Hello everyone

I'm currently working on my thesis to obtain my mechanical engineering degree. I'm designing a thermal energy storage system which basically works as follows:

- during a refrigeration system´s off peak hours, cold water-glycol solution (-10°C) passes through a cylindrical container filled with around 5000 plastic spheres, each sphere contains water/glycol solution.
- this water freezes the solution inside each sphere (these contain a lower glycol concentration in order to achieve freezing at -8°C)
- During on peak hours, hot water at about -6°C passes through the cylindrical storage and must exit at -8°C

All this work is theoretical of course, which brings me to my problem. I've been stuck for some time now trying to figure out the overall heat transfer coefficient of the whole cylinder/spheres arrangement In order to see if the amount of spheres that i've considered will be enough.

To (hopefully) simplify the problema I want to assume that the spheres move very little or not at all as water passes through the thermal storage (in the same fashion water flows through a tube bank)

Can anyone recomend some literature on the subject that might help me? or maybe a software of some sort? Any help will be highly appreciated.

Sorry for my writting and spelling, english is not my first language hehe.

Thanks everyone!