7-34 An array of power transistors, dissipating 5 W of power each, are to be cooled by mounting them on a 25-cm x 25-cm-square aluminum plate and blowing air at 35°C over the plate with a fan at avelocity of 4 m/s. The average temperature of the plate is not to exceed 65°C. Assuming the heat transfer from the back side of the plate to be negligible and disregarding radiation, determine the numberof transistors that can be placed on this plate.FIGURE P7-34AluminumPowerplatetransistor, 5 W35°C25 cmAir →4 m/s-65°C25 cm

Determine the average film temperature by using the information given in the question. Here, Ts is…

Answered: 7-34 An array of power transistors,…

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

An array of power transistors, dissipating 6 W ofpower each, are to be cooled by mounting them on a 25-cm *25-cm-square aluminum plate and blowing air at 35°C overthe plate with a fan at a velocity of 4 m/s. The average temperatureof the plate is not to exceed 65°C. Assuming theheat transfer from the back side of the plate to be negligibleand disregarding radiation, determine the number of transistorsthat can be placed on this plate.
The chilling room of a meat plant is 15 m × 18 m × 5.5 m in size and has a capacity of 350 beef carcasses. The power consumed by the fans and the lights in the chilling room are 22 and 2 kW, respectively, and the room gains heat through its envelope at a rate of 14 kW. The average mass of beef carcasses is 220 kg. The carcasses enter the chilling room at 35C, after they are washed to facilitate evaporative cooling, and are cooled to 16°C in 12 h. The air enters the chilling room at 2.2°C and leaves at 0.5°C. Determine (a) the refrigeration load of the chilling room and (b) the volume flow rate of air. The average specific heats of beef carcasses and air are 3.14 and 1.0 kJ/kg · °C, respectively, and the density of air can be taken to be 1.28 kg/m3 .
The blades of a wind turbine turn a large shaft at a relatively slow speed. The rotational speed is increased by a gearbox that has an efficiency of 0.93. In turn, the gearbox output shaft drives an electric generator with an efficiency of 0.95. The cylindrical nacelle, which houses the gearbox, generator, and associated equipment, is of length L = 6 m and diameter D = 3 m. If the turbine produces P = 2.5 MW of electrical power, and the air and surroundings temperatures are T = 25 oC and Tsur = 20 oC, respectively, determine the minimum possible operating temperature inside the nacelle. The emissivity of the nacelle is 0.83, and the convective heat transfer coefficient is h = 35 W/m2 .K. The surface of the nacelle that is adjacent to the blade hub can be considered to be adiabatic, and solar irradiation may be neglected. Use Fin or N number of fins to reduce the Ts of the nacelle less than 143 oC
An array of power transistors, dissipating 6W of power each, are to be cooled by mounting them on a 25cm x 25xm square aluminum plate and blowing air at 35o over the plate with a fan at a velocity of 4m/s. The average temperature of the plate is not to exceed 65oC. Assuming the heat transfer from the back side of the plate to be negligible and disregarding radiation, determine the number of transistors that can be placed on the plate. Hint 1: This is a flat plate question. DO NOT treat the transistors as a tube bank. How much heat is dissipated across the flat side of the plate (opposite the side the transistors are mounted on). Hint 2: Use the average Reynold’s and Nusselt numbers
An average man has abody surface area of 1.8m2 and a skin temperature of 33degrees celcius .The convection heat transfer coefficient for a clothed person walking in still air is expressed as {h,8.6V^0.53}FOR 0.5<v<2m/s,where V is the walking velocityin m/s.Assuming the average surface temperature of the clothed person to be 30degrees celcius, determine the rate of heat loss from an average man walking in still air at 10degrees celcius by convectionat a walking velocity of (a)0.5m/s (b)1.0m/s (c)1.5m/s (d)2.0m/s
5-39 Air at 1 atm and 300 K blows across a 50-cm-square flat plate at a velocity such thatthe Reynolds number at the downstream edge of the plate is 1.1×105. Heating doesnot begin until halfway along the plate and then the surface temperature is 400 K.Calculate the heat transfer from the plate. Heat transfer-Holman
An average man has a body surface area of 1.8 m2 and a skin temperature of 330C. The convective heat transfer coefficient for a clothed person walking in still air is expressed as h= 8.6V0.53 where V is the walking velocity in m/s. Assuming the average surface temperature of the clothed person to be 300C, determine the rate of heat lost by convection from an average man walking in still air at 100C at a walking velocity of 1.2 m/s.
The heat is dissipated from the plate by convection and radiation into surrounds at 20 C . Take ε =0.8 , σ =5.67×10**-8 and h∞ = 6 W/m**2. K. If the surface temperature of the plate is 50 C ,the value of the heat flux from the plate is :
A long 10-cm-diameter steam pipe whose external surface temperature is 110°C passes through some open area that is not protected against the winds . Determine the rate of heat loss from the pipe per unit of its length when the air is at 1 atm pressure and 10°C and the wind is blowing across the pipe at a velocity of 8 m/s.
Metal plates (k = 150 W/m·K, ρ= 2800 kg/m3, and cp = 900 J/kg·K) with a thickness of 2 cm exiting an oven are conveyed through a 10-m long cooling chamber at a speed of 4 cm/s, as shown in the figure. The plates enter the cooling chamber at an initial temperature of 500°C. The air temperature in the cooling chamber is 15°C, and the plates are cooled with blowing air and the convection heat transfer coefficient is given as a function of the air velocity h(V) = 33V0.8, where h is in W/m2·K and V is in m/s. To prevent any hazard to workers handling the plates, it is necessary to design the cooling process such that the plates exit the cooling chamber at a relatively safe temperature of 50°C or less. Determine the air velocity V and the heat transfer coefficient h such that the temperature of the plates exiting the cooling chamber is at 50C.
Hot engine oil at 150°C is flowing in parallel over a flat plate at a velocity of 3.30 m/s. Surface temperature of the 1.800-m long flat plate is constant at 50°C. The properties of engine oil at Tf = (150°C + 50°C)/2 = 100°C are k = 0.1367 W/m∙K, v = 2.046 × 10−5 m2/s, Pr = 279.1. Determine the local convection heat transfer coefficient at 0.200 m from the leading edge and the average convection heat transfer coefficient. The local convection heat transfer coefficient at 0.200 m from the leading edge is ___ W/m2·K. The average convection heat transfer coefficient is ___ W/m2·K.
A 1.8-m-diameter spherical tank of negligible thickness contains iced water at 0°C. Air at 25°C flows over the tank with a velocity of 7 m/s. Determine the rate of heat transfer to the tank and the rate at which ice melts. The heat of fusion of water at 0°C is 333.7 kJ/kg.

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