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Evan
01-25-2012, 09:51 PM
I have been trying to get this posted for some time now but have run into difficulties. The main problem was discovering that the file was too large to upload to the Google 3D Warehouse. It ended up at around 14 megs and when I tried to upload it I was informed that it couldn't be over ten megabytes. I completely fail to understand why I can upload videos to You Tube up to two gigabytes but am restricted to only 10 megs for Sketchup files.

It took a great deal of time to reduce the file size without compromising the model quality in any way. I had to use every trick I know to reduce byte count for everything from textures to the number of polygons in the model. I was able to do it, just barely.

Anyway, this unit is an air to air heat exchanger. It is for recovering heat from the exhaust air of an electric clothes dryer while not introducing humidity into the home. It is designed to be built for as low cost as possible while still providing a safe, fire resistant device. It is intended to be easy to build with few critical dimensions and readily available materials. Ordinary wood working tools are sufficient even for the metal work that is required.

It makes use of regular aluminum drink cans for the majority of the heat exchanger area with only a few small pieces of aluminum edging trim required for some parts. The enclosure is constructed from melamine faced particleboard for ease of construction, low cost, good looks and fire resistance. The fire resistance is very important and the melamine is why. Melamine is not flammable and a 3/4" thick panel has a burn through time of one hour when subjected to direct flame. The melamine MDF panel should not be substituted.

Note that unlike a condensing dryer this unit is designed to recover heat from a dryer that exhausts heated air and humidity outside. Condensing dryers are not designed to recover heat. The main purpose is to allow venting inside the house when an outside vent isn't practical. Some go as far as using house water to cool the condensor unit and flush the heat down the drain. They are also less efficient than an ordinary dryer as they recirculate slightly damp air in the dryer and take longer to dry clothes.

Because of this this unit it is less likely to condense water in the heat exchanger. Still, full condensation collection is provided in the design. Not shown is the possibility of including a collection funnel in the bottom of the unit and a hole in the bottom of the condensation collection tray that drains into the funnel and then through a hose to wherever is convenient. It could be arranged to drain outside or into a laudry sink. The condensation tray is very easily removed for emptying by opening the right side door and sliding out the tray.

Most dimensions are calculated in fractions of an inch for familiarity to wood workers. The only critical dimensions are the spacing and pattern of the actual aluminum cans that make up the core of the heat exchanger. They have been calculated to provide specific air flows to maximize efficiency of heat transfer. Once the heat exchanger core is constructed the rest of the device may simply be constructed to clearance dimensions not smaller than indicated.

Aluminum sheathing of the exchanger core may be standard aluminum flashing attached with flush screws or simple staples. To save expense regular aluminum cans may be cut open and flattened. That is demonstrated on the back side of the exchanger core.

There are only a few small areas of combustible material (wood) that are directly exposed to the exhaust air from the dryer. The primary parts that are so exposed are the end plates of the exchanger core. They should be treated with fire resistant paint or they could also be covered with aluminum flashing.

The other small areas are indicated as bright yellow and should also be painted the same. Otherwise, the remaining wood parts are only exposed to the inside room air path. The rest of the parts exposed to the dryer exhaust are either metal or melamine which is non-combustible. The inlet is also provided with a metal ember catch tray in the case of a lint fire in the dryer.

The unit is designed to use a standard furnace filter and should not be operated without it. It is to prevent lint build up in the heat exchanger which is the lowest air velocity section. The entire heat exchanger core slides out through the right side door for easy cleaning as required. It is light weight with my best guess at less than 15 lbs. The air seals for the inside air vents on front and back are made from strips of Velcro loop material as it is rugged and easily compressible. It acts in the same way as a brush air seal.

Not all fasteners have been shown as it will be obvious where they are required.

The fans shown are ordinary 80 mm computer case fans. They should be powered by a certified power brick capable of supplying 1 amp at 12 volts. Included in the design is a Sail Switch on the dryer air inlet to automatically turn on the fans when the dryer is in use. A sail switch is easily made or bought at any HVAC supplier. The sail switch is an important part of the design and should not be omitted.

If the fans do not operate when the dryer is running that means the filter needs changing. The sail switch is also a safety indicator since if the air flow falls too low the fans will turn off. As an additional indicator one of the fans (or all of them) should include LED illumination.

The aluminum cans are prepared for construction by removing the top and bottom using an ordinary belt sander. The ends are sanded just enough to cut through the fold of metal that holds the end caps in place. When done carefully the cans will then snap together to form a tube. The cans should be sealed at the junctions with a thin smear of kitchen and bath type silicone sealer. They should also be sealed into the end plates with the same sealer.

Estimated efficiency is from 50% to 80% when constructed as shown. The exchanger core requires 96 cans. Total core exchanger area is approximately 23 square feet or 2.17 sq metres. Including the exterior area of the exchanger core the total heat exchange area is approximately 28 square feet (2.6 sq meters). Tray condensation capacity is 1.5 litres. Input and output connections are shown with 4 inch elbows but other shapes may be used. The overall design shouldn’t be altered significantly as it is intended to provide specific flow velocities at various places to maximize heat transfer and minimise lint build up.

I have done a lot of research and there is nothing on the market anything like this. There are about 77 million electric clothes dryers in North America and if only 10% of these were fitted with a unit that works like this it could save from 1/4 to half a billion dollars per year in energy.

