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Surging in Compressor

Surg ing

Surging is defined as a momentary back-flow through the compressor from the

discharge to the suction. Surging of compressors is the phenomenon which is caused

by the generation of pressure greater than the compressors ability to withstand it thus,

resulting in a violent flow reversal. We say that the compressor is surging when

cyclical reverse and forward flows takes place intermittently.

Causes

Surging, generally occurs when the quantitative rate of gas reaching the suction

end of the compressor gets relatively low as compared to the pressure difference

generated across the compressor. When this situation is reached, the

compressed gas tends to flow back into the compressor to fill the vacant space

as produced by the low input rate of the gas.Surging in compressor occurs when

the mass flow of gas to the compressor falls below acritical level with a high pressure

difference across the machine. When there is not enough gas to replace that being

pushed forward, discharge gas will flow backwardsthrough the compressor towards the

suction side. The gas flowing backward providesmore volume to the suction side and

the compressor picks up and begins to push gasforward again. All of this takes place

very quickly; the backward and forward gas flow causes rapid fluctuations in the flow

and pressure of the system. This 'Surging' in themachine can be very damaging to the

compressor due to heavy vibrations set up in thesystem.

In a turbocharger, where the compressor is operated by exhaust driven turbine,

when the throttle valve is closed fuel intake is halted due to which pressure

begins to build-up at the outlet of compressor until the compressor is no longer

capable of withstanding this high pressure resulting in the backflow of the air. As

this happens, outlet pressure drops which reinstates the forward flow.


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HEAT PUMP

A heat pump is basically anair conditioner with a valve that allows it to operate in

reverse. A heat pump is an electrically-powered device that extracts available heat from

one area (the heat source) and transfers it to another (the heat sink) to either heat or

cool an interior space or to extract heat energy from a fluid. In the case of a fridge, for

example, heat is transferred from the interior of the fridge to the condenser coils at the

back.

For climates with moderate heating and cooling needs, heat pumps offer an

energy-efficient alternative tofurnaces and air conditioners. Like a

refrigerator, a heat pump uses electricity to move heat from a cool space

into a warm one, making the cool space cooler and the warm space

warmer. During the heating season, heat pumps move heat from the cool

outdoors into your warm house; during the cooling season, heat pumps

move heat from your cool house into the warm outdoors. Because

they move heat rather than generate heat, heat pumps can provide up to 4

times the amount of energy they consume.
http://www.daviddarling.info/encyclopedia/A/AE_air_conditioning.htmlhttp://www.daviddarling.info/encyclopedia/F/AE_furnace.htmlhttp://www.daviddarling.info/encyclopedia/F/AE_furnace.htmlhttp://www.daviddarling.info/encyclopedia/A/AE_air_conditioning.html


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TYPES OF HEAT PUMP

The most common type of heat pump is the

Air-Source Heat Pump

It transfers heat between the interior of a building and the outside air. If you heat with

electricity, a heat pump can trim the amount of electricity you use for heating by as

much as 3040%. High-efficiency heat pumps also dehumidify better than standard

central air conditioners, resulting in less energy usage and more cooling comfort in

summer months. However, the efficiency of most air-source heat pumps as a heatsource drops dramatically at low temperatures, generally making them unsuitable for

cold climates.

Duel Fuel Heat Pump
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It is a heating appliance that combines an electricheat pump with a gasfurnace.Dual-

fuel heat pumps are effective in regions where the winter temperature is usually above

freezing (allowing the heat pump to be used much of the time) but can occasionally dropbelow freezing, when the gas furnace provides heat more economically. However, you

need to make sure that the system is set up so that the heat pump is used whenever

possible as it will generally run at a fraction of the cost of the gas furnace.

Mini Split Heat Pump

A type ofheat pump that makes a good retrofit add-on to a house with "non-ducted"

heating systems, such as hydronic (hot water heat), radiant panels, and space heaters(wood, kerosene, propane). Mini-split heat pumps can also be a good choice for room

additions, where extending or installing distribution ductwork is not feasible.
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Higher efficiencies are achieved withgeothermal heat pumps (ground-source or water-

source), which transfer heat between your house and the ground or a nearby water

source. Although they are more costly to install, geothermal heat pumps have low

operating costs because

they take advantage of

relatively constant ground or

water temperatures.

