Here are a few suggestions (OK, more than a few):
1. Definitely get a porta potty to eliminate nighttime walks (and camper steps) when it is cold, dark and wet. (Just between you and me, if it is only you in the camper, get a urine bottle like they use at hospitals and just stay in your nice warm bed :Z )
2. Install a (two way) fan in the roof vent. This will also help when closing the top by running the fan on exhaust to pull in the canvas.
3. build/buy secure steps to get in and out the door.
4. since you will have hookups, get a small electric heater. Consider getting a very small dehumidifier also.
5. Rig up an awning from a tarp and poles for either the entrance when raining or the south/west side for shade.
6. I assume you will take the top down each commuting day for security. You will want to hang lite things, shoe hangars, etc.from the HECO lift bars (I use stuff bags and bungie ties). You will also want to store some stuff in boxes that double as shelves and can quickly be moved from the countertop to the floor. Size boxes to fit under the table and in nooks and crannies.
7. Get a point of use water filter for the sink faucet if you plan to use the water in the tank for cooking/drinking. Make a gray water drain hose and tote (I use a kitty litter container).
8. Make sure you have a new(er) smoke alarm, propane alarm, CO alarm and fire extinguisher.
9. Practice camping in the driveway. Check for light leaks, drafts (you will need to ventilate at night), lighting placement for reading, comfortable cushions, bedding, etc. Add portable stick on LED battery lights for entry, cupboards, etc.
10. Make a checklist for setting up and closing the camper. I even have one for enroute stops. Update as you make misteaks (I mean learn things). :o
11. Upgrade your truck tires at a minimum. Consider suspension upgrades (shocks, timbrens or air bags) You will be much heavier with all your gear, water and a full tank of gas.
12. Have a plan to greet uninvited, unannounced visitors.
13 Have fun!
This suggestion is a project I never followed through on:
Make a bedliner of plywood. Cut a piece from bedliner that will fit up as the closed tailgate when the TC is off the truck. Paint to match.
I envisioned the bedliner "puzzle" parts would also form a hinged storage box that would be secured to the front of the bed when the TC was off the truck.
If you design a successful one, let us know.
As we all know and love how quiet our generators are, we're constantly on the lookout to find ways to further reduce our audio footprint.
I have built several different acoustical reducing designs but have been extremely afraid of causing a problem whereby reducing the airflow will cause the unit to overheat.
This afternoon, I spent a good bit of time with a smoking stick and here is what I've found:
1. Air is drawn into the unit above the plugs on the front.
2. Air is drawn into the unit at the pull start and On/Off openings
3. Air is drawn into the unit near the back where the vents are on both sides.
What surprises me is there is NO air drawn into the unit from the bottom. There are a couple of small holes on the bottom that some air is drawn in, but the main intake is on the front and sides of the unit.
Can or has anyone else done this type of testing yet?
I haven't found an airflow document on the 2000
I made some prototype enclosures and used a baffle at the exhaust end of the unit right at the end of the handle. This seems to completely isolate the inlet air and exhaust air. So far I haven't solved the simultaneous goals of reducing the mechanical noise, exhaust noise with minimum back pressure, and keeping it light and portable.
You need equal air flows to make this work properly.
I am guessing that the Supply air fan sucks from the Hx and the exhaust air fan blows into the Hx from the room side. Your foil plates are deforming so that the space between the plates for air coming in is much larger than the space for air going out. The pressure drop on the supply air fan is probably 2-3 times that of the exhaust air fan. Please correct my guess if I am wrong.
Your Hx 1.0 had very stiff sheet metal plates and had equal air flow.
One solution is to make both fans blow into the Hx, or make both fans blow out of the Hx. This will help equalize pressure across the plates.
The other thing to do is stiffen the foil plates. Take some 1/2 inch wide strips of the coroplast and lightly glue onto the foil with dabs from a glue stick. Line them up in a pattern parallel to the diagonal air flow. Think candy cane stripes alternating on the stacked plates. Make sure the alternating patterns cross so they stack on each other. If you took an X ray of the stacked plates, the strips would show a criss-cross pattern (#).
I tackled this problem in my Hx by:
1) not making my plates very large (about 6" by 10")
2) glueing pieces of coroplast on the center of my plates, and
3) adusting fan speeds separately to compensate for foil deformation and provide equal air flow.
Please keep testing. We are all learning from you.
