{
"metadata": {
"name": ""
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"Chapter 14 : Refrigeration Cycles"
]
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.1 page no : 717"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"T2 = 235; \t\t\t#K\n",
"P = 1.3; \t\t\t#kW\n",
"\n",
"# Calculations and Results\n",
"COP = 14000./P/60./60.;\n",
"print (\"(i) C.O.P. of Carnot refrigerator = %.3f\")% (COP)\n",
"\n",
"T1 = T2/COP + T2;\n",
"t1 = T1-273;\n",
"print (\"(ii) Higher temperature of the cycle = %.3f\")% (t1), (\"0C\")\n",
"\n",
"print (\"(iii) Heat delivered as heat pump\")\n",
"Qabs = 14000./60; \t\t\t#Heat absorbed\n",
"W = P*60;\n",
"Q = Qabs+W;\n",
"print (\"Q = %.3f\")% (Q), (\"kJ/min\")\n",
"\n",
"COP = Q/W;\n",
"print (\"COP of heat pump = %.3f\")% (COP)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) C.O.P. of Carnot refrigerator = 2.991\n",
"(ii) Higher temperature of the cycle = 40.557 0C\n",
"(iii) Heat delivered as heat pump\n",
"Q = 311.333 kJ/min\n",
"COP of heat pump = 3.991\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.2 page no : 718"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"T1 = 308.; \t\t \t #K\n",
"T2 = 258.; \t\t\t #K\n",
"capacity = 12.; \t\t\t#tonne\n",
"\n",
"# Calculations and Results\n",
"COP = T2/(T1-T2);\n",
"print (\"(i) Co-efficient of performance = \"), (COP)\n",
"\n",
"\n",
"print (\"(ii) Heat rejected from the system per hour\")\n",
"W = capacity*14000./5.16;\n",
"Q = capacity*14000.+W;\n",
"print (\"Q = %.3f\")% (Q), (\"kJ/h\")\n",
"\n",
"P = W/60./60.;\n",
"print (\"(iii) Power required = %.3f\")% (P),(\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) Co-efficient of performance = 5.16\n",
"(ii) Heat rejected from the system per hour\n",
"Q = 200558.140 kJ/h\n",
"(iii) Power required = 9.044 kW\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.3 page no : 718"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"T2 = 268.; \t\t\t#K\n",
"T1 = 308.; \t\t\t#K\n",
"Q = 29.; \t\t\t#Heat leakage from the surroundings into the cold storage in kW\n",
"\n",
"# Calculations\n",
"COP_ideal = T2/(T1-T2);\n",
"COP_actual = 1./3*COP_ideal;\n",
"W = Q/COP_actual;\n",
"\n",
"# Results\n",
"print (\"Power required = %.3f\")%(W), (\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Power required = 12.985 kW\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.4 page no : 719"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"T1 = 293.; \t\t\t#K\n",
"T2 = 265.; \t\t\t#K\n",
"T0 = 273.; \t\t\t#K\n",
"L = 335.; \t\t\t#Latent heat of ice in kJ/kg\n",
"cpw = 4.18;\n",
"\n",
"# Calculations\n",
"COP = T2/(T1-T2);\n",
"Rn = cpw*(T1-T0)+L;\n",
"m_ice = COP*3600./Rn;\n",
"\n",
"# Results\n",
"print (\"ice formed per kWh = %.3f\")% (m_ice), (\"kg\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"ice formed per kWh = 81.394 kg\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.5 page no : 719"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"T1 = 291.; \t\t\t#K\n",
"T2 = 265.; \t\t\t#K\n",
"T0 = 273.; \t\t\t#K\n",
"cpw = 4.18; \t\t#kJ/kg\n",
"cpi = 2.09; \t\t#kJ/kg\n",
"L = 334.; \t\t\t#kJ/kg\n",
"m = 400.; \t\t\t#kg\n",
"\n",
"# Calculations\n",
"COP = T2/(T1-T2);\n",
"Rn = cpw*(T1-T0) + L + cpi*(T0-T2);\n",
"W = Rn*m/COP/3600; \t\t\t#kJ/s\n",
"\n",
"# Results\n",
"print (\"Least power = %.3f\")% (W), (\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Least power = 4.644 kW\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.6 page no : 720"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"cpw = 4.18; \t\t\t#kJ/kg\n",
