{
"metadata": {
"name": "",
"signature": "sha256:9c4fb6b8e822716d4e29e95db1a4da7b71b979535df0e47c4729b7b08b5165ec"
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"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"Chapter 7 : Forced Convection Systems"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.1 Page No : 275"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\n",
"# Variables\n",
"Ta = 20;\t\t\t#Temperature of air in degree C\n",
"Tp = 134;\t\t\t#Temperature of heated plate in degree C\n",
"v = 3;\t\t\t#Velocity of flow in m/s\n",
"L = 2;\t\t\t#Length of plate in m\n",
"W = 1.5;\t\t\t#Width of plate in m\n",
"x = 0.4;\t\t\t#Distance of plane from the plate in m\n",
"k = (15.06*10**-6);\t\t\t#Kinematic vismath.cosity in m**2/s\n",
"\n",
"# Calculations\n",
"Re = (v*x)/k;\t\t\t#Reynold number\n",
"q = ((5*x)/math.sqrt(Re))*1000;\t\t\t#Thickness of boundary layer in mm\n",
"Cfx = (0.664/math.sqrt(Re))/10**-3;\t\t\t#Local skin friction coefficient *10**-3\n",
"\n",
"# Results\n",
"print 'Thickness of boundary layer is %3.1f mm Local skin friction coefficient is %3.2f*10**-3'%(q,Cfx)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Thickness of boundary layer is 7.1 mm Local skin friction coefficient is 2.35*10**-3\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.2 Page No : 275"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Ta = 20;\t\t\t#Temperature of air in degree C\n",
"Tp = 134;\t\t\t#Temperature of heated plate in degree C\n",
"v = 3;\t\t\t#Velocity of flow in m/s\n",
"L = 2;\t\t\t#Length of plate in m\n",
"W = 1.5;\t\t\t#Width of plate in m\n",
"x = 0.4;\t\t\t#Distance of plane from the plate in m\n",
"k = (15.06*10**-6);\t\t\t#Kinematic vismath.cosity in m**2/s\n",
"\n",
"# Calculations\n",
"Tf = (Ta+Tp)/2;\t\t\t#Film temperature in degree C\n",
"pw = 0.998;\t\t\t#Density of air at 77 degree C\n",
"Cp = 1009;\t\t\t#Specific heat of air at 77 degree C\n",
"kw = (20.76*10**-6);\t\t\t#Kinematic viscosity of air at 77 degree C\n",
"k = 0.03;\t\t\t#Thermal conductivity of air at 77 degree C\n",
"Pr = 0.697;\t\t\t#prantl number of air at 77 degree C\n",
"Re = (v*x)/kw;\t\t\t#Reynolds number\n",
"Nu = (0.332*Re**0.5*Pr**(1./3));\t\t\t#Nusselts number\n",
"h = (Nu*k)/x;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"h1 = (h*2);\t\t\t#Average value of heat transfer coefficient in W/m**2.K\n",
"Q = h1*x*W*(Tp-Ta);\t\t\t#Heat flow in W\n",
"Q1 = (2*Q);\t\t\t#Heat flow from both sides of the plate in W\n",
"\n",
"# Results\n",
"print 'Heat flow from both sides of the plate is %3.0f W'%(round(Q1,-1))\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Heat flow from both sides of the plate is 1450 W\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.3 Page No : 282"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"# Variables\n",
"Ta = 20;\t\t\t#Temperature of air in degree C\n",
"v = 3;\t\t\t#Velocity of flow in m/s\n",
"L = 2;\t\t\t#Length of plate in m\n",
"W = 1;\t\t\t#Width of plate in m\n",
"x1 = 0.3;\t\t\t#Initial point of the boundary layer in m\n",
"x2 = 0.8;\t\t\t#Final point of the boundary layer in m\n",
"p = 1.17;\t\t\t#Density of air at 20 degree C in kg/m**3\n",
"k = (15*10**-6);\t\t\t#Kinematic vismath.cosity in m**2/s\n",
"Re = (5*10**5);\t\t\t#Reynolds number at the transition frm laminar to turbulant\n",
"\n",
"# Calculations\n",
"x = (k*Re)/v;\t\t \t#Critical length in m\n",
"Rel = (v*L)/k; \t\t\t#Reynolds number\n",
"q = (4.64*L)/math.sqrt(Rel)*1000;\t\t\t#Boundary layer thickness at the trailing edge of plate in mm\n",
"ts = 1.292*(0.5*p*v**2)*math.sqrt(1./Rel);\t#Average shear stress in N/m**2\n",
"F = (2*L*ts);\t\t \t#Drag force on the two sides of the plate in N\n",
"q80 = (4.64*x2)/math.sqrt((v*x2)/k);\t\t\t#Boundray layer thickness at x = 0.8 m\n",
"q30 = (4.64*x1)/math.sqrt((v*x1)/k);\t\t\t#Boundray layer thickness at x = 0.3 m\n",
"m = ((5./8)*p*v*(q80-q30))/10**-3;\t\t\t#Mass flow of air in kg/s\n",
"\n",
"# Results\n",
"print 'Boundary layer thickness at the trailing edge of plate is % 3.2f mm \\n \\\n",
"Drag force on the two sides of the plate is %3.4f N \\n \\\n",
"Mass flow of air is %3.1f*10**-3 kg/s'%(q,F,m)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Boundary layer thickness at the trailing edge of plate is 14.67 mm \n",
