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irina1246 [14]
3 years ago
11

The fins attached to a surface are determined to have an effectiveness of 0.9. Do the rate of heat transfer from the surface dec

rease as a result of the addition of these fins?
Engineering
1 answer:
Nesterboy [21]3 years ago
8 0

Answer: The rate of heat transfer decreases.

Explanation:

Fin effectiveness is defined as the ratio of heat transfer rate from a  finned surface to the heat transfer rate from the same surface if there were no fins.  Its  value is expected to be greater than 1.

Having effectiveness  value of 0.9  which is less than 1 indicates that the heat transfer rate will decrease since a fin effectiveness smaller than 1 shows that the  fin acts as insulation (thermal insulation).

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Two loads connected in parallel draw a total of 2.4 kW at 0.8 pf lagging from a 120-V rms, 60-Hz line. One load absorbs 1.5 kW a
stealth61 [152]

Answer: a) 0.948 b) 117.5µf

Explanation:

Given the load, a total of 2.4kw and 0.8pf

V= 120V, 60 Hz

P= 2.4 kw, cos θ= 80

P= S sin θ - (p/cos θ) sin θ

= P tan θ(cos^-1 (0.8)

=2.4 tan(36.87)= 1.8KVAR

S= 2.4 + j1. 8KVA

1 load absorbs 1.5 kW at 0.707 pf lagging

P= 1.5 kW, cos θ= 0.707 and θ=45 degree

Q= Ptan θ= tan 45°

Q=P=1.5kw

S1= 1.5 +1.5j KVA

S1 + S2= S

2.4+j1.8= 1.5+1.5j + S2

S2= 0.9 + 0.3j KVA

S2= 0.949= 18.43 °

Pf= cos(18.43°) = 0.948

b.) pf to 0.9, a capacitor is needed.

Pf = 0.9

Cos θ= 0.9

θ= 25.84 °

(WC) V^2= P (tan θ1 - tan θ2)

C= 2400 ( tan (36. 87°) - tan (25.84°)) /2 πf × 120^2

f=60, π=22/7

C= 117.5µf

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
What is the sun's degree angle in the sky in summer and in winter?
Vladimir [108]

Answer:

At the time of the summer or winter solstices, the Sun is 23.44° degrees above or below the horizon, respectively, irrespective of time of day.

Explanation:

6 0
2 years ago
A water-filled manometer is used to measure the pressure in an air-filled tank. One leg of the manometer is open to atmosphere.
ddd [48]

Answer:

P = 150.335\,kPa (Option B)

Explanation:

The absolute pressure of the air-filled tank is:

P = 101.3\,kPa + \left(1000\,\frac{kg}{m^{3}} \right)\cdot \left(9.807\,\frac{kg}{m^{3}} \right)\cdot (5\,m)\cdot \left(\frac{1\,kPa}{1000\,Pa} \right)

P = 150.335\,kPa

4 0
3 years ago
Engineers in Russia invented a new way to create colorful art with a __________.
Setler [38]

The Engineers in Russia invented a new way to create colorful art with constructivist art.

<h3>What is constructivist art?</h3>

Constructivist art was aimed to reflect modern industrial society and urban space in art. It uses industrial production forms and modest materials for its art production.

The constructivists proposed to replace traditional art's with a focus on construction as Engineers rather than a painter.

Therefore, the Engineers in Russia invented a new way to create colorful art with constructivist art using construction.

Learn more on constructivist here,

brainly.com/question/14054863

3 0
3 years ago
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