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Svetllana [295]
3 years ago
6

A classroom that normally contains 40 people is to be air-conditioned with window air-conditioning units of 5 kW cooling capacit

y. A person at rest may be assumed to dissi- pate heat at a rate of about 80 Watts. There are 10 light bulbs in the room, each with a rating of 100 W. The rate of heat transfer to the classroom through the walls and the windows is estimated to be 15,000 kJ/h.
a. If the room air is to be maintained at a constant temperature of 21°C, determine the number of window air-conditioning units required.
b. What is the source of heat being generated for the light bulbs and for the students?
Engineering
1 answer:
kap26 [50]3 years ago
4 0

Answer:

Explanation:

a ) Heat energy given out by 40 people

= 40 x 80 = 3200 J in one second

Heat energy given out by 10 light bulbs

= 10 x 100 = 1000 J in one second

Heat transfer by wall = 15000 x 1000 J in one hour

= 15000 x 1000 / 60 x 60

= 4166.67 J in one second

Total energy

= 3200 + 1000 + 4166 .67 J in one second

= 8366.67 J

To drive this much of heat , we need 2 air -conditioner of 5000 W each.

b ) Source of heat for bulb is electrical energy of bulb

For the students , source of heat by student is the bio- chemical reactions taking place in the body of the student which is exothermic.

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Explain in detail the difference between the microstructures of a cold worked sample and Recrystallized sample ?
MrRa [10]

Answer:

A recrystallization process differs mainly from a restoration process (microestructures of a cold worked sample) in that  the first, the microstructure of the final product consists mainly of  high angle borders.

Explanation:

The microstructure of a cold worked material has a high energy stored in dislocations and subgrains. During a heat treatment, this microstructure evolves in order to achieve a more stable state by reducing its energy. The complex microscopic mechanisms that take place during this process have been traditionally encompassed in three categories: restoration, recrystallization and grain growth, which will be discussed later.

These processes generally lead to the total or partial recovery of the original properties of the material (ductility, resistance). They can take place under dynamic conditions, that is, during thermomechanical processing or when the material is subsequently deformed at high temperature, and under static conditions, that is, during a heat treatment after thermomechanical processing.

The term <em>restoration</em> encompasses the following succession of micromechanism: formation of dislocation cells,  annihilation of dislocations within them, formation of subgrains and their growth.

<em>A recrystallization process differs mainly from a restoration process in that in the first one the microstructure of the final product is mainly formed by high-angle borders.</em>

7 0
4 years ago
During an office party, an office worker claims that a can of cold beer on his table warmed up to 20oC by picking up energy from
Contact [7]

Answer:

Yes

Explanation:

As we know that heat transfer take place from high temperature body to low temperature body.

In the given problem ,the temperature of the air is high as compare to the temperature  of can of bear ,so the heat transfer will take place from air to can of bear and at the last stage when temperature of can of bear will become to the temperature of air then heat transfer will be stop.Because temperature of the  both body will become at the same  and this stage is called thermal equilibrium.

So an office worker claim is correct.

4 0
3 years ago
A computer maintenance company wants to 'capture' the knowledge that employees carry around in their heads by creating a databas
galina1969 [7]

Answer: The answer is A. The company is trying to transfer intellectual capital to a knowledge management system

5 0
3 years ago
A solid cylindrical workpiece made of 304 stainless steel is 150 mm in diameter and 100 mm is high. It is reduced in height by 5
goblinko [34]

Answer:

45.3 MN

Explanation:

The forging force at the end of the stroke is given by

F = Y.π.r².[1 + (2μr/3h)]

The final height, h is given as h = 100/2

h = 50 mm

Next, we find the final radius by applying the volume constancy law

volumes before deformation = volumes after deformation

π * 75² * 2 * 100 = π * r² * 2 * 50

75² * 2 = r²

r² = 11250

r = √11250

r = 106 mm

E = In(100/50)

E = 0.69

From the graph flow, we find that Y = 1000 MPa, and thus, we apply the formula

F = Y.π.r².[1 + (2μr/3h)]

F = 1000 * 3.142 * 0.106² * [1 + (2 * 0.2 * 0.106/ 3 * 0.05)]

F = 35.3 * [1 + 0.2826]

F = 35.3 * 1.2826

F = 45.3 MN

7 0
3 years ago
Let be a real-valued signal for which when . Amplitude modulation is preformed to produce the signal . A proposed demodulation t
densk [106]

Answer:

hello your question is incomplete attached below is the complete question

answer : attached below

Explanation:

let ; x(t)  be a real value signal for x ( jw ) = 0 , |w| > 200\pi

g(t) = x ( t ) sin ( 2000 \pi t )

x_{1} (t) = \frac{1}{2}  x(t)  sin ( 4000\pi t )

next we apply Fourier transform

attached below is the remaining part of the solution

6 0
3 years ago
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