Question

You’ve experienced convection cooling if you’ve ever extended your hand out the window of a moving vehicle or into a flowing water stream. With the surface of your hand at a temperature of 30°C, consider the two following conditions.
Condition A: a vehicle speed of 35 km/h in air at -5°C with a convection coefficient of 40 W/m2·K.
Condition B: a velocity of 0.2 m/s in a water stream at 10°C with a convection coefficient of 800 W/m2·K.

What is the convection heat flux for these two condition?

Answer 1

Answer:

Condition A

Heat flux is 1400 W/M^2

Condition B

Heat flux is 12800 w/m^2

Explanation:

Given that:

$T_s$ is given as  30 degree celcius

condition A

Air temperature =  - 5 degree c

convection coefficient h = 40 w/m^2. k

$heat\ flux = \frac{Q}{a}= h\Delta = 40{30 - (-5)} = 1400 w/m^2$

condition A

water temperature  = 10 degree c

convection coefficient = 800 w/m^2.k

$heat\ flux = \frac{Q}{A} = H(\Delta} = 800\times (30-14) = 12800w/m^2$