Lecture_09022009_Compatibility_Mode_

Lecture_09022009_Compatibility_Mode_ - ENGR 301 ENGR 301...

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Unformatted text preview: ENGR 301 ENGR 301 Thermodynamics 9/02/2009 Madison 201 MW 12:00 – 1:15 PM ENGR 301 N.m or J or kg.m2.s-2 Energy ft.lbf Total energy in a system E = macroscopic kinetic energy + potential energy + internal energy flow energy energy electrical energy ENGR 301 microscopic On a unit mass basis (U) u = U/m ENGR 301 (kJ/kg) A closed system whose KE and PE remain constant. Pressure of a flowing fluid is associated with a form of mechanical energy. Flow work/mass = P/ρ Energy content of a flowing fluid/mass flow = e = P/ρ + v2/2 + g Z ENGR 301 emech = P/ρ + v2/2 + g Z Energy associated with flowing fluid ENGR 301 E=me Known: velocity v = 3 m/s volumetric flow rate = 500 m3/s elevation = Z = 90 m To be determined: total mechanical energy/mass in river water power generation potential of river Governing equations: useful mechanical energy of river water = e = v2/2 + g Z power potential = m e assuming zero velocity at lake Density of water = 1000 kg/m3 Solution: e = 4.5 (m/s)2 + (9.81 m/s2)(90 m) = 887.4 m2/s2 or J/kg = 0.887 kJ/kg mass flow rate = (500 m3/s)(1000 kg/m3) = 500,000 kg/s Power generation potential = (0.887 kJ/kg)(500,000 kg/s) = 443,700 kJ/s generation potential (0 kJ/kg)(500 kg/s) 443 kJ/s ENGR 301 = 443.7 MW ENGR 301 Work is energy transfer across boundaries of a closed system that is not heat. Work and heat are energy transfer mechanisms between a system and surroundings across real boundaries. Power = work/time J/s or W, ft lbf/s, hP ENGR 301 ENGR 301 Electric work We = V N Shaft work Wsh = 2 π n T V2 Work for moving a boundary ∫ P dV V1 Work in raising a body Work in accelerating a body ENGR 301 kg m3 m.s 2 kg.m 2 or s2 or J ENGR 301 Known weight of suitcase = m = 30 kg change in elevation = ΔZ = 35 m Desired energy stored in suitcase stored in suitcase Equation W = work done on suitcase = m g ΔZ ΔE = W Solution = (30 kg)(9.81 m/s2)(35 m) = 10300.5 kg.m2/s2 or J = 10.3 kJ ENGR 301 That’s it for today. ENGR 301 • Read chapter 2, sections 2.6 – 2.8, before chapter sections before next lecture. ENGR 301 ...
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This note was uploaded on 11/25/2009 for the course ENGR thermo taught by Professor Staff during the Spring '09 term at University of Louisiana at Lafayette.

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