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"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"Chapter 7 : Thermodynamic property relations"
]
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 7.10 Page No : 259"
]
},
{
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"collapsed": false,
"input": [
"\n",
"import math \n",
"\n",
"# Variables\n",
"T2 = 150. \t\t\t #temperature at which water it is desired to boil water in degree celsius\n",
"P1 = 0.10133\t\t\t #ambient pressure in MPa\n",
"T1 = 100.\t \t\t #temperature at which water boils corresponding at pressure P1 in degree celsius\n",
"del_hv = 2256.94\t\t #enthalpy of vaporization in kJ/kg\n",
"R = 8.314;\t\t \t #universal gas constant in J/molK\n",
"M = 18*10**-3;\t\t\t #molar mass of water in kg/mol\n",
"\n",
"# Calculations\n",
"T1 = T1+273.15\n",
"T2 = T2+273.15\n",
"P2 = P1*(math.exp(((del_hv*10**3*M)*((1./T1)-(1./T2)))/(R)))\n",
"\n",
"# Results\n",
"print \" The approximate pressure at which the boiler is to be operated = %0.3f MPa\"%(P2);\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
" The approximate pressure at which the boiler is to be operated = 0.476 MPa\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 7.11 Page No : 259"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"# Variables\n",
"m = 60. \t\t\t #mass of the person who wants to skate in kg\n",
"T = -2.\t\t\t #temperature of the ice in degree celsius\n",
"A = 15.\t\t\t #area of contact between the skate edges and ice in mm**2\n",
"vs = 1.091*10**-3;\t\t\t #specific volume of ice in m**3/kg (at Tref)\n",
"vf = 1.0*10**-3;\t\t\t #specific volume of water in m**3/kg (at Tref)\n",
"del_hf = 6.002;\t\t \t #enthalpy of melting of ice in kJ/mol\n",
"g = 9.81;\t\t\t #accleration due to gravity in m/s**2\n",
"Tref = 0. \t\t\t #reference temperature at which the specific enthalpy of ice and water are taken in degree celsius\n",
"\n",
"# Calculations\n",
"Tref = Tref+273.15\n",
"del_P = ((m*g)/(A*10**-6))*10**-6\n",
"del_v = (vf-vs)*(18*10**-3);\t\n",
"del_T = (del_P*10**6)/((del_hf*10**3)/(Tref*del_v));\t\t\t \n",
"\n",
"# Results\n",
"print \" The temperature of ice originally = %d degree celsius \"%(T);\n",
"print \" The reduction in melting point of ice due to the additional pressure,computed using the Clayperon equation = %0.2f degree celsius \"%(del_T);\n",
"if del_T