homework 02 heatexchangersjjechura/gasprocessing/...what are the relative merits qf the types of the...
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CBEN408Spring2018 ‐1‐ December28,2017
Homework #2
Problems3.1,3.2(withextrabelow),3.3,&extraproblembelow.Extrafor3.2:Whatistherelativedifferenceinheattransferareaifyouusea1‐2heatexchanger(1shellpass,2tubepasses) instead of pure counter current flow?Consider both thewater on shell side in oneinstance&onthetubesideinanotherinstance.Extraproblem:You’dliketocondense5,000lb/hrofpropaneina4‐passaerialcooler.Considerthefollowing:
Youwanttocondensepropaneatasufficientpressuresothatitwillbesaturatedat120°F. Thepropaneenters asa saturatedgas, exitsasa saturated liquid,& there isnopressure
dropthroughtheexchanger. Ambientairis85°F.Consideritsheatcapacityas0.25Btu/lb·°F. Theexchangershouldhaveaminimum10°Fapproachtemperature.
Answerthefollowing:
Whatmassflowrateofairisneeded(inlb/hr)? If theheat transfercoefficient(basedontheextendedarea) is3.5Btu/hr·ft2·°F thenwhat
surfaceareaisneeded(inft2)?
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