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  1. M

    Two computer fans on top of each other

    If I have a computer fan that provides 50 cfm, and x static pressure. By stacking two of the same type of fans together, in the same direction, will it maintain the cfm but increase the static pressure to ~2x?
  2. M

    Air to Air heat exchanger

    Assuming the above ERV has 50 CFM, I calculated 95% efficiency. inside: 77.5 outside: 105 supply: 79 exhaust: 96 x = 97.2 = 1.8 deg F / deg C * 50 CFM * 0.018 BTU / ft^3 / deg F * 60 min/hr 77.5-105 * x = 2,673 BTU/H (supply - outside) 79-105 * x = 2527 BTU/H 2527/2,673 = .95 I think I...
  3. M

    Air to Air heat exchanger

    Yes i just looked into adopting an already made HRV like that, and its a really good option. I am trying to see how efficient they are but I haven't had much luck trying to find data on it. I then also came across ERV's which would actually even be better for the campervan since humidity is big...
  4. M

    Air to Air heat exchanger

    Also if material doesnt matter, then would 3d printing an exchanger with a much larger surface area and "nuances" to break up the air film be a much better approach? I also found there are thermal conductive filaments e.g. GRAFYLON 3D and TCPOLY I think this is the way to go, now I just need...
  5. M

    Air to Air heat exchanger

    Is it related to the Thermal boundary layer? So would some aluminum fins attached radially around the outside and inside of the inner pipe, which would cause the air to vortex, improve this, by breaking up this film/layer? Or am I misunderstanding this.
  6. M

    Air to Air heat exchanger

    Thank you for that jrmichler! 40% is not that great :( What is the air film (didn't find much on it online), and how could I improve it?
  7. M

    Air to Air heat exchanger

    I built a basic counter flow prototype. It was a warmer day today so I didn't get to test it in negative temperatures ( I will over the next few days). It is a 3"x8' flexible aluminum tube, inside a 4"x8' pvc pipe. using two fans. one fan sucking from out to in, and another fan sucking from in...
  8. M

    Air to Air heat exchanger

    not sure what an economizer is. Yes the reason for exhausting the warm air is to make room for fresh outside air (co2 being the main concern). the source of heat is a 5kw diesel heater. it has a powerful fan (for the space), and i have some aux fans (high static pressure) ill be using. which...
  9. M

    Air to Air heat exchanger

    Came across this: https://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node131.html would "18.5.2 General Counterflow Heat Exchanger" give me what i need?
  10. M

    Air to Air heat exchanger

    75% would be great, but is there any hint that it would be around that? is there a way to do some educated guess at that? And i did seal it as best i could with sprayfoam and foam panels. I have a co2 sensor in there. It can maintain the co2 level for days if i don't open a vent. Here is a...
  11. M

    Air to Air heat exchanger

    Removing heat is not the objective, but a consequence of removing co2, which im trying to mitigate through an exchanger.
  12. M

    Air to Air heat exchanger

    I am considering building this type of heat exchanger, as I have seen several youtube videos on the build. The inside tube is aluminum, I am planning on building one from the top of my roof to nearly the floor, so ill say 5 feet. I am thinking of using a 1.5" inch aluminum tube, and bringing in...
  13. M

    Calculating the coldest outside temperature my campervan can be in and still be warm inside

    Yep thats what i was thinking also. So maybe something for later. thanks!
  14. M

    Calculating the coldest outside temperature my campervan can be in and still be warm inside

    This is what i would like to calculate next, if it would be worth building. I could build it to allow the entering air to exchange with the exiting air. It would be interesting to determine how much of a help it would be to the heater. but my guess is that it would be negligable. the biggest...
  15. M

    Calculating the coldest outside temperature my campervan can be in and still be warm inside

    Thank you I think this is what I needed. So my fresh air exchange at 15cfm is only causing a 1500BTU/h loss? I am trying to understand how that was calculated, but i dont get parts of that formula this part: 0.018BTU/(hr−ft3−degF) Are hr, ft3, degF variable you plugged in or units? what is...
  16. M

    Calculating the coldest outside temperature my campervan can be in and still be warm inside

    Sorry I should have specified im trying to figure out how to calculate just the heat loss from the fresh air exchange. I have already calculated the heat loss through my van insulation from my average R value.
  17. M

    Calculating the coldest outside temperature my campervan can be in and still be warm inside

    I am trying to determine the coldest temperature my campervan can be in, so that the heater is still able to keep the van at 21C, while still being able to blow 15CFM air into and out of the van. Here is an earlier post figuring out the need for ~15cfm per person of fresh air to maintain less...
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