Approximate the human form as an unclothed vertical cylinder of 0.3 m diameter and 1.75 m length with a surface temperature of 30 oC.(a)Calc

Question

Approximate the human form as an unclothed vertical cylinder of 0.3 m diameter and 1.75 m length with a surface temperature of 30 oC.(a)Calculate the heat loss in a 10 m/s wind at 20 oC.(b)What is the heat loss if the skin is covered with a thin layer of water (i.e., sweat) at 30 oC and the relative humidity of the air is 60 %

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Verity 4 years 2021-08-27T12:19:09+00:00 1 Answers 6 views 0

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  1. binhan
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    2021-08-27T12:20:55+00:00
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    Answer:

    q=1118.865W

    Explanation:

    From the question we are told that

    Diameter of the cylinder D=0.3m

    Length of the cylinder L=1.75m

    Surface temperature of cylinder T_s=30 \textdegree C=303k

    Speed of air V=10m/s

    Temperature of air T=20 \textdegree C

    Generally the equation for Reynolds number is mathematically given by

    Re_D=\frac{VD}{v}

    where

    v=15.27*10^-^6

    Re_D=\frac{10*0.3}{15.27*10^-^6}

    Re_D=1.96*10^5

    Generally the equation for Nusselt number is mathematically given by

    N_u=0.6(Re_D)^{0.6}(Pr)^{0.37}

    where

    Prandtl number

    Pr=0.71

    N_u=0.6(Re_D)^{0.6}(Pr)^{0.37}

    N_u=0.6(1.96*10^5)^{0.6}(0.71)^{0.37}

    N_u=791.53

    Generally the equation for convective heat transfer is mathematically given by

    h=Nu \frac{k}{D}

    where

    k=25.7*10^{-3}

    h=791.53*\frac{25.7*10^{-3}}{0.3}

    h=67.81W/m^2K

    Generally the equation for surface area of a cylinder is mathematically given by

    A=\pi DL

    A=\pi *0.3*1.75

    A=1.65m^2

    Generally the equation for convective heat transfer is mathematically given by

    q=h4(T_s-T_{inty)}

    q=(67.81)*1.65*(30-20)\\

    q=1118.865W

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