"\n",
"print (\"(i) Quantity of ice produced\")\n",
"t = 20.; \t\t\t#0C\n",
"L = 335.; \t\t\t#kJ/kg\n",
"capacity = 280.; \t#tonnes\n",
"\n",
"# Calculations and Results\n",
"Q1 = cpw*t + L; \t\t\t#Heat to be extracted per kg of water (to form ice at 0\u00b0C)\n",
"Rn = capacity*14000; \t\t#kJ/h\n",
"m_ice = Rn*24./Q1/1000;\n",
"\n",
"print (\"Quantity of ice produced in 24 hours = %.3f\")% (m_ice), (\"tonnes\")\n",
"\n",
"print (\"(ii) Minimum power required = \"),\n",
"T1 = 298.; \t\t\t#K\n",
"T2 = 263.; \t\t\t#K\n",
"\n",
"COP = T2/(T1-T2);\n",
"W = Rn/COP/3600.; \t\t\t#kJ/s\n",
"print (\"Power required = %.3f\")% (W), (\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) Quantity of ice produced\n",
"Quantity of ice produced in 24 hours = 224.749 tonnes\n",
"(ii) Minimum power required = Power required = 144.909 kW\n"
]
}
],
"prompt_number": 8
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.7 page no : 720"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"cp1 = 1.25; \t\t\t#kJ/kg 0C\n",
"cp2 = 2.93; \t\t\t#kJ/kg 0C\n",
"L = 232. \t\t\t#kJ/kg\n",
"T1 = -3. \t \t\t#0C\n",
"T2 = -8. \t\t \t#0C\n",
"T3 = 25. \t\t\t #0C\n",
"\n",
"\n",
"# Calculations and Results\n",
"Q1 = cp2*(T3-T1) + L + cp1*(T1-T2); \t\t\t#Heat removed in 8 hours from each kg of fish\n",
"Q = Q1*20*1000./8 \t\t\t#Heat removed by the plant /min\n",
"\n",
"capacity = Q/14000.; \t\t\t#tonnes\n",
"print (\"(i) Capacity of the refrigerating plant = %.3f\")% (capacity), (\"tonnes\")\n",
"\n",
"print (\"(ii) Carnot cycle C.O.P. between this temperature range.\")\n",
"T1 = 298.; \t\t\t#K\n",
"T2 = 265.; \t\t\t#K\n",
"\n",
"COP = T2/(T1-T2);\n",
"print (\"COP of reversed carnot cycle = %.3f\")% (COP)\n",
"\n",
"\n",
"print (\"(iii) Power required\")\n",
"COP_actual = 1./3*COP;\n",
"W = Q/COP_actual/3600; \t\t\t#kJ/s\n",
"\n",
"print (\"Power = %.3f\")% (W), (\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) Capacity of the refrigerating plant = 57.195 tonnes\n",
"(ii) Carnot cycle C.O.P. between this temperature range.\n",
"COP of reversed carnot cycle = 8.030\n",
"(iii) Power required\n",
"Power = 83.094 kW\n"
]
}
],
"prompt_number": 9
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.8 page no : 721"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"T1 = 1273.; \t\t#K\n",
"T2 = 298.; \t\t\t#K\n",
"T3 = 268.; \t\t\t#K\n",
"T4 = 298.; \t\t\t#K\n",
"\n",
"# Calculations\n",
"#Let Q2/Q1 = r1, r2 = Q3/Q4;\n",
"r1 = 298./1273; \t\t#Q2/Q1\n",
"r2 = 268./298; \t\t\t#Q3/Q4\n",
"\n",
"#Let Q4/Q1 = r\n",
"r = (1.-r1)/(1-r2);\n",
"\n",
"# Results\n",
"print (\"The ratio in which the heat pump and heat engine share the heating load = %.3f\")% (r)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The ratio in which the heat pump and heat engine share the heating load = 7.608\n"
]
}
],
"prompt_number": 10
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.9 page no : 724"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"y = 1.4;\n",
"n = 1.35;\n",
"cp = 1.003; \t\t#kJ/kg K\n",
"p2 = 1.; \t\t\t#bar\n",
"p1 = 8.; \t\t\t#bar\n",
"T3 = 282.; \t\t\t#K\n",
"T4 = 302.; \t\t\t#K\n",
"T1 = T4;\n",
"\n",
"# Calculations\n",
"T4 = T3*(p1/p2)**((n-1)/n);\n",
"T2 = T1*(p2/p1)**((n-1)/n);\n",
"Q1 = cp*(T3-T2); \t\t\t#Heat extracted from cold chamber per kg of air\n",
"Q2 = cp*(T4-T1); \t\t\t#Heat rejected in the cooling chamber per kg of air\n",
