path: root/Thermal_Engineering_by_A._V._Arasu/ch6.ipynb

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  {
   "cells": [
    {
     "cell_type": "heading",
     "level": 1,
     "metadata": {},
     "source": [
      "Chapter 6 :\n",
      "Refrigeration Cycles"
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.1  Page no : 308"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Variables\n",
      "COP = 8.5;\t\t\t#Co-efficient of performance\n",
      "T1 = 300.;\t\t\t#Room temperature in K\n",
      "T2 = 267.;\t\t\t#Refrigeration temperature in K\n",
      "\n",
      "# Calculations\n",
      "COPmax = T2/(T1-T2);\t\t\t#Maximum COP possible\n",
      "\n",
      "# Results\n",
      "print 'Maximum COP possible is %3.2f  \\\n",
      "\\nSince the COP claimed by the inventor is more than the maximum possible COP\\\n",
      " his claim is not correct'%(COPmax)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Maximum COP possible is 8.09  \n",
        "Since the COP claimed by the inventor is more than the maximum possible COP his claim is not correct\n"
       ]
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.2  Page no : 309"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "# Variables\n",
      "TL = 268.;\t\t\t#Low temperature in K\n",
      "TH = 293.;\t\t\t#High temperature in K\n",
      "t = 24.;\t\t\t#time in hrs\n",
      "C = 2100.;\t\t\t#Capacity of refrigerator in kJ/s\n",
      "Tw = 10.;\t\t\t#Water temperature in oC\n",
      "L = 335.;\t\t\t#Latent heat of ice in kJ/kg\n",
      "\n",
      "# Calculations\n",
      "COP = TL/(TH-TL);\t\t\t#Co-efficient of performance\n",
      "Pmin = C/COP;\t\t\t#Minimum power required in kW\n",
      "Qr = (4.187*(Tw-0))+L;\t\t\t#Heat removed from water in kJ/kg\n",
      "m = C/Qr;\t\t\t#mass of ice formed in kg/s\n",
      "W = (m*t*3600)/1000;\t\t\t#Weight of ice formed in tons\n",
      "\n",
      "# Results\n",
      "print 'Minimum power required is %3.2f kW  \\\n",
      "\\nWeight of ice formed in 24 hours is %3.2f tons'%(Pmin,W)\n",
      "\n",
      "# rounding off error"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Minimum power required is 195.90 kW  \n",
        "Weight of ice formed in 24 hours is 481.44 tons\n"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.3  Page no : 309"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Variables\n",
      "TL = -10.;\t\t\t#Temperature of brine in oC\n",
      "TH = 20.;\t\t\t#Temperature of water in oC\n",
      "L = 335.;\t\t\t#Latent heat of ice in kJ/kg\n",
      "\n",
      "# Calculations\n",
      "Qr = (4.187*(TH-0))+L;\t\t\t#Heat removed from water in kJ/kg\n",
      "COP = (TL+273)/(TH-TL);\t\t\t#Co-efficient of performance\n",
      "mi = (COP*3600)/Qr;\t\t\t#mass of ice formed per kWh in kg\n",
      "\n",
      "# Results\n",
      "print 'Mass of ice formed per kWh is %3.1f kg'%(mi)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Mass of ice formed per kWh is 75.4 kg\n"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.4  Page no : 310"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "# Variables\n",
      "P1 = 1.2;\t\t\t#Pressure at point 1 in bar\n",
      "P2 = 7.;\t\t\t#Pressure at point 2 in bar\n",
      "m = 0.05;\t\t\t#mass flow rate of refrigerant in kg/s\n",
