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Fofino [41]
3 years ago
6

Air at 400 kPa, 980 K enters a turbine operating at steady state and exits at 100 kPa, 670 K. Heat transfer from the turbine occ

urs at an average outer surface temperature of 315 K at the rate of 30 kJ per kg of air flowing. Kinetic and potential energy effects are negligible
Determine

(a) The rate power is developed, in kJ per kg of air flowing,
(b) The rate of entropy production within the turbine, in kJ per kg of air flowing.
Physics
1 answer:
Angelina_Jolie [31]3 years ago
5 0

Answer:

a). \frac{\dot{W}}{m}= 311 kJ/kg

b). \frac{\dot{\sigma _{gen}}}{m}=0.9113 kJ/kg-K

Explanation:

a). The energy rate balance equation in the control volume is given by

\dot{Q} - \dot{W}+m(h_{1}-h_{2})=0

\frac{\dot{Q}}{m} = \frac{\dot{W}}{m}+m(h_{1}-h_{2})

\frac{\dot{W}}{m}= \frac{\dot{Q}}{m}+c_{p}(T_{1}-T_{2})

\frac{\dot{W}}{m}= -30+1.1(980-670)

\frac{\dot{W}}{m}= 311 kJ/kg

b). Entropy produced from the entropy balance equation in a control volume is given by

\frac{\dot{Q}}{T_{boundary}}+\dot{m}(s_{1}-s_{2})+\dot{\sigma _{gen}}=0

\frac{\dot{\sigma _{gen}}}{m}=\frac{-\frac{\dot{Q}}{m}}{T_{boundary}}+(s_{2}-s_{1})

\frac{\dot{\sigma _{gen}}}{m}=\frac{-\frac{\dot{Q}}{m}}{T_{boundary}}+c_{p}ln\frac{T_{2}}{T_{1}}-R.ln\frac{p_{2}}{p_{1}}

\frac{\dot{\sigma _{gen}}}{m}=\frac{-30}{315}+1.1ln\frac{670}{980}-0.287.ln\frac{100}{400}

\frac{\dot{\sigma _{gen}}}{m}=0.0952+0.4183+0.3978

\frac{\dot{\sigma _{gen}}}{m}=0.9113 kJ/kg-K

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How long does it take the baton to complete one spin
sweet [91]

The time it takes the baton to complete one spin will be 0.56 s. Option B is correct.

<h3>What is centripetal acceleration?</h3>

The acceleration needed to move a body in a curved way is understood as centripetal acceleration.

The direction of centripetal acceleration is always in the path of the center of the course. The total acceleration is the result of tangential and centripetal acceleration.

The entire question is;

"How long does it take the baton to complete one spin?

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a.0.31 s

b.0.56 s

c.4.3 s

d.70 s"

The given data in the problem;

Length of baton,L = 0.76 m

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The centripetal acceleration is found by;

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Substitute the given value:

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To learn more about centripetal acceleration, refer to the link;

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Answer:

b

Explanation:

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Magnetic field lines surrounding a magnet are conventionally drawn
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A football is thrown due north across a 40 meter river and it takes 2 seconds to cover that distance.
Alexxx [7]

Answer:

I. Speed = 20m/s

II. Velocity = 20m/s due North.

Explanation:

<u>Given the following data;</u>

Distance = 40m

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To find the speed;

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Substituting into the equation, we have;

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In physics, we use the same formula for calculating speed and velocity. The only difference is that speed is a scalar quantity and as such has magnitude but no direction while velocity is a vector quantity and as such it has both magnitude and direction.

Velocity = \frac{distance}{time}

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