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The smallest car A/C compressor Pages: 12

WyeBee on Mon February 08, 2010 9:12 AM User is offline

Refrigerant Type: R134a

Hi!

Relying on the experience of the forum, I have a small challenge.
I am looking, for a non-automotive application, for the smallest automotive A/C compressor available commercially.
(By small I mean lowest possible displacement, not the physical size)
It has to be pulley driven, so the Prius electric compressor (18CC) is out.
Currently leading is the Sanden 54CC TRSA05, but if there are others out there with lower displacement values I would greatly appreciate some information on type and in which car they are used.

I looked also at the Denso SCS06C, which is used in some small cars, but I could not find its displacement.

Thanks!!

Y.

ice-n-tropics on Mon February 08, 2010 5:50 PM User is offline

WyeBee,
I can make a 18 cc scroll out of a 54 cc TRSA05 if your opportunity justifies my effort.
I saw that SCS06C Denso on Nissan pickups in Brazil
Why do you want small displacement? Power or pumping volume?
I worked with the TRSA05. It has high volumetric and isentropic efficiency, therefore horsepower is optimized. It's used on tiny Hondas in Asia and turns clockwise unlike other Honda scrolls.
The TRSA05 has an extra BTU performance kick because it has a built in oil separator and can live with a small oil charge. This improves heat exchanger performance because there is less oil circulating around the system and a thinner insulating oil layer coating the primary heat exchanger (refrigerant side) surface.
Cordially

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Mon February 08, 2010 at 6:41 PM by ice-n-tropics

bohica2xo on Mon February 08, 2010 6:56 PM User is offline

How about 10cc's? Is that small enough?

A V5 destrokes to a minumum of 10cc, and max stroke is 156cc.

It is not rocket science to adjust the stroke on that compressor.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

WyeBee on Tue February 09, 2010 2:58 AM User is offline

Thanks for the inputs!

The small displacement requirement comes from RPM / Power limits we have. I have been contemplating a variable displacement compressor but had 2 concerns:
1. Would a 156 CC compressor running at 20CC - 40 CC displacement be very inefficient at this point?
2. It seems these compressors are driven by a solenoid which is driven by a dedicated controller. Can one get the control signal portfolio?, so we can set the displacement by ourselves? (i.e. the input to displacement formula).


Thanks

ice-n-tropics on Tue February 09, 2010 11:19 AM User is offline

WyeBee,
A partial stroke 156cc variable compressor fixed at 20 cc swept volume (13% of full stroke) would have low volumetric and isentropic efficiency because:
1) Variable stroke compressors have lower top dead center (TDC) when destroked so that there is a greater factor of safety to prevent the piston from crunching the suction valve.
2) Residual gas on top of the piston in the dead volume (DV) at TDC re-expands and gains super heat (SH) of compression.
3) The DV becomes a larger percentage of the reduced swept volume and volumetric efficiency falls off a cliff.
4) This also applies to the exhausted gas which slips back past the closing discharge valve into the compression chamber as the piston is in the early stage of down stroke. This is called "wire drawing".
5) There is a small gas flow communication path between adjacent cylinders (on each edge of the suction valve) that has a negative blow-by and this becomes a larger percentage of the total also, albeit very little.

It's a WAG as to where the swash plate cam is setting (stroke) while adjusting the control valve. I have never figured out a way to know the exact reduced displacement when adjusting the control valve. Maybe you can figure out a way, better than I, to know the variable cam position). Of course it will change as operating pressures change.

Best solution is to install spacers on the compressor shaft to freeze the pivoting cam's displacement without messing with the control valve. You could do this and run a A/C system while measuring the SH to get an objective rough estimate on efficiency.

What is your potential volume for this application, i.e., how much investment is justified?

A reasonable guess on the Denso is 60cc. I recall it was a little bit more than 60 cc. Idle cooling was punk but price was cheaper than dirt.

What are rpm and power paramaters?

I have a TRSA05 in my hands as we speak. Very sweet!

Cordially,
Hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Tue February 09, 2010 at 11:42 AM by ice-n-tropics

bohica2xo on Tue February 09, 2010 12:10 PM User is offline

Granted a destroked compressor gives up some effeciency, but it should be fine for a prototype. Yes, shim the cam to get the desired stroke.

A scroll compressor will work for what you want - just slow it down a tiny bit, and the output turns to crap. A 60cc scroll is only 60cc's if you spin it up to 85% of the redline...

