A Phase Change Material (PCM) is a substance with a high heat of fusion, which melting and solidifying at certain temperatures, is capable of storing or releasing large amounts of energy. The only phase change used for PCM is the solid-liquid change. Initially, the solid liquid PCM perform like conventional storage materials; their temperature rises as they absorb solar heat. Unlike conventional storage materials, however; when PCM reach the temperature at which they change phase (their melting point) they absorb large amounts of heat without getting hotter. When the ambient temperature in the space around the PCM material drops, the PCM solidifies, releasing its stored latent heat. PCM therefore absorb and emit heat while maintaining a nearly constant temperature. Within the human comfort range of 20 to 30C, latent thermal storage materials are very effective. They store 5 to 74 times more heat per unit volume than conventional storage materials such as water, masonry or rock.
PCM materials have high heats of fusion so they can absorb a lot of energy before melting or solidifying. A PCM temperature remains constant during the phase change, which is useful for keeping the subject at a uniform temperature. A variety of outdoor apparel products with PCM microcapsules, such as sky wear, hunting clothing, boots, gloves and ear warmers are on the market under the trade names Outlast and Comfort.
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About the Authors:
Shyam Barhanpurkar, Mr. Tanveer Malik, Ayush Paharia & Vineet Singh are associated with Shri Vaishnav Institute of Technology and Science, Indore
Mukesh Singh is associated with Uttar Pradesh Textile Technology Institute, Kanpur
This article was originally published in the Textile Review, May, 2012, published by Saket Projects Ltd., Ahmedabad.