{
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"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"Chapter 14 - Psychrometrics"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 1 - Pg 257"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#calculate the partial pressures, dew temperature and density of air, water and specific humidity, Degree of saturation\n",
"#Initialization of variables\n",
"t1=80+460 #R\n",
"ps=0.5069 #psia\n",
"print '%s' %(\"from steam tables,\")\n",
"vs=633.1 #ft^3/lbm\n",
"phi=0.3\n",
"R=85.6\n",
"Ra=53.3\n",
"p=14.696\n",
"#calculations\n",
"tdew=46. #F\n",
"pw=phi*ps\n",
"rhos=1/vs\n",
"rhow=phi*rhos\n",
"rhow2= pw*144/(R*t1)\n",
"pa=p-pw\n",
"rhoa= pa*144/(Ra*t1)\n",
"w=rhow/rhoa\n",
"mu=phi*(p-ps)/(p-pw)\n",
"Ws=0.622*(ps/(p-ps))\n",
"mu2=w/Ws\n",
"#results\n",
"print '%s' %(\"part a\")\n",
"print '%s %.5f %s' %(\"partial pressure of water =\",pw,\"psia\")\n",
"print '%s %d %s' %(\"\\n dew temperature =\",tdew,\"F\")\n",
"print '%s' %(\"part b\")\n",
"print '%s %.6f %s' %(\"density of water =\",rhow,\"lbm/ft^3\")\n",
"print '%s %.6f %s' %(\"\\n in case 2, density of water =\",rhow2,\"lbm/ft^3\")\n",
"print '%s %.6f %s' %(\"\\n density of air =\",rhoa,\"lbm/ft^3\")\n",
"print '%s' %(\"part c\")\n",
"print '%s %.4f %s' %(\"specific humidity =\",w,\"lbm steam/lbm air\")\n",
"print '%s' %(\"part d\")\n",
"print '%s %.3f' %(\"In method 1, Degree of saturation = \",mu)\n",
"print '%s %.3f' %(\"\\n In method 2, Degree of saturation = \",mu2)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"from steam tables,\n",
"part a\n",
"partial pressure of water = 0.15207 psia\n",
"\n",
" dew temperature = 46 F\n",
"part b\n",
"density of water = 0.000474 lbm/ft^3\n",
"\n",
" in case 2, density of water = 0.000474 lbm/ft^3\n",
"\n",
" density of air = 0.072765 lbm/ft^3\n",
"part c\n",
"specific humidity = 0.0065 lbm steam/lbm air\n",
"part d\n",
"In method 1, Degree of saturation = 0.293\n",
"\n",
" In method 2, Degree of saturation = 0.293\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 2 - Pg 258"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#calculate the change in moisture content and change in moisture content\n",
"#Initialization of variables\n",
"p=14.696 #psia\n",
"ps=0.0808 #psia\n",
"ps2=0.5069 #psia\n",
"phi2=0.5\n",
"phi=0.6\n",
"grain=7000.\n",
"#calculations\n",
"pw=phi*ps\n",
"w1=0.622*pw/(p-pw)\n",
"pw2=phi2*ps2\n",
"w2=0.622*pw2/(p-pw2)\n",
"dw=w2-w1\n",
"dwg=dw*grain\n",
"#results\n",
"print '%s %.6f %s' %(\"change in moisture content =\",dw,\" lbm water/lbm dry air\")\n",
"print '%s %.2f %s' %(\"\\n in grains, change =\",dwg,\" grains water/lbm dry air\")\n",
"print '%s' %(\"The answers are a bit different due to rounding off error in textbook\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"change in moisture content = 0.008857 lbm water/lbm dry air\n",
"\n",
" in grains, change = 62.00 grains water/lbm dry air\n",
"The answers are a bit different due to rounding off error in textbook\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 3 - Pg 264"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#calculate the humidity ratio and relative humidity\n",
"#Initialization of variables\n",
"t1=80. #F\n",
"t2=60. #F\n",
"p=14.696 #psia\n",
"ps=0.507 #psia\n",
"pss=0.256 #psia\n",
"cp=0.24\n",
"#calculations\n",
"ws=0.622*pss/(p-pss)\n",
"w=(cp*(t2-t1) + ws*1060)/(1060+ 0.45*(t1-t2))\n",
"pw=w*p/(0.622+w)\n",
"phi=pw/ps*100\n",
"td=46. #F\n",
"#results\n",
