The market for pillow and mattress materials has a demand for foams that feel cool to touch for a double-digit number of seconds elapsed since the initial contact with human body. The ability of a homogeneous material to keep the interface with a human body cooler is measured by thermal effusivity. Since the upper limit of time when the foam should feel cool to touch is a few minutes, only a near-surface layer of the foam must exhibit high thermal effusivity: the deeper layers of the foam do not practically interact with the human body during the above short transient heat transfer and thus can have lower thermal effusivity, and thus lower density, stiffness and cost. In this talk we introduce a practical method of measuring time-dependent "cooling power", which extends the concept of thermal effusivity to materials with spatially varying thermophysical properties. The method utilizes raw data output of a transient plane source instrument, in our case Hot Disk TPS 2500S.
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