" Drag force on the two sides of the plate is 0.0430 N \n",
" Mass flow of air is 7.9*10**-3 kg/s\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.4 Page No : 283"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"# Variables\n",
"P = 8.;\t\t\t#Pressure of air in kN/m**2\n",
"Ta = 250.;\t\t\t#Temperature of air in degree C\n",
"L = 1.;\t\t\t#Length of the palte in m\n",
"W = 0.3;\t\t\t#Width of the plate in m\n",
"v = 8.;\t\t\t#Velocity of air in m/s\n",
"Tp = 78.;\t\t\t#Temperature of plate in degree C\n",
"\n",
"# Calculations\n",
"Tf = (Ta+Tp)/2;\t\t\t#Film temperature in degree C\n",
"Cp = 1018;\t\t\t#Specific heat of air at 164 degree C and 1 atm pressure\n",
"kw = (30.8*10**-6);\t\t\t#Kinematic viscosity of air at 164 degree C and 1 atm pressure\n",
"k = 0.0364;\t\t\t#Thermal conductivity of air at 164 degree C and 1 atm pressure\n",
"Pr = 0.69;\t\t\t#prant number of air at 164 degree C and 1 atm pressure\n",
"k1 = kw*(101330/(P*1000));\t\t\t#Kinematic viscosity of air at 164 degree C and 8kN/m**2 pressure\n",
"Re = (v*L)/k1;\t\t\t#Reynolds number\n",
"h = 0.662*(k/L)*math.sqrt(Re)*Pr**(1./3);\t\t\t#Heat transfer coefficient in W/m.K\n",
"Q = 2*h*L*W*(Ta-Tp);\t\t\t#Rate of heat removal in W\n",
"\n",
"\n",
"# Results\n",
"print 'Rate of heat removal is %3.1f W'%(Q)\n",
"\n",
"#note : answer is slightly different because of rounding off error."
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Rate of heat removal is 314.7 W\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.5 Page No : 286"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"# Variables\n",
"P = 8.;\t\t\t#Pressure of air in kN/m**2\n",
"Ta = 250.;\t\t\t#Temperature of air in degree C\n",
"L = 1.;\t\t\t#Length of the palte in m\n",
"W = 0.3;\t\t\t#Width of the plate in m\n",
"v = 8.;\t\t\t#Velocity of air in m/s\n",
"Tp = 78.;\t\t\t#Temperature of plate in degree C\n",
"R = 287.;\t\t\t#Universal gas constant in J/kg.K\n",
"\n",
"# Calculations\n",
"Tf = (Ta+Tp)/2;\t\t\t#Film temperature in degree C\n",
"Cp = 1018;\t\t\t#Specific heat of air at 164 degree C and 1 atm pressure\n",
"kw = (30.8*10**-6);\t\t\t#Kinematic viscosity of air at 164 degree C and 1 atm pressure\n",
"k = 0.0364;\t\t\t#Thermal conductivity of air at 164 degree C and 1 atm pressure\n",
"Pr = 0.69;\t\t\t#prant number of air at 164 degree C and 1 atm pressure\n",
"k1 = kw*(101330/(P*1000));\t\t\t#Kinematic viscosity of air at 164 degree C and 8kN/m**2 pressure\n",
"Re = (v*L)/k1;\t\t\t#Reynolds number\n",
"h = 0.662*(k/L)*math.sqrt(Re)*Pr**(1./3);\t\t\t#Heat transfer coefficient in W/m.K\n",
"Q = 2*h*L*W*(Ta-Tp);\t\t\t#Rate of heat removal in W\n",
"p = (P*1000)/(R*(Tf+273));\t\t\t#Density in kg/m**3\n",
"St = (h/(p*Cp*v));\t\t\t#Stanton number\n",
"Cfx2 = (St*Pr**(2/3));\t\t\t#Colburn factor\n",
"ts = (Cfx2*p*v**2);\t\t\t#Average shear stress in N/m**2\n",
"D = (0.0186*W*L);\t\t\t#Drag force on one side of plate in N\n",
"D2 = (2*D)/10**-3;\t\t\t#Total drag force on both sides of plate in N\n",
"\n",
"# Results\n",
"print 'The drag force exerted on the plate is %3.2f*10**-3 N'%(D2)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The drag force exerted on the plate is 11.16*10**-3 N\n"
]
}
],
"prompt_number": 8
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.6 Page No : 289"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"L = 1;\t\t\t#Length of the palte in m\n",
"W = 1;\t\t\t#Width of the plate in m\n",
"Ts = 10;\t\t\t#Temperature of free strem air in degree C\n",
"v = 80;\t\t\t#Velocity of free stream air in m/s\n",
"\n",
"# Calculations\n",
"k = 0.025;\t\t\t #Thermal conductivity of air at 10 degree C \n",
"Pr = 0.72;\t\t\t #prant number of air at 10 degree C\n",
"v1 = (14.15*10**-6);\t\t\t #Kinematic viscosity of air at 10 degree C \n",
"Re = (v*L)/v1;\t\t\t #Reynolds number\n",
"q = 0.381*L*Re**(-1./5);\t\t \t#Thickness of the boundary layer at the trailing edge of the plate in m\n",
"Nu = (0.037*Re**(4./5)*Pr**(1./3));\t\t\t#Nusselts number\n",
"h = (Nu*k)/L; \t\t\t#Mean value of the heat transfer coefficient in W/m**2.K\n",
"\n",
"# Results\n",
"print 'Thickness of the boundary layer at the trailing edge of the plate is %3.4f m \\n \\\n",