      "h1 = 340.1;\t\t\t#Enthalpy at point 1 from refrigerant-12 tables in kJ/kg\n",
      "s1 = 1.57135;\t\t\t#Entropy at point 1 from refrigerant-12 tables in kJ/kg-K\n",
      "s2 = 1.57135;\t\t\t#Entropy at point 2 from refrigerant-12 tables in kJ/kg-K\n",
      "h2 = 372.;\t\t\t#Enthalpy at point 2 from refrigerant-12 tables in kJ/kg\n",
      "h3 = 226.575;\t\t\t#Enthalpy at point 3 from refrigerant-12 tables in kJ/kg\n",
      "h4 = 226.575;\t\t\t#Enthalpy at point 4 from refrigerant-12 tables in kJ/kg\n",
      "\n",
      "# Calculations\n",
      "Q2 = m*(h1-h4);\t\t\t#Rate of heat removed from the refrigerated space in kW\n",
      "W = m*(h2-h1);\t\t\t#Power input to the compressor in kW\n",
      "Q1 = m*(h2-h3);\t\t\t#Rate of heat rejection to the environment in kW\n",
      "COP = Q2/W;\t\t\t#Co-efficient of performance\n",
      "\n",
      "# Results\n",
      "print 'Rate of heat removed from the refrigerated space is %3.2f kW  \\\n",
      "\\nPower input to the compressor is %3.3f kW  \\\n",
      "\\nRate of heat rejection to the environment is %3.2f kW  \\\n",
      "\\nCo-efficient of performance is %3.2f'%(Q2,W,Q1,COP)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Rate of heat removed from the refrigerated space is 5.68 kW  \n",
        "Power input to the compressor is 1.595 kW  \n",
        "Rate of heat rejection to the environment is 7.27 kW  \n",
        "Co-efficient of performance is 3.56\n"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.5  Page no : 311"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "# Variables\n",
      "T2 = 40.;\t\t\t#Temperature at point 2 in oC\n",
      "T1 = -10.;\t\t\t#Temperature at point 1 in oC\n",
      "h2 = 367.155;\t\t\t#Enthalpy at point 2 from refrigerant-12 tables in kJ/kg\n",
      "s2 = 1.54057;\t\t\t#Entropy at point 2 from refrigerant-12 tables in kJ/kg-K\n",
      "s1 = 1.54057;\t\t\t#Entropy at point 1 from refrigerant-12 tables in kJ/kg-K\n",
      "sg = 1.56004;\t\t\t#Entropy from refrigerant-12 tables in kJ/kg-K\n",
      "sf = 0.96601;\t\t\t#Entropy from refrigerant-12 tables in kJ/kg-K\n",
      "hf = 190.822;\t\t\t#Enthalpy from refrigerant-12 tables in kJ/kg-K\n",
      "hfg = 156.319;\t\t\t#Enthalpy from refrigerant-12 tables in kJ/kg-K\n",
      "h3 = 238.533;\t\t\t#Enthalpy at point 3 from refrigerant-12 tables in kJ/kg-K\n",
      "h4 = h3;\t\t\t#Enthalpy at point 4 from refrigerant-12 tables in kJ/kg-K\n",
      "\n",
      "# Calculations\n",
      "x1 = (s1-sf)/(sg-sf);\t\t\t#Quality factor\n",
      "h1 = hf+(x1*hfg);\t\t\t#Enthalpy at point 1 from refrigerant-12 tables in kJ/kg\n",
      "COP = (h1-h4)/(h2-h1);\t\t\t#Co-efficient of performance\n",
      "\n",
      "# Results\n",
      "print 'COP of the system is %3.2f'%(COP)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "COP of the system is 4.12\n"
       ]
      }
     ],
     "prompt_number": 5
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.6  Page no : 311"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "# Variables\n",
      "Tc = 35.;\t\t\t#Temperature of condenser in oC\n",
      "Te = -15.;\t\t\t#Temperature of evaporator in oC\n",
      "m = 10.;\t\t\t#Mass of ice per day in tons\n",
      "Tw = 30.;\t\t\t#Temperature of water in oC\n",
