A hair dryer is basically a duct of constant diameter in which a few layers of electric resistors are placed. A small fan pulls the air in and forces it through the resistors where it is heated. If the density of air is 1.20 kg/m3 at the inlet and 1.015 kg/m3 at the exit, determine the percent increase in the velocity of air as it flows through the dryer

Respuesta :

Answer:

Therefore % increase in velocity is 18.23 %

Explanation:

we use the equality of mass flow rate and the areas

[tex]m_1 = m_2\\p_1v_1 = p_2v_2\\p_1A_1v_1 = p_2A_2v_2\\v_2 = \frac{p_1}{p_2} v_1[/tex]

The percentage increase in velocity is

Δ v% = [tex]\frac{v_2 - v_1}{v_1} \\[/tex]100%

= [tex]\frac{p_1}{p_2} v_1 - v_1[/tex].100%

= [tex]\frac{\frac{1.2}{1.015} - 1}{1}[/tex] . 100%

= Therefore % increase in velocity is 18.23 %