I’m reviewing for a test and there is a question from the book that im curious about.

Consider a simple ideal Rankine cycle with a fixed condenser pressure. If the boiler pressure is raised while the turbine inlet temperature is held constant, (select the correct statement)
a. the amount of heat rejected will increase.

b. the cycle efficiency will decrease.

c. the turbine work output will decrease.

d. the moisture content at turbine exit will increase.

e. the pump work input will decrease.

My guess was B because wouldn’t this make the vapor going into the turbine more wet because in an ideal situation you would like the vapor going into the turbine dry for max work output. Am I correct?

Thank you

Best answer:

Answer by gintable
The answer is D: the the moisture content at the turbine exit will decrease.

By raising the pressure, you have less entropy at the turbine entrance, because the pressure is higher, when the temperature is the same. Higher pressure is more “ordered” form of energy than a higher temperature. As a result, the state at the low pressure at the exit of the turbine, is of less entropy as well, which means lower quality. As a design goal, we want high quality steam to exit the turbine, so that the water droplets don’t erode the turbine blades.

It would be great if the efficiency decreased by doing this, because our design strategy would be more straightforward. However instead the efficiency increases upon selecting a higher boiler pressure, resulting in lower quality steam at exit. This is because less heat is required to vaporize steam at higher pressure, and more work is captured with a higher turbine pressure drop.

Pump work increases, in order to raise water across the higher pressure differential.

Give your answer to this question below!

For my final, the professor handed out these questions to use as a review. He said if we know these, we should be fine on the test. My problem is, I don’t know how to do a handful of them. If you could help on them, that would be so appreciated. Thanks!

A chemical plant needed to increase the concentration of sodium chloride from 0.1% to 0.2%. The tank holds 100,000 gallons. A solution of 0.5% is pumped into the tank at 80 gallons per minute, while an equal volume is removed at the other end of the tank at the same time. Assume that there is perfect mixing in the tank.
Write out the differential equations, solve, and determine when the solution will reach 0.2%.

The population of a rare monkey is taken annually. In 1990, the population was estimated at 5000 animals, in 1995, the population was estimated at 6300 animals. Using the logistic population model, estimate the population of monkeys in 2000, 2005, and 2010.
Write out the differential equation and solve it given the conditions above

A warehouse is built without the capacity for heating or cooling. There are two insulation options. One will give the warehouse a time constant of 1 hour while the second will give a time constant of 5 hours. The outside temperature follows a sine wave given below:

Temperature(C) = 24 + 8sin(4π/3 + π t/12)

**Remember that sin (A + B) = sin(A)cos(B) + cos(A)sin(B)

where time (t) is given in 24 hour military. At t=0 (midnight on day 1), the temperature inside the warehouse is 20C
Write out the differential equation for each time constant, and determine what the temperature will be inside the ware house at 8:00 (day 1), 12:00 (day 2), and 20:00 (day 3) for each insulation package. Over the long term, describe the temperature inside the warehouse.

Use the improve Euler method with tolerance to approximate the solution to the following equation at x=1:

y’ = 1 – y + y^3, where y(0) = 0

Use a tolerance of 0.003.
This will require some programming or a spreadsheet.

Best answer:

Answer by BeanCounter
ha ha ha, I just had to take a diff eq final monday!

I can only assume that your prof instructed his/her classes on how to work these exercises during the semester.

you’ve got a mixing model prob, a population model prob, a heating/cooling prob, and also euler there.

all of that was covered in the first half of the semester in the course I took.

so, if you can’t work these exercises this late in the semester, the answer is: you should have studied.

these are all examples of very basic material for a diff eq course. if you study, you can easily learn to solve all of these exercises in a short period of time (few weeks of distracted study).

Know better? Leave your own answer in the comments!

For my final, the professor handed out these questions to use as a review. He said if we know these, we should be fine on the test. My problem is, I don’t know how to do a handful of them. If you could help on them, that would be so appreciated. Thanks!

A chemical plant needed to increase the concentration of sodium chloride from 0.1% to 0.2%. The tank holds 100,000 gallons. A solution of 0.5% is pumped into the tank at 80 gallons per minute, while an equal volume is removed at the other end of the tank at the same time. Assume that there is perfect mixing in the tank.
Write out the differential equations, solve, and determine when the solution will reach 0.2%.