"Mean value of the heat transfer coefficient is %3.0f W/m**2.K'%(q,h)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Thickness of the boundary layer at the trailing edge of the plate is 0.0170 m \n",
" Mean value of the heat transfer coefficient is 209 W/m**2.K\n"
]
}
],
"prompt_number": 8
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.7 Page No : 290"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Ta = 0.;\t\t \t#Temperature of air stream in degree C\n",
"Tp = 90.; \t\t#Temperature of heated plate in degree C\n",
"v = 75.;\t\t \t#Speed of air in m/s\n",
"L = 0.45;\t\t\t#Length of the palte in m\n",
"W = 0.6;\t\t\t#Width of the plate in m\n",
"Re = (5.*10**5);\t\t#Reynolds number at the transition from laminar to turbulant\n",
"\n",
"# Calculations\n",
"Tf = (Ta+Tp)/2;\t\t\t#Film temperature in degree C\n",
"k = 0.028;\t\t\t#Thermal conductivity of air at 10 degree C \n",
"Pr = 0.698;\t\t\t#prant number of air at 10 degree C\n",
"v1 = (17.45*10**-6);\t\t\t#Kinematic viscosity of air at 10 degree C \n",
"x = (Re*v1)/v;\t\t\t#Critical length in m\n",
"Rel = (v*L)/v1;\t\t\t#Reynolds number\n",
"Cfl = ((0.074/Rel**(1./5))-(1740/Rel))/10**-3;\t\t\t#Average value of friction coefficient *10**-3\n",
"Nu = ((0.037*Rel**(4./5))-870)*Pr**(1./3);\t\t\t#Nussults number\n",
"h = (Nu*k)/L;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"Q = (2*h*L*W*Tp);\t\t\t#Rate of energy dissipation in W\n",
"\n",
"# Results\n",
"print 'Average value of friction coefficient is %3.2f*10**-3 \\n \\\n",
"Heat transfer coefficient is %3.0f W/m**2.K \\n \\\n",
"Rate of energy dissipation is %i W'%(Cfl,h,Q)\n",
"\n",
"# note : book answer is wrong"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Average value of friction coefficient is 3.19*10**-3 \n",
" Heat transfer coefficient is 170 W/m**2.K \n",
" Rate of energy dissipation is 8281 W\n"
]
}
],
"prompt_number": 9
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.8 Page No : 296"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"D = 0.3;\t\t\t#Diameter of cylinder in m\n",
"L = 1.7;\t\t\t#Height of cylinder in m\n",
"Ts = 30.;\t\t\t#Surface temperature in degree C\n",
"v = 10.;\t\t\t#Speed of wind in m/s\n",
"Ta = 10.;\t\t\t#Temperature of air in degree C\n",
"\n",
"# Calculations\n",
"Tf = (Ta+Ts)/2;\t\t\t#Film temperature in degree C\n",
"k = 0.0259;\t\t\t#Thermal conductivity of air at 20 degree C \n",
"Pr = 0.707;\t\t\t#prant number of air at 20 degree C\n",
"v1 = (15*10**-6);\t\t\t#Kinematic viscosity of air at 20 degree C\n",
"Re = (v*D)/v1;\t\t\t#Reynolds number\n",
"Nu = 0.027*Re**0.805*Pr**(1./3)\t\t\t#Nusselts number\n",
"h = (Nu*k)/D;\t\t\t#Heat transfer coefficent in W/m**2.K\n",
"Q = (h*3.14*D*L*(Ts-Ta));\t\t\t#Rate of heat loss in W\n",
"\n",
"# Results\n",
"print 'Rate of heat loss is %3.1f W'%(Q)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Rate of heat loss is 1230.9 W\n"
]
}
],
"prompt_number": 11
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.9 Page No : 297"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Ta = 27;\t\t\t#Temperature of air stream in degree C\n",
"v = 0.3;\t\t\t#Velodity of air in m/s\n",
"Q = 100;\t\t\t#Poer of electric bulb in W\n",
"Te = 127;\t\t\t#Temperature of electric bulb in degree C\n",
"D = 0.06;\t\t\t#Diameter of sphere in m\n",
"\n",
"# Calculations\n",
"Tf = (Ta+Te)/2;\t\t\t#Film temperature in degree C\n",
"k = 0.03;\t\t\t#Thermal conductivity of air at 77 degree C \n",
"Pr = 0.697;\t\t\t#prant number of air at 77 degree C\n",
"v1 = (2.08*10**-5);\t\t\t#Kinematic viscosity of air at 77 degree C\n",
"Re = (v*D)/v1;\t\t\t#Reynolds number\n",
"h = (k*0.37*Re**0.6)/D;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"Q = (h*3.14*D**2*(Te-Ta));\t\t\t#Heat transfer rate in W\n",
"Qp = (Q*100)/100;\t\t\t#Percentage of heat lost by forced convection \n",
"\n",
"# Results\n",
"print \"Heat transfer rate is %3.2f W \\n \\\n",
"Percentage of power lost due to convection is %3.2f percent\"%(Q,Qp)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Heat transfer rate is 12.10 W \n",
" Percentage of power lost due to convection is 12.10 percent\n"
]
}
],
"prompt_number": 12
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.10 Page No : 297"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"# Variables\n",
