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"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"Chapter 8: Heat Exchangers"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Ex8.1: Page 504"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"print \"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 8 Example # 8.1 \"\n",
"\n",
"#Outer dia in m\n",
"d = 0.0254;\n",
"#mass flow rate of hot fluid in kg/s\n",
"mh = 6.93;\n",
"#Specific heat of hot fluid n J/kgK\n",
"ch = 3810;\n",
"#Inlet temperature of hot fluid in degree C\n",
"Thin = 65.6;\n",
"#Outlet temperature of hot fluid in degree C\n",
"Thout = 39.4;\n",
"#mass flow rate of cold fluid in kg/s\n",
"mc = 6.3;\n",
"#Specific heat of cold fluid n J/kgK\n",
"cc = 4187;\n",
"#Inlet temperature of cold fluid in degree C\n",
"Tcin = 10;\n",
"#Overall heat transfer coefficient in W/m2K\n",
"U = 568;\n",
"\n",
"#Umath.sing energy balance, outlet temp. of cold fluid in degree C\n",
"Tcout = Tcin+((mh*ch)*(Thin-Thout))/(mc*cc);\n",
"\n",
"#The rate of heat flow in W\n",
"q = (mh*ch)*(Thin-Thout);\n",
"\n",
"print \"Parallel-flow tube and shell\"\n",
"#From Eq. (8.18) the LMTD for parallel flow\n",
"#Temperature difference at inlet in degree K\n",
"deltaTa = Thin-Tcin;\n",
"#Temperature difference at outlet in degree K\n",
"deltaTb = Thout-Tcout;\n",
"#LMTD in degree K\n",
"LMTD = (deltaTa-deltaTb)/log(deltaTa/deltaTb);\n",
"\n",
"#From Eq. (8.16) \n",
"print \"Heat transfer surface area in m2 is\"\n",
"#Heat transfer surface area in m2\n",
"A = q/(U*LMTD)\n",
"print round(A,2)\n",
"\n",
"print \"Counterflow tube and shell\"\n",
"#LMTD in degree K\n",
"LMTD = 29.4;\n",
"\n",
"print \"Heat transfer surface area in m2 is\"\n",
"#Heat transfer surface area in m2\n",
"A = q/(U*LMTD)\n",
"print round(A,2)\n",
"\n",
"A1 = A;#To be used further as a copy of this area\n",
"\n",
"print \"Counterflow exchanger with 2 shell passes and 72 tube passes\"\n",
"\n",
"#Correction factor found from Fig. 8.15 to the mean temperature for counterflow\n",
"P = (Tcout-Tcin)/(Thin-Tcin);\n",
"#Heat capacity ratio\n",
"Z = (mh*ch)/(mc*cc);\n",
"#From the chart of Fig. 8.15, F\u0003= 0.97\n",
"F = 0.97; #F-Factor\n",
"print \"Heat transfer surface area in m2 is\"\n",
"#Heat transfer surface area in m2 is\n",
"A = A1/F\n",
"print round(A,2)\n",
"\n",
"print \"Cross-flow, with one tube pass and one shell pass, shell-side fluid mixed\"\n",
"#Umath.sing same procedure, we get from charts\n",
"F = 0.88; #F-Factor\n",
"print \"Heat transfer surface area in m2 is\"\n",
"#Heat transfer surface area in m2 is\n",
"A = A1/F\n",
"print round(A,2)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 8 Example # 8.1 \n",
"Parallel-flow tube and shell\n",
"Heat transfer surface area in m2 is\n",
"66.51\n",
"Counterflow tube and shell\n",
"Heat transfer surface area in m2 is\n",
"41.43\n",
"Counterflow exchanger with 2 shell passes and 72 tube passes\n",
"Heat transfer surface area in m2 is\n",
"42.71\n",
"Cross-flow, with one tube pass and one shell pass, shell-side fluid mixed\n",
"Heat transfer surface area in m2 is\n",
"47.07\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Ex8.2: Page 510"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"print \"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 8 Example # 8.2 \"\n",
"\n",
"#mass flow rate of hot fluid in kg/s\n",
"mh = 1;\n",
"#Specific heat of hot fluid n J/kgK\n",
"ch = 2100;\n",
"#Inlet temperature of hot fluid in degree C\n",
"Thin = 340;\n",
"#Outlet temperature of hot fluid in degree C\n",
"Thout = 310;\n",
"#Specific heat of cold fluid n J/kgK\n",
"cc = 4187;\n",
"#Inlet temperature of cold fluid in degree C\n",
"Tcin = 290;\n",
"#Outlet temperature of cold fluid in degree C\n",
"Tcout = 300;\n",
"\n",
"#The heat capacity rate of the water in J/kgK is, from Eq. (8.14)\n",
