def funco(framenum):
t = time.clock()
x = 25 + 10 * np.sin(t)
y = HAProps('W', 'T', x + 273.15, 'P', p, 'R', r1)
z = HAProps('W', 'T', x + 273.15, 'P', p, 'R', r2)
a0.set_data(x, y)
a1.set_data(x, z)
def plot(self, ax):
for H in self.H_values:
#Line goes from saturation to zero humidity ratio for this enthalpy
T1 = HAProps('T', 'H', H, 'P', p, 'R', 1.0) - 273.15
T0 = HAProps('T', 'H', H, 'P', p, 'R', 0.0) - 273.15
w1 = HAProps('W', 'H', H, 'P', p, 'R', 1.0)
w0 = HAProps('W', 'H', H, 'P', p, 'R', 0.0)
ax.plot(numpy.r_[T1, T0], numpy.r_[w1, w0], 'r', lw=1)
def plot(self,ax):
xv = Tdb #[K]
for RH in self.RH_values:
yv = [HAProps('W','T',T,'P',p,'R',RH) for T in Tdb]
y = HAProps('W','P',p,'H',self.h,'R',RH)
T_K,w,rot = InlineLabel(xv, yv, y=y, axis = ax)
string = r'$\phi$='+str(RH*100)+'%'
#Make a temporary label to get its bounding box
bbox_opts = dict(boxstyle='square,pad=0.0',fc='white',ec='None',alpha = 0.5)
ax.text(T_K-273.15,w,string,rotation = rot,ha ='center',va='center',bbox=bbox_opts)
def _lib(self):
args = self.args()
P = self._P()
if "Tdb" in self._mode:
tdb = self.kwargs["Tdb"]
else:
tdb = HAProps("Tdb", *args)
tdp = HAProps("Tdp", *args)
twb = HAProps("Twb", *args)
w = HAProps("W", *args)
HR = HAProps("RH", *args)*100
Pvs = HAProps_Aux("p_ws", tdb, self._P_kPa, w)[0]*1000
Pv = Pvs*HR/100
ws = HAProps("W", "P", self._P_kPa, "Tdb", tdb, "RH", 1)
v = HAProps("V", *args)
h = HAProps("H", *args)
return tdp, tdb, twb, P, Pvs, Pv, ws, w, HR, v, h
def funco(framenum,ser,fil):
global t,a,b,x,y,tt,xx,yy
print framenum,
t = time.clock()
try:
(datime, status, relhum, temp) = serialLoop(ser,fil)
#x = 25 + 10 * np.sin(t)
#y = HAProps('W','T',x+273.15,'P',p,'R',r1)
#z = HAProps('W','T',x+273.15,'P',p,'R',r2)
tt.append(t)
for j in range(5):
x = temp[j]
y = HAProps('W','T',x+273.15,'P',p,'R',relhum[j]*0.01)
xx[j].append(x)
yy[j].append(y)
a[j].set_data(x,y)
except KeyboardInterrupt:
print('exciting!')
except TypeError:
pass
def check_HAProps(*args):
val = HAProps(*args)
def check_HAProps(*args):
HAProps(*args)
# Setup for plotting #
######################
p = 101.325
Tdb = numpy.linspace(-10,40,100)+273.15
#Make the figure and the axes
fig=matplotlib.pyplot.figure(figsize=(10,8))
ax=fig.add_axes((0.1,0.1,0.85,0.85))
fig2=matplotlib.pyplot.figure(figsize=(10,8))
ax2=fig2.add_axes((0.1,0.1,0.85,0.85))
ax2.set_xlim((-1,10))
ax2.set_ylim((0,50))
# Saturation line
w = [HAProps('W','T',T,'P',p,'R',1.0) for T in Tdb]
ax.plot(Tdb-273.15,w,lw=2)
# Humidity lines
RHValues = [0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9]
for RH in RHValues:
w = [HAProps('W','T',T,'P',p,'R',RH) for T in Tdb]
ax.plot(Tdb-273.15,w,'b--',lw=1)
# Enthalpy lines
for H in [-20, -10, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90]:
#Line goes from saturation to zero humidity ratio for this enthalpy
T1 = HAProps('T','H',H,'P',p,'R',1.0)-273.15
T0 = HAProps('T','H',H,'P',p,'R',0.0)-273.15
w1 = HAProps('W','H',H,'P',p,'R',1.0)
w0 = HAProps('W','H',H,'P',p,'R',0.0)
def getSaturatedProperties(self, name, h):
#
if (name == "T"):
return (HAProps('T', 'P', 101325, 'H', h, 'R', 1.0) - 273.15)
else:
raise ValueError("name:%s not found" % name)
def getEnthalpy(self, temp, humidityRatio):
return HAProps("H", "T", temp + 273.15, "P", 101325, "R",
humidityRatio) # J/kg dry air
def HerringboneFins(Inputs):
#Source:
#Empirical correlations for heat transfer and flow friction characteristics of herringbone wavy fin-and-tube heat exchangers
#Chi-Chuan Wang, Young-Ming Hwang, Yur-Tsai Lin
#International Journal of Refrigeration, 25, 2002, 637-680
#Properties:
p = Inputs.Air.p #air pressure
W = HAProps('W', 'T', Inputs.Air.Tdb, 'P', p, 'R', Inputs.Air.RH)
#Transport properties of humid air from CoolProp
mu_ha = HAProps('M', 'T', Inputs.Air.Tdb, 'P', p, 'W', W)
k_ha = HAProps('K', 'T', Inputs.Air.Tdb, 'P', p, 'W', W) * 10**3
#Evaluate the mass flow rate based on inlet conditions
Vdot_ha = Inputs.Air.Vdot_ha
# To convert a parameter from per kg_{humid air} to per kg_{dry air}, divide by (1+W)
W = HAProps('W', 'T', Inputs.Air.Tdb, 'P', p, 'R', Inputs.Air.RH)
v_da = HAProps('V', 'T', Inputs.Air.Tdb, 'P', p, 'W', W)
h_da = HAProps('H', 'T', Inputs.Air.Tdb, 'P', p, 'W', W) * 1000
rho_ha = 1 / v_da * (1 + W) #[m^3/kg_ha]
rho_da = 1 / v_da #[m^3/kg_da]
mdot_ha = Vdot_ha * rho_ha #[kg_ha/s]
mdot_da = Vdot_ha * rho_da #[kg_da/s]
#Use a forward difference to calculate cp from cp=dh/dT
dT = 0.0001 #[K]
cp_da = (HAProps('H', 'T', Inputs.Air.Tdb + dT, 'P', p, 'W', W) * 1000 -
h_da) / dT #[J/kg_da/K]
cp_ha = cp_da / (1 + W) #[J/kg_ha/K]
# Check that cs_cp is defined, if so, set it to the value passed in
if (hasattr(Inputs, 'cs_cp')
and Inputs.cs_cp > 0) or (hasattr(Inputs, 'WetDry')
and Inputs.WetDry == 'Wet'):
isWet = True
cs_cp = Inputs.Air.cs_cp
else:
isWet = False
cs_cp = 1.0
#Dimensions and values used for both Reynolds number ranges:
delta_f = Inputs.Fins.t #fin thickness(m)
FPI = Inputs.Fins.FPI #fins per inch
FPM = FPI / 0.0254 #Fins per meter [1/m]
pf = 1 / FPM #Fin pitch (distance between centerlines of fins)
F_s = 1 / FPM - delta_f #Fin spacing(m)
P_t = Inputs.Tubes.Pt #transverse tube pitch (m)
P_L = Inputs.Tubes.Pl #longitudinal tube pitch (m)
D_o = Inputs.Tubes.OD #Outer diameter of tube (m)
D_c = D_o + 2 * delta_f #fin collar outside diameter (m) (tube + 2*fin thickness)
Ltube = Inputs.Tubes.Ltube #length of a single tube [m]
Nfin = Ltube * FPM #Number of fins in the tube sheet [-]
Ntubes_bank = Inputs.Tubes.NTubes_per_bank #tubes per bank
Height = P_t * (
Ntubes_bank + 1
) #Height of heat exchanger [m] # assuming that fin extends 1/2 pt above/below last tube in bundle
A_duct = Height * Ltube #A_duct is the face area [m^2] - equivalent to the duct cross-section #neglecting the additional height of the fins above/below the last tubes in the bundle
Ac = A_duct - delta_f * Nfin * (
Height - D_c * Ntubes_bank
) - Ntubes_bank * D_c * Ltube #Minimum duct cross-sectional area that is not fin or tube(-collar) [m^2]
u_max = mdot_ha / (rho_ha * Ac) #maximum airside velocity [m/s]
Re_Dc = rho_ha * u_max * D_c / mu_ha #from reference #4 of Wang et all. Slightly different notation used in [4]
P_d = Inputs.Fins.Pd #wave height
X_f = Inputs.Fins.xf #projected fin length (m)
tanTheta = P_d / X_f #tangens of corrugation angle
secTheta = sqrt(
X_f * X_f + P_d * P_d
) / X_f ###!!used wavy louvered fins definition - there seems to be a bug in the paper !!
