AC question, accumulator or drier
 

Auto ac systems have a receiver/drier or an accumulator. I've noticed the drier is used in the liquid side of a variable expansion valve system where the accumulator is used in the vapor (low) side of a fixed orifice tube system.

I am wondering if the accumulator is placed in the low side to prevent liquid from reaching the compressor?

Can anyone explain this difference, pros and cons of each?

Yes, the accumulator is designed to keep liquid from the compressor. It also contains the desiccant, a substance that removes water vapor. In a system that contains a receiver drier, the receiver drier contains the desiccant. While both systems should be operating with an efficient condenser and have nothing but liquid refrigerant from that point on, that's not always the case. Orifice tubes can handle bubbly refrigerant better than expansion valves, so they pass on the receiver drier and go the accumulator route. The expansion valve systems tend to stick with the receiver driers to allow for an uniform liquid feed to the expansion valve.

Is one system better than the other? Hard to say. In good condition both cool well enough. I suppose an expansion valve is an extra mechanical part to break and/or leak, but I don't see it often. Sometimes an expansion valve will make noise at a particular RPM or load, but it's rare. Some systems, particularly the dual systems used in vans and Suburbans will have an orifice tube feeding the front evaporator, and an expansion valve for the rear.

To further complicate things, many vehicles have variable orifice tubes, and now many compressors are variable displacement as well.

What's best? Beats me, they all have ups and downs. Personally, I drive with the windows down and the A/C off...

MV

Nice that you can do that in Khali. I used to do the same in Chicago. But here in Texas the four-windows trick just won't cut it when it's 110 outside.

aint that the truth

In the GM systems I see the accumulator is very close to the evaporator.
Any problems with placing it down down the line a bit, halfway between the evap out to comp in?


The Texas heat I can handle but, the heat with 100% humidity is deadly.

You know, I'm not really sure about the downstream mounting. Never really considered it, as the evap outlet and compressor are fairly close together, and the evap housing/firewall offers a good mounting spot. I'll ask around and see if anyone has any thoughts. What sort of project is this on?

As for the no A/C thing... To each their own. I live in CA's central valley and summertime temps are regularly over 110f, though this year has been pleasantly slow to warm up, our first triple digits aren't expected until Thursday. I lived in Phoenix for a few years, and didn't use A/C there either. I also travel to the eastern US, and don't use A/C there either. Heat and humidity both have their ups and downs... but it's nothing you can't adapt to.

MV

Its a Frankenstein AC job in a small block chevy powered W108 280SE.
I'm fiberglassing up the evaporator box this evening and trying to come up with a layout for easy access to everything. The orifice tube is just on the engine bay side of the firewall, accumulator will mount behind the right headlight area. Both service ports will be located near the accumulator along with a sight glass on the liquid line.

Ok, sorry it took so long.

I did have a chance to talk to a refrigeration expert, and it seems that a downstream accumulator mounting is not the way to go. I'm not entirely sure I could explain all the reasons why (he can, me, not as much so), but it has to do with the "flooded" nature of the evaporator in this sort of system. Basically the evap is to have liquid refrigerant pretty much throughout it, and needs to have the space of the accumulator to allow the refrigerant to expand/gassify/boil into in order to absorb the passenger compartment heat.

Sorry it's not what you wanted to hear.

MV

My thought is the acc is not only a device to ensure the pump never pumps liquid but also somewhat of a refridgerant reservoir/filter. I believe that the added length of line from the evap to the accumulator will only act as an increase in acc size. As long as the evap is flooded, as you say, and the compressor never sees liquid it should work. We'll see...

At the moment the evap and cond coils are connected, evacuated and charged to 100psi to check for leaks. They have been sitting on the deck here for a few days as I watch the pressure rise and fall due to temp changes. No leaks. The evap box is all finished.
I hope to get it all installed next week.

By all means, I'd love to know how it works out. Most everyone I asked about it just gave me a blank stare. It may be that it cools, just not as efficiently as possible. Or perhaps it will just have what would be considered an "unacceptable" risk of liquid ingestion. Something you might be ok living with, whereas a manufacturer might not be.

MV