Overview
1. A wooden room has a 0.16-m thick wooden floor [k = 0.141 W/(m C°)] with an area of 20 m2. A fire keeps the interior of the room at a comfortable 20.0 °C while the air temperature in the crawl space below the room is –10.0 °C. What is the rate of heat conduction through the wooden floor?
2. Some skillets are made of different materials but are of the same shape. If one skillet is made out of Copper with thermal conductivity of 390 J/(s × m × C°) and another is made out of Iron with thermal conductivity of 79 J/(s × m × C°). What will be the ratio of the heat energy rate transferred by the two identical (same length and same cross-sectional area) skillets of Copper to Iron?
3. Calculate the rate of heat conduction out of the human body, assuming that the core internal temperature is 37.0 C°, the skin temperature is 34.0 C°, the thickness of the tissues between averages 1.0 cm, and the surface area is 1.40 m2. Please take the thermal conductivity of the body fat as 0.2 J/(s.m.C).
4. (a) Calculate the rate of heat transfer by radiation from a car radiator at 110.0 °C into a 40.0 °C environment, if the radiator has an emissivity of 0.750 and a 1.2-m2 surface area. (b) Is this a significant fraction of the heat transfer by an automobile engine? To answer this, assume a horsepower of and the 200 hp (1.5 kW) and the efficiency of automobile engines as 25%.
5. An object can only transfer heat by either conduction, convection, or radiation. Is this true or false? If true, explain why? If false, give an example and how it transfers energy via more than one process. What are some examples of which heating by conduction is used in everyday processes?