Calculate the net radiant-heat-transfer rate if the two surfaces in Problem 11.18 are black and are connected by a refractory surface with an area of 500 m2. A1 is at 555 K and A2 is at 278 K. What is the refractory surface temperature?

GIVEN

• Rectangular surfaces A1 and A2 connected by a refractory surface A3

• A1 is parallel to and centered 5 m above A2

• Dimensions of A1 = 1 m × 20 m

• A2 is 20 m2

• A3 is 500 m2

• Temperature of A1 (T1) = 555 K

• Temperature of A2 (T2) = 278 K

• A1 and A2 are black

FIND

(a) The net radiating heat transfer rate (q1)

(b) The refractory surface temperature (T3)

SKETCH



PROPERTIES AND CONSTANTS

the Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/(m2 K4)


F12 = 0.427

For the black surfaces A1 and A2

?1 = ?2 = 0 and ?1 = ?2 = 1

J1 = Eb1 and J2 = Eb2 Since q3 = 0

Since q3 = 0, J3 = G3



Since neither A1 nor A2 can see themselves, F11 = F22 = 0

With these simplifications reduces to





The shape factors are calculated below



Solving part (b) first



(a) The rate of heat loss from A1 is





As a check

Physics & Space Science

You might also like to view...

Consider a particle composed of quarks

(a) The negative pion is composed of what combination of up and down quarks? (b) Is the negative pion a baryon or meson? (c) Is the negative pion a lepton or a hadron?

Physics & Space Science

A type Sa galaxy has a larger ________ than type Sc

A) nuclear bulge B) halo C) mass D) number of stars E) spiral structure

Physics & Space Science

A 95 N force exerted at the end of a 0.50 m long torque wrench gives rise to a torque of What is the angle (assumed to be less than 90°) between the wrench handle and the direction of the applied force?

A) 18° B) 14° C) 22° D) 25°

Physics & Space Science

Light is refracted through a diamond. If the angle of incidence is 30°, and the angle of refraction is 12°, what is the index of refraction?

a. 1.3 b. 2.4 c. 2.6 d. 1.8 e. 0.4

Physics & Space Science