def _TwoPhase_Forward(self,w_2phase):
DWS=DWSVals() #DryWetSegment structure
# Store temporary values to be passed to DryWetSegment
DWS.Fins=self.Fins
DWS.FinsType = self.FinsType
DWS.A_a=self.Fins.A_a*w_2phase
DWS.cp_da=self.Fins.cp_da
DWS.eta_a=self.Fins.eta_a
DWS.h_a=self.Fins.h_a #Heat transfer coefficient, not enthalpy
DWS.mdot_da=self.mdot_da*w_2phase
DWS.pin_a=self.Fins.Air.p
DWS.Tdew_r=self.Tdew_r
DWS.Tbubble_r=self.Tbubble_r
DWS.Tin_a=self.Tin_a
DWS.RHin_a=self.Fins.Air.RH
DWS.Tin_r=self.Tsat_r
DWS.A_r=self.A_r_wetted*w_2phase
DWS.cp_r=1.0e15 #In the two-phase region the cp is infinite, use 1e15 as a big number;
DWS.pin_r=self.psat_r
DWS.mdot_r=self.mdot_r
DWS.IsTwoPhase=True
#Target heat transfer to go from inlet quality to saturated vapor
Q_target=self.mdot_r*(self.xout_2phase-self.xin_r)*self.h_fg
if Q_target<0:
raise ValueError('Q_target in Evaporator must be positive')
# Average Refrigerant heat transfer coefficient
DWS.h_r=ShahEvaporation_Average(self.xin_r,self.xout_2phase,self.Ref,self.G_r,self.ID,self.psat_r,Q_target/DWS.A_r,self.Tbubble_r,self.Tdew_r)
#Run the DryWetSegment to carry out the heat and mass transfer analysis
DryWetSegment(DWS)
self.Q_2phase=DWS.Q
self.Q_sensible_2phase=DWS.Q_sensible
self.h_r_2phase=DWS.h_r
self.fdry_2phase=DWS.f_dry
self.Tout_a_2phase=DWS.Tout_a
rho_average=TwoPhaseDensity(self.Ref,self.xin_r,self.xout_2phase,self.Tdew_r,self.Tbubble_r,slipModel='Zivi')
self.Charge_2phase = rho_average * w_2phase * self.V_r
#Frictional pressure drop component
DP_frict=LMPressureGradientAvg(self.xin_r,self.xout_2phase,self.Ref,self.G_r,self.ID,self.Tbubble_r,self.Tdew_r)*self.Lcircuit*w_2phase
#Accelerational pressure drop component
DP_accel=AccelPressureDrop(self.xin_r,self.xout_2phase,self.Ref,self.G_r,self.Tbubble_r,self.Tdew_r)*self.Lcircuit*w_2phase
self.DP_r_2phase=DP_frict+DP_accel;
if self.Verbosity>7:
print w_2phase,DWS.Q,Q_target,self.xin_r,"w_2phase,DWS.Q,Q_target,self.xin_r"
return DWS.Q-Q_target
def _TwoPhaseH_OnePhaseC_Qimposed(self,Inputs):
"""
Hot stream is condensing, cold stream is single phase
"""
h_h_2phase=LongoCondensation((Inputs['xout_h']+Inputs['xin_h'])/2,self.mdot_h/self.A_h_flow,self.Dh_h,self.Ref_h,self.Tbubble_h,self.Tdew_h);
h_c,cp_c,PlateOutput_c=self.PlateHTDP(self.Ref_c, Inputs['Tmean_c'], Inputs['pin_c'],self.mdot_c/self.NgapsCold)
#Use cp calculated from delta h/delta T
cp_c=Inputs['cp_c']
UA_total=1/(1/(h_c*self.A_c_wetted)+1/(h_h_2phase*self.A_h_wetted)+self.PlateThickness/(self.PlateConductivity*(self.A_c_wetted+self.A_h_wetted)/2.))