"D = 0.015;\t\t\t#Diamter of copper bus bar in m\n",
"Ta = 20;\t\t\t#Temperature of air stream in degree C\n",
"v = 1;\t\t\t#Velocity of air in m/s\n",
"Ts = 80;\t\t\t#Surface temperature in degree C\n",
"p = 0.0175;\t\t\t#Resistivity of copper in ohm mm**2/m\n",
"\n",
"# Calculations\n",
"Tf = (Ta+Ts)/2;\t\t\t#Film temperature in degree C\n",
"k = 0.02815;\t\t\t#Thermal conductivity of air at 50 degree C \n",
"Pr = 0.703;\t\t\t#prant number of air at 50 degree C\n",
"v1 = (18.9*10**-6);\t\t\t#Kinematic viscosity of air at 50 degree C\n",
"Re = (v*D)/v1;\t\t\t#Reynolds number\n",
"Nu = 0.3+(((0.62*math.sqrt(Re)*Pr**(1./3))/(1+(0.4/Pr)**(2./3))**(1./4))*(1+(Re/28200.)**(5./8))**(4./5));\t\t\t#Nusselts number\n",
"h = (Nu*k)/D;\t\t\t#Heat transfer coefficent in W/m**2.K\n",
"I = 1000*3.14*D*math.sqrt((h*(Ts-Ta)*D)/(4*p));\t\t\t#Current in A\n",
"\n",
"# Results\n",
"print 'Heat transfer coefficient between the bus bar and cooling air is %3.2f W/m**2.K \\n \\\n",
"Maximum admissible current intensity for the bus bar is %3.0f A'%(h,I)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Heat transfer coefficient between the bus bar and cooling air is 28.31 W/m**2.K \n",
" Maximum admissible current intensity for the bus bar is 899 A\n"
]
}
],
"prompt_number": 14
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.11 Page No : 298"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Ta = 30;\t\t\t#Temperature of air stream in degree C\n",
"v = 25;\t\t\t#Velocity of stream in m/s\n",
"x = 0.05;\t\t\t#Side of a square in m\n",
"D = 0.05;\t\t\t#Diameter of circular cylinder in m\n",
"Ts = 124;\t\t\t#Surface temperature in degree C\n",
"\n",
"# Calculations\n",
"Tf = (Ta+Ts)/2;\t\t\t#Film temperature in degree C\n",
"k = 0.03;\t\t\t#Thermal conductivity of air at 77 degree C \n",
"Pr = 0.7;\t\t\t#prantL number of air at 77 degree C\n",
"v1 = (20.92*10**-6);\t\t\t#Kinematic viscosity of air at 77 degree C\n",
"Re = (v*D)/v1;\t\t\t#Reynolds number\n",
"Nu1 = 0.027*Re**0.805*Pr**(1./3);\t\t\t#Nussults number for circulat tube\n",
"h1 = (Nu1*k)/D;\t\t\t#Heat tansfer coefficient for circular tube in W/m**2.K\n",
"Nu2 = 0.102*Re**0.675*Pr**(1./3);\t\t\t#Nussults number for square tube\n",
"h2 = (Nu2*k)/D;\t\t\t#Heat transfer coefficient for square tube in W/m**2.K\n",
"\n",
"# Results\n",
"print 'Heat transfer coefficient for circular tube is %3.1f W/m**2.K \\n \\\n",
"Heat transfer coefficient for square tube is %3.2f W/m**2.K'%(h1,h2)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Heat transfer coefficient for circular tube is 100.7 W/m**2.K \n",
" Heat transfer coefficient for square tube is 91.02 W/m**2.K\n"
]
}
],
"prompt_number": 15
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.12 Page No : 302"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"n = 7;\t\t\t#Number of rows of tube\n",
"Ta = 15;\t\t\t#Temperature of air in degree C\n",
"v = 6;\t\t\t#Velocity of air in m/s\n",
"ST = 0.0205;\t\t\t#Transverse pitch in m\n",
"SD = 0.0205;\t\t\t#Longitudinal pitch in m\n",
"D = 0.0164;\t\t\t#Outside diameter of the tube in m\n",
"Ts = 70;\t\t\t#Surface temperature in degree C\n",
"\n",
"# Calculations\n",
"Tf = (Ta+Ts)/2;\t\t\t#Film temperature in degree C\n",
"k = 0.0274;\t\t\t#Thermal conductivity of air at 42.5 degree C \n",
"Pr = 0.705;\t\t\t#prant number of air at 42.5 degree C\n",
"v1 = (17.4*10**-6);\t\t\t#Kinematic viscosity of air at 42.5 degree C\n",
"p = 1.217;\t\t\t#Density in kg/m**3\n",
"vmax = (v*ST)/(ST-D);\t\t\t#Maximum velocity in m/s\n",
"Re = (vmax*D)/v1;\t\t\t#Reynolds number\n",
"Nu = (1.13*0.518*Re**0.556*Pr**(1./3))*0.97;\t\t\t#Nusselts number\n",
"h = (Nu*k)/D;\t\t\t#Heat transfer coefficent in W/m**2.K\n",
"f = 0.4;\t\t\t#From Fig. 7.10 on page no 303 \n",
"g = 1.04;\t\t\t#From Fig. 7.10 on page no 303\n",
"dp = (n*f*p*vmax**2*g)/2;\t\t\t#Pressure drop in N/m**2\n",
"\n",
"# Results\n",
"print 'Heat transfer coefficent is %3.2f W/m**2.K \\n \\\n",
"Pressure drop is %3.0f N/m**2'%(h,dp)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Heat transfer coefficent is 252.04 W/m**2.K \n",
" Pressure drop is 1595 N/m**2\n"
]
}
],
"prompt_number": 16
