Model codes update

1. update MED empirical equations
2. update cooling water flow rate calculation
3. modify input tables of VAGMD and RO cost models
4. minor improvements

DesalinationModels/ABS.py

@@ -9,10 +9,10 @@
 import numpy as np
 import math
 import DesalinationModels.IAPWS97_thermo_functions as TD_func
-from DesalinationModels.LT_MED_calculation import lt_med_calculation
-from scipy.optimize import fmin
-from DesalinationModels.VAGMD_batch.SW_functions import SW_Density
 # from DesalinationModels.LT_MED_calculation import lt_med_calculation
+from scipy.optimize import fmin
+from DesalinationModels.VAGMD_batch.SW_functions import SW_Density, BPE, SW_Enthalpy
+from iapws import IAPWS97, SeaWater
 
 class ABS(object):
 
@@ -112,31 +112,55 @@ def design(self):
 
 
 
-        self.STEC = 1/self.GOR * (TD_func.enthalpySatVapTW(self.Ts+273.15)-TD_func.enthalpySatLiqTW(self.Ts+273.15))[0] *1000/3600
-        self.P_req = 1/self.GOR * (TD_func.enthalpySatVapTW(self.Ts+273.15)-TD_func.enthalpySatLiqTW(self.Ts+273.15))[0] *self.Capacity *1000/24/3600
+        self.T_d = self.Tin + 10  # Brine temperature at last effect 
+
+        # Calculate cooling water flow rate
+        Q_loss = 0.054 # System thermal loss
 
+            # mass balance
+        q_d = self.Capacity / 24 # Hourly distillate production (m3/hr)
+        self.q_feed = q_d / self.RR # Feed seawater flow rate (m3/hr)
+        q_b = self.q_feed - q_d # Brine flow rate (m3/hr)
+
+        self.s_b = self.Xf /1000/ (1- self.RR) #  brine salinity (g/L)
+
+            # BPE calculation
+        SW_BPE = BPE(self.T_d, self.s_b)
 
+        self.T_b =  self.T_d + SW_BPE # brine temperature
+        self.T_cool = self.T_d - 3 # cooling reject temperature (Assume DHTP = 3)
 
-        self.T_d = self.Tin + 10  
-        self.T_b = self.T_d + 1  
-        self.DTPH = 3
-        self.T_cool = self.T_d - self.DTPH
-        self.h_b = TD_func.enthalpyreg1(self.T_b + 273.15, 1)    # Enthalpy of the flow at brine temperature
-        self.h_sw = TD_func.enthalpyreg1(self.Tin + 273.15, 1)  
-        self.h_d = TD_func.enthalpyreg1(self.T_d + 273.15, 1)
-        self.h_cool = TD_func.enthalpyreg1(self.T_cool + 273.15, 1)
+            # densities
+        rho_b = SW_Density(self.T_b,'c',self.s_b*1000,'ppm',1,'bar')  # brine density
+        rho_d = SW_Density(self.T_d,'c',0,'ppm',1,'bar')  # distillate density
+        rho_sw= SW_Density(self.Tin,'c',self.Xf,'ppm',1,'bar')  # seawater density
+        rho_f = SW_Density(self.T_cool,'c',self.Xf,'ppm',1,'bar')  # cooling reject density
 
-        brine_s = self.Xf / 1000 / (1- self.RR)        
-        self.brine_d = SW_Density(self.T_b,'c',brine_s,'ppt',1,'bar')
-        self.distillate_d = SW_Density(self.T_b,'c',0,'ppm',1,'bar')     
-        self.average_d = self.brine_d * self.RR + self.distillate_d * (1-self.RR)
+            # enthalpies
+        h_d = IAPWS97(T=273.15+ self.T_d,x=0).h 
+        h_b = SW_Enthalpy(self.T_b, self.s_b)/ 1000
+        h_sw = SW_Enthalpy(self.Tin, self.Xf/1000)/ 1000
+        h_cool = SW_Enthalpy(self.T_cool, self.Xf/1000)/ 1000
 
+            # energy consumption
+        self.STEC = 1/self.GOR * (TD_func.enthalpySatVapTW(self.Ts+273.15)-TD_func.enthalpySatLiqTW(self.Ts+273.15))[0] *rho_d/3600
+        self.P_req = self.STEC *self.Capacity /24 
+
+            # mass flow rates
+        self.m_d = q_d * rho_d / 3600 # distillate mass flow rate (kg/s)
+        self.m_b = q_b * rho_b / 3600 # brine mass flow rate (kg/s)
+        self.m_f = self.q_feed * rho_f / 3600 # feed mass flow rate (kg/s)
+        self.m_sw = ((1-Q_loss)*self.P_req - self.m_b * h_b - self.m_d * h_d + h_cool * self.m_f) / (h_cool - h_sw) # intake + cooling water mass flow rate (kg/s)
+
+
+            # volume flow rates
+        self.q_sw = self.m_sw / rho_sw * 3600 # m3/h
+        self.q_cooling = self.q_sw - self.q_feed 
+
+
+        self.PR = 2326 / self.STEC * 1000 /3600       
 
-        # Calculate cooling water flow rate
-        self.q_cooling = (0.85 * self.P_req * 3600 - self.brine_d * self.qF * (1- self.RR) * self.h_b - self.distillate_d * self.qF * self.RR * self.h_d + self.qF * self.average_d * self.h_sw ) / (self.h_cool - self.h_sw)
 
-        self.PR = 2326 / self.STEC * 1000 /3600
-        self.T_b = 37  # Brine temperature at last effect (T_b = T_d = T_cool = T_cond)
         # Add ABS  
         pp1 = self.Tcond
         pp2 = self.Ts
@@ -201,8 +225,8 @@ def design(self):
         self.design_output.append({'Name':'Brine concentration','Value':brine_s,'Unit':'g/L'})
 
         self.design_output.append({'Name':'Feedwater flow rate','Value':self.qF,'Unit':'m3/h'})     
-        # if self.q_cooling[0] > 0:
-            # self.design_output.append({'Name':'Cooling water flow rate','Value':self.q_cooling[0] / 1000,'Unit':'m3/h'})         
+        if self.q_cooling> 0:
+            self.design_output.append({'Name':'Cooling water flow rate','Value':self.q_cooling ,'Unit':'m3/h'})         
         self.design_output.append({'Name':'The mass flow rate of the steam','Value':self.qs,'Unit':'kg/s'})
         self.design_output.append({'Name':'Specific heat transfer area of MED','Value':self.sA,'Unit':'m2/m3/day'})
         self.design_output.append({'Name':'Specific heat transfer area of the absorption heat pump','Value':self.sA_pump,'Unit':'m2/kW'})