Concept explainers
A spherical aluminum shell of inside diameter
Want to see the full answer?
Check out a sample textbook solutionChapter 12 Solutions
Fundamentals of Heat and Mass Transfer
Additional Engineering Textbook Solutions
Machine Elements in Mechanical Design (6th Edition) (What's New in Trades & Technology)
Fundamentals of Aerodynamics
Introduction To Finite Element Analysis And Design
HEAT+MASS TRANSFER:FUND.+APPL.
Thinking Like an Engineer: An Active Learning Approach (4th Edition)
Vector Mechanics for Engineers: Statics and Dynamics
- 11.31 A large slab of steel 0.1 m thick contains a 0.1 -m-di- ameter circular hole whose axis is normal to the surface. Considering the sides of the hole to be black, specify the rate of radiative heat loss from the hole. The plate is at 811 K, and the surroundings are at 300 K.arrow_forwardA thin, disk-shaped silicon wafer of diameter D=20 cm on a production line must be maintained at a temperature of 100 deg C. The wafer loses heat to the room by convection and radiation from its upper surface, while heat is supplied at a constant flux from below. The surrounding air is at 20 deg C, while all surrounding surfaces (which can be treated as blackbodies) can be approximated to be isothermal at a temperature of 15 deg C. The wafer-to-air heat transfer coefficient is 30 W/m2-K and the emissivity of the wafer’s surface (which can be approximated to be gray) is 0.85. How much heat (in W) must be supplied to the wafer?arrow_forwardA typical car's exterior consists of a thin layer of silica (SiO2) over an opaque painted metal panel. Silica is transparent in the visible wavelengths but offers high reflectance in the near- to mid- infrared wavelengths. The plot on the next page depicts the diffuse spectral reflectivity (pa) of the car's surface: Spectral reflectivity, P₂ 0.8 0.6 0.4 ལ 0.2 0 0.1 1 1 10 Wavelength, λ(μm) 100 If the car's exterior temperature is T₁ = 77°C, determine both the total absorptivity (a) and the total emissivity (a) of the silica-covered panel. Assume that the Sun's temperature is Tsun = 5800 K.arrow_forward
- Two concentric spheres of diameter D = 0.9 m and D2 = 1.2 m are separated by an air space and have surface temperatures of T = 390 Kand T2 = 300 K. (a) If the surfaces are black, what is the net rate of radiation exchange between the spheres, in W? 912 = i w (b) What is the net rate of radiation exchange between the surfaces if they are diffuse and gray with ej = 0.5 and ez = 0.05, in W? 912 = W (c) What is the net rate of radiation exchange if D2 is increased to 20 m, with e, = 0.05, e = 0.5, and D = 0.9 m, in W? 912 = (d) What is the net rate of radiation exchange if the larger sphere behaves as a black body (82 = 1.0) and with e1 = 0.5, D2 = 20 m, and D, = 0.9 m, in W? 412 =arrow_forwardCalculate the radiation in watts per square centimeter from a block of copper at 200°C and at 1000°C. The oxidized copper surface radiates at 0.60 the rate of a black body.arrow_forwardSpectral hemispherical reflectivity distribution of an opaque surface is shown below. Surface is subjected to the spectral irradiation as shown. 1.0 400 a 0.4 200 5 10 15 20 a (um) 5 10 15 2 (um) Calculate the total irradiation on the surface in W/m2 Calculate the irradiation absorbed by the surface in W/m2 3250 || 3750 || 4250|| 5000 || 5750|| 6250|| 7500 1050 || 1200 1400|| 1600|| 1750| 1850 || 2000arrow_forward
- In a biprism experiment, the slit is illuminated by the light of wavelength 5890A.the distance between the slit and eye piece is 0.8m.the two virtual images of the slit are formed 0.2cm apart. Calculate the change in fringe width if the eye piece is displaced 10cm away from the slit.arrow_forwardA half cylindrical shell with a radius of 75 cm is held at 200°C and has an emissivity of 0.4. A long 200°C R= 75 cm cylinder has a diameter of 30 cm and is placed 20°C E= 0.4 D= 30 cm concentrically with the shell. The cylinder is radiatively black. At the instant the cylinder is 20°C, how much heat is exchanged from the shell to the cylinder, per meter length into the page, i.e., Qshell-eylinder/L.arrow_forwardes Check my work Required information Irradiation on a semi-transparent medium is at a rate of 610 W/m2. If 160 W/m2 of the irradiation is reflected from the medium and 130 W/m2 is transmitted through the medium, Determine the absorptivity of the medium. The absorptivity of the medium is.arrow_forward
- Eat И 5000 6000 7000 2(A)arrow_forwardTwo concentric spheres of diameter D = 0.7 m and D2 = 1.2 m are separated by an air space and have surface temperatures of T = 400 K and T, = 300 K. (a) If the surfaces are black, what is the net rate of radiation exchange between the spheres, in W? 912 = (b) What is the net rate of radiation exchange between the surfaces if they are diffuse and gray with & = 0.5 and &2 = 0.05, in W? 912 = W (c) What is the net rate of radiation exchange if D2 is increased to 20 m, with &2 = 0.05, €1 = 0.5, and D1 = 0.7 m, in W? 912 = W (d) What is the net rate of radiation exchange if the larger sphere behaves as a black body (82 = 1.0) and with &1 = 0.5, D2 = 20 m, and D = 0.7 m, in W? 912 = Warrow_forwardTwo parallel gray planes have emissivities of 0.8 and 0.7 and are maintained at 800°C and 1500°C. What is the net radiation energy exchange? What would be the reduction in heat transfer if radiation shield of polished aluminums =0.04 is placed between them.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning