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  3. problem 3 firefighting gear design consider the design of a...

Question: problem 3 firefighting gear design consider the design of a...

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Problem 3 (Firefighting Gear Design) Consider the design of a firefighters protective clothing, referred to as a turncoat, which has three solid layers with two air gaps Moisture barrier (mb) iner (tl) Shell (s) Thermal Fire-side 1 mm 、::..:.:i:::| Firefighter mb Air gap Air gap We are tasked with designing the dimensions of the solid layers to provide the protection firefighters need at a minimal cost. The last thing that needs to get designed is the thickness of the thermal liner, Ltt. The thermal conductivities of the three solid layers are given by the following: Shell ks0.047 W/(m K), moisture barrier kmb 0.012 W/ (m K), and thermal liner ktl = 0.038 W/(rn K). The thicknesses of the shell layer and moisture barrier layer have already been determined to be: Shell layer Ls 0.8 mm and moisture barrier layer Lmb 0.55 mm. Heat transfers in the air gaps by convection. The convection heat transfer coefficients for the air layers is given by hair 25 W(m2 K). The width of both air gaps is 1 mm. Typical conditions for firefighters will see a heat flux into the fire-side of up to ire0.25 W/(cm2). The turncoat must keep the temperature at the surface of the fire fighter below 65°C to avoid burns. Answer the following questions a. Draw the thermal circuit that represents the turncoat, labelling each resistance in the circuit. b. Compute the thickness of the thermal liner needed to protect the firefighter from receiving burns under these conditions.

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