Effects of Indoor Air Temperature on Dry Heat Transfer from a Sleeping Infant: A CFD Study Based on a Validated Model

Indoor air temperature influences heat exchange between sleeping infants and indoor environments, yet its effects on convective and radiative dry heat transfer in ordinary ventilated rooms remain unclear. Using a previously validated three-dimensional CFD model of a realistic 9-month-old nude infant thermal manikin, this study simulated body-surface heat transfer at 18, 21, 23, 25, and 28 °C. A low-Re k-epsilon turbulence model was coupled with a surface-to-surface radiation model to calculate convective and radiative heat fluxes and heat transfer coefficients. Results showed that chamber airflow displaced the infant thermal plume toward the feet, exposing the head to cooler air and creating warmer microclimates around the lower limbs. At 18 °C, whole-body convective and radiative heat fluxes were 76.65 and 68.16 W/m2, respectively; each 1 °C temperature increase reduced them by 5.24 and 3.74 W/m2. Convection dominated at ≤21 °C, while radiation became dominant above 23 °C. The head showed the greatest temperature sensitivity, with convective and radiative heat fluxes decreasing by 61.08 and 41.66 W/m2 from 18 to 28 °C. Empirical equations based on skin-to-environment temperature differences fitted most heat transfer coefficients well (R2 > 0.93), providing boundary condition data for infant thermoregulation modeling and room thermal control.