1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
beks73 [17]
3 years ago
9

An electric air heater consists of a horizontal array of thin metal strips that are each 10 mm long in the direction of an airst

ream that is in parallel flow over the top of the strips. Each strip is 0.2 m wide, and 25 strips are arranged side by side, forming a continuous and smooth surface over which the air flows at 2 m/s. During operation, each strip is maintained at 500°C and the air is at 25°C. What is the rate of convection heat transfer from the first strip? The fifth strip? The tenth strip? All the strips?
Physics
1 answer:
sweet-ann [11.9K]3 years ago
6 0

Answer:

see explanation below

Explanation:

Given that,

T_1 = 500°C

T_2 = 25°C

d = 0.2m

L = 10mm = 0.01m

U₀ = 2m/s

Calculate average temperature

\\T_{avg} = \frac{T_1 + T_2}{2} \\\\T_{avg} = \frac{500 + 25}{2} \\\\T_{avg} = 262.5

262.5 + 273

= 535.5K

From properties of air table A-4 corresponding to T_{avg} = 535.5K \approx 550K

k = 43.9 × 10⁻³W/m.k

v = 47.57 × 10⁻⁶ m²/s

P_r = 0.63

A)

Number for the first strips is equal to

R_e_x = \frac{u_o.L}{v}

R_e_x = \frac{2\times 0.01}{47.57 \times 10^-^6 }\\\\= 420.4

Calculating heat transfer coefficient from the first strip

h_1 = \frac{k}{L} \times 0.664 \times R_e_x^1^/^2 \times P_r^1^/^3

h_1 = \frac{43.9 \times 10^-^3}{0.01} \times 0.664\times420 \times 4^1^/^2 \times 0.683^1^/^3\\\\= 52.6W/km^2

The rate of convection heat transfer from the first strip is

q_1 = h_1\times(L\times d)\times(T_1 - T_2)\\\\q_1 = 52.6 \times (0.01\times0.2)\times(500-25)\\\\q_1 = 50W

The rate of convection heat transfer from the fifth trip is equal to

q_5 = (5 \times h_o_-_5-4\times h_o_-_4) \times(L\times d)\times (T_1 -T_2)

h_o_-_5 = \frac{k}{5L} \times 0.664 \times (\frac{u_o\times 5L}{v} )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.05} \times0.664\times (\frac{2 \times 0.05}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 25.5W/Km^2

Calculating h_o_-_4

h_o_-_4 = \frac{k}{4L} \times 0.664 \times (\frac{u_o\times 4L}{v } )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.04} \times0.664\times (\frac{2 \times 0.04}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 26.3W/Km^2

The rate of convection heat transfer from the tenth strip is

q_1_0 = (10 \times h_o_-_1_0-9\times h_o_-_9) \times(L\times d)\times (T_1 -T_2)

h_o_-_1_0 = \frac{k}{10L} \times 0.664 \times (\frac{u_o\times 10L}{v } )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.1} \times0.664\times (\frac{2 \times 0.1}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 16.6W/Km^2

Calculating

h_o_-_9 = \frac{k}{9L} \times 0.664 \times (\frac{u_o\times 9L}{v } )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.09} \times0.664\times (\frac{2 \times 0.09}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 17.5W/Km^2

Calculating the rate of convection heat transfer from the tenth strip

q_1_0 = (10 \times h_o_-_1_0-9\times h_o_-_9) \times(L\times d)\times (T_1 -T_2)\\\\q_1_0 = (10 \times 16.6 -9\times 17.5) \times(0.01\times 0.2)\times (500 -25)\\\\=8.1W

The rate of convection heat transfer from 25th strip is equal to

q_2_5 = (25 \times h_o_-_2_5-24\times h_o_-_2_4) \times(L\times d)\times (T_1 -T_2)

Calculating h_o_-_2_5

h_o_-_2_5 = \frac{k}{25L} \times 0.664 \times (\frac{u_o\times 25L}{v } )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.25} \times0.664\times (\frac{2 \times 0.25}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 10.5W/Km^2

Calculating h_o_-_2_4

h_o_-_2_4 = \frac{k}{24L} \times 0.664 \times (\frac{u_o\times 24L}{v } )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.24} \times0.664\times (\frac{2 \times 0.24}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 10.7W/Km^2

Calculating the rate of convection heat transfer from the tenth strip

q_2_5 = (25 \times h_o_-_2_5-24\times h_o_-_2_4) \times(L\times d)\times (T_1 -T_2)\\\\q_1_0 = (25 \times 10.5 -24\times 10.7) \times(0.01\times 0.2)\times (500 -25)\\\\=5.4W

You might be interested in
Calculate the area of a square with a length of 5cm
mihalych1998 [28]

Answer:

25cm^2

Explanation:

area of square = side × side

length of side given = 5

area of this square = 5× 5

= 25cm^2

hope it helps

6 0
3 years ago
Read 2 more answers
What is:<br> the fastest car <br> the fastest animal<br> the fastest human<br> the fastest aeroplane
seropon [69]
The Hennessey Venom GT<span> is the fastest road car in the world.
</span>The fastest land animal<span> is the </span>Cheetah
Usain Bolt, the World's fastest<span> man.
</span>The Lockheed SR-71<span> "</span>Blackbird<span>" the fastest airplane.</span>
<span>

</span>
4 0
3 years ago
Read 2 more answers
In a ________________ wave, such as a sound wave, the particles in the medium vibrate in the same direction that the wave travel
Varvara68 [4.7K]
The answer would be A, transverse.
6 0
2 years ago
How does a sound wave transfer energy to your ears ?
KiRa [710]
It transfers energy through the source of the sound. Your ear detects sound waves when vibrating air particles cause your ear drum to vibrate
4 0
3 years ago
Read 2 more answers
It is observed that the time for the ball to strike the ground at b is 2.5 s. determine the speed at which the ball was thrown.
Alika [10]
Ergrexgehtenhyrnsehtrsjyrrsjjrt
6 0
2 years ago
Other questions:
  • The movement of particles from high to low concentration. True or False
    12·1 answer
  • A car increases its speed from 9.6 meters per second to 11.2 meters per second in 4.0 seconds. The average acceleration of the c
    14·2 answers
  • A 1700kg rhino charges at a speed of 50.0km/h. what average force is needed to bring the rhino to a stop in 0.50s?
    8·1 answer
  • A piston-cylinder assembly contains air at a pressure of 30 lbf/in2 and a volume of 0.75 ft3. The air is heated at constant pres
    15·1 answer
  • The variable you want to test is...
    6·1 answer
  • A 17-kg sled is being pulled along the horizontal snow-covered ground by a horizontal force of 33 N. Starting from rest, the sle
    14·1 answer
  • Estimate the average power of a water wave when it hits the chest of an adult standing in the water at the seashore. Assume that
    12·1 answer
  • gAn Olympic diver is on a diving platform 5.40 m above the water. To start her dive, she runs off of the platform with a speed o
    5·1 answer
  • Which of the following can provide direct current?
    10·1 answer
  • 22 Newton force is working on a 1,901 gram object. What is the acceleration in<br> meter/s^2 unit
    8·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!