The population of a rare monkey is taken annually. In 1990, the population was estimated at 5000 animals, in 1995, the population was estimated at 6300 animals. Using the logistic population model, estimate the population of monkeys in 2000, 2005, and 2010.
Write out the differential equation and solve it given the conditions above

A warehouse is built without the capacity for heating or cooling. There are two insulation options. One will give the warehouse a time constant of 1 hour while the second will give a time constant of 5 hours. The outside temperature follows a sine wave given below:

Temperature(C) = 24 + 8sin(4π/3 + π t/12)

**Remember that sin (A + B) = sin(A)cos(B) + cos(A)sin(B)

where time (t) is given in 24 hour military. At t=0 (midnight on day 1), the temperature inside the warehouse is 20C
Write out the differential equation for each time constant, and determine what the temperature will be inside the ware house at 8:00 (day 1), 12:00 (day 2), and 20:00 (day 3) for each insulation package. Over the long term, describe the temperature inside the warehouse.

Use the improve Euler method with tolerance to approximate the solution to the following equation at x=1:

y’ = 1 – y + y^3, where y(0) = 0

Use a tolerance of 0.003.
This will require some programming or a spreadsheet.

Best answer:

Answer by BeanCounter
ha ha ha, I just had to take a diff eq final monday!

I can only assume that your prof instructed his/her classes on how to work these exercises during the semester.

you’ve got a mixing model prob, a population model prob, a heating/cooling prob, and also euler there.

all of that was covered in the first half of the semester in the course I took.

so, if you can’t work these exercises this late in the semester, the answer is: you should have studied.

these are all examples of very basic material for a diff eq course. if you study, you can easily learn to solve all of these exercises in a short period of time (few weeks of distracted study).

Know better? Leave your own answer in the comments!

For my final, the professor handed out these questions to use as a review. He said if we know these, we should be fine on the test. My problem is, I don’t know how to do a handful of them. If you could help on them, that would be so appreciated. Thanks!

A chemical plant needed to increase the concentration of sodium chloride from 0.1% to 0.2%. The tank holds 100,000 gallons. A solution of 0.5% is pumped into the tank at 80 gallons per minute, while an equal volume is removed at the other end of the tank at the same time. Assume that there is perfect mixing in the tank.
Write out the differential equations, solve, and determine when the solution will reach 0.2%.

The population of a rare monkey is taken annually. In 1990, the population was estimated at 5000 animals, in 1995, the population was estimated at 6300 animals. Using the logistic population model, estimate the population of monkeys in 2000, 2005, and 2010.
Write out the differential equation and solve it given the conditions above

A warehouse is built without the capacity for heating or cooling. There are two insulation options. One will give the warehouse a time constant of 1 hour while the second will give a time constant of 5 hours. The outside temperature follows a sine wave given below:

Temperature(C) = 24 + 8sin(4π/3 + π t/12)

**Remember that sin (A + B) = sin(A)cos(B) + cos(A)sin(B)

where time (t) is given in 24 hour military. At t=0 (midnight on day 1), the temperature inside the warehouse is 20C
Write out the differential equation for each time constant, and determine what the temperature will be inside the ware house at 8:00 (day 1), 12:00 (day 2), and 20:00 (day 3) for each insulation package. Over the long term, describe the temperature inside the warehouse.

Use the improve Euler method with tolerance to approximate the solution to the following equation at x=1:

y’ = 1 – y + y^3, where y(0) = 0

Use a tolerance of 0.003.
This will require some programming or a spreadsheet.

Best answer:

Answer by Lol L
y*y’+3y2

Give your answer to this question below!

For my final, the professor handed out these questions to use as a review. He said if we know these, we should be fine on the test. My problem is, I don’t know how to do a handful of them. If you could help on them, that would be so appreciated. Thanks!

A chemical plant needed to increase the concentration of sodium chloride from 0.1% to 0.2%. The tank holds 100,000 gallons. A solution of 0.5% is pumped into the tank at 80 gallons per minute, while an equal volume is removed at the other end of the tank at the same time. Assume that there is perfect mixing in the tank.
Write out the differential equations, solve, and determine when the solution will reach 0.2%.

