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Re-purposing heat exchanger coil in thermal store

Re-purposing heat exchanger coil in thermal store

Re-purposing heat exchanger coil in thermal store

(OP)
Hi,

I hope this post finds fertile ground and someone here can help a relative layman with a very simple, real-world project.

I have a domestic water filled thermal store. I want to add an air-source heat pump to the energy sources feeding into the store. There is a simple coiled tube heat exchanger coil in the lower portion of the store, originally intended to connect to some form of solar hot water system. I have some guide spec's for the heat exchanger, but no graphs or anything to show me how it performs over a range of conditions.

The simplistic data I have states that the coil is rated at 14.6kw based on a flow rate in the coil of 18 litres / min at 80 deg C. The lower parts of the store in which the coil sits would typically be between 20 and 40 deg C. The water in the store could have minimal turbulance (the store quite readily stratifies) or have quite a lot of turbulance when recuirculating pumps are running.

It it possible to get any meaningful indication of the possible performance of the heat exchanger by working backwards from those figures, and adding in some real-world knowledge of how these systems often behave in reality? My approach will have to be to build a test rig and try it out for real (because that's what I can do, and all that matters if if it will do what I want or not) but it would be a huge help if someone could tell me if I'm even in the right ball park or not.

My objective is to have a heat pump that can deliver between 4 and 6 kw into the store. Less than that and it's not really worth the trouble. The heat pump I am looking at has a flow rate of around 2 cubic metres per hour and delivers water / glycol at 35 to 60 deg C.

Thanks for any guidance.

RE: Re-purposing heat exchanger coil in thermal store

What is the coil made of?
You want to at or near the 18 lpm flow. Do you have a pressure drop at that flow?
You would need that in order to make sure that it sizes with your pump.
As the temp difference goes down so will the heat transfer.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

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