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Xelga [282]
3 years ago
11

A pipe is insulated such that the outer radius of the insulation is less than the critical radius. Now the insulation is taken o

ff. Will the rate of heat transfer from the pipe increase or decrease for the same pipe surface temperature?
Engineering
1 answer:
irina [24]3 years ago
7 0

Answer:

the heat transfer from the pipe will decrease when the insulation is taken off for r₂< r_{cr}

where;

r₂ = outer radius

r_{cr} = critical radius

Explanation:

Note that the critical radius of insulation depends on the thermal conductivity of the insulation k and the external convection heat transfer coefficient h .

r_{cr} =\frac{k}{h}

The rate of heat transfer from the cylinder increases with the addition of insulation for outer radius less than  critical radius (r₂< r_{cr}) 0,  and reaches a maximum when r₂ = r_{cr}, and starts to decrease for r₂< r_{cr}. Thus, insulating the pipe may actually increase the rate of heat transfer from the pipe instead of decreasing it when r₂< r_{cr} .

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Windmills slow the air and cause it to fill a larger channel as it passes through the blades. Consider a circular windmill with
Scilla [17]

Answer:

DIAMETER  = 9.797 m

POWER = \dot W = 28.6 kW

Explanation:

Given data:

circular windmill diamter D1 = 8m

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wind speed = 8 m/s

we know that specific volume is given as

v =\frac{RT}{P}

  where v is specific volume of air

considering air pressure is 100 kPa and temperature 20 degree celcius

v =  \frac{0.287\times 293}{100}

v = 0.8409 m^3/ kg

from continuity equation

A_1 V_1 = A_2 V_2

\frac{\pi}{4}D_1^2 V_1 = \frac{\pi}{4}D_1^2 V_2

D_2 = D_1 \sqrt{\frac{V_1}{V_2}}

D_2 = 8 \times \sqrt{\frac{12}{8}}

D_2 = 9.797 m

mass flow rate is given as

\dot m = \frac{A_1 V_1}{v} = \frac{\pi 8^2\times 12}{4\times 0.8049}

\dot m = 717.309 kg/s

the power produced \dot W = \dot m \frac{ V_1^2 - V_2^2}{2} = 717.3009 [\frac{12^2 - 8^2}{2} \times \frac{1 kJ/kg}{1000 m^2/s^2}]

\dot W = 28.6 kW

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U mean how to connect them to your phone?

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Tamiku [17]

Technician B is right say that hard water potting i usually jut a Surface problem that can be wahed off.

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A fully braced structural member in a building is subjected to several different loads, including roof loads of D = 5 k and L_r
allochka39001 [22]

Answer: 37.4K

Explanation:

See attachment

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3 years ago
What are the four categories of engineering materials used in manufacturing?
alexgriva [62]

Answer:

metals, composite, ceramics and polymers.

Explanation:

The four categories of engineering materials used in manufacturing are metals, composite, ceramics and polymers.

i) Metals: Metals are solids made up of atoms held by matrix of electrons. They are good conductors of heat and electricity, ductile and strong.

ii) Composite: This is a combination of two or more materials. They have high strength to weight ratio, stiff, low conductivity. E.g are wood, concrete.

iii) Ceramics: They are inorganic, non-metallic crystalline compounds with high hardness and strength as well as poor conductors of electricity and heat.

iv) Polymers: They  have low weight and are poor conductors of electricity and heat

8 0
3 years ago
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