{
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"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"Chapter 12 : Heat Exchangers"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.1 Page No : 503"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\n",
"#INPUT\n",
"T = 80.;\t\t \t#Bulk Temperature of water in degrees C\n",
"Di = 0.0254;\t\t\t#Inner diameter of steel pipe in m\n",
"Do = 0.0288;\t\t\t#Outer diameter of steel pipe in m\n",
"k = 50.;\t\t\t #Thermal conductivity of steel in W/m.K\n",
"ho = 30800.;\t\t \t#Average convection coefficient in W/m**2.K\n",
"v = 0.50;\t\t \t#Velocity of water in m/s\n",
"# Variables FROM HEAT AND MASS TRANSFER DATA BOOK FOR WATER AT BULK TEMPERATURE OF 80 degree C\n",
"d = 974.;\t\t \t#Density in kg/m**3\n",
"v1 = 0.000000364;\t\t#Kinematic viscosity in m**2/s\n",
"k1 = 0.6687;\t\t\t#Thermal conductivity in W/m.K\n",
"Pr = 2.2;\t\t\t #Prantl Number\n",
"\n",
"# Calculations\n",
"Re = (v*Di)/v1;\t\t\t#Reynold's number\n",
"Nu = (0.023*Re**0.8*Pr**0.4);\t\t\t#Nusselts number\n",
"hi = Nu*(k1/Di);\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"ri = (Di/2);\t\t\t#Inner radius of steel pipe in m\n",
"ro = (Do/2);\t\t\t#Outer radius of steel pipe in m\n",
"U = (1./((1./ho)+((ro/k)*math.log(ro/ri))+(ro/(ri*hi))));\t\t\t#Overall heat transfer coefficient in W/m**2.K\n",
"\n",
"# Results\n",
"print 'Overall heat transfer coefficient is %3.1f W/m**2.K'%(U)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overall heat transfer coefficient is 2591.8 W/m**2.K\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.2 Page No : 504"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"# Variables\n",
"Do = 0.0254;\t\t\t#Outer Diameter of heat exchanger tube in m\n",
"Di = 0.02286;\t\t\t#Inner Diameter of heat exchanger tube in m\n",
"k = 102;\t\t\t#Thermal conductivity of the tube in W/m.K\n",
"hi = 5500;\t\t\t#Heat transfer coefficients at the inner side of tube in W/m**2.K\n",
"ho = 3800;\t\t\t#Heat transfer coefficients at the outer side of tube in W/m**2.K\n",
"Rfi = 0.0002;\t\t\t#Fouling factor in m**2.W.K\n",
"Rfo = 0.0002;\t\t\t#Fouling factor in m**2.W.K\n",
"\n",
"# Calculations\n",
"ro = (Do/2);\t\t\t#Outer radius of heat exchanger tube in m\n",
"ri = (Di/2);\t\t\t#Inner radius of heat exchanger tube in m\n",
"U = (1./((1./ho)+Rfo+((ro/k)*math.log(ro/ri))+((ro*Rfi)/ri)+(ro/(ri*hi))));\t\t\t#Overall heat transfer coefficient in W/m**2.K\n",
"\n",
"# Results\n",
"print 'Overall heat transfer coefficient is %i W/m**2.K'%(U)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overall heat transfer coefficient is 1110 W/m**2.K\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.3 Page No : 509"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"# Variables\n",
"mh = 10000.;\t\t\t#Mass flow rate of oil in kg/h\n",
"ch = 2095.;\t\t\t#Specific heat of oil J/kg.K\n",
"Thi = 80.;\t\t\t#Inlet temperature of oil in degree C\n",
"Tho = 50.;\t\t\t#Outlet temperature of oil in degree C\n",
"mc = 8000.;\t\t\t#Mass flow rate of water in kg/h\n",
"Tci = 25.;\t\t\t#Inlet temperature of water in degree C\n",
"U = 300.;\t\t\t#Overall heat ransfer coefficient in W/m**2.K\n",
"cc = 4180.;\t\t\t#Specific heat of water in J/kg.K\n",
"\n",
"# Calculations\n",
"Q = (mh*ch*(Thi-Tho));\t\t\t#Heat transfer rate in W\n",
"Tco = ((Q/(mc*cc))+Tci);\t\t\t#Outlet temperature of water in degree C\n",
