path: root/Thermodynamics_An_Engineering_Approach/Chapter11.ipynb

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 },
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 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "heading",
     "level": 1,
     "metadata": {},
     "source": [
      "Chapter 11: Refrigeration Cycles"
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 11-1 ,Page No.613"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "#given values\n",
      "P1=0.14;#intial pressure in MPa\n",
      "P2=0.8;#final pressure in MPa\n",
      "m=0.05;#mass flow rate in kg/s\n",
      "\n",
      "#from refrigerant-134a tables\n",
      "h1=239.16;\n",
      "s1=0.94456;\n",
      "h2=275.39;\n",
      "h3=95.47;\n",
      "\n",
      "#calculation\n",
      "s2=s1;#isentropic process \n",
      "h4=h3;#throttling\n",
      "QL=(h1-h4)*m;\n",
      "Wm=m*(h2-h1);\n",
      "Qh=m*(h2-h3);\n",
      "COPR=QL/Wm;\n",
      "print'the rate of heat removal from the refrigerated space %f kW'%round(QL,2);\n",
      "print'the power input to the compressor %f kW'%round(Wm,2);\n",
      "print'the rate of heat rejection to the environment %f kW'%round(Qh);\n",
      "print'the COP of the refrigerator is %f'%round(COPR,2);"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "the rate of heat removal from the refrigerated space 7.180000 kW\n",
        "the power input to the compressor 1.810000 kW\n",
        "the rate of heat rejection to the environment 9.000000 kW\n",
        "the COP of the refrigerator is 3.970000\n"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 11-2 ,Page No.615"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "#given data\n",
      "m=0.05;#mass flow rate in kg/s\n",
      "P1=0.14;#inlet pressure in MPa\n",
      "T1=-10;#inlet temperature in C\n",
      "P2=0.8;#outlet pressure in MPa\n",
      "T2=50;#outlet temperature in C\n",
      "P3=0.72;#condensor pressure in MPa\n",
      "T3=26;#condensor temperature in C\n",
      "\n",
      "#from refrigerant tables\n",
      "h1=246.36;\n",
      "h2=286.69;\n",
      "h3=87.83;\n",
      "h2S=284.21;#at isentropic conditions\n",
      "\n",
      "#calculations\n",
      "h4=h3;#throttling\n",
      "QL=m*(h1-h4);\n",
      "Wm=m*(h2-h1);\n",
      "nC=(h2S-h1)/(h2-h1);\n",
      "COPR=QL/Wm;\n",
      "print'the rate of heat removal from the refrigerated space %f kW'%round(QL,2);\n",
      "print'the power input to the compressor %f kW'%round(Wm,2);\n",
      "print'the isentropic efficiency of the compressor is %f'%round(nC,3);\n",
      "print'the COP of the refrigerator is %f'%round(COPR,2);"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "the rate of heat removal from the refrigerated space 7.930000 kW\n",
        "the power input to the compressor 2.020000 kW\n",
        "the isentropic efficiency of the compressor is 0.939000\n",
        "the COP of the refrigerator is 3.930000\n"
       ]
      }
     ],
     "prompt_number": 5
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 11-3 ,Page No.621"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "#given data\n",
      "mA=0.05;#mass flow rate in kg/s\n",
      "P1=0.14;#inlet pressure in MPa\n",
      "P5=0.32;#pressure at heat exchanger in MPa\n",
      "P7=0.8;#oultet pressure in MPa\n",
      "\n",
      "#from tables\n",
      "h1=239.16;\n",
      "h2=255.93;\n",
      "h3=55.16;\n",
      "h5=251.88;\n",
      "h6=270.92;\n",
      "h7=95.47;\n",
      "\n",
      "#calculations\n",
      "h4=h3;#throttling\n",
      "h8=h7;#throttling\n",
      "# E out = E in\n",
      "# mA*h5 + mB*h3 = mA*h8 + mB*h2\n",
      "mB=mA*(h5-h8)/(h2-h3);\n",
      "QL=mB*(h1-h4);\n",
      "# W in = Wcomp I,in + Wcomp II,in\n",
      "Win=mA*(h6-h5)+mB*(h2-h1);\n",
      "COPR=QL/Win;\n",
      "print'the mass flow rate of the refrigerant through the lower cycle %f kg/s'%round(mB,4);\n",
      "print'the rate of heat removal from the refrigerated space %f kW'%round(QL,2);\n",
      "print'the power input to the compressor %f kW'%round(Win,2);\n",
      "print'the coefficient of performance of this cascade refrigerator is %f'%round(COPR,2);\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "the mass flow rate of the refrigerant through the lower cycle 0.039000 kg/s\n",
        "the rate of heat removal from the refrigerated space 7.170000 kW\n",
        "the power input to the compressor 1.610000 kW\n",
