def test_fluid_heat_transfer_rate(self):
""" Tests the value of the fluid heat transfer rate for a single U-tube
borehole.
"""
from pygfunction.pipes import SingleUTube
from pygfunction.boreholes import Borehole
# Reference solution (Cimmino, 2016)
# Fluid mass flow rate [kg/s]
m_flow = np.array([0.2, 0.3])
T_b = 1.0 # Borehole wall temperature [degC]
# Outlet fluid temperature [degC]
Tf_out = np.array([2.2161, 2.8394])
# Inlet fluid temperature [degC]
Tf_in = np.array([5.0, 5.0])
# Total heat transfer rate [W]
Qf_ref = m_flow*self.cp*(Tf_out - Tf_in)
borehole = Borehole(self.H, 0., self.r_b, 0., 0.)
# Calculate using pipes.SingleUTube()
Qf = np.zeros_like(Qf_ref)
for i in range(len(m_flow)):
pos = [(-self.D_s, 0.), (self.D_s, 0.)]
UTube = SingleUTube(pos, 0., self.r_out, borehole,
self.k_s, self.k_g, self.Rfp, J=0)
# Obtain fluid heat transfer rate
Qf[i] = UTube.get_fluid_heat_extraction_rate(Tf_in[i], T_b,
m_flow[i], self.cp)
self.assertTrue(np.allclose(Qf, Qf_ref, rtol=1e-4, atol=1e-10),
msg='Incorrect value of fluid heat extraction rate.')
def test_outlet_fluid_temperature(self):
""" Tests the value of the outlet fluid temperature for a single U-tube
borehole.
"""
from pygfunction.pipes import SingleUTube
from pygfunction.boreholes import Borehole
# Reference solution (Cimmino, 2016)
# Fluid mass flow rate [kg/s]
m_flow = np.array([0.2, 0.3])
T_b = 1.0 # Borehole wall temperature [degC]
Tf_in = 5.0 # Inlet fluid temperature [degC]
borehole = Borehole(self.H, 0., self.r_b, 0., 0.)
Tf_out_ref = np.array([2.2161, 2.8394])
# Calculate using pipes.SingleUTube()
Tf_out = np.zeros_like(Tf_out_ref)
for i in range(len(m_flow)):
pos = [(-self.D_s, 0.), (self.D_s, 0.)]
UTube = SingleUTube(pos, 0., self.r_out, borehole,
self.k_s, self.k_g, self.Rfp, J=0)
# Obtain outlet fluid temperature
Tf_out[i] = UTube.get_outlet_temperature(Tf_in, T_b,
m_flow[i], self.cp)
self.assertTrue(np.allclose(Tf_out, Tf_out_ref, rtol=1e-4, atol=1e-10),
msg='Incorrect value of outlet fluid temperatures.')
def test_one_borehole_twenty_four_segments(self, rel_tol=1.0e-4):
""" Tests the value of the g-function of one borehole.
"""
from pygfunction.pipes import SingleUTube
from pygfunction.gfunction import equal_inlet_temperature
from pygfunction.boreholes import rectangle_field
# Pipe characteristics (will be overwritten by thermal resistances)
r_out = 0.01
r_in = 0.0075
Ds = 0.06
pos = [(-Ds, 0.), (Ds, 0.)]
k_g = 1.5
# Results of Cimmino (2015)
# Number of line source segments per borehole
nSegments = 24
# Very large time values to approximate steady-state
time = 1.0e20
# Borehole thermal resistances [m.K/W]
Rb = np.array([0.1, 0.3])
# Borehole short-circuit resistance [m.K/W]
Ra = 0.25
g_ref = np.array([6.63770426518980, 6.65263629558422])
# Calculation of the g-function at the same time values
N_1 = 1
N_2 = 1
boreField = rectangle_field(N_1, N_2, self.B, self.B, self.H, self.D,
self.r_b)
g = np.zeros_like(g_ref)
for i in range(len(Rb)):
UTubes = [
SingleUTube(pos, r_in, r_out, borehole, self.k_s, k_g, 0., J=0)
for borehole in boreField
]
# Overwrite borehole resistances
Rd_00 = 2 * Rb[i]
Rd_01 = 2 * Ra * Rd_00 / (2 * Rd_00 - Ra)
for UTube in UTubes:
UTube._Rd[0, 0] = Rd_00
UTube._Rd[1, 1] = Rd_00
UTube._Rd[0, 1] = Rd_01
UTube._Rd[1, 0] = Rd_01
UTube._update_model_variables(self.m_flow, self.cp, nSegments)
g[i] = equal_inlet_temperature(boreField,
UTubes,
self.m_flow,
self.cp,
time,
self.alpha,
nSegments=nSegments)
self.assertTrue(np.allclose(g, g_ref, rtol=rel_tol, atol=1e-10),
msg='Incorrect values of the g-function of one '
'borehole for equal inlet fluid temperature '
'(24 segments).')