The recommended duration to boil eggs in a thermal cup is approximately 8 to 10 minutes. This timeframe ensures that the eggs are fully cooked without overcooking, which can lead to a rubbery texture. The thermal cup maintains a consistent temperature, allowing for even cooking throughout the process.

The reason for this duration lies in the fact that eggs require a certain amount of time to reach the desired doneness. According to the United States Department of Agriculture (USDA), eggs should be cooked to an internal temperature of 160°F (71°C) to ensure safety and prevent the risk of salmonella contamination. Boiling eggs in a thermal cup helps to achieve this temperature efficiently. The thermal properties of the cup keep the water at a steady boil, which is crucial for even cooking. Research indicates that at 212°F (100°C), the boiling point of water, the heat is sufficient to cook the egg whites and yolks thoroughly within the recommended time frame.

Additionally, the thermal cup's design plays a significant role in the cooking process. It typically has a narrow opening that restricts the escape of steam, which helps to maintain the water's temperature and pressure. This controlled environment ensures that the eggs are cooked uniformly without the risk of scorching or cracking. Furthermore, the thermal cup's insulation properties help to retain heat, reducing the need for frequent stirring or adjustments, which can disrupt the cooking process.

In conclusion, boiling eggs in a thermal cup for 8 to 10 minutes is the ideal duration to achieve a perfectly cooked, safe-to-eat result. The combination of the cup's thermal properties and the consistent boiling temperature ensures that the eggs are cooked to the correct internal temperature without overcooking.