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Heat Exchanger/Biological Filter


WEKA

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I am in the process of setting up a cold saltwater tank (15 deg c )of approx 700 litres.

As part of the setup I have constructed a heat exchanger (for cooling) consisting of 0.5 inch polythene tubing (approx 40 metres in 3 circuits) which carries the saltwater thru a glycol mix tank which is cooled by a refridgeration compressor. The cooling will operate for extended periods in the warmer weather. My concern is - will the tubing build up aerobic bacteria and work as a biological filter while the cooling system is operational. If so what will happen to that bacteria if the cooling is not required for some days and there is no circulation thru the tubing. Will I get a burst of nitrates or whatever when the cooling circulation re starts. Will I need to keep the circulation going thru the heat exchanger continuously even when the compressor is not required. Any thoughts on this?

Cheers

Warren

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Yeah, it will build up aerobic bacteria. But, I don't think it'll be enough to worry about. Your best bet, IMO is to simply have water running through it continuously even when the compressor isn't running. Then you don't have to worry about what happens when the water flow is stopped.

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get one of the temp controllers jetski sells, run the through pump all the time, and have the cooler/heaters on the controller... you will prob need heaters in chch! in the deep winter, the controller is very usefull to avoid big hysteresis loops...

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I'd be more concerned about a leak in the tubing letting glycol into the tank. Have you thought of enploying an intermediate liquid and letting the glycol cool the intermediate liquid and then letting that cool your tank water?

Steve

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Hey

Thanks for your comments.

I have an electronic thermostat for the cooler which goes down to 0.1 deg C hysteresis. I had thought I might purchase another for the heating.

The saltwater has a greater head than the glycol so if there is a leak I am hoping it will not be in the direction of the tank.

The main pump has a capacity of around 6000l/hr so I may look at byepassing some of this thru the cooler rather than run a dedicated pump on the cooler 24hrs.

Thanks again for your help.

Cheers

Warren

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