For the average home with two children it could save up to $200 per year in heating cost if you live in a northern tier state or Canada and use an electric dryer. It will save at the least $50 to $100 per year if you use a dryer at all.

The unit can be mounted on the wall or placed on the floor. My estimate for construction cost is from $150 to much less if you use cans as the source of metal for the flat sheathing of the exchanger core. It's designed to make that easy.

I have very carefully engineered this design with attention to ease of construction, safety, minimal material cost and waste and good appearance. I have also carefully designed it for efficient airflows at all points to take maximum advantage of heat transfer. The overall design and dimensions aren't critical at all but should be followed reasonably closely to gain the full advantage of the design.

The file may be downloaded from here:

http://sketchup.google.com/3dwarehouse/details?mid=f085f96e19a1c049b24e451065d1c629

Pictures:

http://ixian.ca/pics9/aer1.jpg

http://ixian.ca/pics9/aer2.jpg

http://ixian.ca/pics9/aer4.jpg

http://ixian.ca/pics9/aerleft.jpg

Evan
01-25-2012, 09:54 PM
These are the air flow patterns.

http://ixian.ca/pics9/aer_sideflow.jpg

http://ixian.ca/pics9/aerexchanger.jpg

A couple of detail close ups:

http://ixian.ca/pics9/aermesh.jpg

http://ixian.ca/pics9/aerbracket1.jpg

Duffy
01-25-2012, 11:28 PM
Looks pretty slick, Evan. One little question:- would you think that there be sufficient benefit to installing "bowties" in each of the cans? It would mean twisting 48 left hand and 48 right hand units out of more cans. This SHOULD greatly increase air turbulence, with attendant reduction in the boundry layer thickness, without much increase in pressure drop. To my mind, it SEEMS like it would be worth it--but maybe not. Quite a bit*more work too!
In our remote Northern communities, they, (Gummint,) should GIVE these away. Deisel-generated power is a tad pricy for clothes dryers!

michigan doug
01-25-2012, 11:31 PM
Excellent. And needed right now by lots of folks I'm sure.

You should have a couple folks build one from the plans and provide feedback. Based on that, make and sell an e-book for $8.50 and make some R&D money.

Finest regards,

troy

mickeyf
01-25-2012, 11:35 PM
ACME!? Anything that's got Wile e coyote's seal of approval works for me! Seriously, looks great!

Evan
01-26-2012, 12:01 AM
I am certain that there won't be laminar airflow through the cans. The air is entering the cans after passing through a random filter and that will insure it is turbulent flow. Entropy isn't known for reversing itself without encouragement in the form of supplied energy.

It's such a simple experiment to do that anybody can do it if they wish. I don't think it would be worth the trouble.

BTW, the SketchUp model is divided into many layers. If you open the layer manager you can turn layers on and off instantly to see inside of the model without taking it apart. One of the layers is the dimensions layer and it is off by default.

dian
01-26-2012, 12:39 AM
how much do you think the efficiency would benefit from having the hot air take a turn in the unit and flowing opposite to the direction of the air to be heated?

elf
01-26-2012, 01:10 AM
Why won't it work with gas dryers?

Evan
01-26-2012, 01:11 AM
It isn't clear and is hard to show that the first transfer takes place before the dryer air enters the core. It is designed to restrict the amount of air that can flow directly up from the hot air inlet and into the filter. There is a lower resistance path along the front and back sides across the entire core and then up over the right side of the core to the filter. Much of the heat transfer will occur there on all sides. If you have a look at the left side parallel view you will see what I mean. The transfer in the core is intended to present the largest heat difference to the up flowing indoor air where it enters at the lower back.

It is the heat difference that governs the amount of heat transfer per unit time. I studied many configurations and calculated flow velocities to come up with this configuration. This is about the 5th complete model that I designed. As I studied each one I found better ways to do this and better ways to save material. This is the beauty of 3D modelling. One of the major constraints was keeping the size such that it could be comfortably mounted above the dryer on the wall. Many people don't have room for another appliance on the floor. That meant that the depth in particular had to be kept as shallow as possible.

This unit doesn't have to be used to warm inside air. It would also serve well to preheat outside incoming air and serve just as well to save energy. Connecting it to an outside air intake would be trivial. If that were done it would be necessary to provide a drain hose for the condensation tray. Using it as an outside air preheater would help eliminate cold drafts around the house that will otherwise be caused by the fact that a clothes dryer pumps out about 6000 cubic feet of air per hour.

dp
01-26-2012, 01:12 AM
The beer can heat exchanger is a pretty popular solar heater design - should work great with the dryer, too. A secondary roll can be a simple addition to make it a pre-heater for water entering the water heater - something that tends to happen on a heavy laundry day. Adding plumbing down the center of the beer/pop cans to carry water to the water heater inlet, possibly to a holding tank, would be the thing to explore. You've already done someting along these lines, as I recall. Because there is little turbulence in the can column much of the waste heat carries on out the back end. If there were a copper pipe in the center then something as simple as a washer shaped disk would turbulate the air as it comes in.

There should probably be some kind of lint separation prior to sending the hot air into the exchanger else it will become a maintenance issue.

Evan
01-26-2012, 01:13 AM
Gas dryers use the outgoing air as the exhaust for the burner. That exhaust contains corrosive fumes from the natural gas in the form of traces of sulphuric acid. It also may exceed the allowed temperature. An electric dryer is absolutely restricted to no more than 200F on the outlet and averages around 130 to 140F.

