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{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Chapter 7 The second law"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Ex:7.2 Pg:192"
]
},
{
"cell_type": "code",
"execution_count": 1,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Entropy in ab part = 0.1213 Btu/lbm R\n",
"\n",
" Entropy in ac part = 0.1688 Btu/lbm R\n",
"\n",
" Efficiency = 9.80 percent\n",
"The answers are a bit different due to rounding off error in textbook\n"
]
}
],
"source": [
"from math import log\n",
"#Initialization of variables\n",
"cv=0.175 #Btu/lbm R\n",
"R0=1.986\n",
"M=29\n",
"T2=1040 #R\n",
"T1=520 #R\n",
"#calculations\n",
"cp=cv+R0/M\n",
"sab=cv*log(T2/T1)\n",
"sac=cp*log(T2/T1)\n",
"dqab=cv*(T2-T1)\n",
"dqca=cp*(T1-T2)\n",
"dqrev=T2*(sac-sab)\n",
"eta=(dqab+dqrev+dqca)/(dqab+dqrev)\n",
"#results\n",
"print \"Entropy in ab part = %.4f Btu/lbm R\"%(sab)\n",
"print \"\\n Entropy in ac part = %.4f Btu/lbm R\"%(sac)\n",
"print \"\\n Efficiency = %.2f percent\"%(eta*100)\n",
"print \"The answers are a bit different due to rounding off error in textbook\""
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Ex:7.3 Pg:193"
]
},
{
"cell_type": "code",
"execution_count": 3,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Change in entropy of the process = 0.0192 Btu/R\n",
"The answer is a bit different due to rounding off error in textbook\n"
]
}
],
"source": [
"from __future__ import division\n",
"from math import log\n",
"#Initialization of variables\n",
"tc=32 #F\n",
"th=80 #F\n",
"mw=5 #lbm\n",
"mi=1 #lbm\n",
"P=14.7 #psia\n",
"cp=1\n",
"#calculations\n",
"t= (-144*mi+tc*mi+th*mw)/(mw+mi)\n",
"ds1=144/(tc+460)\n",
"ds2=cp*log((460+t)/(460+tc))\n",
"dsice=ds1+ds2\n",
"dswater=mw*cp*log((t+460)/(460+th))\n",
"ds=dsice+dswater\n",
"#results\n",
"print \"Change in entropy of the process = %.4f Btu/R\"%(ds)\n",
"print \"The answer is a bit different due to rounding off error in textbook\""
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Ex:7.4 Pg:194"
]
},
{
"cell_type": "code",
"execution_count": 4,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Change in available energy = -3.5 Btu/lbm\n",
"\n",
" The available energy of the isolated system decreased in the amount of -36.5 Btu/lbm\n",
"The answer is a bit different due to rounding off error in textbook\n"
]
}
],
"source": [
"from __future__ import division\n",
"from math import log\n",
"\n",
"#Initialization of variables\n",
"cp=1\n",
"T2=60 #F\n",
"T1=100 #F\n",
"ta=32 #F\n",
"#calculations\n",
"dq=cp*(T2-T1)\n",
"ds=cp*log((460+T2)/(460+T1))\n",
"dE=dq-ds*(ta+460)\n",
"dec=dq-dE\n",
"#results\n",
"print \"Change in available energy = %.1f Btu/lbm\"%(dE)\n",
"print \"\\n The available energy of the isolated system decreased in the amount of %.1f Btu/lbm\"%(dec)\n",
"print \"The answer is a bit different due to rounding off error in textbook\""
]
}
],
"metadata": {
"kernelspec": {
"display_name": "Python 2",
"language": "python",
"name": "python2"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 2
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython2",
"version": "2.7.9"
}
},
"nbformat": 4,
"nbformat_minor": 0
}
|