However, the installation

depends on the size of your

lot, the subsoil, and the

landscape. Ground-source or water-source heat pumps can be used in more extreme

climatic conditions than air-source heat pumps, and customer satisfaction with the

systems is very high.

Absorption Heat Pump

A new type of heat pump for residential systems is the absorption heat pump, also

called a gas-fired heat pump. Absorption heat pumps use heat as their energy source,

and can be driven with a wide variety of heat sources.
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HOW DOES A HEAT PUMP WORK?

A heat pump is like a conventional air conditioner except it also can provide heat in

winter. In the summer, the heat pump collects heat from the house and expels it

outside. In the winter, the heat pump extracts heat from outside air and circulates it

inside the house. The heat pump works best when the outdoor temperature is above

freezing. Below that, supplementary heat often is needed.

A heat pump can save 30 to 60 percent less energy to supply the same heat when

compared to an electric furnace with a resistance heating element.

Heat pump heater is one of the most advanced heaters in the world. According to

Inverse Theory Carnot cycle (Refrigeration Inverse principle), it can use the

decalescence medium with less electricity energy to collect heat from the air or natural

environment, and compress it by the compressor, and then make the secondary

refrigerant to heat the cold water through heat exchanger.

Heat pump heater can protect environment without three wastes and save energy, so it

is gradually substituting traditional heating facilities of fuel, gas and electric boiler and

solar heating water equipment.


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GEOTHERMAL HEAT PUMP

Heat pumps move heat from one place to another - from outside to inside a home, for

example. That's why they're called "heat pumps."

All heat pumps have an outdoor unit (called a condenser) and an indoor unit (an

evaporator coil).

A substance called a refrigerant carries the heat from one area to another. When

compressed, it is a high temperature, high-pressure liquid. If it is allowed to expand, it

turns into a low temperature, low pressure gas. The gas then absorbs heat.

In the winter the normal heat pump system extracts heat from outdoor air and transfers

it inside where it is circulated through your home's ductwork by a fan.

Even cold air contains a great deal of heat; the temperature at which air no longer

carries any heat is well below -200 degrees Fahrenheit. But the coldest temperature

ever recorded in the lower 48 states was -70 degrees, recorded at Roger Pass,

Montana on January 20, 1954. Obviously in such weather, a heat pump would have to

work pretty hard to produce 68-degree temperatures inside your home.

That's why geothermal heat pumps are so efficient.


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WORKING PRINCIPLE:

Geothermal heat pumps are similar to ordinary heat pumps, but instead of using heat

found in outside air, they rely on the stable, even heat of the earth to provide heating, air

conditioning and, in most cases, hot water.

A few feet below the earth's surface, however, the ground remains at a relatively

constant temperature. Although the temperatures vary according to latitude, at six feet

underground, temperatures range from 45 degrees to 75 degrees Fahrenheit.

Ever been inside a cave in the summer? The air underground is a constant, cooler

temperature than the air outside. During the winter, that same constant cave

temperature is warmer than the air outside.

That's the principle behind geothermal heat pumps. In the winter, they move the heat

from the earth into your house. In the summer, they pull the heat from your home and

discharge it into the ground.

Studies show that approximately 70 percent of the energy used in a geothermal heat

pump system is renewable energy from the ground. The earth's constant temperature is

what makes geothermal heat pumps one of the most efficient, comfortable, and quiet

heating and cooling technologies available today. While they may be more costly to

install initially than regular heat pumps, they can produce markedly lower energy bills -

30 percent to 40 percent lower, according to estimates from the U.S. Environmental

Protection Agency, who now includes geothermal heat pumps in the types of products

rated in the Energy Star program. Because they are mechanically simple and outside

parts of the system are below ground and protected from the weather, maintenance

costs are often lower as well.

As an added benefit, systems can be equipped with a device called a "de super heater"

can heat household water, which circulates into the regular water heater tank. In thesummer, heat that is taken from the house and would be expelled into the loop is used

to heat the water for free. In the winter, the de super heater can reduce water-heating

costs by about half, while a conventional water heater meets the rest of the household's

needs. In the spring and fall when temperatures are mild and the heat pump may not be


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operating at all, the regular water heater provides hot water.