      "Ti = -5.;\t\t\t#Temperature of ice in oC\n",
      "nv = 0.65;\t\t\t#Volumetric efficiency\n",
      "N = 1200.;\t\t\t#Speed in rpm\n",
      "x = 1.2;\t\t\t#Stroke to bore ratio\n",
      "na = 0.85;\t\t\t#Adiabatic efficiency\n",
      "nm = 0.95;\t\t\t#Mechanical efficiency\n",
      "S = 4.187;\t\t\t#Specific heat of water in kJ/kg\n",
      "L = 335.;\t\t\t#Latent heat of ice in kJ/kg\n",
      "h1 = 1667.24;\t\t\t#Enthalpy at Te from Ammonia chart in kJ/kg\n",
      "h2 = 1925.;\t\t\t#Enthalpy at Te from Ammonia chart in kJ/kg\n",
      "h4 = 586.41;\t\t\t#Enthalpy at Tc from Ammonia chart in kJ/kg\n",
      "v1 = 0.508;\t\t\t#Specific humidity at Te from Ammonia chart in (m**3)/kg\n",
      "\n",
      "# Calculations\n",
      "Qr = (((m*1000)/24)*((S*(Tw-0))+L+(1.94*(0-Ti))))/3600;\t\t\t#Refrigerating capacity in kW\n",
      "mr = Qr/(h1-h4);\t\t\t#Refrigerant mass flow rate in kg/s\n",
      "T2 = 112;\t\t\t#Discharge temperature in oC\n",
      "D = ((mr*v1*4*60)/(nv*3.14*x*N))**(1./3);\t\t\t#Cylinder diameter in m\n",
      "L = x*D;\t\t\t#Stroke length in m\n",
      "W = (mr*(h2-h1))/(na*nm);\t\t\t#Compressor motor power in kW\n",
      "COPth = (h1-h4)/(h2-h1);\t\t\t#Theoretical COP\n",
      "COPact = Qr/W;\t\t\t#Actual COP\n",
      "\n",
      "# Results\n",
      "print 'Refrigerating capacity of plant is %3.2f kW  \\\n",
      "\\nRefrigerant mass flow rate is %3.4f kg/s  \\\n",
      "\\nDischarge temperature is %3.0f oC  \\\n",
      "\\nCylinder diameter is %3.3f m  \\\n",
      "\\nStroke length is %3.3f m  \\\n",
      "\\nCompressor motor power is %3.2f kW  \\\n",
      "\\nTheoretical COP is %3.2f  \\\n",
      "\\nActual COP is %3.2f'%(Qr,mr,T2,D,L,W,COPth,COPact)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Refrigerating capacity of plant is 54.43 kW  \n",
        "Refrigerant mass flow rate is 0.0504 kg/s  \n",
        "Discharge temperature is 112 oC  \n",
        "Cylinder diameter is 0.128 m  \n",
        "Stroke length is 0.153 m  \n",
        "Compressor motor power is 16.08 kW  \n",
        "Theoretical COP is 4.19  \n",
        "Actual COP is 3.39\n"
       ]
      }
     ],
     "prompt_number": 6
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.7  Page no : 313"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "# Variables\n",
      "T1 = -5.;\t\t\t#Temperature at point 1 in oC\n",
      "T2 = 30.;\t\t\t#Temperature at point 2 in oC\n",
      "m = 13500.;\t\t\t#mass of ice per day in kg\n",
      "Tw = 20.;\t\t\t#Temperature of water in oC\n",
      "COP = 0.6;\t\t\t#Co-efficient of performance\n",
      "h2 = 1709.33;\t\t\t#Enthalpy at point 2 in kJ/kg\n",
      "s2 = 6.16259;\t\t\t#Entropy at point 2 in kJ/kg-K\n",
      "s1 = 6.16259;\t\t\t#Entropy at point 1 in kJ/kg-K\n",
      "sf = 1.8182;\t\t\t#Entropy in kJ/kg-K\n",
      "sg = 6.58542;\t\t\t#Entropy in kJ/kg-K\n",
      "hf = 400.98;\t\t\t#Enthalpy in kJ/kg\n",
      "hfg = 1278.35;\t\t\t#Enthalpy in kJ/kg\n",
      "h4 = 562.75;\t\t\t#Enthalpy at point 4 in kJ/kg\n",
      "S = 4.187;\t\t\t#Specific heat of water in kJ/kg\n",
      "L = 336.;\t\t\t#Latent heat of ice in kJ/kg\n",
      "\n",
      "# Calculations\n",
      "x1 = (s1-sf)/(sg-sf);\t\t\t#Quality factor\n",
