from __future__ import division, print_function,absolute_import
import CoolProp as CP
from CoolProp.CoolProp import PropsSI
from .Correlations import f_h_1phase_Tube,TrhoPhase_ph
from math import log,pi,exp
[docs]class LineSetClass():
def __init__(self,**kwargs):
#Load the parameters passed in
# using the dictionary
self.__dict__.update(kwargs)
[docs] def Update(self,**kwargs):
#Load the parameters passed in
# using the dictionary
self.__dict__.update(kwargs)
[docs] def OutputList(self):
"""
Return a list of parameters for this component for further output
It is a list of tuples, and each tuple is formed of items:
[0] Description of value
[1] Units of value
[2] The value itself
"""
return [
('Length of tube','m',self.L),
('Supply line OD','m',self.OD),
('Supply line ID','m',self.ID),
('Tube Conductivity','W/m-K',self.k_tube),
('Insulation thickness','m',self.t_insul),
('Insulation conductivity','W/m-K',self.k_insul),
('Air overall HTC','W/m^2-K',self.h_air),
('Air Temperature','K',self.T_air),
('Q Total','W',self.Q),
('Pressure drop ','Pa',self.DP),
('Reynolds # Fluid','-',self.Re_fluid),
('Mean HTC Fluid','W/m^2-K',self.h_fluid),
('Charge','kg',self.Charge),
('Inlet Temperature','K',self.Tin),
('Outlet Temperature','K',self.Tout)
]
[docs] def Calculate(self):
#AbstractState
if hasattr(self,'Backend'): #check if backend is given
AS = CP.AbstractState(self.Backend, self.Ref)
if hasattr(self,'MassFrac'):
AS.set_mass_fractions([self.MassFrac])
else: #otherwise, use the defualt backend
AS = CP.AbstractState('HEOS', self.Ref)
self.AS = AS
if not 'IncompressibleBackend' in AS.backend_name():
#Figure out the inlet state
AS.update(CP.PQ_INPUTS, self.pin, 0.0)
self.Tbubble=AS.T() #[K]
AS.update(CP.PQ_INPUTS, self.pin, 1.0)
self.Tdew=AS.T() #[K]
else:
#It is a brine
self.Tbubble = None
self.Tdew = None
self.Tin,self.rhoin,self.Phasein=TrhoPhase_ph(self.AS,self.pin,self.hin,self.Tbubble,self.Tdew)
###Solver shows TwoPhase in the first iteration, the following if statement just to avoid ValueError with CoolProp for pseudo-pure refrigerants
if self.Phasein =='TwoPhase':
self.f_fluid, self.h_fluid, self.Re_fluid=f_h_1phase_Tube(self.mdot, self.ID, self.Tin-1, self.pin, self.AS)
AS.update(CP.PT_INPUTS, self.pin, self.Tin-1)
# Specific heat capacity [J/kg-K]
cp=AS.cpmass()
# Density [kg/m^3]
rho=AS.rhomass()
else: #Single phase
self.f_fluid, self.h_fluid, self.Re_fluid=f_h_1phase_Tube(self.mdot, self.ID, self.Tin, self.pin, self.AS)
AS.update(CP.PT_INPUTS, self.pin, self.Tin)
# Specific heat capacity [J/kg-K]
cp=AS.cpmass()
# Density [kg/m^3]
rho=AS.rhomass()
#Thermal resistance of tube
R_tube=log(self.OD/self.ID)/(2*pi*self.L*self.k_tube)
#Thermal resistance of insulation
R_insul=log((self.OD+2.0*self.t_insul)/self.OD)/(2*pi*self.L*self.k_insul);
#Convective UA for inside the tube
UA_i=pi*self.ID*self.L*self.h_fluid;
#Convective UA for the air-side
UA_o=pi*(self.OD+2*self.t_insul)*self.L*self.h_air;
#Avoid the possibility of division by zero if h_air is zero
if UA_o<1e-12:
UA_o=1e-12
#Overall UA value
UA=1/(1/UA_i+R_tube+R_insul+1/UA_o)
#Outlet fluid temperature [K]
self.Tout=self.T_air-exp(-UA/(self.mdot*cp))*(self.T_air-self.Tin)
#Overall heat transfer rate [W]
self.Q=self.mdot*cp*(self.Tout-self.Tin)
self.hout=self.hin+self.Q/self.mdot
#Pressure drop calculations for single phase refrigerant
v=1./rho
G=self.mdot/(pi*self.ID**2/4.0)
#Pressure gradient using Darcy friction factor
dpdz=-self.f_fluid*v*G**2/(2.*self.ID) #Pressure gradient
self.DP=dpdz*self.L
#Charge in Line set [kg]
self.Charge=pi*self.ID**2/4.0*self.L*rho
if __name__=='__main__':
kwargs={
'L':7.6,
'k_tube':0.19,
't_insul':0.02,
'k_insul':0.036,
'T_air':297,
'Ref': 'R410A',
'Backend': 'HEOS', #choose between: 'HEOS','TTSE&HEOS','BICUBIC&HEOS','REFPROP','SRK','PR'
'h_air':0.0000000001,
'pin': 500000, #Pressure of the fluid at the inlet i.e 500kPa
'hin': PropsSI('H','P',500000,'T',PropsSI('T','P',500000,'Q',0,'R410A')-10,'R410A'), #Enthalpy of the fluid at the inlet i.e subcooled 10K below bubble
'mdot': 0.03 #fluid mass flow rate
}
LineSetSupply = LineSetClass(**kwargs)
LineSetSupply.OD=0.009525
LineSetSupply.ID=0.007986
LineSetSupply.Calculate()
LineSetReturn = LineSetClass(**kwargs)
LineSetReturn.OD=0.01905
LineSetReturn.ID=0.017526
LineSetReturn.Calculate()
print(LineSetSupply.OutputList())
print(LineSetReturn.OutputList())