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2300_les09

# 2300_les09 - III Properties of a Pure Substance G.The...

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1 lesson 9 III. Properties of a Pure Substance G.The Ideal-Gas Equation of State 1. The ideal-gas equation of state models the PvT behavior of gases at low pressure. u u PV NR T or Pv R T = = N = number of moles of gas, kmol T = absolute temperature, K = universal gas constant = 8.314 kJ/(kmol K) V = volume, m 3 v = specific volume, m 3 /kg; , m 3 /kmol R = /M = specific gas constant, kJ/(kg K) M = molecular weight of gas, kg/kmol molar basis mass basis (3-10) PV mRT or Pv RT = = u R u R v lesson 9 III. Properties of a Pure Substance 2. Notes on use of ideal-gas equation of state a. The temperature, T, must be absolute (Kelvin or Rankine) b. The pressure, p, must be absolute c. The universal gas constant, , is different from the specific gas constant, R. Use the most convenient units. R, kPa•m 3 /kg•K , kPa•m 3 /kmol•K Substance or kJ/kg•K or kJ/kmol•K Air 0.287 8.314 Helium 2.077 8.314 Hydrogen 4.124 8.314 Carbon dioxide 0.189 8.314 u R u R

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