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  1. M

    PID or Relay for Circulating Shower

    I am considering using PID (autopid arduino lib), in order to control the heat, with PWM and a 50amp mosfet heating a 40amp 24v heating element in a 3litter tank, but I am thinking, that since the water is going to be circulating, and sometimes losing heat to a person, sometimes falling straight...
  2. M

    LiFePO4 battery heater project (makes sure battery doesn't freeze)

    I think PID is overkill (but would consider it). I am thinking of setting up an array of thermistors around the battery to make sure that they are all above T? Maybe two on top, two on the sides. The battery is about 8"x20". I am building an r10 insulation box around the battery, which will...
  3. M

    How can you determine if a fan is better at blowing or sucking?

    I am trying to determine if they are better placed in positions where they suck or blow. Is there a rule to determining this?
  4. M

    Applying desiccant to surfaces (aluminum sheet or PLA/PETG)

    I will either be using aluminum strips wound up, or 3d printing it out of PLA or PETG. How can I apply a coating of silica to the surface of either of these materials so that it can hold and release the moisture of the incoming air/outgoing air? This is to manage heat and humidity in my...
  5. 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?
  6. M

    B How long will it take to reach 1000ppm CO2 from 2000ppm

    would this be a quadradic equation since its dealing with half life? I think in 500/50 = 10 minutes, the fan would have brought 500 CF of fresh air, but the out fan would have been taking out the same amount of air which includes the fresh air, so at 10 minutes, it should have less then half the...
  7. 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...
  8. M

    Does Polyester resin + catalyst react with uncured polyurethane foam?

    I left it on for about 3 weeks, most of the time it was in below curing temperature, sometimes below freezing, but i gave it about 15 hours of 20c+ to try to cure it. It never did, and still smelt really bad. I decided to rip off the resin that had hardened. Underneath it, the polyurethane foam...
  9. 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...
  10. M

    Can polyester resin eventually cure if it was too cold at first?

    I finally brought in a heater and kept it at about 30C for 3 hours. It still smells like uncured offgassing. Will it ever cure or did the freezing/prolonged cold ruin it and i have to remove it?
  11. M

    Calculating air flow through a tube

    This is for a campervan project I am working on, I am trying to take outside air that is cold (Canadian winter) and mix it into the return air in my diesel heater. I need to hit a specific minimal CFM to maintain proper Co2 levels inside and I would like to be able to calculate this. The axial...
  12. M

    B Does light travel forever?

    I don't think this is what is observed, so where is my understanding wrong?
  13. M

    Why is the CO2 level lower in my house than outside?

    How is this possible? I cant think of what could be absorbing Co2 inside my house, when I am producing it at a pretty high rate. I have my HVAC running on a frequent cycle mode also. I have no plants. The sensor...
  14. M

    Calculating the air flow rate needed to maintain the ideal CO2 concentration in a campervan

    My goal is to determine the ideal amount of air flow, in order to keep co2 below 1000ppm and to minimize heat loss. I calculated the following based off a similar post in this forum, and I am hoping this can be verified so I know that i am in the right ballpark and going in the right direction...
  15. M

    Energy transfer

    how do atoms transfer kenetic energy to each other?
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