Introduction to Heat Transfer

101 SOLVED PROBLEMS

Question: 13.7

Consider an air heater consisting of a semicircular tube for which the plane surface is maintained at 1000 K and the other surface is well insulated. The tube radius is 20 mm, and both surfaces have an emissivity of 0.8. If atmospheric air flows through the tube at 0.01 kg/s and Tm = 400 K, what is ...

Known: Airflow conditions in tubular heater and he...
Question: 13.6

A paint baking oven consists of a long, triangular duct in which a heated surface is maintained at 1200 K and another surface is insulated. Painted panels, which are maintained at 500 K, occupy the third surface. The triangle is of width W = 1 m on a side, and the heated and insulated surfaces have ...

Known: Surface properties of a long triangular duc...
Question: 13.5

A cryogenic fluid flows through a long tube of 20-mm diameter, the outer surface of which is diffuse and gray with ε1 = 0.02 and T1 = 77 K. This tube is concentric with a larger tube of 50-mm diameter, the inner surface of which is diffuse and gray with ε2 = 0.05 and T2 = 300 K. The space between ...

Known: Concentric tube arrangement with diffuse, g...
Question: 13.2

Determine the view factors F12 and F21 for the following geometries: 1. Sphere of diameter D inside a cubical box of length L = D. 2. One side of a diagonal partition within a long square duct. 3. End and side of a circular tube of equal length and diameter. ...

Known: Surface geometries. Find: View factors. Ass...
Question: 13.3

A furnace cavity, which is in the form of a cylinder of 50-mm diameter and 150-mm length, is open at one end to large surroundings that are at 27°C. The bottom of the cavity is heated independently, as are three annular sections that comprise the sides of the cavity. All interior surfaces of the ...

Known: Temperature of furnace surfaces and surroun...
Question: 13.4

In manufacturing, the special coating on a curved solar absorber surface of area A2 = 15 m² is cured by exposing it to an infrared heater of width W = 1 m. The absorber and heater are each of length L = 10 m and are separated by a distance of H = 1 m. The upper surface of the absorber and the lower ...

Known: A curved, solar absorber surface with a spe...
Question: 13.1

Consider a diffuse circular disk of diameter D and area Aj and a plane diffuse surface of area Ai ≪ Aj. The surfaces are parallel, and Ai is located at a distance L from the center of Aj. Obtain an expression for the view factor Fij. ...

Known: Orientation of small surface relative to la...
Question: 12.12

A flat-plate solar collector with no cover plate has a selective absorber surface of emissivity 0.1 and solar absorptivity 0.95. At a given time of day the absorber surface temperature Ts is 120°C when the solar irradiation is 750 W/m², the effective sky temperature is -10°C, and the ambient air ...

Known: Operating conditions for a flat-plate solar...
Question: 12.11

A small, solid metallic sphere has an opaque, diffuse coating for which αλ = 0.8 for λ ≤ 5 μm and αλ = 0.1 for λ > 5 μm. The sphere, which is initially at a uniform temperature of 300 K, is inserted into a large furnace whose walls are at 1200 K. Determine the total, hemispherical absorptivity and ...

Known: Brick wall of surface temperature T_...