"cv = cp/y;\n",
"R = cp-cv;\n",
"W = n/(n-1)*R*((T4-T3) - (T1-T2));\n",
"COP = Q1/W;\n",
"\n",
"# Results\n",
"print (\"COP = %.3f\")% (COP)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"COP = 1.270\n"
]
}
],
"prompt_number": 11
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.10 page no : 726"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"p1 = 1000.; \t\t\t#kPa\n",
"p2 = 100. \t\t\t#kPa\n",
"p4 = p1;\n",
"p3 = p2;\n",
"E = 2000. \t\t\t# Refrigerating effect produced in kJ/min \n",
"T3 = 268.; \t \t\t#K\n",
"T1 = 303.; \t\t \t#K\n",
"y = 1.4;\n",
"\n",
"# Calculations and Results\n",
"print (\"(i) Mass of air circulated per minute\")\n",
"T2 = T1*(p2/p1)**((y-1)/y);\n",
"e = cp*(T3-T2); \t\t\t#Refrigerating effect per kg; kJ/kg\n",
"\n",
"m = E/e;\n",
"print (\"m = %.3f\")% (m), (\"kg/min\")\n",
"\n",
"\n",
"print (\"(ii) Compressor work (Wcomp.), expander work (Wexp.) and cycle work (Wcycle)\")\n",
"T4 = T3*(p4/p3)**((y-1)/y);\n",
"\n",
"Wcomp = y/(y-1)*m*R*(T4-T3);\n",
"print (\"Compressor work = %.3f\")% (Wcomp), (\"kJ/min\")\n",
"\n",
"Wexp = y/(y-1)*m*R*(T1-T2);\n",
"print (\"Expander work = %.3f\")% (Wexp), (\"kJ/min\")\n",
"\n",
"W_cycle = Wcomp-Wexp;\n",
"print (\"Wcycle = %.3f\")% (W_cycle), (\"kJ/min\")\n",
"\n",
"\n",
"print (\"(iii) C.O.P. and power required\")\n",
"COP = E/W_cycle;\n",
"print (\"COP = %.3f\")% (COP)\n",
"\n",
"P = W_cycle/60;\n",
"print (\"Power required = %.3f\")% (P), (\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) Mass of air circulated per minute\n",
"m = 17.954 kg/min\n",
"(ii) Compressor work (Wcomp.), expander work (Wexp.) and cycle work (Wcycle)\n",
"Compressor work = 4491.675 kJ/min\n",
"Expander work = 2630.279 kJ/min\n",
"Wcycle = 1861.395 kJ/min\n",
"(iii) C.O.P. and power required\n",
"COP = 1.074\n",
"Power required = 31.023 kW\n"
]
}
],
"prompt_number": 12
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.11 page no : 727"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"\n",
"# Variables\n",
"y = 1.4;\n",
"cp = 1.003; \t\t#kJ/kg K\n",
"T3 = 289.; \t\t\t#K\n",
"T1 = 314.; \t\t\t#K\n",
"p1 = 5.2; \t\t\t#bar\n",
"p2 = 1.; \t\t\t#bar\n",
"capacity = 6.; \t\t#tonnes\n",
"R = 287.; \t\t\t#J/kg K\n",
"l = 0.2; \t\t\t#m\n",
"\n",
"# Calculations and Results\n",
"T4 = T3*(p1/p2)**((y-1)/y);\n",
"T2 = T1*(p2/p1)**((y-1)/y);\n",
"\n",
"COP = T2/(T1-T2);\n",
"print (\"(i) C.O.P. = %.3f\")%(COP)\n",
"\n",
"e = cp*(T3-T2); \t\t\t#Refrigerating effect per kg of air\n",
"E = capacity*14000; \t\t#Refrigerating effect produced by the refrigerating machine in kJ/h\n",
"\n",
"m = E/e/60;\n",
"print (\"(ii)mass of air in circulation = %.3f\")%(m),(\"kg/min\")\n",
"\n",
"\n",
"V3 = m*R*T3/p2/10**5;\n",
"print (\"(iii)Piston displacement of compressor\"),(\" = %.2f\")%(V3),(\"m^3/min\")\n",
"\n",
"V_swept = V3/2/240;\n",
"\n",
"\n",
"V2 = m*R*T2/p2/10**5;\n",
"V_swept = V2/2/240;\n",
"print (\"Piston displacement of expander\"),(\" = %.3f\")%(V2),(\"m^3/min\")\n",
"\n",
"d_c = math.sqrt(V_swept/l/math.pi*4);\n",
"print (\"(iv)Diameter or bore of the expander cylinder = %.0f\")%(d_c*1000), (\"mm\")\n",
"\n",
"d_c = math.sqrt(V_swept/l/math.pi*4);\n",
"print (\"Diameter or bore of the compressor cylinder = %.0f\")%(d_c*1000),(\"mm\")\n",
"\n",
"W = capacity*14000/COP/3600;\n",
"print (\"(v) Power required to drive the unit\"),(\" = %.3f\")%(W),(\"kW\")\n",
"\n",
"# Answers are slightly different because of rounding error."
