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Amanda [17]
3 years ago
8

Consider a very long, slender rod. One end of the rod is attached to a base surface maintained at Tb, while the surface of the r

od is exposed to an air temperature of 400°C. Thermocouples imbedded in the rod at locations 25 mm and 120 mm from the base surface register temperatures of 335°C and 375°C, respectively.
(a) Calculate the rod base temperature (°C).
(b) Determine the rod length (mm) for the case where the ratio of the heat transfer from a finite length fin to the heat transfer from a very long fin under the same conditions is 99 percent.

Engineering
1 answer:
9966 [12]3 years ago
3 0

Answer:

(a) Calculate the rod base temperature (°C). = 299.86°C

(b) Determine the rod length (mm) for the case where the ratio of the heat transfer from a finite length fin to the heat transfer from a very long fin under the same conditions is 99 percent.  = 0.4325m

Explanation:

see attached file below

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A steam power plant operates on an ideal Rankine cycle with two stages of reheat and has a net power output of 120 MW. Steam ent
uysha [10]

Answer:

a) 40.6%

b)72.19kg/s

Explanation:

The Rankine cycle with two reheat stages has 9 stages in total.

The maximum pressure will be at the first inlet stage of the HP turbine which is stage 3. The minimum pressure will be the exit stage of the condenser because the condenser operates under vacuum pressure which is stage 1.

The following assumptions can be made:

1 - Each component in the cycle is analyzed as an open system operating at steady-state.

  2 - All of the processes are internally reversible.

  3 - The turbine and pump operate adiabatically and are internally reversible, so they are also isentropic.

   4 - Condensate exits the condenser as saturated liquid.

  5 - The effluent from the HP turbine is a saturated vapor.

  6 - No shaft work crosses the system boundary of the boiler or condenser.

   7 - Changes in kinetic and potential energies are negligible

a) The thermal efficiency of the cycle is defined as the work of the cycle divided by the total heat input to the system. The stages that have heat input is stages 2-3, 4-5, 6-7.

For stage 2:

s₁=s₂ assuming isentropic

s_1=0.4762 @ P_1=15MPa

enthalpy will be a compressed liquid so after interpolation

h_2=97.93+(0.4762-0.2932)((180.77-97.93)/(0.5666-0.2932))=153.38kJ/kg

For stage 3:

Superheated steam @ T=500⁰C and P=15MPa

h_3=3310.8kJ/kg

Stage 4:

superheated vapor

P=5MPa

s₃=s₄=6.3480 kJ/kg, we must use interpolation to find h₄

h_4=2925.7-(6.348-6.2111)((3069.3-2925.7)/(6.4516-6.2111))=3007.44kJ/kg

Stage 5:

Superheated steam @ T=500⁰C and P₄=P₅=5 MPa

h_5=3434.7kJ/kg

Stage 6:

Superheated steam at P₆= 1MPa

s₅=s₆

s_6=6.9781

We find h₆ using interpolation from the steam tables:

h_6=2943.1-(6.9781-6.9265)((3051.6-2943.1)/(7.1246-6.9265))=2970.67kJ/kg

Stage 7:

P₇=P₆=1MPa

T=500⁰C superheated steam

h_7=3479.1kJ/kg

The heat into the cycle is:

=(h_3-h_2)+(h_5-h_4)+(h_7-h_6)

=(3310.8-153.38)+(3434.7-3007.44)+(3479.1-2970.67)=4108.74kJ/kg

We can determine the work out by the condenser from stage 9 to stage 1:

Stage 1:

saturated liquid P=5kPa

h_1=137.75kJ/kg

Stage 9:

We assume that its a saturated liquid with quality of 1 at 5kPa and

s₇=s₉ and after interpolation

h_9=2568.53kj/kgK

Qout = [/tex]2568.53-137.75=2430.79kJ/kg[/tex]

The thermal efficiency can be written in terms of qin and qout:

n=1-(q_o/q_i)=1-2430.79/4093.11=0.4061

Efficiency of 40.61%

b)

The mass flow rate can be calculated from the Wnet:

W_n=W_t-W_p

Work of the turbines minus the work of the pumps:

W_n=m((h_3-h_4)+(h_5-h_6)+(h_7-h_9)-(h_1-h_2)

120000=m(1662.33)

m=72.19

mass flow rate of steam is 72.19 kg/s

7 0
3 years ago
(TCO 1) Name one disadvantage of fixed-configuration switches over modular switches. a. Ease of management b. Port security b. F
frutty [35]

Answer:

The answer is A.

Explanation:

Two main types of network switches, modular and fixed configuration switches, are used for connecting the devices with one another provided they are on the same network.

As the name suggests, modular switches can be configured according to your needs and specific situations where you need a different setup.

The one advantage fixed-configuration switches have over the modular switches is that they are easier to operate. You can't change anything for a different application but they are simpler to setup and use, you can just plug them in and start using. They are usually for the more casual end-user and home networks etc.

I hope this answer helps.

5 0
3 years ago
A Geostationary satellite has an 8kW RF transmission pointed at the earth. How much force does that induce on the spacecraft? (N
soldier1979 [14.2K]

Answer:

The force induced on the aircraft is 2.60 N

Solution:

As per the question:

Power transmitted, P_{t} = 8 kW = 8000 W

Now, the force, F is given by:

P_{t} = Force(F)\times velocity(v) = Fv               (1)

where

v = velocity

Now,

For a geo-stationary satellite, the centripetal force, F_{c} is provided by the gravitational force, F_{G}:

F_{c} = F_{G}

\frac{mv^{2}}{R} = \frac{GM_{e}m{R^{2}}

Thus from the above, velocity comes out to be:

v = \sqrt{\frac{GM_{e}}{R}}

v = \sqrt{\frac{6.67\times 10^{- 11}\times 5.979\times 10^{24}}{42166\times 10^{3}}} = 3075.36 m/ s

where

R = R_{e} + H

R = \sqrt{GM_{e}(\frac{T}{2\pi})^{2}}

where

G = Gravitational constant

T = Time period of rotation of Earth

R is calculated as 42166 km

Now, from eqn (1):

8000 = F\times 3075.36

F = 2.60 N

6 0
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Which statement most accurately describes Pascal's law?
marin [14]

Answer:

La  C

Explanation:

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