"T = (Thi-Tco);\t\t\t#Temperature difference between oil inlet temperature and water outlet temperature in degree C\n",
"t = (Tho-Tci);\t\t\t#Temperature difference between oil outlet temperature and water inlet temperature in degree C\n",
"A = (((Q/U)*math.log(t/T))/(3600*(t-T)));\t\t\t#Area of heat exchanger in m**2\n",
"\n",
"# Results\n",
"print 'Area of heat exchanger is %3.2f m**2'%(A)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Area of heat exchanger is 19.23 m**2\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.4 Page No : 510"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"# Variables\n",
"Ch = 2500.;\t\t\t#Capacity rate of hot oil in W/K\n",
"Thi = 360.;\t\t\t#Temperature of hot fluid at the entrance of heat exchanger in degree C\n",
"Tho = 300.;\t\t\t#Temperature of hot fluid at the exit of heat exchanger in degree C\n",
"Tci = 30.;\t\t\t#Temperature of cold fluid at the entrance of heat exchanger in degree C\n",
"Tco = 200.;\t\t\t#Temperature of hot fluid at the exit of heat exchanger in degree C\n",
"U = 800.;\t\t\t#Overall heat transfer coefficient in W/m**2.K\n",
"\n",
"# Calculations\n",
"Q = (Ch*(Thi-Tho));\t\t\t#Heat transfer from the oil in W\n",
"#Parallel flow\n",
"T1 = Thi-Tci;\t\t\t#Temperature difference between hot fluid inlet temperature and cold fluid inlet temperature in degree C\n",
"T2 = Tho-Tco;\t\t\t#Temperature difference between hot fluid outlet temperature and cold fluid outlet temperature in degree C\n",
"Tlm1 = ((T1-T2)/math.log(T1/T2));\t\t\t#LMTD for parallel flow arrangement in degree C\n",
"A1 = (Q/(U*Tlm1));\t\t\t#Area of heat exchanger in m**2\n",
"#Counter flow\n",
"t1 = Thi-Tco;\t\t\t#Temperature difference between hot fluid inlet temperature and cold fluid outlet temperature in degree C\n",
"t2 = Tho-Tci;\t\t\t#Temperature difference between hot fluid outlet temperature and cold fluid inlet temperature in degree C\n",
"Tlm2 = ((t1-t2)/math.log(t1/t2));\t\t\t#LMTD for counter flow arrangement in degree C\n",
"A2 = (Q/(U*Tlm2));\t\t\t#Area of heat exchanger in m**2\n",
"\n",
"# Results\n",
"print 'Area of heat exchanger in parallel flow arrangement is %3.3f m**2 \\n \\\n",
"Area of heat exchanger in counter flow arrangement is %3.3f m**2'%(A1,A2)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Area of heat exchanger in parallel flow arrangement is 0.973 m**2 \n",
" Area of heat exchanger in counter flow arrangement is 0.892 m**2\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.5 Page No : 511"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"# Variables\n",
"ch = 2130.;\t\t\t#Specific heat of oil in J/kg.K\n",
"T1 = 160.;\t\t\t#Temperature of hot fluid (oil) at the entrance of heat exchanger in degree C\n",
"T2 = 60.;\t\t\t#Temperature of hot fluid (oil) at the exit of heat exchanger in degree C\n",
"t1 = 25.;\t\t\t#Temperature of cold fluid (water) at the entrance of heat exchanger in degree C\n",
"d = 0.5;\t\t\t#Inner diameter of the tube in m\n",
"mc = 2.;\t\t\t#Mass flow rate of cooling water in kg/s\n",
"D = 0.7;\t\t\t#outer annulus outer diameter in m\n",
"mh = 2.;\t\t\t#Mass flow rate of hot oil in kg/s\n",
"U = 250.;\t\t\t#Overall heat transfer coefficient in W/m**2.K\n",
"cc = 4186.;\t\t\t#Specific heat of water in J/kg.K\n",
"\n",
"# Calculations\n",
"Q = (mh*ch*(T1-T2));\t\t\t# Required heat transfer rate in W\n",
"t2 = ((Q/(mc*cc))+t1);\t\t\t#Outer water temperature in degree C\n",