Evan
01-26-2012, 01:22 AM
There should probably be some kind of lint separation prior to sending the hot air into the exchanger else it will become a maintenance issue.

Only actual testing will show for sure but I expect most of the lint to end up in the filter. Maintenance will be very easy as the exchanger core is simple and quick to remove so that it can be cleaned if required and the inside of the cabinet can be vacuumed as needed. Adding another restriction before the exchanger would create too much back pressure and might result in overheating of the dryer. It is also possible that the dryer lint filter can be removed entirely. This unit will very effectively prevent having to clean the duct that follows it very often.

There is also no reason that the plan cannot be mirror imaged if that suits the installation better.

Paul Alciatore
01-26-2012, 03:17 AM
OK Evan, let me get this straight. You are using the dryer heat to heat the interior of the house, mostly in the laundry/garage area where the dryer is actually located. Am I right?

This sounds like an A/#1 idea in northern climates, like Canada where you are, AND in the winter time. But even in places like that, I doubt that you would want that extra heat in the summer. So what do you do for summer, bypass it? And more southern climates, like where I live? I would have to pay a lot in AC costs to take that heat back out of the house for about 75% of the year. I have had to insulate the exhaust hose on my dryer as it is about 12-15 feet long and added a lot of heat to my garage, which is becoming my shop.

It occurs to me that there may be some value in recycling that heat back into the dryer instead of using it to heat the house/garage. Or, is this what you are actually doing, perhaps by closing the door to the room the dryer is in so less energy is needed to bring the air the dryer takes in up to temperature?

In other words, where is the actual savings? And, can all electric dryers actually make use of pre-heated air in a safe manner?

Or am I missing something?

Evan
01-26-2012, 03:52 AM
In summer you switch off the fans. No more heat capture. A very simple duct bypass could also be added to eliminate the filter from the system in summer. edit: I had to draw the line somewhere on how many features I included. As it was I was just barely able to make the model fit within the file size limit.

Dryers also waste energy in the summer in hot climates by pumping cooled air out of the house. That is a different matter and I haven't addressed that. This is intended for regions that need winter heating. Regardless of how a house is heated using the waste heat from a vented dryer will contribute to the heating. It is also the most expensive heat that you pay for and it is all thrown away.

In areas with only cool winters that are in humid zones venting the dryer straight into the house will provide too much humidity. We had a discussion on this recently which is what prompted me to design this unit. In the process I discovered that there is absolutely nothing like this available. Other people have thought of it and have lamented the lack of availability. Further, the US and Canadian governments have ignored the possible savings available by reclaiming waste heat from clothes dryers as they have considered it impractical to address.

I think otherwise so I designed this and at a cost level that is very easy to afford. If a commercial unit were to be produced using a similar design it could probably be stamped out from thin sheet metal for less than $50. Selling price would be about $100 with a payback period of well under a year for many households.

I am a "small e" environmentalist and this is an excellent way to reduce energy consumption. I use as a yardstick for the usefulness of energy saving methods the degree of impact it has on current lifestyle as a major factor. This meets that criteria very well and the potential savings are enormous. If just 25 percent of electric dryers were fitted with such a device to recover heat only in the winter it would save over a billion dollars worth of energy per year that is currently pumped out side. It would also improve comfort in a house if outside air were drawn in and preheated by this unit or one like it.

By publishing this here and the model online I hope to generate some visibility for this idea. I do not expect to make any money or patent anything, I just want to see our energy use reduced. That by itself will improve everybody's lifestyle.

I would not suggest trying to recycle heat back into a current dryer. They aren't designed with that in mind and I took great care in this design to make it safe.

wb2vsj
01-26-2012, 08:35 AM
Cool Unit! (or should that be "hot" unit)

Lots of ideas like this are floating around, but yours looks to be the most thought out.

Question - if NG is corrosive, is Propane even more so?

In college we got one of those flap valves diverters which just dump the hot moist air into your laundry room. Nearly shorted out the electrical breaker panel which was in the same room! The CB Panel being metal was much cooler so the vapor condensed on it like crazy. So much so that it had water dripping off it.

Walt

aboard_epsilon
01-26-2012, 08:45 AM
fantastic drawings Evan...very good design .

but i don't get it ..as i said before ...do you not have condensing tumble driers in Canada :confused:

it's true ..with the complexity of yours...AND SUPERIOR DESIGN, that it would be quite a bit more efficient than the innards of my condensing drier ...which doesn't steam the windows up ..so must be working at a quite good efficiency...AND PROBABLY GOOD ENOUGH .

BTW ...The condenser unit in my drier ..despite having very fine screens before it...has to be pulled out ...every 20 loads ..to be flushed in fast running water under the tap to get the fluff out of it...so that it continues to work effectively.

thats item 146 in the diagram below

http://www.espares.co.uk/datastore/ProductDiagrams/376193.gif

all the best.markj

Evan
01-26-2012, 09:02 AM
As I explained earlier a condensing dryer is a different beast. The primary reason for existence is to permit venting inside when venting outside is impractical. In Europe that is frequently the case because of the common use of stone in home construction and the fact that many such homes predate the use of dryers and even electricity. The use of condensing dryers is not to save energy and in fact condensing dryers are less efficient than a regular dryer which is abysmal. Some even use water to assist the condenser which is then flushed down the drain along with the heat.

