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.s2 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 ...
View
Full
Document
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.
 Spring '09
 Staff
 Dynamics

Click to edit the document details