The population of a rare monkey is taken annually. In 1990, the population was estimated at 5000 animals, in 1995, the population was estimated at 6300 animals. Using the logistic population model, estimate the population of monkeys in 2000, 2005, and 2010.
Write out the differential equation and solve it given the conditions above

A warehouse is built without the capacity for heating or cooling. There are two insulation options. One will give the warehouse a time constant of 1 hour while the second will give a time constant of 5 hours. The outside temperature follows a sine wave given below:

Temperature(C) = 24 + 8sin(4π/3 + π t/12)

**Remember that sin (A + B) = sin(A)cos(B) + cos(A)sin(B)

where time (t) is given in 24 hour military. At t=0 (midnight on day 1), the temperature inside the warehouse is 20C
Write out the differential equation for each time constant, and determine what the temperature will be inside the ware house at 8:00 (day 1), 12:00 (day 2), and 20:00 (day 3) for each insulation package. Over the long term, describe the temperature inside the warehouse.

Use the improve Euler method with tolerance to approximate the solution to the following equation at x=1:

y’ = 1 – y + y^3, where y(0) = 0

Use a tolerance of 0.003.
This will require some programming or a spreadsheet.

Best answer:

Answer by kirchwey
I’ll take the 1st question.
dq/dt = -kq, where q = current concentration minus asymptotic concentration (exponential decay)
q(t) = q(0) * e^(-kt)
Rate constant k = 80/(60*100000) = 1.33333E-5 s^-1
(Time constant = 75000 s)
y(asymptote) = 0.005
y(0) = 0.001: q(0) = y(0)-y(asymptote)
y(t) = 0.002: q(t) = y(t)-y(asymptote)
t = ln(q(t)/q(0))/k = 21576 s

The questions I left unanswered are an hour or two of work for someone. You might consider splitting up hairy questions like these.

Know better? Leave your own answer in the comments!

IT WOULD BE GREAT IF YOU KNOW ANYYY ANSWERS TO ANY OF THESE QUESTIONS! THANKS!
vvvv

1. Which is the term for multiple photovoltaic cells linked together to receive a higher energy input from the sun?
A. Solar power station
B. Passive solar system
C. Fuel cell system
D. Photovoltaic array

2. Stone walls warmed by the sun were used by the French and English to
A. warm their cattle barns.
B. heat water for cooking and washing.
C. collect solar energy for storage.
D. extend the growing season.

3. A measure of human impact on the planet that is based on the emission of carbon-based greenhouse gases, such as carbon dioxide, is called a carbon footprint.
True
False

4. How are tidal turbines like modified wind turbines?
A. Tidal turbines are wind turbines over the water.
B. Tidal turbines are turned by tides under the water.
C. Tidal turbines are modified to produce electricity.
D. Tidal turbines do not produce electricity.

5. One focus of research for the development of biofuels is how to make the cellulose of plants easier to digest by
A. manipulating their DNA.
B. improving strains of bacteria.
C. hybridizing two different plants.
D. growing plants near PV cells.

6. You have probably seen photos of windmills out in remote parts of the old west, and even modern windmills in ranchers’ pastures. Which is the best inference about how this wind-capturing technology is used?
A. Windmills use wind to generate electricity for homes and businesses.
B. Windmills drive manual pumps to bring water to tanks for livestock.
C. Windmills create a breeze to cool the area near ranches.
D. Windmills energized the pumps for oil wells in the old west.

7. Which type of energy in waves and tides is converted to electrical energy?
A. Chemical
B. Gravitational
C. Electromagnetic
D. Mechanical

8. There are three major considerations when restructuring our energy portfolio. Two of them are: • Assess the demand for energy. • Know what is available and appropriate in different areas. What is the third consideration?
A. Review economic hardships brought about by reducing fossil fuel use.
B. Research new technologies for extracting oil.
C. Think about the impact each energy source has on the planet.
D. Choose the energy option that is easiest to market to people.

