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3 years ago

14

An inventor tries to sell you his new heat engine that takes in 40 J of heat at 87°C on each cycle, expels 30 J at 27°C, and doe

s 10 J of work. Would it be wise to invest in this engine?

1 answer:

algol133 years ago

5 0

Answer:

NOT WISE

Explanation:

given,

T₁ = 87⁰C = 273 + 87 = 360 K

T₂ = 27⁰C = 273 + 27 = 300 K

work output given = 10 J

efficiency will be equal to :

$\eta = 1 - \dfrac{T_2}{T_1}\\\eta = 1 - \dfrac{300}{360}\\\eta = 0.166$

output delivery = η ₓ input

= 0.166 ₓ 40

= 6.66 J

hence, the output of new engine is less than the old one so, investing in new engine will not be feasible.

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Question

Determine the average water exit velocity

Answer:

53.05 m/s

Explanation:

Given information

Volume flow rate, $Q=16 m^{3}/min$

Diameter d= 8cm= 0.08 m

Assumptions

The flow is jet flow hence momentum-flux correction factor is unity
Gravitational force is not considered
The flow is steady, frictionless and incompressible
Water is discharged to the atmosphere hence pressure is ignored

We know that Q=AV and making v the subject then

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Area, $A=\frac {\pi d^{2}{4}$ where d is the diameter

By substitution

$V=\frac {16\times 4}{\pi 0.08^{2}}=3183.098862 m/min$

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$V=\frac {3183.098862 m/min}{60 s}=53.0516477 m/s\approx 53.05 m/s$

3 0

3 years ago

2.) A fluid moves in a steady manner between two sections in a flow

Talja [164]

Answer:

$250\ \text{lbm/min}$

$625\ \text{ft/min}$

Explanation:

$A_1$ = Area of section 1 = $10\ \text{ft}^2$

$V_1$ = Velocity of water at section 1 = 100 ft/min

$v_1$ = Specific volume at section 1 = $4\ \text{ft}^3/\text{lbm}$

$\rho$ = Density of fluid = $0.2\ \text{lb/ft}^3$

$A_2$ = Area of section 2 = $2\ \text{ft}^2$

Mass flow rate is given by

$m=\rho A_1V_1=\dfrac{A_1V_1}{v_1}\\\Rightarrow m=\dfrac{10\times 100}{4}\\\Rightarrow m=250\ \text{lbm/min}$

The mass flow rate through the pipe is $250\ \text{lbm/min}$

As the mass flowing through the pipe is conserved we know that the mass flow rate at section 2 will be the same as section 1

$m=\rho A_2V_2\\\Rightarrow V_2=\dfrac{m}{\rho A_2}\\\Rightarrow V_2=\dfrac{250}{0.2\times 2}\\\Rightarrow V_2=625\ \text{ft/min}$

The speed at section 2 is $625\ \text{ft/min}$ .

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3 years ago

What factors are likely to promote the formation of stress corrosion cracks?

Naddika [18.5K]

Answer:

Stress corrosion cracking

Explanation:

This occurs when susceptible materials subjected to an environment that causes cracking effect by the production of folds and tensile stress. This also depends upon the nature of the corrosive environment.

Factors like high-temperature water, along with Carbonization and chlorination, static stress, and material properties.

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Mass ,m= 90 x 0.13 x 62.36 lbm

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Answer:

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The step by step and appropriate substitution is as shown in the attachment.

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