A slightly differnt A/C system

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ice-n-tropics
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Re: A slightly differnt A/C system

Postby ice-n-tropics » Mon Sep 04, 2017 6:57 pm

sanden.com has TRSE07 scroll shown with 1KW at 1000rpm. Sanden semihermetic on Honda el vehicle has very small scroll.
txv with low MOP (max operating pressure) to restrict mass flow during cool down may already be incorporated to limit power input.
Isentropic efficiency for scroll at 1000 crpm is in 82 to 86% range.
hotrodac
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Re: A slightly differnt A/C system

Postby bohica2xo » Mon Sep 04, 2017 11:11 pm

Tex, that one looks like it might work - if he can replace the York. The FAA makes what would be a simple upgrade in a car a very difficult thing in an aircraft.

The hermetic 3 phase scroll in the previously linked "electric A/C System" would work for what he needs - but would have lots of hoops to jump through.

Your previous comment about the belt raises an interesting issue. The existing system has a small motor pulley, with very little belt wrap. Aging V belts are notorious for slipping when they look just fine - and never making a noise. Here is the fun part. If the slip is allowing the motor to run at a higher speed while under load, the current can Increase or decrease depending on how it is wound. The problem could be a worn pulley & belt.

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ice-n-tropics
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Re: A slightly differnt A/C system

Postby ice-n-tropics » Tue Sep 05, 2017 2:04 pm

Suspect he has an oil pumper or txv MOP defective.
Goal for rotary wing is total of 50 lbs. so saved weight can divert to fuel (but now at 82 lbs.+). military version 50% of cooling is for electronics.
They actually CNC the air fan for turbo axial rotary fan compactness.
If we could design compact 12,000 rpm motor with 10 cc tiny scroll or vane package the world would beat a path to our doorstep.
hotrodac
Last edited by ice-n-tropics on Thu Sep 07, 2017 7:39 am, edited 3 times in total.
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bohica2xo
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Re: A slightly differnt A/C system

Postby bohica2xo » Tue Sep 05, 2017 4:23 pm

Yeah, we used to make some tiny refrigeration stuff - all 400 hz power. High speeds, light weight. There was always 400 hz available if there was a turbine on board.

With all of the PMDC stuff that is around now, it looks easy... until you see the electrical racket produced by the digital electronics making pseudo-3 phase power with PWM square waves. The easy way to get rid of that noise is Iron. Not a good choice for flying parts.

I did a lot of work with oil flooded screw compressors - what about a tiny one of those? Or perhaps a scroll made from something a little better than soda cans?
ice-n-tropics
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Re: A slightly differnt A/C system

Postby ice-n-tropics » Thu Sep 07, 2017 7:53 am

"Oil flooded screw compressor" : So that is where you gained oil separator expertise.
In early days I stopped radio noise from blower motor by installing diode between motor leads when changing between permanent vs series wound or viceversa..
York application has less than 2% oil circulation ratio (OCR) with proper oil charge because crankcase is isolated from main refrigerant flow.
Early Yorks had very little TDC clearance and bursting head gaskets with liquid slugging, therefore Borg Warner changed to excessive TDC and isentropic efficiency was knackered. Later York changed to RCM (rubber covered metal head gaskets ) to eliminate asbestos but retained crappy TDC clearance. Probably to quieten the beast.
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Re: A slightly differnt A/C system

Postby bohica2xo » Thu Sep 07, 2017 8:46 am

Lots of experience over the past 45 years. Screws were just part of it...

I remember the engineer from Harrison Div. that was teaching the RSES courses explaining the theory behind a 12 to 15% OCR. He explained that the oil became saturated with R12, and foamed in the expansion process. If the system was designed with this in mind the oil carried substantial heat away from the evaporator.
I always wondered how right that was - my experience with separators later indicates that it is true on the compression side of things - the oil picks up a lot of heat.

B.
ice-n-tropics
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Re: A slightly differnt A/C system

Postby ice-n-tropics » Fri Sep 08, 2017 5:53 am

Oil separator improves evaporator heat transfer
Oil (liquid or foam) insulates the warm evaporator tube from the cold refrigerant and negates any imaginary benefit.
hotrodac
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bohica2xo
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Re: A slightly differnt A/C system

Postby bohica2xo » Fri Sep 08, 2017 8:36 am

Yeah, I always wondered about that. I guess in 1970 the evaporators were just oversize to account for the added oil - he only thought there was an actual benefit.

The oil leaving the compressor is carrying the heat from the mechanical parts, while the refrigerant leaving the separator goes on to the condenser for further cooling.

So you are saying I need to increase the C/R in a York? I can mill the deck height a little...

Running the roots blower @ .87 on the little flathead. Static compression is 7.2:1 with 18 psig manifold pressure. Flatheads love boost.
ice-n-tropics
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Re: A slightly differnt A/C system

Postby ice-n-tropics » Fri Sep 08, 2017 4:51 pm

7.2 for supercharger at 18
Above my pay grade but knew CR must be reduced. hope for your success
Are you going to Pikes Peak? I'll be there pretty soon
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bohica2xo
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Re: A slightly differnt A/C system

Postby bohica2xo » Fri Sep 08, 2017 10:44 pm

The Peak lost it's luster for me when the ninnies paved it. Older records should be considered on their own merit, and Paved Peak records listed as a whole new event.

No, the blown flathead will go in a light motorcycle frame - here is the slipper clutch I built for it:
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Should be a great pub sprinter - no shifting, 90mph tops.

Been trying to convince a friend to take one of the flatheads to the salt flats for me - he has some SCTA experience.

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