"cc = ch*((Thin-Thout)/(Tcout-Tcin));\n",
"\n",
"#Temperature ratio P and Z is, from Eq. (8.20)\n",
"P = (Thin-Thout)/(Thin-Tcin); # P Temperature ratio\n",
"Z = (Tcout-Tcin)/(Thin-Thout); # Z Temperature ratio\n",
"\n",
"#From Fig. 8.14, F\u00030.94 and the mean temperature difference in degree K is\n",
"#F Value\n",
"F = 0.94;\n",
"#Temperature difference at inlet in degree K\n",
"deltaTa = Thin-Tcout;\n",
"#Temperature difference at outlet in degree K\n",
"deltaTb = Thout-Tcin;\n",
"#LMTD in degree K\n",
"LMTD = (deltaTa-deltaTb)/log(deltaTa/deltaTb);\n",
"#Mean temperature difference in degree K\n",
"deltaTmean = F*LMTD;\n",
"\n",
"#From Eq. (8.17) the overall conductance in W/K is\n",
"UA = ((mh*ch)*(Thin-Thout))/deltaTmean;\n",
"\n",
"#With reference to the new conditions and Eq. 6.62\n",
"#Conductance in W/K\n",
"UA = UA*((3/4.0)**0.8);\n",
"#Number of transfer units(NTU) value\n",
"NTU = UA/(((3/4.0)*mh)*ch);\n",
"#Heat capacity ratio\n",
"K = (((3/4.0)*mh)*ch)/cc;\n",
"\n",
"#From Fig. 8.20 the effectiveness is equal to 0.61\n",
"#Effectiveness\n",
"E = 0.61;\n",
"#New inlet temperaturre of oil in degree K\n",
"Toilin = 370;\n",
"#From eq. 8.22a\n",
"print \"Outlet temperature of oil in degree K\"\n",
"#Outlet temperature of oil in degree K\n",
"Toilout = Toilin-E*(Toilin-Tcin)\n",
"print round(Toilout,2)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 8 Example # 8.2 \n",
"Outlet temperature of oil in degree K\n",
"321.2\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Ex8.3: Page 511"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"print \"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 8 Example # 8.3 \"\n",
"\n",
"#Airflow rate in kg/s\n",
"mair = 0.75;\n",
"#Inlet temperature of air in degree K\n",
"Tairin = 290;\n",
"#Hot gas flow rate in kg/s\n",
"mgas = 0.6;\n",
"#Inlet temperature of hot gases in degree K\n",
"Tgasin = 1150;\n",
"#wetted perimeter on air side in m\n",
"Pa = 0.703;\n",
"#wetted perimeter on gas side in m\n",
"Pg = 0.416;\n",
"#cross-sectional area of gas passage (per passage) in m2\n",
"Ag = 0.0016;\n",
"#cross-sectional area of air passage (per passage) in m2\n",
"Aa = 0.002275;\n",
"#heat transfer surface area in m2\n",
"A = 2.52;\n",
"\n",
"#Given that unit is of the cross-flow type, with both fluids unmixed.\n",
"\n",
"#length of air duct in m\n",
"La = 0.178;\n",
"#hydraulic diameter of air duct in m\n",
"Dha = (4*Aa)/Pa;\n",
"#length of gas duct in m\n",
"Lg = 0.343;\n",
"#hydraulic diameter of gas duct in m\n",
"Dhg = (4*Ag)/Pg;\n",
"\n",
"#The heat transfer coefficients can be evaluated from Eq. (6.63) for flow\n",
"#in ducts.\n",
"#Heat transfer coefficient for air in W/m2K\n",
"ha = La/Dha;\n",
"#Heat transfer coefficient for gas in W/m2K\n",
"hg = Lg/Dhg;\n",
"\n",
"#Assuming the average air-side bulk temperature to be 573 K and the average\n",
"#gas-side bulk temperature to be 973 K, the properties at those temperatures are, from Appendix 2, Table 28.\n",
"\n",
"#Specific heat of air in J/kgK\n",
"cair = 1047;\n",
"#Thermal conductivity of air in W/mK\n",
"kair = 0.0429;\n",
"#Dynamic vismath.cosity of air in Ns/m2\n",
"muair = 0.0000293;\n",
"#Prandtl number of air\n",
"Prair = 0.71;\n",
"\n",
"#Specific heat of hot gas in J/kgK\n",
"cgas = 1101;\n",
"#Thermal conductivity of hot gas in W/mK\n",
"kgas = 0.0623;\n",
"#Dynamic vismath.cosity of hot gas in Ns/m2\n",
"mugas = 0.00004085;\n",
"#Prandtl number of hot gas\n",
"Prgas = 0.73;\n",
"\n",
"#The mass flow rates per unit area in kg/m2s\n",
"#mass flow rate of air in kg/m2s\n",
"mdotair = mair/(19*Aa);\n",
"#mass flow rate of gas in kg/m2s\n",
"mdotgas = mgas/(18*Ag);\n",
"\n",
"#The Reynolds numbers are\n",
"#Reynolds number for air\n",
"Reair = (mdotair*Dha)/muair;\n",
"#Reynolds number for gas\n",
"Regas = (mdotgas*Dhg)/mugas;\n",