"T = T1-t2; \t \t\t #Change in temperature between inlet tmperature of hot fluid and outlet temperature of cold fluid in degree C\n",
"t = T2-t1;\t \t \t#Change in temperature between outlet tmperature of hot fluid and inlet temperature of cold fluid in degree C\n",
"Tlm = ((T-t)/(math.log(T/t)));\t#Value of LMTD in degree C\n",
"L = (Q/(U*3.14*d*Tlm));\t\t\t#Length of the heat exchanger in m\n",
"\n",
"# Results\n",
"print 'Length of the heat exchanger is %3.2f m'%(L)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Length of the heat exchanger is 19.38 m\n"
]
}
],
"prompt_number": 7
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.6 Page No : 512"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"T = 120.;\t\t\t#Saturated steam temperature in degree C\n",
"U = 1800.;\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"m = 1000.;\t\t\t#mass flow rate of water in kg/h\n",
"t1 = 20.;\t\t\t#Inlet temperature of water in degree C\n",
"t2 = 90.;\t\t\t#Outlet tmperature of water in degree C\n",
"hfg = 2200.;\t\t#Enthalpy of steam in kJ/kg\n",
"c = 4186.;\t\t\t#Specific het of water in J/kg.K\n",
"\n",
"# Calculations\n",
"Tlm = (((T-t1)-(T-t2))/(math.log((T-t1)/(T-t2))));\t\t\t#LMTD in a condenser in degree C\n",
"Q = ((m/3600)*c*(t2-t1));\t \t\t#Rate of heat transfer in W\n",
"A = (Q/(U*Tlm));\t\t \t#Surface area of heat exchanger in m**2 \n",
"ms = ((Q*3600)/(hfg*1000));\t\t \t#Rate of condensation of steam in kg/h\n",
"\n",
"# Results\n",
"print 'Surface area of heat exchanger is %3.2f m**2 \\n \\\n",
"Rate of condensation of steam is %3.1f kg/h'%(A,ms)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Surface area of heat exchanger is 0.78 m**2 \n",
" Rate of condensation of steam is 133.2 kg/h\n"
]
}
],
"prompt_number": 8
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.7 Page No : 516"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"# Variables\n",
"T = 100.;\t\t\t#Temperature of saturated steam in degree C\n",
"t1 = 30.;\t\t\t#Inlet temperature of water in degree C\n",
"t2 = 70.;\t\t\t#Exit temperature of water in degree C\n",
"\n",
"# Calculations\n",
"#COUNTER FLOW\n",
"Tc = (T-t2);\t\t\t#Temperature difference between saturated steam and exit water temperature in degree C\n",
"tc = (T-t1);\t\t\t#Temperature difference between saturated steam and inlet water temperature in degree C\n",
"Tlmc = ((Tc-tc)/math.log(Tc/tc));\t\t\t#LMTD for counter flow in degree C\n",
"\n",
"#PARALLEL FLOW\n",
"Tp = (T-t1);\t\t\t#Temperature difference between saturated steam and inlet water temperature in degree C\n",
"tp = (T-t2);\t\t\t#Temperature difference between saturated steam and exit water temperature in degree C\n",
"Tlmp = ((Tp-tp)/math.log(Tp/tp));\t\t\t#LMTD for counter flow in degree C\n",
"#CROSS FLOW\n",
"R = ((T-T)/(t2-t1));\t\t\t#R value for Correction factor F\n",
"P = ((t2-t1)/(T-t1));\t\t\t#P value for Correction Factor F\n",
"F = 1;\t\t\t#Referring to Fig.12.12 in page no 515\n",
"Tlmx = (F*Tlmc);\t\t\t#LMTD for cross flow in degree C\n",
"\n",
"# Results\n",
"print 'The effective math.log mean temperature difference for: \\\n",
"\\ni)COUNTER FLOW is %3.1f degree C \\\n",
"\\nii)PARALLEL FLOW is %3.1f degree C \\niii)CROSS FLOW is %3.1f degree C'%(Tlmc,Tlmp,Tlmx)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The effective math.log mean temperature difference for: \n",
