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3 years ago

About ceramics: Only can be optically opaque or semi-transparent. a) True b)-False

Engineering

1 answer:

julia-pushkina [17]3 years ago

6 0

Answer: True

Explanation: Ceramics have the property that when the band gap present between the atoms are larger than the light energy then the tend to become opaque because the light scattering is caused . They also show the property of being translucent when there are chances of the light to get a path through the surface of ceramic so they get the light at some parts e.g.porcelain .Therefore the statement given is true that ceramics can be optically opaque or semi-transparent(translucent).

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As the impurity concentration in solid solution of a metal is increased, the tensile strength:________.a) decreasesb) increasesc

valkas [14]

Answer:

Increases

Explanation:

By inhibiting the motion of dislocations by impurities in a solid solutions, is a strengthening mechanism. In solid solutions it is atomic level strengthening resulting from resistance to dislocation motion. Hence, the strength of the alloys can differ with respect to the precipitate's property. Example, the precipitate is stronger (ability to an obstacle to the dislocation motion) than the matrix and it shows an improvement of strength.

5 0

3 years ago

A mass weighing 22 lb stretches a spring 4.5 in. The mass is also attached to a damper with Y coefficient . Determine the value

Dominik [7]

Answer:

Cc= 12.7 lb.sec/ft

Explanation:

Given that

m = 22 lb

g= 32 ft/s²

$m = \dfrac{22}{32}=0.6875\ s^2/ft$

x= 4.5 in

1 in = 0.083 ft

x= 0.375 ft

Spring constant ,K

$K=\dfrac{m}{x}=\dfrac{22}{0.375}$

K= 58.66 lb/ft

The damper coefficient for critically damped system

$C_c=2\sqrt{mK}$

$C_c=2\sqrt{0.6875\times 58.66}$

Cc= 12.7 lb.sec/ft

5 0

3 years ago

In normal operation, a paper mill generates excess steam at 20 bar and 400◦C. It is planned to use this steam as the feed to a t

Keith_Richards [23]

Answer:

The maximum power that can be generated is 127.788 kW

Explanation:

Using the steam table

Enthalpy at 20 bar = 2799 kJ/kg

Enthalpy at 2 bar = 2707 kJ/kg

Change in enthalpy = 2799 - 2707 = 92 kJ/kg

Mass flow rate of steam = 5000 kg/hr = 5000 kJ/hr × 1 hr/3600 s = 1.389 kg/s

Maximum power generated = change in enthalpy × mass flow rate = 92 kJ/kg × 1.389 kg/s = 127.788 kJ/s = 127.788 kW

6 0

3 years ago

Steam enters an adiabatic condenser (heat exchanger) at a mass flow rate of 5.55 kg/s where it condensed to saturated liquid wat

Evgen [1.6K]

Answer:

The minimum mass flow rate will be "330 kg/s".

Explanation:

Given:

For steam,

$m_{s}=5.55 \ kg/s$

$\Delta h=2491 \ kg/kj$

For water,

$\Delta T=10^{\circ}C$

$(Cp)_{w}=4.184 \ kJ/kg^{\circ}C$

They add energy efficiency as condenser becomes adiabatic, with total mass flow rate of minimal vapor,

⇒ $m_{s}\times (\Delta h)=M_{w}\times(Cp)_{w}\times \Delta T$

On putting the estimated values, we get

⇒ $5.55\times 2491=M_{w}\times 4.184\times 10\\$

⇒ $13825.05=M_{w}\times 41.84$

⇒ $M_{w}=330 \ kg/s$

7 0

3 years ago

Steam enters an adiabatic turbine at 8 MPa and 500C with a mass flow rate of 3

Vinil7 [7]

Answer:

a)temperature=69.1C

b)3054Kw

Explanation:

Hello!

To solve this problem follow the steps below, the complete procedure is in the attached image

1. draw a complete outline of the problem

2. to find the temperature at the turbine exit use termodinamic tables to find the saturation temperature at 30kPa

note=Through laboratory tests, thermodynamic tables were developed, these allow to know all the thermodynamic properties of a substance (entropy, enthalpy, pressure, specific volume, internal energy etc ..)

through prior knowledge of two other properties such as pressure and temperature.

3. Using thermodynamic tables find the enthalpy and entropy at the turbine inlet, then find the ideal enthalpy using the entropy of state 1 and the outlet pressure = 30kPa

4. The efficiency of the turbine is defined as the ratio between the real power and the ideal power, with this we find the real enthalpy.

Note: Remember that for a turbine with a single input and output, the power is calculated as the product of the mass flow and the difference in enthalpies.

5. Find the real power of the turbine

3 0

3 years ago