beta = (pi * D_c**2) / (4.0 * P_t * P_L)
oneMbeta = 1.0 - beta #save one operation
D_h = 2.0 * F_s * oneMbeta / (oneMbeta * secTheta + 2 * F_s * beta / D_c
) # hydraulic diameter (m)
N = Inputs.Tubes.Nbank #number of lomgitudunal tube rows (#Number of banks in ACHP-notation)
if Re_Dc < 1000.0:
#Heat transfer
J1 = 0.0045 - 0.491 * pow(Re_Dc, -0.0316 - 0.0171 * log(
N * tanTheta)) * pow(P_L / P_t, -0.109 * log(N * tanTheta)) * pow(
D_c / D_h, 0.542 + 0.0471 * N) * pow(F_s / D_c, 0.984) * pow(
F_s / P_t, -0.349)
J2 = -2.72 + 6.84 * tanTheta
J3 = 2.66 * tanTheta
j = 0.882 * pow(Re_Dc, J1) * pow(D_c / D_h, J2) * pow(
F_s / P_t, J3) * pow(F_s / D_c, -1.58) * pow(tanTheta, -0.2)
#Friction
F1 = -0.574 - 0.137 * pow(log(Re_Dc) - 5.26, 0.245) * pow(
P_t / D_c, -0.765) * pow(D_c / D_h, -0.243) * pow(
F_s / D_h, -0.474) * pow(tanTheta, -0.217) * pow(N, 0.035)
F2 = -3.05 * tanTheta
F3 = -0.192 * N
F4 = -0.646 * tanTheta
f = 4.37 * pow(Re_Dc, F1) * pow(F_s / D_h, F2) * pow(
P_L / P_t, F3) * pow(D_c / D_h, 0.2054) * pow(N, F4)
else:
#Heat transfer
j1 = -0.0545 - 0.0538 * tanTheta - 0.302 * pow(N, -0.24) * pow(
F_s / P_L, -1.3) * pow(P_L / P_t, 0.379) * pow(
P_L / D_h, -1.35) * pow(tanTheta, -0.256)
j2 = -1.29 * pow(P_L / P_t, 1.77 - 9.43 * tanTheta) * pow(
D_c / D_h,
0.229 - 1.43 * tanTheta) * pow(N, -0.166 - 1.08 * tanTheta) * pow(
F_s / P_t, -0.174 * log(0.5 * N))
j = 0.0646 * pow(Re_Dc, j1) * pow(D_c / D_h, j2) * pow(
F_s / P_t, -1.03) * pow(P_L / D_c, 0.432) * pow(
tanTheta, -0.692) * pow(N, -0.737)
#Friction
f1 = -0.141 * pow(F_s / P_L, 0.0512) * pow(tanTheta, -0.472) * pow(
P_L / P_t, 0.35) * pow(P_t / D_h, 0.449 * tanTheta) * pow(
N, -0.049 + 0.237 * tanTheta)
f2 = -0.562 * pow(log(Re_Dc), -0.0923) * pow(N, 0.013)
f3 = 0.302 * pow(Re_Dc, 0.03) * pow(P_t / D_c, 0.026)
f4 = -0.306 + 3.63 * tanTheta
f = 0.228 * pow(Re_Dc, f1) * pow(tanTheta, f2) * pow(
F_s / P_L, f3) * pow(P_L / D_c, f4) * pow(D_c / D_h, 0.383) * pow(
P_L / P_t, -0.247)
Pr = cp_ha * mu_ha / k_ha
h_a = j * rho_ha * u_max * cp_ha / pow(
Pr, 2.0 /
3.0) #air side mean heat transfer coefficient using colborn j-factor
#calcs needed for specific fin types
#additional parameters needed
k_fin = Inputs.Fins.k_fin
Nbank = Inputs.Tubes.Nbank #Number of banks
secTheta = sqrt(X_f * X_f + P_d * P_d) / X_f #secTheta
#Wetted Area of a single fin [m^2]
A_1fin = 2.0 * (
Height * P_L *
(Nbank + 1) * secTheta - Ntubes_bank * Nbank * pi * D_o * D_o / 4
) #assuming that fin extends 1/2 pt in front/after last tube in bundle
# Total wetted area of the fins [m^2]
Af = Nfin * A_1fin
#Total area including tube and fins [m^2]
A = Af + Ntubes_bank * Nbank * pi * D_o * (Ltube - Nfin * delta_f)
r = D_o / 2
X_D = sqrt(P_L * P_L + P_t * P_t / 4) / 2
X_T = P_t / 2
rf_r = 1.27 * X_T / r * sqrt(X_D / X_T - 0.3)
m = sqrt(
2 * h_a * cs_cp /
(k_fin * delta_f)) #cs_cp is the correction for heat/mass transfer
#Using the circular fin correlation of Schmidt
phi = (rf_r - 1) * (1 + 0.35 * log(rf_r))
eta_f = tanh(m * r * phi) / (m * r * phi)
# Fin efficiency based on analysis in
# "FIN EFFICIENCY CALCULATION IN ENHANCED FIN-AND-TUBE HEAT EXCHANGERS IN DRY CONDITIONS"
# by Thomas PERROTIN, Denis CLODIC, International Congress of Refrigeration 2006
# In the paper, there is no 0.1 in the cosine term, but if the cosine term is used without
# the correction, the results are garbage for wet analysis
# Using the offset fins correlation
phi = (rf_r - 1) * (1 +
(0.3 + pow(m *
(rf_r * r - r) / 2.5, 1.5 - rf_r / 12.0) *
(0.26 * pow(rf_r, 0.3) - 0.3)) * log(rf_r))
#finned surface efficiency
eta_f = tanh(m * r * phi) / (m * r * phi) * cos(0.1 * m * r * phi)
#overall surface efficiency
eta_o = 1 - Af / A * (1 - eta_f)
G_c = mdot_ha / Ac #air mass flux
Atube = Ntubes_bank * Nbank * pi * D_o * Ltube # Total outer area of the tubes [m^2]
DeltaP_air = A / Atube / rho_ha * G_c**2 / 2.0 * f #airside pressure drop
#write necessary values back into the given structure
Inputs.A_a = A
Inputs.cp_da = cp_da
Inputs.cp_ha = cp_ha
if isWet == True:
Inputs.eta_a_wet = eta_o
else:
Inputs.eta_a = eta_o
Inputs.h_a = h_a
Inputs.mdot_ha = mdot_ha
Inputs.mdot_da = mdot_da
Inputs.f_a = f
Inputs.dP_a = DeltaP_air
Inputs.Re = Re_Dc
def DryWetSegment(DWS):
"""
Generic solver function for dry-wet mixed surface conditions for a given element.
Can handle superheated, subcooled and two-phase regions.
Does not handle the pressure drops, only HT required to get the dry/wet interface
"""
#List of required parameters
RequiredParameters=['Tin_a','h_a','cp_da','eta_a','A_a','pin_a','RHin_a','Tin_r','pin_r','h_r','cp_r','A_r','mdot_r','Fins']
#Check that all the parameters are included, raise exception otherwise
for param in RequiredParameters:
if not hasattr(DWS,param):
raise AttributeError("Parameter "+param+" is required for DWS class in DryWetSegment")
#Retrieve values from structures defined above
Tin_a=DWS.Tin_a
h_a=DWS.h_a
cp_da=DWS.cp_da
eta_a=DWS.eta_a #from fin correlations, overall airside surface effectiveness
A_a=DWS.A_a
pin_a=DWS.pin_a
RHin_a=DWS.RHin_a
mdot_da=DWS.mdot_da
Tin_r=DWS.Tin_r
pin_r=DWS.pin_r
h_r=DWS.h_r
cp_r=DWS.cp_r
A_r=DWS.A_r
mdot_r=DWS.mdot_r
#Calculate the dewpoint (amongst others)
omega_in=HAProps('W','T',Tin_a,'P',pin_a,'R',RHin_a)
Tdp=HAProps('D','T',Tin_a,'P',pin_a,'W',omega_in)
hin_a=HAProps('H','T',Tin_a,'P',pin_a,'W',omega_in)*1000 #[J/kg_da]
# Internal UA between fluid flow and outside surface (neglecting tube conduction)
UA_i=h_r*A_r #[W/K], from Shah or f_h_1phase_Tube-fct -> Correlations.py
# External UA between wall and free stream
UA_o=eta_a*h_a*A_a #[W/K], from fin correlations
# Internal Ntu
Ntu_i=UA_i/(mdot_r*cp_r) #[-]
# External Ntu (multiplied by eta_a since surface is finned and has lower effectiveness)
Ntu_o=eta_a*h_a*A_a/(mdot_da*cp_da) #[-]
if DWS.IsTwoPhase: #(Two-Phase analysis)
UA=1/(1/(h_a*A_a*eta_a)+1/(h_r*A_r)); #overall heat transfer coefficient
Ntu_dry=UA/(mdot_da*cp_da); #Number of transfer units
epsilon_dry=1-exp(-Ntu_dry); #since Cr=0, e.g. see Incropera - Fundamentals of Heat and Mass Transfer, 2007, p. 690
Q_dry=epsilon_dry*mdot_da*cp_da*(Tin_a-Tin_r);
Tout_a=Tin_a-Q_dry/(mdot_da*cp_da); #outlet temperature, dry fin
T_so_a=(UA_o*Tin_a+UA_i*Tin_r)/(UA_o+UA_i); #inlet surface temperature
T_so_b=(UA_o*Tout_a+UA_i*Tin_r)/(UA_o+UA_i); #outlet surface temperature
if T_so_b>Tdp:
#All dry, since surface at outlet dry
f_dry=1.0
Q=Q_dry #[W]
Q_sensible=Q #[W]
hout_a=hin_a-Q/mdot_da #[J/kg_da]
# Air outlet humidity ratio
DWS.omega_out = omega_in #[kg/kg]
else:
if T_so_a<Tdp:
#All wet, since surface at inlet wet
f_dry=0.0
Q_dry=0.0
T_ac=Tin_a #temp at onset of wetted wall
h_ac=hin_a #enthalpy at onset of wetted surface
else:
# Partially wet and dry
# Air temperature at the interface between wet and dry surface
# Based on equating heat fluxes at the wall which is at dew point UA_i*(Tw-Ti)=UA_o*(To-Tw)
T_ac = Tdp + UA_i/UA_o*(Tdp - Tin_r)
# Dry effectiveness (minimum capacitance on the air side by definition)
epsilon_dry=(Tin_a-T_ac)/(Tin_a-Tin_r)
# Dry fraction found by solving epsilon=1-exp(-f_dry*Ntu) for known epsilon from above equation
f_dry=-1.0/Ntu_dry*log(1.0-epsilon_dry)
# Enthalpy, using air humidity at the interface between wet and dry surfaces, which is same humidity ratio as inlet
h_ac=HAProps('H','T',T_ac,'P',pin_a,'W',omega_in)*1000 #[J/kg_da]
# Dry heat transfer
Q_dry=mdot_da*cp_da*(Tin_a-T_ac)
# Saturation specific heat at mean water temp
c_s=cair_sat(Tin_r)*1000 #[J/kg-K]
# Find new, effective fin efficiency since cs/cp is changed from wetting
# Ratio of specific heats [-]
DWS.Fins.Air.cs_cp=c_s/cp_da
DWS.Fins.WetDry='Wet'
WavyLouveredFins(DWS.Fins)
eta_a_wet=DWS.Fins.eta_a_wet
UA_o=eta_a_wet*h_a*A_a
Ntu_o=eta_a_wet*h_a*A_a/(mdot_da*cp_da)
# Wet analysis overall Ntu for two-phase refrigerant
# Minimum capacitance rate is by definition on the air side
# Ntu_wet is the NTU if the entire two-phase region were to be wetted
UA_wet=1/(c_s/UA_i+cp_da/UA_o)
Ntu_wet=UA_wet/(mdot_da)
# Wet effectiveness [-]
epsilon_wet=1-exp(-(1-f_dry)*Ntu_wet)
# Air saturated at refrigerant saturation temp [J/kg]
h_s_s_o=HAProps('H','T',Tin_r, 'P',pin_a, 'R', 1.0)*1000 #[kJ/kg_da]
# Wet heat transfer [W]
Q_wet=epsilon_wet*mdot_da*(h_ac-h_s_s_o)
# Total heat transfer [W]
Q=Q_wet+Q_dry
# Air exit enthalpy [J/kg]
hout_a=h_ac-Q_wet/mdot_da
# Saturated air temp at effective surface temp [J/kg_da]
h_s_s_e=h_ac-(h_ac-hout_a)/(1-exp(-(1-f_dry)*Ntu_o))
# Effective surface temperature [K]
T_s_e = HAProps('T','H',h_s_s_e/1000.0,'P',pin_a,'R',1.0)
# Outlet dry-bulb temp [K]
Tout_a = T_s_e+(T_ac-T_s_e)*exp(-(1-f_dry)*Ntu_o)
#Sensible heat transfer rate [kW]
Q_sensible=mdot_da*cp_da*(Tin_a-Tout_a)
#Outlet is saturated vapor
Tout_r=DWS.Tdew_r
