Problem Set #7 Heat Transfer Modes 1. A mug of hot coffee (with no lid) sits on a table in a cool room. a. What type(s) of heat transfer is probably occurring at the surface of the coffee? b. What type(s) of heat transfer is probably occurring between the coffee and the interior sides of the mug? c. What type(s) of heat transfer is probably occurring between the sides of the mug and the surrounding air? d. What type(s) of heat transfer is probably occurring between the mug and the walls of the room? 2. Water and iron have the following properties: Water: cp = 4.18 H, k = 0.607 in kg m C Iron: cp = 0.45 E, k = 80.2 in kg m C a. If you wanted to build a Trombe wall (a thermal energy storage device) inside your house, which material would you choose: iron or water? Why? b. Which material would work better to conduct heat away from a hot surface? Why? c. Which material would you expect to have higher electrical conductivity? Why? 3. Consider a heat exchanger like a boiler or a condenser. What are some important parameters (e.g. material properties, dimensions) that you would want to optimize for maximum heat transfer between the two fluids? ows over and outside the tubes - #9 ows through CZ: heat exchanger tubes .___, E::::l w/MB'l/l/ '9 ll 2]