Question

Problem 6.040 As a means of preventing ice formation on the wings of a small, private aircraft, it is proposed that electric resistance heating elements be installed within the wings. To determine representative power requirements, consider nominal flight conditions for which the plane moves at 160 m/s in air that is at a temperature of -23°C. If the characteristic length of the airfoil is L = 2 m and wind tunnel measurements indicate an average friction coefficient of C = 0.0025 for the nominal conditions, what is the average heat flux needed to maintain a surface temperature of T, = 5°C? Physical Properties Mathematical Functions Step 1 Your answer is correct. What is the value of the kinematic viscosity of air at -23°C, 1 atm, in m2/s? 11.44E-6 m/s the tolerance is +/-5% Click if you would like to Show Work for this question: Open Show Work SHOW ANSWER By accessing this question Assistance, you will while you earn points based on the otential Policy set by your instructor. Attempts: 1 of 5 used Step 2 X Your answer is incorrect. Try again. What is the value of the Reynolds number based on the characteristic length? Re 10489510

Answer 1

ANS:

(1)

$\nu =11.44\times 10^{-6}m^{2}/s$

(2)

(3)

$\bar{Nu}_{L} =31338.49$

(4)

$\bar{h} =344.72W/m^{2}.k$

(5)

$\bar{q}'' =9652.16W/m^{2}$

Solution:

Too = -23°C Cf = 0.0025 Giveno V= 160m/s L = 2m Ts=5°C 0 # The properties of ar at Too = 250K → D= ll. 44X106 m2/S Pr=0.72 K= 0.022 W/m.k # The reynolds numbers Reu= VXL 160)x(2) (11.44X10-6) 27972028 D (3) # The modified Reynolds analozzo 213 -> [ 0.6248260] St Pro 213 Po NUL RqXlr NUL Rex Po → The average nusselt number, 113 Nu Isto x Re, X Pyl3

0.0025 )x(27 27972028) x (0.72)!} i: Nu = 31338.49 14 # The arerage heat transfer coefficiento → h = ķx Nu 31338. 2 oo ħ = 344.72] W/m²K 15 q" = ñ x[ Ts-Too 344.72%, * [(st2734) =(-23+273) -11 9657.16 wlm?