113 lines
3.4 KiB
Python
113 lines
3.4 KiB
Python
# tests/cryo_tank/test_tank_model.py
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"""Tests for CryoTank model."""
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import pytest
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import numpy as np
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from cryo_tank.tank_model import CryoTank
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from cryo_tank.heat_leak import MLIHeatLeak
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from cryo_tank.config import (
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V_TOTAL, H_TANK, A_CROSS, A_TOTAL, P_WORKING,
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T_INIT, ULLAGE_FRACTION,
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MDOT_IN_LN2, T_IN_LN2, MDOT_OUT_LN2, T_IN_HE,
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H_CONV_SURFACE, T_ENV,
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)
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def _make_tank(**overrides):
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"""Create a CryoTank with default config and MLI heat leak."""
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kw = dict(
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V_total=V_TOTAL, H_tank=H_TANK,
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P_work=P_WORKING,
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T_init=T_INIT, ullage_fraction=ULLAGE_FRACTION,
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mdot_in_ln2=MDOT_IN_LN2, T_in_ln2=T_IN_LN2,
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mdot_out_ln2=MDOT_OUT_LN2,
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T_in_he=T_IN_HE,
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h_conv=H_CONV_SURFACE, T_env=T_ENV,
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heat_leak_model=MLIHeatLeak(A_total=A_TOTAL, q_mli=1.0),
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)
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kw.update(overrides)
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return CryoTank(**kw)
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class TestGeometry:
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def test_cross_section_area(self):
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tank = _make_tank()
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assert abs(tank.A_cross - 0.8402) < 0.001
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def test_total_surface_area(self):
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tank = _make_tank()
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assert abs(tank.A_total - 3.305) < 0.01
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def test_wetted_area_at_70_percent_fill(self):
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tank = _make_tank()
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level = 0.7 * H_TANK # 0.35 m
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A_wet, A_dry = tank.wetted_areas(level)
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# A_wet = bottom cap + side * level
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expected_wet = A_CROSS + np.pi * tank.D * level
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assert abs(A_wet - expected_wet) < 0.01
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assert abs(A_wet + A_dry - A_TOTAL) < 0.01
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class TestInitialState:
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def test_initial_liquid_mass(self):
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tank = _make_tank()
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y0 = tank.initial_state()
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m_liq = y0[0]
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# rho_LN2(78K, 0.17MPa) ~ 803.3 kg/m3, V_liq = 0.2941 m3
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assert 235 < m_liq < 237 # ~236.25 kg
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def test_initial_fill_fraction(self):
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tank = _make_tank()
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y0 = tank.initial_state()
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info = tank.derive(y0)
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assert abs(info['fill_fraction'] - 0.70) < 0.01
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def test_initial_temperatures(self):
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tank = _make_tank()
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y0 = tank.initial_state()
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info = tank.derive(y0)
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assert abs(info['T_liq'] - T_INIT) < 0.1
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assert abs(info['T_ull'] - T_INIT) < 1.0
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def test_initial_pressure_is_provided_entirely_by_helium(self):
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tank = _make_tank()
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y0 = tank.initial_state()
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info = tank.derive(y0)
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P_He = info['P_He']
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assert abs(P_He - P_WORKING) / P_WORKING < 1e-12
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class TestVolumeRate:
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def test_ullage_volume_rate_includes_liquid_thermal_expansion(self):
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tank = _make_tank(
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mdot_in_ln2=0.0,
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mdot_out_ln2=0.0,
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h_conv=0.0,
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)
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y0 = tank.initial_state()
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info = tank.derive(y0)
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Q_liq_to_ull = 0.0
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Q_leak = tank.heat_leak_model.compute(info['T_liq'], tank.T_env)
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A_wet, A_dry = tank.wetted_areas(info['liquid_level'])
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Q_leak_liq = Q_leak * A_wet / (A_wet + A_dry)
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dU_liq_dt = tank._liquid_energy_rate(
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info, Q_liq_to_ull, Q_leak_liq
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)
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dV_ull_dt = tank._ullage_volume_rate(
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info, tank.dm_liq_dt, dU_liq_dt
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)
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y_next = y0.copy()
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dt = 1.0
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y_next[1] += dU_liq_dt * dt
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finite_difference = (
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tank.derive(y_next)['V_ull'] - info['V_ull']
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) / dt
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assert dV_ull_dt < 0.0
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assert abs(dV_ull_dt - finite_difference) / abs(finite_difference) < 1e-5
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