Which personal cooling system uses phase change technology as the cooling medium?

• A. Phase change technology
• B. Liquid cooling technology
• C. Coolant jacket system
• D. Vapor phase cooling

Answer: (A)

Phase change materials absorb a lot of heat as they change state, so they can keep a surface at a steady, comfortable temperature for a period without continuous power. In a personal cooling system, a pack filled with a phase change material stores cold energy and draws heat from the body as it melts, delivering cooling as long as it changes state. This direct use of a phase change material as the cooling medium is why it fits the question best. The other options describe cooling methods that rely on circulating liquids, surrounding a body with a liquid jacket, or cooling by vaporizing a liquid, rather than using phase change material itself as the cooling medium.