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Old 06-16-17, 01:22 AM   #1
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Default Using an automotive evaporator core?

I'm trying to build a combination water heater/air conditioner on the cheap. I already have a 5,000 BTU compressor, expansion valve, filter, etc. The condenser will be a coil of copper tubing in a container of water.

What I don't have is an evaporator. I'd like to try and use a cheap automotive evaporator core, but, they all have odd non standard connections on them.

I'm wondering if I bought a cheap core like this:
NEW Ford Escort 1987-1990 GL GT LX Base A/C Evaporator Core 54439 OE | eBay
Can I just cut the ends off the aluminum tubes, flare them, and then use standard flare fittings to attach it to the rest of my system?

I suppose it's possible to just braze it to some copper tubing, but, I don't really want to try and braze aluminum.

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Old 06-16-17, 09:52 AM   #2
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If you want to do something like that, just go to a pull a part salvage yard and start looking. My favorite vehicles for this are the minivans and SUV crossover mutts with rear air. The air handler for the rear air is in a super easy to remove area of a rear quarter panel in front of the tail lights. The things connect with brake line (double flare) or power steering (parallel thread plus o-ring) fittings. Most all have a txv included, sized for the evaporator and blower. They also have a drain pan and rubber hose. They work really well with refrigerator compressors. You should be able to get out of there with all the stuff you need for 30 bucks or so.

Since you already have a donor air conditioner and expansion valve, why not run what you brung? The evaporator, fan, and such is already matching. Just remove the condenser and its fan blade and rig up your passive heater piping. The fan motor in those units pulls 150 Watts or so, but reduced motor power gets you less airflow and the resulting block of ice for an evaporator.

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Old 06-16-17, 03:09 PM   #3
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Not really interested in going to a junk yard when I can get a new one on ebay for $20 shipped. No junk yards close to me anyway and they all want an "admission" fee just to look. Would take all day and $30 in gas. Like I said, I don't have an evaporator...just a compressor.
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Old 06-16-17, 05:30 PM   #4
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It should work. I have turned a condenser into a transmission cooler by cutting off the A/C fittings and replacing them with flare nuts.
It can be done as long as the core is a standard diameter.
But the evap coils tend to be bigger. May have to braze something on there to attach to.
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Old 06-16-17, 10:50 PM   #5
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Well, no matter where you live, there is a FLAPS near you. I like NAPA and fisher/federated better than the advance zone. They will be able to order you something that will fit on the other side of that evaporator. Beware: automakers and aftermarket suppliers love to provide expensive proprietary parts. If you don't know exactly what you need, the flaps will gladly keep ordering you custom parts until you get it right. Whatever you order, you will have to chop up to try to make it work. Guess what? No refund, you chopped it up. Go fish.

Beware: this ain't lego blocks. What you end up with has to be strong. Besides being able to hold in hundreds of PSI of pressure, it also has to heat cycle and vibrate.
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Old 06-17-17, 01:11 AM   #6
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Quote:
Originally Posted by jeff5may View Post
If you don't know exactly what you need, the flaps will gladly keep ordering you custom parts until you get it right. Whatever you order, you will have to chop up to try to make it work.
That's the problem, I doubt there are any adapters to convert whatever the evaporator uses to flare...or if there is it would probably be a stack of things, just adding more places to potentially leak. The expansion valve and filter I have are already flare fittings also, so I might as well stay with that if I can.

I guess I'll just have to take a chance on the tubes being a standard size...but $20 isn't bad. I guess it's not the end of the world if I have to try and braze something to it. It would also be nice since it would be oversized, made to take a couple tons of cooling, less likely to ice up with a smaller compressor.

Not to mention the parts store guy would think I'm nuts.
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Old 06-17-17, 09:18 AM   #7
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You know you could juat use a condenser as an evap.
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Old 06-17-17, 09:40 AM   #8
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It looks like the car in question uses quick disconnect fittings and o-ring seals for the connection to the evaporator. You will want to source the fittings and tools to make this connection. I doubt the flaps is going to have a loaner tool for that, but you could get lucky. I'm not sure if the tool is the same as those for fuel and heater hoses, but it looks to be the same type. The parts boss will know what fits and what fittings and seals to use. You may get lucky and find hose ends in the help part section or at the Parker store.

Lookz like dis. I sees me walkin into pull-apart with a yellow thang, a red thang, and a pipe cutter. Walkin out in like 5 minutes with what i needs. YMMV.

Most likely, the evaporator tubes are metric. Standard flares ain't gonna fit. Also, the qd fittings are parts of dedicated assemblies. The one line looks to be part of the receiver dryer, the other a composite rubber aluminum assembly that may or may not have the metering device at the other end. Some of them have a well for the orifice tube, some of them a fitting for an expansion valve. Either way, the salvage yard is going to be the cheapest option. Or you can swedge and flare to inch size. Or you can try not to melt it. Or you can chop up your new part and try not to break it too bad.

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Old 06-17-17, 08:11 PM   #9
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Looks like I found something better:
Outdoor Wood Furnace Boiler Water to Air Heat Exchanger 8X8 american royal
Similar to an evaporator core, but copper and with standard fittings.

I want something compact like that because I am going to build an air box around it and blow the cold air through a flexible duct - kind of like one of those portable units with the hoses you stick out the window.
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Old 06-19-17, 07:06 AM   #10
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That's a water to air heat exchanger. Plumbed way different than a refrigerant to air exchanger. It's rather tiny as well.

The main plumbing issue is that most all evaporator exchangers​ are a long, series connected path. This gives the refrigerant the most time to pick up heat before it exits. The shotgun exchanger you cited has multiple short paths. This is good for water that is really hot, as the inlet pressure is pretty much constant in the header pipe. The flow divides equally between all the paths because the pipes are all flooded. Naturally, if the water enters at temperatures that could burn you, more heat goes into the air.

With refrigerant, what happens is the entering fog or frothy spray falls straight to the bottom of the header. Some liquid could make it through the bottom before it completely vaporizes. Either way, the oil will tend to collect in the bottom and could stagnate there. So this heat exchanger could potentially trap most of your compressor oil and let liquid refrigerant through to the compressor inlet. Both conditions are not good for the longevity of the compressor.

Since you're using the heat exchanger as an evaporator, you have a limited amount of heat transfer available before the thing starts making ice. Maybe 30 or 40 degF of gradient. Making ice isn't a bad thing, as it takes a lot of heat flow to do so. But whenever it happens, your airflow goes way down. The limited amount of surface area (frozen or not) will limit the heat flowing into the piping from the supplied air. This can be calculated if the design parameters of the heat exchanger are known. If not, hope for good luck.


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