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) C.O.P. = 1.662\n",
"(ii)mass of air in circulation = 15.016 kg/min\n",
"(iii)Piston displacement of compressor = 12.45 m^3/min\n",
"Piston displacement of expander = 8.449 m^3/min\n",
"(iv)Diameter or bore of the expander cylinder = 335 mm\n",
"Diameter or bore of the compressor cylinder = 335 mm\n",
"(v) Power required to drive the unit = 14.039 kW\n"
]
}
],
"prompt_number": 7
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.12 page no : 744"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"m = 6.; \t\t\t#kg/min\n",
"n_relative = 0.50; \n",
"cpw = 4.187; \t\t\t#kJ/kg K\n",
"L = 335.; \t\t\t#kJ/kg\n",
"\n",
"h_f2 = 31.4; \t\t\t#kJ/kg\n",
"h_fg2 = 154.; \t\t\t#kJ/kg\n",
"h_f3 = 59.7; \t\t\t#kJ/kg\n",
"h_fg3 = 138.; \t\t\t#kJ/kg\n",
"h_f4 = 59.7; \t\t\t#kJ/kg\n",
"x2 = 0.6;\n",
"s_f3 = 0.2232; \t\t\t#kJ/kg K\n",
"s_f2 = 0.1251; \t\t\t#kJ/kg K\n",
"T2 = 268.; \t\t\t#K\n",
"T3 = 298.; \t\t\t#K\n",
"\n",
"# Calculations\n",
"h2 = h_f2+x2*h_fg2;\n",
"x3 = ((s_f2-s_f3)+x2*(h_fg2/T2))*T3/h_fg3;\n",
"h3 = h_f3+x3*h_fg3;\n",
"h1 = h_f4;\n",
"COP_th = (h2-h1)/(h3-h2); \t\t\t#Theoritical COP\n",
"COP = n_relative*COP_th;\n",
"Q = cpw*(20-0) + L; \t\t\t#Heat extracted from 1 kg of water at 20\u00b0C for the formation of 1 kg of ice at 0\u00b0C\n",
"m_ice = COP*m*(h3-h2)/Q*60*24/1000; \t\t\t#in 24 hours\n",
"\n",
"# Results\n",
"print (\"m_ice = %.3f\")%(m_ice), (\"tonnes\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"m_ice = 0.661 tonnes\n"
]
}
],
"prompt_number": 14
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.13 page no : 745"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"L = 335.; \t\t\t #kJ/kg\n",
"h3 = 1319.22; \t\t\t#kJ/kg\n",
"h1 = 100.04; \t\t\t#kJ/kg\n",
"h4 = h1;\n",
"s_f2 = -2.1338; \t\t#kJ/kg K\n",
"s_g2 = 5.0585; \t\t\t#kJ/kg K\n",
"s_g3 = 4.4852; \t\t\t#kJ/kg K\n",
"h_f2 = -54.56; \t\t\t#kJ/kg\n",
"h_g2 = 1304.99; \t\t#kJ/kg\n",
"\n",
"# Calculations\n",
"x2 = (s_g3-s_f2)/(s_g2-s_f2);\n",
"h2 = h_f2+x2*(h_g2-h_f2);\n",
"COP_theoritical = (h2-h1)/(h3-h2);\n",
"COP_actual = 0.62*COP_theoritical;\n",
"RE = COP_actual*(h3-h2); \t\t\t#Actual refrigerating effect per kg\n",
"Q = 28.*1000.*L/24./3600; \t\t\t#Heat to be extracted per second\n",
"m = Q/RE; \t\t\t#Mass of refrigerant circulated per second\n",
"W = m*(h3-h2);\n",
"\n",
"# Results\n",
"print (\"Power required = %.3f\")%(W), (\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Power required = 19.577 kW\n"
]
}
],
"prompt_number": 15
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.14 page no : 747"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"h_f2 = 158.2; \t\t\t#kJ/kg\n",
"x2 = 0.62;\n",
"h_fg2 = 1280.8;\n",
"h1 = 298.9; \t\t\t#kJ/kg\n",
"h_f4 = h1;\n",
"s_f2 = 0.630; \t\t\t#kJ/kg K\n",
"T2 = 268.; \t\t\t #K\n",
"T3 = 298.; \t\t\t #K\n",
"s_f3 = 1.124; \t\t\t#kJ/kg K\n",
"h_fg3 = 1167.1; \t\t#kJ/kg\n",
"m = 6.4; \t\t\t #kg/min\n",
"cp = 4.187;\n",
"L = 335.; \t\t\t #kJ/kg\n",
"h_f3 = 298.9; \t\t\t#kJ/kg\n",
"\n",
"# Calculations\n",
"h2 = h_f2+x2*h_fg2;\n",
"x3 = ((s_f2-s_f3)+x2*h_fg2/T2)/h_fg3*T3;\n",
"h3 = h_f3+x3*h_fg3;\n",
"COP_theoritical = (h2-h1)/(h3-h2);\n",
"COP_actual = 0.55*COP_theoritical;\n",
"W1 = 81.87 #h3-h2; \t\t\t#Work done per kg of refrigerant\n",
"\n",
"W = m*W1/60; \t\t\t#Work done per second kJ/s\n",
"Q = round(15*cp+L,1);\n",
"m_ice = W*3600.*24/Q;\n",
"\n",
"\n",
"# Results\n",
"print (\"Amount of ice formed in 24 hours = %.3f\")% (m_ice), (\"kg\")\n",
"\n",
"# Note : Answer is slightly different because of rounding error."
