help me economizer for scroll comp

[tranquanghvac]

could anyone tell me what economizer for scroll comp is?
the instructor asks me to search it in copeland website but hardly to find anything.

[US Iceman]

An economizer used in a refrigerant ciruit is typically just a simple heat exchanger (an evaporator). The high-pressure liquid is cooled by the refrigerant flashing on the other side of the heat exchanger.

Think of it like this. If you use an evaporator to cool a liquid (like a water chiller), a typical economizer is just like this. You are cooling liquid refrigerant to improve the cycle efficiency.

I'm not too familiar with scroll compressors, but for this to provide a reasonable energy improvement the refrigerant evaporated on one side of the heat exchanger would have to be admitted into the middle of the compression cycle (or somewhere between suction pressure and discharge pressure).

[Larry2]

Maybe this will help too.

http://www.freepatentsonline.com/6142753.html

[LRAC]

Maybe this will help too.

http://www.freepatentsonline.com/6142753.html

Looked at the site didn't understand a damn word, but hey were not all assembly engineers.

Lrac:confused:

[Larry2]

It was as clear as mud to me too. Here's an experpt from patent 6826918. You can search and view patents at www.uspto.gov (http://www.uspto.gov). To view all the figures, you need to download and install the free viewer.

Stuff shows up there before you see it in the field, so there is lots of interesting and confusing stuff there for curiosity seekers who want to keep up with the latest. I found this by searching "scroll" and "economizer".



AbstractThe invention provides two distinct schematics allowing system performance enhancement through the utilization of an auxiliary heat exchanger and splitting the refrigerant flow into primary and secondary paths. A system performance boost is achieved due to extra subcooling of a primary refrigerant flow in an auxiliary heat exchanger as well as superheat reduction of the combined refrigerant flow entering the compressor and a primary refrigerant flow pressure drop decrease through the evaporator (in comparison to the prior art). The invention offers the superior benefits outlined above with only a moderate cost increment. Also, employment of conventional components only, and no compressor modifications make implementation of the proposed schematics even more attractive.


A refrigerant cycle is able to provide a certain amount of cooling or heating, known as the capacity. One way to increase the capacity of a refrigerant cycle is the use of an economizer circuit. In an economizer circuit, flow downstream of the condenser is split into a main flow and a secondary flow. The secondary flow is passed through an expansion device, which lowers the temperature of the secondary flow. The secondary flow and the main flow are then both passed through an economizer heat exchanger. The main flow is thus cooled, and when it reaches the evaporator, it has an increased cooling capacity. The secondary flow is returned to an intermediate compression point in the compressor. The economizer circuit does provide performance enhancements, however, in some applications the economizer cycle has been seen as too expensive to implement. In particular, the use of the economizer cycle does require modifications to the compressor to receive the returned refrigerant at the intermediate compression point.

I still don't know why taking some of the refrigerant you worked hard to compress and expanding it in a secondary heat exchanger to lower main condensor subcooling improves efficiancy. It's not a perpetual motion machine though, or it wouldn't be there. :)

[NH3LVR]

I still don't know why taking some of the refrigerant you worked hard to compress and expanding it in a secondary heat exchanger to lower main condensor subcooling improves efficiancy. It's not a perpetual motion machine though, or it wouldn't be there. :)

I remember being confused about this myself years ago. It has to do with eliminating flash gas.
If no one remembers the math I will dust off the books and post it.

[US Iceman]

The whole trick to using an economizer is the amount of subcooling you get from the economizer and the pressure of the subcooled liquid coming out of the economizer.

An economizer is simply a heat exchanger in almost all cases. Although, there is one case where it's simply a tank.

When the economizer cools off the liquid, the net refrigeration effect of the liquid is greater, therefore the compressor capacity increases slightly.

Simply thermodynamics.

The small amount of refrigerant used to subcool the larger portion of liquid is injected into the compression process at some pressure between suction and discharge. The injection is usually closer to the compressor suction pressure.

