{ "metadata": { "name": "", "signature": "sha256:1967d26762283e30e4854c10c803a16851680afbc2e91b1d3cee7d16421cae2c" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "heading", "level": 1, "metadata": {}, "source": [ "Boiling and Condensation" ] }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 10.1 Page 632" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "import math\n", "#Operating Conditions\n", "Ts = 118+273. \t\t\t\t;#[K] Surface Temperature\n", "Tsat = 100+273. \t\t\t\t;#[K] Saturated Temperature\n", "D = .3 \t\t\t\t;#[m] Diameter of pan\n", "g = 9.81 \t\t\t\t;#[m^2/s] gravitaional constant\n", "#Table A.6 Saturated water Liquid Properties T = 373 K\n", "rhol = 957.9 \t\t;#[kg/m^3] Density\n", "cp = 4.217*math.pow(10,3) ;#[J/kg] Specific Heat\n", "u = 279*math.pow(10,-6) ;#[N.s/m^2] Viscosity\n", "Pr = 1.76 \t\t;# Prandtl Number\n", "hfg = 2257*math.pow(10,3) ;#[J/kg] Specific Heat\n", "si = 58.9*math.pow(10,-3) \t;#[N/m]\n", "#Table A.6 Saturated water Vapor Properties T = 373 K\n", "rhov = .5956 \t\t;#[kg/m^3] Density\n", "\n", "Te = Ts-Tsat;\n", "#calculations\n", "\n", "#From Table 10.1\n", "C = .0128;\n", "n = 1.;\n", "q = u*hfg*math.pow(g*(rhol-rhov)/si,.5)*math.pow((cp*Te/(C*hfg*math.pow(Pr,n))),3);\n", "qs = q*math.pi*D*D/4.; \t\t\t#Boiling heat transfer rate\n", " \n", "m = qs/hfg; \t\t\t\t\t#Rate of evaporation\n", "\n", "qmax = .149*hfg*rhov*math.pow(si*g*(rhol-rhov)/(rhov*rhov),.25); \t#Critical heat flux\n", "#results\n", "\n", "print '%s %.2f %s' %(\"\\n Boiling Heat transfer rate = \",qs/1000. ,\"kW\")\n", "print '%s %d %s' %(\"\\n Rate of water evaporation due to boiling =\",m*3600 ,\"kg/h\")\n", "print '%s %.2f %s' %(\"\\n Critical Heat flux corresponding to the burnout point =\",qmax/math.pow(10,6) ,\"MW/m^2\");\n", "#END" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", " Boiling Heat transfer rate = 59.13 kW\n", "\n", " Rate of water evaporation due to boiling = 94 kg/h\n", "\n", " Critical Heat flux corresponding to the burnout point = 1.26 MW/m^2\n" ] } ], "prompt_number": 1 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 10.2 Page 635" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "import math\n", "#Operating Conditions\n", "Ts = 255+273. \t\t\t\t\t;#[K] Surface Temperature\n", "Tsat = 100+273. \t\t\t\t\t;#[K] Saturated Temperature\n", "D = 6*math.pow(10,-3) \t;#[m] Diameter of pan\n", "e = 1 \t\t\t\t\t;# emissivity\n", "stfncnstt=5.67*math.pow(10,(-8)) ;# [W/m^2.K^4] - Stefan Boltzmann Constant \n", "g = 9.81 \t\t\t\t\t;#[m^2/s] gravitaional constant\n", "#Table A.6 Saturated water Liquid Properties T = 373 K\n", "rhol = 957.9 \t\t\t;#[kg/m^3] Density\n", "hfg = 2257*math.pow(10,3) \t;#[J/kg] Specific Heat\n", "#Table A.4 Water Vapor Properties T = 450 K\n", "rhov = .4902 \t\t\t;#[kg/m^3] Density\n", "cpv = 1.98*math.pow(10,3) ;#[J/kg.K] Specific Heat\n", "kv = 0.0299 \t\t\t;#[W/m.K] Conductivity\n", "uv = 15.25*math.pow(10,-6) ;#[N.s/m^2] Viscosity\n", "#calculations\n", "\n", "Te = Ts-Tsat;\n", "\n", "hconv = .62*math.pow((kv*kv*kv*rhov*(rhol-rhov)*g*(hfg+.8*cpv*Te)/(uv*D*Te)),.25);\n", "hrad = e*stfncnstt*(math.pow(Ts,4)-math.pow(Tsat,4))/(Ts-Tsat);\n", "\n", "#From eqn 10.9 h^(4/3) = hconv^(4/3) + hrad*h^(1/3)\n", "#Newton Raphson\n", "h=250.; \t\t\t\t\t\t#Initial Assumption\n", "while 1>0 :\n", "\tf = math.pow(h,(4./3.)) - (math.pow(hconv,(4./3.)) + math.pow(hrad*h,(1./3.)));\n", "\tfd = (4./3.)*math.pow(h,(1./3.)) - (1./3.)*hrad*math.pow(h,(-2./3.));\n", "\thn=h-f/fd;\n", "\tz=math.pow(hn,(4./3.)) - (math.pow(hconv,(4./3.)) + math.pow(hrad*hn,(1./3.)))