Question

A circular pipe, with an outside diameter of 30 mm and a wall thickness of 4 mm, is held stationary in a stream of air for which T-30°C, F-1 atm , and V-25 m/s . The pipe, which is made of PVC, experiences cross-flow conditions in the moving air 1) The temperature at the inner surface of the pipe is maintained at 90°C. The outer surface of the pipe is smooth. Also, assume that steady-state conditions exist. Since the outer surface temperature of the pipe is unknown, the film temperature T may be approximately calculated from the inner surface temperature of the pipe in order to evaluate the relevant fluid properties; i.e, T siT). Furthermore, kpvc 0.19 W/(m K) Determine the drag force exerted on the pipe by the stream of air, per unit length of pipe a) Determine the HT rate from the pipe to the air, per unit length, based upon Eq. (1) below. b) Determine the temperature at the outer surface of the pipe based upon this result [Part (b)1. c) Determine the HT rate from the pipe to the air, per unit length, based upon Eq. (2) below. d) Determine the temperature at the outer surface of the pipe based upon this result Part (d) . e)

Answer 1

Sol iven lhat data Do length ob l he.pipe іх rtak. η ae Unity. 2- aoperties culr is Calculated based on -fi. Im temparature.ノTp-TtTao 2 2 J m W/mK r = O. 02 851

Rey nold s num ber, ReSauDo 1.0594, X 25X063 Re = 3.0061 ΧΙδ5 R 3.6 x 104 2xID 325 1.328 3.96 Xİ04 .. Cp = 6.671 X103 Given data . Ta 22mr. 0 30 c VD Hlpr conve Correlahon

for Civcular Gylinder, m o.618 0 618 41 0.028517. : total heat transfr Ti-To geot = As TIDL o 30 n (30p) plyina e Cylinder we ch

the (ovye la horn USinq d) 5 above Eyuati'on is Chuhilstein Convect-on Covrelahior) 3.96 KID <p ヒ -' . то 45-362"С