Or you could use a piston compressor and turn it slower. a 150cc/rev compressor puts out 37.5 cc's with a 90 degree rotation, so a 4:1 underdrive should give you what you are looking for...

Lots of ways to get to 40cc's / rev. It all depends on how much money you have to throw at the project.

If you are looking for 100,000 units, I am sure Ice-N-Tropics can help you.

B.


-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

WyeBee on Tue February 09, 2010 2:47 PM User is offline

Ice-n-tropics,
Some answers, not necessarily in order....
The RPM will be varied between 750 and 5000 RPM, but power will vary with RPM. We are not sure where the best eff point will be and hence the dilemma which compressor to use.
The thought is that Smaller compressors require less power, and should therefore be easier to drive on varying RPM. (cooling capacity required is 1-2 KW)
We are not looking currently to build 100K units, though time may come :-)
I like the idea of playing with a VD compressor while fixing it with spacers. I will certainly get one to play around with.
I opted for Scroll compressors because of their higher eff.
Y.

ice-n-tropics on Tue February 09, 2010 4:44 PM User is offline

WyeBee,
Good luck with the variable compressor. If the power requirement is unsatisfactory for your application, the TRSA design cannot be beat for efficiency (except for dual spinning scroll members).
My study shows the TRSA05 to be 53.9 cc, not 54cc
Looking at all my test data on TRSA05 with 95.5 volumetric efficiency at 4000 rpm:
At typical summer discharge and suction pressure, to provide 2 KW cooling at 4000 rpm would require 18 to 20 cc swept volume.
Another option is to increase the clutch rotor pulley from the normal 103 mm (4 inch) diameter to 278 mm (10.9 inch) to 12 inch, if your application has that much real estate. The pulley balance and radial and axial TIR gets pretty critical at this extreme monster pulley size.
I can design and build one or any quantity (either TRSA02 or monster pulley), which ever you need, if your business justifies the R&D.
Cordially,
Hotrodac


-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

bohica2xo on Tue February 09, 2010 5:16 PM User is offline

A 6.6:1 speed range with a scroll? You have a variable displacment compressor right there.

What is the effeciency of that scroll @ 600rpm? That max effeciency looks great on paper...



Underdriven at full stroke that should work as well as anything.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

ice-n-tropics on Wed February 10, 2010 12:04 PM User is offline

Bohica,
I understand your outlook on scrolls after your bad experience with the Ford variable capacity scroll, but that was not fixed displacement. Ford had 2 bypass ports built into the side walls that were dead volume and knocked 10 to 25% off the volumetric efficiency. Why are almost all the high efficiency hermetic compressor home A/C based on the scroll design?
What was your point about TRSA05 speed ratio/variable compressor? TRSA05 lives at 12000 rpm.

TRSA05 volumetric efficiency (VE) at 1000 rpm is 83% and that's close to what you get if the suction is not restricted, suction super heat is low and excess oil is not a factor. Isentropic efficiency (IE) is 41 to 51% depending on Pd & Ps (not ASHRAE). At 5000 rpm the IE =51 to 61%.

V-5 volumetric at reduced stroke at 1000 rpm would be less that the 72% shown on the full stroke graph for the re-expansion reasons listed earlier. Same applies to the IE. I'm pessimistic toward the high IE of 65% shown on the graph.

An optimist says the glass is half full. The pessimist says it is half empty. The engineer says the glass is twice as big as it needs to be.

This application is power limited, therefore the power draw may be a show stopper at 5000 rpm.
Cordially,
Hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Wed February 10, 2010 at 12:08 PM by ice-n-tropics

NickD on Wed February 10, 2010 8:53 PM User is offline

For some reason, the application of this compressor is lacking, perhaps an AC compressor is not even the best choice.

WyeBee on Thu February 11, 2010 2:05 AM User is offline

As power is the limiting factor, efficiency becomes very important. This is why we are looking for a compressor which will work around its efficiency point at our load requirement.
The compressor functionality is Air conditioning here, so it is quite suitable for the time being. (We have looked at other compressors such as the small bitzers as well)

I like the TRSA05 and trying to get my hands on one. On this side of the world it is not as easy as it may seem... I found it in Ford Ka cars but these are extremely rare here.
There is no Sanden agency here that I am aware of.