else: #(Single-Phase analysis)
#Overall UA
UA = 1 / (1 / (UA_i) + 1 / (UA_o));
# Min and max capacitance rates [W/K]
Cmin = min([cp_r * mdot_r, cp_da * mdot_da])
Cmax = max([cp_r * mdot_r, cp_da * mdot_da])
# Capacitance rate ratio [-]
C_star = Cmin / Cmax
# Ntu overall [-]
Ntu_dry = UA / Cmin
# Counterflow effectiveness [-]
epsilon_dry = ((1 - exp(-Ntu_dry * (1 - C_star))) /
(1 - C_star * exp(-Ntu_dry * (1 - C_star))))
# Dry heat transfer [W]
Q_dry = epsilon_dry*Cmin*(Tin_a-Tin_r)
# Dry-analysis air outlet temp [K]
Tout_a_dry=Tin_a-Q_dry/(mdot_da*cp_da)
# Dry-analysis outlet temp [K]
Tout_r=Tin_r+Q_dry/(mdot_r*cp_r)
# Dry-analysis air outlet enthalpy from energy balance [J/kg]
hout_a=hin_a-Q_dry/mdot_da
# Dry-analysis surface outlet temp [K]
Tout_s=(UA_o*Tout_a_dry+UA_i*Tin_r)/(UA_o+UA_i)
# Dry-analysis surface inlet temp [K]
Tin_s=(UA_o*Tin_a+UA_i*Tout_r)/(UA_o+UA_i)
# Dry-analysis outlet refrigerant temp [K]
Tout_r_dry=Tout_r
# Dry fraction [-]
f_dry=1.0
# Air outlet humidity ratio [-]
DWS.omega_out = omega_in
# If inlet surface temp below dewpoint, whole surface is wetted
if Tin_s<Tdp:
isFullyWet=True
else:
isFullyWet=False
if Tout_s<Tdp or isFullyWet:
# There is some wetting, either the coil is fully wetted or partially wetted
# Loop to get the correct c_s
# Start with the inlet temp as the outlet temp
x1=Tin_r+1 #Lowest possible outlet temperature
x2=Tin_a-1 #Highest possible outlet temperature
eps=1e-8
iter=1
change=999
while ((iter<=3 or change>eps) and iter<100):
if (iter==1):
Tout_r=x1;
if (iter>1):
Tout_r=x2;
Tout_r_start=Tout_r;
# Saturated air enthalpy at the inlet water temperature [J/kg]
h_s_w_i=HAProps('H','T',Tin_r,'P', pin_a, 'R', 1.0)*1000 #[J/kg_da]
# Saturation specific heat at mean water temp [J/kg]
c_s=cair_sat((Tin_r+Tout_r)/2.0)*1000
# Ratio of specific heats [-]
DWS.Fins.Air.cs_cp=c_s/cp_da
# Find new, effective fin efficiency since cs/cp is changed from wetting
WavyLouveredFins(DWS.Fins)
# Effective humid air mass flow ratio
m_star=mdot_da/(mdot_r*(cp_r/c_s))
#compute the new Ntu_owet
Ntu_owet = eta_a*h_a*A_a/(mdot_da*cp_da)
m_star = min([cp_r * mdot_r/c_s, mdot_da])/max([cp_r * mdot_r/c_s, mdot_da])
mdot_min = min([cp_r * mdot_r/c_s, mdot_da])
# Wet-analysis overall Ntu [-]
Ntu_wet=Ntu_o/(1+m_star*(Ntu_owet/Ntu_i))
if(cp_r * mdot_r> c_s * mdot_da):
Ntu_wet=Ntu_o/(1+m_star*(Ntu_owet/Ntu_i))
else:
Ntu_wet=Ntu_i/(1+m_star*(Ntu_i/Ntu_owet))
# Counterflow effectiveness for wet analysis
epsilon_wet = ((1 - exp(-Ntu_wet * (1 - m_star))) /
(1 - m_star * exp(-Ntu_wet * (1 - m_star))))
# Wet-analysis heat transfer rate
Q_wet = epsilon_wet*mdot_min*(hin_a-h_s_w_i)
# Air outlet enthalpy [J/kg_da]
hout_a=hin_a-Q_wet/mdot_da
# Water outlet temp [K]
Tout_r = Tin_r+mdot_da/(mdot_r*cp_r)*(hin_a-hout_a)
# Water outlet saturated surface enthalpy [J/kg_da]
h_s_w_o=HAProps('H','T',Tout_r, 'P',pin_a, 'R', 1.0)*1000 #[J/kg_da]
#Local UA* and c_s
UA_star = 1/(cp_da/eta_a/h_a/A_a+cair_sat((Tin_a+Tout_r)/2.0)*1000/h_r/A_r)
# Wet-analysis surface temperature [K]
Tin_s = Tout_r + UA_star/h_r/A_r*(hin_a-h_s_w_o)
# Wet-analysis saturation enthalpy [J/kg_da]
h_s_s_e=hin_a+(hout_a-hin_a)/(1-exp(-Ntu_owet))
# Surface effective temperature [K]
T_s_e=HAProps('T','H',h_s_s_e/1000.0,'P',pin_a,'R',1.0)
# Air outlet temp based on effective temp [K]
Tout_a=T_s_e + (Tin_a-T_s_e)*exp(-Ntu_o)
#Sensible heat transfer rate [W]
Q_sensible = mdot_da*cp_da*(Tin_a-Tout_a)
# Error between guess and recalculated value [K]
errorToutr=Tout_r-Tout_r_start;
if(iter>500):
print "Superheated region wet analysis T_outr convergence failed"
DWS.Q=Q_dry;
return
if iter==1:
y1=errorToutr
if iter>1:
y2=errorToutr
x3=x2-y2/(y2-y1)*(x2-x1)
change=abs(y2/(y2-y1)*(x2-x1))
y1=y2; x1=x2; x2=x3
if hasattr(DWS,'Verbosity') and DWS.Verbosity>7:
print "Fullwet iter %d Toutr %0.5f dT %g" %(iter,Tout_r,errorToutr)
#Update loop counter
iter+=1
# Fully wetted outlet temperature [K]
Tout_r_wet=Tout_r
# Dry fraction
f_dry=0.0
if (Tin_s>Tdp and not isFullyWet):
#Partially wet and partially dry with single-phase on refrigerant side
"""
-----------------------------------------------------------
|
* Tout_a <---- * T_a,x <---- * Tin_a
|
____________Wet____________| Dry
----------------------------o T_dp ------------------------
|
* Tin_r ----> * T_w,x ----> * Tout_r
|
-----------------------------------------------------------
"""
iter = 1
# Now do an iterative solver to find the fraction of the coil that is wetted
x1=0.0001
x2=0.9999
eps=1e-8
while ((iter<=3 or error>eps) and iter<100):
if iter==1:
f_dry=x1
if iter>1:
f_dry=x2
K=Ntu_dry*(1.0-C_star)
expk = exp(-K*f_dry)
if cp_da*mdot_da < cp_r*mdot_r:
Tout_r_guess = (Tdp + C_star*(Tin_a - Tdp)-expk*(1-K/Ntu_o)*Tin_a)/(1-expk*(1-K/Ntu_o))
else:
Tout_r_guess = (expk*(Tin_a+(C_star-1)*Tdp)-C_star*(1+K/Ntu_o)*Tin_a)/(expk*C_star-C_star*(1+K/Ntu_o))
# Wet and dry effective effectivenesses
epsilon_dry = ((1 - exp(-f_dry*Ntu_dry * (1 - C_star))) /
(1 - C_star * exp(-f_dry*Ntu_dry * (1 - C_star))))
epsilon_wet = ((1 - exp(-(1-f_dry)*Ntu_wet * (1 - m_star))) /
(1 - m_star * exp(-(1-f_dry)*Ntu_wet * (1 - m_star))))
# Temperature of "water" where condensation begins
T_w_x=(Tin_r+(mdot_min)/(cp_r * mdot_r)*epsilon_wet*(hin_a-h_s_w_i-epsilon_dry*Cmin/mdot_da*Tin_a))/(1-(Cmin*mdot_min)/(cp_r * mdot_r * mdot_da)*epsilon_wet*epsilon_dry)
# Temperature of air where condensation begins [K]
# Obtained from energy balance on air side
T_a_x = Tin_a - epsilon_dry*Cmin*(Tin_a - T_w_x)/(mdot_da*cp_da)
# Enthalpy of air where condensation begins
h_a_x = hin_a - cp_da*(Tin_a - T_a_x)
# New "water" temperature (stored temporarily to be able to build change
Tout_r=(Cmin)/(cp_r * mdot_r)*epsilon_dry*Tin_a+(1-(Cmin)/(cp_r * mdot_r)*epsilon_dry)*T_w_x
# Difference between initial guess and outlet
error=Tout_r-Tout_r_guess
if(iter>500):
print "Superheated region wet analysis f_dry convergence failed"
DWS.Q=Q_dry
return
if iter==1:
y1=error
if iter>1:
y2=error
x3=x2-y2/(y2-y1)*(x2-x1)
change=abs(y2/(y2-y1)*(x2-x1))
y1=y2; x1=x2; x2=x3;
if hasattr(DWS,'Verbosity') and DWS.Verbosity>7:
print "Partwet iter %d Toutr_guess %0.5f diff %g f_dry: %g"%(iter,Tout_r_guess,error,f_dry)
#Update loop counter
iter+=1
# Wet-analysis saturation enthalpy [J/kg]
h_s_s_e=h_a_x+(hout_a-h_a_x)/(1-exp(-(1-f_dry)*Ntu_owet))
# Surface effective temperature [K]
T_s_e=HAProps('T','H',h_s_s_e/1000.0,'P',pin_a,'R',1.0)
# Air outlet temp based on effective surface temp [K]
Tout_a=T_s_e + (T_a_x-T_s_e)*exp(-(1-f_dry)*Ntu_o)
# Heat transferred [W]
Q=mdot_r*cp_r*(Tout_r-Tin_r)
# Dry-analysis air outlet enthalpy from energy balance [J/kg]
hout_a=hin_a-Q/mdot_da
#Sensible heat transfer rate [kW]
Q_sensible = mdot_da*cp_da*(Tin_a-Tout_a)
else:
Q=Q_wet
else:
# Coil is fully dry
Tout_a=Tout_a_dry
Q=Q_dry
Q_sensible=Q_dry
DWS.f_dry=f_dry
DWS.omega_out=HAProps('W','T',Tout_a,'P',101.325,'H',hout_a/1000.0)
DWS.RHout_a=HAProps('R','T',Tout_a,'P',101.325,'W',DWS.omega_out)
DWS.Tout_a=Tout_a
DWS.Q=Q
DWS.Q_sensible=Q_sensible
DWS.hout_a=hout_a
DWS.hin_a=hin_a
DWS.Tout_r=Tout_r
def OBJECTIVE(x):
Tevap = x[0]
Tcond = x[1]
Tin_CC = x[2]
if Cycle.Mode == 'AC':
#Condenser heat transfer rate
Qcond = epsilon * Cycle.Condenser.Fins.Air.Vdot_ha / rho_air * (
Cycle.Condenser.Fins.Air.Tdb - Tcond) * 1000
#Compressor power
pevap = Props('P', 'T', Tevap, 'Q', 1.0, Cycle.Ref)
pcond = Props('P', 'T', Tcond, 'Q', 1.0, Cycle.Ref)
Cycle.Compressor.pin_r = pevap
Cycle.Compressor.pout_r = pcond
Cycle.Compressor.Tin_r = Tevap + Cycle.Compressor.DT_sh
Cycle.Compressor.Ref = Cycle.Ref
Cycle.Compressor.Calculate()
W = Cycle.Compressor.W
Qcoolingcoil_dry = epsilon * Cycle.CoolingCoil.Fins.Air.Vdot_ha / rho_air * (
Cycle.CoolingCoil.Fins.Air.Tdb - Tin_CC) * 1000
# Air-side heat transfer UA
CC = Cycle.CoolingCoil
CC.Initialize()
UA_a = CC.Fins.h_a * CC.Fins.A_a * CC.Fins.eta_a
#Air outlet temp from dry analysis
Tout_a = CC.Tin_a - Qcoolingcoil_dry / (CC.Fins.mdot_a *
CC.Fins.cp_a)
# Refrigerant side UA
f, h, Re = Correlations.f_h_1phase_Tube(
Cycle.Pump.mdot_g / CC.Ncircuits, CC.ID, Tin_CC, CC.pin_g,
CC.Ref_g)
UA_r = CC.A_g_wetted * h
#Refrigerant outlet temp
cp_g = Props('C', 'T', Tin_CC, 'P', Cycle.Pump.pin_g,
Cycle.Pump.Ref_g) * 1000
Tout_CC = Tin_CC + Qcoolingcoil_dry / (Cycle.Pump.mdot_g * cp_g)
#Get wall temperatures at inlet and outlet from energy balance
T_so_a = (UA_a * CC.Tin_a + UA_r * Tout_CC) / (UA_a + UA_r)
T_so_b = (UA_a * Tout_a + UA_r * Tin_CC) / (UA_a + UA_r)
Tdewpoint = HAProps(
'D', 'T', CC.Fins.Air.Tdb, 'P', 101.325, 'R', CC.Fins.Air.RH
) #HumAir_Single(CC.Fins.Air.Tdb, 101.325, 'RH',CC.Fins.Air.RH,'DewPoint')
#Now calculate the fully-wet analysis
#Evaporator is bounded by saturated air at the refrigerant temperature.
