def __init__(self, json_data_pipe, json_data_fluid, initial_temp,
print_output):
BasePropertiesClass.__init__(self, json_data_pipe, print_output)
self.fluid = FluidsClass(json_data_fluid, initial_temp, print_output)
try:
self.outer_diameter = json_data_pipe['Outside Diameter']
except: # pragma: no cover
PrintClass.my_print("....'Outside Diameter' key not found", 'warn')
PrintClass.fatal_error(message="Error initializing PipeClass")
try:
self.thickness = json_data_pipe['Wall Thickness']
except: # pragma: no cover
PrintClass.my_print("....'Wall Thickness' key not found", 'warn')
PrintClass.fatal_error(message="Error initializing PipeClass")
self.outer_radius = self.outer_diameter / 2
self.inner_radius = self.outer_radius - self.thickness
self.inner_diameter = self.outer_diameter - 2 * self.thickness
self.resist_pipe_convection = None
self.resist_pipe_conduction = None
self.resist_pipe = None
self.calc_pipe_resistance()
def test_cond(self):
"""
Tests fluid conductivity calculations
Reference values come from Cengel & Ghajar 2015
Cengel, Y.A., & Ghajar, A.J. 2015. Heat and Mass Transfer, Fundamentals and Applications.
McGraw-Hill. New York, New York.
"""
dict_fluid = {
'Type': 'Water',
'Concentration': 100,
'Flow Rate': 0.000303
}
tolerance = 1E-2
curr_tst = FluidsClass(dict_fluid, 20, False)
self.assertAlmostEqual(curr_tst.cond(), 0.598, delta=tolerance)
curr_tst.temperature = 40
self.assertAlmostEqual(curr_tst.cond(), 0.631, delta=tolerance)
curr_tst.temperature = 60
self.assertAlmostEqual(curr_tst.cond(), 0.654, delta=tolerance)
curr_tst.temperature = 80
self.assertAlmostEqual(curr_tst.cond(), 0.670, delta=tolerance)
def test_dens(self):
"""
Tests fluid density calculation routine
Reference values come from Cengel & Ghajar 2015
Cengel, Y.A., & Ghajar, A.J. 2015. Heat and Mass Transfer, Fundamentals and Applications.
McGraw-Hill. New York, New York.
"""
dict_fluid = {
'Type': 'Water',
'Concentration': 100,
'Flow Rate': 0.000303
}
tolerance = 1.0
curr_tst = FluidsClass(dict_fluid, 20, False)
self.assertAlmostEqual(curr_tst.dens(), 998.0, delta=tolerance)
curr_tst.temperature = 40
self.assertAlmostEqual(curr_tst.dens(), 992.1, delta=tolerance)
curr_tst.temperature = 60
self.assertAlmostEqual(curr_tst.dens(), 983.3, delta=tolerance)
curr_tst.temperature = 80
self.assertAlmostEqual(curr_tst.dens(), 971.8, delta=tolerance)
def test_cp(self):
"""
Tests fluid specific heat calculation routine
Reference values come from Cengel & Ghajar 2015
Cengel, Y.A., & Ghajar, A.J. 2015. Heat and Mass Transfer, Fundamentals and Applications.
McGraw-Hill. New York, New York.
"""
dict_fluid = {
'Type': 'Water',
'Concentration': 100,
'Flow Rate': 0.000303
}
tolerance = 4.0
curr_tst = FluidsClass(dict_fluid, 20, False)
self.assertAlmostEqual(curr_tst.cp(), 4182, delta=tolerance)
curr_tst.temperature = 40
self.assertAlmostEqual(curr_tst.cp(), 4179, delta=tolerance)
curr_tst.temperature = 60
self.assertAlmostEqual(curr_tst.cp(), 4185, delta=tolerance)
curr_tst.temperature = 80
self.assertAlmostEqual(curr_tst.cp(), 4197, delta=tolerance)
def test_pr(self):
"""
Tests fluid Prandtl number calculations
Reference values come from Cengel & Ghajar 2015
Cengel, Y.A., & Ghajar, A.J. 2015. Heat and Mass Transfer, Fundamentals and Applications.
McGraw-Hill. New York, New York.