      "h1 = hf+(x1*hfg);\t\t\t#Enthalpy at point 1 from refrigerant-12 tables in kJ/kg\n",
      "COPi = (h1-h4)/(h2-h1);\t\t\t#Ideal COP\n",
      "COPact = COP*COPi;\t\t\t#Actual COP\n",
      "Qr = ((m*S*(Tw-0))+(m*L))/(24*3600);\t\t\t#Total amount of heat removed in kJ/s\n",
      "mr = Qr/(h1-h4);\t\t\t#Circulation rate of ammonia in kg/s\n",
      "W = mr*(h2-h1);\t\t\t#Power required in kW\n",
      "\n",
      "# Results\n",
      "print 'Circulation rate of ammonia is %3.3f kg/s  \\\n",
      "\\nPower required is %3.3f kW  \\\n",
      "\\nCOP is %3.3f'%(mr,W,COPact)\n",
      "\n",
      "# rounding off error"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Circulation rate of ammonia is 0.065 kg/s  \n",
        "Power required is 9.374 kW  \n",
        "COP is 4.198\n"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.8  Page no : 314"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "\n",
      "# Variables\n",
      "Tc = 20.;\t\t\t#Temperature of condenser in oC\n",
      "Te = -25.;\t\t\t#Temperature of evaporator in oC\n",
      "m = 15.;\t\t\t#Mass of ice per day in tons\n",
      "Ts = 5.;\t\t\t#Subcooled temperature in oC\n",
      "Tsh = 10.;\t\t\t#Superheated temperature in oC\n",
      "n = 6.;\t\t\t#No. of cylinders\n",
      "N = 950.;\t\t\t#Speed of compressor in rpm\n",
      "x = 1.;\t\t\t#Stroke to bore ratio\n",
      "h1 = 402.;\t\t\t#Enthalpy at point 1 from R-22 tables in kJ/kg\n",
      "h2 = 442.;\t\t\t#Enthalpy at point 2 from R-22 tables in kJ/kg\n",
      "h3 = 216.;\t\t\t#Enthalpy at point 3 from R-22 tables in kJ/kg\n",
      "h4 = 216.;\t\t\t#Enthalpy at point 4 from R-22 tables in kJ/kg\n",
      "v1 = 2.258;\t\t\t#Specific volume at point 1 in (m**3)/min\n",
      "\n",
      "# Calculations\n",
      "Re = h1-h4;         \t\t\t#Refrigerating effect in kJ/kg\n",
      "mr = (m*14000)/(Re*60);\t\t\t#Mass flow of refrigerant in kg/min\n",
      "Pth = (mr*(h2-h1))/60;\t\t\t#Theoretical power in kW\n",
      "COP = (h1-h4)/(h2-h1);\t\t\t#Co-efficient of performance\n",
      "Dth = v1/n;\t\t\t            #Theoretical print lacement per cylinder\n",
      "D = (((Dth*4)/(3.147*N))**(1./3))*1000;\t\t\t#Theoretical bore of compressor in mm\n",
      "L = D;              \t\t\t#Theoretical stroke of compressor in mm\n",
      "\n",
      "# Results\n",
      "print 'Refrigerating effect is %3.0f kJ/kg  \\\n",
      "\\nMass flow of refrigerant per minute is %3.2f kg/min  \\\n",
      "\\nTheoretical input power is %3.2f kW  COP is %3.2f  \\\n",
      "\\nTheoretical bore of compressor is %3.2f mm  \\\n",
      "\\nTheoretical stroke of compressor is %3.2f mm'%(Re,mr,Pth,COP,D,L)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Refrigerating effect is 186 kJ/kg  \n",
        "Mass flow of refrigerant per minute is 18.82 kg/min  \n",
        "Theoretical input power is 12.54 kW  COP is 4.65  \n",
        "Theoretical bore of compressor is 79.56 mm  \n",
        "Theoretical stroke of compressor is 79.56 mm\n"
       ]
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.9  Page no : 316"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Variables\n",
      "T2 = 40.;\t\t\t#Temperature at point 2 in oC\n",
      "T1 = -5.;\t\t\t#Temperature at point 1 in oC\n",