Europe also has heat pump condensing dryers which are not available at all in North America. They are much more efficient than a regular dryer of any type but the life cycle cost only makes sense with very high cost electricity. They sell for between 1000 and 3000 euros which is 3 to 9 times more than a regular dryer sells for here.

Evan
01-26-2012, 09:23 AM
Question - if NG is corrosive, is Propane even more so?

It all depends on the sulphur content. All fossil fuels naturally contain some sulphur and it must be removed before use. It is never removed entirely but only to some legislated limit. Here, gas operated appliances must use a vent system or chimney that is approved for gas. When I converted one of my chimney flues to gas I had to install a special metal liner to prevent the exhaust from destroying the mortar.

It would be possible to design a heat recovery system that would work with gas but it would need to be made from more expensive materials and would have to be approved. No such code requirement exists for electric dryers.

camdigger
01-26-2012, 10:00 AM
Another source of sulphur in natural gas and propane is the odorants deliberately added to give the gas an offensive odor to alert the user to a leak.

Exhaust gasses are also acidic due to the formation of carbonic? acid - basically the combination of CO2 and water makes a weak acid. It's what gives fizzy water its bitter taste.

Paul Alciatore
01-26-2012, 10:08 AM
Evan said, "Further, the US and Canadian governments have ignored the possible savings available by reclaiming waste heat from clothes dryers as they have considered it impractical to address."

Ahhhh, but we have Obama. I am sure he will send several billion dollars to companies who are fully capable of designing a unit that costs $500 to produce and sells at $1000. But not to worry, he will create a new government agency that will issue regulations requiring them with every dryer in the country.

Seriously, it looks like a good idea and a good design. Do you plan to create a construction article?

Evan
01-26-2012, 10:13 AM
Yep, the odourants are mercaptans which are sulphur compounds that generally all smell like something died. It's what gives a skunk its wonderful aroma.

camdigger
01-26-2012, 10:35 AM
Having reviewed the odd raw gas analysis (by conservative estimate several 10s of 1000s) , I'd hazard a guess that the most acidic corrosive element is the carbonic acid from the witches brew of CO2, CO2, and water vapor from the combustion of the reasonably pure hydrocarbon of the natural gas (mainly CH4) and propane (C3H?).

Gas with sulphur in it STINKS. Most natural gas has the sulphur removed down to the single digit parts per billion range (well below the level detectable by the human sense of smell) before the odorants are added, if there was any sulphur in it to start with.

Evan
01-26-2012, 12:20 PM
Gas with sulphur in it STINKS. Most natural gas has the sulphur removed down to the single digit parts per billion range (well below the level detectable by the human sense of smell) before the odorants are added, if there was any sulphur in it to start with.

All natural gas has sulphur in it and some has a great deal of sulphur. Just ask my brother in law in Alberta. Alberta has plenty of sour gas wells. He is a gas plant consultant. Natural gas (methane) may have up to 5 grains per 100 scf. That is 17 parts per million which is rather a lot more than single parts per billion. Propane may have up to 15 g per 100 scf. Producer gas may have up to 15 g or 50 g depending on region.

The gas will have close to the maximum since it costs money to make it less. As far as the human sense of smell goes about ten percent of the population cannot even detect the odourants, never mind the natural sulphur compounds.

That's where this stuff in Vancouver comes from:

http://ixian.ca/pics9/sulphur.jpg

You can also check here for more information:

http://www.pge.com/pipeline/operations/sulfur/sulfur_info.shtml

http://www.uniongas.com/aboutus/aboutng/composition.asp

http://www.sbcapcd.org/eng/tech/sulfur01.htm

Incidentally, high sulphur producer gas does get delivered sometimes when regular natural gas supplies can't meet very heavy demand. It doesn't happen often but when it does it looks like this (my stove).

http://ixian.ca/pics9/gas.jpg

camdigger
01-26-2012, 12:45 PM
Some does, some doesn't.

Quantities range from undetectable in ppb to 98% by weight (yes 98%)largely dependent on source formation, general area, and burial depth.

Your BIL should be able to verify if he knows nowt about it, obviously you have some larnin' to do:rolleyes:

Note your own sig line... All generalizations....

Evan
01-26-2012, 12:52 PM
Note your own sig line... All generalizations....

Apparently you don't get the paradox.

hojpoj
01-26-2012, 12:55 PM
:rolleyes:

On another note, I recall you mentioning in the Air Heating thread that you had devised an easy method for converting the cans to a usable form. Is that applied to this, and if so could you provide a little insight into what you do?

Evan
01-26-2012, 01:03 PM
Sure thing. Give me a few minutes to make some examples.

BTW, I neglected to answer a question about a construction article. I don't intend to build one myself as I do not need to remove the humidity. However, if you look around your house you will see at least several instances of controlled removal of air from the structure such as the dryer, the range hood, fireplaces, furnace and the bathroom ventilator(s). So where is the controlled source of incoming air????

There isn't any other than windows and doors. What I will be building is an air to air heat exchanger to capture heat from outgoing air and adding it to incoming replacement air. It will use a similar design.

camdigger
01-26-2012, 01:30 PM
So where is the controlled source of incoming air????

There isn't any other than windows and doors. What I will be building is an air to air heat exchanger to capture heat from outgoing air and adding it to incoming replacement air. It will use a similar design.


