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"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": {}
}
]
}
|
