A Phase-Change Neonatal Warmer for Births Where No Incubator Exists: Design and Lumped Thermal Model

Design study (simulated, not measured) of a non-electric neonatal warmer: a 2.5 kg paraffin phase-change mattress melting near 37 C in an insulated wrap, recharged with hot water in a tray guarded by a second phase-change material melting at 40 C. A lumped model of infant heat loss by birth-weight class (radiation, convection, evaporation, conduction) balanced against metabolic production gives hold times of at least 6.2 h for all classes from 1.0 to 3.5 kg at ambient temperatures of 15 C and above (8.6 h for a 1.5 kg infant at 20 C), and 5.0-5.8 h at 10 C. An adiabatic energy bound shows the recharge tray cannot exceed 40 C under the full boiling-water protocol, bounding the pack at 40 C and the skin-side temperature at 37.5 C. Parts cost is $53.40 per warmer plus a shared $65.20 recharge station.