By code, it should be near the furnace and hot water heater.:rolleyes: Mine looks like a simple duct without any kind of damper for control though.

hojpoj
01-26-2012, 02:10 PM
By code, it should be near the furnace and hot water heater.:rolleyes: Mine looks like a simple duct without any kind of damper for control though.

I think that would depend on your installation. Everything inside my house is electric, therefore makeup air ducts wouldn't be required. When my bathroom vent or range hood are running, I know for a fact that the air is getting pulled through the poorly sealed areas of my front door and windows.

Properly scavenging the heat through the controlled venting (e.g., bathroom vent) would be require a lot of retrofits, given their disparate locations. On top of that, airborne grease would gunk up the exchanger for the range hood, and condensation would get to be a big issue in the bathroom vent ducting. Nothing insurmountable, but tough challenges, nonetheless.

Evan
01-26-2012, 02:26 PM
By code, it should be near the furnace and hot water heater

True. I also have a 3" diameter makeup air feed to the gas furnace. However, a dryer will suck out between 6000 and 10,000 cubic feet per hour.

Evan
01-26-2012, 04:41 PM
Here is how the cans are prepared.

First, using a belt sander sand the top and bottom enough to cut through the metal so that the ends can be easily punched out.

http://ixian.ca/pics9/cansand1.jpg

Then sand the bottom further until the top of a can will snap into place. It isn't difficult or very critical.

http://ixian.ca/pics9/cansand2.jpg

Snap them together. They hold quite well and will be easy to seal with silicone. Of course this also applies to making solar collectors.

http://ixian.ca/pics9/cansand3.jpg

madwilliamflint
01-26-2012, 05:44 PM
Glad I saw this thread, my weekend task had previously been to vent the dryer into the heating system with a lint trap in the middle.

It's electric, but it strikes me suddenly that a heat exchange system might be a better way to go.

Evan
01-26-2012, 06:46 PM
If you build an exchanger please post it regardless of what plan you follow. I will be interested to see it.

aostling
01-26-2012, 10:17 PM
Here is how the cans are prepared.


This is the best use of SketchUp that I have seen posted here. Your project inspired me to dig into my box of old textbooks, where I found my 1964 edition of Compact Heat Exchangers, by Kays and London. Kays taught a graduate course from this book, and I thoroughly enjoyed it.

Using aluminum cans is a very practical zero-cost solution. I'm wondering if it might be possible to deform the cans longitudinally, buckling them in some sort of controlled fashion while compressing them to (say) half their height. You would use twice as many cans, doubling the surface area for both hot and cold sides, and increase the overall convective heat transfer coefficient.

Not saying you should do this, just a thought inspired by your clever design.

PS. What does the fine print say, on the text plate affixed to the housing?

Evan
01-26-2012, 10:33 PM
What does the fine print say, on the text plate affixed to the housing?

Download it and find out. :D

quasi
01-26-2012, 11:09 PM
Evan, how you get that kind of drawing/detail out of Sketchup is beyond me. I am very envious.

Evan
01-26-2012, 11:59 PM
I use quite a few "tricks" that I have discovered as well as all the features the program has to offer. One of the tricks is a way to make the rendering engine produce much nicer looking parts. Another isn't a trick at all. I make and use my own textures so the parts look like what they should. That is as easy a taking a picture of galvanized steel for instance and using that picture to paint a part that should look like galvanized steel, which is what I did.

It helps a great deal that I know how a program like this works at the programming level. Some things don't come easy for me, such as particular areas of mathematics. I really have to work at them. Other things like programming logic are intuitive and especially anything to do with visual arts and programming. Don't be too envious. You don't want some of my blind spots and I probably don't want some of yours. We all have things we are good at but nobody is good at everything.

aostling
01-27-2012, 12:02 AM
Download it and find out. :D

I had not noticed your download link. Now I have the model in SketchUp and can see the text detail, and everything else. This must have taken you a month of Sundays (or a Canadian winter).

Evan
01-27-2012, 12:26 AM
It did take a while especially as this is about the fifth complete version. However, I have also been working on some other items at the same time. I have become pretty fast at this type of modelling. There are many different "speed tricks".

This is one of the earlier versions. It actually has greater exchanger surface but the latest version has much better internal design. More importantly, when I showed it to my wife her first comment was that not everyone has room for such a thing on the floor. I hadn't considered that and that prompted a series of redesigns which led to a series of improvements.

http://ixian.ca/pics9/aerv2.jpg

quasi
01-27-2012, 03:08 PM
Evan, I only have one blind spot, but it's a great big mother!

A.K. Boomer
01-28-2012, 10:54 AM
Boy how did I miss this little gem :)

What a sketch up - what attention to detail and what a worthwhile idea as in certain climates this is an idea that is definitely worth pursuing...

One thing iv noticed about Evan is when it comes to efficiencies he does know where (and how) to reclaim many of the losses in a typical household and I cannot help but respect that...

I skimmed over this entire thread and don't have much to add but praise -

however - u guys know me :p and it's all about fine tuning and critiquing so don't get the wrong idea about my following comments.

