Single Phase system (Ideal Gas)

Single Phase system (Ideal Gas) - Liquid and solid Single...

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Unformatted text preview: Liquid and solid Single Phase System Mixture of solid can determined by its mass fraction XA = mass of A ------------total mass of components(A+B + C +….) Density of liquid mixtures:n i=1 n i=1 ( 1/ ρ =Σ xi/ ρ ) or ( ρ = Σ xi ρi ) 1/ or xi Gases Example: What is the density of a mixture containing What 20 wt% A (ρA = 1 g/cm3) and the balance B 20 and (ρB = 2 g/cm3)? Equation of State relates amount (moles), volume, T , P. Many different Equation of State – represents behaviour of real systems Ideal Gas Law - Simplest Equation of State - Most widely used. Ideal gases Ideal or ‘perfect’, means referred STP (standard, temperature and pressure), where:V = 22.415 liters T = 0° C P = 1 atm Ideal gases Equation of State: PV = nRT Assumption: - No interaction between molecules - Molecules has zero volume (no forces exerted on one another), thus will follow the volume of container Valid at low density - Best at high or low pressure? - Best at high or low temperature? 1 Remember!! Ideal Gas Constant The Gas Constant 8.314 m3 Pa/ (mol.K) Gas Constant (usually used in Energy Eqn.) PV = n RT P = absolute pressure of a gas V = volume/ volumetric flow rate of the gas n = number of moles or molar flow rate of the gas R = gas constant T = absolute temperature 0.08314 L. bar/ (mol.K) 0.08206 L. atm/ (mol.K) 62.36 L. mm Hg/ (mol.K) 0.7302 ft3. atm/ (lb-mole. °R) 8.314 J/ (mol.K) 1.987 cal/ (mol.K) 1.9887 Btu/ (lb-mole. °R) 10.73 ft3. psia/ (lb-mole. °R Ideal gas law……. Always use as reference state to predict the condition of gases. Normally in real life seldom gases obey the ideal condition. Application example Suppose the tires on your car are inflated to 32 psig at 25 °C. What is the pressure at -10 °C? Assume that you are at sea level. Standard Conditions Standard Provide a reference point for reporting gas flows Convenient for use in calculations with ideal gas law SI Ts = 0 °C = 273 K Ps =1 atm Vs = 0.022415 ns = 1 gmol m3 (22.415 L) American Engineering Ts = 492 °R (i.e. 32 °F) Ps = 1 atm, ns = 1 lb-mole Society of Petroleum Engineers (common industrial standard) Ts = 60 °F Ps = 14.7 psia Vs = 359 ft3 Gas Flows under Standard Gas Conditions Conditions SCM : Standard cubic meter (m3 STP) SCM SCF : Standard cubic feet (ft3 STP) SCF SCFM : Standard cubic feet per minute (ft3 / min SCFM min STP) STP) SCMH : Standard cubic meters per hour (m3 / hr SCMH hr STP) STP) SCFH : Standard cubic feet per hour (ft3 / hr SCFH hr STP) STP) SCCM : Standard cubic centimeters per minute SCCM Standard (cm3 /min STP) (cm SLPM : Standard liters per minute (lit /min STP) SLPM 2 Standard Condition Equation PV = n RT Gas Mixtures Partial pressure of component A (1 component) pA = yA Ptotal The equation almost similar to ideal gas law but it is used when we have different states(condition ) of gases or unchanged no. of moles PV = PsVs nT ns Ts Dalton’s law total P = sum pf partial pressures Example: At sea level, what is the partial pressure of O2 ? pA = yA Ptotal = 0.21 x 1.0 atm = 0.21 atm Good for both ideal gas and non-ideal gas!! Ideal Gas Mixtures Amagat’s Law - Partial volumes add up to total volume vA + vB + ….. = Vtotal .. Volume fraction = mole fraction Volume i.e : percent by volume = mole percent percent vA = yA Vtotal 3 ...
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