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.13 Page No : 304"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"n = 7;\t\t\t#Number of rows of tube\n",
"Ta = 15;\t\t\t#Temperature of air in degree C\n",
"v = 6;\t\t\t#Velocity of air in m/s\n",
"ST = 0.0205;\t\t\t#Transverse pitch in m\n",
"SD = 0.0205;\t\t\t#Longitudinal pitch in m\n",
"D = 0.0164;\t\t\t#Outside diameter of the tube in m\n",
"Ts = 70;\t\t\t#Surface temperature in degree C\n",
"\n",
"# Calculations\n",
"Tf = (Ta+Ts)/2;\t\t\t#Film temperature in degree C\n",
"k = 0.0253;\t\t\t#Thermal conductivity of air at 15 degree C \n",
"Pr = 0.710;\t\t\t#prant number of air at 15 degree C\n",
"v1 = (14.82*10**-6);\t\t\t#Kinematic viscosity of air at 15 degree C\n",
"p = 1.217;\t\t\t#Density in kg/m**3\n",
"Pr1 = 0.701;\t\t\t#prant number of air at 70 degree C\n",
"vmax = (v*ST)/(ST-D);\t\t\t#Maximum velocity in m/s\n",
"Re = (vmax*D)/v1;\t\t\t#Reynolds number\n",
"Nu = 0.35*Re**0.6*(Pr/Pr1)**0.25;\t\t\t#\n",
"h = (Nu*k)/D;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"\n",
"# Results\n",
"print ' Heat transfer coefficient is %3.1f W/m**2 K'%(h) \n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
" Heat transfer coefficient is 279.5 W/m**2 K\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.14 Page No : 305"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"m = 0.314;\t\t\t#Mass flow rate of air in m**3/s\n",
"n1 = 7;\t\t\t#Number of tubes in the direction of flow\n",
"n2 = 8;\t\t\t#Number of tubes perpendicular to the direction of flow\n",
"L = 1.25;\t\t\t#Length of each tube in m\n",
"D = 0.019;\t\t\t#Outer diameter in m\n",
"ST = 0.0286;\t\t\t#Transverse pitch in m\n",
"SD = 0.038;\t\t\t#Longitudinal pitch in m\n",
"Ta = 200;\t\t\t#Temperature of air in degree C\n",
"Ts = 96;\t\t\t#Surface temperature in degree C\n",
"\n",
"# Calculations\n",
"Tf = (Ta+Ts)/2;\t\t\t#Film temperature in degree C\n",
"k = 0.039;\t\t\t#Thermal conductivity of air at 15 degree C \n",
"Pr = 0.688;\t\t\t#prantl number of air at 15 degree C\n",
"v1 = (3*10**-5);\t\t\t#Kinematic vismath.cosity of air at 15 degree C\n",
"vmax = (m/((ST*n2*L)-(D*n2*L)));\t\t\t#Maximum velocity in m/s\n",
"Re = (vmax*D)/v1;\t\t\t#Reynolds number\n",
"Nu = (0.299*Re**0.602*Pr**(1./3));\t\t\t#Nusselts number\n",
"X = 0.96;\t\t\t#From Table 7.5 on page no.302\n",
"Nux = (X*Nu);\t\t\t#Average nusselts number\n",
"h = (Nux*k)/D;\t\t\t#Convective heat transfer coefficient in W/m**2.K\n",
"\n",
"# Results\n",
"print 'Convective heat transfer coefficient is %3.2f W/m**2.K'%(h)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Convective heat transfer coefficient is 51.58 W/m**2.K\n"
]
}
],
"prompt_number": 18
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.15 Page No : 310"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"D = 0.2;\t\t\t#Diameter of pipeline in m\n",
"\t\t\t#velocity profile is given by u = 96r-190r**2 m/s\n",
"\t\t\t#Temperature profile is given by T = 100(1-2r) degree C\n",
"\n",
"# Calculations\n",
"vmax = (64*(D/2))-(95*(D/2)**2);\t\t\t#Mean velocity in m/s\n",
"T = (2/(vmax*(D/2)**2))*(((9600*(D/2)**3)/3)-((38200*(D/2)**4)/4)+((38000*(D/2)**5)/5));\t\t\t#Average temperature of the fluid in degree C\n",
"\n",
"# Results\n",
"print 'Average temperature of the fluid is %3.2f degree C'%(T)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Average temperature of the fluid is 85.17 degree C\n"
]
}
],
"prompt_number": 19
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.16 Page No : 311"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Di = 0.025;\t\t\t#I.D of the tube in m\n",
"Do = 0.04;\t\t\t#O.D of the tube in m\n",
"m = 5.;\t\t\t#Mass flow rate of water in kg/m\n",
"T = [20.,70.];\t\t\t#Temperature at entry and exit of water in degree C\n",
"Q = 10.**7;\t\t\t#Heat in W/m**3\n",
"Ts = 80.;\t\t\t#Surface temperature in degree C\n",
"Cp = 4179.;\t\t\t#Specific heat of water in J/kg.K\n",
"\n",
"# Calculations\n",
"Tb = (T[0]+T[1])/2;\t\t\t#Film temperature in degree C\n",
"L = ((4*(m/60)*Cp*(T[1]-T[0]))/(3.14*(Do**2-Di**2)*Q));\t\t\t#Length of tube in m\n",
"qs = ((Q*(Do**2-Di**2))/(4*Di));\t\t\t#Heat flux at the surface in W/m**2\n",
"h = (qs/(Ts-T[1]));\t\t\t#Heat transfer coefficient at the outlet in W/m**2.K\n",
"\n",
"\n",
"# Results\n",
