Changeset 120 for trunk/eml

Timestamp:

Jan 17, 2007, 6:11:19 PM (16 years ago)

Author:

gerson bicca

Message:

updated Mheatex model

File:

• trunk/eml/heat_exchangers/Mheatex.mso (modified) (2 diffs)

trunk/eml/heat_exchangers/Mheatex.mso

@@ -84 +84 @@
         LMTD    as temp_delta   (Brief="Logarithmic Mean Temperature Difference");
         UA      as positive     (Unit="W/K");
-
+        DT0     as temp_delta   (Brief="Temperature Difference at Inlet",Lower=1);
+        DTL             as temp_delta   (Brief="Temperature Difference at Outlet",Lower=1);
+        
 SET
 
@@ -131 +133 @@
         Q=UA*LMTD;
 
-#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
-#       Flow Direction 
-#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
+        
+if abs(DT0 - DTL) > 0.05*max(abs([DT0,DTL])) 
+        
+        then
+"Log Mean Temperature Difference"
+        LMTD= (DT0-DTL)/ln(DT0/DTL);
+
+        else
+        
+if DT0*DTL equal 0
+        
+        then
+"Log Mean Temperature Difference"
+        LMTD = 0.5*(DT0+DTL);
+        
+        else
+"Log Mean Temperature Difference"
+        LMTD = 0.5*(DT0+DTL)*(1-(DT0-DTL)^2/(DT0*DTL)*(1+(DT0-DTL)^2/(DT0*DTL)/2)/12);
+        
+end
+        
+end     
+
 
 if Side equal 0 
         
         then
-"Cocurrent Flow LMTD"
-        LMTD = HE.CocurrentLMTD(max(Inlet.Hot.T),min(Outlet.Hot.T),min(Inlet.Cold.T),max(Outlet.Cold.T));
+        
+"Temperature Difference at Inlet"
+        DT0 = max(Inlet.Hot.T) - min(Inlet.Cold.T);
+
+"Temperature Difference at Outlet"
+        DTL = min(Outlet.Hot.T) - max(Outlet.Cold.T);
         
         else
-"Counter Flow LMTD"
-        LMTD = HE.CounterLMTD(max(Inlet.Hot.T),min(Outlet.Hot.T),max(Inlet.Cold.T),min(Outlet.Cold.T));
+        
+"Temperature Difference at Inlet"
+        DT0 = max(Inlet.Hot.T) - max(Outlet.Cold.T);
+
+"Temperature Difference at Outlet"
+        DTL = min(Outlet.Hot.T) - min(Inlet.Cold.T);
         
 end