Back on page 2 you said:
"my fans are both on the outside, and one blows into the Hx and one sucks from the Hx. I learned this causes plate deformation and makes the air flows unequal unless the sucking fan (outlet) is higher speed than the blowing fan (inlet). I am able to compensate by controlling each fan. If both fans blow into the Hx, this problem goes away."
How are you able to see the plate deformation? I'm making another exchanger, this time with aluminum foil and coroplast, but I don't know how I'm going to know if the air pressure is equal (I won't be able to see the plates once they're all stacked together, will I?).
Thanks once again.
I know about deformation of the foil without seeing it because:
1) I read about it in my research, it happens to others, even commercial systems,
2) The measured heating and cooling efficiencies will be farther apart, (remember, yours were very close on Hx 1.0) and
3) I can hear the foil crinkle when I change the fan speeds.
Try putting a small spacer in the center of the plate to reduce deflection.
And let us see your new design. Good luck.
Thanks for keeping us informed with your Hx project. With the data you provided, we can now calculate the Hx system efficiency.
Here are some definitions to help us keep things straight:
Room Air (RA) temperature in the camper
Outside air (OA) outside temperature
Supply air (SA) temperature of air from Hx into the camper
Exhaust air (EA) temperature of air from Hx to outside the TC
Heating side efficiency is: RA-EA / RA-OA.
for day 2: (56-37) / (56-21) = 54%
Cooling side efficiency is: OA-SA / OA-RA
for day 2: (21-38.5) /(21-56) = 50% The average for the HX system is about 52%
You can do the same for water removal efficiency by looking up the wet bulb temperature for each measured dry bulb temperature and relative humidity using a calculator or psychometric chart. It should be about the same efficiency. (I did not calculate-I will leave it to you or others).
Because the heating and cooling efficiencies are about the same means you have balanced air flow and little flex in the plates. This is good.
Fifty percent efficiency means you have opportunity to improve performance.;) For reference, I measured my final unit efficiency as 80% plus or minus about 10%. Ninety percent should be achievable.
Here are some suggestions:
1. See if you have some cross flow leakage. Run just the fan to bring outside air in. See if you have a very small amount of air coming out of the "draw from the camper" tube. If so, try taping the weatherstripping joints in the corner chambers. Repeat with the other fan.
2. Reducing the fan speed will increase the efficiency, probably increase condensation in the Hx and lower power draw from your battery. It will also lower the air changes in the TC. This is a trade off.
3. Add more plates to the Hx. You designed your stack to be the same height as the fan dimension. You could add plates and keep the same height by using thinner weatherstripping spacers (think picture mounting tape). If you build an enclosure, the height can be larger than the fan dimension. Just make sure you seal each corner chamber very well. Insulating the Hx will not make a big difference but insulating or shortening the ducts into and out of the TC may help a bit.
4. Change the shape of the Hx plates. You are asking a few inches of sheet metal to maintain a temperature difference of 30+ degrees from inlet to outlet. Elongate your design of the plates so there is more distance between the diagonal chambers. If you have room, make it twice as long. If you keep the same footprint, consider making small baffles with some weatherstipping on the inside of the plates to redirect some flow towards the "dead air" corners of the Hx.
If you decide to build Hx 2.0, try to make the plates longer, closer together and vertical (for drainage out the EA). Put you inlet duct from the TC to the Hx on the interior away from the walls.
Hope this helps,
Congratulations. From your results, it seems to be working. Here are a few quick thoughts:
The relative humidity at the camper inlet (after heat exchange) should be lower than the outside air, as you observed. Think of relative humidity as the capacity of air to hold moisture, not the amount of moisture. As air is warmed, the relative humidity goes down but the amount of moisture stays the same. Lower RH = more moisture capacity. search "dew point calculator" to help with this.
It would help if you could measure the exchanged air leaving the TC If the leaving temperature is above the dewpoint of the inside air, there will be no condensation. If it is above freezing, then there should not be any ice in the exchanger. The short run of exhaust duct inside your TC may help heat the leaving air above the dewpoint (and lower overall efficiency). The relative humidity of the leaving air should be highest of all.
We may need more info for a more detailed analysis. What do you estimate your airflow (or air changes)? Higher airflow moves more moisture out but will reduce heat transfer. High enough airflow and you may not get any condensation in the system. Note that the duct bends near the fans causes turbulence that wastes some of your fan energy.
In my tests, the condensation was like a fine mist on the cold end of the metal plates. Your horizontal plates could hold a lot of moisture. You might want to tilt the unit with the air outlet at the lowest point.