"i)COUNTER FLOW is 47.2 degree C \n",
"ii)PARALLEL FLOW is 47.2 degree C \n",
"iii)CROSS FLOW is 47.2 degree C\n"
]
}
],
"prompt_number": 11
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.8 Page No : 516"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Ti = 18;\t\t\t#Inlet temperature of Shell fluid in degree C\n",
"To = 6.5;\t\t\t#Outlet temperature of Shell fluid in degree C\n",
"ti = -1.1;\t\t\t#Inlet temperature of Tube fluid in degree C\n",
"to = 2.9;\t\t\t#Outlet temperature of Tube fluid in degree C\n",
"U = 850;\t\t\t#Overall heat transfer coefficient in W/m**2.K\n",
"Q = 6000;\t\t\t#Design heat load in W\n",
"\n",
"# Calculations\n",
"T = (Ti-to);\t\t\t#Temperature difference between shell side inlet fluid and tube side outlet fluid in degree C\n",
"t = (To-ti);\t\t\t#Temperature difference between shell side outlet fluid and tube side inlet fluid in degree C\n",
"Tlm = ((T-t)/math.log(T/t));\t\t\t#LMTD for a counterflow arrangement in degree C\n",
"P = ((to-ti)/(Ti-ti));\t\t\t#P value to calculate correction factor\n",
"R = ((Ti-To)/(to-ti));\t\t\t#R value to calculate correction factor\n",
"F = 0.97\t\t\t#Taking correction factor from fig. 12.9 on page no.514\n",
"A = (Q/(U*F*Tlm));\t\t\t#Area of shell aand tube heat exchanger in m**2\n",
"\n",
"# Results\n",
"print 'Area of shell-and-tube heat exchanger is %3.2f m**2'%(A)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Area of shell-and-tube heat exchanger is 0.67 m**2\n"
]
}
],
"prompt_number": 12
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.9 Page No : 517"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Q = 6000;\t\t\t#Taking design heat load value in W from Example no. 12.8 on page no.516\n",
"U = 850;\t\t\t#Taking overall heat transfer coefficient value in W/m**2.K from Example no. 12.8 on page no.516\n",
"Tlm = 10.92\t\t\t#Taking LMTD for a counterflow arrangement in degree C from Example no. 12.8 on page no.517\n",
"R = 2.875;\t\t\t#Taking R value from Example no. 12.8 on page no.517\n",
"P = 0.209;\t\t\t#Taking P value from Example no. 12.8 on page no.517\n",
"F = 0.985;\t\t\t#Taking correction factor from Fig. 12.10 on page no.514\n",
"\n",
"# Calculations\n",
"A = (Q/(U*F*Tlm));\t\t\t#Area of shell-and-tube heat exchanger in m**2\n",
"\n",
"# Results\n",
"print 'Area of shell aand tube heat exchanger is %3.3f m**2'%(A)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Area of shell aand tube heat exchanger is 0.656 m**2\n"
]
}
],
"prompt_number": 13
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.10 Page No : 517"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Ti = 360.;\t\t\t#Inlet temperature of hot fluid in degree C taken from Example no. 12.4 on page no. 510\n",
"To = 300.;\t\t\t#Outlet temperature of hot fluid in degree C taken from Example no. 12.4 on page no. 510\n",
"ti = 30.;\t\t\t#Inlet temperature of cold fluid in degree C taken from Example no. 12.4 on page no. 510\n",
"to = 200.;\t\t\t#Outlet temperature of cold fluid in degree C taken from Example no. 12.4 on page no. 510\n",
"U = 800.;\t\t\t#Overall heat transfer coefficient in W/m**2.K taken from Example no. 12.4 on page no. 510\n",
"Q = 150000.;\t\t\t#Calculated heat transfer rate in W from Example no. 12.4 on page no. 510 \n",
"Tlm = 210.22\t\t\t#Calculated LMTD for counterflow arrangement in degree C taken from Example no. 12.4 on page no. 511\n",
