Human Comfort and the Physics of Foams

Human Comfort and the Physics of Foams is a current topic in the bedding and furniture industry. Polyurethane (PU) foams are thermally insulating, cushioning materials. Flexible open cell PU foams are used in padding materials for furnitures and bed mattresses, where insulation can be useful, but depending on the local climate, insulation can lead to localized heating that can lead to discomfort. In order to maintain comfort, two factors are needed: (1) preventing overheating, and (2) good cushioning (absence of pressure points). Thermal comfort simulation was conducted using the ASHRAE Human Comfort model, coupled with a multiphysics model taking into account natural convection of air, thermal conduction and mass (water vapor) diffusion phenomena. It is demonstrated that effective diffusivity of water vapor through foam is the critical parameter that determines whether the human body is able to regulate its skin temperature. Pressure relief measurements and simulations were also conducted, using an indenter held at a constant temperature of 23 and 34 °C. The relative insensitivity of the contact pressure to indenter temperature is reported.