I’m just a layman from Australia who understands some of the principles of refrigeration, but have a question which needs an experienced mind!

I was at a friend’s place recently and he has a property with a house about 20 metres from the edge of a river. This river is used for irrigation down stream and water is released through summer. The water is very cold and is also a great trout fishery.

It gets very warm in summer in this part of the world and as we were sitting and talking last week I noticed that he had a refrigerated air conditioner installed. For some reason a light came on in my brain and I had this idea that I could use the cold from the river to cool his house down in summer.
Originally I thought to pump the cold water to the house and run it through a large truck radiator with a fan to move the air over it. But then I realized it would require less energy to move the air over a radiator located in the river.

I ran the idea past a friend and he said it wouldn't work.

Here is the idea:

I want to create a water tight box which sits in the flowing water and is anchored to the bank.

The box has a number of large diameter copper tubes running in the same direction as the river flow.

The box would have an input and output connection to attach ducting to and from the house. A fan would be located somewhere in the loop to move the air from the house, into the box, and back out through the return duct.

The box would have baffles in it to make the air move over as much of the copper as possible.

The water flowing through the copper would soak up the heat from the air as the air moved over the copper.


Here are my friends criticisms:

The idea in principle is Ok but...

The cooling transfer between a liquid to copper to air is extremely inefficient.

Also, the transfer of heat to air is quite efficient so that when you are pumping the air it will heat up very quickly in the pipe.

Also, gases compress where as liquids do no. When you pump the air you will actually compress it and thus add energy and heat.

I would suggest that you just pump the cold water.
You could use a hydraulic ram to pump enough water if the stream is flowing quickly. The pumping of the water will add very little heat to the liquid and if the pipe is well underground it will not heat up too much during the transfer.

The next thing is that you need a very efficient copper radiator to cool the air. A big truck radiator is Ok.
Then you need to pass air across the radiator but this causes problems because the fan adds energy (heat) to the air. So the radiator has to be very cold.

The whole problem is that even if you do all this it still will not work because the water is not cold enough. That is why they use ***** in air-conditioners. The temperature is below zero whilst in the radiator.

I would not bother. Pump the water up to a holding tank and have a cold shower.

Does anyone have any comments for or against?

Thank you very much and I apologise if my idea is too naïve.