91影视

The lower temperature is\({T_2} = {34 \circ }{\rm{C}}\).

The higher temperature is\({T_1} = {37 \circ }{\rm{C}}\).

The total surface area is\(A = 1.5\;{{\rm{m}}{\rm{2}}}\).

The thickness of the tissue is \(l = 4.0\;{\rm{cm}} = 4.0 \times {10{ - 2}}\;{\rm{m}}\).

The rate of heat flow is inversely proportional to the thickness.

The rate of heat flow is \(\frac{Q}{t} = kA\frac{{{T_1} - {T_2}}}{l}\).

The thermal conductivity of the human tissue is \(k = 0.02\;{\rm{J/s}} \cdot {\rm{m}}{ \cdot {\rm{o}}}{\rm{C}}\).

The rate of heat flow through the goose down the jacket is

\(\begin{array}{c}\frac{Q}{t} = kA\frac{{{T_1} - {T_2}}}{l}\\ = \left( {0.2\;{\rm{J/s}} \cdot {\rm{m}}{ \cdot {\rm{o}}}{\rm{C}}} \right)\left( {1.5\;{{\rm{m}}{\rm{2}}}} \right)\frac{{\left( {{{37} \circ }{\rm{C}}} \right) - \left( {{{34} \circ }{\rm{C}}} \right)}}{{4.0 \times {{10}{ - 2}}\;{\rm{m}}}}\\ = 22.5\;{\rm{W}}{\rm{.}}\end{array}\)

Therefore, the rate of heat flow is \(22.5\;{\rm{W}}\).

22.5 W is almost equal to 10% of 230 W.

Hence, it is 10% of the cooling capacity of the human body. Also, convection cooling is necessary.