help with water -> water heat exchanger formula

[syadnom]

I am trying to size a heat exchanger for a solar water heater. It seems that most people online tend to either buy a prebuilt exchanger with some arbitrary "good for 3 people" rating or just wing it. I googled to death but either google is to dumb or I am too dumb to find the answer.

 

Id like to take what I know which is:

 

temperature of incoming water

temperature of water in holding tank

volume / second of incoming water

heat volume of water (4.18 kj/kg) where 1kg=1liter

 

so if I have 40*F incoming water (using *F for degree symbol) and have 160*F water in the holding tank, how many square feet of surface area do I need to get the 40*F water up near 160*F?

 

I would be using copper coil. I can get 1/2" OD copper coil for the best surface area to price ratio so I would use that. 1/2" OD copper has a surface area of 18.5" per 12" length. it has a volume of .0386 liters per 12" length.

 

can someone help me on a formula for the heat transfer from the holding volume to the incoming water over a length or coil or surface area.

 

there are some assumptions here. The holding tanks temperature can be assumed to not be affected by the incoming water. The 160*F goal temp is over the needed temperature as I will be using a tempering valve at about 102-106*F so the the drop in temp in the holding tank from the heat exchange should not be noticed.

 

thanks in advance.

[Externet]

You should not find difficulties in finding heat calculations if stay with kilograms, litres, joules units... and do not toss farenheit, square feet, inches, btu units ... into the mix.