C_c=cp_c*self.mdot_c
Q=Inputs['Q']
Qmax=C_c*(Inputs['Tsat_h']-Inputs['Tin_c'])
epsilon=Q/Qmax
#Cr = 0, so NTU is simply
try:
NTU=-log(1-epsilon)
except:
pass
UA_req=NTU*C_c
w=UA_req/UA_total
rho_c=Props('D','T',Inputs['Tmean_c'], 'P', self.pin_c, self.Ref_c)
Charge_c = w * self.V_c * rho_c
rho_h=TwoPhaseDensity(self.Ref_h,Inputs['xout_h'],Inputs['xin_h'],self.Tdew_h,self.Tbubble_h,slipModel='Zivi')
Charge_h = w * self.V_h * rho_h
#Use Lockhart Martinelli to calculate the pressure drop. Claesson found good agreement using C parameter of 4.67
DP_frict_h=LMPressureGradientAvg(Inputs['xin_h'],Inputs['xout_h'],self.Ref_h,self.mdot_h/self.A_h_flow,self.Dh_h,self.Tbubble_h,self.Tdew_h,C=4.67)*w*self.Lp
#Accelerational pressure drop component
DP_accel_h=-AccelPressureDrop(Inputs['xin_h'],Inputs['xout_h'],self.Ref_h,self.mdot_h/self.A_h_flow,self.Tbubble_h,self.Tdew_h)
#Pack outputs
Outputs={
'w': w,
'Tout_c': Inputs['Tin_c']-Q/(self.mdot_c*cp_c),
'DP_c': -PlateOutput_c['DELTAP'],
'DP_h': DP_frict_h+DP_frict_h,
'Charge_c':Charge_c,
'Charge_h':Charge_h,
'h_h':h_h_2phase,
'h_c':h_c,
}
return dict(Inputs.items()+Outputs.items())
def _TwoPhase_Forward(self, w_2phase=1.0, xout_2phase=1.0):
# Update outlet quality field [-]
self.xout_2phase = xout_2phase
# Heat transfer rate based on inlet quality [W]
self.Q_2phase = self.mdot_r * (self.xout_2phase -
self.xin_r) * self.h_fg
# Heat flux in 2phase section (for Shah correlation) [W/m^2]
q_flux = self.Q_2phase / (w_2phase * self.A_r_wetted)
#
self.h_r_2phase = ShahEvaporation_Average(self.xin_r, 1.0, self.Ref_r,
self.G_r, self.Dh_r,
self.pin_r, q_flux,
self.Tbubble_r, self.Tdew_r)
UA_2phase = w_2phase / (1 / (self.h_g * self.A_g_wetted) + 1 /
(self.h_r_2phase * self.A_r_wetted) + self.Rw)
C_g = self.cp_g * self.mdot_g
Ntu_2phase = UA_2phase / (C_g)
#for Cr=0 and counter flow in two-phase:
epsilon_2phase = 1 - exp(-Ntu_2phase)
Q_2phase_eNTU = epsilon_2phase * C_g * (self.T_g_x - self.Tsat_r)
rho_average = TwoPhaseDensity(self.Ref_r,
self.xin_r,
xout_2phase,
self.Tdew_r,
self.Tbubble_r,
slipModel='Zivi')
self.Charge_r_2phase = rho_average * w_2phase * self.V_r
# Frictional prssure drop component
DP_frict = LMPressureGradientAvg(self.xin_r, xout_2phase, self.Ref_r,
self.G_r, self.Dh_r, self.Tbubble_r,
self.Tdew_r) * w_2phase * self.L
# Accelerational prssure drop component
DP_accel = AccelPressureDrop(self.xin_r, xout_2phase, self.Ref_r,
self.G_r, self.Tbubble_r,
self.Tdew_r) * w_2phase * self.L
self.DP_r_2phase = DP_frict + DP_accel
if self.Verbosity > 4:
print Q_2phase_eNTU - self.Q_2phase
return Q_2phase_eNTU - self.Q_2phase
def _TwoPhase_Forward(self, xout_r_2phase=0.0):
"""
xout_r_2phase: quality of refrigerant at end of two-phase portion
default value is 0.0 (full two phase region)
"""
## Bubble and dew temperatures (same for fluids without glide)
Tbubble = self.Tbubble
Tdew = self.Tdew
## Mean temperature for use in HT relationships
Tsat_r = (Tbubble + Tdew) / 2
h_fg = (PropsSI('H', 'T', Tdew, 'Q', 1, self.Ref) -
PropsSI('H', 'T', Tbubble, 'Q', 0, self.Ref)) #*1000 #J/kg
# This block calculates the average refrigerant heat transfer coefficient by
# integrating the local heat transfer coefficient between
# a quality of 1.0 and the outlet quality
self.h_r_2phase = ShahCondensation_Average(xout_r_2phase, 1.0,
self.Ref, self.G_r, self.ID,
self.psat_r, Tbubble, Tdew)
UA_overall = 1 / (1 /
(self.Fins.eta_a * self.Fins.h_a * self.Fins.A_a) +
1 / (self.h_r_2phase * self.A_r_wetted))
self.epsilon_2phase = 1 - exp(-UA_overall /
(self.mdot_da * self.Fins.cp_da))
self.w_2phase = -self.mdot_r * h_fg * (1.0 - xout_r_2phase) / (
self.mdot_da * self.Fins.cp_da *
(self.Tin_a - Tsat_r) * self.epsilon_2phase)
#Positive Q is heat input to the refrigerant, negative Q is heat output from refrigerant.