h_ai = HAProps(
'H', 'T', CC.Fins.Air.Tdb, 'P', 101.325, 'R', CC.Fins.Air.RH
) #HumAir_Single(CC.Fins.Air.Tdb, 101.325, 'RH', CC.Fins.Air.RH,'Enthalpy')
h_s_w_o = HAProps(
'H', 'T', Tin_CC, 'P', 101.325, 'R',
1) #HumAir_Single(Tin_CC, 101.325, 'RH', 1.0,'Enthalpy')
Qcoolingcoil_wet = epsilon * CC.Fins.Air.Vdot_ha / rho_air * (
h_ai - h_s_w_o) * 1000
#Coil is either fully-wet, fully-dry or partially wet, partially dry
if T_so_a > Tdewpoint and T_so_b > Tdewpoint:
#Fully dry, use dry Q
f_dry = 1.0
elif T_so_a < Tdewpoint and T_so_b < Tdewpoint:
#Fully wet, use wet Q
f_dry = 0.0
else:
f_dry = 1 - (Tdewpoint - T_so_a) / (T_so_b - T_so_a)
Qcoolingcoil = f_dry * Qcoolingcoil_dry + (
1 - f_dry) * Qcoolingcoil_wet
Tin_IHX = Tin_CC + Qcoolingcoil / (Cycle.Pump.mdot_g * cp_g)
QIHX = epsilon * Cycle.Pump.mdot_g * cp_g * (Tin_IHX - Tevap)
Qcond_enthalpy = Cycle.Compressor.mdot_r * (
Cycle.Compressor.hout_r -
Props('H', 'T', Tcond - Cycle.DT_sc_target, 'P', pcond,
Cycle.Ref) * 1000)
resids = [
QIHX + W + Qcond, Qcond + Qcond_enthalpy, Qcoolingcoil - QIHX
]
return resids
elif Cycle.Mode == 'HP':
#Evaporator heat transfer rate
Qevap = epsilon * Cycle.Evaporator.Fins.Air.Vdot_ha / rho_air * (
Cycle.Evaporator.Fins.Air.Tdb - Tevap) * 1000
#Compressor power
pevap = Props('P', 'T', Tevap, 'Q', 1.0, Cycle.Ref)
pcond = Props('P', 'T', Tcond, 'Q', 1.0, Cycle.Ref)
Cycle.Compressor.pin_r = pevap
Cycle.Compressor.pout_r = pcond
Cycle.Compressor.Tin_r = Tevap + Cycle.Evaporator.DT_sh
Cycle.Compressor.Ref = Cycle.Ref
Cycle.Compressor.Calculate()
W = Cycle.Compressor.W
#Evaporator will be dry
Qcoolingcoil = epsilon * Cycle.CoolingCoil.Fins.Air.Vdot_ha / rho_air * (
Tin_CC - Cycle.CoolingCoil.Fins.Air.Tdb) * 1000
cp_g = Props('C', 'T', Tin_CC, 'P', Cycle.Pump.pin_g,
Cycle.Pump.Ref_g) * 1000
Tin_IHX = Tin_CC - Qcoolingcoil / (Cycle.Pump.mdot_g * cp_g)
QIHX = epsilon * Cycle.Pump.mdot_g * cp_g * (Tin_IHX - Tcond)
QIHX_enthalpy = Cycle.Compressor.mdot_r * (
Cycle.Compressor.hout_r -
Props('H', 'T', Tcond - Cycle.DT_sc_target, 'P', pcond,
Cycle.Ref) * 1000)
resids = [
QIHX + W + Qevap, QIHX + QIHX_enthalpy, Qcoolingcoil + QIHX
]
return resids
def plot(self, ax):
w = [HAProps('W', 'T', T, 'P', p, 'R', 1.0) for T in Tdb]
ax.plot(Tdb - 273.15, w, lw=2)
def plot(self, ax):
for RH in self.RH_values:
w = [HAProps('W', 'T', T, 'P', p, 'R', RH) for T in Tdb]
ax.plot(Tdb - 273.15, w, 'r', lw=1)
import numpy as np
import matplotlib.pyplot as plt
from CoolProp.HumidAirProp import HAProps
Tdb = np.linspace(-10, 55, 100) + 273.15
#Make the figure and the axes
fig = plt.figure(figsize=(10, 8))
ax = fig.add_axes((0.15, 0.15, 0.8, 0.8))
ax.set_xlim(Tdb[0] - 273.15, Tdb[-1] - 273.15)
ax.set_ylim(0, 0.03)
ax.set_xlabel(r"Dry bulb temperature [$^{\circ}$C]")
ax.set_ylabel(r"Humidity ratio ($m_{water}/m_{dry\ air}$) [-]")
# Saturation line
w = [HAProps('W', 'T', T, 'P', 101.325, 'R', 1.0) for T in Tdb]
ax.plot(Tdb - 273.15, w, lw=2)
# Humidity lines
RHValues = [0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9]
for RH in RHValues:
w = [HAProps('W', 'T', T, 'P', 101.325, 'R', RH) for T in Tdb]
ax.plot(Tdb - 273.15, w, 'r', lw=1)
# Humidity lines
for H in [-20, -10, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90]:
#Line goes from saturation to zero humidity ratio for this enthalpy
T1 = HAProps('T', 'H', H, 'P', 101.325, 'R', 1.0) - 273.15
T0 = HAProps('T', 'H', H, 'P', 101.325, 'R', 0.0) - 273.15
w1 = HAProps('W', 'H', H, 'P', 101.325, 'R', 1.0)
w0 = HAProps('W', 'H', H, 'P', 101.325, 'R', 0.0)
def getSaturatedProperties(self, name, h):
#
if name == "T":
return HAProps("T", "P", 101325, "H", h, "R", 1.0) - 273.15
else:
raise ValueError("name:%s not found" % name)
def check_type(Tvals, wvals):
HAProps('H','T',Tvals,'P',101.325,'W', wvals)
def calculatePlot(cls, parent):
"""Funtion to calculate point in chart"""
Preferences = ConfigParser()
Preferences.read(conf_dir+"pychemqtrc")
parent.setProgressValue(0)
data = {}
P = parent.inputs.P.value
P_kPa = P/1000
t = cls.LineList("isotdb", Preferences)
# Saturation line
Hs = []
for tdb in t:
Hs.append(HAProps("W", "P", P_kPa, "Tdb", tdb, "RH", 1))
parent.setProgressValue(5*len(Hs)/len(t))
data["t"] = t
data["Hs"] = Hs
# left limit of isow lines
H = cls.LineList("isow", Preferences)
th = []
for w in H:
if w:
tdp = HAProps("Tdp", "P", 101.325, "W", w, "RH", 1)
th.append(Temperature(tdp).config())
else:
tmin = Preferences.getfloat("Psychr", "isotdbStart")
th.append(Temperature(tmin).config())
data["H"] = H
data["th"] = th
# Humidity ratio lines
hr = cls.LineList("isohr", Preferences)
Hr = {}
cont = 0
for i in hr:
Hr[i] = []
for tdb in t:
Hr[i].append(HAProps("W", "P", P_kPa, "Tdb", tdb, "RH", i/100))
cont += 1
parent.progressBar.setValue(5+10*cont/len(hr)/len(Hs))
data["Hr"] = Hr
# Twb
lines = cls.LineList("isotwb", Preferences)
Twb = {}
cont = 0
for T in lines:
ws = HAProps("W", "P", P_kPa, "RH", 1, "Tdb", T)
H = [ws, 0]
_td = HAProps("Tdb", "P", P_kPa, "Twb", T, "RH", 0)
Tw = [Temperature(T).config(), Temperature(_td).config()]
cont += 1
parent.progressBar.setValue(15+75*cont/len(lines))
Twb[T] = (H, Tw)
data["Twb"] = Twb
# v
lines = cls.LineList("isochor", Preferences)
V = {}
# rh = arange(1, -0.05, -0.05)
rh = arange(0.00, 1.05, 0.05)
for cont, v in enumerate(lines):
w = []
Td = []
for r in rh:
try:
w.append(HAProps("W", "P", P_kPa, "RH", r, "V", v))
_td = HAProps("Tdb", "P", P_kPa, "RH", r, "V", v)
Td.append(Temperature(_td).config())
except ValueError:
pass
parent.progressBar.setValue(90+10*cont/len(lines))
V[v] = (Td, w)
data["v"] = V
return data
print("Validation against H.F. Nelson and H.J. Sauer,\"Formulation for High-Temperature Properties for Moist Air\", HVAC&R Research v.8 #3, 2002")
print("Note: More accurate formulation employed than in Nelson. Just for sanity checking")
print("Yields a negative relative humidity for Tdb=5C,Twb=-3C, point omitted")
tdb = [5,5,5,25,25,25,25,50,50,50,50,50,50,50]
twb = [5,2,-1,25,20,15,10,50,40,30,25,22,20,19]
print(" ")
print("Table 6: Adiabatic Saturation")
print("P=101325 Pa, Altitude = 0 m")
print("========================================================================")
print("{Tdb:10s}{Twb:10s}{Tdp:10s}{R:10s}{W:10s}{h:10s}{v:10s}".format(W='W',Twb='Twb',Tdp='Tdp',Tdb='Tdb',v='v',h='h',s='s',R='RH'))
print("{Tdb:10s}{Twb:10s}{Tdp:10s}{R:10s}{W:10s}{h:10s}{v:10s}".format(W='-',Twb='C',Tdp='C',Tdb='C',v='m^3/kg_da',h='kJ/kg_da',s='kJ/kg_da/K',R='%'))
print("------------------------------------------------------------------------")
for (tdb_,twb_) in zip(tdb,twb):
h=HAProps('H','T',tdb_+273.13,'Twb',twb_+273.15,'P',101.325)
tdp=HAProps('Tdp','T',tdb_+273.13,'Twb',twb_+273.15,'P',101.325)-273.15
W=HAProps('W','T',tdb_+273.13,'Twb',twb_+273.15,'P',101.325)
R=HAProps('R','T',tdb_+273.13,'Twb',twb_+273.15,'P',101.325)*100
v=HAProps('V','T',tdb_+273.13,'Twb',twb_+273.15,'P',101.325)
s=0
print("{Tdb:10.2f}{Twb:10.2f}{Tdp:10.2f}{R:10.1f}{W:10.5f}{h:10.2f}{v:10.3f}".format(W=W,Twb=twb_,Tdp=tdp,Tdb=tdb_,v=v,h=h,s=s,R=R))
print("------------------------------------------------------------------------")
print(" ")
print("Table 7: Adiabatic Saturation")
print("P=84,556 Pa, Altitude = 1500 m")
print("========================================================================")
print("{Tdb:10s}{Twb:10s}{Tdp:10s}{R:10s}{W:10s}{h:10s}{v:10s}".format(W='W',Twb='Twb',Tdp='Tdp',Tdb='Tdb',v='v',h='h',s='s',R='RH'))
print("{Tdb:10s}{Twb:10s}{Tdp:10s}{R:10s}{W:10s}{h:10s}{v:10s}".format(W='-',Twb='C',Tdp='C',Tdb='C',v='m^3/kg_da',h='kJ/kg_da',s='kJ/kg_da/K',R='%'))
print("------------------------------------------------------------------------")