Ice-n-tropics - are you aware of a more common car into which this was designed into? We have plenty of 1.0 liter small cars around, but it is not trivial to get manufacturer data
(Asking local compressor shops, they only class compressors based on the car make
(A typical response is - yes I have plenty of Sandens - do you want a Honda Sanden or a Ford Sanden?)

We may end up importing a few from the states...

Y.

Edited: Thu February 11, 2010 at 2:17 AM by WyeBee

NickD on Thu February 11, 2010 5:17 AM User is offline

An AC application spills the beans that this compressor will be pumping refrigerant. Which kind? As just an example of this, we have these half size refrigerators here for dorms that sell for around 80 bucks that get cold enough to keep ice cream as hard as a rock in their tiny freezer compartment. Got one for my daughter for her dorm. Some use R-22 where others use R-134a, a substantial difference in operating pressures. Cheaper to buy the entire refrigerator than just the compressor, can hold it in your hand, the compressor that is, with a 120 VAC motor mounted. Assume you will be driving this compressor from some sort of a motor.

Where is your country? My country is the USA or whatever is left of it.

WyeBee on Thu February 11, 2010 6:20 AM User is offline

The refrigerant is R-134a.
We cannot use the small hermetic compressors, as we have a belt driven application. These also are designed to work in a specific RPM and are mostly piston driven.


I am working and cooling in Israel.

Y.





Edited: Thu February 11, 2010 at 6:23 AM by WyeBee

NickD on Thu February 11, 2010 9:11 AM User is offline

An automotive application? Why the mystery?

WyeBee on Thu February 11, 2010 10:00 AM User is offline

Non-automotive.
Y.

ice-n-tropics on Thu February 11, 2010 1:35 PM User is offline

WyeBee,
The TRSA05 power requirement at 5000 rpm is between 3.52 to 4.94 kW, depending on the pressures.
I'd like to tear down the Bitzer small scroll.
If power and weight are both important, we should consider a TRSA01 turning 10,000 rpm, especially for a ultra light electric motor driven application.
Semihermetic scroll compressors turn 6000 or more with special anti centrifugal counter measures..
I've already been studying my idea for a TRSA02 because the world needs a ultra-lightweight A/C. My future TRSA02, at 5000 rpm, would be about 1.8 KW plus a small surge during engagement. If you install a maximum suction pressure regulating valve, the max. power will be less. Power is proportional to the absolute suction pressure.
You sound as if you are back to considering the TRSA as well as the destroked V-5. Along with the destroked V-5, you could consider the variable capacity SD6V12 (detuned) Sanden on small Euro cars. If your business is R&D on devices for Israel's defense or offense, I'll make my new TRSA05 available, that I am holding in my hand. Tim, our trustworthy forum host, at Arizona Mobile Air, may want to make a buck on a sale to you and he can do export easily (if he has your cash). If Tim needs my TRSA05, it is available. Don't ever tell Sanden, if you have a military application, because Sanden has a global policy as conscientious objector.
You need to have a Sanden SP-10 PAG oil charge matched to the refrigerant quantity. I have SP-10. Scrolls without a built in oil separator normally need 5% minimum oil circulation ratio (OCR) in the suction gas as measured per ASHRAE. The oil separator in the TRSA05 allows that to be reduced to 2 to 3% OCR (it's not a very thorough oil separator). If I understand your application, an oil quantity can be determined.
Cordially,
Hotrodac



-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Thu February 11, 2010 at 2:47 PM by ice-n-tropics

NickD on Fri February 12, 2010 8:56 AM User is offline

In designing an AC system, even non-automotive, first the cooling requirements are defined depending on heat gains or losses, the refrigerant is selected, the required heat exchangers are sized and designed to meet those requirements, then lastly, the compressor is selected to meet those heat exchanger requirements. Power source is defined lastly, but an RPM range of 750 and 5000 RPM was specified from an unknown source.

Just seems to me, this design is being done completely backwards, with all known parameters, a final system optimization is done to compensate for variable parameters. That low 500 RPM specification can really cause problems for low end performance.

If this is a component cooling application, compressorless fluid heat exchangers can be designed using either natural or forced air convection. But how can anyone make recommendations if you don't even know what the application is?

