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Old 03-09-2017, 05:19 PM   #1
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Default A/C experts.........question

For those of you that have a lot of experience or are experts in A/C systems....

Do you think if I had a custom made condensor that is EXACTLY half the size as the factory condensor......made some new lines to fit....and added a 2,000 cfm fan onto it...

Do you think it would still allow the A/C to run cool, cut the cooling potential in half or less.......or would it be a total failure.....???

Thanks.

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Old 03-09-2017, 05:28 PM   #2
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I was always good with A/C. My guess is it would be a failure.
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Old 03-10-2017, 09:40 AM   #3
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The temperature of the gasses will be hell to play with. Since it won't get as cool on the smaller condensor the cut off switch will probably cycle the compressor, alot, to maintain correct high side pressure
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Old 03-10-2017, 11:12 AM   #4
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Whether you have a huge condenser and little air flow across it or a tiny condenser with maximum airflow through it does not matter, the physics is the same; all that matters is enough heat is extracted from the refrigerant so it condenses back into a liquid and there's enough of that liquid available before it hits the orifice valve.
Then the flow volume of refrigerant is basically your cooling capacity, the more that can flow around the system (at faster speed) the more cooling performance you'd have.

On the one hand I'd say yes it would work fine when looking at it from a basic AC/refrigeration perspective,
however if you are in south florida with high heat/humidity at 90 and given the application and knowing oem f-body AC isn't the greatest, then if you have t-tops which makes the cabin more of a greenhouse, the odds would not be in your favor if you were to do such a thing. You should expect to need to run the fan (not necessarily pulling 2000 cfm air) when driving 60mph, it'd all be the quality of airflow through your smaller condenser along with that air leaving from out under the hood to take the heat away.

you said EXACTLY half the size, i'd have to look up the formulas in some refrigeration books but I doubt half the condenser size would equal a 2x factor in other things such as "twice" the airflow through a condenser would make up for 1/2 the size. I would expect something like 1/2 the condenser size equals a 4x or 8x increase in airflow thru it.

if the smaller condenser does not cool enough, that is no different than the larger oem condenser on a very hot day not cooling enough.
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Old 03-10-2017, 02:43 PM   #5
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Whether you have a huge condenser and little air flow across it or a tiny condenser with maximum airflow through it does not matter, the physics is the same; all that matters is enough heat is extracted from the refrigerant so it condenses back into a liquid and there's enough of that liquid available before it hits the orifice valve.
Then the flow volume of refrigerant is basically your cooling capacity, the more that can flow around the system (at faster speed) the more cooling performance you'd have.

On the one hand I'd say yes it would work fine when looking at it from a basic AC/refrigeration perspective,
however if you are in south florida with high heat/humidity at 90 and given the application and knowing oem f-body AC isn't the greatest, then if you have t-tops which makes the cabin more of a greenhouse, the odds would not be in your favor if you were to do such a thing. You should expect to need to run the fan (not necessarily pulling 2000 cfm air) when driving 60mph, it'd all be the quality of airflow through your smaller condenser along with that air leaving from out under the hood to take the heat away.

you said EXACTLY half the size, i'd have to look up the formulas in some refrigeration books but I doubt half the condenser size would equal a 2x factor in other things such as "twice" the airflow through a condenser would make up for 1/2 the size. I would expect something like 1/2 the condenser size equals a 4x or 8x increase in airflow thru it.

if the smaller condenser does not cool enough, that is no different than the larger oem condenser on a very hot day not cooling enough.
If you can run a formula, I'd appreciate it.

Another idea....stack two halves together with a 2,000 cfm fan pushing air through both layers. So the same surface area in total would be there, but the front half would be blowing hot air onto the second layer reducing its cooling capacity.

Or....I could even get away with cutting away the top third of the condensor and actually keeping the lower 2/3 intact. How would that work out you think....?