for (tdb_,twb_) in zip(tdb,twb):
def HotAir(num):
from CoolProp.HumidAirProp import HAProps
if num == '8':
Temp = str(200)
T = 200 + 273.15
elif num == '9':
Temp = str(320)
T = 320 + 273.15
print 'A.' + num + '.1 Psychrometric Properties of Moist Air at 101.325 kPa '
print 'Dry Bulb temperature of ' + Temp + 'C'
s5 = ' ' * 5
print '================================================================'
print "{W:10s}{Twb:10s}{v:10s}{h:10s}{s:10s}{R:10s}".format(W=s5 + ' W',
Twb=s5 + 'Twb',
v=s5 + ' v',
h=s5 + 'h',
s=s5 + ' s',
R=s5 + 'RH')
print "{W:10s}{Twb:10s}{v:10s}{h:10s}{s:10s}{R:10s}".format(
W=' kgw/kg_da',
Twb=' C',
v=' m3/kgda',
h=' kJ/kgda',
s=' kJ/kgda/K',
R=' %')
print '----------------------------------------------------------------'
for W in [
0.0, 0.05, 0.1, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0
]:
h = HAProps('H', 'T', T, 'W', W, 'P', 101.325)
Twb = HAProps('Twb', 'T', T, 'W', W, 'P', 101.325) - 273.15
R = HAProps('R', 'T', T, 'W', W, 'P', 101.325) * 100
v = HAProps('V', 'T', T, 'W', W, 'P', 101.325)
s = HAProps('S', 'T', T, 'W', W, 'P', 101.325)
print "{W:10.2f}{Twb:10.2f}{v:10.3f}{h:10.2f}{s:10.4f}{R:10.4f}".format(
W=W, Twb=Twb, v=v, h=h, s=s, R=R)
print '================================================================'
print ' '
print 'A.' + num + '.2 Psychrometric Properties of Moist Air at 1000 kPa '
print 'Dry Bulb temperature of ' + Temp + 'C'
print '================================================================'
print "{W:10s}{Twb:10s}{v:10s}{h:10s}{s:10s}{R:10s}".format(W=s5 + ' W',
Twb=s5 + 'Twb',
v=s5 + ' v',
h=s5 + 'h',
s=s5 + ' s',
R=s5 + 'RH')
print "{W:10s}{Twb:10s}{v:10s}{h:10s}{s:10s}{R:10s}".format(
W=' kgw/kg_da',
Twb=' C',
v=' m3/kgda',
h=' kJ/kgda',
s=' kJ/kgda/K',
R=' %')
print '----------------------------------------------------------------'
for W in [
0.0, 0.05, 0.1, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0
]:
h = HAProps('H', 'T', T, 'W', W, 'P', 1000)
Twb = HAProps('Twb', 'T', T, 'W', W, 'P', 1000) - 273.15
R = HAProps('R', 'T', T, 'W', W, 'P', 1000) * 100
v = HAProps('V', 'T', T, 'W', W, 'P', 1000)
s = HAProps('S', 'T', T, 'W', W, 'P', 1000)
print "{W:10.2f}{Twb:10.2f}{v:10.3f}{h:10.2f}{s:10.4f}{R:10.4f}".format(
W=W, Twb=Twb, v=v, h=h, s=s, R=R)
print '================================================================'
print ' '
s5 = ' ' * 5
print 'A.' + num + '.3 Psychrometric Properties of Moist Air at 2000 kPa '
print 'Dry Bulb temperature of ' + Temp + 'C'
print '================================================================'
print "{W:10s}{Twb:10s}{v:10s}{h:10s}{s:10s}{R:10s}".format(W=s5 + ' W',
Twb=s5 + 'Twb',
v=s5 + ' v',
h=s5 + 'h',
s=s5 + ' s',
R=s5 + 'RH')
print "{W:10s}{Twb:10s}{v:10s}{h:10s}{s:10s}{R:10s}".format(
W=' kgw/kg_da',
Twb=' C',
v=' m3/kgda',
h=' kJ/kgda',
s=' kJ/kgda/K',
R=' %')
print '----------------------------------------------------------------'
for W in [
0.0, 0.05, 0.1, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0
]:
h = HAProps('H', 'T', T, 'W', W, 'P', 2000)
Twb = HAProps('Twb', 'T', T, 'W', W, 'P', 2000) - 273.15
R = HAProps('R', 'T', T, 'W', W, 'P', 2000) * 100
v = HAProps('V', 'T', T, 'W', W, 'P', 2000)
s = HAProps('S', 'T', T, 'W', W, 'P', 2000)
print "{W:10.2f}{Twb:10.2f}{v:10.3f}{h:10.2f}{s:10.4f}{R:10.4f}".format(
W=W, Twb=Twb, v=v, h=h, s=s, R=R)
print '================================================================'
print ' '
s5 = ' ' * 5
print 'A.' + num + '.4 Psychrometric Properties of Moist Air at 5000 kPa '
print 'Dry Bulb temperature of ' + Temp + 'C'
print '================================================================'
print "{W:10s}{Twb:10s}{v:10s}{h:10s}{s:10s}{R:10s}".format(W=s5 + ' W',
Twb=s5 + 'Twb',
v=s5 + ' v',
h=s5 + 'h',
s=s5 + ' s',
R=s5 + 'RH')
print "{W:10s}{Twb:10s}{v:10s}{h:10s}{s:10s}{R:10s}".format(
W=' kgw/kg_da',
Twb=' C',
v=' m3/kgda',
h=' kJ/kgda',
s=' kJ/kgda/K',
R=' %')
print '----------------------------------------------------------------'
if Temp == '200':
Wrange = [0.0, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30]
else:
Wrange = [
0.0, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, 0.4, 0.5, 0.6, 0.7, 0.8,
0.9, 1.0
]
for W in Wrange:
h = HAProps('H', 'T', T, 'W', W, 'P', 5000)
Twb = HAProps('Twb', 'T', T, 'W', W, 'P', 5000) - 273.15
R = HAProps('R', 'T', T, 'W', W, 'P', 5000) * 100
v = HAProps('V', 'T', T, 'W', W, 'P', 5000)
s = HAProps('S', 'T', T, 'W', W, 'P', 5000)
print "{W:10.2f}{Twb:10.2f}{v:10.3f}{h:10.2f}{s:10.4f}{R:10.4f}".format(
W=W, Twb=Twb, v=v, h=h, s=s, R=R)
print '================================================================'
print ' '
s5 = ' ' * 5
print 'A.' + num + '.5 Psychrometric Properties of Moist Air at 10,000 kPa '
print 'Dry Bulb temperature of ' + Temp + 'C'
print '================================================================'
print "{W:10s}{Twb:10s}{v:10s}{h:10s}{s:10s}{R:10s}".format(W=s5 + ' W',
Twb=s5 + 'Twb',
v=s5 + ' v',
h=s5 + 'h',
s=s5 + ' s',
R=s5 + 'RH')
print "{W:10s}{Twb:10s}{v:10s}{h:10s}{s:10s}{R:10s}".format(
W=' kgw/kg_da',
Twb=' C',
v=' m3/kgda',
h=' kJ/kgda',
s=' kJ/kgda/K',
R=' %')
print '----------------------------------------------------------------'
if Temp == '200':
Wrange = [0.0, 0.05, 0.1]
else:
Wrange = [
0.0, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, 0.4, 0.5, 0.6, 0.7, 0.8,
0.9, 1.0
]
for W in Wrange:
h = HAProps('H', 'T', T, 'W', W, 'P', 10000)
Twb = HAProps('Twb', 'T', T, 'W', W, 'P', 10000) - 273.15
R = HAProps('R', 'T', T, 'W', W, 'P', 10000) * 100
v = HAProps('V', 'T', T, 'W', W, 'P', 10000)
s = HAProps('S', 'T', T, 'W', W, 'P', 10000)
print "{W:10.2f}{Twb:10.2f}{v:10.3f}{h:10.2f}{s:10.4f}{R:10.4f}".format(
W=W, Twb=Twb, v=v, h=h, s=s, R=R)
print '================================================================'
def getEnthalpy(self, temp, humidityRatio):
return HAProps('H', 'T', temp + 273.15, 'P', 101325, 'R',
humidityRatio) #J/kg dry air
def OBJECTIVE(x):
Tevap = x[0]
Tcond = x[1]
#Condensing heat transfer rate from enthalpies
rho_air = 1.1
#Use fixed effectiveness to get a guess for the condenser capacity
Qcond = epsilon * Cycle.Condenser.Fins.Air.Vdot_ha / rho_air * (
Cycle.Condenser.Fins.Air.Tdb - Tcond) * 1000
pevap = Props('P', 'T', Tevap, 'Q', 1.0, Cycle.Ref)
pcond = Props('P', 'T', Tcond, 'Q', 1.0, Cycle.Ref)
Cycle.Compressor.pin_r = pevap
Cycle.Compressor.pout_r = pcond
Cycle.Compressor.Tin_r = Tevap + Cycle.Evaporator.DT_sh
Cycle.Compressor.Ref = Cycle.Ref
Cycle.Compressor.Calculate()
W = Cycle.Compressor.W
# Evaporator fully-dry analysis
Qevap_dry = epsilon * Cycle.Evaporator.Fins.Air.Vdot_ha / rho_air * (
Cycle.Evaporator.Fins.Air.Tdb - Tevap) * 1000
#Air-side heat transfer UA
Evap = Cycle.Evaporator
Evap.mdot_r = Cycle.Compressor.mdot_r
Evap.psat_r = pevap
Evap.Ref = Cycle.Ref
Evap.Initialize()
UA_a = Evap.Fins.h_a * Evap.Fins.A_a * Evap.Fins.eta_a
Tin_a = Evap.Fins.Air.Tdb
Tout_a = Tin_a + Qevap_dry / (Evap.Fins.mdot_da * Evap.Fins.cp_da)
#Refrigerant-side heat transfer UA
UA_r = Evap.A_r_wetted * Correlations.ShahEvaporation_Average(
0.5, 0.5, Cycle.Ref, Evap.G_r, Evap.ID, Evap.psat_r,
Qevap_dry / Evap.A_r_wetted, Evap.Tbubble_r, Evap.Tdew_r)
#Get wall temperatures at inlet and outlet from energy balance
T_so_a = (UA_a * Evap.Tin_a + UA_r * Tevap) / (UA_a + UA_r)
T_so_b = (UA_a * Tout_a + UA_r * Tevap) / (UA_a + UA_r)
Tdewpoint = HAProps('D', 'T', Cycle.Evaporator.Fins.Air.Tdb, 'P',
101.325, 'R', Evap.Fins.Air.RH)
#Now calculate the fully-wet analysis
#Evaporator is bounded by saturated air at the refrigerant temperature.
