cold river water

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.

There is nothing fundamentally wrong with your idea provided the water is cold enough to provide useful cooling. Having your heat exchanger located at the river, and setting up the necessary insulated ductwork to move the cool air to the house will be more problematic than simply pumping the water to a heat exchanger located in the house. This would be particularly the case if the house already had some forced air hvac system you can utilize.

Most air conditioning evaporators operate in the 40°F to 45°F range, not "below zero", Celsius or otherwise... :) And the heat transfer between liquid and copper is better than air to copper. But this is a non-argument as you are already exchanging heat between a liquid and air with a radiator, or an evaporator.

The real question become: how cold is the water in the river? Obviously, 45°F water is plenty cold to do useful cooling. Not that the Prof is an expert on chiller design, but he would think 60°F water might do some useful cooling, though you would not have much in the way of humidity control at this temperature.

Eftimios

I would pump the "cold" stream water into the house and into a holding tank. In this holding tank I would place a small copper coil which would be refigerated, ie: connect a normal refrigeration compressor and cool the cool stream water even further and make it colder. Then pump this cooler water into your truck radiator and blow into the room.

If the stream water is cold enough then you dont have to refrigerate it further in the holding tank. In the summer I guess the water is not going to be cold enough so it requires cooling.

I would not rig up anything near the stream. Pump all the water into the house or near it and set up your equipement there. Study some water chiller designs to give you an idea.

You can also maybe pick up a second hand evaporator from an old cold room and use that instead, better then using a truck radiator.

Will be intresting how this works out. Dont give up. Plenty of experts on this forum who will help you along the way

Gday

I cool my house using well water. My well water is approx. 47F. or 8C. It does a fair job. I used a large (5 Ton) A-Coil from a conventional A/C system and pump the water through the copper tube where the refrigerant would normally flow. I you use a truck radiator you will have condensation dripping everywhere because it is not designed to catch the condensate and route it to a drain. The temperature of most rivers in this area range from approaching the freezing point in the winter to room temp in summer. I presume that is also the case with your river. The best use for your river water would be to use an A/C unit or heat pump with a water coil instead of an outdoor air cooled condenser. The lower head pressure will give you much higher efficiencies. The cost of this equipment, however is more expensive than a regular air cooled split system. If you have a long cooling season, it may be worth the investment. If your river temperature does not rise above 8 or 10 degrees C. in the summer, you can use it to cool directly, but I would use a coil designed for air-conditioning. You also need a pump that can pump 12 to 15 GPM (50 LPM) through the coil. Good Luck

Terrygoodrich...i m greatful to you if you send me a complete cycle with the pump size, evaporator ( Redator size) size etc.
Thanks.

Yo guys,
in school they have teached us that if whe have a TD of 10 degrees whe have an exanche.wich is good for the river temp.for airconditioning the best temperature is 8K. so if we have a room temperature of say 30C° and we can cool it dawn to 22C°,and all of this for nearly no cost of energie ? who are whe to complain then.;-))

Ice

ps; i wish i had a river at 20mtr.

6 year old dead thread been revived. Why didn't you let it rest in peice?

I don't see a problem when new members are searching through our already huge library of posts and find something that is useful for them.
You can't expect that new members only post and read threads of 1 month old.
If they re-open an old thread, then there's chance that nobody will answer it. That's all.

A my good sir Peter I do indeed take this thought into account however look at the thread that brought it up was meer lazy begging all his thinking to be don for him! This thread deserves better imo