Proposed Air Cooling Tower

Discussion on Stirling or "hot air" engines (all types)
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Trevor
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Joined: Sun Nov 06, 2016 4:07 am

Proposed Air Cooling Tower

Post by Trevor » Wed Jun 19, 2019 1:52 am

I am looking at making a cooling tower for one of my hot air model engine. The design will be as below, but I am wondering if anyone out there on the Forum has successfully made something like this that works.
Trev
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Ian S C
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Location: New Zealand

Re: Proposed Air Cooling Tower

Post by Ian S C » Wed Jun 19, 2019 3:33 am

Trevor, this is similar to a cooling system used on some old hit and miss "barn engines", that system (comparing to yours), starts with the water reservoir, through the engine, the outlet is then released over a tent like structure of wire mesh on top of the reservoir. The main thing against this type of cooling on low powered motors is that it requires a water pump, where as the simple way is to use a thermosyphen with the top pipe submerged so that as the hot water rises the cool water is drawn in from the bottom. For extra cooling, an engine driven fan can be made to blow through the radiator.

Ian S C

Your cooling system would need a pump of some sort to circulate the water

Trevor
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Joined: Sun Nov 06, 2016 4:07 am

Re: Proposed Air Cooling Tower

Post by Trevor » Thu Jun 20, 2019 1:09 am

I was going to use a pump with the model using a tower to cool the water. The more I think of it though, it would have to be 400mm high for it to work as a natural ventilated system.
The water at the top would be warm which would get the air flow coming in from the bottom. Feasible I think, However I could use a radiator longitudinal to create a flow from hot to cold with natural airflow as - Maybe
Trev

Ian S C
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Location: New Zealand

Re: Proposed Air Cooling Tower

Post by Ian S C » Thu Jun 20, 2019 2:08 am

Without any maths, my guess is that it looks ok as is, for a bit more air through it a little fan might just get the air moving. My old motor in your Robinson thread has a 12V fan from a computer driven by the generator which also will power a transistor radio. The radiator has 3 rows ot flat tubes removed from a car heater radiator. I tried using the heater unit but it was not very effective, and it was too big and heavy.
Ian S C

Trevor
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Re: Proposed Air Cooling Tower

Post by Trevor » Thu Jun 20, 2019 3:04 am

I see your point Ian. One of the computer radiators are cheap and seem effective as I have used them before. Possible solution is to mount the radiator up at 300mm high with a box fixed around it with vent holes in the bottom. As the radiator gets hot an airflow should start automatically from below as heat rises, much like what you said earlier - I guess we will have to give it a try and see.
I am trying to get away from using a fan and making the unit look impressive as well as showing how a tower works.
I do love your work.
Trev

MikeB
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Re: Proposed Air Cooling Tower

Post by MikeB » Thu Jun 20, 2019 7:09 am

How long would you expect this to run? You would get a very high rate of evaporation from this, which would aid the cooling, but might make it 'unexpectedly' run dry.

Ian S C
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Location: New Zealand

Re: Proposed Air Cooling Tower

Post by Ian S C » Fri Jun 21, 2019 3:03 am

How long is a bit of string? Length of run depends on a number of things, And small hot air motors will run for quite a while after the water is all gone. To overcome the problem you could have a water tank to feed water to the cooling tower with a float valve to control the water level. Also if you put a sloping aluminium roof on the tower with a gutter under the lower edge you can capture the condensate which can be feed back to the water tank.

Ian S C

Trevor
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Joined: Sun Nov 06, 2016 4:07 am

Re: Proposed Air Cooling Tower

Post by Trevor » Sat Jun 22, 2019 1:32 am

Hi Mike and Ian
I would be running the model for a couple of hours. Water evaporation isn't a problem as the bottom tank would be getting topped up as it is being used.
Trev

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