\n", "\tif z < .01:\n", "\t\tbreak;\n", "\th=hn;\n", "\n", "q = h*math.pi*D*Te; \t\t\t\t#power dissipation\n", "#results\n", "\n", "print '%s %d %s' %(\"\\n Power Dissipation per unith length for the cylinder, qs= \",q,\"W/m\");\n", "print '%s' %(\"The answer is a bit different due to rounding off error\")\n", "#END" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", " Power Dissipation per unith length for the cylinder, qs= 730 W/m\n", "The answer is a bit different due to rounding off error\n" ] } ], "prompt_number": 2 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 10.3 Page 648" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "import math\n", "#Operating Conditions\n", "Ts = 50+273. \t\t\t;#[K] Surface Temperature\n", "Tsat = 100+273. \t\t\t;#[K] Saturated Temperature\n", "D = .08 \t\t\t;#[m] Diameter of pan\n", "g = 9.81 \t\t\t;#[m^2/s] gravitaional constant\n", "L = 1 \t\t#[m] Length\n", "#Table A.6 Saturated Vapor Properties p = 1.0133 bars\n", "rhov = .596 \t\t;#[kg/m^3] Density\n", "hfg = 2257*1000. \t;#[J/kg] Specific Heat\n", "#Table A.6 Saturated water Liquid Properties T = 348 K\n", "rhol = 975. \t\t;#[kg/m^3] Density\n", "cpl = 4193. \t; #[J/kg.K] Specific Heat\n", "kl = 0.668 \t;#[W/m.K] Conductivity\n", "ul = 375*math.pow(10,-6) ;#[N.s/m^2] Viscosity\n", "#calculations\n", "\n", "\n", "uvl = ul/rhol \t;#[N.s.m/Kg] Kinematic viscosity\n", "Ja = cpl*(Tsat-Ts)/hfg;\n", "hfg2 = hfg*(1+.68*Ja);\n", "\n", "#Equation 10.43\n", "Re = math.pow((3.70*kl*L*(Tsat-Ts)/(ul*hfg2*math.pow((uvl*uvl/g),.33334))+4.8),.82); #Reynolds number\n", "\n", "#From equation 10.41\n", "hL = Re*ul*hfg2/(4*L*(Tsat-Ts)); \t\t#Transfer coefficient\n", "q = hL*(math.pi*D*L)*(Tsat-Ts); \t\t#Heat transfer rate\n", "\n", "m = q/hfg;\t\t\t\t\t\t\t\t#Rate of condensation\n", "#Using Equation 10.26\n", "delta = math.pow((4*kl*ul*(Tsat-Ts)*L/(g*rhol*(rhol-rhov)*hfg2)),.25);\n", "#results\n", "\n", "print '%s %.2f %s %.4f %s' %(\"\\n Heat Transfer Rate = \",q/1000.,\"kW and Condensation Rates=\",m,\" kg/s\"); \n", "print '%s %.3f %s %.2f %s' %(\"\\n And as del(L)\", delta*1000,\"<< (D/2)\", D/2. ,\"m use of vertical cylinder correlation is justified\");\n", "#END" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "\n", " Heat Transfer Rate = 66.62 kW and Condensation Rates= 0.0295 kg/s\n", "\n", " And as del(L) 0.218 << (D/2) 0.04 m use of vertical cylinder correlation is justified\n" ] } ], "prompt_number": 3 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 10.4 Page 652" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "import math\n", "#Operating Conditions\n", "Ts = 25+273. \t\t\t\t\t;#[K] Surface Temperature\n", "Tsat = 54+273. \t\t\t\t\t;#[K] Saturated Temperature\n", "D = .006 \t\t\t\t\t; #[m] Diameter of pan\n", "g = 9.81 \t\t\t\t\t;#[m^2/s] gravitaional constant\n", "N = 20 \t\t\t\t# No of tubes\n", "\n", "#Table A.6 Saturated Vapor Properties p = 1.015 bar\n", "rhov = .098 \t\t\t\t;#[kg/m^3] Density\n", "hfg = 2373*1000. \t\t\t;#[J/kg] Specific Heat\n", "#Table A.6 Saturated water Liquid Properties Tf = 312.5 K\n", "rhol = 992. \t\t\t\t;#[kg/m^3] Density\n", "cpl = 4178. \t\t\t;#[J/kg.K] Specific Heat\n", "kl = 0.631 \t\t\t; #[W/m.K] Conductivity\n", "ul = 663*math.pow(10,-6) \t; #[N.s/m^2] Viscosity\n", "#calculations\n", "\n", "Ja = cpl*(Tsat-Ts)/hfg;\t\t\t\t\n", "hfg2 = hfg*(1+.68*Ja); \t\t\t\t#Coefficient of condensation\n", "#Equation 10.46\n", "h = .729*math.pow((g*rhol*(rhol-rhov)*kl*kl*kl*hfg2/(N*ul*(Tsat-Ts)*D)),.25);\n", "#Equation 10.34\n", "m1 = h*(math.pi*D)*(Tsat-Ts)/hfg2;\t#Average condensation rate\n", "\n", "m = N*N*m1;\t\t\t\t\t\t\t#Rate per unit length\n", "#results\n", "\n", "print '%s %.3f %s' %(\"\\n For the complete array of tubes, the condensation per unit length is\",m ,\" kg/s.m\");\n", "#END" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "EXAMPLE 10.4 Page 652 \n", "\n", "\n", " For the complete array of tubes, the condensation per unit length is 0.463 kg/s.m\n" ] } ], "prompt_number": 4 } ], "metadata": {} } ] }