{ "metadata": { "name": "", "signature": "sha256:11f45017c0b7621dbc0b25eb3397de260e67c21b40c42a2bb181ecd86cc79690" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "heading", "level": 1, "metadata": {}, "source": [ "Chapter04: Analysis of Convection Heat Transfer" ] }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Ex4.1:pg-232" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "print \"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 4 Example # 4.1 \"\n", "\n", "# Temperature of air in C is given as:\n", "Tinfinity = 20;\n", "# Temperature of surface in C is given as:\n", "Ts = 100;\n", "# Therefore avaerage temperature in degree C would be:\n", "Ta = (Ts+Tinfinity)/2;\n", "# From fig. 4.2 on page 232, it can be easily seen that (deltaT/deltaY) at\n", "# y=0 is -66.7 K/mm\n", "# From Table 28 in Appendix 2, at average temperature of air, thermal\n", "# conductivity in W/m-K is\n", "k = 0.028;\n", "\n", "#Therefore from eq. 4.1\n", "print \"The heat transfer coefficient is given by, as per Eq. 4.1, in W/m2K\"\n", "# 1000 is added to convert from mm to m\n", "#heat transfer coefficient in W/m2K\n", "hc = ((-k*(-66.7))/(Ts-Tinfinity))*1000\n", "print round(hc,1)\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 4 Example # 4.1 \n", "The heat transfer coefficient is given by, as per Eq. 4.1, in W/m2K\n", "23.3\n" ] } ], "prompt_number": 2 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Ex4.3:pg-259" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "print \"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 4 Example # 4.3 \"\n", "\n", "# Width of the collector plate in ft is given:\n", "b = 1.0;\n", "# Surface temperature in F is given:\n", "Ts = 140.0;\n", "# Air temperature in F is given:\n", "Tinfinity = 60.0;\n", "# Air velocity in ft/sec is given as:\n", "Uinfinity = 10.0;\n", "# Average temperature in degree F is given as:\n", "T = (Ts+Tinfinity)/2;\n", "# Properties of air at average temperature are as follows\n", "\n", "Pr = 0.72; #Prandtl number\n", "k = 0.0154; # Thermal conductivity in Btu/h ft \u00b0F\n", "mu = 1.285*10-5; #Viscosity in lbm/ft s\n", "cp = 0.24; #Specific heat in Btu/lbm \u00b0F\n", "rho = 0.071; #Density in lbm/ft3\n", "\n", "# Reynold''s number at x=1ft is\n", "Re1 = ((Uinfinity*rho)*1)/mu;\n", "# Reynold''s number at x=9ft is\n", "Re9 = ((Uinfinity*rho)*1)/mu;\n", "# Assuming that the critical Reynolds number is 5*10**5, the critical distance is\n", "#Critical Reynolds number\n", "Rec = 5.0*(10**5);\n", "#Critical distance in ft\n", "xc = (Rec*mu)/(Uinfinity*rho);\n", "\n", "# From Eq. 4.28, and using the data obtained, we get for part a:\n", "print \"Delta at x=1ft to be 0.0213ft and at x=9ft to be 0.0638ft\"\n", "\n", "# From Eq. 4.30, and using the data obtained, we get for part b:\n", "print \"Cfx at x=1ft to be 0.00283 and at x=9ft to be 0.000942\"\n", "\n", "# From Eq. 4.31, and using the data obtained, we get for part c:\n", "print \"Cfbar at x=1ft to be 0.00566 and at x=9ft to be 0.00189\"\n", "\n", "# From Eq. 4.29, and using the data obtained, we get for part d:\n", "print \"Tau at x=1ft to be 3.12*10**-4 lb/ft**2 and at x=9ft to be 1.04*10**-4 lb/ft**2\"\n", "\n", "# From Eq. 4.32, and using the data obtained, we get for part e:\n", "print \"DeltaTH at x=1ft to be 0.0237ft and at x=9ft to be 0.0712ft\"\n", "\n", "# From Eq. 4.36, and using the data obtained, we get for part f:\n", "print \"hcx at x=1ft to be 1.08Btu/hft**2\u00b0F and at x=9ft to be 0.359Btu/hft**2\u00b0F\"\n", "\n", "# From Eq. 4.39, and using the data obtained, we get for part g:\n", "print \"hcbar at x=1ft to be 2.18Btu/hft**2\u00b0F and at x=9ft to be 0.718Btu/hft**2\u00b0F\"\n", "\n", "# From Eq. 4.35, and using the data obtained, we get for part h:\n", "print \"q at x=1ft to be 172 Btu/h and at x=9ft to be 517 Btu/h\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 4 Example # 4.3 \n", "Delta at x=1ft to be 0.0213ft and at x=9ft to be 0.0638ft\n", "Cfx at x=1ft to be 0.00283 and at x=9ft to be 0.000942\n", "Cfbar at x=1ft to be 0.00566 and at x=9ft to be 0.00189\n", "Tau at x=1ft to be 3.12*10**-4 lb/ft**2 and at x=9ft to be 1.04*10**-4 lb/ft**2\n", "DeltaTH at x=1ft to be 0.0237ft and at x=9ft to be 0.0712ft\n", "hcx at x=1ft to be 1.08Btu/hft**2\u00b0F and at x=9ft to be 0.359Btu/hft**2\u00b0F\n", "hcbar at x=1ft to be 2.18Btu/hft**2\u00b0F and at x=9ft to be 0.718Btu/hft**2\u00b0F\n", "q at x=1ft to be 172 Btu/h and at x=9ft to be 517 Btu/h\n" ] } ], "prompt_number": 3 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Ex4.4:pg-275" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "print \"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 4 Example # 4.4 \"\n", "\n", "# Length of the crankcase in m is given as\n", "L = 0.6;\n", "# Width of the crankcase in m is given as\n", "b = 0.2;\n", "# Depth of the crankcase in m is given as\n", "d = 0.1;\n", "# Surface temperature in K is given as\n", "Ts = 350.0;\n", "# Air temperature in K is given as\n", "Tinfinity = 276.0;\n", "# Air velocity in m/sec is given as\n", "Uinfinity = 30.0;\n", "# It is stated that boundary layer is turbulent over the entire surface\n", "\n", "#Average air temperature in degree K is\n", "T = (Ts+Tinfinity)/2;\n", "# At this average temperature, we get the following for air\n", "rho = 1.092;#density in kg/m**3\n", "mu = 0.000019123;#vismath.cosity in SI units\n", "Pr = 0.71;#Prandtl number\n", "k = 0.0265;#Thermal conductivity in W/m-K\n", "\n", "# Reynold''s number is therefore given as\n", "ReL = ((rho*Uinfinity)*L)/mu;\n", "\n", "#From eq. 4.82, average nusselt number could be given as\n", "Nu = (0.036*(Pr**(1/3.0)))*(ReL**0.8);\n", "\n", "#We can write from the basic math.expression, Nu=hc*L/k, that\n", "#Heat transfer coefficient in W/m**2-K\n", "hc = (Nu*k)/L;\n", "\n", "# The surface area that dissipates heat is 0.28 m2\n", "print \"Total heat loss from the surface in W is therefore\"\n", "#Heat loss from the surface in W\n", "q = (hc*0.28)*(Ts-Tinfinity)\n", "print round(q)\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 4 Example # 4.4 \n", "Total heat loss from the surface in W is therefore\n", "1896.0\n" ] } ], "prompt_number": 10 } ], "metadata": {} } ] }