      "h2 = 367.155;\t\t\t#Enthalpy at point 2 from F-12 tables in kJ/kg\n",
      "sg = 1.55717;\t\t\t#Entropy from F-12 tables in kJ/kg-K\n",
      "s1 = 1.54057;\t\t\t#Entropy at point 1 from F-12 tables in kJ/kg-K\n",
      "sf = 0.98311;\t\t\t#Entropy from F-12 tables in kJ/kg-K\n",
      "hf = 195.394;\t\t\t#Enthalpy from F-12 tables in kJ/kg\n",
      "hfg = 153.934;\t\t\t#Enthalpy from F-12 tables in kJ/kg\n",
      "h4 = 238.533;\t\t\t#Enthalpy at point 4 from F-12 tables in kJ/kg\n",
      "h4s = 218;\t\t\t#Enthalpy at point 4 with subcooling from F-12 tables in kJ/kg\n",
      "\n",
      "# Calculations\n",
      "x1 = (s1-sf)/(sg-sf);\t\t\t#Quality factor\n",
      "h1 = hf+(x1*hfg);\t\t\t#Enthalpy at point 1 from refrigerant-12 tables in kJ/kg\n",
      "COPns = (h1-h4)/(h2-h1);\t\t\t#Co-efficient of performance with no subcooling\n",
      "COPs = (h1-h4s)/(h2-h1);\t\t\t#Co-efficient of performance with subcooling\n",
      "\n",
      "# Results\n",
      "print 'COP with no subcooling is %3.3f  \\\n",
      "\\nCOP with subcooling is %3.3f'%(COPns,COPs)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "COP with no subcooling is 4.773  \n",
        "COP with subcooling is 5.695\n"
       ]
      }
     ],
     "prompt_number": 9
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.10  Page no : 309"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "# Variables\n",
      "Tg = 470.;\t\t\t#Heating temperature in K\n",
      "T0 = 290.;\t\t\t#Cooling temperature in K\n",
      "TL = 270.;\t\t\t#Refrigeration temperature in K\n",
      "\n",
      "# Calculations\n",
      "COP = ((Tg-T0)/Tg)*(TL/(T0-TL));\t\t\t#Ideal COP of absorption refrigeration system\n",
      "\n",
      "# Results\n",
      "print 'Ideal COP of absorption refrigeration system is %3.2f'%(COP)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Ideal COP of absorption refrigeration system is 5.17\n"
       ]
      }
     ],
     "prompt_number": 10
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.11  Page no : 317"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "# Variables\n",
      "T1 = -18.;\t\t\t#Temperature at point 1 in oC\n",
      "T3 = 27.;\t\t\t#Temperature at point 3 in oC\n",
      "rp = 4.;\t\t\t#Pressure ratio\n",
      "m = 0.045;\t\t\t#mass flow rate in kg/s\n",
      "y = 1.4;\t\t\t#Ratio of specific heats\n",
      "Cp = 1.005;\t\t\t#Specific heat at constant pressure in kJ/kg-K\n",
      "\n",
      "# Calculations\n",
      "x = (y-1)/y;\t\t\t#Ratio\n",
      "T2 = (rp**x)*(273+T1);\t\t\t#Temperature at point 2 in K\n",
      "Tmax = T2-273;\t\t\t#Maximum temperature in oC\n",
      "T4 = ((1/rp)**x)*(273+T3);\t\t\t#Temperature at point 4 in K\n",
      "Tmin = T4-273;\t\t\t#Minimum temperature in oC\n",
      "qL = Cp*(T1-Tmin);\t\t\t#Heat rejected\n",
      "Wcin = Cp*(Tmax-T1);\t\t\t#Compressor work\n",
      "Wtout = Cp*(T3-Tmin);\t\t\t#Turbine work\n",
      "Wnet = Wcin-Wtout;\t\t\t#Net work done\n",
      "COP = qL/Wnet;\t\t\t#Co-efficient of performance\n",
      "Qref = m*qL;\t\t\t#Rate of refrigeration in kW\n",
      "\n",
      "# Results\n",
      "print 'Maximum temperature in the cycle is %3.0f oC  \\\n",
      "\\nMinimum temperature in the cycle is %3.0f oC  \\\n",
      "\\nCOP is %3.2f  \\\n",