This is nothing fancy. On some supermarket systems they used to use a separate smaller refrigeration system to pre-cool the main liquid lines from the pack. In effect, the little refrigeration system was an economizer. Except, in this example the economizer outlet pressure was the compressor suction pressure.

You will see this more often on screw compressors.

[Pooh]

One further point is that the outlet of the subcooler/economiser is usually fed into the scroll to cool the winding and also to reduce the density of the refrigerant going into the compressor further increasing the efficiency of the system.

Ian

[US Iceman]

One further point is that the outlet of the subcooler/economiser is usually fed into the scroll to cool the winding and also to reduce the density of the refrigerant going into the compressor further increasing the efficiency of the system.


Now that's interesting. If the vapor off of the economizer is introduced into the motor windings, then the economizer gas is at suction pressure, isn't it? In this case, the only performance benefit is the subcooling at a cost of compressor capacity (plus what you mentioned).

The liquid flashed off to cool the high pressure liquid forms some flash gas. When this gas is introduced into the compressor suction, this volume displaces what the normal gas flow would be returning from the evaporator. Afterall, the compressor will only pump so much gas before the suction pressure rises.

If the flash gas is introduced in between the suction and discharge pressure of the compressor (essentially a side port) the COP should improve. In this type of situation, the cost of compressing the gas (from the economizer) is low. Therefore, you should see the capacity rising faster than the power input.

[Larry2]

http://www.hysave.co.uk/technical/science_technology.html


Here is a related article.

[US Iceman]

The hysave system is not even close to a subcooler/economizer. The little refrigerant pump only boosts the liquid pressure, it does not lower the liquid enthalpy.

It is the point of lowering the liquid enthalpy that generates the capacity increase for the compressor.

[tranquanghvac]

thanhks all your help. I've read
firstgovsearch.gov/search?affiliate=uspto.gov&v%3Aproject=firstgov&query=SCROLL+COMPRESSOR[/url],
and searched over Google but found no real economizer scroll comp image. I wonder if economizer for scroll compressor exists or just theory? still there are schematics. which manufactures have applied this design for their scroll compressors?

[US Iceman]

Try these links:

http://www.container.carrier.com/Files/Container/Global/US-en/TLNov01.pdf?SMSESSION=NO

Or,

Go the Emerson website and register for access to the product bulletins.

https://www.emersonclimatecustomer.com/webapp/wcs/stores/servlet/CTP02_LogIn?krypto=CpToHDs5FDP0JgAfnXT%2FWsi0ZikeROvp0%2B9BYMVRNy1bgck8VtITVA%3D%3D&ddkey=CTP49_SignOffCmd

The bulletin you need is:

AE4-1327 R2, ECONOMIZED VAPOR INJECTION (EVI) COMPRESSORS

[tranquanghvac]

I hardly know where the second fluid flows to after leaving ECO 102. I have attached picture. Could anybody show me the direction of the second fluid in 2 cases?
**"If the economizer valve 116 is opened and the unloader valve 130 is shut, then economizer fluid is injected back into the compressor."
Which line does economizer fluid back to compressor?

**"On the other hand, should the unloader valve 130 be opened and the economizer valve 116 is closed, the refrigerant will pass through the line 25 and by-pass line 51 and back to the suction line 22."
which is "the refrigerant"? the main or the second. If there is the main fluid then it will back to compressor by line 25 and line 22. So in that case there will be no using economizer in scroll compressor right? The main fluid is nolonger be cooled by the second fluid.

Valves 116 and 130 are positioned outside the housing shell. The valve 116 and 130 are controlled to open and close as known by control 15. If the economizer valve 116 is opened and the unloader valve 130 is shut, then economizer fluid is injected back into the compressor. On the other hand, should the unloader valve 130 be opened and the economizer valve 116 is closed, the refrigerant will pass through the line 25 and by-pass line 51 and back to the suction line 22.

[tranquanghvac]

thanks US ICEMAN very much. Now I understand what economizer is. The problem I posted above is just unloaded mode of operation. Thanks to everybody who have me solve this problem.