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Question 10.5: The fleece temperature of a sheep (treated as a cylinder, di...

The fleece temperature of a sheep (treated as a cylinder, diameter 1.0 m) was 40 ºC greater than air temperature in bright sunshine when the windspeed was 0.5 m s^{-1}. Would its convective heat loss be best treated as forced or free convection? Would the boundary layer be most likely laminar or turbulent? Estimate the rate of convective heat loss.

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Re = 0.30 × 0.15/16 × 10^{-6} = 2.8 × 10³,

Gr = 158 × 30³  × 40 = 1.7 × 108,

Gr/Re^{2} = 22, so heat transfer is dominated by free convection and the flow is assumed laminar. Using the relation Nu = 0.48Gr^{0.25} gives Nu = 55, and C = 55 × 27 × 10^{-3} × 40/0.30 = 198 W m^{-2}.

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