      "\\nRate of refrigeration is %3.2f kW'%(Tmax,Tmin,COP,Qref)\n",
      "\n",
      "# rounding off error"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Maximum temperature in the cycle is 106 oC  \n",
        "Minimum temperature in the cycle is -71 oC  \n",
        "COP is 2.06  \n",
        "Rate of refrigeration is 2.40 kW\n"
       ]
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.12  Page no : 318"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Variables\n",
      "P1 = 1.;\t\t\t#Pressure at point 1 in bar\n",
      "T1 = 268.;\t\t\t#Temperature at point 1 in K\n",
      "P2 = 5.;\t\t\t#Pressure at point 2 in bar\n",
      "T3 = 288.;\t\t\t#Temperature at point 3 in K\n",
      "n = 1.3;\t\t\t#Adiabatic gas constant\n",
      "Cp = 1.005;\t\t\t#Specific heat at constant pressure in kJ/kg-K\n",
      "\n",
      "# Calculations\n",
      "x = (n-1)/n;\t\t\t#Ratio\n",
      "T2 = ((P2/P1)**x)*T1;\t\t\t#Temperature at point 2 in K\n",
      "T4 = ((P1/P2)**x)*T3;\t\t\t#Temperature at point 4 in K\n",
      "W = Cp*(T3-T4);\t\t\t#Work developed per kg of air in kJ/kg\n",
      "Re = Cp*(T1-T4);\t\t\t#Refrigerating effect per kg of air in kJ/kg\n",
      "Wnet = Cp*((T2-T1)-(T3-T4));\t\t\t#Net work output in kJ/kg\n",
      "COP = Re/Wnet;\t\t\t#Co-efficient of performance\n",
      "\n",
      "# Results\n",
      "print 'Work developed per kg of air is %3.3f kJ/kg  \\\n",
      "\\nRefrigerating effect per kg of air is %3.3f kJ/kg  \\\n",
      "\\nCOP of the cycle is %3.2f'%(W,Re,COP)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Work developed per kg of air is 89.795 kJ/kg  \n",
        "Refrigerating effect per kg of air is 69.695 kJ/kg  \n",
        "COP of the cycle is 2.22\n"
       ]
      }
     ],
     "prompt_number": 12
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.13  Page no : 319"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "# Variables\n",
      "T1 = 277.;\t\t\t#Temperature at point 1 in K\n",
      "T3 = 328.;\t\t\t#Temperature at point 3 in K\n",
      "P1 = 0.1;\t\t\t#Pressure at point 1 in MPa\n",
      "P2 = 0.3;\t\t\t#Pressure at point 2 in MPa\n",
      "nc = 0.72;\t\t\t#Isentropic efficiency of compressor\n",
      "nt = 0.78;\t\t\t#Isentropic efficiency of turbine\n",
      "y = 1.4;\t\t\t#Adiabatic gas constant\n",
      "Cp = 1.005;\t\t\t#Specific heat at constant pressure in kJ/kg-K\n",
      "m = 3.;\t\t\t#Cooling load in tonnes\n",
      "\n",
      "# Calculations\n",
      "x = (y-1)/y;\t\t\t#Ratio\n",
      "T2s = T1*((P2/P1)**x);\t\t\t#Temperature at point 2s in K\n",
      "T2 = ((T2s-T1)/nc)+T1;\t\t\t#Temerature at point 2 in K\n",
      "T4s = T3*((P1/P2)**x);\t\t\t#Temperature at point 4s in K\n",
      "T4 = T3-((T3-T4s)*nt);\t\t\t#Temperature at point 4 in K\n",
      "Re = Cp*(T1-T4);\t\t\t#Refrigerating effect in kJ/kg\n",
      "Wnet = Cp*((T2-T1)-(T3-T4));\t\t\t#Net work output in kJ/kg\n",
      "COP = Re/Wnet;\t\t\t#Co-efficient of performance\n",
      "P = (m*3.52)/COP;\t\t\t#Driving power required in kW\n",
      "ma = (m*3.52)/Re;\t\t\t#Mass flow rate of air in kg/s\n",
      "\n",
      "# Results\n",
      "print 'COP of refrigerator is %3.2f  \\\n",
      "\\nDriving power required is %3.0f kW  \\\n",
