# BTU storage needed?



## Protech (Sep 22, 2008)

I'm doing a special hydronic system that needs a fairly large heat storage capacity. The working fluid will enter the heat exchanger at about 75F and exit at 180F. A variable speed pump operated by an aqua-stat measuring the working fluid side of the heat exchanger output side pumps the working fluid thru the heat exchanger to keep the working fluid at 180. The working cycle time is 6 hours. The storage cycle time is 144 hours.

Storage fluid will be at 200F at the start of the working cycle and end at no lower than 181F at the end of the working cycle. Storage fluid is 20% methanol by mass/80% tap water.

How much storage capacity do I need? I'm pretty sure this is not a linear process.


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## smellslike$tome (Jun 16, 2008)

I think there is a Colombian guy around here that can hook you right up with that :laughing:!


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## OldSchool (Jan 30, 2010)

Protech said:


> I'm doing a special hydronic system that needs a fairly large heat storage capacity. The working fluid will enter the heat exchanger at about 75F and exit at 180F. A variable speed pump operated by an aqua-stat measuring the working fluid side of the heat exchanger output side pumps the working fluid thru the heat exchanger to keep the working fluid at 180. The working cycle time is 6 hours. The storage cycle time is 144 hours.
> 
> Storage fluid will be at 200F at the start of the working cycle and end at no lower than 181F at the end of the working cycle. Storage fluid is 20% methanol by mass/80% tap water.
> 
> How much storage capacity do I need? I'm pretty sure this is not a linear process.


There is many variables here that are missing.. what size of heat exchanger? GPM of pump of working side. how eff is the plate heat exchanger? 

I take it that you are using solar to heat the storage tank and the working side is going to the hot water tank.

The numbers I am getting are huge.... a quick calculation I got would be about 3,600 Gallons

I may be wrong but the storage would have to be very high if it was solar that was heating the storage tank.


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