How Do They Compare?

Surveys taken by utilities have found that homeowners using geothermal heat pumpsrate them highly when compared to conventional systems.More than 95 percent of all

geothermal heat pump owners would recommend a similar system to their friends and

family.

Cost

You will have to add the cost of drilling to the total amount of the project. The final cost

will depend on whether your system will drill vertically deep underground or will put the

loops in a horizontal fashion a shorter distance below ground. The cost of drilling also

will vary depending on the terrain and other factors.

Durability

Geothermal heat pumps are durable and require little maintenance. They have fewer

mechanical components than other systems, and most of those components are underground,

sheltered from the weather. The underground piping used in the system is often guaranteed to

last 25 to 50 years and is virtually worry-free. The components inside the house are small andeasily accessible for maintenance. Warm and cool airs are distributed through ductwork, just as

in a regular forced-air system.

Since geothermal systems have no outside condensing units like air conditioners, they are

quieter to operate.

How Do They Work?

Remember, a geothermal heat pump doesn't create heat by burning fuel, like a furnace

does. Instead, in winter it collects the Earth's natural heat through a series of pipes,

called a loop, installed below the surface of the ground or submersed in a pond or lake.

Fluid circulates through the loop and carries the heat to the house. There, an electrically

driven compressor and a heat exchanger concentrate the Earth's energy and release it

inside the home at a higher temperature. Ductwork distributes the heat to different

rooms.


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In summer, the process is reversed. The underground loop draws excess heat from the

house and allows it to be absorbed by the Earth. The system cools your home in the

same way that a refrigerator keeps your food cool - by drawing heat from the interior,

not by blowing in cold air.

The geothermal loop that is buried underground is typically made of high-density

polyethylene, a tough plastic that is extraordinarily durable but which allows heat to

pass through efficiently. When installers connect sections of pipe, they heat fuse the

joints, making the connections stronger than the pipe itself. The fluid in the loop is water

or an environmentally safe antifreeze solution that circulates through the pipes in a

closed system.

Another type of geothermal system uses a loop of copper piping placed underground.

When refrigerant is pumped through the loop, heat is transferred directly through the

copper to the earth.

Types of Loops

Geothermal heat pump systems are usually not do-it-yourself projects. To ensure good

results, the piping should be installed by professionals who follow procedures

established by the International Ground Source Heat Pump Association (IGSHPA).

Designing the system also calls for professional expertise: the length of the loop

depends upon a number of factors, including the type of loop configuration used; your

home's heating and air conditioning load; local soil conditions and landscaping; and the

severity of your climate. Larger homes requiring more heating or air conditioning

generally need larger loops than smaller homes. Homes in climates where temperatures

are extreme also generally require larger loops.

Here are the typical loop configurations:


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Horizontal Ground Closed Loops

This type is usually the most cost effective when trenches are easy to dig and the size

of the yard is adequate. Workers use trenchers or backhoes to dig the trenches three to

six feet below the ground in which they lay a series of parallel plastic pipes. They

backfill the trench, taking care not to allow sharp rocks or debris to damage the pipes.

Fluid runs through the pipe in a closed system. A typical horizontal loop will be 400 to

600 feet long for each ton of heating and cooling.

Vertical Ground Closed Loops

This type of loop is used where there is little yard space, when surface rocks make

digging impractical, or when you want to disrupt the landscape as little as possible.

Vertical holes 150 to 450 feet deep - much like wells - are bored in the ground, and a

single loop of pipe with a U-bend at the bottom is inserted before the hole is backfilled.

Each vertical pipe is then connected to a horizontal underground pipe that carries fluid

in a closed system to and from the indoor exchange unit. Vertical loops are generally


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more expensive to install, but require less piping than horizontal loops because the

Earth's temperature is more stable farther below the surface.

Pond Closed Loops

This type of loop design may be the most economical when a home is near a body of

water such as a shallow pond or lake. Fluid circulates underwater through polyethylene

piping in a closed system, just as it does through ground loops. The pipes may be coiled

in a slinky shape to fit more of it into a given amount of space. Since it is a closed

system, it results in no adverse impacts on the aquatic system.

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