      "\\nMass flow rate of air is %3.2f kg/s'%(COP,P,ma)\n",
      "\n",
      "# rounding off error"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "COP of refrigerator is 0.25  \n",
        "Driving power required is  43 kW  \n",
        "Mass flow rate of air is 0.59 kg/s\n"
       ]
      }
     ],
     "prompt_number": 11
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.14  Page no : 321"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Variables\n",
      "P1 = 2.5;\t\t\t#Pressure at point 1 in bar\n",
      "P3 = 9.;\t\t\t#Pressure at point 3 in bar\n",
      "COPr = 0.65;\t\t\t#Ratio of actual COP to the theoretical COP\n",
      "m = 5.;\t\t\t#Refrigerant flow in kg/min\n",
      "T1 = 309;\t\t\t#Temperature at point 1 in K\n",
      "T2s = 300;\t\t\t#Temperature at point 2s in K\n",
      "h1 = 570.3;\t\t\t#Enthalpy at P1 from the given tables in kJ/kg\n",
      "h4 = 456.4;\t\t\t#Enthalpy at P3 from the given tables in kJ/kg\n",
      "h2g = 585.3;\t\t\t#Enthalpy at P3 from the given tables in kJ/kg\n",
      "s2 = 4.76;\t\t\t#Entropy at P1 from the given tables in kJ/kg-K\n",
      "s2g = 4.74;\t\t\t#Entropy at P3 from the given tables in kJ/kg-K\n",
      "Cp = 0.67;\t\t\t#Specific heat at P3 in kJ/kg-K\n",
      "\n",
      "# Calculations\n",
      "T2 = (2.718**((s2-s2g)/Cp))*T2s;\t\t\t#Temperature at point 2 in K\n",
      "h2 = h2g+(Cp*(T2-T2s));\t\t\t#Enthalpy at point 2 in kJ/kg\n",
      "COPR = (h1-h4)/(h2-h1);\t\t\t#Refrigerant COP\n",
      "COPact = COPr*COPR;\t\t\t#Actual COP\n",
      "qL = COPact*(h2-h1);\t\t\t#Heat rejected in kJ/kg\n",
      "QL = ((m*qL*60)/3600)/3.516;\t\t\t#Cooling produced per kg of refrigerant in tonnes of refrigeration\n",
      "\n",
      "# Results\n",
      "print 'Theoretical COP is %3.2f  \\\n",
      "\\nNet cooling produced per hour is %3.2f TR'%(COPR,QL)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Theoretical COP is 5.40  \n",
        "Net cooling produced per hour is 1.75 TR\n"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.15  Page no : 322"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Variables\n",
      "T2 = 298.;\t\t\t#Temperature at point 2 in K\n",
      "T1 = 268.;\t\t\t#Temperature at point 1 in K\n",
      "hf1 = -7.54;\t\t\t#Liquid Enthalpy at T1 in kJ/kg\n",
      "x1 = 0.6;\t\t\t#Quality factor 1\n",
      "hfg1 = 245.3;\t\t\t#Latent heat at T1 in kJ/kg\n",
      "sf1 = 0.251;\t\t\t#Liquid Entropy at T1 in kJ/kg-K\n",
      "s1 = 0.507;\t\t\t#Entropy at point 1 in kJ/kg-K\n",
      "hfg2 = 121.4;\t\t\t#Latent heat at T2 in kJ/kg\n",
      "hf2 = 81.3;\t\t\t#Liquid Enthalpy at T2 in kJ/kg\n",
      "h4 = hf2;\t\t\t#Enthalpy at point 4 in kJ/kg\n",
      "\n",
      "# Calculations\n",
      "h1 = hf1+(x1*hfg1);\t\t\t#Enthalpy at point 1 in kJ/kg\n",
      "x2 = ((s1-sf1)*T2)/hfg2;\t\t\t#Quality factor 2\n",
      "h2 = hf2+(x2*hfg2);\t\t\t#Enthalpy at point 2 in kJ/kg\n",
      "COP = (h1-h4)/(h2-h1);\t\t\t#COP of the machine\n",
      "\n",
      "# Results\n",
      "print 'COP of the machine is %3.2f'%(COP)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "COP of the machine is 3.25\n"
       ]
      }
     ],
     "prompt_number": 15
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.16  Page no : 323"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "\n",
