(238e) Thermostatic Self-Heating Coffee Cup

Most of the papers presented this week are about large industrial processes or microscopic phenomena, but engineering is also applied to everyday household objects. There is a potential market for self-heating coffee and soup cups. Previous attempts to produce such a product have resulted in cups that provide warm coffee in cold weather and scalding hot coffee in hot weather. The problem with these cups is that they provide the same temperature rise no matter when or where they are used. This paper describes the development of a cup which will provide the same final drinking temperature over a wide range of operating conditions. First, there needs to be enough energy available to heat the beverage when it starts at a cold temperature. Second we need to prevent all of this energy from overheating the beverage when it starts at a hot temperature. We solve this problem by sensing the beverage temperature, and stopping the reaction when the beverage temperature reaches the desired drinking temperature. Beverage manufacturers are only willing to pay pennies per cup for this feature. We have developed an analog chemical system to accomplish this. We put a chemical that will stop the reaction in a container that is sealed with a material that will melt at the desired drinking temperature. This seal must be placed so that it is in thermal contact with the beverage, but thermally insulated from the reaction mixture, which reaches 100°C as soon as the reaction is active. We will show two mechanical implementations of this device, and examples using a reactant complexing agent or a catalyst poison.