With a Wave heater pumping out moisture, you may need to increase the exchanger plate area and airflow to keep up. You might also test the inlet closer to the top of the heater to capture moisture before it gets to the walls and condenses.
Great first test. Your unit is certainly more simple to build than mine. I hope it works well.
You have some good ideas that work in theory. However, there are some real life limitations that others have already expressed.
Your post is about heat recovery from a combustion appliance. The danger of cross contamination trumps all other engineering considerations since CO from combustion will kill mammals, including the human kind. Reduction of oxygen and a build up of CO2 from combustion in living spaces is also a concern.
Your furnace, which recovers heat from direct fire combustion, has a heavy, welded heat exchanger that is designed for safety over efficiency. Almost all systems that recover heat from engines for space heating use the cooling water or oil to a radiator. This liquid to air design eliminates the possibility of cross contamination. For example, if you had a radiator on the exhaust of the generator piped to a heater core inside the TC, then you have eliminated the cross contamination, but now have high cost, fan energy and lower efficiency.
My portable, plate, air to air heat exchanger design exchanges heat from inside air to outside air and does not attempt to recover heat from a combustion source. It would fail any cross contamination test you could suggest.
A shell and tube (or tube in a tube) air heat exchanger design could meet the safety concerns but I believe it would have low efficiency (for air), and be costly in first cost and energy (fan) cost.
Wes, I hope you can design around these limitations, but please address cross contamination first if you suggest recovering heat from the exhaust of a combustion applicance (generator, plat heater, stove, water heater, etc) in a TC.
Let me know if you have any questions. PM me if you prefer.
PS The fuel cell above does not use combustion. Someone please find me a 2 kW, light weight, affordable fuel cell with heat recovery!
If I made you feel too critical, maybe I was jumping to conclusions? :h
Hopefully, everyone will feel free to comment and discuss. I studied the subject a bit and chose one design (after trial and error) but there must be other (and better?) designs that would work for TC use.
The elongated rectangle seems to me to have the largest, practical surface/area. I believe that is one reason commercial air to air units use closely spaced plates. The triange tube might work ok if there was an advantage in manufacturing or reusing existing material. The flat plate design is easy for me to replicate and stack.
The gradient of humidity is also valid, especially if there is no air movement in the space. This could be important if there was a measurabe improvement in moisture removal with the intake at the ceiling. I'll agree with your theory until proven otherwise.
I first tried using a sling psychrometer for measurement. I couldn't measure outlets accurately because there is no room to sling :E. It is not accurate in slow moving air. Next, I used a remote sensor with humidity output but I could not get repeatable results.
Wes, thanks again for your thoughts. Maybe with input from you and others, a better design will result.
Thanks for taking us on your TC owner journey (and giving me insight to my sunlite TC).
I particularly enjoy you sharing your dilema of how many toys to take on the big trip. Many TC'ers have to balance the nimbleness of the rig versus taking our complete tool shop and toy box on the road.
Consider that a credit card, personality and bartering skills can get you the same experience using some else's toys when on the road.
As you share more decisions about what to take and leave behind, you will get more posts, "been there, done that."
My philosophy is everything should have 2-3 uses to minimize size and weight. For example, I have a hitch carrier on the back with a built in step and box to hold bug spray, flashlight, etc. Chairs, firewood etc. go on the carrier. I modified the carrier with a hitch extender so I can put the bike rack on too. Now I am thinking of modifying the bike with electric assist for more range. (my exploring rig)
I also have a goal post rack for the front that connects to a roof rack that can carry a porabote and a roof top carrier over the hood. (my fishing rig). Maybe not applicable to you as your rig do not seem to have roof clearance. (end of ramble):B
Keep posting, we are reading.
Oh goody, more air to air discussion.:Z
Humidity is lighter than air.
True in theory but I think stratification by temperature is more a factor in the TC than by relative humidity. In my design, I use small flexible hoses (ducts) to position the inlet and outlet where I want. In my field tests, I put the fresh air outlet near my pillow at night. I can put the outlet on the ceiling if desired.
What about condensation freezing in very cold temps.
