Question: Primary/Secondary storage, delta T

[Nofossil]

I have a couple questions about primary/secondary design. I understand the flexibility inherent in the idea that each source and load is independent and can have its own flow rate. I have a harder time understanding how to take advantage of storage effectively, and how to manage delta T for loads and sources. I'm looking for enlightenment (as always).

• For those of you with primary/secondary designs, what sort of temperature drop do you typically see in the primary loop?
  
• Is it normal to plumb high temp loads upstream from low-temp loads?
• What approaches do people use for charging vs. discharging storage (top-to-bottom vs. bottom-to-top flow)?
• Is it common to vary flow in the primary loop to maximize delta T, or is the goal to have primary flow fast enough to minimize delta T?

Thanks for helping me get my hands around this.

 

[ewdudley]

If you're in the design phase, then the buffer-tank/hydraulic-separator form of primary-secondary might be a better starting point. Differing supply and return temperatures can be routed to and from differing elevations in the tank. There was a presentation linked-to that showed an elevated buffer fed by gravity from storage that looked pretty slick.

 

[Nofossil]

If you're in the design phase, then the buffer-tank/hydraulic-separator form of primary-secondary might be a better starting point. Differing supply and return temperatures can be routed to and from differing elevations in the tank. There was a presentation linked-to that showed an elevated buffer fed by gravity from storage that looked pretty slick.

Thanks - I really like the hydraulic separator. I've just run into a lot of primary/secondary applications and I don't feel like I understand that approach as well as I'd like to.