"print 'Length of tube is %3.3f m \\nHeat transfer coefficient at the outlet is %3.0f W/m**2.K'%(L,h)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Length of tube is 2.275 m \n",
"Heat transfer coefficient at the outlet is 9750 W/m**2.K\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.17 Page No : 312"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"k = 0.175;\t\t\t#Thermal conductivity in W/m.K\n",
"Di = 0.006;\t\t\t#I.D of the tube in m\n",
"L = 8;\t\t\t#Length of the tube in m\n",
"dT = 50;\t\t\t#Mean temperature difference in degree C\n",
"\n",
"# Calculations\n",
"h = (3.66*k)/Di;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"Q = (h*3.14*Di*L*dT);\t\t\t#Heat transfer rate in W\n",
"\n",
"# Results\n",
"print 'Heat transfer coefficient is %3.2f W/m**2.K Heat transfer rate is %3.0f W'%(h,Q)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Heat transfer coefficient is 106.75 W/m**2.K Heat transfer rate is 804 W\n"
]
}
],
"prompt_number": 21
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.18 Page No : 312"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Ti = 25;\t\t\t#Initial temperature of water in degree C\n",
"D = 0.05;\t\t\t#Diamter of the tube in m\n",
"Re = 1600;\t\t\t#Reynolds number\n",
"q = 800;\t\t\t#Heat flux in W/m\n",
"Tf = 50;\t\t\t#Final temperature of water in degree C\n",
"\n",
"# Calculations\n",
"k = 0.61;\t\t\t#Thermal conductivity of water at 25 degree C in W/m.K\n",
"u = (915*10**-6);\t\t\t#Dynamic viscosity in N.s/m**2\n",
"m = (Re*3.14*D*u)/4;\t\t\t#Mass flow rate of water in kg/s\n",
"h = (4.364*k)/D;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"qs = (q/(3.14*D));\t\t\t#Constant heat flux in W/m**2\n",
"Cp = 4178;\t\t\t#Specific heat of water in J/kg.K\n",
"L = ((m*Cp*(Tf-Ti))/q);\t\t\t#Length of the tube in m\n",
"\n",
"# Results\n",
"print 'Average heat transfer coefficient is %3.2f W/m**2.K \\n \\\n",
"Length of the tube is %3.3f m'%(h,L)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Average heat transfer coefficient is 53.24 W/m**2.K \n",
" Length of the tube is 7.502 m\n"
]
}
],
"prompt_number": 22
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.19 Page No : 314"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Di = 0.015;\t\t\t#I.D of the tube in m\n",
"Tb = 60;\t\t\t#Temperature of the tube in degree C\n",
"m = 10;\t\t\t#Flow rate of water in ml/s\n",
"Ti = 20;\t\t\t#Temperature of water at entry in degree C\n",
"x = 1;\t\t\t#Dismath.tance form the plane in m\n",
"Tx = 34;\t\t\t#Temperature of water at 1 m dismath.tance in degree C\n",
"\n",
"# Calculations\n",
"Tbm = (Ti+Tx)/2;\t\t\t#Mean value of bulk temperature in degree C\n",
"pw = 997;\t\t\t#Density of air at 27 degree C in kg/m**3\n",
"Cp = 4180;\t\t\t#Specific heat of air at 27 degree C in J/kg.K\n",
"u = (855*10**-6);\t\t\t#Dynamic vismath.cosity of air at 27 degree C in N.s/m**2\n",
"k = 0.613;\t\t\t#Thermal conductivity of air at 27 degree C in W/m.K\n",
"Pr = 5.83;\t\t\t#prantl number of air at 27 degree C\n",
"us = (464*10**-6);\t\t\t#Dynamic vismath.cosity of air at 60 degree C in Ns/m**2\n",
"um = (m*10**-6)/((3.14/4)*Di**2);\t\t\t#Mean speed in m/s\n",
"Re = (pw*um*Di)/u;\t\t\t#Reynolds number\n",
"Nu = 3.66+((0.0668*(Di/x)*Re*Pr)/(1+(0.04*((Di/x)*Re*Pr)**(2./3))));\t\t\t#Nusselts number in Haussen correlation\n",
"Nux = (1.86*((Re*Pr)/(x/Di))**(1./3)*(u/us)**0.14);\t\t\t#Nusselsts number in Sieder - Tate correlation \n",
"\n",
"# Results\n",
"print 'Nusselts number in Haussen correlation is %3.2f \\n \\\n",
"Nusselsts number in Sieder - Tate correlation is %3.3f'%(Nu,Nux)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Nusselts number in Haussen correlation is 6.90 \n",
" Nusselsts number in Sieder - Tate correlation is 8.964\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.20 Page No : 318"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Tw = 50;\t\t\t#Temperature of water in degree C\n",
"Di = 0.005;\t\t\t#Inner diameter of the tube in m\n",
"L = 0.5;\t\t\t#Length of the tube in m\n",
"v = 1;\t\t\t#Mean velocity in m/s\n",
"Ts = 30;\t\t\t#Surface temperature in degree C\n",
"\n",
"# Calculations\n",
"Tf = (Tw+Ts)/2;\t\t\t#Film temperature in degree C\n",
"k = 0.039;\t\t\t#Thermal conductivity of air at 15 degree C \n",
