Sub-cooling question

[Indy2010]

A quick question, I am thinking sub-cooling provides greater refrigerant density at the evaporator. Is this correct?

[NoNickName]

It's been discussed several times in the forum. Use the search feature.

[Indy2010]

Thanks, I like to think I'm resourceful and know how to search. However so far I've failed to find the specific answer to my question despite a couple of weeks of reading here

Sure there are many similar and extremely interesting posts, but as far as I have not found any which have addressed my question, which was tailored specifically to hopefully get a quick answer.

If anyone has a link to a thread which may lead to an answer or put me on the right track I'd be grateful.

With my limited knowledge on the subject it's quite possible I'm not using the appropriate terms while searching..



and still searching

[Sandro Baptista]

A quick question, I am thinking sub-cooling provides greater refrigerant density at the evaporator. Is this correct?

If you cool the liquid it will have a higher density (but unless you have great sub-cooling you will not have appreciate difference...I'm sorry the question but what's the interest of increasing the density?

[Brian_UK]

Document here referring to NH3 but has a nice chart showing density change with sub-cooling, may help you...

http://www.google.co.uk/url?sa=t&sou...b3LbCA&cad=rja

[big bear]

Good Question !! but why would you be interested like stated about density at Triple point I.e Expansion . If refrigerant is at triple point after expansion then how can it become dense ? Any way from what i Know about sub cooling is that it is usually best At body warmth ie 36k Before it Goes through expansion . Sub cooled liquid has condensed from the condenser From Hot gas ,saturation to vapour then saturation into liquid (Fullly condensed) . Through Expansion (Triple point ) ,liquid to vapour, Vapoiur to gas, heat absortion, superheat to gas. ratios are 80% liquid 15% vapour 5% gas @ triple point (after expansion) . Answer to your question i am sure is ' No ' It does nt provide greater refrigerant density at the evaporator BUT is always going to be denser before the evaporator / expansion valve fully SUB COOLED i e Liquid form :-)

[NoNickName]

Density of liquid is irrelevant to subcooling.

[mad fridgie]

If you sub cool (more) the liquid line prior to the expansion device, then after the expansion device you would have less flash gas (compared to a lesser level of sub cooling) so the refrigerant stream at this point would be more dense (liquid vapour mix) I think this is the question you were asking

[Sridhar1312]

Any refrigerant when sub cooled density will go up.The crux of sub cooling is more the sub cooling better as it reduces the flash gas and increases refrigeration effect.
Sub cooling circuit is predominantly 10 to 15 degree F as optimum in majority of the equipments. Further high sub cooling may not be economical design.

[Indy2010]

Thanks for all the great directions, Ok so "Density of liquid is irrelevant to sub-cooling" I can see that; but am more interested with the effects of sub-cooling on density, in reasoning the benefits of sub-cooling.

"more sub-cooling is better as it reduces the flash gas" H'mmmm.. Ok had to look that up! But understood now thx.

As I read on I'm beginning to understand that maybe density has little consequence in relation to flash gas prevention.

Also found Google way better at searching articles in this forum than the forum default search engine

[Josip]

Hi, Indy2010

Thanks for all the great directions, Ok so "Density of liquid is irrelevant to sub-cooling" I can see that; but am more interested with the effects of sub-cooling on density, in reasoning the benefits of sub-cooling.

"more sub-cooling is better as it reduces the flash gas" H'mmmm.. Ok had to look that up! But understood now thx.

As I read on I'm beginning to understand that maybe density has little consequence in relation to flash gas prevention.

Also found Google way better at searching articles in this forum than the forum default search engine

http://www.brighthub.com/engineering/mechanical/articles/34725.aspx#ixzz1DwtVVL00[/URL]]

What is Subcooling?

Before we discuss subcooling and super heating, it is essential to understand what refrigeration is. Refrigeration is the extraction of heat, or the transmission of heat by mechanical methods, from one location to another. Subcooling in refrigeration implies cooling the refrigerant in liquid state, at uniform pressure, to a temperature that is less than the saturation temperature, which corresponds to condenser pressure.

Advantages Of Subcooling

• Refrigeration is improved when a liquid refrigerant is subcooled by a circulation of cold water in the heat exchanger or by some other methods. As a general rule, a 1% increase in refrigeration can be achieved for every 2 degrees of liquid subcooling obtained. Due to this characteristic, designs of condensers have been changed to achieve obtain liquid subcooling.

• Production of flash gas is reduced during the process of expansion.

• Greater latitude is achieved in management of piping and location of evaporator.

Methods Of Subcooling

Refrigerant can be subcooled by following methods:

• By improving and carrying out modifications in condensers so that subcooling arrangement is included.
• By Installing internal and external heat exchangers to provide subcooling.

Read more: http://www.brighthub.com/engineering...#ixzz1DwtVVL00

Hope this helps a little

regarding search engines RE Forums vs Google .... it is normal that Google has a better one, do you agree...

but, when you fail with Google-happen nothing, you stay alone, but if you fail at RE forums we are coming to help ....

Best regards, Josip

[Indy2010]

Sorry I think my meaning was misunderstood.. more that the forum might benefit greatly if it were to use google as the search engine, which is able to filter relevant info on this forum with better results then the default version. You'll find many vBulletin forums using google these days, it also brings many advanced search functions

[Koopy]

So if 8k subcooling is what is required to ensure that cappie bubbles cannot exist in the system, my question is:

Would it be better to measure my subcooling just before my expansion device? Besides systems with liquid receivers, I
Find that most systems don't compensate for liquid to be banking that high during full loads. So when load drops we bank liquid into the condenser loosing capacity.

[Koopy]

Cappie should read vapor

[Indy2010]

Thanks Josip, a great read

[Josip]

Hi, Indy2010

Thanks Josip, a great read

I'm glad to be able to help


N.B.
Don't worry about search engines .... it was a joke

"I was using Google too,
to find a link for you"

.... maybe I can sell this to Google as a watchword ...


Best regards, Josip

[lana]

Hi there,

As mentioned before, after expansion process some of the liquid flashes into vapour. If the liquid is sub-cooled then there will be more liquid after expansion process. More liquid in the evaporator means more capacity.
Now, when there is a receiver then the liquid going out of it is actually saturated. This also was discussed here in this forum a few years ago. If you use a suction-liquid line heat exchanger then you get real sub-cooled liquid before the TEV. In double-stage compressors when a sub-cooler is used, a high sub-cooling is obtained which increases the capacity substantially.
Cheers