Sure Chill Vaccine Refrigerator
Sure Chill works on the principle that water is at its densest at 4ËšC. Water, not ice, surrounds a Sure Chill refrigeration compartment. When power is supplied to the refrigerator, the water cools and ice is formed above the compartment leaving only water at 4ËšC cooling the contents. When the power is switched off, the water warms and rises while the ice begins to melt. This keeps only water at a perfect 4ËšC cooling the contents of the compartment. The system can operate like this, without any power whatsoever, for many days.