        "the coefficient of performance of this cascade refrigerator is 4.460000\n"
       ]
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 11-4 ,Page No.624"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "#given data\n",
      "P1=0.14;#inlet pressure in MPa\n",
      "P5=0.32;#throttled pressure in MPa\n",
      "P7=0.8;#oultet pressure in MPa\n",
      "\n",
      "#from tables\n",
      "h1=239.16;\n",
      "h2=255.93;\n",
      "h3=251.88;\n",
      "h5=95.47;\n",
      "h7=55.16;\n",
      "\n",
      "#from saturated liquid-vapour table\n",
      "#at P=0.32 MPa\n",
      "hf=55.16;\n",
      "hfg=196.71;\n",
      "\n",
      "#calculations\n",
      "h8=h7;#throttling\n",
      "h6=h5;#throttling\n",
      "#the quality at state 6\n",
      "x6=(h6-hf)/hfg;\n",
      "qL=(1-x6)*(h1-h8);\n",
      "# W in = Wcomp I,in + Wcomp II,in\n",
      "#enthalaoy at state 9\n",
      "# E out = E in\n",
      "h9=x6*h3+(1-x6)*h2;\n",
      "# s9 = s4 i.e isentropic process\n",
      "#at 0.8MPa and s4=0.9416 kJ/kg\n",
      "h4=274.48;\n",
      "Win=(1-x6)*(h2-h1)+(1)*(h4-h9);\n",
      "COPR=qL/Win;\n",
      "print'the fraction of the refrigerant that evaporates as it is throttled to the flash chamber is %f'%round(x6,4);\n",
      "print'the amount of heat removed from the refrigerated space %f kJ/kg'%round(qL,1);\n",
      "print'the compressor work per unit mass of refrigerant flowing through the condensor %f kJ/kg'%round(Win,2);\n",
      "print'the coefficient of performance is %f'%round(COPR,2)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "the fraction of the refrigerant that evaporates as it is throttled to the flash chamber is 0.204900\n",
        "the amount of heat removed from the refrigerated space 146.300000 kJ/kg\n",
        "the compressor work per unit mass of refrigerant flowing through the condensor 32.710000 kJ/kg\n",
        "the coefficient of performance is 4.470000\n"
       ]
      }
     ],
     "prompt_number": 10
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 11-5 ,Page No.630"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "#given data\n",
      "m=0.1;#mass flow rate in lbm/s\n",
      "T1=0+460;#refigerated space at temperature in R\n",
      "T3=80+460;#temperature of surrounding medium in R\n",
      "\n",
      "#from Table A\u201317E\n",
      "# at T1\n",
      "h1=109.90;\n",
      "Pr1=.7913;\n",
      "#pressure ratio at compressor is 4\n",
      "Pr2=4*Pr1;\n",
      "#at Pr2\n",
      "h2=163.5;\n",
      "T2=683;\n",
      "#at T3\n",
      "h3=129.06;\n",
      "Pr3=1.3860;\n",
      "#pressure ratio at compressor is 4\n",
      "Pr4=Pr3/4;\n",
      "#at Pr4\n",
      "h4=86.7;\n",
      "T4=363;\n",
      "\n",
      "#calculations\n",
      "qL=h1-h4;\n",
      "Wout=h3-h4;\n",
      "Win=h2-h1;\n",
      "COPR=qL/(Win-Wout);\n",
      "Qrefrig=m*qL;\n",
      "print'the minimum temperatures in the cycle %f F'%round(T4-460);\n",
      "print'the maximum temperatures in the cycle %f F'%round(T2-460);\n",
      "print'the coefficient of performance is %f'%round(COPR,2)\n",
      "print'the rate of refrigeration for a mass flow rate of 0.1 lbm/s. %f Btu/s'%round(Qrefrig,2)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "the minimum temperatures in the cycle -97.000000 F\n",
        "the maximum temperatures in the cycle 223.000000 F\n",
        "the coefficient of performance is 2.060000\n",
        "the rate of refrigeration for a mass flow rate of 0.1 lbm/s. 2.320000 Btu/s\n"
       ]
      }
     ],
     "prompt_number": 13
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 11-6 ,Page No.636"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "#given data\n",
      "COPR=0.1;#refrigerator COP\n",
      "T1=20;#intial temp in C\n",
      "T2=4;#final temp in C\n",
      "t=30*60;#total time required in sec\n",
      "V=0.350;#volumne of can in L\n",
      "\n",
      "#constants used\n",
      "p=1;#on kg/L\n",
      "c=4.18;#in kJ/kg-C from Table A-3\n",
      "\n",
      "#calculations\n",
      "m=p*V;\n",
      "Qcooling=m*c*(T1-T2)/t*1000;#converted in W by multiplying by 1000\n",
      "Win=Qcooling/COPR;\n",
      "print'the average electric power consumed by the thermoelectric refrigerator %i W'%round(Win)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "the average electric power consumed by the thermoelectric refrigerator 130 W\n"
       ]
      }
     ],
     "prompt_number": 14
    }
   ],
   "metadata": {}
  }
 ]
}