1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
g100num [7]
3 years ago
7

A single insulated duct flow experiment using air operating at steady-state is performed in a lab. One measurement location (Sta

te 1) provides a velocity of 75 m/s, temperature of 67oC, and pressure of 0.95 bar. Another measurement location (State 2) has a pressure of 0.8 bar, velocity of 310 m/s and temperature of 22oC. The scientist neglected to note the direction. a) What is the entropy change from State 2 to State 1? (in kJ/kg)? b) What is the direction of the flow? Prove and explain why.

Physics
1 answer:
weqwewe [10]3 years ago
3 0

Answer:

a) -0.0934 kJ/kg. K

b) The direction of flow is from right to left.

Explanation:

A free flow diagram of the horizontal insulated duct is as shown below.

NOW,

Let assume that the direction of flow is from left to right and consider the following relation for the entropy rate balance equation for a control volume as:

\frac{\sigma_{cv}}{m}= (s_2-s_1) \geq  0 \ \ \ -------> \ \ \ 1

Now; if the value for this relation is greater than zero; then we conclude that our assumption is correct.

If the value is less than zero; then we conclude that the assumption is wrong.

Then, the flow is said to be  in the opposite direction

Formula for the change in specific entropy can be calculated as:

s_2-s_1 = s^0(T_2) - s^0(T_1)-R \ In ( \frac{P_2}{P-1}) \ \ \  ------->  \ \ \ 2

where;

s_1, s_2 , s^0(T_2), s^0(T1) are specific entropies

R = universal gas constant

P_1 = pressure at location 1

P_2 = pressure at location 2

We obtain the specific properties of air at temperature at T_1 = (67°C + 273)K = 340 K from the table A-22 ( Ideal gas properties of air)

s^0(T1) = 1.8279 kJ/kg.K

We also obtain the specific properties of air at temperature T_2 = 22°C + 273) K = 295 K

From the table A- 22

s^0(T_2) = 1.68515 kJ/kg . K

R = \frac{8.314 kJ}{28.97 kg.K}

P_1 = 0.95 bar

P_2 = 0.8 bar

Now replacing our values  into equation (2) from above; we have;

s_2-s_1 = s^0(T_2) -s^0(T_1)-R \ In (\frac{P_2}{P_1} )

s_2-s_1 = 1.68515 -1.8279-\frac{8.314}{28.97}  \ In (\frac{0.8}{0.95} )

s_2-s_1 = 1.68515 -1.8279+ 0.0493

s_2-s_1 =-0.0934 \  kJ/kg.K

Equating our result to equation (1)

s_2-s_1 \geq 0\\-0.0934 \leq 0

Therefore , our assumption is wrong and the direction of flow is said to be from right to left.

We therefore conclude that the direction of flow is from right to left.

You might be interested in
Question 2
Yakvenalex [24]

Answer:

B

Explanation:

6 0
2 years ago
What did copernicus say about the motion of the sun?.
eimsori [14]

the sun was stationary in the center of the universe and the earth revolved around it....

8 0
2 years ago
If the frequency of the motion of a simple harmonic oscillator is doubled, by what factor does the maximum speed of the oscillat
Maksim231197 [3]

Answer:

If the frequency of the motion of a simple harmonic oscillator is doubled , then maximum speed of the oscillator changes by the factor 2

Explanation:

We know that in a simple harmonic oscillator the maximum speed is given by

    v_{max} = Aw

  Here A is amplitude which is constant , so from above equation we see that maximum speed is directly proportional to w\\ of the oscillation .

  Since  w = 2 \pi f

      v_{max}^{|}/v_{max} = 2f/f = 2

  Where v_{max}^{|} is the maximum speed when frequency is doubled .

6 0
3 years ago
A person should be able to find all the answers to their science questions in the text
Vsevolod [243]
TRUE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
4 0
3 years ago
Read 2 more answers
Is the alien theory a scientific claim? Why or why not?
spin [16.1K]
I'm not sure what the alien Theory says or if there really is such a theory. If the theory says that aliens definitely exist and that they have visited Earth in the past then the theory is totally and completely without any kind of support. It's not scientific in any way because there is no evidence for such a claim. It may be thought to be probable but no solid evidence has ever been presented.
8 0
3 years ago
Read 2 more answers
Other questions:
  • Two balls have their centers 2.0 m apart. One ball has a mass of m1 = 7.9 kg. The other has a mass of m2 = 6.1 kg. What is the g
    12·1 answer
  • Air resistance is an example of what type of friction?
    11·1 answer
  • If you place a 50 Volt power source across a 10 Ohm resistor, what will the current<br> be?
    10·1 answer
  • What type of speed looks at a particular point in time?
    8·1 answer
  • How are energy and distance up the ramp related
    15·1 answer
  • As amplitude of a wave increases, the
    6·1 answer
  • A football punter wants to kick the ball so that it is in the air for 4.2 s and lands 55 m from where it was kicked. Assume that
    10·1 answer
  • Where is a good place to check your pulse?
    7·2 answers
  • Please help me with science! :,)
    9·1 answer
  • A bag is dropped onto the street from the roof of a 32 m high building. How long does it take for the bag to fall?
    11·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!