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Amount of ice formed in 24 hours = 1896.717 kg\n"
]
}
],
"prompt_number": 14
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.15 page no : 748"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"RE = 5*14000./3600; \t#Total refrigeration produced in kg/s\n",
"h2 = 183.19; \t\t\t#kJ/kg\n",
"h3 = 209.41; \t\t\t#kJ/kg\n",
"h4 = 74.59; \t\t\t#kJ/kg\n",
"h1 = h4;\n",
"\n",
"# Calculations and Results\n",
"RE_net = h2-h1; \t\t\t#Net refrigerating effect produced per kg\n",
"m = RE/RE_net; \n",
"print (\"(i) The refrigerant flow rate\"),(\" = %.3f\")% (m), (\"kg/s\")\n",
"\n",
"\n",
"COP = (h2-h1)/(h3-h2);\n",
"print (\"(ii) The C.O.P. = %.3f\")% (COP)\n",
"\n",
"\n",
"P = m*(h3-h2);\n",
"print (\"(iii) The power required to drive the compressor = %.3f\")%(P), (\"kW\")\n",
"\n",
"rate = m*(h3-h4);\n",
"print (\"(iv) The rate of heat rejection to the condenser = %.3f\")%(rate),(\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) The refrigerant flow rate = 0.179 kg/s\n",
"(ii) The C.O.P. = 4.142\n",
"(iii) The power required to drive the compressor = 4.695 kW\n",
"(iv) The rate of heat rejection to the condenser = 24.139 kW\n"
]
}
],
"prompt_number": 12
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.16 page no : 749"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print (\"(iii)\")\n",
"\n",
"# Variables\n",
"h2 = 344.927; \t\t\t#kJ/kg\n",
"h4 = 228.538; \t\t\t#kJ/kg\n",
"h1 = h4;\n",
"cpv = 0.611; \t\t\t#/kJ/kg0C\n",
"# s2 = s3\n",
"t3 = 39.995; \t\t\t#0C\n",
"\n",
"# Calculations\n",
"h3 = 363.575+cpv*(t3-30);\n",
"Rn = h2-h1;\n",
"W = h3-h2;\n",
"COP = Rn/W;\n",
"\n",
"# Results\n",
"print (\"COP = %.3f\")% (COP)\n",
"\n",
"cp = 2.0935; \t\t\t#kJ/kg 0C\n",
"Q = 2400./24./3600*(4.187*(15-0)+335+cp*(0-(-5)))\n",
"\n",
"W = Q/COP;\n",
"print (\"Work required = %.3f\")% (W), (\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(iii)\n",
"COP = 4.702\n",
"Work required = 2.412 kW\n"
]
}
],
"prompt_number": 13
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.17 page no : 751"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"h2 = 352.; \t\t\t#kJ/kg\n",
"h3 = 374.; \t\t\t#kJ/kg\n",
"h4 = 221.; \t\t\t#kJ/kg\n",
"h1 = h4;\n",
"v2 = 0.08; \t\t\t#m**3/kg\n",
"rpm = 500.;\n",
"D = 0.2;\n",
"L = 0.15;\n",
"n_vol = 0.85;\n",
"\n",
"# Calculations\n",
"RE = h2-h1;\n",
"V = math.pi/4*D**2*L*rpm*2*n_vol;\n",
"m = V/v2;\n",
"\n",
"# Results\n",
"print (\"(ii)Mass of refrigerant circulated per minute = %.3f\")% (m), (\"kg/min\")\n",
"\n",
"cc = 50.*(h2-h1)*60./14000.;\n",
"print (\"(iii) Cooling capacity in tonnes of refrigeration = %.3f\")%(cc), (\"TR\")\n",
"\n",
"COP = (h2-h1)/(h3-h2);\n",
"print (\"(iv)COP = %.3f\")% (COP)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(ii)Mass of refrigerant circulated per minute = 50.069 kg/min\n",
"(iii) Cooling capacity in tonnes of refrigeration = 28.071 TR\n",
"(iv)COP = 5.955\n"
]
}
],
"prompt_number": 15
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.18 page no : 751"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"te = -10.; \t\t\t#0C\n",
"tc = 40.; \t\t\t#0C\n",
"h3 = 220.; \t\t\t#kJ/kg\n",
"h2 = 183.1; \t\t\t#kJ/kg\n",
"h1 = 74.53; \t\t\t#kJ/kg\n",
"h_f4 = 26.85; \t\t\t#kJ/kg\n",
"m = 1.; \t\t\t#kg\n",
"\n",
"# Calculations and Results\n",
"COP = (h2-h1)/(h3-h2);\n",
"print (\"(i) The C.O.P. the cycle = %.3f\")%(COP)\n",
"\n",
"RC = m*(h2-h1);\n",
"print (\"(ii) Refrigerating capacity = %.3f\")%(RC),(\"kJ/min\")\n",
"\n",
"CP = m*(h3-h2)/60;\n",
"print (\"Compressor power = %.3f\")% (CP), (\"kJ/s\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) The C.O.P. the cycle = 2.942\n",
"(ii) Refrigerating capacity = 108.570 kJ/min\n",
