Problem 4.21[Difficulty: 3]Given:Data on flow into and out of tankFind:Time at which exit pump is switched on; time at which drain is opened; flow rate into drainSolution:Basic equationtMCV∂∂CSρV→⋅A→⋅()∑+0=Assumptions: 1) Uniform flow 2) Incompressible flowAfter inlet pump is ontMCV∂∂CSρV→⋅A→⋅∑+tMtank∂∂ρVin⋅Ain⋅−=0=tMtank∂∂ρAtank⋅dhdt⋅=ρVin⋅Ain⋅=dhdtVinAinAtank⋅=VinDinDtank⎛⎜⎝⎞⎠2⋅=where h is the level of water in the tankHence the time to reach hexit= 0.7 m istexithexitdhdt=hexitVinDtankDin⎛⎜⎝⎞⎠2⋅=texit0.7 m⋅15×sm⋅3m⋅0.1 m⋅⎛⎝⎞⎠2×=texit126 s=After exit pump is ontMCV∂∂CSρV→⋅A→⋅∑+tMtank∂∂ρVin⋅Ain⋅−ρVexit⋅Aexit⋅+=0=Atankdhdt⋅VinAin⋅VexitAexit⋅−=dhdtVinAinAtank⋅VexitAexitAtank⋅−=VinDinDtank⎛⎜⎝⎞⎠2⋅VexitDexitDtank⎛⎜⎝⎞⎠2⋅−=Hence the time to reach h
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This note was uploaded on 10/19/2011 for the course EGN 3353C taught by Professor Lear during the Fall '07 term at University of Florida.