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svetoff [14.1K]
3 years ago
8

A heated plate is built into the wall of a large room. The room is maintained at 300 K. The exposed surface of the plate is main

tained at 400 K by a heater attached to the back of the plate. Assume the sides of the plate and back of the heater are perfectly insulated. The exposed surface of the plate (area 0.1 m^2 ) has an emissivity of 0.3 and a convection heat transfer coefficient of 6 W/m^2K with the room and air temperature of 300 K. Show resistance circuit for this problem and draw a picture to show relevant heat modes on system to receive full points. Calculate the following:
a. Find the net radiant heat flux from the plate surface, q1"=____
b. The required heater power, P=______
c. The radiosity of the plate surface, J1=
Engineering
1 answer:
myrzilka [38]3 years ago
7 0

Answer:

B

Explanation:

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nirvana33 [79]

Answer:

False.

Explanation:

False. The pressure is above pressure at critical point (22.064 MPa.), the limit where pressure can prevent boiling.

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Explanation:

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2 years ago
Water at atmospheric pressure boils on the surface of a large horizontal copper tube. The heat flux is 90% of the critical value
masya89 [10]

Answer:

The tube surface temperature immediately after installation is 120.4°C and after prolonged service is 110.8°C

Explanation:

The properties of water at 100°C and 1 atm are:

pL = 957.9 kg/m³

pV = 0.596 kg/m³

ΔHL = 2257 kJ/kg

CpL = 4.217 kJ/kg K

uL = 279x10⁻⁶Ns/m²

KL = 0.68 W/m K

σ = 58.9x10³N/m

When the water boils on the surface its heat flux is:

q=0.149h_{fg} \rho _{v} (\frac{\sigma (\rho _{L}-\rho _{v})}{\rho _{v}^{2} }  )^{1/4} =0.149*2257*0.596*(\frac{58.9x10^{-3}*(957.9-0.596) }{0.596^{2} } )^{1/4} =18703.42W/m^{2}

For copper-water, the properties are:

Cfg = 0.0128

The heat flux is:

qn = 0.9 * 18703.42 = 16833.078 W/m²

q_{n} =uK(\frac{g(\rho_{L}-\rho _{v})     }{\sigma })^{1/2} (\frac{c_{pL}*deltaT }{c_{fg}h_{fg}Pr  } \\16833.078=279x10^{-6} *2257x10^{3} (\frac{9.8*(957.9-0.596)}{0.596} )^{1/2} *(\frac{4.127x10^{3}*delta-T }{0.0128*2257x10^{3}*1.76 } )^{3} \\delta-T=20.4

The tube surface temperature immediately after installation is:

Tinst = 100 + 20.4 = 120.4°C

For rough surfaces, Cfg = 0.0068. Using the same equation:

ΔT = 10.8°C

The tube surface temperature after prolonged service is:

Tprolo = 100 + 10.8 = 110.8°C

8 0
3 years ago
You are hitting a nail with a hammer (mass of hammer =1.8lb) the initial velocity of the hammer is 50 mph (73.33 ft/sec). The ti
Archy [21]

Answer:

The nail exerts a force of 573.88 Pounds on the Hammer in positive j direction.

Explanation:

Since we know that the force is the rate at which the momentum of an object changes.

Mathematically \overrightarrow{F}=\frac{\Delta \overrightarrow{p}}{\Delta t}

The momentum of any body is defines as \overrightarrow{p}=mass\times \overrightarrow{v}

In the above problem we see that the moumentum of the hammer is reduced to zero in 0.023 seconds thus the force on the hammer is calculated using the above relations as

\overrightarrow{F}=\frac{m(\overrightarrow{v_{f}}-\overrightarrow{v_{i}})}{\Delta t}

\overrightarrow{F}=\frac{m(0-(-73.33)}{0.23}=\frac{1.8\times 73.33}{0.23}=573.88Pounds

6 0
3 years ago
g A pedometer treats walking 2,000 steps as walking 1 mile. Write a program whose input is the number of steps, and whose output
Nataly [62]

Answer:

# Program is written in Python Programming Language

# Comments are used for explanatory purpose

# Program starts here

# Accept input

Steps = input (Number of Steps: ")

# Calculate distance

distance = float(2000) * float(steps)

#Print Formatted Result

print('%0.2f' % distance)

# End of Program

.--------

The above program converts number of steps to miles.

At line 5, the number of steps is inputted and stored in variable named Steps.

At line 6, the number of miles is calculated by multiplying 2000 by the content of variable Steps

The result is printed at line 8

8 0
2 years ago
Read 2 more answers
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