1D) (5 points) In a plane wall, there is internal heat gener…

1D) (5 points) In a plane wall, there is internal heat generation  and the wall is thermally insulated on its left side. The right side of the wall is cooled by forced convection with a fluid temperature of 20 ℃ and a convection coefficient of 500 W/m2K. If wall’s thickness is 30 mm, what would be the wall’s temperature on its right surface (Ts)?

1B) (5 points) Consider a room whose air temperature is main…

1B) (5 points) Consider a room whose air temperature is maintained at 23ºC, while the walls of the room are nominally at 25°C. The exposed surface of a person in the room may be assumed to be at a temperature of 32°C and to have an emissivity of 0.91. Stefan-Boltzmann constant is 5.67´10-8 W/m2K4. Calculate the following.  Heat flux due to radiation from a person to surrounding wall.

Problem 3. (40 points) An air-cooled heat sink with 9 plate…

Problem 3. (40 points) An air-cooled heat sink with 9 plate fins is used to maintain a CPU at 80°C. There is contact resistance of  between the CPU and the base of the sink. Thermal conductivity of the heat sink is 160 W/(m×K). Geometric variables are as follow: fin thickness (tf) = 2 mm, fin length (Lf) = 12 mm, cross-sectional shape of CPU = 2 cm x 2 cm (square), heat sink’s base thickness (tb) = 3 mm. Air temperature is 25°C and convection coefficient is 50 W/(m2K). Ignore internal heat generation and radiation heat transfer. Assume that the fin tips are adiabatic. Draw a thermal resistance circuit that expresses the heat transfer from the CPU’s top surface to air. Below the circuit show the expressions for thermal resistances (e.g., expression for a radiation resistance is 1/hrA). Then, determine the 1) total resistance in K/W (or °C/W) 2) overall fin efficiency and 3) heat rate from CPU to air in W.