"Pr = 0.688;\t\t\t#prant number of air at 15 degree C\n",
"p = 990;\t\t\t#Density of air at 50 degree C in kg/m**3\n",
"Cp = 4178;\t\t\t#Specific heat of air at 50 degree C in J/kg.K\n",
"v1 = (5.67*10**-7);\t\t\t#Kinematic viscosity of air at 50 degree C\n",
"v2 = (6.57*10**-7);\t\t\t#Kinematic viscosity of air at 40 degree C\n",
"Re = (v*Di)/v1;\t\t\t#Reynolds number\n",
"h = ((0.316/8)*((v*Di*10)/v2)**(-0.25)*p*Cp*v*(4.34)**(-2./3));\t\t\t#Heat transfer coefficient umath.sing the Colburn anamath.logy in W/m**2.K\n",
"\n",
"# Results\n",
"print 'Heat transfer coefficient using the Colburn analogy is %3.0f W/m**2.K'%(h)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Heat transfer coefficient using the Colburn analogy is 3697 W/m**2.K\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.21 Page No : 319"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Ti = 50;\t\t\t#Temperature of water at inlet in degree C\n",
"D = 0.015;\t\t\t#Diameter of tube in m\n",
"L = 3;\t\t\t#Length of the tube in m\n",
"v = 1;\t\t\t#Velocity of flow in m/s\n",
"Tb = 90;\t\t\t#Temperature of tube wall in degree C\n",
"Tf = 64;\t\t\t#Exit temperature of water in degree C\n",
"\n",
"# Calculations\n",
"Tm = (Ti+Tf)/2;\t\t\t#Bulk mean temperature in degree C\n",
"p = 990;\t\t\t#Density of air at 57 degree C in kg/m**3\n",
"Cp = 4184;\t\t\t#Specific heat of air at 57 degree C in J/kg.K\n",
"u = (0.517*10**-6);\t\t\t#Kinematic viscosity of air at 57 degree C in m**2/s\n",
"k = 0.65;\t\t\t#Thermal conductivity of air at 57 degree C in W/m.K\n",
"Pr = 3.15;\t\t\t#prantl number of air at 57 degree C \n",
"Re = (v*D)/u;\t\t\t#Reynolds number\n",
"Nu = (0.023*Re**(4./5)*Pr**0.4);\t\t\t#Nusselts number\n",
"h = (Nu*k)/D;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"Q = (h*3.14*D*L*(Tb-Tm))/1000;\t\t\t#Rate of heat transfered in kW\n",
"\n",
"# Results\n",
"print 'Heat transfer coefficient is %3.0f W/m**2.K \\nRate of heat transfered is %3.2f kW'%(h,Q)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Heat transfer coefficient is 5861 W/m**2.K \n",
"Rate of heat transfered is 27.33 kW\n"
]
}
],
"prompt_number": 27
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.22 Page No : 320"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"D = 0.022;\t\t\t#Diamter of the tube in m\n",
"v = 2;\t\t\t#Average velocity in m/s\n",
"Tw = 95;\t\t\t#Temperature of tube wall in degree C\n",
"T = [15,60];\t\t\t#Initial and final temperature of water in degree C\n",
"\n",
"# Calculations\n",
"Tm = (T[0]+T[1])/2;\t\t\t#Bulk mean temperature in degree C\n",
"p = 990;\t\t\t#Density of air at 37.5 degree C in kg/m**3\n",
"Cp = 4160;\t\t\t#Specific heat of air at 37.5 degree C in J/kg.K\n",
"u = (0.69*10**-3);\t\t\t#Dynamic viscosity of air at 37.5 degree C in Ns/m**2\n",
"k = 0.63;\t\t\t#Thermal conductivity of air at 37.5 degree C in W/m.K\n",
"us = (0.3*10**-3);\t\t\t#Dynamic viscosity of air at 37.5 degree C in Ns/m**2\n",
"Re = (p*v*D)/u;\t\t\t#Reynolds number\n",
"Pr = (u*Cp)/k;\t\t\t#Prantl number\n",
"Nu = (0.027*Re**(4./5)*Pr**(1./3)*(u/us)**0.14);\t\t\t#Nusselts number\n",
"h = (Nu*k)/D;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"\n",
"# Results\n",
"print 'Heat transfer coefficient is %3.0f W/m**2.K'%(h)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Heat transfer coefficient is 9969 W/m**2.K\n"
]
}
],
"prompt_number": 28
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.23 Page No : 320"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"D = 0.05;\t\t\t#Diamter of the tube in m\n",
"T = 147;\t\t\t#Average temperature in degree C\n",
"v = 0.8;\t\t\t#Flow vwlocity in m/s\n",
"Tw = 200;\t\t\t#Wall temperature in degree C\n",
"L = 2;\t\t\t#Length of the tube in m\n",
"\n",
"# Calculations\n",
"p = 812.1;\t\t\t#Density in kg/m**3 of oil at 147 degree C\n",
"Cp = 2427;\t\t\t#Specific heat of oil at 147 degree C in J/kg.K\n",
"u = (6.94*10**-6);\t\t\t#Kinematic viscosity of oil at 147 degree C in m**2/s\n",
"k = 0.133;\t\t\t#Thermal conductivity of oil at 147 degree C in W/m.K\n",
"Pr = 103;\t\t\t#prantl number of oil at 147 degree C \n",
"Re = (v*D)/u;\t\t\t#Reynolds number\n",
"Nu = (0.036*Re**0.8*Pr**(1./3)*(D/L)**0.055);\t\t\t#Nussults number\n",
"h = (Nu*k)/D;\t\t\t#Average heat transfer coefficient in W/m**2.K\n",