Some guys brought up the internal flow of the cans and I can see that a little ---- but u got soooooooooooo much surface area that I believe you have at least a fair exchange rate and the little internal flanges of the cans probably turbulent enough of the air to create enough of a change (and are probably better in one direction of flow vs the other)
My only real addition here is if there's still a small "jet stream" riding directly down the middle due to everything being "uniform" why not put the cans on their sides --- Youv already got it covered for milking the heat off the cans externally be it whether their stacked or not due to all the break up of currents - so why not go for the best on the inside exchange (kinda like the "slant fin" boiler exchangers - make the air work against the sides)

The only thing else is this;

It would also improve comfort in a house if outside air were drawn in and preheated by this unit or one like it.

While this is true it comes at a price ---- now your taking very cold air and having to heat it up --- depending on the dryer design it will either have to run longer(to get the same job done) or the element will have a much higher run cycle so even if your recapturing close to all the waste heat is still is (in most cases) your most expensive form of heat (disregard if you have electric heat)
Better to preheat and make up for the "dragged in" losses with your cheap heat source in my opinion...;)

other than that --- very freekin impressive!

Evan
01-28-2012, 11:18 AM
why not put the cans on their sides

That was my first design until I realized that condensation must run downhill. It also must run through a can that is inserted inside the can below it to prevent leakage. Therefore each can is inverted and is inserted into the bottom of the can below.

As for preheating outside air it is only going to come in to the extent that the inside of the house is under negative pressure. That being the case the pressure will equalize no matter where it comes in. It may as well be heated by air that is warm and leaving anyway. It beats the heck out of freezing cold air coming in under the doors and around opening windows and building up ice all over the inside of the transom/window sill. At 40 below ice even builds up on the inside of double glazed windows. Weather stripping is never perfect.

lakeside53
01-28-2012, 11:58 AM
Yes, it's a 2 part problem. Pumping all the hot air outside and replacing it with cold outside air which as Evan points out, will happen anyhow.


I look forward to the updated design (already!) that does a true exchange of heat from exhaust to the incoming air. In my case this would feed back into my air ducts.

moe1942
01-28-2012, 12:07 PM
Forgive me if I missed something since I didn't read every page but since our dryer only gets used twice aweek for less than an hour the benefit would be small. In my climate a passive solar heater would be more efficient.

Evan
01-28-2012, 12:41 PM
You are in a zone that wouldn't benefit much if at all. The old fashioned way is still the best money saver if you don't have too much local pollution. Hang the clothes outside to dry. We do whenever possible and the clothes sure smell nice.

Evan
01-28-2012, 03:30 PM
This is how the melamine faced MDF fits in a 4 x 8 foot sheet.

http://ixian.ca/pics9/sheet.jpg

A.K. Boomer
01-29-2012, 10:42 AM
That was my first design until I realized that condensation must run downhill. It also must run through a can that is inserted inside the can below it to prevent leakage. Therefore each can is inverted and is inserted into the bottom of the can below.


That makes sense - and even though a milder slant design could allow for both draining and dissipation it would waste interior space - add complexities and make the unit even more bulky - I think you have enough flow break up of the air just in the flanges and the amount of surface area of all the cans insures that its going to be one "slow ride" which is also beneficial to exchange rate, also - pumping the heat down from top to bottom is well thought out too... You built the biggest bang for the buck



As for preheating outside air it is only going to come in to the extent that the inside of the house is under negative pressure. That being the case the pressure will equalize no matter where it comes in. It may as well be heated by air that is warm and leaving anyway. It beats the heck out of freezing cold air coming in under the doors and around opening windows and building up ice all over the inside of the transom/window sill. At 40 below ice even builds up on the inside of double glazed windows. Weather stripping is never perfect.


Totally in agreement - as long as your running the intake air THROUGH your waste heat reclaimer - having it sit off to the side and having your intake somewhere else is going to create extreme warm spots and extreme cool spots and to best take advantage of the savings with keeping the house comfortable you want the intake air running directly through your exchangers - in doing so your also creating the greatest temperature variances and therefore efficiencies --- We both know There is no other appliance that even comes close to putting a home under negative pressure like the typical clothes dryer - be it gas or electric --- It's very operating principle is maximum amount of CFM with heat, that is how cloths get dry... it can easily out consume (in CFM) a gas furnace that can heat a 4,000 sq. foot home,



So --- Do pipe the intake air that the dryer needs directly to the outside - but have it come in and run it DIRECTLY through your exchangers to milk the waste heat off - then aim the pre-heated air directly towards the dryer's pickup area --- If it's capable of heating up the air higher than that of ambient house temps then the cloths get dryer faster so less energies are being used AND there is absolutely ZERO negative draw in the house itself so there is massive amounts of savings there - it's a win win for sure...


This gives me another idea - your unit would work great for short dryer exhaust runs - but if you have a run that's 20ft. or more you could do all this without even using your unit --- by either a pipe inside a pipe or a large pipe with a sealed integral spiral baffle inside - special intake and exhaust couplings on the end that seal and divert so you can segregate the two for both separate lines to the machine and also a special 180 degree opposed venting and intake adapter outside...

lakeside53
01-29-2012, 12:21 PM
This gives me another idea - your unit would work great for short dryer exhaust runs - but if you have a run that's 20ft. or more you could do all this without even using your unit --- by either a pipe inside a pipe or a large pipe with a sealed integral spiral baffle inside - special intake and exhaust couplings on the end that seal and divert so you can segregate the two for both separate lines to the machine and also a special 180 degree opposed venting and intake adapter outside...


yes... twin wall woodstove or fireplace insert chimney pipe (not "b-vent" used with gas appliances) - stainless interior liner, galv external. Exhaust up the center, fresh air back in the outer ring. You can get 90's 45's etc so making length wouldn't be difficult in an attic or crawl space. Would need to keep the condendsate flow "downhill". Rats... I've thrown away hundreds of feet of this stuff from remodels! You can get some fancy split exits/intakes as used with "on demand" water heaters.