"\n",
"# Calculations\n",
"P = ((to-ti)/(Ti-ti));\t\t\t#P value for calculation of correction factor\n",
"R = ((Ti-To)/(to-ti));\t\t\t#R value for calculation of correction factor\n",
"F = 0.98;\t\t\t#Correction Factor value taken from Fig.12.11 on page no.515\n",
"A = (Q/(U*F*Tlm));\t\t\t#Required surface area in a cross flow heat exchanger in m**2\n",
"\n",
"# Results\n",
"print 'The required surface area in a cross flow heat exchanger is %3.2f m**2'%(A)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The required surface area in a cross flow heat exchanger is 0.91 m**2\n"
]
}
],
"prompt_number": 14
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.11 Page No : 518"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"# Variables\n",
"mc = 4.;\t\t\t#Mass flow rate of cold water in kg/s\n",
"Tci = 38.;\t\t\t#Inlet Temperature of cold water in degree C\n",
"Tco = 55.;\t\t\t#Outlet Temperature of cold water in degree C\n",
"D = 0.02;\t\t\t#Diameter of the tube in m\n",
"v = 0.35;\t\t\t#Velocity of water in m/s\n",
"Thi = 95.;\t\t\t#Inlet Temperature of hot water in degree C\n",
"mh = 2.;\t\t\t#Mass flow rate of hot water in kg/s\n",
"L = 2.;\t\t\t #Length of the tube in m\n",
"U = 1500.;\t\t\t#Overall heat transfer coefficient in W/m**2.K\n",
"c = 4186.;\t\t\t#Specific heat of water in J/kg.K\n",
"d = 1000.;\t\t\t#Density of water in kg/m**3\n",
"\n",
"# Calculations\n",
"Q = (mc*c*(Tco-Tci));\t\t\t#Heat transfer rate for cold fluid in W\n",
"Tho = (Thi-(Q/(mh*c)));\t\t\t#Outlet temperature of hot fluid in degree C\n",
"T = Thi-Tco;\t\t\t#Difference of temperature between hot water inlet and cold water outlet in degree C\n",
"t = Tho-Tci;\t\t\t#Difference of temperature between hot water outlet and cold water inlet in degree C\n",
"Tlm = ((T-t)/math.log(T/t));\t\t\t#LMTD for counterflow heat exchanger\n",
"A = (Q/(U*Tlm));\t\t\t#Area of heat exchanger in m**2\n",
"A1 = (mc/(d*v));\t\t\t#Total flow area in m**2\n",
"n = ((A1*4)/(3.14*D**2));\t\t\t#Number of tubes\n",
"L = (A/(36*3.14*D));\t\t\t#Length of each tube taking n = 36 in m\n",
"N = 2;\t\t\t#Since this length is greater than the permitted length of 2m, we must use more than one tube pass. Let us try 2 tube passes\n",
"P = ((Tco-Tci)/(Thi-Tci));\t\t\t#P value for calculation of correction factor\n",
"R = ((Thi-Tho)/(Tco-Tci));\t\t\t#R value for calculation of correction factor\n",
"F = 0.9;\t\t\t#Corrction Factor from Fig.12.9 on page no. 514 \n",
"A2 = (Q/(U*F*Tlm));\t\t\t#Total area required for one shall pass,2 tube pass exchanger in m**2\n",
"L1 = (A2/(2*36*3.14*D));\t\t\t#Length of tube per pass taking n = 36 in m\n",
"\n",
"# Results\n",
"print 'Number of tubes per pass is %.f \\n \\\n",
"Number of passes is %i \\n \\\n",
"Length of tube per pass is %3.3f m'%(n,N,L1)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Number of tubes per pass is 36 \n",
" Number of passes is 2 \n",
" Length of tube per pass is 1.518 m\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.12 Page No : 524"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"# Variables\n",
"mh = 250.;\t\t\t#Mass flow rate of hot liquid in kg/h\n",
"ch = 3350.;\t\t\t#Specific heat of hot liquid in J/kg.K\n",
"Thi = 120.;\t\t\t#Inlet temperature of hot liquid in degree C\n",
"mc = 1000.;\t\t\t#Mass flow rate of cold liquid in kg/h\n",
"Tci = 10.;\t\t\t#Inlet temperature of cold liquid in degree C\n",