"Compressor power = 0.615 kJ/s\n"
]
}
],
"prompt_number": 20
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.19 page no : 752"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\n",
"# Variables\n",
"h2 = 178.61; \t\t\t#kJ/kg\n",
"h3a = 203.05; \t\t\t#kJ/kg\n",
"h_f4 = 74.53; \t\t\t#kJ/kg\n",
"h1 = h_f4;\n",
"s3a = 0.682; \t\t\t#kJ/kg K\n",
"s2 = 0.7082; \t\t\t#kJ/kg K\n",
"cp = 0.747; \t\t\t#kJ/kg K\n",
"T3a = 313.; \t\t\t#K\n",
"CE = 20.; \t\t\t #Cooling effect\n",
"C = 0.03;\n",
"v_g = 0.1088;\n",
"p_d = 9.607;\n",
"p_s = 1.509;\n",
"n = 1.13;\n",
"\n",
"# Calculations\n",
"m = CE/(h2-h1);\n",
"T3 = T3a*math.e**((s2-s3a)/cp)\n",
"h3 = h3a+cp*(T3-T3a);\n",
"P = m*(h3-h2);\n",
"\n",
"# Results\n",
"print (\"Power required by the machine = %.3f\")%(P), (\"kW\")\n",
"\n",
"n_vol = 1+C-C*(p_d/p_s)**(1./n); \t\t\t#Volumetric efficiency\n",
"V1 = m*v_g; \t\t\t #volume of refrigerant at the intake conditions\n",
"V_swept = V1/n_vol;\n",
"\n",
"V = V_swept*60./300;\n",
"print (\"Piston print lacement = %.5f\")% (V), (\"m**3\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Power required by the machine = 6.300 kW\n",
"Piston print lacement = 0.00478 m**3\n"
]
}
],
"prompt_number": 16
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.20 page no : 754"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\n",
"# Variables\n",
"h2 = 1450.22; \t\t\t#kJ/kg\n",
"h3a = 1488.57; \t\t\t#kJ/kg\n",
"h_f4 = 366.072; \t\t#kJ/kg\n",
"cpl2 = 4.556; \t\t\t#kJ/kg K\n",
"cpv1 = 2.492; \t\t\t#kJ/kg K\n",
"cpv2 = 2.903; \t\t\t#kJ/kg K\n",
"T1 = 303.; \t\t\t #K\n",
"T2 = 308.; \t\t\t #K\n",
"s3a = 5.2086; \t\t\t#kJ/kg K\n",
"s2 = 5.755; \t\t\t#kJ/kg K\n",
"T3a = 308.; \t\t\t#K\n",
"N = 1000.;\n",
"\n",
"# Calculations\n",
"h_f4a = h_f4-cpl2*(T2-T1);\n",
"h1 = h_f4a;\n",
"T3 = T3a*math.e**((s2-s3a)/cpv2);\n",
"h3 = h3a+cpv2*(T3-T3a);\n",
"m = 50./(h2-h1);\n",
"\n",
"# Results\n",
"P = m*(h3-h2);\n",
"print (\"(i) Power required = %.3f\")%(P), (\"kW\")\n",
"\n",
"print (\"(ii) Cylinder dimensions \")\n",
"D = (m*4*60/math.pi/1.2/N/0.417477)**(1./3);\n",
"print (\"Diameter of cylinder = %.3f\")% (D), (\"m\")\n",
"\n",
"L = 1.2*D;\n",
"print (\"Length of the cylinder = %.3f\")% (L), (\"m\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) Power required = 10.096 kW\n",
"(ii) Cylinder dimensions \n",
"Diameter of cylinder = 0.190 m\n",
"Length of the cylinder = 0.228 m\n"
]
}
],
"prompt_number": 22
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.21 page no : 756"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"cooling_load = 150.; #W\n",
"n_vol = 0.8;\n",
"N = 720.; \t\t\t#rpm\n",
"h2 = 183.; \t\t\t#kJ/kg\n",
"h1 = 74.5; \t\t\t#kJ/kg\n",
"v2 = 0.08; \t\t\t#m**3/kg\n",
"\n",
"# Calculations\n",
"m = cooling_load/(108.5*1000);\n",
"d = m*v2/n_vol;\n",
"\n",
"# Results\n",
"print (\"Mass flow rate of the refrigerant = %.6f\")% (m),(\"kJ/s\")\n",
"\n",
"print (\"Displacement volume of the compressor = %6f\")% (d), (\"m**3/s\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Mass flow rate of the refrigerant = 0.001382 kJ/s\n",
"Displacement volume of the compressor = 0.000138 m**3/s\n"
]
}
],
"prompt_number": 18
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.22 page no : 757"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"h2 = 183.2; \t\t\t#kJ/kg\n",
"h3 = 222.6; \t\t\t#kJ/kg\n",
"h4 = 84.9 \t\t\t#kJ/kg\n",
"v2 = 0.0767; \t\t\t#m**3/kg\n",
"v3 = 0.0164; \t\t\t#m**3/kg\n",
"v4 = 0.00083; \t\t\t#m**3/kg\n",
"\n",
"# Calculations\n",
"V = 1.5*1000*10**(-6); \t\t\t#Piston print lacement volume m**3/revolution\n",
"n_vol = 0.80;\n",
"\n",
"print (\"(i) Power rating of the compressor (kW)\")\n",