Makes you wonder why the energy code doesn't mandate some form of recovery from dryers. They pretty much do with everything else.

Evan
01-29-2012, 05:04 PM
Makes you wonder why the energy code doesn't mandate some form of recovery from dryers. They pretty much do with everything else.

Because North America is way behind in energy efficiency regulations and enforcement. There are regulations in Europe that mandate minimum efficiency standards for dryers. The standard dryers sold here don't come close to qualifying. It isn't just dryers but the washing machine is involved. Washing machines in Europe are designed to spin about three times as fast as ones here. That alone cuts drying time by at least 50%.

Of course part of that is the differences in tort law. If you stick your hand into a 1000 G spin dry cycle and it is ripped off that is just too bad in Europe. Same reason they don't fence the tracks for the 320 KMh ICE trains.

A.K. Boomer
01-29-2012, 06:30 PM
Iv always wondered why there's two machines, with a front loader washer you already have 90 percent of the stuff needed to turn it into a dryer also --- Yes there would be certain challenges - but if you kept the internal tub dryer intake and exhaust venting high and had some internal splashpoof vent gates then why not?

talk about convenience --- just throw your cloths in dirty - go - and get them out clean and dry whenever...

aboard_epsilon
01-29-2012, 06:47 PM
Iv always wondered why there's two machines, with a front loader washer you already have 90 percent of the stuff needed to turn it into a dryer also --- Yes there would be certain challenges - but if you kept the internal tub dryer intake and exhaust venting high and had some internal splashpoof vent gates then why not?

talk about convenience --- just throw your cloths in dirty - go - and get them out clean and dry whenever...

We have combined washer driers in Europe ..they are very unreliable .

too complicated for their own good .

all the best.markj

lakeside53
01-29-2012, 07:45 PM
Because North America is way behind in energy efficiency regulations and enforcement. There are regulations in Europe that mandate minimum efficiency standards for dryers. The standard dryers sold here don't come close to qualifying. It isn't just dryers but the washing machine is involved. Washing machines in Europe are designed to spin about three times as fast as ones here. That alone cuts drying time by at least 50%.

Of course part of that is the differences in tort law. If you stick your hand into a 1000 G spin dry cycle and it is ripped off that is just too bad in Europe. Same reason they don't fence the tracks for the 320 KMh ICE trains.


You can buy European machines here. I have a pair of Asko's.. swmbo insisted... expensive to buy - about 3x the typical USA models. The washer is 1500 rpm (adjustable) and uses very little water. The dryer still pumps outside.

No way to get your hand into the machine or the machine open without it going though a bunch of checks and it releasing a lock.

Evan
01-29-2012, 08:10 PM
Not bad. With a radius of about 8 inches 1500 rpm gives 500 gees.

A.K. Boomer
01-29-2012, 08:25 PM
We have combined washer driers in Europe ..they are very unreliable .

too complicated for their own good .

all the best.markj



There's no reason why they can't be built to be durable - and with all attention focused on one machine that already has close to 90 percent of the components needed then the overall quality of the unit can be kept extremely high and at a price that still comes in cheaper than two separate units...

I do realize there may be a slight overall dimension change to allow for the heating elements and ducting - but many washers nowadays have vast amounts of free space also.

The same motor - the same drum - the same outside cabinet,

two modified control dials --- whats not to like?

unreliable? there's no reason for that other than poor engineering and poor quality components - it should be as reliable as anything else, So the motor and drum are doing double time - use better bearings - so there's higher quality more expensive silicone seals in the washer parts to handle the dryers heat factor --- so what - again - one machine is doing the job of two...

lakeside53
01-29-2012, 08:33 PM
Not bad. With a radius of about 8 inches 1500 rpm gives 500 gees.


No wonder the cat doesn't like it.;)

Quadra
11-27-2012, 05:18 PM
Evan I really would like to build one of these but have no experience with sketchup. Is it possible to extract the plans or a cut sheet in PDF? I have downloaded the free Sketchup and was able to view the object, rotate it and even strip the listed assemblies... but what I really need is a set of drawings/plans ( and more experience with this sort of software :confused: )

Evan
11-27-2012, 06:26 PM
You may download the Sketchup model of the sheet layout here:

http://ixian.ca/airtoair/air_to_air_heat_exchanger_parts_layout.skp

BTW, welcome to the forum.

The website for it is here

http://ixian.ca/airtoair/exchanger.htm

J Tiers
11-27-2012, 09:42 PM
Evan: if that model is your washing machine, it's inefficient.......

We got a front loader years ago, and it has been good ever since.... uses less water, so less has to be heated, and it spins at 1100 rpm, the clothes come out just damp, not soppy as with many top loaders.

Dry time is half what it used to be, a huge improvement right there.

Ours is a Whirlpool "Duet" washer, some others are not as good.

Evan
11-27-2012, 11:15 PM
If you mean the washing machine in the drawing earlier, that is one I scraped off the 3D warehouse as a filler for the model. We have an old Maytag with water saver cycles. We are very accustomed to not wasting water as we have been on low flow wells for the last 42 years. I doubt we use more than 30 gallons a day if that.