h_ai = HAProps('H', 'T', Cycle.Evaporator.Fins.Air.Tdb, 'P', 101.325,
'R', Cycle.Evaporator.Fins.Air.RH) * 1000 #[J/kg_da]
h_s_w_o = HAProps('H', 'T', Tevap, 'P', 101.325, 'R',
1.0) * 1000 #[J/kg_da]
Qevap_wet = epsilon * Cycle.Evaporator.Fins.Air.Vdot_ha / rho_air * (
h_ai - h_s_w_o)
#Coil is either fully-wet, fully-dry or partially wet, partially dry
if T_so_a > Tdewpoint and T_so_b > Tdewpoint:
#Fully dry, use dry Q
f_dry = 1.0
elif T_so_a < Tdewpoint and T_so_b < Tdewpoint:
#Fully wet, use wet Q
f_dry = 0.0
else:
f_dry = 1 - (Tdewpoint - T_so_a) / (T_so_b - T_so_a)
Qevap = f_dry * Qevap_dry + (1 - f_dry) * Qevap_wet
Qcond_enthalpy = Cycle.Compressor.mdot_r * (
Cycle.Compressor.hout_r -
Props('H', 'T', Tcond - Cycle.DT_sc_target, 'P', pcond,
Cycle.Ref) * 1000)
resids = [Qevap + W + Qcond, Qcond + Qcond_enthalpy] #,Qevap,f_dry]
return resids
def PlainFins(Inputs):
#Source:
#Heat transfer and friction characteristics of plain fin-and-tube heat exchangers, part II: Correlation
#Chi-Chuan Wang, Kuan-Yu Chi, Chun-Jung Chang
#Properties:
p = Inputs.Air.p #air pressure
W = HAProps('W', 'T', Inputs.Air.Tdb, 'P', p, 'R', Inputs.Air.RH)
#Transport properties of humid air from CoolProp
mu_ha = HAProps('M', 'T', Inputs.Air.Tdb, 'P', p, 'W', W)
k_ha = HAProps('K', 'T', Inputs.Air.Tdb, 'P', p, 'W', W) * 10**3
#Evaluate the mass flow rate based on inlet conditions
Vdot_ha = Inputs.Air.Vdot_ha
# To convert a parameter from per kg_{humid air} to per kg_{dry air}, divide by (1+W)
W = HAProps('W', 'T', Inputs.Air.Tdb, 'P', p, 'R', Inputs.Air.RH)
v_da = HAProps('V', 'T', Inputs.Air.Tdb, 'P', p, 'W', W)
h_da = HAProps('H', 'T', Inputs.Air.Tdb, 'P', p, 'W', W) * 1000
rho_ha = 1 / v_da * (1 + W) #[m^3/kg_ha]
rho_da = 1 / v_da #[m^3/kg_da]
mdot_ha = Vdot_ha * rho_ha #[kg_ha/s]
mdot_da = Vdot_ha * rho_da #[kg_da/s]
#Use a forward difference to calculate cp from cp=dh/dT
dT = 0.0001 #[K]
cp_da = (HAProps('H', 'T', Inputs.Air.Tdb + dT, 'P', p, 'W', W) * 1000 -
h_da) / dT #[J/kg_da/K]
cp_ha = cp_da / (1 + W) #[J/kg_ha/K]
# Check that cs_cp is defined, if so, set it to the value passed in
if (hasattr(Inputs, 'cs_cp')
and Inputs.cs_cp > 0) or (hasattr(Inputs, 'WetDry')
and Inputs.WetDry == 'Wet'):
isWet = True
cs_cp = Inputs.Air.cs_cp
else:
isWet = False
cs_cp = 1.0
#Dimensions and values used for both Reynolds number ranges:
delta_f = Inputs.Fins.t #fin thickness(m)
FPI = Inputs.Fins.FPI #fins per inch
FPM = FPI / 0.0254 #Fins per meter [1/m]
F_p = 1 / FPM #Fin pitch (distance between centerlines of fins)
F_s = 1 / FPM - delta_f #Fin spacing(m)
P_t = Inputs.Tubes.Pt #transverse tube pitch (m)
P_L = Inputs.Tubes.Pl #longitudinal tube pitch (m)
D_o = Inputs.Tubes.OD #Outer diameter of tube (m)
D_c = D_o + 2 * delta_f #fin collar outside diameter (m) (tube + 2*fin thickness)
Ltube = Inputs.Tubes.Ltube #length of a single tube [m]
Nfin = Ltube * FPM #Number of fins in the tube sheet [-]
Ntubes_bank = Inputs.Tubes.NTubes_per_bank #tubes per bank
Height = P_t * (
Ntubes_bank + 1
) #Height of heat exchanger [m] # assuming that fin extends 1/2 pt above/below last tube in bundle
A_duct = Height * Ltube #A_duct is the face area [m^2] - equivalent to the duct cross-section #neglecting the additional height of the fins above/below the last tubes in the bundle
A_c = A_duct - delta_f * Nfin * (
Height - D_c * Ntubes_bank
) - Ntubes_bank * D_c * Ltube #Minimum duct cross-sectional area that is not fin or tube(-collar) [m^2]
u_max = mdot_ha / (rho_ha * A_c) #maximum airside velocity [m/s]
Re_Dc = rho_ha * u_max * D_c / mu_ha #from reference #4 of Wang et all. Slightly different notation used in [4]
N = Inputs.Tubes.Nbank #number of lomgitudunal tube rows (#Number of banks in ACHP-notation)
L = (
N + 1
) * P_L #depth of heat exchanger in airflow direction, assuming fins extends 1/2 bank oer the first and last tube
Nbank = N #to be able to reuse equations
#Wetted Area of a single fin [m^2]
A_1fin = 2.0 * (
Height * P_L * (Nbank + 1) - Ntubes_bank * Nbank * pi * D_c * D_c / 4
) #assuming that fin extends 1/2 pt in front/after last tube in bundle
# Total wetted area of the fins [m^2]
Af = Nfin * A_1fin
#Total area including tube and fins [m^2]
A_o = Af + Ntubes_bank * Nbank * pi * D_c * (Ltube - Nfin * delta_f)
D_h = 4 * A_c * L / A_o #Hydraulic diameter
#heat transfer
if N == 1:
P1 = 1.9 - 0.23 * log(Re_Dc)
P2 = -0.236 + 0.126 * log(Re_Dc)
j = 0.108 * pow(Re_Dc, -0.29) * pow(P_t / P_L, P1) * pow(
F_p / D_h, -1.084) * pow(F_p / D_h, -0.786) * pow(F_p / P_t, P2)
if N >= 2:
P3 = -0.361 - 0.042 * N / log(Re_Dc) + 0.158 * log(N *
(F_p / D_c)**0.41)
P4 = -1.224 - 0.076 * pow(P_L / D_h, 1.42) / log(Re_Dc)
P5 = -0.083 + 0.058 * N / log(Re_Dc)
P6 = -5.735 + 1.21 * log(Re_Dc / N)
j = 0.086 * pow(Re_Dc, P3) * pow(N, P4) * pow(F_p / D_c, P5) * pow(
F_p / D_h, P6) * pow(F_p / P_t, -0.93)
#pressure drop
F1 = -0.764 + 0.739 * P_t / P_L + 0.177 * F_p / D_c - 0.00758 / N
F2 = -15.689 + 64.021 / log(Re_Dc)
F3 = 1.696 - 15.695 * log(Re_Dc)
f = 0.0267 * pow(Re_Dc, F1) * pow(P_t / P_L, F2) * pow(F_p / D_c, F3)
Pr = cp_ha * mu_ha / k_ha
h_a = j * rho_ha * u_max * cp_ha / pow(
Pr, 2.0 /
3.0) #air side mean heat transfer coefficient using colborn j-factor
#calcs needed for specific fin types
#additional parameters needed
k_fin = Inputs.Fins.k_fin
#Total area including tube and fins [m^2]
A = A_o
r = D_o / 2
X_D = sqrt(P_L * P_L + P_t * P_t / 4) / 2
X_T = P_t / 2
rf_r = 1.27 * X_T / r * sqrt(X_D / X_T - 0.3)
m = sqrt(
2 * h_a * cs_cp /
(k_fin * delta_f)) #cs_cp is the correction for heat/mass transfer
#Using the circular fin correlation of Schmidt
phi = (rf_r - 1) * (1 + 0.35 * log(rf_r))
eta_f = tanh(m * r * phi) / (m * r * phi)
# Fin efficiency based on analysis in
# "FIN EFFICIENCY CALCULATION IN ENHANCED FIN-AND-TUBE HEAT EXCHANGERS IN DRY CONDITIONS"
# by Thomas PERROTIN, Denis CLODIC, International Congress of Refrigeration 2006
# In the paper, there is no 0.1 in the cosine term, but if the cosine term is used without
# the correction, the results are garbage for wet analysis
# Using the offset fins correlation
phi = (rf_r - 1) * (1 +
(0.3 + pow(m *
(rf_r * r - r) / 2.5, 1.5 - rf_r / 12.0) *
(0.26 * pow(rf_r, 0.3) - 0.3)) * log(rf_r))
#finned surface efficiency
eta_f = tanh(m * r * phi) / (m * r * phi) * cos(0.1 * m * r * phi)
#overall surface efficiency
eta_o = 1 - Af / A * (1 - eta_f)
G_c = mdot_ha / A_c #air mass flux
Atube = Ntubes_bank * Nbank * pi * D_o * Ltube # Total outer area of the tubes [m^2]
DeltaP_air = A / Atube / rho_ha * G_c**2 / 2.0 * f #airside pressure drop
#write necessary values back into the given structure
Inputs.A_a = A
Inputs.cp_da = cp_da
Inputs.cp_ha = cp_ha
if isWet == True:
Inputs.eta_a_wet = eta_o
else:
Inputs.eta_a = eta_o
Inputs.h_a = h_a
Inputs.mdot_ha = mdot_ha
Inputs.mdot_da = mdot_da
Inputs.f_a = f
Inputs.dP_a = DeltaP_air
Inputs.Re = Re_Dc
print "Warning! The PlainFins seem to be buggy, better use HerringboneFins with small waveiness"
# -*- coding: utf-8 -*-
"""
Created on Tue Jun 10 12:05:27 2014
@author: nfette
"""
#import the things you need
from CoolProp.HumidAirProp import HAProps, HAProps_Aux
#Enthalpy (kJ per kg dry air) as a function of temperature, pressure,
# and relative humidity at dry bulb temperature T of 25C, pressure
# P of one atmosphere, relative humidity R of 50%
h = HAProps('H', 'T', 298.15, 'P', 101.325, 'R', 0.5)
print h
# 50.4249283433
#Temperature of saturated air at the previous enthalpy
T = HAProps('T', 'P', 101.325, 'H', h, 'R', 1.0)
print T
# 290.962168888
#Temperature of saturated air - order of inputs doesn't matter
T = HAProps('T', 'H', h, 'R', 1.0, 'P', 101.325)
print T
# 290.962168888
print 'Saturated air at 101.325 kPa'
s5 = ' ' * 5
print '===================================================='
print "{T:8s}{W:10s}{v:10s}{h:10s}{s:10s}".format(W=s5 + ' Ws',
v=s5 + ' v',
h=s5 + 'h',
s=s5 + ' s',
T=' T')
print "{T:8s}{W:10s}{v:10s}{h:10s}{s:10s}".format(W=' kgw/kg_da',
v=' m3/kgda',
h=' kJ/kgda',
s=' kJ/kgda/K',
T=' C')
print '----------------------------------------------------'
for T in np.linspace(-60, 0, 13) + 273.15:
h = HAProps('H', 'T', T, 'R', 1.0, 'P', 101.325)
Twb = HAProps('Twb', 'T', T, 'R', 1.0, 'P', 101.325) - 273.15
W = HAProps('W', 'T', T, 'R', 1.0, 'P', 101.325)
v = HAProps('V', 'T', T, 'R', 1.0, 'P', 101.325)
s = HAProps('S', 'T', T, 'R', 1.0, 'P', 101.325)
print "{T:8.0f}{W:10.7f}{v:10.4f}{h:10.3f}{s:10.4f}".format(W=W,
T=T - 273.15,