"discharge = V*1600*n_vol; \t\t\t#Compressor discharge\n",
"m = discharge/v2;\n",
"\n",
"P = m/60*(h3-h2); \t\t\t#kW\n",
"print (\"Power = %.3f\")% (P), (\"kW\")\n",
"\n",
"\n",
"RE = m/60*(h2-h4);\n",
"print (\"(ii) Refrigerating effect = %.3f\")% (RE), (\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) Power rating of the compressor (kW)\n",
"Power = 16.438 kW\n",
"(ii) Refrigerating effect = 41.012 kW\n"
]
}
],
"prompt_number": 24
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.23 page no : 757"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Variables\n",
"COP = 6.5;\n",
"W = 50.; \t\t\t#kW\n",
"h3a = 201.45; \t\t\t#kJ/kg\n",
"h_f4 = 69.55; \t\t\t#kJ/kg\n",
"h1 = h_f4;\n",
"h2 = 187.53; \t\t\t#kJ/kg\n",
"cp = 0.6155; \t\t\t#kJ/kg\n",
"t3a = 35.; \t\t\t#0C\n",
"\n",
"# Calculations\n",
"RC = W*COP; \t\t\t#Refrigerating capacity\n",
"Q1 = h2-h_f4; \t\t\t#Heat extracted per kg of refrigerant\n",
"rate = RC/Q1; \t\t\t#Refrigerant flow rate\n",
"Q2 = W/rate; \t\t\t#Heat input per kg\n",
"h = h2+Q2; \t\t\t#Enthalpy of vapour after compression\n",
"Q = h-h3a; \t\t\t#Superheat\n",
"\n",
"t3 = Q/cp+t3a;\n",
"\n",
"# Results\n",
"print (\"The refrigerant temperature = %.3f\")% (t3), (\"\u00b0C\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The refrigerant temperature = 41.874 \u00b0C\n"
]
}
],
"prompt_number": 19
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.24 page no : 758"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math\n",
"\n",
"# Variables\n",
"Q1 = 500.; \t\t\t#total heating requirement of 500 kJ/min\n",
"n_compressor = 0.8;\n",
"s1 = 0.7035; \t\t\t#kJ/kg K\n",
"s2 = 0.6799; \t\t\t#kJ/kg K\n",
"T2 = 322.31; \t\t\t#K\n",
"cp = 0.7; \t\t\t #kJ/kg K\n",
"h_v2 = 206.24; \t\t\t#kJ/kg\n",
"h_l2 = 84.21; \t\t\t#kJ/kg\n",
"h_v1 = 182.07 \t\t\t#kJ/kg\n",
"\n",
"# Calculations\n",
"Q2 = Q1/n_compressor; \t\t\t#Heat rejected by the cycle\n",
"\n",
"#Entropy of dry saturated vapour at 2 bar = Entropy of superheated vapour at 12 bar\n",
"T = T2*math.e**((s1-s2)/cp);\n",
"\n",
"H = h_v2+cp*(T-T2); \t\t\t#Enthalpy of superheated vapour at 12 bar\n",
"Q3 = H-h_l2; \t\t\t#Heat rejected per cycle\n",
"m = Q2/Q3; \t\t\t#kg/min\n",
"W = m*(H-h_v1)/60; \t\t\t#kW\n",
"W_actual = W/n_compressor;\n",
"\n",
"# Results\n",
"print (\"Power = %.3f\")% (W_actual), (\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Power = 3.201 kW\n"
]
}
],
"prompt_number": 26
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.25 page no : 759"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"# Variables\n",
"h2a = 183.2; \t\t\t#kJ/kg K\n",
"cpv = 0.733; \t\t\t#Vapour specific heat in kJ/kg K\n",
"cpl = 1.235; \t\t\t#Liquid specific heat in kJ/kg K\n",
"s2a = 0.7020; \t\t\t#Entropy of vapour in kJ/kg K\n",
"s3a = 0.6854; \t\t\t#Entropy of vapour in kJ/kg K\n",
"T2 = 270.; \t\t\t #K\n",
"T2a = 263.; \t\t\t#K\n",
"T3a = 303.; \t\t\t#K\n",
"h3a = 199.6; \t\t\t#kJ/kg\n",
"h_f4 = 64.6; \t\t\t#kJ/kg\n",
"dT4 = 6.; \t\t\t #dT4 = T4-T4a\n",
"v2a = 0.0767;\n",
"n = 2.; \t\t\t #number of cylinder\n",
"\n",
"# Calculations and Results\n",
"h2 = h2a+cpv*(T2-T2a);\n",
"s2 = s2a+cpv*math.log(T2/T2a);\n",
"T3 = T3a*math.e**((s2-s3a)/cpv);\n",
"h3 = h3a+cpv*(T3-T3a);\n",
"h_f4a = h_f4-cpl*dT4;\n",
"h1 = h_f4a;\n",
"v2 = v2a/T2a*T2;\n",
"\n",
"RE = h2-h1;\n",
"print (\"(i) Refrigerating effect per kg = \"), (RE), (\"kJ/kg\")\n",
"\n",
"m = 2400/RE;\n",
"print (\"(ii) Mass of refrigerant to be circulated per minute = %.3f\")% (m), (\"kg/min\")\n",
"\n",
"v = m*v2;\n",
"print (\"(iii) Theoretical piston print lacement per minute = %.3f\")%(v), (\"m**3/min\")\n",
"\n",
"P = m/60*(h3-h2);\n",
"print (\"(iv) Theoretical power required to run the compressor = %.3f\")% (P), (\"kW\")\n",
