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diff --git a/Thermal_Engineering_by_A._V._Arasu/ch6.ipynb b/Thermal_Engineering_by_A._V._Arasu/ch6.ipynb new file mode 100644 index 00000000..f0f6f415 --- /dev/null +++ b/Thermal_Engineering_by_A._V._Arasu/ch6.ipynb @@ -0,0 +1,901 @@ +{ + "metadata": { + "name": "", + "signature": "sha256:4962285b4f62f2bf376e81ac1782d3fcaba245abd75f93d7b849812ce5c45ab3" + }, + "nbformat": 3, + "nbformat_minor": 0, + "worksheets": [ + { + "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": {} + } + ] +}
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