9. Which part of a fuel cell provides energy to a device?
A. Anode
B. Cathode
C. Electrons
D. Protons

10. The type of nuclear reaction in the sun is called nuclear fission, which is the same type that produces nuclear power in reactors here on Earth.
True
False

11. What is one limitation to harvesting solar energy from a solar array or solar power plant?
A. The energy costs nothing.
B. It is a nonrenewable source of energy.
C. They require large amounts of land.
D. They emit particulate pollution.

12. How is hydrogen gas like gasoline and ethanol? In what very important way, with regard to global climate change, is hydrogen gas different from carbon-based fuels?

Only 200 characters are allowed

13. Which of the following could be a significant issue to be addressed during the development of nuclear fusion energy?
A. Disposing of the radioactive waste produced
B. Dealing with atmospheric byproducts
C. Shielding nearby communities and wildlife from gamma radiation
D. Reducing the area needed to install a nuclear fusion power plant

14. Imagine a field of tidal turbines along a coastline where whales have been sighted frequently. Which is not a way in which a tidal farm could affect the whales?
A. The blades could confuse them.
B. The electrical field could alter their migration patterns.
C. The motion might drive their food source away.
D. The turbines could change the direction of ocean currents.

15. Fuel cells have a limitation that is self-defeating as an alternative energy source. In addition to expense, which of the following is a limitation of hydrogen fuel cell technology?
A. It is not available everywhere.
B. It is not very efficient.
C. It uses fossil fuels as a source of hydrogen.
D. It emits a particulate pollution.

16. Earth’s mantle exists under the surface everywhere on Earth, and geothermal energy is derived from the heat in the mantle. Explain why, despite these facts, geothermal energy is not available everywhere.
A. Many populations do not have the resources to run geothermal plants.
B. In some areas, the heat of the mantle is too deep to reach.
C. Many people are opposed to the use of a risky way to get energy.
D. Some areas do not have water resources to make steam.

17. By increasing our use of renewable resources, we can decrease our use of fossil fuels and
A. increase our carbon footprint.
B. extend the time fossil fuels will be available.

Best answer:

Answer by Wade
All of the smart people on here, including myself, are going to tell you to do your own homework. Why would anyone in their right mind take the time to do this for you?

Know better? Leave your own answer in the comments!

Warming could spark water scramble: experts By Timothy Gardner
Wed Apr 11, 6:42 PM ET

NEW YORK (Reuters) – Climate change could diminish North American water supplies and trigger disputes between the United States and Canada over water reserves already stressed by industry and agriculture, U.N. experts said on Wednesday.

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More heat waves like those that killed more than 100 people in the United States in 2006, storms like the killer hurricanes that struck the Gulf of Mexico in 2005 and wildfires are likely in North America as temperatures rise, according to a new report that provided regional details on a U.N. climate panel study on global warming issued in Brussels on April 6.

Severe weather already costs North America tens of billions of dollars annually in productivity and damaged property, and those costs are expected to rise, the U.N. report said.

The broadest effects of climate change will be water problems across the entire continent — including more frequent droughts, urban flooding and a scramble for water from the Great Lakes, which border both the United States and Canada.

“Water was an issue in every region … but in very different ways and very different places,” Michael MacCracken, a review editor of the report, said in a telephone interview.

Unlike many continents, North America has no east to west mountain ranges that limit droughts by forcing rapidly moving wet air to release rain, said MacCracken, also chief scientist for climate change at the Climate Institute, a Washington-based nonprofit group.

Cities will also be threatened as glacial melt leads to higher ocean levels. Late in the 21st century, severe flooding that occurs in New York once every 500 years could happen as often as once in 50 years, putting at risk much of the infrastructure in the New York region, the report said.

Droughts would also occur more often in the U.S. Midwest and Southwest as warmer temperatures evaporate soil moisture.

Those droughts could diminish underground supplies like the Edwards Aquifer in Texas, which supplies 2 million people with water, by up to 40 percent, and cut levels of the Ogallala aquifer which underlies eight U.S. states, the report said.

During droughts like the Dust Bowl of the 1930s, U.S. farmers pumped water from underground aquifers to save their fields through irrigation. “Much of that water is now gone,” said MacCracken. “We’ve used up our savings bank.”

