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Re: Idea for an air cooled condenser.
Posted: Fri Oct 21, 2022 1:08 am
by Hügelwilli
Let's see what the math says:
Air has a heat capacity of 1.005 kJ/kg/K what is 0.28 Wh/kg/K. This means to heat up 1kg air 1°C needs 1h 0.28W.
Now lets assume you have air inlet temperature 20°C and outlet 80°C. This means you have a span of 60°C.
Now 0.28Wh/kg/K x 60deltaK = 16.8Wh/kg. This means each kg air can handle 15.8Wh.
So 5500W / 16.8Wh/kg = 327kg/h
This is 327000lt/h air, because 1kg air = 1000lt
And 327000lt/h = 91lt per second air.
So you need minimum 91lt per second air no matter how large your condenser is. The only way to reduce this is less wattage or a colder air. With air at 0°C you would have a span of 80°C instead of 60, what means you would need only 91 x 60 / 80 = 68lt air per second.
Re: Idea for an air cooled condenser.
Posted: Fri Oct 21, 2022 1:20 am
by Yummyrum
Nice math Hugel
What practical fan would you suggest that could move that volume of air ?
Re: Idea for an air cooled condenser.
Posted: Fri Oct 21, 2022 2:33 am
by Hügelwilli
I have no idea.
My post is meant to see if this project will fail due to the efforts and to show that you cannot solve it with more and more surface area like with added fins for example.
Re: Idea for an air cooled condenser.
Posted: Fri Oct 21, 2022 2:35 am
by shadylane
Hügelwilli wrote: ↑Fri Oct 21, 2022 1:08 am
Now lets assume you have air inlet temperature 20°C and outlet 80°C.
I know the answer.
It's going to get hot enough to kill skitters in the still shed.
Re: Idea for an air cooled condenser.
Posted: Fri Oct 21, 2022 2:39 am
by shadylane
Hügelwilli wrote: ↑Fri Oct 21, 2022 2:33 am
you cannot solve it with more and more surface area like with added fins
I think the more surface area provided by cooling fins, the better.
Re: Idea for an air cooled condenser.
Posted: Fri Oct 21, 2022 2:56 am
by Hügelwilli
shadylane wrote: ↑Fri Oct 21, 2022 2:39 am
Hügelwilli wrote: ↑Fri Oct 21, 2022 2:33 am
you cannot solve it with more and more surface area like with added fins
I think the more surface area provided by cooling fins, the better.
To get to the 80°C after the condenser, added fins can help. But I don't know if they are needed. If you get 80°C air temperature after the condenser without fins, added fins won't help, because -assuming the vapor temperature is 80°C-, this won't heat up air to more than 80°C. The heat hast to go to somewhere. If the air is already at 80°C, nothing will help to get more cooling.
Re: Idea for an air cooled condenser.
Posted: Fri Oct 21, 2022 3:53 am
by googe
The fins have to be at a minimum the amount of energy output, the fan has to match the conductivity of the fins. Huge is right.
Re: Idea for an air cooled condenser.
Posted: Fri Oct 21, 2022 7:32 am
by squigglefunk
Hügelwilli wrote: ↑Fri Oct 21, 2022 1:08 am
Let's see what the math says:
Air has a heat capacity of 1.005 kJ/kg/K what is 0.28 Wh/kg/K. This means to heat up 1kg air 1°C needs 1h 0.28W.
Now lets assume you have air inlet temperature 20°C and outlet 80°C. This means you have a span of 60°C.
Now 0.28Wh/kg/K x 60deltaK = 16.8Wh/kg. This means each kg air can handle 15.8Wh.
So 5500W / 16.8Wh/kg = 327kg/h
This is 327000lt/h air, because 1kg air = 1000lt
And 327000lt/h = 91lt per second air.
So you need minimum 91lt per second air no matter how large your condenser is. The only way to reduce this is less wattage or a colder air. With air at 0°C you would have a span of 80°C instead of 60, what means you would need only 91 x 60 / 80 = 68lt air per second.
Re: Idea for an air cooled condenser.
Posted: Fri Oct 21, 2022 7:41 am
by Hügelwilli
So he doesn't like it and can help only with a meme.
Re: Idea for an air cooled condenser.
Posted: Fri Oct 21, 2022 2:32 pm
by shadylane
If the air outlet temp is 80'c I'd use a bigger fan.
Re: Idea for an air cooled condenser.
Posted: Fri Oct 21, 2022 3:14 pm
by Hügelwilli
If I ran a fan that moves 91lt air per second in my shed I would not think about using a bigger one.
Re: Idea for an air cooled condenser.
Posted: Sat Oct 22, 2022 2:26 am
by Chauncey
200 cfm bathroom exhaust fan may work...
Re: Idea for an air cooled condenser.
Posted: Sat Oct 22, 2022 3:03 am
by shadylane
Chauncey wrote: ↑Sat Oct 22, 2022 2:26 am
200 cfm bathroom exhaust fan may work...
Now that I've thought about it.
The 6" inline fan I suggested earlier only flows 170 cfm.
I don't think that's a big enough fan either.
I used a cheap window fan, It's rated at something like 2000 cfm.
If you want small and high CFM.
Ya need a blower instead of a fan.
Re: Idea for an air cooled condenser.
Posted: Sat Oct 22, 2022 3:23 am
by Chauncey
I'm looking hard at Mason jars design...I'm thinking I can take that and improve upon it some...
Re: Idea for an air cooled condenser.
Posted: Tue Oct 25, 2022 10:25 am
by squigglefunk
Hügelwilli wrote: ↑Fri Oct 21, 2022 7:41 am
So he doesn't like it and can help only with a meme.
no I was just saying I am bad at math and it confuses me lol