#Heat is removed here from the refrigerant since it is condensing
self.Q_2phase = self.epsilon_2phase * self.Fins.cp_da * self.mdot_da * self.w_2phase * (
self.Tin_a - Tsat_r)
self.xout_2phase = xout_r_2phase
# Frictional pressure drop component
DP_frict = LMPressureGradientAvg(self.xout_2phase, 1.0, self.Ref,
self.G_r, self.ID, Tbubble,
Tdew) * self.Lcircuit * self.w_2phase
#Accelerational pressure drop component
DP_accel = -AccelPressureDrop(self.xout_2phase, 1.0, self.Ref,
self.G_r, Tbubble,
Tdew) * self.Lcircuit * self.w_2phase
# Total pressure drop is the sum of accelerational and frictional components (neglecting gravitational effects)
self.DP_r_2phase = DP_frict + DP_accel
rho_average = TwoPhaseDensity(self.Ref,
self.xout_2phase,
1.0,
self.Tdew,
self.Tbubble,
slipModel='Zivi')
self.Charge_2phase = rho_average * self.w_2phase * self.V_r
if self.Verbosity > 7:
print '2phase cond resid', self.w_2phase - (1 - self.w_superheat)
print 'h_r_2phase', self.h_r_2phase
#Calculate an effective pseudo-subcooling based on the equality
# cp*DT_sc=-dx*h_fg
cp_satL = PropsSI('C', 'T', self.Tbubble, 'Q', 0.0, self.Ref) #*1000
self.DT_sc_2phase = -self.xout_2phase * h_fg / (cp_satL)
#If the quality is being solved for, the length of the two-phase and subcooled
# sections should add to the length of the HX. Return the residual
return self.w_2phase - (1 - self.w_superheat)
def _OnePhaseH_TwoPhaseC_Qimposed(self,Inputs):
"""
The hot stream is all single phase, and the cold stream is evaporating
"""
#Calculate the mean temperature for the single-phase fluid
h_h,cp_h,PlateOutput_h=self.PlateHTDP(self.Ref_h, Inputs['Tmean_h'], Inputs['pin_h'],self.mdot_h/self.NgapsHot)
#Use cp calculated from delta h/delta T
cp_h=Inputs['cp_h']
#Mole mass of refrigerant for Cooper correlation
M=Props('M','T',0,'P',0,self.Ref_c)
#Reduced pressure for Cooper Correlation
pstar=Inputs['pin_c']/Props('E','T',0,'P',0,self.Ref_c)
change=999
w=1
Q=Inputs['Q']
"""
The Cooper Pool boiling relationship is a function of the heat flux,
therefore the heat flux must be iteratively determined
"""
while abs(change)>1e-6:
q_flux=Q/(w*self.A_c_wetted)
#Heat transfer coefficient from Cooper Pool Boiling
h_c_2phase=Cooper_PoolBoiling(pstar,1.0,q_flux,M) #1.5 correction factor comes from Claesson Thesis on plate HX
G=self.mdot_c/self.A_c_flow
Dh=self.Dh_c
x=(Inputs['xin_c']+Inputs['xout_c'])/2
UA_total=1/(1/(h_h*self.A_h_wetted)+1/(h_c_2phase*self.A_c_wetted)+self.PlateThickness/(self.PlateConductivity*self.A_c_wetted))
C_h=cp_h*self.mdot_h
Qmax=C_h*(Inputs['Tin_h']-Inputs['Tsat_c'])
epsilon=Q/Qmax
if epsilon>=1.0:
epsilon=1.0-1e-12
NTU=-log(1-epsilon)
UA_req=NTU*C_h
change=UA_req/UA_total-w
w=UA_req/UA_total
#Refrigerant charge
rho_h=Props('D','T',Inputs['Tmean_h'], 'P', self.pin_h, self.Ref_h)
Charge_h = w * self.V_h * rho_h
rho_c=TwoPhaseDensity(self.Ref_c,Inputs['xin_c'],Inputs['xout_c'],self.Tdew_c,self.Tbubble_c,slipModel='Zivi')
Charge_c = rho_c * w * self.V_c
#Use Lockhart Martinelli to calculate the pressure drop. Claesson found good agreement using C parameter of 4.67
DP_frict_c=LMPressureGradientAvg(Inputs['xin_c'],Inputs['xout_c'],self.Ref_c,self.mdot_c/self.A_c_flow,self.Dh_c,self.Tbubble_c,self.Tdew_c,C=4.67)*w*self.Lp
#Accelerational pressure drop component
DP_accel_c=AccelPressureDrop(Inputs['xin_c'],Inputs['xout_c'],self.Ref_c,self.mdot_c/self.A_c_flow,self.Tbubble_c,self.Tdew_c)
#Pack outputs
Outputs={
'w':w,
'Tout_h': Inputs['Tin_h']-Q/(self.mdot_h*cp_h),
'Charge_c': Charge_c,
'Charge_h': Charge_h,
'DP_h': -PlateOutput_h['DELTAP'],
'DP_c': DP_frict_c+DP_accel_c,
'h_h':h_h,
'h_c':h_c_2phase,
'q_flux':q_flux
}
return dict(Inputs.items()+Outputs.items())