13.48 An electronic device dissipating 50 W is attached tothe inner surface of an isothermal cubical containerthat is 120 mm on a side. The container is locatedin the much larger service bay of the space shuttle,which is evacuated and whose walls are at 150 K. Ifthe outer surface of the container has an emissivity of0.8 and the thermal resistance between the surface andthe device is 0.1 K/W, what are the temperatures ofthe surface and the device? All surfaces of the con-tainer may be assumed to exchange radiation with theservice bay, and heat transfer through the containerrestraint may be neglected.

Answered: Image /qna-images/answer/a222ae50-52f8-4dd2-b384-653b4dfd4f22.jpg

Answered: 13.48 An electronic device dissipating…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

See similar textbooks

Similar questions

- A furnace can be considered like a long semicylindrical duct of diameter D = 5 m. The base (1) and the dome (2) of the furnace have emissivity's of 0.5 and 0.9 and are maintained at uniform temperatures of 305 and 1000 K, respectively. a- Draw the network of the system. b- Calculate total resistance. b- Determine the net rate of radiation heat transfer per unit length from the dome to the base surface.
7) Given a window of 20 ft facing east at 40° north latitude, estimate the cooling load due to solar radiation at 4:00 pm for a day in June. Assume the window does not have any interior shading and the shading coefficient is 0.2 (in Btu/hr) (a) 105 (d) 276 (b) 430 (c) 314 (c) 225
PROBLEM 4: A black thermocouple is inside a chamber with black walls. If the air around the thermocouple is at 20°C, the walls are at 100-C, and the heat transfer coefficient between the thermocouple and the air is 75 W/m²K, what temperature will the thermocouple read?
Consider a silicon wafer positioned in a furnace that is zone-heated on the top section and cooled on the lower section. The wafer is placed such that the top and bottom surfaces of the wafer exchange radiation with the hot and cold zones respectively of the furnace. The zone temperatures are Tsur,h = 1050 K and Tsur.e = 330 K. The emissivity and thickness of the wafer are e = 0.65 and d = 0.78 mm, respectively. With the ambient gas at T. = 700 K, convection heat transfer coefficients at the upper and lower surfaces of the wafer are 8 and 4 W/m²-K. Find the steady-state temperature of the wafer, in K. Tw i K
5. A horizontal uninsulated steam pipe passes through a large room whose wall and ambient air are at 300 K. The air in the room is quiescent. The pipe of 150-mm diameter has an emissivity of 0.85 and an outer surface temperature of 400 K. Calculate the heat loss per unit length from the pipe.
A composite wall is comprised of two large plates separated by sheets of refractory insulation. In the installation process, the sheets of thickness L = 50 mm and thermal conductivity k = 0.05 W/mK are separated at 1-m intervals by gaps of width w = 10 mm. The hot and cold plates have temperatures and emissivities of T1 = 400 deg C, emissivity1 = 0.85 and T2 = 35 deg C, emissivity2 = 0.5, respectively. Assume that the plates and insulation are diffuse-gray surfaces. %3D Determine the heat loss by radiation through the gap per unit length of the composite wall (normal to the page). Recognizing that the gaps are located on a 1-m spacing, determine what fraction of the total heat loss through the composite wall is due to transfer by radiation through the insulation gap. Hot side Gap w = 10 mm A. 47 W/m, 9.2% T1 = 400°C B. 47 W/m, 10.2% L = 50 mm C. 37 W/m, 10.2% D. 37 W/m, 9.2% T2 = 35°C Cold side 1 m Insulation, k = 0.05 W/m-K
A long electrical conductor of 10 mm diameter is concentric with a refrigerated cylindrical tube of 50 mm diameter whose surface has an emissivity of 0.9 and temperature of 27 °C. The electrical conductor has a surface emissivity of 0.6 and dissipates 6.0 W per meter length. Assuming that the space between the two surfaces is empty, calculate the surface temperature of the conductor.
A tube pipe is heated to a temperature of 150°C with an outside diameter of 12cm and it’s enclosed in a large room of 20°C. Calculate the radiant heat loss per unit length, if the surface emissivity is 0.65.
2. A heater is a thin vertical panel 1.0m long and 0.7m high and is used in a warehouse to keep workers warm. The heater has air circulating on each side. Assume the maximum temperature of the panel is 60°C (already above the board line that is safe for human hands to touch briefly without getting hurt). Assume the room air temperature is 18°C but the warehouse wall temperature is 5°C. Model the surface with an emittance of 0.9 and Vair = 1.57x105 m²/s. a. Determine the maximum power rating for the heater. b. Now if you run the heat by standing on its side (it will be 1.0 m high and 0.7 m long), determine the surface temperature. c. Compare case a and b and explain any differences you see.
4. The surface temperature of a planet is T, and the measured temperature is Tm (i.e. the temper- ature measured at the top-of-atmosphere based on the upwards flux Ft there). Assume radiative equilibrium. (a) Show that the infrared optical depth of the planet's surface 7 is related to the surface temperature T, and the measured temperature Tm by Calculate the infrared optical depth at the surfaces of (a) Earth, where T, = 300 K and Tm = 250 K. (b) Venus, where T, = 750 K and Tm = 230 K. (c) Mars, where T, = 240 K and T, = 220 K.
. Calculate the heat transfer rate per m² area by radiation between the surfaces of two long cylinders having radii 100 mm and 50 mm respectively. The smaller cylinder being in the larger cylinder. The axes of the cylinders are parallel to each other and separated by a distance of 20 mm. The surfaces of inner and outer cylinders are maintained at 127°C and 27°C respectively. The emissivity of both the surfaces is 0.5.
Example 7.9 The filament of a 75 W light bulb may be considered a black body radiating into a black enclosure at 70°C.The filament diameter is 0.10 mm and length is 50 mm. Considering the radiation, determine the filament temperature.

SEE MORE QUESTIONS

Recommended textbooks for you

Elements Of Electromagnetics

Mechanical Engineering

ISBN:

9780190698614

Author:

Sadiku, Matthew N. O.

Publisher:

Oxford University Press

Mechanics of Materials (10th Edition)

Mechanical Engineering

ISBN:

9780134319650

Author:

Russell C. Hibbeler

Publisher:

PEARSON

Thermodynamics: An Engineering Approach

Mechanical Engineering

ISBN:

9781259822674

Author:

Yunus A. Cengel Dr., Michael A. Boles

Publisher:

McGraw-Hill Education

Elements Of Electromagnetics

Mechanical Engineering

ISBN:

9780190698614

Author:

Sadiku, Matthew N. O.

Publisher:

Oxford University Press

Mechanics of Materials (10th Edition)

Mechanical Engineering

ISBN:

9780134319650

Author:

Russell C. Hibbeler

Publisher:

PEARSON

Thermodynamics: An Engineering Approach

Mechanical Engineering

ISBN:

9781259822674

Author:

Yunus A. Cengel Dr., Michael A. Boles

Publisher:

McGraw-Hill Education

Control Systems Engineering

Mechanical Engineering

ISBN:

9781118170519

Author:

Norman S. Nise

Publisher:

WILEY

Mechanics of Materials (MindTap Course List)

Mechanical Engineering

ISBN:

9781337093347

Author:

Barry J. Goodno, James M. Gere

Publisher:

Cengage Learning

Engineering Mechanics: Statics

Mechanical Engineering

ISBN:

9781118807330

Author:

James L. Meriam, L. G. Kraige, J. N. Bolton

Publisher:

WILEY

SEE MORE TEXTBOOKS