"print '%s %.4f %s' %(\"\\n humidity ratio =\",w,\"lbm/lbm dry air\")\n",
"print '%s %.1f %s' %(\"\\n relative humidity =\",phi,\" percent\")\n",
"print '%s %d %s' %(\"\\n Dew point =\",td,\"F\")\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"\n",
" humidity ratio = 0.0064 lbm/lbm dry air\n",
"\n",
" relative humidity = 29.7 percent\n",
"\n",
" Dew point = 46 F\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 4 - Pg 264"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#calculate the enthalpy and sigma function\n",
"#Initialization of variables\n",
"W=0.0065 #lbm/lbm of dry air\n",
"t=80. #F\n",
"td=60. #F\n",
"#calculations\n",
"H=0.24*t+W*(1060+0.45*t)\n",
"sig=H-W*(td-32)\n",
"Ws=0.0111\n",
"H2=0.24*td+Ws*(1060+0.45*td)\n",
"sig2=H2-Ws*(td-32)\n",
"#results\n",
"print '%s %.2f %s' %(\"In case 1, enthalpy =\",H,\" Btu/lbm dry air\")\n",
"print '%s %.2f %s' %(\"\\n In case 1, sigma function =\",sig,\" Btu/lbm dry air\")\n",
"print '%s %.2f %s' %(\"\\n In case 2, enthalpy =\",H2,\" Btu/lbm dry air\")\n",
"print '%s %.2f %s' %(\"\\n In case 2, sigma function =\",sig2,\" Btu/lbm dry air\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"In case 1, enthalpy = 26.32 Btu/lbm dry air\n",
"\n",
" In case 1, sigma function = 26.14 Btu/lbm dry air\n",
"\n",
" In case 2, enthalpy = 26.47 Btu/lbm dry air\n",
"\n",
" In case 2, sigma function = 26.15 Btu/lbm dry air\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 5 - Pg 264"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#calculate the Enthalpy and heat added\n",
"#Initialization of variables\n",
"t1=30. #F\n",
"t2=60. #F\n",
"t3=80. #F\n",
"W1=0.00206\n",
"W2=0.01090\n",
"#calculations\n",
"cm1=0.24+0.45*W1\n",
"H1=cm1*t1+W1*1060\n",
"cm2=0.24+0.45*W2\n",
"H2=cm2*t3+W2*1060\n",
"hf=t2-32\n",
"dq=H2-H1-(W2-W1)*hf\n",
"#results\n",
"print '%s %.2f %s' %(\"In case 1, Enthalpy =\",H1,\" Btu/lbm dry air\")\n",
"print '%s %.2f %s' %(\"\\n In case 2, Enthalpy =\",H2,\" Btu/lbm dry air\")\n",
"print '%s %.2f %s' %(\"\\n Heat added =\",dq,\" Btu/lbm dry air\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"In case 1, Enthalpy = 9.41 Btu/lbm dry air\n",
"\n",
" In case 2, Enthalpy = 31.15 Btu/lbm dry air\n",
"\n",
" Heat added = 21.49 Btu/lbm dry air\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 6 - Pg 265"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#calculate the partial pressure and dew temperature, density of air, water and specific humidity\n",
"#Initialization of variables\n",
"pw=0.15#psia\n",
"print '%s' %(\"using psychrometric charts,\")\n",
"tdew=46 #F\n",
"#calculations\n",
"va=13.74 #ft^3/lbm dry air\n",
"rhoa=1./va\n",
"V=13.74\n",
"mw=46/7000.\n",
"rhow=mw/V\n",
"w=0.00657\n",
"#results\n",
"print '%s' %(\"part a\")\n",
"print '%s %.2f %s' %(\"partial pressure of water =\",pw,\" psia\")\n",
"print '%s %d %s' %(\"\\n dew temperature =\",tdew,\"F\")\n",
"print '%s' %(\"part b\")\n",
"print '%s %.6f %s' %(\"density of water =\",rhow,\"lbm/ft^3\")\n",
"print '%s %.4f %s' %(\"\\n density of air =\",rhoa,\"lbm/ft^3\")\n",
"print '%s' %(\"part c\")\n",
"print '%s %.5f %s' %(\"specific humidity =\",w,\"lbm steam/lbm air\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"using psychrometric charts,\n",
"part a\n",
"partial pressure of water = 0.15 psia\n",
"\n",
" dew temperature = 46 F\n",
"part b\n",
"density of water = 0.000478 lbm/ft^3\n",
"\n",
" density of air = 0.0728 lbm/ft^3\n",
"part c\n",
"specific humidity = 0.00657 lbm steam/lbm air\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7 - Pg 266"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#calculate the Enthalpy change\n",
"#Initialization of variables\n",
"W1=0.00206 #lbm/lbm dry air\n",
"W2=0.01090 #lbm/lbm dry air\n",
"t=60 #F\n",
"#calculations\n",
"dw=W1-W2\n",
"\n",
"hs=144.4\n",
"hs2=66.8-32\n",
"w1=14.4 #Btu/lbm\n",
"ws1=20 #Btu/lbm\n",
"w2=76.3 #Btu/lbm\n",
"ws2=98.5 #Btu/lbm\n",
"dwh1=-(w1-ws1)/7000. *hs\n",
"H1=9.3+dwh1\n",
"dwh2=(w2-ws2)/7000. *hs2\n",
"H2=31.3+dwh2\n",
"dwc=dw*(t-32)\n",
"dq=H2-H1+dwc\n",
"#results\n",
"print '%s %.2f %s' %(\"Enthalpy change =\",dq,\" Btu/lbm dry air\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Enthalpy change = 21.53 Btu/lbm dry air\n"
]
}
],
"prompt_number": 7
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 8 - Pg 267"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#calculate the humidity and Temperature\n",
"#Initialization of variables\n",
"print '%s' %(\"From psychrometric charts,\")\n",
"va1=13 #ft^3/lbm dry air\n",
"va2=13.88 #ft^3/lbm dry air\n",
"flow=2000. #cfm\n",
"#calculations\n",
"ma1= flow/va1\n",
"ma2=flow/va2\n",
"t=62.5# F\n",
"phi=0.83 #percent\n",
"#results\n",
"print '%s %.2f' %(\"humidity = \",phi)\n",
"print '%s %.1f %s' %(\"\\n Temperature =\",t,\" F\")\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"From psychrometric charts,\n",
"humidity = 0.83\n",
"\n",
" Temperature = 62.5 F\n"
]
}
],
"prompt_number": 8
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 9 - Pg 270"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#calculate the dry bulb temperature and percent humidity\n",
"#Initialization of variables\n",
"t=90 #F\n",
"ts=67.2 #F\n",
"phi=0.3\n",
"per=0.8\n",
"#calculations\n",
"dep=t-ts\n",
"dt=dep*per\n",
"tf=t-dt\n",
"print '%s' %(\"from psychrometric charts,\")\n",
"phi2=0.8\n",
"#results\n",
"print '%s %.2f %s' %(\"Dry bulb temperature =\",tf,\" F\")\n",
"print '%s %.2f' %(\"\\n percent humidity = \",phi2)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"from psychrometric charts,\n",
"Dry bulb temperature = 71.76 F\n",
"\n",
" percent humidity = 0.80\n"
]
}
],
"prompt_number": 9
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 10 - Pg 271"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#calculate the cooling range and Approach. Also calculate the amount of water cooled and percentage of water lost \n",
"#Initialization of variables\n",
"m=1. #lbm\n",
"t1=100. #F\n",
"t2=75. #F\n",
"db=65. #F\n",
"print '%s' %(\"From psychrometric charts,\")\n",
"t11=82 #F\n",
"phi1=0.4\n",
"H1=30. #Btu/lbm dry air\n",
"w1=65. #grains/lbm dry air\n",
"w2=250. #grains/lbm dry air\n",
"#calculations\n",
"cr=t1-t2\n",
"appr=t2-db\n",
"dmf3=(w2-w1)*0.0001427\n",
"hf3=68.\n",
"hf4=43.\n",
"H2=62.2\n",
"H1=30.\n",
"mf4= (H1-H2+ dmf3*hf3)/(hf4-hf3)\n",
"per=dmf3/(dmf3+mf4)*100\n",
"#results\n",
"print '%s %d %s' %(\"cooling range =\",cr,\"F\")\n",
"print '%s %d %s' %(\"\\n Approach =\",appr,\"F\")\n",
"print '%s %.3f %s' %(\"\\n amount of water cooled per pound of dry air =\",mf4,\"lbm dry air/lbm dry air\")\n",
"print '%s %.2f %s' %(\"\\n percentage of water lost by evaporation =\",per,\"percent\")\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"From psychrometric charts,\n",
"cooling range = 25 F\n",
"\n",
" Approach = 10 F\n",
"\n",
" amount of water cooled per pound of dry air = 1.216 lbm dry air/lbm dry air\n",
"\n",
" percentage of water lost by evaporation = 2.12 percent\n"
]
}
],
"prompt_number": 10
}
],
"metadata": {}
}
]
}