The Thermal Effusivity (W√s/m2K) of two fabric samples, both with moisture-wicking properties, were compared against each other in a performance test. A sample of generic athletic wear was compared to a sample of fabric designed to have superior moisture-wicking properties. The samples were measured using TPS-EFF (Transient Plane Source-Effusivity) at different moisture levels.
TPS-EFF is a portable thermal effusivity meter for textiles with a thermal effusivity measurement range of 35 to 1700 (W√s/m2K) and a temperature range of -10 ºC to 50 ºC. A single measurement can be set to 2 or 10 seconds in duration. The experiment was conducted in accordance with the ASTM D7984-16 standard of testing method.
Thermal effusivity is most typically measured to predict how ‘cool’ or ‘warm’ a textile feels. It has a square root proportionality to the density, thermal conductivity, and specific heat capacity of the material. Dry fabrics often contain pockets of air between the strands, resulting in thermal effusivity values that are typically low. When dry fabrics are exposed to moisture, the air is replaced by water, which has a much higher thermal effusivity. This will cause the fabric to exhibit a higher thermal effusivity value when wet, making it feel ‘cooler’.
In this experiment, the thermal effusivity of two fabric samples were measured at varying moisture levels using TPS-EFF for a touch time of 2 seconds. Higher levels of moisture mean higher water saturation in the fabric. Therefore, measurements at higher levels of moisture should yield higher effusivity values compared to thermal measurements when the fabric is dry.