7-28 A transformer that is 10-cm long, 6.2-cm wide, and 5-cm high is to be cooled by attaching a 10-cm x 6.2-cm-wide polished aluminum heat sink (emissivity = 0.03) to its top surface. The heat sink hasseven fins, which are 5-mm high, 2-mm thick, and 10-cm long. A fan blows air at 25°C parallel to the passages between the fins. The heat sinkheat sink is not to exceed 60°C. Assuming the fins and the base plate to be nearly isothermal and the radiation heat transfer to be negligible, determine the minimum free-stream velocity the fan needs tosupply to avoid overheating. Assume the flow is laminar over the entire finned surface of the transformer.to dissipate 12 W of heat, and the base temperature of theFIGURE P7-28Air25°C60°C-Fins0.5 cm10 cmTransformer5 cm12 W+6.2 cm -

Answered: Image /qna-images/answer/8e202b86-7be7-4409-ace7-b48be04cbc01.jpg

Answered: 7-28 A transformer that is 10-cm long,…

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 transformer that is 1.5 m long, 0.062 m wide, and 0.05 m high is to be cooled by attaching a 1.5-m x 0.062-m-wide polished aluminum heat sink to its top surface. The heat sink has seven fins, which are 0.024 m high, 2 mm thick, and 1.5 m long. A fan blows air at 25°C parallel to the passages between the fins. The heat sink is to dissipate 30 W of heat and the base temperature of the heat sink is not to exceed 60°C. Assuming the heat sink to be black anodized and thus to have an effective emissivity of 0.90, determine the minimum free-stream velocity the fan needs to supply to avoid overheating. Assume the flow is laminar over the entire finned surface of the transformer. Note that in radiation calculations the base area (1.5-m x 0.062-m) is to be used, not the total surface area. The properties of air at 1 atm and the film temperature of (T+ T)/2 = (60 + 25)/2 = 42.5°C are k= 0.02681 W/m-°C, v = 1.726 x 1o-5 m2/s, and Pr = 0.7248. (Round the final answer to one decimal place.) Air…
A domestic refrigerator with inner dimensions of 0.7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 ˚C. The bodies consist of two 10-mm-thick layers of Aluminium (k = 225 W/mK) separated by a 30 mm polyurethane insulation (k=0.028 W/mK). If the average convection heat transfer coefficient at the inner and outer surfaces are 11.6 W/m2K and 14.5 W/m2K respectively, calculate: the resistance(R) for the Aluminium near the outer thermal layer in K/W to 8 decimal places this question is from thermodynamics
Finned heat sinks are used to keep computer chips in an acceptable temperature range. The heat sink base is 53 mm x 57 mm, and the maximum allowable chip temperature is 75 C. An array of 54 aluminum fins (k = 237 W/m*K) which have a square cross-section (3 mm x 3 mm) are attached to the heat sink. The length of each fin is 30 mm. The cooling air supplied to the heat sink is 25 C. If the convection heat transfer coefficient is 125 W/m2*K, what is the heat transfer rate (in W) from the heat sink, assuming adiabatic fin tips? (Hint: heat transfer does not solely occur from the fins.)
A domestic refrigerator with inner dimensions of 0.7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 ˚C. The bodies consist of two 10-mm-thick layers of Aluminium (k = 225 W/mK) separated by a 30 mm polyurethane insulation (k=0.028 W/mK). If the average convection heat transfer coefficient at the inner and outer surfaces are 11.6 W/m2K and 14.5 W/m2K respectively, calculate: the resistance(R) for the Aluminium near the inner thermal layer in K/W to 8 decimal places.
A 12cm outside diameter and 10cm inside diameter cast iron pipe with conductivity of 80W/m-K has 4 cm of polystyrene insulation with conductivity of 0.027W/m-K. Saturated steam at 500degC is flowing through pipe and the outside surface temperature is 60degC. Determine the temperature of the outside surface of the pipe.
An industrial freezer is designed to operate with an internal air temperature of -20°C when the external air temperature is 27°C, and the internal and external heattransfer coefficients are 8 W/m2 -K and 12 W/m2 -K, respectively. The walls of thefreezer are composite construction, comprising an inner layer of plastic (k = 0.33 W/m-K, and thickness of 10 mm), and an outer layer of stainless steel (k = 15 W/m-K, and thickness of 3 mm). Sandwiched between these two layers is a layer of insulation material with k = 0.07 W/m-K. Find the width (mm) of the insulation thatis required to reduce the convective heat loss to 60 W/m2.
Steam at To1= 320°C flows through a cast iron pipe (k = 80 W/mK) with inner and outer diameters of D1= 5cm and D2 = 5.5 cm, respectively. The pipe is covered with 3-cm-thick glass wool insulation with k = 0.05 W/mk(Figure Q2). Heat is lost to the surroundings (To2 = 5°C) by natural convection and radiation, with a combinedheat transfer coefficient of h2 = 18 W/m2.K.(a) Taking the heat transfer coefficient inside the pipe to be h1 = 60 W/m2 K, Calculate the rate of heat lossfrom steam per unit length of pipe.(b) Calculate the temperature differences between the pipe shell and the insulation. Someone comments that a microwave oven can be viewed as a conventional oven with zero convectionresistance at the surface of the food. Is this a correct statement? Discuss the reason.
The 5-mm-thick bottom of a 200-mm-diameter pan may be made from aluminum (k = 240 W/m.K) or copper (k = 390 W/m-K). When used to boil water, the surface of the bottom exposed to the water is nominally at 110°C and heat is transferred from the stove to the pan at a rate of 1200 W. What is the temperature of the surface in contact with the stove for each of the two materials? Aluminum: T = i °℃ Copper: T = °℃ i
A thin board of 0.5 cm thickness is exposed to a fluid of T, = 22°C and h = 30 W/m².K from one side with an emissivity of 0.7 where it faces a surrounding whose temperature is Tsur = 30°C. A heat flux of q" = 3500 W/m? is applied to the other side. Each side has an area of 12cm×12cm. Tsur (a) If the board has the following properties: k = 15.1 W/m.K, c, = 480 J/kg.K and p = 8055 kg/m², express an equation for the variation of temperature with respect to time. (b) Find the initial time rate of change of the board temperature if the initial board temperature is q" h 50°C.
A glass window with an area of 0.625 m² is installed in the wooden outside wall of a room. The wall dimensions are 25 x 3.05 m. The wood has a k of 0.151W/m.K and is 3.05 cm thick. The glass has a k of 0.692W/m.K and is 5.0 mm thick. The temperature of the inside room is 27°C and outside air temperature is 268K. (1)What is the heat loss through wooden wall and glass window q(W) ? (2) What are the total heat loss?
16-90 An electric heater with the total surface area of 0.25 m² and emissivity 0.75 is in a room where the air has a temperature of 20°C and the walls are at 10°C. When the heater consumes 500 W of electric power, its surface has a steady temperature of 120°C. Determine the temperature of the heater surface when it consumes 700 W. Solve the problem (a) assuming negligible radiation and (b) taking radiation into consideration. Based on your results, comment on the assumption made in part (a). We Too, h FIGURE P16-90 Ts Α, ε Qconv Qrad Tw

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