Tight underground water supplies could kick off a scramble for large above-ground supplies in the Great Lakes, the report said. Spats have already occurred over diversion of the lakes’ water for distant cities and farms, while calls have increased for channeling water to the Mississippi River to supply U.S. cities during hot summers.

Problems are also expected to intensify as warmer temperatures lower water levels through evaporation. “Climate change will exacerbate these issues and create new challenges for binational cooperation,” the report said.

The tension could be heightened by the fact that a majority of the Canadian population lives close to the Great Lakes, while only a small fraction of the U.S. population reside nearby, MacCracken said.

Best answer:

Answer by Aumharan G
Look at this way, if there is a day of terror weather and North America’s infastructure is gone then our savings accounts, cash, stocks all don’t mean jack and it’s up to who can survive the best. Guess how people ensure they survive without infastructure?

What do you think? Answer below!

Tessa Jowell, the Labour MP and previous Olympic minister, is showing up as a location on Google Maps. The map positions her in in the eastern portion of the Palace of Westminster, a little ways south of the clock tower. She doesn’t show up at all on embedded versions of the map, and there are no other MPs listed, though nearby points of interest such as St Stephen’s Timms Tavern and Big Ben …

Read more on Londonist

Before going any farther Yahoo Answer Point Hunters can forget to put an answer on my question if you do I’ll report you. The terms: I’ll choose the most constructive answer and those asking for a mach will be reported. Rate with a detailed review, oppinion or comment on each and a team overall. I don’t use legendaries. I would like to have each Pokemon rated out of 10 and the team overall. Answers copied directly from Smogon and any other Pokemon site will NOT be taken. I won’t change any pokemon for any of your suggestion. This is not a competition team so don’t go with the OU metagame.

Steelix (Rock head) lvl 100
Careful@ Leftovers
Ev: Max HP and Max Spcl Def
Gyro Ball (less the speed is the more power it have)
Thunder Fang
Earthquake
Curse (boost attack and def and lower speed)

Heracross (Gut) lvl 100
Adamant@ Salac Berry
Ev: Max Attack and Max Speed
Endure
Reversal
Stone Edge
Mega Horn

Kingdra (Swift Swim) lvl 100
Modest@ Damp Rock
Ev: max Speed and max SpAtk
Hydro Pump
Ice Beam
Dragon Pulse
Rain Dance

Houndoom (Flash Fire) lvl 100
Modest@ Focus Sash
Ev: max Speed and max SpAtk
Flamethrower
Dark Pulse
Hidden Power(Electric)
Nasty Plot

Crobat (Inner Focus) lvl 100
Modest@ Life Orb
Ev: Max Sp Atk and Max Speed
Sludge Bomb
Heat Wave
Shadow Ball
Nasty Plot

Espeon (Synchronize) lvl 100
Modest@ Expert Belt
Ev: Max Speed and Max SpAtk
Psychic
Hidden Power (Ice)
Shadow Ball
Calm Mind

Thanks in advance

Best answer:

Answer by Connor N
overall the team is excellent i would n’t change it ether my team usually only has 2 or 3 pokemon with lvl 100 and then i get bored lol. but great team.

What do you think? Answer below!

Consider a simple ideal Rankine cycle. If the condenser pressure is raised while keeping turbine inlet state the same, (select the correct statement)

a. the pump work input will increase.

b. the amount of heat rejected will decrease.

c. the turbine work output will increase.

d. the cycle efficiency will decrease.

e. the moisture content at turbine exit will increase.

This is for test reviews im trying to gain more of an understanding of the rankine cycle i appreciate teh help

Best answer:

Answer by Ivan A
a. the pump work input will increase.=> Nope, the pump work will decrease as the pressure difference low-high has been decreased.

b. the amount of heat rejected will decrease.=> Yes, there is less heat removal required to bring the water to a saturated liquid state (quality factor = 0 ).

c. the turbine work output will increase.=> Nope, the steam was let to expand less so the output work will decrease.

d. the cycle efficiency will decrease.=> Nope, because even though the work output has been decreased, the work needed at the pump has also been decreased. These two offset out, efficiency remains the same.

e. the moisture content at turbine exit will increase.=> Nope, the quality factor is larger if you increase the pressure at the condenser (assuming that the turbine is an isentropic expansion).

Add your own answer in the comments!