- #1
lando45
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- TL;DR Summary
- Yesterday I built a homemade AC unit, it works quite well but I think I can increase its efficiency.
Hi guys,
I used to post on here quite a bit back in 2005-2007 when I was studying Physics in school, I remember it always being a great resource so hopefully I can get some similar help with this "real life" problem I'm having now!
We are having a mini-heatwave here in the UK the last few days, making it really difficult to sleep comfortably at night. I started looking into the idea of getting an AC unit installed in our bedroom, but as I was searching around online I saw this video pop up on YouTube:
So I thought, why not try to make that as a fun DIY project! I sourced all the parts and constructed it yesterday. Only difference to the one in the video is that instead of installing the air outlet pipe and the fan directly into the lid of the coolbox, I have instead got a bit of insulating board which acts as the lid and I have installed the air outlet pipe into the insulating board (this way, I can still use the coolbox as a coolbox when I need to). Below is a picture of my setup:
We used it last night for the first time, I put a big frozen block inside (approx 20litres). The air that came out was cool (definitely cooler than if you just had the fan aimed at you directly), but I wouldn't say it felt truly cold like a proper Air Conditioner. By the time we woke up this morning the ice was all melted, I don't know at what stage of the night that happened. I think there's room for improvement. Bearing in mind I haven't studied physics for 13 years, my knowledge of the theory is very rusty but below is a few of the questions I had!
1) What effect will increasing the amount of ice have? Would it a) decrease the temperature of the air output, b) keep the cold air blowing out for longer or c) both?
2) Is the "empty space" in the box a factor? The coolbox I have there is about 90litres I think, if I'm only putting e.g. 20litres of ice in, that leaves 70litres of empty space. If I used a smaller coolbox e.g. 40litres, would that have any effect?
3) Does the shape of the ice I put in make a difference? Last night I put in one big block. If I used the same amount of ice but split up into smaller cubes, what difference would that make? My instinct says it would make the air colder as the total surface area of the ice would be greater, but perhaps the ice would melt quicker which might cancel that out
4) Does the speed/power of the fan make a difference? Presumably it does, the fan I used there has 4 settings (Off, 1, 2 and 3) - I used 3. Would a stronger/more powerful fan mean more air output through the outlet pipe?
5) Does the positioning of the ice within the box make a difference? I feel like if there was just one big ice block resting on the base of the cool box, that wouldn't work as well as if the ice was elevated and the air from the fan could circulate all around the block. Perhaps if I rested the ice block on an elevated grille it would work better
Those were all the questions I had, would be great if anyone has any input. Any other ideas/suggestions of course also welcome! Thanks
EDIT: One other question that I forgot to include!
6) I saw some people in the comments of the YouTube video suggest that including salt with the ice would make it colder. How does that work? I think mixing salt to the water prior to freezing would lower the freezing point to below 0degC. So my freezer would take longer to freeze it, but then it would stay frozen for longer overnight (and at a colder temperature)?
EDIT2: And another..
7) Would this be more effective at night with the bedroom windows/door open or closed?
I used to post on here quite a bit back in 2005-2007 when I was studying Physics in school, I remember it always being a great resource so hopefully I can get some similar help with this "real life" problem I'm having now!
We are having a mini-heatwave here in the UK the last few days, making it really difficult to sleep comfortably at night. I started looking into the idea of getting an AC unit installed in our bedroom, but as I was searching around online I saw this video pop up on YouTube:
So I thought, why not try to make that as a fun DIY project! I sourced all the parts and constructed it yesterday. Only difference to the one in the video is that instead of installing the air outlet pipe and the fan directly into the lid of the coolbox, I have instead got a bit of insulating board which acts as the lid and I have installed the air outlet pipe into the insulating board (this way, I can still use the coolbox as a coolbox when I need to). Below is a picture of my setup:
1) What effect will increasing the amount of ice have? Would it a) decrease the temperature of the air output, b) keep the cold air blowing out for longer or c) both?
2) Is the "empty space" in the box a factor? The coolbox I have there is about 90litres I think, if I'm only putting e.g. 20litres of ice in, that leaves 70litres of empty space. If I used a smaller coolbox e.g. 40litres, would that have any effect?
3) Does the shape of the ice I put in make a difference? Last night I put in one big block. If I used the same amount of ice but split up into smaller cubes, what difference would that make? My instinct says it would make the air colder as the total surface area of the ice would be greater, but perhaps the ice would melt quicker which might cancel that out
4) Does the speed/power of the fan make a difference? Presumably it does, the fan I used there has 4 settings (Off, 1, 2 and 3) - I used 3. Would a stronger/more powerful fan mean more air output through the outlet pipe?
5) Does the positioning of the ice within the box make a difference? I feel like if there was just one big ice block resting on the base of the cool box, that wouldn't work as well as if the ice was elevated and the air from the fan could circulate all around the block. Perhaps if I rested the ice block on an elevated grille it would work better
Those were all the questions I had, would be great if anyone has any input. Any other ideas/suggestions of course also welcome! Thanks
EDIT: One other question that I forgot to include!
6) I saw some people in the comments of the YouTube video suggest that including salt with the ice would make it colder. How does that work? I think mixing salt to the water prior to freezing would lower the freezing point to below 0degC. So my freezer would take longer to freeze it, but then it would stay frozen for longer overnight (and at a colder temperature)?
EDIT2: And another..
7) Would this be more effective at night with the bedroom windows/door open or closed?
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