2. It is common (although not always socially acceptable) to cool a bowl of soup by blowing over the surface of the liquid. Consider a bowl of about 14 cm (5.5 in.) diameter. The exhaled air is essentially at body temperature near 98.6 F. The temperature of the soup is likely near 80 C, and the temperature of the top 1 cm of the liquid (from which y will extract your first spoonful) needs to be 50 C or lower. The convection coefficient for this type of airflow over a liquid or solid is roughly 100 W/m -K. How much heat will you have to extract to avoid burning your tongue

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Heat removal to cool the soup The amount of heat you need to extract to cool the top layer of soup ... View the full answer