Changeset 386 for trunk/eml


Ignore:
Timestamp:
Oct 10, 2007, 5:45:23 PM (15 years ago)
Author:
gerson bicca
Message:

updated PHE model

Location:
trunk/eml/heat_exchangers
Files:
2 edited

Legend:

Unmodified
Added
Removed
  • trunk/eml/heat_exchangers/HEX_Engine.mso

    r384 r386  
    449449end
    450450
    451 Model Thermal_PHE as LMTD_Basic
     451Model Thermal_PHE
    452452
    453453ATTRIBUTES
  • trunk/eml/heat_exchangers/PHE.mso

    r384 r386  
    5454
    5555== Setting The PHE Option Parameters ==
    56 *Method: NTU or LMTD
    5756*SideOne: cold or hot
    5857
     
    7271outer NComp             as Integer      (Brief="Number of Chemical Components");
    7372        Pi                              as constant     (Brief="Pi Number",Default=3.14159265, Symbol = "\pi");
    74         Kp1(15)                 as constant     (Brief="First constant in Kumar calculation for Pressure Drop");
    75         Kp2(15)                 as constant     (Brief="Second constant in Kumar calculation for Pressure Drop");
    76         Kc1(14)                 as constant     (Brief="First constant in Kumar calculation for Heat Transfer");
    77         Kc2(14)                 as constant     (Brief="Second constant Kumar calculation for Heat Transfer");
     73        N1                      as Integer      (Brief="Auxiliar Constant");
     74        N2                      as Integer      (Brief="Auxiliar Constant");
     75        Kp1(N1)                 as constant     (Brief="First constant in Kumar calculation for Pressure Drop");
     76        Kp2(N1)                 as constant     (Brief="Second constant in Kumar calculation for Pressure Drop");
     77        Kc1(N2)                 as constant     (Brief="First constant in Kumar calculation for Heat Transfer");
     78        Kc2(N2)                 as constant     (Brief="Second constant Kumar calculation for Heat Transfer");
    7879        M(NComp)                as molweight    (Brief="Component Mol Weight");
    7980       
    8081        ChevronAngle    as Switcher             (Brief="Chevron Corrugation Inclination Angle in Degrees ",Valid=["30 Deg","45 Deg","50 Deg","60 Deg","65 Deg"],Default="30 Deg");
    81         Method                  as Switcher             (Brief="Method of Thermal Calculation",Valid=["NTU","LMTD"],Default="NTU");
    8282        SideOne                 as Switcher             (Brief="Fluid Alocation in the Side I - (The odd channels)",Valid=["hot","cold"],Default="hot");
    8383        Nchannels               as Integer              (Brief="Total Number of Channels in The Whole Heat Exchanger");
     
    115115
    116116 SET
     117#"Vector Length of constants for Kumar's calculating Pressure Drop"
     118        N1 = 15;
     119
     120#"Vector Length of constants for Kumar's calculating Heat Transfer"
     121        N2 = 14;
    117122
    118123#"First constant for Kumar's calculating Pressure Drop"
     
    147152
    148153#"Ports Area"
    149         Aports=Pi*Dports*Dports/4;
     154        Aports=0.25*Pi*Dports*Dports;
    150155       
    151156#"Channel Area"
     
    659664        Thermal.Ud*(1/HotSide.HeatTransfer.hcoeff +pt/Kwall+1/ColdSide.HeatTransfer.hcoeff + Rfc + Rfh)=1;
    660665
    661  switch Method
    662        
    663         case "LMTD":
    664        
    665 "Duty"
    666         Thermal.Q = Thermal.Ud*Atotal*Thermal.LMTD*Thermal.Fc;
    667        
    668         case "NTU":
    669 
    670 "Duty"
     666 "Duty"
    671667        Thermal.Q = Thermal.Eft*Thermal.Cmin*(InletHot.T-InletCold.T);
    672668
    673  end
    674 
    675 "Temperature Difference at Inlet - Counter Flow"
    676         Thermal.DT0 = InletHot.T - OutletCold.T;
    677 
    678 "Temperature Difference at Outlet - Counter Flow"
    679         Thermal.DTL = OutletHot.T - InletCold.T;
    680 
    681 "Heat Capacity Ratio"
     669 "Heat Capacity Ratio"
    682670        Thermal.Cr =Thermal.Cmin/Thermal.Cmax;
    683671
     
    703691        ColdSide.HeatTransfer.NTU*ColdSide.HeatTransfer.WCp = Thermal.Ud*Atotal;
    704692
    705  if Thermal.Cr equal 1 # To be Fixed: Effectiveness in true counter flow !
     693if Thermal.Cr equal 1 # To be Fixed: Effectiveness in true counter flow !
    706694       
    707695        then
    708696"Effectiveness in Counter Flow"
    709         Thermal.Eft = Thermal.NTU/(1+Thermal.NTU);
    710        
    711 "LMTD Correction Factor"
    712         Thermal.Fc =Thermal.Eft/(1.0001-Thermal.Eft)/Thermal.NTU;
     697        Thermal.Eft*(1+Thermal.NTU) = Thermal.NTU;
    713698       
    714699        else
    715700"Effectiveness in Counter Flow"
    716         Thermal.Eft = (1-exp(-Thermal.NTU*(1-Thermal.Cr)))/(1-Thermal.Cr*exp(-Thermal.NTU*(1-Thermal.Cr)));
    717 
    718 "LMTD Correction Factor"
    719         Thermal.Fc =(ln(abs(1-Thermal.Eft*Thermal.Cr))-ln(abs(1-Thermal.Eft)))/(Thermal.NTU*(1-Thermal.Cr));
    720        
    721  end
     701        Thermal.NTU = (1/(Thermal.Cr-1))*ln(abs((Thermal.Eft-1)/(Thermal.Cr*Thermal.Eft-1)));
    722702
    723703end
     704
     705end
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