Short-Time Transient Thermal Behaviour in Textile Fabrics—The Dual Phase Approach

Short-time thermal exchange (0–20 s) between human skin and textile surfaces determines initial warm–cool sensations, which influences comfort perception. Classical Fourier models predicting a √t cannot fully describe this early transient phase, particularly for porous or heterogeneous materials such as fabrics. This study investigates the early and short-time temperature response of a fingertip to contact with eight woven and knitted fabrics of different compositions, densities, thermal resistances, and thicknesses, measured under controlled laboratory conditions using a fine-gauge thermocouple at the skin–fabric interface. Experimental temperature–time data, when converted to the Laplace domain, exhibited slopes corresponding to time-domain exponents of t^⅙, t^¼, and occasionally t^⅒, all lower than the classical diffusion exponent of ½.The dual-phase lag (DPL) model was applied to interpret these deviations through two lag times—τq (heat flux) and τT (temperature gradient)—and their ratio Z = τT/τq, which controls the slope of the Laplace-domain response. DPL curves reproduced the observed exponents without additional empirical parameters. The results show that short-time heat transfer depends strongly on textile structure: higher thickness leads to slower transient responses (“warmer” feel), whereas denser fabrics promote faster equilibration (“cooler” feel). This dual-phase interpretation bridges physical heat transfer with tactile thermal perception, providing a predictive framework for the design of textiles with thermal properties.