Development of a Human Sensation-Relevant Method for Measuring Phase Change Materials

摘要

Phase change material (PCM) applications are expanding in sportswear, protective apparel, and in consumer goods industries. ASTM D7024-04, Standard Test Method for Steady State and Dynamic Thermal Performance of Textile Materials, previously was used to evaluate these fabrics. Although the method was based in sound science, it had little practical application to the industry and was not widely embraced. ASTM D7024-04 has since been withdrawn without replacement. In order to provide the industry with a suitable tool for evaluating PCM impact on human sensation, Thermetrics has developed an instrument and methodology to accurately characterize transient and steady-state fluxes in a range of environmental scenarios. The dynamic hot plate (DHP) extends the guarded hot plate concept to measure instantaneous heat flux. The addition of active cooling mimics the human circulatory system and allows continuous measurement under sustained thermal load and elevated ambient temperatures. Typically in these scenarios, conventional guarded hot plate devices overheat and are unable to measure the transient heat fluxes. The DHP was initially validated using measurements of test specimens with known thermal and PCM properties. After this validation, specific methodologies for evaluating PCM fabrics/materials were developed. These methods were focused on evaluating cool-to-touch sensation and cooling performance in uncompensable work environments. The proposed DHP instrument and methodology have demonstrated the ability to detect and quantify PCM in fabric samples. The resulting measure of performance is based on actual skin energy exchange, allowing the use of measurements to assess sensory impact and physiological relevance.