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
Leno4ka [110]
2 years ago
10

A boiler operates at steady state. The entering water is saturated liquid at P = 5 bar and has a flow rate of 10,000 kg/hr. The

existing steam is also at P = 5 bar and T = 400o C. The pipe entering the boiler is 8 cm in diameter, and the pipe leaving the boiler is 30 cm in diameter. What is the rate at which heat is added in the boiler?
Chemistry
1 answer:
stira [4]2 years ago
4 0

Answer:

The rate at which heat is added in the boiler is 8128.610 kilowatts.

Explanation:

A boiler is a device that works at steady state, whose function is pressurizing and heating water. All gravitational electric and magnetic effects can be neglected. From First Law of Thermodynamics the boiler is characterized by the following model:

\dot Q_{in} + \dot H_{in}-\dot H_{out} + \dot K_{in} - \dot K_{out}= 0 (Eq. 1)

Where:

\dot Q_{in} - Heat transfer rate, measured in kilowatts.

\dot H_{in}, \dot H_{out} - Inlet and outlet fluid enthalpy rates, measured in kilowatts.

\dot K_{in}, \dot K_{out} - Inlet and outlet kinetic energy rate, measured in kilowatts.

And by the Principle of Mass Conservation we have that:

\dot m_{in}-\dot m_{out} = 0 (Eq. 2)

Where \dot m_{in} and \dot m_{out} are mass flows at entrance and exit of the boiler, measured in kilograms per second.

Then, we clear the heat transfer rate and expand (Eq. 1) by definitions of enthalpy and kinetic energy, as well as (Eq. 2):

\dot Q_{in} = \dot H_{out}-\dot H_{in}+\dot K_{out}-\dot K_{in}

\dot Q_{in} = \dot m \cdot \left[(h_{out}-h_{in}\right)+\frac{1}{2}\cdot (v_{out}^{2}-v_{in}^{2})\left] (Eq. 3)

Speeds of fluid entering and exiting the boiler (v), measured in meters per second, are found by applying the following formula:

\dot m = \left(\frac{\pi}{4} \right)\cdot \frac{D^{2}\cdot v}{\nu}

v = \frac{4\cdot \dot m\cdot \nu}{\pi\cdot D^{2}} (Eq. 4)

Where:

\nu - Specific volume of fluid, measured in cubic meters per kilogram.

D - Inner diameter of pipe, measured in meters.

Entrance (\dot m = 2.778\,\frac{kg}{s}, \nu_{in} = 0.001093\,\frac{m^{3}}{kg} and D_{in} = 0.08\,m)

v_{in} = \frac{4\cdot \left(2.778\,\frac{kg}{m^{3}} \right)\cdot \left(0.001093\,\frac{m^{3}}{kg} \right)}{\pi\cdot (0.08\,m)^{2}}

v_{in}\approx 0.604\,\frac{m}{s}

Specific enthalpy at given conditions is:

h_{in} = 640.09\,\frac{kJ}{kg} (From Saturated Water tables)

Exit (\dot m = 2.778\,\frac{kg}{s}, \nu_{out} = 0.61731\,\frac{m^{3}}{kg} and D_{out} = 0.30\,m)

v_{out} = \frac{4\cdot \left(2.778\,\frac{kg}{m^{3}} \right)\cdot \left(0.61731\,\frac{m^{3}}{kg} \right)}{\pi\cdot (0.30\,m)^{2}}

v_{out} \approx 24.261\,\frac{m}{s}

Specific enthalpy at given conditions is:

h_{out} = 3272.4\,\frac{kJ}{kg} (From Superheated Steam tables)

If we know that \dot m = 2.778\,\frac{kg}{s}, h_{in} = 640.09\,\frac{kJ}{kg}, h_{out} = 3272.4\,\frac{kJ}{kg}, v_{in}\approx 0.604\,\frac{m}{s}, v_{out} \approx 24.261\,\frac{m}{s}, the heat transfer rate is:

\dot Q = \left(2.778\,\frac{kg}{s} \right)\cdot \left\{ \left(3272.4\,\frac{kJ}{kg}-640.09\,\frac{kJ}{kg}  \right)+\frac{1}{2}\cdot \left[\left(24.261\,\frac{m}{s} \right)^{2}-\left(0.604\,\frac{m}{s} \right)^{2}\right]  \right\}

\dot Q = 8128.610\,kW

The rate at which heat is added in the boiler is 8128.610 kilowatts.

You might be interested in
How many moles are in 158 grams of LiCl
Usimov [2.4K]

Answer:

Number of moles = 3.73 mol

Explanation:

Given data:

Mass of LiCl = 158 g

Number of moles = ?

Solution:

Formula:

Number of moles = mass/ molar mass

Molar mass of LiCl = 42.4 g/mol

Number of moles =  158 g / 42.4 g/mol

Number of moles = 3.73 mol

7 0
3 years ago
If an isotope of an element has 40 neutrons and a mass number of 79, how many electrons must it have?
34kurt

Answer: 39 electrons

Explanation: Subtract 79 by 40 to get the atomic number (amount of protons) which is 39. The number of electrons must be the same as the number of protons if it's not an ionic compound so the amount of electrons is the same amount of protons.

5 0
3 years ago
Which object has particles with the most kinetic energy?
Pavlova-9 [17]

Answer:

b

Explanation:

because it is moving so it has kinetic energy

6 0
2 years ago
X = (2 x 103)(7 x 105)
Sonbull [250]

Answer:

x=1.4*10^9

or choice a

Hope this helps and please mark me brainliest! <3 >//<

3 0
2 years ago
Read 2 more answers
Nitrogen makes up 78.08% of the volume of Earth's atmosphere, and oxygen makes up 20.95% of the volume. The total air pressure a
cestrela7 [59]
D. All of the other answer choices
In the case of gases, the molar fraction is equivalent to the volume fraction which is also equal to the partial pressure fraction. Therefore, all of the given questions may be answered using the data that has been provided.
3 0
3 years ago
Other questions:
  • Hydroxyl radicals react with and eliminate many atmospheric pollutants. However, the hydroxyl radical does not clean up everythi
    15·1 answer
  • "what are the half lives for uranium-235 and uranium-238?"
    12·1 answer
  • Question 26(Multiple Choice Worth 1 points) [01.03]Which of the following statements does not support scientific evidence of the
    5·1 answer
  • Which subatomic particle helps identify an elements identify
    9·1 answer
  • The number of protons in the nucleus is always equal to the number of neutrons. True or False?
    10·2 answers
  • Ill give u brainliest pls help
    9·2 answers
  • How many grams of magnesium metal will react completely with 5.2 liters of 4.0 M HCl? Show all of the work needed to solve this
    12·1 answer
  • __________are when the Sun, Earth, and moon align in a straight line, the tides are higher than normal high
    10·1 answer
  • No FILES PLZZ
    8·2 answers
  • A hypothetical element, E, has two stable isotopes. One isotope has a natural abundance of 68.037% and has an atomic mass of 46.
    7·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!