"\n",
"# Results\n",
"print 'Average heat transfer coefficient is %3.1f W/m**2.K'%(h)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Average heat transfer coefficient is 373.7 W/m**2.K\n"
]
}
],
"prompt_number": 29
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.24 Page No : 321"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"D = [0.4,0.8];\t\t\t#Dimensions of the trunk duct in m\n",
"Ta = 20;\t\t\t#Temperature of air in degree C\n",
"v = 7;\t\t\t#Velocity of air in m/s\n",
"v1 = (15.06*10**-6);\t\t\t#Kinematic viscosity in m**2/s\n",
"a = (7.71*10**-2);\t\t\t#Thermal diffusivity in m**2/h\n",
"k = 0.0259;\t\t\t#Thermal conductivity in W/m.K\n",
"\n",
"# Calculations\n",
"Dh = (4*(D[0]*D[1]))/(2*(D[0]+D[1]));\t\t\t#Value of Dh in m\n",
"Re = (v*Dh)/v1;\t\t\t#Reynolds number\n",
"Pr = (v1/a)*3600;\t\t\t#Prantl number\n",
"Nu = (0.023*Re**(4./5)*Pr**0.4);\t\t\t#Nussults number\n",
"h = (Nu*k)/Dh;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"Q = (h*(2*(D[0]+D[1])));\t\t\t#Heat leakage per unit length per unit difference in W\n",
"\n",
"# Results\n",
"print 'Heat leakage per unit length per unit difference is %3.2f W'%(Q)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Heat leakage per unit length per unit difference is 48.14 W\n"
]
}
],
"prompt_number": 31
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.25 Page No : 322"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Di = 0.03125;\t\t\t#I.D of the annulus in m\n",
"Do = 0.05;\t\t\t#O.D of the annulus in m\n",
"Ts = 50;\t\t\t#Outer surface temperature in degree C\n",
"Ti = 16;\t\t\t#Temeperature at which air enters in degree C\n",
"Tf = 32;\t\t\t#Temperature at which air exits in degree C\n",
"v = 30;\t\t\t#Flow rate in m/s\n",
"\n",
"# Calculations\n",
"Tb = (Ti+Tf)/2;\t\t\t#Mean bulk temperature of air in degree C\n",
"p = 1.614;\t\t\t#Density in kg/m**3 of air at 24 degree C\n",
"Cp = 1007;\t\t\t#Specific heat of air at 24 degree C in J/kg.K\n",
"u = (15.9*10**-6);\t\t\t#Kinematic viscosity of air at 24 degree C in m**2/s\n",
"k = 0.0263;\t\t\t#Thermal conductivity of air at 24 degree C in W/m.K\n",
"Pr = 0.707;\t\t\t#prantl number of air at 24 degree C\n",
"Dh = (4*(3.14/4)*(Do**2-Di**2))/(3.14*(Do+Di));\t\t\t#Hydraulic diameter in m\n",
"Re = (v*Dh)/u;\t\t\t#Reynolds number\n",
"Nu = (0.023*Re**0.8*Pr**0.4);\t\t\t#Nussults number\n",
"h = (Nu*k)/Dh;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"\n",
"# Results\n",
"print 'Heat transfer coefficient is %3.1f W/m**2.K'%(h)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Heat transfer coefficient is 122.3 W/m**2.K\n"
]
}
],
"prompt_number": 33
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.26 Page No : 324"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"T = [120,149];\t\t\t#Initail and final temperatures in degree C\n",
"m = 2.3;\t\t\t#Mass flow rate in kg/s\n",
"D = 0.025;\t\t\t#Diameter of the tube in m\n",
"Ts = 200;\t\t\t#Surface temperature in degree C\n",
"\n",
"# Calculations\n",
"Tb = (T[0]+T[1])/2;\t\t\t#Bulk mean temperature in degree C\n",
"p = 916;\t\t\t#Density in kg/m**3 of air at 134.5 degree C\n",
"Cp = 1356.6;\t\t\t#Specific heat of air at 134.5 degree C in J/kg.K\n",
"u = (0.594*10**-6);\t\t\t#Kinematic viscosity of air at 134.5 degree C in m**2/s\n",
"k = 84.9;\t\t\t#Thermal conductivity of air at 134.5 degree C in W/m.K\n",
"Pr = 0.0087;\t\t\t#prantl number of air at 134.5 degree C\n",
"Q = (m*Cp*(T[1]-T[0]))/1000;\t\t\t#Total heat transfer in kW\n",
"v = (m/(p*(3.14/4)*D**2));\t\t\t#Velocity of flow in m/s\n",
"Re = (v*D)/u;\t\t\t#Reynolds number\n",
"Pe = (Pr*Re);\t\t\t#Peclet number\n",
"Nu = (4.82+(0.0185*Pe**0.827));\t\t\t#Nussults number\n",
"h = (Nu*k)/D;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"L = ((Q*1000)/(h*3.14*D*(Ts-Tb)));\t\t\t#Minimum length of the tube in m if the wall temperature is not to exceed 200 degree C\n",
"\n",
"# Results\n",
"print 'Minimum length of the tube if the wall temperature is not to exceed 200 degree C is %3.3f m'%(L)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Minimum length of the tube if the wall temperature is not to exceed 200 degree C is 0.361 m\n"
]
}
],
"prompt_number": 34
}
],
"metadata": {}
}
]
}