"\n",
"#Umath.sing Eq. (6.63), the average heat transfer coefficients in W/m2K\n",
"hair = (((0.023*kair)*(Reair**0.8))*(Prair**0.4))/Dha;\n",
"\n",
"#Since La/DHa=13.8, we must correct this heat transfer coefficient for\n",
"#entrance effects, per Eq. (6.68). The correction factor is 1.377.\n",
"#Corrected heat transfer coefficient of air in W/m2K\n",
"hair = 1.377*hair;\n",
"\n",
"#Similarly for hot gas\n",
"#Heat transfer coefficient in W/m2K\n",
"hgas = (((0.023*kgas)*(Regas**0.8))*(Prgas**0.4))/Dhg;\n",
"#Correction factor=1.27;\n",
"#Corrected heat transfer coefficient of gas in W/m2K\n",
"hgas = 1.27*hgas;\n",
"\n",
"#Overall conductance in W/K\n",
"UA = 1/(1/(hair*A)+1/(hgas*A));\n",
"\n",
"#The number of transfer units, based on the gas, which has the smaller heat capacity rate\n",
"NTU = UA/(mgas*cgas);\n",
"\n",
"#The heat capacity-rate ratio\n",
"Z = (mgas*cgas)/(mair*cair);\n",
"\n",
"#and from Fig. 8.21, the effectiveness is approximately 0.13.\n",
"#Effectiveness\n",
"E = 0.13;\n",
"\n",
"print \"Gas outlet temperature in degree K\"\n",
"#Gas outlet temperature in degree K\n",
"Tgasout = Tgasin-E*(Tgasin-Tairin)\n",
"print round(Tgasout)\n",
"\n",
"print \"Air outlet temperature in degree K\"\n",
"#Gas outlet temperature in degree K\n",
"Tairout = Tairin+(Z*E)*(Tgasin-Tairin)\n",
"print round(Tairout)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 8 Example # 8.3 \n",
"Gas outlet temperature in degree K\n",
"1038.0\n",
"Air outlet temperature in degree K\n",
"384.0\n"
]
}
],
"prompt_number": 7
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Ex8.4: Page 514"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"print \"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 8 Example # 8.4 \"\n",
"\n",
"#Pressure of steam in inches of Hg\n",
"P = 4;\n",
"#At this pressure, temperture of condenmath.sing steam in degree F\n",
"Thin = 125.4;\n",
"\n",
"#Flow rate of seawater in lb/s\n",
"mw = 25000.0;\n",
"#Specific heat of water in Btu/lb F\n",
"c = 0.95;\n",
"#Inlet and outlet temperature of seawater in degree F\n",
"Tcin = 60.0;\n",
"Tcout = 110.0;\n",
"#Heat transfer coefficient of steam in Btu/h ft2 F\n",
"hsteam = 600.0;\n",
"#Heat transfer coefficient of water in Btu/h ft2 F\n",
"hwater = 300.0;\n",
"#Outer diameter in inches\n",
"OD = 1.125;\n",
"#Inner diameters in inches\n",
"ID = 0.995;\n",
"\n",
"#required effectiveness of the exchanger\n",
"E = (Tcout-Tcin)/(Thin-Tcin);\n",
"\n",
"#For a condenser, Cmin/Cmax=0, and from Fig. 8.20, NTU =\u00031.4.\n",
"NTU = 1.4;\n",
"\n",
"#The fouling factors from Table 8.2 are 0.0005 h ft2\u00b0F/Btu for both sides of the tubes.\n",
"#F-Factor\n",
"F = 0.0005;\n",
"\n",
"#The overall design heat-transfer coefficient in Btu/h ft2 F per unit outside area of tube is, from Eq. (8.6)\n",
"U = 1/(1/hsteam+F+(OD/((2*12)*60))*log(OD/ID)+(F*OD)/ID+OD/(hwater*ID));\n",
"\n",
"#The total area A is 20*pi*D*L, and math.since U*A/Cmin=1.4\n",
"\n",
"print \"The length of the tube in ft is\"\n",
"#The length of the tube in ft\n",
"L = (((1.4*mw)*c)*12)/(((Tcin*math.pi)*OD)*U)\n",
"print round(L,1)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 8 Example # 8.4 \n",
"The length of the tube in ft is\n",
"12.4\n"
]
}
],
"prompt_number": 11
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Ex8.5: Page 523"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"print \"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 8 Example # 8.5 \"\n",
"\n",
"print \"There is no computations in this example.\"\n",
"print \"It is theoretical\"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Principles of Heat Transfer, 7th Ed. Frank Kreith et. al Chapter - 8 Example # 8.5 \n",
"There is no computations in this example.\n",
"It is theoretical\n"
]
}
],
"prompt_number": 12
}
],
"metadata": {}
}
]
}