I believe this is a problem with all air to air systems and with so-so solutions. In commercial units they use heating elements to quickly defrost the plates. My design would definitely freeze as it is partially located outside. (I know, build two and alternate them!) :B
First, I would design the "condensation zone" to drain before the "frost zone" if possible. Second, make a "frost zone" that can be quickly heated and drained. One solution is to temporarily heat the air intake with a hair dryer and drain it. Another would be to thermally couple the "frost zone" to the exhaust of your fossil fuel heat source or water heater. The ideal solution would be a mechanical gravity separation of ice from the exchanger with minimum thermal energy. More practical, incorporate a small peltier dehumidifier into the design. Cold side on the exhaust and warm side on the inlet (runaround heat pump design). Perhaps repurpose a consumer dehumidifier for very low air flow (high removal efficiency, low fan energy). I am of little help here since I don't care to be a below freezing camper.;)
The ideal triangular tube exchanger.
Exchanger design must balance thermal transfer through conduction (metal) and convection (air) and pressure drop (volume, velocity and fan energy). There would be a lot of pressure drop (turbulence) in the tube design and separating the chambers challenging. I opted for maximizing plate surface area, volume and minimizing pressure drop with low velocity and low fan energy (for boondocking).
Cost/availability of a commercial air to air exchanger.
I am not aware of any portable units (but I certainly don't know everything). Home and commercial systems are kinda expensive, the size of a small air handler, heavy, and require constant fan energy.
Place a small piece of disposable air filter on the inlets. Also, I can disassemble mine for cleaning/replacement.
Use of coroplast.
This is a threefer. First, it is a complete repurpose (and free to me!). Second, the uniform channels direct the air between the alternate chambers through the plate. Third, it forms the rigid frame and uniform thickness (for sealing) for each plate. (There is a fourth, the undocumented drainage channel)
Thanks for the insights and discussion.
First, thanks for the link to the exchanger at Make Projects. I did not see that one when I designed mine. Actually, I am glad I did not have it as a reference. IMHO their design has a number of deficiencies that are not resolved and may have mislead me. I cannot envision drilling all those holes accurately!
As for your project, redouble your efforts! Try heavy duty aluminum foil. Get some coroplast but make your frame with a combination of weatherstrip tape (or foamboard) and coroplast strips-just tape the pieces together. You can make the box from plastic sheet, coroplast or sheet metal. I don't recommend wood or cardboard with condensation.
I first sought out an ammo box to get a straight sided box and found the replica plastic sports box for mine.
Keep trying. If it was easy, everyone on this forum would have two!
Hi CC, (May I call you CC?)
Too early to critique. I use weatherstrip to isolate the four chambers. This is a low pressure device so weatherstrip should work.
Suggest you mock up with cardboard to test function, fans and confirm dimensions before cutting aluminum.
Think about drainage-maybe sloping the plates down to one corner (the corner with inside air exhaust).
I cannot envison a heat exchanger without an enclosure. It was a challenge to find the right box. Most plastic containers are designed to nest with sloping walls-hard to seal.
Give us a progress report.
Has anyone bought or made a 5th-wheel kingpin type support for the overhead bed when you take your camper off the truck? I know many folks simply don't worry about it but my husband and I would be more comfortable if we had some type of support for the bed. The idea of tipping the camper over when we're both sleeping doesn't thrill us. We have Maverick 9-foot camper mounted on a GMC 2500 heavy duty truck. Thanks for any help.
Perception is sometimes as important as fact. It is more important that you are comfortable. Go to harbor freight and get two "2 in 1 support/cargo bars." Use them under the overhang until you are comfortable without them. Then use them as cargo bars in the truck.
That's a really great arrangement, Rick!
I'd love to have a porta-bote...how do you like yours? Is it pretty easy to get on/off the rack?
Hi again Francesca,
The bote works well for my wife and I for lake fishing. More stable than a canoe. We use an electric trolling motor and portable wheels for launch and landing. You can do a lot of customizing (seats, rod holders, etc.) but it will increase the setup and takedown time. They last forever. Mine is the older model (20+ years old).
I have the Thule boat loader over the driver door that pulls out and allows you to lift one end and then the other of the 50 lb hull. Very easy to load and tie down.
How has the heat exchanger been treating you over the past year? I'm thinking of doing this myself and wondering if you've enjoyed less moisture and nice warm nights.
I only slept a few nights in the TC this year, and none in extreme moisture conditions.
However, I did use it with the fresh air hose positioned near my pillow. I did not open the fan hatch or lower hatch and had no moisture on the canvas the next morning. No cold drafts from the overhead hatch either.
As far as nice and warm, I would need to insulate the fabric of my pop up to see a big difference!