- #1

Nanu Nana

- 95

- 5

## Homework Statement

Through a (cylindrical) heating tube, warm air has to flow with a velocity of 3m/s in order to heat a rectangular spacewhich is 12 m long, 10 m wide and 2.5 m high. How large the radius of the tube should be if the air in the room get refreshed every 15 minutes ? Assume that the air-density in the tube and in the room are equal.

## Homework Equations

Continuity equation

A1 x v1 = A2 x v2[/B]

## The Attempt at a Solution

Flowrate = Volume/ t V/t = A x v

Flowrate = 12x10x2.5 = 300 m3 / 900 s = 0.33

0.33 = A2 x 3m/s

A2= 0.111 m^2

So to find the radius you have to use area of cilinder

A=pi x 2x (r)^2

0.111= pi x 2x (r)^2

r= 0.132 m why do i get this answer ?? . Its wrong .answer has to be 0.1881 [/B]