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  3. 5 a firefighters protective clothing referred to as a turnost...

Question: 5 a firefighters protective clothing referred to as a turnost...

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5. A firefighters protective clothing, referred to as a turnost coat, is typically constracted as an ensemble of three layers separated by air gaps, as shown schematically Moisture barrier (mb) liner (t shell (s) Thermal k, L Air gap Air gap Representative diemensioes and thermal conductivitics for the layers are as follows Layer Thickness (mm) k(W/m -K) Shell (s) Moisture harrier (mb) Thermal liner (t) 0.8 0.55 3.5 0.047 0012 0.038 The air gaps between the layers are 1 am thick, and heat is transferred by condaction and radiation exchange through the stagnant air. The linearized radiation coefficient for a gap may be approximated as, hrad 4T2g. where T represents the average temperature of the two surfaces comprising the gap, and the radiation flux across the gap may be expressed as qrd rad (T1 -T2) a) Represent the turnout coat by a thermal circuit, labeling all thermal resistances. Calculate the thermal resistances per unit area (m K/W) for each of the layers and each of the gaps. Assume that a value of T 473 K may be used to approximate the radiation resistance of both gaps. k of air at 473 K and 1 atm is 0.0382 WmK b) For a pre-flash-over fire environment in which firefighters often work,刍 typical radiant beat na on the fire-side ofthe ณmout coat is 0.25 wem, what is the outer surface temperature of the turnout coat if the inner surface temperatuse is 65 *C, a condition that would results in burn injury?
6. Hot water at 100 °C floras through a steel pipe with inner diameter 20 cm, outer diameter 26 cm, k-25 WimK. The pipe is covered by 2 cm of insulation (k 0018 Wm K). The pipe is located in a room where the ambient temperature is 25 °C. The convection heat transfer coefficient inside tht pipe is 120 w/n.K, outside the insulation is 3 win. K. a) What is the total resistance of the system per meter? b) What is the overall heat transfer coefficient based on outside area (per meter)? c) What is the heat transfer rate per meter?
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