Design Blueprint: School Batch Solar Water Pasteurizer — Build Specification Derived from the Counterflow Heat-Recovery Pasteurizer Paper

DESIGN BLUEPRINT — SIMULATED, NOT MEASURED — NOT BUILT. A complete build specification for an institutional batch solar water pasteurizer that heats each 50.0 litre charge to 65 C, holds it for 10 minutes, and discharges it through a counterflow heat exchanger against the next raw charge. Derived from the source paper: https://doi.org/10.5281/zenodo.24108834. Design basis: the enteric-virus class sets the treatment (9.0 min at 65 C for a 6-log reduction; a 1 min hold gives it only 0.67 log), the specified 10 min hold gives log reductions of 20.0, 10.0 and 6.67 for Escherichia coli, Salmonella spp. and the virus class, counterflow heat recovery at effectiveness 0.70 gives a net energy of 50.23 kJ per litre (0.160 of the sensible heat of boiling) and preheats the incoming charge to 53.0 C. The school unit is sized at 200 litres per day in 4 cycles: a collector of 1.12 m2 (1.40 m x 0.80 m), a batch tank of 55.0 litres nominal volume, an exchanger requiring NTU 2.333 and UA 813.9 W/K at a 10 minute exchange, and a closed treated-water storage vessel of 220 litres nominal volume. The blueprint gives dimensions and layout, a bill of materials in generic specification classes, an assembly sequence, the operating envelope including the half-output overcast day at 89.6 litres per square metre, critical fits tied to the lethality figures (above all temperature measurement at the coldest point of the batch), failure modes including short-hold virus survival and exchanger fouling, a condition-based maintenance schedule, and the measurements a first build must make. Nothing has been built or measured; every derived quantity is reproducible from the accompanying compute.py.