This entire thread seems crazy to me.

ice-n-tropics on Fri February 12, 2010 9:29 AM User is offline

WyeBee,
The smallest Asian Honda is the only car that I know uses the TRSA05. Maybe it's made in the Philippines.
For Sanden contacts:
I met Mr. Alex in Frankfurt when I was a consultant on A/C with variable compressors. He said his company in Israel "ALEX Air Conditioning" uses Sanden scrolls on Busses. You could ask ALEX for Sanden contacts and supply route.
Cordially,
Hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Fri February 12, 2010 at 9:44 AM by ice-n-tropics

WyeBee on Mon February 15, 2010 9:15 AM User is offline

Thank you all for the valuable information. It is quite helpful. We are gathering more data and I'll keep you posted on updates.
By the way, there is innovation in Israel that is not military :-)

NickD on Mon February 15, 2010 11:39 AM User is offline

What's stopping you from designing and tooling your own compressor? Don't know anything about your patent system, if like ours, can be an applications patent where the components suited for the job can also be claimed. Using off the shelve stuff, anyone can see and duplicate it.

ice-n-tropics on Mon February 15, 2010 4:38 PM User is offline

WyeBee,
Some random thoughts on scrolls:
Maybe you are cooling something other than a vehicle, as Nick said, the application is not specified.
2KW =6,830 BTU will not keep a full size vehicle cold at 100F. Electric vehicles have tried 5000 to 7000 BTU 320/360 volt hermetic or semi-hermetic scroll compressor, but above 90 degrees you would need a chiller suit.
Honda EV has a Sanden electric driven tiny scroll.
Electric or hydraulic driven scrolls can vary performance to meet cooling requirements but the motor has a efficiency penalty.
We used a 1800 BTU suit lined with a anti-freeze tubing circuit for the driver of the Bradley. It uses 2 TRS090 18,000 BTU high side units with custom 28 volt clutches (by Hotrod) driven by individual 28 volt motors. There was just no way to keep occupants comfortable except forced convection spot cooling or liquid conduction at 130F.
Israel uses 2 compressors with independent A/C systems on their tanks so that if one fails during battle, the occupants do not have to open the hatch and stick their head out and the electronics stay cool. They even leak check the systems with a helium mass spectrometer before charging the systems. Real smart engineers.
The low rpm diesel Hum-vee A/C cooling was pitiful with the factory OEM A/C R-4. The porous gravity casting R-4 will only contain refrigerant about 2 weeks. A overspeed TRSA12 60,000 BTU, was tried which cooled OK but required too much condenser and evaporator fan electrical power.
The Stryker with hydraulic driven dual TRS090 topped 40,000 BTU but still needed to utilize spot cooling.
Class 8 heavy trucks get by with no-idle auxiliary A/C units powered by 8 to 15 hp diesel engines, with ratings generally between 8000 to 12000 BTU using piston compressor. Usually they use a thermal curtain to partition off a reduced area for the sleeper bunk and do OK for cooling.
Most energy limited applications choose a scroll.
GM Trailblazer recently switched from the TRSA12 to a Mitsubishi scroll. Maybe Mitsubishi has a small scroll.
Let Tim or I know if you want this TRSA05.
Cordially,
Hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

NickD on Mon February 15, 2010 5:50 PM User is offline

WyeBee did state this is a non-automotive, non military application, ha, he is good at keeping us guessing. Didn't realize the Hum-Vee AC system was that poor and losing refrigerant that quickly? But the EPA has no say with the military, they can do whatever they want to.

WyeBee on Thu February 18, 2010 4:26 AM User is offline

We got the Bitzer in. This is one cute little machine. Looks like design of the 50s, but it is a small piston (I think 28cc) compressor...
Y.

ice-n-tropics on Thu February 18, 2010 1:11 PM User is offline

I had some good experience with Bitzer for a semi-hermetic piston compressor with R-404A for a minus 40 degree test chamber.
Bitzer knows how to deal with liquid slugging in the suction if they understand the application.
By the way, Sanden Singapore has R-404A compressors for low temp application with appropriate oil.
Heat pumps have embraced the scroll because scrolls can survive heavy liquid slugging.
In 1974 York/Borg Warner was having valve failures due to liquid slugging on port installed BEHR A/C for Mercedes. BEHR used a lower than normal TXV superheat spec. They solved the failures by increasing TDC and modifying the holes in the valve plate.
These counter measures hurt the isentropic and volumetric efficiency.
All this to say, be careful of liquid slugging on piston special applications.
Cordially,
Hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

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