"""
dict_fluid = {
'Type': 'Water',
'Concentration': 100,
'Flow Rate': 0.000303
}
tolerance = 1E-1
curr_tst = FluidsClass(dict_fluid, 20, False)
self.assertAlmostEqual(curr_tst.pr(), 7.01, delta=tolerance)
curr_tst.temperature = 40
self.assertAlmostEqual(curr_tst.pr(), 4.32, delta=tolerance)
curr_tst.temperature = 60
self.assertAlmostEqual(curr_tst.pr(), 2.99, delta=tolerance)
curr_tst.temperature = 80
self.assertAlmostEqual(curr_tst.pr(), 2.22, delta=tolerance)
class PipeClass(BasePropertiesClass):
def __init__(self, json_data_pipe, json_data_fluid, initial_temp,
print_output):
BasePropertiesClass.__init__(self, json_data_pipe, print_output)
self.fluid = FluidsClass(json_data_fluid, initial_temp, print_output)
try:
self.outer_diameter = json_data_pipe['Outside Diameter']
except: # pragma: no cover
PrintClass.my_print("....'Outside Diameter' key not found", 'warn')
PrintClass.fatal_error(message="Error initializing PipeClass")
try:
self.thickness = json_data_pipe['Wall Thickness']
except: # pragma: no cover
PrintClass.my_print("....'Wall Thickness' key not found", 'warn')
PrintClass.fatal_error(message="Error initializing PipeClass")
self.outer_radius = self.outer_diameter / 2
self.inner_radius = self.outer_radius - self.thickness
self.inner_diameter = self.outer_diameter - 2 * self.thickness
self.resist_pipe_convection = None
self.resist_pipe_conduction = None
self.resist_pipe = None
self.calc_pipe_resistance()
def calc_pipe_conduction_resistance(self):
"""
Calculates the thermal resistance of a pipe, in [K/(W/m)].
Javed, S. & Spitler, J.D. 2016. 'Accuracy of Borehole Thermal Resistance Calculation Methods
for Grouted Single U-tube Ground Heat Exchangers.' J. Energy Engineering. Draft in progress.
"""
self.resist_pipe_conduction = np.log(self.outer_diameter / self.inner_diameter) / \
(2 * np.pi * self.conductivity)
return self.resist_pipe_conduction
def calc_pipe_convection_resistance(self):
"""
Calculates the convection resistance using Gnielinski and Petukov, in [k/(W/m)]
Gneilinski, V. 1976. 'New equations for heat and mass transfer in turbulent pipe and channel flow.'
International Chemical Engineering 16(1976), pp. 359-368.
"""
lower_limit = 2000
upper_limit = 4000
re = 4 * self.fluid.mass_flow_rate / \
(self.fluid.visc() * np.pi * self.inner_diameter)
if re < lower_limit:
nu = 4.01 # laminar mean(4.36, 3.66)
elif lower_limit <= re < upper_limit:
nu_low = 4.01 # laminar
f = self.friction_factor(re) # turbulent
pr = self.fluid.pr()
nu_high = (f / 8) * (re - 1000) * pr / \
(1 + 12.7 * (f / 8) ** 0.5 * (pr ** (2 / 3) - 1))
sigma = 1 / (1 + np.exp(-(re - 3000) / 150)) # smoothing function
nu = (1 - sigma) * nu_low + sigma * nu_high
else:
f = self.friction_factor(re)
pr = self.fluid.pr()
nu = (f / 8) * (re - 1000) * pr / \
(1 + 12.7 * (f / 8) ** 0.5 * (pr ** (2 / 3) - 1))
h = nu * self.fluid.cond() / self.inner_diameter
self.resist_pipe_convection = 1 / (h * np.pi * self.inner_diameter)
return self.resist_pipe_convection
def friction_factor(self, re):
"""
Calculates the friction factor in smooth tubes
Petukov, B.S. 1970. 'Heat transfer and friction in turbulent pipe flow with variable physical properties.'
In Advances in Heat Transfer, ed. T.F. Irvine and J.P. Hartnett, Vol. 6. New York Academic Press.
"""
# limits picked be within about 1% of actual values
lower_limit = 1500
upper_limit = 5000
if re < lower_limit:
return 64.0 / re # pure laminar flow
elif lower_limit <= re < upper_limit:
f_low = 64.0 / re # pure laminar flow
# pure turbulent flow
f_high = (0.79 * np.log(re) - 1.64)**(-2.0)
sf = 1 / (1 + np.exp(-(re - 3000.0) / 450.0)) # smoothing function
return (1 - sf) * f_low + sf * f_high
else:
return (0.79 * np.log(re) - 1.64)**(-2.0) # pure turbulent flow
def calc_pipe_resistance(self):
"""
Calculates the combined conduction and convection pipe resistance
Javed, S. & Spitler, J.D. 2016. 'Accuracy of Borehole Thermal Resistance Calculation Methods
for Grouted Single U-tube Ground Heat Exchangers.' J. Energy Engineering. Draft in progress.
Equation 3
"""
self.resist_pipe = self.calc_pipe_convection_resistance(
) + self.calc_pipe_conduction_resistance()
return self.resist_pipe