 1.\t \t\t #discharge pressure of air in MPa\n", "n_c = 0.8\t\t\t #isentropic efficiency of the compressor (no unit)\n", "gaamma = 1.4\t\t #ratio of molar specific heat capacities (no unit)\n", "R = 8.314\t\t\t #universal gas constant in J/molK\n", "\n", "# Calculations\n", "Ti = Ti+273.15\n", "Te = Ti*(((Pe*10**6)/(Pi*10**6))**((gaamma-1)/gaamma))\n", "W_s = (((R*gaamma)/(gaamma-1))*(Te-Ti))*10**-3;\t\t\t\n", "Ws = W_s/n_c\n", "Te_actual = ((Ws*10**3*(gaamma-1))/(R*gaamma))+Ti\n", "\n", "# Results\n", "print \" The exit temperature of air = %0.2f K\"%(Te_actual);\n", "print \" The power consumed by the compressor = %f kW/mol\"%(Ws);" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ " The exit temperature of air = 645.01 K\n", " The power consumed by the compressor = 10.093262 kW/mol\n" ] } ], "prompt_number": 23 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.20 Page No : 187" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "Ti = 30.\t\t\t #temperature of saturated liquid water in degree celsius\n", "m = 500.\t\t\t #mass flow rate of water being pumped in kg/s\n", "P2 = 3. \t\t\t #preesure maintained in the boiler in MPa\n", "n_p = 0.75;\t\t\t #isentropic efficiency of the pump (no unit)\n", "\n", "# Calculations\n", "#For saturated liquid water at Ti\n", "vf = 0.0010043\n", "P1 = 4.241;\t\t\n", "\n", "Ws_m = (vf*((P2*10**6)-(P1*10**3)))*10**-3\n", "Ws_act_m = Ws_m/n_p;\t\t\t \n", "P = ((Ws_act_m*10**3)*m)*10**-6;\n", "\n", "# Results\n", "print \" The power consumed by the pump = %d MW\"%(P);" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ " The power consumed by the pump = 2 MW\n" ] } ], "prompt_number": 24 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.21 Page No : 188" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "# Variables\n", "Pi = 3.\t\t\t #pressure of dry saturated steam entering the nozzle in bar\n", "Xe = 0.98\t\t #quality of steam exiting the nozzle (no unit)\n", "Pe = 2.\t\t\t #pressure of steam exiting the nozzle in bar\n", "\n", "# Calculations\n", "#For steam at Pi\n", "hi = 2724.7\n", "he = 2652.8\n", "V2_2_s = hi-he\n", "\n", "#For steam at Pe\n", "hf = 504.70\n", "hg = 2706.3\n", "he_act = ((1-Xe)*hf)+(Xe*hg)\n", "V2_2 = hi-he_act;\t\t\t\n", "n_N = (V2_2)/(V2_2_s)\t\t\n", "\n", "# Results\n", "print \" The isentropic efficiency of the nozzle = %0.3f \"%(n_N);\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ " The isentropic efficiency of the nozzle = 0.868 \n" ] } ], "prompt_number": 25 } ], "metadata": {} } ] }