v=v,
h=h,
s=s)
print '===================================================='
print ' '
print 'A.6.2 Psychrometric Properties of Moist Air at 0C and Above'
print 'Saturated air at 101.325 kPa'
s5 = ' ' * 5
print '===================================================='
def WavyLouveredFins(Inputs):
"""
# Correlations from:
# Chi-Chuan Wang and Yu-Min Tsai and Ding-Chong Lu, 1998, "Comprehensive
# Study of Convex-Louver and Wavy Fin-and-Tube Heat Exchangers", Journal
# of Thermophysics and Heat Transfer
|| - xf ->
^ == ==
| == | == ==
Pd == | == ==
| == | == ==
= == s ==
|
|
|
== ==
== == ==
== == ==
== == ==
== ==
t: thickness of fin plate
Pf: fin pitch (centerline-to-centerline distance between fins)
Pd: indentation for waviness (not including fin thickness)
s: fin spacing (free space between fins) = Pf-t
|-- Pl -|
___ |
/ \ |
= | | |
| \ ___ / |
| |
| ___
| / \ |
Pt | | D
| \ ___ / |
|
| ___
| / \
= | |
\ ___ /
"""
Ntubes_bank = Inputs.Tubes.NTubes_per_bank #tubes per bank
Nbank = Inputs.Tubes.Nbank #Number of banks
Ltube = Inputs.Tubes.Ltube #length of a single tube
D = Inputs.Tubes.OD #Outer diameter of tube
Pl = Inputs.Tubes.Pl #Horizontal spacing between banks (center to center)
Pt = Inputs.Tubes.Pt #Vertical spacing between tubes in a bank (center to center)
FPI = Inputs.Fins.FPI
pd = Inputs.Fins.Pd
xf = Inputs.Fins.xf
t = Inputs.Fins.t
k_fin = Inputs.Fins.k_fin
Vdot_ha = Inputs.Air.Vdot_ha
p = Inputs.Air.p
if hasattr(Inputs, 'Tmean'):
Temp = Inputs.Air.Tmean
else:
Temp = Inputs.Air.Tdb
if hasattr(Inputs, 'RHmean'):
RHin = Inputs.Air.RHmean
else:
RHin = Inputs.Air.RH
# Check that cs_cp is defined, if so, set it to the value passed in
if (hasattr(Inputs, 'cs_cp')
and Inputs.cs_cp > 0) or (hasattr(Inputs, 'WetDry')
and Inputs.WetDry == 'Wet'):
isWet = True
cs_cp = Inputs.Air.cs_cp
else:
isWet = False
cs_cp = 1.0
#Film temperature [K]
Tfilm = Temp
#Fins per meter [1/m]
FPM = FPI / 0.0254
#Fin pitch (distance between centerlines of fins)
pf = 1 / FPM
#Spacing between fins
s = 1 / FPM - t
#Height of heat exchanger [m]
Height = Pt * (
Ntubes_bank + 1
) #assuming that fin extends 1/2 pt above/below last tube in bundle
#A_duct is the face area [m^2] equivalent to the duct cross-section
A_duct = Height * Ltube #neglecting the additional height of the fins above/below the last tubes in the bundle
#Number of fins in the tube sheet [-]
Nfin = Ltube * FPM
#Secant of theta is the area enhancement factor [-]
# It captures the increase in area due to the waviness of the fins
sec_theta = sqrt(xf * xf + pd * pd) / xf
# Duct cross-sectional area that is not fin or tube [m^2]
Ac = A_duct - t * Nfin * (Height -
D * Ntubes_bank) - Ntubes_bank * D * Ltube
# Total outer area of the tubes [m^2]
Atube = Ntubes_bank * Nbank * pi * D * Ltube
#Wetted Area of a single fin [m^2]
A_1fin = 2.0 * (
Height * Pl *
(Nbank + 1) * sec_theta - Ntubes_bank * Nbank * pi * D * D / 4
) #assuming that fin extends 1/2 pt in front/after last tube in bundle
# Total wetted area of the fins [m^2]
Af = Nfin * A_1fin
#Total area including tube and fins [m^2]
A = Af + Ntubes_bank * Nbank * pi * D * (Ltube - Nfin * t)
#Evaluate the mass flow rate based on inlet conditions
# To convert a parameter from per kg_{humid air} to per kg_{dry air}, divide by (1+W)
W = HAProps('W', 'T', Inputs.Air.Tdb, 'P', p, 'R', Inputs.Air.RH)
v_da = HAProps('V', 'T', Inputs.Air.Tdb, 'P', p, 'W', W)
h_da = HAProps('H', 'T', Inputs.Air.Tdb, 'P', p, 'W', W) * 1000
rho_ha = 1 / v_da * (1 + W) #[m^3/kg_ha]
rho_da = 1 / v_da #[m^3/kg_da]
mdot_ha = Vdot_ha * rho_ha #[kg_ha/s]
mdot_da = Vdot_ha * rho_da #[kg_da/s]
umax = mdot_ha / (rho_ha * Ac) #[m/s]
#Use a forward difference to calculate cp from cp=dh/dT
dT = 0.0001 #[K]
cp_da = (HAProps('H', 'T', Inputs.Air.Tdb + dT, 'P', p, 'W', W) * 1000 -
h_da) / dT #[J/kg_da/K]
cp_ha = cp_da / (1 + W) #[J/kg_ha/K]
#Transport properties of humid air from CoolProp
mu_ha = HAProps('M', 'T', Inputs.Air.Tdb, 'P', p, 'W', W)
k_ha = HAProps('K', 'T', Inputs.Air.Tdb, 'P', p, 'W', W) * 10**3
#Dimensionless Groups
Pr = cp_ha * mu_ha / k_ha
Re_D = rho_ha * umax * D / mu_ha
#Heat transfer
j = 16.06 * pow(Re_D, -1.02 *
(pf / D) - 0.256) * pow(A / Atube, -0.601) * pow(
Nbank, -0.069) * pow(pf / D, 0.84) #Colburn j-Factor
h_a = j * rho_ha * umax * cp_ha / pow(
Pr, 2.0 / 3.0) #air side mean heat transfer coefficient
#air side pressure drop correlations
if (Re_D < 1e3):
fa_total = 0.264 * (0.105 + 0.708 * exp(-Re_D / 225.0)) * pow(
Re_D, -0.637) * pow(A / Atube, 0.263) * pow(pf / D, -0.317)
else:
fa_total = 0.768 * (0.0494 + 0.142 * exp(-Re_D / 1180.0)) * pow(
A / Atube, 0.0195) * pow(pf / D, -0.121)
#calcs needed for specific fin types
r = D / 2
X_D = sqrt(Pl * Pl + Pt * Pt / 4) / 2
X_T = Pt / 2
rf_r = 1.27 * X_T / r * sqrt(X_D / X_T - 0.3)
m = sqrt(2 * h_a * cs_cp /
(k_fin * t)) #cs_cp is the correction for heat/mass transfer
#Using the circular fin correlation of Schmidt
phi = (rf_r - 1) * (1 + 0.35 * log(rf_r))
eta_f = tanh(m * r * phi) / (m * r * phi)
# Fin efficiency based on analysis in
# "FIN EFFICIENCY CALCULATION IN ENHANCED FIN-AND-TUBE HEAT EXCHANGERS IN DRY CONDITIONS"
# by Thomas PERROTIN, Denis CLODIC, International Congress of Refrigeration 2006
# In the paper, there is no 0.1 in the cosine term, but if the cosine term is used without
# the correction, the results are garbage for wet analysis
# Using the offset fins correlation
phi = (rf_r - 1) * (1 +
(0.3 + pow(m *
(rf_r * r - r) / 2.5, 1.5 - rf_r / 12.0) *
(0.26 * pow(rf_r, 0.3) - 0.3)) * log(rf_r))
#finned surface efficiency
eta_f = tanh(m * r * phi) / (m * r * phi) * cos(0.1 * m * r * phi)
#overall surface efficiency
eta_o = 1 - Af / A * (1 - eta_f)
G_c = mdot_ha / Ac #air mass flux
DeltaP_air = A / Atube / rho_ha * G_c**2 / 2.0 * fa_total #airside pressure drop
#write necessary values back into the given structure
Inputs.A_a = A
Inputs.cp_da = cp_da
Inputs.cp_ha = cp_ha
if isWet == True:
Inputs.eta_a_wet = eta_o
else:
Inputs.eta_a = eta_o
Inputs.h_a = h_a
Inputs.mdot_ha = mdot_ha
Inputs.mdot_da = mdot_da
Inputs.f_a = fa_total
Inputs.dP_a = DeltaP_air
Inputs.Re = Re_D
def Calculate(self):
#calculate evaporator without consideration of pressure drop for HT
self.Initialize()
# Input and output thermodynamic properties
ssatL=Props('S','T',self.Tbubble_r,'Q',0,self.Ref)*1000
ssatV=Props('S','T',self.Tdew_r,'Q',1,self.Ref)*1000
hsatL=Props('H','T',self.Tbubble_r,'Q',0,self.Ref)*1000
hsatV=Props('H','T',self.Tdew_r,'Q',1,self.Ref)*1000
#Must give enthalpy and pressure as inputs
#print "in evaporator-enthalpies","hin_r,hsatL,hsatV",self.hin_r,hsatL,hsatV,"self.Tbubble_r,self.psat_r",self.Tbubble_r,self.psat_r
#print "self.__dict__ in Evaporator.py",self.__dict__
#print "hin_r in Evaporator.py",self.hin_r
self.xin_r=(self.hin_r-hsatL)/(hsatV-hsatL)
self.sin_r=self.xin_r*ssatV+(1-self.xin_r)*ssatL
self.hin_r=self.xin_r*hsatV+(1-self.xin_r)*hsatL
self.Tin_r=self.xin_r*self.Tdew_r+(1-self.xin_r)*self.Tbubble_r
#Begin by assuming that you go all the way to saturated vapor at least
self.xout_2phase=1.0
if self.Tin_a<(self.Tin_r+0.3):
#too close to saturation temperature - set capacity to 0
print "!!!!!!!!!!!!!!!!!!!!!warning - setting capacity to 0 and neglecting pressure drop in evaporator!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
if self.xin_r<1.0:
#since no capacity, everything just goes out as it came in
self.w_2phase=1.0
self.w_superheat=0.0
existsSuperheat=False
else:
self.w_2phase=0.0
self.w_superheat=1.0
existsSuperheat=True
self.Q_2phase=0
self.Charge_2phase=0
self.Q_sensible_2phase=0
self.h_r_2phase=0.0
self.DP_r_2phase=0.0
self.xout_2phase=99 #EES-style
self.Tout_a_2phase=self.Tin_a #since we have no two-phase capacity
self.omega_out_2phase=0.0
self.Q_superheat=0.0
self.h_r_superheat=0.0
self.Re_r_superheat=0.0
self.Charge_superheat=0.0
self.Q_sensible_superheat=0.0
self.Tout_a_superheat=0.0
self.DP_r_superheat=0.0
self.fdry_superheat=0.0
self.omega_out_superheat=0.0
elif self.xin_r<1.0 and self._TwoPhase_Forward(1.0)<0:
#print "assuming two-phase",self.xin_r
# Evaporator outlet is in two-phase region, use all the area and find the outlet quality
existsSuperheat=False
self.w_2phase=1.0
def OBJECTIVE(xout):
self.xout_2phase=xout
Q_target=self.mdot_r*(xout-self.xin_r)*(hsatV-hsatL)
self._TwoPhase_Forward(self.w_2phase)
#print "in Evaporator xout_objective",self.xin_r,xout,self.Q_2phase,Q_target
return self.Q_2phase-Q_target
