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{
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"name": "",
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"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": {}
}
]
}
|
