Question 3: An electronic device with a temperature of 84°C (shown in golden colour) is embedded inside a composite plastic tube which is equipped with three fins (shown in blue) to enhance the convective heat transfer with the surrounding air. The composite tube is held horizontally. The temperature drop along the fins can be ignored due to their high thermal conductivity. The outer ring of the fins (shown in brown) is insulated. The ambient temperature is 20°C. 3a. Draw the thermal resistance circuit of the system 3b. Derive the energy balance of the system 3c. Find the thermo-physical properties of the air and aluminium

show a detailed solution to the problem. the solution is correct (use to double check)

2. A heater is a thin vertical panel 1.0m long and 0.7m high and is used in a warehouse to keep workers warm. The heater has air circulating on each side. Assume the maximum temperature of the panel is 60°C (already above the board line that is safe for human hands to touch briefly without getting hurt). Assume the room air temperature is 18°C but the warehouse wall temperature is 5°C. Model the surface with an emittance of 0.9 and Vair = 1.57x105 m²/s. a. Determine the maximum power rating for the heater. b. Now if you run the heat by standing on its side (it will be 1.0 m high and 0.7 m long), determine the surface temperature. c. Compare case a and b and explain any differences you see.

Question: a) We want to increase heat transfer by placing fans to provide forced convection to reduce the length of the pipe necessary (Note that the outside surface temperature of the pipe remains the same at 100oC). What is the rate of heat transfer from pipe to the air per meter length if the air speed over the pipe surface is 5m/s? What is the total length of the pipe necessary? Problem: Consider a rectangular warehouse with the dimensions of 40m long x 20m widex10m height. The overall heat transfer coefficient for all sidewalls is Uwall=0.3 W/m2K (Approx. R=20 hr.ft2.oF/Btu) and for the flat roof, it is Uroof= 0.20W/m2K. The floor can be assumed to be insulated and we can ignore the heat transfer through the doors, etc. We want to maintain the inside air temperature at 15oC while the outside temperature is 0oC by using a thin-walled, 5.0cm diameter copper pipe that carries steam. Steam enters the pipe as saturated vapor at 100oC. So, as it starts losing heat to the inside air, it…

After you exercise for a while, you may notice that your skin turns red. (A) How is the blood flow in your limb changes as a response to the exercise? When your skin turns red, how has the temperature changed at the skin surface (Tskin)? (B) During exercise, does the total heat generation rate inside your body increase or decrease from that in normal conditions? (C) What is the relationship between the total heat generation rate and the total heat loss from the skin surface to the environment by convection? Neglect sweating and radiation. (D) The total heat loss from the skin surface to the environment is hA(Tskir-Tair). Based on this convection equation and results in (C), how has the skin temperature changed during exercise? Does Tskin increase or decrease from that in normal conditions? Is this consistent with that in (A)?