CF-1.1 COMPANION / FABRICATION AND HEAT-MEASUREMENT NOTES
Physical measurements: 0. This companion does not alter the frozen 12-pair
flow endpoint or turn a design requirement into a measured specification.

KEEP THE GAP A MECHANICAL DIMENSION
The copper lands must make hard contact. An external seal may seal the joint;
it must not act as a spacer or intrude into the channel. Inspect the groove,
lid flatness and assembled gap at several positions. Record the clamp method
and keep it identical across all thermal blocks. The four M3 fasteners and
washers in the CAD are installation geometry, not a qualified torque setting.
A fabricator must establish the clamp/preload and verify that assembly and
thermal cycling do not change the gap uncontrollably.

Uniform contraction of a homogeneous copper article changes its dimensions.
A channel with the same nominal groove is not automatically an identical
micrometre-scale gap at both temperatures. Record or bound the warm-to-cold
gap change, including its measurement uncertainty and repeatability. A simple
viscous-channel sensitivity is proportional to gap cubed: a 0.2% gap opening
can cause approximately 0.6% more flow in that limit. This is an attribution
screen, not a correction valid for every adapter or developing flow. Without
a defensible geometry bound, report the net assembled-article temperature
effect; do not attribute the entire change to gas properties alone.

PRESSURE AND TEMPERATURE PLANES
Keep the pressure source and main flow meter warm. The quiet inlet reservoir
supplies a total-pressure reference; a flush static tap in the downstream
straight must not point into the flow. Record every actual tap position and
compare with the pressure at those same positions in the as-built numerical
model. Tubing, tap offsets and controller stability belong to the installed
head uncertainty. Never substitute a sealed-port regulator specification for
flowing-air head stability. The primary result still compares the same actual
article at the same measured pressure head, with its frozen pair-matching rule.

The four selected wall probes sit in blind pockets. Their contact, insertion,
readout timing and self-heating need installed-chain calibration. A bath
setpoint is not a wall-temperature measurement. Keep the dewpoint margin and
both warm/cold leak blanks. Rejected blocks remain in the data record.

OPTIONAL GAS-SIDE CALORIMETRY / A SECONDARY OUTCOME
The primary endpoint is mass-flow change. Cooling electrical input is not
itself a measurement of heat removed from the gas. To measure a secondary
heat balance, add an insulated mixing section after the DUT pressure plane
and two calibrated gas-temperature chains at recorded inlet/outlet planes.
Select low-conduction probes and verify conduction, radiation, response time,
spatial mixing and pressure disturbance in the installed arrangement. Target
an installed temperature bound of 0.10 K per chain over the working range;
this is a requirement to demonstrate, not a claimed catalogue capability.

For steady dry air, the net gas heat loss between the instrument planes is
  Q_gas = m_dot * [h(T_in)-h(T_out) + (U_in^2-U_out^2)/2].
A first narrow-range screen may use cp=1005 J/(kg K), with a declared property
bound. Use an appropriate traceable gas-property source for the final reduction.
Propagate the calibrated flow, temperature, property and velocity bounds.
A downstream mixing chamber can pick up ambient heat. Measure/bound that
pickup with a blank and the same physical arrangement. Q_gas between those
planes is not automatically the copper-core cooling duty.

Keep this secondary result separate from the preregistered flow decision.
If temperature/mixing measurements are absent, label gas-side heat removal
NOT MEASURED. Do not replace it with the one-dimensional model's watts.

COUNT THE COMPLETE ELECTRICAL AND THERMAL EVENT
Log the blower, bath/chiller, coolant pump, trim heaters and controls with
separate meters, including stabilisation and the return to the starting state.
Record initial/final bath temperature and inventory if stored cold is used.
No net-energy or self-recharge conclusion follows from increased mass flow.
The air-flow result, gas heat balance and complete operating-energy balance
are distinct reported quantities.