      "# Variables\n",
      "P1 = 25.;\t\t\t#Pressure at point 1 in bar\n",
      "P2 = 60.;\t\t\t#Pressure at point 2 in bar\n",
      "h2 = 208.1;\t\t\t#Vapour enthalpy at P2 in kJ/kg\n",
      "h3 = 61.9;\t\t\t#Liquid enthalpy at P2 in kJ/kg\n",
      "h4 = h3;\t\t\t#Liquid enthalpy at P2 in kJ/kg\n",
      "s2 = 0.703;\t\t\t#Vapour entropy at P2 in kJ/kg-K\n",
      "sf1 = -0.075;\t\t\t#Liquid entropy at P1 in kJ/kg-K\n",
      "sfg1 = 0.971;\t\t\t#Entropy in kJ/kg-K\n",
      "hf1 = -18.4;\t\t\t#Liquid Enthalpy at P1 in kJ/kg\n",
      "hfg1 = 252.9;\t\t\t#Latent heat at P1 in kJ/kg\n",
      "m = 5.;\t\t\t#Refrigerant flow in kg/min\n",
      "\n",
      "# Calculations\n",
      "x1 = (s2-sf1)/sfg1;\t\t\t#Quality factor 1\n",
      "h1 = hf1+(x1*hfg1);\t\t\t#Enthalpy at point 1 in kJ/kg\n",
      "COP = (h1-h4)/(h2-h1);\t\t\t#Co-efficient of performance\n",
      "QL = (m*(h1-h4))/60;\t\t\t#Capacity of the refrigerator in kW\n",
      "\n",
      "# Results\n",
      "print 'COP of refrigerator is %3.2f  \\\n",
      "\\nCapacity of refrigerator is %3.2f kW'%(COP,QL)\n",
      "\n",
      "# rounding off error"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "COP of refrigerator is 5.13  \n",
        "Capacity of refrigerator is 10.19 kW\n"
       ]
      }
     ],
     "prompt_number": 12
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 6.17  Page no : 324"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "\n",
      "import math \n",
      "\n",
      "# Variables\n",
      "T1 = 271.;\t\t\t#Temperature at point 1 in K\n",
      "T = 265.;\t\t\t#Temperature at point 1' in K\n",
      "Ta = 303.;\t\t\t#Temperature at point 2' in K\n",
      "Cpv = 0.733;\t\t\t#Specific heat of vapour in kJ/kg\n",
      "Cpl = 1.235;\t\t\t#Specific heat of liquid in kJ/kg\n",
      "h = 184.07;\t\t\t#Liquid enthalpy at T in kJ/kg\n",
      "s = 0.7;\t\t\t#Entropy at point 1' in kJ/kg-K\n",
      "sa = 0.685;\t\t\t#Vapour entropy at Ta in kJ/kg-K\n",
      "ha = 199.62;\t\t\t#Enthalpy at point 2' in kJ/kg\n",
      "hfb = 64.59;\t\t\t#Liquid enthalpy at Ta in kJ/kg\n",
      "DT3 = 5.;\t\t\t#Temperature difference in oC\n",
      "Q = 2532.;\t\t\t#Refrigeration capacity in kJ/min\n",
      "\n",
      "# Calculations\n",
      "s2 = s+(Cpv*((math.log(T1/T))/(math.log(2.718))));\t\t\t#Entropy at point 1 in kJ/kg-K\n",
      "h1 = h+(Cpv*(T1-T));\t\t\t#Enthalpy at point 1 in kJ/kg-K\n",
      "T2 = (2.718**((s2-sa)/Cpv))*Ta;\t\t\t#Temperature at point 2 in K\n",
      "h2 = ha+(Cpv*(T2-Ta));\t\t\t#Enthalpy at point 2 in kJ/kg\n",
      "h4 = hfb-(Cpl*DT3);\t\t\t#Enthalpy at point 4 in kJ/kg\n",
      "COP = (h1-h4)/(h2-h1);\t\t\t#Co-efficient of performance\n",
      "m = Q/(h1-h4);\t\t\t#Mass flow rate of refrigerant in kJ/min\n",
      "P = (m*(h2-h1))/(60*12);\t\t\t#Power required in kW/TR\n",
      "\n",
      "# Results\n",
      "print 'COP is %3.2f  \\\n",
      "\\nTheoretical power required per tonne of refrigeration is %3.3f kW/TR'%(COP,P)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "COP is 6.23  \n",
        "Theoretical power required per tonne of refrigeration is 0.564 kW/TR\n"
       ]
      }
     ],
     "prompt_number": 17
    }
   ],
   "metadata": {}
  }
 ]
}