"U = 1160.;\t\t\t#Overall heat transfer coefficient in W/m**2.K\n",
"A = 0.25;\t\t\t#Surface area of heat exchanger in m**2\n",
"cc = 4186.;\t\t\t#Specific heat of cold liquid in J/kg.K\n",
"\n",
"# Calculations\n",
"Cc = ((mc*cc)/3600);\t\t\t#Heat capacity rate for cold liquid in W/K\n",
"Ch = ((mh*ch)/3600);\t\t\t#Heat capacity rate for hot liquid in W/K\n",
"Cmin = min(Cc,Ch);\t\t\t#Minimum heat capacity rate in W/K\n",
"Cmax = max(Cc,Ch);\t\t\t#Maximum heat capacity rate in W/K\n",
"r = (Cmin/Cmax);\t\t\t#Ratio of min amd max heat capacity rates\n",
"NTU = ((U*A)/Cmin);\t\t\t#Number of transfer units\n",
"e = ((1-math.exp(-NTU*(1+r)))/(1+r));\t\t\t#Effectiveness for a parallel flow heat exchanger\n",
"Qmax = (Cmin*(Thi-Tci));\t\t\t#Maximum possible heat transfer rate in W\n",
"Q = (e*Qmax);\t\t\t#Actual rate of heat transfer in W\n",
"Tco = ((Q/Cc)+Tci);\t\t\t#Outlet temperature of cold liquid in degree C\n",
"Tho = (Thi-(Q/Ch));\t\t\t#Outlet temperature of hot liquid in degree C\n",
"\n",
"\n",
"# Results\n",
"print 'Effectiveness for a parallel flow heat exchanger is %3.3f \\n \\\n",
"Outlet temperature of water is %3.2f degree C \\n \\\n",
"Outlet temperature of cooled liquid is %3.2f degree C'%(e,Tco,Tho)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Effectiveness for a parallel flow heat exchanger is 0.647 \n",
" Outlet temperature of water is 24.23 degree C \n",
" Outlet temperature of cooled liquid is 48.87 degree C\n"
]
}
],
"prompt_number": 18
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.13 Page No : 527"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Tci = 15.;\t\t\t#Inlet temperature of water in degree C\n",
"mc = 1300.;\t\t\t#Mass flow rate of water in kg/h\n",
"ch = 2000.;\t\t\t#Specific heat of oil in J/kg.K\n",
"mh = 550.;\t\t\t#Mass flow rate of oil in kg/h\n",
"Thi = 94.;\t\t\t#Inlet temperature of oil in degree C\n",
"A = 1.;\t\t\t #Area of heat exchanger in m**2\n",
"U = 1075.;\t\t\t#Overall heat transfer coefficient in W/m**2.K\n",
"cc = 4186.;\t\t\t#Specific heat of water in J/kg.K\n",
"\n",
"# Calculations\n",
"Cc = ((mc*cc)/3600);\t\t\t#Heat capacity of water in W/K\n",
"Ch = ((mh*ch)/3600);\t\t\t#Heat capacity of oil in W/K\n",
"Cmin = min(Cc,Ch);\t\t\t#Minimum heat capacity in W/K\n",
"Cmax = max(Cc,Ch);\t\t\t#Maximum heat capacity in W/K\n",
"r = (Cmin/Cmax);\t\t\t#Ratio of min and max heat capacity\n",
"NTU = ((U*A)/Cmin);\t\t\t#Number of transfer Units\n",
"e = 0.94\t\t\t#Effectiveness of heat exchanger from Fig. 12.15 on page no.524\n",
"Qmax = (Cmin*(Thi-Tci));\t\t\t#Maximum possible heat transfer rate in W\n",
"Q = (e*Qmax);\t\t\t#Actual heat transfer rate in W\n",
"Tco = ((Q/Cc)+Tci);\t\t\t#Outlet Temperature of water in degree C\n",
"Tho = (Thi-(Q/Ch));\t\t\t#Outlet Temperature of oil in degree C\n",
"\n",
"# Results\n",
"print 'The total heat transfer is %3.1f W \\n \\\n",
"Outlet Temperature of water is %i degree C \\n \\\n",
"Outlet Temperature of oil is %3.2f degree C'%(Q,Tco,Tho)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The total heat transfer is 22690.6 W \n",
" Outlet Temperature of water is 30 degree C \n",
" Outlet Temperature of oil is 19.74 degree C\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.14 Page No : 528"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"N = 3000.;\t\t\t#Number of brass tubes\n",
"D = 0.02;\t\t\t#Diameter of brass tube in m\n",
