Question

For heat transfer purposes, a standing man can be mod-eled as a 30-cm-diameter, 170-cm-long vertical cylinderwith both the top and bottom surfaces insulated and with theside surface at an average temperature of 34°C. For a con-vection heat transfer coefficient of 15 W/m2·K, determinethe rate of heat loss from this man by convection in still airat 20°C. What would your answer

Answer 1

Answer:

Rate of Heat Loss = 336 W

Explanation:

First, we will find the surface area of the cylinder that is modelled as the man:

$Area = A = (2\pi r)(l)$

where,

r = radius of cylinder = 30 cm/2 = 15 cm = 0.15 m

l = length of cylinder = 170 cm = 1.7 m

Therefore,

$A = 2\pi(0.15\ m)(1.7\ m)\\A = 1.6\ m^2$

Now, we will calculate the rate of heat loss:

$Rate\ of\ Heat\ Loss = hA\Delta T$

where,

h = convective heat tranfer  coefficient = 15 W/m²K

ΔT = Temperature difference = 34°C - 20°C = 14°C

Therefore,

$Rate\ of\ Heat\ Loss = (15\ W/m^2K)(1.6\ m^2)(14\ K)$

Rate of Heat Loss = 336 W