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 Advanced Thermodynamics Advanced Thermodynamics Physics Help Forum Jul 9th 2013, 09:51 AM #1 Junior Member   Join Date: Jul 2013 Posts: 1 heat exchanger exergy analysis i am having a problem with heat exchanger (tube and fin) exergy analysis... the problem which i am having looks like this: in one of the cases air (mass flow of air: m,a=0,71 kg/s) is entering the heat exchanger with temperature T,aIN=21C and relative humidity RH,aIN=57%, air is cooled to the state where it has temperature T,aOUT=19C and RH,aOUT=64%. Water entering the heat exchanger has T,wIN=7C and on the outlet T,wOUT=14,91C, mass flow of water is 0,043 kg/s. for exergy calculation: air inlet entalpy and entropy h,aIN=43,55 kJ/kg and s,aIN=0,1552 kJ/kgK. Air inlet conditions are the same as dead end state conditions. Air outlet enthalpy and entropy are h,aOUT=41,50 kJ/kg and s,aOUT=0,1487 kJ/kgK. water enthalpy and entropy: h,wIN=29,52 kJ/kg; s,wIN=0,1064 kJ/kgK; h,wOUT=62,68 kJ/kgK;s,wOUT=0,2231 kJ/kgK. Water enthalpy and entropy at dead end state (21C): h,w0=88,18 kJ/kg and s,w0=0,3107 kJ/kgK. calculated exergies, air: ex,aIN=0 kj/kg;(ex,aIN*m,a): Ex,aIN=0 kW, ex,aOUT=0,1330 kJ/kg, Ex,aOUT=0,0944 kW calculated exergies, water: ex,wIN=1,4348 kJ/kg, Ex,wIN=0,0627, ex,wOUT=0,2675 kJ/kg, Ex,wOUT=0,0117 kW if i calculate second law efficiency ( outlet exergies/inlet exergies), i get efficiency: 1,69 !? i do not know where could be a mistake... enthalpy and entropy values seems to be correct... any ideas? Thanks a lot!  Tags analysis, exchanger, exergy, heat Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post Yara Advanced Thermodynamics 1 Jun 10th 2016 04:32 AM MStudent Thermodynamics and Fluid Mechanics 0 Apr 25th 2015 07:10 AM phobo Advanced Thermodynamics 0 Oct 24th 2014 11:50 AM andrew0437 Advanced Thermodynamics 0 Dec 10th 2013 05:34 PM Cute Thermodynamics and Fluid Mechanics 0 Dec 5th 2008 09:41 PM