"\n",
"Q = m*(h3-h_f4a);\n",
"print (\"(v) Heat removed through the condenser per min = %.3f\")% (Q), (\"kJ/min\")\n",
"\n",
"print (\"(vi) Theoretical bore (d) and stroke (l)\")\n",
"d = (v/n/math.pi*4/1.25/1000)**(1./3)*1000;\n",
"print (\"Theroritical bore = %.3f\")% (d), (\"mm\")\n",
"\n",
"l = 1.25*d;\n",
"print (\"stroke = %.3f\")% (l), (\"mm\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) Refrigerating effect per kg = 131.141 kJ/kg\n",
"(ii) Mass of refrigerant to be circulated per minute = 18.301 kg/min\n",
"(iii) Theoretical piston print lacement per minute = 1.441 m**3/min\n",
"(iv) Theoretical power required to run the compressor = 6.833 kW\n",
"(v) Heat removed through the condenser per min = 2809.995 kJ/min\n",
"(vi) Theoretical bore (d) and stroke (l)\n",
"Theroritical bore = 90.202 mm\n",
"stroke = 112.752 mm\n"
]
}
],
"prompt_number": 27
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.26 page no : 761"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"# Variables\n",
"h2 = 1597.; \t\t\t#kJ/kg\n",
"h3 = 1790.; \t\t\t#kJ/kg\n",
"h4 = 513.; \t\t\t#kJ/kg\n",
"h1 = h4;\n",
"t3 = 58.; \t\t\t#0C\n",
"x1 = 0.13;\n",
"tc = 27.; \t\t\t#0C\n",
"capacity = 10.5; \t\t\t#tonnes\n",
"\n",
"# Calculations and Results\n",
"t = t3-tc;\n",
"print (\"(i) Condition of the vapour at the outlet of the compressor = \"), (t), (\"C\")\n",
"\n",
"print (\"(ii) Condition of vapour at entrance to evaporator = \"), (x1)\n",
"\n",
"COP = (h2-h1)/(h3-h2);\n",
"print (\"(iii)COP = %.3f\") %(COP)\n",
"\n",
"P = capacity*14000./COP/3600;\n",
"print (\"(iv) Power required = %.3f\")% (P), (\"kW\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) Condition of the vapour at the outlet of the compressor = 31.0 C\n",
"(ii) Condition of vapour at entrance to evaporator = 0.13\n",
"(iii)COP = 5.617\n",
"(iv) Power required = 7.270 kW\n"
]
}
],
"prompt_number": 21
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 14.27 page no : 762"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"import math \n",
"\n",
"# Variables\n",
"h2 = 615.; \t\t\t#kJ/kg\n",
"h3 = 664.; \t\t\t#kJ/kg\n",
"h4 = 446.; \t\t\t#kJ/kg\n",
"h1 = h4;\n",
"v2 = 0.14; \t\t\t#m**3/kg\n",
"capacity = 20.; \t#tonnes\n",
"n = 6.; \t\t\t#number of cylinder\n",
"\n",
"# Calculations and Results\n",
"RE = h2-h1;\n",
"print (\"(i) Refrigerating effect per kg = \"), (RE), (\"kJ/kg\")\n",
"\n",
"m = capacity*14000./RE/60.;\n",
"print (\"(ii) Mass of refrigerant to be circulated per minute = %.3f\")% (m), (\"kg/min\")\n",
"\n",
"v = v2*m;\n",
"print (\"(iii) Theoretical piston print lacement = %.3f\")% (v), (\"m**3/min\")\n",
"\n",
"P = m/60*(h3-h2);\n",
"print (\"(iv) Theoretical power = %.3f\")% (P), (\"kW\")\n",
"\n",
"COP = (h2-h1)/(h3-h2);\n",
"print (\"(v)COP = %.3f\")% (COP)\n",
"\n",
"Q = m*(h3-h4);\n",
"print (\"(vi) Heat removed through the condenser = %.3f\")% (Q), (\"kJ/min\")\n",
"\n",
"print (\"(vii) Theoretical print lacement per minute per cylinder\")\n",
"\n",
"d = (v/n*4/math.pi/950.)**(1./3)*1000.;\n",
"print (\"Diameter of cylinder = %.3f\")% (d), (\"mm\")\n",
"\n",
"l = d;\n",
"print (\"Stroke length = %.3f\")% (l), (\"mm\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(i) Refrigerating effect per kg = 169.0 kJ/kg\n",
"(ii) Mass of refrigerant to be circulated per minute = 27.613 kg/min\n",
"(iii) Theoretical piston print lacement = 3.866 m**3/min\n",
"(iv) Theoretical power = 22.551 kW\n",
"(v)COP = 3.449\n",
"(vi) Heat removed through the condenser = 6019.724 kJ/min\n",
"(vii) Theoretical print lacement per minute per cylinder\n",
"Diameter of cylinder = 95.227 mm\n",
"Stroke length = 95.227 mm\n"
]
}
],
"prompt_number": 30
}
],
"metadata": {}
}
]
}