Lew Hartswick
11-28-2012, 09:25 AM
Iv always wondered why there's two machines, with a front loader washer you already have 90 percent of the stuff needed to turn it into a dryer also --- Yes there would be certain challenges - but if you kept the internal tub dryer intake and exhaust venting high and had some internal splashpoof vent gates then why not?

talk about convenience --- just throw your cloths in dirty - go - and get them out clean and dry whenever...

On the order of 50 years ago, my sister-in-law in PA had exactly such a machine.
I'm sure it was USA made at that time. The big and I mean BIG disadvantage to it
was it had to evaporate all the residue water from the wash cycle before it could
even begin to dry the clothes. What a STUPID idea!!!
...lew...

jason.weir
11-28-2012, 01:25 PM
Evan - none of the pictures show up on http://ixian.ca/airtoair/exchanger.htm - or is it just me?

Jason

Deja Vu
11-28-2012, 01:59 PM
I think it might be on your end. I'm seeing all the photos/pics/diagrams.

Evan
11-28-2012, 02:07 PM
The web page does work so you have something on your end that is preventing them from showing. A lot depends on how you are accessing the web page.

jason.weir
11-28-2012, 02:23 PM
Odd - the images don't show in Firefox but work fine in IE... Jason

Evan
11-28-2012, 02:30 PM
In Firefox select from the menu bar Tools>Options>Content and make sure that Load images automatically is checked.

bob_s
11-28-2012, 03:41 PM
Evan:

Have you made any performance measurements on the heat exchanger?

Evan
11-28-2012, 04:20 PM
I haven't and won't be building one. We don't need one. I vent all dryer air inside with a furnace filter. We need all the moisture we can get. The humidity inside right now is 27% and the highest I have ever seen it here is about 55%. We live in a semi arid zone with about 12 to 14 inches total precip per year.

derekm
11-30-2012, 09:25 AM
anyone seen this? - mechanical heat recovering made out of election posters (corex, coradex)
http://www.ewp.rpi.edu/hartford/users/papers/engr/ernesto/pastor/MEP/Other/References/Counter%20Flow%20Heat%20Exchanger.pdf

Bill736
11-30-2012, 10:47 PM
Provided you can effectively remove the lint without any danger of overheating , and control the moisture so that it doesn't condense on every cold window in the room, the principle limitation I see is this: of a 168 hour week, my dryer is on for only 2.5 hours ( three loads of laundry). That's only 1.5 % of the time, and the dryer would only supply about 25 % of my winter house heating needs while it is on. That equals one third of one percent of my house heating needs, and I'd have to disconnect it in the summer. Hardly worth the effort for me, considering I don't even want the humidity. And, if the humidity is too high, the moisture may permeate your wall and ceiling insulation, condense, and cause greater heat losses. It might wind up being a losing proposition for some people. It's a bit like furnace flue add-on heat exchangers; the energy is there, but it's not that simple to make it all work effectively. I will admit, however, that in your particular climate, it's a bit irritating to see that heat and moisture going directly outside. I run my dryer metal ducts 20 feet through my garage, and I recover some heat without the moisture. I've had no lint buildup within the ducts. I think our forum friend in Germany has a better idea; just fill your house with nice looking women, and they're good for something like 75 watts each.

huntinguy
12-01-2012, 02:29 AM
That looks very suspiciously like the Franklin stove. slick idea.

Evan
12-01-2012, 02:13 PM
just fill your house with nice looking women, and they're good for something like 75 watts each.

Up to 200 watts if they are moving...http://ixian.ca/pics9/biggrin.gif

Gwen
01-07-2013, 12:19 PM
Hi Evan,

Found your idea this weekend online, and would like to start constructing an exchanger as soon as possible. I have not been able to get the drawings to download. Whatever the .skp file is, I have tried everything possible to get it to open, I have downloaded the program, tried IE instead of Mozilla, Nothing is working.

What can you suggest at this point.?? Thank you for your help.

madwilliamflint
01-07-2013, 12:27 PM
Hi Evan,

Found your idea this weekend online, and would like to start constructing an exchanger as soon as possible. I have not been able to get the drawings to download. Whatever the .skp file is, I have tried everything possible to get it to open, I have downloaded the program, tried IE instead of Mozilla, Nothing is working.

What can you suggest at this point.?? Thank you for your help.


What you're looking for here is SketchUp (http://www.sketchup.com/). It's a free 3d modelling package. Pretty easy to learn and sufficiently robust for a lot of "real work."

Rexarino
01-07-2013, 03:17 PM
Thank you for the reply madwilliamflint, I appreciate it. I did download the Sketchup, but when I try to open up the 9.6MB file only one drawing appears, it is all different colors, but no measurements or dimensions. I have to be honest I do not have any experience with Sketchup so I do not really know what I am doing, could you explain how to find any other documentations that are in this 9.6 MB file.. Thank you again!!

co_farmer
01-07-2013, 04:46 PM
Evan. You have put in so much effort, that I hesitate to bring up the fault you have not addressed. Did you do a Google search for "building code dryer vent"? If you do, you will discover your design will never pass the building codes in the US. The minimum size for dryer vent is 4 inches and made of metal. There are other code failures, but you can research them.

Beautiful work, however.

Paul