#Use a solver to find outlet quality
brentq(OBJECTIVE,self.xin_r,1.0)
self.w_superheat=0.0
self.Q_superheat=0.0
self.h_r_superheat=0.0
self.Re_r_superheat=0.0
self.Charge_superheat=0.0
self.Q_sensible_superheat=0.0
self.Tout_a_superheat=0.0
self.DP_r_superheat=0.0
self.fdry_superheat=0.0
self.omega_out_superheat=0.0
else: #have superheated inlet conditions
existsSuperheat=True
# Evaporator outlet is in superheated region, everything is ok
if self.xin_r<1.0: #need to find outlet quality
self.w_2phase=brentq(self._TwoPhase_Forward,0.00000000001,0.9999999999)
if hasattr(self, 'plotit'):
if self.plotit==True:
#plot how self._TwoPhase_Forward behaves
import pylab as plt
w_guesses=np.linspace(0.00000000001,0.9999999999,20)
w_resids=np.zeros(len(w_guesses))
for i in range(len(w_guesses)):
w_resids[i]=self._TwoPhase_Forward(w_guesses[i])
print "w_resids",w_resids
fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot(w_guesses, w_resids)
ax.set_title("residual for 2-phase fraction")
plt.show()
T_inlet_r=self.Tdew_r #saturated inlet to sensible section
else: #have superheated conditions, two phase section doesn't exist
self.w_2phase=0.0
self.Q_2phase=0
self.Charge_2phase=0
self.Q_sensible_2phase=0
self.h_r_2phase=0.0
self.DP_r_2phase=0.0
self.xout_2phase=99 #EES-style
self.Tout_a_2phase=self.Tin_a #since we have no two-phase capacity
self.omega_out_2phase=0.0
T_inlet_r=Props('T','H',self.hin_r/1000.0, 'P', self.psat_r, self.Ref) #calculated inlet temperature based on enthalpy
if self.Tin_a<T_inlet_r:
print "Evap: inlet air temperature smaller than refrigerant temperature, two phase doesn't exist",self.Tin_a,"<",T_inlet_r,"self.hin_r/1000.0",self.hin_r/1000.0,"self.psat_r",self.psat_r
raise ValueError
if self.cp_r_iter: #solve for proper cp
print "using iteration to find better estimate for cp_r"
try:
def objective_cp(x0):
self.cp_r=1000.0*(Props('C','T',self.Tdew_r+x0*0.3333, 'P', self.psat_r, self.Ref)+Props('C','T',self.Tdew_r+x0, 'P', self.psat_r, self.Ref)+Props('C','T',self.Tdew_r+1.66667*x0, 'P', self.psat_r, self.Ref))/3.0 #average value
self._Superheat_Forward(1-self.w_2phase)
return self.Tdew_r-2*x0-self.Tout_r
brentq_result=brentq(objective_cp,0,50)
print "accuracy of cp-iteration loop of evaporator -objective_cp(brentq_result)",objective_cp(brentq_result),brentq_result, -(self.Tdew_r-self.Tout_r)/2.0,self.cp_r
except:
#if above approach does not work, do not iterate.
self.cp_r=1000.0*Props('C','T',self.Tdew_r+3, 'P', self.psat_r, self.Ref)
print "warning-cp_r iter in Evaporator did not work. using non-iteratively solved value for superheat instead", self.cp_r,self.w_2phase
self._Superheat_Forward(1-self.w_2phase,T_inlet_r)
else: #use fixed point cp assuming 6K superheat
self.cp_r=1000.0*Props('C','T',self.Tdew_r+3, 'P', self.psat_r, self.Ref)
self._Superheat_Forward(1-self.w_2phase,T_inlet_r)
self.Q=self.Q_superheat+self.Q_2phase
self.Charge=self.Charge_superheat+self.Charge_2phase
if self.Verbosity>4:
print self.Q,"Evaporator.Q"
self.Capacity=self.Q-self.Fins.Air.FanPower
#Sensible heat ratio [-]
if self.Q>0.0:
self.SHR=(self.Q_sensible_2phase+self.Q_sensible_superheat)/self.Q
else:
self.SHR=1.0 #
#Average air outlet values (area fraction weighted average, neglecting influence of different air mass flowrate due to viscosity/density changes with change of omega or temperature)
self.Tout_a=self.w_superheat*self.Tout_a_superheat+self.w_2phase*self.Tout_a_2phase
self.omega_out=self.w_superheat*self.omega_out_superheat+self.w_2phase*self.omega_out_2phase
self.Fins.Air.RH_out=HAProps('R','T',self.Tout_a,'P',101.325,'W',self.omega_out) #neglect pressure drop across evaporator
self.DP_r=self.DP_r_superheat+self.DP_r_2phase
self.pout_r=self.psat_r+self.DP_r/1000.0 #pressure drop negative and in Pa
#limit minimum outlset pressure
if self.pout_r<10:
print "warning - outlet pressure in evaporator too low - limiting to allow for solver to find correct value"
self.pout_r=30#kPa
#Outlet enthalpy obtained from energy balance
self.hout_r=self.hin_r+self.Q/self.mdot_r
#print "debug Evaporator - self.hin_r,",self.hin_r/1000.0,self.hout_r/1000.0," self.Tin_a", self.Fins.Air.Tdb,"self.Fins.mdot_ha",self.Fins.mdot_ha
#Outlet superheat an temperature (in case of two phase)
if existsSuperheat:
try:
self.Tout_r=newton(lambda T: Props('H','T',T,'P',self.pout_r,self.Ref)-self.hout_r/1000.0,Props('T','P',self.pout_r,'Q',1.0,self.Ref))
except:
print "problem iwith calculating Tout_r in evaporator.py"
print "self.hout_r/1000.0",self.hout_r/1000.0,"self.hin_r/1000.0",self.hin_r/1000.0,"Props('H','Q',1.0,'P',self.pout_r,self.Ref)",Props('H','Q',1.0,'P',self.pout_r,self.Ref),"self.pout_r",self.pout_r,"self.psat_r",self.psat_r,"self.mdot_r",self.mdot_r,"self.xin_r",self.xin_r
print "Props('H','Q',0.0,'P',self.pout_r,self.Ref)",Props('H','Q',0.0,'P',self.pout_r,self.Ref),"self.Tin_a,self.Tsat_r",self.Tin_a,self.Tsat_r,"self.DP_r/1000.0",self.DP_r/1000.0,self.Q,self.Q_superheat,self.Q_2phase,existsSuperheat,self.w_2phase
print self.Fins.cp_da
print "neglecting pressure drop in sh-section for normal evaproator (no issue for Calcuilate_PD, since result will be overwritten)"
if self.w_2phase<1e-11:
print "neglecting capacity of two phase section, since likely not converged properly due to small fraction of two-phase area (self.w_2phase=",self.w_2phase
self.Q_2phase=0.0
self.Q=self.Q_superheat+self.Q_2phase
#recalculate Outlet enthalpy obtained from energy balance
self.hout_r=self.hin_r+self.Q/self.mdot_r
print "self.hout_r",self.hout_r
self.Tout_r=newton(lambda T: Props('H','T',T,'P',self.psat_r,self.Ref)-self.hout_r/1000.0,Props('T','P',self.psat_r,'Q',1.0,self.Ref))
self.sout_r=Props('S','T',self.Tout_r,'P',self.pin_r,self.Ref)*1000.0
self.DT_sh_calc=self.Tout_r-self.Tdew_r
else:
xout_r=(self.hout_r-hsatL)/(hsatV-hsatL)
self.sout_r=ssatV*xout_r+(1-xout_r)*ssatL
self.DT_sh_calc=(self.hout_r-hsatV)/(Props('C','T',self.Tdew_r,'Q',1,self.Ref)*1000.0) #continuous superheat
self.Tout_r=Props('T','P',self.pout_r,'Q',xout_r,self.Ref) #saturated temperature at outlet quality
self.hmean_r=self.w_2phase*self.h_r_2phase+self.w_superheat*self.h_r_superheat
self.UA_r=self.hmean_r*self.A_r_wetted
self.UA_a=self.Fins.h_a*self.Fins.A_a*self.Fins.eta_a
#Build a vector of temperatures at each point where there is a phase transition along the averaged circuit
if existsSuperheat:
#Insert the shoulder point
Tv=[self.Tin_r,self.Tdew_r,self.Tout_r]
x=[0,max(self.w_2phase,0.9999999),1]
else:
Tv=[self.Tin_r,xout_r*self.Tdew_r+(1-xout_r)*self.Tbubble_r]
x=[0,1]
#Determine each bend temperature by interpolation
#------------------------------------------------
#Number of bends (including inlet and outlet of coil)
Nbends=1+self.Lcircuit/self.Ltube
#x-position of each point
xv=np.linspace(0,1,Nbends)
self.Tbends=interp1d(x,Tv)(xv)
self.existsSuperheat=existsSuperheat #needed for Calculate_PD()
def calculatePlot(cls, parent):
"""Funtion to calculate points in chart"""
data = {}
P = Preferences.getfloat("General", "P")
P_kPa = P/1000
t = cls.LineList("isotdb", Preferences)
# Saturation line
Hs = []
for tdb in t:
Hs.append(HAProps("W", "P", P_kPa, "Tdb", tdb, "RH", 1))
parent.progressBar.setValue(5*len(Hs)/len(t))
data["t"] = t
data["Hs"] = Hs
# left limit of isow lines
H = cls.LineList("isow", Preferences)
th = []
for w in H:
if w:
tdp = HAProps("Tdp", "P", 101.325, "W", w, "RH", 1)
th.append(tdp-273.15)
else:
tmin = Preferences.getfloat("Psychr", "isotdbStart")
th.append(tmin-273.15)
data["H"] = H
data["th"] = th
# Humidity ratio lines
hr = cls.LineList("isohr", Preferences)
Hr = {}
cont = 0
for i in hr:
Hr[i] = []
for tdb in t:
Hr[i].append(HAProps("W", "P", P_kPa, "Tdb", tdb, "RH", i/100.))
cont += 1
parent.progressBar.setValue(5+10*cont/len(hr)/len(Hs))
data["Hr"] = Hr
# Twb
lines = cls.LineList("isotwb", Preferences)
Twb = {}
cont = 0
for T in lines:
ws = HAProps("W", "P", P_kPa, "RH", 1, "Tdb", T)
H = [ws, 0]
Tw = [T-273.15, HAProps("Tdb", "P", P_kPa, "Twb", T, "RH", 0)-273.15]
cont += 1
parent.progressBar.setValue(15+75*cont/len(lines))
Twb[T] = (H, Tw)
data["Twb"] = Twb
# v
lines = cls.LineList("isochor", Preferences)
V = {}
rh = np.arange(1, -0.05, -0.05)
for cont, v in enumerate(lines):
w = []
Td = []
for r in rh:
w.append(HAProps("W", "P", P_kPa, "RH", r, "V", v))
Td.append(HAProps("Tdb", "P", P_kPa, "RH", r, "V", v)-273.15)
parent.progressBar.setValue(90+10*cont/len(lines))
V[v] = (Td, w)
data["v"] = V
return data