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Old 03-18-2017, 10:03 AM   #6
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if you mean cutting apart a condenser then trying to re-solder or braze it back together, i think that's a bad idea. i doubt it could be done, unless it's one of the old style that's a just a single tube. i don't know the details of what you are working on but if the condenser you have to start with is an old style that's too large then you can replace it with a modern parallel-flow style condenser which can be smaller than the original and perform the same or possibly better. but if you are already starting with a parallel flow type condenser and you need smaller then your best bet is to just find one that is smaller in size to fit your needs.

http://www.techchoiceparts.com/condenser
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Old 03-18-2017, 01:18 PM   #7
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http://www.engineeringtoolbox.com/co...fer-d_430.html

here's most of what you need to ballpark whether or not what you want to do will work and under what outside temperature conditions. based on basic heat transfer h = q / ▲t. q is amount of heat transferred in watt/m^2. h = heat transfer coeff. The big thing to keep in mind is it's not just heat transfer, it's "convective heat transfer" and a limit quickly happens when using air where greater ▲t no longer happens with greater airflow.

Surface area is NOT the LxW dimension of the condenser, you would need to calculate the surface area of the sum of all the pipes that make up the condenser that would expose the heated refrigerant inside to the airflow. For the old style serpentine condenser it is easy, the parallel-flow style not so much but the parallel-flow style will have a much larger value for area which is why they work better.

surface temp = temperature of condenser pipes that are exposed to airflow. ac compressor discharge temps never should be more than 225F, and the temp of that refrigerant will be reduced by time it gets to condenser. Touch/measure the inlet pipe just before condenser and use whatever that temperature would be, figure 45-70C.

air temp = 30C or 86F outside air temp

convective heat transfer coeff in watts/m^2 K taken from that "air-heat transfer coef" chart in link, where x axis is velocity in m/s. This is not your cfm (cubic feet minute) value since this value needs to relate to the speed of air across the heat exchanger... or rather how fast the heat exchanger moves thru air of a given temperature. Again this is tricky because the condenser is not in a free air stream = 60mph when you drive 60mph, it is stacked in front of the radiator then you have the engine bay behind it. for your new 2000 cfm capable fan, do not use "2000 ft/min" that is based on volume of air. you have to calculate it down to a linear velocity based on the size of the fan shroud and condenser it's mounted to.

but if you drive 30 mph = 14 m/s, and 60 mph = 27 m/s which is already off their x-axis on the chart, but as you can see the curve flat lines around 35 w/m2 k. When the AC is on I know the pcm turns the oem radiator fans on at low speed no matter what whenever vehicle is below 30 mph.

You can try backing out some values by knowing others,
compare the effect of a small 5000 btu/hr ac home window unit and how that feels so expect a car AC as being able to do 1/2 ton AC cooling = 6000 btu/hr = 1760 watts. So the car condenser & fan setup must be able to extract that much heat in watts out of the system, figure at least 1000 watts on a not super hot but sunny day. But more if you have glass t-tops.

in the end what really matters now is how oversized or conservative the oem was in designing the ac system and sizing the condenser, and because of material cost and smaller is always cheaper/easier for other various reasons that i suspect the oem condenser size is already as small as it could be.
what this means is if you go smaller then you must rely on a greater difference in delta-t (outside air temperature colder to hotter condenser temperature). For a given outside air temp don't expect more airflow thru condenser to help if at all, based on that air-heat chart making out around 35 watts/m^2 K.
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Old 03-18-2017, 03:26 PM   #8
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if you mean cutting apart a condenser then trying to re-solder or braze it back together, i think that's a bad idea. i doubt it could be done, unless it's one of the old style that's a just a single tube. i don't know the details of what you are working on but if the condenser you have to start with is an old style that's too large then you can replace it with a modern parallel-flow style condenser which can be smaller than the original and perform the same or possibly better. but if you are already starting with a parallel flow type condenser and you need smaller then your best bet is to just find one that is smaller in size to fit your needs.

http://www.techchoiceparts.com/condenser
If I find a condensor out of any vehicle....and run lines to/from it...will it work the same as my factory LS1 condensor, if it was exactly the same size?

Or does it have to be a certain kind of condensor?

I simply want to have a smaller condensor.....say 14x14 with a 13x13 2,000cfm fan attached to it.

If that will allow my A/C to blow very cold, I'll do it.

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Old 03-18-2017, 03:31 PM   #9
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If our LS1 style condensors are Serpentine.......than maybe just going to a better Parallel type might do the trick.....and use a smaller one of course.

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