"Tci = 20.;\t\t\t#Inlet temperature of cooling water in degree C\n",
"mc = 3000.;\t\t\t#Mass flow rate of cooling water in kg/s\n",
"ho = 15500.;\t\t\t#Heat transfer coefficient for condensation in W/m**2.K\n",
"Q = (2.3*10**8);\t\t\t#Heat load of the condenser in W\n",
"Thi = 50.;\t\t\t#Temperature at which steam condenses in degree C\n",
"hfg = 2380.\t\t\t#Enthalpy of liquid vapour mixture in kJ/kg\n",
"m = 1.;\t\t\t#Flow rate of each tube in kg/s\n",
"Cc = 4180.;\t\t\t#Specific heat of water in J/kg.K\n",
"#Properties of water at 300K from data book\n",
"Cc = 4186.;\t\t\t#Specific heat in J/kg.K\n",
"mu = (855.*10**-6);\t\t\t#Dynamic vismath.cosity in Ns/m**2\n",
"k = 0.613;\t\t\t#Thermal Conductivity in W/mK\n",
"Pr = 5.83\t\t\t#Prantl number\n",
"\n",
"# Calculations\n",
"Tco = ((Q/(mc*Cc))+Tci);\t\t\t#Outlet temperature of cooling water in degree C\n",
"Re = ((4*m)/(3.1415*D*mu));\t\t\t#Reynold's number\n",
"Nu = (0.023*Re**(4./5)*Pr**(2./5));\t\t\t#Nusselts number\n",
"hi = (Nu*(k/D));\t\t\t#Heat transfer coefficient in W/m**2.K\n",
"U = (1./((1./ho)+(1./hi)));\t\t\t#Overall heat transfer coefficient in W/m**2.K\n",
"Cmin = (mc*Cc);\t\t\t#Minimum heat capacity in W/K\n",
"Qmax = (Cmin*(Thi-Tci));\t\t\t#Maximum heat transfer rate in W\n",
"e = (Q/Qmax);\t\t\t#Effectiveness of heat transfer\n",
"NTU = 0.8;\t\t\t#Number of transfer units from Fig. 12.16 on page no.525 \n",
"A = ((NTU*Cmin)/U);\t\t\t#Area of heat exchanger in m**2\n",
"L = (A/(2*N*3.1415*D));\t\t\t#Length of tube per pass in m\n",
"ms = (Q/(hfg*1000));\t\t\t#Amount of steam condensed in kg/s\n",
"\n",
"# Results\n",
"print 'The outlet temperature of the cooling water is %3.2f degree C \\n \\\n",
"The overall heat transfer coefficient is %3.1f W/m**2.K \\n \\\n",
"Tube length per pass using NTU method is %3.2f m \\n \\\n",
"The rate of condensation of steam is %3.0f kg/s'%(Tco,U,L,ms)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The outlet temperature of the cooling water is 38.32 degree C \n",
" The overall heat transfer coefficient is 6525.8 W/m**2.K \n",
" Tube length per pass using NTU method is 4.08 m \n",
" The rate of condensation of steam is 97 kg/s\n"
]
}
],
"prompt_number": 20
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.15 Page No : 530"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Tci = 5.;\t\t\t#Inlet temperature of water in degree C\n",
"mc = 4600.;\t\t\t#Mass flow rate of water in kg/h\n",
"mh = 4000.;\t\t\t#Mass flow rate of air in kg/h\n",
"Thi = 40.;\t\t\t#Inlet temperature of air in degree C\n",
"U = 150.;\t\t\t#Overall heat transfer coefficient in W/m**2.K\n",
"A = 25.;\t\t\t#Area of heat exchanger in m**2\n",
"Cc = 4180.;\t\t\t#Specific heat of water in J/kg.K\n",
"Ch = 1010.;\t\t\t#Specific heat of air in J/kg.K\n",
"\n",
"# Calculations\n",
"C1 = ((mh*Ch)/3600);\t\t\t#Heat capacity of air in W/K\n",
"C2 = ((mc*Cc)/3600);\t\t\t#Heat capacity of water in W/K\n",
"Cmin = min(C1,C2);\t\t\t#Minimum value of heat capacity in W/K\n",
"Cmax = max(C1,C2);\t\t\t#Maximum value of heat capacity in W/K\n",
"r = (Cmin/Cmax);\t\t\t#Ratio of min and max heat capacity in W/K\n",
"NTU = ((U*A)/Cmin);\t\t\t#Number of heat transfer units\n",
"e = 0.92;\t\t\t#Effectiveness of heat exchanger from Fig. 12.18 on page no.526\n",
"Q = (e*Cmin*(Thi-Tci));\t\t\t#Heat transfer rate in W\n",
