1- This cartoon is can be yours truly as I often get up in the night only to nap on the couch. More importantly, Mr Tinkerson made a coffee only to let it cool on a table, which is perfect for a convection problem. Let's assume the cup is a typical cup with a top rim diameter of 75.0 mm. Judging by the steam above the cup-o-coffee it must be at a typical 175 degF. If the room temperature is 19.0 degC, what is the rate (W) of heat transfer via convection from the top of the coffee into the room? Assume h= 5.2 J/s*m^2* Cdeg

2- In this popular cartoon strip, Hi is in front of a large typical 1950's single pane window of his home. It's in the evening in early fall. Temperature outside is a cool 12.5 degC and the temperature inside is a confortable 21.1 degC. At what rate (W) is heat lost through the 1.19 m by 1.75 m glass window pane that is 6.05 mm thick? Hmmm, Maybe Hi and Lois should think about replacement a window??

Table 13.1 Thermal Conductivityes of Selected Materials Thermal Conductivity, k Substance [J/(s . m . Co)] Metals Aluminum 240 Brass 110 Copper 390 Iron 79 Lead 35 Silver 420 Steel (stainless) 14 Gases Air 0.0256 Hydrogen (H2) 0.180 Nitrogen (N2) 0.0258 Oxygen (02) 0.0265 Other Materials Asbestos 0.090 Body fat 0.20 Concrete 1.1 Diamond 2450 Glass 0.80 Goose down 0.025 Ice (0 .C) 2.2 Styrofoam 0.010 Water 0.60 Wood (oak) 0.15 Wool 0.040 Except as noted, the values pertain to temperatures near 20 .C