"Tco = ((Q/C2)+Tci);\t\t\t#Outlet temperature of water in degree C\n",
"Tho = (Thi-(Q/C1));\t\t\t#Outlet temperature of air in degree C\n",
"\n",
"# Results\n",
"print 'The exit temperature of water is %3.1f degree C \\n \\\n",
"The exit temperature of air is %3.1f degree C'%(Tco,Tho)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The exit temperature of water is 11.8 degree C \n",
" The exit temperature of air is 7.8 degree C\n"
]
}
],
"prompt_number": 21
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.16 Page No : 532"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"A = 15.82;\t\t\t#Total outside area of heat exchanger in m**2\n",
"Thi = 110;\t\t\t#Inlet temperature of oil in degree C\n",
"Ch = 1900;\t\t\t#Specific heat of oil in J/kg.K\n",
"mh = 170.9;\t\t\t#Mass flow rate of oil in kg/min\n",
"mc = 68;\t\t\t#Mass flow rate of water in kg/min\n",
"Tci = 35;\t\t\t#Inlet temperature of water in degree C\n",
"U = 320;\t\t\t#Overall heat transfer coefficient in W/m**2.K\n",
"Cc = 4186;\t\t\t#Specific heat of water in J/kg.K\n",
"\n",
"# Calculations\n",
"C1 = ((mh*Ch)/60);\t\t\t#Heat capacity of oil in W/K\n",
"C2 = ((mc*Cc)/60);\t\t\t#Heat capacity of water in W/K\n",
"D = (U*A*((1./C1)-(1./C2)));\t\t\t#Constant\n",
"r = (C1/C2);\t\t\t#Ratio of heat capacity of oil and water\n",
"Tho = Thi-(((Thi-Tci)*(1-math.exp(D)))/(r-math.exp(D)));\t\t\t#Outlet temperature of oil in degree C\n",
"Tco = Tci+(r*(Thi-Tho));\t\t\t#Outlet temperature of water in degree C\n",
"\n",
"# Results\n",
"print 'The exit temperature of oil is %3.2f degree C \\n \\\n",
" The exit temperature of water is %3.1f degree C'%(Tho,Tco)\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The exit temperature of oil is 74.97 degree C \n",
" The exit temperature of water is 75.0 degree C\n"
]
}
],
"prompt_number": 23
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.17 Page No : 533"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"Tci = 20.;\t\t\t#Inlet temperature of water in degree C\n",
"Tco = 50.;\t\t\t#Outlet temperature of water in degree C\n",
"Th = 120.;\t\t\t#Temperature at which steam condenses in degree C\n",
"newTci = 15.;\t\t\t#New Inlet temperature of water in degree C\n",
"\n",
"# Calculations\n",
"newTco = (((Tco-Tci)*(Th-newTci))/(Th-Tci))+newTci;\t\t\t#New outlet temperature of water in degree C\n",
"\n",
"# Results\n",
"print 'New outlet temperature of water is %3.1f degree C'%(newTco)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"New outlet temperature of water is 46.5 degree C\n"
]
}
],
"prompt_number": 24
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 12.18 Page No : 534"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"T = 100;\t\t\t#Total length of tubes in m\n",
"\n",
"\n",
"# Calculations\n",
"D = ((3.14*4000)/(3.14*30000))**0.5;\t\t\t#Diameter of the exchanger in m\n",
"L = (2./(3.1415*D**2));\t\t\t#Length of the exchanger in m\n",
"Cost = (10000+(15000*D**3*L)+(2000*D*L));\t\t\t#Optimal math.cost in Rs\n",
"\n",
"# Results\n",
"print 'The diameter of the exchanger is %3.3f m \\n \\\n",
"The Length of the exchanger is %3.2f m \\n \\\n",
"Optimal cost is %3.0f Rs'%(D,L,Cost)\n",
"\n",
"# note : rounding error."
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The diameter of the exchanger is 0.365 m \n",
" The Length of the exchanger is 4.77 m \n",
" Optimal cost is 16974 Rs\n"
]
}
],
"prompt_number": 8
}
],
"metadata": {}
}
]
}